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.     

Fatigue behavior of rubberized asphalt concrete mixtures containing warm asphalt additives

The long-term performance of pavement is associated with various factors such as pavement structure, materials, traffic loading, and environmental conditions. Improving the understanding of the fatigue behavior of the specific rubberized warm mix asphalt (WMA) is helpful in recycling the scrap tires and saving energy. This study explores the utilization of the conventional fatigue analysis approach in investigating the fatigue life of rubberized asphalt concrete mixtures containing the WMA additive. The fatigue beams were made with one rubber type (?40 mesh ambient crumb rubber), two aggregate sources, two WMA additives (Asphamin^® and Sasobit^®), and tested at 20 °C. A total of eight mixtures were performed and 29 fatigue beams were tested in this study. The test results indicated that the addition of crumb rubber and WMA additive not only reduced the mixing and compaction temperatures of rubberized asphalt mixtures offset by crumb rubber but also effectively extended the long-term performance of pavement when compared with conventional asphalt pavement. In addition, the exponential function forms are efficient in achieving the correlations between the dissipated energy and load cycle as well as mixture stiffness and load cycle.     

温拌沥青混合料现场施工质量对比研究

为了评价温拌沥青混合料(WMA)在施工过程中的差异性,采用三种不同的温拌技术(Evotherm、Sasobit、Foamed)制备了8种温拌沥青混合料,对沥青混合料的含水率和集料对沥青的吸收量、面层温度的均匀性、碾压次数和面层的现场密度进行监测。研究结果表明:WMA中的含水率略高于HMA;HMA和WMA的吸收沥青含量没有显著统计学差异;WMA,铺筑后面层的温度明显低于HMA;HMA和WMA在压实度上没有明显的差别。     

温拌沥青混合料的半圆弯抗与水敏感性试验研究

疲劳破坏和水损害是温拌沥青路面重要的破坏类型之一。采用由三个现场项目提供的8种温拌沥青混合料(Evotherm、Sasobit、Foamed),进行半圆弯抗(SCB)试验和改进Lottman试验(AASHTO T283)分别评价WMA的抗疲劳性能与水稳定性。结果表明:与相应的HMA比较, WMA表现出相近或更高的Jc值;WMA技术的使用提高了沥青混合料的抗断裂性能;温拌沥青混合料和普通热拌沥青混合料的水敏感性没有显著差异。     

Laboratory evaluation of WMA mixture for use in airport pavement rehabilitation

The concept of warm mix asphalt (WMA) gives a promise for rehabilitating airport pavement to realize quick turnover to traffic after construction, however, laboratory and field data in terms of the performance-related properties are significantly lacking for using WMA in airfield in Japan. To fill this gap, three WMA mixtures (different gradations) were systematically investigated compared with the conventional airfield used hot mix asphalt (HMA) through a series of laboratory tests in terms of wheel tracking test, submerged wheel tracking test, raveling test, static bending and fatigue bending test. These WMA mixtures were made at two production temperatures (30 and 50 °С lower than the normal, respectively) by incorporating a commercially sold additive. Results showed that overall, the WMA mixture with a coarse gradation produced at the temperature 30 °С lower than the normal exhibited a comparable performance compared with the control HMA mixture, and it was further recommended for use in airport pavement rehabilitation.     

Characterization of warm mix asphalt binders containing artificially long-term aged binders

Reclaimed asphalt pavement (RAP) comprises one of the largest recycled materials, and warm mix asphalt (WMA) technologies become more commonly used due to their promising advantages in the United States and Europe. This paper addresses the laboratory investigation of performance properties of WMA binders containing aged binders. The recycled binders with the additives were produced using two (i.e., zeolite Aspha-min^® and wax Sasobit^®) of the available warm asphalt processes. The recycled WMA binders were artificially short-term and then long-term aged through the rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were carried out on the binders through the rotational viscometer, the dynamic shear rheometer (DSR), and the bending beam rheometer (BBR). In general, the results of this study indicated that (1) the additives and aged binders played an important role in determination of the binder properties; (2) the use of lower PG grade as a virgin binder (PG 58-28 in this study) was critical on offsetting the increase of binder stiffness caused by the addition of WMA additives and aged binders; and (3) even at the low recycling percentage of 15%, the lower PG grade was needed to get the results meeting current Superpave binder requirements.     

