粗集料棱角性对OGFC多孔沥青混合料性能的影响

采用洛杉矶磨耗机对粗集料进行不同程度磨耗后,按照OGFC-10、OGFC-13和OGFC-16等3种级配制备了12种OGFC沥青混合料。在室内借助集料图像测量系统得到了不同OGFC沥青混合料的粗集料棱角性综合值Ic,并测试了各沥青混合料的相关路用性能。结果表明,当集料级配相同时,粗集料棱角性下降会造成OGFC沥青混合料马歇尔稳定度、动稳定度、空隙率和抗滑性能均有明显下降,但对渗水性能影响不大。当集料级配不同时,3种OGFC沥青混合料中,随着粗集料棱角性综合值Ic的下降,OGFC-16的马歇尔稳定度、动稳定度和抗滑性能下降最明显,OGFC-10的空隙率下降最明显。     

集料骨架特性的分形分析和细观模型评价

为了研究组成沥青混合料的集料骨架特性,利用分形理论计算了集料级配分形维数,基于离散元方法从细观角度描述了集料颗粒间的接触状态,追踪了颗粒间的接触力和分布,并以车辙试验验证了5种沥青混合料的集料骨架抗变形能力。结果表明:对于相同最大公称粒径的沥青混合料,SMA-20的分形维数、接触力、动稳定度比AC-20分别增大2.93%、43.10%、9.28%,SMA-16的分形维数、接触力、动稳定度比AC-16分别增大3.03%、19.25%、25.64%,AC-16的分形维数和动稳定度比OGFC-16分别增大3.40%、4.88%,但SMA-16的接触力小于OGFC-16;分形维数、接触力和动稳定度越大,集料骨架越稳定,抗变形能力越强。     

改性彩色沥青路面色彩耐久性与抗滑性能研究

为提高彩色沥青路面色彩耐久性并研究其抗滑性能,采用有机硅-聚丙酸酯(silane-modified polyacrylate, SMP)对彩色沥青玛蹄脂碎石混合料(color stone mastic asphalt, CSMA)和彩色开级配抗滑表层(color open graded friction course, COGFC)2种混合料改性,借助小型加速加载设备进行对彩色沥青路面进行色彩耐久性评价,并通过三维扫描仪进行路面纹理信息采集,分析路面三维参数与其抗滑性能之间的关系。结果表明,SMP改性剂可有效提高CSMA、COGFC两种混合料的抗磨耗能力,提升彩色沥青色彩耐久性;CSMA及COGFC路面抗滑性能受到不同三维参数的影响,路面的摩擦系数模型由各自相关因子控制,增加路面暴露的集料数量和使用尖角集料能使彩色沥青路面的抗滑性能得到提升。     

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。     

路用高抗滑集料耐磨性能评价与机理分析

集料耐磨耗性能对沥青路面抗滑性能起着决定性作用。采用洛杉矶磨耗试验研究了煅烧铝矾土、玄武岩和花岗岩集料的磨耗损失率和集料形态特性参数随磨耗次数的变化规律;利用皮尔森相关系数分析了集料磨耗损失率和形态特征参数的相关性,并构建了磨耗损失率与分形维数变化率及维氏硬度的关系模型;采用SEM和XRD测试手段分析了集料的耐磨机理。结果表明,88#煅烧铝矾土集料的抗磨耗性能明显优于75#煅烧铝矾土、玄武岩和花岗岩,其主要抗磨耗成分为刚玉和莫来石;所构建的模型能够较好地反映出集料磨耗损失率与分形维数变化率及维氏硬度的关系。研究成果为路面抗滑性能的提升与持久提供了新思路。     

热拌超薄罩面Superpave-5抗滑性能影响因素分析

本文采用锁轮式测定车对美国印第安纳州六条Superpave-5路面通车1年后的抗滑系数进行测试,结合室内试验分析了矿料性质、混合料体积指标和级配对Superpave-5路面抗滑性能的影响,建立了各影响因素与Superpave-5路面抗滑系数之间的关系,提出了影响Superpave-5路面抗滑性能的关键指标、筛孔及推荐级配走向。结果表明:空隙率和沥青饱和度是影响Superpave-5路面抗滑性能的关键指标,与路面抗滑系数之间的斯皮尔曼等级相关系数分别为0.8281和-0.6571;1.18mm筛孔通过率与Superpave-5路面抗滑系数间的灰熵关联度最大(达到0.9914),是影响其抗滑性能的关键筛孔;优化Superpave-5主骨架级配和调整第一控制筛孔(PCS)的通过率,使级配走向位于PCS下方均对提高Superpave-5路面的抗滑性能具有重要作用。     

