Recycling sediment, calcium carbide slag and ground granulated blast-furnace slag into novel and sustainable cementitious binder for production of eco-friendly mortar

The generation of dredged sediments (DS) exerts a heavy burden on the surrounding environment. Traditional landfills of DS not only contaminate the environment, but also waste precious resources. In this study, DS from Taihu Lake, together with calcium carbide slag (CCS) and ground granulated blast-furnace slag (GGBS), was used as supplementary cementitious materials (SCM) to replace cement to develop a novel cementitious binder for the production of mortar. The effects of varying contents of DS, CCS, and GGBS on the properties of the specimens were systematically investigated. The results showed that the incorporation of DS in cement mortar led to a reduction in the flexural and compressive strength at all curing ages in a dosage dependent manner due to a rather weak pozzolanic activity. The addition of GGBS in the specimen significantly increased the 28-d flexural and compressive strength, which was even higher than that of the samples with the same amount of cement. More importantly, this beneficial effect was more obvious in the co-existence of GGBS and CCS because of the formation of more C-S-H gel (with a simultaneously high pH) revealed by XRD, SEM and TG analysis. The optimum mechanical properties were obtained by a combination of 60% OPC, 20% DS, 10% GGBS, and 10% CCS. Whereas, the mix with a higher content of DS (20% OPC, 60%DS, 10% GGBS and 10% CCS) can be potentially used for controlled low-strength materials. The application of the developed product in eco-friendly construction materials can sustainably alleviate the burden of DS, CCS, and GGBS on the environment.