钢桥面铺装常用改性沥青高温性能关键指标分析

通过多应力蠕变恢复(MSCR)试验,分析了3种高性能改性沥青(A、B、C沥青)和SBS改性沥青(D沥青)的不可恢复蠕变柔量(Jnr)、蠕变恢复率(R)及相应的应力敏感性指标;通过室内车辙试验和动态蠕变试验,分析了4种改性沥青混合料的高温抗变形性能指标及其相关性.结果 表明:与B、D沥青相比,A、C沥青在不同应力条件下的Jnr值较小,R值较大,对应力的敏感程度较低;A、C沥青混合料的高温性能要明显优于B、D沥青混合料;相较于室内车辙试验,动态蠕变试验与改性沥青Jnr、R之间的相关性更好;使用高应力(3.2、6.4、12.8 kPa)条件下MSCR试验获取的Jnr及R值来评价改性沥青混合料的高温性能较为合理;A、C沥青的应用可以显著提升钢桥面铺装磨耗层的高温稳定性.     

基于MSCR试验的改性沥青高温性能评价

应用多应力蠕变恢复(MSCR)试验,对SBS改性沥青、胶粉改性沥青和高强沥青在不同温度下的不可恢复蠕变柔量Jnr与应力敏感性指标Jnr-diff进行了分析,依据AASHTO MP19-10标准对3种改性沥青进行了交通分级,并采用改性沥青混合料三轴动态蠕变试验进行了验证.结果表明:在非线性范围内应力和温度对改性沥青抗永久变形能力的影响具有等效性;随着温度的升高,改性沥青流变性能的线性范围逐渐变窄,应力敏感性更为显著;胶粉改性沥青在低应力区间的高温性能优秀,但是其线性范围很小,当应力或温度提高时胶粉改性沥青的流变性能迅速进入非线性范围,高温性能急剧衰减;不同应力和温度下改性沥青高温性能的排序发生改变,基于AASHTO MP19-10标准的交通分级能够反映改性沥青的这一特性.     

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.     

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.     

改性沥青混合料高温性能及其评价方法

为研究改性沥青混合料的高温性能,设计了分别添加3种抗车辙剂的Sup20沥青混合料,并采用改进车辙试验,以回归段动稳定度(DRS)与相对变形率δ等指标评价了这3种沥青混合料的高温稳定性能.结果表明:与传统动稳定度(DS)评价指标相比,改性沥青混合料的DRS与δ具有很好的相关性,更适用于评价DS值较大的改性沥青混合料高温稳定性.     

TB复合高模量剂改性沥青的黏弹特性及混合料性能研究

基于DSR、MSCR、BBR试验,研究TB(Terminal Blend)复合高模量剂改性沥青的的黏弹特性,并与20%TB(胶粉)沥青、5%SBS改性沥青进行了对比分析。通过车辙试验、低温弯曲试验与疲劳试验,对比分析了TB复合高模量剂改性沥青混合料的高低温性能和疲劳特性。结果表明,掺加高模量剂能显著改善TB(胶粉)沥青的中温和高温黏弹特性,提高抗车辙因子、增大弹性恢复率、降低不可恢复蠕变柔量;增加TB胶粉掺量能降低复合改性沥青的低温PG分级;(20%、25%)TB胶粉+(6%、8%)KT-1高模量剂复合改性沥青混合料的抗车辙性能、力学性能和抗疲劳耐久性能均优于5%SBS改性沥青混合料,TB复合高模量剂改性沥青混合料适用于高温重载地区沥青路面。     

PE-Y改生沥青混合料高温稳定性试验研究

以室内车辙试验作为基本试验方法,引入综合稳定指数C作为评价指标,对PE-Y改性沥青混合料的高温稳定性进行了研究.试验结果表明,掺加PE-Y抗车辙剂后,对提高紧密骨架密实结构沥青混合料的高温稳定性效果显著,SK90#基质沥青的自身品质及其与PE-Y抗车辙剂的搭配组合效果最好.PE-Y变形体的加筋嵌挤、胶粘作用对提高混合料的高温稳定性效果十分显著,即便在很高的温度条件下,PE-Y变形体交织搭桥形成的空间网络结构仍然能够发挥作用;而且能够降低沥青混合科的水敏感性,使得混合料在荷载、高温和水耦合作用的严酷条件下,仍然具有较强的抵抗永久变形的能力.     

应力吸收层沥青混合料性能研究

采用2种Strata-T改性沥青,通过单轴贯入试验及复合车辙试验分析了应力吸收层(SAMI)沥青混合料的抗剪性能;通过0～25℃小梁弯曲试验及15,25℃疲劳试验,分析了SAMI沥青混合料在不同温度下的弯拉及疲劳性能;同时将SAMI沥青混合料与SBS改性沥青混合料(AC5)的主要性能进行了对比分析.结果表明:设置SAMI的路面结构其抗车辙能力并不会显著降低,SAMI沥青混合料在O～25℃均具有很好的变形能力,并得到了SAMI沥青混合料的疲劳方程.     

