Salt scaling resistance of highway concrete containing pre-wetted lightweight fine aggregate as internal curing agents

Internal curing technology using pre-wetted lightweight fine aggregates (LWFAs) as additives has been proved as an effective means for mitigating both autogenous shrinkage and early-age cracking under the sealed-cured conditions. However, concrete structures (i.e. pavements and bridge decks) can be subjected to severe environmental loadings such as de-icing salt and freeze/thaw cycles. In this study, the salt scaling-resistant properties are investigated on concretes containing two types of pre-wetted LWFAs as partial replacement of sand at water-to-cement ratio (w/c) of 0.3 and 0.4. The results reveal that concretes containing pre-wetted LWFA are more sensitive to salt scaling damage because of the higher degree of saturation of concrete and low strength of LWFA. The hydraulic and crystallisation pressures generated in the pores of LWFA might be the major contributor for the crushing of LWFA and the consequent damage in concrete. Air-entraining admixture must be used in the LWFA concrete in order to achieve sufficient frost resistance.