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This study examines the flexural behavior of reinforced concrete (RC) one-way slabs strengthened with near-surface mounted (NSM) basalt fiber-reinforced polymer (BFRP) bars. Ten RC slabs were subjected to four-point loading until failure. Various parameters including the steel reinforcement ratio (0.48and 0.95%), the NSM-BFRP reinforcement ratio (0.17, 0.25, and 0.35%), and two types of epoxy adhesives (Sikadur-30 and NSM-Gel) were investigated. The experimental results demonstrated the remarkable efficacy of the NSM-BFRP bars in enhancing the flexural performance of the strengthened slabs, especially those with lower steel reinforcement ratios. Compared to the control slabs, the ultimate loads were increased by 51‐123% and 21‐44% for slabs with 0.48 and 0.95% steel reinforcement ratios, respectively, while the ductility indices were increased by 10‐53% and 29‐79%. The type of the epoxy adhesive used had minimal impact on the flexural behavior of the strengthened slabs. Failure primarily occurred due to steel yielding followed by the rupture of the NSM-BFRP bars or by concrete crushing, depending on the reinforcement ratio provided. The cracking, yield, and ultimate loads of the strengthened slabs were predicted using the formulations of ACI 440.2R [3] guideline. Good agreement between the predicted and the experimental results were obtained, with ACI formulations being on the conservative side. • NSM-BFRP increased slab load capacity by up to 124%. • Effectiveness of NSM-BFRP varied based on steel reinforcement ratios. • Strengthened slabs exhibited improved ductility with ductility indices increasing up to 79%. • Failure modes differed based on both steel and NSM-BFRP reinforcement ratios. • Experimental results aligned well with ACI 440.2 R (2017) predictions. [ABSTRACT FROM AUTHOR]

This study investigated the flexural performance of one-way reinforced concrete (RC) slabs strengthened with two distinct strengthening systems: near – surface mounted (NSM) bars and externally bonded (EB) carbon fiber-reinforced polymer (FRP) strips. The NSM bars comprised four types: carbon FRP (CFRP), basalt FRP (BFRP), glass FRP (GFRP), and stainless – steel (SS) bars. The NSM – strengthened slabs showcased substantial enhancements in yield and ultimate load capacity, ranging from 20 % to 55 % and 59–123 %, respectively. In comparison, those strengthened with EB – CFRP strips displayed increases from 46 % to 107 % and 45–177 %, respectively, depending on the axial stiffness ratio of the strengthening system provided. Furthermore, the slabs reinforced with NSM–BFRP bars showed an 11–25 % improvement in their ductility indices. In contrast, the slabs reinforced with EB experienced a decrease in ductility ranging from 38 % to 50 %. This reduction was attributed to the differences in the modes of failure observed in both strengthening systems. The rupture of the NSM–FRP bars and the strain readings associated at the end of testing confirmed that the tensile strength of the NSM–FRP bars was fully exploited whereas the EB–CFRP strips utilized only 29–36 % of their ultimate tensile strain due to debonding. A finite element (FE) model was formulated to anticipate the behavior of the strengthened slabs. A strong correlation between the numerical predictions and the experimental outcomes was observed. The experimental–to–numerical ratios of the ultimate load ranged between 1.0 and 1.08 for the NSM–strengthened slabs and between 0.98 and 1.38 for the EB–strengthened slabs. This validated the FE models' ability to capture the nonlinear performance of the strengthened slabs. • Effectiveness of NSM-FRP varied based on the type of FRP bars. • NSM-FRP bars increased yield and ultimate loads up to 55 and 123 %, respectively. • NSM-strengthened slabs exhibited improved ductility with indices increasing up to 25 %. • EB-strengthened slabs failed due to debonding of the CFRP strips. • NSM-FRP systems are more effective in restoring the ductility of RC slabs. [ABSTRACT FROM AUTHOR]