Currently, the costs of building materials, especially cement, are increasing. Waste marble powder (WMP) could be used as a cement replacement material to produce environmentally friendly concrete to help preserve resources and reduce environmental pollution. The study’s goals are (1) to evaluate the effects of using marble powder in place of cement in high-strength concrete (HSC) on the material’s mechanical properties and durability characteristics. (2) The study is expanded to assess the effect of using partial WMP on the shear behavior of HSC beams under static loads. Eight half-scale simply supported reinforced beams with and without WMP have been tested. Each beam’s cross-section was 120 × 200 mm, and each beam had a total length of 1000 mm. The ratios of the used WMP were 0%, 2.5%, 5%, 7.5% by weight, and two different stirrup ratios, 0% and 0.47%, were used. When applied to HSC beams with and without WMP, the shear strength provisions of two of the most used codes, such as the locally used Egyptian Code (ECP 207) and the internationally used American Concrete Institute’s (ACI-2019), were examined. Using the ABAQUS software, the experimental results were compared to the findings of the nonlinear finite element analysis. The results established that partial replacement of cement by WMP led to increases in the concrete’s compressive and tensile strengths of about 15% and 16%, respectively. When tested specimens were exposed to acid attack, there were slight losses in weight and compressive strength (1.25% to 2.47%) for both with and without the addition of WMP. Both the concrete with and without WMP showed the same level of water absorption. Additionally, WMP led to an enhancement in the shear capacities for all beams. Increasing the WMP ratio from 0% to 2.5%, 5%, and 7.5% increased the shear capacity by about 13%, 20%, and 28%, respectively, for beams without stirrups, while for beams with stirrups, the shear capacity improved by 12%, 19%, and 25%, respectively. The enhancement in the beams’ shear capacities could be attributed to the advanced concrete matrix produced by WMP’s extremely small particle size.
Two unique approaches were proposed to strengthen the bond between the glass fiber reinforcement polymer (GFRP) and the RC concrete surfaces. The two bonding materials are epoxy (EP) and geopolymer (GPP) with different ratios of short glass fibers (SGF). The experimental program includes seven reinforced concrete (RC) beams that have the same cross-section (150 mm × 200 mm) and are 1500 mm in length. The first beam is the control beam (B0-Control). The next three beams B1-0-GPP, B2-0.6-GPP, and B3-1.2-GPP have GPP with SGF ratios of 0%, 0.6%, and 1.2%, respectively. The last three beams B4-0-EP, B5-0.6-EP, and B6-1.2-EP have EP with SGF ratios of 0%, 0.6%, and 1.2%, respectively. The results show that the failure loads of beams B1-0-GPP, B2-0.60-GPP, and B3-1.2-GPP are greater than the control beam B0-Control by approximately 20.80%, 25.60%, and 31.40%, respectively, whereas the failure loads of beams B4-0-EP, B5-0.6-EP, and B6-1.2-EP are greater than the B0-Control by approximately 16.90%, 26.90%, and 26.10%, respectively; it is also noted that debonding occurs. In addition to the adhesive material, GPP has a great effect on increasing the beam’s failure load capacity due to the enhanced interfacial bond shear strength. Additionally, a finite-element program ABAQUS is performed to verify the experimental results.
Many structural elements are subjected to a significant torsional moment that affects the structural design and may require strengthening. This paper presents different effective strengthening techniques to enhance the torsional capacity of reinforced concrete (RC) beams. An experimental and numerical investigation was undertaken to evaluate the efficacy of utilizing various strengthening systems. The experimental program included six full-scale RC beams with a cross-section dimension of (150 mm × 300 mm) and a length of 1500 mm, split into one beam without strengthening as a control beam, and six beams strengthened with various materials. The various strengthening materials were wrapped aluminum strips with anchorage bolts, wrapped stainless steel strips with anchorage bolts, wrapped glass fiber reinforcement polymer (GFRP), one layer of wrapped steel wire, and two layers of wrapped steel wire meshes along the beam. The results showed that the ultimate torque of the beam strengthened by wrapped aluminum strips and the beam strengthened by wrapped stainless steel strips was larger than the control beam by about 32% and 40%, respectively, because the strips acted as an external reinforcement. In addition to the strengthening systems, using aluminum strips and stainless steel strips is effective in raising the capacity to a similar degree despite the high cost of the stainless steel strips. The ultimate torque of the beams strengthened by GFRP, one-layered wrapped steel wire meshes, and two-layered wrapped steel wire meshes along the beam is larger than the control beam by about 62%, 118%, and 163%, respectively, in addition to the ultimate angle of twist, which was larger than the control beam by about 53%, 93%, and 126%, respectively. This showed that the strengthening using the two-layered wrapped steel wire meshes along the beam would be very significant in increasing the ultimate torque strength. Moreover, the strengthened beam by two-layered fully wrapped steel wire meshes along the beam developed the highest ductility factor compared to all strengthened beams; in contrast, the beam strengthened by GFRP had less ductility. To verify the outcomes of the experimental tests, a finite-element program, ABAQUS, was performed. Finally, an excellent agreement between the experimental and numerical results was obtained.
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