Application of Recycled Tires in Improving the Seismic Performance of Railway Embankments

Rapid growth of populations and extension of societies leads to the production of waste by-products, which puts a burden on landfills. To address this issue, tire derived aggregates (TDA) from scrap tires have been used as road embankments in several projects. Three different test sections using different TDA, and TDA and soil mixtures, were constructed at the Integrated Road Research Facility test road in Edmonton, Alberta, Canada. Based on falling weight deflectometer tests in different months, the fatigue life performance of the TDA embankments was evaluated against that of a conventional control section using the measured horizontal strains at the bottom of the asphalt layer and the Asphalt Institute’s fatigue model. The results showed satisfactory performance of all three TDA test sections and significantly longer fatigue lives as opposed to the fatigue life of the control section. This analysis showed compelling evidence regarding the long-term performance of TDA material as road embankments in construction projects.

Although some discarded tires are reused in various applications, a considerable number end up in landfills, where they pose diverse environmental problems. Waste tires that are shredded to produce tire-derived aggregates (TDA) can be reused in geotechnical engineering applications. Many studies have already been conducted to examine the behavior of pure TDA and soil-TDA mixtures. However, few studies have investigated the behavior of larger TDA particles, 20 to 75 mm in size, mixed with various types of soil at percentages ranging from 0% to 100%. In this study, TDA was mixed with gravelly, sandy, and clayey soils to determine the optimum soil-TDA mixtures for each soil type. A large-scale direct shear box (305 mm × 305 mm × 220 mm) was used, and the mixtures were examined with a series of direct shear tests at confining pressures of 50.1, 98.8, and 196.4 kPa. The test results indicated that the addition of TDA to the considered soils significantly reduces the dry unit weight, making the mixtures attractive for applications requiring lightweight fill materials. It was found that adding TDA to gravel decreases the shear resistance for all considered TDA contents. On the contrary, adding up to 10% TDA by weight to the sandy or clayey soils was found to increase the shear resistance of the mixtures. Adding up to 10% TDA by weight to the clayey soil also sharply increased the angle of internal friction from 18.8° to 32.3°. Moreover, it was also found that the addition of 25% TDA by weight to the gravelly or sandy soils can reduce the lateral earth pressure on buried structures by up to 20%. In comparison, adding 10% TDA to clay resulted in a 36% reduction in the lateral earth pressure.

ABSTRACTTire recycling and reuse in North America and worldwide have increased considerably, with the aim of reducing the harmful effects of scrap tires on the environment. Accordingly, the use of tire derived aggregates (TDA) in civil engineering applications is on the rise at an unprecedented rate. In comparison to conventional backfill aggregates, TDA is an inexpensive, lightweight material that costs about 25% of the cost of conventional backfill. Thus, there is an increasing trend of using TDA under shallow foundations as a lightweight backfill alternative. However, limited information exists for the design of shallow foundations built on TDA. Hence, the main objective of this paper is to develop a simplified design procedure for shallow foundations built over a TDA layer. Rigorous finite element models were developed and validated using field tests results. Subsequently regression analyses were used to develop the proposed ultimate bearing capacity equation, taking into account the granular layer thickness, TDA layer thickness, footing width, footing shape, footing depth, and the allowable settlement.

Tire-derived aggregate (TDA) is an entirely recycled material created by processing scrap tires, which are shredded into a fundamental geometric shape, typically measuring from 5 to 30 cm in size. TDA possesses desirable properties such as low earth pressure, improved drainage, and a lightweight structure, making it an ideal material for numerous civil engineering applications. Unfortunately, the environmental suitability of TDA use has previously been questioned. This article outlines that TDA does not release a significant amount of potentially toxic compounds, the leaching rate in surrounding water environments is low, and TDA can even be a medium to remove nutrients and toxic organic and inorganic compounds commonly found in agricultural land and urban runoff. This study aims to collect the most up-to-date scientific data on the environmental impact of scrap tires and evaluate the data specifically for TDA applications in civil and environmental engineering applications. TDA has been proven to be an environmentally safe, long-lasting, cost-effective, and sustainable resource with many potential applications in civil engineering. Guidelines should be developed for specific projects to achieve a circular economy for end-of-life tires in the form of TDA to avoid potential environmental issues and problems.

The number of scrap tires discarded worldwide is increasing annually. Stockpiling these tires is not a viable option due to environmental concerns and space limitations. Landfilling is likewise unacceptable and is not permitted in many areas. Recycling these tires is the best alternative. Shredding scrap tires to create a product known as tire-derived aggregate (TDA) is one of the most environmentally friendly methods of recycling scrap tires. In the past few decades, TDA and TDA-soil mixtures have been used increasingly in civil engineering projects. Nevertheless, only limited research has so far been conducted on TDA and TDA mixed with soil. In addition, the majority of past research has focused on TDA particles that do not have steel wires and are small in size. In the present research, triaxial tests were performed on various mixtures of TDA with sand or gravel. Each sample was subjected to three different confining pressures. The results of the tests are presented and discussed, and empirical equations are proposed to match the laboratory results.

