短切PAN基碳纤维导电沥青混合料性能试验研究

为了确定碳纤维导电沥青混合料的合理碳纤维掺量,选用短切聚丙烯腈(PAN)基碳纤维作为导电相材料,通过大量室内试验分析了碳纤维掺量对导电沥青混合料AC-13C的马歇尔性能和导电性能的影响,并验证了其路用性能。结果显示,相同油石比下,随着碳纤维掺量的增加,导电沥青混合料的毛体积密度、沥青饱和度和马歇尔稳定度呈先增后减的变化趋势,空隙率和矿料间隙率呈先减后增的变化关系,而流值一直增大。通过对碳纤维掺量不同范围的沥青混合料分别采用AC、调整和SMA的技术标准,确定了合理的最佳油石比,且最佳油石比与碳纤维掺量之间呈良好的半对数相关关系。同时,在最佳油石比下,导电沥青混合料电阻率的对数与碳纤维掺量之间呈良好的幂函数关系,且0.1%碳纤维掺量的沥青混合料的各项路用性能指标均达到气候条件要求高的改性沥青混合料和SMA的技术要求。因此,适宜的碳纤维掺量对导电沥青混合料可起到优良的增强作用,并形成稳定的导电网络,综合各项性能和导电发热的技术要求,建议碳纤维的适宜掺量取0.1%。     

沥青混合料的工作和易性实验研究

依据AASHTO规范设计AC-13沥青混凝土,选择两种具有代表性的温拌剂Advera和Sasobit.采用旋转压实剪切实验机(GTM)成型试件,从力学指标(剪应力)及做功改变试件空隙率两方面,探讨了沥青混合料的工作和易性.实验结果表明:温拌沥青混合料的工作和易性在适宜拌和压实温度范围内较热拌沥青混合料的好;推荐采用8％空隙率时的旋转压实次数作为沥青混合料工作和易性的评价指标.     

基于沥青混合料性能的NovaChip超薄磨耗层工作性能研究

基于NovaChip超薄磨耗层沥青混合料的材料性能,对沥青、集料、矿粉等材料质量进行了严格的控制,根据集料的筛分结果进行了级配初选,而后根据实际情况选取了对应的试验级配,并通过试验确定了沥青混合料的最佳油石比,进而对沥青混合料进行了水稳定性、高温稳定性、析漏试验等各方面的验证。将确定好的配合比应用于实际工程中,经过长时间的观测以确定超薄磨耗层的工作性能,结果表明超薄磨耗层的应用,可以有效地降低噪音,提高路面抗滑性,保护路基,延长路面使用寿命。     

沥青-集料粘附性评价方法研究进展

沥青与集料胶浆界面是沥青混合料最薄弱的地方,会直接影响其结构强度、水稳性、疲劳性等主要性能,从而制约沥青路面的服役寿命。水稳性是长期以来制约沥青路面性能的棘手问题,沥青-集料间的界面粘附是解决水稳性的关键所在。但是,因为混合料本身组成和界面粘附机理的复杂性,所以至今没有一种普遍认同的标准试验方法来测试沥青与集料的粘附性。本文从定性和定量两个角度详细总结沥青与集料粘附性评价方法的研究现状,并对比分析了各评价方法的优缺点及适用条件,以及提出了各种方法存在的问题,为后期新的评价方法的提出和新材料的选用提供参考。     

基于大样本的沥青与粗集料原料对混合料水稳定性的影响分析

沥青与粗集料的种类与质量是决定沥青路面质量的关键因素,为定量表征不同沥青型号、生产厂家、粗集料性质等对沥青混合料水稳定性的影响,分析相同种类、不同产地沥青混合料水稳定性差异的显著性水平。本研究基于大样本的沥青混合料生产配合比数据库,采用大数据分析方法,定量研究沥青与集料各参数差异对混合料水稳定性的影响程度。首先通过秩和检验法分析了不同沥青与粗集料种类组合之间水稳定性指标的差异性,然后通过广义因素方差分析法研究了不同厂家相同型号沥青混合料水稳定性的差异水平。研究表明,对于各种混合料的水稳定性:玄武岩与石灰岩性能相当;改性沥青优于普通沥青;标准沥青混合料(SUP)优于基质沥青(AC);公称粒径越小水稳定性越好;沥青生产厂家对沥青混合料的水稳定性影响不显著。基于大样本的分析方法适用于沥青混合料水稳定性分析,沥青标号、最大公称粒径及级配对混合料的浸水残留稳定比(MS0)的影响显著性高于对其冻融劈裂强度比(TSR)的影响显著性。     

