Crumb Rubber Asphalt Mixture Research Articles

Effect of nano silica on the performance of modified crumb rubber bitumen and asphalt mixtures

Effect of nano silica on the performance of modified crumb rubber bitumen and asphalt mixtures

Modeling and design optimization of dense graded modified crumb rubber asphalt mixtures using response surface methodology

Modification of asphalt pavement materials by using recycled waste tires in form of crumb rubber (CRM) is getting significant importance for saving resources as well as protecting ecosystem. So, in this study the crumb rubber size and percentage content effect on the performance properties of binder and mixtures were evaluated. A detailed experimental program has been performed using design expert software considering the variables like rubber size and content and their responses which were viscosity, Indirect Tensile strength (ITS), Tensile strength ratio (TSR) durability and Resilient Modulus (Mr). The viscosity of control binder with the addition of crumb rubber at high temperatures showed good improvement. The performance properties viz., ITS, TSR and Mr showed similar behavior as the size and content of crumb rubber increased under different loading conditions. The statistical models prepared using the analysis tool were found significant and well fitted based on high R2 (>0.80), high adequate precision value (>4), insignificant lack of fit and low p-value. Analysis of variance (ANOVA) model theoretical results generated by the response surface methodology (RSM) analysis were further validated by the experiments with <5 % of error showing good agreement between theoretical and experimental results. Study results showed that modified binder with 10 % crumb rubber passing sieve No. 40 in mixtures showed good improvement of mechanical properties indicating the potential source of recycled waste material usage in the pavement construction.

Designand Properties of Crumb Rubber Aggregates Additive in Hot Mixture Asphalt Concrete

Abstract: This research aims to establish the design and properties of crumb rubber aggregates additive in hot mixture asphalt concrete. Rubber crumb is rubber waste which is processed through mechanical grinding or tire milling into small splinters. The objective of this research is to have high durability of flexible pavement with different percentages of crumb rubber. The experiment was done respectively through several phases as follows: preparation, quality examination of materials such as aggregate and asphalt, mixed-planning, and specimen testing implementation with Marshall Test. Properties of crumb rubberlike type stability and flow of durability can affect the different stability and flexibility of pavement. The data collected from the laboratory experiments were presented in different forms like tables, charts, diagrams, etc. The results from the crumb rubber asphalt mixture show that there is an increase in the amount of crumb rubber in a mixture of hot mix concrete asphalt. This mixture can increase the Marshall stability by 2.5 % crumb rubber higher than the other mixtures with crumb rubber.

A Multiscale Study of Moisture Influence on the Crumb Rubber Asphalt Mixture Interface

In order to study the influence of moisture on the interface of crumb rubber–asphalt (CR) mixture, the interface bonding performance and crack resistance of a crumb rubber–asphalt mixture under dry and wet conditions were studied at three scales. At the macroscale, the characteristics of medium temperature fatigue cracking and low temperature fracture were studied by semi-circular bending tensile test (SCB) on the example of digital image correlation (DIC) technique. At the microscale, the surface energy of CR with basalt and limestone was measured using the contact angle measurement test, and then the adhesion work was calculated and analyzed. At the molecular scale, the model of CR, the model of basalt representative mineral (augite) and limestone representative mineral (calcite) were studied by molecular dynamics simulation. The relationship between these three scales was further explored to reveal the mechanism of the damage of moisture on the interface deterioration of the CR mixture. The results show that moisture has a certain effect on the interface of the CR mixture, which is characterized by macroscopically reducing the crack resistance of the asphalt mixture, microscopically reducing the adhesion ability between the asphalt and the aggregate and weakening the interaction between the asphalt and aggregate molecules at the molecular scale. Molecular dynamics can accurately simulate the deterioration of micro asphalt-aggregate adhesion under the damage of moisture. The decrease in microadhesion leads to the decrease in the crack resistance of the macro-CR mixture.

