Tire Crumb Research Articles

Compressive stress-strain response of freshly compressed rubberized concrete: An experimental and theoretical study

Although using crumb tire rubber concrete (CTRC) in constructing structural elements is accompanied by various environmental and economic advantages, it always comes with challenges due to a significant loss in some mechanical properties of this concrete type. To tackle this challenge, a novel technique of compressing fresh concrete was used, and its impacts on improving the mechanical features of CTRC were investigated. For this purpose, concrete specimens containing crumb tire rubber (CTR), as the fine aggregate substitute, were constructed considering the variables of the water-to-cement ratio (w/c), volume percentage of CTR, and the fresh concrete pressure level as a fraction of steel tube (mold) yielding stress. After the application of a specified short-term pressure to the fresh mix inside the steel molds and the time required for the concrete setting, the steel tubes were removed after curing, and the concrete core alone was exposed to an axial compressive load. According to the test results, the mechanical properties, weight loss resulting from compressing the fresh concrete, energy absorption, failure pattern, the concrete microstructure, water absorption, and porosity were evaluated. By applying an initial axial pressure of 25–80 MPa on the mixes containing 0 %, 15 %, and 30 % CTR replacing the fine aggregate, the compressive strength, the ultimate strain, the toughness, and the initial modulus of elasticity experienced 100–140 % increase, 130–420 % increase, 120–1140 % increase, and 66–70 % decrease, respectively, compared with the uncompressed specimen. Finally, a regression analysis was employed to propose prediction models for the compressive capacity, modulus of elasticity, peak strain, ultimate strain, and relative toughness of freshly compressed concrete containing CTR particles; these models show proper agreement with the experimental results.

Effect of salt erosion on interfacial adhesion of waste tire crumb rubber-modified asphalt mixtures: A molecular dynamics study

In this study, a wetting and migration model was established using the molecular dynamics simulation method. Through in-depth analysis of parameters such as contact angle, mean square displacement, and work of adhesion, the dynamic wetting and migration characteristics of salt solution were explored, and the damage mechanism of waste tire crumb rubber-modified asphalt mixtures under salt erosion was revealed. The results showed that compared with an aqueous solution, the salt solution was more likely to be adsorbed and dispersed on the asphalt surface. This exacerbated its damage. However, the presence of salt ions reduced the wetting effect of the solution on the aggregate surface and reduced the migration rate of the solution at the asphalt-aggregate interface. Significant diffusion of Na+ and Cl- ions occurs during salt solution migration, while SO42- ions mainly accumulate near the aggregate surface. In addition, salt solution migration alters the distribution of asphalt components. This further affects the interface adhesion effect. The inclusion of crumb rubber can effectively reduce the sensitivity of asphalt to salt solutions and enhance its hydrophobicity. Simultaneously, it enhances the adhesion strength and stability of the asphalt. This effectively obstructs the intrusion of water molecules and salt ions.

In vitro human oral bioaccessibility assessment of hazardous chemicals, including N, N′-substituted-p-phenylenediamines, coming from recycled tire crumb rubber

Tires, apart from being formed by rubber and filling materials, contain organic compounds added to make them resistant and durable. The widely use of recycled tire crumb rubber (RTCR), main product of the shredding process of end-of-life tires, can cause human exposure to these chemicals due to its use in synthetic football fields and kid's playgrounds. In 2023, the European Commission banned the use of recycled tire crumb rubber in synthetic fields, giving eight years to replace the used material. This study intends to assess the oral bioaccessibility of antiozonants, crosslinking and vulcanizer agents present in RTCR. With this purpose, the Unified Bioaccessibility Method (BARGE) was used to simulate the material ingestion. RTCR is put into contact with the four simulated biological fluids including saliva, gastric and duodenal juice and bile, attempting to simulate human digestion. Afterwards, the organic compounds present in the fluid need to be extracted and Solid-phase extraction (SPE) was the technique selected after being optimized to obtain the best extraction conditions. Ultrasound assisted extraction was performed to evaluate the total concentration of the target compounds in the crumb rubber matrixes. Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was employed to identify and quantify the target compounds. The results showed the bioaccessibility of all the studied analytes, with values ranging from 0.1 % up to 70 %. Benzothiazole was the compound with the highest bioaccessibility with a mean value of 40 % and concentrations reaching 32000 ng g−1 in the bioaccessible fraction. N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine and its transformation product ((4-Methylpentan-2-yl)amino)-5-(phenylamino)cyclohexa-2,5-diene-1,4-dione) showed an average bioaccessibility of 0.1 % and 1.8 %, respectively, the latter being present in all the analysed samples.

