Astm mnl 49 2014

Lobo User’s Guide to ASTM Specification C94/C94M on Ready-Mixed Concrete: NRMCA National Ready Mixed Concrete Association 900 Spring Street Silver Spring, MD 20910, USA Printed in the U.

D Gene Daniel and Colin L Lobo User’s Guide to ASTM Specification C94/C94M on Ready-Mixed Concrete:

NRMCA National Ready Mixed Concrete Association

900 Spring Street Silver Spring, MD 20910, USA

Printed in the U.S.A.

Library of Congress Cataloging-in-Publication Data

Daniel, D Gene,

1934- [User’s guide to ASTM specification C94 on ready-mixed concrete]

 User’s guide to ASTM specification C94/C94M on ready-mixed concrete / D Gene Daniel, Colin L Lobo 2nd edition   pages cm

 Revised edition of: User’s guide to ASTM specification C94 on ready-mixed concrete / D Gene Daniel and Colin L Lobo 2005.

 Includes bibliographical references and index.

 ISBN 978-0-8031-7054-4 (alk paper)

1 Ready-mixed concrete–Specifications–United States I Lobo, Colin L., 1961- II Title

Photocopy Rights

Authorization to photocopy items for internal, personal, or educational classroom use of specific clients, is granted

by ASTM International provided that the appropriate fee is paid to ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Tel: 610-834-9634; online: http://www.astm.org/copyright/

ASTM International is not responsible, as a body, for the statements and opinions advanced in the publication ASTM International does not endorse any products represented in this publication.

Foreword

THIS PUBLICATION, User’s Guide to ASTM Specification C94/C94M on Ready-Mixed Concrete,

was co-published by ASTM International and the National Ready Mixed Concrete Association (NRMCA) It was both authored and edited by D Gene Daniel, concrete consultant, Claremore, Oklahoma; and Colin L Lobo, National Ready Mixed Concrete Association, Silver Spring, Maryland This publication was sponsored by Committee C09 on Concrete and Concrete Aggregates and it is the second edition of Manual 49 of ASTM’s manual series

Contents

Preface vii Introduction xi

11 Mixers and Agitators 91

12 Mixing and Delivery 101

13 Use of Nonagitating Equipment 121

14 Batch Ticket Information 123

15 Plant Inspection 129

16 Practices, Test Methods, and Reporting 131

17 Sampling and Testing Fresh Concrete 141

18 Strength 149

19 Failure to Meet Strength Requirements 159

20 Keywords 163

21 Annex A1 Concrete Uniformity Requirements (Mandatory Information) 165

22 Appendix (Nonmandatory Information) 171 Index 179

Preface

What is astM?

To fully understand ASTM C94/C94M, Specification on

Ready-Mixed Concrete, it is necessary to understand ASTM and the

consensus process for developing standards such as ASTM C94/

C94M Getting a view of ASTM from its conception takes us

back more than a century The time period involved is between

the American Civil War, which ended in 1865, and World War

I, which began in 1914 The true beginning of ASTM coincided

with the Spanish-American War fought in 1898

The world, and more specifically the United States, was in

the midst of the second phase of the Industrial Revolution

Major advances in communication and transportation were

taking place in a country that in the late 1890s consisted of 45

states The diesel engine, electrical power, and the steel industry

were all coming into prominence The United States was a

growing, developing, and prosperous nation with industrial

corporations, some of which have gone on to grow into giants

that remain today William McKinley was elected President in

1896, re-elected in 1900, and assassinated in 1901

This growth period and the industrial revolution were

the backdrop that fostered ASTM The North American

rail-road network was expanding in all directions less than 30

years after the completion of the first transcontinental

rail-road Charles Dudley, holder of a Ph.D from Yale University,

was a chemist for the Pennsylvania Railroad Mr Dudley’s

degree preceded by two years Custer’s Last Stand at the Battle

of the Little Big Horn in the hills of Montana A portion of

Mr Dudley’s duties included doing research to develop more

durable steel for use as rails and writing a specification

con-veying those findings to the rail manufacturers Mr Dudley’s

ideas did not always coincide with those of the steel

manufac-turers or the other railroads that were buying steel rails

These problems of differing viewpoints led to the first

meet-ings of manufacturers, chemists, engineers, and others in the

steel and railroad or bridge business to develop standards

everyone could tolerate The idea that emerged was that good

material standards require the input of manufacturers,

designers, builders, and users This was the idea in June of

1898 when ASTM was first formed under another name,

American Section of the International Association for Testing Materials From the first meeting, the goal was to develop consensus standards

The first committee dealing with cement, C01, was formed

in 1902, and the concrete and concrete aggregates committee, C09, formed in 1914

The scope of ASTM has continued to expand, and its name has continued to change The name today is ASTM International, reflecting both its wide use and a broad international member-ship From the original 70 members, ASTM International (ASTM) has grown to more than 30,000 members For the 100 plus years of its existence, the committee work has remained in the hands of volunteers

100 people, including manufacturers of ready-mixed crete, private engineers from design firms and material testing firms, state highway department engineers, representa-tives of federal agencies, representatives of trade organizations, professors from foreign and domestic universities, contractors, and representatives from concrete material producers, such

con-as cement and chemical admixtures, con-as well con-as others who have a relationship to the industry Most of these people are engineers or scientists whose daily activities involve them with the concrete industry Most, but not all, live in the United States

Subcommittee C09.40 is only one of many subcommittees that function as a part of the Committee C09 on Concrete and Concrete Aggregates The main body of Committee C09 divides into approximately 29 subcommittees to develop consensus standards for the concrete and concrete aggregates industry

astM standards developMent process

ASTM standards development follows a consensus process

con-sistent with requirements of the American National Standards

Institute (ANSI) ANSI facilitates the development of American

National Standards (ANS) by accrediting the procedures of

standards developing organizations (SDOs) like ASTM

International SDOs work cooperatively to develop voluntary

national consensus standards An important requirement is to

ensure the voting producer representation on the committee is

balanced between voting representation by users and by general

interest members Each company or entity is assigned one vote,

and additional representatives from that entity are provided a

nonvoting status This ensures that the interests of one

particu-lar group do not bias the development of the standard and that

all viewpoints are addressed The development of standards

through consensus requires time and compromise but ensures,

for the most part, that the standards developed satisfy all

affected groups American National Standards development

process is usually referred to as “open” standards development

In this sense, “open” refers to a process used by a recognized

body for developing and approving a standard This ensures a

collaborative, balanced, and consensus-based approval process

The content of these standards may relate to products,

pro-cesses, services, systems, or personnel

New standards or revisions to existing standards within

ASTM usually begin within a task group of a subcommittee

The task group develops a written ballot that is submitted for

letter ballot to the subcommittee Reviewing subcommittee

ballots and voting is both a privilege and a responsibility of

committee membership When a subcommittee member casts

a negative vote on a ballot item, an explanation of what the voter

objects to and what changes could be made to satisfy the

concerns of the negative voter is required

For a ballot to become valid, at least 60 % of the voting

subcommittee members must have voted For a ballot item to

be successful, two thirds of the eligible voting members must

vote affirmatively on a ballot item To advance to the next

level, the subcommittee vote must be positive for two thirds or

more of those voting In reality, each negative vote of a

mem-ber, voting or nonvoting, is vetted, or the ballot item

with-drawn and revised, if possible, into a new subcommittee

ballot

The item is then either re-balloted at the subcommittee

level, or with the approval of the committee chairman the

revised item may be balloted concurrently at both the

sub-committee and sub-committee levels The sub-committee level

involves all the members of the various subcommittees In

the case of the Committee C09 this involves approximately

29 subcommittees and 700 members Committee C09 meets

in June and December each year with a usual attendance of

150 to 200 members It is at these semiannual meetings that

each negative ballot is vetted and voted on

At the committee level a ballot item must receive

affir-mative votes on at least 90 % of the votes cast for approval

If approved at the committee level, the balloted item is approaching ASTM membership approval

Simultaneously with the committee level vote, the posed change is also subject to a vote by the entire ASTM Society, which includes all the ASTM members in various committees No voting percentages are required at this level, but negative votes must again be considered

pro-The consensus system also provides for an appeal by a ative voter The appeals system varies depending upon the grounds stated for the appeal A Committee on Standards assures that due process is followed

neg-The primary point of the entire process is that each negative voter’s voice and arguments are heard, and the sub-committee or committee is then afforded the opportunity to vote on an issue based on the thoughts and reasoning of one member of the group A single objection often influences others and alters the content of a proposal or kills the proposal completely ASTM firmly believes in the old adage that two heads are better than one and has set up a system to ensure that each member’s voice is heard

original astM specification for ready-Mixed concrete

The original C-9 (now C09) committee required six years (1914–1920) to issue its first standard The first standard addressed the proper means of molding and storing concrete cylinders in the field and described methods still in use today The first product specification was issued in 1933 as a ten-tative specification for ready-mixed concrete The topics cov-ered did not vary much from today’s standard, over 75 years later

The specification has been revised many times since approved in 1935 and continues to undergo revisions to remain

in step with technological advances, such as load-cell weighing, and environmental issues, such as limiting plant runoff water

by the use of non-potable water in the batching process

The roots of a successful specification go back to the abilities of the committee who prior to 1933 published a com-prehensive document prescribing the materials, proportioning, mixing, delivery, quality, inspection, testing, and acceptance of ready-mixed concrete for delivery to the job site ready for use

An equivalent specification to ASTM C94/C94M is published by the American Association of State Highway and Transportation Officials (AASHTO) M 157 Standard Specification for Ready-Mixed Concrete As the association name implies, this organization includes representatives from each state and some other entities involved in construction of transportation infrastructure Development of AASHTO stan-dards does not follow the typical consensus process because AASHTO limits voting interests to designers and users (state departments of transportation) and excludes industry repre-sentation AASHTO Subcommittee on Materials reviews changes to ASTM standards and chooses to ballot these changes

to the AASHTO standards Some AASHTO standards are

Preface ix

essentially very similar to ASTM standards AASHTO M 157 is

structured slightly differently than ASTM C94/C94M, but the

technical differences are relatively minor There are several

sections of ASTM C94/C94M that are not covered in AASHTO

M 157 The greatest difference between the two specifications is

in the category of ordering information ASTM C94/C94M has

three options, providing more latitude to the purchaser

AASHTO M 157 does not provide a section on ordering Instead

ASSHTO M 157 has a quality of concrete section that concerns

submittals to the engineer by the contractor or the

proportion-ing prescribed by the engineer and directed to the contractor

Another difference between the two sets of standards is in the

reference to the use of mixing water in concrete ASTM C94/

C94M references ASTM C1602 A note at the end of AASHTO M

157 recognizes these differences and suggests, “users other than

specifying agencies should consider ASTM C94.” State highway

agencies vary in their reference to ASTM or AASHTO

standards

hoW to use astM C94/C94M

The most common usage of ASTM C94/C94M is as a reference

document within a design professional’s specification for

cast-in-place concrete A statement such as “Unless otherwise

spec-ified, use materials, measure, batch, and mix concrete

materials and concrete and deliver concrete in approved

equipment, all in conformance with ASTM C94/C94M” within

the concrete specifications for a project specify the strength,

slump, air content, aggregate size, and other variable factors named in Section 6, Ordering Information, will be provided.Other methods are suitable if the questions in Ordering Information are answered A purchase order with a ready-mix

concrete manufacturer may simply state “Produce and deliver

concrete as per C94.”

An important violation that can cause trouble is using excerpts from ASTM C94/C94M or any other specification with-out a careful reading of the entire document for related seg-ments Unfortunately some design professionals follow this cut and paste style It is best to use the complete document by reference

hoW to use this guide

The chapters in this book reflect the sections of C94/C94M Text from C94/C94M is reproduced in italicized text followed

by a discussion of the section Sentences in the specification are cross-referenced and discussed in the text with identifica-

tions S1, S2, etc Tables, figures, and numerical examples are

numbered sequentially by chapter number, except for tables excerpted from C94/C94M, which retain the actual table num-ber from C94/C94M

disclaiMer

This book represents the interpretation of the authors ing ASTM C94/C94M and does not represent the views of ASTM International or Subcommittee C09.40

Introduction

astM designation: C94/C94M-13 standard

specification for ready-Mixed concrete

This is the official number and title for the ASTM specification

for ready-mixed concrete Portions of the designation remain

constant, and other parts are always subject to change An

anal-ysis of the parts of the alphanumeric identification for the

“Specification for Ready-Mixed Concrete” entails four

segments:

C94 includes the group designation “C” (which comes from

the 19 ASTM committees currently grouped under the “C”

des-ignation, of which committee C09 is one)

ASTM Committee C09 is responsible for this ready-mixed

concrete specification The permanent number 94 was assigned

in numerical sequence from all of the C committee standards when first developed

“C94M” means this specification is a combined standard that includes metric (SI) values as well as inch-pound values

The hyphenated numerals following the serial designation represent the last two digits of the year the standard originated

or was last revised An ε1 superscript (ε1) following the year designation would indicate that an editorial change has been made later than the substantive changes of 2013

Footnotes on the title page are self-explanatory.1

1 This specification is under the jurisdiction of ASTM Committee C09 on Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee C09.40 on Ready-Mixed Concrete.

