Rubber Granules Research Articles

ERASSTRI - European Risk Assessment Study on Synthetic Turf Rubber Infill – Part 1: Analysis of infill samples

End-of-life tyre (ELT)-derived rubber granules are used as synthetic turf infill on sports fields. They contain various chemical substances and there are concerns that exposure to these substances might be harmful for human health. This Europe-wide risk assessment study addresses these concerns. As the first part, chemical substances in samples from recycling companies and from sports fields were analysed. 86 coated and non-coated ELT granule samples from sites in 14 European countries were investigated, together with ten non-ELT materials. An extensive list of potentially relevant substances was compiled, and the infill materials were analysed for these substances, using GC and HPLC methods. Volatilisation of substances was studied in emission chambers. Polycyclic aromatic hydrocarbons (sum of 8 REACH PAHs) were identified at average concentrations below 10 mg/kg. Substances found at higher concentrations in rubber granules were aluminium (arithmetic mean in uncoated samples from sports fields 5383 mg/kg) and cobalt (168 mg/kg), benzothiazole (48 mg/kg) and 2-hydroxybenzothiazole (34 mg/kg), 6PPD (571 mg/kg) and DPG (51 mg/kg), and 4-tert-octylphenol (14 mg/kg). In addition, the following volatiles were found to evaporate from crumb rubber in emission chambers: benzothiazole, tert-butylamine, cyclohexanone, methyl isobutyl ketone, 2-heptanone and saturated aliphatic hydrocarbons higher than C9. With this comprehensive survey we created a profound database on concentrations of chemical substances in ELT-derived infill material, which is essential for a reliable risk assessment. The results were used to inform subsequent investigations (migration studies, exposure monitoring survey).

ERASSTRI - European Risk Assessment Study on Synthetic Turf Rubber Infill – Part 2: Migration and monitoring studies

End-of-life tyre (ELT)-derived rubber granules are used as synthetic turf infill on sports fields. They contain various chemical substances and there are concerns that exposure to these substances might be harmful for human health. In this second part of a Europe-wide study to address these concerns migration of substances from rubber granules to artificial body fluids (sweat, saliva, gastric juice) was tested and exposure measurements at sports fields were performed to improve the database for exposure assessment. Some PAHs, aluminium, cobalt, benzothiazole, tert-butylamine, MIBK, 4-tert-octylphenol, bisphenol A, and the phthalates DINP and DEHP were found in at least some samples of sweat simulant. The migration rates calculated with these data were used to inform the dermal exposure assessment. In artificial saliva and gastric juice, only aluminium, cobalt, 4-tert-octylphenol and MIBK were detected and migrated fractions were calculated. Bioaccessibility from rubber granules in the gastrointestinal tract was estimated conservatively, assuming complete availability for most substances. In addition, air samples from 17 sports fields in six European countries were analysed. There were no increased concentrations of metals (aluminium, cobalt), PAHs, or other semivolatile substances in air samples, but some volatiles (MIBK: 95th percentile: 18 μg/m3, benzothiazole: 95th perc.: 7 μg/m3, tert-butylamine: 95th perc.: 31 μg/m3, 2-heptanone: 95th perc.: 0.4 μg/m3, cyclohexanone: 95th perc.: 1.5 μg/m3, and saturated aliphatic hydrocarbons >C9: 95th perc.: 26 μg/m3) were slightly increased in a few samples. In addition, skin wipe samples were obtained from 43 sportspeople after playing on synthetic turfs. Only aluminium was detected above the limit of quantification in these samples (95th perc.: 0.84 mg/sample). These data are important input for risk characterisation as performed in the final study phase. Bioaccessibility data are used for estimating oral and dermal exposure of sportspeople, and air measurements are essential for inhalation exposure assessment.

Effect of Stress Rotation and Intermediate Stress Ratio on Monotonic Behavior of Granulated Rubber–Sand Mixtures

AbstractThe rotational failure of backfills and embankments is known to be involved with inhering anisotropic effects resulting from different stress paths along the rotational shear plane. The gra...