Characterization of light components in rubber-oil mixtures reclaimed asphalt and their effect on the self-healing performance of asphalt

The aging process of asphalt pavement results in the loss of light components (saturates and aromatics) in asphalt, necessitating the use of regenerators for restoration. The study examined the variation pattern of light components in reclaimed asphalt and their effect on the self-healing performance of asphalt after regeneration. Two types of aged asphalt were analyzed using low-temperature co-pyrolysis products of waste tire crumb rubber (WTCR) and waste cooking oil (WCO). The reclaimed asphalt was fractionated into light components using the SARA (saturates, aromatics, resins, and asphaltenes) method. The regenerator containing the highest concentration of light components was identified through the Soxhlet extraction test. The compound compositions and functional groups of the light components in reclaimed asphalt were characterized using gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared spectroscopy (FTIR). Moreover, the self-healing performance of the reclaimed asphalt was evaluated using a dynamic shear rheometer (DSR). The results indicate that the 260-1-WROM regenerator produced an optimal content of light components under pyrolysis conditions at 260 °C for 1 h. Incorporating the 260-1-WROM regenerator in RTFO resulted in an increase in hopanoids, oxygenates, heterocyclics, and aromas. Similarly, the PAV regeneration process exhibited elevated levels of paraffins, hopanoids, oxygenates, alkanes, heterocyclics, and aromatic compounds. However, the presence of 260-1-WROM failed to increase the contents of steroids. Both types of reclaimed asphalts exhibited superior self-healing capabilities compared to 70#A, RTFO, and PAV. This suggests that 260-1-WROM effectively restored the light components in the aged asphalt, thereby optimizing the flowability of the reclaimed asphalt and enhancing its self-healing properties. Given the above findings, the recommended dosage for 260-1-WROM is 8 % for RTFO and 10 % for PAV.

Rheological behaviour of modified binders for different loading conditions and temperatures: A case of using pig tallow and crumb rubber from end–of–life tyres

This study investigates alternatives to Styrene-Butadiene-Styrene (SBS) polymer in asphalt mixtures by evaluating End-Of-Life tire (ELT) crumb rubber (CR) and fatty acid amide wax (FAA) derived from pig tallow. The research focuses on triple modification of binders with SBS, ELT and FAA to improve performance and reuse waste and industrial by-products in an economical and environmentally responsible manner. The results show that the incorporation of ELT and FAA significantly reduces the SBS content, achieving a 73 % improvement in elastic performance according to Multiple Stress Creep Recovery (MSCR) tests. In addition, this combination improves peak stress and fatigue life in Linear Amplitude Sweep (LAS) tests, demonstrating potential benefits in asphalt mixtures. The study concludes that the combination of pig tallow and end-of-life tire materials doubles the yield energy (Yield Energy of Asphalt Binders, BYET) compared to samples with higher SBS content. In particular, a modification with 6 % CR, 3 % SBS and 2 % FAA doubles the toughness (Er) of a binder with 5 % SBS. This contributes to higher tensile strength in asphalt mixtures, promoting sustainability and efficiency in the road construction industry. This study provides a deeper understanding of how the combination of ELT, FAA and SBS can optimize the properties of asphalt mixtures, highlighting the potential of these additives to improve performance, reduce costs and minimize environmental impact.

