Properties enhancement of ternary blended geopolymer mortar with fibres / Adel Kassem Farag Gaddafi

Adel Kassem Farag , Gaddafi (2024) Properties enhancement of ternary blended geopolymer mortar with fibres / Adel Kassem Farag Gaddafi. PhD thesis, Universiti Malaya.

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Abstract

This thesis presents a comprehensive examination of two distinct aspects of construction materials: the development of ambient-cured geopolymer mortar and the enhancement of its ductility through fiber reinforcement. The investigation encompasses various properties and attributes critical to the understanding and application of these materials. First, the study focused on the development of ambient-cured geopolymer as a potential ordinary Portland cement (OPC) substitute. Ternary geopolymer mixes were examined for their workability, density, ultra-sonic velocity (UPV), compressive strength, X-ray diffraction (XRD) analysis, and scanning electron microscope (SEM) analysis. The study explored various proportions of ground granulated blast furnace slag (GGBS) at 10%, 20%, and 30% by weight as replacements in a fly ash (FA)-based mixes. The mixes included palm oil waste materials, such as palm oil fuel ash (POFA), ecoprocessed pozzolan (EPP) and palm oil clinker sand (POC) sand. The UPV values increased with higher GGBS content but were adversely affected by voids in POC sand. Compressive strength improved over time with inclusion 30% GGBS replacement exhibit a remarkable 60% after 28 days. XRD analysis confirmed the existence of amorphous geopolymers. SEM analysis showed GGBS reduced voids, leading to denser microstructures. In parallel, the study investigates the development of fiber-reinforced geopolymer mortar. Geopolymers, a subset of ceramic materials, exhibit a brittle nature. The experimental work involved the study of polypropylene (PP) and micro steel (MS) fibers added to fiber-reinforced geopolymer mortar (FRGM) at volume fractions of 0.5%, 1%, and 1.5%. The investigation assessed a range of hardened properties, including compressive strength, splitting tensile strength, modulus of elasticity (MoE), and UPV. The research assessed load-deflection response and compressive stress-strain behavior, focusing on toughness and ductility. The bonding between the fibers and the mortar matrix was examined using field emission scanning electron microscopy (FESEM). The addition of 0.5% PP fibers and up to 1.5% MS fibers marginally improved compressive strength by up to 25% and MoE by up to 14%, with corresponding increments in splitting tensile strengths enhanced by 27% and 177%, respectively. The incorporation of 1.5% fiber volume into the non-fibrous mix resulted in an average improvement of 50 N.m and 13 N.m in flexural toughness (T150) for MS and PP mixes, respectively. The equivalent flexural strength ratio for 0.5%, 1%, and 1.5% MS and PP composites ranged from 180% to 240% and 47% to 89%, indicating an improvement in the material's ductility and overall performance in bending applications. The gradual increase in MS fiber volume significantly enhances compressive toughness in mining sand geopolymer mortars, with mixes containing 0.5%, 1%, and 1.5% fibers showing up to 2.67 times improvement. Remarkably, when entirely replacing mining sand with POC sand, it demonstrates outstanding improvements in stress-strain graph results. The POC sand mixes demonstrated substantial strain enhancements. The plain mix showed a strain at failure of 0.001687 mm/mm, which increased by 84%, 185%,\ and 197% with the addition of 0.5%, 1%, and 1.5% fibers, respectively. Moreover, 1.5% MS fiber addition resulted in a 562% improvement in compressive toughness compared to the plain POC sand mix. In elevated exposure, the 1.5% MS mix exhibited significant performance increases: 42%, 69%, and 100% improvements at 200°C, 400°C, and 600°C, respectively, compared to the non-fibrous control mix. In conclusion, this research presents vital insights into the development of ambient-cured fiber-reinforced geopolymer and the enhancement of its ductility through fiber reinforcement. These materials offer the potential for sustainable and environmentally friendly applications in construction and infrastructure projects.

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