水性环氧树脂改性乳化沥青混合料性能

为了解决现有冷拌冷铺沥青混合料性能不足的问题,研究了水性环氧树脂改性乳化沥青混合料的性能.采用先乳化后改性的方法制备了水性环氧树脂改性乳化沥青,利用击实试验和马歇尔设计方法确定了混合料的最佳外掺水量和最佳乳化沥青用量,对比分析了其击实和养生方式,并利用车辙试验、低温弯曲破坏试验、浸水马歇尔试验、疲劳试验等分别评价了其高温性能、低温性能、水稳定性能和疲劳性能.试验结果表明:采用第一次击实50次、110℃养生24 h、第二次击实25次、室温静置24 h的最佳击实和养生方式,可使水性环氧树脂改性乳化沥青混合料的密度、空隙率、水分挥发量和稳定度达到最优.同时,与热拌沥青混合料性能相比,水性环氧树脂改性乳化沥青混合料的高温性能优越,低温性能和疲劳性能不足,水稳定性能基本保持一致.     

养生方法对泡沫沥青冷再生混合料性能的影响

为了更真实模拟现场养生状况,设计开放养生、半密封养生及半密封+全密封养生(“组合”养生)3种养生方式,并采用力学试验对3种养生条件下泡沫沥青冷再生混合料的含水率、劈裂强度( indirect tensile strength, ITS)、无侧限抗压强度( unconfined compressive strength,UCS)及抗剪参数的发展规律进行研究;同时,通过CT扫描试验对混合料内部空隙结构进行分析。结果表明：不同养生方式下,混合料内部水分迁移路径和散失速率不一致,导致混合料养生过程中含水率及强度发展规律不一致;含水率与混合料终期养生强度密切相关;不同养生条件下混合料的内摩擦角变化规律基本一致,而黏聚力受含水率影响明显;半密封及“组合”养生水分散失速率慢,养生过程中被水化产物包裹的水分产生的水蒸气压力会破坏原有空隙结构,从而揭示了不同养生方式的空隙分布机理并推荐半密封养生36 h+全密封养生36 h作为泡沫沥青冷再生混合料中长期养生方法。     

Curing behavior of epoxy asphalt

The curing process of epoxy asphalt was analyzed by Fourier transform infrared (FT-IR) spectroscopy. Effect of curing temperature on viscosity of epoxy asphalt, and changes of mechanical properties with curing time were investigated. The evolution of concentration of epoxy band was followed as a function of the applied curing process. The experimental results indicate that the curing reaction rate of epoxy asphalt is invariable before 70 min at 120 °C, and it decreases when curing time exceeds 70 min. The viscosity of epoxy asphalt increases slowly with curing time at initial curing stage. But it increases quickly after initial curing stage and the initial curing time decreases as the curing temperature increases. The tensile strength increases slowly at incipient curing stage and increases rapidly when curing time is form 20 min to 70 min. The elongation at break shows a decrease with curing time, but it exceeds 200% after cured.     

环氧树脂体系固化反应动力学特征

采用非等温差式扫描量热方法(DSC)对双酚A型环氧树脂(E-51)与日本TAF环氧沥青(J-2)固化剂的固化反应动力学特征进行了研究.根据不同升温速率下环氧树脂体系固化反应的DSC曲线特征,通过n级自催化反应模型,求解出固化反应动力学参数,进而得到其固化反应动力学方程,探讨其固化反应机理.试验结果表明,通过固化反应动力学模型所得到的曲线与试验得到的DSC曲线吻合较好,所确立的模型在5～25 K/min的升温速率下能较好地描述环氧树脂体系固化反应过程,为研究环氧沥青固化机理提供理论基础,有利于制定和完善环氧沥青合理的固化工艺.     