Experimental study on freeze-thaw failure of concrete incorporating waste tire crumb rubber and analytical evaluation of frost resistance

The incorporation of waste tire crumb rubber into concrete in appropriate size and content not only facilitates the recycling and safe disposal of waste tires but also enhances concrete frost resistance. The exploration of the frost resistance of rubberized concrete is necessary to fill the major gap of standard evaluation guidelines for rubberized concrete. Through rigorous testing and analysis of parameters such as Wn, Pn, and XEdtn of the rubberized concrete incorporating waste tire crumb rubber ranged from 1.0 % to 5.0 % during rapid freeze-thaw cycles, the study clarified the mechanisms by which crumb rubber affects concrete frost resistance. An increase in durability life was noted as rubber content increased, but a decline occurred when rubber content exceeded 3.0 %. Additionally, pretreating crumb rubber further enhanced frost resistance. The durability life of concrete samples with 3.0 % rubber content reached 275 freeze-thaw cycles. Rubberized concrete containing 2.0–4.0 % crumb rubber saw at least a 25-cycle increase by pretreating crumb rubber, and 5.9–17.9 % increase for Pn compared to that of the concrete with untreated crumb rubber reaching the failure state. The inclusion of crumb rubber altered concrete mesoscopic pore structure and the bonding performance of concrete matrix interface, thereby affecting its frost resistance and failure state. A new set of evaluation equations was developed to quantify the frost resistance of rubberized concrete, providing a robust method for assessing the freeze-thaw response of concrete integrated with waste tire crumb rubber. The DFM proposed in this study proves to be more advanced and effective than existing methods for evaluating frost resistance of rubberized concrete.

Strength behaviour of soil blended with two waste materials-fly ash and tire crumbs with cement

Abstract The rapid development in the economy has led to a growing need for electricity and automobiles, leading to the production of large quantities of fly ash (FA) and discarded tires. The safe disposal of these materials has become a significant problem. FA and scrap tyre derived material has some useful properties which can be beneficially used for enhancing the engineering properties of soil. Therefore, the study investigates the combined impact of FA and scrap tire-derived material on the stress-strain-strength behaviour of a fine-grained residual lateritic soil, incorporating a cementing agent. The research involves compaction tests followed by triaxial compression tests, where FA content added at an increment of 15% starting from 20% by weight of soil. The maximum FA content used in the mix is 50% by weight of soil. Tyre crumb (TC) which is a scrap tire-derived material, is also included in the study, with TC content ranging from 5% to 10% by weight. Additionally, 2% by weight of cement is added to each soil mix as a binding agent. Specimens are compacted in accordance with specific compaction parameters and subsequently cured for duration of up to 28 days. Strength tests are then carried out on those specimens to analyse their strength behaviour. This research primarily examines the shear strength characteristics of soil blended with FA, cement, and TC, emphasizing their geotechnical performance. Addition of 5% TC increases the peak deviator stress of cemented mix having 50% FA content from 1351 kPa to 2710 kPa at 300 kPa confining pressure and 28 days curing period. The inclusion of TC to soil-FA-cement blends is noted to significantly enhance shear strength when compared to mixes without tire crumb. Also, the stress-strain behaviour of soil is significantly influenced by addition of FA and cement in the presence of TC. Therefore, there is an ample scope of utilization of soil-fly ash-cement-TC mixes in geotechnical applications.

