Search

Copyright of Transportation Science & Technolgy is the property of Transportation Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: Evaluate the performance of progressive collapse of full-scale three-dimensional structure (3D) beam-slab substructures with and without the presence of reinforced concrete (RC) balconies using two concrete mixes [normal concrete (NC) and rubberized concrete (RuC)]. Design/methodology/approach: This study examines two concrete mixes to evaluate the progressive collapse performance of full-scale 3D beam-slab substructures with and without the presence of RC balconies using the finite element (FE) method. Findings: The results showed that the vertical loads that affect the structures of the specimens after including the balconies in the modeling increased by an average of 29.3% compared with those of the specimens without balconies. The specimens with balconies exhibited higher resistance to progressive collapse in comparison with the specimens without balconies. Moreover, the RuC specimens performed very efficiently during the catenary stage, which significantly enhanced robustness to substantial deformation to delay or mitigate the progressive collapse risk. Originality/value: All the experimental and numerical studies of the RC beam-slab substructures under progressive collapse scenarios are limited and do not consider the balcony's presence in the building. Although balconies represent a common feature of multistory residential buildings, their presence in the building has more likely caused the failure of this building compared with a building without balconies. However, balconies are an external extension of RC slabs, which can provide extra resistance through tensile membrane action (TMA) or compressive membrane action (CMA). All those gaps have not been investigated yet. [ABSTRACT FROM AUTHOR]

In the current study, multi-walled carbon nanotubes (MWCNTs) were added to the crumb rubber concrete (CRC) to enhance its physical, mechanical, and fire-resistance properties. A comprehensive investigation into thirteen distinct concrete mixes incorporating rubber aggregate (RA) at levels of 5, 10, and 15%, combined with varying percentages (0, 0.1, 0.2, and 0.3%) of MWCNTs particles, evaluated workability, density, compressive strength, split tensile strength, and flexural strength of MWCNT-mixed CRC at ambient and elevated temperatures (200, 400, and 600 °C). The study demonstrated that MWCNTs, used as a partial substitute for cement in CRC, significantly improved concrete properties, enhancing density, flexural strength, split tensile strength, and compressive strength. Notably, adding 0.2% MWCNTs to CRC resulted in remarkable increases: 0.96% in density, 21.91% in 28-day compressive strength, 10.19% in split tensile strength, and 15% in flexural strength. The workability of CRC decreased with the inclusion of MWCNTs. Furthermore, results indicated that MWCNTs bolstered the residual compressive, tensile, and flexural strengths of rubberized concrete at elevated temperatures, with substantial improvements particularly evident at 200 °C. The present work was focused on the analysis of feasibility of MWCNT mixed CRC toward sustainable construction practices by comparing its physical, mechanical, and fire resistance properties with conventional concrete. [ABSTRACT FROM AUTHOR]

Several researches conducted on rubberized concrete in the past but very few researchers explained the bonding effect of the waste tire rubber particles with different cementitious materials. In this research the effect of the fineness of the micro silica and its bonding with the rubber particles is studied. To check the influence of fractional replacement of cement using micro silica and discarded tire rubber as limited substitution of sand with providing pre-treatment to rubber particles, this experimental investigation has been conducted on concrete with varying percentage switch of cement using micro silica (SF), especially micro-silica was used in this study to exchange with cement by its weight. SF exchanged cement from 0% to 12% with an incremental ratio of 3%. Along with this, the sand was fractionally replaced using pretreated crumb rubber (CR) particles derived from end-of-life tires. The replacement ratio changed by 5% by the volume of sand, ranging from 0% to 20%. The pre-treatment process for CR was done using Sodium Hydroxide (NaOH) of 1 Molarity, for achieving good bonding between cementitious material paste and rubber particles. Distinct fresh and hydrated concrete properties were assessed and compared with normal concrete (NC) having 0% SF and 0% CR. 17 concrete mixtures in all, together with the control mix, were assessed in this study with varying amounts of SF and CR. The bonding structure and impermeability were enhanced by using SF in concrete with promising enhancement in mechanical strengths. Based on the outcomes obtained from this research, the optimal proportion for partial substitution of cement and sand by SF and CR was fixed for the desired grade of concrete to provide an innovative form of concrete to the construction industry.

This study aims to examine the permeability and acid and sulfate attack of waste rubber-substituted concrete containing recycled rubber in three different grain size classes (chips, crumb and powder) with two different water/cement (w/c) ratios (0.4 and 0.5). Waste rubber at different ratios (0%, 4%, 8%, 12%, 16%, 20%, and 24%) was used in concrete by replacing fine and coarse aggregates. Sorptivity, electrical resistivity, and acid and sulfate attack tests were conducted on concrete cured for 90 days. Although the capillarity coefficient values increased with the waste rubber replacement ratio increase, a decrease occurred after the 20% waste rubber replacement ratio. In 12% waste rubber-substituted concrete (0.4WR12) with a water/cement ratio of 0.4, the electrical resistivity value (8.3 kΩ.cm) was the highest, and concretes with low permeability could be produced. As a result of the use of 16% waste rubber in the concrete, 75% less compressive strength loss was observed after the acid attack compared to the control concrete. In concrete with a water/cement ratio of 0.5, when the waste rubber ratio increased by up to 16%, the compressive strength losses caused by the sulfate attack decreased dramatically (95.76% less) compared to the control concrete. The rubberized concrete with a water/cement ratio of 0.5 showed high resistance to acid and sulfate attacks. The experiment results showed that 12% to 16% waste rubbers are ideal ratios. In this study, the water/cement ratio was a valuable parameter for the waste rubber ratio in rubberized concrete. [ABSTRACT FROM AUTHOR]

In coastal regions, the deterioration of structures and bridges due to environmental conditions and corrosion is a significant concern. To combat these issues, the use of corrosion-resistant materials like fiber-reinforced polymers (FRPs) materials, engineered cementitious composites (ECCs), and rubberized ECCs (RECC) shows promise as normal concrete (NC) alternatives by providing increased ductility and energy absorption properties. The effectiveness of confining concrete columns using GFRP tubes with ECC/RECC was assessed in this research by evaluating their performance through compression and push-out tests. The study explored key parameters such as GFRP tube thickness and the presence of shear connectors along the tube height, as well as examining various types of concrete. Additionally, a comprehensive parametric investigation utilizing finite element analysis (FEA) was conducted to analyze how different factors influence the behavior of confined concrete columns. These factors included the effect of GFRP tube thickness and diameter on the overall behavior of different types of confined concretes. The results demonstrate that GFRP tubes significantly enhance column capacity, while the presence of ECC/RECC exhibits even greater improvements in capacity, stiffness, and toughness compared to NC. This approach shows promise in reinforcing coastal infrastructure and addressing corrosion-related concerns effectively. [ABSTRACT FROM AUTHOR]

