Enhancement of ultra-fine slag on compressive strength of solid waste-based cementitious materials: Towards low carbon emissions

Utilization of solid wastes in building materials can reduce the amount of cement and thus reduce carbon emissions. However, low compressive strength largely restrained the development of solid waste-based cementitious materials (SWBCM). In this study, steel slag (SS), phosphogypsum (PG), and ground granulated blast-furnace slag (GGBS) were used to prepare SWBCM. Ultra-fine slag (UFS) was used to partially replace raw GGBS in SWBCM, with intent to enhance the compressive strength of SS-PG-GGBS binders. Results showed that the strength of SS-PG-GGBS mortars was 17.0 MPa and 24.0 MPa at 7 d and 28 d, while 20% UFS mortars were 33.2 MPa and 44.9 MPa. The reason was that the high activity of UFS and nucleation-inducing effect could accelerate early hydration of SS-PG-GGBS, and the higher hydration degree of GGBS and the refined pore structure enhanced the later strength. Additionally, the promotion mechanism of UFS on SS-PG-GGBS system was proposed. These results showed an effective method to promote the strength of SWBCM. This type of binders showed greatly potential in low carbon cementitious materials.