Systematic review of debonding anchorage and mixed mode interface behaviour in basalt fibre reinforced polymer strengthened reinforced concrete beams

A corpus of 54 full-text-appraised studies was synthesised to determine how bond transfer, anchorage and mixed-mode fracture govern basalt fibre-reinforced polymer (BFRP) strengthening of reinforced-concrete (RC) beams. The corrected PRISMA 2020 flow comprised 923 identified records, 284 records retained after database filtering, 214 unique records screened, 187 reports assessed for eligibility and 54 included studies. Externally bonded (EB) sheets and plates, near-surface-mounted (NSM) bars and ropes, and BFRP grids embedded in polymer cement mortar, engineered cementitious composite or engineered geopolymer composite were analysed as mechanically distinct systems. A structured quantitative narrative synthesis was adopted rather than a meta-analysis because the studies used non-equivalent beam geometries, strengthening ratios, control definitions, loading protocols, outcome metrics and failure classifications, while variance estimates required for statistical weighting were frequently unavailable. Across the included evidence, steel-plate anchorage increased ultimate load by 46.7% relative to its study control, epoxy anchors increased ultimate load by 13.1% and BFRP strain utilisation by 43.5%, anchored U-wraps increased ultimate capacity by approximately 56%, and BFRP-grid cementitious systems reported ultimate-load gains of up to 83.1%; these values are study-specific signals rather than pooled effect estimates. EB systems were primarily governed by intermediate-crack and plate-end debonding, whereas NSM systems were governed by groove-end splitting, pull-out and concrete-cover separation. The review further identifies the BFRP-specific cohesive parameters requiring calibration, including normal and shear stiffness, damage-initiation tractions, Mode I and Mode II fracture energies, mixed-mode interaction exponent, adhesive thickness, substrate fracture properties, width effects, anchorage stiffness and environmental degradation functions. Evidence was interpreted according to directness, with core BFRP beam and interface experiments separated from modelling studies, boundary BFRP evidence and non-BFRP comparator evidence. Existing ACI, fib, CSA and Eurocode-related guidance provides a transferable FRP design structure but does not remove the need for BFRP-specific interface qualification. The principal conclusion is that reliable BFRP strengthening should be designed as an integrated material-interface-anchorage system, with conclusions interpreted as directional because of substantial inter-study heterogeneity.