Evaluation of Mixture Performance Recycled Asphalt Pavement Materials as Base Layer with or without Rejuvenator into the Asphalt

The binder properties were determined in accordance with Chinese standard such as ductility test,which allowed to measure the distance in centimeters that a standard briquette of asphalt had been stretched before breaking.Then,penetration test was carried out in order to know some properties of the asphalt,which are the hardness and the softness.Finally,softening point test was carried out in order to determine the temperature at which the bitumen attains a particular degree of softening under the specification of the test.According to Chinese standard for performance tests,firstly,Marshall test was carried out in order to measure the theoretical density,air voids,voids filled with asphalt,stability,flow,and voids in mineral aggregate of asphalt specimens.Secondly,Freeze-thaw splitting test was carried out in order to determine Splitting strength ratio.Finally,dynamic stability (rutting) test was carried out to determine average dynamic stability.Beside the tests carried out,the gradation of the extracted aggregate in accordance with American Association of State Highway and Transportation Officials was carried out to determine the dimensions of the particles weight distribution.Furthermore,both the percentage of recycled asphalt pavement materials and binder in mixture were determined to know how much of the new material during the mixture was needed.However,two specimens were used to evaluate the performance of recycled asphalt pavement materials.One specimen of recycled asphalt pavement materials was ten years old,and another one of recycled asphalt pavement materials was five years old.The results show that the conditions of the environment such as moisture,temperature,and age,decrease the ductility and penetration properties of binder when increase the softening point property of binder.Then the gradation of recycled asphalt pavement aggregate is of the required values to reuse in the mixture,while the flow ratio,the splitting strength ratio,and the dynamic stability ratio,are less than the required value test.With regard to the properties of mixture of recycled asphalt pavement material binder with rejuvenator,the results show that when the penetration and ductility versus percentage of rejuvenator increase,softening point versus percentage of rejuvenator decreases.Also,when the bitumen and rejuvenator percentage increase,the air voids decrease.Consequently,voids filled with asphalt and voids in the mineral aggregate increase.Moreover,the theoretical density and stability values decrease in a mixture containing four-point fifty percent to six percent of bitumen and rejuvenator,whereas the flow values increase.More interestingly,with four percent to four-point fifty percent mixture ratio of bitumen and rejuvenator,density,stability,and flow values increase.The splitting strength ratio values of mixtures and the dynamic stability test (rutting test) values of mixtures with forty percent of specimen one and specimen two respectively are greater than the required value of the standard test.In addition,the high percentage of rejuvenator increases the rut of pavement,in the same manner,the low percentage of rejuvenator induces low rut.In conclusion,the binder content from recycled materials without rejuvenator seems not be sufficient to be reused on the new pavement while the aged recycled material seems to be performed better than no aged recycled material with rejuvenator into bitumen.Then,the rejuvenator can influence the bitumen properties and performance of the pavement.Finally,the pavement made by only recycled pavement materials as a base layer appears to be more economical but cannot be more effective than the pavement made by mixture of new and recycled pavement materials as a base layer.     

Performance evaluation of open-graded epoxy asphalt concrete with two nominal maximum aggregate sizes

Open-graded friction course(OGFC) is applied to pavement surfaces to increase driving safety under wet conditions, and recently, to reduce tire/pavement noise. The durability of OGFC, however, has been a concern since conventional OGFC mixes last typically less than ten years before major maintenance or rehabilitation is needed. This work investigates a new open-graded asphalt mixture that uses epoxy asphalt as binder to improve mix durability. One type of epoxy asphalt that has been successfully applied to dense-graded asphalt concrete for bridge deck paving was selected. A procedure of compacting the mix into slab specimens was developed and a series of laboratory tests were conducted to evaluate the performance of the new mix, including Cantabro loss, permeability, friction, shear strength, and wheel rutting tests. Results show superior overall performance of the open-graded epoxy asphalt mix compared to conventional open-graded asphalt mix. There are also preliminary indications that the OGFC mix with 4.75-mm NMAS gradation can improve the resistance performance to raveling, while the OGFC mix with 9.5-mm NMAS gradation can improve the performance of surface friction at a high slip speed.     

