Sand-rubber Mixtures Research Articles

Digital Image Processing on Segregation of Rubber Sand Mixture

Digital Image Processing on Segregation of Rubber Sand Mixture

Sand and concrete interface behaviour of particulate rubber-sand-fly ash mixture

ABSTRACT Recycled rubber tire mixed with sand has been examined as embankment material, retaining wall backfill and buried pipes backfill. Applications of these mixtures in the field would experience two kinds of interfaces, one is between the structure and the mixture and the other is between the mixture and the existing ground. Therefore the present study examines the interface behaviours of pure rubber, sand-rubber mixture and fly ash-rubber mixture with concrete and sand interface. In the present study, the concrete and the sand interface behaviour of the material and mixtures are examined. The test results show that the interface friction angle of sand-particulate materials is higher than that of concrete-particulate materials. In addition, fly ash-rubber mixture possesses higher interface shear strength than that of the sand-rubber mixture. Further, the interface coefficient is observed to vary from 0.85 to 1 for sand-rubber mixture and fly ash-rubber mixture with concrete and sand interfaces.

Correction to: Influence of Sand-Rubber Mixtures Backfill on Mechanical Properties of Bridge Abutment and Foundation Piles

Correction to: Influence of Sand-Rubber Mixtures Backfill on Mechanical Properties of Bridge Abutment and Foundation Piles

Density and Shear Strength of Particulate Rubber Mixed with Sand and Fly Ash

AbstractThe present study examines the behavior of particulate rubber–sand mixtures (PRSM) due to the replacement of sand with fly ash. Particulate rubber (PR) of different gravimetric proportions ...

Influence of Sand-Rubber Mixtures Backfill on Mechanical Properties of Bridge Abutment and Foundation Piles

Sand-rubber mixtures have the advantages of light weight, high strength, and low price. In this study, three-dimensional finite element simulation was carried out in GTS MIDAS based on the elastoplastic constitutive model to investigate the response of bridge abutments to sand-rubber mixtures backfills under static load condition. Four different backfill materials were used and compared in the modeling. The settlement of abutment foundation, displacements of bridge abutment and foundation pile, and bending moment of the piles were analyzed. The results show that the sand-rubber mixtures backfill can significantly decrease the settlement of foundation, and the displacements of bridge abutment and foundation pile as compared to the backfill soil. Such decrease is more prominent as the rubber content increases. The use of sand-rubber mixtures replacing the soft soil layer or as a backfill material not can only reduce the upper load acting on foundation soils and improve the stability and static performance of bridge abutment, but also solve the problem of waste rubber recycling and potential environmental pollution to meet the increasing demand of road construction materials for the rapid development of highway engineering, resulting in huge economic and social benefits with a wide range of engineering applications.

Mechanical properties and time-dependent behaviour of sand-granulated rubber mixtures

ABSTRACTThe use of granulated recycled rubber as a lightweight material in civil engineering applications has been widely growing over the past 20 years. Processed waste tires mixed with soils have been introduced as lightweight fills for slopes, retaining walls, and embankments. It has also been considered as a damping material under foundations in seismic zones. Understanding the properties of sand-rubber mixtures is essential to evaluate its performance in geotechnical applications. Isotopically consolidated drained (CD) triaxial tests were conducted to investigate the effect of rubber size, content and saturation condition on the mechanical properties of sand-rubber mixtures. Moreover, the compressibility of the sand-rubber mixtures under sustained loading was investigated through one dimensional consolidation tests. The unit weight, shear strength and stiffness of sand-rubber mixtures decreased whereas deformability increased at increased rubber content. A non-linear stress-strain response was observed, that changed from brittle to ductile behaviour at increased rubber content. Sand-rubber mixtures, under one dimensional loading, exhibited significant settlement that increased as rubber content increased.

Full-scale experimental study on screening effectiveness of SRM-filled trench barriers

Vibration induced by different sources can be seriously harmful to structures and occupants and their isolation has gained importance during recent years with rapid urbanisation. Trench barriers (open or filled) have been used for isolating such unwanted vibrations, but few experimental studies have investigated the effects of different parameters on vibration reduction. This paper provides results of a series of full-scale field experiments conducted to investigate the effect of open and filled trenches on vibration screening. A sand–rubber mixture (SRM) was used to fill the trench as a lightweight, high-energy-absorbing and environmentally friendly material. Results confirmed that the SRM-filled trench can be used as an efficient, low-cost and easily constructed system for reducing ground vibration. In some cases, the performance level of SRM-filled trenches was close to that of open ones. The use of geophones that could record vibrations in three dimensions demonstrated that trench barriers can isolate vertical vibrations better than horizontal and transversal ones.