Chapter 1 | Scope

1.1 S1 This specification covers ready-mixed concrete as defined

in 3.2.2 S2 Requirements for quality of concrete shall be either

as hereinafter specified or as specified by the purchaser S3 In

any case where the requirements of the purchaser differ from

these in this specification, the purchaser’s specification shall

govern S4 This specification does not cover the placement,

consolidation, curing, or protection of the concrete after delivery

to the purchaser.

The first sentence (S1) identifies that what follows is a

specification Merriam-Webster’s Collegiate Dictionary, Tenth

Edition, defines a specification as a detailed precise presentation

of something and a statement of legal particulars The Sixth

Edition of the Shorter Oxford English Dictionary (SOED) offers

a similar definition The referenced document, ASTM

Specification C94/C94M, meets both of these criteria It is a

detailed precise presentation dealing with the minimum

requirements for both manufacturing and delivering

ready-mixed concrete Another common definition of specification

used by ACI and ASTM is an explicit set of requirements to be

satisfied by a material, product, system, or service C94/C94M is a

specification for a material in the same vein as C150/C150M is for

cement and C33/C33M is for concrete aggregates

The purpose of this document is to form a statement of

legal particulars to be available for reference in a project

specifi-cation, purchase order (written or oral), or contract The legal

particulars describe the minimum requirements for

manufac-turing and delivering ready-mixed concrete Specifications for

materials establish separate and joint responsibilities for the

manufacturer and the purchaser of the material ASTM

C94/C94M additionally states responsibilities for the testing

agency (laboratory) that tests and evaluates the product for

con-formance with the purchaser’s requirements or project

specifications

The end of the statement references ready-mixed concrete

as defined in Section 3.2.2, Terminology The Terminology

section is new to C94/C94M Ready-mixed concrete is defined

as concrete manufactured and delivered to a purchaser in a fresh

state The indication is that immediately following

manufac-ture, delivery to the purchaser (or authorized agent) shall be of

concrete in a fresh state Because concrete in its fluid state from the point of manufacture changes its characteristics with time

and has a relatively short shelf-life, the use of the term fresh

indicates that it should be recently or newly manufactured when it is delivered At the time and place of delivery (dis-charge), the concrete is expected to be moldable, allowing it to take the shape of the conveying equipment and the forms into which it is placed and finished by the purchaser’s authorized agents

As we move on into the next portion of this section, it is important to understand the different situations in which ASTM C94/C94M is used Initially, ASTM C94/C94M is invoked

by reference in most major public and private construction The project specification establishes a contract between the owner and his representative (the designer and specifier) and a con-tractor This requires the concrete manufacturer (producer), as the material supplier, to agree to conform to C94/C94M in a contract with the purchaser, who may be the general contractor

or a concrete contractor Secondarily, in smaller jobs where no specification is in place, ASTM C94/C94M establishes the basis

of the agreement between the concrete manufacturer ducer) and the purchaser, perhaps a homeowner Finally, an important use of C94/C94M is its incorporation by reference in locally adopted building codes that protect public safety and other interests Code requirements are binding on the owner and are passed down to the contractor through the contract documents and to the concrete manufacturer through a pur-chase order from the contractor In all these situations it is important for the purchaser to inform the concrete manufac-turer of the pertinent code or specification requirements as they apply to the requirements for concrete Preferably a copy of the project specification in its entirety should be provided to the concrete manufacturer If the purchaser only states a strength requirement but fails to state requirements for durability, such

(pro-as water-cementitious materials ratio, or other prequalification requirements for the mixture, the product cannot be priced correctly, and the concrete manufacturer cannot bear responsi-bility for requirements that are not clearly stated in a purchase order In this discussion it is understood that the purchaser of ready-mixed concrete may not be the entity establishing

requirements in the project specification, and communication

of the owner’s needs must occur for a project to be successful

The second sentence (S2) focuses on the purchaser’s right

to alter the ready-mixed concrete quality portion of the

specifi-cation ASTM C94/C94M is intended to be a general reference

specification for a material; it cannot cover all specific

require-ments for a particular project The purchaser can order concrete

in accordance with ASTM C94/C94M and add or change clauses

in the specification that are pertinent to the project or local

con-ditions For example, in hot weather the purchaser may require

the concrete be discharged in less than 1 ½ h or permit an

extended haul time for remote location placements The

pur-chaser can specify concrete be manufactured in a plant mixer

(central-mixed) rather than truck-mixed concrete The

pur-chaser has the right to specify the use of a cement complying

with a specific cement specification, such as one of the cements

from ASTM C1157/C1157M, Performance Specification for

Hydraulic Cement or for that matter a specific brand of cement

as well as the type The purchaser may place restrictions on

inclusion of calcium chloride and products containing chloride

additions in accordance with ACI 318-11 Building Code

Requirements for Structural Concrete [1] or ACI 301-10,

Specifications for Structural Concrete [2] In short, the purchaser

may alter any portion of this specification that impacts the

required quality of the product as the purchaser desires The

variations desired by the purchaser, however, should be clearly

stated to the manufacturer before a price (or a competitive bid)

is requested Alterations in specification requirements can have

a significant affect on the cost, and thereby the price, of the

con-crete mixture

More questionable changes to C94/C94M are factors that

attempt to change the responsibility chain One example is

changing the requirements for concrete to the point of

place-ment at the end of a pump line, instead of at the point of

dis-charge from the delivery vehicle This would cause a change in

custody of the concrete to one over which the manufacturer has

no control and for which the manufacturer cannot assure the

quality because of the uncertainty associated with the effects on

concrete created by the placement method Such a change in the

project testing location must be included in the contract

docu-ments and requires an established line of responsibility for the

concrete between the manufacturer’s discharge and transport

and placement by others These issues must then be discussed in

a pre construction meeting This is an important part of the

pricing decision for concrete Because the sampling techniques

at the placement area have a major influence on the measured

concrete properties, it is essential that the preconstruction

con-ference include precise sampling details that are acceptable to

all parties Concrete manufacturers will also typically not

accept responsibility for the quality of the product if

adjust-ments are made (beyond those permitted by C94/C94M) or if

products are added by the purchaser at the job site

The third sentence (S3) makes it clear that the purchaser

may specify exactly what is believed to be best for the

purchaser or the project, as may be the case Perhaps after a ready-mixed concrete supplier is selected, the specifier deter-mines that it is in the best interest of the project to add a restriction that the concrete aggregates meet the optional alkali-silica reactivity (ASR) requirements of ASTM C33/C33M

Specification for Concrete Aggregates The purchaser should

communicate this to the concrete manufacturer, and if a price agreement was reached prior to establishing these require-ments, the supplier has every right to demand monetary com-pensation for the change The point here is that the concrete should not be delivered until an agreement is reached, and in this example concrete containing aggregates that do not meet the specified ASR requirements should not be delivered The project specification or purchaser’s requirements override stated quality requirements in ASTM C94/C94M and shall gov-ern but must be established before the price for the concrete

is set

The fourth sentence (S4) defines what this specification

does not cover The specification does not cover or address the placement of the concrete, the consolidation of the con-crete, the finishing of the concrete, the curing methods, or the protection of the concrete after delivery to the purchaser This specification is solely intended for the production and manufacture of concrete These listed items are the responsi-bility of the purchaser or owner after the concrete has been discharged from the concrete delivery unit Other reference

specifications, such as ACI 301, Standard Specifications for Structural Concrete, address the subsequent operations that

are listed in S4 After the concrete leaves the discharge chute

or tailgate in an acceptable condition, the purchaser becomes responsible for all future phases of this product This does not negate the supplier’s responsibility for the concrete achieving the specified design strength at the specified age (unless the purchaser or designated agent directed an unspecified altera-tion of concrete mixture or its properties), but it does mean that the strength tests for approval or rejection shall be made

on samples taken from the delivery vehicle at discharge and not from another location Placement of the concrete, which

is excluded from this specification by this sentence, certainly includes movement by pumping When parties other than the supplier begin to alter or handle the concrete, they assume certain responsibilities for the finished product After the concrete leaves the discharge chute and goes into a concrete bucket, a power buggy, a concrete pump, or onto a conveyor belt, or is pulled and moved by a laborer; changes may occur

to the concrete over which the supplier has no control The effects of these operations on the quality of the concrete are not addressed within this specification Within the scope of the C94/C94M specification, this is a sentence that the pur-chaser cannot alter The purchaser cannot extend the manu-facturer’s responsibility to include testing at the pump discharge Testing can be wherever the purchaser desires, but the responsibility of the manufacturer stops at the discharge from the delivery vehicle

Scope 3

1.2 S1 The values stated in either SI units shown in brackets, or

inch-pound units are to be regarded separately as standard S2

The values stated in each system may not be exact equivalents;

therefore, each system shall be used independently of the

other S3 Combining values from the two systems may result in

non-conformance with the standard.

Throughout the specification for ready-mixed concrete,

units of measure are used, usually for mass (weight) or volume

In combined standards such as ASTM C94/C94M, the SI units

are enclosed in brackets [ ] S2 instructs that either set of units

may be used, but they are not to be intermixed For example,

slump should not be specified in mm and then measured in

inches If the International System of Units (SI) is used for one

item, all items should be expressed and measured in SI units

Intermixing the two measurement systems could result in non-

conformance as cautioned in S3.

1.3 S1 As used throughout this specification the manufacturer

produces ready-mixed concrete S2 The purchaser buys

ready-mixed concrete.

S1 states that anywhere the term “manufacturer” is used

within ASTM C94/C94M, it is referencing the ready-mixed

con-crete producer In the original tentative ready-mixed concon-crete

specification published in 1933 (ASTM C 94-33T), the term

“manufacturer” was used throughout to refer to the

ready-mixed concrete manufacturer The language of the standard

changed in the 1960s to include references to the actual

con-tractor, but has now reverted back to labeling the concrete

pro-ducer as the manufacturer The term “propro-ducer” is used to

include delivery and job-site items related to the delivery of

concrete The term “contractor” has been used only one time in

Section 17.1 This single reference to “contractor” is used when a

job-site item involves the general contractor as well as the

pro-ducer The referenced item involves access, assistance, and

sam-pling, all of which may take place at the job site This is a location

presumed to be under the primary authority of the general

contractor

The second sentence (S2) identifies the purchaser as the

person or entity buying the concrete and includes the general

contractor or a concrete subcontractor who orders concrete for

the owner In this capacity, as well as some others, these

con-tractors are the owner’s representatives The Architect/Engineer

(A/E) is also in the owner representative category, but the A/E

may not be directly involved in purchasing concrete or a party

to the purchase order

ASTM C94/C94M is written to the purchaser or general

contractor to allow the owner to identify who is ultimately

responsible for the entire concreting operation ASTM C94/C94M

is also written in an attempt to separate the responsibilities of

the concrete manufacturing process and product delivery from

the overall responsibilities of the general contractor or a

con-crete subcontractor This separation is needed for clarity in a

purchase order for concrete or a delivered materials contract whether written or oral

1.4 S1 The text of this standard references notes and footnotes

which provide explanatory material S2 These notes and

footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard.

The notes and footnotes provide information that is advisory

or explanatory They do not include mandatory requirements Language and statements in notes cannot imply or be implied to state a requirement of the specification These nonmandatory notes are identified in numeric order as “Note 6” or other appro-priate number in numerical order of appearance Footnotes com-monly identify sources of reference materials or jurisdiction within ASTM for both the standard and for its future alterations They direct the user of the standard to additional information related to the provision These references are not typically stan-dards written in mandatory language and are not included in Section 2, Referenced Documents

An important distinction must be made for notes panying tables or figures (no figures exist within ASTM C94/C94M) The notes with tables form a part of the table and are mandatory

accom-as are the requirements within the table These notes are shown

as “A,” “B,” or “C” in alphabetical order for each table Notes to tables within the standard use these uppercase letters to link the referenced note to the text within the table and may detail additional requirements or further clarify the requirement in the table

1.5 S1 This standard does not purport to address all the safety concerns, if any, associated with its use S2 It is the responsibility

of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use S3 (Warning–Fresh hydraulic

cementitious mixtures are caustic and may cause chemical burns to skin and tissue upon prolonged use 2 )

ASTM requires a safety caveat in the Scope section of

many of its documents S1 simply states that C94/C94M makes

no attempt to speak to any of the safety issues that may be encountered during the use of concrete or concrete handling equipment or other issues associated with concreting work

S2 places the burden of safety education and safe working

practices on the user of the standard ASTM is not and should not be involved in any manner with safety procedures or prac-tices When ASTM standards start including dos and dont’s on safety practices, there is no reasonable stopping point The user

is forewarned that health considerations and compliance with regulatory requirements are the responsibility of the user and not that of ASTM

S3 identifies that fresh concrete made with hydraulic

cementitious materials is caustic and therefore could cause burns to skin and tissue This does not violate the information

provided in the discussion of S2 because it is simply a warning

that the user should be aware that concrete can be harmful to

humans if precautions are not taken The responsibility to

determine what precautions are best for the particular

situa-tion, considering the user’s circumstances, continues to rest on

the user In fresh (unhardened) concrete, the hydration of

hydraulic cementitious materials with water results in an

alka-line solution, typically measured by its pH The pH of a solution

is a measure of its acidity or alkalinity Most people realize the

danger of contact with acids and that concentrated alkaline

solution within concrete poses a similar risk This is not a

con-cern after concrete sets and hardens Contact with fresh or

unhardened concrete can cause burning or irritation to skin

and tissue Abrasion with skin can exacerbate the situation

People working with fresh concrete should wear waterproof

gloves and boots and clothing that covers and protects the skin

Concrete on skin or any clothing should be washed off as quickly as possible Eyes should be flushed with clean water immediately after contact Some individuals are more sensitive

to contact with concrete and can experience severe burns and allergic reactions A specific time limit for contact cannot be stated If persistent or severe discomfort is experienced, imme-diate medical attention should be sought

References

[1] ACI Committee 318, “Building Code Requirements for Structural Concrete,” ACI 318-11, American Concrete Institute, Farmington Hill, MI, 2011, pp 57–63.