Recently developed multi-scale fiber (i.e., CaCO3 whisker, polyvinyl alcohol (PVA) fiber, and steel fiber) reinforced rubberized concrete exhibits excellent mechanical properties and spalling resistance at high temperatures. Measurement of macro properties such as strength and Young's modulus cannot reveal and characterize damage mechanisms, particularly those relating to the multi-scale fiber strengthening effect. In this study, acoustic emission (AE) technology is applied to investigate the impact of multi-scale fiber on the damage evolution of rubberized concrete exposed to high temperatures, under the uniaxial compression and tension loading processes. The mechanical properties, AE event location, peak frequency, b-value, the ratio of rise time to amplitude (RA), average frequency (AF) values, and AE energy of specimens are investigated. The results show that the number of events observed using AE gradually increases as the loading progresses. The crumb rubber and fibers inhibit the generation and development of the cracks. It is concluded that both the peak frequency and b-value reflect the extension process of cracks. As the cracks develop from the micro scale to the macro scale, the peak frequency tends to be distributed in a lower frequency range, and the b-value decreases gradually. At the peak stress point, the AE energy increases rapidly and the b-value decreases. The specimens without multi-scale fibers exhibit brittle failure, while the specimens with fibers exhibit ductile failure. In addition, adding multi-scale fibers and crumb rubber increases the peak frequency in the medium and high frequency ranges, indicating a positive effect on inhibiting crack development. After being subjected to high temperatures, the maximum and minimum b-values decrease, reflecting an increase in the number of initial cracks due to thermal damage. Meanwhile, the RA and AF values are used to classify tensile and shear cracks. The specimens fracture with more shear cracks under compression, and there are more tensile cracks in specimens with multi-scale fibers under tension. [ABSTRACT FROM AUTHOR]

As a sustainable solution, employing recycled tire rubber aggregates in the production of concrete is of considerable interest. However, the applicability of rubberized concretes in construction is restricted due to their relatively low mechanical performance. Using rubberized concrete as a filling material in a steel tube provides a suitable solution for overcoming this issue and for using it effectively as a load‐bearing element. The objective of this study is to examine the impact of the material characteristics of the sustainable rubberized concrete‐filled steel tube (Ru‐CFST) and develop a design model based on ultimate strength prediction for the axially loaded Ru‐CFST stub columns with varying contents of tire rubber aggregate. The model was developed through the gene expression programming (GEP) technique by employing the experimental test results to determine the ultimate compressive strength of Ru‐CFST columns. Based on the principal component analysis, the sectional properties of the load‐bearing element (such as outer diameter, thickness, and length), material strengths (such as rubberized concrete and steel tube strengths), and rubber content were determined as statistically significant parameters affecting the ultimate axial strength of Ru‐CFST stub columns and thus, they were considered in the stage of the model generation. Furthermore, the proposed model's performance was compared to that of available models suggested for traditional CFST columns by commonly employed design codes, namely, ACI, AIJ, AISC, CSA, EC4, and GB. Based on the statistical analysis of the results, it can be concluded that the existing formulations have a relatively acceptable randomness and scatter of observations within the distribution, while the proposed design model gives a more accurate prediction for the ultimate bearing capacity of axially loaded Ru‐CFST columns with the highest R‐squared value of about 0.99 and the comparatively lowest mean absolute percent error of 7.54. It can be stated that the proposed GEP‐based design model will encourage engineers to use such sustainable structural members in their designs and constructions. [ABSTRACT FROM AUTHOR]

This paper innovatively proposes a method of 180 °C high-temperature stirring pretreatment for waste rubber particles and compares this method with untreated, NaOH-treated, and silane coupling agent KH570-treated waste rubber particles. Fourier-transform infrared spectroscopy, X-ray diffraction analysis, water contact angle measurement, scanning electron microscopy, and energy-dispersive X-ray study are used to investigate the effects and mechanisms of different pretreatment methods on waste rubber particles. The results indicate that compared to NaOH-treated and KH570-treated waste rubber particles, the 180 °C high-temperature-stirred pretreated waste rubber particles show significantly improved cleanliness and form a hard oxide film. The study also investigates the effects of different pretreatment methods on the mechanical properties and interface binding performance of rubber concrete made from pretreated waste rubber particles. The results demonstrate that rubber concrete prepared using 180 °C high-temperature-stirred pretreated waste rubber particles substituting 20% fine aggregate exhibits the best mechanical properties and interface bonding performance. The compressive strength recovery rates after 7 and 28 days are 41.6% and 37.3%, respectively; the split tensile strength recovery rates are 47.3% and 60.6%; the axial compressive strength recovery rates are 34.1% and 18.8%; and the static compression moduli of elasticity recovery rates are 46.8% and 26.3%. High-temperature stirring pretreatment of waste rubber particles is simple to operate and suitable for scaled production. Its pretreatment effect is superior to those of the KH570 and NaOH methods, providing a reference value for the scalable application of waste rubber particles as a substitute for fine aggregate in rubber concrete. [ABSTRACT FROM AUTHOR]

Rubberized concrete (RC) has received widespread attention due to its energy absorption and crack resistance properties. However, due to its low compressive strength, it is not recommended for structural applications. The rubber size and content affect RC's mechanical properties. This study investigated and formulated the behavior of RC with different particle sizes and contents under dynamic and static loading. Quasi-static compressive and dynamic tests were conducted on RC with varying content of rubber (0–30%) and rubber sizes (0.1–20 mm). It was found that the rubber particle size was 0.5mm and the rubber content was 2%. An equation was derived from the experimental data to forecast the impact of rubber size and content on compressive strength. Additionally, by combining the literature and this research's data, a model was established based on neural networks to predict the strength of RC. SHPB tests were carried out to study the stress–strain curves under dynamic load. The peak stress, fragment analysis, and energy absorption of RC with varying content of rubber and rubber sizes at three different strain rates (100 s−1, 160 s−1, and 290 s−1) were investigated. Equations describing the relationship between dynamic increase factor (DIF), rubber material content, and strain rate on different particle sizes were obtained by fitting. The DIF increased as the content of the rubber increased. By analyzing energy absorption data, it was found that the optimal ratio for energy absorption was RC-0.5-30, RC-0.1-30, and RC-10-30 at strain rates of 100 s−1, 160 s−1, and 290 s−1. This study could be a good guideline for other researchers to easily select the content and size of the rubber in RC for their applications. It also has a positive significance in promoting the development of green building materials. [ABSTRACT FROM AUTHOR]

