纳米复合改性沥青混合料路用性能研究

为评价纳米复合改性沥青混合料的路用性能,对纳米ZnO改性沥青混合料、纳米ZnO/TiO_2改性沥青混合料以及纳米ZnO/TiO_2/SBS复合改性沥青混合料进行了高温性能试验、小梁弯曲试验、劈裂试验及相关耐久性试验,并与基质沥青混合料和SBS改性沥青混合料进行对比分析.结果表明:上述3种纳米改性沥青混合料的高温稳定性、低温抗裂性、间接抗拉性和耐久性均优于基质沥青混合料,其中纳米ZnO/TiO_2/SBS复合改性沥青混合料的上述性能优于SBS改性沥青混合料.由此可见,纳米材料可显著改善沥青混合料的性能,纳米复合改性沥青的性能优于聚合物改性沥青,将其应用于道路是可行的.     

橡胶粉改性沥青混合料路用性能分析

为研究橡胶粉改性沥青混合料及其路用性能,基于实体工程,对橡胶粉的改性机理进行了分析,并对间断级配橡胶粉改性沥青混合料进行了配合比设计,在此基础上,对间断级配橡胶粉改性沥青混合料的路用性能进行了验证,试验结果表明,利用废旧橡胶粉对沥青进行改性,能够有效提升沥青的粘结性能与温度敏感性能,其成型的间断级配沥青混合料具有优良的路用性能。     

双改性新工艺对大孔隙沥青混合料性能的影响

大孔隙沥青混合料一般要求其沥青为高黏改性沥青.致力于研究一种SBS湿法和橡胶粉干法双改性大孔隙沥青混合料生产工艺(简称橡胶粉干拌法).首先,对用该新工艺制备的大孔隙沥青混合料的宏观性能进行评价并与比较试样进行对比,借由原子力显微镜(AFM)及红外光谱(FTIR)分析改性沥青微观性能.结果表明:湿拌法沥青混合料高温动稳定...     

橡胶粉和抗车辙剂复合改性沥青混合料的性能研究

采用橡胶粉和抗车辙剂对沥青混合料进行改性,对不同改性沥青混合料的高低温性能、水稳定性能和耐疲劳性能进行对照试验。分析了橡胶粉和抗车辙剂的共同作用机理,验证了采用橡胶粉和抗车辙剂进行复合改性可以使沥青混合料兼有2种材料分别改性的优点,具备更加优良的路用性能。     

杜仲胶/硫磺对橡胶粉改性沥青与混合料性能的影响研究

基于橡胶粉改性沥青的针入度指标和流变性能体系指标,分析了杜仲胶和硫磺掺量对橡胶粉改性沥青性能的影响,通过室内试验分析杜仲胶与硫磺复合改性橡胶沥青混合料的路用性能和耐久性。结果表明,掺加杜仲胶可显著提高橡胶粉改性沥青的高低温性能、弹性恢复性能、抗永久变形性能,增大抗车辙因子和疲劳因子,降低劲度模量、增大蠕变斜率。复合掺加杜仲胶和硫磺改善了橡胶粉改性沥青的热存储稳定性,可实现橡胶沥青的工厂定制化生产和远距离运输。杜仲胶与硫磺复合改性橡胶沥青混合料具有优异的路用性能和抗疲劳性能,杜仲胶和硫磺的最佳掺量分别为4%～6%、0.5%。     

橡胶沥青混凝土应用技术研究

介绍了废旧橡胶粉用于道路改性沥青材料的现状,对橡胶沥青的生产工艺、改性机理、改性效果进行了分析和总结。在公路工程中应用橡胶粉,不仅能改善沥青混合料的路用性能,而且具有显著的经济效益和社会效益,应大力推广。     

RHW-GCR橡胶粉改性沥青及沥青混合料在广西南宁的应用研究

介绍了橡胶改性沥青及沥青混合料的研究现状、作用机理,以及RHW-GCR新型改性高强橡胶粉改性沥青及沥青混合料的技术指标试验结果,讨论了RHW-GCR橡胶粉改性沥青混合料的抗水损害性能、高温稳定性能以及抗疲劳性能,并介绍了RHW-GCR橡胶粉改性沥青及沥青混合料在广西南宁等地的应用情况,最后初步提出了RHW-GCR橡胶粉改性沥青及沥青混合料技术指标标准,为今后橡胶改性沥青及沥青混合料的设计及施工提供一定参考。     