Utilização de borrachas trituradas em formas granulares na compactação de solo: uma nova possibilidade para melhor destinação de resíduos

Esta pesquisa tem por objetivo apresentar um estudo realizado experimentalmente do comportamento do solo com adição de borrachas trituradas, provenientes de pneus inservíveis, no intuito de promover uma nova destinação a estes resíduos sólidos. Adicionou-se às amostras de solo compactado percentuais de borrachas granuladas resultantes da trituração de pneus, sem a parte metálica de sua estrutura. Para simular a compactação de solos em obras de infraestrutura, especificamente de estradas, realizou-se ensaios de caracterização do maciço, sendo eles: a análise granulométrica, densidade real (DR), limite de liquidez (LL), plasticidade (LP), índice de plasticidade (IP) e ensaios de compactação (massa específica seca do solo e umidade ótima). Os ensaios foram padronizados possibilitando quantificar o comportamento no sentido de destinar esses materiais mantendo a qualidade inicial dos solos de Teresina, Piauí ou quaisquer outras regiões que tenham solos com características similares em que foram produzidos solos padrão (sem adição) e em misturas com 1% a 5% de borracha. Nos resultados observou-se que ao adicionar os percentuais não houve alterações consideráveis no grau de compactação do solo havendo a possibilidade de serem descartados em solos compactados sem que haja perda no desempenho e a qualidade do maciço. Dessa forma este seria um meio de descarte sustentável de borrachas com o propósito de reduzir os impactos ambientais que esses tipos de resíduos geram para o meio ambiente.

Hardened and transfer properties of self-compacting concretes containing pre-coated rubber aggregates with crushed dune sand

Many researchers believe that the adhesion failure between rubber and cement paste is one of the main reasons the strength of concrete containing these aggregates drops sharply. This paper provides strength and durability experiment results which reveal the effect of pre-coating rubber granules with crushed dune sand in terms of their mechanical performance, these tests aimed to enhance the durability properties of self-compacting concretes (SCC) transfer properties and structure. Results show that mechanical properties of SCC made with treated rubber granules are improved compared with concrete mix made with the untreated rubber. Natural sand is replaced with 2.5% of rubber granules pre-coating with (0–20%) of crushed dune sand as partial replacement of cement. The compressive strength of SCC rises with the proportionate increase of the crushed dune sand percentage. This could confirm the strengthening of the transition zone (between cement paste and rubber aggregate) by introducing siliceous additions with high fineness.

Dynamic probabilistic material flow analysis of rubber release from tires into the environment

The presence of microplastics in the environment is currently receiving a lot of attention. Rubber particles from tire wear have been estimated in several mass emission inventories to be a major contributor to the total microplastic release. This work used dynamic probabilistic material flow analysis to quantify the flows of rubber particles from tires to roads and further onto soils and surface waters of Switzerland. The model considered the whole life-cycle of tires from import over the use phase to the end-of-life and the re-use of scrap tires. Uncertainties of model parameters and data variability were considered by using a probabilistic approach. Mass flows onto soils and through road drainage by both uncontrolled dispersal and engineered systems are considered. In addition, the release of rubber from artificial turfs was included. The accumulation of rubber particles in the environment was quantified over the time frame from 1988 to 2018. The results show that in 2018, 1.29 ± 0.45 kg/capita of rubber was emitted from tire wear (97%) and rubber granules (3%). Street cleaning and waste water treatment removed around 26% of this rubber mass before finally reaching the receiving environmental compartment, resulting in an effective input of 0.96 ± 0.35 kg/capita of rubber in 2018 into the natural environment. Most of this mass (74%) was deposited on roadside soils (up to 5 m distance from road), 22% flowed into surface waters and the remaining part (4%) was emitted to soils. The dynamic modeling showed an increase of the input into the environment by about 10% from 1990 to 2018. The ban of sewage sludge application on soils resulted in a marked decrease in the amount transferred to soils after the year 2000. In total, 219 ± 22 ktonnes of rubber particles have accumulated in the environment since 1988 in Switzerland.

