Sand Rubber Research Articles

Performance of geocell reinforced rubber sand mixtures under undrained triaxial test

Large quantities of scrap tires are produced by the automobile industry each year, which causes disposal challenges and impacts the environment. However, scrap tires exhibit various properties, including tensile strength, abrasion resistance, durability, thermal conductivity, elasticity, and more. Due to their versatile characteristics, these scrap tires can be utilized as construction materials for various civil engineering works to reduce their negative environmental effects and conserve natural resources. This study aims to understand the shear strength behaviours exhibited by geocell-reinforced mixtures of rubber and sand through the unconsolidated undrained triaxial test. Various parameters, including rubber sizes (425 μm to 12 mm), rubber contents (10% to 40% by volume), confining pressures (50 to 300 kPa), and geocell heights (0.2H to 0.8H, where H is the height of triaxial sample), were systematically examined to understand their impact on shear strength characteristics. The experimental findings reveal that deviatoric stress is enhanced with increasing confining pressure and rubber sizes. The maximum benefits of the rubber-sand mixture were observed at 30% rubber content. Geocell-reinforced rubber sand mixture has a higher shear strength with respect to the unreinforced mixture. Furthermore, the energy absorption capacity of the geocell-reinforced rubber sand mixtures was much better as compared to either the clean sand or rubber-sand mixture. The findings of this research demonstrate that geocellreinforced rubber sand mixtures are suitable for various geotechnical engineering works.

DEM analysis of the load transfer mechanism of sand-rubber mixtures subjected to constrained compression

Despite the significant progresses in the multi-scale studies of sand-rubber mixtures, the load-transfer mechanism within the soft-rigid granulate networks is highly unexplored. In this study, roles of sand and rubber particles in different contact networks subjected to constrained compression were investigated using DEM. The simulations were respectively calibrated using experimental data at element and grain scales, providing an opportunity to look at the role of rubber within whole granulate networks. When the behavior of mixtures is dominated by sand (rubber content <30%), the constitutive responses at sand - sand, sand - rubber and rubber - rubber contacts can be described by the Hertz contact model; within this range, the rubber majorly formulates the weak and intermediate contacts, but sliding fraction in the strong network increases with rubber content. A more homogeneous fabric and a lower deviatoric stress at the strong network were observed after rubber inclusion.

Experimental Investigation on the Compressive Behavior of Rubber–Sand Mixtures under Repeated Loading–Unloading

Experimental Investigation on the Compressive Behavior of Rubber–Sand Mixtures under Repeated Loading–Unloading

Experimental analyses of high-filled cut-and-cover tunnel for reduction of the earth pressure

ABSTRACT The pressure distribution over buried structures like pipes and tunnels are considered a main factor in the economic design of such structures. This study shows the effect of using crumb rubber mixed with sand and geogrid layers to enhance the soil pressure distribution over that buried structure. That method is titled a high-filled cut-and-cover (HFCCT) construction method. Crumb rubber particles pieces mixed with sand as a lightweight fill material (LFM) in HFCCT are used to reduce the vertical earth pressure (VEP) on that buried tunnel. Geogrid reinforcement layer above the HFCCT system to strengthen the soil layers above the tunnels were implemental. A physical model is built to simulate such conditions by applying external loads to the treated soil layers above the tunnel. The strains are measured on the external body of the tunnel, while the soil pressure is assessed through pressure gauges around the tunnel. The results obtained from the crumb rubber models are compared with those obtained from the geogrid model. It was deduced that using crumb rubber and geogrid, reduces the earth pressure above the cut-and-cover tunnel (CCT). As compared to the use of geogrid, the utilization of rubber as a substitute for soil results in a 27% drop in pressure. The obtained results show that the use of geogrids in sandy soils leads to uniform stress, while using rubber sand could reduce the maximum stress of the soil above the tunnel.

