两种沥青胶浆的疲劳及自愈合性能试验

为了研究沥青胶浆的疲劳及自愈合特性,利用动态剪切流变仪（DSR）进行时间扫描及疲劳-愈合-再疲劳测试,并通过原子力显微镜（AFM）对细观结构进行观测,比较分析了不同粉胶比下基质沥青胶浆和苯乙烯-丁二烯-苯乙烯嵌段共聚物（SBS）改性沥青胶浆的疲劳性能,以及在常温（25℃）下3个不同间歇期的自愈合性能。试验发现：SBS沥青胶浆具有更好的疲劳和自愈合性能,两种沥青胶浆疲劳寿命均随粉胶比的增大而增加,同一粉胶比条件下,更长的间歇期有利于其自愈合,过大或者过小的粉胶比都会降低沥青胶浆的自愈合性能;AFM观测结果表明：基质沥青胶浆出现明显的"蜂状结构",粉胶比增加,矿粉吸附更多的沥青质,"蜂状结构"变多,与沥青界面内聚力作用增强,提高了抗疲劳性能,SBS改性剂与沥青相容性良好,改性沥青胶浆没有出现"蜂状结构",改性剂的加入增强了分子间内聚力,有助于提高抗疲劳性能,因此建议路面材料选用改性沥青胶浆。     

Dynamic mechanical characterization of asphalt concrete mixes with modified asphalt binders

The primary objective of this work is to characterize and compare the dynamic mechanical behavior of asphalt concrete mixes with styrene butadiene styrene (SBS) polymer and crumb rubber modified asphalt binders with the behavior of mixes with unmodified viscosity grade asphalt binders. Asphalt binders are characterized for their physical and rheological properties. Simple performance tests like dynamic modulus, dynamic and static creep tests are carried out at varying temperatures and time. Dynamic modulus master curves constructed using numerical optimization technique is used to explain the time and temperature dependency of modified and unmodified asphalt binder mixes. Creep parameters estimated through regression analysis explained the permanent deformation characteristics of asphalt concrete mixes. From the dynamic mechanical characterization studies, it is found that asphalt concrete mixes with SBS polymer modified asphalt binder showed significantly higher values of dynamic modulus and reduced rate of deformation at higher temperatures when compared to asphalt concrete mixes with crumb rubber and unmodified asphalt binders. From the concept of energy dissipation, it is found that SBS polymer modification substantially reduces the energy loss at higher temperatures. Multi-factorial analysis of variance carried out using generalized liner model showed that temperature, frequency and asphalt binder type significant influences the mechanical response of asphalt concrete mixes. The mechanical response of SBS polymer modified asphalt binders are significantly correlated with the rutting resistance of asphalt concrete mixes.     

Improvements on asphalt mixtures rutting performance characterization by the use of low shear viscosity

The relationship between the rutting performance of dense asphalt concretes and the low shear viscosity (LSV) of different asphalt binders was analysed in a previous work. A LSV limit was found for the original asphalt to prevent the rutting of the mixtures, and in addition, a model to predict the rutting performance based on the LSV of the asphalt binder was validated. With the aim of amplifying the criterion previously found, the performances of micro and stone mastic asphalt mixtures are studied in this work. Conventional, multigrade and polymer modified asphalts were used as binders. Considering that the properties of original and aged asphalts must be taken into account for a better asphalt binder characterization, LSV measurements on aged asphalts were also done in order to analyse their relationship to the mixtures rutting performance. The micro and stone mastic asphalt mixtures showed a similar behaviour as the dense grade asphalt concrete in the previous study. Regarding the control of rutting, a LSV limit of 500 Pa.s was found for original asphalts, while 2,000 Pa.s was the limit for aged asphalt binders. The model to predict the rutting performance of asphalt mixtures was amplified, incorporating both original and aged asphalt LSVs as appropriate input data.     

