Analysis of alternative water sources for use in the manufacture of concrete

Queensland University of Technology School of Physical and Chemical Sciences Analysis of alternative water sources for use in the manufacture of concrete This thesis is submitted as pa

Queensland University of Technology

School of Physical and Chemical Sciences

Analysis of alternative water sources for use in the manufacture of concrete

This thesis is submitted as partial fulfilment

of the requirements for the degree of

Maters of Applied Science

By

Leigh M McCarthy B.Sc

Supervisor: Dr Serge Kokot Assoc Supervisor: Prof Ray L Frost

Abstract

In Australia and many other countries worldwide, water used in the manufacture of concrete must be potable At present, it is currently thought that concrete properties are highly influenced by the water type used and its proportion in the concrete mix, but actually there is little knowledge of the effects of different, alternative water sources used in concrete mix design Therefore, the identification of the level and nature of contamination in available water sources and their subsequent influence on concrete properties is becoming increasingly important Of most interest, is the recycled washout water currently used by batch plants as mixing water for concrete Recycled washout water is the water used onsite for a variety of purposes, including washing of truck agitator bowls, wetting down of aggregate and run off

This report presents current information on the quality of concrete mixing water in terms of mandatory limits and guidelines on impurities as well as investigating the impact of recycled washout water on concrete performance It also explores new sources of recycled water in terms of their quality and suitability for use in concrete production

The complete recycling of washout water has been considered for use in concrete mixing plants because of the great benefit in terms of reducing the cost of waste disposal cost and environmental conservation The objective of this study was to investigate the effects of using washout water on the properties of fresh and hardened concrete This was carried out

by utilizing a 10 week sampling program from three representative sites across South East Queensland The sample sites chosen represented a cross-section of plant recycling methods, from most effective to least effective The washout water samples collected from each site were then analysed in accordance with Standards Association of Australia AS/NZS 5667.1 :1998 These tests revealed that, compared with tap water, the washout water was

higher in alkalinity, pH, and total dissolved solids content However, washout water with a total dissolved solids content of less than 6% could be used in the production of concrete with acceptable strength and durability These results were then interpreted using chemometric techniques of Principal Component Analysis, SIMCA and the Multi-Criteria Decision Making methods PROMETHEE and GAIA were used to rank the samples from cleanest to unclean

It was found that even the simplest purifying processes provided water suitable for the manufacture of concrete form wash out water These results were compared to a series of alternative water sources The water sources included treated effluent, sea water and dam water and were subject to the same testing parameters as the reference set Analysis of these results also found that despite having higher levels of both organic and inorganic properties, the waters complied with the parameter thresholds given in the American Standard Test Method (ASTM) C913-08 All of the alternative sources were found to be suitable sources of water for the manufacture of plain concrete

Statement of Originality

The work contained in this thesis has not been previously submitted to meet requirements for an award at this or any other higher education institution To the best of my knowledge and belief, the thesis contains no material previously published or written by another person except where due reference is made

Signature _

Leigh M McCarthy

Date _

Acknowledgements

This project would not have been possible without the support of many people Many thanks

to Dr Serge Kokot and Prof Ray Frost for their direction, assistance, and guidance In particular my supervisor, Dr Serge Kokot, who read my numerous revisions and helped make some sense of the confusion Thanks are also due to Mr Glenn Carson, Dr Dak Bakewash and Mr Russel Gutsky from Readymix for their assistance and for providing me with the financial means to complete this project I would also like to thank Dr Wayde Martens whose help was integral in the completion of this thesis Also thanks to my fellow postgraduate students, who sympathized with my complaints, understood my frustrations and most of all offered guidance and support

And finally, thanks go to my family and friends who endured this long process with me, always offering support and love Thanks to my parents who were unwavering in their encouragement and support and who, through years of patience and hard work afforded me

a sense of ambition and self, allowing me to reach for my goals To my sister Clare thanks for your patience, understanding and tolerance of my disappointments and for sharing my triumphs Lastly, to my brother Sean whose own achievements served as a reminder that only your best effort will do

