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.

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

In order to utilize the expansive property of the slag-sulphate cement to make high-strength construction materials, suitable mixtures of slag-lime-gypsum (S-L-G) were studied on 1:3 cement-sand mortars. The strength under constrained condition was found to be substantially higher than that under free condition as a function of curing time. The strength under constrained condition was also dependent on expansion and composition up to a certain extent, after which a stable behaviour was observed. This was ascribed to the stabilization of the morphology at longer time. A mechanistic model has been proposed to explain the higher strength under constrained condition by the difference of expansion at different time intervals being normalized to a unit L/G ratio.

Enhancement of Strength of Expansive Cements of Slag-Lime-Gypsum System by Setting under Constraint

Compressive strengths of the lime-slag cements prepared from slags of composition in the system CaO-Al2O3-SiO2 reported in Part I of the paper have been correlated statistically with relevant factors, such as degree of hydration of slags, amount of slag per briquette and fractional volume of the test briquettes occupied by lime, slag and sand. Degree of hydration and amount of slag per briquette were combined into one by multiplying them, the product being a measure of the amount of hydrated material present in a test piece. The final relation was found as where C = compressive strength lb/in.2 Hm = product of degree of hydration of slag and amount of slag/briquette P = percent volume packed.

Hydraulicity of glassy slags of the system CaO-Al2O3SiO2: II. Compressive strength of slag-lime mixtures in relation to hydration of slags and packed volume of solids

D. Lahiri

Papers

Hydraulicity of glassy slags of the system CaO-Al2O3SiO2: II. Compressive strength of slag-lime mixtures in relation to hydration of slags and packed volume of solids