New Materials for Binder-Pitch Production

Research on decreasing the consumption of coal tar and expanding the range of materials used in binder-pitch production by adding coal extracts and chemical byproducts is reviewed. The liquid byproducts employed are tall oil, semicoking tar, and residues of styrene distillation; the solid byproducts are rubber granules and polycarbonate wastes.

Nuomici-Inspired Universal Strategy for Boosting Piezoresistive Sensitivity and Elasticity of Polymer Nanocomposite-Based Strain Sensors.

Electrically conductive polymer composites (CPCs) are potential alternatives to conventional strain gauges due to their tunable sensitivity and strain ranges. Currently, to achieve very high piezoresistive sensitivity in thermoplastic-based CPCs with Gauge factors GF above 20 at low tensile strains (ε ≤ 5%) is a big challenge, but critical for structural health monitoring application in infrastructures. Here, inspired by the unique structures of a famous Chinese food, nuomici, we coat carbon nanotubes (CNTs) onto sticky acrylic rubber (AR) granules (ARG) to form nuomici-like CNT@ARG composite granules, which are employed as unique conductive filler to fabricate highly piezoresistive and flexible CPCs based on poly(vinylidene fluoride) (PVDF). This strategy of localizing CNTs densely on the surface of touching rubbery particles resulted in a much more sensitive elastic conductive network built by the CNT@AR composite and showed a big gain effect. The resultant PVDF/CNT@AR nanocomposites (AR content ranging from 0 to 10 wt %) show extremely high piezoresistive sensitivity at low strain, depending on the AR content. In particular, the GF value of PVDF with 1.5 wt % CNT@10 wt % AR is 41 at 5% strain, which is more than one magnitude higher than that (ca. 3) of traditional PVDF/CNT nanocomposite sensors. Moreover, the elongation at break increases by about 60% with the addition of 1.5 wt CNT@10 wt % AR. This study introduces a universal effective strategy for tailoring the mechanical properties and strain sensitivity of conductive network in CPCs, which is critical for the fabrication of high-performance strain sensors.

Strength and ductility behaviour of rubberised cemented clayey soil

This paper reports the strength and ductility behaviour of rubber-granulate-reinforced cemented clayey soil and rubber-fibre-reinforced cemented clayey soil. The load–deformation behaviour of specimens was analysed in terms of absolute toughness and toughness index (TI) for further screening of the curves. A 5·08 and 3·46% improvement in the unconfined compressive strength and 16·74 and 8·60% improvement in the split tensile strength of the clayey soil was observed with the addition of rubber granulates and fibres up to 2·5 and 5%, respectively. However, increasing the content of granulates and fibres led to reductions in strength. The rate of strength reduction in granulate-reinforced soil was found to be higher than in that containing fibre. The absolute toughness and TI of soil mixed with 5 and 7·5% of granulates and fibres were found to be higher compared to values for other inclusions. Overall, the inclusion of rubber particles led to a decrease in initial stiffness, improved ductility and strain hardening in specimens subject to compressive load. However, in comparison with the ductile behaviour of fibre-reinforced soil under tensile loads, granulates were found to be ineffective in changing the soil's brittle behaviour.

HORMIGÓN SUSTENTABLE BASADO EN FIBRAS DE NEUMÁTICOS FUERA DE USO

Waste tires are considered to be massive trash and are usually abandoned in legal or illegal landfills. Their abandonment is associated with environmental impacts on land use and visual pollution, among others. Conversely, its recycling allows to valorize these residues by generating by-products such as rubber granules, steel fibers and textile fibers for new industrial applications. Several studies report the use of rubber and steel fibers of waste tires in concrete. The objective of this research was to compare the mechanical strength of concrete without the addition of tires residues (control group) at the ages of 7, 17 and 28 days, to concrete added with commercial steel fiber, and rubber and steel fibers from waste tires. The doses used were 50 kg/m 3 in concrete with commercial steel fiber, 10.5 and 7 kg/m 3 in concrete with recycled rubber granules, and 50 and 35 kg/m 3 in concrete with recycled steel fibers. The results indicated that concretes with the addition of rubber and steel fibers showed in all cases a slight decrease in the compressive strength c ompared to the witness at the age of 28 days. Conversely, concrete with the addition of steel and rubber fibers presented better flexural strength than the witness concrete, except in the case of concrete with 50 kg/m 3 of recycled steel fiber.

