桥梁无缝伸缩缝沥青胶结料流变性能研究

利用动态剪切流变仪对桥梁无缝伸缩缝沥青胶结料进行了温度扫描试验、高温蠕变试验和低温应力松弛试验。试验结果表明,无缝伸缩缝沥青胶结料温度敏感性低,车辙因子等于1kPa时对应的温度超过120℃。适用于温带和寒带的无缝伸缩缝沥青胶结料60℃蠕变应变分别为1.68%和6.1%。无缝伸缩缝沥青胶结料低温应力松弛迅速,60s内可以松弛97%的应力,可很好地避免伸缩缝材料及伸缩缝材料与路面界面位置的应力积累,应力松弛能力可以作为评价无缝伸缩缝沥青胶结料的关键指标。     

基于BBR试验的无缝伸缩缝沥青胶结料低温性能分析

为选用适合的性能指标评价无缝伸缩缝沥青胶结料低温性能,选用SHRP计划中的弯曲流变仪(BBR)研究低温工作状态下两种新型无缝伸缩缝沥青胶结料的蠕变性能,并结合材料力学性能通过编程方法获得胶结料的应力松弛性能。试验结果显示,相比于传统低温性能指标,BBR试验指标能够极大程度减少由于高粘弹沥青性能带来的制模等误差,测试结果更准确、合理。     

短期老化对桥梁无缝伸缩缝沥青胶结料的影响

通过薄膜烘箱老化试验(TFOT)模拟无缝伸缩缝沥青胶结料的高温短期老化过程,分析老化后沥青胶结料的质量损失、弹性回复率以及流变性能。试验结果表明高温老化导致沥青胶结料中轻组分挥发,低温弹性回复下降,高低温复合模量增加,但相位角变化较小,车辙因子和疲劳因子大体呈增趋势。短期老化后沥青胶结料仍表现出很好的粘弹性,有利于保持其使用性能。     

特立尼达湖改性沥青性能研究

特立尼达湖沥青(TLA沥青)是世界著名的天然沥青,技术性能指标非常稳定.对基质沥青和TLA改性沥青的常规性能和流变性能进行分析.采用动态剪切流变仪(DSR)进行温度扫描和频率扫描试验,以评价沥青胶结料的流变性能;采用蠕变试验评价其抵抗变形的恢复能力.试验结果表明,TLA改性沥青较基质沥青有更好的高温性能,且TLA沥青掺量对沥青胶结料的性能有重要影响.     

改性剂对沥青胶结料性能指标影响的研究分析

研究了TPS、路孚8000及Sasobit改性剂对沥青胶结料性能的影响,试验结果表明:三种新型添加剂对高温稳定性均有较大提高,TPS对低温抗裂性也有较大提高,以改善沥青胶结料的高温性能和低温性能。     

基于DSR的沥青胶结料自愈合评价指标分析

为充分认识沥青胶结料自愈合评价指标的适用性,通过动态剪切流变仪(DSR)进行"疲劳-愈合-疲劳"试验,对比分析5种常见沥青胶结料自愈合评价指标(HI_1～HI_5),得到不同自愈合时间、不同损伤程度下70~#基质沥青、SBS改性沥青和橡胶改性沥青的自愈合能力,并讨论了各指标的优缺点及适用性.结果表明:不同自愈合评价指标下,3种沥青胶结料自愈合能力排序不同;HI_1可区分不同条件下沥青胶结料的自愈合程度,自愈合时间较短时更敏感;HI_2仅适用于评价相同损伤程度的沥青胶结料自愈合性能;HI_3可反映自愈合后沥青胶结料疲劳损伤的恢复程度;HI_4不仅受沥青胶结料承受荷载作用能力的影响,还与其初始复数模量的恢复能力有关,不适用于评价沥青胶结料自愈合能力;HI_5同时考虑了沥青胶结料初始复数模量和疲劳损伤的恢复,可反映沥青胶结料综合性能的恢复能力,最适合作为沥青胶结料自愈合性能评价指标.     

