Dynamic Behaviour of Pond Ash Mixed with Coir and Crumb Rubber

An experimental program was conducted to determine the dynamic properties of pond ash(PA)and pond ash mixed with admixtures like crumb rubber(CR)and coir fiber(CF)which are wastes of different industries.Additives CR and CF were mixed separately with pond ash in a percentage ranging from 0%–20%at an interval of 5%and 0%–2%at an interval of 0.5%by weight of pond ash,respectively.Dynamic properties(Shear modulus,Number of cycles to initiate liquefaction,Degradation index and Damping ratio)for pond ash mixes were determined using strain-controlled cyclic tri-axial apparatus.The shear strain was kept constant at 1.2%and the frequency varied from 0.4 to 1 Hz.Liquefaction resistance improves when crumb rubber is added to pond ash,however adding Coir fiber to pond ash has essentially no effect on the number of cycles required to initiate liquefaction.The dynamic shear modulus decreases when crumb rubber was mixed in pond ash whereas when coir fiber is added to pond ash,the dynamic shear modulus increases significantly.A mix of PA,CR,and CF was also tried to balance the number of cycles required to initiate liquefaction and shear modulus.The mixed sample in the proportion of PA(84%)+CR(15)+CF(1%)can be termed a balanced mix as the number of cycles to initiate liquefaction was more than all PA-CF mixes and also the shear modulus was more than all PA-CR mixes.Damping ratio increases with increasing frequency of loading(0.4 to 1 Hz).

Using Crumb Rubber to Improve the Properties of Concrete from the Sustainability Point of View

In the past decade,the economy of China has been increasing at a remarkable speed,which causes the rapid increase of automobile industry.Researches in past years demonstrated that the incorporation of crumb rubber into concrete reduces the mechanical strength of concrete.However,properties such as plastic shrinkage cracking resistance,dry shrinkage cracking resistance,frost resistance,impact resistance,fatigue resistance etc.are improved due to the deformable feature of crumb rubber.Therefore,it is expected that using crumb rubber in concrete not only improves the properties of the material,but also reduces the environmental pressure of handling waste tires.

Performance Characterization of CR/PU Asphalt for Potential Application in Assembled Fast-Repairing Engineering

Conventional repairing methods for asphalt pavement have some inconveniences,such as insufficient strength,and are typically time-consuming.To address these issues,this study proposes a new technological method to design and prepare a high-performance assembled asphalt concrete block for fast repair of the potholes.A series of composite modified asphalt binders with 10%crumb rubber(CR)and different dosages(0%,1%,3%,5%)of polyurethane(PU)are examined to determine the optimized binder.Subsequently,the corresponding asphalt mixtures are prepared for further comparison and assessment of engineering properties,such as moistureinduced damage,high-temperature deformation,and low-temperature cracking characteristics.The test results show that PU can significantly improve the high-temperature performance and hardness of(crumb rubber modified asphalt)CRMA binder;3%PU contributes allowing the resistance of CRMA mixture to moisture-induced damage at higher levels,particularly under water whole immersion;as 3%PU is added,the high-temperature rutting deformation resistance of the CRMA mixture increases significantly,and the low-temperature anti-cracking properties are also improved slightly.Therefore,the innovatively designed high-quality assembled fast-repairing asphalt concrete block is recommended as an appropriate option for highway maintenance.

Modification of Bitumen with Desulfurized Crumb Rubber in the Present of Reactive Additives

Bitumen was modified with desulfurized crumb rubber (DCR) in the present of reac tive additives. The effect of the kinds and content of the reactive additive on prop erties of DCR modified bitumen (DCRMB) was investigated. The morphology of DCRMB was characterized by SEM and the changes of the chemical structure of DCRMB wit hout and with the addition of the reactive additive were analyzed by FTIR. The e xperimented results show that the softening point,the elasticity recovery and th e storage stability of DCRMB were improved significantly by the addition of the reactive additive. This is because that a network structure of rubber in DCRMB w as formed and the chemical reaction between C=C double bonds in bitumen and DCR has happened after the reactive additive was added into DCRMB.

