Plastic shrinkage of composites related to response in tension

What is it about?

It is well understood that the early-age properties of cementitious materials influences its long term performance. Cementitious materials experience high moisture loss at early age resulting in volumetric shrinkage. When this shrinkage is restrained, tensile stresses develop resulting in cracking of the material. This issue is more pronounced at early-age when the tensile strength of cementitious materials is not fully developed. There are many methods and models available to predict the drying shrinkage of concrete. However, the relationship between early age uniaxial tensile strength and restrained shrinkage cracking characteristics at early age is not well understood. Uniaxial tests were conducted on dog-bone specimens made using various fiber types including glass, cellulose and three types of synthetic fibers. Tensile characteristics including stress versus strain plots for all the specimens along with stress at peak, post crack strength at 2 mm deflection along with elongation at peak are calculated and presented in this paper. Plastic shrinkage cracking results obtained using an innovative test developed by the authors were correlated to these tensile strength results. Results indicate that post crack residual tensile strength at early-age is inversely proportional to the total crack area resulting from restrained shrinkage. The effectiveness of various fiber types is also discussed in the paper.

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