Utilization of Quarry Waste and Granulated Rubber Mix as Lightweight Backfill Material

In the present investigation, an attempt has been made to propose a lightweight backfill material using industrial wastes, namely quarry waste and granulated rubber. Granulated rubber was added in varying percentages (5%, 10%, 15%, 20%, 25%, and 30%) to quarry waste for obtaining lightweight material. Laboratory investigation has been performed in the present study to examine the physical, chemical, and geotechnical properties of quarry waste and the geotechnical behavior of quarry waste–granulated rubber (QWGR) mixes. Using granulated rubber as additive, the unit weight of quarry waste material was found to reduce from 21.8 to 14.1 kN/m3 for QWGR30 mix. The friction angle of quarry waste was obtained to be 51.2°, which increased by about 14° with rubber addition for the QWGR30 mix. The permeability of quarry waste was found to improve from fine sand to coarse sand range with the granulated rubber inclusion, making it an efficient backfill material. QWGR30 mix was found to be an efficient lightweight backfill material with reduced lateral pressure by about 73% and 85% compared to quarry waste and conventional sand, respectively. The economic savings of the project on backfill material by using QWGR30 over conventional sand would be around 8.35%.

Short- and medium-chain chlorinated paraffins in commercial rubber track products and raw materials.

Short- and medium-chain chlorinated paraffins (SCCPs and MCCPs) in commercial rubber track products and raw materials (rubber granules and adhesives) were investigated by two-dimensional gas chromatography with electron-capture negative-ionization mass spectrometry (GC × GC-ECNI-MS). The mean SCCP and MCCP concentrations in the rubber track products were 3.64 × 103 and 4.14 × 104 μg/g, respectively. The mean SCCP concentration in the products was significantly higher than those in the rubber granules (2.78 μg/g), but in the same order of magnitude as those in the adhesives (3.34 × 103 μg/g). The SCCP concentrations in almost half of the rubber track products and four fifths of the adhesives exceeded the limit (1.5 g/kg) set in Chinese standard GB 36246-2018. The dominant SCCP and MCCP congeners in the rubber track products were similar to those in the relevant adhesives but different from those in the paired granules. Principal component analysis and contribution calculations indicated that chlorinated paraffins (CPs) in adhesives could be the main sources of CPs in rubber track products. The high CP concentrations found in rubber track products are of special concern because of the relatively high exposures for children and negative effect on human health and environment.

Influence of the addition of styrene-butadiene rubber on the dynamic properties of polymer concrete for machine tool applications

In this study, the influence of the addition of styrene-butadiene rubber on the dynamic properties of polymer concrete was investigated. A 10% volume addition of styrene-butadiene rubber granulate with three different grain gradations was used for the tests. The modal study was carried out in the 0 to 2000 Hz frequency range. The response function for a single impulse excitation was tested. The relaxation time after excitation, the modes of natural vibrations and the amplitude of the transfer function values as well as vibration damping ratios were also compared. Finally, conclusions were formulated regarding the application of the styrene-butadiene rubber additive as a material to improve the dynamic properties of polymer concrete. The best results were obtained for a sample made with a 10% styrene-butadiene rubber volume addition with grain sizes from 0.6 to 2 mm. In this case, the biggest decrease of the amplitude of the transfer function value was 76%, while the biggest increase of the damping ratio was 431.5%, in comparison with the clear polymer concrete sample. The worst results were obtained for a sample made with a 10% styrene-butadiene rubber volume addition with grain sizes from 2.5 to 6 mm. In this case, the longest relaxation time of the sample, the increase of the amplitude of the transfer function value and the decrease in the damping coefficient were recorded.

