【作者】 李微；

【导师】 韩森；

【作者基本信息】 长安大学 ， 道路与铁道工程， 2021， 博士

【摘要】 橡胶改性沥青高温、低温及疲劳性能表现突出,但其与集料的粘附性却因现有研究方法的局限性,一直备受争议。而粘附性是影响沥青路面耐久性的重要因素之一,在经受降雨等不利因素影响时,沥青与骨料之间良好的粘附性是保证路面不发生水损害的先决条件。开级配磨耗层（Open grade friction course,OGFC）因含有大量的连通空隙及丰富的表面构造而具有优良的降噪、排水和抗滑性能,也正是由于其结构的独特性,水分更易通过连通空隙进入混合料内部,由此对沥青与集料的粘附性提出了更高的要求。自20世纪70年代将橡胶改性沥青应用于OGFC以来,人们大都致力于渗透性、降噪性以及高、低温性能的研究,鲜少关注其综合抗水损害性能表现。对此,本文以橡胶改性沥青粘附及损伤-愈合特性为研究对象,为完善橡胶改性沥青粘附性评价体系,应用宏观、微观以及分子和原子尺度的多种研究方法,研究多因素影响下橡胶改性沥青（胶浆）粘附及自愈合作用规律,揭示橡胶改性沥青粘附及自愈合机理及应力-应变行为,探讨OGFC橡胶改性沥青混合料抗水损害性能及断裂损伤-愈合表现,由此为实际工程橡胶沥青路面,尤其是橡胶沥青大空隙OGFC路面综合抗水损害性能改善提供理论依据。本文主要分为以下几个部分:基于拉拔强度（Binder bond strength,BBS）试验,建立了橡胶改性沥青（胶浆）粘附性的评价方法。分析了粘附沥青的石料基底加热温度、沥青膜厚度、水作用温度及拉拔速率对试验结果的影响,推荐试件制备方便、且能获得较大拉拔强度的四种控制参数的合适取值依次为:170℃、0.2mm、40℃和0.7MPa/s。探索了基质沥青类型、胶粉掺量和细度、改性剂类型、石料性质、抗剥落剂及盐蚀和冻融循环、矿粉类型、粉胶比及胶浆膜厚度等因素对橡胶沥青（胶浆）与集料粘附性的影响规律。结果表明,基质沥青芳香分含量越高、胶粉掺量越小、细度越大,制得的橡胶沥青粘附性越好。SBS改性剂和胶粉的加入均不利于基质沥青的粘附性,石墨烯则能够在一定程度上改善沥青粘附性。集料Si O₂含量、盐蚀和冻融循环均会减小橡胶沥青粘附性。三种因素对橡胶沥青胶浆拉拔强度的影响程度为:膜厚度>矿粉类型>粉胶比。基于BBS试验提出了评价橡胶改性沥青（胶浆）愈合性能的方法,分析了水分、愈合时间、愈合温度、愈合方式、胶粉掺量和细度、矿粉类型和改性剂类型等多因素对橡胶改性沥青（胶浆）愈合性能的影响。结果表明,干燥状态愈合时间越长,一定范围内温度越高,对愈合越有利。水作用下,随时间延续和温度提高,愈合率呈现先增加后减小最后趋于稳定的变化规律。橡胶沥青（胶浆）愈合过程中,同时伴随水分子润湿和扩散作用下沥青（胶浆）断裂界面凹坑的形成-贯穿-聚合-扩张破坏过程,胶粉掺量越小、细度越大、矿粉Si O₂含量越大,破坏程度越大,对愈合越不利。冻融加速了愈合过程中的橡胶沥青与石料粘附界面破坏,破坏形式由沥青内聚破坏逐渐转为界面粘附破坏。通过原子力显微镜（AFM）形貌图和力曲线、红外光谱（IR）官能团以及动态剪切流变仪（DSR）粘度曲线,揭示了橡胶改性沥青粘附和愈合机理。结果表明,胶粉改变了沥青蜂形结构分布状态和尺寸,增大了沥青弹性模量,减小了纳观表面粗糙度和粘附力;饱和C-H指数、脂肪族指数以及芳香族化合物C=C（C=O）指数与橡胶沥青粘附性具有较好的相关性;胶粉与沥青反应过程中减少了基本没有支链的芳香分以及分子量更小的饱和分,增加了含有大量支链的沥青质含量,增大了沥青分子链结构指数MMHC和活化能Ea,导致愈合率降低。胶粉颗粒本身并不具备愈合的潜质,颗粒的交互作用是影响橡胶沥青纳观粘附力和愈合性能的原因之一,将体系中的颗粒分离后,橡胶沥青基体的粘附性和愈合性增大。采用分子动力学（MD）方法,从原子和分子尺度解释了橡胶改性沥青内聚性/粘附性及自愈合机理,分析了水分、温度、胶粉掺量、沥青类型等因素对橡胶改性沥青内聚/粘附性、自愈合性的影响规律,探索了拉伸过程中橡胶改性沥青的力学表现。结果表明,水分子通过置换掉部分沥青分子,减小了沥青分子间的范德华力和静电力,导致沥青分子的内聚能/粘附能及拉伸最大应力和断裂功减小。温度升高会减小沥青分子间范德华力的取向力,降低分子间力对分子的束缚作用,增加沥青内水分子的扩散系数,导致内聚能/粘附能和拉伸最大应力和断裂功降低。与Si O₂相比,Ca O（Ca CO₃）和Mg O与水分子吸附力更小,与橡胶沥青粘附性更好。橡胶分子与沥青分子间的内聚能小于两个沥青分子之间的内聚能,胶粉掺量越大,橡胶沥青内聚能越小,水分子扩散系数越小。沥青的愈合行为即是沥青12类分子的扩散过程,各分子扩散系数越大,愈合性能越好,在橡胶沥青分子愈合中,起主导作用的是胶质中的C₄₀H₆₀S分子和C₁₈H₁₀S₂分子、芳香分中的C₃₀H₄₆分子、饱和分中的C₃₀H₆₂分子。橡胶改性沥青拉伸最大应力小于基质沥青,但达到最大应力时对应应变值及断裂功更大。利用汉堡浸水车辙试验（HWTT）和半圆弯曲（SCB）试验探究了橡胶改性沥青应用于OGFC级配中的抗水损害及断裂损伤-愈合性能,主要分析了级配类型、公称最大粒径、胶粉掺量、改性剂类型、集料类型及胶浆厚度等因素的影响规律。结果表明,橡胶改性沥青在三种典型级配混合料的抗水损害和断裂-愈合能力有以下规律:SMA-13>AC-13>OGFC-13。对于OGFC橡胶改性沥青混合料,公称最大粒径越大,HWTT表现越好,但SCB愈合性能越差;胶粉掺量较低时,HWTT和SCB均表现较差,当胶粉掺量增至20%时,两种性能均显著提高;SBS/橡胶改性沥青（3.5%SBS+内掺15%胶粉）综合性能最佳;石灰岩混合料性能优于玄武岩和辉绿岩,花岗岩混合料总体表现最差。胶浆厚度和裂纹分布是影响混合料愈合性能的两个非常重要的因素,但OGFC混合料的裂纹形式多样,尺寸各异,这些不规则裂缝是导致其愈合性能无序化的关键,甚至会掩盖足够厚度的胶浆所来的愈合优势。BBS愈合率比拉拔强度更适合评价OGFC橡胶改性沥青混合料抗水损害性能,但并不适用于评价其断裂损伤-愈合性能。更多还原

【Abstract】 Asphalt rubber(AR)has excellent high-temperature,low-temperature and fatigue properties,but its adhesion has been controversial due to the limitations of existing research methods.Adhesion is one of the important factors affecting the durability of asphalt pavement.When subjected by adverse factors such as rainfall,the good adhesion between asphalt and aggregate is the prerequisite to ensure that the pavement will not suffer water damage prematurely.Open graded wearing course(OGFC)has outstanding noise reduction,drainage and skid resistance due to its large number of connected voids and rich surface structure.However,considering to its unique structure,it is easier for water to enter into the mixture through connected voids,which puts forward higher requirements for the adhesion between asphalt and aggregate.Since the AR was applied to OGFC in the 1970 s,numerous scholars have been committed to the research on permeability,noise reduction,high and low temperature performance,but little attention has been paid to its comprehensive water damage resistance.In this context,this paper takes the adhesive