Effects of high friction aggregate and PG Plus binder on rutting resistance of hot mix asphalt mixtures

The rutting resistance of hot mix asphalt (HMA) Superpave? mixes in surface course materials was investigated using asphalt material characterisation tests and a digital imaging processing (DIP) technique. The effects of the type of aggregate, the type of binder and the binder content on rutting resistance were quantified. Two types of aggregate were examined: Superpave? SP12.5 and high friction SP12.5 FC2. Both a modified (PG Plus) and an unmodified binders were considered at the optimum binder content and the optimum content plus an additional 0.5%. To accurately identify the effect of each variable, the shear upheave of these mixes was also quantified. The DIP technique involved estimating the number of aggregate contacts, the total contact length and internal structure index of two-dimensional images of the experimentally tested samples. The results showed that both the rutting resistance and stiffness of HMA surface mixes were sensitive to aggregate type, binder type and binder content. A high friction aggregate provided a better internal structure characteristic, as well as superior rutting resistance and stiffness for HMA mixes. The use of PG Plus and the addition of 0.5% to the optimum binder content negatively affected HMA stiffness and rutting resistance. However, the levels of rutting resistance for all mixes were acceptable (rut depth < 12.5 mm), even when the shear upheave was considered. Internal structure indices measured by DIP were effective for capturing changes in the internal HMA structure with respect to aggregate type and asphalt cement content.     

Investigating the effect of nanoparticles on the rutting behaviour of hot-mix asphalt

Rutting is considered as one of the major damages in asphalt mixtures. In this study, different types of nanoparticles such as TiO₂, Al₂O₃, Fe₂O₃ and ZnO in different percentages were added to the base asphalt binder in order to decrease the rutting potential of hot-mix asphalt (HMA). In the first step, asphalt binder tests for characteristics such as penetration grade, ductility, softening point and viscosity were performed on the asphalt binder modified by the nanoparticles. Then, after preparing HMA samples, the static creep test was done at two stress levels at a specific temperature. Results of this study showed that using the nanoparticles improved the behavioural properties of the asphalt binder and decreased rutting in asphalt mix samples. Furthermore, scanning electron microscope images taken from the asphalt binder samples modified by the nanoparticles demonstrated that these nanoparticles were properly distributed in the asphalt binder space and had a positive effect on the rutting performance of the asphalt mixes.     

反应性弹性体三元共聚物改性沥青及其混合料性能与机制

采用黏度试验和动态剪切流变试验研究了反应性弹性体三元共聚物（RET）对基质沥青与苯乙烯-丁二烯-苯乙烯嵌段共聚物（SBS）改性沥青性能的影响,通过原子力显微镜（AFM）分析了SBS改性沥青和RET-SBS改性沥青的表面形貌特征,并采用车辙试验、低温弯曲试验、弯曲疲劳试验及加速加载试验评价了RET改性沥青混合料的各项技术性能,最后通过Weibull分布,分析了不同RET改性沥青混合料在不同失效概率下的疲劳性能。结果表明：RET的掺入提高了沥青的黏度和抗车辙因子,对沥青的高温性能有较大改善;通过掺入RET-SBS,增加了改性沥青中的黏性成分;相较于SBS改性沥青,RET-SBS改性沥青的表面粗糙度显著增大;RET改性剂能够明显改善沥青混合料的高温稳定性;RET与SBS改性剂复配,可有效弥补RET对沥青混合料低温性能的不足,明显改善沥青混合料的疲劳性能和高温长期稳定性。     

Fatigue and healing performance assessment of asphalt binder from rheological and chemical characteristics

The fatigue and healing performance of asphalt binder affect the durability of asphalt concrete and by extension, asphalt pavements. The objectives of this paper are to (1) estimate the fatigue and healing characteristics of asphalt binder by newly developed linear amplitude sweep (LAS) and LAS-based Healing (LASH) protocols, and (2) investigate the relationship between chemical composition of asphalt and engineering performance. Three neat asphalt binders (Pen-30, Pen-50 and Pen-70) and one SBS modified binder are selected for this study. Experimental results indicate that the SBS binder has advanced fatigue resistance among all tested binders and the softer neat binder with a higher penetration grade generally displays better fatigue performance. The fatigue failure occurrence is a significant threshold for healing potential comparison. The rate of healing (H^R) results suggest that the best healing potential is with Pen-70 binder in pre-failure conditions followed by the SBS binder, Pen-50 and Pen-30 binders. However, the SBS binder presents better healing performance than Pen-70 binder in post-failure condition. Further solvency fractionation, into saturates, aromatics, resins and asphaltenes, indicates that the asphaltene content is negatively proportional to the quantified binder fatigue life whereas the H^R index is found to be well correlated to the weight percents of saturates and ratio of saturates to aromatics (S/Ar). The combined use of LAS and LASH tests is recommended for effectively distinguishing and designing the fatigue-healing performance of neat and modified asphalt binders. Limiting the contents of asphaltenes would be of help to improve the binder fatigue resistance and either saturates percent or S/Ar parameter should be considered to assure the self-healing potential of asphalt binder.     

