Tire Crumb Rubber Research Articles

Experimental investigation on the influence of novel catalyst in co-pyrolysis of polymeric waste: Characterization of oil and preparation of char reinforced composites

A massive challenge in handling and disposing the polymeric waste, generated by the growing human population and continuous development, has been faced currently as a result of human negligence. Fortunately, among many methods to deal with the problem of increasing polymer debris in the environment, pyrolysis stands out due to its efficiency and accessibility. In the present study, automobile plastic scrap (APS) and tyre crumb rubber (TCR) materials as a combination were subjected to co-pyrolysis using a novel catalyst (NOVC-FZP) that was synthesized using ferrocene and zeolite as precursors. Thermogravimetric analysis (TGA) of the raw materials (APS and TCR) shows single-stage decomposition at 402 °C and 340 °C, respectively. Gas chromatography-mass spectroscopy (GC-MS) analysis confirms higher production of the hydrocarbon (HC) groups in the oil with NOVC-FZP as compared to the neat oil (without NOVC-FZP). The cetane index of the oil with NOVC-FZP was found to be 22 and the calorific value of the same was 9162 Cal/g. A very high proportion of gasoline (86.8% of oil) was found in the oil resulting from the catalyzed pyrolysis. Solid product char (SPC) obtained through pyrolysis was incorporated into linear low-density polyethylene (LLDPE) to form LLDPE/SPC composite (LCC) for use in several applications rather than disposing it off. Higher mechanical properties like tensile strength, hardness as well as enhanced dielectric constant were exhibited by the prepared LCC.

Rubberized geopolymer composites: Effect of filler surface treatment

Existing waste tire management strategies such as landfill, warehousing, incineration, and pyrolysis are associated with significant emissions of hazardous compounds including gases, heavy metals, and oils. A sustainable rubber waste disposal strategy is immobilizing them in a crushed form in eco-friendly geopolymer (GP) matrices. However, the implementation of this approach is constrained by the strength degradation of rubberized geopolymer composites. In order to solve this problem, this article includes a comparative investigation of the effect of various physical and chemical pre-treatments of tire crumb rubber (CR) with NaOH, H2SO4, (CH3)2CO and KMnO₄ solutions, as well as ultraviolet radiation, on the mechanical performances and microstructure of rubberized fly ash-based GP composites. It has been established that the best effects are demonstrated by treatment with an aqueous solution of potassium permanganate; oxidative reactions with the solution lead to the formation of surface-active functional groups on the rubber. As a result, there is more than a twofold increase in the hydrophilicity of CR particles, estimated from the mass of adsorbed water vapor (from 1.5 to 3.3 wt%). This provides a strong adhesive contact of the filler with the geopolymer matrix, which favorably affects the change in the mechanical properties of the composites. The compressive strength in this case has been increased from 12.8 MPa (GP/untreated CR composite) to 15.5 MPa at addition of 10.0 wt% KMnO4 treated CR. Further optimization of the composition and of the curing mode of the geopolymer binder can potentially provide an additional positive effect in this aspect.

Post-fire flexural behavior of functionally graded fiber-reinforced concrete containing rubber

The optimal distribution of steel fibers over different layers of concrete can be considered as an appropriate method in improving the structural performance and reducing the cost of fiber-reinforced concrete members. In addition, the use of waste tire rubber in concrete mixes, as one of the practical ways to address environmental problems, is highly significant. Thus, this study aimed to evaluate the flexural behavior of functionally graded steel fiber-reinforced concrete containing recycled tire crumb rubber, as a volume replacement of sand, after exposure to elevated temperatures. Little information is available in the literature regarding this subject. To achieve this goal, a set of 54 one-, two-, and three-layer concrete beam specimens with different fiber volume fractions (0, 0.25, 0.5, 1, and 1.25%), but the same overall fiber content, and different volume percentages of the waste tire rubber (0, 5, and 10%) were exposed to different temperatures (23, 300, and 600oC). Afterward, the parameters affecting the post-heating flexural performance of concrete, including flexural strength and stiffness, toughness, fracture energy, and load-deflection diagrams, along with the compressive strength and weight loss of concrete specimens, were evaluated. The results indicated that the flexural strength and stiffness of the three-layer concrete beams respectively increased by 10 and 7%, compared to the one-layer beam specimens with the same fiber content. However, the flexural performance of the two-layer beams was reduced relative to those with one layer and equal fiber content. Besides, the flexural strength, toughness, fracture energy, and stiffness were reduced by approximately 10% when a 10% of natural sand was replaced with tire rubber in the threelayer specimens compared to the corresponding beams without crumb rubber. Although the flexural properties of concrete specimens increased with increasing the temperature up to 300oC, these properties degraded significantly with elevating the temperature up to 600oC, leading to a sharp increase in the deflection at peak load.

