ACI SP-220-2004 Autogenous Deformation of Concrete《混凝土的自生变形》.pdf

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1、 Autogenous Deformation of Concrete Editors Ole Mejlhede Jensen Dale P. Benz Pietro Lura h international- SP-220 First printing, March 2004 DISCUSSION of individual papers in this symposium may be submitted in accordance with general requirements of the AC1 Publication Policy to AC1 headquarters at

2、the address given below. Closing date for submission of discussion is October 2004. All discussion approved by the Technical Activities Committee along with closing remarks by the authors will be published in the January-February 2005 issue of either AC1 Structural Journal or AC1 Materials Journal d

3、epending on the subject emphasis of the individual paper. The Institute is not responsible for the statements or opinions expressed in its publications. Institute publications are not able to, nor intended to, supplant individual training, responsibility, or judgment of the user, or the supplier, of

4、 the information presented. The papers in this volume have been reviewed under Institute publication procedures by individuals expert in the subject areas of the papers. Copyright O 2004 AMERICAN CONCRETE INSTITUTE P.O. Box 9094 Farmington Hills, Michigan 48333-9094 All rights reserved, including ri

5、ghts of reproduction and use in any form or by any means, including the making of copies by any photo process, or by any electronic or mechanical device, printed or written or oral, or recording for sound or visual reproduction or for use in any knowledge or retrieval system or device, unless permis

6、sion in writing is obtained from the copyright proprietors. Printed in the United States of America Editorial production: Lindsay K. Kennedy Library of Congress catalog card number: 2004103246 ISBN: 0-8703 1- 143-3 PREFACE Autogenous deformation of concrete is the free deformation of sealed concrete

7、 at a constant temperature. A number of observed problems with early-age cracking of high- performance concrete can be attributed to this phenomenon. During the last 10 years, this has led to an increased focus on autogenous deformation within both concrete practice and concrete research. Since 1996

8、, there has been enough interest to hold yearly international conferences entirely devoted to this subject. The papers in this publication were presented at two consecutive half-day sessions at the American Concrete Institutes Fall Convention in Phoenix, Arizona, October 2002. All papers were review

9、ed according to AC1 procedures. This publication and the sessions were sponsored by AC1 Committee 236, Material Science of Concrete. The 12 presentations from eight different countries indicate the broad, global research efforts dealing with autogenous deformation, and the well-attended-of up to 90

10、people-show that this interest is shared by the general concrete community. Attendees left with an understanding of the complexity of the autogenous deformation of concrete. The sessions showed that cooperation and more research are needed. At the AC1 2002 Fall Convention, the international materiai

11、s research organization, RILEM, took steps to promote further research and cooperation within this area. Two technical committees held initial meetings with the involvement of many AC1 members. More collaborative research will be carried out! Copenhagen, Denmark, and Santa Cruz, Bolivia, October 200

12、3. Ole Mejlhede Jensen Dale P. Bentz Pietro Lura I 0.Mejlhede Jensen , i eaWC=025 u b) Figure 2 - Correlation between Ca(OH), content (a) or C/S ratio of the C-S-H (b) and degree of hydration, for cement pastes with W/C ranging from 0.25 to 0.60 and cured at T = 20C, from 3 hours up to 2 years. 7 6

13、-5 -A Figure 3 - Comparison between initial and final setting times obtained from Vicat needle, chemical threshold (precipitation of Ca(OH), detected by TGA), and autogenous shrinkage knee-point, for cement pastes cured at various temperatures. 18 Baroghel-Bouny et al. e) T - 48C Figure 4 - Evolutio

14、n of chemical shrinkage of cement pastes with various W/C. Figure 5 - Initial slope of the chemical shrinkage vs. age plot, as a function of temperature, for cement pastes with various W/C. fi1n.;s,a:Jsemw7tiB 3 6 B 12 $5 ?8 nesI 103 f to 9 12 is 4% 21 2t o 53 5 P 36 30 d 40 45 so: 9 uf tS age h) a.

15、 degwe ofhydraitn Figure 7 - Evolution of volumetric autogenous shrinkage of cement pastes with W/C = 0.25 and cured at various temperatures (ages below 24 hours). -20C 60C - I 1 $0 loo t000 1om 100000 Pore radius (nmf Figure 8 - Pore size distribution measured by MIP on hcp with W/C = 0.50, after 2

16、8-day curing at 20 or 60C. L(_f a 20 A 30 .i 40 50 Figure 9 - Evolution of volumetric autogenous shrinkage between Q = 7% and Q = 50%. for cement pastes with W/C = 0.25 and cured at various temperatures (ages below 24 hours). 20 Baroghel-Bouny et al. 1 1 6, . l i O 2 Age (hoursf a 10 Figure 1 O - Co

17、mparison between chemical shrinkage and volumetric autogenous shrinkage of cement pastes with W/C = 0.25 and cured at T = 50C. - 1500 Y f 1250 Y - WfC =0.30 -m- W/C =0.35 -+- W/C=0.40 -“- WIC = 0.45 -Ci- W/C =O50 ci, 1000 750 $ 500 2 250 .- O m go 3 -250 a -500 O 50 100 150 200 250 300 350 400 Age (

18、days) Figure 1 1 - One-dimensional autogenous deformation measured from initial Vicat setting time on 020x160-mm sealed samples of cement pastes with various W/C, at T = 20+1 OC. 5 1500 8I 4 1000 80 4 -1000 .- 5 500 e -500 49 0,2 0.3 0,4 0.5 0,6 07 WIC Figure 12 - Correlation between one-dimensional

19、 autogenous deformation (measured at T = 2011 OC) and W/C, at the ages of 28 and 360 days. Autogenous Deformation of Concrete 21 ,300 40 7 ,.L50 v E150 2 J 50 5 10 - +o 8% c-r $00 ga P 5 a %O 10 loo 1000 to000 iooooo 1000000 0 Pore radius (4 O2 0.3 0,4 05 0,6 0,7 WIG a) pore size distribution at 28 days b) porosity vs. tVX Figure 13 - Results obtained by MIP on hep with various W/C, after curing at T=2011“C. 22 Baroghel-Bouny et al.