Cracking resistance and sustainability assessment of alkali-activated slag concrete incorporating lightweight aggregate

This study aims to evaluate the cracking resistance and sustainability performance of alkali-activated slag (AAS) concretes incorporating pre-wetted lightweight aggregates (LWAs). Three replacement rates (0, 50%, and 100%) of natural coarse aggregates (NAs) with pre-wetted LWAs are used, while the ordinary Portland cement (OPC) concrete alternatives are considered as control samples. The results showed that incorporating pre-wetted LWAs effectively improved the cracking resistance of the AAS concretes, and the effect was more evident as the LWA contents increased. The cracking age of the AAS concretes was delayed from 5.6 d to 8.9 d and 10.6 d with 50% and 100% replacement of NAs by LWAs, respectively. Meanwhile, a desirable result was that the AAS concretes could still endure relatively high tensile stress after the initial cracking. The larger tensile stress could be undertook with the increase in LWA contents. Although the incorporation of LWA slightly increased the environmental burdens of the concrete alternatives, the energy consumption and five environmental impact categories of the AAS concretes were reduced by more than 20% and 40%, respectively, compared to those of OPC concretes with the same LWA content. Similar results were found in the calculation of life-cycle cost. Even for the AAS concretes with 100% LWA content, the significant environmental and economic benefits were still obviously obtained compared to the OPC concretes without LWA.