Abstract
Geopolymer concrete (GPC) offers a sustainable alternative to ordinary Portland cement (OPC) concrete by utilizing industrial by-products such as fly ash (FA) and ground granulated blast furnace slag (GGBS). However, most GPC formulations require heat curing to achieve desirable mechanical properties, limiting their precast applications. This study investigates the development of FA-GGBS-based GPC suitable for ambient curing, targeting precast applications. A total of 15 GPC mixes with varying FA/GGBS ratios (100:0, 70:30, 50:50, 30:70, 0:100) and alkali activator modulus (Ms = 1.0, 1.2, 1.5) were prepared and cured at ambient temperature (25±2°C, 65±5% RH) for 28 days. Compressive strength, flexural strength, and workability (slump) were measured. Microstructural analysis via XRD and SEM was conducted to understand phase evolution. Results show that GGBS addition significantly enhances early-age strength and setting time, with optimal performance at 50% GGBS replacement and Ms = 1.2, achieving 28-day compressive strength of 48.6 MPa and flexural strength of 5.2 MPa. Workability decreased with higher GGBS content. XRD revealed formation of C-A-S-H and N-A-S-H gels, while SEM indicated denser microstructure at higher GGBS. The developed GPC meets precast concrete strength requirements and reduces carbon emissions by up to 70% compared to OPC. This study demonstrates the feasibility of ambient-cured FA-GGBS GPC for sustainable precast construction.
Keywords
geopolymer concrete, fly ash, ground granulated blast furnace slag, ambient curing, precast applications, compressive strength, microstructure, sustainability