Strengthening and repairing of a one-way solid slab exposed to thermal effect using CFRP Grid

Exposure of reinforced concrete (RC) elements to high temperatures, leads to severe deterioration in mechanical properties. Carbon Fiber Reinforced Polymer (CFRP) have recently emerged as a promising method for strengthening fire-damaged RC members due to their high strength-to-weight ratio and ease of installation. This study evaluates the effectiveness of CFRP grids in strengthening and repairing thermally damaged one-way RC solid slabs. Eight slabs (1800 × 500 × 100 mm) were cast and exposed to a uniform temperature of 600°C. Three CFRP grid configurations were examined: two slices, three slices, and a full-surface application. The performance of the slabs was assessed through experimental testing, numerical modeling, and theoretical analysis. The experimental results demonstrated significant recovery and enhancement of structural capacity, with ultimate load increases of 11.1 % to 29.9 % for strengthened slabs and 19.3 % to 41.4 % for repaired slabs relative to their control specimens. The stiffness of repaired slabs increased by up to 117 %, while peak deflection decreased by 47 %. In addition, the numerical results exhibited strong correlation with experimental results, showing deviations below 12 % in ultimate load and 8 % in deflection, validating the adopted nonlinear modeling approach. Finally, the theoretical results based on ACI 440.2R-17 showed close agreement with experimental results, with predicted capacities by only 2.2 %–7.1 % for strengthened slabs and 2.2 %–14.2 % for repaired slabs. The study demonstrates the effectiveness of CFRP grid in restoring the mechanical performance of reinforced concrete slabs exposed to elevated temperatures.