Experimental evaluation of mechanically stabilized earth walls with recycled crumb rubbers

Traditional techniques for treatment of waste rubber, such as burning, generate some highly non- degradable synthetic materials that cause unrepairable environmental damages by releasing heavy metals, such as arsenic, chromium, lead, manganese and nickel. For this, scrap tires are used as light- weight alternative materials in many engineering applications, such as retaining wall backfilling. In the present study, 90 laboratory models were prepared to evaluate the stability of mechanically stabilized earth （MSE） walls with plate anchors. Then, the bearing capacity and horizontal displacements of the retaining walls were monitored by exerting a static loading to investigate the effects of adding different contents （5 wt%, 10 wt%, 15 wt% and 20 wt%） of recycled crumb rubber （RCR） to the fill of a mechanically stabilized retaining wall with plate anchors. To visualize the critical slip surface of the wall, the particle image velocimetry （PIV） technique was employed. Results showed that the circular anchor plates almost continually provided a higher bearing capacity and wall stability than the square plates. Moreover, the backfill with 15 wt% RCR provided the maximum bearing capacity of the wall. Increasing the weight percentage of RCR to 20 wt% resulted in a significant reduction in horizontal displacement of the wall, which occurred due to the decrease in lateral earth pressure against the whole walls. An increase in RCR content resulted in the decrease in the formation of failure wedge and the expansion of the wall slip surface, and the failure wedge did not form in the sand mixtures with 15 wt% and 20 wt% RCRs.

The Mechanism of Asphalt Modification by Crumb Rubber

To investigate the mechanism of asphalt modification by crumb rubber,the interactions between FCC slurry and rubber particles were evaluated at different temperatures and time.The rules of the change in mass of SARA composition in FCC slurry were obtained before and after its interaction with rubber particles,which showed that crumb rubber not only absorbed saturates and aromatics but also resins.Asphaltenes promoted the desulfurization or degradation of crumb rubber during the interaction between asphalt and crumb rubber.

Microscopic and Dynamic Rheological Characteristics of Crumb Rubber Modified Asphalt

A test for crumb rubber modified asphalt containing 20% crumb rubber particles（30 mesh） was performed using a scanning electron microscope（SEM）.The experimental results indicate that the crumb rubber particles are evenly distributed in the asphalt.Shear rate sweep and shear-temperature sweep tests on the crumb rubber modified asphalt at-20-80 ℃ using a dynamic shear rheology（DSR） instrument,were carried out.The tests show that the complex modulus decreases with increasing temperature;at equivalent temperature,higher load frequencies lead to a larger complex modulus,and this value increasingly decreases as the temperature increases;the phase angle increases with temperature and decreases as the load frequency increases.It can be concluded that the rutting resistance limiting temperature of crumb rubber modified asphalt is 78 ℃,and the anti-fatigue limiting temperature is 16 ℃,which shows that the asphalt has preferable rutting resistance characteristics at high temperature,as well as anti-fatigue characteristics.In addition,the complex modulus master curve at different temperatures was plotted according to the time temperature equivalence principle,which allows the study of the dynamic state behavior of crumb rubber modified asphalt at a wide range of load frequency.

Microstructure and Properties of Desulfurized Crumb Rubber Modified Bitumen

The microstructures of general crumb rubber(CR), dynamic desulfurized crumb rubber(DDCR) and high speed agitation desulfurized crumb rubber(HSADCR) modified bitumens were investigated by a fluorescence microscope, and the physical properties of these three modified bitumens were studied.The results show that the dynamic desulfuration can improve the swelling capacity of crumb rubber in bitumen by destroying the sulfuratized bond of the crumb rubber,but the reunion of rubber particles during dynamic desulfuration also makes the swelling and the DDCR in bitumen difficult, so properties of the DDCR modified bitumen are not superior to the general crumb rubber modified bitumen.However,high speed agitation desulfuration can not only improve the swelling capacity of crumb rubber in bitumen,but also avoid the reunion of rubber particles,so some properties of bitumen can be improved by the modification of HSADCR.

