Effect of Oil Palm Fiber Content on the Physical and Mechanical Properties and Microstructure of High-Calcium Fly Ash Geopolymer Paste

Abstract

This paper investigates the effect of oil palm fiber content on the physical and mechanical properties and microstructure of high-calcium fly ash geopolymer paste. The oil palm fiber was added to the mixture at 0, 1, 2, and 3% by weight of fly ash. Sodium hydroxide (NaOH) and sodium silicate $$(\hbox {Na}_{2}\hbox {SiO}_{3})$$ were used as liquid alkaline activators. The bulk density, compressive strength, flexural strength, pore size distribution, scanning electron microscopy, and thermal conductivity of geopolymer paste were determined. Test results showed that the bulk density of high-calcium geopolymer paste containing oil palm fibers decreased with increasing fiber content. The increase oil palm fiber content decreased the compressive strength of geopolymer paste but enhanced the flexural strength and toughness and changed the failure behavior of geopolymer composite. In addition, the pore size and total porosity also increased with the increase in fiber content, while the thermal conductivity was reduced. The addition of oil palm fiber can improve the flexural strength and thermal conductivity of geopolymer paste and could thus be developed into a fiber-reinforced composite for construction purposes.