Table of Contents

1 Introduction 12

1.1 Prologue 12

1.2 Concrete and its constituents 15

1.3 Cement and aggregates 17

1.3.1 Hydration reactions of cement 21

1.3.2 Cement Hydration Products 23

1.3.3 Admixtures 25

1.4 Water Quality, its properties and influence on concrete 26

2 Methodology 29

2.1 Sample Guidelines 29

2.2 Sample Preparation 29

2.3 Equipment and Materials 31

2.4 Chemical Preservatives 31

2.5 Sampling Methods and Procedures 31

2.6 Preparation of Concrete Cylinders 33

2.7 Instrumental Analysis 34

2.8 Instrumentation used for the analysis of water samples 35

2.8.1 Measurement of pH 35

2.8.2 Measurement of Relative Alkalinity 36

2.8.3 Measurement of Electrical Conductivity 37

2.8.4 Measurement of Total Dissolved Solids 38

2.8.5 Measurement of Chloride 39

2.8.6 Compressive strength Analysis of concrete samples 40

2.9 Multi Criteria Decision Making Methods 42

2.9.1 Chemometric Analysis 42

2.10 Multicriteria Decision Making (MCDM) 51

2.10.1 Preference Ranking Organisation Method for Enrichment Evaluation (PROMETHEE) 52

2.10.2 Geometric Analysis for Interactive Aid (GAIA) 54

3 Compilation of baseline data for water quality 55

3.1 Washout Waters – Building a baseline 55

3.2 Concrete Plant sites throughout SE-Qld 56

3.2.1 Southport Concrete Plant 56

3.2.2 Beenleigh Concrete Plant 56

3.2.3 Murarrie Concrete Plant 56

3.3 Analysis of Baseline Water 58

3.4 Simple Analysis of Baseline Water Sample Results 58

3.5 Chemometric interpretation of Water Quality data 62

3.6 Chemometric Analysis of Baseline Samples 66

3.6.1 Principal Component Analysis 66

3.6.2 PROMETHEE and GAIA 72

3.7 Chapter Summary 80

4 Analysis of Alternative Water Sources for Comparison 81

4.1 Location of alternative water source sampling sites 81

4.2 Southport Sea Water 83

4.2.1 Southport Treated Effluent 83

4.2.2 Kawana Treated Effluent 83

4.2.3 Coolum Bore Water 83

4.2.4 Gympie Bore water 84

4.2.5 Ipswich River Water 84

4.2.6 Murarrie Bore Water 84

4.2.7 Coomera Dam Water 84

4.2.8 Coomera Bore water 84

4.3 Analysis of Alternative Water Sources 86

4.4 Analysis according to water type 88

4.4.1 Sea Water 88

4.4.2 Treated Effluent 89

4.4.3 Bore Water 91

4.4.4 Dam and River Water 91

4.5 Chemometric analysis of alternative water source samples 93

4.5.1 PCA analysis 93

4.5.2 SIMCA 97

4.5.3 Fuzzy Clustering 103

4.5.4 PROMETHEE and GAIA 105

4.6 Chapter Summary 116

5 Concluding Remarks 117

6 References 119

Table of figures

Figure 2.1 Testing Apparatus used to determine Compressive Strength 40

Figure 2.2 Example of Principal Component Analysis 46

Figure 3.1 Biplot with baseline sample results with IRMV and compressive strength results 67 Figure 3.2 PCA Biplot of PC1 vs PC2 with all variables including compressive strength results 69

Figure 3.3 GAIA plot showing reference variables and baseline sample sites with compressive strength results 73

Figure 3.4 GAIA plot showing reference variables and baseline sample sites 77

Figure 4.1 PC1 v PC2 for alternative water source results 92

Figure 4.2 PC1 v PC2 all Alternative and all Baseline samples with compressive strength results 94

Figure 4.3 Cooman Plot For Murarrie and Coomera Dam including RSD values 100

Figure 4.4 Cooman Plot For Murarrie and Sea Water including RSD values 100

Figure 4.5 Plot of Discrimination power vs variables for Southport & Murarrie 106

Figure 4.6 GAIA plot for all Alternative and all Baseline samples 109

Figure 4.7 GAIA Plot for all Alternative and all Baseline samples with compressive strength results 114

Table of tables

Table 1.1 - Chemical and physical composition of ordinary Portland cement 16

Table 2.1 - Specifications for sample preservation 30

Table 2.2 Preference functions in PROMETHEE 50

Table 2.3 – sample matrix 52

Table 3.1 Average Values over 10 week period for each plant and Tap Water compared to the Tolerable Limits 57

Table 3.2 Metal Concentrations from Southport, Beenleigh and Murarrie 60

Table 3.3 Readymix Water Specification Guidelines 65

Table 3.4 PROMETHEE Net Ranking for Southport and Murarrie using Internal Readymix Variables and Compressive strength results 71

Table 3.5 PROMETHEE Net Ranking for the Baseline Data using Internal Readymix Variables Only 75

Table 4.1 Typical composition of sea water* 82

Table 4.2 Comparison between Average Alternative Water Source Results and Compressive strength Results with Baseline samples and Tap water 85

Table 4.3 PCA models for SIMCA 96

Table 4.4 SIMCA fit to Southport RSDcrit=0.45, p=0.05 98

Table 4.5 SIMCA fit to Murarrie where RSDcrit = 1.13, p= 0.05 98

Table 4.6 Hard clustering for Alternative Water Samples 102

Table 4.7 Soft clustering for Alternative Water Samples 104

Table 4.8 PROMETHEE Net ranking of alternative water sources 107

Table 4.9 PROMETHEE Net Ranking for all Alternative and all Baseline samples with Compressive strength Results 112

1 Introduction

1.1 Prologue

Second only to water, concrete is the most consumed substance, with three tonnes used per person per year [1] Twice as much concrete is used in construction as all other building materials combined [2] Thus, there is little doubt that concrete will remain in use well into the future As demand increases for this fundamental building material, studies such as the one presented here will continue to be carried out in the hope of optimising the characteristics and properties, ensuring that concrete remains environmentally friendly and affordable This study is aimed at understanding the role of water quality in concrete

manufacture In order to accomplish this aim, this study has set out to identify key elements,

variables and characteristics necessary for a water source to be considered a viable option within the concrete industry

Concrete consists of aggregates, sand, cementitious material, admixtures and water which are mixed together to provide a uniform plastic material [3] This plastic material gradually sets after a period of one to three hours which increases in strength, particularly over the first month of its life [4] Varying the mix of cement, sand and aggregate used in a concrete blend consequently enables its use in a wide range of applications Products can be designed, coloured and shaped to accommodate a variety of environmental conditions, architectural requirements and to withstand a wide range of loads, stresses and impacts With the increasing demand for high quality water, a large quantity of chemical agents must be used

in the water purification process, which in turn generates enormous amounts of waste wash water [5] Of all the options for wash water disposal, reuse has been considered most economical and environmentally sound

This study evaluated the possibility of incorporating wash water in the making of concrete The goal was to search for the optimal specifications to maximize the replacement of potable water with an alternative source

