Construction materials and structures proceedings (pg 1 224)

El-Maaddawy and Omar Al-Rawashdah Static and dynamic testing of RC-slabs with high strength concrete overlay 980 Norbert Randl and Csaba Simon xix Construction Materials and Structures :

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CONSTRUCTION MATERIALS AND STRUCTURES

Construction Materials and Structures : Proceedings of the First International Conference on Construction Materials and Structures,

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edited by S.O Ekolu, et al., IOS Press, 2014 ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/hustvn-ebooks/detail.action?docID=1920292 Created from hustvn-ebooks on 2017-09-05 00:45:13.

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or transmitted, in any form or by any means, without prior written permission from the publisher

Distributor in the USA and Canada

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4502 Rachael Manor Drive

The publisher is not responsible for the use which might be made of the following information

PRINTED IN THE NETHERLANDS

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Preface

The first International Conference on Construction Materials and Structures (ICCMATS2014) was held in Johannesburg, South Africa from 24–26 November 2014 The event was locally considered to be a major onset for promotion and stimulation of research and engineering applications in the fields of materials and their structural im-plications on physical infrastructure The core value of the conference was embedded

on science and engineering as a necessary vehicle for addressing infrastructure needs and related modern socio-economic concerns, of the global community The event also served to strengthen existing relationships and to establish new directions between South Africa as a country and research leader in the African continent, and other coun-tries within and outside the continent including Europe, China, North America, to men-tion but a few

The Proceedings of this conference contain about two hundred peer-reviewed papers from fifty-one countries, making this a truly international event They include ten keynote speeches by some of the leading academics, researchers and international experts from Canada, USA, Turkey, United Kingdom, Uganda, New Zealand, South Africa, Qatar, and Japan

The geographical location and timing of this event demanded special consideration

on issues of developing countries where the severe lack of a critical mass of academics, research scientists and engineers undermines efforts to attain sustainable development

In developing countries, the fast population growth promotes rapid urbanization; ing in high poverty and mortality, aggravation of poor housing conditions, dispropor-tionately high energy demands and environmental degradation due to human activity, among other social ills Besides these negative issues, most of these countries are on a significant economic growth trajectory, but remain in dire need for impactful and sus-tainable physical infrastructure In an attempt to confront these concerns, the Interna-tional Conference on Construction Materials and Structures was organized to bring together international experts from several countries to discuss scientific research and share advances in technology Against this backdrop, ICCMATS 2014 was used as a platform for sharing of cutting-edge theories, techniques and scientific advances by some of the foremost scientists and researchers worldwide The event provided insights for addressing issues of modern local infrastructure, and inspired future advancements, innovations and emerging researchers

result-Consistent with the technical focus of the conference, high quality papers

present-ed in these Procepresent-edings coverpresent-ed a range of fields, categorizpresent-ed into nine (9) sub-topics and five (5) main themes viz materials and characterization, durability of construction materials, structural implications and service life, sustainability and the environment, building science and construction All the papers that were submitted for ICCMATS

2014 were fully peer-reviewed, a task undertaken by the International Scientific mittee (ISC) The acceptance of the papers for publishing in these Proceedings was based on the recommendations provided in the reviewer reports Sincere gratitude is due to the individual members of the ISC and all reviewers for their important contri-bution of ensuring the high quality of these Proceedings

Com-Construction Materials and Structures

S.O Ekolu et al (Eds.)

IOS Press, 2014

v

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The following organizations are gratefully acknowledged for their significant nancial and technical support to the conference: The National Research Foundation of South Africa, Council of Geoscience (South Africa), Concrete Society of Southern Africa, Johannesburg Convention Bureau, The American Concrete Institute and RILEM

fi-On behalf of the Organising Committee, the Editors of the Proceedings wish to tend special thanks to all authors for the technical contribution of their high quality research, expertise and knowledge through these Proceedings In addition, the dilem-mas of resource planning for participation in the conference, placed high demands on the authors; for which collective applause is in order for all authors who participated in the event

ex-Finally, thanks are due to all members of the Conference Organizing Committee, the Conference Secretarial team, the Dean of the Faculty of Engineering and the Built Environment at the University of Johannesburg (UJ), academic and technical staff of the UJ Department of Civil Engineering Science, partners from Harbin Institute of Technology, research students and all those who contributed to the running and success

of the event It was a rewarding programme to all those involved, not excluding the wider scientific community In that regard, this event’s continuity into the future is anticipated

Editors: Stephen O Ekolu Morgan Dundu Xiaojian Gao vi

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ICCMATS 2014 Committees Organizing Committee

Prof Morgan Dundu (Co-Chair)

University of Johannesburg

Dr Stephen O Ekolu (Co-Chair/Coordinator)

University of Johannesburg

Prof Xiaojian Gao

Harbin Institute of Technology (Co-Chair)

The Advanced Cement Institute

Local Advisory Committee

Engr Balu Tabaaro

University of Johannesburg, South Africa

Mnr Pierre van Tonder

Mnr Bruce Raath

B.A Raath and Associates Johannesburg, South Africa

vii

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International Scientific Committee

Prof Hakim Abdelgader

Tripoli University, Libya

Dr Hamid Akbarazadeh

McGill University, Canada

Prof Mark Alexander

University of Cape Town, South Africa

Prof Henry Alinaitwe

Makerere University, Uganda

Dr Janis Anderson

University of Latvia, Latvia

Prof Nicolae Angelescu

Valahia University, Romania

Prof Abdul Awal

University of Technology, Malaysia

Prof Hans Beushausen

Prof Billy Boshoff

University of Stellenbosch, South Africa

Dr Souleymane Diop

Council of Geoscience, South Africa

Dr Sydney du Plessis

Prof Amr S El-Dieb

United Arab Emirates University, United Arab Emirates

Prof George Fanourakis

Prof David W Fowler

The University of Texas at Austin, United States of America

Prof Suresh B Gholse

Nagpur University, India

Prof Douglas Hooton

University of Toronto, Canada

Prof Kei-chi Imamoto

Tokyo University of Science, Japan

Dr Maria Kaszynska

University of Szczecinie, Poland

Prof Agnieszka J Klemm

Caledonian University, United Kingdom

viii

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Prof M Iqbal Khan

King Saud University, Saudi Arabia

ICECON Res Inst for Construction Equipment, Romania

Prof Wassim Raphael

Saint-Joseph University, Lebanon

Prof Ali Rizwan

National University of Science and Technology, Pakistan

Prof Marios Soutsos

Queen’s University, United Kingdom

Dr Shaikh Faiz Uddin Ahmed

Curtin University of Technology, Australia

Dr Celeste B Viljoen

University of Stellenbosch, South Africa

Prof Keijin Wang

Iowa State University, United States of America

Prof Nadia Fahim Youssef

Housing & Building National Research Center, Egypt

Prof Yamei Zhang

Southeast University, China

Prof Alphose Zingoni

ix

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Contents

Preface v Stephen O Ekolu, Morgan Dundu and Xiaojian Gao

Kejin Wang and Gilson R Lomboy

Low-damage earthquake-resistant structures achieved through movability

Nawawi Chouw

Severe plastic deformation as a new processing for enhancing the performance

Hiroyuki Miyamoto, Rifai Muhammad and Hiroshi Fujiwara

Optimizing coefficient of thermal expansion of concrete and its importance

Md Sarwar Siddiqui and David W Fowler

Superabsorbent polymers in cementitious composites with fly ash cements –

Agnieszka J Klemm, Karol S Sikora and David E Wiggins

Steel hysteretic damper featuring displacement dependent hardening

Murat Dicleli and Ali Salem Milani

Failure of structure in East Africa with focus on the causes of failures

Henry Mwanaki Alinaitwe and Stephen Ekolu

Caijun Shi, Zemei Wu, Dehui Wang and Linmei Wu

Green road construction using discarded materials: a holistic overview

Ramzi Taha

xi

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1 Materials and characterisation