Mechanical properties evaluation of crumb rubber asphalt mixture for elastic trackbed

As a new type of railway structure, the elastic trackbed can avoid the inherent limitations of railway ballast tracks and slab tracks. Therefore, it is of great significance to provide excellent materials for the elastic trackbed. In this paper, the feasibility of applying crumb rubber asphalt mixture (CRM) to the railway trackbed is preliminarily investigated by evaluating the mechanical properties of CRM. The static modulus, vertical deformation and lateral stability of CRM for the elastic trackbed are characterized via the uniaxial compression test as well as the interfacial shear test. In addition, via the dynamic creep test, the temperature susceptibility, the viscoelastic behaviours as well as the creep compliance master curve of CRM are studied. The uniaxial compression results show that the stiffness of CRM with 3 wt% and 6 wt% crumb rubber particles decreases compared with the ordinary asphalt mixture. And the vertical deformation can also meet the requirements of the elastic trackbed. Furthermore, it is shown from the shear test that the interfacial strength, which presents a linear relationship with temperature, can provide satisfactory lateral stability of the elastic trackbed. Additionally, the dynamic creep test results reveal that the addition of 3 wt% crumb rubber will not lead to excessive accumulation and the increased temperature susceptibility of permanent deformation at high temperature. The viscoelastic parameters gained from the dynamic creep test also show that asphalt mixture with 6 wt% crumb rubber particles shows the worst resistance to deformation despite having the best recovery performance. Finally, the creep compliance master curve of CRM between 10-2 to 109 domain can be obtained by horizontally shifting the creep curves at high temperature. And the horizontal shift factors can be gained. Then, the long-term deformation of the elastic trackbed under the dynamic train load can be predicted by using the equivalent conversion loading time from the short-term dynamic creep test results at 25 ℃ and 0.25 MPa.

Functional and environmental performance of plant-produced crumb rubber asphalt mixtures using the dry process

Incorporating crumb rubber (CR) using the dry process, directly in the asphalt mixture rather than into the bituminous binder requires no plant retrofitting, and therefore is the most practical industrial method for CR incorporation into asphalt mixtures. Nevertheless, very few large scale studies have been conducted. This work uses a holistic approach and reports on the functional and environmental performance of asphalt mixtures with different concentrations of CR fabricated employing the dry process in asphalt plants. Gaseous emissions were monitored during the production and laboratory leaching tests simulating the release of pollutants during rain, was conducted to evaluate the toxicology of both the CR material alone and the modified asphalt mixtures. In addition, laboratory compacted samples were tested to assess their fatigue behavior. Furthermore, noise relevant surface properties of large roller compacted slabs were evaluated before and after being subjected to a load simulator (MMLS3) to evaluate their resistance to permanent deformation. The results confirm that comparable performance can be achieved with the incorporation of CR using the dry process for high performance surfaces such as semi-dense asphalt, which usually require the use of polymer modified binders. Environmental performance improvement can be achieved by a washing step of the CR material that could remove polar CR additives which have commonly been used as vulcanization accelerator during rubber production.

Mechanical Properties Evaluation of Crumb Rubber Asphalt Mixture for Elastic Trackbed

Mechanical Properties Evaluation of Crumb Rubber Asphalt Mixture for Elastic Trackbed

Normalized comparative study on fatigue characteristics of different pavement materials

At present, many test methods and models have been used to evaluate the fatigue performance of pavement materials. However, different test methods and material types have a significant impact on the fatigue result evaluation. Thus, to evaluate the fatigue characteristics of different pavement materials under diverse test methods, the strength and fatigue performance of three pavement materials were characterized through direct tension, uniaxial compression, and indirect tensile tests at multiple loading rates and stress levels. In this paper, three pavement materials, such as SBS-modified asphalt mixture (SBS-MAM), crumb rubber asphalt mixtures (CRAM), and cement-stabilized macadam (CSM), were tested. On this basis, the strength yield surface models related to loading rates and the fatigue normalized unified model of three pavement materials under various stress states were established. Comparing the differences among the three pavement materials' fatigue performance, the results show that the fatigue results of the three pavement materials were completely different under dissimilar test methods. The conventional fatigue equation cannot evaluate the influence of specimen size and stress state on fatigue performance. However, the fatigue normalization model established in this paper can settle these problems. It is also clear that the fatigue performance of CSM is superior to those of the other two mixtures when the stress level is small. However, the fatigue life of CSM is significantly more sensitive to the stress level than those of the other two mixtures. Based on the establishment and comparative analysis of the normalized models of fatigue characteristics of different pavement materials, the scientific conversion of pavement material fatigue to structural fatigue is realized, which provides sights into the anti-fatigue design of pavement structures.