高模量改性剂的作用机理及应用研究

以70#石油沥青、SBS改性沥青和高模量改性沥青为研究对象,通过流变试验,定量研究了高模量改性剂掺量对沥青黏弹特性的影响,并与SBS改性沥青进行了对比分析,结合荧光显微试验,研究了高模量改性剂的改性机理;基于车辙试验和动态模量试验,分析比较了高模量改性沥青混合料和SBS改性沥青混合料在路用性能方面的差异.结果表明:高模量改性剂在改善基质沥青的高温性能和黏弹性能方面具有良好的效果,其掺量为6.67％时改性效果优于SBS改性沥青;高模量改性剂颗粒可以在沥青中溶胀发育,形成聚合物链接,改善了沥青的黏弹特性;与SBS改性沥青混合料相比,高模量改性沥青混合料的抵御变形能力更好,在高温地区的使用性能优越.     

特立尼达湖改性沥青路用性能试验研究

进行了特立尼达湖沥青的路用性能试验研究,包括特立尼达湖改性沥青掺量的确定及配制,特立尼达湖改性沥青的针入度、延度、软化点及布氏旋转粘度试验。通过对特立尼达湖改性沥青的路用性能试验研究,初步确定了用25%和33%的湖沥青掺量,进行沥青混合料试验比对,同时和基质沥青混合料进行对比。沥青混合料试验前,首先进行了原材料的选择及3种沥青混合料的配合比设计,确定了各自的最佳沥青用量。通过对沥青混合料的水稳定性研究、高温性能及低温抗裂性能研究,分析得出33%掺量的特立尼达湖改性沥青能够提高沥青混合料的水稳定性及高温稳定性等路用性能。     

废旧塑料（RPE）改性沥青混合料性能优化研究

为了改善和提升改性沥青性能及混合料的路用性能,选取掺量为4%、6%、8%、10%的废旧聚乙烯（Recycle Polyethylene,RPE）对基质沥青进行了改性,并在不同混合温度（160、170、180℃）和搅拌时间（1.0、1.5、2.0 h）下进行了针入度、延度和软化点试验。研究了不同改性工艺条件对RPE改性沥青常规性能的影响,确定了最佳改性工艺条件,并比较了最佳改性条件下普通沥青混合料与RPE改性沥青混合料的力学性能。通过高温车辙、低温弯曲和水稳定性等试验评价了RPE改性沥青混合料的路用性能。研究结果表明：普通沥青混合料中最佳沥青掺量为5.16%,RPE改性沥青混合料中最佳RPE掺量为6.5%;在170℃的混合温度和1.5 h的搅拌时间下,RPE改性沥青混合料的性能最佳;RPE改性沥青混合料的力学性能优于普通沥青混合料,高温性能和水稳定性得到了提升,低温性能降低。     

多尺度纳米材料对再生沥青长期老化性能的影响

研究了由不同掺量有机蛭石（OEVMT）和纳米氧化锌（Nano ZnO）组成的多尺度纳米材料对再生沥青长期热氧和光氧老化性能的影响。利用薄膜烘箱对普通基质沥青进行老化以制得老化沥青,采用熔融共混方法,先将老化沥青、普通基质沥青以及再生剂按照一定的比例混合以制得再生沥青,再将多尺度纳米材料加入到再生沥青中制得多尺度纳米材料改性再生沥青。采用压力老化箱老化（PAV）和加速紫外光老化（UV）分别模拟再生沥青的长期热氧老化和光氧老化条件。通过传统物理性能试验和动态剪切流变试验评价了再生沥青的老化性能。结果表明:添加多尺度纳米材料提高了再生沥青老化前的高温稳定性、剪切变形抵抗力和弹性行为,但一定程度上削弱了其低温塑性变形能力;多尺度纳米材料有效改善了再生沥青长期热氧和光氧老化抵抗力;综合考虑长期老化性能数据,多尺度纳米材料的推荐掺量（质量分数）为1%OEVMT+3%NanoZnO。     

水泥乳化沥青混合料性能的影响因素

针对外界因素对乳化沥青混合料性能的不同影响,通过室内试验研究了成型工艺和结合料等因素对密级配水泥乳化沥青混合料力学性能的影响,并结合扫描电镜(SEM)分析了相关机理.结果表明:采用四步成型工艺制备的混合料其马歇尔性能指标最优.水泥、乳化沥青用量明显影响混合料力学性能,乳化沥青用量不变时,增加水泥用量,混合料稳定度、抗压强度和抗压模量、抗折强度和抗折模量均明显提高;水泥用量不变时,随着乳化沥青用量的增加,混合料相应性能指标降低;推荐水泥、乳化沥青用量分别为3%和8%(以集料质量计).结合料的影响机理总结为水泥加速乳化沥青破乳、水化产物改善浆体结构、提高浆体与集料界面黏结和乳化沥青延缓水泥水化等四个方面.     