Within this scenario, re-envisioning industrial wastes as alternative raw materials becomes of interest, both economically and logistically, for a wide range of applications which includes the fabrication of concrete As such, there have been comprehensive studies detailing possible alternative water sources suitable for the production of concrete Previous research, such as that carried out by Al-Harty, Borger, and Chatveera has focused on what effect minerals, salts and impurities contained in the water have on the properties and performance of fresh and hardened concrete [1, 5, 6] Results obtained in these studies indicate that the use of non-potable water yields lower compressive strength in comparison

to concrete made with potable water

Previous research in this field, carried out by Muszynski, Sandrolini and Su, has utilised treated effluent water samples, water from streams, lakes and sea water for concrete construction [2, 7, 8] These studies however were not carried out within Australia, thus the results found were not obtained in light of Australian Standards [9, 10] Such studies also imply that the concrete produced was not made of common aggregates and cement found in Australia And, whilst the results obtained will serve as a useful guideline to the behaviour of wet, hardening and hardened concrete, the analytical results obtained in such studies have not, as yet, been coupled with chemometrics methodology Hence, this study aims to build

on previous investigations by combining instrumental and structural analysis with chemometrics

The novel application of Multi-Criteria Decision Making (MCDM) methods of data analysis will also be carried out to complement chemometrics findings Chemometrics was applied to compare and discriminate individual samples, as this MCDM is primarily concerned with the extraction of significant information from the data which has been characterised into chemical, physico-chemical and structural components [11, 12]

This study sought to research and develop, the combination of instrumental analysis with chemometrics to provide a rapid method for assessing the suitability of a variety of water sources for use in concrete production These would be developed such there would be no lasting harmful effects to its properties and characteristics of the resultant concrete This was performed with the primary objectives:

• To build a comprehensive water quality baseline with specific parameters outlining

the suitable elemental, physico-chemical and structural properties of water for use in concrete manufacture

• To develop elemental, physico-chemical and structural guidelines with the aid of

chemometrics, and the novel application of Multi-Criteria Decision Making Methods ensuring optimal water and concrete results

• To undertake an investigation into the suitability of alternative water sources,

employing chemometrics

• To report the results clearly, enabling industry to use the information to ensure that

changes are made to increase the cleanliness and quality of water and subsequently improve the performance of the resultant concrete

The remainder of this chapter will focus on the role of water in concrete production, as well

as provide an introduction to the composition of concrete It will also introduce the chemometric techniques utilised for this study and conclude with an examination of the

instrumental techniques utilised in this project Chapter 2 describes the materials, procedures and chemometrics aspects utilised in this work Chapter 3 is concerned with the instrumental study of water samples and concrete test cylinders Chapter 4 focuses on the chemometric modelling abilities of water from a cross-section of treatment plants and will concentrate on a novel investigation of alternative water sources through instrumental and chemometric modelling

1.2 Concrete and its constituents

Concrete is one of the most widely used construction materials [4, 13] It is a durable and high strength material that has a low permeability Both the fresh and hardened states of concrete must fulfil the intended purpose of its use Consistency and cohesiveness are the two most important properties when concrete is in its fresh state, as they must facilitate compaction and transportation without segregation [14] When in the hardened state, it is imperative that the compressive strength of concrete lies within the required limits The compressive strength affects density, impermeability, tensile strength and chemical resistance

Concrete is a construction material that is made from cement, aggregate such as gravel and sand, water and admixtures [15, 16] It solidifies and hardens after mixing and placement due to a chemical process known as hydration In order for concrete to be manufactured, water must react with the cement, which bonds the other components together, eventually creating a stone-like material Whilst concrete is the final monolithic product, cement is a vital component and acts as the bonding material [17]

Table 1.1 - Chemical and physical composition of ordinary Portland cement

*H F W Taylor, Cement Chemistry, 2nd Ed., Academic Press, London (1997)

1.3 Cement and aggregates

Cement is a basic ingredient of concrete, mortar and plaster The most common type of hydraulic cement, Portland cement, consists of a mixture of oxides of calcium, silicon and aluminium can be seen in Table 1.1 Discovered by an English engineer Joseph Aspdin in

1824, it is manufactured primarily from limestone, clay minerals and gypsum in a high temperature process that drives off carbon dioxide and chemically combines the primary ingredients into new compounds [18, 19] Hydraulic cements harden and set after the addition of water as a result of chemical reactions with the mixing water and after hardening, retain strength and stability even under water [18-20]

Cement and water form a paste coating each particle of stone and sand The hydration reaction causes cement paste to harden and gain strength [21, 22] This reaction is vital for the properties attained in the final concrete mix, and as such, the characteristics of the concrete are determined by the quality of the paste The strength of the paste, in turn, depends on the ratio of water to cement which is measured but the weight of mixing [23-27] This is the weight of the mixing water divided by the weight of the cement High-quality concrete is produced by lowering the water-cement ratio as much as possible but always trying to retain enough water to ensure the workability of fresh concrete A higher quality concrete is produced if less water is used, provided the concrete is properly placed, consolidated, and cured

A low water-to-cement (w/c) ratio is needed to achieve strong concrete It would seem therefore that by merely keeping the cement content high, one could use enough water for good workability and still have a low w/c ratio [6, 24, 27] The problem is that cement is the most costly of the basic ingredients Thus, in order to ensure an economical and practical concrete mix, both fine and coarse aggregates are utilised to make up the bulk of the concrete mixture And as such the quality of aggregates is very important [28, 29] Fine aggregate (sand) is made up of particles which can pass through a 3/8 inch sieve whilst coarse aggregates are larger than 3/8 inch in size [28] It is however becoming common for recycled aggregates from construction, demolition and excavation waste to be used as partial replacements of natural aggregates, while a number of manufactured aggregates, including air-cooled blast furnace slag and bottom ash are also permitted [30, 31] While recycling building materials is important, the shape, size, density and strength of such aggregate particles can vary significantly, and can therefore adversely influence the properties of the concrete

Concrete is a blend of natural materials, and often has natural imperfections The performance of exterior concrete slabs is significantly influenced by the entrainment of microscopic air bubbles into the concrete [32] An air entrainment admixture causes microscopic air bubbles to form throughout the concrete that function as relief valves when water in the concrete freezes, helping to prevent surface deterioration