Strength and Deformation of Sand-Tire Rubber Mixtures (STRM): An Experimental Study

Abstract Waste material such as used tires is increasing every year, which poses environmental problems. However, such material has been used in several geotechnical applications as alternative lightweight backfill in highway embankments and/or behind retaining walls, providing environmental, economic and technical benefits. These applications require knowledge of engineering properties of soil-tire rubber mixtures. The present study aims to show the possibility of tire rubber usage in sand by evaluating the shear strength and deformability of sand mixed with granulated rubber, in weight percentages between 0 and 50%. The tire rubber content was found to influence the stress-strain and deformation behavior of the mixtures. The shear strength of sand mixed with 10% or 20% tire rubber was higher than that measured for sand only. However, the trend for TRC = 30–50% was different. Samples with a rubber content of 30-50% exhibited a rapid decrease in the stress ratio compared with that of sand. The major principal strain at maximum stress ratio was found to increase with increasing tire rubber content. However, it was observed that the lateral strains (minor and intermediate principal strains) of samples reduced significantly with the addition of tire rubber to the sand.

Effects of inclusion of granulated rubber tires on the mechanical behaviour of a compressive sand

Drained triaxial shearing tests were performed on a well-graded compressive sand (completely decomposed granite, CDG) and its mixtures with granulated rubber tires to investigate the effects of rubber size and content on their mechanical behaviour. Three sizes of rubber particles, GR1, GR2, and GR3, were used with size ratios to CDG (D50,rubber : D50,CDG) of 0.9, 3.5, and 7.2, respectively, and the rubber content ranged from 0% to 30%. The results show that for CDG–GR1 mixtures, the strength decreases with increasing rubber content, while for CDG–GR2 and CDG–GR3 mixtures, the strength decreases only at 10% rubber content and then increases markedly with increasing rubber content. The increase of strength is mainly because the inclusion of large rubber particles widens the particle size distributions of the mixtures, resulting in denser packings. The denser packings also lead to a decrease in compressibility. At larger size ratio and higher rubber content, the CDG–rubber mixtures show higher shear strength and lower compressibility than pure CDG, which indicates the CDG–rubber mixtures are very suitable to be used as filling materials.

Eco-Efficient Fiber-Reinforced Preplaced Recycled Aggregate Concrete under Impact Loading

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

Chlorinated Paraffins in Car Tires Recycled to Rubber Granulates and Playground Tiles.

Chlorinated paraffins (CPs) are used in various products to improve their physicochemical characteristics. Due to recycling, CPs may end up in “new” recycled products. In this study we investigated CPs present in end-of-life car tires that are recycled to rubber granulates used on artificial soccer fields, and playground tiles. The ∑CP(C10-C30) concentrations ranged from 1.5 to 67 μg/g in car tires, 13–67 μg/g in rubber granulates, and 16–74 μg/g in playground tiles. MCCPs were the dominant CP group with an average contribution of 72%. LCCPs up to C30, were detected for the first time in car tires, rubber granulates, and playground tiles. The CPs application in tires is unclear, the low CP concentrations found in this study (<0.007%) could possibly indicate contamination during the manufacturing process. The presence of CPs in the granulates and tiles, in addition to the multiple chemicals already detected, emphasizes the need to further investigate the migration and leaching behavior, in order to assess potential risks of CPs for humans and the environment. The presence of CPs in car tires may be another source of CPs for the environment. The CP volume brought into the environment by tire wear particles (TWP) from car tires in the European Union, is estimated at 2.0–89 tons annually.

Public Perceptions of Contentious Risk: The Case of Rubber Granulate in the Netherlands.

