Evaluation of shrinkage induced cracking in early age concrete: From ring test to circular column

Abstract

This article focuses on the modeling of shrinkage stress and evaluation of shrinkage induced cracking in early-age concrete. In the modeling, an integrative model for autogenous and drying shrinkage predictions of concrete at early-age is introduced first. Second, a model taking both cement hydration and moisture diffusion into account is used to calculate the distribution of internal humidity in concrete. Using above two models, the distribution of shrinkage stress in concrete ring and column at early-age from concrete cast are calculated. Meanwhile, the ring test is utilized to identify the time of shrinkage cracking of three kinds of concretes with compressive strength at 28 days around 30, 50, and 80 MPa. Based on model and ring test results, the shrinkage induced cracking tendency of concrete columns made of the three kinds of concretes is evaluated individually. The model results show that before drying, a uniform shrinkage strain along radial direction of a concrete column or ring is expected. After surface drying, shrinkage gradient along the radial direction is significant and the maximum and minimum shrinkage occur at the outer surface and the center of column or interior surface of the ring, respectively. The distribution of shrinkage stress along the radial direction of the ring or column is nonlinear and the nonlinearity is strong close to the drying surface. Due to the difference on restraint condition, lower shrinkage induced cracking tendency is expected in concrete column than that of steel restraint concrete ring, even both of them having the exact same outer diameter.