粗集料棱角性对温拌沥青混合料水稳定性的影响研究

为了研究粗集料的棱角性对温拌沥青混合料水稳定性的影响,采用洛杉矶法对石灰岩粗集料分别磨耗0、250、500、750、1 000次,对不同棱角性的石灰岩粗集料和Sasobit温拌沥青制备而成的温拌沥青混合料进行体积指标和路用性能的测试。试验结果表明:图像分析法可以作为观测粗集料棱角性的方法;粒径较小的粗集料棱角性较高;石灰岩粗集料棱角性随磨耗次数的增加而线性降低;尖锐棱角是影响温拌沥青混合料水稳定性的重要因素之一,它会降低温拌沥青混合料的水稳定性,采用经过磨耗的石灰岩粗集料制备成的温拌沥青混合料水稳定性有大幅度提高。     

细集料特性对沥青混合料路用性能的影响研究

目前,我国高速公路路面主要以沥青路面作为主要路面形式,沥青混合料的路用性能对路面质量有很大的影响。为了验证沥青混合料路用性能与细集料性质之间的关系,分别采用车辙试验进行沥青混合料的高温稳定性测试;采用浸水马歇尔和冻融劈裂试验来验证细集料性质对沥青混合料水稳定性的影响;利用摆式系数摩擦测定仪来测试沥青混合料车辙板的抗滑性能。试验表明:使用棱角性丰富的细集料更有益于沥青混合料的高温抗车辙能力和提高沥青路面的摩擦系数;使用碱性和泥土质量分数低的细集料有助于提高沥青混合料的水稳定性。     

钢渣沥青混合料性能研究

测试了钢渣的基本性能和对比研究了钢渣和玄武岩沥青混合料的水稳定性和高、低温性能。结果表明,钢渣集料的各项基本指标均满足规范要求,且其表面有许多孔隙结构。集料图像测试系统(AIMS)分析结果显示钢渣的球形度要小于玄武岩,棱角性和微观纹理均大于玄武岩。钢渣沥青混合料的高、低温性能均优于玄武岩沥青混合料,其水稳定性与玄武岩沥青混合料差别不大。     

钢渣沥青混合料性能研究

测试了钢渣的基本性能和对比研究了钢渣和玄武岩沥青混合料的水稳定性和高、低温性能。结果表明,钢渣集料的各项基本指标均满足规范要求,且其表面有许多孔隙结构。集料图像测试系统(AIMS)分析结果显示钢渣的球形度要小于玄武岩,棱角性和微观纹理均大于玄武岩。钢渣沥青混合料的高、低温性能均优于玄武岩沥青混合料,其水稳定性与玄武岩沥青混合料差别不大。     

沥青-集料界面黏附性衰减机理研究

以表面自由能理论、衰减全反射红外光谱(FTIR-ATR)和原子力显微镜(AFM)等方法,从宏观和微观角度对水侵蚀作用下沥青-集料界面黏附性衰减机理进行了研究,并探讨了沥青老化对该衰减过程的影响.结果表明:以羟基伸缩振动峰面积为指标,可评价沥青含水量随浸水时间延长而增加的变化规律;沥青老化后,导致水在沥青中的扩散速率加快,使水更易扩散至沥青-集料界面处,并对第1扩散阶段扩散系数的影响更为显著;沥青的老化使得沥青-集料界面处的黏附性降低,且在有水存在的情况下沥青膜更倾向于被水从集料表面取代,从而发生剥落;不同油源的沥青浸水后的微观结构改变十分相似,表明其与水的作用机理相同.     

粗集料形态特征的定量评价指标研究

为了提出能够合理评价粗集料形态特征(形状、棱角)的定量指标,采用洛杉矶磨耗仪对4.75~9.5mm,9.5~13.2mm,13.2~16mm,16~19mm共4档粗集料分别磨耗0,600,1 200次,以改变粗集料的形态特征,然后通过自主研制的粗集料形态特征研究系统(MASCA)测得粗集料轴向系数、凸度、粗糙度、棱角参数、圆度、分形维数共6个定量评价指标值,并运用二元方差法比较它们对颗粒形态变化的敏感性,发现分形维数是能够合理评价粗集料形态特征的最优定量指标.为验证这一结论,利用磨耗得到的不同形态特征的粗集料分别成型AC-16,SAC-16,SMA-16级配类型混合料试件进行车辙试验和贯入剪切试验,验证结果表明分形维数与沥青混合料高温性能之间具有很好的相关性.     

