Microscopic and Dynamic Rheological Characteristics of Crumb Rubber Modified Asphalt

A test for crumb rubber modified asphalt containing 20% crumb rubber particles（30 mesh） was performed using a scanning electron microscope（SEM）.The experimental results indicate that the crumb rubber particles are evenly distributed in the asphalt.Shear rate sweep and shear-temperature sweep tests on the crumb rubber modified asphalt at-20-80 ℃ using a dynamic shear rheology（DSR） instrument,were carried out.The tests show that the complex modulus decreases with increasing temperature;at equivalent temperature,higher load frequencies lead to a larger complex modulus,and this value increasingly decreases as the temperature increases;the phase angle increases with temperature and decreases as the load frequency increases.It can be concluded that the rutting resistance limiting temperature of crumb rubber modified asphalt is 78 ℃,and the anti-fatigue limiting temperature is 16 ℃,which shows that the asphalt has preferable rutting resistance characteristics at high temperature,as well as anti-fatigue characteristics.In addition,the complex modulus master curve at different temperatures was plotted according to the time temperature equivalence principle,which allows the study of the dynamic state behavior of crumb rubber modified asphalt at a wide range of load frequency.

Creep Characteristics of Crumb Rubber Modified Asphalt Binder

Crumb rubber modified asphalt containing 20 percent crumb rubber particles of 30 mesh has been examined by Scanning Electron Microscope （SEM） to observe the microcosmic appearance and the characteristic distribution of crumb rubber particles in asphalt. The SEM pictures reveal that the crumb rubber particles distribute evenly in the asphalt and they are compatible well with asphalt. The shear creep test of crumb rubber modified asphalt was carried out at -10 ℃ and 40 ℃ by Dynamic Shear Rheology （DSR）. The shearing deformation at different temperature and creep stiffness modulus curve at loading stage of crumb rubber modified asphalt have been measured. The stiffness modulus of crumb rubber modified asphalt is much temperature sensitive and it decays much quick at the early stage of loading than normal asphalt. The rate of decay of stiffness modulus is slow at the subsequent stage and stiffness modulus approaches to a stable value at the final stage at a higher temperature. In addition, Burgers model is suitable to describe and simulate experimental results of viscoelastic properties of the crumb rubber modified asphalt.

Laboratory investigation on effects of organic montmorillonite on performance of crumb rubber modified asphalt

In this paper,organic montmorillonite(OMMT)was added into crumb rubber modified asphalt(CRMA)to improve its high temperature performance,anti-aging performance and storage stability.The effects of different OMMT content on properties of CRMA were studied.The rutting factor obtained by dynamic shear rheological(DSR)test was adopted to evaluate the high-temperature performance.The creep stiffness and m value determined by the bending beam rheometer(BBR)test were employed to evaluate the low-temperature performance.The softening point,ductility,rutting factor before and after rolling thin film ovens test(RTFOT)and pressure aging vessel test(PAV)were compared to characterize the aging properties.Moreover,the segregation test after being reserved for 48 h and 7 d was conducted,and the softening point and rutting factor of upper and lower layers of segregation pipe were adopted to evaluate the storage stability.The results indicated that the high-temperature performance and anti-aging performance were developed with the increasing content of OMMT,while the low-temperature performance deteriorated.The storage stability was improved with the increasing content of OMMT before the content exceeded 4%,after which the storage stability declined.Taking account of all factors,it is suggested that the optimum content of OMMT is 3%−4%.