This study addresses the critical challenge of estimating compressive stress in rubberized recycled aggregate concrete, a key concern for sustainable construction. By integrating empirical data and machine learning techniques, particularly Extra Gradient Boosting (XGBoost), this research aims to enhance predictive models for structural performance assurance. Utilizing a dataset comprising 3840 stress-strain responses collected from 60 rubberized concrete mixtures, with 12 input variables, the study employs statistical analyses and regression to validate the model's performance. The XGBoost model demonstrates robust predictive capability, with low mean absolute error values (1.551 for testing and 0.967 for training) and high a20−index (0.917 for testing and 0.933 for training), effectively predicting compressive stress. Key factors influencing compressive stress were identified through Shapley's additive explanations. The developed model offers a practical tool for predicting stress-strain behavior in rubberized concrete formulations, with implications for mix design optimization and testing cost reduction. Additionally, the introduction of a user-friendly GUI facilitates interaction with the developed XGBoost model, further enhancing its practical application in sustainable construction practices. This study also includes the comprehensive database utilized in modeling, along with the developed Python code, provided as supplementary files. Future directions include exploring the influence of different types and sizes of rubber aggregates on concrete, particularly in high-strength and ultra-high-strength mixtures, and investigating the impact of outliers on model prediction performance.

This paper presents an experimental study on how crumb rubber particles from waste tires and corrugated round steel fibers affect the mechanical behavior of concrete. In addition to the standard plain mix and five combinations of mixes composed of 0.5%, 1.0%, and 1.5% ratios, three steel fiber and crumb rubber mixes, 0.5%, 1.0%, and 2.0% weight of sand, coarse aggregate, cement, and silica fume were evaluated. The percentage of silica fume that replaced the weight of the cement in this study was 8%. The fresh properties of the 12 mixtures in terms of slump and density were studied. After 28 days of curing 36 cubes, 36 cylinders, and 12 prisms, the hardened properties were determined by evaluating the mean compressive, split, and flexural strengths. The results indicate that a synergetic effect is observed for the combination of crumb rubber and corrugated round steel fibers to improve the fresh and hardened properties of concrete. Adding fiber reinforcement to concrete can mitigate the negative impacts of rubber, and vice versa. According to the combination content, increases in compressive strength, tensile strength, and flexural strength of up to 49.04%, 38.60%, and 75.76%, respectively, were achieved compared with the control combination. This validates the applicability of the proposed mathematical prediction formulation to evaluate the compressive strength, split tensile strength, and modulus of rupture of rubberized fibrous concrete in terms of fiber and rubber ratios. Based on these results, a promising solution for tire disposal is to recycle waste rubber for fibrous concrete applications. [ABSTRACT FROM AUTHOR]

The use of concrete-filled steel tube (CFST) piers has attracted widespread attention due to their high load-bearing capacity, excellent ductility, and superior seismic performance. Given their role as bridge substructures responsible for transmitting seismic loads, the ability of CFST piers to dissipate energy under seismic conditions significantly impacts bridge safety. This study investigates rubberized concrete-filled corrugated steel tube (RuCFCST) pier as a solution for addressing issues such as local buckling, bulging, or tearing damage in CFST columns during seismic loading. Four 1:4 scale pier specimens were subjected to pseudostatic tests to determine the effects of the axial compression ratio, filling concrete type, and connection method on the damage development, failure mode, strain distribution, and seismic performance of the pier specimens. In addition, a reliable nonlinear finite element model was established to evaluate sensitive parameters such as the length–diameter ratio, axial compression ratio, diameter-to-thickness ratio, and confinement factor. The influence of each parameter on this type of composite pier was revealed. The results showed that the flexural strength of corrugated steel tubes filled with rubber concrete was 17.4% lower than that of ordinary concrete tubes, but the ductility coefficient was 24.3% higher. When the axial compression ratio is increased from 0.2 to 0.3, the flexural strength of the composite pier increases by 16.8%, while the ductility coefficient decreases by 8%. Additionally, utilizing embedded connections reduces the flexural strength by 16.4%, but it increases the ductility coefficient by 45.9%. Finite element analysis revealed that the confinement factor was the metric with the highest sensitivity in relation to the flexural strength of the pier. This research is a novel and comprehensive exploration of the seismic performance of RuCFCST piers that provides experimental and numerical support for transitioning from conventional CFSTs to this innovative structural solution. [ABSTRACT FROM AUTHOR]

Eco-friendly recycled tire-derived rubberized concrete is an environmentally conscious alternative employed in civil engineering for diverse purposes, enhancing the characteristics of concrete. In this paper, the research focuses on examining the drying shrinkage, creep, impact, and post-impact and creep behavior of concrete incorporating rubber. Four groups of cylindrical samples, each with a diameter of 150 mm and a length of 300 mm, were subjected to a consistent load corresponding to 0.25 of the bearing load capacity determined through compression tests on identical concrete mixtures. The testing spanned a year, during which measurements were taken for total strain, dependent strain, creep, and shrinkage. The concrete mixtures were formulated with crumb rubber in place of fine aggregate sand, with varying percentages (0%, 10%, 20%, and 30%). To emphasize distinctions in outcomes across mixtures with different crumb rubber proportions, tests for compression, indirect tension, flexural strength, and impact resistance were carried out at intervals of 28 days, three months, six months, and one year. The examination and contrast of the four combinations demonstrated notable effects on both concrete creep and impact energy due to the addition of rubber particles. Despite this, shrinkage showed minimal influence. In general, there was a decrease in the compressive strength of rubberized concrete. The concrete compressive strength decreased by 25–35%, 45–50%, and 55–65% for rubberized concrete incorporating 10%, 20%, and 30% crumb rubber, respectively. Furthermore, it was observed that creep negatively affects the impact resistance of non-rubberized concrete. Nevertheless, including rubber helps mitigate the effect of creep on the impact resistance, resulting in a reduction ranging from 6% to 12% across rubber percentages from 10% to 30%.

