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With the rise in the adoption of recycled aggregate for construction, investigation on ways to improve its quality has been wide spread. The major factor that affects the quality of recycled aggregate is the large amount of cement mortar that remains on the surface of the recycled aggregate. This attached mortar results in higher porosity, higher water absorption rates, and thus a weaker interfacial zone between new cement mortar and aggregates, weakening the strength and mechanical performance of concrete made from recycled aggregate. This paper attempts to compare the effect of chemical as well as mechanical treatment approaches in reducing the mortar attached to aggregate. Six series of concrete mixtures are prepared using natural aggregate, recycled aggregate, recycled aggregate treated with HCl and H2SO4, recycled aggregate obtained after scrubbing treatment, and heating and scrubbing treatment. The physical and mechanical properties of these aggregates, and their strength and performance of recycled aggregate concrete are determined. The results show that treatment with H2SO4, and heating and scrubbing yield, aggregate with reduced water absorption and other desired properties of natural aggregate. The concrete made out of these treated aggregates are able to achieve strength and performance characteristics on par with natural aggregate concrete.
Purushothaman et al. (2014) studied this question.