Long-term behaviour of concrete produced with recycled lightweight expanded clay aggregate concrete

In this paper some of the main long-term properties of concrete produced with recycled aggregates obtained from crushing both structural and non-structural lightweight concrete (LWC) are analysed. The properties studied are drying shrinkage, capillary and immersion absorption, and carbonation and chloride penetration resistance. A comprehensive experimental study was carried out on a series of concrete mixes in which ratios of 20%, 50% and 100% of two types of coarse lightweight aggregates (LWA) were replaced with two types of recycled lightweight concrete aggregates (RLCA). Long-term shrinkage is affected by the paste adhered to LWA and increases as the replacement ratio of LWA with RLCA goes up. However, the internal curing promoted by RLCA reduces the early shrinkage. In terms of durability, the experimental results show that generally all the properties studied decay due to the progressive replacement of structural LWA with RLCA. However, despite the general reduction of long-term properties, recycled lightweight concrete (RLWC) can be also durable, regardless of the type of RLCA. Moreover, it is shown that even for low to moderate strength RLWC the mechanism of carbonation is not a determinant factor for durability. On the other hand, the carbonation and chloride penetration resistance of concrete with non-structural LWA tends to improve with the incorporation of RLCA. It can thus be concluded that RLWC may be a viable and more cost-effective alternative solution, especially given its higher structural efficiency. In addition, RLCA obtained from non-structural LWC can be incorporated in concrete without significantly compromising its durability.