Utilization of waste tires in the process of thermal cracking of vacuum gas oil

The process of thermal cracking of vacuum gas oil (VGO) with the addition of 10% tire crumb at a temperature of 500 °C and feed rate of 1 h- ¹ was studied. In the course of the study experiments were carried out, which showed that the introduction of tire crumb into the composition of VG promotes the acceleration of conversion of the heavy fraction of VG. Addition of 10% of tire crumb has a positive effect on the cracking process, which is expressed in the increase in the yield of diesel fraction by weight by 2%. Analysis of the material balance of the thermal cracking process of crushed tire crumb shows that under these conditions tire crumb was poorly subjected to thermal transformation. The yield of gasoline fraction and light gas oil fraction in the catalyst composition was only 1% and 7.4% by weight, respectively. The conversion of tire crumb into light fractions including gas oil reached 20.5%. Addition of 10% by weight of tire crumb to the composition of vacuum gas oil increases the yield of gasoline and diesel fractions (light gas oil fractions), while reducing the amount of heavy gas oil. The increase in the yield of diesel fraction is 4% by weight, and the total conversion of blended feedstock reaches 59.5%. Thus, the addition of tire crumb to the composition of vacuum gas oil practically does not affect the total conversion, but increases the yield of light gas oil. This allows us to conclude that the introduction of tire crumb contributes to a more efficient conversion of heavy fractions of vacuum gas oil. After hydrotreating process the obtained diesel and gasoline fractions can be successfully used as components of automotive fuels. Thus, the addition of tire crumb to the thermal cracking process of vacuum gas oil not only improves the conversion of heavy fractions, but also increases the yield of valuable products such as diesel fuel, which is important for the refining industry.

Effect of Scrap Tyre Crumb Rubber (STCR) and Lime on the California Bearing Ratio (CBR) of Non-Lateritic Soil

Nigeria is one of the countries generating many used tyres with only small quantity utilized for different local use and the remaining large quantity dumped in different areas as waste. In this study non – laterite soil was stabilized with 3 % Scrap Tyre Crumb Rubber (STCR) and 5.0, 7.5, 10.0, 12.5 and 15.0 % lime for use as road construction material. Atterberg limit tests, compaction (using West African Standard energy) and California Bearing Ratio (CBR) tests were carried out using standard methods, on the natural non-lateritic soil and the treated soil specimens. Preliminary test on the soil was carried out which classified the soil as A-6 (9) and CL in accordance with ASHTO and USCS classification systems respectively. Compaction and California Bearing Ratio (CBR) parameters of the treated non-lateritic showed a great improvement as the MDD increased from 1.68 Mg/m3 to 1.88 Mg/m3 while the OMC reduced from 17.1 % to 14 %. Both soaked and unsoaked CBR values equally increased to 109 % and 103 % respectively with the addition of lime up to 15% plus 3% STCR waste. Based on results obtained from the study, the use of a mixture of 15% lime and 3% STCR waste, are recommended for the treatment of non-lateritic soil for road construction purposes.

Experimental investigation on the mechanical properties of cement mortar containing recycled tire crumbs reinforced with polypropylene, oil palm and banana fibers

The automotive industry discards a large number of end-of-life tires annually, creating a growing global environmental hazard. The incorporation of crumb rubber derived from waste tires into construction materials is considered one of several alternatives for sustainably reusing these waste materials. The addition of fibers as reinforcements would address the typical degradation caused by the crumb rubber in cement composites. Fibers sourced from plants and recycled synthetics offer a practical and eco-friendly reinforcement material that is both cost-effective and easy to procure. However, two challenges emerge from these choices. Firstly, natural fibers exhibit substantial regional variations, resulting in differences in their properties and inconsistent performance. Secondly, recycled materials also demonstrate variation due to disparities in production and manufacturing processes. As a result, incorporating these fibers into cement-based materials has produced conflicting outcomes due to these inherent variations, rendering practical application unfavorable. Therefore, this study attempts to promote the adoption of sustainable practices by addressing the lack of available performance-based data for the utilization of these fiber variants in the design of cement mixtures. The data would allow engineers to integrate these mixtures into commercial designs for practical in-situ construction. A total of 18 novel cement-based mixtures containing different types of fibers, chemical admixture, and discarded crumb waste were formulated and evaluated in fresh and hardened properties. A multifaceted approach was also undertaken to further hybridize the fibers and quantify the synergistic effects within the investigated cement matrice. The results indicate that the incorporation of polypropylene and oil palm fibers enhances compressive and tensile strength, although there is a general weakening observed in flexural strength. In the case of hybrid fibers, a successful combination of polypropylene and banana fibers is evident, showing a positive hybrid effect coefficient compared to a negative coefficient for polypropylene-oil palm fiber combinations.

