Enhancing the aggregate impact value and water absorption of demolition waste coarse aggregates with various treatment methods

Recycled aggregate (RA) from construction and demolition waste can readily be used to replace natural aggregate in concrete. Nonetheless, the poor quality of RA adversely affects the properties of recycled aggregate concrete, limiting its use to only non-structural applications. This study examined the effects of various treatment methods by testing the aggregate impact value (AIV) and water absorption (WA) of recycled coarse aggregate before and after treatments as an indicator to examine the efficiency of these treatments. The results showed that the untreated RA achieved 17% and 6.1% for AIV and WA, respectively. Accelerated carbonation treatment at 50% CO2 concentration level for six days of CO2 exposure time achieved the best results among other carbonation conditions, showing 11% and 46% enhancements in the AIV and WA, respectively. The RA treated with cyclic limewater combined with accelerated carbonation exhibited better improvement in the AIV and WA compared to the sole use of accelerated carbonation treatment. Coating RA with cement-silica fume slurry at 0.1 mm coating thickness was found to be optimal, achieving 12% and 54% enhancements in the AIV and WA, respectively. Soaking RA in a 10% Portland cement - pulverized fuel ash - silica fume solution for 4 h was found to be optimal, recording enhancements of 13% and 54% in the AIV and the WA, respectively among other soaking solutions. Soaking RA in 5% sodium silicate – silica fume solution for 4 h was found to be optimal, obtaining 8% and 33% enhancements in the AIV and the WA, respectively. The treatment techniques proposed can be a powerful tool for promoting the use of RA in the construction industry.