Search Results (10)

Globally, 1.5 billion annual tire outputs generate a substantial volume of end-of-life tires (ELTs), creating significant environmental challenges. Despite increased recovery rates, ELT management costs in Europe underscore the need for proactive strategies to mitigate environmental and health risks. This study comprehensively evaluates the environmental impact of disposal methods, including landfilling, incineration, and crumb rubber production, using Life Cycle Assessment (LCA) via the OpenLCA software 2.0.2. While incineration is sometimes identified as a disposal method, unprocessed scrap tires have potential applications in civil engineering that can better align with sustainability goals. Detailed ELT composition analysis reveals significant recycling potential, with car and truck tires containing 10–20% steel fiber content, less than 1–8% textile fibers, and approximately 80% natural and synthetic rubber content. Recycling 1 ton of ELTs saves an estimated 1.4–1.6 tons of CO_2 Eq. compared to incineration. Mechanical recycling and application of recycled crumb rubber in concrete show significant environmental advantages, reducing mass density by approximately 55% and enhancing ductility by up to 40%, according to material testing results. These properties make crumb rubber particularly suitable for acoustic and resilient applications. Additionally, its elasticity and durability offer effective solutions for shoreline reinforcement, mitigating erosion and providing stability during flooding events. When used as a replacement for river sand in cement composites, crumb rubber contributes to a 24.06% reduction in CO₂ emissions, highlighting its potential for environmentally friendly construction. Full article

Fiber concrete exhibits superior performance in various aspects compared to plain concrete and has been widely researched and applied worldwide. However, many industrially made fibers are expensive, and their cost has to be considered before use; thus, it would be economically valuable to find inexpensive fibers with excellent properties to make fiber concrete. Rural areas have many rich straw resources to be disposed of; at the same time, the rapid development of the automobile industry has introduced a large number of used tires containing steel wire with a very low reuse rate. These two low-cost materials can be processed to make fibers, making the study of mechanical properties regarding their incorporation into concrete practically significant for reducing the cost of fiber concrete. Based on this, a three-factor, three-level orthogonal test was conducted to investigate the effects of different dosages of corn straw fibers and scrap steel fibers, as well as the water–cement ratio, on the mechanical properties of concrete. The optimum level of each factor for blended straw–waste-steel-fiber concrete with different mechanical properties was obtained using the polar and ANOVA methods. It was found that the compressive strength, splitting tensile strength, flexural strength, and impact resistance of the specimens after fiber dosing were better than those of plain concrete specimens with the same water–cement ratio. The maximum improvement was 14.96% in cubic compressive strength, 42.90% in tensile strength, and 16.30% in flexural strength, while the maximum improvement in impact energy consumption at the final crack was 228.03%. Combined with SEM microanalysis, the two fibers formed a stronger whole with the C-S-H gel. When the specimen was subjected to load, the two fibers were able to withstand part of the load, thus enhancing the load-bearing capacity. Finally, the optimal mix ratio of blended straw–scrap-steel-fiber concrete was determined to be 0.8% corn straw fibers by volume, 0.6% scrap steel fibers by volume, and a 0.45 water–cement ratio by combining the weights of the levels of each factor under its four different mechanical properties through hierarchical analysis. This analysis of mechanical properties provides a reference for practical applications in future projects. Full article

Ultrahigh-performance fiber-reinforced cement-based composite (UHPFRC) made with waste derived from scrap tires and oil refineries was tested in this study. The UHPFRC sample exhibited a maximum compressive strength of about 189 MPa at the end of 28 days. Steel fibers were recovered from scrap tires and were added up to 3% by volume in the UHPFRC samples. Such additions reduced cement flow by 11% but improved compressive strength by 21%. The equilibrium catalyst particles (ECAT) disposed of by oil refineries were used in amounts of up to 15% by weight as a replacement for cement in such UHPFRC samples. These aluminosilicate materials are spherical in shape and have a porous microstructure, which was found to reduce the cement flow by absorbing more free water onto their surfaces. They also reduced the heat and strength developments at early stages. However, the total cost of the final cement-based mixture and associated CO₂ emissions were reduced by up to 7% and 15% due to the inclusion of the ECAT particles. These findings help to optimize the ECAT and recovered steel fibers in the UHPFRC mix design, and such waste valorization strategies can help achieve the goal of becoming carbon neutral. Full article

