New Route of Tire Rubber Devulcanization Using Silanes.

The disposal of tires at the end of their lifespan results in societal and environmental issues. To tackle this, recycling and reuse are effective solutions. Among various recycling methods, devulcanization is considered to be a very sustainable option, as it involves the controlled breakdown of crosslinks while maintaining the polymer backbones. The objective of this study is to develop a sustainable devulcanization process for passenger car tire rubber using silanes. In this study, a thermo-mechanical-chemical devulcanization process was conducted to screen six potential devulcanization aids (DAs). Silanes were chosen as they are widely used in tire rubber as coupling agents for silica. The efficiency of the devulcanization was studied by the degree of network breakdown, miscibility of the devulcanized material, and mechanical properties of the de- and revulcanized material. Compared to the parent compound, a 55-60% network breakdown was achieved for the devulcanizate along with 50-55% of tensile strength recovery. In addition to superior devulcanization efficiency, this DA offers a sustainable alternative to the conventional ones, such as di-phenyl-di-sulphide, due to its compliance with safety regulations. The devulcanizate can be utilized in high-performance applications, such as tires and seals, while 100% devulcanizate can be employed in low-strength technical rubber products.

An economic analysis of scrap tire pyrolysis, potential and new opportunities.

Scrap tire recycling is a concern for local and national governments because of the associated environmental hazards. As motor vehicle use increases around the globe, fueled by booming demand in the emerging market, more governments are imposing stringent recycling rules for scrap tires. New and emerging technologies have been introduced to solve the recycling problem. Pyrolysis, which involves the decomposition of materials at elevated temperatures under inert conditions, converts scrap tires into gas and liquid fuels and these products can be used by other industries such as chemical, energy and transportation industries. The feasibility of pyrolysis depends on several factors, including the material content of the scrap tire and market value of the products. Current and past market conditions suggest that pyrolysis plants can be run profitably as independent operations. This study evaluated the economic potential of the pyrolysis industry based on evolving market conditions and forecasts the potential market size based on the volume of scrap tires expected to come into the market in the next 20 years. Separate models were used for market predictions for Europe and Turkey. The economic benefits of using scrap tire pyrolysis were discussed, including the potential monetary value of adopting such policies for Turkey.

Concrete with a High Content of End-of-Life Tire Materials for Flexural Strengthening of Reinforced Concrete Structures.

This research investigates the performance of Steel Fiber Reinforced Rubberized Concrete (SFRRC) that incorporates high volumes of End-of-life tire materials, (i.e., both rubber particles and recycled tire steel fibers) in strengthening existing reinforced concrete (RC) beams. The mechanical and durability properties were determined for an environmentally friendly SFRRC mixture that incorporates a large volume (60% by volume aggregate replacement) of rubber particles and is solely reinforced by recycled tire steel fibers. The material was assessed experimentally under flexural, compressive and impact loading, and thus results led to the development of a numerical model using the Finite Element Method. Furthermore, a numerical study on full-scale structural members was conducted, focusing on conventional RC beams strengthened with SFRRC layers. This research presents the first study where SFRRC is examined for structural strengthening of existing RC beams, aiming to enable the use of such novel materials in structural applications. The results were compared to respective results of beams strengthened with conventional RC layers. The study reveals that incorporation of End-of-life tire materials in concrete not only serves the purpose of recycling End-of-life tire products, but can also contribute to unique properties such as energy dissipation not attained by conventional concrete and therefore leading to superior performance as flexural strengthening material. It was found that by incorporating 60% by volume rubber particles in combination with recycled steel fibers, it increased the damping ratio of concrete by 75.4%. Furthermore, SFRRC was proven effective in enhancing the energy dissipation of existing structural members.

The Influence of Fly Ash on the Mechanical Properties of Water Immersed All Waste Composites.