桥梁无缝伸缩缝材料力学性能试验分析

对英国BJ200-Green无缝伸缩缝材料进行了室内力学性能试验分析,重点对无缝伸缩缝胶结料及其混合料的高温稳定性和低温柔性进行检测。胶结料试验结果表明其软化点为84℃,低温界面粘粘强度为0.85 MPa,在1min内应力松弛可达到80%,具有很好的应力松弛能力。车辙试验结果表明在1万次加载作用下其永久变形小于15%,低温弯曲最大破坏应变大于20 000μm/m,具有很好的高温稳定性和低温柔性。     

聚合物彩色胶结料老化特性研究

针对多数彩色路面服役2～3年后出现的胶结料老化现象,开展聚合物彩色胶结料及其老化特性研究。采用正交试验设计方法,选用SEBS聚合物、树脂、橡胶油、颜料等制备不同材料组成的彩色胶结料,采用旋转薄膜法模拟彩色胶结料在拌和施工中的老化。采用蠕变-恢复试验参数分析彩色胶结料老化前后的力学性能,研究老化对蠕变-恢复性能的影响规律,探究各原材料与老化性能的相关性。结果表明,橡胶油和SEBS是影响抗老化性能的主要因素,在一定范围内,橡胶油越少,SEBS越多,彩色胶结料的抗老化性能越良好。     

高模量沥青胶结料路用性能流变学分析

以基质沥青、高模量改性沥青和SBS改性沥青的路用性能为研究对象,通过常规流变学试验方法,对比研究了高模量外掺剂和SBS改性剂对基质沥青黏弹特性的定性影响,并量化分析了不同外掺剂种类对基质沥青路用性能的影响;通过多应力重复蠕变恢复试验,对比研究了高模量外掺剂和SBS改性剂在提高基质沥青抗车辙能力上的差异和提高效果;基于加速疲劳试验方法对上述三大类沥青胶结料的疲劳损伤及失效特性进行对比研究,分析比较了不同沥青胶结料在疲劳损伤演化和疲劳寿命方面的差异.结果表明:RA(resin alloy)和PR(PR plasts)这2种常用高模量外掺剂在提高沥青胶结料劲度模量方面具有相近的效应;三大类沥青胶结料在相同试验温度条件下的永久变形抵抗能力排序为:高模量改性沥青SBS改性沥青基质沥青;三大类沥青胶结料疲劳寿命的排序为:SBS改性沥青高模量改性沥青基质沥青;此外,在使用相同基质沥青的条件下,掺加RA的高模量改性沥青比掺加PR的高模量改性沥青具有更好的抗疲劳性能.     

再生材料对旧沥青路面胶结料的再生性能影响研究

为分析不同再生材料对旧沥青路面胶结料再生性能的影响,基于实际工程抽提回收得到不同老化程度的旧沥青路面胶结料,应用新沥青材料与两种黏度等级的再生剂调配旧沥青路面胶结料制备成再生沥青,分析再生沥青的黏度与针入度指标的变化规律,并对不同再生方法的再生效果进行了比较。试验结果表明:新沥青材料对旧沥青路面胶结料的再生能力有限,再生剂对旧沥青路面胶结料性能指标的改善远优于新沥青;低黏度的再生剂能较好地恢复旧沥青路面胶结料的针入度指标,但对于老化程度较低的旧沥青路面胶结料,会使其黏度指标下降过快,而不能保证再生沥青的高温性能;建议老化等级较低的旧沥青路面胶结料采用黏度等级较高的再生剂再生的方法,老化等级较重的旧沥青路面胶结料采用黏度等级较低的再生剂与新沥青共同再生的方法。     

基于流变性能试验的沥青高温性能评价指标研究

采用基质沥青、SBS改性沥青、高模量改性沥青和高黏度改性沥青,进行了常规性能试验、复数剪切试验、重复蠕变试验和广义剪切模量试验,测试几种沥青的软化点与当量软化点、车辙因子与改进车辙因子、蠕变模量和广义剪切模量等高温性能指标.通过对比分析各指标的区分度,以及沥青性能与沥青混合料车辙性能的相关性,发现蠕变模量和软化点与动稳定度拟合关系最好,建议采用蠕变模量作为沥青高温性能评价指标,软化点作为质量控制指标.     

