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Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 13 Abstracts search results
Document:
SP220-06
Date:
March 1, 2004
Author(s):
E. Tazawa
Publication:
Symposium Papers
Volume:
220
Abstract:
Investigation into the mechanism of shrinkage is essential for the engineering purposes to mitigate cracking of concrete structures. Because comprehensive analysis of unit processes of self deformations is inevitable for systematic understanding of interaction between various self deformations, such as drying shrinkage, autogenous shrinkage and thermal deformation etc.,or their influences on stress generation and crack extension or crack propagation. In this paper one example of this trial is presented based on analysis of relationship between weight loss and drying shrinkage measured by ASTM method. By this analysis, it is shown that unit processes involved in these physical phenomena are not so simple as can be stated by Fick's diffusion theory. Depending upon duration of underwater curing or degree of hydration, unit processes are drastically varied suggesting that variation in microstructure gives rise to quite different situations for desiccation and deformation. Based on these models, relation and interaction between drying shrinkage and autogenous shrinkage is discussed.
DOI:
10.14359/13151
SP220-07
M. D. D'Ambrosia, D. A. Lange, and Z. C. Grasley
Volumetric instability of concrete is a primary cause for early age cracking of concrete pavements and structures. Creep and shrinkage of concrete were studied under restrained conditions and under constant applied load during the first week after casting. Early age behavior was characterized by a uniaxial test that measures shrinkage strain and restrained shrinkage stress. The extent of stress relaxation by tensile creep is determined using simple superposition analysis. The experimental measurements are compared with some current creep and shrinkage models to assess their validity for early age prediction. The B3 model has been previously modified to accommodate early age creep, and this modification was employed in the current study. Test results for normal concrete mixes with different w/c are discussed and compared to model predictions. Comparisons show that the B3 model is accurate when the early age modifications are employed.
10.14359/13152
SP220-08
J.-P. Charron, B. Bissonnette, J. Marchand, and M. Pigeon
A restrained shrinkage apparatus was adapted to study the early-age behavior of hydrating cement-based materials in various thermal conditions. The intent of this paper is to provide information on the latest version of the DRS (Discretized restrained shrinkage) experimental setup and test procedure. In addition, the test reproducibility is evidenced through selected series of experiments. First, results that show the temperature control efficiency and the uniformity of the temperature field within the specimens are provided. Then, the results of tests performed to evaluate both hardware and material effects are presented. According to these results, the temperature controlled DRS test shows much promise in the quest of better understanding and characterizing the early-age behavior of cement-based materials. It definitely should help in tackling the related cracking problems.
10.14359/13153
SP220-03
K. S. Douglas and K. C. Hover
This paper evaluates a test method for measuring bulk, autogenous volume changes in cement paste and mortar. In this test method, paste and mortar were sealed in latex membranes and submerged in water. The weight of the specimens was recorded periodically, both in air and submerged in water, and their volume change was calculated using Archimedes' principle. Several sources of error in the test method were identified, and measures were taken to account for some of this error. It was concluded that the experimental error for this test may be quite substantial as the test duration increases, and therefore this test method is most suited for measuring the early age volume changes of cement paste and mortar.
10.14359/13148
SP220-04
P. Lura, Y. E. Guang, and K. van Breugel
In this paper, measurements of non-evaporable water content, chemical shrinkage, autogenous deformation, internal relative humidity (RH), pore solution composition, and early-age elastic modulus are presented and discussed. All experiments were performed on Portland cement and blast-furnace slag (BFS) cement pastes. Self-desiccation shrinkage of the BFS cement paste was modeled based on the RH measurements, following the capillary-tension approach. The main findings of this study are: 1) self-desiccation shrinkage can be related to self-desiccation both for Portland and for BFS cement pastes, taking into account the influence of the dissolved salts in the pore solution, 2) the BFS cement paste studied shows pronounced self-desiccation and self-desiccation shrinkage, mainly caused by its very fine pore structure.
10.14359/13149
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