沥青混合料车辙试验前后其体积参数变化规律分析

研究沥青混合料车辙试验前后其体积参数对提高沥青混合料高温稳定性具有重要意义。采用轮碾法成型沥青混合料试件,并对试件钻芯取样,分析芯样的空隙率、矿料间隙率和沥青饱和度等体积参数。结果表明:辙槽处芯样的空隙率明显小于车辙前的;油石比在4.0%附近时,轮迹两侧的空隙率大于等于车辙前的,随着油石比的增大,轮迹两侧的空隙率减小并小于车辙前的;辙槽处芯样的空隙率要小于轮迹两侧的。     

沥青混合料永久变形过程中粗集料空间运动分析

编写了三维不规则多面体粗集料的随机生成程序,重构了包含粗集料、沥青砂浆及空隙的沥青混合料车辙试件的三维离散元模型.通过对三维离散元模型进行数字切割获取了沥青混合料车辙试件的二维离散元模型,对沥青混合料车辙试件二维离散元模型中微观组成结构之间的接触赋予了相应的微观接触模型及模型参数.进行了沥青混合料车辙试验的二维离散元模拟,分析了沥青混合料永久变形过程中粗集料的平动和转动.结果表明:二维离散元模型能够较为精确地描述粗集料在沥青混合料永久变形过程中的空间运动情况,从而为今后沥青混合料车辙形成机理的探讨提供新的研究方式.     

影响SMA高温稳定性因素的试验研究

SMA沥青混合料的高温稳定性对其路用性能有很大的影响。通过室内马歇尔和车辙试验,对可能影响SMA高温稳定性的因素进行了分析。试验结果表明SMA的高温稳定性与其级配、沥青用量、试验温度、碾压次数、粗集料骨架间隙率密切相关。本文仅就以上几个影响因素进行讨论。     

陶砂细集料对沥青混合料阻热性能的影响

为了提高沥青混合料的抗车辙性能,将粒径为0.6～4.75 mm的陶砂依照不同比例等体积替代细集料掺入到沥青混合料中,对各陶粒掺量下的沥青混合料试件进行路用性能及室内外辐射试验。结果表明,添加陶粒可以明显提高沥青混合料的高温稳定性,降低导热系数,增强阻热能力,陶砂的最佳掺量为60%,此时陶砂沥青混合料具有良好的抗车辙性能。     

不同温度与荷载作用下的胶粉复合改性沥青混合料抗车辙性能试验研究

探讨了不同荷载、不同温度对胶粉复合改性沥青混合料高温性能的影响,并对黏结料分别为基质沥青、SBS改性沥青、胶粉改性沥青及胶粉复合改性沥青的4种类型混合料抗车辙性能进行对比分析。采用车辙试验机,对碾压成型的试件,参照"沥青混合料车辙试验"T0719—2011中规定的方法进行车辙试验,得出了4种沥青混合料在不同荷载、不同温度下的动稳定度DS,并对动稳定度DS进行分析:掺加复合剂后,胶粉复合改性沥青混合料的抗车辙性能改善显著,且温度与荷载越大,改善效果越明显。     

沥青混合料车辙试件成型控制研究

回顾了典型车辙试验试件成型控制指标与标准的不同,并且分析了加利福利亚HVS测试结果.分析发现:经历长时间的汽车荷载作用后,轮迹下现场空隙率可能不低于4%;由现场初始空隙率变化至使用期末空隙率,压密变形对车辙深度的贡献率较小,蠕变变形仍然是车辙深度的主要贡献者.因此,建议车辙试件成型采用预期现场初始空隙率作为控制指标.最后通过试验分析,建议热拌密级配沥青混合料(DGAC)成型空隙率按照(7.0±1.0)%进行控制,沥青玛蹄脂碎石混合料(SMA)成型空隙率按照(5.5±0.5)%进行控制.     