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。     

考虑松弛的沥青混合料疲劳损伤累计模型研究

根据应变控制疲劳试验的受力特点,通过分解沥青混合料应变,控制疲劳试验输入和输出响应,分析沥青混合料应变控制疲劳试验过程中的松弛现象.基于损伤力学和粘弹理论,分析由应力松弛引起的疲劳损伤和演化规律,建立考虑应力松弛沥青混合料疲劳损伤累计模型.相同条件下一组大样本疲劳试验结果与模型计算结果的对比表明,提出的损伤演化模型不仅拟合效果良好,且揭示沥青混合料在重复载荷作用下初期模量衰减的粘弹非线性本质,有利于沥青混合料疲劳研究和寿命预测.     

基于差示扫描量热法的环氧沥青固化特征分析

采用非等温差示扫描量热法(DSC)对环氧沥青及环氧树脂体系的固化反应特征进行了研究。根据不同升温速率下反应物体系固化反应的DSC特征曲线,探讨其固化反应特征,为优化环氧沥青的固化及施工工艺提供基础。试验结果表明,环氧树脂固化后,提高了沥青材料的凝胶温度、固化温度以及后处理温度,从而显著提高了环氧沥青的热稳定性特别是耐高温性能。进一步研究发现,在环氧沥青固化特征的研究中需要考虑扩散作用的影响,从而提出带部分扩散控制的环氧沥青固化反应特征。     

基于微观力学的沥青混合料黏弹性预测

利用微观力学和逾渗理论预测了沥青混合料的黏弹性能。将沥青混合料看作刚性粗集料颗粒夹杂于黏弹性沥青砂浆基体内的复合材料,在Laplace空间域内利用Mori-Tanaka等效夹杂理论和宏观平均理论,建立了从沥青砂浆黏弹性预报沥青混合料黏弹性的模型。基于逾渗理论修正了模型中的参数,并与静态蠕变试验结果进行了对比。结果发现:粗集料对黏弹性沥青基体性能具有增强作用,沥青混合料黏弹本构方程可以表示为粗集料增强系数与沥青基体黏弹本构方程的乘积形式。微观力学预测的增强系数较试验值偏小,误差分析发现,产生偏差的主要原因是Mori-Tanaka方法考虑集料间相互作用较弱,当粗集料体积分数较大时,预测模型精度下降。通过逾渗理论对粗集料体积分数修正后的结果与试验值较吻合。     

基于高温和粘结性能的橡胶沥青胶浆性能研究

为了掌握橡胶沥青混合料的本质特性,采用锥入度试验和拉拔试验,研究了胶粉掺量和矿粉掺量对橡胶沥青胶浆抗剪强度和粘结强度的影响规律,发现胶粉对橡胶沥青胶浆粘结强度的影响大于矿粉,而对其剪切强度的影响不及矿粉。在此基础上,根据两者的交互作用提出了胶浆中胶粉和矿粉掺量的比例系数r∶f,进一步分析了r∶f对橡胶沥青胶浆高温性能、粘结性能的影响规律,推荐r∶f一般不宜小于0.4,且粉油比不宜过小或过大,胶粉内掺掺量范围宜为15%～21%。     

