Engineering Application and Development of Anti-skid Sand

In view of the increasing cement concrete pavement in China,the proportion of road non-slip surface layer is large,the winter slippery performance is insufficient and the later non-slip treatment is difficult. Through the concrete construction and post-application and development of the anti-skid sand in the road and bridge,the feasible anti-skid optimization measures are put forward.     

福州城区道路大气PM10单颗粒形貌分析

本文应用扫描电子显微镜-能谱仪(SEM-EDX)技术分析福州城区道路大气中PM10颗粒物的形貌特征、粒径分布和元素组成.研究表明,福州城区道路大气中PM10颗粒物形貌多样,以小于0.5μm的细粒子为主,粒子数量随着粒径增大而减少.大气颗粒物类型主要有烟尘集合体、飞灰颗粒、矿物颗粒、生物颗粒等.福州城区道路大气颗粒物污染...     

The effects on accidents of studded tires and laws banning their use: a meta-analysis of evaluation studies

Studies that have evaluated the effects on accidents of studded tires are reviewed. There are two types of evaluation studies with respect to the safety effects of studded tires: (1) Studies of the effect on automobile accident rates of using studded tires; and (2) studies of the effect on accidents of banning the use of studded tires. The results of studies of the effects of studded tires on automobile accident rates are found to vary substantially, depending on the quality of the study design. Recent studies employing multivariate techniques of analysis to control for confounding factors, attribute to studded tires minor declines in automobile accident rates of 5% for snow- or ice-covered roads, 2% for bare roads and 4% for all road surfaces combined. The results of these studies are consistent with the most recent estimates of the effect on accidents of banning studded tires. It is concluded that studded tires probably confer a slight safety benefit during wintertime.     

钢渣沥青混凝土技术及其应用研究进展

钢渣常被当成工业废弃物处置,但其碱性强、棱角丰富,兼具有优异的力学特性,可以改善沥青混凝土的抗水损害、抗高温变形以及耐磨和抗滑等性能,被认为是可替代天然矿质集料的理想筑路材料。近年来道路建设对集料用量的高需求与天然集料短缺之间的矛盾越来越突出,钢渣沥青混凝土技术因而成为备受关注的热点。概述了钢渣的材料特性以及钢渣沥青混凝土的设计与性能,介绍了钢渣沥青混凝土的实际应用情况,研究了钢渣沥青混凝土长期应用后的路面性能变化,最后对钢渣沥青混凝土未来的发展趋势进行了展望。     

道路旁大气悬浮微粒的理化特性及污染源解析(英文)

旨在探讨道路旁悬浮微粒之理化成分,并解析其可能的污染来源。悬浮微粒采样作业于2003年5月～2004年1月期间进行,悬浮微粒样本采集时间包括春、夏、秋、冬四季的假日与非假日,所采集的悬浮微粒样本经化学成分分析可得水溶性离子成分与金属元素成分,并透过化学质量平衡受体模式及逆轨迹模式进行污染源解析。测量结果显示,假日的大气悬浮微粒PM10浓度高于非假日,而假日与非假日的总悬浮颗粒则无明显变化。此外,道路旁悬浮微粒PM10主要受非交通源的长程传输与当地的交通源所影响,而总悬浮颗粒则主要源自于附近道路的车行及逸散扬尘。另就悬浮微粒化学成分而言,金属元素成分以Ca、Fe、Al最多,水溶性离子成分则主要为SO42-、NO3-、NH4+等二次污染物。受体模式及逆轨迹模式分析结果得知,污染来源主要为交通污染及道路扬尘,然而,亦有相当部分的污染来自上风处的非交通源。     

Effect of full-size and down-scaled accelerated traffic loading on pavement behavior

Accelerated pavement testing (APT) is an effective testing procedure to evaluate asphalt pavements. With APT it is possible to determine and measure the structural response and pavement performance under a controlled, accelerated damage accumulation in a compressed period of time. However, different types of APT technologies can lead to different results. Full-size loading devices simulate road traffic accurately, but are expensive, while down-scaled size simulators are cost effective, nevertheless further away from reality. In this work, two types of APT mobile load simulators with different loading characteristics are compared with respect to pavement response in the field and in the laboratory. The MLS10 is a full-size simulator, whereas the MMLS3 is a one-third scale device. The relationship between the devices was studied in terms of the measured strains induced by both machines in the same pavement. Therefore, a testing field was instrumented with strain gauges and first trafficked with MLS10. Later, a slab of the instrumented pavement was cut off the road and tested in the laboratory with the smaller MMLS3. Furthermore, the structure of the pavement was modelled with a viscoelastic finite element method model and the moving loads of both machines were simulated considering size, speed and approximate footprints of their tires. As for the pavement materials, the properties of the different asphalt layers were determined in the laboratory. Experimentally acquired strain data were used to validate the models. Stress fields under different loading and environmental conditions were analysed and compared. The evaluation shows that the models can predict the pavement response under different loading conditions. However, they still need to be improved to increase the accuracy under different conditions. Further, the analysis of the strains show that both load simulators induce a different stress–strain situation and scaling of the pavement should be considered.     