and damage-healing properties of AR as the research object,with the aim to establish and develop the adhesion evaluation system of AR.Combined with various research methods at macro,micro,molecular and atomic scales,this paper explores the law of adhesive and self-healing of AR(mastic)under the influence of multiple factors,reveals the adhesion and self-healing mechanism and stress-strain behavior of AR,and discusses the water damage resistance and fracture damage-healing performance of OGFC AR mixture.It provides a theoretical basis for the improvement of comprehensive water damage resistance of practical engineering,especially OGFC pavement.The main structure of this study can be divided into the following parts.Based on the binder bond strength(BBS)test,one method for evaluating the adhesion of AR(mastic)and aggregate is established.It is found that the slab heating temperature,asphalt film thickness,water bath curing temperature and loading rate are closely related to the test results,and the values of the four factors are recommended as follows: 170℃,0.2mm,40℃and 0.7MPa/s respectively.In addition,the effects of base asphalt(BA)type,crumb rubber(CR)content and fineness,composite modifier type,aggregate properties,anti stripping agent(ASA),salt corrosion and freeze-thaw cycle,filler type,the ratio of filler to binder and mastic thickness of AR mastic on the adhesion between AR(mastic)and aggregate are analyzed.The results show that the higher the aromatic content of BA,the smaller the amount of CR and the greater the fineness,the better the adhesion of AR.Both of SBS and CR are not conducive to the adhesion of BA,while graphene is beneficial to the improvement of asphalt adhesion.The Si O2 content of aggregate,salt corrosion and freeze-thaw cycle will reduce the adhesion of AR.The influence degree of three factors on the adhesion of AR mastic is: film thickness >filler type > the ratio of filler to binder.Based on the BBS test,a method is proposed to evaluate the healing performance of AR(mastic).The effects of water,healing time and temperature,healing mode,CR content,filler type and composite modifier type on the healing performance of AR(mastic)are investigated.In dry state,the longer the healing time,the higher the temperature in a certain range,the more beneficial to the healing potential of AR.However,it is found that under the action of water,with the increase of time and temperature,the healing rate firstly increased,then decreased and finally tended to be stable.The healing process of AR(mastic)is accompanied by the failure process of weak channel formation-penetration-polymerization-expansion in asphalt(mastic)fracture interface with the wetting and diffusion of water molecule.The greater the failure degree,the smaller the CR amount,the greater the Si O2 content of filler,and the more unfavorable to the healing potential of AR(mastic).Freeze-thaw accelerates the damage of the adhesive interface between AR and aggregate in the healing process,the failure mode gradually changes from asphalt cohesive failure to interface adhesion failure.The adhesive and healing mechanism of AR was revealed by the morphology and force curve of atomic force microscope(AFM),the functional groups of infrared spectroscopy(IR)and viscosity curve of dynamic shear rheometer(DSR).Results show that CR changes the distribution state and size of the bee structure,increases the elastic modulus of asphalt,and decreases the surface roughness and adhesion force of nano-sized asphalt.Additionally,there is a good correlation between the adhesion of AR and,and.During the reaction between CR and BA,the aromatic with basically no branched chain and the saturated