Influence of Treatment Methods of Recycled Concrete Aggregate on Behavior of High Strength Concrete

Worldwide the concrete industry has started embracing the utilization of recycled concrete aggregates (RCAs) resulting from demolition and construction waste as full or partial substituents in the production of high-strength concrete (HSC) due to their economic and environmental benefits. Several parameters were experimentally investigated in this study. The first parameter analyzed the effect of replacing varying percentages of coarse aggregate with recycled aggregate. The second parameter examined the influence of two aggregate sizes (10 and 20 mm). The third parameter was intended for investigating the influence of three different RCA treatment methods utilizing sodium silicate immersion, cement slurry, and the Los Angeles (LA) abrasion simulation. The test results generally indicated degradation in the engineering properties of concrete produced using untreated RCA compared to the control. The degree of reduction increased as the replacement percentage was increased regardless of the aggregate size. The reduction in compressive strength appeared to have a more pronounced effect in comparison to the splitting tensile strength. The use of treated RCA improved concrete slump by 15-35%. This also caused enhancement in the engineering properties, especially for the LA abrasion mechanical treatment, which was very promising for both aggregate sizes. In comparison with the untreated RCA, the relative enhancement in water absorption was up to 76%, whereas splitting tensile and compressive strengths increased by 3-50% and 5-60%, respectively.