室内外老化沥青混合料动态模量评价

为对室内外老化条件下沥青混合料的动态模量特征进行比较和评价,按照北京市五环路上、中、下3个面层的结构与材料类型,在室内成型SMA-16,AC-25,AC-30沥青混合料试件,分别进行不同老化程度下的间接拉伸疲劳试验,根据时-温等效原理建立不同老化程度沥青混合料的动态模量主曲线,并与室外自然老化13a的沥青路面芯样进行对比,研究室内外老化的关系.结果表明:老化效应对沥青混合料动态模量的影响随试验温度升高而逐渐增强;沥青混合料动态模量对老化效应的敏感程度依次为:AC-25AC-30SMA-16;间接拉伸试验条件下3种沥青混合料室内外老化的动态模量主曲线差异不大,可以通过室内老化试验对室外路面沥青混合料的动态模量进行评价.     

复合式SMA桥面铺装混合料配比设计及高温抗车辙性能研究

为了提升桥面铺装的高温抗车辙性能,采用马歇尔配合比设计方法对3种SMA沥青混合料分别进行级配设计及体积指标验证,选用轮辙试验和车辙试验对所设计的5种复合式SMA桥面铺装结构组合的高温性能评价指标进行测试.结果表明,SMA混合料沥青析漏损失及飞散损失均满足技术要求,SMA具有合理的最大沥青用量,且粘附性良好;提出的5种复...     

Mechanistic analysis of ST and SBS-modified flexible pavements

This paper deals with the viability of using starch (ST) and styrene–butadiene–styrene (SBS) as an additive in stone matrix asphalt (SMA) mixtures. A 5% of ST and SBS by weight of bitumen were blended with (70/100)-paving grade asphalt. Unmodified and modified bitumen were subjected to physiochemical tests. The performance tests including, Marshall stability, tensile strength, tensile strength ratio and resilient modulus were carried out on unmodified and modified SMA mixtures. A mechanistic-empirical design approach was used for estimating the improvement in service life of the pavement or reduction in thickness of SMA and base layer for the same service life due to modification the SMA mixtures. The analyses of test results show that the moisture damage and temperature susceptibility can be reduced by the inclusion of ST and SBS in the asphalt mixture. The results also revealed that ST-modifier can be used as anti-stripping agent, and reduced plant emissions and energy consumption by 30%, as well as it shows resistant to fuels, most common chemicals and solvents. The results of multi-layer elastic analysis presented herein indicate that the pavement consisting of ST and SBS-modified SMA as a surface layer is beneficial in reducing the construction materials. In addition, the safe pavement design criteria of unmodified and modified SMA mixtures based on the anisotropic elasticity analysis through finite-element simulation were obtained and reported herein.     

钢纤维沥青混合料路面性能及应用研究

为防止低温地区沥青路面的开裂和提高沥青路面疲劳寿命,通过室内试验研究了钢纤维沥青混合料的物理力学性能,包括钢纤维沥青混合料的马歇尔稳定度、动稳定度、常温、低温劈裂强度、纤维防腐方法等,分析了钢纤维对沥青混合料性能影响的机理。通过试验路研究了钢纤维沥青路面的现场拌和施工工艺和使用效果,研究结果表明：沥青混合料中加入钢纤维可使低温劈裂强度明显提高,开裂时的变形显著增大,从而改善沥青路面的低温抗裂性能,同时钢纤维对常温条件下沥青混合料的抗拉强度和高温抗车辙性能有一定改善,钢纤维沥青路面的施工工艺与普通沥青混凝土     

钢渣沥青混合料疲劳性能及改善机理

采用钢渣替代部分粗集料,制备了4种钢渣掺量的沥青混合料,并对其进行不同应变水平下的四点弯曲疲劳试验,分析钢渣掺量和应变水平对混合料疲劳性能的影响,以揭示疲劳性能改善机理.结果表明:随着钢渣掺量的增加,沥青混合料疲劳寿命呈先增加后降低的趋势,峰值出现在钢渣掺量为30%(质量分数)时;钢渣沥青混合料初始劲度模量和疲劳寿命均随着应变水平的增大而降低;疲劳损伤演化过程可分为失稳、平衡、失效3个发展阶段,疲劳失效劲度模量衰减比S_r/S_(50)小于50%,并随着应变水平的增大而逐渐减小;疲劳裂纹扩展主要发生在矿料-沥青界面处,且受应变水平影响较大;钢渣的化学性质和表面构造在改善界面相结构方面起到了交互黏附和嵌入锚固作用,用钢渣作为粗集料可显著提升沥青混合料的疲劳性能.     