Effect of warm mix additives on the interfacial bonding characteristics of asphalt binders

The quality of the interfacial bonding between asphalt binder and aggregates plays a significant role in determining the durability of asphalt mixtures. Warm mix asphalt (WMA) modifiers have been used extensively in the last decade primarily to reduce production and compaction temperatures as well as to improve workability of asphalt mixtures. This study aimed to provide better understanding of the effects of these WMA modifiers on the interfacial bonding between asphalt binders and aggregates. The evaluation focused on measuring surface energy of binders in unaged and aged states and aggregates and then calculating energy parameters that describe the potential of a given asphalt-aggregate combination to resist fatigue cracking and moisture damage. Results show that the combination of asphalt-WMA additive, as well as the content applied of WMA additive has a significant impact on the fatigue cracking and moisture damage resistance. The results suggest that it is poor practice to use a given type and percentage of WMA modifier without regard for binder type. Instead, test methods are recommended to evaluate the compatibility of asphalt binder, WMA additive type/content, and aggregates for improved performance at different conditions.     

Investigation of fatigue and fracture properties of asphalt mixtures modified with carbon nanotubes

Load‐induced cracking is one of the primary forms of distress in asphalt pavements at intermediate temperatures. Binder modification is a good alternative to promote the cracking resistance of asphalt mixtures. In the current research study, the effects of carbon nanotubes as a binder modifier on the fatigue and fracture performance of asphalt mixtures are investigated. The carbon nanotubes are added at five different percentages ranging from 0.2% to 1.5% to the base binder to study their effects on the fracture resistance and fatigue life of the asphalt mixtures. Using the cracked semi‐circular bend specimen, the critical value of J‐integral (Jc) was obtained for the investigated modified asphalt mixtures. Also, the fatigue behaviour of asphalt mixtures was studied using flexural beam fatigue test specimen. By employing the ratio of dissipated energy change approach, the plateau value of tested mixtures was determined as a measure of fatigue performance. Results showed that the carbon nanotubes can enhance both fracture resistance and fatigue performance of tested asphalt mixtures especially at higher percentages of the carbon nanotube.     

The use of asphalt low shear viscosity to predict permanent deformation performance of asphalt concrete

The permanent deformation performance of asphalt concrete is strongly dependent on the rheological properties of the asphalt binder. It has been recognized that the asphalt’s low shear viscosity (LSV) characterizes the mixture’s rutting resistance. At the same time, the pavement temperature is one of the main factors that significantly affect the mixture performance. In this work the rutting performance of mixtures prepared with the same aggregate gradation and different binders [conventional (C), multigrade (M) and polymer modified (PM) asphalts] were evaluated by using wheel tracking tests (WTT) performed at 50, 60, 70 and 80°C; in parallel, the LSV of asphalts were measured at the same temperatures. The relationship between the asphalt’s LSV and rutting, to predict asphalt mixture performance, was discussed and a criterion to consider the effect of LSV is proposed.     

老化对改性沥青微观结构及疲劳性能的影响

为了研究老化对改性沥青微观结构及疲劳性能的影响,通过沥青常规指标测试试验、动态剪切流变（DSR）试验和AFM测试试验,从宏细观角度分析了老化前后苯乙烯-丁二烯-苯乙烯三嵌段共聚物（SBS）改性沥青和胶粉改性沥青的针入度、延度和软化点及疲劳性能、微观结构的变化情况。结果表明：随着老化程度的加深,两种改性沥青的稠度、硬度增加,高温性能得到改善,而温度敏感性变低,低温抗裂性能变差。综合分析针入度比、延度比和软化点比得出胶粉改性沥青的抗老化性能优于SBS改性沥青;随温度的降低、频率的增大和老化程度的加深,两种改性沥青的抗疲劳性能变差;微观结构观测结果显示,SBS改性沥青具有"蜂型结构",老化后"蜂型结构"的体积增大、高度增加、数量减少;胶粉改性沥青没有"蜂型结构",胶粉颗粒与沥青在共混共融过程中发生溶胀、脱硫和降解等行为会影响沥青中"蜂型结构"的形成;老化前后胶粉改性沥青表面形貌粗糙度和高度变化不大;胶粉改性沥青的抗疲劳、抗老化和高温性能总体优于SBS改性沥青。     