[2] ACI Committee 301, “Specifications for Structural Concrete,”

ACI 301–10, American Concrete Institute, Farmington Hills, MI,

2010, pp 21–25.

Chapter 2 | Referenced Documents

Every document referenced within ASTM C94/C94M is listed in

Table 2.A with a cross-reference to the section where the

refer-enced document appears in the specification ASTM referrefer-enced

documents do not carry a date because the reference is always to

the latest edition of each document The superscript number after

an ASTM standard refers to the footnote at the bottom of the

page providing the ASTM volume number in which the standard

appears

The term ASTM Standard refers collectively to all ASTM

documents included in the reference list Four types of

stan-dards are included within the ASTM C94/C94M reference list;

there are three Practices, eight Test Methods, thirteen Specifications,

and one Terminology standard All of the specifications

refer-enced within ASTM C94/C94M are requirements for specific

ingredient materials used in the manufacture of concrete

“Test Method” is a standard procedure that produces a

numerical result These standards describe a test procedure in

sufficient detail such that consistent results are produced when

the procedure is repeated following its instructions

Three of the referenced standards carry the title “Practice.”

Common industry vernacular often identifies a Practice as a

Test Method A Practice, like a Test Method, describes a tive standardized procedure or set of instructions for a specific operation The three Practices referenced in Table 2.A describe sampling freshly mixed concrete (C172/C172M); making and curing concrete test specimens in the field (C31/C31M); the duties, responsibilities, and minimum technical requirements

defini-of testing laboratory personnel; and the minimum technical requirements for their laboratory equipment (C1077) The major difference between a Practice and a Test Method is that a Test Method produces a numerical result while a Practice does not.Section 2.2 in Table 2.A provides a list of American Concrete Institute (ACI) documents referenced within ASTM C94/C94M A  footnote at the bottom of the page provides an address for obtaining copies of any desired ACI document

Section 2.3 in Table 2.A provides a list of other documents referenced within ASTM C94/C94M At this time the only doc-ument listed in this section is one published by the National Institute of Standards and Technology (NIST) A footnote at the bottom of the page provides the address for obtaining a copy of the referenced document

TABLE 2.A Referenced Document Index

TABLE 2.A  (continued)

C618 Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete 5.2.2

and Criteria for Testing Agency Evaluation

16.2, 17.2

2.2 ACI Documents 2

211.1 Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete Table 1, Footnote C,

Note 6, Note 7 211.2

2.2 Other Documents 3

1 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website.

2 Available from American Concrete Institute (ACI), P.O Box 9094 , Farmington Hills, MI 48333-9094, http://www.concrete.org.

3 NIST Handbook 105-1 (revised 1990), “Specifications and Tolerances for Reference Standards and Field Standard Weights and Measures-1 Specifications and Tolerances for Field Standard Weights (NIST Class F),” National Institute of Standards and Technology, U.S Department of Commerce, http://www.nist.gov/pml/ wmd/upload/105-1.pdf.

ASTM C125 Standard Terminology Relating to Concrete

and Concrete Aggregates contains definitions that are

com-mon to all standards under the jurisdiction of ASTM

Committee C09 and is the direct responsibility of

Subcommittee C09.91 on Terminology Definitions contained

in C125 have the same meaning in all C09 standards unless

otherwise stated within a C09 standard

3.2 Definitions of Terms Specific to This Standard:

3.2.1 concrete, central-mixed, n—ready-mixed concrete mixed

completely in a stationary mixer

Section 3.2.1 defines a specific manufacturing process of

ready-mixed concrete, which is defined in 3.2.2 In the

central-mixed manufacturing process, the ingredients of concrete are

measured and batched into a stationary or plant mixer and

completely mixed into a homogenous concrete mixture The

mixed concrete is then discharged into a delivery vehicle and

transported to the job site or location of placement

Central-mixed concrete can be delivered in truck mixers, agitators, or

nonagitating vehicles (dump trucks) Further adjustments to

the mixture are only possible if the concrete is discharged into a

truck mixer Central-mixed concrete is manufactured in fixed

plants located remotely from the placement site or from

porta-ble plants that are set up at or close to the point of placement

Portable plants are generally temporarily set up for pavement or

other building projects requiring large volumes of concrete

Central-mixed concrete accounts for approximately 20 % of the

ready-mixed concrete manufactured in the United States,

pri-marily in larger metropolitan areas and is the primary

manu-facturing method in countries other than the United States In

general, central-mixed concrete facilitates greater speed of

pro-duction and reduces the rate of wear of mixers on delivery

vehi-cles Central-mixed concrete is used for manufacture of all

precast concrete products For complete mixing in a stationary mixer, central-mixed concrete should be mixed for a minimum time and this is generally controlled by a timing device that prevents discharge of the load before the established mixing time has elapsed

3.2.2 concrete, ready-mixed, n—concrete manufactured and

delivered to a purchaser in a fresh state

The qualifier in this definition is the adjective mixed.” Concrete is defined in C125 as a composite material that consists essentially of a binding medium within which are embedded particles or fragments of aggregate; in hydraulic- cement concrete, the binder is formed from a mixture of hydraulic cement and water The term ready-mix is an adjective defined

“ready-by Webster’s New World College Dictionary, Fourth Edition

(2009) as “ready to be used just as it is or after the addition of liquid/ready-mix concrete.” In the first version of ASTM Standard C94 published in 1935, the term Ready Mixed Concrete

is used to describe mixed concrete delivered to the work ready for use This definition was necessary to distinguish ready-mixed concrete from concrete mixed at a job site, which was the common process used prior to the 1920s The revolving drum mixers mounted on trucks were developed in the late 1920s and started the evolution of the ready-mixed concrete industry The common usage of the term “ready-mixed concrete” did not become prevalent until after World War II in the early 1950s More recently, this term distinguishes ready-mixed concrete from precast concrete, where concrete products are manufactured at a plant location and transported for erection at

a structure

3.2.3 concrete, shrink-mixed, n—ready-mixed concrete

par-tially mixed in a stationary mixer with mixing completed in a truck mixer

The term “shrink-mixed concrete” is not commonly used and subsequently is not always understood, even by some peo-ple in the concrete industry Shrink-mixed concrete is a varia-tion of central-mixed concrete in which the mixing time in the

stationary mixer is shorter than the time required to achieve a

homogenous mixture The term “shrink” refers to a reduction

of the total bulk volume of the raw ingredients into a smaller

volume of a partially mixed concrete batch The concrete is only

partially mixed to allow for a faster production rate and the

mixing of the batch to produce a homogenous concrete mixture

is completed in the truck mixer For shrink mixing the mixing

time is reduced to about ½ min, which allows for faster

move-ment of truck mixers through the plant and facilitates a faster

rate of delivery A quicker production time is advantageous

when a project demands tighter turnaround or the concrete

producer needs to increase production Shrink-mixed concrete

must be transferred to a truck mixer and cannot be discharged

into agitators or non agitating vehicles Shrink mixing is also

often employed with a smaller capacity plant mixer that will

require two loads of con crete to be batched, partially mixed,

and discharged into one truck mixer

3.2.4 concrete, truck-mixed, n—ready-mixed concrete

com-pletely mixed in a truck mixer

This definition applies to all ready-mixed concrete that is

manufactured by mixing in a truck mixer This is the other

process of manufacture where a stationary or plant mixer is not

used Other terms used include dry-batch and transit-mixed In

both central-mixed and shrink-mixed concrete, at least a portion

of the mixing occurs in a stationary or plant mixer prior to

dis-charge into a delivery vehicle For truck-mixed concrete the raw

ingredients that com pose the concrete mixture are measured

individually then charged into a truck-mounted mixing drum

The mixing begins while the materials are being charged into

the revolving drum The drum’s mixing speed varies somewhat

with each drum manufacturer, but is normally in a range of 16 to

24 revolutions per minute (rpm)

The amount of mixing required for truck-mixed concrete

is prescribed in Section 12.5 as 70 to 100 revolutions at mixing

speed A homogeneous concrete mixture should be achieved

within 100 revolutions at mixing speed In the United States,

most ready-mixed concrete plants historically were set up to

produce truck-mixed concrete As indicated earlier, currently

about 80 % of the ready-mixed concrete produced in the United

States is truck-mixed concrete The high-speed revolutions at

mixing speed normally take place in the batch plant loading

position and in the yard, before the vehicles enter the adjacent

roadway When traveling to the job site and when waiting to

discharge, the concrete mixture is maintained in a

homoge-nous condition by rotating the mixer at an agitating speed that

varies between 2 to 4 rpm Often a final mixing cycle at mixing

speed is performed just before concrete is discharged at the

job site

A variation on truck-mixed concrete uses an add-on piece

of equipment called a “slurry mixer.” In a slurry mixer, the

cementitious materials, water, and some of the admixtures are measured and mixed into a slurry then charged into the truck mixer with the aggregates This is still considered truck-mixed concrete

Although concrete is batched and delivered in a wide range

of weather conditions, no definitions are needed for cold weather or hot weather within concrete plants ASTM C94/C94M

does not use the terms Cold Region, Moderate or Warm Region,

or Hot Region in describing plants These terms are not used in

C94/C94M because this specification does not delve into specific plant requirements for temperature control of ingredient materials or of concrete Section 12.8 is the only part of the specification that addresses temperature requirements for con-crete, and it makes no specific demands on a plant for temper-ature controls of concrete Nonetheless it may be helpful to users to understand the primary differences to be expected between these three categories (i.e., cold, moderate or warm, and hot) of plants

The need for enclosing cold region plants or even moderate weather region plants depends upon the manufacturer’s loca-tion and customer base location In some very cold regions public construction ceases in winter Many contractors in cold regions do not possess the equipment or experience to place concrete in extreme weather Without a demand, no need for the extra cost of equipping a plant to furnish cold weather con-crete exists In rural areas in cold weather states it is not uncom-mon for ready-mixed concrete plants to shut down for the entire winter See Figs 3.A, 3.B, 3.C, and 3.D for examples of ready-mixed concrete plants in different weather regions

TABLE 3.A  Batch Plant Refinements Available to Accommodate Weather Regions

Entire plant is enclosed

Hot water available for concrete Yes Yes (Usually) Yes (Occasionally) Chilled water or ice

availability Yes (Occasionally) Yes (Usually) YesAccelerating admixture

available

Retarding admixture available

Admixture tank freezing protection

Terminology 9

FIG 3.A  Open features of a concrete plant in hot weather region.

FIG 3.B  Aerial view of concrete plant in hot weather region.

FIG 3.C  Partially enclosed plant in a cold weather region.

FIG 3.D  Enclosed plant in a cold weather region.

Chapter 4 | Basis of Purchase

4.1 S1 The basis of purchase shall be a cubic yard or cubic metre

of fresh concrete as discharged from the transportation unit.