Compressive Strength and Tensile Bond Strength of Rubber Tire Crumb Mortar Mixed with Fly Ash

Currently, rubber tire crumbs have been utilized as an additive in the civil engineering field. The addition of rubber tire crumbs to the mortar can result in a decrease in the compressive strength of the mortar so its use is very limited due to its low compressive strength. One of the suggested applications is the use of RTC mortar as a mortar joint in masonry walls, but its effect on the bond strength of the mortar with the brick has not been studied. In the research, apart from the effect of compressive strength, the effect of using fly ash on the tensile bond strength between mortar and clay bricks was also observed. The tests were carried out in the laboratory following the ASTM C 109M-07 standards for compressive strength tests, and ASTM C 952-02 for tensile bond strength. The specimens were in the form of 50x50x50 mm3 cube-mortar and cross-bricks totalling 48 each. Besides that, the influence of the age of testing was also observed, namely at the age of 14, 28, and 56 days. The test results show that the addition of fly ash can increase the compressive strength of rubber tire mortar, but decrease the tensile bond strength between mortar and clay bricks.

Use Crumb Rubber Chips in Partial Substitution of Coarse Aggregate While Preparing Concrete

Abstract: The purpose of this experimental investigation is to examine the behaviour features of rubberized concrete, which has coarse aggregate in place of some of the tyre rubber. Over 270 million scrap tyres are thought to be produced annually. One of the main problems in India is the disposal of discarded tyres in landfills, which is the responsibility of local governments and municipalities. Because it is not biodegradable, there are serious concerns to human health, the environment, and fire. The most promising uses of tyres in engineering are as aggregates for asphalt and concrete, artificial reefs, and erosion management, aside from gasoline obtained from tyres. Concrete's characteristics could be greatly improved in a variety of ways by using recycled tyre rubber as part of the aggregate. One of the most often used building materials is concrete. Because of this, the building sector is constantly looking for new applications and uses for its products, as well as ways to improve them while keeping costs down. The reference concrete specimen is made of M30 grade concrete. Rubber chips from scrap tyres have been utilised in place of traditional coarse aggregate as coarse aggregate. This will enable the efficient and widespread handling of rubber tyre waste in addition to enabling the sustainable use of the aggregates that are already accessible to us. After separating the rubber tyre waste into coarse chips, this tyre crumb aggregate is applied in increments of 5%, 10%, or 15% to replace the coarse aggregate. In order to determine the best way to employ crumb rubber as coarse aggregate in concrete, this study assessed the workability and compressive strength of rubberized concrete

Analytical evaluation of stress–strain behavior of rubberized concrete incorporating waste tire crumb rubber

The advancement of rubberized concrete technology and its application in engineering can significantly promote the complete recycling and safe disposal of waste tire rubber. Integrating crumb rubber into concrete alters its compressive stress–strain behavior. This study investigated the stress–strain characteristics of rubberized concrete containing waste tire crumb rubber, addressing the absence of standard guidelines for the design of rubberized concrete. By examining the complete stress–strain curves of rubberized concrete, key parameters such as peak stress, initial elastic modulus, peak strain and secant modulus were meticulously evaluated. The study delved into the mechanisms through which crumb rubber influences the stress–strain behavior of concrete, considering factors including variations in rubber content and pretreatment methods. The experimental data were analyzed using conventional concrete constitutive theories to quantify the impact of crumb rubber on rubberized concrete's stress–strain relationship. Significant variations were observed, including a notable decline in strength with increasing rubber content. For instance, increasing the rubber content from 0.0% to 5.0% led to reductions of 44.2% in peak stress and 47.0% in secant modulus compared to the reference concrete. In addition, pretreating the crumb rubber markedly improved rubberized concrete strength, and the peak stress of concrete with 1.0%–5.0% pretreated crumb rubber increased by an average of 7.0% compared to that with untreated crumb rubber. The study identified that crumb rubber's inclusion significantly altered the coordination of stress and strain in concrete, thereby affecting its stress–strain behavior. A set of evaluation equations for the stress–strain relationship of rubberized concrete was developed, offering a reliable method for predicting its behavior. This research fills a critical gap in the analytical assessment of rubberized concrete and marks a significant stride towards its broader use in sustainable construction practices.

