Strengthening of thin reinforced concrete slabs with CFRP laminates

Abstract

Over the years, engineers and researchers have been working continuously to reduce the dead loads on buildings by reducing the sizes of structural elements. Slabs add significant dead load to buildings compared to other structural members. Accordingly, reducing the slab thickness can drastically reduce the dead loads of buildings. Such reduction in dead load will allow engineers to construct taller buildingswith long spans using relatively smaller columns and foundations. The aim of this paper is to study the flexural performance of thin reinforced concrete (RC) slabs cast with high strength concrete when externally strengthened with carbon fibre reinforced polymer (CFRP) laminates at their soffit. Two groups of slab specimens having a thickness of 75 mm were cast with a concrete compressive strength of 50 MPa and 100 MPa, respectively. The first group (C50) consists of three specimens strengthened in flexure with one and two layers of CFRP laminates. The second group (C100) consists of two slab specimens. The first slab is the control slab and the second specimen was strengthened with one layer of CFRP laminate. The test results of the first group with one and two layers of CFRP laminates indicated that the flexural strength have been increased by 69% and 126%, respectively over the control un-strengthened slab. However, for the second group, the flexural capacity of the strengthened slab was increased by 48% of that of the control specimen. The preliminary results from this study have shown that, the thin RC slabs can carry significantly higher loads in buildings if externally strengthened with CFRP laminates. It was also observed that as the concrete strength increases, the gain in flexural capacity of RC slabs from CFRP reinforcement decreases. Based on the results of this pilot study, the authors will expand the test matrix in a future study to examine the effect of several parameters including concrete compressive strength, reinforcement ratio, and number of CFRP layers on the performance of thin RC slabs.