Only one basis of purchasing concrete is recognized by this

specification, and that is in units of volume by cubic yards or

cubic metres The idea of purchasing concrete by the job or by

calculated plan volumes or by total weights is not considered a

feasible approach If the contractor could pay a lump sum for all

of the concrete in a job without measurements of plan

dimen-sions, the overruns, and variations in levelness and grading of

the subgrade, job wastes could be enormous One example of

how job wastes might occur is when slabs designated as 4 in

thick on the plans become 5 to 6 in thick in actuality; that can

increase the required volume by 30 % or more If concrete is

sold on the basis of weight, rather than by volume, the effects of

varying air content, aggregate density, or the batching

varia-tions of ingredient materials could produce an accuracy

prob-lem as well as represent a bookkeeping nightmare

The purchase of concrete by volume is a time tested and

reasonable approach that does not penalize anyone The volume

approach makes it relatively simple for the purchaser to

com-municate orders as needed and minimizes the potential for

batching or bookkeeping problems Some situations or

prod-ucts, including pervious concrete and roller-compacted

con-crete, may require resorting to other bases of sale, such as by

weight Because of the effects of field consolidation for these

applications, estimating the required volume of concrete can be

difficult C94/C94M does not address these situations

“Freshly mixed,” as discharged from the mixer, is a

straightforward set of circumstances describing when and

how the volume furnished is to be measured Trying to

mea-sure the volume of hardened concrete placed is difficult A

slab-on-grade would look like Swiss cheese with all the core

holes needed to verify compliance with a required average

thickness Thus, the unhardened state is the best condition for

volume measurements Water and air make up a portion of

the concrete volume With air-entrained concrete, the volume

of water and air is about 25 % of the total volume Water is

chemically consumed by the hydration reaction, and the

excess water evaporates from the concrete Additionally, air

content tends to decrease with manipulation and tion of the product The volume of hardened concrete can be 2

consolida-to 4 % less than that of the fresh concrete as placed The freshly mixed and newly discharged concrete provides the only accu-rate measurement of volume as mixed and as delivered Thus, one cubic yard (27 ft3) or one cubic metre of fresh concrete is the specified unit volumetric measure for the purchase of con-crete The purchaser expects 27 ft3 to be discharged for each cubic yard for which he is charged

There are several reasons for discrepancies in yield [1] Batching tolerances can produce minor discrepancies on indi-vidual loads Air contents could be low, producing a slight shortage Failure to make mixture adjustments due to seasonal variations can be another reason for yield variations For instance a mixture designed for summer use may require 3 to

4 gal less water to achieve the same slump as the same mixture batched in winter [2,3].1,2 This will reduce the volume by 0.40

to 0.50 ft3/yd3 A mixture proportioned for 27.2 ft3 per design cubic yard in the summer can be easily reduced to 26.8 ft3 per design cubic yard during the winter season when batched to achieve the same slump A common occurrence in the sum-mer is for entrained air contents to be lower A drop of 1.5 % due to a higher ambient or concrete temperature also reduces the yield by 0.40 ft3/yd3

4.2 S1 The volume of fresh concrete in a given batch shall be determined from the total mass of the batch divided by the density

of the concrete S2 The total mass of the batch shall be determined

as the net mass of the concrete in the batch as delivered, including the total mixing water as defined in 9.3 S3 The density shall

be determined in accordance with Test Method C138/C138M

1 The 3 to 4 gal [25–33 lb] cited in the example represents a temperature change of 40 to 50°F when using Fig 118 in the Bureau of Reclamation’s

Concrete Manual [2] Gaynor, Meininger, and Khan [3] provide smaller changes in water contents, but their material only deals in 30°F temperature differences Slump losses depend on several factors, including

temperature, mixture proportions, aggregate gradations, and delivery times The latter effect is displayed in Gaynor, Meininger, and Khan [3].

2 Research and technical papers currently express concrete batch water in lb/yd 3 Because a high percentage of concrete batch plants continue to measure batch water in gal/yd 3 , the latter measuring unit is deemed appropriate for this publication The conversion factor is: 1 gal of water = 8.33 lb.

S4 The yield shall be determined as the average of at least three

measurements, one from each of three different transportation

units sampled in accordance with Practice C172/C172M

The term mass is preferred to the more commonly used

term weight Mass is a measure of how much material or matter

is contained in an object Weight is a measure of force resulting

from the effect of gravity on the mass of an object Mass of a

material does not change with altitude and the associated

change in gravitational force The mass of an object remains

constant This is the reason that we use the term “mass” rather

than “weight.” Within the context of the practical use of ASTM

C94/C94M, the user may substitute the concept of weight

any-time the term mass is encountered Scales are calibrated to

measure objects of certified mass and account for the different

gravitational pull at the location of use

Sentence one (S1) provides the basic method of checking

the concrete yield or volume of concrete discharged from a load

Mathematically this can be stated as follows:

Yield Total mass (weight) of the batch

Density of concret

=

eeThe term in the denominator is the mass per unit volume

and also referred to as unit weight

EXAMPLE 4.A Yield calculation.

If the total mass of ingredients batched in a truck mixer is

32,000 lb, and the density of a sample of concrete from the truck

mixer is determined to be 146.0 lb/ft3, the yield of the batch is

The total mass (weight) of a batch may be determined by

either of two methods S2 broadly describes these two methods

The usual option is to begin with the sum of the masses (weight)

of all materials in the batch, including water from all sources as

described in Section 9.3, including water introduced in the form

of admixtures plus additions such as fibers An alternate that is

seldom used is to determine the mass (weight) of concrete as

delivered This option requires weighing the concrete and truck

before delivery then weighing the empty truck after delivery

The difference is the net mass of the concrete as delivered This

option is very difficult in practice because it involves accounting

for factors that change the weight of the truck, such as fuel used

and water used for washing This rather complicated method

should be reserved for situations when it is suspected that the

batch plant scales are not indicating accurate weights

The primary method of checking the concrete yield is by measuring the total mass (weight) of all the materials in the batch This is determined from a computer printout for the batch plus water injected at the job site In the absence of com-puterized batch recording systems at the plant, an accurate manually written record of the batched quantities is required

S3 and S4 provide specific instructions on the only

accept-able method of determining the density (unit weight) of the concrete The specific steps are as follows:

1 Obtain samples in accordance with ASTM Practice C172/C172M In accordance with this practice, the sample should be obtained from the middle portion of the load

2 Use ASTM Test Method C138/C138M to determine the sity The size of the container depends on the nominal max-imum aggregate size in the concrete Use a container of not less than 0.20 ft3 [6 L] to measure the density The container should conform to requirements of C29/C29M or C231/C231M, and its volume has to be accurately determined in accor-dance with C29/C29M See Fig 4.A

den-3 Repeat the density measurement from each of three or more loads

4 Calculate the yield of each load using the mass of concrete and the measured density

5 Average the yield determined from three or more loads

A numerical example of the prescribed procedure with notes is illustrated in Example 4.B.

In Step 1, ASTM C172/C172M dictates collecting the samples from two or more portions of the discharge at regularly spaced intervals from the middle part of the batch The portions of the samples should be collected within 15 min of one another The final sample should be combined into a well-mixed composite sample The density (unit weight) test should be commenced

Fig 4.A  Measuring the density of concrete (0.25 ft 3 container with concrete struck with plate; 0.50 ft 3 container also shown), ASTM C138/C138M.

Basis of Purchase 13

within 5 min after obtaining the final portion of the composite

sample Some would debate the need for the 5-min limit for the

commencement of the density test, but a portion of what is being

checked is the air content, which is the specific purpose for this

time limit

Step 2 applies to the specifics of the test method, C138/

C138M The minimum volume of the container should be 0.20 ft3

[6 L] Read the referenced standards carefully for details of

pro-cedures The density is to be determined to the nearest 0.1 lb/ft3

Previous versions of C94/C94M required a minimum 0.5 ft3

con-tainer for potential improved accuracy, but these are seldom

used by technicians at job sites, and this requirement was

changed to stipulate that the container be a minimum size

based on the nominal maximum size of coarse aggregate in the

concrete For most concrete mixtures made with a nominal

maximum size aggregate of 1 in or less, the base of the pressure

meter test (C231/C231M) will comply with this requirement A

common deficiency is the lack of calibration of the measure for

the accurate determination of its volume in accordance with

ASTM C29/C29M The most common error in performing the

density determination when using a Type B air meter is to omit the use of the plate required by C138/C138M Without the use of the plate, the chance of obtaining an erroneous density value increases These deficiencies are magnified when the measured density is used to estimate the yield by at least two orders of magnitude of the error

Steps 3, 4, and 5 are self-explanatory and simple to follow, yet they can have a significant impact on final yield determina-tion To obtain the yield, information from each of three or more batches is required As per this section, the average yield is then calculated from these determinations on separate batches This is illustrated in Example 4.B

The relative yield is the ratio of the actual yield to the yield the mix was designed to achieve This is a segment of the calcu-lations outlined in C138/C138M Average relative yield of the three loads of Example 4.C is 1.010 Any number equal to or greater than 1.0 indicates a satisfactory yield for the purchaser Another yield calculation example along with descriptions of the process

appears in NRMCA Publication Number 159, Fourth Edition [4].ASTM C94/C94M does not indicate any limits for acceptable relative yields or tolerances on the yield as ordered Section 4.1 does say the basis of purchase shall be on the volume as dis-charged Considering the allowable tolerance for batching and the accuracy in measuring the density of concrete, a reasonable expectation is for the actual yield to be within 1 % of the design yield Compensation for this type of potential error is handled in the mixture design process by some manufacturers [5]

Very often when density tests of fresh concrete are sured and yield is checked, there is a dispute concerning yield When this is the case, an expeditious procedure to resolve this

mea-is for both the manufacturer and purchaser to have qualified technicians representing each party working in tandem and independently measuring the density on the separate samples from same loads or measuring the density from the same sam-ple from each load This is illustrated in Example 4.C This example also outlines the detailed calculations of the density measurement

Fig 4.B  Yield is determined as the average from three loads.

Sample 3 truck mixers Run unit weight on each sample

EXAMPLE 4.B Yield and relative yield calculations.

A The free moisture content associated with the batched wet aggregates make up part of the mixing water.

B Lines 6 and 7 are measured in gallons and changed to pounds by multiplying gallons by 8.33lb/gal.

C Line 8 is the total sum of lines 2–7.

D Line 9 is taken from Example 4.C on page 14.

Note 1—It should be understood that the volume of hardened

concrete may be, or appear to be, less than expected due to waste

and spillage, over-excavation, spreading forms, some loss of

entrained air, or settlement of wet mixtures, none of which are the

responsibility of the producer.

This note is advisory to the manufacturer (producer) and the

purchaser on some of the items that can result in a discrepancy

of yield as ordered It informs the purchaser that when

con-crete hardens, its volume will be less than its volume in a wet

state As mentioned, this is due to the loss of water because of

hydration with cement and evaporation of excess water This

change in volume will be approximately 2 % [2] Part of the

total group of losses includes a mortar coating inside the mixer

drum, primarily on the fins This mortar coating may amount

to 400 to 600 lb (less than a wheelbarrow) and usually only

affects the first load of the day [6] Over-excavation or a low

subgrade excavation needs no explanation, but a relatively

small variation in the depth of a slab on grade will amount to

a substantial difference in actual versus calculated volume of

concrete Spreading and bowing forms cause numerous

com-plaints The lateral pressure from fresh concrete can be 2000 lb/ft2

in a wall and over 3000 lb/ft2 in a column [7,8] Pressures of

these magnitudes will certainly stretch form ties and cause

bows in forming materials and increase the quantity of

con-crete needed to fill the forms On structural slabs the areas

between supports will deflect under the mass (weight) of the

fresh concrete and require a quantity greater than plan

mea-surements to produce a level floor The loss of entrained air by

handling, such as through a pump, will reduce the concrete

volume equivalent to the loss of the volume of air Pump line coatings also account for lost concrete With wet mixtures there will be settlement as the excess water collects on the sur-face and evaporates or in trench or subgrade conditions as the concrete’s excess water is absorbed by the earth Some amount

of waste and spillage when delivering and placing concrete will occur, and concrete will be lost to multiple wheelbarrow loads by technicians sampling and testing concrete

There are many scenarios that require ordering more crete than plan quantities indicate necessary Knowledgeable contractors allow for these contingencies by ordering about 3 to

con-5 % excess concrete above that calculated from form or section dimension [9] For slabs on grade, unformed footings, or irregular shaped trenches, losses easily may be in the range of 5

to 12 % or more [10] One estimating guide places waste (lost) concrete at 5 to 10 % [11] An important aspect to ensuring the correct amount of concrete is to reevaluate the quantity needed

as the end of placing a section or the end of the day approaches and communicate any correction to the concrete plant The goal

should be to avoid ordering a clean-up load of less than 3 yd3 to complete a pour and to also avoid returning an excessive quan-tity of concrete to the batch plant

Can a container 3 by 3 by 3 ft be constructed and one cubic

yard of concrete ordered to check the producer’s yield? The answer is no According to ASTM C94/C94M, this is not an acceptable method of checking the furnished yield of ready-mixed concrete Water losses may occur due to absorption by the box material; bowing of form materials will certainly occur; grout may escape the corner seams; entrained air may be lost; and the mortar coating on drum fins will be disproportionally

EXAMPLE 4.C Concrete density (unit weight) test.

A PT = Purchaser’s Technician; RMT = Ready-Mixed Concrete Producer’s Technician.

B The third set (load 5) is omitted from the calculations because the difference exceeds the acceptable range for two properly conducted tests on the same sample in the precision statement of ASTM C138/C138M The allowable difference by two technicians is 2.31 lb/ft 3

Basis of Purchase 15

excessive as compared to a full load, particularly for loads other

than the first load of the day Constructing such a container and

using it to measure one cubic yard of concrete is, however, used

to check the yield of concrete produced by volumetric batching

and continuous mixing under ASTM C685/C685M Determining

the yield in accordance with ASTM C138/C138M and checking a

minimum of three loads for density (unit weight) with the mass

per batch works and is the best method of resolving questions

or establishing the true yield of a mixture

References

[1] National Ready Mixed Concrete Association (NRMCA),

“Discrepancies in Yield,” CIP 8 Concrete in Practice, National

Ready Mixed Concrete Association, Silver Spring, MD, 2000, 2 pp.

[2] Bureau of Reclamation, Concrete Manual, 8th ed Rev., U.S

Department of the Interior, Bureau of Reclamation, Denver,

CO, 1981, pp 256–553.

[3] Gaynor, R D., Meininger, R C., and Khan, T S., “Effect of

Temperature and Delivery Time on Concrete Proportions,”

Temperature Effects on Concrete, ASTM STP 858, T R Naik, Ed.,

ASTM International, West Conshohocken, PA, 1985, pp 68–87.

[4] National Ready Mixed Concrete Association (NRMCA),

“Concrete Plant Operators Manual,” Publication No 159,

4th ed., National Ready Mixed Concrete Association, Silver Spring, MD, 1999 (Reprint 2005 with minor editorial changes), pp 8–9.