The paper presents new value-added composite materials prepared by recycling tire rubber, polyethene terephthalate (PET), high-density polyethene (HDPE), wood sawdust, and fly ash. The composites were manufactured through the compression molding technique for three temperatures (150 °C, 160 °C, and 190 °C) previously optimized. The addition of fly ash as reinforcement in polymer blends is a viable route to improve the composite" properties. The paper aims to assess the effect of fly ash on the mechanical properties and water stability of the new all waste composites considering their applications as outdoor products. The static tensile (stress-strain behavior) and compression properties of the composites were tested. The fly ash composites were characterized in terms of wetting behavior and surface energies (contact angle measurements); chemical structure of the new interface developed between composite" components (FTIR analysis), crystalline structure (XRD analysis), surface morphology and topography (SEM, AFM). The addition of fly ash promoted the development of the hybrid interfaces in the new composites, as FTIR analysis has shown, which, in turn, greatly improved the mechanical and water resistance. The novel all waste composites exhibited lower surface energies, larger contact angles, and smoother morphologies when compared to those with no fly ash. Overall, the study results have revealed that fly ash has improved the mechanical strength and water stability of the composites through the formation of strong hybrid interfaces. The study results show optimal water stability and tensile strength for 0.5% fly ash composites cured at 190 °C and optimal compressive strength with good water stability for 1% fly ash composite cured at 150 °C.

Preparation and Properties of Sustainable Brake Pads with Recycled End-of-Life Tire Rubber Particles.

Sustainable composite brake pads were processed by employing recycled end-of-life tire (ELT) rubber particles obtained by means of cryogenic grinding and ambient grinding. The effect of the grinding mechanism and concentration of ELT rubber particles was then reported. From the friction result test, better behavior in terms of coefficient of friction (COF) was obtained when 3% of ELT rubber particles were introduced into the composite. It was demonstrated that the size of the particles is not as determinant as the friction mechanism in the wear properties of the sustainable brake pads. Whereas, while increasing the ELT rubber particle size acts as detrimental to the COF either in the ambient or cryogenic grinding, at high friction distances, the better adhesion of the particles because of the rough surface of the particles subjected to ambient grinding enhances the long-life behavior of the composite brake pads.

Gestión de llantas usadas en la ciudad de Tunja, Boyacá (Colombia) / Management of used tires in the city of Tunja, Boyacá (Colombia)

RESUMEN Millones de llantas se producen anualmente para satisfacer la demanda mundial, asociada al incremento en la generación de llantas usadas. Su manejo es un desafío, considerando que la disposición en rellenos sanitarios ya no está permitida en algunos países, incluyendo Colombia, entre otras razones, por su alta resistencia biológica y química a la degradación, por lo cual, su inadecuado manejo y la falta de mecanismos de gestión, genera impactos negativos en la salud y el ambiente. Se realizó un estudio sobre la gestión de llantas usadas en Tunja, Boyacá (Colombia), con el fin de indagar aspectos relacionados con su disposición y manejo, al igual que sobre el conocimiento de programas posconsumo, aprovechamiento y cumplimiento de la normatividad ambiental vigente. Para la recolección de información primaria, se aplicaron encuestas estructuradas, a empresas registradas ante la Cámara de Comercio del municipio, que efectuaran actividades relacionadas con la generación de llantas usadas, tales como servitecas, talleres de mecánica o montallantas. El estudio mostró que los mayores generadores de este residuo son los montallantas, con una media entre 20 y 40 unidades mensuales, en mayor porcentaje de Rines 13 y 14, esto indicaría una proyección de 360 llantas anualmente por establecimiento, sin considerar los sitios no legalmente registrados. De manera general, para el avance en la gestión de llantas usadas en Tunja, se recomienda el desarrollo de alternativas, de manera articulada, entre los diferentes actores directamente involucrados, tales como productores, gestores, distribuidores y comercializadores, consumidores y autoridades ambientales regionales y municipales.