SAK温拌沥青添加剂应用研究

通过分析不同掺量沥青胶结料性能,得出SAK添加剂的适宜掺量为沥青用量的3%,采用SAK掺量为3%的沥青拌制温拌沥青混合料,进行了温拌沥青混合料的性能验证,试验结果表明,采用3%掺量SAK添加剂的沥青混合料能够满足路用性能要求。     

Effects of rejuvenator on performance-based properties of rejuvenated asphalt binder and mixtures

Firstly, the performance-based properties of rejuvenated aged asphalt binders, i.e., the blends of aged binders containing a rejuvenator at various percentages, were investigated under high, intermediate and low temperatures. The tests were conducted on the blends at three stages as follows: no aging, rolling thin film oven (RTFO) residuals and as well RTFO + pressure aging vessel (PAV) residuals through dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests. Optimum concentrations of the rejuvenator needed for the blends to reach a target PG grade were obtained from the blending charts of the rejuvenated aged binders in terms of performance properties. The rejuvenator is a soft binder containing a low asphaltene content of 2 wt%. Secondly, selected performance-based properties were conducted on hot mix asphalt (HMA) using the rejuvenated aged binder and a virgin HMA as a control mixture. Results showed that the rejuvenator affected significantly the performance-based properties of both the rejuvenated aged binders and the mixtures containing the rejuvenated aged binders. It was possible to get optimum concentrations of the rejuvenator using the blending charts so that the rejuvenated binders reach a target PG grade. The mean value of the concentrations was proved to be more reliable through the performance-based properties of the mixtures if it is used for a design value for recycling. The properties of the asphalt paving mixtures with the rejuvenated binders were even improved or in the same level as the properties of the virgin mixtures.     

Rheology of warm mix asphalt binders with aged binders

This study addresses the rheological investigation of properties of warm mix asphalt (WMA) binders containing long-term aged binders. The recycled binders with the additives were produced using two (i.e., zeolite Aspha-min® and wax Sasobit®) of the available warm asphalt processes. The main rheological factors selected in this study were relationships between loading and response as a function of time, temperature and frequency using a Bohlin Dynamic Shear Rheometer II. The results indicated that the addition of Sasobit® into recycled binders played an important role in determination of the binder properties evaluated in this study. The use of lower performance grade (PG) as a virgin binder (PG 58-28 in this study) was critical on offsetting the change of rheological binder properties due to the warm additives and the aged binders.     

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.     

The mechanical properties of asphalt mixtures with Recycled Concrete Aggregates

The need for sustainable asphalt highway design and construction is becoming a priority within the asphalt transportation industry. This trend is necessitated by the high diminishing rate of construction materials, pressing demand on existing landfill sites, rising dumping fees, and reduced emissions into the environment. Recycled Concrete Aggregates (RCA) as sustainable aggregates in Hot Mix Asphalt (HMA) is therefore investigated in this research project. The objective of this study is to characterize the mechanical properties of asphalt mixtures with recycled concrete aggregates for low volume roads (herein, the equivalent standard axle load number is low). In this study, the RCA is substituted for Michigan traprock virgin aggregates (VA) in a light traffic volume HMA (control mix) at the rate of 25, 35, 50 and 75. The hybrid VA-RCA HMA is then assessed using the Superpave™ mix performance specifications. The rutting potential using Asphalt Pavement Analyzer (APA), Dynamic Modulus (E1), Tensile Strength Ratio (TSR) for moisture susceptibility, Indirect Tensile Test (IDT) resilient modulus and the Construction Energy Index (CEI) are determined to evaluate the field performance suitability or otherwise of the mix. All 4 hybrid VA-RCA HMA mixes passed the minimum rutting specification of 8 mm. The master curves for the hybrid mixes showed that the dynamic stiffness of the hybrid mixes were less than that of the control 4E1 mix, and it decreased when the RCA increased in the mix. In terms of moisture susceptibility, the tensile strength ratio increased with decreasing RCA; with only the 75% of RCA in the mix failing to meet the specification criterion. The compaction energy index proved that using RCA would save some amount of compaction energy. It is recommended that a certain amount of RCA in HMA is acceptable for low volume roads.     

有机化合物改性沥青的性能研究

有机镁化合物(OMAGC)和有机锰化合物(OMANC)具有良好的温度稳定性,这些合成物能够添加到沥青中作为改性剂。在掺配浓度为3%的条件下,通过对AH-70基质沥青及其混合料的BBR试验、DSR试验、水稳定性试验和抗老化试验,验证了该类型改性剂能提高沥青的低温性能以及热拌沥青混合料的水稳定性和抗老化能力,适合在寒冷地区使用。     

回收料掺量对温拌再生沥青混合料性能的影响

通过室内试验研究了回收沥青混合料(RAP)掺量(质量分数)对Evotherm温拌再生沥青混合料高温稳定性、低温性能、水稳定性及疲劳性能的影响.结果表明:采用Evotherm温拌技术可将RAP掺量提高到50%;温拌再生沥青混合料的高温稳定性、水稳定性及低温性能均随RAP掺量的增加先升后降,且在RAP掺量为30%~40%时出现峰值;疲劳性能随RAP掺量的增加逐渐降低,且应变水平越高降低幅度越大;温拌再生沥青混合料的高温稳定性、水稳定性较热拌再生沥青混合料差,疲劳性能优于热拌再生沥青混合料;在相同RAP掺量下,温拌再生沥青混合料与热拌再生沥青混合料的低温性能相当.     