Release of Zinc and Polycyclic Aromatic Hydrocarbons From Tire Crumb Rubber and Toxicity of Leachate to Daphnia magna: Effects of Tire Source and Photoaging.

Tire crumb rubber (TCR) has been widely used in artificial turf fields, however, the potential environmental risk of TCR and the effect of sunlight exposure are scarcely studied. Here, we evaluated leachability of Zn and polycyclic aromatic hydrocarbons (PAHs) in four types of TCRs and acute toxicity of leachates to Daphnia magna. The results showed that all types of TCRs tested released Zn (0.20-1.3μg/g) and PAHs (9.4-17μg/g) but only two were lethal to D. magna (mortality 73%). Notably, ultraviolet (UV) irradiation induced TCR to generate acidic leachate (pH ~ 4.8), which contained 24- and 1.2-fold higher concentrations of Zn and PAHs and therefore was more toxic to D. magna than that in the absence of UV treatment. These findings demonstrate source-dependent toxicity of TCR and highlight the need to consider the effect of photoaging when evaluating the environmental risks of TCR.

Optimising the Performance Of Crumb Rubber Modified Concrete

The issue of management of end of life tyre (EOLT) rubber or crumb rubber presents major social, environmental and economic challenges especially for Small Island Developing States (SIDS) such as Trinidad and Tobago. A successful measure in foreign jurisdictions is to utilize this waste material for civil construction as a substitute for natural aggregate however this strategy has not yet been applied in Trinidad and Tobago. Since the properties of concrete and the influence of additives are dependent on the source and chemical composition of the parent cement, research and scientific studies utilizing Trinidad Portland cement are necessary but lacking. This paper filled this information gap necessary to develop a rubberized Trinidad Portland Type IP concrete. Crumb rubber (0-10%) rubber was added to concrete as a replacement for fine aggregate using a water to cement ratio of 0.5 and cured over 3-28 days. Standard compressive strength, splitting tensile strength and slump tests were performed and the results statistically analysed. Microscopic features of adhesion and disruption characteristics were observed using Scanning Electron Micrography (SEM -EDS). Concrete mixtures using Trinidad Portland cement and crumb rubber at dosages 2 - 4 wt% resulted in a material with properties similar to the unmodified material with compressive strengths achieving the required specification of 20 MPa after 28 days. This study suggests that there is significant potential in valorising the concept of recycling tyre waste into modified crumb rubber concrete as a sustainable waste management option.

Simultaneous removal of multiple polycyclic aromatic hydrocarbons (PAHs) from urban stormwater using low-cost agricultural/industrial byproducts as sorbents

The potential of five low-cost and globally available sorbents, including three raw waste products – waste tire crumb rubber (WTCR), coconut coir fiber (CCF) and blast furnace slag (BFS) – and two modified materials – biochar (BC) and iron coated biochar (FeBC) – were evaluated for removing a mixture of polycyclic aromatic hydrocarbons (PAHs): pyrene (PYR), phenanthrene (PHE), acenaphthylene (ACY) and naphthalene (NAP) from simulated stormwater. The physicochemical characteristics of the sorbents were assessed by BET-N2 surface area, CHN elemental analysis, FTIR and scanning electron microscope (SEM-EDS). The experimental data were well described by both linear and Freundlich isotherm and pseudo-second order kinetic models. The adsorption rate was mainly controlled by the film diffusion mass transfer mechanism. The magnitude of PAHs partition coefficients (Kd) followed the order of BC > FeBC > WTCR > CCF ≫ BFS, ranging from 80 to 390,000 L/kg. The sorption Kd values were positively correlated with both aromaticity of sorbents and octanol-water partition coefficients (Kow) of PAHs. Solution ionic strength and pH did not have significant effects on the sorption of PAHs by all sorbents. In contrast, humic acid, as dissolved organic carbon, decreased sorption capacities of WTCR and CCF, and increased sorption efficiency of BFS, which was confirmed with field-collected real stormwater. The hydrophobic π–π interactions were the main mechanism for the sorption of PAHs by various sorbents. These findings are promising for future development of cost-effective sorption filters for removal of hydrophobic organic pollutants from urban stormwater runoff.

