Flexural Performance, Crack Propagation and Durability of Geopolymer Concrete Beams Reinforced with Basalt Fibre-Reinforced Polymer (BFRP) Bars Under Sustained Loading

Author(s): Rajiv S. Nambiar

Affiliation: Department of Structural Engineering, Sri Venkateswara Institute of Technology

Page No: 31-36

Volume issue & Publishing Year: Volume 3, Issue 7, 2026/07/05

Journal: International Journal of Modern Engineering and Management | IJMEM

ISSN NO: 3048-8230

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Abstract:

The convergence of geopolymer concrete (GPC) — an alkali-activated binder system that eliminates Ordinary Portland Cement and reduces CO₂ emissions by up to 80% — with corrosion-immune basalt fibre-reinforced polymer (BFRP) reinforcement bars represents a structurally and environmentally compelling alternative to conventional reinforced concrete (RC) construction. Despite the established individual merits of each technology, systematic experimental data on the composite flexural behaviour, long-term crack width evolution, and durability of GPC-BFRP beams under sustained service loads remain scarce, particularly for fly-ash/GGBS-based GPC systems activated with sodium silicate and sodium hydroxide — the binder chemistry most relevant to Indian industrial by-product availability. This study fabricates and tests twelve GPC beams (150×250×1800 mm) reinforced with BFRP bars at two reinforcement ratios (ρ = 0.8% and 1.4%) and subjects them to four-point flexural loading at 40%, 60%, and 80% of ultimate capacity for sustained periods of 90 and 180 days. Flexural stiffness, mid-span deflection, crack spacing, and maximum crack width are monitored at 7-day intervals using digital image correlation (DIC). Companion OPC-RC and GPC-steel beams serve as reference systems. GPC-BFRP beams at ρ = 1.4% sustain 60% loading for 180 days with maximum crack widths of 0.21 mm — below the IS 456:2000 serviceability limit of 0.3 mm — and show 18% less long-term deflection than equivalent OPC-RC beams, attributed to GPC’s superior creep resistance. Failure modes in GPC-BFRP beams are governed by concrete compression crushing rather than bar rupture, confirming desirable over-reinforced ductile mechanisms. Accelerated chloride immersion testing (3.5% NaCl, 90 days) reveals zero corrosion-induced cracking in GPC-BFRP beams versus visible surface cracking in GPC-steel and OPC-steel reference beams, validating the system’s durability advantage for coastal infrastructure.

Keywords:

geopolymer concrete, basalt FRP, BFRP reinforcement, fly ash, GGBS, flexural behaviour, crack width, DIC, sustained loading, durability, corrosion-free concrete

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