Shrinkage and strength of fibre-reinforced geopolymer using binary and ternary binders

Portland cement production accounts for 7–8% of global carbon dioxide emissions, driving the need for sustainable alternatives. This study develops self-compacting geopolymer concrete (SCGPC) using ground granulated blast furnace slag (GGBS), low-calcium fly ash (FA) and microsilica (MS) as precursors, reinforced with steel (ST) and polypropylene (PP) fibres. Sixteen SCGPC mixes with 8 M and 12 M alkaline molarities were tested for fresh, mechanical and durability properties. The mixes achieved slump flow (650–700 mm), T50 (3–5 s), and L-box ratio (>0.8), meeting EFNARC standards. The SCGPC mix with 1% ST fibres and 12 M molarity exhibited a compressive strength of 96.83 MPa, tensile strength of 4.89 MPa and water absorption of 2.1–3.5%. ST fibres reduced drying shrinkage by 11% (603 microstrain as opposed to 677 microstrain in self-compacting concrete), while hybrid ST + PP mixes retained 80% compressive strength at 600°C. Analysis of variance and M5P modelling (R² = 0.88) confirmed the significant influence of superplasticiser (81.74%) and fibre content (14.37%). SCGPC offers a high-performance, eco-friendly alternative to Portland cement concrete, with superior shrinkage control and fire resistance. This makes SCGPC a promising material for fire-resistant structural applications, promoting sustainable construction practices.