Wei-Zhi Chen

Properties of recycled aggregate concrete (RAC) are influenced by the composition and particle size distribution of recycled coarse aggregate (RCA). The study herein designed seven distinct groups of RACs with varying aggregate fractal dimensions (D) and one group of natural concrete (NAC). The impact of D on the workability, compressive strength, resistance to chloride ion penetration, and carbonation resistance of RAC was measured. It was found that an increase in the D value led to a decrease in the slump and slump flow, with the compressive strength and chloride ion penetration increasing and then decreasing, and carbonation gradually declined. The optimal fractal dimension was thereby determined to be 2.547 by a strength model accommodating two parameters of D and the curing age. Additionally, the mass percentage of each particle size for the corresponding gradation was presented. The compressive strength and chloride permeation resistance of RAC (D = 1.0) relative to RAC (D = 2.5) was increased by 16.7% and 13.3%, respectively. Furthermore, the carbonation depth of RAC (D = 2.5) was comparable to that of NAC. Additionally, the carbonation resistance of RAC was influenced by both the size distribution and the degree of natural carbonation of RCA, resulting in four distinct features relative to NAC. It is thereby feasible to enhance RAC performance through the manipulation of RCA’s fractal dimensions.

The rising amount of construction and demolition wastes (C & DWs) is triggering serious environmental and social problems globally. This study conducted an experimental investigation of basalt fiber (BF)-reinforced concrete with recycled aggregates (RAs) sourced from C & DWs. The flexural strength, the flexural to compressive strength ratio, and the drying shrinkage are set as indicators for the evaluation of the coupling effect of BF and RA in concrete. Results show that BF generated a significant effect on the flexural strength until the BF dosage was no higher than 1%. The excessive mixing amount of BF, though it still contributed to a positive effect on elevating the flexural strength, was of a reduced utility. Regarding the flexural to compressive strength ratio (denoted as ratio), BF and RA jointly produced a positive synergistic effect. In addition, the BF was verified as competent in curbing the adverse effect of RA incorporation upon the drying shrinkage. Relative to the benchmark concrete which contains 100% RA and no BF, 1% BF contributed to a 31.6% reduction in the drying shrinkage. The results prove that BF reinforcement is a feasible and promising approach to curb the drawbacks of RA concrete.