苯乙烯-丁二烯嵌段共聚物与废橡胶粉复合改性高黏沥青及混合料性能研究

为了评价高黏改性剂对沥青性能的影响,采用高速剪切法制备了苯乙烯-丁二烯嵌段共聚物(SBS)改性沥青、废橡胶粉改性沥青和两种SBS/橡胶粉复合改性高黏沥青。通过三大指标试验、黏度试验、高温车辙试验和低温小梁弯曲试验,研究了高黏沥青的高低温性能、感温性能及沥青混合料路用性能。结果表明:4种改性沥青的高低温性能随各自改性剂掺量的增加逐渐提高,掺加10%北美岩沥青或2.5%多聚磷酸(PPA)的高黏沥青感温性能更稳定,较大幅度提升了黏度值,高温性能改善明显;掺加2.5%PPA的高黏沥青及其混合料能够更好地抵抗高温条件下的性能衰减,保证了使用效果,更适用于温度较高地区;掺加10%北美岩沥青的高黏沥青及其混合料在低温条件下性能良好,推荐在低温地区使用。     

粉煤灰／海泡石纤维复合沥青混合料的制备与性能研究

从海泡石纤维和粉煤灰纤维的微观结构特性出发，进行粉煤灰，海泡石复合纤维增强沥青复合材料的制备。通过路用性能试验，研究了海泡石纤维和粉煤灰纤维对沥青混合料性能的影响以及结合机理。结果表明，添加适量海泡石和粉煤灰纤维可以制备性能优良的纤维复合沥青混合料。海泡石纤维对沥青表现极强吸持能力，有效调节沥青与胶浆的含量。粉煤灰纤维在沥青中主要起加固和改善混合料的作用。两种纤维的添加，使沥青混合料的高温变形性、水稳定性、低温抗裂性和抗疲劳性等显著提高。     

Effect of warm mix asphalt chemical additives on the mechanical performance of asphalt binders

Warm mix asphalt (WMA) has become very popular in asphalt pavement construction because it allows reducing both energy consumptions and carbon emissions. WMA can be obtained by using different types of additives and can be produced, applied, and compacted at temperatures 20–40 °C lower than hot mix asphalt. WMA additives allow reducing the working temperatures without compromising the final performance of the asphalt concrete. Many WMA additives are available on the worldwide market and some of them reduce the viscosity of asphalts binder (organic additives or foam) whereas others do not act on this sense (chemical additives). This study focuses on the effect of chemical additives on the performance of asphalt binders for WMA production. To this purpose, a neat bitumen, a polymer modified bitumen (PMB) and two different chemical additives were selected. All the binders were characterized through conventional tests, DSR, MSCR, FTIR and microscopic analysis. The result clearly showed that the influence of the chemical additives on the neat bitumen is negligible or non-existent. On the contrary, significant changes were observed in the modified bitumen properties. Specifically, chemical additives reduce the viscosity temperature susceptibility of PMBs in the temperature range between 80 and 140 °C, increase the rutting resistance potential and the elastic response of PMBs at high temperatures. Moreover, a morphological inspection supported the modifications observed in the rheological properties of PMBs.     

TerminalBlend废胶粉-纳米SiO_2改性沥青粘温关系及低温韧性

为评价废胶粉-纳米复合改性沥青的高温抗变形性、流变特性及低温韧性,制备了湿法Terminal Blend胶粉-纳米SiO_2复合改性沥青,并借助旋转粘度、针入度、软化点、5℃和15℃延度试验进行了性能表征,还基于实测表观粘度拟合了复合改性沥青粘度-温度关系。结果表明:掺加纳米SiO_2后,复合改性沥青针入度减小,软化点升高,高温抗变形性能得到改善,且纳米SiO_2掺量越大,改善越显著;纳米SiO_2掺量4%时5℃延度比未掺前提高约37.5%。此外,复合改性沥青高温粘度较基质沥青和未纳米改性时有所增加,但135℃粘度不超过1500cP,施工和易性良好;粘度数据拟合还表明在135~200℃温度域内,复合改性沥青粘温关系符合较好的指数关系。     

Effects of recycled asphalt pavements on the fatigue life of asphalt under different strain levels and loading frequencies