水泥混凝土路面国产环氧沥青防水层的性能分析

为了确定环氧沥青防水层材料在水泥混凝土路面防水应用的适用性及耐久性,结合某特大桥的水泥路面防水层材料施工应用实践,开展了系列试验.结果表明：（1）国产环氧沥青材料、SBS改性沥青材料和FYT材料进行粘附强度对比,其平均抗剪强度依次为1.98、0.39、0.33 MPa; 20℃下拉拔强度分别为1.98、0.98、0.83 MPa; 50℃下其拉拔强度分别为0.73 MPa、流淌、0.08 MPa.（2）用中和与未中和的国产环氧沥青进行抗拉强度对比,20℃下未中和的环氧沥青与混凝土7、4d的拉拔强度分别仅为0.53、1.64 MPa; 20℃下中和的环氧沥青与混凝土7、4d的拉拔强度分别达到0.9、2.0 MPa,20℃下中和的环氧沥青与钢板之间的拉拔强度达到7.8 MPa.（3）用国产环氧沥青材料与美国环氧沥青材料进行短期老化试验对比,国产环氧沥青的粘度略有增加,变形性能变化较小,抗拉强度变化较大,而美国环氧沥青老化前后各项指标变化均很小.结果表明,国产环氧沥青防水材料的各项指标与其他防水材料的性能相比具有一定的优越性,能达到国家标准要求,将国产环氧沥青防水材料应用到水泥混凝土桥面防水是可行的.     

Effects of Aggregate Size and Specimen Scale on Asphalt Mixture Cracking Using a Micromechanical Simulation Approach

A micromechanical model based on discrete element method(DEM) was employed to investigate the effects of aggregate size and specimen scale on the cracking behavior of asphalt mixture. An algorithm for generating three-dimensional aggregates that can reflect the realistic geometry such as shape, size and fracture surface of aggregate particles was developed using a user-defined procedure coded with FISH language in particle flow code in three-dimensions(PFC3 D). The parallel-bond model(PBM), linear contact model(LCM), and slip model(SM), whose sets of micro parameters were obtained by comparing experimental tests with numerical simulation results, were used to characterize the internal contact behavior of asphalt mixture. Digital asphalt mixture specimens were used to simulate the effects of aggregate size and specimen scale on the cracking behavior by the indirect tensile(IDT) test. Some conclusions can be drawn as follows: Both cracks and IDT strength decrease with increasing aggregate size. However, the heterogeneity of contact-force distribution augments with increasing aggregate size, especially with 13.2-16 mm aggregate. The aggregate size of 4.75-9.5 mm dominates in forming skeleton structure for asphalt mixture. The IDT strength decreases and cracks augment with increasing sample scale. The crack growth can be well interpreted from the perspective of energy analysis. The conclusions show that the proposed micromechanical model is suitable for the simulation of crack propagation. This study provides an assistant tool to further study the cracking behavior of particle-reinforced composites material such as asphalt mixture and Portland cement concrete.     

沥青结合料疲劳失效定义与失效准则

为了更好地理解沥青结合料的疲劳失效特性,以黏弹连续介质损伤力学为分析手段,通过加速疲劳试验和传统时间扫描疲劳试验系统研究了基质沥青和改性沥青在不同加载条件下的疲劳失效行为.研究发现,基于虚应变能理论提出的将最大存储虚应变能指标作为沥青加速疲劳试验中的疲劳失效新定义,与现象学指标相位角峰值有着很好的等效性,并和时间扫描试验中的疲劳失效定义保持了一致,进而依据疲劳失效定义建立了虚应变能释放率和材料疲劳寿命之间的特性关系准则.该特性准则与试验方法和加载条件无关,可作为统一的疲劳失效准则运用于沥青结合料的疲劳性能预测.     

一种非传统高分子粘结剂改良黏土的强度试验研究

通过室内无侧限抗压强度试验和直接剪切试验研究了不同浓度粘结剂对黏土强度的影响。试验结果表明,粘结剂的加入可以提高黏土体的强度。改良后,黏土的无侧限抗压强度和黏聚力随养护时间的增加均有提高;当养护时间一定时,随着粘结剂含量的增加,黏土的黏聚力和无侧限抗压强度也随之增加,当浓度增加至3%时,黏土的无侧限抗压强度相比2%浓度添加量出现下降。     