聚氨酯/环氧树脂基混合料型耐久长效道路交通标线材料组合优化研究

现有道路交通标线技术在材料组成、材料质量以及标线涂层结构等方面均有不足，导致道路标线的耐久性和功能性无法长期得到保证，大量标线处于低性能服役状态。鉴于此，本工作自主研发一种混合料型道路交通标线，在保证其路用性能与道路表面层性能相协调的前提下，可提升标线的光度性能，通过室内试验和蒙特卡洛模拟的方法验证其作为道路反光标线的可行性。研究结果表明，混合料主体集料为熔融石英砂;最佳级配类型为AK-13(a)级配，SMA-10级配和MS-3级配次之，最后为MS-2级配和AC-5级配;胶粘剂体系为3016LV(A/B)，且最佳胶粘剂用量为9%;胶粘剂刷涂量为250～275 g/m²;面撒玻璃珠最佳撒布量为750～800 g/m²，处置后标线的逆反射亮度系数可达到195 mcd·m^-2·lx^-1，具有良好的光度性能;通过构建材料组合中基本因素与各性能指标之间的数学关系，采用蒙特卡洛模拟方法利用MATLAB软件进行模拟计算，得出最优材料组合的解集，结合室内试验结果，确定混合料型道路标线的最佳材料组合方案为:集料采用熔...     

细粒式薄表层沥青混合料中粗集料的骨架特性

为研究薄表层沥青混合料的骨架特性,同时为保证公称最大粒径9. 5 mm(UTL-10)矿料级配的稳定性,在4. 75 mm与9. 5 mm筛孔中间增设7. 5 mm筛孔,通过捣实密度试验分析了不同粗集料配比的集料骨架间隙率(VCA)。同时,提出了利用粗集料-沥青胶浆试件的单轴贯入试验来研究不同组合的粗集料抗剪强度相关参数,确定了薄表层粗集料的级配设计控制指标,最终给出了薄表层粗集料的推荐配比范围。结果表明:集料内摩阻角φ能够很好地反映粗集料级配的骨架强度稳定性;采用VCA和内摩阻角φ双重指标可以有效控制薄表层沥青混合料的粗集料配比设计;公称最大粒径为13. 2 mm(UTL-13)矿料级配三档集料含量的推荐范围分别为12. 5%～22. 2%,37. 5%～44. 4%,33. 3%～50%;UTL-10三档集料含量的推荐范围分别为10%～16. 7%,40%～50%,33. 3%～50%。     

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。     

基于关联性的玄武岩纤维沥青胶浆及其混合料性能研究

为全面提升玄武岩纤维沥青混合料性能,研究了纤维类型及玄武岩纤维长度、掺量等因素对沥青胶浆抗裂性能、抗剪性能及流变特性的影响规律;基于纤维胶浆与纤维沥青混合料性能的关联性分析,揭示了玄武岩纤维对沥青混合料性能的细观增强机制。结果表明:玄武岩纤维对沥青胶浆的抗裂性能及流变特性影响显著,其极限拉力和车辙因子分别达到原沥青胶浆的4.5倍及1.08倍;纤维沥青胶浆高温流变特性与其沥青混合料高温稳定性变化规律存在差异,而前者抗裂性能与后者低温抗裂性能关联性较强;玄武岩纤维与沥青胶结料、集料之间形成三维网状结构,有利于抑制裂缝扩展。     

基于离散元方法的沥青混合料力链演化及分布量化分析

为了研究沥青混合料内部颗粒间力链的演化及分布规律,以AC-13沥青混合料作为研究对象,利用离散元方法重构沥青混合料数字试件,模拟简单性能试验,提取试件内部颗粒间的力链信息进行力链演化、概率分布和角度分布分析。结果表明,通过比较预测结果和实测结果,基于离散元方法重构的AC-13沥青混合料细观模型用于模拟其细观力学特性是可行的。试件内部力链空间分布具有各向异性,以垂直方向的压力力链为主,承受大部分的半正弦荷载。法向力链概率分布随加载时间的变化规律基本一致,法向接触力与平均法向接触力比值f最小时,概率分布出现最大值,f=1.75时,概率分布再次达到峰值,然后逐渐减小并趋于稳定。法向力链角度分布主要位于90°和270°附近,第一、二象限的角度分布比例远大于第三、四象限,60~120°、30~150°中法向力链角度分布比例均大于70%,最小为72.733%。     

Rutting evaluation of stone mastic asphalt for basalt and basalt–limestone aggregate combinations