This paper reports on the perceptions of risk related to practicing sports on fields containing rubber granulate infill, and preferences for mitigation measures, among people with and without offspring exposed to rubber granulate. Two repeated surveys were conducted among members of the general population and parents of children aged under 18, in the middle of a dynamic public discussion about the potential health risks of exposure to rubber granulate. The first survey (N = 1033) was administered in December 2016 at a time characterized by considerable public uncertainty and contrasting opinions in the public risk debate. The second survey (N = 782) was conducted in January 2017 after the publication of a risk assessment report, which concluded that practicing sport on fields containing rubber granulate is safe. Multilevel analyses were performed to study changes in perceptions of risk and mitigation preferences in the time between the two surveys, the influence of being familiar with new information following the risk assessment report, and the differences in the perceptions of risk and mitigation preferences between groups with and without offspring exposed to rubber granulate. The results of this study show that, initially, a substantial proportion of the Dutch public perceived practicing sports on fields containing rubber granulate as a potential health threat to children. Over time, after publication of a new risk assessment study stating that practicing sports on fields containing rubber granulate is safe, perceived risk and preferences for mitigation of this risk decreased, especially among those who were familiar with the new information. Parents of children under the age of 18, in particular those with children who were exposed to rubber granulate, were more likely to perceive the risk as higher and to prefer a stricter mitigation policy. These insights may be important to inform public health communication strategies with respect to the timing and tailoring of risk messages to various groups.

The fire characteristics of the Municipal noise absorbing screen

This article deals with the fire resistance of an innovative noise protection – so called the Municipal noise absorbing screen and its resistance in other dangerous situations with the occurrence of fire. The article briefly describes the characteristics of the noise absorbing screen’s element which is made mostly of the cemented rubber granulate. Due to its geometrical, spatial and material solution the Municipal noise absorbing screen innovatively extends technical opportunities in the field of noise reduction from the rail transport, especially in the urbanized areas. This article also covers the problems of possible causes of fire considering the real installation of the element into the tramway track. The main focus of the article lies in the selection of possible dangerous fire situations. In connection with this, within the experimental part there were carried out reaction to fire tests according to the arranged fire scenarios. There were realized three basic tests in total and their several modifications. In order to that the article describes the effects of the flame on the noise absorbing screen’s element and its damage. Final part is dedicated to the summary of all results from the previous experiments and their comparison. Last but not least there are designed future construction improvements of the element.

Tire waste management system in Cyprus in the framework of circular economy strategy.

Worldwide, waste raised from tires counts 1.3-1.5 billion tonnes/year and by the end of 2025, is expected to be more than 2.5 billion tonnes. On 2013, the EU countries reached 3.6 million tonnes of used tires. However, the cheapest treatment method since now is landfilling and is considered to be a major threat for the environment and the public health. In Cyprus, the total tires that were imported on 2015 was 835,142 pieces (5.8% more than the 2014), which were equal to 9638 t, while at the same time, the total waste from those tires were 6629 tonnes. Moreover, the cement industry used 6691 tonnes of tires as alternative fuel. Until now, there are three management systems in place in Cyprus, for the end-of-life tires (ELTs). The collection of ELTs on 2011 was 1817 tonnes while at the end of 2016 was 7201 tonnes. The main treatment methods in Cyprus are the use of ELTs as alternative fuel in cement industry or to produce rubber granules (609-2738 tonnes/year) to be used to construct artificial surfaces or substrate for artificial lawn grounds and limited to pyrolysis (324-837 tonnes/year). At the same time, the environmental fees for the collection of tires varies and depends on the tire category. Furthermore, the market share of ELTs is up to 1.5 million € and the total recovery index from the market is closed to 90% the last 6 years (2013-2017). This paper evaluates and assess the existing tire waste management system (TWMS) in Cyprus in order to promote strength and weakness as well as to propose a holistic management system in insular communities in order to adopt the targets set by the concept of circular economy. The SWOT analysis identified as the main weaknesses the absence from the legislation of specific target for the recovery index of tires and the absence of any centralized logistic system to control the existing management systems while the main threats includes bureaucracy and the absence of technical and economic data which will guarantee the financial viability of a centralized treatment unit.