In recent years, the alarming number of terrorist attacks has highlighted the critical need for extensive research aimed at fortifying structures against explosion-induced loads. However, the insufficient energy absorption and brittleness of conventional concrete make it ineffective in withstanding blast loading, encouraging researchers to explore innovative strategies for augmenting the energy dissipation capabilities of construction materials. This study specifically delves into the incorporation of recycled rubber, a sustainable and environmentally friendly solution to the pressing issue of scrap tire disposal. The primary focus of this research revolves around the integration of rubber recycling and steel fibers into concrete, with the ultimate goal of enhancing the dynamic response of reinforced concrete (RC) beams. This novel approach not only contributes to the structural resilience required for resisting blast impacts, but also aligns with eco-friendly practices by reusing recycled rubber. A meticulous numerical investigation was undertaken to comprehensively assess the static and blast response of these augmented beams. The numerical study involved developing finite element (FE) models using ABAQUS version 6.14 for static implicit analysis and LS-DYNA R11 for blast explicit simulations. The ABAQUS model was validated against previous experimental testing for load–displacement and failure patterns. Similarly, the LS-DYNA model was validated for blast pressure in accordance with UFC-3-340 standards and for material response under blast loading, utilizing existing experimental data. The numerical models were designed to accommodate varying weight percentages of rubber, ranging from 5% to 20%, and a consistent 1.0% incorporation of steel fibers. This comprehensive analysis aims to provide valuable insights into the efficacy of these materials in improving the structural integrity and blast resistance of RC beams, thereby contributing to the development of more secure and sustainable construction practices. By reducing the reinforcement ratio in order to meet the minimum code requirements, it became evident that the failures of the rubberized RC beams tended to exhibit ductility on the tension side under static loading. In addition, the increase in the reinforcement ratio correlated with a higher failure load and decreased deflection. Furthermore, the findings indicated an optimal concrete mixture characterized by improved ductility, energy absorption, and blast load capacity, achieved by combining 5–10% rubber with steel fibers. Full article

In this study, the impacts of different proportions of tension reinforcement and waste lathe scraps on the failure and bending behavior of reinforced concrete beams (RCBs) are clearly detected considering empirical tests. Firstly, material strength and consistency test and then ½ scaled beam test have been carried out. For this purpose, a total of 12 specimens were produced in the laboratory and then tested to examine the failure mechanism under flexure. Two variables have been selected in creating text matrix. These are the longitudinal tension reinforcement ratio in beams (three different level) and volumetric ratio of waste lathe scraps (four different level: 0%, 1%, 2% and 3%). The produced simply supported beams were subjected to a two-point bending test. To prevent shear failure, sufficient stirrups have been used. Thus, a change in the bending behavior was observed during each test. With the addition of 1%, 2% and 3% waste lathe scraps, compressive strength escalated by 11.2%, 21.7% and 32.5%, respectively, compared to concrete without waste. According to slump test results, as the waste lathe scraps proportion in the concrete mixture is increased, the concrete consistency diminishes. Apart from the material tests, the following results were obtained from the tests performed on the beams. It is detected that with the addition of lathe waste, the mechanical features of beams improved. It is observed that different proportions of tension reinforcement and waste lathe scraps had different failure and bending impacts on the RCBs. While there was no significant change in stiffness and strength, ductility increased considerably with the addition of lathe waste. Full article

The amount of steel waste produced is on the increase due to improvements in steel manufacturing industries. The increase in such wastes causes significant environmental problems and, furthermore, a large area is also required to store these waste products. Instead of disposing of these wastes, the reuse of them in different industries is an important success in terms of both reducing environmental pollution and providing low-cost products. From this motivation, the effect of lathe scrap fibers generated from Computer Numerical Control (CNC) lathe machine tools on concrete performance was investigated in this study. Pursuant to this aim and considering different fiber content, an experimental study was conducted on some test specimens. Workability and slump values of concrete produced with different lathe scrap fibers were determined, and these properties were compared with those of plain concrete. For the hardened concrete, 150 mm × 150 mm × 150 mm cubic specimens and cylindrical specimens with a diameter of 100 mm and a height of 200 mm were tested to identify compressive strength and splitting tensile strength of the concrete produced with different volume fracture of lathe waste scrap (0%, 1%, 2% and 3%). With the addition of the lathe scrap, the compressive and splitting tensile strength of fiber-reinforced concrete increases, but after a certain value of steel fiber content, there is a decrease in workability. Next, a three-point bending test was carried out on samples with dimensions of 100 × 100 × 400 mm and a span length of 300 mm to obtain the flexure behavior of different mixtures. It has been shown that the flexural strength of fiber-reinforced concrete increases with an increasing content of waste lathe. Furthermore, microstructural analysis was performed to observe the interaction between lathe scrap fiber and concrete. Good adhesion was observed between the steel fiber and cementitious concrete. According to the results obtained, waste lathe scrap fiber also worked as a good crack arrestor. Lastly, practical empirical equations were developed to calculate the compressive strength and splitting tensile strength of fiber-reinforced concrete produced with waste lathe scrap. Full article

