岩沥青改性沥青混合料路用性能试验研究

岩沥青改性剂与基质沥青具有优良的配伍性,但不同掺量的岩沥青对沥青混合料的力学性能影响很大。本研究以AC-13沥青混合料级配为基准,通过室内对比试验,对基质沥青混合料和不同掺量下的岩沥青改性沥青混合料的高温稳定性、低温抗裂性、水稳定性、疲劳耐久性等力学性能进行研究,以期为岩沥青改性沥青混合料的掺量标准提供参考。

应对极端气候的橡胶粉SBS复合改性沥青成套技术研究与应用

本项目面向寒冷季冻地区公路沥青路面使用需求,系统研究了极端气候条件下橡胶粉与SBS复合改性沥青及混合料应用成套技术问题,揭示了橡胶粉与SBS复合改性沥肯的作用机理、提出了复合改性沥青的工厂化工艺参数、复合改性沥青及混合料路用性能评价指标、温拌技术等系列创新性成果。研究成果在吉林省多条高速公路工程建设中进行了应用,路用效果良好,经济社会效益显著,有效提高了季冻区沥青路面应对极端气候的能力。

粘流态沥青粘度分析

从微观角度分析了粘流态沥青粘度的影响因素 ,然后采用 Brookfield旋转粘度仪对改性及非改性沥青进行粘度试验 ,分析沥青在改性前后粘度的变化特征 ,从而揭示了沥青的改性机理 。

Laboratory evaluation of epoxy resin modified asphalt mixtures

The pavement performance of epoxy resin modified asphalt mixtures was investigated by the Marshall test, the indirect tensile test, the rutting test, the three-pointed bending test and the composite beam fatigue test. In comparison with the performance of epoxy resin modified asphalt mixtures, the performance of stone matrix asphalt mixtures （SMA10） was also investigated. The rutting test and composite beam fatigue test results show that the epoxy resin modified asphalt mixtures can improve permanent deformation and fatigue characteristics. They also show lower temperature susceptibility and greater resistance to moisture damage compared to the SMA10. Findings from the research indicate that the epoxy resin modified asphalt mixture provides an optional material for the pavement of long-span steel bridges in China due to profound performance and economic advantages.

Rutting resistance of asphalt mixtures in the middle course

In order to improve the rutting resistance of asphalt mixtures in the middle course to reduce the rutting of asphalt pavement, the influence of different types of gradation with their own optimal asphaltaggregate ratios is analyzed. Some investigations are made out on the mixture in the middle course through the modified wheel tracking test in air bath and the Hamburg wheel tracking test （HWTT） in water bath, and the results of which are compared with the corresponding research in Germany. Results show that the Sup20 and the modified AC-20I have better performance than that of AC-20I under the same test conditions. In addition, the high-quality bitumen and hard aggregate can improve the rutting performance of the mixture in water-submerged conditions. The selection of modified asphalt, hard aggregate and a reasonable gradation are essential to the improvement of the rutting resistance of the mixtures used in the middle course.

Evaluation of modification effect of epoxy resin based on performance of asphalt mixtures

Based on the analysis of the main failures discovered in pavement on steel deck plate and the demanding service condition of the pavement on steel deck, high-temperature rutting test, low-temperature bending test and controlled stress flexural fatigue test are used to study the performance of asphalt mixtures modified by epoxy resin including high-temperature stability, low-temperature cracking-resistance, and fatigue cracking-resistance, which are served to evaluate the modification effect of epoxy resin of different contents. With the addition of epoxy resin, all the three performances are improved greatly. However, when the amount of epoxy resin added is over a certain value, the modification effect will be stable with no extra benefit detected. Finally, in terms of the properties of the three respects, 20%, 30%, 30% are given separately as the proposal adding contents.

Study on High Temperature Behaviour of Gussasphalt

Rutting is one of the most damages in the asphalt surfaces for the orthotropic steel bridge decks. With Hamburg wheel tracking device, the suitable test conditions for Gussasphalt in Germany are pointed out, the high temperature behaviour of Gussasphalt with different binders are tested and compared. The polymer modified binder has higher resistance stability to rutting. The retained time and mixed frequency have obvious effects on Gussasphalt behaviour during Gussasphalt retained period.

Study on low temperature performance of Gussasphalt on steel decks with hard bitumen

Using a Hamburg wheel-track test device, the resistance to rutting of Gussasphalt is tested and compared. Gussasphalt with hard bitumen has good resistance to rutting. The related resistance abilities to cracking at low temperature of Gussasphalt are tested and compared through flexural experiments and the composite structure fatigue test with temperature dropping. Gussasphalt with high performance polymer modified bitumen has a longer fatigue life and a lower breaking temperature; they can be used in the future surfaces for steel bridge decks in Germany.