TPS改性剂对透水性沥青混合料老化性能的影响

通过对不同TPS改性剂掺量的透水性沥青混合料进行短、长期老化,采用间接拉伸试验检测老化前后沥青混合料的力学性能,来评价TPS改性剂掺量对透水性沥青混合料老化性能的影响。结果表明,随着TPS掺量增加,透水性沥青混合料抗老化性能呈下降趋势。     

High temperature properties of wax modified binders and asphalt mixtures

The influence of adding two commercial waxes (FT-paraffin and polyethylene wax) to binders of penetration grades 50/70 and 160/220 were investigated for high temperature performance of binders and asphalt concrete mixtures. Binder properties were determined by conventional test methods, dynamic mechanical analysis and bending beam rheometer testing. The high temperature properties of asphalt concrete were investigated using the French rutting tester.The addition of FT-paraffin and polyethylene wax increased the rutting resistance of mixtures for both types of binder. The FT-paraffin modified asphalt mixtures showed the best rutting resistance.Adding polyethylene wax showed the highest stiffening effect in terms of rutting factor by DMA for the binders. However, this could not be verified in asphalt mixture testing. Adding FT-paraffin improved the rutting resistance of asphalt mixtures containing low or high penetration binder, but for the mixture containing high penetration binder the specification limit was exceeded.     

Study on properties of recycled tire rubber modified asphalt mixtures using dry process

To minimize waste tires pollution and improve properties of asphalt mixtures, properties of recycled tire rubber modified asphalt mixtures using dry process are studied in laboratory. Tests of three types asphalt mixtures containing different rubber content (1%, 2% and 3% by weight of total mix) and a control mixture without rubber were conducted. Based on results of rutting tests (60 °C), indirect tensile tests (−10 °C) and variance analysis, the addition of recycled tire rubber in asphalt mixtures using dry process could improve engineering properties of asphalt mixtures, and the rubber content has a significant effect on the performance of resistance to permanent deformation at high temperature and cracking at low temperature.     

Laboratory comparison study for the use of stone matrix asphalt in hot weather climates

Stone matrix asphalt (SMA) is a hot mixture asphalt consisting of a coarse aggregate skeleton and a high binder content mortar. It was developed in Germany during the mid-1960s and it has been used in Europe for more than 20 years to provide better rutting resistance and to resist studded tyre wear. The main objective of this research study was to compare the performance of the normally used dense graded asphalt mixtures, named in this research as control mixtures, and SMA mixtures. Samples from both mixtures were fabricated at their optimum asphalt contents that were 5.3% for control mixtures and 6.9% for SMA mixtures. Comparison performance tests that included Marshall stability, loss of Marshall stability, split tensile strength, loss of split tensile strength, resilient modulus, fatigue, and rutting testing were performed on both mixtures. Test results showed that although the control mixtures have higher compressive and tensile strengths, SMA mixtures have higher durability and resilience properties. In addition, although the research could not prove the superiority of SMA in rutting resistance because of the limited sample sizes, field performance of SMA mixtures proves its superiority. Therefore, especially in hot weather climates, these properties, (durability, resilience and rutting resistance) give SMA mixtures advantages over dense graded mixtures.     

High temperature properties of rubberized binders containing warm asphalt additives

Several studies have been conducted evaluating the properties of warm mix asphalt (WMA), and it is observed that warm asphalt additives work in different ways to either reduce the viscosity of the binder or to allow better workability of the mix at lower temperatures. In terms of rubberized asphalt mixtures, they are compacted at a higher temperature than conventional mixtures, based on the field experience. If the technologies of warm mix asphalt are incorporated, it is expected to reduce the mixing and compaction temperatures of rubberized asphalt mixtures to those of conventional mixtures. This paper presents the high temperature properties of rubberized binders containing warm asphalt additives. Rubberized binders were produced at 10% by binder weight using five binder sources, and the binders with the additives were produced using two (i.e. Aspha-min^® and Sasobit^®) of the available processes and artificially short-term aged through the rolling thin film oven (RTFO) method. Tests were conducted on the binders using the rotational viscometer and the Dynamic Shear Rheometer. The results indicated that the viscosity properties of rubberized binders can be changed significantly through the use of warm asphalt additives. Also, the addition of the additives was found to improve rutting resistance of the rubberized binders.     

