Study on pore characteristics of recycled aggregate concrete mixed with glazed hollow beads at high temperatures based on 3-D reconstruction of computed tomography images

Abstract

High temperatures can have a profound impact on the internal pore structure of concrete, which consequently deteriorates its mechanical properties. In order to examine the effect of high temperatures on the microstructural characteristics and residual mechanical properties of recycled aggregate concrete mixed with glazed hollow beads (RATIC), the cube compressive strength test and CT test were carried out on RATIC specimens treated at the different temperatures. Through three-dimensional reconstruction of CT images, the three-dimensional microstructure of the RATIC after the high-temperature treatment were obtained to analyze the variation in its internal pores with the temperature, and to elaborate on the mechanism for the deterioration of its mechanical properties from the perspective of microstructural characteristics of pores. The results show that the glazed hollow bead (GHB) can slow down the spread of heat in the concrete and renders a positive effect on the heat-induced damage resistance of concrete. The incorporation of the GHB effectively optimizes the pore structure of the RATIC and reduces the pore distortion caused by the high temperature. In addition, the quantitative relationship between the pore characteristic parameters and the residual compressive strength of RATIC was investigated, and a computational model was obtained to characterize the relationship between the pore characteristic parameters and the residual compressive strength using nonlinear analysis.