Strength and microstructure characteristics of the recycled rubber tire-sand mixtures as lightweight backfill.

The disposal of scrap rubber tires has induced critical environmental issue worldwide due to the rapid increase in the number of vehicles. Recycled scrap tires as a construction material in civil engineering have significant environmental benefits from a waste management perspective. A systematic study that deals with strength and microstructure characteristics of the rubber-sand mixtures is initiated, and mechanical response of the mixtures is discussed in this investigation. Experiments were conducted to evaluate the effects of rubber fraction on the basic properties including mass density (ρ), stress-strain characteristics, shear strength, and unconfined compression strength (q u) of the rubber-sand mixtures. Additionally, scanning electron microscopy (SEM) was carried out to reveal the microstructure characteristics of the mixtures with various rubber fractions. A discussion on the micromechanics of the mixtures also was conducted. This study demonstrates that the ρ, friction angle, and q u decrease linearly with an increase in rubber fraction, whereas shear strain at peak increases. The stress-strain characteristics of the rubber-sand mixtures shift from brittle to ductile as the rubber fraction increase. These changes are attributed to remarkably lower stiffness and higher compressibility of the rubber particle compared with those of the conventional mineral aggregates. With an increase in the rubber fraction, the mechanical response of rubber-sand mixtures exhibits two types: sand-like material and rubber-like material. Rubber particle possesses the capacity to prevent the contacted sand particles from sliding at lower rubber fraction, whereas it transmits the applied loadings as the rubber fraction increased. This outcome reinforces the practicability of using recycled rubber tire-sand mixtures as a lightweight backfill in subbase/base applications.

Mechanical Parameters of Rubber-Sand Mixtures for Numerical Analysis of a Road Embankment

Waste production is one of the greatest problems of the modern world. It is inevitably related to the increase of industrialization. One of the most difficult, and growing in amounts, waste is scrap tyres. The most common method of utilization of end-of-life tyres by their incineration raises much concern in terms of air pollution. More sustainable seems to reuse the tyre derived products – rubber in particular – in civil engineering, where the interesting properties of this material may be effectively utilized. This paper presents results of direct shear strength tests on sand-rubber mixtures, which were next applied to a numerical FEM (finite element method) model of a road embankment built on soft ground. The laboratory tests, conducted for two types of scrap tyre rubber granulates (0.5 – 2 mm and 1 – 5 mm in size) mixed with medium fluvial sand in various proportions (5, 10, 30 and 50% by weight), proved that the unit weight of the mixtures is distinctly smaller that the unit weight of sand alone and at 50% rubber content it drops by half. The internal angle of friction stays almost unchanged for the mixtures with up to 10% of rubber (33 - 37°), but decreases by about 10° when the rubber content increases to 50%. In most of the cases analysed, the cohesion intercept is higher in case of sand-rubber mixtures when compared to sand alone. The numerical model simulated a 4.5 m high embankment with a 3 m thick layer made of sand-rubber mixtures, containing 0%, 10% or 30% of the waste product, founded on a weak subsoil (with a 3 m layer of organic soil). The results showed that stability factor of the structure built with the layer containing 30% of the coarser rubber granulate has increased from 1.60 – for sand only, to 2.15. The embankment was also able to carry load increased from 32 kPa to 45.5 kPa and its base showed much smaller settlement. The results prove that the use of tyre derived aggregates in embankment construction is not only an effective way of utilization of this problematic waste, but can also improve behaviour of such a structure.

Experimental study on dynamic properties of sand-rubber mixtures in a small range of shearing strain amplitudes

Sand-rubber mixtures has characteristics of light weight, cheap and environmental-friendly, thereby it has a great potential to be used in geotechnical engineering for sustainable development. Dynamic properties (i.e. shear modulus and damping ratio) of sand-rubber mixtures in a small range of shearing strain amplitudes (i.e. 10-6-10-4) were investigated in this study through a series of resonant column tests. The effects of shearing strain amplitude, confining pressure and rubber content on dynamic shear modulus (G), maximum dynamic shear modulus (Gmax), damping ratio (D) and dynamic shear modulus ratio G/Gmax of the mixtures were also discussed. Based on the analyses of the relationship among confining pressure, rubber content and Gmax, an empirical formula for predicting Gmax considering the effects of confining pressure and rubber content was also proposed. The model prediction agreed with the experimental results very well.

Effect of rubber content on the unstable behaviour of sand–rubber mixtures under static loading: a micro-mechanical study

While it has been acknowledged from cyclic laboratory tests that the inclusion of rubber particles increases liquefaction resistance, little attention has been paid to the influence of rubber conte...

Influence of Particle Type on the Mechanics of Sand–Rubber Mixtures

AbstractTriaxial and oedometer tests were used to demonstrate that a critical state framework can be applied to sand–rubber mixtures of similar soil grain and rubber sizes. It described well the be...

