Performance Improvement of High-Strength Concrete Using Processed Recycled Aggregates

Abstract

This study examines the use of recycled concrete aggregate (RCA), derived from construction and demolition (C&D) waste, as a substitute for natural aggregates in high-strength concrete. RCA generally retains adhered cement mortar, which increases water absorption and weakens the aggregate matrix interface. Aggressive removal may also damage the parent aggregate, further impairing its performance. To address these challenges, recycled aggregates were processed through repeated grinding and incorporated into M75-grade concrete using a two-stage mixing method.

The results demonstrate notable improvements in both mechanical and durability properties. While durability indicators like water absorption, sorptivity, chloride ion penetration, drying shrinkage, and abrasion resistance reached the levels of natural aggregate concrete, workability, compressive strength, tensile strength, and their ratio had shown a notable improvement. With optimized processing and mixing, the performance gap narrowed to within 10% of virgin aggregate concrete. Remarkably, 70 MPa strength was achieved with 100% RCA, with the improved tensile-to-compressive strength ratio confirming a stronger aggregate–matrix bond.