Microstructural and Macroperformance of Recycled Mortar with High-Quality Recycled Aggregate and Powder from High-Performance Concrete Waste

Abstract

The amount of high-performance concrete (HPC) in construction engineering is growing at a predictable high rate following rapid urban development. However, the utilization of HPC waste as secondary building materials has received little attention until now because previous investigations have focused on the reclamation of ordinary concrete waste. Therefore, this work studied the characterization of mortar containing high-quality recycled aggregate (HRA) and high-quality recycled powder (HRP), both sourced from HPC waste. HRP contains some active components, and the pore structure of paste incorporated with HRP is finer than that of paste containing ordinary recycled powder. Incorporating HRP in paste shortens the setting time and improves the fluidity, and mixing HRA with coarse surface benefits the performance of interfacial transition zone. Incorporating HRA and HRP can both reduce the drying shrinkage, and the maximum shrinkage value of HRA mixed mortar is obviously lower than that of ordinary recycled-aggregate mixed mortar. The mechanical strength first increases and then drops with the HRA incorporation. The incorporated HRP reduces the mechanical strength, but decreasing HRP particle size enhances the mechanical strength of mortar. The water absorption of mortar increases as HRA or HRP is incorporated, but decreasing HRP particle size reduces the water absorption of HRP-incorporated mortar. The mortar with both HRA and HRP has a distinct lower water absorption than the mortar with both ordinary recycled aggregate and powder. High-quality recycled mortar owning good performance can be made by intermixing a suitable amount of HRA and HRP.