Relationship between PSV and in situ friction: a Norwegian case study

Polishing of the aggregates used in pavements may reduce the friction of the road surface, which in turn may lead to slippery, hazardous conditions in traffic. Although the use of studded tyres leads to wearing of the pavement and thus prevents the aggregate becoming smooth, it also results in the generation of airborne dust. As a consequence, the trend to reduce the use of studded tyres and increase the use of wear-resistant aggregate has resulted in more polishing. The paper reports some analyses of polished stone values for the aggregates most commonly used in Norway and considers whether there is a correlation between the polished stone value and in situ friction for mixtures of aggregates with varying polishing and wearing properties.      

Evaluating skid resistance of different asphalt concrete mixes

At all stages of pavement life, the highway surface should have some sort of roughness to facilitate friction between car wheels and pavement surface. Skid resistance is a measure of the resistance of pavement surface to sliding or skidding of the vehicle. It is a relationship between the vertical force and the horizontal force developed as a tire slides along the pavement surface. The texture of the pavement surface and its ability to resist the polishing effect of traffic is of prime importance in providing skidding resistance. Polishing of the aggregate is the reduction in microtexture, resulting in the smoothing and rounding of exposed aggregates. This process is caused by particle wear on a microscopic scale. It is a common fact that the lower the skid resistance value, the higher the percentage of the traffic accidents, especially during the wet seasons. Having a low skid resistance value at an asphalt concrete surface might be attributed to one or more of the following reasons: (1) use of higher asphalt content than recommended by the mix design procedure, (2) the Marshall mix design procedure itself, (3) used aggregate gradation, and (4) aggregate quality. To evaluate these factors, a comparative study was performed to find the British Pendulum Skid Resistance Number for a number of mixes. These mixes included, an asphalt concrete mix using local aggregate at the optimum Marshall asphalt content, mixes with 0.5% and 1.0% asphalt contents higher than Marshall optimum asphalt content, a mix designed using Superpave design procedure, a mix with steel slag to replace 30% of limestone aggregate, and a mix with stone matrix aggregate gradation. It was found that the mix with 30% slag has the highest skid number followed by Superpave, SMA, and Marshall mixes, respectively. It was also observed that increasing the asphalt content above the optimal asphalt content value decreases the skid resistance of these mixes.     

沥青路面沥青混合料针对性设计

由于沥青混合料设计不合理,造成沥青路面产生严重的车辙,因此沥青混合料原材料选择和配合比设计要充分考虑其对路面高温稳定性能的影响。从矿料的颗粒形状和化学性质、沥青性质、矿料级配、沥青混合料空隙率、矿料间隙率、路面中面层沥青混合料性能等方面对沥青路面车辙产生的原因进行了分析,提出了针对车辙产生原因的沥青混合料设计措施。     

沥青混合料抗剪强度影响因素评价指标研究

较高的抗剪强度可以保证沥青混合料在高温下具有良好的抵抗永久变形的能力。主要采用单轴贯入试验,就如何选择高性能沥青混合料的材料设计参数指标进行了研究。研究结果表明,除了沥青的性能外,粗集料、特别是细集料的性能对沥青混合料抗剪性能也有极大的影响。在进行沥青混合料设计时,采用高棱角性指标的粗、细集料以及高粘度的沥青来提高沥青混合料的整体抗剪强度。并且在施工时控制混合料的压实度以确保沥青路面的长期性能。     

Influences of crumb rubber size and type on reclaimed asphalt pavement (RAP) mixtures

Over the years, recycling has become one of the most attractive pavement rehabilitation alternatives, and different recycling methods are now available to address specific pavement distresses and structural needs. The objective of this study was to investigate and evaluate the engineering properties of crumb rubber size and type influences on reclaimed asphalt pavement (RAP) mixtures. The experimental design for this study included the use of three rubber sizes and two rubber types (ambient or cryogenic) in the mixture containing 25% RAP mixtures. In this study, the results of the experiments indicated that the addition of crumb rubber was helpful in increasing the voids in mineral aggregate (VMA) in Superpave mix design and improving rutting resistance of mixture regardless of rubber size and type. On the other hand, indirect tensile strength (ITS) values show no significant difference for mixtures made with three type rubber sizes. However, the increase of rubber size, regardless of rubber type, reduced the resilient modulus values but extended the fatigue life of the modified mixtures.     

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.     

