The Effect of Slag Cement Substitution on the Water – cement Ratio , Setting Time and Compression Strength of Mortar at the age of 14 and 28 Days

Abstract

The use of industrial waste as a component of nowadays building material has become of major importance due to the underlining of environmental and sustainability issues. Among these materials is Ground Granulated Blast Furnace Slag (GGBFS), often referred to as slag-cement. The material is a residue produced during the steel refining process. The cementitious nature of the product makes it most suitable for ordinary Portland cement (PC) substitution. However, the behavior of this slag-cement in terms of development time and strength has not been defined in great details. In the construction industry, time is of major importance, a prolonged hydration process could delay the overall process. This research work focused on the setting time and strength response of slag-cement in mortar. The ratio of mortar constituent of cement-to-sand was 1 : 3. The percentage of slag-cement substitute to PC was 0%, 25%, 50% and 75% to the cement weight. The compressive strength was tested at the age of 14 days and 28 days. The results of the analysis showed that at a 25% slag-cement substitution a very significant increase in strength was shown. The increase was more pronounced at the age of 28 days when compared to 14 days and recorded to be 31.90%. As for the 50% and 75% slag-cement substitution, no significant increase in strength improvement was noticed. The test results showed a 2.66% enhancement for the 50% slag- cement substitution and a 2.45% increase for a 75% slag-cement replacement. The study also showed that slag-cement required a higher water-cement factor for the normal consistency