Experimental Analysis of Fly Ash Based Geopolymer Concrete Incorporating Potassium Hydroxide for Use in Rigid Pavement Construction

Abstract

The escalating menace of global warming and the skyrocketing expenses associated with raw materials in cement production, numerous researchers in the construction industry are actively seeking alternative, environmentally friendly (green), and economically viable materials to manufacture concrete. Cement is widely regarded as the second most used material in the world after water. One such method that has gained attention is the use of geopolymer concrete, specifically fly ash-based geopolymer concrete (FGPC). This research project focuses on the experimental analysis of fly ash-based geopolymer concrete (FGPC) and its applicability in highway construction. The aim is to explore environmentally friendly and cost-effective alternatives to traditional cement-based concrete. This study compares the mechanical properties of ordinary Portland cement concrete (OPCC) and FGPC. Three different batches of concrete are investigated: OPCC as the control mix, FGPC, and FGPC with 5% cement as an admixture. The mix proportions are kept similar to ensure a fair comparison. Mechanical strength tests, including compression strength, splitting, and three-point flexural tests, are conducted OPCC and FGPC samples. Potassium hydroxide with molarity 14 and Na2SiO3 solutions were used as alkaline activator in this study. The experimental results revealed that when FGPC is subjected to higher temperatures of 60°C (oven curing), a significant 8% enhancement in compressive strength is observed after 7 days, surpassing the performance of the control mix at 28 days. Moreover, incorporating a 5% cement admixture into FGPC leads to a notable 4% boost in compressive strength after 28 days, compared to the control mix. In terms of flexural strength, FGPC exhibits slightly superior values to the control mix after 7 days. However, FGPC with 5% cement as an admixture, when cured under ambient conditions, shows a significant 15% increase in flexural strength at 28 days compared to the control mix. Three-point flexural test was also conducted, the results indicate that FGPC pavements have similar thickness to OPCC pavements. However, when FGPC is combined with a 5% cement admixture and used in ambient curing, there is an 8% reduction in pavement thickness compared to OPCC pavements. This reduction suggests that FGPC with a cement admixture can optimize material usage and reduce overall construction costs. The cost analysis demonstrates the economic viability of using FGPC in pavement construction. FGPC pavements can reduce costs by 12% compared to OPCC rigid pavements. Furthermore, FGPC with a 5% cement admixture shows a cost reduction of 16% compared to OPCC pavements. These cost savings highlight the attractiveness of FGPC as a sustainable and cost-effective option for infrastructure development.