透水沥青混合料的热物特性与热阻功能

为研究透水沥青混合料的热物性,基于热力学理论计算比较了透水沥青混合料和密级配沥青混合料的热导率、比热容、热扩散率等指标,并对透水沥青混合料的热物性指标与空隙率、含水率的关系展开分析;通过设计室内光照试验,测得相同的传热条件下两种材料表面和底部的温度变化。理论计算结果表明同密级配沥青混合料相比,透水沥青混合料的热导率降低约20%,热扩散率降低约10%;室内温度测试结果显示,透水沥青混合料试件表面较密级配沥青混合料试件温度低2～2.5℃,底部温度低3～3.5℃,说明透水沥青混合料具有热阻功能,对气温荷载变化的抵抗能力较强,验证了理论计算结果。     

钢渣掺量对橡胶沥青混合料ARAC-13性能的影响

为提高钢铁废渣的综合利用率和经济效益、优化环境,采用体积替代法进行钢渣沥青混合料组成设计,通过设计膨胀破坏试验新方法分析钢渣沥青混合料的体积稳定性,基于车辙试验、冻融劈裂试验和低温小梁弯曲试验等,开展不同钢渣掺量下的ARAC-13沥青混合料路用性能研究,并依托广西滨海公路项目对钢渣沥青混合料路面进行经济效益评估。结果表明,ARAC-13沥青混合料的毛体积相对密度和最佳油石比均与钢渣掺量呈正相关性,钢渣掺量的增加会降低混合料的体积稳定性,增大体积膨胀风险。当钢渣100%等体积替代粗集料时,ARAC-13沥青混合料的动稳定度、残留稳定度、冻融劈裂强度比、最大弯拉应变(-10℃)、摆值和构造深度均有不同程度的提高,可显著提升ARAC-13沥青混合料的路用性能,且可节约7.0%左右的材料成本,具有较大的应用前景和经济价值。     

沥青混合料汉堡车辙试验评价研究综述

为规范使用汉堡车辙试验(Hamburg wheel-track device,HWTD)评价沥青混合料的高温抗车辙性能和水稳性能,科学地指导试验操作程序、相关数据处理和评价指标计算等,总结和探讨了HWTD相关的试验条件、圆柱型试件影响因素、车辙深度预测模型、点位选取原则、评价指标的获取与计算方法等的现状和存在的问题,并展望了进一步的研究方向。研究结果表明,试验条件直接影响着混合料的性能评价,其试验温度、评价标准和荷载作用次数等的确定与选取应充分考虑沥青等级和环境气候的差异;并基于圆柱型试件拼接缝对混合料受力特性和车辙深度点位选取的影响,提出了相应的改善措施。相关评价指标计算模型的引入弥补了现有个别评价指标求取不明确的缺陷,为混合料性能的科学评价和区分提供指导,也为我国相关HWTD规范的制定奠定基础。     

PE抗车辙剂沥青混合料施工技术应用研究

结合PE抗车辙剂沥青混合料的施工情况,提出了PE抗车辙剂改性沥青混合料的生产和施工工艺.施工结果表明,干拌时间直接影响PE抗车辙剂与矿料的均匀熔融和沥青混合料的质量均匀性,拌和温度、施工温度则影响PE抗车辙剂沥青混合料碾压效果和施工质量.     

静水作用下沥青混合料强度衰减规律

将现场取芯的沥青混合料试件真空饱水后长期放置于静水中,定期测定试件的吸水率,采用劈裂试验和冻融劈裂试验测定试件的劈裂强度和TSR,采用60℃劈裂试验及无侧限抗压强度试验测定粘结力和内摩擦角,运用两种拟合方法对沥青混合料粘结力和内摩擦角变化趋势进行拟合。结果表明,沥青混合料试件初期阶段吸水率迅速增加,后期水分进入微空隙,吸水率增加缓慢;长期静水作用下沥青混合料的劈裂强度和冻融劈裂强度比均下降,前6个月下降速率较大,后期逐渐变慢,前期的下降速率是后期的3~4倍。在长达12个月的静水作用下,沥青混合料粘结力下降0.08 MPa,呈线性变化;内摩擦角下降10.3°,呈二次抛物线变化。     