SMA沥青玛蹄酯施工要点

<正>沥青玛蹄酯碎石:由沥青玛蹄酯填充于间断级配的粗集料骨架的间隙中成为一体的沥青混合料,简称"SMA"。沥青玛蹄脂碎石混合料是当前国际上公认的一种抗变形能力强,耐久性较好的沥青面层混合料。由于粗集料的良好嵌挤,混合料有很好的高温抗车辙能力,同时由于沥青玛蹄脂的粘结作用,低温变形性能和水稳定性也有较好的改善。添加纤维稳定剂,使沥青结合料保持高粘度,其摊铺和压实效果较好。间断级配在表面形成大孔隙,构造深度大,抗滑性能也有提高。同     

SBS改性剂对沥青混合料高温稳定性的影响

以AC-16混合料的3种级配为研究对象,通过室内车辙试验分析了3种级配在不同SBS改性剂掺量下的高温稳定性。分析结果表明:随着SBS改性剂掺量的增加,沥青混合料的动稳定度DS会明显增大,车辙深度RD会明显减小;较粗集料的沥青混合料的动稳定度明显高于较细集料沥青混合料的动稳定度。     

多孔沥青混合料旋转压实效果研究

基于数字图像处理技术,分析多孔沥青混合料试件的断面数字化信息,研究混合料的旋转压实特性。以粗集料水平的分布特征、改进的颗粒面积比和空隙率的分布等特性描述混合料的均匀性,为研究多孔沥青混合料的均匀性提供参考。结果表明,在足够的旋转压实功下,粗集料截面几何中心对称且沿直径方向分布均匀。空隙率沿试件高度方向呈两端大、中部低分布。     

浅议改性沥青及SMA路面的施工与质量管理

SMA沥青混合料是一种以沥青、矿粉、纤维稳定剂和少量的细粉组成的沥青马蹄脂填充间断级配的粗集料骨架间隙而组成的沥青混合料,它最基本的组成是碎石骨架和沥青马蹄脂结合料两大部分,其强度是依靠粗集料在沥青混合料中的骨架嵌挤作用和沥青马蹄脂胶结料粘结裹覆作用形成的,因而它具有很好的耐久性、抗高温稳定性、抗低温开裂、抗滑性及较好的排水性能,尤其是抗高温车辙和低温裂缝以及疲劳性能尤为突出,被广泛的应用于高速公路和一些重载交通的抗滑表层。本文对改性沥青SMA路面施工质量管理及施工中应注意的一些问题进行了说明。     

Framework for developing a static strength test for measuring deformation resistance of asphalt concrete mixtures

This study deals with a strength property which is showing high correlation with rutting resistance of asphalt mixtures. The test procedure was developed by applying a load to the compacted asphalt samples and calculating the strength by using the deformation of the mixture at the failure point. To evaluate the validity of this test, various mixtures were prepared with two aggregates and seven binders using four loading head types at the loading speed of 50.8 mm/min at 60 °C. Maximum load and deformation were recorded for each test and deformation strength, S_D, was calculated using a newly developed equation. For the same mixture, wheel tracking test was performed and two rut parameters, depth of rut and dynamic stability were obtained. The relationship between S_D and rut parameters was evaluated using regression analyses. In most cases, R² values were found to be over 0.9. This test procedure is still under development; however, current results indicate that it might be a simple test to predict the deformation resistance of asphalt mixtures at high temperatures.     

高温下橡胶沥青胶浆特性及矿料级配优化分析

为改善橡胶沥青混合料的高温性能,提出以橡胶沥青胶浆和矿料级配为主要研究对象的优化思路。通过室内试验,首先研究粉胶比对橡胶沥青胶浆抗车辙因子和相位角的影响;然后结合橡胶沥青的特异性,对其橡胶沥青混合料的矿料级配进行选择和调整,将动稳定度和相对变形作为混合料高温性能评价指标,得出优化后的矿料级配。研究结果表明,提高橡胶沥青混合料高温稳定性的措施有:适当调整粉胶比,控制在1.2左右为宜;以水泥取代矿粉作为混合料的填料;以传统SMA级配为基础,对混合料级配作出调整,适当降低填料比例,能够实现橡胶沥青混合料高温稳定性的优化。     

SMA沥青路面施工质量的有效控制

SMA沥青碎石混合料在路面具有抗车撤、抗裂、抗滑、泌水及耐久等优点,因此在施工工艺和质量控制方面比普通沥青混凝土路面的要求标准更高。结合重庆机场二期扩建场区道路的工程实践,从施工过程中的材料质量、拌合、运输、摊铺、碾压、接缝处理六个生产环节入手,提出了有效控制SMA路面施工质量的关键点。     