粗骨料对沥青混凝土开裂阻力影响分析

沥青混凝土是典型的非均匀材料,在进行力学分析时通常是将其视为均匀、各向同性体,但是理论分析结果很难与实际相符合。同时均质化假设也很难解释含大粒径骨料的沥青碎石作为防裂层的抗裂性能优于小粒径沥青混凝土的现象。笔者通过在均质的沥青混凝土引入一个粗骨料,应用断裂力学平面有限元程序系统地分析了粗骨料对沥青混凝土抗裂性能的影响,分析结果可以较好地解释大粒径沥青混凝土的抗裂性能优于小粒径沥青混凝土的机理。因此,使用大粒径骨料沥青混泥土能够改善路面的使用寿命。     

沙尘期间大气颗粒PM_(10)与PM_(2.5)化学组分的浓度变化及来源研究

于2006年3月—4月北京沙尘发生期间,监测了沙尘与非沙尘期间悬浮颗粒PM10和PM2.5质量浓度,分析了样品中无机水溶性离子和金属元素。结果显示:沙尘天气导致PM10和PM2.5质量浓度上升,粗颗粒物质量浓度明显上升,细颗粒物受到的影响相对较小。SO42-、NO3-和NH4+为PM10与PM2.5主要水溶性离子。沙尘与非沙尘期间SO42-、NO3-和NH4+浓度变化表现出不稳定性,可能与沙尘的强度和持续时间、来源有关,沙尘下来自于土壤源Ca2+和Mg2+浓度都显然提高。沙尘期间Sc、Ti、V、Cr、Mn、Co、Ni、Rb和Cs金属元素浓度高于非沙尘期间浓度,并且富集因子系数都小于10,说明主要来自于自然源,而Zn、Se、Cd、Pb和Bi这5种元素浓度随沙尘的侵入并没增加其含量,反而使浓度有所下降,富集因子和富集程度对比表明这些元素主要来自于当地污染源。     

道路旁大气悬浮微粒之理化特性及污染源解析

旨在探讨道路旁悬浮微粒之理化成分,并解析其可能的污染来源.悬浮微粒采样作业于2003年5月～2004年1月期间进行,悬浮微粒样本采集时间包括春、夏、秋、冬四季的假日与非假日,所采集的悬浮微粒样本经化学成分分析可得水溶性离子成分与金属元素成分,并透过化学质量平衡受体模式及逆轨迹模式进行污染源解析.测量结果显示,假日的大气悬浮微粒PM10浓度高于非假日,而假日与非假目的总悬浮颗粒则无明显变化.此外,道路旁悬浮微粒PM10主要受非交通源的长程传输与当地的交通源所影响,而总悬浮颗粒则主要源自于附近道路的车行及逸散扬尘.另就悬浮微粒化学成分而言,金属元素成分以Ca、Fe、Al最多,水溶性离子成分则主要为SO42-、NO3-、NH4+等二次污染物.受体模式及逆轨迹模式分析结果得知,污染来源主要为交通污染及道路扬尘,然而,亦有相当部分的污染来自上风处的非交通源.     

Properties of cold bonded quarry dust coarse aggregates and its use in concrete

In this study, artificial coarse aggregates are prepared by a cold bonding technique. The waste materials, namely, fly ash and quarry dust, are used for the preparation of the cold bonded artificial aggregate. Portland cement is used as the binder material. The independent variables considered for the preparation of the artificial aggregate are cement and fly ash contents. The properties of the artificial aggregate are determined and regression models are proposed for predicting these properties. The strength and workability of concrete containing artificial aggregate is determined. The slump loss of concrete containing artificial aggregate is found to be gradual. The concretes with strengths of up to 30 MPa is prepared using artificial aggregates. The study promotes the use of waste material and supports sustainable construction practices.     

The effects of studded tires on fatal crashes with passenger cars and the benefits of electronic stability control (ESC) in Swedish winter driving

This study set out to examine the effects of studded tires on fatal crashes on roads covered with ice or snow in Sweden and also to investigate the extra benefits of electronic stability control (ESC) during the winter months. Two different studies are presented in this paper. Both studies used an induced exposure approach. In the main study, 369 in-depth studies of fatal crashes with passenger cars were analyzed to determine whether loss-of-control (LOC) had been a major component or not. Only crashes involving cars without ESC and equipped with approved studded or non-studded winter tires were analyzed. The additional study used police-reported crashes that occurred during the winter seasons 2003–2010, involving passenger cars with and without ESC. While police records in Sweden do not include any tire information, it was assumed that most cars involved in crashes during the winter period would be equipped with studded tires.     