Performance Characterization of CR/PU Asphalt for Potential Application in Assembled Fast-Repairing Engineering

Conventional repairing methods for asphalt pavement have some inconveniences,such as insufficient strength,and are typically time-consuming.To address these issues,this study proposes a new technological method to design and prepare a high-performance assembled asphalt concrete block for fast repair of the potholes.A series of composite modified asphalt binders with 10%crumb rubber(CR)and different dosages(0%,1%,3%,5%)of polyurethane(PU)are examined to determine the optimized binder.Subsequently,the corresponding asphalt mixtures are prepared for further comparison and assessment of engineering properties,such as moistureinduced damage,high-temperature deformation,and low-temperature cracking characteristics.The test results show that PU can significantly improve the high-temperature performance and hardness of(crumb rubber modified asphalt)CRMA binder;3%PU contributes allowing the resistance of CRMA mixture to moisture-induced damage at higher levels,particularly under water whole immersion;as 3%PU is added,the high-temperature rutting deformation resistance of the CRMA mixture increases significantly,and the low-temperature anti-cracking properties are also improved slightly.Therefore,the innovatively designed high-quality assembled fast-repairing asphalt concrete block is recommended as an appropriate option for highway maintenance.

Using thermodynamic parameters to study self-healing and interface properties of crumb rubber modified asphalt based on molecular dynamics simulation

The thermodynamic property of asphalt binder is changed by the addition of crumb rubber,which in turn influences the self-healing property as well as the cohesion and adhesion within the asphalt-aggregate system.This study investigated the self-healing and interface properties of crumb rubber modified asphalt(CRMA)using thermodynamic parameters based on the molecular simulation approach.The molecular models of CRMA were built with representative structures of the virgin asphalt and the crumb rubber.The aggregate was represented by SiO2 and Al2O3 crystals.The selfhealing capability was evaluated with the thermodynamic parameter wetting time,work of cohesion and diffusivity.The interface properties were evaluated by characterizing the adhesion capability,the debonding potential and the moisture susceptibility of the asphalt-aggregate interface.The self-healing capability of CRMA is found to decrease as the rubber content increases.The asphalt-Al2O3 interface with higher rubber content has stronger adhesion and moisture stability.But the influence of crumb rubber on the interfacial properties of asphalt-SiO2 interface has no statistical significance.Comparing with the interfacial properties of the asphalt-SiO2 interface,the asphalt-Al2O3 interface is found to have a stronger adhesion but a worse moisture susceptibility for its enormous thermodynamic potential for water to displace the asphalt binder.

硫化橡胶沥青和脱硫橡胶沥青的性能评估

文中采用扫描电子显微镜(SEM)观察了硫化橡胶粉和脱硫橡胶粉的微观形貌.以硫化橡胶粉和脱硫橡胶粉作为改性剂制备了改性沥青,并以基质沥青作为对照组,评估了三种沥青的高温性能和低温抗裂性能.通过红外光谱分析了其改性机理.结果表明:硫化胶粉颗粒表面光滑,棱角明显,颗粒相对分散.脱硫胶粉颗粒表面粗糙,颗粒有团聚现象.硫化胶粉改性沥青的粘度最大,脱硫胶粉改性沥青粘度次之,基质沥青的粘度最小.胶粉脱硫可以降低沥青的温度敏感度.硫化胶粉的高温抗车辙性能和低温抗裂性能均优于脱硫胶粉改性沥青.硫化胶粉改性沥青和脱硫胶粉改性沥青其主要以物理混溶为主.

Effect of SBS and crumb rubber on asphalt modification:A review of the properties and practical application

Owing to the environmental protection potential and the desirable high performance capabilities,asphalt rubber(AR)and styrene-butadiene-styrene(SBS)modified asphalt have been widely used.However,the poor construction workability and segregation issues of AR,along with the exorbitant cost of SBS modified asphalt,are of the serious problems that plague their application scope.Moreover,SBS/crumb rubber(CR)modified asphalt is gradually becoming widespread and it therefore becomes incumbent to find appropriate ways to mitigate the issues that may limit its use.As a consequence,it becomes crucial to analyze the interaction between CR and SBS modifiers in the composite mixture,as well as evaluate the influence of modifier dosage on the performance of the modified asphalt.This study presents a comprehensive review of the effects of SBS modifier,CR modifier and composite SBS/CR on the performance of modified asphalts.Macro analysis and micro analysis,including analysis on the conventional physical properties,are carried out.It can uncover the interaction between modifier and asphalt,which reveals how the modifiers influence the properties of modified asphalts.This study will serve as a source of invaluable information to researchers,engineers,and designers,informing them the development,potential and challenges of the CR,SBS and SBS/CR modified asphalts,the optimum contents to attain the best performance along with the mechanism involved.