Laboratory and Field Investigations of Polymer and Crumb Rubber Modified Bitumen

In this paper, properties of new kind of modified bitumen are presented. Bituminous binder was modified with mix modification using polymer and additive of crumb rubber. Terminal blend process at the refinery was applied to produce the mixed modified binder. Laboratory tests were focused on the characterization of the properties of 45/80-55 CR binder with comparison to reference 50/70 and conventional polymer modified 45/80-55 bitumen. Based on conventional binder tests such as penetration, softening point and Fraass breaking point as well as BBR （bending beam rheometer） and DSR （dynamic shear rheometer） tests, rheological properties were investigated. For determination of stability of the polymer and crumb rubber, modified bitumen tube testing method was used. Based on the results analysis, improvement of the viscoelastic properties of polymer and crumb rubber modified bitumen was observed. Conventional properties and stability tests showed that it is possible to pass standard requirements for polymer modified bitumen. Mixed modification and terminal blend allow to use crumb rubber as a modifier with elimination of the separation of crumb rubber during transportation and storage at high temperature. In this paper, experience from filed sections with use of the asphalt mixture with new kind of modified bitumen is presented.

Physical and Mechanical Properties of Crumb Rubber Mortar(CRM)with Interfacial Modifiers

Eight interfacial modifiers were used to improve the interfacial bonding strength between the crumb rubber and matrix of Crumb Rubber Mortar （CRM）, and the physical and mechanical properties and microstructure of CRM were also studied. The results show that, the interfacial modifiers obviously improve the interface bonding strength between the crumb rubber and matrix and the whole strength of CRM, and silicone modified styrene-acryl ate-emulsion has the best effect. The rubber-cement matrix interface was proved by SEM that the interfacial modifiers treated rubber showed good adhesion to the matrix.

Mechanism behind Time Dependent Elasticity of Crumb Rubber-Nano-Asphalt Hybrids Using Discrete Relaxation Spectrum

Crumb rubber powder is a successfully used renewable material obtained from waste tire rubber,which has been incorporated into paving asphalt since the 1930s due to its good resistance to deformation and fatigue as well as its eco-friendly performance.In this study,carbon nanotubes and nano silica were incorporated into the terminal blend crumb rubber modified asphalt technology to remedy the issues of excessive desulfurization and degradation of ground tyre rubber with this technology.The mechanism behind the high temperature delayed elastic properties of the crumb rubber-nano-asphalt hybrids was experimentally investigated based on discrete relaxation spectrum.Development of the discrete relaxation spectra was accomplished by fitting on the 60℃ storage modulus data tested by the dynamic shear rheometer using the generalized Maxwell model.Subsequently,the feasibility of characterizing delayed asphalt elasticity using main relaxation time was verified by test results from the 60℃ creep and recovery test.Results indicated that the crumb rubber-nano-asphalt hybrids exhibited arrheodictic behavior and the asphalt elasticity was strengthened by two nano agents.Moreover,the elasticity reinforcement with carbon nanotubes was greater than with nano silica.Additionally,a good correlation was observed between the 60℃ zero shear viscosity and main relaxation time,and greater 60℃ zero shear viscosity was correlated to longer main relaxation times.Furthermore,longer main relaxation time of the asphalt was related to greater average recovery rate in the creep and recovery test.This research is expected to shed some light on the mechanism behind time-dependent elasticity of crumb rubber modified asphalt from the perspective of polymer physics.

Creep Characteristics of Crumb Rubber Modified Asphalt Binder

Crumb rubber modified asphalt containing 20 percent crumb rubber particles of 30 mesh has been examined by Scanning Electron Microscope （SEM） to observe the microcosmic appearance and the characteristic distribution of crumb rubber particles in asphalt. The SEM pictures reveal that the crumb rubber particles distribute evenly in the asphalt and they are compatible well with asphalt. The shear creep test of crumb rubber modified asphalt was carried out at -10 ℃ and 40 ℃ by Dynamic Shear Rheology （DSR）. The shearing deformation at different temperature and creep stiffness modulus curve at loading stage of crumb rubber modified asphalt have been measured. The stiffness modulus of crumb rubber modified asphalt is much temperature sensitive and it decays much quick at the early stage of loading than normal asphalt. The rate of decay of stiffness modulus is slow at the subsequent stage and stiffness modulus approaches to a stable value at the final stage at a higher temperature. In addition, Burgers model is suitable to describe and simulate experimental results of viscoelastic properties of the crumb rubber modified asphalt.

Interaction Theory of Asphalt and Rubber

Through scanning electron microscope （SEM）, spectral analysis, and component analysis tests, the interaction theory between asphalt and rubber was discussed. It is concluded that rubber powder become soft and bond together with each other after being mixed with asphalt. The asphalt changes from a smooth homogeneous matter to a continuous mixing system which is composed of rubber powder and asphalt. The interaction is mainly physical diffusion, but there are some chemical reactions in the process, especially at long reaction time.