Cementitious materials and concrete

Structural and mechanical characterization of high alumina additivated

Nicolae Angelescu, Cristina Stancu and Vasile Bratu

Investigation on the suitability of borrow pit sand as fine aggregate

Amadou Adamou and Munachi U Nnebe

H.S Abdelgader, A.M Othman, A.S El-Baden and N Angelescu

Reuse of non-metallic residues from aluminium recycling industry

Diana Bajare, Girts Bumanis, Aleksandrs Korjakins and Laura Sele

Study of properties of steel fiber reinforced concrete for possible applications

Asad-ur-Rehman Khan and Tatheer Zahra

Dina M Sadek, Sh.K Amin and N.F Youssef

Estimation of concrete properties at early age by thermal stress device 162

Sang Lyul Cha and Jin Keun Kim

Effects of recycled aggregates on the properties of fresh and hardened

concrete 168 B.N Makhathini, A Dawneerangen and A.T Shohniwa

An examination of natural pozzolans in Uganda for low-strength

Dans N Naturinda and Anthony G Kerali

Mechanical properties and microscopic structure of cement based materials

Xiqiang Lin, Zhongnan Song, Tao Zhang and Liang Huo

Experimental research on mechanical properties of engineered cementitious

composites 189 Guoyou Li, Liang Huo, Tao Zhang and Hang Yao

Study on drying shrinkage cracking characteristics of steel chip reinforced

Sunhee Hong, Shinya Kimura, Yuichi Sato and Yoshio Kaneko

The effect of steel and polypropylene fibres in the mechanical properties

S.P Yap, Ubagaram Johnson Alengaram and Mohd Zamin Jumaat

Utilization of ceramic wastes as replacement of portland cements 208

Viviana Rahhal, Edgardo Irassar, Cristina Castellano, Zbyšek Pavlík

and Robert Černý

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Rheology of portland cement pastes with siliceous mineral additions 214 Viviana Rahhal, César Pedrajas, Edgardo Irassar and Rafael Talero

Cement calorimetry with different condition of calcium sulfate and water

Horacio Donza and Viviana Rahhal

Foam concrete landfill use in landslide hazardous area in West Şırnak Road 226 Yıldırım İ Tosun

Pozzolans as a binder for affordable building materials in Uganda 232 William Balu-Tabaaro

Effect of temperature on rheological performances of fresh SCC mixture 240 Huan Ye, Xiaojian Gao and Hui Wang

Assessing the effect of procurement source of scoria rocks on the pozzolanic

Galal Fares, A Alhozaimy, A Al-Negheimish and Omer A Alawad

Potential South African standard sand for cement mortar testing and research 253 Stephen O Ekolu

A study of thermal conductivity of wood ash blended cement mortar 261 Akeem Ayinde Raheem, Ibrahim Akinyemi Akinteye and Saheed A Lasisi

Behavior of high-volume fly ash concrete in mass concrete applications 268 Anton K Schindler and Kevin P Keith

Microstructure and durability characteristics of self-curing concrete 276 Amr S El-Dieb, Tamer A El-Maaddawy and Abdelrahman Al-Sallamin

Emem-Obong Emmanuel Agbenyeku and Felix Ndubisi Okonta

Ultrasonic pulse velocity used to predict the compressive strength of structural

J Alexandre Bogas, M Glória Gomes, Sofia Real and Jorge Pontes

Influence of different grinding types on granulometry of recycled glass 305 Karel Dvořák, Marcela Fridrichová and Petr Dobrovolný

Material properties of bottom ash and welding slag as fine aggregates

Karthikeyan Jayakumar and Ananthi Arunachalam

The use of waste materials for the production of an hydraulic mortar based

Bartolomeo Megna, Laura Ercoli and Giovanni Rizzo

Effects of polycarboxylate-based superplasticizer on rheological

Samer Al-Martini, Omar F Najim and Waddah Al Hawat

Influence of a new viscosity modifying admixture on the performance

Stephen O Ekolu and Jean-Bosco Kazurikanyo

xiii

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Effect of microfines mineral admixtures on rheology of blended cement paste 339

