Impact of chloride intrusion on the pore structure of recycled aggregate concrete based on the recycled aggregate porous interface

摘要

This study presents the experimental results of pore structure change in recycled aggregate concrete (RAC) with a 100% replacement ratio subjected to chloride intrusion, comprehensively considered with dry-wet cycles, flexural loading, and temperature. The pore structure of the mortar was determined by mercury intrusion porosimetry, and the scanning electron microscope used to observe the apparent morphology of old and new mortar. The changes in the chemical composition of specimens after chloride intrusion were measured by X-ray diffraction. The results showed that Cl- intrusion led to the formation of a large number of new pores in the original pores that were smaller than the original pore size. The range of the original pore size distribution was also reduced. The increase in temperature increased the rate of dissolution and migration of products between the pores and promoted changes in the pore structure. A large number of connected micro-cracks were generated between the pores under flexural load conditions, which provided additional space for product recrystallization and reshaped the original crack space. The changes in the characteristics of pore structure of old mortar were generally more extensive than those of new mortar after Cl intrusion. Based on the experimental results, a model for RA dual partition-interface pore network is proposed by considering the old mortar, new mortar, old-new mortar interface, and old aggregate-old mortar interface to analyze the mechanism of change of pore structure. (C) 2020 Elsevier Ltd. All rights reserved.