Effects of a combined admixture of slag powder and thermally treated flue gas desulphurization (FGD) gypsum on the compressive strength and durability of concrete

In this paper, the effects of a combined admixture of slag powder and thermally treated flue gas desulphurization (FGD) gypsum on the compressive strength and durability of concrete were explored. The gypsum was baked at a proper temperature of 200°C for 60 min; it was then mixed with slag powder to form the type-G slag powder in which SO₃ content was controlled at the optimum ratio of 3.5%. Concretes containing the type-G slag powder or ordinary slag powder were further contrasted on the compressive strength and durability. The results showed that the compressive strength, resistance to chloride, and resistance to gas permeability of concrete with the type-G slag powder were higher than that with ordinary slag powder. Additionally, there were no negative effects on concrete against sulfate attack. The combination of the two byproducts, slag powder and thermally treated FGD gypsum, provided synergistic benefits above that of ordinary slag powder alone.