GMA浇筑式沥青混合料的制备及性能

以特立尼达湖沥青（TLA）和A-70# 基质沥青配制了复合沥青,并将其与集料拌和得到浇筑式沥青混合料（GMA）,重点研究了沥青胶结料和拌和时间对GMA混合料性能的影响。结果表明:随着沥青胶结料中TLA质量分数的增加,沥青胶结料的热温度敏感性降低,混合料性的流动性变差、硬度变大,TLA最佳的质量分数为70%;混合料拌和时间的延长,沥青胶结料的老化程度增大,混合料的高温性能、流动性变好,但冲击韧性（抗疲劳性）降低,最佳的拌和时间为1.5~3.5 h。     

冷补沥青混合料的制备工艺研究及性能评价

在对SMA与LB两种级配进行比选分析的基础上,研究了击实次数、冷补液拌制工艺和柴油挥发量等参数对冷补沥青混合料马歇尔稳定度等性能的影响规律。研究结果表明:LB与SMA的马歇尔稳定度接近,空隙率为13.42%,有利于柴油挥发及后期强度的发展;提高初始击实次数有利于提升混合料的马歇尔稳定度和水稳定性能;混合料采用添加剂与稀释剂预混再与沥青混合的工艺具有更优的性能,其马歇尔稳定度为6.86 kN,浸水残留稳定度为84.1%;当养护条件为25 ℃时,柴油挥发量小,试件强度未形成,当养护条件为110 ℃时,混合料的马歇尔稳定度与浸水残留稳定度显著提升,分别为5.89 kN与80.6%,说明柴油挥发量对于混合料强度形成影响较大;最优工艺条件下,混合料马歇尔稳定度为8.04 kN,浸水残留稳定度为86.8%,破损率为5.3%。     

不同沥青胶结料重复蠕变试验研究

利用重复蠕变试验,对3种不同类型沥青结合料进行高温性能评价,试验结果表明,橡胶沥青高温性能明显优于SBS改性沥青,基质沥青最差。对不同粉胶比橡胶沥青胶浆试验分析发现,累积变形增长率随粉胶比变化呈现出峰值关系,粉胶比为0.3时橡胶沥青胶浆高温性能最差,进行橡胶沥青混合料设计时,粉胶比应尽量远离此值。     

赛欧铺改性沥青混合料温拌技术

赛欧铺是一种硫磺沥青改性剂.在AC-16C级配沥青混合料掺入18％的赛欧铺,通过室内试验对赛欧铺改性沥青混合料的高温稳定性和水稳定性进行研究;并对比了赛欧铺改性沥青混合料不养生和养生7天以及14天的力学性能的差异.试验结果表明：赛欧铺改性沥青混合料的高温稳定性得到了较大的改善,其水稳定性没有太明显的提高,但是,抗剥落剂的增加可在提高AC-16C混合料的高温稳定性的同时提高其水稳定性.养生14天相较于养生7天以及不养生,对加赛欧普的AC-16C混合料的高温稳定性和水稳定性有较大的提高,尤其是高温稳定性,因此,养生对于加赛欧普的AC-16C混合料至关重要.     

含盐高湿环境下沥青混合料耐久性

为了研究含盐高湿环境下沥青混合料的耐久性,以不同温度和不同质量浓度盐溶液模拟含盐高湿环境进行汉堡车辙试验,并通过试验比较不同类型沥青混合料在含盐高湿环境下的耐久性,使用Origin 8.0对板状和圆柱形的车辙试验结果进行非线性指数拟合,提出含盐高湿环境沥青混合料耐久性的试验评价指标和检测方法,最后分析含盐高湿环境对沥青混合料的侵蚀机理.结果表明:采用改性沥青作结合料可以显著提高含盐高湿环境下沥青混合料的耐久性;含盐高湿环境下,普通AC混合料的耐久性较差,而SMA混合料的耐久性优于其他类型混合料;60℃、70℃圆柱形试件浸水车辙变形率可以作为沥青路面耐久性的评价和检测指标;高温、盐分、水分及其耦合效应是引起沥青混合料耐久性降低的主要原因.