Thermal insulation and durability of alkali-activated lightweight slag mortar modified with silica fume and fly ash

Abstract

Green building indices prioritize energy efficiency, which in turn promotes sustainable development. One of the most energy-consuming sectors globally is the building sector. Developing green insulating materials based on byproducts has environmental benefits and profits in reducing energy consumption in the building sector and other sectors. This study aimed to develop thermal insulating materials based on byproducts for binders and expanded perlite (EP) for fine aggregate cured at room temperature. Alkali-activated lightweight slag mortars with/without foaming agent were prepared. To increase the efficiency of the thermal insulation, the slag was partially replaced with a fixed ratio of silica fume (SF) (15%) and different ratios of fly ash (FA) (15%, 40% and 65%). After room temperature curing, the bulk density, mechanical strength, accelerated aging resistance, water absorption, total porosity and thermal conductivity were measured. The selected samples were examined using sophisticated tools. The results showed that the selected byproducts can be efficiently employed as insulation materials, of which the obtained results of thermal conductivity, bulk density, total porosity, water absorption, compressive strength and flexural strength were in the range of 0.172–0.082 W/mK, 1191.6–450 kg/m3, 33.2–48.7%, 28–45.1%, 12.48–1.5 MPa and 3.43–0.46 MPa, respectively. All the studied specimens exhibited strength reduction after accelerating aging, but the reduction rate was mitigated by increasing the FA content. Increasing FA content has a benefit in increasing the efficiency of thermal insulation.