基质沥青与 SBS 改性剂的相容性分析

研究了4种基质沥青及其与SBS改性剂的相容性关系。测定SK90号、克炼90号、中海90号和东海90号4种沥青和改性剂的溶解度参数分别为9.35(4.1868J/cm^3)1/2、9.48(4.1868J/cm^3)1/2、9.73(4.1868J/cm^3)1/2、9.88(4.1868J/cm^3)1/2和9.28(4.1868J/cm^3)1/2。元素分析表明,SK90号沥青具有更高的不饱和度(H/C=1.41),且含有较多的硫元素(5.86%)。红外光谱分析表明,沥青以物理共混改性为主,并出现反应性共混;荧光显微照片验证了其相容性关系。

Evaluation of rutting performance of stone matrix asphalt mixtures containing warm mix additives

Permanent deformation or rutting, one of the most important distresses in flexible pavements, has long been a problem in asphalt mixtures and thus a great deal of research has been focused on the development of a rheological parameter that would address the rutting susceptibility of both unmodified and modified bituminous binders. In this research, three warm mix additives(Sasobit, Rheofalt and Zycotherm) were used to modify 60-70 penetration grade base binder. The rutting potential of both modified and unmodified binders were evaluated through the multiple stress creep recovery(MSCR)-based parameter, nonrecoverable compliance(Jnr) and recovery parameter(R). Several performance tests carried on stone matrix asphalt(SMA) mixtures comprising different nominal maximum aggregate sizes(NMASs, 9.5, 12.5 and 19 mm), like Marshall stability, dynamic and static creep and Hamburg wheel tracking tests to evaluate their rutting performance. The objective of this work is to correlate MSCR test results to performance. Results indicate that for the range of the gradations investigated in this work, increasing the nominal maximum aggregate size of the gradation would increase the permanent deformation resistance of the SMA mixture. Addition of 3% sasobit to base binder leads an increase in Jnr100 about 82%. Addition of 2% rheofalt to base binder leads an recovery increase of about 9.76 % and 27.44% in stress levels of 100 and 3200 Pa, respectively. The results reveal that rutting resistance of mixtures improves as Jnr decreases. The use of the MSCR test in the rutting characterization of bituminous binders is highly recommended based on the results of this work.

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.

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.

Permanent deformation response parameters of asphalt mixtures for a new mix-confined repeated load test

The main objective of this work is to propose new mixture response parameters and to compare correlations with rut depths and sensitivity of permanent deformation response parameters based on field extracted cores and lab-mixed duplicates. A new "mix-confined" test is developed and four new parameters for this test are proposed. Correlation coefficients with rut depths and coefficients of variation (sensitivity) are compared between the four new and two existing parameters. Some parameters are recommended to be used for the newly developed test. The results show that, newly developed test can capture the changes of permanent deformation of asphalt mixtures. Only one new parameter (D1 of Stephen Price model) and one existing parameter (flow number, Fn ) have strong correlations with rut depths of asphalt pavements (R2 greater than 0.7) and have relative small sensitivity (coefficient of variation, COV, less than 30%). For polymer modified asphalt mixtures, the parameter D1 rather than Fn should be used. These findings can be used to check the permanent deformation of asphalt mixture during the mix design.

Investigation of Swelling and Dissolution Process of Natural Rubber in Aromatic Oil

Aromatic oil has been used to promote the properties of crumb rubber modified asphalt which is an ideal method to deal with the resource utilization of waste rubber tires and by-product of refinery. Furfural extract oil(FEO) was separated into the light fraction and the heavy fraction. Swelling and dissolution process of natural rubber sheet in these three oil samples was investigated to shed light on the interaction mechanism. Crumb rubber also interacted on FEO and asphalt respectively. Energy dispersive spectrometer(EDS), thermo-gravimetric analysis(TGA) and scanning electron microscope(SEM) were used to characterize the chemical and structural properties of processed rubber. The chemical composition of processed oils and asphalt was investigated by using the hydrocarbon group analysis(SARA) and gel permeation chromatography. The results revealed that the swelling rate and mass loss of rubber in oils were much higher than those in asphalt and rose with an increasing processing temperature. The heavy fraction of FEO had more diffusion and dissolving capability than the light fraction, whilst compatibility was observed between the heavy fraction and the light fraction. Selective absorption was not observed in the study and detachment of dissolved rubber was disseminated from the outside to the inside. The cross-linking degree of the residue rubber was unchanged with the processing time, and sulfur predominantly remained in the undissolved rubber. Dissolution of crumbed rubber in oils was attributed to devulcanization, while that in the asphalt was mainly attributed to depolymerization.

