Potential application of thermally treated calcium carbide residue as solid CaO activator for No-cement slag-FGDG composite

Extensive utilization of Portland cement in the construction industry increases environmental impact due to a substantial CO2 emission. The present study intends to introduce a one-part solid activated composite to cope with the excessive cement utilization and disadvantages of conventional two-part alkali-activated materials. Thermally treated calcium carbide residue (TCCR) was used as a solid activator to make the no-cement cementitious one-part composite. In addition, the composite used the ground granulated blast furnace slag (GGBFS) and the flue gas desulphurized gypsum (FGDG) as an supplementary sulphate source. The effects of varying TCCR and FGDG contents in the phase change mechanism and the fresh and hardened properties of the composite matrix were evaluated based on strength, durability and microstructural examinations. Experimental results showed that increasing TCCR contents could increase the hydration reaction due to evolved alkalinity and heat, while excessive addition resulted in poor workability. The activated composite of 12 % TCCR showed an acceptable mechanical behaviour and a compressive strength of 28.10 MPa at the testing age of 28 days, while the value increased by 54.27 % with a 5 % FGDG addition. During the hydration phases, ettringite and calcium hydroxide were predominant in the hydrated gels of silica and alumina.