Enhancing energy absorption in rubber–sand (Ru–San) composite blocks against ballistic impact: a multi-objective optimisation approach

Enhancing energy absorption in rubber–sand (Ru–San) composite blocks against ballistic impact: a multi-objective optimisation approach

Rubber-sand infilled soilbags as seismic isolation cushions: experimental validation

This study proposes the use of soil bags filled with a rubber sand mixture (SFRSM) to address the issue of weak stability associated with rubber-sand layers for seismic isolation. To evaluate the dynamic characteristics of the SFRSM, large-scale cyclic simple shear tests were conducted to investigate the effects of rubber content, vertical pressure, shear displacement amplitude, fill percentage, and laying scheme. Furthermore, shaking table tests were carried out to evaluate the impact of vibration intensity and frequency on the seismic isolation of SFRSM layers. The results indicate that (1) Compared to the rubber-sand layer, the SFRSM exhibits a lower shear modulus and higher damping, indicating its potential for greater seismic isolation and energy dissipation. (2) The dynamic characteristics of the SFRSM were significantly influenced by the fill percentage and laying scheme, suggesting that an effective isolator capable of withstanding various external conditions could be developed. (3) The isolating effect of the SFRSM layer is attributed to its ability to dampen high-frequency vibration components effectively. Additionally, the threshold frequency required to trigger attenuation decreases with an increasing number of SFRSM layers. In summary, these experimental results provide evidence that the proposed innovative strategy enhances the strength and vertical stiffness of the original rubber-sand layer, making it well-suited for seismic design applications in low-rise buildings in less-developed regions. Highlights 1. A novel seismic isolation strategy using the soil bags filled with rubber-sand mixture (SFRSM) was proposed. 2. Large-scale cyclic simple shear tests were conducted to evaluate the dynamic properties of SFRSM. 3. The influence of key parameters on the dynamic shear modulus and damping ratio of SFRSM was analysed. 4. The proposed strategy is well suited for the seismic design of low-rise buildings in less-developed regions.

Experimental Study on the Critical-State and Energy Dissipation Behaviors of Rubber–Sand Mixtures

Experimental Study on the Critical-State and Energy Dissipation Behaviors of Rubber–Sand Mixtures

Magnetic activation water Technology improved reused crumb rubber cement mortar

This experimental study explores the impact of Magnetic Activation of Water (MAW) on the fresh and hardened properties of Reused Crumb-Rubber Mortar (RCRM). Eight different mortar formulations were produced, comprising four variants using potable water (DW) and four utilizing MAW, with varying percentages of Reused Crumb Rubber Sand (RCRS) substituted for natural sand at rates of 0%, 4%, 8%, and 12%. The analyses of fresh properties indicated that MAW effectively reduced entrapped air and improved the consistency of the RCRM mixtures. In terms of hardened properties, MAW demonstrated a significant enhancement in compressive strength and hydration kinetics of RCRM compared to those made with DW. This innovative approach of employing magnetic activation not only addresses compatibility and heterogeneity challenges typically associated with rubber-cement mixtures but also offers a viable solution for incorporating waste rubber into cement composites. Ultimately, this research presents a promising avenue for improving the mechanical and physical characteristics of recycled materials in sustainable construction practices.

Applicability of critical void ratio theory for liquefaction potential assessment of Rubber Sand Mixture (RSM)

Applicability of critical void ratio theory for liquefaction potential assessment of Rubber Sand Mixture (RSM)

A Dynamic Assessment of Rubber–Sand Mixtures as Subgrade Materials during Vibratory Roller Compaction through DEM Simulation in 2D

The accumulation of discarded tire rubber poses significant challenges in terms of land usage and environmental hazards. To address this issue, this article explores the potential reuse of rubber in roadbed engineering. This study conducts a comprehensive examination of the vibration compaction process involving a vibratory roller and rubber–sand mixtures, utilizing the discrete element method (DEM) in a two-dimensional (2D) framework to investigate the impact of dynamic vibration compaction on sand mixtures with varying rubber contents under different roller working conditions, while also evaluating the associated energy consumption. The results reveal that both the rubber content and operational parameters of the roller significantly influence compaction vibration effects. Notably, optimal rolling frequency, velocity, and rolling mass show correlations with the rubber content. Furthermore, this research provides a microscopic understanding of the compaction process, offering detailed insights into displacement fields, velocity fields, and contact forces.