Laboratory investigation on effects of organic montmorillonite on performance of crumb rubber modified asphalt

In this paper,organic montmorillonite(OMMT)was added into crumb rubber modified asphalt(CRMA)to improve its high temperature performance,anti-aging performance and storage stability.The effects of different OMMT content on properties of CRMA were studied.The rutting factor obtained by dynamic shear rheological(DSR)test was adopted to evaluate the high-temperature performance.The creep stiffness and m value determined by the bending beam rheometer(BBR)test were employed to evaluate the low-temperature performance.The softening point,ductility,rutting factor before and after rolling thin film ovens test(RTFOT)and pressure aging vessel test(PAV)were compared to characterize the aging properties.Moreover,the segregation test after being reserved for 48 h and 7 d was conducted,and the softening point and rutting factor of upper and lower layers of segregation pipe were adopted to evaluate the storage stability.The results indicated that the high-temperature performance and anti-aging performance were developed with the increasing content of OMMT,while the low-temperature performance deteriorated.The storage stability was improved with the increasing content of OMMT before the content exceeded 4%,after which the storage stability declined.Taking account of all factors,it is suggested that the optimum content of OMMT is 3%−4%.

Rheological properties and microscopic mechanism of waste cooking oil activated waste crumb rubber modified asphalt

In this paper,the surface activated crumb rubber with waste cooking oil(WCO)was studied to improve the performance of crumb rubber modified asphalt.The activated waste crumb rubber modified asphalt(OCRMA)with different amount of crumb rubber was prepared to study the microscopic appearance of OCRMA by scanning electron microscope and fluorescence microscope and analyze the surface performance.The rheological properties and microscopic mechanism of OCRMA were characterized by dynamic shear rheological test,multiple stress creep recovery(MSCR)test,BBR test and infrared spectroscopy.The results show that the dissolution degree of waste crumb rubber is improved after WCO activation,and the compatibility with asphalt components is enhanced,and the stable cross-linking structure is formed,which improves the asphalt performance.The several new absorption peaks,which were obvious,were all caused by the composition of WCO,that is,there was no significant chemical change during the interaction between the activated crumb rubber and base asphalt.Compared with the common waste crumb rubber modified asphalt(CRMA),activation with WCO can significantly reduce the viscosity of CRMA,decrease the difference of segregation softening point by 27%,and enhance the low temperature performance by 30%.The aging degree is greatly reduced,and the anti-aging performance of OCRMA is increased by about 20%with the same dosage.The high temperature performance,though higher than that of base asphalt,decreases to some extent.After comprehensive analysis,the optimal dosage of crumb rubber for OCRMA is 30%.

Study on Low-Temperature Properties of the Asphalt Modified by Carbon Nanotubes(CNTs)and Crumb Rubber(CR)

The effect of adding crumb rubber(CR)and carbon nanotubes(CNTs)on the low-temperature properties of virgin asphalt was studied.Using the force-ductility test and the bending beam rheometer(BBR)test,the deformation resistance and rheological properties of asphalt samples at low temperatures were evaluated,respectively.Based on the result of BBR test,the creep functions of the Burgers model and the Zener model were used to fit the low-temperature creep characteristics of the asphalt samples.Furthermore,the differential scanning calorimetry(DSC)test and the attenuated total reflection-Fourier transform infrared spectroscopy(ATR-FTIR)test were utilized to appraise the low-temperature stability and chemical properties of asphalt samples,respectively.The results showed that CR significantly improved the low-temperature properties of virgin asphalt,while CNTs had little effect.Moreover,during the degradation of CR,aromatic and aliphatic components were released.In particular,the aliphatic components of CR-modified asphalt were much higher than those of virgin asphalt,which had a significant effect on improving the low-temperature properties of the asphalt.The DSC test results showed that CR enhanced the low-temperature stability of the asphalt,while the addition of CNTs presented a slightly negative effect.

