The compaction characteristics of hot mixed asphalt mixtures

The quality of compaction is important to the performance of hot mixed asphalt(HMA) pavement. Most premature failures of asphalt pavement are concerned with poor compaction. Compaction characteristic of HMA mixtures were studied. Compaction tests were done with typical widely used HMA mixtures, including dense gradation asphalt mixtures with different nominal maximum aggregate size(AC13,AC20,AC25), and mixtures with different gradation(AC13, SMA13,Sup13 and OGFC13). HMA mixtures were sampled at different compaction temperature and Marshall blow numbers, varying between 60 and 175 ℃ and between 15 and 75 lows, respectively. The compaction characteristics of these mixtures were evaluated. The results showed that the Marshall stability and volumetric properties were significantly affected by the compaction temperature. Mixtures with the same NMAS but different type of gradation need different compaction energy to get the designed density.     

Relationship between polymerization degree and cementitious activity of iron ore tailings

The aim of this study is to understand the relationship between the polymerization degree and cementitious activity of iron ore tailings.In light of the poor usage of iron ore tailings,stockpile samples from Tangshan were studied in terms of their ability to become cementitious materials.Compound thermal activation was used to improve the cementitious properties of the tailings,while analyzing methods,such as X-ray diffraction (XRD),infrared spectroscopy (IR),nuclear magnetic resonance (NMR),and X-ray photo...     

应力吸收层沥青混合料的力学性能评价

为评价应力吸收层沥青混合料的力学性能,在室内试验测定沥青材料技术性能的基础上,基于马歇尔设计法,针对齐鲁70#沥青、稳定型橡胶改性沥青及应力吸收沥青设计了三种砂粒式应力吸收层沥青混合料。通过基本性能试验系统测定应力吸收层沥青混合料的动态模量,并建立动态模量和相位角的主曲线,主要探索了以齐鲁70#、稳定型橡胶改性沥青及应力吸收沥青作为胶结料的应力吸收层沥青混合料的力学特性。结果表明,稳定型橡胶改性沥青和应力吸收沥青作为胶结料用于应力吸收层均有良好的力学性能。     

硫磺改性沥青混合料基本性能的研究

为考察硫磺改性沥青混合料的路用性能,选取AC-13和AC-20两种混合料类型、4种不同的硫磺掺量（硫磺占硫磺改性沥青胶结料的质量百分比分别为0%、30%、35%、40%）作为对比,采用浸水马歇尔试验、冻融劈裂试验、汉堡车辙试验测试了其水稳定性能,采用车辙试验、三点小梁弯曲试验和Overlay Tester试验分别测试了其高温性能、低温性能与疲劳性能,采用动态模量试验获得了其力学参数. 结果表明: 添加质量分数为30%硫磺后,AC-13和AC-20沥青混合料动稳定度分别提高了18%和26%,疲劳开裂性能有所提高, 低温性能没有明显改变. 添加不同质量分数的硫磺,沥青混合料的水稳定性能明显降低,其中AC-13沥青混合料在添加40%硫磺时冻融劈裂强度比下降达22%. 动态模量测试表明硫磺改性沥青混合料与普通沥青混合料动态模量变化趋势相同,但-10 ℃~54 ℃温度区间较普通沥青混合料动态模量要高.     

Effect of loading condition and temperature on dynamic properties of asphalt mixtures

In order to study the effects of loading condition and temperature on the dynamic properties of asphalt mixtures, the dynamic loading tests on different loading condition (various speeds and loads under a certain roughness) and temperature conditions were performed. The experimental result show that the dynamic properties of asphalt mixtures are influenced by vehicle load and speed, besides, the effects of temperature on dynamic properties of asphalt mixture are significant.     

Evaluation on Moisture Resistance of Asphalt Mixture with Active Mineral Powder

A new type of filler named 'active mineral powder' (AMP) was introduced and applied in asphalt mixture in order to improve the adhesive property of gneiss or granite aggregates and asphalt. The treated mixtures contained 2% AMP by weight of the total aggregates as filler. The moisture stabilization properties of various combined mixtures were analyzed using the adhesive test,Marshall stability and indirect tensile strength tests. Five frost-thaw cycles test was conducted to further investigate the effect of active filler on asphalt mixtures in the indirect tensile strength experiment. The results show that active filler improves the moisture stability of mixtures with gneiss and granite. The active mechanism of AMP was also discussed in this paper.     

Waste Materials to Replace Natural Resources

A number of waste materials were studied on their application into asphalt mixtures. Materials tested were plastic waste as (soft) granular material,ceramic waste from electrical insulators,foundry sand and sintered granulate from burned household waste. Both plastic waste,crushed ceramics and large fractions of sintered household waste could be used as partial replacement for coarse aggregates. Foundry sand could partially replace natural sand in asphalt mixtures. The first step of the study was to find out if the waste materials could satisfy basic requirements and for some if their leaching behavior was acceptable. In the next phase mixtures were designed and mechanical tests were done on several mixtures with waste components to determine indirect tensile strength,stiffness,fatigue. In order to estimate the water sensitivity of some mixtures,retained indirect tension tests were done. The properties are reported and compared with each other and reference mixtures. From the research it becomes clear that it takes a lot of work to replace virgin materials in asphalt mixtures with waste materials.     