Utilizing waste crumb rubber and substituting cement in concrete with industrial waste materials, such as ground granulated blast furnace slag (GBFS), represents a promising pathway towards achieving sustainable development. This study assesses the inclusion of waste rubber powder (RP) alongside graphene nanoplatelets (GnPs) and an efficient surfactant (Tween 80), in conjunction with GBFS in concrete, in terms of acoustical and mechanical properties. The RP content varied from 4 % to 18 % as a replacement for sand, while GnPs (0.1 % to 0.7 %) and GBFS (30 %) were utilized as substitutes for cement. The compressive (CS), flexural (FS), tensile strength (TS), sound absorption (α), and noise reduction coefficient (NRC) of the modified rubberized concrete were experimentally and theoretically evaluated. The outcomes revealed that the optimum content of RP and GnPs was 11 % and 0.4 %, respectively, in which the CS, FS, and TS were 49.5 MPa, 6.3 MPa, and 2.7 MPa, respectively, compared to the control mix (45.5 MPa, 5.2 MPa, and 2.5 MPa). In addition, the sound absorption and noise reduction coefficient of the modified rubberized concrete were 0.556 at a frequency of 1760 Hz and 0.16, respectively, compared to the control mix (0.53, 0.109), while the highest value of α (0.603) was achieved when the rubber content was 18 %. It can be concluded that the proposed concrete mixture fulfilled the requirements of both mechanical and acoustical properties as well as enhanced sustainability by addressing waste disposal and minimizing CO2 emissions. It also suggests a feasible direction for further exploration into its performance under elevated temperatures and aggressive environmental conditions.

Abstract In this paper, an experimental study was conducted to examine the static and dynamic behaviors of rubberized fiber-reinforced concrete (RFRC). Crumb rubber was partially replaced from sand at volume fractions of 0%, 5%, 10%, 15%, and 20%. Steel fibers (SFs) with fiber volume fractions (Vf%) of 0%, 0.5%, 1%, and 1.5% were used for the production of FRCs, while polypropylene fiber (PPF) with Vf% = 0.4% was adopted to produce others FRCs. A combination of 0.4% PPF and 1% SF was used for hybrid FRC. The static properties were evaluated through compression, indirect tension, and flexural tests. However, the drop weight impact test was conducted to assess the dynamic property by estimating the impact energy. It was observed that the replacement of sand with rubber reduced all mechanical properties of concrete. In the case of RFRC, a reduction in compressive strength, compared to samples without fibers, was noted, and this reduction increased with higher Vf%. Both toughness indices and fracture energy were affected slightly by increasing rubber percentages while markedly increased with higher Vf%. However, adding rubber and/or fibers enhanced the impact energy of concrete.

To investigate the confining effect and axial compressive behavior of rubberized concrete (RuC) confined by steel tube, axial compression tests were carried out on 12 circular RuC cylinders confined by steel tube. The cylinders considered parameters such as steel tube thicknesses (2 mm, 3 mm, 4 mm) and rubber volume replacement ratios of the fine aggregates (0%, 10%, 20%, and 30%). It was observed that the compressive strength of RuC decreases as the rubber volume replacement ratio increases. However, an increase in steel tube thickness enhances the confining effect of the core RuC, leading to an increase in its compressive strength and the corresponding strain, similar to that of conventional concrete. Moreover, post-peak curves are more likely to exhibit a strengthening part in confined concrete with more rubber content. Furthermore, a model was developed to determine the compressive strength of RuC confined by steel tube. Finally, an axial stress-strain model of steel tube confined RuC was proposed, which was validated against test results. [ABSTRACT FROM AUTHOR]

In this investigation crumb rubber was pre-treated with the alkaline solutions of NaOH and Chloride of lime (calcium hypochlorite) for one day before employing in concrete as a fractional substitute of sand. The replacement levels were kept at 5% and 10%. Fresh and hardened densities, workability and thermal conductivity of rubberized concrete were investigated. Results revealed that the workability of the rubberized concrete decreased with the increase in their percentage. The incorporation of treated rubberized particles also reduced the density of the end products. The thermal conductivity was reduced by 50% by incorporating 10% treated crumb rubber. The use of crumb rubber to develop rubberized concrete will decrease the geohazard produced by the blazing and disposal of trash tire rubber. [ABSTRACT FROM AUTHOR]

In this investigation crumb rubber was pre-treated with the alkaline solutions of NaOH and Chloride of lime (calcium hypochlorite) for one day before employing in concrete as a fractional substitute of sand. The substitute proportions were fixed as 5% and 10%. Compressive, flexural, and split cylinder strengths of rubberized concrete were investigated. Rubberized concrete was also evaluated in terms of porosity. The incorporation of treated rubberized particles reduced the strength of the end products. The porosity was enhanced by incorporating treated crumb rubber. However, the concrete samples having crumb rubber treated with bleaching powder provided comparatively better results in terms of strength as well as water absorption. The use of crumb rubber to develop rubberized concrete will decrease the geohazard produced by the blazing and disposal of trash tire rubber. [ABSTRACT FROM AUTHOR]

Applying waste tire rubber as rubber aggregate (RA) in concrete is advantageous from the perspective of environmental sustainability. This study examines the action of graphene oxide (GO) on the durability properties of high-strength rubberised concrete (RC). The durability characteristics of concrete were assessed with the help of acid attack, water sorptivity, and rapid chloride penetration test (RCPT) on the hardened concrete specimens for the test periods of 7, 28, 56, and 90 days each. Acid attack tests (mass loss and compressive strength loss) were performed after immersing the concrete specimens in hydrochloric (HCl) and sulphuric (H2SO4) acids for the stipulated periods. The increased mass and compressive strength losses were observed with the incorporation of RA in concrete, which was finally mitigated by the action of GO in concrete. Water absorption was increased by RA alone but was reduced after the incorporation of GO in this RC. It was also observed that the chloride penetration was reduced after the incorporation of RA and GO in conventional concrete (CC). This study concludes that GO excellently strengthens the long-term durability properties of the RC. [ABSTRACT FROM AUTHOR]

In addressing the dual challenges of sustainable waste management and environmental conservation in the construction industry, particularly the disposal of waste tire crumb rubber (CR) and the demand for eco-friendly building materials, this study explores a novel solution. It examines the sustainable incorporation of waste tire crumb rubber and mineral additions—namely silica fume (SF), marble slurry powder (MSP), and fly ash (FA)—as partial substitutes for natural fine aggregates and cement in concrete. Through comprehensive testing of seventeen concrete samples, the study reveals that the specific mix of R10S5M10F15 that contained 10% crumb rubber as replacement of fine aggregates, and 5% silica fume, 10% marble slurry powder and 15% fly ash as replacements of cement, not only achieves compressive and split tensile strength comparable to the control mix, while the 90 days flexural strength was improved by 4.48%; credited to SF's pozzolanic action and the filler effects of MSP and FA, but also that the inclusion of CR, while reducing compressive strength due to material variations, enhances ductility and improves resistance to sulfate and acid attacks, despite increasing water absorption. The primary goal of this research is to investigate the feasibility and effectiveness of using waste materials in concrete to foster more sustainable construction practices. The objectives include a detailed assessment of the mechanical properties and durability of concrete incorporating these waste materials, aiming to determine the optimal mix proportions for their effective utilization. This study's novelty lies in its detailed analysis of the synergistic effects of combining CR, SF, MSP, and FA in concrete, contributing to the field by offering a sustainable alternative approach to traditional concrete formulations and highlighting the delicate balance required for optimized concrete performance. [ABSTRACT FROM AUTHOR]