Improved Resistance to Cracking of a Cement Mortar through the Incorporation of Crumb Rubber

Within a context of sustainable development, innovative processes for various applications to recycle rubber are put in place to make aggregates or crumb rubber. These uses include sports floor coverings, to manufacture of sealants, sound absorbing walls, to make roads, as an alternative fuel in cement kilns, etc. In this study, the addition of crumb rubber to mortar was investigated through optical and mechanical tests. The results showed that the incorporation of crumb rubber from used tires into mortar produced a better resistance to shrinkage cracking, but a compressive strength/tensile is reduced. This feature could lend itself to making playgrounds and sports grounds more absorbing and flexible, which would allow a more significant fall to be withstood without injury and consequently enhance the safety of playgrounds.

FREEZE/THAW PERFORMANCE OF CONCRETE USING GRANULATED RUBBER CRUMB

This paper evaluates the properties and use of recycled rubber tyres in the form of rubber crumb as a freeze/thaw protection agent when used in concrete.Reusing scrap tyres in the form of rubber crumb in concrete could benefit the environment by contributing to the percentage of tyres used for a variety of recycling processes such as carpet underlay or tyre derived fuel,thus reducing disposal of tyres to landfill sites and the chemical usage of air entraining agents as a means of achieving freeze/thaw protection.Concrete cubes of 100mm were produced from design mixes which have been classified as plain,air entrained and rubber crumb and subjected to freeze/thaw cycles at 5 days of age.Thawing was conducted in water to ensure full saturation of pores and maximum stress on the concrete samples.The rubber crumb and plain concrete mixes were compared against the freeze/thaw performance of that entrained with air.Air entrainment is known to protect against freeze/thaw action.Rubber crumb when used at a 0.5%addition by volume provided the optimum freeze/thaw protection whilst maintaining the maximum compressive strength.The research shows that rubber crumb was effective at providing freeze/thaw protection albeit with a reduced compressive strength when compared to air entrained concrete.The practical constraints of the test program were time and freezer space so the test was limited to 50 freeze/thaw cycles,which was sufficient for conclusions to be drawn.This paper contributes to the understanding of the effects of varying doses of rubber crumb in concrete when used as a freeze/thaw protection additive.The final compressive strength of the concrete mixes tested at freeze/thaw and non freeze/thaw conditions are determined.The compaction of concrete is raised as an area of concern with regard to rubber particle separation within the plastic phase of the concrete’s life.

The Viscosity-reducing Mechanism of Organic Wax Additive on CRMA

CRMA was prepared by mixing PG 64-22 asphalt with crumb rubber powder of 40 mesh size and 18% by weight of the asphalt. Sasobit, a typical organic wax additive, was selected and added into CRMA. A series of tests, namely, brookfield viscosity, environmental scanning electron microscope（ESEM）, component test, differential scanning calorimeter（DSC）, fourier transform infrared spectroscopy （FTIR） and nuclear magnetic resonance （NMR） were conducted on CRMA with and without organic wax additive, and microcosmic appearance, component content and molecular structure of various asphalt binders were obtained. The test results indicate that the addition of Sasobit~ into CRMA can effectively change the contents of components： the content of asphaltenes increases relatively, while saturates decreases. In addition, the interaction between various components of CRMA is weakened, and the state of equilibrium between the dispersant and dispersed phase is changed at the same time. That is why the viscosity decreases after the organic wax additive is added into CRMA.

Effect of SBS and crumb rubber on asphalt modification:A review of the properties and practical application

Owing to the environmental protection potential and the desirable high performance capabilities,asphalt rubber(AR)and styrene-butadiene-styrene(SBS)modified asphalt have been widely used.However,the poor construction workability and segregation issues of AR,along with the exorbitant cost of SBS modified asphalt,are of the serious problems that plague their application scope.Moreover,SBS/crumb rubber(CR)modified asphalt is gradually becoming widespread and it therefore becomes incumbent to find appropriate ways to mitigate the issues that may limit its use.As a consequence,it becomes crucial to analyze the interaction between CR and SBS modifiers in the composite mixture,as well as evaluate the influence of modifier dosage on the performance of the modified asphalt.This study presents a comprehensive review of the effects of SBS modifier,CR modifier and composite SBS/CR on the performance of modified asphalts.Macro analysis and micro analysis,including analysis on the conventional physical properties,are carried out.It can uncover the interaction between modifier and asphalt,which reveals how the modifiers influence the properties of modified asphalts.This study will serve as a source of invaluable information to researchers,engineers,and designers,informing them the development,potential and challenges of the CR,SBS and SBS/CR modified asphalts,the optimum contents to attain the best performance along with the mechanism involved.