Calculation of Shrinkage Stress in Early-Age Concrete Pavements. II: Calculation of Shrinkage Stress

Abstract

This paper focuses on modeling of the shrinkage stress in concrete pavements that experience nonlinear shrinkage strain through the depth of the slab. A closed form of an analytical solution of shrinkage stress is developed. In the modeling, the nonlinear shrinkage strain through the depth of the slab is divided into three components, as follows: (1) uniform, (2) linear, and (3) nonlinear shrinkage. Afterwards, the shrinkage stress resulting from each component is calculated separately. The total shrinkage stress is then obtained by summing the three stress components together. Using the model, the distribution of the shrinkage stress in concrete pavements at an early age from concrete casting is calculated and analyzed. The model results show that the developed law of shrinkage stress in pavement is consistent with the development of shrinkage strain. Within the stage of the shrinkage strain uniformly developed, a uniform shrinkage stress is expected throughout the slab. In the stage with a shrinkage strain gradient, a stress gradient is also expected. With respect to the condition that the slab top experiences drying, the distribution of the shrinkage stress along the pavement depth is apparently nonlinear and the nonlinearity is stronger in the area close to the drying surface. The maximum and minimum tensile shrinkage stresses occur at the top and bottom, respectively, of the middle section of the slab in this case. Concrete strength can significantly influence the magnitude of the shrinkage stress and its distribution in the slab. For a given age and location, a higher concrete strength corresponds with a larger shrinkage stress and stress gradient.