Evaluation of aggregate-binder bond strength using the BBS device for different road materials and conditions

ABSTRACT Bonding strength between asphalt and aggregate is considered an important feature that governs the future performance of flexible pavements. This study investigated five factors that have the potential to affect this bonding strength. Two asphalt penetration grades (60/70 and 85/100) in addition to various types of substrates (limestone, granite, marble and basalt) were used to prepare specimens to be tested by the Binder Bond Strength (BBS) test. Three aging levels (unaged, short-term aged and long-term aged) with four types of modifiers (Crumb Tire Rubber, Nano Silica, Nano Clay and Microcrystalline Synthetic Wax) were implemented for two specimen conditioning methods (dry and wet). Statistical analysis was performed to measure the influence of these factors on the asphalt-aggregate bonding strength. The results showed that aggregate type and modifier type had the most effect on the bonding strength with relatively no effect of binder type. Moreover, long term aging and two types of modifiers (Nano Silica and Crumb Tire Rubber) were found to significantly increase the Pull-Off Tensile Strength (POTS), which is a measure of the asphalt-aggregate bonding strength. Failure type was mainly cohesive in the dry condition then transformed to adhesive when specimens are exposed to moisture.

Evaluate the effect of acid attack on rubberised concrete using crumb tyre rubber and replacement of cement by alccofine

Concrete is the generally used building material for many kinds of structure attributable to its durability. The rubber is generated in huge quantities as waste doesn't have helpful disposal until currently. Thus, crumb tyre is used as the partial replacement of fine aggregate in the present study. The most parameters investigated during this study is M30 grade concrete as per IS 10262-2019 with the partial substitute of fine aggregate by crumb tyre rubber in the ratio of 5%, 10%, 15% and 20%. During this mix, the optimum value of crumb rubber is found out. Then alccofine is mixed in the ratio of 5%, 10% and 15% at the optimum percentage of crumb rubber. This study is evaluating the impact of crumb rubber tyre on the compressive strength and durability at the age of 7 and 28 days. The compressive strength decreases because of the crumb tyre rubber increases in the concrete which affects the bond between the rubber tyre and other concrete ingredients. The alccofine is employed to increment the reduced strength of concrete due to the utilization of waste tyre crumb rubber. Usage of alccofine showed good results in terms of compressive strength at normal curing as well as in the acid curing. The present research study helps to overcome the solid waste and used as new material in the concrete.

Pavement and Noise Reduction Performance of Open‐Graded Asphalt Friction Course Improved by Waste Tire Crumb Rubber

To further reveal the road performance and noise reduction performance of open‐graded friction course (OGFC), the crumb rubber prepared by adding waste tires were considered, and the performance requirements of the material were put forward. To avoid the influence of rubber particle swelling on aggregate, the special gradation and mix proportion of OGFC mixture were designed, and the particle size of 4.75 mm was proposed as the control size. The test results show that the aggregate forms a good embedded structure. The resilient modulus, deformation performance, and fatigue performance of R‐OGFC asphalt mixture with different crumb rubber contents were studied. According to the test results, the rubber particle content under the best road performance and noise reduction effect was proposed. The results show that, after adding a certain amount of crumb rubber, the performance of asphalt mixture has been greatly improved, especially the dynamic stability has been improved by 84%. Although the resilient modulus has decreased by 10%, the creep performance has decreased by 37%, and the fatigue life has decreased by 31% (2% rubber content), the noise reduction can reach 3.6–8.6 dB, and the noise reduction performance is significant. This shows that the best content of rubber particles is between 1.5% and 2%, and the R‐OGFC mixture modified by rubber has a good application prospect.

Reaction mechanism and rheological properties of waste cooking oil pre-desulfurized crumb tire rubber/SBS composite modified asphalt

Waste cooking oil (WCO) is proved to be effective in desulfurization of crumb tire rubber (CTR), which can be considered as a sustainable desulfurization technology and an alternative way to solve the poor storage stability of asphalt rubber. However, WCO pre-desulfurized CTR (ODR) modified asphalt displays a compromised high-temperature performance, leading to a limited application of ODR in asphalt modification. In this study, ODR/styrene–butadiene-styrene (SBS) composite modified asphalt was developed to make up the loss of high-temperature performance. The reaction mechanism of ODR/SBS composite modified asphalts with and without sulfur was investigated via Fourier transform infrared spectroscopy (FTIR), gel permeation chromatograph (GPC) and fluorescence microscope (FM). Rheological tests were conducted to clarify the effects of ODR, SBS and sulfur on the rheological behavior of the modified asphalt. FTIR, GPC and FM results proved that crosslinking reaction occurred during the composite modification of ODR, SBS copolymer and base asphalt in the presence of sulfur with moderate content, forming a continuous and homogeneous microstructure with a significantly increased large molecular weight, which is less prone to produce phase segregation. The ODR composite modified asphalt with 3 wt% SBS and 0.4 wt% sulfur presents the best rutting resistance due to the increase of the elastic network structure and cracking resistance due to the presence of WCO and the released rubber chain. The above composite modified asphalt meets the standard traffic level at 76 °C and the specification at −34 according to the multiple stress creep recovery and bending beam rheometer tests.

