The rapid increase in traffic loads and frequencies has rendered conventional asphalt pavement inadequate to maintain its durability under tropical climates.This challenge has necessitated the exploration of new sourc...The rapid increase in traffic loads and frequencies has rendered conventional asphalt pavement inadequate to maintain its durability under tropical climates.This challenge has necessitated the exploration of new sources of modified asphalt with enhanced stiffness and superior performance at high temperatures.Natural rubber(NR)is a renewable biopolymer that has received growing interest as a modifier for asphalt binders.Cup lump rubber(CLR),a type of NR,is used to enhance asphalt properties and improve the performance of road pavements.This study evaluates the influence of wax-based surfactants(WS)on CLR-modified asphalt binder(CMB).The assessment focuses on changes in chemical characteristics,rheological behaviour,activation energy,and morphology.Four concentrations of WS(0.1%,0.15%,0.2%,and 0.25%)were incorporated into CMB.Analysis of CMB chemical changes showed that viscosity increased due to higher sulfoxide,carbonyl,and aromatic bond indices.These chemical modifications contributed to improved resistance of the binder to heat-induced deterioration.In both unaged and aged CMB samples,the incorporation of WS reduced the sulfoxide index of the binder.Rheological analysis indicated that CMB improved rutting resistance and anti-ageing performance,while WS further enhanced fatigue resistance.Activation energy analysis suggested that the combination of CMB with 0.15%WS produced the most favourable enhancement.Micrograph results showed that WS improved binder homogeneity and interconnectivity.In conclusion,the findings indicated that incorporating 0.15%WS into CMB enhanced the performance and durability of the asphalt pavement.展开更多
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...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.展开更多
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 conte...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%.展开更多
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...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.展开更多
The addition of high-content crumb rubber(HCCR)in asphalt can effectively address waste tire pollution and provide sustainable environmental and economic advantages.However,the practical application of conventional ru...The addition of high-content crumb rubber(HCCR)in asphalt can effectively address waste tire pollution and provide sustainable environmental and economic advantages.However,the practical application of conventional rubberized binders is significantly limited by high viscosity and poor storage stability.To address these issues,researchers have pretreated crumb rubber(CR)with oil,but high-temperature performance remains insufficient.Therefore,this study aimed to optimize the viscosity,storage stability,and rheological properties of high-content crumb rubber-modified asphalt(HCCRMA)by varying the pretreatment levels of CR and incorporating various additives,including styrene-butadiene-styrene(SBS),deoiled asphalt(DA),or recycled low-density polyethylene(RLDPE).In addition,CR was pretreated with waste cooking oil(WCO)at various ratios,pre-swelling temperatures,and times.The results show that DA exhibits excellent storage stability and lower viscosity compared with other modifiers in HCCRMA,and the 4%RLDPE with pretreated HCCR has the greatest high-temperature rutting resistance.The inclusion of RLDPE increases the stiffness and elasticity of the modified asphalt,which results in greater high-temperature performance.Additionally,the fluorescence microscopy(FM)test confirms that SBS exhibits better dispersion than other modifiers and forms a more homogeneous phase separation in the HCCRMA.All in all,this research achieved an optimal balance of storage stability and rheological properties in asphalt modified with pretreated HCCR and 6%SBS,which provides a valuable reference for performance improvement of HCCR-modified binders.展开更多
Waste rubber-modified asphalt has good anti-aging properties and can significantly improve the service life of asphalt pavements. For domestic and foreign scholars of rubber modified asphalt thermal oxygen aging, phot...Waste rubber-modified asphalt has good anti-aging properties and can significantly improve the service life of asphalt pavements. For domestic and foreign scholars of rubber modified asphalt thermal oxygen aging, photo-oxidative aging and water aging some behavioural research, and rubber asphalt aging after the characteristics of the research progress are reviewed. Especially rubber-modified asphalt after light, water and other multi-factor agingsituations, the aging situation is more serious, for rubber-modified asphalt mixture aging, rubber asphalt anti-aging process research and analysis means are still very few, the future research must have more thinking.展开更多
The poor fatigue properties and high rigidity of cement asphalt emulsion treated mis(CETM) have for a long time been problems restricting its further development making it impossible for C-ETMto be used as surface lay...The poor fatigue properties and high rigidity of cement asphalt emulsion treated mis(CETM) have for a long time been problems restricting its further development making it impossible for C-ETMto be used as surface layer materials. In this paper, a new kind of cement asphalt emulsion composite-rubberized asphalt emulsion modified Portland cement concrete (RACC) was proposed, which was formed by dispersing rubberized aSPhalt emulsion coated coarse aggregates into cement mortar matrix. In order to evaluate systematically the performance of RACC, laboratory tests with nearly one thousand SPecimen were conducted for resilient modulus, fatigue properties, ultimate ban and length,abrasion, temperature contraction, and dry shrinkage. The experimental results show that the problems existed in C-ETM have to a great extends been solved by RACc. To verify the field performance and inquire into paving technology, teSt road appearsatlsfactory it is concluded that when thed ape surface laycr of semi-rigid base course, RACC is more for surface layer material than both Portland cement concrete(PCC) and asphalt concrete(AC)展开更多
