Finite-Element Modeling of Early-Age Concrete Stress Development

Abstract

Early-age cracking of concrete may influence the long-term durability of a structure. Cracking occurs when the tensile stress in concrete exceeds its tensile strength. Early-age stress development in concrete is influenced by temperature changes, modulus of elasticity, creep or stress relaxation, shrinkage and coefficient of thermal expansion, and the degree of restraint. Three-dimensional finite-element analysis was used to model the early-age stress development of concrete, and a rate-type creep analysis was used herein. Four creep compliance models, including the B3 Model, Modified B3 Model, B3 Model with RT, and B4 Model were incorporated in the finite-element model. Experimental results from restraint of volume change tests with a rigid cracking frame were used to assess the accuracy of the finite-element analysis. The experimental tests included 63 concrete mixtures, which contained varying cementitious materials, mixture proportions, temperature histories, aggregate types, water:cementitious materials ratios, and chemical admixtures. The results showed that the finite-element model provides accurate predictions of measured early-age concrete stresses. The Modified B3 Model provided the most accurate prediction of the measured early-age concrete stresses.