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This detailed review looks at how carbon fiber-reinforced polymer (CFRP) may be used to improve the flexural capacity of reinforced concrete (RC) beams. It investigates the history, characteristics, and research trends of FRP composites, assesses various flexural strengthening methods utilizing FRP, and addresses the predictive power of finite-element (FE) modeling. The assessment highlights the importance of enhanced design codes, failure mode mitigation, and improved predictive modeling methodologies. It emphasizes the advantages of improving FRP reinforcement levels to meet code expectations and covers issues, such as FRP laminate delamination and debonding. The findings highlight the need of balancing load capacity and structural ductility, as well as the importance of material behavior and failure processes in accurate prediction. Overall, this review offers valuable insights for future research and engineering practice to optimize flexural strengthening with CFRP in RC beams.

In this study, the efficacy of strengthening of reinforced concrete (RC) beams in shear by utilizing high-performance fiber-reinforced concrete (HPFRC) was explored. The shear strengthening was achieved by epoxy bonding of prefabricated HPFRC strips or plates onto the beams. The beams were strengthened utilizing two different strengthening schemes: (i) plates side strengthening (ii) vertical strips applied at shear critical sections. The behavior of the two configurations was compared to the behavior of non-shear reinforced and shear-reinforced RC beams. The high-performance concrete (HPC) utilized contains 1.5% of steel fibers per volume of HPC mortar and is known as HPFRC. Parameters determined were the flexural strength and compressive strength of HPFRC mortar. The obtained results revealed that HPFRC realized a 28-day flexural strength of 20 MPa and a compressive strength of 108 MPa. Moreover, HPFRC strengthened RC beams experienced an increased in strength capacity of about 50% for plates and 36% for vertical strips compared to the RC beams with no stirrups. The results for HPFRC strengthened beams with plates were superior compared to those of the stirrup-reinforced beams, whereas the results of HPFRC strips strengthened beams were almost identical to the stirrup-reinforced beams. Also observed, was an improvement in the ductility of the beams with the best results achieved when employing HPFRC plates and strips.HighlightsShear Strengthening of RC beams by HPFRC plates utilizing two methods.Precast HPFRC plates bonded by epoxy adhesive and anchored.Continuous shear strengthening resulted in high-capacity enhancement and ductility.

Concrete, the construction industry’s most utilized construction material, has transformed the environment and the modern built-up lifestyle. Although concrete is a first-rate supplier to the carbon footprint, it is imperative for buildings to display sustainable characteristics. Scholars have explored techniques to lessen the carbon footprint and the way to put into effect strategic waste control plans in which waste is reused. This study explores the dual benefits wherein concrete ingredients are replaced through abandoned waste which reduces the unwanted waste materials that have a substantial carbon footprint and thus results in the recycling of waste as part of a sustainable economic system. In this study, timber ash is utilized as a partial substitute for sand and cement, crumb rubber and waste glass as a partial substitute for sand, recycled concrete, and waste glass as a substitute for gravel. Characteristics studies were done to check the influence of each waste replacement on the modulus of elasticity of concrete. More than sixty-five combinations of waste have been examined to attain the modulus of elasticity of concrete. A total of about 200 concrete cylinders were cast to provide at least three cylinders for each generated data point. Three different ASTM standards were utilized to determine the modulus of elasticity of each mix. Four mixes comprising of the combination of two waste materials and two mixes comprising of the combination of three waste materials replacing natural materials were determined to exhibit an equal or superior modulus of elasticity of the control mix of 25 GPa.

In the construction industry, concrete is the most utilized building material. It is produced from different natural resources such as sand and gravel, as well as cement. The production of concrete is causing harm to the environment, yet its use became a necessity. To solve this humongous environmental challenge, many researchers devoted a considerable effort to partially replacing concrete mix components with waste material derived from glass, plastics, aluminum, wood ash, construction and demolition wastes, or tires. In the current study, a novel effort was conducted to incorporate all the above-mentioned wastes in a concrete mix design and to assess its performance. Five recycled mix designs were explored and based on the concrete mechanical properties derived, an optimum mix was realized. The optimum mix incorporated the following waste percentages: 2% crumb rubber (CR) partially replacing sand, 20% powdered glass (PG) partially replacing sand, 50% recycled concrete aggregates (RCA) partially replacing coarse aggregates, and the addition of 0.5% plastic. The optimum recycled mix was utilized to cast a real-life-size reinforced concrete beam which was compared to a normal mix beam.