Maulik M Panseriya, U.V Dave and A.K Tiwari

Research on a novel technology of FRP bonded to concrete substrate without

adhesive 347 Ming Li, Yunpeng Liu, Muyu Liu and Fazhou Wang

Riaan Combrinck and William Peter Boshoff

Initial study to determine the tensile material properties of fresh concrete 362

Jan Diederick Dippenaar, Riaan Combrinck and William Peter Boshoff

Blended cements based on C&DW: its influence in the pozzolanicity 370

E Asensio, C Medina, M.I Sánchez de Rojas and M Frías

Use of crushed brick aggregate in structural concrete: properties

Sunanda Paul and Gopinandan Dey

Syed Ali Rizwan, Qamar uz Zaman and Thomas A Bier

Sibusiso Hlatshwayo and Reinhold Amtsbüchler

An investigation into the use of Piliostigma Thonningii Pod Ash as an admixture

Suleiman Mannir

Material selection and mix design of radiation shielding concrete 404

Stephen Ekolu and Mokgobi A Ramushu

J Alexandre Bogas, M Glória Gomes, Sofia Real and Jorge Pontes

Effect of partial replacement of sand in concrete with steel-file particles 420

Musibau Ajibade Salau, Kolawole Adisa Olonade

and Oyesola Sunday Ajiboye

Mechanical properties of green concrete with Palm Nut Shell as low cost

aggregate 427 Emem-Obong Emmanuel Agbenyeku and Felix Ndubisi Okonta

M Iqbal Khan and Shehab Mourad

The effect of different PPC binders, partially replaced by fly ash properties,

Omar Almuwbber, Rainer Haldenwang and Irina Masalova

Lowering the embodied CO2 by using fly ash concrete internally cured

Mohammed S Meddah, T Nukushina, S Seiki and R Sato

xiv

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Geopolymers and polymers

Polyfurfuryl alcohol – a waste from sugarcane bagasse as a construction

material 461 Rakesh Kumar

Cyril Attwell

Development of geopolymer mortar using palm oil fuel ash-blast furnace

Azizul Islam, U Johnson Alengaram, Mohd Zamin Jumaat

and Iftekhair Ibnul Bashar

The development of sustainable geopolymer mortar from fly ash-palm oil

Iftekhair Ibnul Bashar, Ubagaram Johnson Alengaram,

Mohd Zamin Jumaat and Azizul Islam

Amr S El-Dieb and Ehab E Shehab

Engineering properties of Class-F fly ash-based geopolymer concrete 495

M Albitar, P Visintin and M.S Mohamed Ali

M Albitar, M.S Mohamed Ali and P Visintin

Steel-slag and activators ratio impacts on the shrinkage of alkaline activated

Moruf O Yusuf, Megat A.M Johari, Zainal A Ahmad and M Maslehuddin

Use of self-compacting geopolymer concrete in a precast environment –

Warren McKenzie

EVA/intumescent agent flame retardant composite materials using

Ji-Won Park, Jung-Hun Lee, Hee-Chun Choi, Hyun-Joong Kim,

Hyun-Min Jang and Jung-Yun Choi

Evolution in physical modeling of structural built-up in polymer concrete

Dionys Van Gemert

Natural fibre reinforced polymer-concrete composite for future bridge

Libo Yan and Nawawi Chouw

Bituminous materials and pavements

Road conditions and engineering performance of subgrade soils in part

N.O Adebisi, S.A Adeniji and F.O Akintayo

xv

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The application of polymer coated aggregates in flexible pavement 560

Reshma Rughooputh and Najeeb Ahmad Fokeerbux

Use of waste plastics and scrap rubber tyre in the wearing course

Reshma Rughooputh and Nishley Ravikesh Gunesh

Influence of curing time and compaction on black cotton soil stabilized

A Maneli, W.K Kupolati, J.M Ndambuki and O.S Abiola

Marta Wasilewska

Response modelling of recycled concrete and masonry in pavements 587

F Barisanga, C Rudman and K Jenkins

Nura Usman

Effect of different additives on fatigue behavior of asphalt mixtures 601

Amin Daghighi and Ali Nahvi

Characterization of lateritic soils/gravels for their suitability as a pavement

D.R Biswal, S.R Dash and U.C Sahoo

Proposing a realistic frequency for fatigue tests using Artificial Neural

Network 613 Ali Khodaii and Attila Hassanzadeh Zonouzy

Polymer modified bitumen asphalt, a proposed solution for UAE pavement

deterioration 620 Reem Sabouni and Ahmed Al-Ghazali

Investigating the packing condition of porous asphalt mixture using Discrete

Mengjia Chen and Yiik Diew Wong

Comparison of in-situ and lab-measured void contents for a bituminous

Lewis Kabwe Kizyalla and Stephen Ekolu

Brick and block masonry

xvi

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Physical, chemical and pozzolanic properties of bricks of X-X zone

İnci Güldoğan, Yücel Güney and Erol Mehmet Altinsapan

Cement stabilization of laterite-quarry dust mixture for interlocking brick

production 676 Amana Ocholi and Manasseh Joel

Effect of wetting and air curing durations on strength of stabilized

sands 683 Lerato J Moatlhodi and Felix N Okonta

Material science and nanotechnology

Phase transitions and microstructural characterization of martensite in copper

O Adiguzel

Afshan Naz, Syed Ali Rizwan, Naveed Z Ali, Thomas A Bier

and Hameed Ullah

Influence of the characteristic of input materials on formation and properties

Vit Cerny and Rostislav Drochytka

Thin spray rock liners with different concentrations of nanoclays 709

P van Tonder and C.J Booysen

Effects of multi-walled carbon nanotubes on strength and interfacial

P Van Tonder and T.T Mafokoane

Molecular dynamics research of triple junctions structure of tilt

Gennady Poletaev, Darya Dmitrienko, Vadim Diabdenkov,

Vladimir Mikrukov and Mikhail Starostenkov

Analysis of elongation variance of tendons using stress-strain graphs 734

Morgan Dundu and Sebastian Rupieper

2 Durability of construction materials

Performance of corrosion inhibiting admixtures in a marine environment 749

Ian N Robertson

Stephen O Ekolu

xvii

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Effects of sulphuric acid on the compressive strength of blended

Kolawole Adisa Olonade, Akinropo Musiliu Olajumoke,

Ayoade Oluwaseun Omotosho and Funso Ayobami Oyekunle

Properties of self-consolidating concrete containing limestone filler 772

Daman Panesar and Mohammad Aqel

Evaluation of sulphate attack on concrete incorporating high volume palm oil

I.A Shehu, A.S.M.A Awal, S Mohammad and A Sulaiman

Stephen O Ekolu and Adam Ngwenya

Sulphate resistance of concrete made with moderately high alumina slag 797

Stephen O Ekolu and Adam Ngwenya

Stephen Ekolu

Comparison of moisture equilibrium of cement-based materials in presence

M Seaidpour and L Wadsö

Chloride penetration into concrete with compressive load-induced cracks 819

M.Y Balqis, H.M Jonkers and E Schlangen

Indicative tests on the effect of fly ash-β cyclodextrin composite on mortar

B.D Ikotun, G.C Fanourakis and S Mishra

Durability of mortars and concretes containing scoria-based blended cements 835

Aref Mohammad Alswaidani and Samira Dib Aliyan

Effect of surface treatments on abrasion and permeation properties of clay

concretes 848 Fitsum Solomon and Stephen Ekolu

3 Structural implications, performance and service life

Reinforced concrete and structural composites

Impact of environmental exposure on concrete strength in highway bridges

Hilary Bakamwesiga, Jackson Mwakali, Stephen Sengendo

and Sven Thelandersson

Strength and behaviour of steel fibre reinforced self-compacting rubberised

Bharati Raj, N Ganesan and A.P Shashikala

Effects of pit-sand on shear capacity of reinforced concrete space framed

Lekan Makanju Olanitori and Joseph Olaseinde Afolayan

xviii

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An experimental study on acoustic emission of a notched three point

Zohra Dahou and Abdelkhalek Benmiloud

G.M Bukasa and M Dundu

Infrared thermography as a diagnostic tool for subsurface assessments

Matthew Scott and Deon Kruger

The stress-related material damping of rigid frame bridge with corrugated

Liu Baodong, Li Weilong, Li Pengfei and Lv Wenjuan

Evaluating concrete with high-performance steel fibers using double-punch

testing 917 Aaron P Woods, Richard Klingner, James Jirsa, Shih-Ho Chao,

Netra Karki and Oguzhan Bayrak

Relationship between the wide-flange steel and the long-term deformation

Gyeong-Hee An and Jin-Keun Kim

Experimental bond behaviour between textile reinforced cement

and concrete: Review of the existing test methods and the analysis

Maciej Wozniak, Tine Tysmans, John Vantomme and Sven De Sutter

Relation between crack width and corrosion degree in elements of concrete

Oscar A Cabrera, Néstor F Ortega, Luis P Traversa and Horacio Donza

Investigation of prestressed hollow core concrete slabs at elevated

temperatures 946 Ehab Ellobody

Behaviour of reinforced concrete slabs strengthened by concrete overlays 956

Wael Ibrahim, Mohamed El-adawy and Gouda Ghanem

Study on the mechanical property recovery of concrete subjected to elevated

temperatures 963 Qingtao Li, Guanglin Yuan and Qianjin Shu

Shear behavior of ultra-high-strength steel fiber-reinforced self-compacting

Amr S El-Dieb, Tamer A El-Maaddawy and Omar Al-Rawashdah

Static and dynamic testing of RC-slabs with high strength concrete overlay 980

Norbert Randl and Csaba Simon

xix

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Effect of the loading condition on the restoring force characteristics

