Durability assessment of concrete containing surface pretreated coarse recycled concrete aggregates

Recycled aggregate concrete (RAC) made with recycled concrete aggregates (RCA) is different from conventional concrete cast with natural aggregates due to the adhered cement mortar on RCAs to the former. Hence, the properties of concrete especially durability are expected to be affected when the RCAs are incorporated in the concrete mix. In this paper, two surface pretreatment methods were investigated to enhance the properties of RCAs and the durability performance of mixes was studied. The RCAs were coated by silica fume slurry manually and in the desiccator, namely RACCM and RACCD methods, respectively. The replacement level of coarse RCAs was considered at 100% in the mixes. Furthermore, three effective water-to-cement ratios (0.30, 0.35, and 0.40) were used. Tests were undertaken to establish the compressive strength, ultrasonic pulse velocity (UPV), electrical resistivity (ER), and chloride ion penetration resistance of each mix. Results indicated that compressive strength declined with the incorporation of RCAs and both pretreatment methods obviously enhanced the ER and chloride ion penetration resistance, which was significantly governed by silica fume slurry. More interestingly, test results indicated that the surface treatment methods were effective in reducing total charge passed. The RACCM method showed relatively more efficient results than RACCD.