Mechanical properties of tire chip and cement stabilised red clay

ABSTRACT Reutilisation of waste tire chips to improve red clay is of great significance to environmental protection. The mechanical properties of tire chip and cement stabilised red clay (TCCSRC) at different proportions were investigated through compaction, compression, unconfined compression strength (UCS), and direct shear tests. The UCS and shear strength of TCCSRCs with different proportions were tested and analysed at their optimal moisture content (OMC). The results indicated that the porosity ratio, UCS, shear strength, and cohesion of TCCSRC decreased with increasing tire chip content. The addition of cement increased the sample UCS and shear strength. When the content of tire crumb is 20% and the cement content is 5%, the specimens show good performance in all basic properties, including UCS can reach 1034.3 kPa; the shear strength can reach 46.7 kPa when the axial pressure is 150 kPa.

Enhancing Concrete Performance with Crumb Rubber and Waste Materials: A Study on Mechanical and Durability Properties

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.

Experimental study and predictive modelling of damping ratio in hybrid polymer concrete

The improved damping capacity of concrete materials is crucial for many applications, especially the ones exposed to dynamic external forces. This study explores the optimal circumstances of copolymer composite binder, ratio of fine to coarse aggregate, curing time, size and content of tyre crumb rubber on enhancing damping ratio of hybrid polymer concrete. Owing to the limitation of conventional models and experimental methods in effectively handling the multiple and complicated relationship between the input parameters of the hybrid polymer concrete and its damping capacity, two robust machine leaning models including extreme gradient boosting (XGB), and artificial neural network (ANN) algorithms were developed to predict the values of damping ratio from an experimental database of 196 samples. Multiple linear regression (MLR) was employed in this study as a benchmark for comparing with the ANN and XGB methods. The results indicate that the considered algorithms yield accurate models for predicting the damping ratio of HPC composites. However, ANN and XGB outperform MLR with an impressive R-square of 0.985 and 0.981, respectively versus 0.875. Analysing the importance of input features using the XGB algorithm also reveals that the curing time has the highest impact on predicting the damping ratio. The volume fractions of resin matrix and crumb rubber are the next most important features. The crumb rubber size, within the studied range, appears to be the least impactful one.

Physical, strength and acoustic properties of lightweight cement composite with preplaced chemically-treated crumb rubber

The valorisation of waste tyre crumb rubber (CR) as a sustainable construction material can alleviate environmental pollution and save natural aggregate consumption. However, its use in cement composite can result in a significant loss of strength due to weak adhesion and the non-uniform dispersion of CR. To compensate this strength loss, this research aims to investigate the innovative incorporation of chemically treated CR via the preplaced aggregate mixing (PM) method in producing a lightweight cement composite. The CR was treated with different chemicals, namely soaking in potassium permanganate and sulphuric acid solutions. The findings reveal a significant improvement in compressive strength (up to 160%) and water absorption reduction (from 20% to 175%) using the chemically treated CR and PM mixing methods, producing a lightweight cement composite with a density of about 1535 kg/m3. The SEM observation demonstrates the improvement in the CR–paste interface due to the treatment of the CR and the PM mixing methods, and due to the chemical treatment, which improved the wettability of the CR. On the other hand, the sound absorption and noise reduction coefficient of the chemically treated CR lightweight cement composite was almost similar for both the normal mixing (NM) and the PM methods. Overall, the results demonstrate that the CR treatment with sulphuric acid is promising for the PM method to produce a lightweight cement composite.