Laboratory and field evaluation of asphalt pavement surface friction resistance

Pavement surface friction is a significant factor for driving safety and plays a critical role in reducing wet-pavement crashes. However, the current asphalt mixture design procedure does not directly consider friction as a requirement. The objective of this study was to develop a surface friction prediction model that can be used during a wearing course mixture design. To achieve the objective, an experimental study was conducted on the frictional characteristics of typical wearing course mixtures in Louisiana. Twelve wearing course mixtures including dense-graded and open-graded mixes with different combinations of aggregate sources were evaluated in laboratory using an accelerated polishing and testing procedure considering both micro-and macro texture properties. In addition, the surface frictional properties of asphalt mixtures were measured on twenty-two selected asphalt pavement sections using different in situ devices including Dynamic Friction Tester (DFT), Circular Texture Meter (CTM), and Lock-Wheel Skid Trailer (LWST). The results have led to develop a procedure for predicting pavement end-of-life skid resistance based on the aggregate blend polish stone value, gradation parameters, and traffic, which is suited in checking whether the selected aggregates in a wearing course mix design would meet field friction requirements under a certain design traffic polishing.     

高粘度沥青SMA钢桥面铺装面层性能研究与应用

介绍高粘度沥青SMA钢桥面铺装层的设计,同时采用新的铺装形式,改变沥青混合料与钢板的直接接触方式,通过AMP-100二阶反应型桥面防水粘结层与高粘沥青碎石封层相结合的方式,使SMA铺装层的抗高温车辙能力、抗裂性、界面抗剪切强度均得到了显著提高,该方案已成功运用于某道路拓宽改造工程的跨铁路桥面铺装.     

Predicting stripping and moisture induced damage of asphalt concrete prepared with polymer modified bitumen and hydrated lime

Many highway agencies have been experiencing premature failures that decrease the performance and service life of pavements. One of the major causes of premature pavement failure is the moisture damage of the asphalt concrete layer. Many variables affect the amount of water damage in the asphalt concrete layer such as the type of aggregate, bitumen, mixture design and construction, level of traffic, environment, and the additive properties that are introduced to the bitumen, aggregate or bitumen–aggregate mixture.This study is aimed to determine the effect of additives such as hydrated lime as well as elastomeric (SBS) and plastomeric (EVA) polymer modified bitumen (PMB) on the stripping potential and moisture susceptibility characteristics of hot mix asphalt (HMA) containing different types of aggregate (basalt–limestone aggregate mixture and limestone aggregate). The stripping properties and moisture susceptibility characteristics of the samples have been evaluated by means of captured images and the Nicholson stripping test (ASTM D 1664) as well as the modified Lottman test (AASHTO T 283), respectively.The results indicated that hydrated lime addition and polymer modification increased the resistance of asphalt mixtures to the detrimental effect of water. Moreover, it was found out that samples prepared with SBS PMB exhibited more resistance to water damage compared to samples prepared with EVA PMB.     

Reproducing ten years of road ageing — Accelerated carbonation and leaching of EAF steel slag

Reuse of industrial aggregates is still hindered by concern for their long-term properties. This paper proposes a laboratory method for accelerated ageing of steel slag, to predict environmental and technical properties, starting from fresh slag. Ageing processes in a 10-year old asphalt road with steel slag of electric arc furnace (EAF) type in the subbase were identified by scanning electron microscopy (SEM) and leaching tests. Samples from the road centre and the pavement edge were compared with each other and with samples of fresh slag. It was found that slag from the pavement edge showed traces of carbonation and leaching processes, whereas the road centre material was nearly identical to fresh slag, in spite of an accessible particle structure. Batches of moisturized road centre material exposed to oxygen, nitrogen or carbon dioxide (CO₂) were used for accelerated ageing. Time (7-14 days), temperature (20-40 °C) and initial slag moisture content (8-20%) were varied to achieve the carbonation (decrease in pH) and leaching that was observed in the pavement edge material. After ageing, water was added to assess leaching of metals and macroelements. 12% moisture, CO₂ and seven days at 40 °C gave the lowest pH value. This also reproduced the observed ageing effect for Ca, Cu, Ba, Fe, Mn, Pb, Ca (decreased leaching) and for V, Si, and Al (increased leaching). However, ageing effects on SO₄, DOC and Cr were not reproduced.     

