Quality improvement of recycled aggregates using the acid treatment method and the strength characteristics of the resulting mortar

This study was conducted with the aim to chemically remove the cement paste attached to the aggregate surface using acidic substances. Sulfuric and hydrochloric acids were used as the acidic substances, and after analyzing the quality characteristics of the aggregates following the acid treatment, a mortar test was performed using the aggregates. The results showed that the acid-treated recycled aggregates were superior to the original aggregates and the recycled aggregates that were manufactured using natural water in terms of density, absorption ratio and solid volume percentage. Based on this, it was determined that acid treatment was effective in improving the quality of recycled fine aggregates. In addition, the results of reviewing the strength characteristics of the mortar obtained using the acid-treated aggregates showed that the residue substances remaining in the recycled fine aggregates after reacting with the cement paste had a negative impact on the concrete strength. Based on this, it was determined that in case of improving the quality of recycled aggregates by acid treatment, there needs to be strict management of the products of the reaction with the acid in order for the aggregates to be used in structural construction.