Investigation into Durability of Concrete Made of Recycled Masonry Coarse Aggregate and Pozzola

This study examines the effect of varying levels of recycled masonry coarse aggregates (RMCA) on the durability properties of recycled concrete (RC). Four series of RC were produced with RMCA replacement levels of 0%, 25%, 50%, and 100%. To enhance the properties of the RC, different dosages of silica fume (SF), natural zeolite (NZ), and fly ash (FA) were used as partial replacements for cement. A total of 40 mixed designs were prepared, and key properties, including compressive strength (CS), water absorption by capillarity (WAC), water absorption by immersion (WAI), electrical resistance (ER), and rapid chloride ion penetration (RCPT), were evaluated. The results indicated that the target CS of 40 MPa at 28 days could be achieved in RC containing up to 50% RMCA with 5% or 10% SF and 10% NZ. In terms of durability, significant reductions in WAI, WAC, ER, and RCPT were observed in RC with 100% RMCA. Furthermore, the combination of 10% NZ and up to 50% RMCA replacement resulted in a 19% reduction in WAI. A low risk of chloride ion penetration was found in mixtures containing 5% and 10% SF, regardless of the RMCA replacement level. However, the use of various percentages of class F of FA, due to its chemical composition and limited cementitious properties, did not lead to improvements in CS, WAC, WAI, ER, or RCPT.