The cracking characteristics of the polymer-modified asphalt mixture before and after aging based on the digital image correlation technology

To study the effect of thermo-oxidative aging on the cracking characteristics of the crumb rubber asphalt mixture (CR-MA) and the styrene–butadienestyrene asphalt mixture (SBS-MA), the image acquisition of loading processes of the semi-circular bending (SCB) test of two polymer-modified asphalt mixtures was carried out by the digital image correlation (DIC) technology. The horizontal strain of test specimens during loading processes was calculated by the VIC-3D software. The new indexes for evaluating the meso-cracking characteristic of asphalt mixtures were proposed. Through the bending beam rheological (BBR) test of asphalt and the contact angle measurement test of asphalt-aggregates, the cracking characteristics of CR-MA and SBS-MA were analyzed from two aspects of cohesion and adhesion failure before and after aging. The results indicated that the new indexes (the horizontal strain density DE and the horizontal strain toughness JE) for evaluating the meso-cracking characteristic of asphalt mixtures had a good correlation with the results of BBR and the contact angle measurement test. The cracking resistance and adhesion of two polymer-modified asphalt were reduced after aging, which led to the decline in the cracking resistance of CR-MA and SBS-MA. The cracking resistance and adhesion of CR-modified asphalt were better than that of SBS-modified asphalt under the same conditions, which meant the cracking resistance of CR-MA was better than that of SBS-MA before and after aging. Compared with SBS-MA, CR-MA had more excellent anti-aging properties.

A New Type of Crumb Rubber Asphalt Mixture: A Dry Process Design and Performance Evaluation

To obtain a crumb rubber asphalt mixture with excellent performance, this study combined trans-polyoctenamer rubber (TOR), crumb rubber, and other additives to establish a new type of crumb rubber (CRT). The objective of this study was to design and evaluate the road performance of the new type of crumb rubber asphalt mixture (CRTAM) with a skeleton dense texture through a dry process. First, the skeleton intrusion compact volume method was used to optimize the grading of coarse and fine aggregates, and the design of the CRTAM gradation was carried out through the same and unequal volume replacement grading method. Then, three types of road performance were analyzed: high-temperature stability, low-temperature crack resistance, and water stability. The results showed that 2% and 2.5% CRT met a low-temperature index with equal volume substitution, and the six gradations obtained by unequal volume replacement with 2% CRT complied with the requirements of a skeleton dense texture. When the substitution ratio was 1.5 and 0.5, the high-temperature performance was better. In addition, when the substitution ratio was 0.5, the flexural strain energy density was the highest and the low-temperature performance was the best. Including considerations of economic benefits, it is recommended that the CRT content be 2% and the substitution ratio be 0.5.

Durability Evaluation Study for Crumb Rubber–Asphalt Pavement

In this study, the failure mechanism of crumb rubber–asphalt pavement was analyzed under the combined effects of low temperature, water, and traffic load. The investigation was carried out based on the mechanical and deformational properties of crumb rubber–asphalt mixture and the typical environmental and load conditions such pavement is typically exposed to. A method was proposed for objective evaluation of the interfacial adhesion between rubber crumbs and asphalt through consideration of the effects of the characteristics of the materials and the working environment. The main evaluation method used herein included the indirect tensile strength test under freeze–thaw–boiling cycle, and the Cántabro abrasion test under water-immersion was adopted as an auxiliary method. The evaluation system has the advantages of simple implementation, realistic simulation of the actual working state of the mixture, and reliable results. Moreover, it is a durability evaluation method that can be specifically applied to asphalt mixtures with some special aggregates or stone mastic asphalt (SMA) mixtures.

Crumb rubber asphalt mixtures by dry process: Assessment after eight years of use on a low/medium trafficked pavement

Abstract This article addresses the 8 years behaviour of a crumb rubber asphalt mixture produced by the dry process (ARdry). Structural and functional characteristics of the pavement were surveyed at the opening to traffic after rehabilitation (2009) and 8 years after (2017). Both situations were compared for structural soundness with data from Falling Weight Deflectometer (FWD) campaigns; and for functional characteristics, using indicators for roughness, skid resistance, texture, and a quality index (QI) based on those indicators together with information extracted from drilled samples and a visual survey. The comparison permits to state that ARdry behaved in a very robust way.

