PSI - Issue 42

Jamal A. Abdalla et al. / Procedia Structural Integrity 42 (2022) 1231–1238 Abdalla et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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in construction, require a large amount of energy. To reduce the significant carbon footprint resulting from the use of concrete as a construction material, several studies were conducted to develop more sustainable concrete using recycled aggregates, natural fibres and by-product cementitious materials (Abdalla et al. (2022); Hawileh et al. (2017); Thomas et al. (2021); (Abhilash et al. (2021)). Another sustainable solution to produce concrete is to use recycled aggregates concrete (RAC) (Lapko and Grygo (2013); Skariah Thomas et al. (2022)). Studies have shown that the use of RAC in concrete has beneficial effects in terms of reducing greenhouse gas emissions and non-renewable energy consumption (Mercante et al. (2012); Younis et al. (2022)). An alternative approach could be to retrofit existing reinforced concrete (RC) structures instead of demolishing and building new structures. One method that has been deemed effective in strengthening RC structures is conducted via bonding fiber reinforced polymer (FRP) composites onto the concrete surface. FRPs could be bonded to the tension face of RC beam to enhance its flexural capacity, or in the form of complete wraps or U-wraps in the transverse direction to enhance its shear capacity. In general, shear failures are catastrophic and brittle; hence, to take full advantage of the ductility of the RC member, it is important to ensure that flexure failure rather than shear governs the ultimate strength (Khalifa and Nanni (2000)). Therefore, the use of FRP materials could be essential in many cases to improve the shear capacity of RC beams. The advantages of using FRP materials in the external strengthening of RC structures, rather than the conventional methods, include high strength-to-weight ratio, versatility, non-corrosive nature, and durability (Abdalla et al. (2020); Mhanna et al. (2021)). FRPs also serve the purpose of reducing the harm on the environment, while maintaining a high level of strength in the concrete (Naser et al. (2019)). Several experimental investigations studied the effect of using RAC on the shear behavior of beams (Arezoumandi et al. (2014); Ignjatovic et al. (2017); Ju et al. (2021); Pradhan et al. (2018); Setkit et al. (2021)). A study by Ignjatovic et al. (2017) investigated the effect of replacing natural aggregate concrete (NAC) with 50 and 100% RAC on the shear strength of RC beams. It was concluded that the failure modes, crack patterns, load at which the first crack occurred, strain in the steel and concrete, and shear strengths of the beams with same amount of shear reinforcement were similar, regardless of the amount of recycled aggregates. Similarly, Arezoumandi et al. (2014) the tested twelve beams to examine the effect of using RAC on the shear strength of the RC beams. Test results indicated that the shear capacity of the RAC beams decreased by 5-12% compared to NAC beams, depending on the longitudinal reinforcement ratio. However, no significant difference was observed in the crack pattern, crack development, and load – deflection response between the two sets of beams. In a statistical study conducted by Ju et al. (2021), the authors collected data base from the literature to identify the strength margin between RAC and NAC concrete beams. Findings from that study showed that for beams without shear reinforcement, the shear strength of RAC beams was slightly lower than NAC beams. On the other hand, for the beams with shear reinforcement, the statistical results did not show any difference in the shear capacity between RAC and NAC beams. A similar conclusion was reported by Pradhan et al. (2018), where a 14% drop was noted in the shear capacity of the RAC beams without stirrups compared with their NAC counterparts. Thus, the available literature verifies that the use of RAC in beams provides a sustainable solution to several environmental issues such as the depletion of natural aggregate and capacity of landfills without compensating the strength. Numerous research investigations were conducted to study the strength enhancement and performance of RC beams strengthened in shear with FRP composites (Abuodeh et al. (2020); Alotaibi et al. (2019); Chen et al. (2017); Mhanna et al. (2019); Mohamed et al. (2020); Mohamed et al. (2018); Nawaz et al. (2016); Oller et al. (2019)). However, there is gap in the literature on the effect of strengthening RC beams composed of RAC with FRP laminates. This study aims at reducing the environmental impact by using RAC, while maintaining the shear strength parameter using FRP composites. To satisfy the aim of the study, four RC specimens were cast, two of which were comprised of RAC and the other two were made of NAC for comparison purpose. All specimens did not include any internal shear reinforcement and the strengthening scheme that was investigated was the CFRP U-wraps. Test results in terms of failure modes, shear capacity, strain in the CFRP, and shear force-deflection graphs were analysed. In addition, the shear capacity of the tested beams was predicted using the ACI 318-19 (2019) and ACI440.2R-17 (2017) design provisions.