Investigations on the hydration characteristics of blended ferroaluminate cement containing granulated blast furnace slag

Ferroaluminate cement (FAC), a low-carbon binder with high corrosion resistance, is not commonly utilized because of its high cost. It is more affordable to partially replace FAC with supplementary cementitious material (SCM) such as granulated blast furnace slag (GBFS). However, there have been few studies on the properties of GBFS-FAC binary binder systems, in order to make a good understanding of the properties of FAC blended with GBFS, the effect of GBFS on the hydration and hardened properties of FAC was investigated from hydration heat, compressive strength, chloride penetration resistance, hydration products, pore structure, etc., and the simulated pore solutions of FAC and OPC were prepared and characterized to explore the hydration mechanism of GBFS in FAC environment. The results indicated that GBFS incorporation slowed down the hydration rate and significantly altered the hydration process of FAC such as delaying the formation of ettringite. When the GBFS content was more than 20%, the amount of hydration exotherm peaks of FAC blended with GBFS decreased due to the disappearance of the third exothermic peak. Adding GBFS did not affect the phase assemblage, but reduced the amount of hydration products and increased the porosity of the samples, resulting in the deterioration of the compressive strength and chloride penetration resistance (with the GBFS content increasing from 0% to 30%, the 28d compressive strength decreased from 44.25 MPa to 31.86 MPa). The hydration activity of GBFS in FAC pore solution was lower compared to that in OPC pore solution, due to the lower Ca and S concentrations, lower pH, and lower conductivity of FAC pore solutions.