高黏改性沥青高温黏弹特性指标区分度分析

为得到能准确区分高黏改性沥青高温性能的评价指标,分别对3种高黏改性沥青(高黏改性剂掺量均为12%)及基质沥青进行滞后环、动态剪切流变(DSR)和软化点等试验,并采用沥青混合料车辙试验进行了验证,基于沥青混合料试验结果对3种高黏改性沥青的高温性能评价指标作了一致性和区分度分析.结果表明:3种高黏改性剂的掺入均可提高基质沥青的黏弹特性和高温性能,但改性效果不同;不同高温评价指标基本能对3种高黏改性沥青的高温性能做出一致性评价,但区分能力不同,其中滞后环试验技术指标和Carreau模型拟合的零剪切黏度(ZSV)值区分度和评价效果最好,而车辙因子和软化点较差.     

Variance analysis and performance evaluation of different crumb rubber modified (CRM) asphalt

In order to sort some important factors affecting the performances of CRM asphalt and evaluate the performances of different CRM asphalt, this study encompassed one kind of base asphalt binder, four kinds of crumb rubber, tread rubber (TR), heavy truck (HT), small truck (ST) and agriculture tire (AT) crumb rubber, two kinds of particle size, 60 mesh and 80 mesh, and three contents. Softening point, low temperature ductility, and penetration index are selected as basic evaluation indicators in analysis. Variance analysis shows that the crumb rubber content is the primary affecting factor in general, followed by the crumb rubber type, and particle size comes last. The greater the crumb rubber content is, the higher the softening point and the penetration index are, and the smaller the low temperature ductility is. Modified effects between 60 mesh and 80 mesh don’t manifest significant difference. The modified effects of TR-crumb rubber and HT-crumb rubber are better while the low temperature ductility of AT-CRM asphalt is the worst. Also according to the results of DSR and BBR test, TR-CRM asphalt has a better and comprehensive performance at the crumb rubber content of 20% by weight of base asphalt binder, and, if the price is also considered, selecting HT-CRM asphalt with the crumb rubber content of 15% is ideal. The study also finds an interesting phenomenon that the rutting factors of CRM asphalt may be remarkably different, although the softening points of them are the same.     

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.     

The effect of crumb rubber modifier (CRM) on the performance properties of rubberized binders in HMA pavements

The application of crumb rubber modifier (CRM) in asphalt mixtures is intended to improve the properties of binder by reducing the binder’s inherent temperature susceptibility. During the interaction with asphalt binder, the CRM particles absorb a portion of the oils in asphalt binder and the particles swell; therefore increasing the viscosity and stiffness of the CRM binder. Still, the performance properties of CRM binders in hot mix asphalt (HMA) pavement are considered to be unclear due to the various interaction effects of CRM with asphalt binders, depending on the CRM percentage, source and size. In this study, a laboratory investigation was conducted on the properties of CRM binders as a function of CRM processing method and percentages. A total of twenty-four CRM binders (3 binder sources * 2 CRM processing methods * 4 CRM percentages) were produced and artificially aged through an accelerated aging process. Evaluation of the CRM binders included the following testing procedures: Viscosity at high temperature, performance properties at high and intermediate temperatures, and cracking properties at low temperature. The results from this study indicated that the higher CRM percentages for CRM binders seemed to lead to a higher viscosity, a better rutting resistance and a less chance for low temperature cracking. In general, the ambient CRM was found to be more effective on producing the CRM binders that are more viscous and less susceptible to rutting and cracking.     