Emission reduction agents: A solution to inhibit the emission of harmful volatile organic compounds from crumb rubber modified bitumen

Volatile organic compounds (VOCs) in bitumen fumes pose health risks to workers. Adding end-of-life tire crumb rubber (CR) to bitumen increases VOC emissions. To promote cleaner asphalt production, recycled materials like cementitious materials, activated carbon, zeolite, and geopolymers were incorporated into crumb rubber modified bitumen and explored as emission reduction agents (ERAs). Proton-transfer-reaction time-of-flight mass spectrometry was used to compare VOC emissions across blends. ERAs reduced emissions by at least 33%, with Portland cement, activated carbon, and geopolymer-based fly ash achieving up to 58%, 49%, and 48% reduction, respectively. Multivariable regression analyses showed that the BET surface area, BJH adsorption cumulative surface area, BJH desorption cumulative surface area, and average pore diameter of the ERAs were the predominant factors contributing to the reduction of VOC emissions.

Assessment of a Non-Destructive Testing Method Using Ultrasonic Pulse Velocity to Determine the Compressive Strength of Rubberized Bricks Produced with Lime Kiln Dust Waste

This paper presents a comprehensive study in which non-destructive testing utilizing ultrasonic pulse velocity (UPV), considering both pressure (P) waves and shear (S) waves, was used to assess the compressive strength (CS) of rubberized bricks. These innovative bricks were manufactured by blending lime kiln dust (LKD) waste with ground granulated blast furnace slag (GGBFS), sand, and fine waste tire crumb rubber (WTCR). This study introduces mathematical models to explain the relationships between the results of destructive tests (DTs), specifically compression strength (CS) tests, and non-destructive tests (NDTs) employing UPV. These models were subsequently used to conduct validation exercises to accurately predict the strength of the rubberized bricks produced. The outcomes of the validation tests underscore the effectiveness of the UPV method in predicting the CS of rubberized eco-friendly bricks produced using an LKD-GGBFS blend. Importantly, the prediction using the power model exhibited minimal errors, confirming the utility of the UPV method as a reliable tool for assessing the compressive strength of such sustainable construction materials. This research contributes to advancing the field of eco-friendly construction materials and highlights the practical applicability of non-destructive ultrasonic testing in assessing their structural properties.

Synergetic Effects of Waste Engine Oil and Crumb Tyre Rubber on Bitumen Modification

Bitumen is a widely used road infrastructure material exhibiting black color and sticky consistency and is known for its versatile use and thermoplastic nature. In recent years, predicting road life has been arduous due to increasing traffic, global warming, and ever-changing stresses on pavements. Meanwhile, a large amount of waste engine oil (WEO) and vehicle tyres from various automobiles is disposed of into the atmosphere as hazardous waste. Relatedly, heavy metals and the huge capital involved in the sustainable treatment of these materials have been challenging. Therefore, this study aims to analyze modified bitumen using (WEO) in combination with waste crumb tyre rubber (CTR), thus reducing virgin bitumen (VB) use and making bitumen a sustainable material. During the characterization of modified bitumen, the following WEO concentrations were utilized: 3%, 5%, 7%, and 9%, and the following CTR concentrations: 5%, 7%, 9%, 12%, and 15%. The properties of modified and virgin bitumen were compared. It has been found that the blend of 5% CTR and 9% WEO exhibit the highest penetration value and the lowest softening temperature of all the samples examined. As a result, this mixture can be used to reduce the excessive brittleness of bitumen to a greater extent. Moreover, the flash and fire point values have increased after modification, while the ductility and specific gravity values have decreased. In summary, the modified bitumen has shown promising results regarding physical changes in bitumen.