Traditional pavement is prone to cracks,and other distresses in cold regions.In this case,asphalt modification is a common technique used to improve the performance of asphalt.This study attempts to compare the low te...Traditional pavement is prone to cracks,and other distresses in cold regions.In this case,asphalt modification is a common technique used to improve the performance of asphalt.This study attempts to compare the low temperature properties of three modified asphalts.For this purpose,the addition of crumb rubber(CR),modified crumb rubber(MCR),and styrene-butadiene-styrene(SBS)to the base asphalt,respectively,and CR modified asphalt,MCR modified asphalt,and SBS modified asphalt is firstly prepared.Then,the asphalt specimens are subjected to a thin film oven test(TFOT)and pressurized aging vessel(PAV)test.The bending beam rheometer(BBR)test is conducted to compare the rheology characteristics and anti-aging performance of three modified asphalts.Furthermore,the low temperature performance of three modified asphalts is compared by three approaches based on the performance grade(PG),critical low temperature,and Burgers model.The BBR results show that the CR modified asphalt has the best low temperature performance.However,the CR modified asphalt show poor aging resistance,SBS modified asphalt,and MCR modified asphalt have better aging resistance.In terms of the Burgers model,it is established to analyze the resistance to low temperature cracking of four asphalts from the perspective of viscoelastic properties.Different viscoelastic parameters indicate that the low temperature performance of CR modified asphalt is superior to the other asphalts,which is consistent with the result of the critical low temperatures.展开更多
The research and development of high-performance pavement materials has been intensified owing to the demand for long-life pavements.This study is performed to develop a novel pavement material using waste rubber powd...The research and development of high-performance pavement materials has been intensified owing to the demand for long-life pavements.This study is performed to develop a novel pavement material using waste rubber powder,waste lubricating by-product(LBP),and asphalt.Subsequently,the aging properties and aging mechanism of activated waste rubber powder modified asphalt(ARMA)are investigated based on its rheological properties and microcharacterization.The rheological results show that,compared with waste rubber powder modified asphalt(RMA),ARMA offers a higher aging resistance and a longer fatigue life.A comparison and analysis of the rheological aging parameters of ARMA and RMA show that LBP activation diminishes the aging sensitivity of ARMA.The microcharacterization result shows that the aging of ARMA may be caused by the fact that LBP-activated waste rubber powder is more reactive and can form a dense colloidal structure with asphalt.Therefore,the evaporation loss of asphalt light components by heat and the damage to the colloidal structure by oxygen during the aging process are impeded,and the thermal-oxidative aging resistance of ARMA is improved.展开更多
The California Department of Transportation （Caltrans） has been using scrap tire rubber in asphalt pavements since the 1970s in chip seals and the 1980s in rubberized hot mix asphalt（RHMA）. Both the wet （field bl...The California Department of Transportation （Caltrans） has been using scrap tire rubber in asphalt pavements since the 1970s in chip seals and the 1980s in rubberized hot mix asphalt（RHMA）. Both the wet （field blend） and dry processes were used in early trials. Caltrans has also used rubber modified binders containing both crumb rubber modifier and polymer modifier that could be manufactured at a refinery facility, a terminal blend wet process. Since the beginning of this century, Caltrans increased the use of scrap tire rubber in paving projects and invested considerable resources in developing technically sound, cost effective, and environmentally friendly strategies for using scrap tire rubber in roadway applications. By the end of year 2010, approximately 31% of all hot mix asphalt （HMA） placed by Caltrans was rubberized HMA, roughly 1.2 million tons. Caltrans efforts in using asphalt rubber products were also demonstrated in its research and technology development. These included the construction of two full-scale field experiments, five warranty projects, and an accelerated pavement study using a heavy vehicle simulator. Additionally, terminal blend asphalt rubber and rubberized warm mix asphalts began to be experimented on trial basis. This paper provides a comprehensive review of Caltrans experience over four decades with asphalt rubber products. Current practices and future outlook are also discussed.展开更多
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, nam...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.展开更多
基金the financial support provided under the Fundamental Research Grant Scheme(FRGS),Project Code:FRGS/1/2021/TK01/USM/02/1,which made this research possible,The kind assistance and collaboration of all material suppliers were also gratefully acknowledged.Additional appreciation is extended to the Public Works Department Malaysia for the scholarship provided through the Hadiah Latihan Persekutuan programme for professional and managerial officers pursuing doctoral studies(JPA-1-840622086040)The APC was funded by Prof.Hui Yao from Beijing University of Technology.
