Synergistic enhancement of compression and post-crack response in GFRP-reinforced concrete slabs using CFRP laminates and sheets

This paper explores the compressive behavior of concrete slabs to gain a clearer understanding of their compressive strength and deformation characteristics under loading. A series of experimental tests were carried out, in which the slabs were subjected to uniformly distributed loads applied through a hydraulic jack. Their deflection responses were measured precisely using a Linear Variable Differential Transformer (LVDT). The study placed particular emphasis on evaluating how the integration of Glass Fiber Reinforced Polymer (GFRP) bars together with Carbon Fiber Reinforced Polymer (CFRP) laminates could enhance the slabs’ compressive resistance. A total of five slab specimens with different reinforcement schemes were investigated. The unstrengthened reference slab (S1) exhibited a peak compressive strength of 35.61 MPa, with a vertical strain at failure of 7.13%. Slab S2, strengthened with a 50 mm-wide CFRP laminate in one direction, achieved a peak compressive strength of 52.35 MPa and a vertical strain at failure of 3.13%. When a 50 mm-wide CFRP laminate was applied in both directions (Slab S3), the peak compressive capacity increased further to 57.70 MPa, with a vertical strain of 3.04% at failure. Slab S4, reinforced with a 500 mm-wide CFRP sheet in a single direction, reached 49.65 MPa peak compressive strength with a vertical strain at failure of 2.35%, while Slab S5, which incorporated a 500 mm-wide CFRP sheet in two directions, attained 54.05 MPa peak compressive strength with a vertical strain at failure of 2.28%. The findings confirm that combining GFRP bars with CFRP laminates considerably improves the compressive performance of concrete slabs. Reinforcement in both directions was more effective than one-directional configurations, providing better load-carrying capacity and reduced deformation. Among all specimens, Slab S3 demonstrated the most favorable behavior, achieving the highest peak compressive strength, highlighting its potential as a reliable solution for future strengthening strategies. Overall, these results offer valuable insights for the design of concrete elements requiring improved compressive resistance and resilience under varied loading conditions.