Wenjun Gao, Hisanori Otsuka and Yukihide Kajita

A study on behavior of reinforced concrete columns subjected to axial

compression 998 P.K Gupta and V.K Verma

Parametric study of non-uniform thickness rectangular concrete filled steel

P.K Gupta and S.K Katariya

Load-deflection curve prediction of RC beams strengthened by externally

Asad-ur-Rehman Khan and Fawwad Masood

New investigations of butt-jointed precast and in-situ concrete columns 1022

Daniel Wolff, Manuel Koob, Markus Blatt and Jens Minnert

Innovative structural frame using composite precast concrete components,

Won-Kee Hong, Chaeyeon Lim, Joongsoo Park and Sunkuk Kim

Flexural behavior of RC Beams with local steel – experimental investigation 1038

Shehab Mourad, Abdelhamid Charif and M Iqbal Khan

Experimental study of time dependent bond transfer length under pure

Behnam Vakhshouri and Felix Shami Nejadi

Willem F van Ede and Stephen Ekolu

Understanding the influence of marine microclimates on the durability

Olukayode O Alao, Mark Alexander and Hans Beushausen

Yoosuf Essopjee and Morgan Dundu

Flexural failure modes of steel plate-strengthened reinforced concrete

elements 1074 Akinropo Musiliu Olajumoke and Morgan Dundu

Methods for flexural strengthening of reinforced concrete elements using

Akinropo Musiliu Olajumoke and Morgan Dundu

Structural steel and other metals

Behaviour and design of a double track open timber floor plate girder

Ehab Ellobody

xx

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Kinetic study of steel emissivity and its effect on steel behaviour under fire

condition 1100 Han Fang, Man Biu Wong and Yu Bai

Low cycle fatigue performance of integral bridge steel H-piles subjected

Murat Dicleli and Semih Erhan

Buckling behavior of 6082-T6 aluminum alloy columns with box-section

Ximei Zhai, Lijuan Sun and Yuanzheng Zhao

Anthony F Gee and Primus V Mtenga

A critical review on current and proposed structural fire engineering codes

Richard Walls, Celeste Viljoen, Hennie De Clercq and Johan Retief

Factors that influence friction in tendons of unbonded post-tensioning

systems 1141 Morgan Dundu and Michelle Ward

Morgan Dundu and Vongani Chabalala

Structural masonry and timber

Nebojša Mojsilović

Per-Anders Daerga, Ulf Arne Girhammar and Bo Källsner

Sheathing-to-framing fasteners in light wood-framed buildings as finite

Michał Baszeń and Czesław Miedziałowski

Repair of masonry arch bridges with respect to longitudinal cracking

Tríona Byrne and Dermot O’Dwyer

The conservation state of the wooden roof of the National Museum

Bartolomeo Megna and Giovanni Liotta

Modelling, simulation and computation

Macro vs mesoscale modelling of fracture in concrete beams: size effect

N Aissaoui, S Ghezali and M Matallah

Ilmir Valiakhmetov

xxi

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Analysis of hopper eccentricity effect on granular flow in three-dimensional

M Benyamine, N Fezzioui, O Hami, M Djermane and A Slimani

A constitutive model for shape memory alloys, visualizing internal

Seyed Amirodin Sadrnejad

Brittle material damage pro-elasticity model for rock made structures 1233

Seyed Amirodin Sadrnejad

Target column overdesign factor of steel frames considering system

reliability 1242 Yan-Gang Zhao, Zhao-Hui Lu and Mohammad Sharfuddin

Effect of shear wall in improving the reliability of RC frame buildings

Mohamed A Dahesh, Ahmet Tuken and Nadeem A Siddiqui

Prediction on short-term burst pressure of plastic pipe reinforced

Xiangpeng Luo, Jinyang Zheng, Ping Xu, Weican Guo and Jianfeng Shi

Neural network model for predicting deterioration of bridge components

Md Saeed Hasan, Sujeeva Setunge and David W Law

Information-based formulation of a creep model using a new experimental

database 1274 Wassim Raphael, Laurent Touma and Alaa Chateauneuf

Testing and nonlinear numerical modelling of fibre pull-out mechanism

Faisal Abdulle and Robert Xiao

Parameter identification for supports and cracks in beams with non-classical

Ljubov Feklistova and Helle Hein

Ashok Kumar Ahuja and Ritu Raj

Evaluation of the scale effect for the tensile strength of aligned flax

Jānis Andersons

Flexural behavior of RC beams with local steel: analytical investigation 1317

Abdelhamid Charif, Shehab Mourad and M Iqbal Khan

Simplified torsional strength of reinforced and prestressed concrete beams 1325

Khaldoun N Rahal

Effect of clay-concrete lining on canal seepage towards the drainage

Fitsum Solomon and Stephen Ekolu

xxii

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4 Sustainability, waste utilization and the environment

Achieving building sustainability using sustainable building envelope 1345

Joseph Iwaro and Abrahams Mwasha

Amir B Meibodi and H Kew

Ines Othmen, Philippe Poullain and Nordine Leklou

Foam concrete production with şırnak mine waste claystone and fly ash 1364

Yıldırım İ Tosun

Michiel Haas

Joaquín Díaz, Laura Álvarez Antón and Kareem Tarek Anis

Compressive strength and durability of fly ash stabilized dolomitic waste

Ikechukwu F Aneke and Felix N Okonta

Lerato J Moatlhodi and Felix N Okonta

Salim Barbhuiya, Aminul Laskar and Arnesh Das

Radiological assessment of high density shielding concrete for neutron

radiography 1409 Stephen Ekolu and Mokgobi A Ramushu

Permeable reactive barriers for acid mine drainage treatment: a review 1416

Ayanda N Shabalala, Stephen O Ekolu and Souleymane Diop

Bottom ash and fly ash wastes as alkalinising reagents for neutralising acid

Stephen O Ekolu, Souleymane Diop and Firehiwot Azene

Potentiodynamic polarization study of the corrosion characteristics of acid

Stephen O Ekolu, Souleymane Diop and Firehiwot Azene

5 Building science and construction

Comparison of simple linear regression and multiple linear regression

Heni Fitriani and Phil Lewis

The effects of natural and artificial UV exposure on the physical properties

Adriano Coutinho Zuzarte and Deon Kruger

xxiii

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Thermal characterization of heat reflective coating for building application 1461 Bal Mukund Suman

