Properties of Basalt Fiber-reinforced Lightweight Geopolymer Mortars Produced with Expanded Glass Aggregate

Abstract

Geopolymers are environmentally friendly binders with high mechanical properties and good durability characteristics. The advantages provided by geopolymers can be combined with the benefits of lightweight concrete. However, the number of studies on geopolymers produced with lightweight aggregates is limited. This study investigated the properties of fly-ash based geopolymer mortars prepared with expanded glass aggregate, as well as the influence of fiber addition on these mortar properties. For this purpose, fresh unit weight, water absorption, compressive strength and high-temperature resistance (upon exposure to 900°C) of the mortars were determined. The inclusion ratios of fibers were 0.1%, 0.2% and 0.4% by volume. Sodium silicate and sodium hydroxide were used as activators, and curing was carried out at 90°C for 24 hours in a laboratory-type oven. In addition to lightweight mortars, conventional geopolymer mortars were produced with limestone aggregate with similar gradation, and the obtained results were compared. The results have shown that the compressive strength of the reference mortar was 31.9 MPa, the use of expanded glass aggregate reduced the strength to 8.2 MPa, meanwhile, the fresh unit weight decreased by approximately 50%. After the hightemperature experiment, the compressive strength of the reference mortar decreased by 40%, while the strengths of lightweight mortars increased in the range of 61.3% to 76.4%. It was also determined that the use of fiber did not have a significant effect on compressive strength and unit weight. The results proved that it is possible to produce expanded glass aggregate-bearing lightweight geopolymer mortars with acceptable mechanical properties.