Early age properties of self-compacting concrete - age properties of self-compacting concrete...
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Early age properties of self-compacting concrete Effects of fine aggregate and limestone filler
OSKAR ESPING Department of Civil and Environmental Engineering Building Technology CHALMERS UNIVERSITY OF TECHNOLOGY Gteborg, Sweden 2007
THESIS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
Early age properties of self-compacting concrete
- Effects of fine aggregate and limestone filler
Department of Civil and Environmental Engineering
CHALMERS UNIVERSITY OF TECHNOLOGY
Gteborg, Sweden 2007
II CHALMERS, Civil and Environmental Engineering
Early age properties of self-compacting concrete - Effects of fine aggregate and limestone filler OSKAR ESPING ISBN 978-91-7291-890-0 Oskar Esping, 2007 Doktorsavhandlingar vid Chalmers tekniska hgskola Ny serie nr 2571 ISSN 0346-718X Department of Civil and Environmental Engineering Building Technology Chalmers University of Technology SE-412 96 Gteborg Sweden Telephone: +46 (0)31-772 1000 http://www.chalmers.se Chalmers Reproservice Gteborg, Sweden 2007
IIICHALMERS, Civil and Environmental Engineering
Early age properties of self-compacting concrete - Effects of fine aggregate and limestone filler Oskar ESPING Department of Civil and Environmental Engineering Building Technology Chalmers University of Technology
Self-compacting concrete (SCC) is a sensitive mix, strongly dependent on the composition and the characteristics of its constituents. It has to possess the incompatible properties of high flowability together with high segregation resistance, a balance made possible by the dispersing effect of water-reducing admixture combined with cohesiveness produced by a high concentration of fine particles. These fines and their effects on the early age properties of the SCC have been in focus in this present dissertation.
The effect of the specific surface area of gravel and limestone filler on the rheology of SCC was evaluated. Performed experiments clearly demonstrated that traditional methods for geometric characterization of the fines (size distribution, water absorption, fineness modulus, etc.) are not sufficient to ensure consistent quality of SCC. By measuring the specific surface area with a simplified gas adsorption method, BET(H2O), it was found that the specific surface area of a normal gravel, accepted by traditional methods for production of SCC, can vary up to 7000 m2/kg. A model is proposed, based on an assumption that 30 full molecular layers of water covering the particle surface are required to provide lubrication sufficient to create flowability, where a change in specific area is translated to a change in water demand for the concrete mix. It is suggested that an increase in BET(H2O)-area of 1000 m2/kg corresponds to an increase in water demand by approximately 0.85% by mass of the filler or gravel content for constant flowability.
Furthermore, the influence of mix design and fines BET(H2O)-area on the SCCs early-age deformation was demonstrated. The autogenous (sealed) deformation was measured with a specially developed concrete dilatometer, together with capillary pore pressure and temperature. It is suggested that that autogenous shrinkage and rate of evaporation are the main factors promoting the risk of plastic shrinkage cracking. An increased particle surface decreased the rate and magnitude of evaporation, and consequently reduced the plastic cracking tendency, despite an increase in autogenous shrinkage.
Key words: self-compacting concrete, rheology, autogenous deformation, plastic shrinkage, pore pressure, limestone filler, specific surface area, BET
IV CHALMERS, Civil and Environmental Engineering
The work presented in this doctoral thesis is based on the following papers, referred to in the text by their Roman numbers:
I. Slump flow values vs. Bingham parameters for high flowable mortars and concretes Esping O., Accepted for publication in 5th International RILEM Symposium on Self-Compacting Concrete, 3-5 September 2007, Ghent, Belgium, 2007.
II. Methods for characterisation of fillers and fines for self-compacting concrete Esping O., 3rd International RILEM Symposium on Self-Compacting Concrete, PRO 33, 1720 August, pp 208-219, Reykjavik, Iceland, 2003.
III. SCC flowability: Effect of changes in particle surface area, and how to compensate for this Esping O., Accepted for publication in 5th International RILEM Symposium on Self-Compacting Concrete, 3-5 September, Ghent, Belgium, 2007.
IV. Investigation of autogenous deformation in self-compacting concrete Esping O., International RILEM conference on Volume Changes of Hardening Concrete, 20-23 August, pp 273-282, Lyngby, Denmark, 2006.
V. Investigation of early age deformation in self-compacting concrete Esping O., Lfgren I., 2nd International Symposium on Advances in Concrete Ccience, 11-15 September, Quebec, Canada, 2006.