Superpave沥青路面技术的应用研究

通过Superpave沥青路面工程的实践,介绍了Superpave混合料的设计中材料选择、集料结构选取、设计级配、沥青用量确定、混合料水敏感性评价等内容。介绍了几个Superpave沥青路面工程的设计结果以及跟踪性能观测资料。说明Superpave沥青路面具有优良的高温稳定性、较好的路面均匀性及路面服务性能;Superpave混合料设计体系是个相对科学合理的沥青混合料设计体系。     

The effect of mineralogy,texture and mechanical properties of anti-skid and asphalt aggregates on urban dust,stages II and lll

Urban road dust is formed during wintertime when cars use studded tyres and when anti-skid aggregate particles are being crushed under tyres. A road simulator fitted with studded and friction winter tyres was used in three test series in order to investigate dust formation at tyre and pavement interface with various anti-skid materials and tyre types. The bedrock and glaciofluvial anti-skid aggregates tested had variable mechanical–physical and mineralogical properties. A special emphasis was put on the particle size distribution of anti-skid materials and on asphalt aggregate characteristics. The proportions of particles <10 μm from asphalt vs anti-skid aggregate was defined with SEM/EDX. The results of this study indicate that the particle size distribution is the most important property of anti-skid aggregates, and that the wearing process of asphalt pavement “is not homogenous” with friction and studded tyres, and with various anti-skid aggregates. The mechanical–mineralogical relationship between anti-skid and asphalt aggregates is one decisive factor in PM₁₀ formation and these properties affect the proportions of PM₁₀ (anti-skid vs asphalt aggregate). Friction tyres and anti-skid aggregates with lower average hardness compared to asphalt aggregate cannot wear harder minerals (e.g., quartz) of the pavement aggregate homogeneously.      

河西特殊气候环境条件下公路沥青混凝土面层设计实践

柳敦二级公路维修改造工程地处敦煌市戈壁滩内,大温差、强紫外线等自然条件对沥青路面设计提出了较高要求。为了能满足该条件下沥青路面的设计要求,本文结合柳敦二级公路沥青混凝土面层设计实践,分析沥青混凝土路面结构组合原则,提出沥青路面面层结构设计方案。通过分析沥青混合料设计过程及指标发现,混合料油石比应比室内目标配合比设计的油石比小,其中AM-16混合料沥青饱和度宜在55%以下且尽量趋近50%,AC-13C混合料沥青饱和度宜小于70%并尽量接近65%。     

A predictive equation for dynamic modulus of asphalt mixtures used in Korea

The dynamic modulus of an asphalt mixture is widely used as an important material property in mechanistic–empirical (ME) pavement design and analysis because it accounts temperature and time-dependent asphalt mixture modulus. The aim of this study is to evaluate the dynamic modulus of asphalt mixtures used in Korea and develop a predictive equation for Korea ME pavement design guide based on the results of dynamic modulus tests. Asphalt mixtures contained a granite aggregate with PG 58-22 and PG 64-22 asphalt binders were tested at five different temperatures (−10, 5, 21, 40, and 55 °C) and six different loading frequencies (0.1, 0.5, 1, 5, 10, and 25 Hz). A predictive equation was constructed based on the test data, and compared and verified between the measured and the predicted dynamic modulus. From the results, it was found that the predictive equation correlated well with the measured values.     

沥青路面就地热再生工艺及实践

在厂拌冷再生、就地冷再生、厂拌热再生和就地热再生等沥青路面再生方法中,就地热再生工艺适用于沥青道路面层的维修养护,具有节省材料及运输费用,断路施工时间短等优点.介绍沥青路面就地热再生工艺的特点、发展及应用情况,以加拿大马泰克公司生产的AR2000型就地热再生机组的施工实践为例,对就地热再生设备的施工工艺及热再生路面的质量进行试验研究,对热再生路面的质量控制提出建议.     

浅析农村公路沥青路面推移的问题

简述了沥青路面的推移现象,结合近年来农村公路建设中出现的问题,从交通量大小、超载车辆情况、路线纵坡设计、基层材料等方面分析了沥青路面产生推移的原因,并提出了防治措施,以提高沥青路面施工质量,确保沥青混合料的均匀性及表面平整度。     

A review of mix design and evaluation research for permeable friction course mixtures

Permeable friction course (PFC) mixtures constitute one of the best options for surface paving, since they offer advantages (as compared to dense-graded hot mix asphalt) in terms of safety, economy, and environment. However, mix design and evaluation of PFC mixtures still require improvement and standardization to further promote the reliable use of these mixtures. This paper summarizes an extensive literature review focused on the basic aspects integrated in the mix design and evaluation of PFC mixtures. Although substantial advances related to these topics were reported since implementation of PFC mixtures in the 1990’s, there is still a need for integration of several of these advances in an improved mix design procedure. The paper also identifies areas that require additional research, including the optimization of the balance between mixture functionality and durability and replacement of the indirect assessment of these important aspects.     