Macro and micro analyses of static and dynamic shear characteristics of geogrid and rubber–sand mixture interface

A rubber–sand mixture (RSM) can be used as a novel type of geotechnical material in reinforced roadbeds and other projects owing to its being elastic and environment friendly. To explore the static and dynamic shear characteristics of the geogrid and RSM interface, monotonic direct shear (MDS), cyclic direct shear (CDS), and post-cyclic monotonic direct shear (PCDS) experiments were performed in this study. The effects of rubber content (χ) and particle size ratio (r) on the interface shear characteristics were studied. A dynamic model of the rubber–sand mixture was established using PFC3D, and mesoscopic analysis of the cyclic shear process was conducted. The results of the CDS experiments indicated that the peak shear stress with χ = 10 % was the largest. The peak strength and residual strength of PCDS were larger than those of MDS under the same χ and r. After cyclic shearing, the interface apparent cohesion of various rubber contents and particle size ratios increased by 78 % ∼ 172 %. During cyclic shearing, the porosity and particle energy in the shear box changed periodically, and the porosity near the interface was slightly higher than that in the other areas. The kinetic energy of the particles was closely related to the shear displacement.

Numerical Simulation of Geotechnical Isolation of Building Subjected to Earthquake Using Rubber Sand Mixtures

The use of recycled rubber in various civil engineering applications has seen a considerable rise in recent years. The rubber-soil mixture can exhibit a higher energy absorption capacity than soil alone, which would reduce the energy applied to structures, the stresses, and shocks they undergo. Base isolation is the process of isolating the base of a structure to limit the effects of earthquakes, so that the seismic forces applied to the base of the bedrock cannot move with the same intensity towards the super structure.In this work, the beneficial effects of rubber mixtures (RSM) in mitigating earthquakes when these mixtures are inserted as layers in the soil profile are highlighted; the approach is based on a method of using worn tires for seismic protection applications for infrastructures subjected to seismic loads. It involves mixing particles from used tires with soil materials and placing the mixtures under the foundation of the building as geotechnical insulation systems for vibration absorption.The foundation of a four-storey building is implanted in a soil profile in which a layer of rubber-sand mixture (RSM) has been inserted; to perform the role of seismic isolation when subjected to seismic excitation.The investigation is focused on the variation in the thickness of the layer on the one hand (between 1m and 4m), and on the other hand on the position of this layer in the soil mass (top, middle and bottom of the profile).The peaks of horizontal accelerations recorded at the base and top of the structure show that the sand-rubber mixture has adequate and promising potential for their application as seismic isolation materials for low-rise buildings. Moreover, the thickness of the layer and its location are two very determining parameters in the improvement of the performances of these RSM mixtures, especially in terms of reduction of the acceleration peak recorded.

Shaking table study on rubber-sand mixture cored composite block as low-cost isolation bearing for rural houses

Historical and recent earthquakes have caused severe damage to rural houses worldwide, which are often characterized by low story heights, high stiffness, and limited budgets. In this regard, low-cost seismic isolation strategies hold great potential for protecting low- and medium-rise buildings. This paper proposes a novel rubber sand mixture cored composite block (RSMCB) as a low-cost alternative to conventional expensive isolation bearings. The construction of the RSMCB involves filling the hollow of a plain concrete block with a lightweight material made of granulated rubber and natural sand and then covering the surface with a square brick slightly smaller than the hollow's size. To evaluate the effectiveness of the RSMCB, a series of shaking table tests were conducted, covering factors of rubber content, cover plate size, upper block mass, and paving mode. The results indicate that the utilization of the RSMCB layer effectively mitigates large displacement in the superstructure during the cyclic loading, thereby functioning as an energy dissipation and seismic reduction measure. Moreover, the isolation effect of the RSMCB layer increases with the seismic intensity attributed to the nonlinear variation of dynamic parameters of the mixed granular material with shear strain. These findings suggest that the proposed isolation strategy improves the strength and vertical stiffness of the original sand-rubber layer, making it a desirable and sustainable solution for seismic design applications in rural housing.