文摘The rapid increase in traffic loads and frequencies has rendered conventional asphalt pavement inadequate to maintain its durability under tropical climates.This challenge has necessitated the exploration of new sources of modified asphalt with enhanced stiffness and superior performance at high temperatures.Natural rubber(NR)is a renewable biopolymer that has received growing interest as a modifier for asphalt binders.Cup lump rubber(CLR),a type of NR,is used to enhance asphalt properties and improve the performance of road pavements.This study evaluates the influence of wax-based surfactants(WS)on CLR-modified asphalt binder(CMB).The assessment focuses on changes in chemical characteristics,rheological behaviour,activation energy,and morphology.Four concentrations of WS(0.1%,0.15%,0.2%,and 0.25%)were incorporated into CMB.Analysis of CMB chemical changes showed that viscosity increased due to higher sulfoxide,carbonyl,and aromatic bond indices.These chemical modifications contributed to improved resistance of the binder to heat-induced deterioration.In both unaged and aged CMB samples,the incorporation of WS reduced the sulfoxide index of the binder.Rheological analysis indicated that CMB improved rutting resistance and anti-ageing performance,while WS further enhanced fatigue resistance.Activation energy analysis suggested that the combination of CMB with 0.15%WS produced the most favourable enhancement.Micrograph results showed that WS improved binder homogeneity and interconnectivity.In conclusion,the findings indicated that incorporating 0.15%WS into CMB enhanced the performance and durability of the asphalt pavement.
基金Funded by the Communication Science and Technology Foundation of Inner Mongolia (NJ-2005-25)
文摘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.
基金Projects(51838001,51878070,51908069)supported by the National Natural Science Foundation of China。
文摘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%.
基金Funded by Inner Mongolia Communication Technology Project (No.NJ-2005-25)
文摘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.
基金supported by the Transportation Science and Technology Program of Henan Province(grant number:2023-4-2)the Key Research and Development Program of Ningxia Science and Technology Department(grant number:2022BEG02008)+2 种基金China Communications Construction Group Co.,Ltd.Science and Technology R&D Project(grant number:2021KJW02)the Research and Development Program of Henan Transportation Investment Group Co.,Ltd.(grant number:HNJT2025-1-9)the Postdoctoral Fellowship Program of CPSF(grand number:GZC20251139).
文摘The addition of high-content crumb rubber(HCCR)in asphalt can effectively address waste tire pollution and provide sustainable environmental and economic advantages.However,the practical application of conventional rubberized binders is significantly limited by high viscosity and poor storage stability.To address these issues,researchers have pretreated crumb rubber(CR)with oil,but high-temperature performance remains insufficient.Therefore,this study aimed to optimize the viscosity,storage stability,and rheological properties of high-content crumb rubber-modified asphalt(HCCRMA)by varying the pretreatment levels of CR and incorporating various additives,including styrene-butadiene-styrene(SBS),deoiled asphalt(DA),or recycled low-density polyethylene(RLDPE).In addition,CR was pretreated with waste cooking oil(WCO)at various ratios,pre-swelling temperatures,and times.The results show that DA exhibits excellent storage stability and lower viscosity compared with other modifiers in HCCRMA,and the 4%RLDPE with pretreated HCCR has the greatest high-temperature rutting resistance.The inclusion of RLDPE increases the stiffness and elasticity of the modified asphalt,which results in greater high-temperature performance.Additionally,the fluorescence microscopy(FM)test confirms that SBS exhibits better dispersion than other modifiers and forms a more homogeneous phase separation in the HCCRMA.All in all,this research achieved an optimal balance of storage stability and rheological properties in asphalt modified with pretreated HCCR and 6%SBS,which provides a valuable reference for performance improvement of HCCR-modified binders.
文摘Waste rubber-modified asphalt has good anti-aging properties and can significantly improve the service life of asphalt pavements. For domestic and foreign scholars of rubber modified asphalt thermal oxygen aging, photo-oxidative aging and water aging some behavioural research, and rubber asphalt aging after the characteristics of the research progress are reviewed. Especially rubber-modified asphalt after light, water and other multi-factor agingsituations, the aging situation is more serious, for rubber-modified asphalt mixture aging, rubber asphalt anti-aging process research and analysis means are still very few, the future research must have more thinking.