[5] Malisch, Ward R and Suprenant, Bruce A., “No Minus Tolerance on Yield,” The Concrete Producer, May 1998, Hanley Wood, LLC, Chicago, Illinois, 1998, 2 pp.

[6] Lobo, C L and Gaynor, Richard D., “Ready Mixed Concrete,”

Significance of Tests and Properties of Concrete and Making Materials, ASTM STP 169D, J F Lamond and

Concrete-J H Pielert, Eds., ASTM International, West Conshohocken,

PA, 2006, p 534.

[7] Hurd, M K., Formwork for Concrete, ACI Committee 347, Special Publication No 4, 6th ed., American Concrete Institute, Farmington Hills, MI, 1995, pp 5-11–5-13.

[8] McCormac, J C., Design of Reinforced Concrete, Harper &

Row, Publishers, Inc., New York, 1978, pp 450–453.

[9] Richardson Engineering Services, Inc., General Construction Estimating Standards, Vol 1, 1982–1983 ed., San Marcos, CA,

Chapter 5 | Materials

5.1 In the absence of designated applicable materials

specifications, the following materials specifications shall be

used:

This sentence informs the specifier and purchaser to be

explicit when stating requirements for the quality of raw

materi-als, the use of specific materimateri-als, the use of a particular brand of

product, or a combination of the three Without any such

special or specific requirements or a complete list of material

requirements, the ready-mixed concrete manufacturer is

obli-gated to meet the default requirements as listed in Section 5

Note that it is not the manufacturer’s obligation to determine

the appropriate types of materials based upon a set of project

criteria It is the responsibility of the purchaser or the

desig-nated agent to determine specific material criteria and to

iden-tify these specific criteria to the manufacturer (producer) in

advance of pricing and ordering Defaults are provided for

some, but not all, materials The purchaser may need to provide

specific information for some of the applicable materials listed

for the project

The purchaser or specifier should be careful in planning

for or ordering a material not in regular use by the producer

or in the geographic area For example, specifying special

cement not in regular use may require special dedication of a

silo and very possibly extra transportation charges to bring

the cement from a mill much farther away than the one whose

products are in regular use in the area White cement fits this

category of material Decorative aggregate for use in

architec-tural work from a special source may entail significant

addi-tional freight charges The use of a particular chemical

admixture brand may be prohibitive if that chemical

admix-ture company is not active in the geographic market of the

project The use of a specific class of fly ash or grade of slag

cement may be prohibitive in a region where it is not

gener-ally available due to transportation costs and the need for a

dedicated silo The use of any special cementitious material

may be subject to the availability of a silo that can be

dedi-cated to that product When a large volume of concrete is

involved, the additional cost or equipment required for a

specialty material may be justified

Concrete is normally produced using materials available in the geographic area of the manufacturer, and requests or speci-fications for major variations from these materials typically result in a higher price and, for a small project, may result in the purchaser not being successful in finding a willing manufac-turer Another important consideration is the impact on quality

of concrete if the manufacturer does not have experience using

a material because it’s not typically used in that manufacturer’s familiar local market Fig 5.A shows one cubic yard of concrete

5.2 Cementitious Materials 5.2.1 Hydraulic Cement—S1 Hydraulic cement shall conform

to Specification C150/C150M , Specification C595/C595M , or Specification C1157/C1157M

Cements acceptable under ASTM C94/C94M are quite varied, and although only three specifications are listed, each specification includes six or more specific types of cement ASTM Specification C9 [1,2] was the original cement specification In 1940, the Standard Specification for Portland Cement was issued under the new designation, ASTM C150 This specification, like all ASTM Standards, is now con-stantly reviewed and updated to keep pace with new technol-ogy and evolving needs

The name “portland cement” originated in 1824 with John Aspdin, an English bricklayer, when he used it as a trade name for his new cement produced in England He patented his new product, composed of limestone powder and argil-laceous soil (clay), which included calcining (heated to a high temperature, but without fusion) [3] Mr Aspdin named

his product Portland Cement because its color was so similar

to an oolitic limestone quarried as a building stone on the Isle of Portland, England The Portland limestone (whitbed ledge) was a durable stone with excellent weathering quali-ties that placed it in high demand for use in government buildings [4] The name portland cement stuck, even though the manufacturing process was modified by I C Johnson of Swanscombe, England in 1845 Mr Johnson determined that

heating to a much higher temperature resulted in semi-

vitrification (partially liquefied) [5,6] The material was then

pulverized, and cement very similar to this material was

produced in millions of tons per year for over the next

150 years

Definitions as they currently appear in ASTM Terminology

Relating to Hydraulic Cement (C219) are:

Portland cement, n—a hydraulic cement produced by

pul-verizing clinker, consisting essentially of crystalline

hydrau-lic calcium sihydrau-licates, and usually containing one or more of

the following: water, calcium sulfate, up to 5 % limestone,

and processing additions

Portland-cement clinker, n—a clinker, partially fused by

pyroprocessing, consisting predominately of crystalline

hydraulic calcium silicates

Portland cement is called a hydraulic cement because in

the presence of water, a chemical reaction called hydration

occurs resulting in setting and hardening This hydration

reac-tion occurs even when the material is submerged in water

Other cementing materials such as asphalt cement or plaster

are not hydraulic cements ASTM C219 provides the remaining

principles for the definition in terms of clinker and the

pow-dered product, cement, resulting from the pulverized clinker

The clinker, usually less than 2 in in diameter, is formed when

a closely controlled raw feed is heated to a temperature in the

range of 2550–2900°F in the cement kiln This heating process

causes the various raw materials to undergo conversion to the

cement compounds, predominately calcium silicates The

tri-calcium silicate (C3S) and the dicalcium silicate (C2S) compounds

make up more than 70 % of the product we call portland

cement The third part of the ASTM definition states that the

portland cement usually contains calcium sulfate (CaSO4),

typically in the form of gypsum (used to control the time of set),

and is now permitted to contain up to 5 % finely ground

lime-stone in addition to inorganic or organic processing additions

The basic portland cement (hydraulic cement) product being described contains four major constituents The two larg-est components are identified as C3S and C2S These chemical notations are industry-accepted abbreviations for lengthy chemical formulas The major constituent C3S reacts rapidly and contributes to early-age strength development The hydration of

C3S generates heat and increases the temperature of concrete The C2S phase contributes to strength development at later ages (over 28 days), and the hydration of C2S produces lower overall heat of hydration A third major component in the cement is tricalcium aluminate (C3A) The C3A is responsible for starting the initial hydration process and contributes to the early-age heat and strength at one to three days [7] Even though C3A aids the early strength, its content is often minimized due to unfa-vorable reactions with soluble sulfates contained in soil or water that come in contact with concrete A typical quantity of C3A is approximately 10 %; while in a sulfate resistant cement, the C3A

is held to a maximum of 8 % C3A is very reactive and utes to heat of hydration; reducing the percentage content of

contrib-C3A will lower the heat of hydration The last of the four major constituents, by percentage, is tetracalcium aluminoferrite (C4AF) This compound has little effect on cement performance The presence of this compound gives portland cement its gray color The iron oxide in the raw feed also serves as a flux to permit lower operating kiln temperatures during the manufac-ture of cement, thereby saving energy

The raw materials used in the manufacture of cement are

in the two basic categories of calcareous and argillaceous materials The compounds previously described are formed primarily by combining calcium oxide (CaO), silica (SiO2), alu-mina (Al2O3), and iron oxide (Fe2O3), which come primarily from limestone (the CaO); clay or shale as a common source of silica (SiO2); clay, shale, or fly ash as a source of alumina (Al2O3); and iron ore, clay, or mill scale as the iron oxide (Fe2O3) source.Limestone is the primary source of calcium oxide (CaO) for the manufacture of cement The other common raw materi-als include clay, shale, and fly ash Every clay-like deposit is not suitable for commercial cement due to mineral impurities, the presence of other soil types, or even because of excessive exca-vation and transportation costs All clay minerals, however, do contain silica and alumina, two of the minerals needed to man-ufacture cement Kaolinite, which is the most prevalent clay mineral, is often used, but other forms of clay, such as illite, are usually desired [8] because of a higher silica-alumina ratio [9]

A potentially detrimental characteristic of illite is the presence

of potassium, which contributes to the alkali content of the ished cement It is not unusual for clay to contain iron oxide (Fe2O3) The quantity of iron oxide often is approximately one half that of alumina [10]

fin-During the clinker grinding process gypsum, or another form of calcium sulfate (CaSO4), is added to control the early reactions of C3A and thereby delay and control set times of the finished cement There are other raw materials that are used in the manufacture of cement, but the same basic chemical

FIG 5.A  Typical composition of 1 cubic yard of concrete.

WeightVolume

Water Sand

Coarse Aggregate

Materials 19

compounds must be formed A comprehensive list of potential

raw materials is contained in PCA’s Design and Control of

Concrete Mixtures [6]

The raw materials will contain other constituents in

addi-tion to the primary oxides These minor components make up

approximately 5 % of the final product Some can be quite

important, such as the alkali oxides (sodium oxide (Na2O) and

potassium oxide (K2O)), which usually total less than 1.3 % [11]

The difference between 1.3 % and 0.60 % could seem

insignifi-cant, but with the alkali oxides it is not The 0.60 % alkali oxide,

expressed as sodium oxide equivalent (Na2Oe) in cement, is an

arbitrarily assigned limiting value between high and

low-alkali cements based on historical performance of cement

ASTM C150/C150M uses the term Equivalent Alkalies (%) to

provide the desired equivalent total alkali values on a mill test

report This is often expressed as Na2O eq and is equal to (Na2O +

0.658 K2O)

A high-alkali cement combined with an alkali-reactive

aggregate in concrete may create long-term durability

prob-lems Aggregate containing certain forms of silica will react

with alkalies to form products that cause expansive forces

These forces may be severe enough to cause cracking in the

con-crete ASTM C33/C33M states that these reactive aggregates are

not prohibited when used with cement containing less than

0.60 % alkalies calculated as sodium oxide equivalent (Na2O +

0.685 K2O) There have been cases of alkali reactive expansions

occurring even when the cement contained less than 0.60 %

equivalent alkalies [12] Some specifications place limits on the

total alkalies in the concrete mixture rather than placing limits

on the cement alkali percentage These specifications generally

limit total alkali content to 5 lb/yd3 [3 kg/m3] [13,14,15] The

American Association of State Highway and Transportation

Officials (AASHTO) has published a provisional practice

addressing alkali aggregate reactions and in that publication

make recommendations for mitigating alkali-silica reaction

(ASR) in structures [16] Their guidance establishes different

levels of protection based upon the type of structure and the

degree of aggregate reactivity The option for limiting the

max-imum alkali content in concrete varies from 5 lb/yd3 down to

3 lb/yd3 Oberholster, van Aardt, and Brandt [17] do not suggest

a specific alkali limit but do point out that the total alkali

con-tent in concrete is determined by the total cement concon-tent Their

research demonstrated that the same total equivalent alkali

content of two cements did not necessarily produce the same

quantities of water-soluble and active-alkali contents Further

discussions of the raw materials or processes of cement

manu-facture are beyond the scope of this discussion of ASTM

C94/C94M There are numerous good publications on the

subject available through the various societies involved

with the manufacture or regulation of cement properties [18,19]

The selection of a cement depends on several factors, some

of which are discussed in ACI 225R-99 (09) Guide to the

Selection and Use of Hydraulic Cements [7] The type of project

may dictate a desired type of cement due to specific

characteristics The availability of that desired cement may become the deciding factor Availability cannot be over empha-sized as a selection factor The manufacturer’s ability to dedicate

a silo to the special cement will also be a consideration Each of these factors should be considered in selecting and specifying cement The selection process for acceptable cement types applicable for the concrete and its service conditions is the responsibility of the purchaser If a type of cementitious material

is not specified, the manufacturer (producer) may use any cement available that will produce concrete of the specified properties

ASTM Specification for Portland Cement (C150/C150M) is a combination prescriptive and performance specification ASTM C150/C150M contains prescriptive requirements on the chemical composition for each of ten types of cement included ASTM C150/C150M also includes some performance require-ments such as cube strengths and time of set Each of these cements is classified as a portland cement as indicated by the specification title

• Type I—General purpose cement is the predominant

prod-uct manufactured in most cement plants It is the cement commonly used for interior slabs on the ground, interior structural slabs for low to moderate height multi-story buildings, pavements, sidewalks, curbs, box culverts, water reservoirs, bridges, building foundations, and precast con-crete products It can be used in any application where its normal heat of hydration is not a problem and where the concrete is subject to negligible sulfate quantities in the soil

or water

• Type II—Moderate sulfate resistance is for general use,

especially when moderate sulfate resistance is desired Type

II has an 8 % maximum limit on the tricalcium aluminate (C3A) content and a mean value of 6 % according to ACI 225R [7] Type II cement may be used in concrete for struc-tures adjacent to soil or water that tests in the moderate sulfate exposure range based on Bureau of Reclamation evaluation [20,21] and ACI 318-11 Building Code Requirements for Structural Concrete [22] Type II1 may be used as the cement when concrete is adjacent to seawater The rate of strength gain of Type II cement may be some-what slower than Type I

• Type I/II—General construction cement is not a separate

type of product as defined in ASTM C150/C150M It is a Type II cement that for marketing purposes is often desig-nated as Type I/II because it also meets the requirements for Type I and can be used as such (See Note 1 of ASTM C150/C150M)

1 A Type I cement alone is not recommended in these circumstances

Either a Type II cement or a Type I cement combined with a pozzolan that has been determined to improve sulfate resistance or a blended cement identified for this use should be utilized.

