QUANTITATIVE CORRELATION BETWEEN AGGREGATE WATER ABSORPTION AND CONCRETE STRENGTH IN MULTI-CYCLE RECYCLING

This study investigated the influence of quality enhancement of multi-recycled aggregates on the performance of concrete. First-generation (RA1) and second-generation (RA2) recycled aggregates were subjected to three conditions – untreated, mechanically treated, and chemically treated – and the corresponding concretes incorporating these aggregates as coarse aggregate were evaluated in terms of workability and compressive strength. For untreated RAs, water absorption sharply increased with increasing recycling cycles, accompanied by a marked decrease in density. These changes resulted in a slump loss of 47 % and a compressive strength reduction of up to 13 %. Mechanical treatment slightly reduced the water absorption, but the improvement was marginal for RA2. In contrast, chemical treatment improved the physical properties of both RA1 and RA2, bringing them close to those of natural aggregate, and the corresponding concretes achieved strengths equivalent to those of natural aggregate concrete. According to regression analysis, a strong negative linear correlation was observed, indicating that a 1 % reduction in water absorption of RAs leads to an approximate 1.9 % increase in compressive strength of concretes. The findings of this study indicate that improving the properties of RAs can effectively enhance the performance of concrete and demonstrate the feasibility of repeated recycling, regardless of the number of recycling cycles.