废旧胶粉/SBS复合改性沥青高温抗车辙性能研究

为提升沥青结合料的高温抗车辙性能,本研究使用CR和SBS两种聚合物对基质沥青进行复合改性。首先,基于常规的沥青性能试验(针入度、软化点和延度试验),对不同掺量下的CR和SBS单一聚合物改性沥青进行高-低温性能研究;继而,利用常规性能试验研究CR掺量对废旧胶粉/SBS复合改性沥青性能的影响,其中SBS掺量固定为2%,仅改变复合改性沥青中CR的掺量;最后,基于动态流动剪切仪(Dynamic Shear Rheometer,DSR)对废旧胶粉/SBS复合改性沥青进行多应力蠕变松弛(Multiple Stress Creep and Recovery,MSCR)试验,利用不可恢复蠕变柔量(Jnr)和应变恢复率(R)两个指标进一步研究废旧胶粉/SBS复合改性沥青高温抗车辙性能。结果表明,2%SBS和12%CR复合改性沥青的抗车辙性能优异,甚至优于SBS掺量为4.5%的SBS改性沥青。

轻度解交联橡胶粉干法改性SMA13性能研究

通过沥青混合料车辙试验、小梁弯曲试验、冻融劈裂及浸水马歇尔试验,研究了不同掺量轻度解交联橡胶粉(LDCR)对干法改性SMA13高温性能、低温性能与水稳定性的影响。结果表明,掺入LDCR提高了SMA13的高温性能,尤其当掺量≥2%时,混合料的动稳定度超过4.5%SBS改性SMA13(对照组);2%掺量的LDCR干法改性SMA13低温抗裂性最优;总体上LDCR干法改性SMA13的水稳定性低于对照组。综合考虑,LDCR的最佳掺量为2%,与对照组相比,可降低材料成本约5%。

物理硬化下橡胶复合改性沥青低温抗裂性能研究

由于研究寒冷地区橡胶复合改性沥青(CRMA)材料物理硬化前、后低温抗裂性能的变化规律对提升寒区公路工程质量具有重要意义,所以采用单边切口弯曲梁(SENB)试验研究了物理硬化作用对CRMA低温抗裂性能的影响机制,即试验前将沥青小梁试样分别在-12、-18、-24℃的无水乙醇溶液中恒温1、12、24、36、48 h来模拟沥青不同程度的物理硬化。研究结果表明:改性沥青恒温24 h后低温抗裂性能下降速度逐渐平缓,物理硬化程度趋于饱和;改性沥青物理硬化程度随温度的降低呈正态分布,而不是温度越低,物理硬化程度就越严重;-18℃时,改性沥青的物理硬化程度最大;SBS改性沥青(SBSMA)的抗物理硬化能力优于CRMA,但物理硬化前后CRMA的低温抗裂性能均远优于SBSMA,更加适用于寒冷地区公路工程。因此推荐采用基于SENB试验恒温24 h后的断裂能指标来表征寒区改性沥青材料的低温抗裂性能。

SBS与胶粉复合改性沥青制备及多孔混合料性能评价

为利用废胶粉(crumbrubber,CR)制备用于多孔沥青混合料(porousasphalt,PA)的高黏改性沥青,通过SBS与CR复合并添加增粘剂与稳定剂制备了高黏改性沥青,根据针入度、软化点、延度和60℃动力黏度确定了SBS与CR的最佳比例及增黏剂用量,并研究了PA-13的路用性能。结果表明:SBS与胶粉对沥青针入度和软化点具有一定改善作用,然而SBS对沥青延度改善作用有限且胶粉对其有负面影响;SBS与胶粉均能提高沥青的动力黏度,且根据性能推荐高黏改性沥青中SBS、胶粉、增粘剂的用量分别为5.5%、14%、3%;PA-13路用性能测试成果表明自制的高黏改性沥青能够为混合料提供杰出的高低温和水稳定性。此外,与高黏沥青相关文献相比,自制高黏沥青性能优良。