Steel fibers are widely extracted from scrap tyres, causing environmental concerns. This paper presents the use of steel fibers in variable proportions extracted from scrap tyres. The enhancement of the confinement was envisaged through the addition of steel fibers obtained from scrap tyres. The study included an experimental program for the development of constitutive material models for ordinary Portland cement (OPC) concrete and concrete with added steel fibers. A mix design was carried out for OPC, targeting a compressive strength of 3000 psi. Steel fibers were added to OPC in ratios of 1.0% to 3.0%, with an increment of 0.5%. Concrete columns, with cross-sectional dimensions of 6 × 6 inches and a length of 30 inches, were cast with both OPC and fiber-reinforced concrete. The column confinement was evaluated with a different spacing of ties (3- and 4-inch center-to-center). Compression tests on the concrete columns indicate that the addition of steel fibers to a concrete matrix results in an appreciable increase in strength and ductility. Overall, increasing the percentage of steel fibers increased the compression strength and the ductility of concrete. The maximum strain in the concrete containing 2.5% steel fibers increased by 285% as compared to the concrete containing 1% of steel fibers. An optimum percentage of 2.5% steel fibers added to the concrete resulted in a 39% increase in compressive strength, accompanied by a significant improvement in ductility. The optimum content of steel fibers, when used in confined columns, showed that confined compression strength increased with the addition of steel fibers. However, it is recommended that additional columns on the basis of the optimum steel fiber content shall be tested to evaluate their effectiveness in reducing the stirrup spacing. Full article

The rapid growth in waste tire disposal has become a severe environmental concern in recent decades. Recycling rubber and steel fibers from wasted tires as construction materials helps counteract this imminent environmental crisis, mainly improving the performance of cement-based materials. Consequently, the present article aims to evaluate the potential use of waste tire steel fibers (i.e., WTSF) incorporated in the manufacture of soil–cement blocks, considering their compressive resistance as a primary output variable of comparison. The experimental methodology applied in this study comprised the elaboration of threefold mixtures of soil–cement blocks, all of them with 10% by weight in Portland cement, but with different volumetric additions of WTSF (i.e., 0%, 0.75%, and 1.5%). The assessment’s outcomes revealed that the addition of 0.75% WTSF does not have a statistically significant influence on the compressive resistance of the samples. On the contrary, specimens with 1.5% WTSF displayed a 20% increase (on average) in their compressive strength. All the tested samples’ results exhibited good agreement with the minimum requirements of the different standards considered. The compressive resistance was evaluated in the first place because it is the primary provision demanded by the specifications for applying soil–cement materials in building constructions. However, further research on the physical and mechanical properties of WTSF soil–cement blocks is compulsory; an assessment of the durability of soil–cement blocks with WTSF should also be carried out. Full article

With the rapid growth in the manufacturing industry and increased urbanization, higher amounts of composite material waste are being produced, causing severe threats to the environment. These environmental concerns, coupled with the fact that undergraduate students typically have minimal experience in research, have initiated the need at the UAE University to promote research among undergraduate students, leading to the development of a summer undergraduate research program. In this study, a recycling methodology is presented to test lab-fabricated Carbon-Fiber-Reinforced Polymer (CFRP) for potential applications in industrial composite waste. The work was conducted by two groups of undergraduate students at the UAE University. The methodology involved the chemical dissolution of the composite waste, followed by compression molding and adequate heat treatment for rapid curing of CFRP. Subsequently, the CFRP samples were divided into three groups based on their geometrical distinctions. The mechanical properties (i.e., modulus of elasticity and compressive strength) were determined through material testing, and the results were then compared with steel for prompt reference. The results revealed that the values of mechanical properties range from 2 to 4.3 GPa for the modulus of elasticity and from 203.7 to 301.5 MPa for the compressive strength. These values are considered competitive and optimal, and as such, carbon fiber waste can be used as an alternate material for various structural applications. The inconsistencies in the values are due to discrepancies in the procedure as a result of the lack of specialized equipment for handling CFRP waste material. The study concluded that the properties of CFRP composite prepreg scrap tend to be reusable instead of disposable. Despite the meager experimental discrepancies, test values and mechanical properties indicate that CFRP composite can be successfully used as a material for nonstructural applications. Full article

This study explores highly eco-efficient preplaced aggregate concrete mixtures having superior tensile characteristics and impact resistance developed for pavement and infrastructure applications. A fully recycled granular skeleton consisting of recycled concrete aggregate and recycled tire rubber granules, and steel wire fibers from scrap tires are first placed in the formwork, then injected with a flowable grout. Considering its very high recycled content and limited mixing and placement energy (only the grout is mixed, and no mechanical vibration is needed), this material has exceptional sustainability features and offers superior time and cost savings. Moreover, typical problems of rapid loss of workability due to the high-water absorption of recycled aggregates and the floating of lightweight tire rubber granules are prevented since the aggregates are preplaced in the formwork. The much higher granular content and its denser skeleton reduce the cementitious dosage substantially and provide high volume stability against shrinkage and thermal strains. The behavior under impact loading of this sustainable preplaced recycled aggregate concrete, incorporating randomly dispersed steel wire fibers retrieved from scrap tires, was investigated using a drop weight impact test. The results show that recycled tire steel wire fibers significantly enhanced the tensile and impact properties. A two-parameter Weibull distribution provided an accurate prediction of the impact failure strength of the preplaced recycled aggregate concrete mixtures, allowing to avert additional costly laboratory experiments. Full article