Evaluation of Liquefaction Potential in Sand–Tire Crumb Mixtures Using the Energy Approach

This research explores performance of the energy approach for evaluating the liquefaction potential of sand–tire crumb mixtures. Thirty-six stress-controlled undrained cyclic torsional tests were performed under three different confining pressures on samples with different rubber contents. The effect of such parameters as the rubber content and confining pressure on liquefaction behavior of sand–rubber mixtures was studied using the energy approach. Test results indicated that, unlike the observations made on the pure sand sample, in the case of sand–rubber mixture with 25% rubber content, when the initial liquefaction is triggered, the dissipated shear energy increases with continued cyclic loading. The increasing trend is stopped when the pore water pressure reached the initial consolidation stress (Ru = 1). This observation indicates that for the case of sand–tire crumb mixture, the dissipated energy per volume is associated only with the progression of pore water pressure. Moreover, the results show that the required energy for liquefaction occurrence decreases with the increase in the rubber content. The minimum amount of required energy is determined for mixtures with 10% rubber content. As the result, the inclusion of crumb rubber decreases the liquefaction resistance of sand. However, when the rubber content increases from 10 to 25%, the resistance to liquefaction improves. The generation rate for mixture with 25% rubber content is somewhat faster than that of the clean sand and the mixture with 10% tire crumbs, as it is expected.

Properties of Shredded Roof Membrane–Sand Mixture and Its Application as Retaining Wall Backfill under Static and Earthquake Loads

About 20 billion square feet of Ethylene Propylene Diene Monomer (EPDM) rubber is installed on roofs in the United States and most of them will be reaching the end of their lifespan soon. The purpose of this study is to investigate potential reuses of this rubber in Civil Engineering projects rather than disposing it into landfills. First, laboratory tests were performed on various shredded rubber-sand mixtures to quantify the basic geotechnical engineering properties. The laboratory test results show that the shredded rubber-sand mixture is lightweight with good drainage properties and has shear strength parameters comparable to sand. This indicates that the rubber-sand mixture has potential to be used for retaining wall backfill and many other projects. To assess the economic advantage of using shredded rubber-sand mixtures as a lightweight backfill for retaining walls subjected to static and earthquake loadings, geotechnical designs of a 6 m tall gravity cantilever retaining wall were performed. The computed volume of concrete to build the structural components and volume of backfill material were compared with those of conventional sand backfill. Results show significant reductions in the volume of concrete and backfill material in both static and earthquake loading conditions when the portion of shredded rubber increased in the mixture.

Micromechanical analyses of the effect of rubber size and content on sand-rubber mixtures at the critical state

This study presents a series of monotonic drained triaxial tests consisting of mixtures of sand (stiff) and rubber (soft) particles simulated by the discrete element method (DEM). Sets of mixtures were prepared with different rubber size ratio of 1, 2.5 and 5 and contents ranging from 0% to 30% by weight. The numerical samples were sheared up to large axial strains to reach a critical state. The slope of the critical state lines is strongly affected when the rubber size is the same as sand. When rubber size increases, the critical state lines shift downward with little effect on the slope. While it is generally accepted that, for the given range of rubber contents used in the study, the sand-rubber mixture strength increases when adding rubber particles, the results from this study suggest that said strength diminishes as rubber size is incremented. Micro-scale information, including coordination number, geometrical and mechanical anisotropy, was obtained for all the tests. Regardless of the rubber particle size, rubber-sand contacts represent an important contribution to the overall strength of the material; however, the rubber particle size dictates how said contribution takes place. These findings highlight the importance of understanding new geomaterials to practicing engineers that different size ratios and rubber contents have positive or negative effect of strength and deformability and the choice of a sand-rubber mixture has to be based on the project nature.

Dynamic response of bridge abutment to sand-rubber mixtures backfill under seismic loading conditions

China is located between the Pacific Ocean seismic belt and the Eurasian seismic belt where the seismic activity is frequent. Bridge plays a key role in transportation lifeline, but its construction and maintenance face potential seismic hazard in China, which may lead to a huge economic loss. This study investigates the dynamic response of bridge abutment to sand-rubber mixtures backfill under seismic loading conditions by finite element method. Sand-rubber mixtures is composed of waste fibers, rubber particles, sand and water with a certain mixing ratio and dry density It has been used as an anti-seismic backfill material for slopes, retaining walls, bridge structures and other geo-structures. A series of numerical simulations was carried out to evaluate the effectiveness of this new material as backfill material for bridge abutment. The seismic performance of bridge abutment with different backfill materials was analyzed with respect to settlements and accelerations of ground, foundation pile and bridge abutment. The results show that the sand-rubber mixture can be used as backfill material, and has a great potential in reducing the settlements and accelerations of ground and foundation pile.

