Utilization of Fly Ash, Rice Husk Ash, and Palm Oil Fuel Ash in Glass Fiber–Reinforced Concrete

Abstract

This paper presents the use of widely available fly ash (FA), rice husk ash (RHA), and palm oil fuel ash (POFA) in Thailand to make glass fiber–reinforced concrete (GFRC). These substitutes were used to replace ASTM Type I portland cement by 0 (control), 10, 20, 30, and 40%. The particle sizes of FA, RHA, and POFA were improved by grinding in a ball mill until 95% of the particles could pass through standard sieve size no. 325. An external-spray-mix machine was employed to produce all specimens with 5% by weight of alkaline-resistant (AR) glass fibers. The GFRC specimens were investigated for water absorption, bending strength, bending strain, and toughness at 7, 28, 56, and 180 days. Throughout this period the specimens were submersed in water at room temperature (25°C). All specimens were prepared and tested according to the BS-EN 1170-5 standard. Test results showed that, for both GFRC panels with and without cement replacement by FA, RHA, and POFA, the limit of proportionality (LOP) increased with an increase in the age of curing, whereas the modulus of rupture (MOR) increased initially and then started to drop gradually. Scanning electron microscopy showed that calcium hydroxide deposition within the filaments of glass fiber made it more brittle. This might be the cause of the reduction of MOR. It is recommended that up to 20% of FA, RHA, or POFA be used to replace portland cement without affecting the physical properties of GFRC, which includes the benefits of lowering cost and helping to reduce