Impact of traditional and modern building materials on the thermal behavior

and energy consumption of a courtyard house in the hot and dry climate 1468 Nạma Fezzioui, Mébirika Benyamine, Saleh Larbi, Belkacem Draoui

and Claude-Alain Roulet

Assessment of the involvement of qualified professionals in building

Catherine Mayowa Ikumapayi, Chinwuba Arum and Reuben P Omale

Thermal insulation of crumb-rubber mortar for building walls application 1481 Mukaila Yinka Sanni, Ocholi Amana and Pinder Ejeh Stephen

Precast concrete fencing units in low cost domestic housing in South

Stella M Mlasi

The environmental performance of a reinforced precast concrete slab

Magdalena Hajdukiewicz, Jérémy Lebrêne and Jamie Goggins

Foam geopolymers: state of the art and preliminary experimental results 1503 Zahra Abdollahnejad, F Pacheco Torgal and J.L Barroso De Aguiar

Quality assurance in low-cost housing construction projects in the metropole 1510 Manelisi Rarani and Stanley Fore

Performance measurement of quality of houses: development of a building

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Keynote papers

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Achieving concrete durability for specified

service-life in chloride exposures

R Doug HOOTON1

Department of Civil Engineering, University of Toronto

Abstract Obtaining durability for a known service life in chloride exposures

requires knowledge of the concrete properties, relevant transport processes, depth

of cover as well as minimization of cracking and construction defects For example, imperfect curing can result in depth-dependent effects on resistance to chloride ingress Several service life models with various levels of sophistication exist for prediction of time-to-corrosion of concrete structures exposed to chlorides The model inputs have uncertainty associated with them such as boundary conditions (level of saturation and temperature), cover depths, diffusion coefficients, time- dependent changes, and rates of buildup of chlorides at the surface The performance test methods used to obtain predictive model inputs as well as how models handle these properties have a dramatic impact on predicted service lives

Very few models deal with the influence of cracks or the fact that concrete in the cover zone will almost certainly have a higher diffusion coefficient than the bulk concrete as the result of imperfect curing or compaction While many models account for variability in input properties, they will never be able to account for extremes in construction defects Therefore, to ensure the reliability of service life predictions and to attain a concrete structure that achieves its predicted potential, designers, contractors and suppliers need to work together to ensure proper detailing, minimize defects, and adopt adequate, yet achievable, curing procedures

As well, concrete structures are often exposed to other destructive elements in addition to chlorides (eg frost, ASR) and this adds another level of complexity since regardless of cause, cracks will accelerate the ingress of chlorides These issues are discussed along with the need to use performance-based specifications together with predictive models

Keywords Chloride ingress, diffusion, construction defects, cracks, performance

specifications, uncertainty

Introduction

Concrete is a durable material and the most widely used construction material Reinforced concrete structures can be designed to be resilient to severe storms, fire and earthquakes as well as to be durable in severe environmental exposures Whether from marine or de-icing salts, chloride corrosion of steel reinforcement is the biggest challenge for both builders and owners of concrete structures In addition to using materials and mix designs that will resist chloride ingress, construction detailing and practices have a large impact on durability Achievement of concrete durability in-place

1

Corresponding author: Dept of Civil Engineering, University of Toronto, Toronto, ON, Canada,

M5S1A4, hooton@civ.utoronto.ca

Construction Materials and Structures

S.O Ekolu et al (Eds.)

IOS Press, 2014

doi:10.3233/978-1-61499-466-4-3

3

edited by S.O Ekolu, et al., IOS Press, 2014 ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/hustvn-ebooks/detail.action?docID=1920292.

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is more likely with the use of appropriate performance specifications since temperature control, adequate compaction, protection of fresh concrete, and curing need to be detailed in specifications as well as requirements for sufficient inspection and testing to ensure that the specifications are being met

In order to quantify the service life in severe environments, numerous predictive models have been developed over the last 25 years, especially related to the time-to-corrosion of reinforced concrete exposed to marine or de-icer salts While early chloride ingress models, based on Fick’s second law of diffusion were overly simplistic, newer models account for time-dependent changes in diffusion, the time to build up of surface chloride concentration, chloride binding and, in some cases, depth-dependent diffusion However, diffusion is only one mechanism of ingress of fluids including aggressive ions such as chlorides Other mechanisms including capillary absorption, permeability, and wick action can greatly accelerate ingress of chlorides, and some models have added terms to account for their effects Taking a different approach, more fundamental multi-species models have been developed (such as STADIUM [1, 2]) that use effective diffusion values for different ions and account for their interactions and the nature of the pore structure and transport processes In addition, deterministic models only provide average predictions which are not realistic given the level of uncertainty in concrete composition, rebar placement, and transport properties However some models, such as DuraCrete [3] and LIFE-365 Version 2 [4] are at least semi-probabilistic and typically standard deviations as well as average values for each

input value are used The fib 2010 model code has incorporated some aspects of the

Duracrete model [5] Aspects of modelling will be discussed in more detail

1 Design of durable concrete mixtures

Concrete mixtures that will be durable in aggressive exposures need to have low water/binder ratio, low unit water content, and contain appropriate levels of supplementary cementing materials Typically, in order to minimize concrete permeability, a w/b of no higher than 0.40 is required Using optimized total aggregate gradations and water-reducing admixtures, the unit water content can often be reduced

to 135-140 L/m3,minimizing the paste volume fraction, thus reducing permeability while reducing thermal and drying shrinkage Appropriate levels of supplementary cementing materials have many benefits in reducing paste permeability, reducing the porosity of the interfacial transition zones surrounding aggregates Slag and fly ash will improve permeability at later ages, and silica fume improves properties at early ages, so ternary mixtures will work synergistically to improve initial properties and provide long-term benefits In addition, SCMs improve the chloride binding capacity of the matrix, due to the lower Ca/Si ratio of the C-S-H and the incorporation of alumina into the hydrates, forming C-A-S-H [6, 7, 8]

Binder contents should be minimized, consistent with obtaining workable concrete,

in order to minimize volume changes due to hydration temperatures and due to shrinkage This will help minimize early-age cracking potential

2 Types of performance testing

Tests are or can be performed at various stages in construction

R.D Hooton / Achieving Concrete Durability for Speciﬁed Service-Life in Chloride Exposures

4

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x Pre-qualification Tests: Used by producers to demonstrate that a concrete mixture, when placed and cured under defined conditions, can meet the specification requirements and, if needed, provide input data for service life prediction These tests often require significant lead time to complete and may include tests needed as inputs to service life models

x Identity Tests: Performed when the concrete arrives on-site but before concrete is placed to demonstrate that the concrete being supplied is equivalent to the mixture that was pre-qualified (Similar to a DNA test) Unfortunately the range of identity tests that can be performed prior to acceptance of the truck load of concrete are quite limited Typically, slump or slump flow is measured, and air content is determined Useful information on concrete uniformity and air content can also be obtained from measuring the fresh density of the concrete, and some owners, such as the New York/New Jersey Port Authority have adopted the AASHTO microwave test to determine the water content of the delivered concrete [9] (as a partial check on w/cm (assuming that the cementitious materials are typically batched accurately) related to unintentional or deliberately added water)

x Quality Control: To document that the concrete supplied meets strength and other specification limits (a) at the change of ownership (the point of discharge from the truck) and (b) at the point of placement to demonstrate that pre-qualified placing practices are being followed

x In-Place Testing: Using NDT and/or tests on cores extracted from the structure

to ensure that the combination of the concrete supplied and the placement and curing methods used resulted in achieving the owner-defined performance levels This is required in the End Result Specifications (ERS) used by several highway agencies

