Impact of Silica Fume on the Mechanical Characteristics of Lime-Based Lightweight Geopolymer Mortar

In recent years, geopolymer has been used as a cement replacement in the production of eco-friendly mortar and concrete. Most research used fly ash and slag as base materials for producing geopolymers. This work aimed to use lime as the base material for a geopolymer, with aluminum powder, to produce lightweight geopolymer mortar with different replacement levels of silica fume to enhance its properties. Many tests were done to find out the behavior of this type of mortar, such as bulk density, compressive strength, tensile splitting strength, flexural strength, and sorptivity. In addition, a statistical analysis was carried out on results after 28 days of casting. The results showed that the fresh density decreased from 1997.8 to 1783.7 kg/m3 when replacing up to 10% of lime with silica fume, and the hardened density decreased from 1896 to 1673.6 kg/m3 for the identical replacement level. Compressive, splitting tensile, and flexural strength decreased with increasing silica fume replacement level up to 10%. The sorptivity index increased with increasing silica fume replacement level.