胶粉复合改性沥青的研制及工业化生产

以某公司加工的环烷基和中间基原油为原料,通过优化原油配比,采用常减压蒸馏工艺,通过控制减压蒸馏工艺条件,生产出符合技术标准要求且能够用于改性沥青的基质沥青原料。通过筛选与基质沥青配伍性好的胶粉、助剂添加比例及工艺条件优化,研制出符合技术规范要求的胶粉复合改性沥青并进行了工业试生产。对工业生产的产品检测及专业部门鉴定结果表明,胶粉复合改性沥青产品各项技术指标符合JT/T798-2019《路用废胎胶粉橡胶沥青》技术要求,成功实现了工业化生产和应用。

胶粉改性沥青在高速公路路面养护中的应用研究

以京张高速公路养护实况为例,针对胶粉改性沥青在高速公路路面养护中的应用进行探讨,介绍了胶粉改性沥青中沥青、集料、矿料级配掺配的各项指标要求,分析了最佳油石比的确定方法,对制备完成的胶粉改性沥青混合料进行高温稳定性和低温抗裂性检验,结果均满足相关规范的要求。

废胎胶粉和天然胶乳改性沥青的老化和流变性能研究

【目的】研究废胎胶粉和天然胶乳改性沥青的耐老化和流变性能。【方法】利用天然橡胶(Natural Rubber,NR)胶乳和废胎胶粉(Crumb Rubber,CR)制备橡胶沥青,通过针入度、软化点、延度和动态剪切流变试验,对比分析基质沥青和橡胶改性沥青老化前后常规性能和流变性能。【结果】结果表明,CR和NR胶乳的加入降低了橡胶沥青的针入度等级,提高了橡胶沥青的软化点和延度。与常规沥青相比,CR掺量高达8%,NR胶乳掺量高达4%时,橡胶沥青的复数模量和抗车辙性能均得到了显著提高。【结论】CR和NR胶乳的加入可提高改性沥青的总体性能,改善沥青路面的耐久性。

基于分子动力学模拟的胶粉改性沥青自愈合性能研究

采用沥青十二分子模型和丁苯橡胶(SBR)分子模型,建立了基质沥青和胶粉改性沥青自愈合模型,并利用分子动力学模拟研究了不同温度下沥青自愈合过程中沥青分子的运动规律和扩散行为。从密度、扩散系数、内聚能密度和相对浓度多个指标评价了沥青分子和胶粉改性沥青模型的自愈合能力。研究结果表明,胶粉改性沥青自愈合模型的密度达到稳定的时间早于基质沥青。两个模型自愈合扩散系数随着温度的升高而增大。在各温度条件下,胶粉改性沥青整体扩散系数较大,说明胶粉的添加能显著增大沥青的扩散系数,自愈合性能较基质沥青更好。从相对浓度的变化来看,沥青的自愈合可以分为扩散、接触、相互融合三个阶段,胶粉改性沥青模型的相对浓度数值趋近为1的时间早于基质沥青自愈合模型。该计算结果与密度、均方位移具有一致性,都说明胶粉改性沥青自愈合效果好于基质沥青。