The danger of fire is present always and everywhere. The imminent danger depends upon the actual type and length of fire exposure. Reinforced concrete structural members are loadbearing components in buildup structures and are therefore at high risk, since the entire structure might potentially collapse upon their failure. Thus, it is imperative to comprehend the behavior of reinforced concrete members at high temperatures in case of fire. In this study, the mechanical properties of concrete exposed to high temperatures were experimentally determined through the testing of 27 concrete cylinder starting at room temperature and increasing up to 260 °C. The concrete material behavior was implemented into the ABAQUS software and a finite simulation of reinforced concrete beams exposed to actual fire conditions were conducted. The finite element models compared favorably with the available experimental results. Thus, providing a valuable tool that allows for the prediction of failure in case of a fire event.

ABSTRACT Latexes including polyvinyl acetate (PVA) and styrene-butadiene rubber (SBR) are widely used to improve adhesion and bond properties of cementitious-based repair materials. The main objective of this paper is to evaluate the effect of such polymers on stability of highly flowable self-consolidating concrete (SCC) during placement and until onset of hardening. Also, the bond properties to existing concrete substrate and steel bars are investigated. Two series of mixtures prepared with relatively low to high water-to-binder ratio and incorporating 5–15 % polymers were tested. Special emphasis was placed to highlight the altered stability responses including flowability, viscosity, passing ability, and segregation resistance with respect to the European Guidelines for SCC. Remarkable improvements in the concrete-bar bond stresses were noticed with PVA and SBR additions. This was attributed to improved concrete elasticity and tensile splitting strength that increased contribution of material bearing strength around the steel bars.

The effect of styrene-butadiene rubber (SBR) latexes on stability of semi-lightweight self-consolidating concrete and bond to embedded steel bars is not well understood. Five mixture series prepared with various lightweight aggregate (LWA) and SBR concentrations were considered in this project; the free water content was adjusted to secure compressive strength of 40 ± 3.5 MPa (5.8 ± 0.5 ksi). Test results have shown that SBR additions lead to reduced concrete flow velocity and passing ability; however, improved static stability such as bleeding and segregation. The bond properties to steel bars, particularly the initial stiffness of load versus slip curves, remarkably increased with SBR additions. This was related to the coupled effect of reduced concrete bleeding that promotes creation of hydration compounds at the steel-concrete transition zone and presence of SBR polymers that help relaxing stresses during loading. A series of regression statistical models was developed to predict the combined effect of free water, viscosity modifier, LWA, and SBR on stability and bond properties.

Concrete, the most consumed man-made material worldwide, has shaped the environment and the modern world. Even though concrete is a major contributor to the carbon footprint, it is indispensable for building the sustainable world of tomorrow. Researchers have been exploring ways to reduce the carbon footprint and to implement strategical waste management plans in which wastes are repurposed. Pollution has been a challenge for almost all countries, especially with the increase in the release of greenhouse gases in the atmosphere and the emissions resulting from wastes in unmanaged landfills. Additionally, the areas available for landfills have become scarce. Daily all around the world, generated are wastes such as wood ash, waste glass, used tires, construction debris, and demolition wastes. These wastes usually accumulate in landfills for years, as they are mostly nondecomposable. This research explores a solution to this twofold problem in which concrete components are replaced by wastes and by-products, which in return reduces the need for raw materials that have a significant carbon footprint and repurposes wastes as part of a circular economy. In this research, wood ash is used as a partial replacement of cement and sand, fine crushed glass and crumb rubber as partial replacements of sand, and crushed glass and recycled concrete aggregates as partial replacements of gravel. The optimum eco-friendly structural concrete mix was determined to be the combined mix consisting of 5% wood ash as a partial replacement of cement; 20% wood ash, 20% fine crushed glass, and 2% crumb rubber as partial replacements of sand; and 5% crushed glass and 50% recycled concrete aggregates as partial replacements of coarse aggregates. By mass, the recycled waste materials constituted 32% of the mix, translating into 34% of its volume. Additionally, identified were mixes that may be used for structural applications.

This research project is undertaken to assess the effect of washout loss on the drop in bond properties of reinforcing steel bars embedded in underwater concrete (UWC). Special emphasis was placed to evaluate bond using the same concrete mixtures that were subjected to washout. Testing was realized using the beam-end specimen method, and parameters evaluated included level of washout loss, bar diameter, and concrete cover. Test results showed that bond between steel and UWC is affected by the level of washout loss, which in turn is directly influenced by the mixture composition. Similarly to bond in concrete cast and consolidated above water, the ultimate UWC bond strength increases for smaller bar diameters and higher confinement reflected by increased concrete covers. UWC mixtures with increased washout losses exhibited higher drops in compressive, tensile, and bond strengths, as compared to concrete cast above water. Two boxes depending on the level of washout loss, i.e. from 4.2 to 6.9 % and from 8.8 to 10.8 %, have been proposed to predict the extent of bond decrease in UWC mixtures.