STRESS-STRAIN RELATIONSHIP OF GEOPOLYMER CONCRETE UNDER COMPRESSIVE LOADING

Abstract

This research aimed to comprehensively investigate the stress-strain relationship of geopolymer concrete (GPC) under compressive loading. Geopolymer concrete was prepared by fly ash from Mae Moh Power Plant, Thailand and activated through sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) solutions. The NaOH concentration was fixed at ten molar, and the solution-to-fly ash ratio was set to 0.6. Four different ratios of Na₂SiO₃/NaOH (0.50, 0.75, 0.85 and 1.00) were employed to prepare GPC specimens. The specimens were designed as short columns with cross-sectional dimensions of 200 mm x 200 mm and a height of 500 mm. The specimens were divided into two sets and subjected to different curing regimes. One set was cured at 65°C for 48 hours and then tested at seven days of age, while the other set was cured at ambient temperature and tested after reaching the age of 28 days. The compressive strength of the specimens was evaluated using the ASTM C39 standard for testing cylindrical samples. The results revealed that the compressive strength was found to be positively correlated with the ratio of sodium silicate to sodium hydroxide, curing temperature, and curing time. Furthermore, the stress-strain relationship of the GPC specimens was modeled using the stress-strain equations of concrete, and appropriate formulas were derived from the data obtained. These equations can be implemented to accurately predict the stress-strain behavior of GPC in structural applications for construction, facilitating its broader adoption as a durable and sustainable alternative to conventional concrete.