This study examines the creep deformations and long-term strength properties of rubberized one-part alkali-activated concrete with relatively high rubber content, which have not been previously reported. The aluminosilicate precursors used in the mix design are blast furnace slag and fly ash at a ratio of 4-to-1, while anhydrous sodium metasilicate is used as the solid activator. Crumb rubber particles are used to replace 30% and 60% by volume of the total natural aggregates, and a nonrubberized one-part alkali-activated concrete mix is also prepared for comparison purposes. The creep specimens are subjected to two levels of sustained loads, representing 10% and 20% of the 28-day compressive strength. The creep loads are applied after 28 days of ambient curing, and creep deformations are monitored for a period of 1 year. The results clearly show a deterioration in mechanical properties with higher rubber content, regardless of the testing age. The compressive strength and elastic modulus of the unloaded and loaded creep specimens, tested at an age of 393 days, are generally lower than that observed for similar specimens tested at 28 days. The axial and lateral crushing strains of the specimens tested at 393 days are significantly higher than their counterparts tested at 28 days. The creep strains, measured over 365 days, increase as the applied stress level increases, but reduce with higher rubber content. The creep coefficients and specific creep values of the tested specimens over 365 days experience a reduction as the applied stress level increases, while the opposite is seen as the rubber content increases. The creep coefficients of rubberized one-part alkali-activated concrete are generally higher than those given by prediction models in various codes for conventional concrete. The rate of creep development is also more significant than conventional concrete and does not show signs of slowing down after 365 days of sustained loading. [ABSTRACT FROM AUTHOR]

The escalating environmental impact of non-biodegradable waste, particularly from discarded tires, necessitates innovative recycling strategies. This study explores the potential of incorporating pre-treated crumb rubber from waste tires into concrete mixtures as a sustainable alternative to traditional coarse aggregates. A comprehensive experimental investigation was conducted to evaluate the fresh-state properties, workability, and mechanical behavior of rubberized concrete. The study focused on varying proportions of pre-treated rubber particles, substituting 10%, 20%, 30%, and 40% of conventional coarse aggregates by volume. These rubber particles were treated with cement paste to enhance bonding strength within the composite material. Standard tests were employed to assess the properties of the rubberized concrete, including density, slump, and compressive strength. The findings reveal that the incorporation of recycled tire rubber as a partial aggregate replacement notably impacts the workability and mechanical properties of the concrete. However, this reduction is mitigated when a concrete superplasticizer is utilized. Furthermore, the research indicates a decrease in the failure load of rubberized concrete composite slabs, ranging from 15% to 58%, compared to those constructed with traditional aggregates. Additionally, a significant reduction in the initial cracking load was observed. These outcomes offer critical insights into the structural and mechanical implications of using pre-treated rubber particles in concrete. While the decrease in mechanical performance poses challenges, the study illuminates pathways for enhancing the sustainability of concrete through the innovative reuse of waste materials. This approach not only addresses environmental concerns but also opens new avenues for the development of more sustainable construction materials. [ABSTRACT FROM AUTHOR]

The mechanical behavior of steel–concrete–steel (SCS) sandwich composite structures under low- or high-velocity impact loading has garnered increasing attention from researchers in recent decades. However, to date, limited effort has been dedicated to studying the residual resistance of SCS sandwich composite structures following impact damage. In a previous investigation, the authors developed a rubberized lightweight high-ductility cement composite (RLHDC) for implementation in double-layer steel–RLHDC–steel composite panels and examined the dynamic response of these panels under impact. To further explore the residual performance of impact-damaged composite panels, the present study conducts flexural tests on nine such panels. The study quantifies and analyzes the effects of various connector types, connector spacing, number of concrete layers, rubber powder content, and number of impacts on the residual flexural resistance of the impact-damaged composite panels. Detailed analysis is conducted on the failure modes, load–displacement curves, strain curves, and load–slip curves of the impact-damaged specimens. The test results reveal that the impact-damaged composite panels experience flexural failure with bond slip under static load. The residual flexural performance is found to be sensitive to the number of concrete layers and number of impacts. Finite element (FE) simulations are performed using LS-DYNA to investigate the residual flexural behavior of the impact-damaged composite panels. The restart method is employed in the simulations to mimic the post-impact static loading scenario. The agreement between the FE results and the experimental findings validates the model and provides a straightforward and effective approach for studying the residual performance of composite structures. An expanded parameter analysis leveraging the calibrated FE model indicates that the steel plate's thickness and strength predominantly influence the composite panel's residual resistance, whereas the influence from concrete strength proves less consequential. [ABSTRACT FROM AUTHOR]

This research aims to assess the rheological and mechanical characteristics of Self-compacting concrete (SCC) incorporating waste tire rubber aggregates (WRTA) as an interim substitute for coarse aggregates. However, the standard experimental modeling approach has significant obstacles when it comes to overcoming the nonlinearity and environmental susceptibility of concrete parts. Therefore, linear regression (LR) and extreme gradient boosting (XGBoost) were used as two standard single machine learning (ML) models to predict the aforementioned rubberized SCC features. In this study, conventional coarse aggregates were supplanted with WRTA at 0%, 5%, 10%, and 20% to uncover the optimal proportion of coarse aggregates substituting rubber. To find the optimum amount of WRTA to use as a substitute, the study follows the impacts of rubber on the self-compacting rubberized concrete's (SCRC) rheological and mechanical characteristics. The consequences on fresh properties were investigated by the slump flow, J-ring, and V-funnel tests, while compressive and splitting tensile strengths tests were conducted to assess mechanical properties. Increasing WRTA test outputs indicated a deterioration in workability and hardened qualities. While a 10% swapping ratio is deemed feasible for producing SCRC, optimal results were achieved by reducing environmental impacts and efficiently managing a significant volume of rubber tire waste with a 5% substitution of rubber within the coarse aggregates. The research findings indicated a noticeable decrease in fresh properties as the WRTA content increased. Notably, after 28 days, a 10% WRTA substitution led to a 34% reduction in compressive strength and a 28% decrease in splitting tensile strength, satisfying ACI standards. Furthermore, XGBoost demonstrated superior predictive performance with the highest R2 values, outperforming the LR model and affirming its efficacy in delivering more accurate predictions.

