Mechanical properties, flexural behaviour, and ductility characteristics of fibre-reinforced geopolymer mortar: Fid-Bau Portal

Mechanical properties, flexural behaviour, and ductility characteristics of fibre-reinforced geopolymer mortar

Farag Gaddafi, Adel Kassem / Johnson Alengaram, U. / Muhamad Bunnori, Norazura / Ibrahim Muhammad, S.I. / Ibrahim, Shaliza / Sumesh, Mathialagan

Abstract

Highlights • FA with EPP were considered as a sustainable replacement material to produce geopolymer mortar. • Flexural and deflection behaviours of FRGM varied depending on the fiber types. • FRGM specimens had a significant reduction in residual compressive strength, especially at 600 °C. • The use of MS fibers in geopolymer mortar could overcome its brittleness to certain extent.

Abstract This study aims to explore the potential of ambient-cured geopolymer as a substitute for ordinary Portland cement (OPC)-based mortar. However, due to their brittle nature, geopolymer materials require reinforcement to enhance ductility. To address this, an experimental program was conducted to investigate the effects of adding polypropylene (PP) and micro steel (MS) fibers to fiber-reinforced geopolymer mortar (FRGM) at volume fractions of 0%, 0.5%, 1%, and 1.5%. The ternary blended geopolymer mortar consisting of fly ash (FA), and ground granular blast furnace slag (GGBS), along with a novel pozzolan called eco-processed pozzolan (EPP) was investigated. The present study assessed the hardened properties of the FRGM, including compressive strength, splitting tensile strength, modulus of elasticity (MoE), ultrasonic pulse velocity (UPV), and the compressive strength of the material when exposed to elevated temperatures. The aim of this study was also to investigate the load–deflection response in terms of deflection, load, flexural strength, and toughening mechanisms; and also, the bonding between the fibers and the mortar matrix was examined using field emission scanning electron microscopy (FESEM). The results indicated that including 0.5% PP fibers and up to 1.5% MS fibers marginally improved compressive strength and MoE. The corresponding increments in splitting tensile strengths were 5% and 134%, respectively. The addition of fibers improved the fracture parameters of the FRGM. The inclusion of both MS and PP fibers significantly enhanced post-cracking flexural and toughness energy. At deflection L/150, MS fiber mixes exhibited 4–5 times higher toughness energy than PP fiber mixes, and also its evidently observed in the FESEM micrographs. The incorporation of 1.5% fiber volume to non-fibrous mix resulted in an improvement of 43.2 N.m. and 10.1 N.m. in toughness (T150) for MS and PP mixes, respectively. At an elevated temperature of 600 °C, the FRGM specimens gained a massive reduction in compressive strength, with the maximum result being at 87% for 1.5PP and 71% for 0.5MS. Overall, the MS fiber-reinforced geopolymer mixes exhibited superior performance as compared to PP fibers.