沥青混合料温拌技术研究与应用

结合厦门市文兴隧道沥青路面工程,对温拌沥青混合料的拌和、摊铺碾压等施工技术进行系统研究,提出了从混合料的拌和、摊铺、碾压施工工艺,温度控制等关键技术,为温拌沥青路面施工质量的控制,提供依据和参考。     

Laboratory evaluation of fatigue characteristics of recycled asphalt mixture

This paper presents the results of a laboratory study of evaluating the fatigue characteristics of hot-mix asphalt (HMA) mixtures using different testing methods. In this study, the fatigue performance of HMA mixtures was evaluated with the Superpave indirect tension (IDT) tests and beam fatigue test. The HMA mixtures containing 0%, 10%, 20%, and 30% of recycled asphalt pavement (RAP) were plant prepared with one source of aggregate, limestone, and one type of binder, PG 64–22. The fatigue properties tested included indirect tensile strength (ITS), failure strain, toughness index (TI), resilient modulus, DCSE_f, energy ratio, plateau value, and load cycles to failure. The results from this study indicated that both Superpave IDT and beam fatigue tests agreed with each other in ranking the fatigue resistance of mixtures when proper procedures were followed.     

疲劳荷载下冻融循环对CR-WMA开裂特性的影响

以温拌胶粉改性沥青混合料(CR-WMA)和热拌胶粉改性沥青混合料(CR-HMA)为研究对象,对经盐冻融循环和水冻融循环作用下的半圆试件进行三点弯曲重复加载试验,同时利用数字图像(DIC)相关技术对其开裂特性进行研究.结果表明:采用开裂位置附近点的水平应变(EXX)和以全场水平应变定义的损伤变量均可反映CR-WMA和CR-HMA在疲劳荷载作用下的抗开裂性能;CR-WMA和CR-HMA的抗疲劳开裂性能随着盐冻融循环和水冻融循环作用次数的增加而降低,且盐冻融作用对其影响大于水冻融作用;无论盐冻融还是水冻融作用,CR-WMA的抗疲劳开裂性能均优于CR-HMA.     

温拌沥青混合料在广东高速公路中的应用研究

指出了温拌沥青混合料(WMA)是一种节能环保型路面材料,在室内对掺Sasobit添加剂的WMA与同材料的HMA的路用性能进行了对比试验研究,结果显示:在拌和与压实温度比HMA低30℃时,WMA具有与HMA相当甚至更好的路用性能;拌和与压实温度的降低,混合料发生水损害的几率会增加,建议添加抗剥落剂来改善WMA的抗水损害能力;此外,Sasobit掺量过多可能会对WMA低温抗裂性能有不利影响。     

Evaluation of internal resistance in hot-mix asphalt (HMA) concrete

Accurate quantification of aggregate properties is essential for understanding their influence on hot-mix asphalt (HMA) concrete and for selecting aggregates to produce high-quality paving mixture. The objectives of this study are to develop a method to measure internal resistance in HMA mixtures and to evaluate the effect of different gradations on the rutting of mixes. Analysis showed that a HMA mix could be made more resistant to rutting by specifying an adequate range of the fine aggregate passing through the 4.75-mm (No. 4) sieve. The lower the fine aggregate percentage, the greater the difference between the coarse aggregate void volume and the total volume of fines. This indicated that the aggregate interlocking greatly occurred in the coarse aggregate. The image evaluation of aggregate morphological characteristic demonstrated that a stable aggregate skeleton resulted in more internal resistance.     

The effects of damage evaluation techniques on the prediction of environmental damage in asphalt mixtures

The main objective of this study was to investigate the effects of evaluation methods on the prediction of environmental damage (stripping) of hot mix asphalt (HMA). To achieve this objective, four different environmental damage evaluation techniques were used to evaluate asphalt mixtures prepared using different mix parameters. The environmental damage evaluation techniques include either percent reduction in indirect tensile strength or Marshall stability or percent increase in static creep deformation due to environmental damage. In addition, theTexas boiling test which is based on visual evaluation of the percent of coated aggregate was used for environmental damage evaluation.     

一种温拌剂对SBS改性沥青性能影响研究

研究了一种自制温拌剂对SBS改性沥青的物理性能和燃烧性能的影响,并通过动态剪切流变仪(DSR)温度扫描试验分析自制温拌剂对SBS改性沥青流变性能的影响。针入度、延度、软化点试验结果表明:自制温拌剂的加入能使沥青的稠度增加,能降低沥青的温度敏感性,提高沥青的高温性能;极限氧指数试验结果表明:温拌剂的加入能提高SBS改性沥青的阻燃性能;温度扫描试验结果表明:与SBS改性沥青相比,掺加6%温拌剂的SBS沥青有更大的复合模量、车辙因子、疲劳因子,更小的相位角,这说明温拌剂的加入提高了SBS改性沥青的车辙性能和疲劳性能。