Rubberized geopolymer concrete (RuGPC) is a new, environmentally safe building material requiring less energy and carbon footmark than normal cement-based systems, which can significantly reduce global warming concerns. Using waste rubber tyres by incorporating them in concrete as a substitute for natural aggregate, helps to reduce pollution and depletion of natural resources. Research shows that incorporating waste crumb rubber in geopolymer concrete (GPC) can reduce carbon dioxide emissions by 90% compared to ordinary Portland cement (OPC) and attain sufficient and mechanical properties and durability. This paper reviews the material properties of RuGPC and the possible structural application. It can be concluded, that RuGPC can substitute normal concrete (NC) particularly due to its impact resistance, and energy absorption performance. However, more research still needs to be conducted to be able to come up with practical design standards and conduct full-scale studies on RuGPC elements structurally to promote its practicability.

The use of rubber in concrete to partially substitute mineral aggregates is an effort to decrease the global amount of scrap tires. This study investigates the behavior of rubberized concrete (RC) with various replacement ratios (0–50%) by volume and replacement type (fine, coarse, and fine-coarse) using soft computing techniques. The uniaxial compressive strength (CS), elastic modulus (EM), and ductility (D) are measured, and the effect of rubber content and the rubber aggregate type on the properties of RC is investigated. Scanning electron microscopy and X-ray diffraction analyses are made to determine its microstructural and chemical composition. This article compares the efficiency of two RC models using a recently developed artificial intelligence technique, i.e., gene expression programming (GEP) and conventional technique, i.e., response surface method (RSM). Statistical models are developed to predict the CS, TS, EM, and D. The mathematical models are validated using determination coefficient (R 2) and adjusted coefficient (R 2adj), and they are found to be significant. Furthermore, both methods (i.e., RSM and GEP) are very well correlated with the experimental data. The GEP is found to be more effective at predicting the experimental test results for RC. The projected methods can be executed for any practical value of RC.

This paper innovatively proposes a method of 180 °C high-temperature stirring pretreatment for waste rubber particles and compares this method with untreated, NaOH-treated, and silane coupling agent KH570-treated waste rubber particles. Fourier-transform infrared spectroscopy, X-ray diffraction analysis, water contact angle measurement, scanning electron microscopy, and energy-dispersive X-ray study are used to investigate the effects and mechanisms of different pretreatment methods on waste rubber particles. The results indicate that compared to NaOH-treated and KH570-treated waste rubber particles, the 180 °C high-temperature-stirred pretreated waste rubber particles show significantly improved cleanliness and form a hard oxide film. The study also investigates the effects of different pretreatment methods on the mechanical properties and interface binding performance of rubber concrete made from pretreated waste rubber particles. The results demonstrate that rubber concrete prepared using 180 °C high-temperature-stirred pretreated waste rubber particles substituting 20% fine aggregate exhibits the best mechanical properties and interface bonding performance. The compressive strength recovery rates after 7 and 28 days are 41.6% and 37.3%, respectively; the split tensile strength recovery rates are 47.3% and 60.6%; the axial compressive strength recovery rates are 34.1% and 18.8%; and the static compression moduli of elasticity recovery rates are 46.8% and 26.3%. High-temperature stirring pretreatment of waste rubber particles is simple to operate and suitable for scaled production. Its pretreatment effect is superior to those of the KH570 and NaOH methods, providing a reference value for the scalable application of waste rubber particles as a substitute for fine aggregate in rubber concrete.

In this technology era, sustainable construction practices have become quite imperative. The exploration of alternative materials to reduce the environmental footprint is of paramount importance. This research paper delves into an exhaustive investigation concerning the utilization of recycled coarse aggregates (RCA) and rubber particles (RP) in concrete. It contributes to the growing body of knowledge aimed at fostering sustainable development in the construction industry by reducing waste, promoting recycling, and mitigating the environmental footprint of building materials. The objective of the study is to evaluate the potential benefits and limitations associated with incorporating these materials, thereby providing a sustainable alternative to conventional concrete. In this research, construction and demolition waste were recycled and used as RCA as a fractional switch of natural coarse aggregate (NCA) from 0% to 100%, with an increment of 20% replacement of NCA in concrete. The RP received from discarded tires generated as automobile industry waste were used as a volumetric fractional substitution of sand in concrete from 0% to 20%, with a 5% increment. No pre-treatment for RCA and RP was carried out before their utilization in concrete. A total of 26 mixes, including control concrete without NCA and RP, with a design strength of 40 MPa, were prepared and tested. Concrete mixes were examined for workability, density, mechanical, and durability properties. It was found that the concrete with 60% RCA and 10% RP showed satisfactory results in evaluation with the strength parameters of control concrete, as the compressive strength obtained for this concrete mix is 40.18 MPa, similar to the control mix. The optimization for RCA and RP was conducted using Response Surface Methodology (RSM). The major concern observed was a rise in water absorption with an increase in the percentage replacement of NCA and natural sand by RCA and RP. Findings from the investigation illustrate a promising prospect for the use of RCA and RP in concrete applications, displaying competent mechanical properties and enhanced durability under certain conditions, offering a viable option for environmentally friendly construction practices. However, the research also sheds light on some constraints and challenges, such as the variability in the quality of RCA and the necessity for meticulous quality control to ensure the reliability and consistency of the end product. It is discerned that further refinement in processing techniques and quality assurance measures is pivotal for mainstream adoption of RCA and RP in concrete construction.

Waste tyre rubber has become an environmental and health concern that needs to be sustainably managed to avoid fire hazards and save natural resources. This research work aims to study the structural behavior of glass fiber reinforced polymer (glass-FRP) reinforced rubberized concrete (GRC) compressive elements under monotonic axial compression loads. Nine GRC circular compressive elements with different axial and crosswise reinforcement ratios were fabricated. All the elements were 300 mm in diameter and 1200 mm in height. A 3D nonlinear finite element equation (FEM) was suggested for the GRC compressive elements using a commercial package ABAQUS. A parametric study has been done to examine the effect of various parameters of GRC elements. The test outcomes revealed that the ductility of GRC elements ameliorated with the lessening in the spaces of glass-FRP ties. The addition of rubberized concrete improved the ductility of GRC elements. The damage to GRC elements occurred due to the vertical cracking along the height of the elements. The estimates of FEM were in close agreement with the test outcomes. The suggested empirical equation depending on the 600 test elements, which considered the lateral confinement effect of FRP ties, presented higher accuracy than previous equations.