The purpose of this study is to investigate the rutting of basalt and basalt–limestone aggregate combinations for coarser and finer SMA mixtures with a Laboratoire Central des Ponts et Chaussées (LCPC) wheel tracking test. The sensitivity of the LCPC wheel tracking test was also evaluated with different maximum aggregate sizes and changes in gradation. The coarse aggregate in the mixture was basalt. Four different rock combinations were designed with basalt and limestone aggregates for filler and fine fractions. In addition to the gradation evaluation, the maximum aggregate size effects were studied with four gradations. Decreasing the maximum aggregate size is at the utmost importance on rutting resistance, according to the gradation and mineralogical factors of aggregate. It is believed that limestone aggregate can be used as filler and fine fractions in SMA with basalt. This matter has great importance for shortage of basalt aggregate quarries and management difficulties for these quarries. This provides added value for Turkey’s highway investments. Rutting resistance of SMA mixture relatively decreased in the incorporation of limestone aggregate in the SMA mixture gradation as fine or filler aggregate (an average of 0.24% for SMA11 and SMA12, and 0.41% for SMA21 and SMA22). This low-level rutting difference can easily be observed with LCPC wheel tracking tests. Reliability of LCPC test was clearly demonstrated.     

Processing conditions—fracture toughness relationships of asphalt concrete mixtures

The effect of processing conditions (dynamic compaction) on the fatigue crack propagation behaviour of AC-20 asphalt concrete mixture was studied. Beams were prepared from AC-20 asphalt binder containing 8% asphalt by weight with and without dynamic compaction. The gradation used was Ohio Department of Transportation item 403, and was kept the same. Flexural static tests were conducted to determine the effect of dynamic compaction on both the ultimate strength and flexural modulus. Flexural fatigue tests were conducted on three identical notched specimens prepared using each of the two compaction techniques. Parameters controlling the crack propagation process were evaluated; namely, the energy release rate and the change in work, W _i expended on damage formation and history dependent viscous dissipation processes within the active zone (region ahead of the crack tip). The modified crack layer (MCL) model was employed to extract the specific energy of damage, , a material parameter characteristic of the asphalt concrete mixture's resistance to crack propagation, and the dissipative coefficient, . It has been found that the dynamically and statically compacted AC-20 mixture displayed superior fracture resistance, as reflected in and . Also, the ultimate strength and modulus increased by about two-fold. Scanning electron microscopic examination revealed an obvious change in the morphology of the fracture surface. This is manifested in the appearance of a finer more dense texture in the case of the dynamically and statically compacted mixture. In addition, smaller more frequent dimples in binder rich areas are indicative of better adhesion between the binder and the aggregate. This in turn contributes to the increased fracture resistance of the dynamically and statically compacted AC-20 asphalt concrete mixture.     

沥青混合料合成级配的均匀性评价

为研究不同粒径组成的颗粒状混合物和不同的级配组成的沥青混合料的路用性能,本文中以紧密填充理论为基础,假设不同粒径的颗粒逐级紧密填充,采用均匀指数评价合成级配的均匀性,在最佳沥青含量下进行性能试验。结果表明,沥青混合料在MCA=0.4～0.6之间存在较大的稳定度和流值,最小的压实比值和势能指数值,有良好的稳定性。最大公称粒径为16 mm的合成级配、均匀指数应控制在0.55～0.60之间具有较好的路用性能。     

A parametric study on the influence of steel wool fibers in dense asphalt concrete

Environmental conditions combined with traffic loads contribute to premature deterioration of asphalt concrete pavements, reducing their strength and durability over time. To improve it, fibers can be incorporated in the mixture. Additionally, electrically conductive fibers can be used for self-healing purposes. In this context, this paper evaluates the influence of flexible steel fibers (steel wool) on the mechanical and physical properties of dense asphalt concrete. With these purposes, 25 different mixtures, with the same aggregate gradation and amount of bitumen, but with two different fibers lengths, four different percentages, and four different diameters of steel wool have been considered. Additionally, the influence of fibers on test specimens with three different types of damage: water damage, salt water damage and ageing have been evaluated through particle loss tests. Moreover, the influence of different temperatures on the flexural strength of dense asphalt concrete with steel wool fibers has been studied. It was found that steel wool fibers do not significantly improve the mechanical properties and damage resistance of dense asphalt concrete. On the other hand, steel wool fibers can change the air void distribution of a mixture, and therefore even reduce its particle loss resistance. As a recommendation, it is indicated that, for induction heating purposes, short fibers, with big diameters should be used, since they do not seem to alter the original properties of dense asphalt concrete.     