Theoretical calculation model for the thermal conductivity of scrap tire rubber–sand mixtures based on soil components

Theoretical calculation model for the thermal conductivity of scrap tire rubber–sand mixtures based on soil components

Stress–strain–strength behavior of geosynthetic reinforced rubber–sand mixtures

Stress–strain–strength behavior of geosynthetic reinforced rubber–sand mixtures

Experimental Study on the Effect of Ultrafine Mineral Admixtures on the Mechanical Properties of Cement Mortar

Objective: The effect of ultrafine mineral admixtures on the mechanical properties of grouting mortar was studied. Methods: In this paper, the compressive strength and flexural strength of the mortar with different contents of ultrafine mineral admixture replacing cement were tested respectively, and the heat of hydration was tested. XRD and SEM were used to analyze the changes in the microstructure characteristics after the addition of ultrafine mineral admixture. Results: after the addition of 5% ultrafine mineral admixture, the fluidity of cement slurry decreased by 25. 3%, and the fluidity gradually decreased with the gradual increase of ultrafine mineral admixture. With the addition of superfine mineral addition, The compressive strength increased steadily and gradually decreased thereafter, while the content of superfine mineral added was 20%, the strength of rubber sand reached the maximum value at 28 days, which increased by 23. 76% compared with the test block without admixture. The flexural strength of 3d and 7d of rubber sand was weakened by the incorporation of ultrafine mineral admixture, and the flexural strength of 28d increased slowly with the incorporation of ultrafine admixture, and the flexural strength value reached the maximum when the dosage was 25%. The heat of hydration and microstructure analysis showed that the sand system produced more hydrated calcium silicate gel filling into the structure of the sand after the addition of ultrafine mineral admixture. Conclusion: a certain amount of ultrafine mineral admixture has remarkable influence on the compression strength of rubber sand, and the flexural strength of 3d and 7d is weakened, and increases the flexural strength of 28d.

Experimental Static and Dynamic Characteristics of Recycled Waste Tire Rubber Particle-Cement-Sand Composite Soil.

To investigate the static and dynamic characteristics of rubber-sand composite soil (RS soil) reinforced with cement, a series of triaxial compression tests and resonant column tests was performed by considering the influence of rubber content (10%, 20%, 30%, 40%, and 50%), cement content (0, 1.5, 2.5, 3.5 and 4.0 g/100 mL), and effective consolidation confining pressure (50, 100, and 150 kPa). Compared with the RS soil, the addition of cement significantly improved the shear strength of a cement-rubber-sand composite soil (RCS soil), based on an undrained shear test. The increase in cement content not only makes the elastic modulus and cohesion of the RCS soil increase but also reduces the internal friction angle of the RCS soil. With the increase in rubber content, the failure of the RCS soil samples changes from strain-softening to hardening, and the prediction equation of the initial elastic modulus of the RCS soil is given herein when the recommended cement content is 3.5 g/100 mL. The effects of rubber content, cement content, and effective confining pressure on the dynamic shear modulus and damping ratio of the RCS soil were studied via the resonant column test. The test results show that the increase in rubber content slows down the modulus attenuation of the RCS soil, but increases its damping ratio. The test results also show that the increase in cement content makes the bonding force between particles greater so that the modulus attenuation of the RCS soil becomes slower and the damping ratio is reduced. At the same time, according to the change rule of the maximum dynamic shear modulus of the RCS soil with the rubber content, when the recommended cement content is 3.5 g/100 mL, an empirical formula and recommended value of the shear modulus Gmax of the RCS soil are proposed.