集料分布对沥青混合料劈裂强度影响数值分析

基于数字图像处理,研究沥青混合料集料分布状态.采用有限元法建立基于沥青混合料二维截面的劈裂试验模型,数值分析集料分布状态对虚拟劈裂试验力学性能的影响,并通过室内劈裂试验进行验证.研究结果表明：基于数字图像处理,通过集料分布状态指标可以评价沥青混合料集料分布状态;集料公称最大粒径增大,沥青混合料集料分布状态变差;集料分布状态与沥青混合料虚拟劈裂试验力学性能变异性存在明显的相关性,集料分布状态越差,通过沥青混合料虚拟劈裂试验计算得到的压头反力均值的变异系数越大.     

Effect of aggregate gradation on low temperature performance of asphalt paving mixtures

Low temperature cracking has become one of the important factors that diminish asphalt pavement’s ride quality and service life.Especially in cold region,cracking caused by low temperature is the main distress form.This paper discussed the effect of aggregate gradation on the low temperature performance in asphalt paving mixtures.A total of 11 asphalt mixtures with 11 different aggregate gradations and one asphalt binder content were studied.Volumetric properties of the coarse aggregate and asphalt mixtures showed aggregate grading has a significant impact on the degree of aggregate interlock in asphalt mixtures.A trend is existed in the low temperature performance with the change of gradation.With the aid of mathematic statistics,it indicates gradation affects the low temperature performance significantly.The findings also indicate the relationship between the degree of aggregate interlock in asphalt mixtures and the low temperature performance:With the stone-to-stone contact developed,the mixture has a high energy to resist contract and deformation at low temperature.The properties of fine aggregate and asphalt play an important part in resisting low temperature cracking in floating structure.But it provides lower energy to resist low temperature cracking compared to the skeleton structure.     

有机化累托石改性沥青的制备及性能研究

采用熔融插层法制备了有机化累托石(OREC)改性沥青,利用X射线衍射(XRD)表征了OREC改性沥青的微观结构,研究了OREC用量对改性沥青物理性能和粘度的影响,并通过薄膜烘箱(TFOT)和压力老化(PAV)对基质沥青和改性沥青老化性能进行了比较。结果表明:OREC可与沥青熔融插层形成剥离型纳米复合结构;OREC与沥青熔融共混后,沥青的软化点和粘度均增大;与普通沥青相比,经TFOT和PAV老化后,OREC改性沥青的软化点增量和粘度增加率显著减小,表明OREC可有效改善沥青耐老化性能。     

重载沥青路面结构组合的抗车辙性能分析

为研究结构组合对沥青混合料抗车辙性能的影响,首先对所设计的7种沥青混合料进行动态模量及单层车辙试验,得到基本材料参数及抗车辙性能;然后对7种混合料组合而成的3种路面结构在重载条件下进行双层结构车辙试验,并与单层车辙试验结果进行对比分析;最后,应用光纤光栅智能测试技术对实际路面进行现场应变测试,根据不同路面结构三向应变测试结果评价实际重载沥青路面结构的抗车辙性能．结果表明,单层车辙试验难以准确反映路面结构的抗车辙性能,而双层车辙试验效果良好．在设计抗车辙路面时要考虑不同面层的模量组合,才能最大程度地发挥各层混合料的抗车辙性能．     

Investigation of Chemical Properties by NMR During the Laboratory Aging of Asphalt

In this work,the chemical properties of asphalt were evaluated during the laboratory aging. The rolling thin film oven (RTFO),termed as short-term aging,and pressurized aging vessel (PAV),termed as long-term aging. Tests were used to simulate the laboratory aging of this asphalt. The performance characteristics of asphalt depends the chemical composition of asphalt. NMR spectroscopy enables etailed information about the Carbon-and-hydrogen types of asphalt without separating it into different components. Carbon and proton NMR measurements of asphalt showed that isomerization was the main chemical reactions of hydrocarbon groups following aging. The Corbett fractionation procedure was used to separate fresh and aged asphalts into four generic fractions,namely; asphaltenes,aromatics,resins and saturates were applied to evaluate the chemical changes that occurred during the aging processes.     