ABSTRACT Millions of tires are produced annually to satisfy the world demand, which is associated with an increase in the generation of used tire. Their management is a challenge considering that disposal in sanitary landfills is not allowed in some countries, including Colombia, due to their high biological and chemical resistance to degradation; therefore, their inadequate handling and the lack of management mechanisms generate negative impacts on health and the environment. A study was conducted on the management of used tires in Tunja, Boyacá (Colombia), to inquire aspects related to their disposal and management in the city, as well as on the knowledge of post-consumer programs, use, and compliance with current environmental regulations. For the collection of primary information, structured surveys were applied to companies registered with the Chamber of Commerce of the municipality that carry out activities related to the generation of used tires, such as service shops, mechanic shops or tire repair shops. The study showed that the largest generators of this waste are tire assemblers, with an average of between 20 and 40 units per month, with a higher percentage of rims 13 and 14, which would indicate a projection of 360 tires annually per establishment, without considering the sites that are not legally registered. In general, for the progress in the management of used tires in Tunja, the development of alternatives is recommended in an articulated manner between the different actors directly involved, such as producers, managers, distributors and marketers, consumers, and regional and municipal environmental authorities.

Sustainable mobility: The route of tires through the circular economy model.

Until nowadays, the concept of the 3Rs (Reduce, Reuse, Recycle) has tried to develop responsible consumption habits. Nonetheless, the rise of ecological thinking has generated the appearance of four new Rs in addition to these basic 3Rs; the currently 7Rs (Reduce, Reuse, Recycle, Redesign, Renew, Repair and Recover) which refer to the actions necessary to achieve the change towards a circular economy (CE) model. This model aims at extending the lifetime of the resources through their rational and efficient use to generate value repeatedly, reducing costs and waste. In this review, we examine the route followed by tires from the CE perspective, analyzing end-of-life strategies that aim to improve the circular flow of tire rubber materials. We discuss the most relevant studies on the "7Rs" concepts applied to tires, comparing different scientific approaches, as well as their industrial and commercial implementation. We also illustrate the drawbacks and feasibility of each of the R-hierarchy strategies. From the early stages of production to the post-consumption step, the path that tires trail within this CE model evidences the commitment and efforts towards the development of effective management schemes for achieving a real sustainable mobility.

Lightweight Cement Conglomerates Based on End-of-Life Tire Rubber: Effect of the Grain Size, Dosage and Addition of Perlite on the Physical and Mechanical Properties.

Lightweight cement mortars containing end-of-life tire rubber (TR) as aggregate were prepared and characterized by rheological, thermal, mechanical, microstructural, and wetting tests. The mixtures were obtained after total replacement of the conventional sand aggregate with untreated TR with different grain sizes (0-2 mm and 2-4 mm) and distributions (25%, 32%, and 40% by weight). The mortars showed lower thermal conductivities (≈90%) with respect to the sand reference due to the differences in the conductivities of the two phases associated with the low density of the aggregates and, to a minor extent, to the lack of adhesion of tire to the cement paste (evidenced by microstructural detection). In this respect, a decrease of the thermal conductivities was observed with the increase of the TR weight percentage together with a decrease of fluidity of the fresh mixture and a decrease of the mechanical strengths. The addition of expanded perlite (P, 0-1 mm grain size) to the mixture allowed us to obtain mortars with an improvement of the mechanical strengths and negligible modification of the thermal properties. Moreover, in this case, a decrease of the thermal conductivities was observed with the increase of the P/TR dosage together with a decrease of fluidity and of the mechanical strengths. TR mortars showed discrete cracks after failure without separation of the two parts of the specimens, and similar results were observed in the case of the perlite/TR samples thanks to the rubber particles bridging the crack faces. The super-elastic properties of the specimens were also observed in the impact compression tests in which the best performances of the tire and P/TR composites were evidenced by a deep groove before complete failure. Moreover, these mortars showed very low water penetration through the surface and also through the bulk of the samples thanks to the hydrophobic nature of the end-of-life aggregate, which makes these environmentally sustainable materials suitable for indoor and outdoor elements.