Strength and bonding properties of rubberised geopolymer based semi rigid repair material for use as surface road repair pavement

One-part semi rigid geopolymer is rarely used because of lacking in standardisation testing methods and optimisation for the mix ingredients. Much less one-part geopolymer formulated using industry by product treated crumb rubber (CR) to produce semi rigid geopolymer for road surface repair. The question whether one-part geopolymer incorporating industry by product and treated crumb rubber can achieve mechanical performance and sufficient interfacial bonding as repair material, is becoming a focus of the present work. Therefore, the present study was conducted aimed to produce sustainable semi rigid geopolymer repair material for road surface. This present study developed and evaluated a one-part semi-rigid geopolymer repair material formulated using industrial by-products and CR treated with 5% sodium hydroxide, aiming to enhance mechanical performance and interfacial bonding as a sustainable alternative to conventional repair material. Ground granulated blast furnace slag (GGBS) was used as the primary precursor, while fly ash (FA, Class F) and waste clay tiles (WCT) were incorporated as partial replacements at 10%, 20%, 30%, 40%, and 50%. Precursor-to-solid activator ratios of 90:10 and 80:20 were evaluated to determine the optimum activator content. All specimens were cured under ambient conditions (25 ± 2°C) and tested at 3, 14, and 28 days. Treated CR was used as sand replacement at 5%, 10%, 15%, and 20%. Surface preparation applied to concrete and asphalt substrates included as-cast (AC), wire-brushed (WB), and drilled-hole (DH) methods. Raw materials and binders were characterised using chemical, phase, and microstructural analyses to support interpretation of strength development mechanisms. Fresh and hardened properties were evaluated through workability, setting time, compressive strength, water absorption, abrasion resistance, and bi-surface shear bond strength tests on ordinary portland cement (OPC) concrete and hot mix asphalt (HMA) substrates. Wheel-tracking tests were also conducted to assess rutting resistance on asphalt specimens. The results indicated that one-part geopolymer repair binders incorporating GGBS, FA, and WCT exhibit strong potential for semi-rigid repair applications, achieving great strength development under ambient curing. The optimum mix, comprising 70% GGBS and 30% WCT with a 90:10 solid activator ratio, achieved a compressive strength of 69.16 MPa at 28 days. Incorporation of 15% treated CR resulted in a compressive strength of 52.80 MPa at 28 days, indicating improved deformation tolerance while maintaining adequate strength. The best bonding performance was achieved using the DH surface preparation method, producing bond strengths of 8.69 MPa on concrete and 7.58 MPa on asphalt. Under DH surface preparation, the roughness average (Ra) values were 11.24 µm for concrete and 10.34 µm for asphalt. The developed repair material also demonstrated good rutting resistance, with a rutting depth of only 0.6 mm under wheel-tracking conditions. Overall, the findings confirmed that the proposed one-part semi-rigid geopolymer repair material is suitable for surface road repair applications.