Influence of Feldspar and Ground Granulated Blast-furnace slag as a partial cement replacement on mechanical properties and thermal durability and environmental impacts of cement mortars

Abstract

The production of cement generates vast quantities of carbon dioxide (CO2). The environmental significance of using waste materials in concrete and mortar mixtures has lately gained the attention of researchers. The use of Feldspar as a replacement for cement has been investigated in prior studies. However, in this study, Ground Granulated Blast-furnace Slag (GGBS) has been added to Feldspar in an effort to increase the mechanical properties and durability of mortars and decrease their environmental impacts as a novel approach. To assess their effects on the various properties of mortars, two series of 20 mix designs with varying water to cement ratios of 0.40 and 0.35 were evaluated. The impacts of substituting cement with Feldspar and GGBS on the mechanical properties of mortars are studied by compressive strength test at 7, 28, and 90 days, the flexural strength test at 28 and 90 days, and the direct tensile strength test at 28 days of curing and each mixture was evaluated for water absorption and electrical resistance. To investigate the thermal durability of mortars, residual compressive strength after exposure at 100◦C, 200◦C, 400◦C, and 600◦C was tested. Images from Scanning Electron Microscope (SEM) were also utilized to evaluate the microstructure of samples. In addition, the global warming potential (GWP) was examined for CO2 emissions. Results indicated that increasing the ratio of GGBS and Feldspar lowered the mechanical characteristics of binary mixes, whereas ternary mixtures exhibited more divergent patterns. Substituting additives for cement remarkably increased the residual compressive strength after 200◦C in most mixes compared to the control samples. Also, Increasing the ratio of additives in mixtures significantly reduced their total CO2 emissions in both water to cement, particularly in ternary mixtures including 10% Feldspar and 30% GGBS with roughly 33% decrease.