Traditionally, concrete producers and contractors are often just interested in prequalification and quality control testing However, owners are interested in performance of the hardened concrete in the structure, a number of highway agencies in North America have adopted or are currently considering the use of ERS where contractors are paid based on consistently meeting specified performance requirements using in-place testing of concrete in the structure A number of these agencies have developed ERS with defined financial bonuses for consistently meeting performance, and penalties for failure to meet the in-place requirements If performance is lower than

a certain threshold, removal can be required Regardless, of the type of performance specification adopted, the acceptance criteria and the responsibilities of the various parties in cases of failure need to be clearly defined

While there are many types of aggressive exposures which could potentially require a multitude of durability tests, for resistance in all aggressive exposures the

“permeability” or fluid penetration resistance of concrete needs to be minimized Therefore, adoption of one or more tests for measuring fluid penetration resistance is fundamental to ensuring durable concrete

Most deterioration processes involve two stages Initially, aggressive fluids (water, ionic solutions with dissolved salts, gases) need to penetrate or be transported through the capillary pore structure of the concrete to reaction sites (e.g., chlorides penetrating

to reinforcement, or sulfates penetrating to reactive aluminates) prior to the actual chemical or physical deterioration reactions Therefore, a standard acceptance test or

R.D Hooton / Achieving Concrete Durability for Speciﬁed Service-Life in Chloride Exposures 5

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tests to measure rates of ingress of aggressive fluids, or a related rapid index test, is fundamental to the development of performance-based durability specifications However, before tests are adopted in specifications, they must not only be shown to be useful and reliable, they must also be standardized and should include precision data based on interlaboratory evaluations (as is required for ASTM test methods), in order

to set realistic specification limits that take account of test variability Many tests have been proposed by researchers, but only a few have been found to be sufficiently robust

to be adopted in recognised standards Some interlaboratory data on non-destructive tests of concrete cover quality have been published [10, 11]

However, to be effective, the relevant mechanisms of fluid ingress for the environmental exposure of the structure or of specific structural elements need to be determined and appropriate test methods need to be adopted Potential transport mechanisms include capillary absorption, diffusion, permeability and wick action, all

of which are time-dependent Many service life models only account for diffusion, but that is only one mechanism of chloride ingress Capillary absorption into unsaturated near-surface zones can allow rapid ingress of dissolved ions in the so-called convection zone of the concrete cover In some cases, pressure heads are also involved so permeability will also accelerate ingress In the cases of tunnel liners, pipes, and slabs-on-grade, wick action from the air boundary can evaporate water from the near-surface capillary pores, leaving behind a buildup of precipitated chloride salts [12, 13, 14]

Test methods related to measurement of various durability properties exist in various standards (e.g CSA, ASTM, AASHTO, US Corps of Engineers (CRD), and individual Departments of Transportation (DOT) in North America) Limits based on some of these test methods are specified in ACI, CSA and individual DOT specifications, amongst many others Currently, standard test methods and/or limits do not exist for all of the relevant durability or performance concerns As well, existing test methods are not always sufficiently rapid, accurate, or repeatable, nor do they necessarily adequately represent any or all of the in-situ exposure conditions The lack

of adequate performance-related test methods for concrete is one of the main factors that inhibit the move from prescriptive to performance specifications

Limits on specific penetration resistance properties such as bulk chloride diffusion (ASTM C1556 [15], Nordtest NT Build 443 [16]), and water sorptivity (ASTM C1585 [17]) may be suitable for adoption in HPC specifications during pre-qualification and

as inputs into predictive service life models, they are too time consuming to be used for acceptance purposes For acceptance testing, a rapid permeability-index test should also

be tested during prequalification and limits set that relate to the desired limits in the diffusion and sorptivity tests Such rapid index tests include the ASTM C1202 [18] (adopted in CSA A23.1 [19]), the Rapid Chloride Migration Test (Nordtest NT492 [20]

or AASHTO TP-64 [21]), a resistivity test [22, 23], or a chloride conductivity test [24] Because it is relatively simple, rapid and due to familiarity with its use, the ASTM C1202 test has become widely used for this purpose in North America However, there

is current activity at ASTM to adopt much simpler surface and bulk resistivity tests that may eventually replace the C1202 test Many of these test methods are discussed by Lane et al [25]

In 2004, the Canadian CSA A23.1 concrete standard introduced limits for the ASTM C1202 rapid chloride penetration test for prequalification of concrete mixtures

to meet (a) C-1 exposure conditions (concrete exposed to freezing in a saturated condition with de-icer salts, 35 MPa, air-entrained, 0.40 w/cm max.) of 1500 coulombs

at 56 days, and (b) C-XL exposure (similar exposure as the C-1 but where extended

6

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service life is required, 50 MPa, air-entrained, 0.37 w/cm max.) of 1000 coulombs at 56 days These limits effectively mandated the use of either blended cements or SCM’s in all such concretes since 100% Portland cement concretes would be unable to meet these limits The limits were set at 56 days of age to allow concretes containing slag or fly ash, that develop their properties more slowly, to be able to meet them

In 2009, CSA A23.1 [19] was revised to include statistical limits for acceptance purposes The CSA coulomb limits were originally intended for prequalification, so notes were added that the 1500 coulomb requirement for Exposure Class C-1 an average value with no single result to be greater than 1750 coulombs Similar wording was added for the high-performance C-XL Exposure Class concrete, except with different coulomb values (average of 1000, with no single value to exceed 1250) The

2014 revision has moved these notes into the body of the specification It is expected that the next revision will include a much simpler and less costly bulk resistivity test method and limits that will likely replace the C1202 test

