Durability and shrinkage performance of self-compacting concrete containing recycled fine clay brick aggregate

Abstract

Making effective use of recycled fine clay brick aggregate (RFCBA) is of benefit to reserve natural resources and protect the environment. The RFCBA has a high-water absorption capacity, which means it can be potentially used as internal curing agent for low water-to-binder concrete mix. The current study uses RFCBA to replace natural fine aggregate in self-compacting concrete (SSC) and investigates the influence of RFCBA dosage and its moisture content (saturated surface dry and oven dried) on the internal relative humidity (RH), free shrinkage and restrained shrinkage performances under drying, as well as the freezing-thawing resistance and chloride ion penetration resistance abilities. The results show that the use of the RFCBA can effectively mitigate the internal RH drop of SCC under drying. This significantly reduces the drying shrinkage and crack risk under restrained condition. The chloride ion penetrability test indicates that the use of RFCBA reduces the chloride ion penetration resistance ability of SCC. However, the chloride ion penetrability of SCC having a RFCBA substitution ratio up to 100% remains very low after 56-day curing. Furthermore, on the one hand, the free-thawing resistance of SCC is reduced when saturated RFCBA is used. On the other hand, the use of dried RFCBA can increase the free-thawing resistance of SCC. Nevertheless, the SCC possesses a F200 frost resistance with a replacement level of 100% saturated RFCBA.