灌河特大桥沥青桥面铺装施工质量控制

结合灌河特大桥沥青桥面铺装施工实例,详细介绍了施工中存在的施工难点及其主要的对策,包括沥青混合料配合比控制,测量放样和标高控制,沥青混合料的拌和控制,混合料温度的控制,作业面检查,交通管制及混合料运输,混合料摊铺,以及混合料压实成型。针对该特大桥沥青桥面摊铺技术以及所采取的碾压技术措施和工艺措施,确保了工程质量。     

高弹体改性沥青SMA-10在钢桥面中的应用研究

本文通过高弹体改性沥青SMA-10混合料在田安大桥钢桥面铺装的实际应用,对高弹体改性沥青和矿料的选择,配合比的设计,高弹体改性沥青混合料性能检验进行了研究,配制了符合当地实际特点的高弹体改性沥青SMA-10混合料,最终确定最佳油石比为6.6%。通过工程实例应用,积累了较为丰富的经验,为今后类似工程的施工提供借鉴和参考。     

Nonlinear properties analysis on rutting behaviour of bituminous materials with different air void contents

Rutting is one of the major distresses of flexible pavement. It is defined as the formation of longitudinal depressions along the wheel paths caused by the progressive movement of materials under traffic loading in the asphalt pavement layers or in the underlying base through consolidation or plastic flow. This structural damage has a negative financial impact to the economy. In this study, the rutting behaviour of bituminous materials with different air void contents was investigated. The dynamic cyclic compression testing was carried out to establish nonlinear material models with multiple regression technique. With the specified material models, finite element analysis was carried out to study the rutting behaviour of the wearing course materials with different air void contents in a flexible pavement structure. The simulation result shows that the rutting depth is small at the air void contents of 4.5–8% for wearing course materials. However, for the air void contents above or below this range, the rutting resistance reduces, and thus the rutting depth increases. To verify this simulation result, wheel tracking tests were performed to obtain laboratory data, and the test data was found to be very close to the simulated one. This proved that the developed nonlinear model is applicable to simulate the rutting performance of bituminous mixture and it is a convenient and economical method to be used for the design of bituminous mixtures for both new and rehabilitated pavements.     

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.     

排水性沥青路面在汉十高速公路养护工程中的应用

湖北省汉十高速公路管理处针对雨天路面积水而引发交通事故这一难题,率先在湖北省高速公路养护工程中提出排水性沥青路面技术,并邀请多方专家对此进行技术咨询,研究决定在汉十孝襄段K79+280～K80+500十汉向、K123+000～K122+700汉十向、K125+750～126+150.5十汉向、K151+275～K152+17十汉向四处路面积水严重路段,实施排水性沥青路面加铺方案,并对此排水性沥青路面进行了技术总结,包括路面结构设计方案、排水性沥青混合料组成设计、排水性沥青路面施工、路用性能检验及其关键环节。实际测试表明湖北汉十高速公路排水性沥青路面具有良好的路表服务特性,说明设计方案与施工工艺合理,质量可靠,性能优良,彻底解决了路面积水,确保道路安全畅通。     

基层模量对重载交通沥青路面受力特性的影响分析

基层模量的取值将直接影响到路面结构的受力特性,它是是路面设计的重要力学参数之一。本文系统分析基层模量变化对重载交通沥青路面路表弯沉、基层层底拉应力、底基层层底拉应力的影响,并阐述了其影响规律。结果表明．基层模量对重载交通沥青路面的受力与变形特性具有显著的影响,提高基层模量值将显著减小路表弯沉值底基层层底拉应力,而基层本身的层底拉应力值将增大,需要在路面设计中充分重视。     

基于层位分工论的材料组成设计

基于层位分工论，对沥青各面层的沥青和集料的性质提出了进一步的要求，并对如何适当提高沥青混合料相应的配合比设计检验指标要求进行了阐述，使设计出的混合料更加符合不同面层的实际要求，进一步完善沥青混合料材料的组成设计。