Structural Characteristics of Mesophase Spheres Prepared from Coal Tar Pitch Modified by Phenolic Resin

Mesocarbon microbeads （MCMB） were prepared from coal tar pitch modified by phenolic resin and from the same pitch modified by phenolic resin and hexamethylenetetramine at 440℃ for lh. By investigating the morphology of mesophase spheres and the structure of the MCMB carbonized at 1000℃ for lh using scanning electron microscope （SEM） and XRD, it was found that phenolic resin accelerated the formation and coalescence of mesophase spheres. Some of the obtained MCMB were hi- or tri-spheres with the distorted microtextural carbon layers. Hexamethylenetetramine in the pitch modified by phenolic resin accelerated the condensation of phenolic resin and consequently expedited the combination of mesophase spheres, which was proved by the formation of some tetra-spheres. Owing to the cross-linkage of the additives, MCMB with complex structure were obtained.

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%.

Viscoelastic Characteristics of Asphalt Binders at Softening Point Temperature

In this paper, in order to investigate the viscoelasticity of asphalt binder at the softening point temperature, more than 30 different asphalt binders were selected and tested by dynamic rheological scan method using a dynamic shear rheometer(DSR). The softening points and the rheological parameters of the asphalt samples were measured and analyzed. The results indicated that at the softening point temperature the neat asphalt and the SBS modified asphalt showed two different rheological states. The neat asphalt binders had a majority of viscous components in viscoelastic composition, with the phase angles being mostly higher than 80 o. The SBS modified binders had lower phase angles, with their elasticity still retained. Meanwhile, the Shapiro-Wilk normality test showed that at a confidence level of 0.05, at whatever aging state, the neat asphalt had a stable complex modulus corresponding to the softening point, which was 13.034 kPa at a standard deviation of 2.105 kPa under the same test condition. The softening point of neat asphalt binder can be calculated via the equivalent modulus rule. It is found out that there is a good relationship between the calculated and the measured softening points. And it is suggested that more data are needed to validate this finding.

Rolling thin film oven test investigation for polymer modified asphalt

Rolling Thin Film Oven Test （RTFOT） is the AASHTO T240 standard method to simulate asphalt plant mix aging. But it has proven inadequate in aging polymer-modified asphalts （PMA）. NCHRP 9-10 offered a modified RTFOT （MRTFOT） by adding a steel rod in each bottle. Since construction temperature of PMA mixture is 10 ℃ -20 ℃ higher than that of conventional asphalt mixtures in the field, elevating RTFOT temperature for PMA is necessary for adequate aging and proper simulation. Six PMAs with various PG grades and sources were aged with RTFO at elevated temperatures. Some were also treated with MRTFOT for comparison. SHRP performance grade and phase angle were used as indicators to analyze the effects of RTFOT under different conditions. The results show that elevating the temperature is more effective than using rods. And PMA RTFOT temperature could be determined by equiviscous principle. From limited data, O. 25 Pa ~ s is tentatively proposed as critical viscosity for PMA, but still more work is necessary to validate this. Given the fact that equiviscous principle is seldom used in field practice, a simple approach was proposed： 173 ℃ is used for RTFOT of PG70 PMAs （grading herein from un-aged asphalts） , while 178 ℃ is for PMAs of PG76 or PG82 and 20 ℃ higher than standard 163 ℃ is necessary for PG 88 or stiffer PMAs.

Laboratory Evaluation of the Stiffness Modulus of a Modified Bituminous Concrete with PR PLAST Sahara

Uneven roads surface can be observed on bituminous pavements. This is due to moving loads and climate conditions. If the observed deformations exceed the elastic limit, important damages can occur, so new materials are used to improve the stiffness modulus of bituminous mixtures. To achieve this, a modified bituminous concrete by addition of the PR PLAST Sahara （produced by PR industries and PLAST for Plastic） mainly used in arid region has been studied. The use of this additive at various percentages 0.1, 0.3, 0.6 and 0.9 by weight of bituminous concrete has been investigated to determine its stiffness modulus. An experimental design using the Taguchi tables has been elaborated to reduce the number of tests. Marshall and NAT （Nottingham asphalt tester） tests have been carried out, and a mathematical model of the stiffness modulus has been proposed.