Fatigue lives of Hot Mix Asphalt (HMA) and binder have been studied separately for a long time. However, fatigue lives of HMA containing Recycled Asphalt Pavement (RAP) and the binder extracted from the same HMA containing RAP have not been studied yet. This study examines the effects of RAP, loading frequency and strain level on the fatigue lives of asphalt mixtures and binders. In addition, the relationship between the fatigue lives of asphalt mixture and binder is determined. Beam fatigue tests were conducted to determine the fatigue behaviors of two asphalt mixtures: one with 35% RAP and the other without RAP. To evaluate binder’s fatigue behavior, binders were extracted and recovered from these two mixtures. Then, fatigue lives of these two binders were determined using time sweep and Linear Amplitude Sweep (LAS) tests. Results show that presence of RAP in mixture causes a decrease in the mixture’s fatigue life, whereas it causes an increase in the fatigue life of binder. As expected, an increase in loading frequency results in an increase in the fatigue lives of asphalt mixture as well as binder. In addition, increase in strain level causes a decrease in the fatigue lives of both mixtures and binders. Fatigue lives of binders from time sweep and LAS tests show a good correlation with the mixture’s fatigue life by the beam fatigue test.     

Performance of porous asphalt mixture with various additives

The objective of this study is to evaluate the approaches to improve the durability and strength of the porous asphalt through laboratory testing. Porous asphalt specimens were prepared using three types of binders: high-viscosity binder (HVB), PG76-22 and PG70-22. Various additives: fibre, hydrated lime and DBS polymer, were utilised in the porous asphalt. Comprehensive laboratory tests, including strength test, binder draindown test, Cantabro abrasion test, moisture susceptibility test, rutting test, thermal stress restrained sample test, and permeability test, were conducted. It is found that HVB significantly improved the overall performance of the porous asphalt; DBS additive improved its high-temperature performance, but lowered the cracking resistance at low temperature as well as the durability; fibre enhanced its durability and anti-cracking performance at low temperature; hydrated lime improved its moisture stability while weakening its durability. It is concluded that HVB and polyester fibre should be used in all porous asphalt; DBS additive is good for porous asphalt in high-temperature areas, and hydrated lime can be added to porous asphalt in rainy areas.     

多聚磷酸改性沥青研究现状及展望

为明确多聚磷酸(PPA)改性沥青的研究现状,系统阐述了PPA对沥青的改性机理,归纳了PPA改性沥青的制备工艺,重点梳理了PPA对沥青路用性能的影响规律,论述了PPA改性沥青未来研究的发展方向。分析结果表明:PPA改性沥青的作用机理和制备工艺研究不足是制约其在我国推广使用的重要原因;PPA的添加能明显改善沥青的高温性能和抗老化性能,其对沥青水稳定性的影响取决于集料和沥青类型等多方面因素,而PPA改性沥青的低温性能和疲劳特性目前尚无定论,有待进一步研究。     

Effect of ageing on different modified bituminous binders: comparison between RTFOT and radiation ageing

Standard laboratory ageing methods of bitumen only take into account the effect of thermo-oxidation during the service life of a pavement but the effect of high energy cosmic radiation on site is not simulated in these procedures. The aim of the present work is to compare the laboratory simulated short term bitumen ageing (rolling thin film oven test) with ageing produced by short exposures of bitumen samples to Ultra Violet and gamma radiation. The influence of ageing agents on the thermal properties and rheological performance of the pristine and modified bitumen binders has been evaluated in this study. The thermal behavior of various aged bitumens is characterized by both isothermal as well as non-isothermal thermogravimetric analysis. The thermoanalytic investigations on bituminous samples are carried out to evaluate the thermal stabilities and activation energies of the binders and the life time prediction of the materials is made with the help of the kinetic information. It is found that modified bituminous binders are more resistant to heat and radiation. Different rheological tests are conducted by dynamic shear rheometer to examine the effect of ageing in terms of bitumen oxidation and polymer phase degradation which has a major consequence on high temperature rutting or low temperature cracking. Type of modifier is found to be of decisive importance. Creep and recovery tests show that the structure-time dependency of pristine aged bitumen is influenced much by stress and temperature than in the case of modified aged bitumens. The study has revealed that the elastomeric modifier protects the bituminous binder more than plastic modifier or nano filler. Finally, a fair correlation has been made between standard RTFO ageing and radiation aging.     

复合胶粉改性沥青的微观结构与流变特性

在基质沥青中加入18%的废胎橡胶粉和2%的SBS,通过湿法得到复合胶粉改性沥青（CCRMA）。采用扫描电镜（SEM）和动态力学的方法（DSR）研究了改性沥青的微观结构和较宽温度范围的流变性能;通过对复数模量主曲线的拟合,在更宽频率范围内研究该沥青的流变特性。结果表明,胶粉颗粒的表面网状结构可很好地吸附沥青,改性后的沥青...