component with smaller molecular weight are reduced,the content of asphaltene with a large number of branched chains is increased,and then the Methylene plus methyl hydrogen to carbon(MMHC)and activation energy Ea of asphalt are increased,resulting in the reduction of healing rate(HR).CR do not have healing potential,and the interaction of CR and BA is one of the main reasons affecting the nano adhesion and healing performance of AR.After separating the CR from the AR system,the adhesion and HR of residual asphalt increase.Molecular dynamics(MD)method was used to deeply explain the cohesion/adhesion and self-healing mechanism of AR from atomic and molecular scales.The effects of water,temperature,CR content and asphalt type on the cohesion/adhesion and self-healing of AR were evaluated,and the mechanical performance of AR in the process of stretching was explored.It is concluded that water molecules replace some asphalt molecules and reduce the van der Waals force and electrostatic force between asphalt molecules,resulting in the reduction of cohesion energy/adhesion energy,tensile maximum stress and fracture work of asphalt molecules.The increase of temperature can reduce the orientation force of van der Waals force between asphalt molecules,increase the diffusion coefficient of water molecules in asphalt,and then reduce cohesion energy/adhesion energy,tensile maximum stress and fracture work.Compared to Ca O(Ca CO3)and Mg O,Si O2 has the strongest adsorption capacity for water molecules and the worst adhesion with AR.It is drawn that the cohesion energy between rubber molecules and asphalt molecules is less than that between two asphalt molecules.The greater the amount of CR,the smaller the cohesion energy of AR and the smaller the water molecular diffusion coefficient.The healing process of AR is the diffusion process of asphalt small molecules.The greater the diffusion coefficient of asphalt small molecules,the better the healing potential.C40H60 S and C18H10S2 in resin,C30H46 in aromatic and C30H62 in saturation fraction play a leading role in the healing process of AR.The Hamburg wheel tracking test(HWTT)and the semi circular bending(SCB)test are adopted to explore the water damage resistance and fracture damage-healing performance of AR OGFC.The effects of gradation type,nominal maximum aggregate size(NMAS),CR content,modifier type,aggregate type and mastic thickness are analyzed.Analysis shows that the water damage resistance and fracture-healing performance of AR used in three typical graded mixtures are as follows: SMA-13 > AC-13 > OGFC-13.For the AR OGFC,the larger the NMAS,the better the performance of HWTT,but the worse the healing performance of SCB.When the CR content is small,the performance of the water damage resistance and fracture-healing performance are poor.As the CR increase to 20%,both properties are significantly improved.SBS/CR composite modified asphalt(3.5% SBS+15% CR)has the best comprehensive performance.The performance of limestone mixture is better than that of basalt and diabase,and the overall performance of granite mixture is the worst.Mastic thickness and crack distribution are two very important factors affecting the healing performance of the mixture.However,the cracks forms and sizes of AR OGFC are extremely various and irregular.Therefore,the crack irregularity is the key factor to the disorder of the healing performance of AR OGFC,and it even can cover up the healing advantage of sufficient mastic thickness.Compared to binder bond strength,HR in BBS test is more suitable to evaluate the water damage resistance of AR OGFC,while it is inappropriate to assess its fracture damage-healing performance.更多还原