Investigation of the micro-mechanics of sand–rubber mixtures at very small strains

This study presents a series of discrete element method (DEM) simulations consisting of mixtures of stiff (sand) and soft (rubber) particles, subjected to monotonic triaxial shearing under constant volume at very small strains where pure elasticity governs the behaviour of the samples. The elastic shear moduli of the simulated pure sand and pure rubber samples were first calibrated to values reported in previous experimental works. Sand–rubber mixtures were then simulated with a focus on small-strain stiffness to examine the role of rubber content on the prevailed micro-mechanisms of the samples. The macro-mechanical response of the numerical mixtures showed a decrease in the elastic shear modulus and the deviatoric stress as the soft particle content increased, in line with observations from laboratory tests. Micro-scale information including coordination number, fabric tensor and normal contact force anisotropy was obtained for all tests and the contribution of each type of contact, i.e. sand–sand, rubber–sand or rubber–rubber, in the overall response of the samples, was analysed. The contact force network in the mixtures changed from being sand-dominated to rubber-dominated, with the presence of an intermediate zone in between rubber and sand particles forming a stable contact force network mainly by sand–rubber contacts. Each type of contact was seen to contribute differently to the deviatoric stress in the system as the rubber content increased.

Experimental study on behavior of soil-waste tire mixtures

Waste tires are extensively being used in civil engineering applications to improve flexibility and elastic properties of the base foundation material. Moreover, by using pure tires or soil-tire mixtures, rubber stockpiles which cause lots of environmental contaminations are being consumed. The objective of this research is to study the strength and modulus variations of sands when combined with rubber materials in different sizes and percentages. To this reason, triaxial experiments were performed on various sand-rubber mixtures using static triaxial apparatus. Samples were constructed at the maximum dry density and optimum moisture content to consider engineering applications in dry regions. The results show that rubber content and rubber-sand particle size ratio,D50,r/D50,s, significantly affect the mixture behavior in the manner which increase in the former and decrease in the latter leads to more softening behavior. Furthermore, specific combination of sand and rubber which may improve the elastic properties of the mixture is proposed as a base flexible layer.

Sand – rubber mixtures submitted to isotropic loading: a minimal model

The volume of scrap tyres, an undesired urban waste, is increasing rapidly in every country. Mixing sand and rubber particles as a lightweight backfill is one of the possible alternatives to avoid stockpiling them in the environment. This paper presents a minimal model aiming to capture the evolution of the void ratio of sand-rubber mixtures undergoing an isotropic compression loading. It is based on the idea that, submitted to a pressure, the rubber chips deform and partially fill the porous space of the system, leading to a decrease of the void ratio with increasing pressure. Our simple approach is capable of reproducing experimental data for two types of sand (a rounded one and a sub-angular one) and up to mixtures composed of 50% of rubber.

Experimental and numerical investigation of footing behaviour on multi-layered rubber-reinforced soil

This paper describes the beneficial effects of multiple layers of rubber–sand mixture (RSM). The plate load tests, using circular plate of 300 mm diameter, were performed at an outdoor test pit, dug in natural ground with dimensions of 2000 × 2000 mm in plan and 720 mm in depth to facilitate realistic test conditions. The rubber used in the RSM layers was granulated rubber, produced from waste tires. The optimum thickness of the RSM layer was determined to be approximately 0.4 times the footing diameter. By increasing the number of RSM layers, the bearing capacity of the foundation can be increased and the footing settlement reduced. The influence of the number of RSM layers on bearing capacity and settlement become almost insignificant beyond three layers of RSM, particularly at low settlement ratios. At a ratio of settlement to plate diameter of 4%, the values of bearing pressure for the installation with one, two, three and four layers of RSM were about 1.26, 1.47, 1.52 and 1.54 times greater, respectively, than that for the unreinforced installation. Layers of the RSM reduced the vertical stress transferred through the foundation depth by distributing the load over a wider area. For example, at an applied footing pressure of 560 kPa, the transferred pressure at a depth of 570 mm was about 58, 45 and 35% for one, two and three layers of RSM, respectively, compared to the transferred stress in the unreinforced bed. By numerical analysis, it was found that the presence of soil-rubber layers resulted in expansion of passive zones in the foundation due to the effectiveness of the confinement provided by the rubber inclusions, and this tends to make the bed deflect less. On the basis of this study, the concept of using multiple RSM layers has not only been shown to improve the performance of foundations under heavy loading, but also, the environmental impacts of waste tires are attenuated by re-using their rubber as part of a composite soil material in civil engineering works.