Stress and damage in concrete induced by pipe cooling at mesoscopic scale

Abstract

Pipe cooling is one of the most important measures of mass concrete temperature control, but pipe cooling has its advantages and disadvantages. Inappropriate pipe-cooling water temperature may result in excessive stress and crack. Considering the fact that concrete is a type of three-phase composite material and the sizes of cooling pipe and aggregate are basically on the same scale, the mesoscopic heterogeneity of concrete may have a great effect on the stress field surrounding the pipe. This article computes the pipe cooling-induced stress and damage and analyzes the differences between the homogeneous model and heterogeneous model based on mesoscopic mechanics. In this study, both linear elastic analysis and nonlinear damage analysis are performed; elastic modulus and creep are used as a function of concrete age; and several factors such as temperature difference, multistep cooling mode, and earlier cooling are also studied. The research results show that due to the mesoscopic heterogeneity characteristics of concrete, there is a great deal of difference between homogeneous model and heterogeneous model; pipe cooling can lead to large residual stress around the aggregate and produce a large range of damage, and previous homogeneous model indeed underestimates the effect of cooling-induced stress; using multistep cooling and early cooling mode can reduce this damage; the coolinginduced damage has significant influence on the anti-crack performance of concrete. In the final, based on the research results, the temperature difference between the concrete and pipe water of the second-phase cooling was recommended to be controlled at approximately 5°C.