During hydration and hardening, concrete needs to develop certain physical and chemical properties Among other qualities, mechanical strength, low moisture permeability, and chemical and volumetric stability are necessary There are many characteristics that affect concrete and its properties, all of which depend on the specific mix being used [30]

Workability is the ability of a fresh or plastic concrete mix to fill the mould properly without reducing the concrete's quality Workability depends on water content, aggregate size, cementitious content and level of hydration, but can also be modified by adding chemical admixtures [33] Raising the water content or adding chemical admixtures will increase a concrete‟s workability Excessive water will lead to increased bleeding and/or segregation of aggregates with the resulting concrete having reduced quality The use of an aggregate with

an undesirable gradation can result in a very harsh mix design with a very low slump, which cannot be readily made more workable by addition of reasonable amounts of water [16]

Cement requires time to fully hydrate before it acquires strength and hardness, thus concrete must be cured once it has been placed Curing is the process of keeping concrete under a specific environmental condition until hydration is relatively complete [16] Good curing is usually undertaken in a moist environment with a controlled temperature This is necessary as a moist environment promotes hydration, since increased hydration lowers permeability and increases strength resulting in a higher quality material [34] Improper curing can lead to several serviceability problems including cracking, increased scaling, and reduced abrasion resistance

Compressive strength of concrete determines how much pressure concrete can withstand before cracking and weakening This compressive strength depends mainly on the properties and quality of the cement paste and the aggregate [35, 36] If the aggregate consists of a soft or weak material, the concrete will also be weak The strength of the concrete can be controlled by choosing the mix proportions provided that good quality aggregates are used and the correct manufacturing procedures are followed If not enough water was added to the mix, the cement paste remains too dry and stiff and the concrete will

be weak If too much water was added, making the cement paste too thin, the concrete will again be weak [37]

Concrete has relatively high compressive strength, but significantly lower tensile strength and as a result, concrete always fails from tensile stresses The practical implication of this is that concrete elements subjected to tensile stresses must be reinforced Concrete is most often constructed with the addition of steel or fibre reinforcement The reinforcement can be

by bars, mesh, or fibres [38]

As concrete is a liquid which hydrates to a solid, plastic shrinkage cracks can occur soon after placement; but if the evaporation rate is high, they often can occur during finishing operations Aggregate interlock and steel reinforcement in structural members often negates the effects of plastic shrinkage cracks, rendering them aesthetic in nature [38] Properly tooled control joints or saw cuts in slabs provide a plane of weakness so that cracks occur unseen inside the joint, making a more aesthetic presentation In very high strength concrete mixtures, the strength of the aggregate can be a limiting factor to the ultimate compressive strength In concretes with a high water-cement ratio the use of coarse aggregate with a round shape may reduce aggregate interlock [39, 40]

Concrete has a very low coefficient of thermal expansion However, if no provision is made for expansion very large forces can be created, causing cracks in parts of the structure not capable of withstanding the force or the repeated cycles of expansion and contraction [41]

As concrete matures it continues to shrink, due to the ongoing reaction taking place in the material, although the rate of shrinkage falls relatively quickly and keeps reducing over time The relative shrinkage and expansion of concrete and brickwork require careful accommodation when the two forms of construction interface

Since the hydration of cement is so significant, the following section examines in detail the process of hydration, explaining the reactions that occur and their influence on the final concrete product

1.3.1 Hydration reactions of cement

The formation of water-containing compounds facilitates the hardening and setting of hydraulic cements [42] The reaction and the reaction products are referred to as hydration and hydrates respectively When cement and water are mixed together, the reactions which occur are mostly exothermic An indication of the rate at which the minerals are reacting, is given by monitoring the rate at which heat is evolved using a technique called conduction calorimetry

During the process of heat evolution three principal reactions occur [6] Firstly, during hydration and hardening, concrete develops certain physical and chemical qualities including mechanical strength, low moisture permeability, and chemical and volumetric stability Each

of these characteristics effect the produced concrete however, the water to cement ratio

has the greatest effect on the quality of concrete [1, 43]

Almost immediately on adding water, some of the clinker sulphates and gypsum dissolve, producing an alkaline, sulfate-rich solution Soon after mixing, the crystals of calcium aluminate (Ca3Al2O6), hereby annotated as (C3A), reacts with the water to form an aluminate-rich gel [44] The gel reacts with sulfate in solution to form small rod-like crystals

of ettringite ((CaO)6(Al2O3)(SO3)3·32 H2O) (C3A) hydration is a strongly exothermic reaction but it does not last long, typically only a few minutes and is followed by a period of a few hours of relatively low heat evolution This is called the dormant or induction period

The first part of the dormant period corresponds to the time when it is most beneficial for the concrete to be placed As the dormant period progresses, the paste becomes too stiff to be workable At the end of the dormant period, the alite (Ca3SiO5) and belite (Ca2SiO4) in the cement start to hydrate, with the formation of calcium silicate hydrate and calcium hydroxide

During this phase, an increase of calcium hydroxide occurs as a result of hydrolysis of tricalcium silicate Equation 1.1

Equation 1.1

2Ca3SiO5 + 6H2O  3 Ca(OH)2 + Ca3Si2O7.3H2O

Thus, on the addition of water, calcium silicate rapidly reacts to release calcium ions, hydroxide ions, and a large amount of heat The pH quickly rises to over 12 because of the release of hydroxide (OH-) ions This initial hydrolysis slows down quickly after heat evolution begins to decrease The reaction slowly continues producing calcium and hydroxide ions until the system becomes saturated Once this occurs, the calcium hydroxide starts to crystallize Simultaneously, calcium silicate hydrate begins to form Ions are precipitated out of solution accelerating the reaction of tricalcium silicate to calcium and hydroxide ions This corresponds to the main period of cement hydration, during which time concrete strength increases The cement grains react from the surface inwards, and the anhydrous particles become smaller (C3A) hydration also continues, as fresh crystals

become accessible to water

The cement paste immediately stiffens and increases with time After reaching a certain level

of hardness, a second reaction takes place which promotes the immediate set of the concrete