Tire rubber waste is globally accumulated every year. Therefore, a solution to this problem should be found since, if landfilled, it is not biodegradable and causes environmental issues. One of the most effective ways is recycling those wastes or using them as a replacement for normal aggregate in the concrete mixture, which has high impact resistance and toughness; thus, it will be a good choice. In this study, 135 data were collected from previous literature to develop a model for the prediction of rubberized concrete compressive strength; the database comprised different mixture proportions, the maximum size of the rubber (1–40 mm), and the rubber percentage (0–100%) replacing natural fine and coarse aggregates were among the input parameters in addition to cement content (380–500 kg/m3) water content (129–228 kg/m3), fine aggregate content (0–925 kg/m3), coarse aggregate content (0–1303 kg/m3), and curing time of the samples (1–96 Days); then the collected data were used in developing Multi Expression Programming (MEP), Artificial Neural Network (ANN), Multi Adaptive Regression Spline (MARS), and Nonlinear Regression (NLR) Models for predicting compressive strength (CS) of rubberized concrete. The parametric analysis reveals that as the maximum rubber size increases, the reduction in compressive strength becomes more pronounced. Notably, this strength decline is more significant when rubber replaces coarse aggregate than its replacement of fine aggregate. Among the input parameters considered, it is evident that the fine aggregate content exerts the most substantial influence on the compressive strength of rubberized concrete. Its impact on predicting compressive strength surpasses other factors, with the concrete samples' curing time ranking second in importance. According to the assessment tools, the ANN model performed better than other developed models, with high R2 and lower RMSE, MAE, SI, and MAPE. Additionally, ANN and MARS models predicted the CS of different sizes better than MEP and NLR models. Subsequently, we employed the collected data to develop predictive models using Multi Expression Programming (MEP), Artificial Neural Network (ANN), Multi Adaptive Regression Spline (MARS), and Nonlinear Regression (NLR) techniques to forecast the compressive strength (CS) of rubberized concrete. The statistical analysis tools assessed the performance of these developed models through various evaluation criteria, including the Coefficient of Determination (R2), Root Mean Square Error (RMSE), Mean Absolute Error (MAE), Scatter Index (SI), and Mean Absolute Percentage Error (MAPE). In summary, our study underscores the efficacy of recycling rubber materials in concrete production. It presents a powerful predictive model for assessing the compressive strength of rubberized concrete, with the ANN model standing out as the most accurate and reliable choice for this purpose.

The proliferation of discarded rubber tires is rapidly increasing at a concerning pace. Driven by the significant movement towards promoting environmental sustainability and mitigating the adverse environmental impact associated with non-biodegradable waste rubber tires, the objective of this study is to identify a viable and ecologically responsible resolution to the issue of discarded tires. This study experimentally focuses on the structural response and load-carrying capacity of reinforced concrete (RC) short columns containing crumb rubber as a partial replacement for fine aggregate after being exposed to temperatures of 27 °C, 300 °C, and 500 °C. Four concrete mixes were produced in which the natural fine aggregate (NFA) was partially replaced by CR with ratios of 0%, 5%, 10%, and 20% in volume. Twelve columns (three columns from each mix) were cast and tested under concentric loading. The experimental results showed that the workability and compressive strength of the concrete mixes decreased with increasing the CR replacement ratio. The residual failure load of columns decreased with increasing CR quantities and heating temperatures. The CR quantity had a more considerable impact on the decline of the column capacity than the heating temperatures. Analytical equations from international standards ACI 318–14, CSA A23.3, and previously existing equations were applied to study the validity of these equations in predicting the failure load of heated rubberized RC columns. Finally, a proposed equation for predicting the failure load of the columns is developed. The predicted failure loads obtained from the proposed equation were compared to the experimental results. The predictions from the proposed equation were in good agreement with the experimental data. Different statistical tests were done to compare the predictions from the proposed equation and previously existing equations for predicting the failure load of heated rubberized RC columns.

Waste tire rubber is one of the most concerning environmental pollution issues. With the increasing demand for automobile production, the rate of waste tire generation has also increased. However, these tires often end up stockpiled and not properly disposed of. This non-biodegradable waste poses severe fire, environmental, and health risks. Due to the progressively severe environmental problems caused by the disposal of waste tires, the feasibility of using such elastic waste materials as an alternative to natural aggregates has become a research topic. The main objective of this research is to investigate the changes in the mechanical and durability properties of concrete with the inclusion of waste tire rubber at specific contents. A total of 80 cylinders measuring 100 mm × 200 mm were cast with waste tire aggregate as a partial replacement for natural coarse aggregate (5% and 10% by weight of natural coarse aggregate). A surface treatment of tire aggregate using a cement coating was performed to study its effect on concrete properties. This research indicates a noticeable reduction in the compressive and split tensile strength of concrete containing untreated waste tire rubber compared to normal concrete made with natural aggregates. However, an improvement was observed when the surface of tire aggregates was coated with cement grout. Additionally, it was noted that the slump value, water absorption, and porosity increased as the percentage of rubber increased. Nevertheless, unlike normal concrete, the failure pattern in tire-mixed concrete occurs gently and uniformly, indicating ductile behavior.

Abstract Recycling scrap tires provides an alternative source of fine aggregates for the production of rubberized concrete and this will lead to significant increase in concrete frost resistance, environmental protection, and conservation of natural sand and gravel resources. In this paper, a total of 25 groups of rubberized concrete were produced by adding scrap tire rubber particles of different sizes, contents, and pretreatment methods to replace the fine aggregate, and their compressive strength during freeze–thaw cycles was studied from both the macro- and meso-perspectives. The results indicated that the decrease in concrete strength and weight was notably restricted by the presence of rubber particles during freeze–thaw cycles. The rubber fine aggregate with smaller particle sizes enhanced the concrete frost resistance more significantly, and the F 100 of concrete with rubber particles of 1.0–2.0 mm increased from 76.6 to 86.5% by increasing the rubber content from 0.0 to 5.6%. The effects of rubber fine aggregate on concrete compressive strength during freeze–thaw cycles were quantified. On this basis, a forecast model for rubberized concrete compressive strength in freeze–thaw cycles was proposed, and the effects of the particle size, content, and pretreatment of the rubber particles were considered. The calculated results agreed well with the test results both in this study and the relevant peer studies, indicating that the model can provide a good reference for the design and engineering application of rubberized concrete in frigid environments.

Recycling end-of-life tires is a global problem that requires an urgent solution. Storing and preserving these tires is a challenge that delays facing potential problems instead of solving the problem. In this context, recycling waste tires without harming the environment and at low costs has been the focus of many researchers. For a few decades, the possibility of these tires to be granulated to the size of aggregate for concrete and then be replaced with natural aggregate has been a subject of research by scientists studying in this field. In this regard, this study aims to experimentally investigate the influence of waste rubber aggregate on some engineering properties of concrete, such as, ultrasonic pulse velocity-based quality assessment, abrasion resistance, and thermal conductivity characteristics as well as the mechanical performance, namely, compressive strength. Another significant side of the study was to establish a statistical relationship and correlation between the w/c ratio and substitution level of waste rubber aggregate and the experimental outputs. The experimental study indicated that the waste rubber aggregate decreased the compressive strength of the concretes whereas it improved the thermal conductivity characteristics and abrasion resistance of the concretes manufactured in this study. On the other hand, the statistical analysis revealed that the input parameters have meaningful effects on the engineering properties of the concretes, and there is a strong correlation between these properties.