文摘The poor fatigue properties and high rigidity of cement asphalt emulsion treated mis(CETM) have for a long time been problems restricting its further development making it impossible for C-ETMto be used as surface layer materials. In this paper, a new kind of cement asphalt emulsion composite-rubberized asphalt emulsion modified Portland cement concrete (RACC) was proposed, which was formed by dispersing rubberized aSPhalt emulsion coated coarse aggregates into cement mortar matrix. In order to evaluate systematically the performance of RACC, laboratory tests with nearly one thousand SPecimen were conducted for resilient modulus, fatigue properties, ultimate ban and length,abrasion, temperature contraction, and dry shrinkage. The experimental results show that the problems existed in C-ETM have to a great extends been solved by RACc. To verify the field performance and inquire into paving technology, teSt road appearsatlsfactory it is concluded that when thed ape surface laycr of semi-rigid base course, RACC is more for surface layer material than both Portland cement concrete(PCC) and asphalt concrete(AC)
基金supported by the Scientific and Technological Project in Shaanxi Province(2022KW-37)。
文摘Traditional pavement is prone to cracks,and other distresses in cold regions.In this case,asphalt modification is a common technique used to improve the performance of asphalt.This study attempts to compare the low temperature properties of three modified asphalts.For this purpose,the addition of crumb rubber(CR),modified crumb rubber(MCR),and styrene-butadiene-styrene(SBS)to the base asphalt,respectively,and CR modified asphalt,MCR modified asphalt,and SBS modified asphalt is firstly prepared.Then,the asphalt specimens are subjected to a thin film oven test(TFOT)and pressurized aging vessel(PAV)test.The bending beam rheometer(BBR)test is conducted to compare the rheology characteristics and anti-aging performance of three modified asphalts.Furthermore,the low temperature performance of three modified asphalts is compared by three approaches based on the performance grade(PG),critical low temperature,and Burgers model.The BBR results show that the CR modified asphalt has the best low temperature performance.However,the CR modified asphalt show poor aging resistance,SBS modified asphalt,and MCR modified asphalt have better aging resistance.In terms of the Burgers model,it is established to analyze the resistance to low temperature cracking of four asphalts from the perspective of viscoelastic properties.Different viscoelastic parameters indicate that the low temperature performance of CR modified asphalt is superior to the other asphalts,which is consistent with the result of the critical low temperatures.
基金supported by the National Natural Science Foundation of China(Grant No.51778136)the Technology Research and Development Project of China Railway(No.J2019G003)The authors would like to thank the staff at the National Demonstration Center for Experimental Road and Traffic Engineering Education(Southeast University)for their active contributions to this study.
文摘The research and development of high-performance pavement materials has been intensified owing to the demand for long-life pavements.This study is performed to develop a novel pavement material using waste rubber powder,waste lubricating by-product(LBP),and asphalt.Subsequently,the aging properties and aging mechanism of activated waste rubber powder modified asphalt(ARMA)are investigated based on its rheological properties and microcharacterization.The rheological results show that,compared with waste rubber powder modified asphalt(RMA),ARMA offers a higher aging resistance and a longer fatigue life.A comparison and analysis of the rheological aging parameters of ARMA and RMA show that LBP activation diminishes the aging sensitivity of ARMA.The microcharacterization result shows that the aging of ARMA may be caused by the fact that LBP-activated waste rubber powder is more reactive and can form a dense colloidal structure with asphalt.Therefore,the evaporation loss of asphalt light components by heat and the damage to the colloidal structure by oxygen during the aging process are impeded,and the thermal-oxidative aging resistance of ARMA is improved.
文摘The California Department of Transportation （Caltrans） has been using scrap tire rubber in asphalt pavements since the 1970s in chip seals and the 1980s in rubberized hot mix asphalt（RHMA）. Both the wet （field blend） and dry processes were used in early trials. Caltrans has also used rubber modified binders containing both crumb rubber modifier and polymer modifier that could be manufactured at a refinery facility, a terminal blend wet process. Since the beginning of this century, Caltrans increased the use of scrap tire rubber in paving projects and invested considerable resources in developing technically sound, cost effective, and environmentally friendly strategies for using scrap tire rubber in roadway applications. By the end of year 2010, approximately 31% of all hot mix asphalt （HMA） placed by Caltrans was rubberized HMA, roughly 1.2 million tons. Caltrans efforts in using asphalt rubber products were also demonstrated in its research and technology development. These included the construction of two full-scale field experiments, five warranty projects, and an accelerated pavement study using a heavy vehicle simulator. Additionally, terminal blend asphalt rubber and rubberized warm mix asphalts began to be experimented on trial basis. This paper provides a comprehensive review of Caltrans experience over four decades with asphalt rubber products. Current practices and future outlook are also discussed.
基金Fund by the National Natural Science Found Project of China(NSFC)(No.51278173)the Science and Technology Project of Jiangsu Provincial Communications Department(No.SBK201120606)
文摘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.