Equation 1.2

Ca3(AlO3)2 + 6H2O  Ca6(AlO3)2.6H2O

When gypsum (CaSO4 2H2O) is added to the cement, as it is in most hydraulic cements, the hydration reaction of tricalcium aluminate is altered (Equation 1.3) The reaction of tricalcium aluminate with water forms calcium aluminate trisulphate hydrate (ettringite) Once

the system is free of gypsum, calcium aluminate monosulphate hydrate (monosulphate) forms as in Equation 1.4

1.3.2 Cement Hydration Products

The products of the reaction between cement and water are termed 'hydration products.' When concrete is manufactured using Portland cement as the cementitious material there are four main types of hydration product:

Calcium silicate hydrate: this is the main hydration product and is the main source of

concrete strength It is often abbreviated, using notation, to 'C-S-H,' the dashes indicating that no strict ratio of SiO2 to CaO is inferred The Si/Ca ratio is somewhat variable but typically approximately 0.45-0.50

Calcium hydroxide - Ca(OH)2: often abbreviated, as 'CH.' CH is formed mainly from alite

hydration Alite has a Ca/Si ratio of 3:1 and C-S-H has a Si/Ca ratio of approximately 2:1, so excess lime is available from alite hydration and this produces CH

Ettringite: Ettringite is present as rod-like crystals in the early stages of cement hydration

The chemical formula for ettringite is Ca6[Al(OH)6]2(SO4)3.26H2O

Monosulfate: Monosulfate tends to occur in the later stages of hydration, after a few days

Usually, it replaces ettringite, either fully or partly The chemical formula for monosulfate is C3A.CaSO4.12H2O Both ettringite and monosulfate are compounds of C3A, CaSO4

Al-Fe-tri (Aft) and Al-Fe-mono (AFm) phases: Ettringite is a member of a group known as

AFt phases The general definitions of these phases are somewhat technical [4, 40], but ettringite is an AFt phase because it contains three (tri) molecules of anhydrite when written

as C3A.3CaSO4.32H2O and monosulfate is an AFm phase because it contains one mono) molecule of anhydrite when written as C3A.CaSO4.12H2O[45]

(m-Important points to note about AFm and AFt phases are that:

 They contain large amounts of water, especially the AFt phases

 They contain different ratios of sulfur to aluminium

 Aluminium can be partly-replaced by iron in both AFm and AFt phases

 Sulfate ion in the AFm phases can be replaced by other anions; a one-for-one substitution if the anion is doubly-charged (e.g.: carbonate, CO2-) or one-for-two if the substituent anion is singly-charged (e.g.: hydroxyl, OH- or chloride, Cl-) The sulfate in ettringite can be replaced by carbonate or, probably, partly replaced by two hydroxyl ions [4, 40]

Monosulfate gradually replaces ettringite in many concretes because the ratio of available alumina to sulfate increases with continued cement hydration On mixing cement with water, most of the sulfate is readily available to dissolve, but much of the C3A is contained inside cement grains with no initial access to water Continued hydration gradually releases alumina and the proportion of ettringite decreases as that of monosulfate increases

If there is eventually more alumina than sulfate available, the entire sulfate will exist as monosulfate, with any additional alumina present as the hydroxyl-substituted AFm phase If there is an excess of sulfate, the cement paste will contain a mixture of monosulfate and ettringite Near the concrete surface, carbonation will release sulfate as carbonate ions replace sulfate in the ettringite and monosulfate phases

1.3.3 Admixtures

Admixtures often strengthen, speed up or slow down the setting time, and help to protect concrete against the effects of temperature changes and exposure Therefore admixtures tend to counteract any forces that negatively affect concrete [46] Often in the form of powder or fluids, admixtures are added to the concrete to give it certain characteristics not obtainable with plain concrete mixes [46] In normal use, admixture dosages are less than 5% by mass of cement, and are added to the concrete at the time of batching or mixing The most common types of admixtures are [46-48]:

 Accelerators speed up the hydration (hardening) of the concrete

 Retarders slow the hydration of concrete, and are used in large or difficult pours where partial setting before the pour is complete is undesirable

 Air-entrainers add and distribute tiny air bubbles in the concrete, which will reduce damage during freeze-thaw cycles thereby increasing the concrete's durability

 Plasticizers (water-reducing admixtures) increase the workability of plastic or "fresh" concrete, allowing it to be placed more easily, with less consolidating effort

 Superplasticisers (high-range water-reducing plasticizers) which have fewer deleterious effects when used to significantly increase workability Alternatively, plasticizers can be used to reduce the water content of a concrete (and have been

called water reducers due to this application) while maintaining workability This

improves its strength and durability characteristics

 Pigments can be used to change the colour of concrete, for aesthetics

 Corrosion inhibitors are used to minimize the corrosion of steel and steel bars in concrete

 Bonding agents are used to create a bond between old and new concrete

 Pumping aids improve pumpability, thicken the paste, and reduce thinning of the

Invaluable to concrete production, mineral admixtures are used primarily to reduce the cost

of concrete construction, to modify the properties of hardened concrete, to ensure the quality

of concrete during mixing, transporting, placing, and curing and to overcome certain emergencies during concrete operations And, in order to ensure the reliability, attributes of concrete remain constant, concrete is routinely analysed both chemically and physically Chemical analyses include extraction, as well as wet and spectrochemical methods

1.4 Water Quality, its properties and influence on concrete

In general, the increasing industrial activity and the rising cost of natural mineral resources, and forcing the ready-mixed concrete industry to review the logistics of raw materials supply

A lack of potable water, an integral constituent of concrete, has resulted in the search for possible alternatives While almost any natural water that is drinkable and has no pronounced taste or odour may be used as mixing water for concrete, the rising cost of such waters has prompted research such as this [49] However, the substitution of potable water with another source has many associated problems and risks that must be eliminated in order to ensure the quality and performance of concrete remains unchanged