基于表面能理论的沥青混合料抗剥落性能

基于表面能理论和黏附剥落模型,采用Wilhelmy吊片法和躺滴法分别测试沥青与集料的表面能参数,计算沥青与集料的黏附功、剥落功及沥青混合料水稳定性评价指标ER,对在不同条件下、掺加不同抗剥落剂的沥青混合料的水稳定性能进行分析.结果表明:基于黏附剥落模型的评价指标ER与反映沥青混合料水稳定性的宏观指标之间存在良好的相关性,ER值越大,沥青混合料的抗剥落性能越好;抗剥落剂能够有效提高沥青的表面能,提升沥青自身的黏聚功以及沥青与集料的黏附功,降低水对沥青与集料的剥落功,从而改善沥青混合料的水稳定性能;经历热老化、浸水、冰冻和冻融条件后,抗剥落剂仍能对沥青混合料的水稳定性起到改善效果.     

温拌沥青混合料水稳定性评价研究

从拌和及成型温度出发,采用浸水马歇尔试验和冻融劈裂试验对原样沥青及两种温拌沥青混合料的水稳定性进行评价,并结合集料与沥青黏附性试验进行比较分析。研究表明,Evotherm DAT温拌沥青混合料的水稳定性优于原样沥青混合料,Saso WAM温拌沥青混合料的水稳定性略低于原样沥青混合料;冻融劈裂试验与水煮法试验评价的水稳定性相关性较好,浸水马歇尔试验由于试件空隙率低,不能真实反映混合料的水损害,建议以冻融劈裂试验结果为主评价温拌沥青混合料的水稳定性。     

集料含泥量对沥青混合料水稳定性影响探究

分析集料表层的洁净程度对集料、沥青黏附性的影响情况,从沥青混合料水稳性优化方法着手,以消石灰来提升沥青混合料水稳定性,并针对此种方式进行评估,以期为相关工程提供借鉴。     

硫磺沥青混合料水稳定性分析

为了分析硫磺沥青混合料的水稳定性,寻找改善硫磺沥青混合料水稳定性的方法,采用改进水煮法检测了硫化沥青与集料的黏附性,通过四组分分析和接触角分析研究了硫化沥青与集料的黏附性;采用冻融劈裂强度试验、车辙试验以及低温弯曲试验研究了硫磺用量、空隙率以及抗剥落剂对硫磺沥青混合料水稳定性的影响.结果表明,在一定条件下,硫磺可改变沥青的组成,并改善沥青与集料的黏附性;硫磺用量、空隙率及抗剥落剂对硫磺沥青混合料的水稳定性具有非常大的影响.     

Evaluation of image analysis techniques for quantifying aggregate shape characteristics

Form, texture, and angularity are among the properties of aggregates that have a significant effect on the performance of hot-mix asphalt, hydraulic cement concrete, and unbound base and subbase layers. Imaging techniques have provided a good means to quantify aggregate shape properties rapidly in spite of the fact that they might differ in the mathematical procedure and the instrumental setup they utilize. The validity of the mathematical procedure is essential for the results to be useful in quantifying aggregate shape. Some of the most widely used aggregate shape analysis techniques were evaluated in this paper. The analysis results revealed that some of the available analysis methods are influenced by both angularity and form changes and, consequently, are not suitable to distinguish between these two characteristics. Also, some of the analysis methods are quite adequate to measure both texture and angularity when changes are made to the image resolution and magnification level. The following analysis methods are recommended: wavelet analysis of gray images for texture; both the gradient method and tracing the change in slope of a particle outline method for angularity; aspect ratio for 2-dimensional form; and sphericity or the proportions of the three particle dimensions for 3-dimensional form.     