Static and Dynamic Compressive Stress-Strain Behavior of Recycled Tire Crumb Rubber Mortar

Crumb rubber mortar (CRM) made from scrap tires can be used in highway, high-speed railways, and airport pavements as a structural material, which may help solving the problems of raw material shortage and waste tire pollution at the same time. To develop it, a systematic study of the stress-strain behavior of CRM under static and dynamic compression is therefore very important. In this paper, the CRM specimens containing four different contents of crumb rubber (5%, 10%, 15%, 20%) and four different rubber particle sizes (30 mesh and 50 mesh, 60 mesh, 80 mesh) were prepared to study the workability of fresh CRM and the stress-strain curve of hardened CRM under static compression and dynamic compression. The result shows that the fluidity of CRM decreases obviously with the addition of crumb rubber and the increase of fine particle rubber size. The CRM, when the incorporating crumb rubber increased in the mortar, presented a decrease in its static compressive strength and modulus of elasticity, but an increase in its critical strain and compressive toughness. The CRM also showed an obvious strain rate effect. When the incorporated rubber contents remained constant, the CRM increased its dynamic compressive strength and DIF with the increase of strain rates. Similar to that in the static compressive test, the addition of crumb rubber has a positive effect in enhancing the deformation and energy absorption properties under dynamic impact loading.

Concrete containing waste recycled glass, plastic and rubber as sand replacement

Extensive research has been conducted during the past three decades to include waste plastic, rubber and glass in concrete. Recent interest to include these materials in concrete can be ascribed to the growing need for innovative waste disposal, as well as to minimise raw material usage. However, this research domain and application has not yet gained popularity and urgency in countries with an abundance of aggregates, such as South Africa. For these materials to be a viable option to be used as a concrete constituent in these countries, concretes produced using these materials should retain satisfactory properties. This study investigates various fresh, mechanical and durability properties, utilising waste ground Low-Density Polyethylene (LDPE) plastic, crumb tyre rubber, and crushed clear flat glass as a partial fine aggregate replacement, using materials sourced in South Africa. Two replacement contents are investigated: 15% and 30%, replacing fine aggregate by volume. The results show that plastic, rubber and glass decrease concrete workability, and increase air content. It also demonstrates that glass improves the mechanical and durability properties of concrete. Concrete containing low plastic content has promising mechanical properties but performs poorly in durability. Rubber significantly impacts the mechanical and durability properties of concrete negatively.

Prediction of shear behavior of steel fiber-reinforced rubberized concrete beams reinforced with glass fiber-reinforced polymer (GFRP) bars

A combination of fiber-reinforced polymer (FRP) reinforcing bars and steel fibers can be employed in locations of a structure with reinforcement congestion instead of the conventional combination of steel rebars and stirrups. In this study, first, the shear performance of the FRP bar-reinforced concrete beams containing steel fibers and crumb tire rubber without shear reinforcement was evaluated, and then an analytical model was proposed to predict their shear capacity and achieve a relationship between the first cracking moment and the shear capacity. Furthermore, an empirical equation was derived from the experimental data of 30 beams of the present research together with a database extracted from the results reported in other research to calculate the share of concrete in the shear capacity of this type of beam. Through evaluating the proposed equation against those given by different codes and those developed by other researchers, it was revealed that most existing shear strength prediction equations give an underestimated value for this parameter in beams having FRP reinforcing bars, while the present equation provides more accurate results. These results make the proposed model suitable for accurately designing FRP bar-embedded concrete beams containing steel fibers and crumb tire rubber.