Geotechnical Seismic Isolation System Based on Rubber-Sand Mixtures for Rural Residence Buildings: Shaking Table Test

The anti-seismic problem of rural residential buildings is the weak link of seismic retrofitting in China. Recently, geotechnical seismic isolation (GSI) technology based on rubber-sand mixtures (GSI-RSM) using rubber-sand mixtures (RSM) between the structural foundation and the foundation soil has been proven to have the possibility of potential applications in rural residential buildings. Many theoretical studies exist on the effectiveness of seismic isolation of the GSI-RSM system, but few studies on either the seismic response test of model buildings placed on the RSM layer or the large-scale shaking table test exist. Therefore, this study considers a large shaking table test performed on a 1/4 single-story masonry structure model with and without a GSI-RSM system by selecting a standard input ground motion and varying input acceleration amplitudes. The test results show that the GSI-RSM system can reduce the seismic response of superstructures. The isolation effect of the GSI-RSM system is low in small earthquakes and increases with increasing earthquake magnitude. Overall, the RSM layer can filter part of the high-frequency components of the earthquake to transmit to the superstructure and consume more seismic energy by generating friction slip in the interaction with the structural foundation.

Dynamic behavior of geocell-reinforced rubber sand mixtures under cyclic simple shear loading

Due to the attributes of low shear modulus and high initial damping, rubber sand mixtures (RSM) can be used as a soil alternative to reduce ground motions when seismic loads are of great concern. However, when RSM is used as a vibration isolation material for geotechnical seismic isolation systems, it suffers from a lack of load-bearing capacity. To overcome this, a three-dimensional interconnected geocell (one type of geosynthetics) is placed within RSM to increase the vertical confinement of the system. In this technical note, to investigate the shear modulus and damping ratio of geocell-reinforced RSM, large-scale cyclic triaxial tests were conducted on specimens prepared with four granulated rubber contents (by weight) and sheared under different cyclic shear strain amplitudes. The results show that Geocell reinforcement can restrict the development of local shear bands in the specimen, weaken the anti-S-shaped characteristics of hysteresis loops and enhance the damping ratio of RSM at large strain amplitudes. The tuck net effect causes an increase in the normal stress of both contact particles, and then leads to the degradation rate of the maximum shear modulus of RSM varying with the rubber content and vertical pressure. The normalized shear modulus degradation curves show the influence range of geocell reinforcement, and demonstrate that a rubber content of 20% for reinforced specimen may be an optimal value from the perspective of the stability of dynamic properties. Additionally, the quantitative analysis of the effect of geocell reinforcement on the mechanical behavior of RSM can provide a reference for subsequent theoretical research and engineering applications.

Experimental study on cyclic shear characteristics of geogrid and rubber–sand mixture interface

Rubber–sand mixtures are an excellent alternative backfill material in geotechnical engineering. To study the dynamic shear characteristics of the geogrid and rubber–sand mixture interface, cyclic direct shear tests were conducted to analyse the effects of rubber content, particle size ratio (r), normal stress, and shear displacement amplitude (A). The variation law of shear stiffness and damping ratio was also analysed. The results revealed that, as the rubber content increased, the shape of the hysteresis loop evolved from a full fusiform to a flat state; as r decreased, the hysteresis loop became flatter. The peak shear stress was the largest (increased by 5.4%–15.7%) when the rubber content was 10%. When the rubber contents were 10% and 30%, as r increased, the interface peak shear stress increased. The geogrid and rubber–sand mixture interface exhibited shear hardening when A = 3 mm and shear softening when A = 12 mm. When A = 6 mm, the interface with rubber contents of 10%, 30% and 50% tended to transition from shear softening to shear hardening. The damping ratio was the largest (increased by 9.3%) when the rubber content was 10%. Additionally, as r increased, the shear stiffness and damping ratio increased.