Unified Imaging Approach for Measuring Aggregate Angularity and Texture

The effect of fine aggregate morphologic properties on asphalt mixtures' behavior is well recognized. However, the current procedures for measuring fine aggregate properties are at best indirect indicators of these properties. The indirect nature of the current measurements has led to inconsistency in predicting the extent to which the measured properties influence pavement performance. Two independent methods that integrate several aspects of image-analysis techniques are presented for quantifying angularity and texture of fine aggregates. The first technique relies on the change of aggregate shape as it is subjected to a number of erosion-dilatation morphologic operations. The second technique uses the change of an object perimeter with its shape. The analysis shows that the two methods are able to capture aggregate shape at two different scales. Angularity is captured using low-resolution images, whereas surface texture is captured using high-resolution images. The presented image-analysis techniques have potential benefit in quantifying the effects of texture and angularity on asphalt pavement performance.     

Quantification of coarse aggregate shape in concrete

The objective of this study is to choose indices for the characterization of aggregate form and angularity for large scale application. For this purpose, several parameters for aggregate form and angularity featured in previous research are presented. Then, based on these established parameters, 200 coarse quartzite aggregates are analyzed herein by using image processing technology. This paper also analyzes the statistical distributions of parameters for aggregate form and angularity as well as the correlation between form and angularity parameters. It was determined that the parameters for form or angularity of coarse aggregates could be fitted by either normal distribution or log-normal distribution at a 95% confidence level. Some of the form parameters were influenced by changes in angularity characteristics, while aspect ratio and angularity using outline slope, area ratio and radius angularity index, and aspect ratio and angularity index were independent of each other, respectively; and consequently, the independent parameters could be used to quantify the aggregate form and angularity for the purpose to study the influence of aggregate shape on the mechanical behavior of concrete. Furthermore, results from this study’s in-depth investigations showed that the aspect ratio and the angularity index can further understanding of the effects of coarse aggregates form and angularity on concrete mechanical properties, respectively. Finally, coarse aggregates with the same content, type and surfaces texture, but different aspect ratios and angularity indices were used to study the influence of coarse aggregate form and angularity on the behavior of concrete. It was revealed that the splitting tensile strength of concrete increased with increases in the aspect ratio or angularity index of coarse aggregates.     

改善安山岩沥青混合料压实与水稳定性能研究

安山岩集料棱角性丰富,难压实,属于中性集料,水稳定性差,给安山岩的级配设计和推广使用造成了困难。根据安山岩物理化学性质的特殊性,提出了掺配部分石灰岩细集料代替安山岩细集料方法来设计安山岩沥青混合料。采用该方法生产的安山岩沥青混合料,具有良好的压实性能和水稳定性。     

Virtual modeling of asphalt mixture beam using density and distributional controls of aggregate contact

The characteristic indicators of aggregate contacts in asphalt mixtures, including the number, orientation, and area of contact regions, significantly affect skeleton morphology and mixture stability. To investigate the influence of indicators on mixture stability, structures with diverse characteristics of aggregate contacts are required. This study proposes an algorithm for the virtual modeling of asphalt mixture beams, which supports the density and distributional controls of aggregate contacts in the microstructure. The methodology comprises three main steps: (1) three-dimensional models of coarse aggregates conforming to the predefined gradation and volumetric content are randomly selected from a digital library of realistic aggregates, (2) contact relations of aggregates are established during the adaptive arrangement of aggregates in samples with prescribed control parameters of aggregate contact using self-developed codes, and (3) air voids are randomly scattered in the sample without overlapping aggregates according to the volumetric content of the air voids, and an asphalt mortar model is then constructed using Boolean operations. Four beam samples with different contact characteristics were obtained using the proposed method to conduct simulations of three-point bending tests. The number and spatial distribution of aggregate contacts in beam models are consistent with the prescribed parameters, showing the reliability of the proposed method for the control of aggregate contact in asphalt mixtures. A comprehensive comparison of the results of the laboratory test and simulations validates the ability of the digital beam to capture the macroscale response of asphalt mixtures. Furthermore, simulation results indicate that the sample with the greatest number and distribution uniformity of aggregate contacts has the largest peak strength and fracture energy, which is beneficial for the understanding of the relationship between the indicators of aggregate contacts and the rutting and fatigue resistance of mixtures.     

