Treatment of recycled concrete aggregate to enhance concrete performance

Recycled concrete aggregates (RCA) have received the attention of several researchers over the last few decades to overcome aggregate shortages and to push towards sustainable and environmental-friendly concrete. Nevertheless, utilizing recycled aggregates at a full replacement level may cause a reduction in its fresh, mechanical, and durability characteristics compared to concrete produced with normal coarse aggregates (NCA). This study aims at investigating the following influencing parameters: (a) four replacement levels of 0%, 33%, 67%, and 100% of recycled aggregate, (b) two maximum aggregate sizes of 10 and 20 mm, and (c) three treatment methods of (i) cement-silica fume slurry treatment (T1), (ii) sodium silicate solution treatment (T2), and (iii) Los Angeles (LA) abrasion treatment (T3). The test results revealed that the fresh properties of concrete were negatively impacted by the utilization of the untreated RCA, especially at higher replacement levels, irrespective of maximum aggregate sizes. The treated RCA with T1, T2, and T3 enhanced the concrete slump by 15%-35% compared to the untreated RCA. While the reduction in compressive strength for the untreated specimens was noticeable compared to the control specimens. The enhancement in the compressive strength for the treated RCA by T1, T2, and T3 was more pronounced regardless of the maximum aggregate size. The reduction in the water absorption for the treated RCA was clearly noticeable for the bigger aggregate size (20 mm) than that of 10 mm.