Results of fourteen two-span continuous deep beams made from ordinary reinforced concrete (ORC) as a reference and rubberized reinforced concrete (RRC) is presented and discussed in this research. The main parameters are the rubber ratios as a replacement with coarse and fine aggregate and the shear span/depth ratio (a/h) is 1.33 and 1.66. Chip and crumb rubbers were used to replace coarse and fine aggregate respectively in four different amounts by volume (5%, 10%, 15%, and 20%). The proposed mix shows an ability to replace 20% of the aggregate (coarse or fine), and the production is still structural concrete. All beams design to fail in shear. The main crack is formatted between the intermediate support and the applied load diagonally. In spite of the inclusion of waste tire rubber in concrete having specific apparent degradations, the potential benefit seems to overlook the adverse effects and also provides the primary significant value of resolution for rubber waste problems. The results show that 20% volumetric substitution of natural coarse or fine aggregates with tier rubber reduced the ultimate load of continuous deep beams by 32.06% and 32.65% but significantly increases the ultimate deflection by 83.07% and 106.28% respectively. The ductility of rubberized continuous deep beams increased up to 36.95% when the replacement ratio of crumb rubber is 20%.

The current experimental research encompasses the outcome of the pre-treatment of rubber fiber (RF) derived from discarded tires when utilized in concrete as a limited substitution of sand by its volume. To overcome the causes of reduction in strengths of concrete after inclusion of rubber particles (RP) as fractional or complete replacement of fine aggregates, three different pre-treatments are adopted in this study by using sodium hydroxide (NaOH), hydrochloric acid (HCL), and water spray method, and the obtained results compared with controlled concrete and rubberized concrete (RC) with untreated RF. The fine aggregates from concrete are swapped with discarded tire RFs of size 2.36–1.18 mm and a maximum length of 20 mm from 0% to 20% with an increase of 5%. RC's mechanical properties are studied, and they are contrasted with those of controlled concrete that has no sand substitute. Fresh properties like workability, density, and hardened properties such as compressive, flexural, and splitting tensile strengths were assessed. In addition to this abrasion resistance to check wear and tear of concrete, load–displacement relationship, elastic modulus, and microstructural analysis of RC were also studied. The research study investigated that the strengths varied with the pre-treatment methods adopted. Altered concrete with RFs has shown the enhancement in strengths for a replacement of sand by RFs up to a certain limit of replacement. The maximum reduction in strengths is observed for concrete with a 20% inclusion of untreated RFs as a substitution for sand. Concrete with 10% RFs pretreated with NaOH and HCL has shown enhancements in strength and decline in rate of reduction for strengths as compared to controlled concrete and concrete with untreated RFs. Based on the major findings of this study, the better strain rate behavior of RC was observed.

Rubberized concrete (RC) has received widespread attention due to its energy absorption and crack resistance properties. However, due to its low compressive strength, it is not recommended for structural applications. The rubber size and content affect RC’s mechanical properties. This study investigated and formulated the behavior of RC with different particle sizes and contents under dynamic and static loading. Quasi-static compressive and dynamic tests were conducted on RC with varying content of rubber (0–30%) and rubber sizes (0.1–20 mm). It was found that the rubber particle size was 0.5mm and the rubber content was 2%. An equation was derived from the experimental data to forecast the impact of rubber size and content on compressive strength. Additionally, by combining the literature and this research’s data, a model was established based on neural networks to predict the strength of RC. SHPB tests were carried out to study the stress–strain curves under dynamic load. The peak stress, fragment analysis, and energy absorption of RC with varying content of rubber and rubber sizes at three different strain rates (100 s−1, 160 s−1, and 290 s−1) were investigated. Equations describing the relationship between dynamic increase factor (DIF), rubber material content, and strain rate on different particle sizes were obtained by fitting. The DIF increased as the content of the rubber increased. By analyzing energy absorption data, it was found that the optimal ratio for energy absorption was RC-0.5-30, RC-0.1-30, and RC-10-30 at strain rates of 100 s−1, 160 s−1, and 290 s−1. This study could be a good guideline for other researchers to easily select the content and size of the rubber in RC for their applications. It also has a positive significance in promoting the development of green building materials.

The main aim of this research is to investigate and mathematically express the relationship between the mixture proportions of rubberized concrete and its thermal conductivity performance. For that purpose, a dataset with a wide range of experimental variables was compiled from the studies available in the literature and one of the most important and widely used machine learning methods, called Artificial Neural Networks, was chosen to establish this mathematical expression strongly and consistently. Two important criteria were taken into consideration when compiling the dataset: firstly, the aggregate had to be of natural normal weight and secondly, the rubber aggregate had to be derived from waste tire and not treated. A reliable, functional, and robust empirical model to estimate the thermal conductivity coefficient of the rubberized concrete was generated in the scope of this study based on the input parameters like cement content (c), water-to-cement ratio (w/c), natural aggregate-to-cement ratio (na/c), rubber aggregate-to-cement ratio (ra/c), and rubber type (rt). The estimation capability of the model was validated using a dataset that the model never faced and was evaluated based on some statistical metrics like R2, MAPE, MSE, etc. The R2, MAPE, and MSE values of the trained model were about 0.984, 4.62%, and 0.002, respectively. Both validation and statistical evaluation results revealed that the model can accurately and reliably estimate the thermal conductivity coefficient of the rubberized concrete. Besides, the statistical metrics of the developed model were in the acceptable range for such models. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Approximately 246 million waste tires are generated annually in the United States. That is roughly three tires per four individuals in the country. Most tires end up in landfills, adversely affecting the environment. In the last two decades, researchers have explored using tire chips in concrete to replace a portion of coarse aggregates. Past studies have indicated that up to 50% of coarse aggregates in concrete can be replaced with tire chips. This research proposes using recycled rubber tires and rubber chips in concrete columns. The tires are used as external transverse reinforcement in plain concrete columns. The tires function as formwork during the pour while providing confinement after curing. The concepts in this research can be used for retrofitting structures with inadequate foundations and constructing new structures. After analyzing the data from this research, the axial compressive test of confined columns was 50% greater on average than unconfined columns. The confinement effectiveness ratio for all confined specimens was greater than one. [ABSTRACT FROM AUTHOR]