橡胶粉改性沥青的研究

研究了胶粉的种类、粒径、用量及沥青的种类对胶粉改性沥青性能的影响 ,并通过荧光显微镜的观察探讨了胶粉对沥青的改性机理。结果表明 :两种胶粉 (胎胶粉和鞋胶粉 )对沥青性能的改善并无明显的差异 ;胶粉的粒径对沥青的改性有一定的影响 ,但若胶粉在沥青中溶胀性有限 ,对沥青改性并非胶粉越细越好 ;胶粉用量在 2 0 %以内 ,对沥青改性有显著作用 ,继续增大胶粉用量 ,沥青性能的改善幅度明显减小 ;沥青中轻组份含量对胶粉改性沥青的性能有很大影响 ,轻质组份含量大 ,可渗入胶粉内部使其发生溶胀 ,有利于沥青性能的改善。

废旧橡胶粉改性沥青研究进展

介绍了废旧橡胶粉改性沥青的国内外应用状况,分析了胶粉改性沥青的特点、机理、方法以及胶粉改性沥青的贮存稳定性和感温性等。指出将废旧橡胶粉用于改性沥青,既能提高沥青的性能,又有利于废旧橡胶的循环利用,减少环境污染,有着良好的发展前景。提出我国应尽快制定出废旧橡胶粉改性沥青的行业标准规范。

橡胶改性沥青及老化特征微观尺度分析

为了在微观尺度下分析橡胶改性沥青及老化特征,制备了普通橡胶沥青和脱硫橡胶沥青,首先分析了两种橡胶改性沥青制作前后橡胶颗粒的变化特征,然后通过凝胶渗透色谱实验建立了两种橡胶改性沥青的分子量分布与宏观路用性能的对应关系,最后综合宏观技术指标与红外光谱半定量分析研究了两种橡胶改性沥青的老化特征。结果表明,经过高速剪切工艺大粒径的脱硫橡胶粒在沥青里大多分散成无明显颗粒的细小物质,而普通橡胶粉剪切后基本保持其原有颗粒核心;普通橡胶沥青具有最高的大分子LMS的比例,这与其最优异的高温稳定性与低温抗裂性相对应;普通橡胶沥青的TFOT短期老化中存在着强烈的胶粉持续溶胀作用,但在PAV长期老化中主要发生氧化老化作用,而脱硫橡胶沥青的TFOT短期老化和PAV长期老化均以沥青的氧化老化为主;普通橡胶沥青比脱硫橡胶沥青更加耐受TFOT短期老化。

深度降解橡胶改性沥青的流变性能

针对传统橡胶沥青混溶速度慢、黏度大、加工难度高和掺量低等问题,采用螺杆反应挤出法对橡胶粉进行深度降解(溶胶质量分数大于50%),使其能在低温下快速混溶于沥青改性.结合常规测试和动态流变学分析研究了橡胶粉来源、掺量对使用温度下沥青流变性能和加工流变性能的影响.结果表明:深度降解橡胶粉能较快分散于沥青中;橡胶粉来源、掺量可影响改性沥青的高低温流变性能及加工流变性能;在不显著增加改性沥青黏度的情况下,深度降解橡胶粉的掺量(质量分数)可达50%以上.

SBS/废胶粉复合改性沥青的性能

以AH-70为基质沥青,加入经糠醛抽出油预溶胀的苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS),外掺胶粉制备复合改性沥青(SBS/CRMA)。通过正交试验考察糠醛抽出油掺量、胶粉掺量、搅拌温度和搅拌时间对改性沥青性能的影响,采用动态剪切流变仪对SBS/CRMA、SBS改性沥青(SBSMA)和胶粉改性沥青(CRMA)的流变性能进行分析,并通过荧光显微镜观察SBS/CRMA的微观结构。由正交试验得到最优方案为:糠醛抽出油掺量8%(质量分数)、胶粉掺量25%(质量分数)、搅拌温度210℃和搅拌时间2.5h。在最优方案下制得SBS/CRMA的5℃延度为327mm、软化点为78.0℃、弹性恢复91.6%。SBS/CRMA在低温下更柔韧,高温下更坚硬,温度敏感性降低,抗车辙形变能力增强。结合荧光显微镜结构图,提出了SBS/CRMA的三维网络结构模型。