The principal considerations on the quality of mixing water are those related to the effect on workability, strength and durability The suitability of waters can be identified by carrying out performance tests such as compressive strength, as well as their adherence to guidelines which set limits for certain chemical properties, including sulphate, chlorides and total dissolved solids, in order to ensure the durability of concrete

Concrete is intended to be strong, durable and resilient; a key factor that determines these properties is the water/cement (w/c) ratio This ratio describes the mass ratio of water to cement where a lower w/c ratio will yield a concrete which is stronger and more durable,

while a higher w/c ratio yields a concrete with a larger slump, so it may be placed more easily Cement paste is the material formed by combination of water and cementitious materials; that part of the concrete which is not aggregate or reinforcing [13] The workability

or consistency is affected by the water content, the amount of cement paste in the overall mix and the physical characteristics (maximum size, shape, and grading) of the aggregates Each of the valuable characteristics requires the use of water that will support not hinder the complex reactions that ensure the concrete manufacturing process is successful [13]

It is commonly thought that excessive impurities in mixing water not only may affect setting time and concrete strength, but also may cause efflorescence, staining, corrosion of reinforcement, volume instability, and reduced durability [7, 14] Thus, specifications usually set limits on chlorides, sulfates, alkalis, and solids in mixing water to ensure minimal adverse effects to the resultant concrete Currently, unless tests can be performed to determine the effect the impurity has on various properties of fresh, hardening and hardened concrete potable water must be used Previous research coupling analytical techniques to determine impurities, with chemometric methodologies to identify their relationships and influence was

used, by Shrestha and Kazama [13, 50] This research facilitated the characterisation of

impurities as well as an evaluation of water quality and offered conclusions as to its suitability for final use These water quality indicators can be categorised as:

 Biological: bacteria, algae

 Physical: temperature, turbidity and clarity, colour, salinity, suspended solids, dissolved

solids

 Chemical: pH, dissolved oxygen, biological oxygen demand, nutrients including nitrogen

and phosphorus, organic and inorganic compounds including toxicants

 Aesthetic: odours, taints, colour, floating matter

Measurements of these indicators can be used to determine and monitor changes in water quality, and determine whether the quality of the water is suitable for use in concrete production

The design of water quality monitoring programs is a complex and specialised field and as such, this study intended to incorporate as many parameters as possible The range of indicators measured throughout this research is further detailed in Chapter 2 Although drinking water is currently the only water accepted by Australian standards for use in the manufacture of concrete, some waters that are not fit for drinking may be suitable for concrete [9, 10]

The water quality information gained by research and tests such as this can then be used to develop management programs and action plans to ensure that suitable water sources are adopted

2 Methodology

2.1 Sample Guidelines

Water from various sources is often sampled and analysed in order to determine the presence of any toxic chemicals, potentially harmful pathogens, its fitness for human consumption, and as an important indicator of any environmental changes [51] The design

of water quality monitoring programs is a complex and specialised field [52] The range of indicators that can be measured is wide and other indicators may be adopted in the future The cost of a monitoring program to assess all possible contaminants is often prohibitive, so resources are usually directed towards assessing contaminants that are important for the local environment or for a specific use of the water [52] This water quality information can then be used to develop management programs and action plans to ensure that water quality is protected

Correct sampling, storage and transportation are critical to the accuracy of analysis When trying to obtain meaningful and reproducible data it is important that many key elements are undertaken to ensure that the results are accurate, precise and reliable [51] Firstly, each sample must be collected in a manner consistent with the handling and preservation principles enunciated in Standards Association of Australia (1998) AS/NZS 5667.1:1998 [53]

2.2 Sample Preparation

Sample preparation is a key procedure in modern chemical analysis By some estimates, 80% of the work activity and operating cost in an analytical lab is spent preparing samples

60-Table 2.1 - Specifications for sample preservation Analyte Container Preservative Transportation

TKN Polythene Acidify with H2SO4 Transport chilled to lab

pH, EC, Alkalinity Polythene Fill to exclude air Transport chilled to lab

BOD, COD, NH3,

NO2, NO3

Polythene Fill to exclude air Store at 1oC to 4oC

Al, As, Ba, Cd, Ca, Cr,

Co, Cu, Fe, Pb, Mg,

Mn, Ni, Se, Zn

Polythene Acidify with 1mL HNO3

to pH<2

None

2.3 Equipment and Materials

It is important to use correct containers Otherwise, the analysis may be adversely affected Whilst plastic bottles are normally sufficient for water sampling, other specific analysis types require different sample bottle types The most common type of analysis- Drinking water

analysis (DWA) requires 500 mL to 1L polyethylene container The other most common

analysis of water samples is known as extended water analysis (EWA) and also requires a

500 mL Polyethylene in addition to a 100 mL glass bottle specially preserved for mercury For testing of oil and grease and TRH (Hydrocarbons) or other organics, two separate glass bottles are required as the entire sample (500 mL) is used for each analysis Specifications and guidelines for the collection and preservation of water samples are further explained in Table 2.1 To ensure sample integrity the samples were stored in refrigerated boxes, and packed with ice whilst being transported to the laboratory for analysis

2.4 Chemical Preservatives

Once a sample is taken, some of its quality characteristics can change naturally To keep these changes to a practical minimum, certain chemicals are added as preservatives All containers used throughout this study were pre-treated with the correct preservatives ensuring the quality and integrity of all samples

2.5 Sampling Methods and Procedures

The accuracy of a water analysis is very much dependent on the sampling method used and the time elapsed between sampling and analysis Firstly it was ensured that the sampling vessels were cleaned prior to sampling by rinsing the bottle three times in the water to be sampled

