Mechanical Properties of Ultra-Lightweight Geopolymer Composite after Elevated Temperature Exposure

Abstract

This paper investigates the mechanical properties of a new type of ultra-lightweight geopolymer composite (ULGC) exposed to elevated temperatures up to 700 °C. This ULGC materials, using ground granulated blast furnace slag, fly ash, and silica fume as the precursor as well as fly ash cenosphere as lightweight aggregates, has a density of less than 1400 kg/m3 and compressive strength up to 40 MPa and thus it has high structural efficiency compared to other types of concrete materials. The effect of polyvinyl alcohol (PVA) fiber dosage and PVA fiber length on the compressive strength, bending strength as well as mass loss of ULGCs after elevated temperature exposure were evaluated, combining a two-factor analysis of variance. The results indicated that when the temperature was below 300 °C, the PVA fiber could improve the mechanical properties of ULGC. However, when the temperature was higher than 300 °C, due to the melting of fibers, the positive effect of fiber dosage on bending strength significantly reduced, and fiber dosage exhibited a negative effect on compressive strength. The ULGCs containing 6mm and 18mm fibers showed better bending strength, while the effect of fiber length on compressive strength of ULGC was negligible.