3 Identity tests and the monolith approach

A challenging issue in implementation of performance specifications is the establishment of identity tests to confirm, at the start of a contract, that the concrete mixture being delivered is the correct one Of necessity, these tests need to be done at the point of discharge from the truck and provide immediate confirmation that the mixture is essentially the same as the pre-qualified one So how can it be determined that the measured slump, density, and air content, even if they are in the approved range, actually represent the concrete pre-qualified by the supplier to meet the specified strength and durability criteria? In connection with pre-qualification and constructability tests made by the authors for a proposed nuclear power station, casting

of a pre-concreting monolith test procedure has been used [26] A similar performance approach was also developed for a series of underground transit stations In these trials

an insulated one cubic meter cube, suitably instrumented with thermocouples, was used

as a pre-construction approval process Specified performance criteria based on data and cores extracted from the monolith, were compressive strength, impermeability, freeze-thaw resistance, maximum temperatures, and temperature gradients There are

no instant tests for most of these properties so the monolith approach allows the Owner’s design professional to check all the specified properties of the mixture that the contractor proposes to use The sketch in Figure 1 shows a cross-section of the monolith with locations of thermocouples (TC) If needed to better determine thermal gradients, additional thermocouples can be added The form is insulated so that curing

is similar to the internal conditions in the mass concrete base slab For this project compression tests up to 120 days were required, plus testing of in-place entrained air void systems, in-place rapid chloride permeability, and temperature gradients and maxima at all locations The in-place tests were made on cores drilled from the monolith at different ages On behalf of the owner the fabrication, concrete placing, compaction and curing can be witnessed The owner can then make the tests on the concrete listed above and confirm that the concrete meets all strength and durability requirements From then on, the total responsibility for the quality of concrete delivered placed and cured rests with the contractor and the concrete supplier This approach requires significant lead time, typically in excess of 3 months, but on most major contracts this is typically not a problem

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Figure 1 Sketch of insulated one cubic metre monolith used for pre-qualification of concrete mixtures,

showing locations of thermocouples (TC) [26]

4 Roles and responsibilities in performance specifications

Adoption of true performance-based specifications presupposes that we have a clear understanding of all the performance issues that can affect concrete It also assumes that there are appropriate performance test methods in place to evaluate all of the performance issues for: concrete materials, fresh concrete, hardened concrete, and durability It also assumes that performance can either be measured in time to affect the outcome, and/or can be used to pre-qualify concrete mixtures Most parties to construction are familiar with testing for fresh properties and strength of concrete, but the biggest challenges in this regard relate to requirements for durability [27, 28, 29] While there are many types of aggressive exposures which might require a multitude of durability tests, the common element is that most aggressive exposures require that the permeability or fluid penetration resistance of concrete be minimized Therefore adoption of one or more tests for penetration resistance is fundamental to ensuring durable concrete

The Canadian concrete standard CSA A23.1-09 [19] outlines the requirements and responsibilities for use in performance-based concrete specifications The responsibilities of the various parties need to be clearly defined with a performance specification This has been documented in CSA A23.1-09, as shown in Table 1 In addition, Annex J to that standard explains each of the table items in more detail

5 Implementation of performance specifications

The onus for meeting performance clearly rests with the producer up to point of placement Since in-place performance is also affected by the contractor’s placement methods, the producer must work with the contractor to ensure the owner’s performance requirements are achieved: eg the contractor (not the owner/specifier)

8

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should set the target slump to allow for proper placement and compaction for the situation, and the producer needs to design and provide this without reducing the intended performance of the hardened concrete

Even if performance requirements are clearly stated in a specification, experience suggests that the successful implementation of a contract depends significantly on a dialogue between the contractors bidding for a contract and the Owner’s design professional Recent experience on a major HPC project suggests that where this requirement is established as an absolute and where there is constant and open communication across the construction team, all members will come to recognize the benefits of this approach

A few important points are as follows:

• Require all contract bidders to attend a pre-bid meeting to hear about special requirements—so they cannot complain afterwards that they missed some of the performance requirements

• Make contractors, including subcontractors, detail in their bid how they intend

to meet the special requirements part of the bid submittal eg Concrete placement methods, protection, curing, hot/cold weather provisions

• Do not accept low-price bids that are not responsive to the special requirements

• Once work has commenced, require pre-pour meetings for important placements: The contractors, the suppliers, the subcontractors, including the finishers need to be aware of what needs to be done to ensure that the concrete can be delivered, placed, compacted, protected, finished, and cured to achieve the performance objectives Even the person who will be fog misting, or applying other protective measures needs to be there to understand why it is important

• During construction, the owner must be notified of any errors or problems without delay together with documentation and communication of the action being taken to rectify the problem

Achieving the owner’s performance requirements requires more cooperation between the concrete suppliers, the contractors, and concrete finishers than often exists

in typical practice This type of information is detailed in Annex J of CSA A23.1-09 [19]

6 Minimizing construction defects

Construction detailing and practices as well as defects can significantly affect actual penetration rates of aggressive ions and fluids, but are rarely quantified or modeled Almost no current service life prediction models can deal with the influence of cracks

or the fact that concrete in the cover zone will almost certainly have a higher diffusion coefficient than the bulk concrete as the result of imperfect curing or compaction An example of the variation in properties of similar bridge structures is given by Tikalsky

et al [30]

It is the unpredictable areas of poorly compacted, poorly cured, or cracked concrete with less than the design depth of cover which will severely shorten the predicted time to corrosion, regardless of what model is used Therefore, one of the most effective ways to obtain the model-predicted service life of a structure is to

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address these site issues prior to and during construction Pre-construction and pour meetings mentioned previously are effective in ensuring that the contractor and sub-contractors understand the issues and have the required labor, materials and equipment on site to ensure best practices are followed

pre-As well, inspection of formwork placement and reinforcement cover depths prior

to each placement of concrete can be used to correct areas of low cover deficiencies In probability-based models, a common approach is to assume an average and range of properties such as concrete cover depth But by correcting cover deficiencies prior to concrete placement, the variability in predicted service life can be significantly reduced For example at the newest parking garage at Toronto’s Pearson airport, this process of inspection prior to placement led to a standard deviation in cover depth of only 3 mm over a huge deck area (Figure 2) (the specified cover was 40 mm), significantly below the CSA A23.1 [19] allowable variation of 10 mm [31]

The ability to adequately place, vibrate and compact concrete in areas of congested reinforcement also needs to be established, preferably with test of mock ups but also by letting the contractor select the required workability required for the situation given the available equipment and labour The concrete supplier can then design appropriate mixtures for the contractor’s required workability To address compaction and curing, cores extracted from the in-place concrete can be tested to assess the in-place performance of the final structural element (to avoid drilling cores from precast elements, extra elements for coring can be cast with the structural elements)

Figure 2 Range of measured in-place concrete cover on parking garage deck slab when inspected before

placement (Specified cover = 40 mm) [31]

6.1 Predictive Models

Since corrosion of reinforcement is the largest single cause of deterioration of reinforced concrete structures, most models have focused on this, and mainly due to chloride ingress The earliest chloride ingress models assumed that diffusion is the only mechanism of chloride ingress Crank's solution [32] to Fick's second law can be used to determine the diffusion constant (Dc) of the concrete from chloride concentration profiles

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where C(x,t) = the chloride concentration at depth (x) and time (t)

C s = the chloride concentration at the concrete surface

erf [ ] = the error function (values can be obtained from standard tables for various values of the

number within the brackets)

Typically, chloride profiles are obtained from a particular concrete which has been exposed to a solution of known chloride concentration after a fixed length of time Careful use of a milling machine can provide samples for chloride concentration profiles at 0.5 to 1 mm intervals Such tests have been standardized as Nordtest NT Build 443[16] and ASTM C 1556 [15] The numeric solution to Fick’s 2nd law can then be used with Dc and Cs as inputs to predict the time to critical chloride concentration, C(x,t) at the depth of cover, x