Failure of greenstone, jasper and cataclasite aggregate in bituminous concrete due to studded tyres: Similarities and differences

In wintertime, the use of studded tyres is common in the Nordic countries, steeply in creasing road wear. Apart from reducing surface quality and durability, the airborne dust presents a potential health hazard. To reduce road wear and dust release, there is a tendency to use harder and more wear-resistant aggregate materials.On the roads in and around Trondheim, mid-Norway, three types of aggregate material are common: greenstone, jasper and ‘mylonite’, in fact a cataclasite. Extensive laboratory testing suggests that cataclasite aggregate has better wear resistance than greenstone, but less than jasper [Erichsen E, Schiellerup H, Gautneb, H, Ottesen RT, Broekmans M. Road dust in Trondheim — analysis of the mineral content of airborne dust. (In Norwegian.) Geological Survey of Norway, NGU-report 2004. 037; 2004. p. 73]. However , observations on fluorescence-impregnated plane and thin sections demonstrate that in practice, cataclasite wears faster than greenstone, which may be attributed to its oriented fabric, as opposed to the random fabric in greenstone and jasper. The original article by Rosiwal from 1896 [Rosiwal A. Neue Untersuchungser gebnisse über die Härte von Mineralien und Gesteine. Verhandlungen der kaiserlich-königlichen geologischen Reichsanstalt, vol. 17/18; 1896. p. 475–491] on abrasion hardness and anisotropy provides an elegant explanation for the field observations.     

Optimal proportion of studded tyres in traffic flow to prevent polishing of an icy road

Studded tyres can significantly wear the road surface and increase particle emissions from the road surface, which has a negative impact on air quality in urban areas. However, road wear might have a positive aspect by roughening the road surface and thus preventing polishing. As a consequence, other vehicles than the ones using studded tyres might also benefit from the usage of studded tyres. The impact of the proportion of studded tyres in the traffic flow on the tyre–ice friction coefficient was studied with a fleet of real cars in a closed environment under strict procedural control. The results show that a proportion of 25–50% studded tyres in the traffic flow is enough to prevent ice from developing in a manner that is critically slippery for non-studded winter tyres. It was also observed that the visual appearance of the ice surface does not indicate if the ice has become more slippery or not.     

Effects on concrete durability of using recycled ceramic aggregates

Ceramic waste from ceramic and construction industries is one of the most important parts in the global volume of construction and demolition waste (CDW). Ceramic waste may have several uses, one of which as coarse aggregate for concrete artefacts. Within a research campaign in course at Instituto Superior Técnico (IST), concerning the reuse and recycling of CDW, the viability of replacing primary limestone aggregates with ceramic waste on the production of concrete pavement slabs has been studied. Compression and bending tests previously performed have shown the mechanical suitability of replacing, at least partially, limestone aggregates with ceramic recycled ones. In this paper, the results of the water absorption tests, either by capillarity or by immersion, and the results of the abrasion resistance tests are presented, all related to long-term concrete durability.     

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.     

再生骨料掺配比对再生透水混凝土性能的影响

为研究再生骨料在透水混凝土（RPC）中的应用,选用废弃路面素混凝土块为再生骨料来源,设计2种系列,研究再生骨料透水混凝土中再生骨料掺配问题,即分别以粒径9.5~19.0 mm,再生骨料按0%、25%、50%、75%和100%（基准）质量替代同粒径天然骨料碎石（系列1）和以4.75~9.5 mm、9.5~19.0 mm两种粒径,再生骨料按0∶1、1∶1、1∶2、2∶1、2∶3和3∶2掺比（系列2）制备RPC,并分析其物理、力学、透水性能及其相互关系,得到了合理的再生骨料替代率和双粒级掺比,在1∶1和2∶1掺配下能够得到较好的强度及透水性能。通过切割试块的图像化处理,分析其孔隙分布特征和趋势,并将平面孔隙率、等效孔径和透水系数联系起来。结果表明,再生透水混凝土的透水能力主要取决于截面孔隙个数和面积。     

Forensic investigation of the cause(s) of slippery ultra-thin bonded wearing course of an asphalt pavement: influence of aggregate mineralogical compositions

The cause(s) of slippery ultra-thin bonded wearing course (UTBWC) of an asphalt pavement was investigated. Petrographic analysis showed that the aggregate used in the UTBWC is mainly limestone with an average acid-insoluble residue of 5.1%. Coefficient of friction tests were performed both on a comparative UTBWC from Virginia with a different aggregate mineralogy VA-UTBWC and on slabs extracted from the slippery UTBWC pavement overlay. The tests clearly showed that the slippery UTBWC overlay sharply declined throughout the polishing process, consistent with the aggregate mineralogical composition and its low amount of acid-insoluble residue. In contrast, the comparative VA-UTBWC mix showed a gradual increase and then decrease in friction with continued polishing. This investigation clearly showed that the cause of the slippery asphalt pavement problem of the road mainly attributed to limestone aggregate polishing.     

