Effect of MgO on Hydraulicity of Slag in the System CaO-Al2O3-SiO2-MgO

TLDR: In this article, the hydraulicity of slags was estimated from the compressive strengths of 1:3 mortars, the cements being prepared from 1.8 parts slag and 1 part hydrated lime by volume.

Abstract: Slags having three different SiO2: Al2O3 ratios (1.2,1.9 and 2.6) and three different CaO contents (44%, 39% and 34%) were prepared. These slags were classified into nine series, in each of which Al2O3 and SiO2 were kept constant and CaO was replaced by MgO in molecular proportion. The hydraulicity of these slags was estimated from the compressive strengths of 1:3 mortars, the cements being prepared from 1.8 parts slag and 1 part hydrated lime by volume. The soundness of the cements produced from some of these slags and portland cement was also measured. Hydraulicity of slag had a tendency to decrease when CaO was molecularly replaced by MgO and it practically did not change when CaO of slag was replaced by MgO on weight basis. Compressive strength increased with the increase of CaO and Al2O3 content of slag and decreased with increase of SiO2 content. The cements produced from high-magnesia slags were perfectly sound and did not show any dimensional instability.