机场SMA高温变形中集料倾角变化规律

为探究机场重载下SMA(沥青玛蹄脂碎石混合料)的车辙变形特性,同时为建立沥青混合料细观模型提供数据支持,针对SMA高温变形过程中集料倾角的变化规律开展研究.采用车辙试件取芯方式,研究沥青混合料在高温及高荷载作用下集料倾角随碾压次数的变化规律.基于X-射线CT技术获取并重构了碾压前后沥青混合料的三维数字图像,提取了数字试件沿轮迹方向和垂直轮迹方向的二维图像,采用MATLAB编写图像的批量处理程序,获取二值化图像,进行集料倾角的计算和统计.结果表明:沥青混合料集料倾角的累计分布概率符合三参数威布尔分布;混合料集料倾角在0°~20°分布最多;碾压后,沿轮迹方向0°~20°区间集料倾角概率保持增大,垂直轮迹方向40°~60°区间集料倾角概率保持增大;沿轮迹方向集料倾角变化与车辙变形线性相关;掺加70#沥青的SMA集料较掺加SBS改性沥青的SMA集料倾角更易偏转.     

Potential of recycled fine aggregates powder as filler in asphalt mixture

The main objective of this study is to investigate the potential of using recycled fine aggregates powder (RFAP) as filler in asphalt mixtures. RFAP is a by-product of the production of Recycled Concrete Aggregate (RCA). The disposal of RFAP may cause many serious environmental problems. It is necessary to find potential usage to avoid these problems.In this study, RFAP is used as filler in asphalt mixture by totally replacing conventional limestone powder (LP). Firstly, the properties of RFAP is studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and X-ray fluorescence spectroscopy (XRF). Then the indirect tensile strength and modulus tests, three-point bending tests, dynamic creep tests and fatigue tests are conducted to compare the properties between asphalt mixtures with RFAP and traditional asphalt mixture with LP. Results indicate that RFAP can improve the properties of asphalt mixture, such as including water sensitivity and fatigue resistance. However, it may cause a little decrease of the low-temperature performance. All the results indicate that the RFAP can be used in asphalt pavement, especially in hot regions.     

钢渣沥青混凝土路面抗滑性能研究

路面的抗滑性能是保证行车安全的一个重要指标。集料的抗磨耐滑性能对路面的抗滑性能有着重要意义。该文在对钢渣路面抗滑性能进行了8年的追踪调查后发现,钢渣有着良好的物理力学性能,与传统路面相比,钢渣路面抗滑性能衰减较慢,可以显著提高路面的抗滑性能。     

Effect of glass cullet on the improvement of the dynamic behaviour of asphalt concrete

The stiffness modulus is one of the most important parameters for the prediction of pavement strength against dynamic loads. Previous research indicated that glass can reduce the construction costs of asphalt concrete pavements while providing better dynamic behaviour because of its unique properties. In this research, the behaviour of Hot Mix Asphalt (HMA) in different temperature conditions depending on the variation of the admixture contents and the gradation of the aggregates will be evaluated. Afterwards, for the first time, models for the prediction of the stiffness modulus of waste glass–asphalt in terms of three different parameters including temperature, percentage of additives and the aggregate gradation will be presented. The results of this research are indicative of an improvement in the dynamic behaviour of glass–asphalt mixture in comparison with conventional HMA mixtures.     

掺钢渣混合料在道路工程中的应用研究

依托项目工程将掺钢渣混合料应用到路面面层与基层中,分别铺设SMA-13和AC-16钢渣沥青混合料面层试验段、水泥稳定钢渣碎石混合料和水泥粉煤灰稳定钢渣碎石混合料基层试验段,并对试验段检测指标进行研究和跟踪评价。结果表明,试验路段相关技术指标满足规范要求,运营过程中路面无明显病害,验证了掺钢渣混合料在路面面层与基层应用中的可靠性与可行性。     

Effect of carbon black on the dynamic moduli of asphalt mixtures and its master curves