细集料对沥青混合料体积和高温特性的影响

通过2种细集料(天然砂、机制砂)、2种级配(AC-13、Sup-12.5)沥青混合料的试验研究,分析了细集料类型和禁区对混合料体积指标和高温动稳定度的影响,结果表明机制砂更能有效提高混合料的高温性能,禁区的存在可有效限制细集料特别是天然砂的用量,以明显提高沥青混合料重载作用下混合料的动稳定度。而体积参数结果表明,Superpave设计方法中用固定空隙率4%标准来确定最佳沥青用量的方法是否合理有待进一步验证。     

Effects of Fibers on the Dynamie Properties of Asphalt Mixtures

The dynamic characteristics of fiber-modified asphalt mixture were investigated. Cellulose fiber, polyester fiber and mineral fiber were used as additives for asphalt mixture, and the dosage was 0.3%, 0.3%, 0.4%, respectively. Dynamic modulus test using SuperPave simple performance tester （SPT） was conducted to study the dynamic modulus （E＇） and phase angle （δ） for the control asphalt mixture and fiber-modified ones at various temperatures and frequencies. Experimental results show that all fiber-modified asphalt mixtures have higher dynamic modulus compared with control mixture. The dynamic modulus master curves of each type of asphalt mixtures are determined based on nonlinear least square regression in accordance with the time- temperature superposition theory at a control temperature （21.1℃）. The fatigue parameter E^＊×sinδ and rutting parameter E^＊/sinδ of asphalt mixture are adopted to study the fatigue and rutting-resistance properties, and experimental results indicate that such properties can be improved by fiber additives.     

掺加旧料对温拌沥青混合料疲劳性能的影响分析

温拌再生沥青混合料是基于沥青温拌技术和再生技术发展而来的新型环保型沥青混合料.对掺加旧料（RAP）的温拌沥青混合料的疲劳性能进行了评价,分析了不同旧料掺量对疲劳性能的影响.疲劳试验采用小梁三分点加载方法,进行了旧料掺量为0%、15%、30%、45%以及60%的混合料疲劳试验.试验结果表明,旧料掺量越大,疲劳性能越差;30%为温拌沥青混合料的临界旧料掺量,此掺量为疲劳性能的＂性能拐点＂,超过此掺量后疲劳性能大幅衰减.     

Statistical analysis of the asphalt mixtures volumetric properties

Based on statistics principle, random error and systematic error were considered and the volumetric properties of the two mixtures types, namely A and B, were statistically analyzed using different distribution methods. Seventy-two samples of mixture A and fifty-two of mixture B were fabricated using the Marshall method. The probability distributions were compared on the basis of goodness of fit. Weibull model was found to be most appropriate model for describing the asphalt mixtures volumetric properties distribution. The two-parameter Weibull distribution function applied well to model the bulk specific gravity and voids filled with asphalt data, whereas, the three-parameter Weibull distribution appeared to be more appropriate in the discussing of air voids and voids in mineral aggregate. The experimetal results is revealed that compared with the mean value, the peak value of Weibull distribution was suggested as an alternative and more powerful parameter for describing the test data distribution characteristic. The analysis of test results also revealed that there were significant differences in the volumetric properties of the two tested mixtures for the same confidence level. The confidence interval decreased with the decreasing in reliability.     

再生SBS改性沥青混合料再度老化性能的研究

主要研究再生SBS改性沥青混合料的抗老化性能.对沥青进行24 h、48 h TFOT老化,分别模拟沥青的中度和重度老化,然后将老化沥青再生,对再生沥青拌制的混合料及新鲜沥青混合料进行室内短期与长期老化,并对老化后的沥青混合料进行性能试验与对比评价,分析了再生沥青混合料的抗老化性能及其老化规律,评价再生沥青混合料的耐久性.     

不同级配类型沥青混合料抗剪性能研究

为了评价不同级配类型沥青混合料的抗剪性能,采用单轴贯入法对混合料进行抗剪试验。试验结果表明,级配对混合料的抗剪性能影响显著。对于密级配沥青混合料(AC),细级配混合料的抗剪性能优于粗级配混合料;随着公称最大粒径的增大,混合料的抗剪强度迅速降低。而对于间断级配沥青混合料(SAC),其抗剪强度则随公称最大粒径的增大而增加。所以从抗剪角度来说,悬浮密实的AC系列混合料适合采用小粒径,而骨架密实的SAC系列混合料则适合采用大粒径。同时试验结果还显示SBS改性沥青能有效的改善混合料的抗剪性能。据此,可以更加合理的选择混合料。     

水泥代替矿粉对沥青混合料性能的影响分析

通过分析矿粉和水泥在沥青混合料中的作用机理,分别以不同比例的水泥代替矿粉,对沥青胶浆做延度、软化点、DSR、BBR等试验;同时,以AK-16和SAC-16为例,用不同比例的水泥代替矿粉,分别做浸水马歇尔试验、单轴压缩试验、动稳定度等试验,分析水泥代替矿粉后对沥青混合料的高、低温性能和水稳性等性能变化。试验结果表明,以一定比例的水泥代替矿粉可以有效的改善沥青混合料的性能。     

Research on Alkaline Filler Flame-Retarded Asphalt Pavement

1 IntroductionDesign Specifications ofHighway Tunnel(JTG D70-2004)[1]specifies that all the highway tunnels may useconcrete pavement . When necessary the flame-retardedasphalt pavement may be used.The article explains whyall the accidents in Zhejiang highway tunnel occurred inconcrete pavements instead of in asphalt pavements .It isbecause the concrete pavement’s anti-skid coefficient andthe friction force decreased speedy. In addition, com-pared with concrete pavements ,the asphalt pavem…