Quantifying the effect of modified mixture volumetrics and compaction effort on skid resistance of asphalt pavements

ABSTRACT This paper aims to quantify the effect of modified mixture volumetrics and compaction effort on surface characteristics of asphalt pavements. Specimens were prepared using PG 64-10 asphalt binder mixed with crushed limestone aggregate. Three types of asphalt modifiers were added; Crumb Tire Rubber (CTR), Microcrystalline Synthetic Wax (MSW) and Nano Silica (NS). In addition, specimens were adjusted at 4% air void and were compacted at Design Number of Gyrations (Ndes) = 119 and 82 to simulate high and low levels of traffic, respectively. Research findings revealed that Air Voids Volume (Va) and Effective Binder Volume (Vbe) exert a significant effect on the surface frictional properties. Additionally, the ratio of Va to Vbe, expressed as Pv, was also investigated to study the combined effect of Va and Vbe on surface friction results. It was concluded that Pv has a considerable role in the evaluation process. It was also shown that increasing the level of compaction would result in a positive effect on British Pendulum Number (BPN) measurements and the opposite is true in terms of macrotexture measurements. Furthermore, CTR-modified mixtures exhibited the highest values of friction and macrotexture followed by NS-modified mixtures. MSW-modified and unmodified mixtures exhibited the least fractional characteristics.

Viability of producing sustainable asphalt mixtures with crumb rubber bitumen at reduced temperatures

The construction and maintenance of road pavements need to be undertaken to ensure proper economic and social growth. Considering the high environmental impact that the production of asphalt mixtures for road pavements entails, in terms of energy consumption and greenhouse gas (GHG) emissions, these operations must follow the global transition towards more sustainable development practices. In response to this, previous research has been focused on the development of manufacturing low temperature asphalt mixtures and the use of recycled modifiers such as tire crumb rubber to improve their durability. However, the use of high dosages of the latter reduces mixture workability, thus requiring high manufacturing temperatures to reduce the viscosity of the binder, and therefore limiting the advancement towards more sustainable mixtures. In this regard, further knowledge is needed on this topic to promote the combination of such techniques to maximise their advantages. This study aims to check the viability of producing asphalt mixtures with high crumb rubber contents at reduced temperatures, testing their workability, stiffness, cohesion, resistance to permanent deformations and resistance to moisture damage. Results show that it is possible to manufacture viable, warm, rubberised asphalt mixtures at 150 °C using a high penetration bitumen and reduce this temperature to 130 °C (45 °C less than conventional rubberised asphalt mixtures) by including warm additives, without compromising their mechanical performance.

Long-term mechanical and durable properties of waste tires rubber crumbs replaced GBFS modified concretes

The disposal of rubbers from the waste tyres remains the main environmental concern worldwide unless recycled in an eco-friendly way. The incorporation of these wastes into the concretes as replacement agent for some of the natural aggregates is strategized as one of the possible solutions. Based on these factors, this study evaluates the effects of the tire rubber crumb wastes (TRCWs) at various contents (5, 10, 20 and 30% of volume) and granulated blast furnace slag (GBFS) as the fine and coarse aggregates replacement on the properties of newly designed concretes. Twelve batches of such concretes are prepared by blending the industrial wastes including the GBFS and TRCWs with ordinary Portland cement (OPC). The mechanical and durability performance of these modified concretes are analyzed using slump, compressive, tensile, flexural strength, and resistance to acid attack tests. The concrete modified with 20% of GBFS as OPC replacement shows enhanced mechanical traits wherein the compressive strength after the curing age of 28 days is higher (42.8 MPa) than the OPC control mix (33.8 MPa). Moreover, the mix designed with 5% of TRCWs as fine or/and coarse aggregates replacement is nearly 14.8% compared to the OPC specimens. The results show that the TRCWs substitution up to a limit of 10% of the river sand and gravel into the concrete can be effective without any strength loss. It is established that the use of TRCWs into concrete will not only be the cost-effective alternative but can be an environmental remedy and renewable resource for developing construction materials, leading to sustainability (minimization of the depletion of natural resources including river sand and gravel).

Source-related smart suspect screening in the aqueous environment: search for tire-derived persistent and mobile trace organic contaminants in surface waters

