Lightweight concrete containing recycled aggregates

This study investigated the replacement of fine concrete aggregates with recycled aggregate. The results showed that the effect of recycled aggregate, so that, replacing 25, 50, 75 and 100 % of natural aggregate led to an 8, 23, 15 and 11 %, respectively, increase in the compressive strength of lightweight concrete samples. Based on these results, a microstructural analysis of the contact zone of the concrete using various types of aggregate was conducted. The shrinkage and expansion development of samples containing recycled aggregate formed from demolished waste differed from that of ordinary concrete, and the findings over 90 days indicated the impact of the substitution percentage in the recycled aggregates contained in the mixture. When 100 % fine natural aggregate was replaced with recycled aggregate, expansion increased by 15 % at 14 days and shrinkage increased by 45 % at 90 days as compared to references. Cement hydration in concrete mixes using different types of aggregates has been investigated by using an X-ray diffraction. The results showed that the sample without recycled aggregate from demolition waste LW-1 contained the maximum amount of C3S and C2S compared to the sample with recycled aggregate from demolition waste LW-5, which can harden when interacting with water. The concrete samples used to evaluate the abrasion resistance were first cured for 28 days. The results revealed that the abrasion Delta h values for samples containing recycled aggregate were lower than that for the reference samples.