Analysing Properties of Asphalt Concrete Modified with Crumb Rubber Compare to Other Mixture

Several researchers have been undertake in finding alternative materials in order to be used as a modifier in asphalt mixture for the purpose of improving its properties. This research presents a study of laboratory evaluation on the performance of hot-mixed asphalt (HMA) using crumb rubber as an additive. It is noted that crumb rubber was identified to have potency as a modifier in HMA due to the elastic behavior exposed by the rubber particles, especially in reducing the rutting potential. This study fine crumb rubber Shred (2.36-0.85 mm) obtained by ambient-temperature grinding process from discarded truck tires, was used to modify asphalt concert. The fine crumb rubber with different contents, i.e. 2.5%, 5%, 7.5% and 10%, was incorporated into the mixture by using dry and wet process method in differentent temperatures. The Marshal properties, Unconfined Compressive Strength (UCS), Indirect Tensile Strength test (ITS) and Indirect Tensile Strength Modulus (ITSM), Permeability were conducted. The result showed that marshal stability, Marshal Quotient, Voids in Mix (VIM) and Voids in mineral aggregate (VMA) decreased with the increasing crumb rubber modifier. However, Marshal Flow and Void filled with asphalt (VFWA) increased when crumb rubber modifier was increased. The crumb rubber asphalt mixture result indicated has increased amount of crumb rubber in asphalt concrete mixture will decrease the Marshall Stability and permeability test shows that asphalt concrete without crumb rubber lower than AC with crumb rubber strength compare to other mixture.

Experimental study of stable crumb rubber asphalt and asphalt mixture

This study aims to analyze the road performance of plant-produced crumb rubber asphalt (PRA) based on wet process by comparing with base asphalt, styrene–butadienestyrene (SBS) modified asphalt, and field-produced rubber asphalt (FRA). Through infrared spectrum (IR) analysis and differential scanning calorimeter (DSC) tests, the microstructure of each binder were analyzed and compared. Dynamic Shearing Rheometer (DSR) with different test modes were utilized to analyze the rutting resistance and fatigue property of each binder while Bending Beam Rheometer (BBR) test was used to analyze the low-temperature properties of each binder. Asphalt mixtures were prepared with different binders and the road performances including high-temperature rutting resistance, low-temperature cracking resistance, moisture stability and fatigue failure resistance were evaluated. The findings indicate that the plant-produced crumb rubber asphalt shows good storage stability and satisfied road properties compared to other binders while the asphalt mixture prepared with plant-produced crumb rubber asphalt shows satisfied road performances. In general, the study indicates that the plant-produced crumb rubber asphalt could be a promising replacement for SBS modified asphalt based on the mixture type evaluated.

Study on affecting factors of interface crack for asphalt mixture based on microstructure

A crumb rubber (CR) asphalt mixture was tested using a combination of semi-circular bending (SCB) and the digital speckle correlation method (DSCM) to analyze the change of the displacement and strain fields during loading. The two-dimensional (2D) cohesive zone model (CZM) of the CR asphalt mixture semi-circular specimen was established by the finite element analysis software ABAQUS, which was used to carry out numerical simulations. The reliability of the simulation results were tested using the DSCM results. The DSCM and CZM numerical simulation were combined to study the affecting factors of the asphalt mixture interface crack in terms of its microcosmic view. The results show that the finite element simulation results highly inosculated the DSCM test result. The results of the finite element cohesive zone model simulation indicate that the interface crack of the asphalt mixture was mainly effected by critical stress, interface angle of inclination, interface length, and interface location. The stress intensity factor calculated by the finite element shows that the asphalt mixture crack expansion was mainly affected by the crack length, crack angle of inclination, and crack location.

Mechanism and Performance Evaluation of Different Crumb Rubber Modified Asphalt

This study aims to characterize the mechanism and performance of different crumb rubber modified asphalt including the desulfurized crumb rubber asphalt and the common crumb rubber asphalt. Component analysis and Gel Permeation Chromatography test were used to reveal the performance mechanism of different crumb rubber asphalt. Superpave tests were conducted for performance evaluation of different crumb rubber asphalt at the low and high temperatures. Separation test was conducted to compare the storage stability of different crumb rubber asphalt. Mix designs and performance tests were conducted to evaluate the high temperature rutting resistance, low temperature cracking resistance, moisture stability, and fatigue life of different rubber asphalt mixtures. The results show that the crumb rubber mainly exists in asphalt independently while most of the desulfurized rubber can be digested into asphalt and partially changes the components and microstructure of asphalt. The most obvious difference between the crumb rubber asphalt and the desulfurized rubber asphalt was observed for viscosities. The crumb rubber asphalt show better performance than the desulfurized rubber asphalt based on Superpave performance testing results, while the desulfurized rubber asphalt shows better storage stability. Compared to the crumb rubber asphalt mixture, the compaction temperature of desulfurized rubber asphalt mixture can be lowered by 10 to 20℃ to achieve the same performance requirements.