Shallow foundations on lightweight TDA backfill: Field tests and 3D numerical modelling

There is a growing interest in reusing scrap tires in civil engineering applications. Previous studies have shown that there are many promising applications in civil engineering. In most of these applications, scrap tires are not used directly but are shredded to form a product referred to as tire-derived aggregate (TDA). Unlike most other civil engineering materials, TDA has not yet been subjected to sufficient experimental scrutiny to identify its physical properties. Most of the experiments conducted on TDA have been limited to small TDA shreds with no steel wires. This study aims to address this problem through a series of consolidated drained triaxial tests on TDA using a large-scale triaxial apparatus. The results of the tests are presented, discussed and fitted to empirical equations. In addition, an empirical hyperbolic material model that represents the test results has been developed based on the hyperbolic model of Duncan and Chang. .

The major objective of this research study, believed to be the first of its kind, was to explore the swelling and absorption rate of tire-derived aggregate (TDA) modified using postconsumer recycled (PCR) plastics in optimum blend proportions. Further, TDA was utilized in developing plastics-modified rubberized asphalt mixtures through an innovative semi-dry approach aimed at applications in subsurface layers, such as the base or subbase of a pavement system. The research included: (i) physical and thermochemical characterization of raw materials; (ii) blending of 16 combinations of PCR plastics-modified asphalt (PA) binder; (iii) rheological assessment of PA blends, including performance grade, multiple stress creep recovery, and optimization; (iv) preparation of 18 combinations of modified TDA (MTDA) products utilizing optimized PA blend; (v) asphalt absorption tests on TDA and MTDA to determine swelling and asphalt absorption rates; and (vi) microscopy of MTDA particles. Thermochemical characterization revealed promising binding compatibility of TDA, PCR plastics, and hydraulic lime (HL), owing to their distinct thermal and chemical properties, while rheological assessment confirmed that PA blends with higher polyethylene terephthalate dosages significantly improved rutting resistance and elasticity for TDA modification. Additionally, the inclusion of PCR plastics and HL in MTDA reduced the absorption capacity and uncontrolled swelling of the unprocessed TDA three- or four-fold. It is envisioned that this study will promote a feasible waste management solution to address recycling of both waste tires and plastics by conserving natural resources and pave the way to create perpetual and resilient infrastructure.

Understanding the role of biofilms and estimation of life-span of a tire derived aggregates-based underground stormwater treatment system

The low in-place density of tire derived aggregate (TDA) makes them attractive for use as lightweight fill for embankments constructed on weak ground and backfill for retaining walls. TDA, also known as tire shreds or chips, are scrap tires that have been cut into 50 to 300mm (2 to 12 in.) pieces. There are many examples of projects that have successfully used TDA as lightweight fill. However, as illustrated by three projects built in 1995 that experienced internal heating reactions, car is needed to properly design and construct TDA fills. The underlying cause of these problems was a combination of oxidation of exposed steel belts and freshly cut surfaces on rubber pieces. The lessons learned from these projects resulted in design guidelines to limit internal heating of TDA fills. Nine projects have now been built in accordance with the guidelines. Internal measurements show that TDA temperatures are similar to background soil levels, indicating the effectiveness of the guidelines. Moreover, effective construction specifications have been developed that often result in lower construction costs than competing lightweight fill materials.

Approximately 250 million tires are discarded each year in the United States and 20 million in Canada. Finding sustainable ways to dispose these tires continues to be a problem throughout the world not only in North America. Disposal issues along with a continuing increase in tire production have resulted in an increase in tire stockpiles, 30 % of these tires end up occupying valuable landfill space. Tire Derived Aggregates (TDA) made from scrap tires have a compacted dry unit weight of 6.9 kN/m3 and a specific gravity of 1.06 making their use as lightweight fill material especially for highway embankments over soft soils very advantageous. Using TDA as fill material not only provide a new construction material but also help to provide sustainable solution for several environmental and economic problems. Previous studies have shown that the addition of Tire Derived Aggregates (TDA) to sand results in a fill material which is characterized by its higher shear strength compared to that of 100 % sand. While there have been several studies investigating various properties and situations involving TDA’s, there remain areas that still require exploration. The effect of soil/aggregate gradation on shear strength is one of particular interest. All of the research conducted to date investigated only the sand gradation mixed with uniform TDA gradation. None of the conducted research investigated the interaction between the gradation of the two materials and its effect on the performance of the fill mixture. The main goal of this paper is to gain an understanding of this interaction in aim of producing better fill mixtures with enhanced characteristics.

Tire recycling and reuse in North America and worldwide have increased considerably, intending to reduce the harmful effects of scrap tires on the environment. Accordingly, the use of tire derived aggregates (TDA) as backfill material in civil engineering applications is on the rise at an unprecedented rate. However, to use TDA in the construction industry, its strength and stiffness parameters properties must be evaluated. One key factor that is known to influence the strength and stiffness of backfill material is the particle size of the used material. Hence, in this paper, a series of large-scale triaxial tests on five TDA samples with different maximum particle size, Dmax, of 19.05, 25.4, 38.1, 50.8 and 76.2 mm were conducted to investigate the effect of the particle size on the obtained results. The tests were done under consolidated drained conditions using three confining pressures of 50, 100, and 200 kPa. The results showed that the shear strength of TDA increase by increasing the maximum particle size while the cohesion did not show a specific trend. Moreover, the samples exhibited an increase in the secant elastic modulus by increasing the particle size.

18 - Tire-derived aggregate applications in civil engineering

Tyre derived aggregates and waste rock blends: Resilient moduli characteristics

Experimental assessment of cyclic behavior of sand-fouled ballast mixed with tire derived aggregates