Experimental investigation of basic oxygen furnace slag used as aggregate in asphalt mixture

Chinese researchers have commenced a great deal of researches on the development of application fields of basic oxygen steel making furnace slag (BOF slag) for many years. Lots of new applications and properties have been found, but few of them in asphalt mixture of road construction engineering. This paper discussed the feasibility of BOF steel slag used as aggregate in asphalt pavement by two points of view including BOF steel slag's physical and micro-properties as well as steel slag asphalt materials and pavement performances. For the former part, this paper mainly concerned the mechanochemistry and physical changes of the steel slag and studied it by performing XRD, SEM, TG and mercury porosimeter analysis and testing method. In the second part, this paper intended to use BOF steel slag as raw material, and design steel slag SMA mixture. By using traditional rutting test, soak wheel track and modified Lottman test, the high temperature stability and water resistance ability were tested. Single axes compression test and indirect tensile test were performed to evaluate the low temperature crack resistance performance and fatigue characteristic. Simultaneously, by observing steel slag SMA pavement which was paved successfully. A follow-up study to evaluate the performance of the experimental pavement confirmed that the experimental pavement was comparable with conventional asphalt pavement, even superior to the later in some aspects. All of above test results and analysis had only one main purpose that this paper validated the opinion that using BOF slag in asphalt concrete is feasible. So this paper suggested that treated and tested steel slag should be used in a more extensive range, especially in asphalt mixture paving projects in such an abundant steel slag resource region.     

Characterization of stripping properties of stone material in asphalt

Aggregates and bitumen together form a composite called asphalt concrete pavement. Moisture damage to asphalt concrete pavement can occur as stripping, and is a common problem that can lead to costly repairs. There is therefore a need to understand which stone aggregates adhere best to bituminous binder and result in a minimum of stripping. Lifshitz used the refractive index to estimate the dispersive non-polar van der Waal’s interaction component of adhesion, the predominant component in adhesion between minerals and bituminous binder. The impact of an intervening thin medium such as air or water on the adhesion can be estimated using Hamaker’s coefficient, which in turn can be related to stripping potential. Aggregates consist of minerals and minerals consist of different elements. The objective of this study was to investigate variation in the dispersive component of minerals via their refractive indices using data from mineral data sheets. The influence of the position of elements in the periodic table and chemical composition on refractive index of minerals was examined in order to classify mineral aggregates for asphalt road building with regard to dispersive adhesive properties and expected resistance to stripping. It is clear from this study that the elemental composition of a mineral will affect its refractive index and hence its dispersive adhesion to bitumen. Aggregates and minerals have been classified according to degree of stripping in the literature. In this study it was shown that aggregates and minerals that have a refractive index higher than approximately 1.6 are expected to be less susceptible to stripping. Also, minerals containing alkali metals are sensitive to stripping since they are partially soluble in water.     

Lidar characterization of crystalline silica generation and transport from a sand and gravel plant

Light detection and ranging (Lidar) remote sensing two-dimensional vertical and horizontal scans collected downwind of a sand and gravel plant were used to evaluate the generation and transport of geologic fugitive dust emitted by quarry operations. The lidar data give unsurpassed spatial resolution of the emitted dust, but lack quantitative particulate matter (PM) mass concentration data. Estimates of the airborne PM10 and crystalline silica concentrations were determined using linear relationships between point monitor PM10 and quartz content data with the lidar backscatter signal collected from the point monitor location. Lidar vertical profiles at different distances downwind from the plant were used to quantify the PM10 and quartz horizontal fluxes at 2-m vertical resolution as well as off-site emission factors. Emission factors on the order of 65-110 kg of PM10 (10-30 kg quartz) per daily truck activity or 2-4 kg/t product shipped (0.5-1 kg quartz/t) were quantified for this facility. The lidar results identify numerous elevated plumes at heights >30 m and maximum plume heights of 100 m that cannot be practically sampled by conventional point sampler arrays. The PM10 and quartz mass flux was greatest at 10-25 m height and decreased with distance from the main operation. Measures of facility activity were useful for explaining differences in mass flux and emission rates between days. The study results highlight the capabilities of lidar remote sensing for determining the spatial distribution of fugitive dust emitted by area sources with intermittent and spatially diverse dust generation rates.