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This thesis presents an experimental study of creep and shrinkage of concrete made from local limestone aggregate and type III cement. The cylindrical test specimens were exposed to the atmosphere in order to observe the effects that variations of temperature and relative humidity had upon creep and shrinkage. These effects are shown by graphical presentations in the thesis. Creep strains for the five month period of investigation are shown graphically for each of four conditions of stress, 1000 psi constant stress 1000 psi variable stress 500 psi constant stress, and 500 psi variable stress. Exponential equations for these surveys were derived from the creep data of the five month study. Ultimate creep values were predicted from these equations and are presented together with their respective creep coefficients. These values are given to represent the anticipated creep for limestone aggregate concrete subjected to field conditions. / Master of Science

Thesis: M.S., Massachusetts Institute of Technology, Department of Civil Engineering, 1976 / Bibliography: leaves 126-131. / by Joseph A. Martore. / M.S. / M.S. Massachusetts Institute of Technology, Department of Civil Engineering

Time dependent deformations in concrete, both creep and shrinkage, play a critical role in prestressed concrete structures, such as bridge girders, nuclear containment vessels, etc. These strains result in lossess, through release of prestress, and thereby influence the safety of these structures. The present study comprises of an experimental and analytical program to assess the levels of creep and shrinkage in normal and heavy density concrete. The experimental program includes tests on creep using standard cylinder specimen, while shrinkage studies have been conducted using prism specimen, both under controlled environmental conditions. The experimental results suggest that creep and shrinkage strains are higher in heavy density concrete than in normal concrete. This may be attributed to the relatively smaller pore structure of heavy density concrete, that results in larger availability of free water and a relatively slower hydration process in comparison to normal concrete. While there is some scatter in the results, creep strains decrease with age of loading and both creep and shrinkage strains are smaller when the relative humidity is higher. Statistical model reported in the literature for normal concrete is able to predict the test results for both normal and heavy density concrete quite well. Long term predictions of creep and shrinkage using this model, accounting for uncertainties, is also projected and shown to predict some long term measured results not used in the model calibration. The long term predictions are sensitive to the initial data used in model calibration.

published_or_final_version / abstract / Civil Engineering / Doctoral / Doctor of Philosophy

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