高模量沥青混合料温度粘弹性能研究

采用多应力蠕变恢复试验(MSCR)和车辙试验表征高模量沥青的粘弹性与高温稳定性,通过微观测试分析了改性剂在沥青中的分散程度。通过动态模量试验,研究了高低温条件下高模量沥青混合料模量与相位角的变化规律,采用疲劳试验研究了材料在动态荷载作用下的服役寿命。试验结果表明:高模量改性沥青在高温下的不可恢复蠕变量仅为基质沥青的17%,约为抗车辙剂改性沥青的27%,高模量改性剂的分散性较抗车辙剂更佳;沥青混合料的动稳定度与沥青的蠕变柔量(Jnr3.2)成反比,高模量沥青混合料具有较好的温度稳定性,可延长道路的使用寿命,适用于温度跨度大的重载地区。     

不同温度与荷载作用下的胶粉复合改性沥青混合料抗车辙性能试验研究

探讨了不同荷载、不同温度对胶粉复合改性沥青混合料高温性能的影响,并对黏结料分别为基质沥青、SBS改性沥青、胶粉改性沥青及胶粉复合改性沥青的4种类型混合料抗车辙性能进行对比分析。采用车辙试验机,对碾压成型的试件,参照"沥青混合料车辙试验"T0719—2011中规定的方法进行车辙试验,得出了4种沥青混合料在不同荷载、不同温度下的动稳定度DS,并对动稳定度DS进行分析:掺加复合剂后,胶粉复合改性沥青混合料的抗车辙性能改善显著,且温度与荷载越大,改善效果越明显。     

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.     

The effect of styrene–butadiene–rubber/montmorillonite modification on the characteristics and properties of asphalt

In order to study the effect of styrene–butadiene–rubber/montmorillonite (SBR/MMT) modification on the characteristics and properties of asphalt, modified asphalts were prepared by incorporating MMT into SBR and mixing this into asphalt. The X-ray diffraction (XRD) results show that SBR/MMT composites may form an intercalated structure and SBR/MMT modified asphalts may form an exfoliated structure. The morphologies of the samples have been characterized by fluorescent microscopy. The results indicate that SBR/MMT modified asphalts formed an ideal fine network structure. The addition of SBR/MMT to asphalt increased both the softening point and viscosity and decreased the penetration of the modified asphalts at high temperatures. High-temperature storage stability tests indicated that the modified asphalts are very stable in some SRB/MMT, SBR/MMT content range. Especially, the modified asphalts exhibited higher complex modulus (G¹) and lower damping factor (tan δ). It implies that SBR/MMT displays improved viscoelastic properties, resulting in enhancing its resistance to rutting at high temperature.     

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.     

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.     

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.     

无缝伸缩缝沥青胶结料高温性能指标区分评价

为优选无缝伸缩缝沥青胶结料类型,提高无缝伸缩缝弹塑体高温稳定性,对选用的3种无缝伸缩缝沥青胶结料分别开展沥青基本性能试验、动态剪切温度扫描试验和多应力蠕变恢复试验,采用软化点、车辙因子与相位角,以及蠕变恢复率和不可恢复蠕变柔度等指标来评价3种无缝伸缩缝沥青胶结料的高温性能,并进行一致性和区分度分析,最后结合沥青混合料车辙试验进行验证.试验结果表明:受弹塑体中沥青胶结料聚合物掺量高及其高延迟弹性恢复能力的影响,国内外现行关于无缝伸缩缝沥青胶结料规范采用的软化点、车辙因子等指标对无缝伸缩缝沥青胶结料高温性能评价的一致性存在偏差,而基于多应力蠕变恢复试验的黏弹特性指标具有较好的一致性,且区分度明显.因此推荐采用区分度和一致性更可靠的多应力蠕变恢复试验作为评价无缝伸缩缝沥青胶结料高温性能的关键控制指标.     

Laboratory performance comparison of the elastomer-modified asphalt mixtures

In this study, permanent deformation test results on the cylindrical samples produced with the Marshall compaction were compared with the wheel-tracking test results. Three different elastomeric polymer modifiers (OL, EL, and SB) were used. Repeated creep and LCPC wheel-tracking tests were realized at different loading conditions and temperatures. Repeated creep tests at 40 °C temperature do not correlate well with the LCPC wheel-tracking test results at high temperature (60 °C). Performance level of the elastomeric-modified asphalt mixtures can be different for same mixtures at different performance approaches. The evaluation of the dynamic creep test showed that the test can be used as an indicator of potential rutting, but the results in these cases should be confirmed with other more reliable tests. Also it is thought that gradation changing is more effectual than compaction effort types in view of evaluating efficiency of rutting test methods.