PSI - Issue 54

Jamal A. Abdalla et al. / Procedia Structural Integrity 54 (2024) 609–616 Abdalla et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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construction has gained significant attention as a sustainable solution. Recycled aggregates are obtained from various sources, including construction and demolition waste, and can be processed to meet the required specifications for concrete production (Skariah Thomas et al., (2022)). By incorporating recycled aggregates into concrete, the demand for natural resources, such as virgin aggregates, is reduced, leading to a decrease in energy consumption and carbon emissions associated with aggregate extraction and transportation (Zhang et al., (2023)). Moreover, the utilization of recycled aggregates helps divert waste from landfills and promotes a circular economy approach. The application of recycled aggregates in reinforced concrete beams was studied in previous investigations (Hawileh et al., (2023); Simões et al., (2023); Skariah Thomas et al., (2022); Xiao et al., (2013); Zhang et al., (2023)). Research findings have indicated that incorporating recycled aggregates in concrete brings positive outcomes by lowering both greenhouse gas emissions and the consumption of non-renewable energy sources. Previous studies have examined the effect of using recycled aggregates in concrete beams on their shear capacity, providing insights into the behavior of such beams (Abdalla, et al., (2022); Arezoumandi et al., (2014); Ignjatović et al., (2017); Younis et al., (2022)). The findings of these studies have indicated that the incorporation of recycled aggregates can have either a positive or negative effects on the shear capacity of concrete beams. On the positive side, some studies have reported that beams with recycled aggregates can exhibit similar or even higher shear capacities compared to beams made with natural aggregates (Arezoumandi et al., (2014); Ignjatović et al., (2017)) . This is attributed to the rough texture of recycled aggregates, which can enhance interlocking and improve shear transfer between the aggregates and the matrix. The increased interlocking effect can lead to a more efficient load transfer mechanism and enhanced shear resistance. However, other studies have reported a reduction in the shear capacity of beams containing recycled aggregates (Ju et al., (2021)). This reduction is mainly attributed to the lower compressive strength and stiffness of concrete with recycled aggregates, which can adversely affect the overall shear behavior. The reduced compressive strength may result in premature crushing of the concrete in the compression zone, leading to a decrease in shear capacity (Hawileh et al., (2023)). Additionally, the higher water absorption of recycled aggregates may affect the bond between the aggregates and the matrix, reducing the shear transfer efficiency and weakening the shear resistance (Pradhan et al., (2018)). It is important to note that the specific characteristics of the recycled aggregates, such as their quality, grading, and content, can significantly influence the shear capacity of the concrete beams. Strengthening of deficient structures is also considered a sustainable solution to keep them at a certain performance level instead of demolishing them. Strengthening using fiber-reinforced polymers (FRP) composites has emerged as a versatile and effective solution in the field of structural engineering. The use of FRP composites for shear strengthening offers several advantages, including ease of application, lightweight nature, and minimal disruption to the existing structure during installation. Numerous experimental studies have demonstrated the effectiveness of FRP in increasing the shear capacity, improving crack control, and enhancing the ductility of RC beams (Abdalla, et al., (2022); Abuodeh et al., (2020); Alotaibi et al., (2020); Dong et al., (2013); Hawileh et al., (2015); Kuchma et al., (2011); Mhanna et al., (2020); Mhanna, (2021); Mhanna, et al., (2021a), (2021b)). Using RAC in combination with externally bonded shear reinforcement, not only addresses structural deficiencies but also contributes to the overall sustainability of the construction industry by minimizing resource depletion and waste generation. Therefore, investigating the behavior of normal and recycled aggregates concrete beams strengthened with different types of externally bonded shear reinforcement is crucial in promoting environmentally friendly construction practices. All previous studies investigated shear strengthening of RC beams with normal aggregate concrete (NAC). There is a lack of studies in the literature that considers the effect of shear strengthening of RC beams with recycled aggregate concrete (RAC). One previous study conducted by the authors of this paper (Abdalla et al., (2022)) explored the effect of shear strengthening of NAC and RAC beams with CFRP U-wraps. They concluded that strengthening RAC beams resulted in a 60% increase in the shear capacity compared to a 36% increase observed in NAC beams. The primary objective of this investigation is to assess the influence of enhancing the shear capacity of shear deficient RAC beams through the application of CFRP laminates. Five RAC beams were cast, of which four were subjected to various CFRP shear strengthening configurations: U-wraps adhesively bonded at a 45º angle, vertical U wraps, continuous U-wraps extending along the entire shear span, and side-bonded laminates. Additionally, one RAC specimen was intentionally left unstrengthened to serve as a control benchmark. To establish a basis for comparison, an additional set of NAC beams were fabricated, with four of them strengthened using analogous CFRP methodologies employed in the RAC beam group, while one beam remained unstrengthened. The structural response of all beams