SBR胶乳掺量对改性乳化沥青性能的影响

为研究丁苯橡胶(SBR)胶乳掺量对改性乳化沥青性能的影响,对不同SBR胶乳掺量的改性乳化沥青进行针入度、软化点、延度和储存稳定性试验,并采用动态剪切流变仪(DSR)和弯曲梁流变仪(BBR)测试了SBR胶乳掺量对改性乳化沥青高低温性能的影响.结果 表明:随着SBR胶乳掺量的增加,改性乳化沥青的延度、软化点及软化点差逐渐增大,针入度降低;相同温度下,随着SBR胶乳掺量的增加,改性乳化沥青的复数模量、车辙因子和蠕变速率逐渐增大,劲度模量、相位角逐渐减小;综合考虑SBR胶乳掺量对改性乳化沥青各项性能指标的影响,SBR胶乳的建议掺量为4％.     

基于重复蠕变的改性沥青非线性黏弹响应分析

对4种改性沥青和1种基质沥青进行高温条件下较宽应力范围的重复蠕变试验,计算不同温度和应力水平下的不可恢复蠕变柔量Junr,分析改性沥青黏弹响应从线性到非线性的变化规律,再选择夏季沥青路面典型高温下沥青非线性响应区域内的Junr值,与沥青混合料车辙试验结果进行相关性分析.结果表明：随着温度升高,沥青的线性范围明显减小;进入非线性响应区域后,Junr值迅速增大,沥青抗永久变形能力明显降低;改性沥青的高温性能在不同温度和应力水平下存在差异,在较高温度和应力下,高强改性沥青的高温性能最优;有限样本条件下,沥青在非线性响应区域内的Junr值与沥青混合料车辙试验结果相关性较好,说明沥青混合料永久变形与沥青非线性黏弹响应关系密切.     

Evaluating permanent deformation in asphalt rubber mixtures

Permanent deformation or rutting, one of the most important distresses in flexible pavements, has long been a problem in asphalt mixtures, mainly in countries with high temperatures such as Brazil. Throughout the years, researchers have used different test methods to estimate the rutting performance of asphalt mixtures. One of the alternatives to reduce permanent deformation in asphalt pavement layers is through the use of mixtures produced with asphalt rubber. Crumb rubber from waste tires introduced into the asphalt is one of suitable application to dispose the tires and used as an additive to enhance the properties of the conventional asphalts. This work aims at comparing the rutting performance of asphalt rubber mixtures (with dense and gap-graded aggregate gradation) with the conventional dense graded mixture most used in Brazil. The asphalt rubber mixtures were produced by the wet process using continuous blend and terminal blend asphalt rubber. To study their performance, two laboratory tests, the Repeated Simple Shear Test at Constant Height (RSST-CH) and the Accelerated Pavement Testing Simulator Test (wheel tracking) were carried out. The testing results confirmed that the use of asphalt rubber binder improves significantly the resistance to rutting. The highest resistance is presented by the mixtures produced with continuous blend binders and gap-graded aggregate gradation. The results of both testing apparatus can be correlated by a linear relationship. The testing results allowed concluding that the characteristics of the asphalt rubber binders cannot be used to predict the permanent deformation resistance of the asphalt rubber mixtures.     

Preparation and rheological characterization of asphalt binders reinforced with layered silicate nanoparticles

Bentonite clay (BT) and organically modified bentonite (OBT) were used to reinforce and modify a bituminous paving asphalt binder. The modified asphalt binders were produced by melt processing under sonication and shearing stresses. The interlayer spacing of silicate layers in bentonite, organically modified bentonite and the modified asphalt binders were analyzed by wide angle X-ray diffraction (WAXD). The softening point, viscosity and ductility of the modified asphalts were tested as a function of clay content and clay type. The dynamic shear rheological tests showed that the modified asphalts have higher rutting resistance. Bending beam rheometer (BBR) test results for aged specimens (through rolling thin film oven (RTFO) and pressure aging vessel (PAV)) indicated that adding BT and OBT can significantly improve low temperature rheological properties and cracking of asphalt.