Determination of fine aggregate angularity in relation with the resistance to rutting of hot-mix asphalt

Rutting in asphalt pavements continues to create problems for pavement agencies. One factor that has been identified in determining asphalt pavement rutting susceptibility is the fine aggregate angularity (FAA) in the asphalt aggregate mix. The aim of this study is to investigate the angularity of fine aggregate produced in Turkey and to draw the attention of design engineers to this subject. To examine the relative effect of angularity of fine aggregate on the passing time through an orifice, material was obtained from 30 different sources which represent a wide range of materials used in Turkey. This collection offered a variety of geometric irregularities. The aggregates included 4 natural sands and 26 crushed aggregates. ASTM C128 “Specific Gravity Test of Fine Aggregate” and AFNOR P18-564 “Determination of Flow Rate of Fine Aggregate” which has been adopted by AFNOR were performed on each sample. Rutting tests were then performed on four different aggregate samples which had different FAA values and which were crushed by different crusher types. Test results bring to light that factors like the mineralogical properties of the fine aggregate and the crusher type must be considered in determining the angularity of fine aggregate. Also rutting test results showed that higher FAA values increased resistance to rutting of hot-mix asphalt.     

采用原子力显微镜评价集料的微纳观特征

为了研究石灰岩和玄武岩集料的微纳观特征,利用原子力显微镜(AFM)测试了其表面纹理与黏附力,并导入SPSS软件校验了数据的稳定性和区分度,对比分析了石灰岩与玄武岩集料在微纳观特征上的异同.结果表明:AFM可有效测试集料的表面纹理,数据稳定性强,区分度高,但测试集料的黏附力时,数据的随机性大,存在着一定的误差;石灰岩表面纹理粗糙、黏附力峰值较高、分布比较随机,与沥青之间的黏结呈"散点式"分布,而玄武岩表面纹理光滑、具有流纹结构,黏附力峰值较低、分布比较均匀,与沥青之间的黏结呈"整体式"分布.     

添加剂对凝灰岩沥青混合料粘附性能影响

为改善凝灰岩沥青混合料的粘附性能,以掺水泥和抗剥落剂凝灰岩沥青混合料为研究对象,选取石灰岩沥青混合料为对比试样,通过水煮法试验、老化前后水稳定性试验,对凝灰岩沥青混合料的粘附性能研究。结果表明:掺入适量添加剂可使凝灰岩集料的粘附等级显著提高,并接近石灰岩集料等级;掺水泥对凝灰岩沥青混合料老化后残留稳定度和冻融劈裂强度比的提升效果均优于掺抗剥落剂,与不掺添加剂的凝灰岩沥青混合料相比,水泥掺量2%、3%下,凝灰岩沥青混合料的老化后残留稳定度分别提高了21.5%、21.7%,冻融劈裂强度比分别增大了16.7%、15.3%,均接近于石灰岩沥青混合料。掺液体抗剥落剂对凝灰岩沥青混合料的冻融劈裂强度比提升效果欠佳。     

谈基于防滑性能的碎石沥青混合料的设计

碎石沥青混合料是根据贝雷法和粗骨料空隙填充法设计的.最佳沥青用量根据试验确定.碎石沥青混凝土表面纹理深度有着不同空隙率,利用磨损试验机对碎石沥青混合物和普通沥青混合物进行磨损试验.测实结果表明,表面纹理深度随着沥青石油比例的降低而增加.最佳沥青用量的碎石沥青混合物具有良好的防滑性.沥青混合料的BPN穿用时间的增加而减小,但减小的程度是不同的.随着磨损时间的增加,碎石沥青混合物比普通沥青混合物衰减的慢,表明碎石沥青混合物防滑性的衰减量较小.碎石沥青混合物的其它性质显示劈裂强度和模量均比普通沥青的高,其高温性能和水稳定性也能满足技术要求.