The sample was then collected directly into the sample container, from the centre of the

sampling site, where the velocity is highest It was important to hold the mouth of the sampling container well above the base of the channel, to avoid picking up any settled solids As the water depth permitted, the mouth of the sample container was held approximately 10 cm below the water surface The bottle was then filled to the top with as little air as possible remaining, and sealed tightly The cap on the container was screwed tight and the details on the container label were checked All samples were properly labelled with details of the source, date of sampling, sampler‟s name and address and the intended use of the water Once the sample had been successfully taken it was placed in plastic bag that was then sealed with tape This package was then packed in sample carrier It was ensured that crushed ice surrounded the containers

When collecting the sample, great care must be taken to prevent accidental contamination of the sterile sample container and the sample itself To prevent this, these general rules were followed:

- Do not touch the neck of the container, or the inside of the cap or stopper

- Do not sneeze or cough into or over the sample container, or near the sampling point

- Keep the container capped until immediately before filling Once it is opened, avoid breathing over it, for example turn your head or hold the container at arm’s length, moving it upwards and away from yourself while sampling

- Do not allow sample to become contaminated by any dirt or other foreign matter near the sampling point; if practicable, remove it before collecting the sample

- If sampling from a body of water which has enough depth to immerse the sterile container, hold the container by the sides and keep it nearly upright as you lower it into the water

Documentation accompanied these samples as specified in Standards Association of Australia (1998) AS/NZS 5667.1:1998, and APHA (1998) section 1060 [9, 54] Samples were also analysed within the maximum holding times specified

2.6 Preparation of Concrete Cylinders

Values obtained through compressive strength tests are often affected by the size and shape of the specimen, batching, mixing procedures, the methods of sampling, molding,fabrication technique, sample age, temperature and moisture conditions during curing [55] Thus there are specific protocols that should be followed to ensure each cylinder

is cured and tested following established Australian Association of Standards (AS1012.14 1991) and ASTM C93108 procedures [56, 57]

-In order to properly prepare concrete cylinders for compressive strength testing it is important to follow some critical procedures Firstly, it is necessary to use molds that conform to both the AS and ASTM Standards [56, 57] These molds come in a variety of shapes and sizes depending on the testing regime being used Once the appropriate mold is chosen, in this case 150mm, a standard rod or vibrator is used to consolidate the concrete, which ensures no layers form The completed cylinders are then initially cured at the jobsite for the first 48 hours They are then transported back to an accredited laboratory and immersed in water which is maintained at a temperature of 27°C After this initial curing the cylinders are demolded and placed into another curing tank in accordance with ASTM C91308 The mass of the cylinder and cylinder diameter are also recorded at this stage

Once the cylinders reach the appropriate age, in this case 7 and 28 days, they are then submitted for compressive strength testing

2.7 Instrumental Analysis

Water samples are often analysed in a laboratory to gain important information Chemical or biological composition can adversely affect crops, soils, humans, animals, or equipment The accuracy of a water analysis is very much dependent on the sampling method used, as well

as the subsequent calibration and validation of all instruments and results Thus, measurements of specific indicators can be used to monitor changes in, water quality, and determine whether the quality of the water is suitable for its intended use

It is imperative to rely on testing fundamental properties of concrete in both its fresh and hardened state In order to successfully achieve this, concrete is typically sampled whilst it is being poured, and testing protocols require that samples be cured under laboratory conditions ensuring the reliability and consistency of results The hardened compressive strength as well as the durability of concrete and its slump, often referred to as workability, all affect the overall quality of the hardened concrete, standard concrete tests measure the plastic properties of concrete prior to and during placement

For most analyses (High Performance Liquid Chromatography, Gas Chromatography, spectrophometery, etc.), the sample must be properly prepared in solution for subsequent analysis [58, 59] Other analytical techniques require different sample preparation such as drying and or sieving and each method is equally important when trying to ensure that the accuracy and precision are fit for purpose

In general, calibration is an operation that relates a dependant variable to an independent variable for measuring a system under given conditions Calibration includes the selection of the model (its functional form), the estimation of model parameters as well as the errors, and the validation and verification of the model

2.8 Instrumentation used for the analysis of water samples

2.8.1 Measurement of pH

pH is a measure of the acidity or alkalinity of a solution Solutions with a pH less than seven are considered acidic, while those with a pH greater than seven are considered basic (alkaline) pH 7 is considered neutral because it is the pH of pure water at 25 °C pH is formally dependent upon the activity of hydrogen ions (H+), but for very pure dilute solutions, the molarity may be used as a substitute with some sacrifice of accuracy [60] The pH reading of a solution is usually obtained by comparing unknown solutions to those of known

pH, and there are several ways of doing this

2.8.1.1 Apparatus

The pH was measured using a pH meter A pH meter consists of a potentiometer connected electrically to two electrodes, called indicator and reference electrodes [59] The indicator electrode contains a membrane of special glass separating two liquids: one is a solution of known pH, the other the test solution, of unknown pH The solution of known pH is in contact with an electrolyte containing AgCl crystals while the reference electrode usually contains a saturated solution of potassium chloride (KCl)

With the use of a voltmeter, a voltage difference was produced across the membrane, proportional to the pH difference of the two liquids This voltage was read using a voltmeter with high input impedance The e.m.f of the glass/reference electrode cell was measured with the use of a 5.5 digit voltmeter, thus sensitivity was high, at + 0.001 pH units

2.8.1.2 Procedure

After both the buffer solution and the water sample were brought to the same temperature (25oC), the temperature of the sample was then measured and recorded so that the temperature compensation control on the pH meter could be set The electrode was then rinsed and immersed in the sample When the e.m.f reading stabilised a reading was taken

2.8.2 Measurement of Relative Alkalinity

Acidity and alkalinity measurements are used to assist in establishing levels of chemical treatment to control scale, corrosion, and other adverse chemical equilibria In all of these test methods the hydrogen or hydroxyl ions present in water by virtue of the dissociation or hydrolysis of its solutes, or both, are neutralized by titration with standard acid (alkalinity)

