Investigation on the Effect of Concentration of NaOH with Partial Replacement of Fine Aggregate in Polyurethane-Foamed Geopolymer Concrete

This study explores the effects of Polyurethane Foam (PUF) as fine aggregate and different NaOH molarity (M) to analyze the rheological behavior, hardened properties and microstructural behavior of Geopolymer concrete (GPC) and to optimize the fine aggregate replacement and NaOH molarity. For this purpose, In the PUF-GPC mix, the NaOH molarity of GPC varied from 10 to 14 at intervals of 2 with 1.5 % superplasticizers (SP) to improve the workability of GPC. The optimum workability and strength were attained at 15% of PUF replacement and 12 molarity of NaOH from slump values, compressive, split tensile, and flexural strength results. The results indicate that the optimal NaOH molarity of 12 M, with 15% PUF replacement, achieves the highest compressive strength (40.4 MPa), split tensile strength (5.15 MPa), and flexural strength (5.98 MPa) at 28 days. These findings highlight the potential of PUF-based GPC with optimized NaOH molarity as a sustainable alternative in construction applications. This study concluded that 15% PUF replacement and 12 M NaOH concentration with binder contents (fly ash-50% and GGBS-50%) and SP (2%) based GPC provided better workability, strength and microstructural behaviour.