A variant of suspect screening by liquid chromatography–high-resolution mass spectrometry (LC-HRMS) is proposed in this study: Samples of a potential source of contamination and of an environmental sample close to this source are first analyzed in a non-targeted manner to select source-related suspects and to identify them. The suspect list compiled from such an exercise is then applied to LC-HRMS data of environmental samples to ascribe and to identify persistent and mobile contaminants in the water cycle that may originate from the source under study. This approach was applied to tire crumb rubber (source) and road dust (close to source); by comparison of the two data sets, 88% of the features detected in tire leachate could be excluded. Of the 48 suspects remaining, a total of 41 could be tentatively identified as either related to hexamethoxymethyl melamine or cyclic amines, benzothiazoles, or glycols. Subsequently, environmental samples were searched for these suspects: 85% were determined in an urban creek after a combined sewer overflow and 67% in the influent of a municipal wastewater treatment plant (WWTP). These exceptionally high rates of positive findings prove that this source-related smart suspect screening effectively directs the effort of selecting and identifying unknown contaminants to those related to the source of interest. The WWTP effluent and the urban creek during dry weather also showed the presence of numerous contaminants that may stem from tire and road wear particles (TRWP) in road runoff. Contribution from other sources, however, cannot be ruled out.Graphical abstract

Performance of Crumb Rubber and Nano Fly Ash Based Ferro-Geopolymer Panels under Impact Load

This paper presents an experimental investigation into the impact performance of Ferro-cement panels incorporating a significant proportion of geopolymer mortar. This panel could be an effective replacement for prefabricated roof and floor deck construction elements. In this study, the geopolymer mortar includes wastes disposed from industries like ground granulated blast furnace slag (GGBFS) and flyash as their base material which contributes to reduced CO2 emission. The pore filling and element densifying mechanism is enhanced by the addition of Nano flyash. The fine aggregate is replaced up to 5% with treated tyre crumb rubber which can be utilized as a sustainable construction material. The cast panel was cured at 80oC for 48 hours in the oven. The incorporation of Expanded Metal Mesh into geopolymer mortar results in higher impact load absorption capacity rather than other kind of reinforcing meshes. The GGBFS based Geopolymer results in 17% higher compressive strength than fly ash based geopolymer because of its good bonding nature. The Nano fly ash based geopolymer gives 35 MPa in compressive strength and 902.52 joules in impact energy absorption which is greatest among all panels because of its densifying effect of mortar.

Batch-scale remediation of toluene contaminated groundwater using PRB system with tyre crumb rubber and sand mixture

The objective of the study is to examine the potential of TCR (tyre crumb rubber) particles to remediate toluene contaminated aquifers by using them as the reactive constituent of permeable reactive barriers (PRB). The objective is achieved by performing laboratory experiments to identify toluene adsorption capacity and rate of toluene removal of the optimal TCR-sand mix. Adsorption isotherms and Kc-Co relations (Kc: distribution coefficient, Co: initial toluene concentration) identified the optimum mix (2.5 % TCR-97.5 % sand mix) for remediation of toluene contaminated water. Batch experiments showed that toluene adsorption by TCR particles is endothermic and is energetically favoured at higher temperature. Adsorption of the non-polar molecule by TCR particles obeyed bi-linear, pseudo first order kinetics. The carbon-black component of TCR particles adsorbed significant amount of toluene during the initial contact period (10−60 min). Scatchard analysis, Freundlich isotherm and DR (Dubinin-Radushkevich) equation indicated that toluene is adsorbed by van der Waals attraction at energetically heterogenous sites of TCR particles. The near irreversible toluene adsorption in the laboratory experiment is attributed to physical entrapment of the non-polar molecules in the medium and fine pores of TCR particles. Batch experiment results predict that unit PRB column constructed with 2.5 % TCR-97.5 % sand mix can remediate 11,013 K L of toluene contaminated (0.15 mg/L) groundwater near instantaneously.

Compressive performance of steel fiber-reinforced rubberized concrete core detached from heated CFST

In this study, the compressive behavior of concrete cores detached from the high-strength concrete-filled steel tube (CFST) members reinforced with steel fibers and containing crumb tire rubber was investigated experimentally after exposure to elevated temperatures. The test variables included the diameter-to-thickness ratio of the steel tube, volume content of crumb rubber replacing natural sand, volume fraction of steel fibers, and temperature. After the exposure of the CFST specimens to the elevated temperatures and subsequently removing the steel tubes, the detached concrete core was subjected to the axial compression test, and the parameters of compressive strength, modulus of elasticity, strain at peak stress, and weight loss, stress-strain relationship together with the ultrasonic pulse velocity, visual appearance, and failure mode were evaluated. Using the experimental results, expressions were developed to predict the mechanical properties of the concrete core at elevated temperatures taking into account the steel tube wall thickness. The findings indicated that increasing the thickness of the steel tube had a greater damaging effect on the heated concrete core, while in the fiber-reinforced specimens, this damaging effect was lower. Moreover, the addition of crumb rubber to the concrete mix as the natural sand replacement degraded the mechanical properties of the heated and unheated concrete core.