Laboratory comparison of the crumb-rubber and SBS modified bitumen and hot mix asphalt

The use of crumb rubber (CR) recycled from waste tires using an ambient grinding process was evaluated at two stages in asphalt formulation. First, bitumen modified with crumb rubber was evaluated by rotational viscometery (RV), dynamic shear rheometry (DSR) and conventional binder tests. Hot asphalt mixtures including crumb-rubber-modified bitumen were then evaluated by determining the permanent and fatigue characteristics and stiffness moduli of control and modified mixtures. The properties of the crumb-rubber-modified bitumen and asphalt mixtures were compared to different contents of styrene–butadiene–styrene (SBS) modified-bitumen and asphalt mixtures. The tests showed that to achieve the same performance, as with SBS-modification, the CR-content must be used at much higher than SBS. 8%-CR modification was determined as the most suitable content according to both binder and mixture tests.     

Laboratory evaluation of the effects of short-term oven aging on asphalt binders in asphalt mixtures using HP-GPC

Both the RTFO (rolling-thin film oven) aging of asphalt binders and the STOA (short-term oven aging) of asphalt mixtures are designed to simulate aging during the construction of hot mix asphalt (HMA) pavements. Many studies have been conducted evaluating the aging effects on asphalt binders since their properties can be easily measured using many conventional tests, such as rotational viscometer, DSR (dynamic shear rheometer), and BBR (bending beam rheometer). However, studies on asphalt mixture aging have been limited to mechanical properties such as strength and fatigue characteristics because considerable effort is required to identify the aging of the asphalt binder in a mixture. This study evaluated the effects of short-term oven aging on asphalt mixtures using the GPC (gel-permeation chromatography) procedure. Nine asphalt mixtures, using three different binder sources, were prepared and five short-term aging methods were used to evaluate these mixes. For comparison, the RTFO aging was also conducted for nine asphalt binders. The aging of a binder within asphalt mixtures, including polymer-modified mixtures, could be identified under various short-term aging conditions. Statistical analysis of the GPC test results indicated that two commonly used short-term aging methods in the laboratory, a 154 °C oven aging for 2 h and a 135 °C oven aging for 4 h, are not significantly different, based on the increase in the large molecular size (LMS) ratios. The RTFO aging method was found to have less effect on binder aging than the short-term oven aging methods of asphalt mixtures.     

Two- and three-dimensional micromechanical viscoelastic finite element modeling of stone-based materials with X-ray computed tomography images

This paper presents 2D and 3D micromechanical finite element (FE) models to predict the viscoelastic properties including dynamic modulus and phase angle of stone-based materials (using an example of asphalt mixtures). Heterogeneous asphalt mixtures are consisted of very irregular aggregates, asphalt matrix and a small amount of air voids. The internal microstructure of asphalt mixtures was captured with X-ray computed tomography (CT) imaging techniques. The 2D and 3D digital samples were created with the reconfiguration of the scanned horizontal surface images. The FE mesh of digital samples was generated with the locations of image pixels within each aggregate and asphalt matrix. Along the boundary of these two phases, the aggregate and matrix FEs share the nodes to connect the deformation. The micromechanical FE model was accomplished by incorporating the captured microstructure and ingredient properties (viscoelastic asphalt matrix and elastic aggregates). The generalized Maxwell model was applied for viscoelastic asphalt matrix with calibrated parameters from the nonlinear regression analysis of the lab test data. The displacement-based FE simulations were conducted for the uniaxial compression under sinusoidal cyclic loading. Overall, the predicted dynamic modulus and phase angle from 2D and 3D micromechanical models were compared favorably with lab test data of the asphalt mixture specimens. The 3D simulation with digital samples generated better prediction than the 2D models. These results indicate that the developed micromechanical FE models have the ability to accurately predict the global viscoelastic properties of the stone-based materials.