基于表面自由能理论研究改性沥青-集料复合材料黏附性能

基于表面自由能理论,首先测定不同沥青、集料与已知试剂的接触角,然后通过相关公式计算得到沥青-集料复合材料的黏附功、剥落功及水稳定性指标ER,并分析老化前后沥青-集料复合材料的黏附性变化。研究结果表明:沥青-集料复合材料的黏附过程和剥落过程均对外放热且自发进行;同种沥青不同集料的复合材料黏附性和抵抗水损害能力排序为沥青-石灰岩沥青-玄武岩沥青-花岗岩,不同沥青同种集料复合材料黏附性强弱和抵抗水损害能力排序为复合改性沥青(CM)-集料胶粉改性沥青(CRM)-集料苯乙烯-丁二烯-苯乙烯改性沥青(SBSM)-集料复合材料;老化后沥青-集料复合材料的黏附性能和抵抗水损害能力均呈现下降趋势,且压力老化(PAV)比旋转薄膜烘箱老化(RTFOT)更为明显,但老化过程并未改变沥青与集料间的配伍性;对三种改性沥青的SEM图像进行分析,发现老化后沥青与集料界面黏结特性发生变化,导致沥青-集料复合材料黏附能力下降。     

Mechanical and structural assessment of laboratory- and field-compacted asphalt mixtures

Compaction forms an integral part in the formation of the aggregate orientation and structure of an asphalt mixture and therefore has a profound influence on its final volumetric and mechanical performance. This article describes the influence of various forms of laboratory (gyratory, vibratory and slab-roller) and field compaction on the internal structure of asphalt specimens and subsequently on their mechanical properties, particularly stiffness and permanent deformation. A 2D image capturing and image analysis system has been used together with alternative specimen sizes and orientations to quantify the internal aggregate structure (orientation and segregation) for a range of typically used continuously graded asphalt mixtures. The results show that in terms of aggregate orientation, slab-compacted specimens tend to mimic field compaction better than gyratory and vibratory compaction. The mechanical properties of slab-compacted specimens also tend to be closer to that of field cores. However, the results also show that through careful selection of specimen size, specimen orientation and compaction variables, even mould-based compaction methods can be utilised with particular asphalt mixtures to represent field-compacted asphalt mixtures.     

基于非线性疲劳损伤的沥青路面轴载换算

为了建立沥青混合料的非线性疲劳损伤演化方程, 同时为完善沥青路面的轴载换算方法, 首先进行沥青混合料的配合比设计, 确定矿料级配及最佳油石比, 然后从损伤力学基本理论出发, 定义模量衰减为其疲劳损伤参量, 由此推导得到了疲劳损伤方程, 并以此方程对小梁直接拉伸疲劳试验结果进行拟合, 得到了模型参数和损伤随应力比的变化规律, 建立了沥青路面轴载换算新方法。结果表明:沥青混合料的疲劳损伤演化具有明显的非线性, 用Miner线性疲劳损伤理论来描述沥青路面疲劳损伤演化过程不合适, 由此推导得到的轴载换算方法偏不安全, 建立在非线性疲劳损伤演化基础上的轴载换算方法考虑了加载历史和损伤历史的影响。     

Internal structure evolution of asphalt mixtures during freeze–thaw cycles

This paper is an attempt to identify the internal structure evolution within asphalt mixtures under freeze–thaw cycles. Three types of asphalt mixtures were fabricated in the laboratory. X-ray computed tomography technology was employed to capture internal structure within samples before and after the freeze–thaw test. A set of image analysis procedures for extracting the internal structure properties was used to analyze the changes in air void distributions and to evaluate the internal structure evolution under freeze–thaw cycles. Results of X-ray CT image processing illustrated a dramatical degradation in internal structure after the freeze–thaw tests. The change in internal structure mainly occurs in three ways: (1) expansion of existing individual voids, (2) coalescing of two separated air voids, and (3) formation of new voids. Interestingly, the internal structure properties for three types of asphalt mixtures differs from each other and results in various forms of internal structure evolution and micro-crack formation under freeze–thaw cycles. In addition, the differences in internal structure degradation were also evaluated with the levels of water saturation and design void content, indicating their important role in the study of freeze–thaw damage of asphalt mixtures and in the design of asphalt mixtures in cold regions.     

