Flexural behavior of all lightweight reinforced concrete beams externally strengthened with CFRP sheets

The usage of structural Lightweight concrete (LWC) has increased over the years and received significant attention owing to its lower density, better economical design, and mechanical properties as compared to conventional normal weight concrete (NWC). However, limited research efforts and codes provisions deal with retrofitting and strengthening of lightweight concrete structures. Therefore, the main objective of this investigation is to evaluate the flexural performance of all lightweight concrete (ALWC) beams externally strengthened using Carbon Fibre Reinforced Polymer (CFRP) sheets. A total of fifteen ALWC beams were divided into three series based on their reinforcement ratio and strengthened with externally bonded CFRP sheets. The test variables studied in the experimental program were the effective reinforcement ratio, number of CFRP layers, and the percentage of pre-loading. All the beams were tested under four-point bending and the experimental results show that the CFRP sheet has significantly increased the ultimate load carrying capacity of pre-loaded and non-preloaded strengthened specimens. The increase in flexural capacity ranged from 28% to 102% over the unstrengthened control specimen. The ultimate load capacity was also predicted using different design standards and compared with the experimental load. The comparison showed that the current design standards have overestimated the flexural capacity of CFRP strengthened ALWC specimens.