Freeze-thaw resistance of concrete containing mixed aggregate and construction and demolition waste-additioned cement in water and de-icing salts

Abstract

Durability is a key property in concrete structures exposed to freeze–thaw cycles, particularly where the concrete mix includes recycled materials. This study explores 25% or 50% replacement of natural with mixed recycled aggregate (MRA) from construction and demolition waste (CDW), in concrete mixes prepared with recycled cement (including 25% fired clay-based waste and called OPC-CDW) or with ordinary Portland cement (OPC) and its effect on structural concrete resistance to freeze–thaw cycles (exposure classes XF1 to XF4). The findings show that the inclusion of MRA and OPC-CDW affect the material differently depending on the type of exposure. In concrete exposed to water, MRA induce a decline in load capacity, whereas OPC-CDW raised strength. The opposite was observed in concrete in contact with de-icing salts. The recycled concrete designed, proved to resist freeze–thaw cycles conducted in water (XF1 and XF3), whilst the presence of de-icing salts (XF2 and XF4) compromised their durability. In such cases additional measures would be needed for in the design and construction of structures built with recycled concrete.