Modulus is one of the main parameters during the design of asphalt pavement structure, the newest specifications of China gives the dynamic moduli ranges of commonly used asphalt mixtures with base asphalt (BA) or styrene-butadiene-styrene modified asphalt (SBS MA), while the moduli ranges of mixtures with carbon black modified asphalt (CB MA) are not recommended. To investigate the CB effect on the dynamic moduli of CB MA mixtures, one commonly used asphalt mixture (AC-20) was designed with BA, SBS MA, and CB MA, respectively. Then, the uniaxial compression dynamic modulus tests were conducted at different temperatures and loading frequencies, the master curves of asphalt mixtures were analyzed based on the time-temperature equivalence principle. The results show that with increasing loading frequency, the temperature dependence of dynamic moduli of all asphalt mixtures tend to be less obvious. Both SBS and CB can decrease the temperature sensitivity of asphalt mixture, the SBS MA mixture has the lowest temperature sensitivity, followed by CB MA and BA mixture. In addition, CB and SBS can obviously improve the dynamic modulus of the BA mixture, enhance the anti-deformation performance of pavement structure, and the improvement effect of CB is almost the same with SBS.     

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.     

纳米复合改性沥青混合料路用性能研究

为评价纳米复合改性沥青混合料的路用性能,对纳米ZnO改性沥青混合料、纳米ZnO/TiO_2改性沥青混合料以及纳米ZnO/TiO_2/SBS复合改性沥青混合料进行了高温性能试验、小梁弯曲试验、劈裂试验及相关耐久性试验,并与基质沥青混合料和SBS改性沥青混合料进行对比分析.结果表明:上述3种纳米改性沥青混合料的高温稳定性、低温抗裂性、间接抗拉性和耐久性均优于基质沥青混合料,其中纳米ZnO/TiO_2/SBS复合改性沥青混合料的上述性能优于SBS改性沥青混合料.由此可见,纳米材料可显著改善沥青混合料的性能,纳米复合改性沥青的性能优于聚合物改性沥青,将其应用于道路是可行的.     

SMA路面物理力学性能的试验研究

在调研分析国内外SMA路面发展应用现状的基础上,结合SMA路面的路用性能、组成特点和形成机理,对SMA混合料进行了深入的性能实验研究,内容主要包括:矿料级配对混合料高温及水稳定性的研究和力学性能的分析,研究认为:SMA沥青混合料对沥青混合料的水稳定性、低温抗裂性能、抗老化性能和路面排水能力及高速行车的抗滑能力都有明显提高,并解决了高温稳定性好、耐久性差的矛盾。     

废旧橡塑改性沥青及混合料的技术性能研究

利用自主研发的废旧橡胶塑料复合改性剂制备了废旧橡塑改性沥青,通过室内试验评价了废旧橡塑改性沥青的技术性能.在此基础上,以废旧橡塑改性沥青作为胶结料制备了AC-13型沥青混合料,测试了其高温性能、低温性能、水稳定性和疲劳性能,并与山东省常用的SBS改性沥青和橡胶改性沥青技术性能进行了对比.结果表明:废旧橡塑改性沥青及其沥青混合料具有高温稳定性和水稳定性优势,低温性能介于橡胶改性沥青和SBS改性沥青之间,疲劳性能接近SBS改性沥青.利用废旧橡胶和废旧塑料的各自优势对沥青进行复合改性,在提高沥青混合料路用性能方面具有发展潜力.     

Effect of copper slag as a fine aggregate on the properties of cement mortars and concrete

An experimental investigation was conducted to study the effect of using copper slag as a fine aggregate on the properties of cement mortars and concrete. Various mortar and concrete mixtures were prepared with different proportions of copper slag ranging from 0% (for the control mixture) to 100% as fine aggregates replacement. Cement mortar mixtures were evaluated for compressive strength, whereas concrete mixtures were evaluated for workability, density, compressive strength, tensile strength, flexural strength and durability. The results obtained for cement mortars revealed that all mixtures with different copper slag proportions yielded comparable or higher compressive strength than that of the control mixture. Also, there was more than 70% improvement in the compressive strength of mortars with 50% copper slag substitution in comparison with the control mixture. The results obtained for concrete indicated that there is a slight increase in density of nearly 5% as copper slag content increases, whereas the workability increased significantly as copper slag percentage increased compared with the control mixture. A substitution of up to 40–50% copper slag as a sand replacement yielded comparable strength to that of the control mixture. However, addition of more copper slag resulted in strength reduction due to the increase in the free water content in the mix. Also, the results demonstrated that surface water absorption decreased as copper slag content increases up to 50% replacement. Beyond that, the absorption rate increased rapidly and the percentage volume of the permeable voids was comparable to the control mixture. Therefore, it is recommended that up to 40–50% (by weight of sand) of copper slag can be used as a replacement for fine aggregates in order to obtain a concrete with good strength and durability requirements.