Influence of cobinders on durability and mechanical properties of alkali-activated magnesium aluminosilicate binders from soapstone

Abstract Alkali-activated magnesium aluminosilicate binders using only soapstone have been found to develop low strength and unacceptable durability properties. One of the effective solutions to enhance mechanical and durability properties of these binders could be using cobinders. Since cobinders are rich in different chemical components, the addition of different cobinders has different impacts on the mechanical performance and durability. This study investigates the influences of replacing 20% (in wt.%) of soapstone by different cobinders (metakaolin, lime, stone wool, and silica fume) on the mechanical strength (compressive and flexural strength), drying shrinkage, and durability (acid attack, high temperature, carbonation, water absorption by immersion, and capillary action). Moreover, the impacts of this replacement were analyzed by thermogravimetry analysis and X-ray diffraction. The results showed that the type of used cobinder has a great impact on the mechanical and durability performances of alkali-activated soapstone binders. In general, the lowest performance in the hardened-state properties resulted from the addition of lime as a cobinder, while each of the other cobinders had the best performance in one aspect of hardened-state properties.