Later models included time-dependent (m) [33] and depth-dependent [34, 35] diffusion coefficients and time-dependent buildup of surface chlorides (Cs(t)) [36], and chloride binding [6, 8, 37] Some models use apparent or bulk diffusion coefficients (Da) based on total (acid soluble) chloride penetration profiles and make corrections for chloride binding while others have used effective diffusion coefficients (De) It is far easier to obtain reliable measurements of total chloride content (acid soluble chloride contents) by dissolving samples in nitric acid Unfortunately, this includes any bound chlorides and if not accounted for, this has a significant impact on service life predictions [37] While it is only the water-soluble chlorides that will act to depassivate the steel reinforcement, the methods for obtaining water-soluble chlorides are somewhat arbitrary and are difficult to define Under some conditions, such as carbonation [8], almost all bound chlorides can be released Another issue is that all materials contain some chlorides and there will be a background level of chloride throughout the concrete For example, in Toronto and Chicago, the crushed limestone coarse aggregates typically contain significant chlorides, but unless the aggregate is crushed to powder, these chlorides are effectively insoluble as they are encased inside the coarse particles If the background chloride in concrete is effectively insoluble, then

a correction should be made to subtract these background values when acid soluble chlorides are being determined; for models, this typically has to be done anyway as diffusion rates are impacted by the chloride gradient

Some models have included terms that also account for permeability and absorption while a few can account for conditions where pore systems are less than saturated throughout the thickness of the element As stated earlier, it is important to consider other mechanisms of chloride ingress than diffusion such as absorption into unsaturated surfaces is a rapid process with time spans in the order of minutes or hours while diffusion ingress is measured in time spans of years As well, evaporation due to wick action [12, 13, 14] can act to concentrate deleterious levels of precipitated salts in pores below the evaporative surfaces (although that mechanism becomes less important with concretes having a discontinuous capillary pore structure ie at w/c < 0.45) Wick action is also important for damage due to physical sulfate and other types of salt attack

Cracks wider than 0.05 to 0.10 mm accelerate chloride ingress [38, 39] but predictive models have not progressed to the point where the impacts of cracks on chloride ingress can be quantified In practice, the emphasis must be placed on minimizing cracking as well as the width of cracks

It is known that there is variability in all properties of reinforced concrete, so models, such as DuraCrete [3], and Version 2 of LIFE-365 [4] have taken probabilistic approaches using inputs of both average and standard deviation for each input value A

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typical example of input values needed in LIFE-365 is shown in Table 2 More simplistic stochastic models only give average time predictions that are well beyond the decision point required for structural repair since repairs are often initiated when only 5 or 10% of surfaces are exhibiting corrosion damage

ecision point required for structural repair since repairs are often initiated w

5 or 10% of surfaces are exhibiting corrosion damage

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Table 2 Example of average values and standard deviations inputs to LIFE-365 [4]

Variable Units Average

Value

Standard Deviation

Coefficient of Variation, %

Chloride Bulk Diffusion, Da

at 28 days

m 2 /s 8.87 x 10 -12 2.22 x 10 -12 25 Time-dependent coefficient, m - 0.20 0.05 25

Once the transport processes are modeled, another area that needs further attention

is the critical chloride threshold for initiation of corrosion Published values vary by more than an order of magnitude More recent work has recognized the usefulness of the chloride to hydroxyl ion ratio as being more meaningful (taking into account different cement contents and types of cementing materials), but even these values vary

by more than an order of magnitude [an extensive review is given in [40] This subject

is the current subject of study by RILEM committee CTC

Lastly, to increase confidence in their use, model predictions need to be calibrated against chloride ingress in structures A series of 8-15 year old parking and bridge decks exposed to de-icer salts were cored and chloride profiles were compared to model predictions; it was generally found that the Life-365 model predictions were conservative [41]

7 Summary

Achieving durability requires more than selecting an appropriate concrete mixture, construction practices and details also impact durability In addition, performance specifications, making use of appropriate durability tests and limits, can help in the achievement of durable structures While not perfect, performance approaches to durability design are being used successfully in large infrastructure projects and focus attention to the whole construction process and not just to the concrete mixture being supplied To quantify durability in chloride exposures, there have been impressive achievements in the development of predictive service-life models in the last 25 years This is especially true in the area of time to onset of reinforcement corrosion where models have developed beyond application of very simplistic Fick’s 2nd Law methods

to much more sophisticated multi-mechanistic, time-dependent, probabilistic transport models Test methods have been developed to provide input values for these models, but often these tests are time-consuming, making them unsuitable beyond prequalification purposes Some of these tests also suffer from high levels of variability Faster, more reliable test methods will provide better predictions and will

be better suited for quality assurance purposes during construction In the meantime, rapid index tests can be used for that purpose

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Trang 40

Nanoparticle modified concrete materials: opportunities, challenges and prosperities

Kejin WANG1 and Gilson R LOMBOY

Department of Civil, Construction and Environmental Engineering,

Iowa State University, Ames, IA 50010, USA

Abstract Research and applications of nanoparticles in concrete materials are

rapidly increasing because fundamental properties of concrete (such as rheology, strength, transport properties, fracture behavior, etc.) are strongly influenced by the material properties at the nanoscale Use of nanomaterials in concrete can also enhance sustainability and reduce negative environmental impact through reduction in cement use, energy and natural material consumptions during production and service In this paper, the needs and opportunities of use of nanoparticle modified concrete are highlighted The challenges in nanoparticle processing (such as dispersion and stabilization) are addressed Recent developments in characterization methods (such as Raman spectroscopy, nanoindentation, modulus mapping, peak-force quantitative nanomechanical mapping and atomic force microscopy) are reviewed Effects of nanoparticles (such as nanosilica, nanolimestone and nanoclay) on concrete rheology, hydration, microstructure development, mechanical properties, and durability are discussed

Keywords Nanoparticles, Processing, Characterization, Rheology, Hydration,

Strength, Durability

Needs and opportunities

Concrete has been the most widely used construction material since 1800s when Portland cement was invented Today, rapid globalization and technological change are demanding modern infrastructuresto meet the growing needs for quality of life, global competiveness, and sustainability As a result, the standards for functionality, constructability, serviceability, durability, environmental impacts, and life-cycle assessment of concrete are rising

Recently, many breakthroughs of concrete technology have been made from the use of nanomaterials in concrete, which facilitates meeting the above-mentioned growing needs [1,2] Some examples include (a) super-performance concrete featured with enhanced strength, fracture resistance, and ductility by using carbon nanotubes, nanosilica, etc., (b) sustainable cementitious materials featured with energy conservation and CO2 emission reduction by using nanolimestone, nanoclay, etc., (c) microbial protection and air purification resulting from photoactivation of titanium

1

Corresponding author: Iowa State University, Department of Civil, Construction and Environmental Engineering, 492 Town Engineering, Ames, IA 50010, USA; E-mail kejinw@iastate.edu

Construction Materials and Structures

S.O Ekolu et al (Eds.) IOS Press, 2014

doi:10.3233/978-1-61499-466-4-16

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