基于数字散斑相关法的聚合物改性沥青混合料抗裂性能

为分析冻融循环对苯乙烯-丁二烯-苯乙烯（SBS）和橡胶粉（CR）改性沥青混合料抗裂性能的影响,首先,分别对盐溶液冻融循环和水溶液冻融循环改性沥青混合料进行了半圆试件弯拉试验,同时采用数字散斑相关法（DSCT）对加载过程试件表面的散斑图像进行处理,提取试件表面随着载荷变化的位移场和应变场信息;然后,通过分析变形场信息确定沥青混合料的抗裂性能,并与断裂韧性试验结果进行对比。结果表明:水平应变较适合用于对沥青混合料的抗裂性能开展特性研究;由水平应变-时间曲线可知,冻融循环后SBS和CR改性沥青混合料的抗裂性能均有所劣化,且盐溶液冻融循环对沥青混合料抗裂性能的影响要大于水溶液冻融循环的;与SBS改性沥青混合料相比,CR改性沥青混合料的抗裂性能较好。所得结论表明DSCT的分析结果与断裂韧性试验的分析结果一致,采用DSCT评价沥青混合料的抗裂性能是可行的。      

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.     

基于细观力学的沥青混合料动态模量预测

为了建立能够表征组分材料性能及细观结构特征的沥青混合料动态模量预测模型, 根据复合材料细观力学理论, 将沥青混合料视为由沥青胶浆包裹的集料颗粒嵌入于有效沥青混合料介质中的复合材料, 考虑集料尺寸、级配组成和空隙的影响, 建立了沥青混合料动态模量三相细观力学预测模型。结合组分材料性能研究, 应用该预测模型求解得到了动态模量, 其与试验值比较结果表明, 预测值较试验值小, 产生此差异的原因可归结为模型的适用条件与真实细观结构的差别;据此对预测模型进行了修正, 提出了考虑沥青膜厚度的动态模量细观力学分析方法;鉴于集料与沥青胶浆之间的力学特性差异, 简化了预测模型求解参数, 给出了参数值的范围。     

Molecular dynamics simulation of asphalt-aggregate interface adhesion strength with moisture effect

This study developed an atomistic simulation framework based on the classical molecular dynamics (MD) method to study the moisture-induced damage at the asphalt-aggregate interface. The interface adhesion strength of the asphalt–quartz system was predicted using MD simulation for the first time. The interface stress-separation curve under tension that was obtained from MD simulation resembles the failure behaviour measured from the pull-off strength conducted at the macroscopic scale. The results show that the presence of moisture at the asphalt–quartz interface significantly reduces the interface adhesion strength. The interface failure process is affected by the chemical compositions of asphalt. The interface adhesion strength decreases as the moisture content increases or the temperature increases. It was found that the atomistic model size (number of atoms) and the loading rate in MD simulation have considerable effects on the predicted interface adhesion strength. The findings from MD simulation provide fundamental understanding of material failure at the atomistic scale that cannot be observed at the normal experimental testing environment for asphalt materials. The MD simulation results can be potentially calibrated and utilised as inputs for higher scale micromechanical models to predict bulk mechanical responses of asphalt mixtures.     

Indirect determination of size effect on strength of asphalt mixtures at low temperatures

Low temperature cracking of asphalt pavements is a major distress in cold regions. Accurate assessment of strength of asphalt mixtures at low temperatures is of great importance for ensuring the structural integrity of asphalt pavements. It has been shown that asphalt mixtures behave in a quasibrittle manner at low temperatures and consequently its nominal strength strongly depends on the structure size. The size effect on the strength of asphalt mixtures can be directly measured by testing geometrically similar specimens with a sufficiently large size range. Recent studies have shown in theory that for quasibrittle structures, which fail at the macrocrack initiation from one representative volume element, the mean size effect curve can also be derived from the scaling of strength statistics based on the finite weakest link model. This paper presents a comprehensive experimental investigation on the strength statistics as well as the size effect on the mean strength of asphalt mixtures at ?24 °C. It is shown that the size effect on mean structural strength can be obtained by strength histogram testing on specimens of a single size. The present study also indicates that the three-parameter Weibull distribution is not applicable for asphalt mixtures.