2.8.2.1 Apparatus

In order to determine the relative alkalinity of the water samples using titration, it is necessary to have a burette, volumetric pipette, graduated cylinder, digital balance and Sulfuric acid titrant

2.8.2.2 Procedure

Once the samples were correctly filtered and the pH system calibrated the electrodes, sensors, beaker, stir bar, delivery tube were washed with deionized water Then, a clean dry

burette was filled with 0.01639N sulfuric acid titrant and the selected volume of sample was

transferred to a clean beaker Then using a magnetic stirrer the sample is made homogenous Next, the pH and temperature sensors were rinsed with deionized water Once the sensor has been inserted into the beaker, measurement of the initial pH and temperature was conducted

Once this has been completed titration can begin While stirring the sample slowly and continuously the pH is measured after each addition of titrant, ensuring that 15 to 20 seconds after each addition is allowed for equilibration, before recording the pH The titrant was cautiously added drop by drop in 0.01 mL increments

It was then necessary to use the following equations to calculate alkalinity and carbonate

species from inflection points with 0.01639N sulfuric acid:

Alkalinity (mg/L as CaCO 3 ) = 1000/mLs ´ (0.8202 ´ mLa) ´ CF

2.8.3 Measurement of Electrical Conductivity

Electrical conductivity of water is used as an indicator of its salinity and its concentration of dissolved salts Conductivity of a solution is found by measuring the resistance of the solution inside a cell of known dimensions That is, a water samples ability to conduct an electric current when an electrical potential difference is placed across a conductor is measured It is the movement of the charges that gives rise to an electric current which is then recorded The conductivity is defined as the ratio of the current density to the electric field strength

2.8.3.1 Apparatus

Electrical Conductivity of the water samples was determined using a sensor consisting of two metal electrodes which protrude into the water A constant voltage (V) is applied across the electrodes An electrical current (I) flows through the water due to this voltage and is proportional to the concentration of dissolved ions in the water The more conductive the water is, the higher the electrical current reported which is measured electronically The measuring system used controlled the voltage, frequency and current density so as to minimize errors due to electrode polarization and capacitance

2.8.3.2 Procedure

Before measurement could begin calibration was undertake To do this, the standard solution at (25oC) was poured into two containers the electrodes were rinsed with deionised water and immersed in the calibration solution of known conductivity The electrode was then removed and rinsed with deionised water and placed into the sample 1 minute Once the voltage meter had stabilised a measurement was recorded

2.8.4 Measurement of Total Dissolved Solids

The two principal methods of measuring total dissolved solids are gravimetry and electrical conductivity Gravimetric methods are the most accurate and involve evaporating the liquid solvent to leave a residue which can subsequently be weighed with a precision analytical balance (normally capable of 0001 gram accuracy) [61] This method is generally the best, and was utilised for this study

2.8.4.1 Apparatus

The process of Gravimetry requires the drying and filtration of the water sample For this analytical balances were used The analytical balance is the most accurate and precise instrument in an environmental laboratory Objects of up to 100 grams may be weighed to 6 significant figures Volumetric glassware was also used and is accurate to no more than 4 significant figures

2.8.4.2 Procedure

Each sample of water contained both dissolved and suspended solids and was therefore treated using both filtration and evaporation First, the sample was dried to a constant, reproducible weight by drying in a 103° C to 110° C oven for 1 hour and allowed to cool to room temperature in a desiccator It was then weighed, and heated again for about 30

minutes The sample was cooled and weighed a second time The procedure was repeated until successive weights agreed to within 0.3 mg This weight was then recorded

2.8.5 Measurement of Chloride

To detect chloride ions present, Ion-exchange chromatography is employed Here retention

is based on the attraction between solute ions and charged sites bound to the stationary phase Ions of the same charge are excluded Some types of Ion Exchangers include: (1) Polystyrene resins- allows cross linkage which increases the stability of the chain Higher cross linkage reduces swerving, which increases the equilibration time and ultimately improves selectivity (2) Cellulose and dextran ion exchangers (gels)-These possess larger pore sizes and low charge densities making them suitable for protein separation (3) Controlled-pore glass or porous silica In general, ion exchangers favour the binding of ions

of higher charge and smaller radius

2.8.5.1 Apparatus

Class A volumetric flasks were used It was necessary to have an Ion chromatograph, with

an auto sampler In this case a Dionex AS50 (AS-50) Autosampler was used Class A volumetric pipettes, and Vials, were also used Certified anion standard reference solution, containing 100-ppm chloride and sulfate was used as the reagent Deionized or distilled water, and Sodium bicarbonate eluent concentration, were also required for the ion chromatograph

2.8.5.2 Procedure

First, 50 ml of the filtered sample was transferred into a 500 ml volumetric flask and diluted

to the mark then shaken to ensure a homogenous mixture Next, the ion chromatograph was

were poured into properly labelled sample vials Then, one prepared standard and one deionized water blank were run after every four to five samples to check the accuracy of the chromatograph The samples were analysed using the ion chromatograph to determine the concentration of the chloride ions

2.8.6 Compressive strength Analysis of concrete samples

In most cases the type of construction initially chosen will have sufficient design and material strength data available to satisfy one that the method and type of construction chosen is suitable for the structure to be built Material testing and practice plays a vital part to the integrity of the material and the satisfaction of all parties concerned in the production of concrete In order to successfully achieve this, concrete is typically sampled whilst being placed, and testing protocols require that samples be cured under laboratory conditions ensuring the reliability and consistency of results

Figure 2.1 Testing Apparatus used to determine Compressive Strength

The hardened compressive strength affects the overall quality of hardened concrete [10] The compressive strength is measured by breaking cylindrical concrete specimens in a compression testing machine [36, 62]