This designation for portland cement sees common usage in

many areas

• Type II (MH)—Moderate heat of hydration and moderate

sulfate resistance cement is used in general construction,

especially when moderate heat of hydration and moderate

sulfate resistance is desired In addition to the maximum

limit of 8 % on the C3A content that ensures moderate sulfate

resistance, this cement type has a maximum limit of 100

on the sum (C3S + 4.75C3A) As indicated earlier these

cement compounds contribute the most to heat of hydration

The lower heat of hydration is often desired for large

founda-tions, piers, abutments, heavy retaining walls, or other mass

concrete members for which it is desirable to reduce a

tem-perature gradient between the surface and the interior mass

where heat builds up Other modifications to concrete

mixtures, such as the use of supplementary cementitious

materials, are also used to reduce heat of hydration in mass

concrete structures

• Type III—High early strength cement is intended for use

when high strengths are needed at early ages, such as with

slip-formed structures, precast concrete, cast-in-place

con-crete with an early form removal requirement, or for any

project with moderate dimensions needing quick strengths

to allow for early opening to service Type III cement is very

similar to Type I cement in chemical composition Some

cement mills use modest increases of C3S to help achieve

higher early strengths The primary difference, however, is

physical in that Type III is ground to a greater fineness, thus

creating a greater surface area for increasing the rate of

hydration A separate use of high early strength concrete is

to substitute it for Type I or Type II cement during cold

weather, taking advantage of its early and increased heat of

hydration, thus reducing the length of cold weather

protec-tion periods High early strength also results in a quicker

time of set and shorter finishing time The faster reactions

also result in a cement that produces a higher heat of

hydra-tion than Type I and Type II cements

• Type IV—Low heat of hydration cement was developed for

use in massive structures, such as dams, where thermal

cracking is a potential problem due to excessive heat,

some-thing that might happen when other ASTM C150/C150M

portland cements are used This product is generally not

available in the United States A cement company, however,

could manufacture Type IV cement if a large enough

quan-tity was needed for a specific project The demand for Type

IV cement became very low as other more economical

alter-natives became available and acceptable to achieve the same

effects For example, Type II (MH) cement with the

moder-ate heat option and with a portion of the portland cement

replaced by slag cement or pozzolans will reduce the heat of

hydration at early ages of the concrete Either method of

reducing the heat of hydration also will reduce early and

ultimate strengths and will slow the rate of gain in strength

The extent of the reduced rate of strength gain may need to

be determined in the laboratory prior to commencement of

a project

• Type V—High sulfate resistant portland cement is

primar-ily used for concrete exposed to severe sulfate conditions These conditions may be from soil, groundwater, or certain industrial waste waters The improved resistance of this cement to sulfate attack is made possible by placing a maxi-mum limit on the tricalcium aluminate (C3A) of 5 % Type V portland cement is not always readily available except in areas where it is commonly used Other options to improve the sulfate resistance of concrete are to use slag cement or pozzolans as a portion of the cementitious materials in con-crete, by selecting a C595/C595M blended cement that incor-porates slag or pozzolan at the mill, or by selecting an appropriate C1157/C1157M Type MS or HS cement Determining the availability of a specific type of cement prior to including it in a specification or an order for ready-mixed concrete is prudent Because of the high sulfate con-tent in soils in California, Nevada, and other western states, Type V cement is generally the predominantly used cement

in those regions The northeastern United States has a erate number of mills producing Type V A good source of information concerning availability of a specific cement is

mod-the U.S and Canadian Portland Cement Industry: Plant Information Summary [23] published by the Portland Cement Association This document contains a list of prod-ucts produced by each mill

Guidance on the selection of a multitude of available portland and blended cements are provided in ACI 225R,

ACI 201.2R Guide to Durable Concrete [24], or PCA’s Design and Control of Concrete Mixtures [25] Requirements for use

of specific types of cements are addressed in ACI 318-11,

Building Code for Structural Concrete [22], and ACI 301-10,

Specifications for Structural Concrete [26] ACI 318

pro-vides alternative requirements to evaluate combinations of cementitious materials for sulfate resistance by ASTM C1012/C1012M Test Method for Length Change of Hydraulic Cement Mortars Exposed to a Sulfate Solution These tests require 6 to 18 months for completion A precautionary

statement concerning ACI 350-06, Code Requirements for Environmental Engineering Concrete Structures [27], is that requirements in this standard may be more restrictive than those in ACI 318

ASTM C150/C150M also includes optional requirements for portland cements Table 2 includes optional composi-tional requirements and Table 4 includes optional physical requirements For example, an optional requirement avail-able for each of the various types is a maximum equivalent alkali content of 0.60 % Other optional requirements include strength at different ages, heat of hydration, or eval-uation of sulfate resistance Invoking optional requirements are generally done by the purchaser of large quantities of cement and may be passed on from a project specification for concrete Invoking an optional requirement for cement

Materials 21

may require changing the manufacturing process and will

not be feasible for small quantities or on smaller projects If

the cement types regularly available in a geographic area do

not include low-alkali cements or sulfate resistant cements,

care should be exercised in specifying such cements

Alternatively the use of supplementary cementitious

materi-als in concrete can satisfy a similar need Special cements or

special cementitious materials may involve greater costs,

longer haul distances, and a dedicated silo or silos

• Air-entrained portland cement—Each of the types of

port-land cement in ASTM C150/C150M can be manufactured by

intergrinding an air-entraining material These cements are

formulated to provide air entrainment for concrete exposed

to freezing and thawing conditions These cements are

des-ignated by the letter “A” following the type designation

Most air-entrained concrete is achieved by means of a

chemical admixture, meeting ASTM Specification for

Air-Entraining Admixtures for Concrete (C260/C260M), placed

in a batch of concrete during the mixing process using a

non-air-entrained cement Because of the limited demand,

air-entrained cements are not always available These

cements may be used on specific paving jobs or in rural areas

with small batching operations A Type IA may be the only

option for the purchaser In these situations, a one-silo

oper-ation may only stock air-entrained cement and no chemical

admixtures Nothing improves consistency more than

lim-iting optional materials, and at some plants, each driver may

batch his own load The air-entrained cements make it

impossible to accidentally omit air entrainment, but

fluctu-ating air contents with slump and temperature changes

cannot be controlled

ASTM Specification for Blended Hydraulic Cements

(C595/595M) is a combination prescriptive and performance

specification Each of the ASTM C595/C595M cements has

spe-cific compositional requirements, which account for the

pre-scriptive portion of the specification, and each has specified

physical requirements for items such as cube strength, autoclave

expansion, time of set, and mortar expansion among other

requirements There are many types of hydraulic cements

included in this specification, plus an air-entrained (A) version

of each

Most of these hydraulic cements use portland cement as

the major component, but due to the differences in the finished

composition, properties, and method of manufacture, they do

not satisfy the definition of a portland cement All are produced

by blending a portland or other cement (C1157/C1157M) and

granulated blast-furnace slag (slag)2, pozzolan, limestone, or a

combination of these, hence the name “blended cement.”

2 The term slag is used to represent a by-product from an iron blast

furnace The cement manufacturer can use granules of quenched slag

and intergrind it with clinker or a previously ground slag to either

intergrind or blend with cement The term slag cement is used for

Blended cements may not be available in some geographic areas [23] It is prudent to check on availability before specify-ing the use of any blended cement Availability will depend upon demand and transportation costs for the material being blended with the portland cement or the availability of accept-able supplementary cementitious materials in a region While the use of blended cement is more common in Europe, the gen-eral practice in the United States is that supplementary cemen-titious materials (SCM) are batched at the ready-mixed concrete plant This system allows concrete for different purposes to have differing quantities of supplementary cementitious materials The average quantity of blended cement used in the United States is about 3 % of total cement consumption; this figure is based on reports published by the U.S Geological Survey

A positive perspective on using blended cements is that the material being added during the combining procedure has usu-ally been processed from a product that otherwise would be wasted Therefore, as a group, blended cements are environ-mentally friendly The materials being combined are also often optimized for performance by the cement manufacturer, and incompatibilities can be reduced compared to when ingredients are separately added at a concrete plant

The C595/C595M blended cement specification was duced by the ASTM Committee C01 in 1967 These cement specifications and manufacturing methods have changed over the intervening years to allow increases in the quantities of slag, pozzolan, and limestone to increase the number of specific products available

intro-The portland cement portion of a blended cement may meet either C150/C150M or C1157/C1157M cement specifications The blending may be accomplished by intergrinding or simply blending the two or three products to produce a homogeneous cement product Compositional limits preclude deleterious materials The standard invokes uniformity requirements by placing range limits on SiO2, Al2O3, and CaO Physical require-ments include requirements for fineness, autoclave expansion, time of setting, air content of mortar, compressive strength, heat of hydration, length change, and measurements for sulfate resistance and for controlling alkali-silica reactions

Blended cements consist of four primary categories: Type

IS, Type IP, Type IL, and Type IT Type IS is a blend of lic cement and slag; Type IP is a blend of hydraulic cement and pozzolan, generally fly ash; Type IL is a blend of hydraulic cement and limestone (15 % maximum); and Type IT is a ternary blend of hydraulic cement, slag, limestone, and pozzo-lans Another part of the notation used is a numerical value in parenthesis indicating the quantity of the blended supplemen-tary material or limestone in the cement For example, a Type

hydrau-IP (30) contains a pozzolan, and there is 30 % by mass of the pozzolan in the blended cement

ground granulated blast furnace slag that has hydraulic characteristics

In previous versions of C595, this term was used for blended cement containing slag in excess of 70 % by mass.

Each mill may have their own specific blend or blends of

materials meeting the prescribed limits of C595/C595M The

primary restrictions that may be of interest to many designers

are that slag in Type IS cement must be held to a maximum of

95 %, and pozzolan in a Type IP cement should not exceed 40 %

Note 7 of C595/C595M-13 is of particular interest It states:

The attainment of an intimate and uniform blend of two or

more types of fine materials is difficult Consequently

ade-quate equipment and controls must be provided by the

man-ufacturer The purchasers should assure themselves of the

adequacy of the blending operation.

Note that blended cements do not have a minimum

pozzo-lan requirement and that ACI 301-10 Section 4 requires that if

fly ash is used, the minimum amount shall be 15 % by mass

Also be aware that ACI 318-11 does not permit the use of

blended cement Type IS (≥70) These standards also place

max-imum limits on the quantity of supplementary cementitious

materials that can be used in concrete that will be subject to

deicing salt applications due to concern related to increased

potential of scaling This applies to the SCM in the blended

cement or if it is separately added The ACI 350-06 Code

Requirements for Environmental Engineering Concrete

Structures [27] and other codes should also be checked for

spe-cific use exclusions or limitations

General comments regarding ASTM C595/C595M blended

cements are for the purpose of alerting users to batch plant

possibilities and capabilities ASTM C595/C595M places a ± 5 %

range on the slag, pozzolan, or limestone quantity in blended

cement Variations of this extent are not expected due to

possi-ble customer complaints, but they are permitted Section 9 of

ASTM C94/C94M requires additions of SCM batched in

con-crete should be within ± 1 % of the total desired quantity of

both cement and cement with added cementitious materials

The idea that blended cement from the mill is more uniform

than a batch plant produced mixture would therefore appear to

be a myth An advantage of the batch plant combination is the

ability to alter the percentage of mixture components to meet

the specific needs of the project or season Some advantages of

a mill-blended cement product are that the chemistry of the

blend is optimized for improved performance with

accompa-nying test data for the blended product; faster batching is

per-mitted; and the need for an extra silo is eliminated

When a specifier desires a blended cement or has no

objec-tion to its use, it will often be prudent for the specificaobjec-tions to

spell out all desired limits for supplementary cementitious

materials, if required, and to allow either appropriate ASTM

C595/C595M blended cements or batch plant mixing of the

cementitious materials

Type IS—Portland blast-furnace slag cement is a blend of

portland cement and fine granulated blast-furnace slag A

dividing line for IS cements is 70 % slag Less than 70 % slag is

one category, and ± 70 % up to 95 % slag is another category The designation for blended cements with only slag as the blended ingredient is IS (X), where “(X)” is the target quantity of slag to a whole percent of the finished cement by mass Thus an

IS (60) contains 60 % slag and the remainder is portland or other hydraulic cement If the blended cement contains 80 % slag, the designation is IS (80) Because the total slag is above 70 %, the chemical and physical requirements are altered from those for cement with less than 70 % slag Hydrated lime is permitted

in IS (≥70) cements, but these cements are not commonly used

in ready-mixed concrete Type IS is a cement suitable for the same general construction uses as Type I portland cement The time of set for Type IS may be somewhat longer than for Type I, particularly in cooler weather, and the early-age strengths for Type IS may be somewhat lower than that for Type I The time

of set increases with the percentage of slag in the cement Research indicates that the addition of slag to cement will prob-ably increase drying shrinkage of the mortar The shrinkage increase at 50 % slag replacement for portland cement ranged from 125 % to nearly 150 % in one test series [28]

