Investigation on residual bond strength and microstructure characteristics of fiber-reinforced geopolymer concrete at elevated temperature

Abstract

Fiber-reinforced geopolymer concrete has been attracting attention and interest worldwide due to its sustainable properties. However, few studies have reported the pull-out behaviour of fiber-reinforced geopolymer concrete (GPC) at elevated temperatures. In order to bridge this knowledge gap, a series of detailed investigations aimed to investigate the effect of elevated temperatures on the mechanical and microstructure properties of fiber-reinforced geopolymer concrete. In the present investigation, crimped steel fibers (SF), polypropylene fibers (PF), basalt (BF), and hybrid fibers such as SF:PF and PF:BF is employed to develop the GPC. Alkaline activators such as sodium hydroxide (NaOH) of 8 M and 10 M and Na2SiO3/NaOH ratios of 2.5 are used in the production of M35 and M40 grade GPC. Compressive strength, weight loss, crack pattern, bond strength, and microstructure of fiber-reinforced GPC specimens have been evaluated, after exposing to higher temperature following ISO 834 standard fire curve. Results from the conducted tests show that adding various types of fibers improves the compressive strength and bond strength of the GPC specimens. More specifically, amongst all tested specimens, the exposed GPC-BF shows lesser weight loss and higher residual compressive strength with fewer cracks on the surface of the specimens. on the other hand, GPC with SF shows higher residual bond strength than other fiber-reinforced GPC specimens. Microstructure analysis (SEM/EDAX) confirms the extent of damage and contribution of fiber in the temperature-exposed GPC. A statistical relationship and correlation has been obtained between compressive and bond strength.