Characteristics of desulfurized rubber asphalt and mixture

This paper investigated the modification mechanism of the desulfurized rubber asphalt, and compared its performances with those of crumb rubber asphalt. The microstructures of desulfurized rubber asphalt and crumb rubber asphalt were identified by using the scanning electron microscope technology, component analysis and infrared spectrum analysis. Conventional and Strategic Highway Research Program (SHRP) performance tests were conducted to evaluate the performances of desulfurized rubber asphalt and crumb rubber asphalt. Mixture performance tests were also performed to characterize the high temperature rutting resistance, low temperature cracking resistance, moisture stability and fatigue life of the desulfurized rubber asphalt mixture and crumb rubber asphalt mixture. It was found that the modification mechanisms of desulfurized rubber asphalt and crumb rubber asphalt are different. The desulfurized rubber can integrate into the asphalt while the crumb rubber mainly exists incompatibly in asphalt. This difference results in the various performances between the desulfurized rubber asphalt and crumb rubber asphalt. Both crumb rubber and desulfurized rubber can improve the performance of asphalt binder and mixture, but the desulfurized rubber asphalt has much lower viscosity and better storage stability than the crumb rubber asphalt. The preparing temperature of the desulfurized rubber asphalt mixture can be reduced by 10∼20°C compared to the crumb rubber asphalt mixture. Moreover, without the interference of solid rubber particles, the desulfurized rubber asphalt can be used in dense-graded asphalt mixture while crumb rubber asphalt mixture tends to use gap gradation with high asphalt content.

Mechanical performance of dry process fine crumb rubber asphalt mixtures placed on the Portuguese road network

This paper evaluates the mechanical response of two gap-graded asphalt rubber mixtures manufactured by the dry process (ARdry). The observed behaviour is compared with that of a similar gap-graded mixture without rubber granulate, used as reference. The laboratory results are also compared with analogous asphalt rubber mixes produced elsewhere by the wet process (ARwet). The blends were produced in a plant and laid in trial sections and on the Portuguese road EN 370, in order to collect representative specimens for laboratory testing. The mechanical evaluation of the mixes was carried out by repetitive four-point bending tests and wheel-tracking tests. The laboratory results and the behaviour observed on the EN 370 allow us to conclude that mechanical performance of the tested ARdry is better than that measured for the reference blend, and is at the same level of performance as ARwet, provided that a proper mixture design and some construction directives are used.

Study on Durability of Granulated Crumb Rubber Asphalt Pavement Based on TPS High-Viscosity Asphalt

In order to improve the durability of granulated crumb rubber asphalt pavement, different amount of TPS modifier are added into granulated crumb rubber asphalt mixture to do tests of water-boiling, water immersion, immersing Marshall, cantabro immersion and some other indoor experiments. Through comparing with base asphalt and SBS modified asphalt, we found that the adhesion ability of asphalt and mineral aggregate and crumb rubber were granulated after adding TPS modifier. The water stability of granulated crumb rubber asphalt mixture is improved. The durability of granulated crumb rubber asphalt mixture has also been improved dramatically. In additions, the optimum mixing volume of TPS for granulated crumb rubber asphalt mixture is 12%; the mixing temperature of asphalt mixture is 185°C.

Research on Ice-Broken Effect of Granulated Rubber Asphalt Mixture High-Elastic Deck Pavement on Bridge

They are researched about the influence of ice-broken performance of granulated crumb rubber amount of admixture, thickness of pavement layer, thickness of ice layer and temperature to granulated crumb rubber asphalt mixture by the method of laboratory simulation test. From the research it is indicated that the closer the granulated crumb rubber approach to upper surface of mixture, the larger the amount of admixture is, the more thickness the surface of granulated crumb rubber asphalt mixture is, the better effect of wiping ice off will be. With the reduction of temperature and increase of ice layer thickness, the effect of wiping ice off through granulated crumb rubber asphalt mixture will weaken gradually.