Strengthening of High Strength Reinforced Concrete Slabs with CFRP Laminates
Mahmoud, Hasan Saleh
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During the last few decades, engineers and researchers used high-strength concrete to cast reinforced concrete (RC) structures. Accordingly, the dead weight of buildings and structures were reduced significantly, which allowed engineers to construct higher and larger buildings. Reinforced concrete slabs are the largest structural members in buildings. This research aims to reduce the thickness of RC slabs using high-strength concrete strengthened with carbon reinforced polymers (CFRP) laminates in flexural. In this study the behavior of 100 mm thick RC slabs with different concrete compressive strengths of 40, 70, and 100 MPa was inspected. A total of 54 RC slab specimens were cast and tested under two-point loading until failure. The specimens were divided into three groups having different flexural steel reinforcement ratios of 0.45, 1.00, and 1.79%, respectively. Each group of specimens was strengthened with one and two layers of CFRP sheets, which were externally attached to the soffit of the RC slabs, to enhance their flexural capacity. The test results indicated an increase in the load-carrying capacity of the strengthened slabs in the range between 12 to 378 %. It was also observed that the highest contribution was for those specimens with low reinforcement ratio, in which their control specimens failed by tensile membrane action. The mid-span deflection response curves and load-carrying capacity of the slabs were also predicted with a good level of accuracy using the design guidelines of ACI 440-2R-08. In conclusion, strengthening of high-strength thin RC slabs with CFRP laminates is a valid choice to enhance their flexural behavior, with a minimal increase in their dead load, due to the lightweight of the CFRP laminates.