基于Burgers黏弹性模型的沥青路面蠕变变形规律三维有限元分析

针对不同温度条件下沥青路面的蠕变变形问题,以Burgers模型为理论依据,利用数据分析软件Origin8.1对不同温度下的蠕变试验曲线进行拟合分析,得出Burgers模型中E1、E2、η1、η2四个蠕变方程参数,采用Laplace变换与逆变换将Burgers蠕变方程转化为Prony级数,由此得到不同温度下沥青混合料的相对松弛模量g1、g2及松弛时间τ1、τ2,供ANSYS调用分析。利用三维有限元数值法对不同温度及加载时长下的沥青路面蠕变变形分布规律进行数值分析计算。结果表明:不同温度下路表蠕变变形横向范围均为0.88 m,变形向轮迹外侧延伸范围较内侧更广;温度越高,路表所产生的应变越大,60℃时路表会发生应变突变,路面经受5.4×106累计当量标准轴载通行次数后将产生1 cm的车辙,对沥青路面的高温稳定性提出了更高的要求。     

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.     

Utilization of steel slag as aggregates for stone mastic asphalt (SMA) mixtures

Steel slag is a byproduct making up a portion of 15–20% of iron output in an integrated steel mill. Most of them are deposited in slag storing yards and thus results in many serious environment problems in China. This paper aims to explore the feasibility of utilizing steel slag as aggregates in stone mastic asphalt (SMA) mixtures, and properties of such asphalt mixtures are evaluated as well. X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) were employed to study the compositions, structure and morphology of aggregates. Volume properties and pavement performances of SMA mixture with steel slag were also evaluated as compared to that with basalt as aggregates. Results indicated that volume properties of SMA mixture with steel slag satisfied the related specifications and expansion rate was below 1% after 7 days. When compared with basalt, high temperature property and the resistance to low temperature cracking of SMA mixture were improved by using steel slag as aggregate. In-service SMA pavement with steel slag also presented excellent performance on roughness and British Pendulum Number (BPN) coefficient of surface.     

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.     

Two- and three-dimensional micromechanical viscoelastic finite element modeling of stone-based materials with X-ray computed tomography images

This paper presents 2D and 3D micromechanical finite element (FE) models to predict the viscoelastic properties including dynamic modulus and phase angle of stone-based materials (using an example of asphalt mixtures). Heterogeneous asphalt mixtures are consisted of very irregular aggregates, asphalt matrix and a small amount of air voids. The internal microstructure of asphalt mixtures was captured with X-ray computed tomography (CT) imaging techniques. The 2D and 3D digital samples were created with the reconfiguration of the scanned horizontal surface images. The FE mesh of digital samples was generated with the locations of image pixels within each aggregate and asphalt matrix. Along the boundary of these two phases, the aggregate and matrix FEs share the nodes to connect the deformation. The micromechanical FE model was accomplished by incorporating the captured microstructure and ingredient properties (viscoelastic asphalt matrix and elastic aggregates). The generalized Maxwell model was applied for viscoelastic asphalt matrix with calibrated parameters from the nonlinear regression analysis of the lab test data. The displacement-based FE simulations were conducted for the uniaxial compression under sinusoidal cyclic loading. Overall, the predicted dynamic modulus and phase angle from 2D and 3D micromechanical models were compared favorably with lab test data of the asphalt mixture specimens. The 3D simulation with digital samples generated better prediction than the 2D models. These results indicate that the developed micromechanical FE models have the ability to accurately predict the global viscoelastic properties of the stone-based materials.     

A laboratory study on stone matrix asphalt using ground tire rubber

This research investigated the feasibility using asphalt rubber (AR), produced by blending ground tire rubber (GTR) with an asphalt, as a binder for stone matrix asphalt (SMA). Two different sizes of GTR produced in Taiwan were used. The potential performance of AR–SMA mixtures was also evaluated. The results of this study showed that it was not feasible to produce a suitable SMA mixture using an asphalt rubber made by blending an AC-20 with 30% coarse GTR with a maximum size of 0.85 mm. However, SMA mixtures meeting typical volumetric requirements for SMA could be produced using an asphalt rubber containing 20% of a fine GTR with a maximum size of 0.6 mm. No fiber was needed to prevent drain-down when this asphalt rubber was used. The AR–SMA mixtures were not significantly different from the conventional SMA mixtures in terms of moisture susceptibility from the results of AASHTO T283 tests. The results of the wheel tracking tests at 60 °C show that rutting resistance of AR–SMA mixtures was better than that of the conventional SMA mixtures.