There are several very positive effects of combining slag with portland cement Workability is improved partially because the slag particles do not react with mixing water in fresh concrete Also, when substituting slag for portland cement on a pound-per-pound basis, there is a greater paste volume due to the lower particle density (specific gravity) of the slag Portland cement has a relative density of 3.15, and slag’s density ranges from 2.85 to 2.99.3 This relationship can increase the absolute volume of cementitious material by 5 %

or more for equivalent weights used

The permeability of concrete containing slag is improved This produces a concrete that transports less water and fewer chlorides within the concrete Sulfate resistance is improved by the inclusion of slag in blended cement Alkali-silica reactivity also is reduced by the use of slag as a component of the total cementitious material

• Type IP—Portland-pozzolan cement is a blend of

hydrau-lic cement and up to 40 % pozzolan by mass The pozzolan may be a natural pozzolan or fly ash if it meets the require-ments of C595/C595M Table 3 The physical requirements for Type IP are identical to those for Type IS (<70) and Type IL, but they are somewhat different with respect to chemical requirements The naming practice for a portland-pozzolan cement is similar to that used for Type IS, slag blends A Type IP (17) contains 17 % pozzolan and 83 % portland or hydraulic cement Type IP is a cement that is suitable for general construction Note that fly ash or other pozzolans

3 The units for density of cement or other cementitious materials are reported in mg/m 3 or g/cm 3 Specific gravity or relative density is a unitless quantity and the density of cement is determined by multiplying

this by the unit weight or density of water For purposes of calculating volumes for proportioning concrete, the density and specific gravity numbers are used interchangeably (ASTM C188, Test Method for Density of Hydraulic Cement)

Materials 23

are prohibited by ACI 318 from comprising more than 25 %

of the cementitious material if the concrete is subject to

application of deicing chemicals This restriction applies

regardless of where or how the pozzolan is blended with the

portland cement A slower time of set should be expected

with a Type IP than with a Type I portland cement

Pozzolan includes more than fly ash Natural pozzolans

in current usage are processed, calcined, and ground clays of

various compositions These include calcined clays, calcined

shales, and metakaolin (a high purity calcined kaolin clay)

Calcining is the heating of the selected materials to a

pre-scribed temperature below 2000°F to change the material’s

structure without causing fusion The calcined materials are

then ground to the desired fineness Other natural

pozzo-lans that may be used in the manufacture of Type IP cements

include diatomaceous earth, opaline chert, tuffs, volcanic

ash, and volcanic pumicites [29] Alternatively, pozzolans

conforming to ASTM C618 can be used as a separately

batched material during the production of concrete

• Type IL—Portland limestone cement is a blend of portland

or hydraulic cement that contains between 5 % and 15 %

limestone by mass Note that portland cement that conforms

to C150/C150M is permitted to contain up to 5 % limestone by

mass The limestone in the primary cement of the blended

cement product must also be included when stating the

quantity of limestone in the designation of the blended

cement There are restrictions on both the limestone and the

blended product The limestone must be produced initially

from a sedimentary rock and have a calcium carbonate content

of at least 70 % by mass, and it must meet the Table 2

require-ments of C595/C595M-13 These limits apply to maximum

clay content (measured by the methylene blue index4)and

total organic carbon The ability to include larger quantities

of limestone in cement reduces the carbon dioxide (CO2)

associated with the unit mass of finished cement, an

impor-tant consideration for the cement and concrete industries

in sustainable construction

Although it has been demonstrated that limestone takes

part in a chemical reaction with the portland cement, the

degree of this reaction is small and limited Limestone is

referred to as a filler rather than an SCM However, strength

benefits have been observed with optimized particle size

distribution of the limestone and the blended cement

beyond what might be expected from a filler If a binary

blended cement contains 12 % limestone it is identified as

a Type IL (12)

• Type IT—Ternary blended cement is a blend that contains

hydraulic cement and portions of two other constituents of

either slag, pozzolan, or limestone The slag and limestone

4 There are several Methylene Blue tests available to determine the

presence of harmful clays The Methylene Blue Index referenced for use

in C595/C595M is detailed in Annex A2 of the specification This is the

only approved test to verify acceptability of a limestone product for use

in blended cement.

portions may consist of two different pozzolans, slag and a pozzolan or limestone, or a pozzolan and limestone These may be combined by intergrinding, blending, or a combina-tion of these processes

The Type IT blends carry the “IT” as the initial fier The second identifier is the product “S,” “L,” or “P,” whichever is greater by mass The third identifier is the mass

identi-of the least identi-of the three components Sample identifier names are IT (S30)(L10) indicating 30 % slag, 10 % limestone, and

60 % portland or hydraulic cement Another sample would

be IT (P20)(S20) When the two minor constituents are the same percentage in the blend, the order of the listing is alphabetical

The maximum pozzolan content of a ternary blended cement is 40 %, matching the maximum permitted for the Type IP The maximum slag content in a ternary blended cement is less than 70 %, rather than 95 % as it is for the binary Type IS The maximum combined content of slag plus pozzolan or limestone for a ternary blend is less than

70 % The maximum limestone for a ternary blend remains

at 15 %

Options for blended cement include air entrainment (A) as previously mentioned This option is available to each cement manufacturer and depends upon the market for availability to purchasers Specifics are not provided within the specification, but ordering information includes the addition of optional accelerators, retarders, and water reducers Sulfate resistance blended cement is available for both moderate (MS) and high (HS) resistance The sulfate resistance is qualified by expan-sion tests from 6 months to 1 year by ASTM C1012/1012M Type IL and Type IT with limestone are not permitted to be designated for sulfate resistance (MS) or (HS) and at this time should not be used in concrete exposed to higher concentration levels of water soluble sulfates in soil or water This might change in the future when research can demonstrate that blended cements contain-ing greater than 5 % limestone are acceptable for use in sulfate exposure conditions Blended cements with reduced heat of hydration are available with both moderate (MH) and low heat (LH) of hydration Heat of hydration is quantified by measured heat using ASTM C186

ASTM Specification for Hydraulic Cement (C1157/C1157M) is

a performance-based specification for cement The Scope of ASTM C1157/C1157M states: There are no restrictions on the composition of the cement or its constituents The general

requirements of ASTM C1157/C1157M for hydraulic cements seem less restrictive than the ASTM C150/C150M requirements C1157/C1157M contains no minimum fineness requirement, and the allowable time of set range is broader than that for ASTM C150/C150M portland cements These hydraulic cement requirements tend to be more focused on the long-range durability aspects and less on short-term time of set than ASTM C150/C150M for Types I and II portland cements

The ASTM C1157/C1157M for hydraulic cements, however, can

include the ASTM C150/C150M portland cements and

ASTM C595/C595M blended hydraulic cements For example,

ASTM C150/C150M, Type I may meet requirements for ASTM

C1157/C1157M, Type GU, depending upon ASTM C151 autoclave

expansion test and compressive strength test results

The minimum and maximum performance requirements

are the only restrictions on materials used in ASTM C1157/

C1157M cements Analyses of chemical composition for both

the individual constituents, which are either interground or

blended, and the finished product are required This provides

the user an opportunity to monitor consistency of the finished

product through mill test reports Trial batches are suggested to

verify required compressive strengths being produced by the

blended cement

The ASTM C1157/C1157M hydraulic cement types and their

uses can be summarized by relating to ASTM C150/C150M

type usages [6] If restrictions are placed on the quantities of

supplementary cementitious materials in concrete, the

sup-plier of the cement can be asked to provide information on the

general composition of blended cement that conforms to

ASTM C1157/C1157M, even though this is not part of the

materi-als certification and reporting requirements in the

specification

• Type GU—General use cement is for general construction

as an ASTM C150/C150M, Type I would be used

• Type MH—Moderate heat of hydration cement reduces the

usual hydration rate and the resulting heat Type MH

com-pares to an ASTM C150/C150M, Type II with moderate heat

requirement

• Type HE—High early strength hydraulic cement produces

the highest one and three-day strengths of the ASTM C1157/

C1157M cements Its ASTM C150/C150M equivalent is Type III

• Type LH—Low heat of hydration hydraulic cement is a

replacement for ASTM C150/C150M, Type IV Its primary use

is for very massive structures to reduce the potential for

thermal cracking due to excessive heat of hydration

Early-age strengths are very low, with the minimum requirement

being 1600 psi at 7 days

• Type MS—Moderate sulfate resistance cement is

compara-ble to ASTM C150/C150M, Type II portland cement The

properties of this cement provide resistance to moderate

sulfate exposure when the concrete has a low

water-cementi-tious materials ratio

• Type HS—High sulfate resistance is provided by this

cement with usages comparable to an ASTM C150/C150M,

Type V portland cement Early-age strengths are low

• Option R—Low reactivity with alkali-reactive aggregates

may be specified with any of the six basic types included in

the ASTM C1157/C1157M specification

The Canadian Standards use this nomenclature for cements in

their specification for cement, CSA A3000

5.2.2 Supplementary Cementitious Materials—S1 Coal fly

ash or natural pozzolans shall conform to Specification C618 S2 Slag cement shall conform to Specification C989/ C989M Silica fume shall conform to Specification C1240

The term “Supplementary Cementitious Materials” or

“SCM” has replaced “mineral admixtures,” and several recent publications, including ones by Neville [30] and Kosmatka, Kerkhoff, and Panarese [6] support the shift in nomenclature When possible it is preferable to use the name of the specific cementitious material referenced A nonscientific, but

thought-provoking view for deleting the term mineral ture is provided by Neville [31], who takes the stance that the term admixture “conjures up, a minor component, something

admix-added to the main mix, yet some of the supplementary

cementi-tious materials (mineral admixtures) are present in large quantities.”

The term pozzolan needs some discussion The term is

defined in ASTM C125 as:

pozzolan, n—a siliceous or siliceous and aluminous material

that in itself possesses little or no cementitious value but will,

in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary tem-peratures to form compounds possessing cementitious properties

The hydration of portland cement results in the formation

of calcium silicate hydrate that provides the cementing ties The by-product of this hydration reaction is calcium hydroxide, or lime, which amounts to about 25 % of the result-ing hydration products and provides no performance benefits

proper-in concrete It has been observed proper-in microscopic evaluations that calcium hydroxide crystallizes around aggregate particles and results in a zone of weakness where cracking initiates and fluids can penetrate into concrete Pozzolanic materials react with and reduce calcium hydroxide forming additional cemen-titious calcium silicate hydrates Most pozzolans, like fly ash and silica fume, are essentially by-products from another pro-cess that typically would be discarded and disposed of in land-fills Their use in concrete allows them to be diverted from the waste stream and provides beneficial performance properties to concrete

ASTM C618 Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete is the most

common of SCMs identified in this group Fly ash is a lanic material that is generated from burning coal in coal-fired power-generating plants The material is the finely divided residue that is captured from the exhaust systems Fly ash par-

pozzo-ticles are frozen into solid parpozzo-ticles from a liquid state and are

generally amorphous (noncrystalline) spherical-shaped cles The amorphous characteristic makes them reactive as a pozzolan Fly ash has been used in concrete since the 1930s in

parti-Materials 25

the construction of dams and in other applications Its use as a

beneficial cementitious material in concrete is well established

The composition of fly ash varies depending on the type of coal

being burned to create the fly ash ASTM C618 classifies fly ash

in two categories: Class C and Class F The primary parameter

used for this classification is the sum of SiO2, Al2O3, and Fe2O3

This sum of oxides decreases as the CaO content in the fly ash

increases Different types of fly ash, from different sources,

perform quite differently; it should not be assumed that two

different types of fly ash with the same ASTM classification will

have the same performance characteristics

Fly ash is used as a portion of the cementitious materials in

concrete, commonly 15 to 35 % by mass When used, fly ash

produces many positive attributes for the concrete Workability

is improved due to the spherical shape of the particles, and the

water required for a target slump is reduced Fly ash provides

higher long-term strength gains, lower permeability, lower

heat of hydration, and often a minimal decrease of drying

shrinkage Fly ash concrete mixtures tend to bleed at a slower

rate, and the combination of slower setting and slower bleeding

can lead to premature finishing resulting in surface

delamina-tions of concrete flatwork

Class F fly ash is produced from the burning of bituminous or

anthracite coal The major sources of this coal are Pennsylvania,

West Virginia, Kentucky, Ohio, and Illinois Almost all of these

types of coal are found east of a longitudinal-running line that

begins in the middle of North Dakota and extends due south

through the middle of Texas There are some scattered spots of

bituminous coal across the western states and along the Pacific

coast As a general rule, Class F fly ash is found east of the

Mississippi River, and Class C fly ash is primarily found west

of it [32]