The effect of aggregate gradation on creep and moisture susceptibility performance of warm mix asphalt

It is clear that the purpose of mixture design is to select optimum asphalt content for a desired aggregate structure to meet the prescribed criteria. Aggregate makes up high proportion of volume and mass of mixtures; hence, it is considered as an important constituent of asphalt concrete. This study postulates that the gradation is an important characteristic of the aggregate in adoption of the optimum mixture. One aggregate source, three gradations and different percentages of Sasobit^® was used to manufacture hot mix asphalt and warm mix asphalt. The test results indicated that the aggregate gradation affects the rutting resistance and especially the moisture susceptibility of the introduced mixtures, differently. Rutting resistance was evaluated using the flow number parameter, and in order to determine the moisture sensitivity mechanism, a mechanical and visual inspection tests were carried out. At the end, it is concluded that the optimum aggregate gradation for these two types of mixtures is different.     

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%。     

An empirical approach for the optimisation of aggregate combinations for self-compacting concrete

The fresh and hardened properties of self-compacting concrete (SCC) depend on number of factors such as paste composition, paste content, aggregate content, aggregate gradation etc. In the present investigation, the influence of the packing density of aggregates on the properties of SCC was evaluated. Experiments were conducted to measure the packing density for different combinations of aggregates precisely. A ternary packing diagram (TPD) was developed based on the packing density of measured and interpolated data. Considering the limitations in generalising the TPD and the difficulty involved in adopting mathematical models for aggregates, an attempt was made to establish a simple method for the selection of the combination of aggregates resulting in maximum packing density from the particle size distribution of aggregates (represented by the Coefficient of uniformity??C _u). Further, studies were extended to investigate the effect of aggregate packing density on fresh and hardened SCC properties. The results indicate that for a constant paste volume and paste composition, with increase in packing density of aggregates, the fresh properties and the compressive strength of SCC were improved positively. An attempt was also made to identify the influence of 10 different proportions of aggregates having the same packing density on the properties of SCC. The results indicate that at the same aggregate packing density, the fresh concrete properties were influenced significantly by the choice of the aggregate combination, while there was little or no influence on the hardened properties. Furthermore, the experimental data obtained was used for supplementary validation of the existing model (compressible packing model) for predicting the packing density and the fresh behaviour of SCC.     

基于CAVF级配设计方法的环氧沥青混合料路用性能研究

为研究环氧沥青混合料耐久性不足、易脆裂等问题,优化其路用性能质量,采用CAVF级配设计方法和常规马歇尔方法进行了环氧沥青混合料高温稳定性试验、低温抗裂性试验、低温蠕变试验及水稳定性试验;通过调整级配、环氧沥青类型和温度等因素对其进行研究分析。结果显示:CAVF级配显著改善了环氧沥青混合料的高温力学稳定性和抗车辙能力,并且降低了温度对环氧沥青混合料高温力学强度的劣化作用;低温弯曲试验发现环氧沥青混合料具有较强的温度敏感性(与普通沥青混合料相比),最大弯拉应变值随温度的降低呈线性下降趋势,采用CAVF级配在一定程度上能够弥补温度对其的劣化作用;水稳定性试验显示随试验浸泡时间的延长和循环次数的增加,其高温水稳定性能和低温水稳定性能均出现显著劣化作用,这与低温蠕变应变变形影响规律相同。汇总研究成果,表明CAVF级配较适用于环氧沥青混合料,能够降低或避免常规级配设计方法出现的缺陷性问题,可为实体工程应用提供技术支持。     

Interrelationship between uncompacted void content of aggregates and asphalt concrete properties

It is a well known fact that morphological characteristics of aggregates influence the mechanical response of asphalt concrete (AC). Uncompacted void content (UVC) of aggregate is often related to their morphological characteristics. A detailed experimental study was performed to explore relationship between UVC and mechanical response of AC. Initially, aggregates were artificially smoothened using Los Angles abrasion testing machine. UVC was then evaluated using blended aggregates at five levels of smoothness/texture. Increasing aggregate smoothness resulted in decreased UVC values. Higher UVC was obtained with a finer gradation compared to coarse gradation. Three AC mixtures prepared using these smoothened aggregates were tested for their strength and flow properties. A linear, strong positive correlation was found between UVC and Marshall parameters (stability, Marshall quotient). This can be attributed to interparticle resistance developed during mechanical loading. Parabolic relations were found between UVC and retained Marshall parameters. The retained Marshall parameters was found to be a function of UVC. It is concluded that UVC can be effectively used to capture changes in aggregate morphology and AC response.