VI. Effect of limestone filler BET(H2O)-area on the fresh and hardened properties of self-compacting concrete Esping O., Submitted for publication in Cement and Concrete Research, 2007
VCHALMERS, Civil and Environmental Engineering
APPENDED PAPERS IV
1 INTRODUCTION 1
1.1 Background 1
1.2 Objective and limitations 2
1.3 Disposition of the thesis 3
1.4 Original features 3
2 RHEOLOGY 5
2.1 Introduction 5
2.2 Particle suspensions 7
2.3 Measuring techniques 22
2.4 Concluding remarks 27
3 EARLY-AGE DEFORMATION 29
3.1 Introduction 29
3.2 Plastic shrinkage cracking 31
3.3 Mechanisms of early-age deformation 32
3.4 Measuring techniques and methods 42
3.5 Concluding remarks 47
4 EXPERIMENTAL WORK 49
4.1 Introduction 49
4.2 Materials and mix design 50
4.3 Particle quantifications 53
4.4 Mortar and concrete quantifications 62
4.5 Concluding remarks 72
VI CHALMERS, Civil and Environmental Engineering
5 FINAL DISCUSSION AND CONCLUSIONS 73
5.1 Discussion 73
5.2 General conclusions 75
5.3 Suggestions for future research 76
6 REFERENCES 79
APPENDIX A: BET(H2O) 91
APPENDIX B: CONCRETE DIGITAL DILATOMETER 99
APPENDIX C: CONCRETE CRACKING RING TEST 105
APPENDIX D: GLOSSARY 111
PAPER I: SLUMP FLOW VALUES VS. BINGHAM PARAMETERS FOR HIGH FLOWABLE MORTARS AND CONCRETES
PAPER II: METHODS FOR CHARACTERISATION OF FILLERS AND FINES FOR SCC
PAPER III: SCC FLOWABILITY: EFFECT OF CHANGES IN PARTICLE SURFACE AREA, AND HOW TO COMPENSATE FOR THIS
PAPER IV: INVESTIGATION OF AUTOGENOUS DEFORMATION IN SCC
PAPER V: INVESTIGATION OF EARLY AGE DEFORMATION IN SCC
PAPER VI: EFFECT OF LIMESTONE FILLER BET(H2O)-AREA ON THE FRESH AND HARDENED PROPERTIES OF SCC
VIICHALMERS, Civil and Environmental Engineering
The work presented in this doctoral thesis is one of the two outcomes of the project Industrial building with in-situ cast concrete New concepts, which was made possible by a donation from Thomas Concrete Group / AB Frdig Betong to Chalmers University of Technology. The work has been conducted at the Department of Civil and Environmental Engineering (Chalmers University of Technology) and at the research centre of Thomas Concrete Group in Gteborg, during the period 2001-2007. During the first years this thesis was carried out under the supervision of Professor Lars-Olof Nilsson now at Lund University of Technology, and during the remaining years under Professor Tang Luping at Chalmers University of Technology. Professor Per-Erik Petersson at the Swedish National Testing and Research Institute has acted as assisting supervisor. I am most grateful for their support and assistance.
Grateful thanks are also addressed to:
Annika Wirje, Frdig Betong AB Jan-Erik Lindqvist, Swedish National Testing and Research Institute Martin Hansson, Sika Mats Karlsson, Thomas Concrete Group AB Mette Geiker, Technical University of Denmark Olafur Wallevik, The Icelandic Building Research Institute Peter Billberg, Swedish Cement and Concrete Research Institute Sten Rodenstam, Nordkalk AB
Special thanks are due to Thomas Concrete Group and AB Frdig Betong for their generous donation, support and confidence in me.
I would like to extend my special thanks to Ingemar Lfgren and Professor Tomas Kutti at Thomas Concrete Group AB for their involvement in this work, and for their indispensable help, guidance, encouragement and always valuable advice.
Finally, I would like to thank my future wife, Lotta, and children Albin and Elin, for supporting and having patience with me during my doctoral studies.
It is my hope that this paper will be reviewed critically. Any viewpoints, comments and suggestions about the text should be directed to me.
By the nature of an experimental investigation, each question is often answered with many new questions. And with knowledge arises a question whether the experimental course of action could be made in a more proper way. It ought to be noted that the purpose of a PhD study is educational, and that the work presented in this doctoral thesis is mainly intended as a personal learning process, not to produce unique or useful results. Yet it has to be performed with a scientific approach and to fulfil certain requirements of quality, which I hope to have achieved for the benefit of future research.
Gteborg, February 2007
VIII CHALMERS, Civil and Environmental Engineering