The current study aimed to examine the value of applying the hybridization approach to study the flexural behavior of hybrid reinforced concrete beams including two different concrete types: normal strength concrete and reactive powder concrete. In addition, carbon fiber-reinforced polymer bars and glass fiber-reinforced polymer bars were bonded in the tension face of the hybrid RC beams utilizing the near-surface-mounted technique. Eight simply supported reinforced concrete beams were tested. The hybridization technique enhanced the flexural behavior and increased the first crack and ultimate loads. Furthermore, the hybrid beams are stiffer than that of a normal beam, and it became even stiffer as the reactive powder concrete layer thickness increased. The hybrid beams that were strengthened with carbon fiber-reinforced polymer bars displayed higher load capacity by about 20% more than those strengthened with glass fiber-reinforced polymer bars.

This study explores the potential of calcium carbide residue (CCR) as an alternative activator for ground granulated blast-furnace slag (GGBS) to reduce reliance on ordinary Portland cement (OPC) in mortar production. A series of OPC-GGBS-CCR ternary binders were prepared and evaluated for their fresh and mechanical properties over various curing periods. The findings showed that mortars’ fresh and mechanical characteristics were significantly improved with longer curing times, suggesting CCR’s potential to efficiently activate GGBS, thereby benefiting the environment and economy. Significant enhancements in compressive strengths were observed after 7 days of curing, with increases of 44%, and 69–144% for OPC and OPC-GGBS-CCR ternary binders, respectively, while the utilization of activated binders led to flexural strength growth compared to three days of curing, with improvements of 70–173% for OPC-GGBS-CCR ternary binders, respectively. Microstructural analyses confirmed accelerated hydration and increased product formation due to CCR’s calcium content. An optimal mix ratio of OPC:GGBS:CCR = 1:1:0.5 demonstrated mechanical properties comparable to OPC mortars after 28 days, highlighting CCR’s potential for sustainable cementitious materials.

In order to better understand the mechanical properties of lightweight cement-based composite concrete (LWC), expanded polystyrene (EPS) beads are used as lightweight aggregate (LWA) in this paper. 50%, 70%, and 90% of EPS foam beads by volume are used to partially replace normal fine aggregate in different EPS concrete compositions. In addition, Ordinary Portland cement (OPC) was substituted with silica fume (SF) in EPS concrete at varying weight percentages of 15%. Nine mixes are made in order to examine the properties of EPS concrete. In the testing program, fresh density, slump, compressive strength, splitting tensile strength, flexural strength, thermal conductivity, and absorption are all determined. Although workability is improved, the mechanical properties of concrete are generally decreased when EPS beads are used. The addition of silica fume (SF) successfully counteracted the mixture’s overall decline in mechanical properties across all the mixtures that have been used. More solid material can be found per square inch of surface area in materials with a higher density, which results in more continuous heat-conduction pathways. In comparison to the control mix, the compressive strength of the polystyrene modified mixes showed a noticeable decline, falling by roughly 62% for P-50%, 69% for P-70%, and 71% for P-90%. In contrast, mixes P-90%-1.2, P-90%-1.4, and P-90%-1.6 reduced absolute strength compared to P-90%; their performance is nonetheless noteworthy because of their extraordinarily high EPS content. Despite having lesser absolute strengths than P-90%, mixes of P-90%-1.2, P-90%-1.4, and P-90%-1.6 nevertheless performed admirably considering their remarkably high EPS content.

The amount of plastic waste produced worldwide has been steadily rising. Manufacturing processes, service industries, and municipal solid waste produce a significant amount of waste plastic. One common construction and industrial waste that could be employed as shear reinforcement in concrete beams for specified purposes is the plastic waste strips, since they have relatively high tensile strength. Such plastic strips are used to tie clay bricks, floor finishing tiles, walkway finishing blocks, curbstones, and so on in different industrial products. This study examines an approach that uses plastic waste strips in place of conventional stirrups to enhance the shear performance of reinforced concrete (RC) beams. A set of shear tests was performed on carefully constructed 150 mm width × 225 mm depth × 1400 mm length beam specimens to evaluate failure mechanisms, modes of failure, crack patterns, and shear strength. All beams have the same flexural requirements, so they were ensured to fail by exceeding their shear strength under the applied load. This study examined five concrete beams that were reinforced internally using plastic waste strips in the shear region, as well as one control beam. The tested beams were reinforced using various strip spacings and configurations. The results of the tests indicated that increasing the plastic waste strips improved the concrete section shear strength. As the number of plastic strips in the section increases, the distance between each strip is drastically reduced, increasing the shear capacity of the beam. The experimental results indicate that the beam with six vertical plastic waste strips in its section has a 75% higher shear strength capacity than the reference beam without any transverse reinforcement. In addition, shear resistance is higher in the beam with plastic strips at 45° and 135° inclined angles than in the beam with vertical plastic strips in the same amount of plastic strips. Based on these findings, reinforced concrete beams can be utilized for specific purposes by employing plastic waste strips as transverse reinforcement to resist internal shear forces.

This paper studies the effect of fire exposure on the mechanical properties of lightweight concrete (LWC) made with expanded clay and sustainable hybrid aggregates (a mix of 50% LECA and 50% Ponza). Lightweight concrete is increasingly used in construction due to its lower weight and improved fire resistance compared to normal concrete. The experiment involved replacing limestone aggregates with 100 % LECA or a mix of 50% LECA and 50% Ponza in concrete samples. A total of 60 specimens (cubes, cylinders, and prisms) were prepared and heated at (300, 400, 500, and 600) °C for one hour to simulate fire conditions. The impact of high temperatures on compressive and indirect tensile strengths was analyzed. Results indicate that the mechanical properties of lightweight concrete (LWC) decline as temperature rises, with significant decreases especially above 400°C. Using hybrid aggregates improved the thermal stability and fire resistance of the concrete, reduced spalling risk, and optimized insulation compared to conventional aggregates. These findings support the use of lightweight concrete in fire-resistant structural elements by expanding our understanding of how it responds to fire exposure.

One definition of environmental sustainability is one that permits the maintenance of long-term environmental quality while preventing the depletion or degradation of natural resources. In the realm of concrete production, engineers are becoming more interested in sustainable development, which includes using locally available resources and repurposing industrial and agricultural waste in building construction as a potential remedy for economic and environmental problems. The purpose of the study is to determine how various ratios of waste steel and polypropylene fibers affect the compressive strength, tensile strength, flexural strength and density of reactive powder concrete composite at different ages. According to the test results, Mix 6, which contains 100% waste steel fiber and 0% polypropylene fiber, improves the mechanical properties of reactive powder concrete by 29% in compressive strength, 47% in tensile strength, 29% in flexural strength, and 6.1% in density when compared to the reference mix. Reactive powder concrete’s waste steel fiber content has been shown to effectively reduce cracking and increase splitting tensile strength. Statistical analysis using ANOVA and Tukey HSD confirmed that fiber type has a significant effect on the compressive strength of RPC, with mixes containing higher proportions of waste steel fibers demonstrating superior performance.