ASTM C618 classifies fly ash as Class F when the sum (SiO2 +

Al2O3 + Fe2O3) is equal to or greater than 70 % by mass Class F

fly ash typically contains low quantities of CaO, though some

sources of Class F fly ash may have CaO around 10 to 12 %

Class F fly ash will not set and harden when mixed with water

It only contributes to cementitious properties when

incorpo-rated in concrete with portland cement Class F fly ash is

there-fore a pozzolan in the true sense of the definition

Class F fly ash is usually effective in reducing alkali-silica

reactivity (ASR) because of higher SiO2 contents and lower CaO

contents [33] Class F fly ash also improves sulfate resistance

when used in concrete

Setting time can be slower with Class F fly ash, especially

with cooler temperature concrete mixtures [34] The setting

time of mixtures with Class F fly ash is also typically observed

to be slower than with mixtures containing Class C fly ash, but

there also may be more variability in setting time with the Class F

fly ash Class F fly ash tends to have a higher unburned carbon

content as measured by loss on ignition (LOI), and this tends to

be more variable between shipments from the same source

Certain forms of unburned carbon affect the dosage

requirements for air-entraining admixtures to produce the desired air content in the concrete The unburned carbon may absorb the air-entraining admixture during mixing and deliv-ery, thus reducing air contents as much as 60 % (2 or 3 % of air content) during the delivery process [35] Typically concrete mixtures containing Class F fly ash will require a higher dosage

of air-entraining admixture to obtain the required air content

in concrete Removal of excessive carbon in fly ash is plished by reburning or electrostatic separation processes to make it more uniform and useable in concrete These processed fly ashes achieve uniform entrained air contents when used in concrete Stickiness of the mixture with higher fly ash substitu-tion rates can also be a problem with Class F fly ash and affects the ability to finish these mixtures

accom-Class C fly ash is produced from burning sub-bituminous

coal or lignite The predominate sources of sub-bituminous coal and known reserves are in Wyoming, Colorado, New Mexico, and Montana Besides having pozzolanic characteris-tics, Class C fly ash has cementing properties due to a higher lime (CaO) content

Class C fly ash, with a higher CaO content (generally greater than 12 %), are typically not effective in mitigating alkali-silica reactivity (ASR) Some Class C fly ash is effective in reducing ASR but need to be used at a higher percentage of the mass of cementitious materials Class C fly ash is also not effec-tive in improving sulfate resistance of concrete since they typi-cally contain C3A or other forms of aluminate that increase the potential for sulfate attack [12,36,37]

A characteristic of Class C fly ash is that normal setting characteristics are observed in hot weather, but may result in significant retardation in cold weather Compatibility with admixtures can also result in severe retardation of setting char-acteristics The quantity of Class C fly ash used in the mixture proportionally affects setting time of the concrete

Class N pozzolans include both raw and calcined natural

pozzolans Some naturally occurring materials have pozzolanic properties, while others obtain these characteristics after heat treatment, typically referred to as calcination Pozzolanic char-acteristics are achieved by heating and rapidly cooling a material composed of SiO2 among other ingredients to an amorphous or glassy (non-crystalline) form A volcanic tuff from the Naples, Italy area was combined with lime and water many centuries ago to produce a cement-like product that would harden even under water The best volcanic tuff (ash) came from the famous Vesuvius volcano near a village named Pozzuoli The name given to the material was pozzolana [38] Volcanic ash tends to

be too variable to be used predictably in concrete Other natural pozzolans include pumicite, diatomaceous earth, opaline cherts, and opaline shales [29] Natural pozzolans are available throughout the United States, but most of those testing satisfac-tory for use are located west of the Mississippi River [39] These materials can be used in the same manner as fly ash with proper

evaluation in concrete mixtures prior to use Improvements to

concrete properties cannot be generally stated because of the

wide range of materials that can be used as Class N pozzolans

Calcined clays and shales are the more frequently used

natural pozzolans in blended cements under C595/C595M They

are most frequently added at the cement mill rather than at the

concrete batch plant because they are seldom available as

sepa-rate ingredients These products are often effective in

combat-ing alkali-silica reactivity Permeability of the concrete is

lowered, reducing water penetration Resistance to sulfate

attack is generally improved depending on the composition of

the pozzolan Pozzolans will decrease the heat of hydration,

increase the setting time of concrete, and the air-entraining

admixture dosage to obtain a specific air content usually will

need to be increased The 25 % limit on pozzolan by ACI 318 for

concrete exposed to deicing chemicals should be observed

Metakaolin is a manufactured natural pozzolan obtained from

calcining kaolintic clay Kaolinite is a very prevalent and very

stable clay mineral High-reactivity metakaolin (HRM) is a

cal-cined kaolinite clay of higher purity available in some areas of

the United States The purity and fineness makes HRM a very

reactive pozzolanic material, and its use in concrete is

compara-ble to that of silica fume These materials qualify as a Class N

pozzolan under ASTM C618 As compared to a portland

cement-only concrete mixture, concrete with 5 to 10 % HRM is

expected to have higher early-age and ultimate strengths

Drying shrinkage, resistance to chloride ion penetration, and

mitigation of ASR are beneficial characteristics provided to

concrete with reactivity metakaolin This can be a

high-cost supplementary cementitious material due to the

process-ing involved, but it is often used in a ternary mixture (three

cementitious materials) with cement and fly ash or slag to

pro-duce improved concrete at nominal overall cost increase The

product is available in bulk or bagged quantities HRM, due to

its white color, has little effect on the concrete color and can

lighten the color of concrete when necessary for architectural

applications HRM particles are typically larger than silica

fume particles and may produce a mixture that is not as sticky

when finishing Bleeding of newly placed fresh concrete

mix-tures is reduced, similar to silica fume concrete Close attention

must be given to wind, humidity, and temperature to prevent

plastic shrinkage cracking

Rice-husk ash meets the requirements for a C618, Class N

pozzolan It is a product produced by controlled calcinations of

rice hulls It has particle sizes similar to fly ash and produces the

same concrete attributes as other pozzolans Mehta [40]

pro-vides data revealing significant increases in compressive

strength and reductions in permeability with the substitution

of rice-husk ash for 15 % of the cement Test results have been

good for both ordinary concrete mixtures and high strength

mixtures The husks (hulls) are a waste product, but turning

them into ash by means of controlled calcination is expensive,

so it is not a widely available, cost competitive supplementary cementitious material in the United States

Slag cement is defined by ASTM C989/C989M Specification for Slag Cement for Use in Concrete and Mortars Slag is a by-product

from the manufacture of iron in a blast furnace and is a tial waste product Molten slag is tapped off separately from molten iron as it exits the blast furnace If it is rapidly cooled with water, it solidifies into a noncrystalline glassy material that makes it cementitious Slag that is air cooled is used as aggregate for base or in concrete The granulated slag is ground to fine-ness similar to or greater than that of portland cement Slag cement was previously known as “ground granulated blast furnace slag” (GGBFS), which is a deprecated term Slag cement

poten-is a cementitious, as opposed to a pozzolanic, material By itself, slag cement with water will take a long time to set and gain strength Its hydration is activated by lime and alkalies when used with portland cement in concrete

ASTM C989/C989M classifies slag cement into three grades (80, 100, and 120) based on the slag activity index (SAI) The SAI is the ratio of the compressive strength of 1:1 slag cement: portland cement mortar to the compressive strength of a port-land cement mortar Compressive strength is measured on mortar cubes ASTM C989/C989M establishes minimum limits for individual tests and average values of SAI for 7-day and 28-day strengths The higher grade of slag has better strength producing properties This material is used as a separately added SCM ingredient in concrete at the concrete production facility Slag is also used as an ingredient in manufacturing blended cements under ASTM C595/C595M blended cements and ASTM C1157/C1157M

Slag cement is used in the range of 25 to 70 % by mass of cementitious materials Typical use is at 50 %, but this percent-age may be reduced to 30 to 35 % in cooler weather because of the slower setting time Slag cement is a bulk product that is not readily available in all areas due to transportation costs Its availability is generally associated with location of iron manu-facture or ports where imported slag is shipped in Attributes of slag cement include improved resistance to sulfate attack, miti-gation of ASR with potentially reactive aggregates, improved workability, reduced permeability, and higher ultimate con-crete strengths due to the continued later age hydration [41] Higher quantities of slag, in the range of 70 to 80 % by mass of cementitious materials, have been used successfully in mass concrete structures to reduce temperature rise due to heat of hydration The almost white color of the slag cement provides concrete with a lighter and brighter color

The setting time of concrete mixtures with slag cement is usually longer than that for portland cement mixtures, particu-larly in cold weather In cold weather, slag cement percentages may need to be reduced and chemical accelerators considered for use Concrete with slag cement has an improved finishabil-ity but also has a significantly reduced rate of bleeding Concrete made with slag cement requires more attention to curing

Materials 27

practices than portland cement mixtures require This is true of

any combination of cementitious materials that lower both the

heat of hydration and early strengths ACI 318 places a

maxi-mum limit of 50 % by mass of cementitious material for

con-crete that will be exposed to application of deicing chemicals

Silica fume is defined by ASTM C1240 Specification for Silica

Fume Used in Cementitious Mixtures Silica fume is a very finely

divided pozzolanic material produced by-product collected

from exhaust gases during the production of silicon metal or

ferrosilicon alloys The silica fume particles are on average

1/100 the size of cement particles Because of the small particle

size, silica fume is densified to agglomerate the fine particles

These agglomerations are broken up when mixing concrete to

disperse the fine particles Although silica fume is a pozzolanic

material, it is not covered by ASTM C618 because it is not a coal

fly ash; it is not a raw or calcined product; and it will not meet

the maximum water requirement of ASTM C618 Table 2 ASTM

C1240 includes both chemical and physical requirements for

silica fume

Silica fume requires special knowledge of handling,

mix-ing, and use that is not typical of other supplementary

cementi-tious materials On smaller projects silica fume may be

purchased and used in bags Bulk silica fume must be unloaded

at lower pressures than cement and may require unloading

times in the range of four hours More mixing time and smaller

batch sizes may be necessary in order to achieve thorough

mix-ing [42] Batching sequence may need to be changed to allow

some attrition with coarse aggregate to break up agglomeration

of densified particles Project specifications allowing for

alternatives or addressing more detail than those in ASTM

C94/C94M may also be required

Silica fume is used in typical dosages of 3 to 12 % of the mass

of cementitious materials and usually requires a high-range

water reducer It is a very effective pozzolan; most of its

pozzo-lanic activity happens at early ages The most notable attributes

of silica fume concrete are high strengths, reduced abrasion,

greatly reduced permeability, improved resistance to chemical

attack, mitigation of ASR, and improved resistance to sulfate

attack Due to its contribution to properties at earlier ages, silica

fume is often used in combination with fly ash and slag cement

in ternary systems to offset some of the deficiencies those

materi-als have at early ages Concrete containing silica fume at around

7 % or greater will typically be used in concretes with a low

water-cementitious material (w/cm) ratio with high-range

water-reducing admixture, and these mixtures tend to be sticky

These mixtures also do not bleed and need special precautions

and adjustments to placing, finishing, and curing practices to

minimize potential for plastic shrinkage and early-age cracking

Silica fume is permitted to be batched in bulk quantities

with the cement Section 9.1 currently requires the cement to be

batched first The batching systems seek to achieve a target total

after each material is batched, rather than a specific quantity of

each material, and tolerances are set on cumulative targets

Because silica fume is used in smaller quantities and also because small variations of silica fume have such a pronounced effect on the concrete, a revision to the batching accuracy requirements for silica fume is a goal of Subcommittee C09.40

ASTM C1697—A material specification not mentioned in C94/ C94M is ASTM C1697 Specification for Blended Supplementary Cementi-tious Materials This new specification presents mandatory physical requirements and some optional physical requirements for blends of SCMs (pozzolans, silica fume, and slag cement) The purpose is to establish some primary standards for the blending or intergrinding of two or three

of these SCMs that individually meet their respective ASTM standards This specification is intended for those blending the products at a cement or SCM production facility to produce a single ingredient for incorporation in concrete

5.3 Aggregates—S1 Normal weight aggregates shall conform

to Specification C33/C33M S2 Lightweight aggregates shall conform to Specification C330/330M and heavyweight aggregates shall conform to Specification C637

Aggregates comprise approximately 70 % of the concrete volume and can be the constituents with the greatest variability

It is essential that control be exercised over the quality of the aggregate, both fine and coarse There are numerous quality tests with minimum requirements in each specification

ASTM C33/C33M addresses fine aggregate properties of grading, organic impurities, soundness testing, and deleterious substances ASTM C33/C33M provides the option of additional requirements in its Section 4 on ordering and specifying infor-mation The specifier and purchaser are afforded the opportu-nity to invoke a restriction on reactivity (alkali-aggregate reaction) Other choices include considering which salt, sodium sulfate, or magnesium sulfate, is to be used in the sulfate sound-ness test; what the appropriate maximum limit for minus 75-µm (No 200) material, if other than 3.0 %, is; and what the appropriate maximum limit for coal and lignite, if other than

1.0 %, is Recent alterations to the requirements for fine

aggre-gate have made manufactured sand a viable option in graphic areas in which natural sand supplies are being depleted.Coarse aggregate is the ingredient that occupies the largest volume in concrete ASTM C33/C33M has a lengthy list of requirements for coarse aggregate and also presents some deci-sions the specifier must make Coarse aggregate properties for which there are specific limits are clay lumps and friable parti-cles, chert, minus 75-µm (No 200) sieve material, coal and lignite, abrasion characteristics, and soundness test Section 4

geo-of ASTM C33/C33M assigns the responsibility to the specifier for several items, including selecting a grading size number or nominal maximum size or a grading band from multiple size aggregates Any desired grading may be specified instead of selecting a standard size The requirement for specialized grad-ing often will become an economic issue because it may force