Simulation of rheological behavior of asphalt mixture with lattice model

A three-dimensional(3D) lattice model for predicting the rheological behavior of asphalt mixtures was presented.In this model asphalt mixtures were described as a two-phase composite material consisting of asphalt sand and coarse aggregates distributed randomly.Asphalt sand was regarded as a viscoelastic material and aggregates as an elastic material.The rheological response of asphalt mixture subjected to different constant stresses was simulated.The calibrated overall creep strain shows a good approximation to experimental results.     

Effect of rejuvenators on performance and microstructure of aged asphalt

A composite rejuvenator was used for the rejuvenation of aged asphalt in comparison with the common rejuvenator. The effects of the rejuvenators on the performance and microstructure of the aged asphalt were investigated by physical properties tests, dynamic shear rheometer and atomic force microscopy. The results indicate that the physical and rheological properties of the aged asphalt are restored more significantly by the composite rejuvenator than the common rejuvenator, which can be ascribed to the effective recovery of microstmcture of the aged asphalt. The composite rejuvenator has the potential to be used for the rejuvenation of severely aged asphalt since it can restore the colloidal structure of the aged asphalt effectively through composition regulation and chemical reactions between the composite rejuvenator and asphaltenes.     

CA砂浆的流变特性

CA砂浆是应用在板式轨道结构中的一种新型有机无机复合灌浆材料,其流变性能直接决定CA砂浆的灌注效果.通过流变仪研究了新拌CA浆体的瞬态与稳态流变特性及其影响因素.结果表明,CA浆体属于非牛顿流体,表现在低剪切速率时,CA浆体的粘度随时间先减小后增大;中高剪切速率时,其粘度先随时间减小后趋于稳定.在绝对水灰比固定条件下,随着沥青乳液与水泥质量比、硅灰和流变助剂掺量的增大,CA浆体的粘度增加;随着粉煤灰掺量的增加,CA浆体粘度略有降低.     

沥青路面再生方法的试验研究[D]

为了解决不同环境因素对路面工程中未经压实的再生沥青混合料(recycled asphalt mixture, RAP)老化程度影响的问题,以松散的再生沥青混合料为研究对象,利用特制的室内模拟老化试验装置,通过控制温度、湿度、老化时间、氧气浓度等因素,对新制备密级配沥青混合料AC-13进行特定环境条件下模拟老化试验. 结果表明:松散RAP混合料的老化程度随试验温度升高而增加,随空气湿度增加和氧气浓度下降而降低;不同试验温度下,沥青老化的成长速度和试验终值均不相同,表明老化过程中的化学反应因温度不同而有所差异;在通入纯氮气的试验中,沥青没有发生任何老化作用,表明沥青的老化只受氧化作用影响;环球法测软化点的试验结果对温度变化较为敏感,动态剪切流变仪(dynamic shear rheometer,DSR)测定的动态复数剪切模量在表征沥青老化程度时存在一定迟滞效应;老化后沥青混合料低温性能出现衰减,主要原因是沥青长期老化作用导致.

     

Experimental evaluation on high temperature rheological properties of various fiber modified asphalt binders

High temperature rheological properties of fiber modified asphalt binders and impact of the type and content on such properties were studied.Three types of fiber,including polyester(PET),polyacrylonitrile(PAN) and cellulose(CEL),a control content(0%) and four levels of fiber content(2%,4%,6% and 8% by total asphalt binder mass) were used with asphalt binders.The high temperature rheological properties,consisting of complex modulus(G*) and phase angle δ,were measured using SHRP’s dynamic shear rheometer(DSR) between 46-82 ℃.Experimental results indicate that the changes of G* and tan δ of fiber modified asphalt binders with the increase of test temperature tend to slow down,and the temperature susceptibility is improved obviously compared to that of original asphalt binder.Fiber modification results in the increase of rutting parameter(G*/sin δ) at high temperatures,the decrease of temperature susceptibility,and further improved high temperature performance of asphalt binder.An excellent correlation exhibits between fiber content and high temperature performance of asphalt binder.Moreover,fiber type also has different influences on the improvement of G*/sin δ,G*/sin δ of PET and PAN fiber asphalt binders are both higher than that of CEL fiber,but G*/sin δ of CEL fiber is still higher than that of original asphalt.However,there is a critical fiber content when fibers start to interact with each other.Therefore,based on the critical fiber content and economic consideration,the optimum fiber contents for various fiber-modified asphalt binders are obtained.     

高吸水共聚共混物的制备及流变性的研究

制备丙烯酸／丙烯酰胺／聚乙烯醇高吸水共聚共混物，研究引发剂浓度对共聚共混物相对分子质量的影响以及聚合原液的流变性能，并制备出共聚共混物纤维，并用电镜观察其结构，结果表明：当引发剂浓度为0．4％时，共聚物的相对分子质量最大；共聚共混物属于切力变稀流体；共聚共混物纤维吸水率高于共聚物纤维。     

自然因素作用下沥青老化化学机理分析

利用化学分析方法，探讨了沥青在热、光、氧、臭氧等自然因素作用下可能发生的老化化学反应．指出在通常的自然条件下，沥青中各组分会自行发生热氧化老化、光氧老化、臭氧老化等老化反应，分析提出了这一过程中的化学反应方程式．从化学反应角度揭示了沥青老化的化学机理．     

沥青混合料流变历程与模量演变

为了解沥青混合料的流变特性,采用MMLS3进行沥青混合料的足尺（Full scale）加速加载试验,并利用便携式路面分析仪对沥青混合料流变后的隆起和下陷部分的地震波模量进行测量.试验结果表明：在荷载作用下,沥青混合料下陷量与隆起量的变化值不等;并且下陷处的地震波模量逐渐增大并趋于稳定,而隆起处的地震波模量在逐渐减小.试...     

SBS与沥青的相互作用性分析

为了研究SBS（styrene-butadiene-styrene）/HON（Honeywell Titan^TM）复合改性沥青的流变性能,选取2种SBS和2种HON改性剂制备复合改性沥青,采用布氏旋转黏度计分析了复合改性沥青的黏温性能,采用动态剪切流变仪（DSR）、低温弯曲流变仪（BBR）分别评价复合改性沥青的高温及低温流变性能.结果表明：HON可有效改善沥青的黏温性能,降低施工温度,并可提高沥青的高温流变性能;SBS可明显改善沥青材料的高温流变性能,并可在一定程度上提高沥青材料的低温流变性能.

     

Analyses of Dynamic Rheological Behavior of Polymer Melt Based on Novel Experimental Equipment and Procedures

By introducing a vibrating force field into the extrusion process of polymer melt, an expertmental equipment of coustant velocity type dynamic rheometer of capillary (CVDRC) was designed. A set of experimental procedures was established, by which the dynamic, rheologieal parameters of polyner can be acquired, and a set of dora management methods to undrgo time-domain orfreqneney-domain analysis was set up for dynavior rheological data of polymer melt. Meantime, the characterization formala of polymer melt ‘ s rheological behavior in a vibrating force field was set up. The instantaneous value of capillary entry pressure, capillary volume flow rate and their phase difference were meusured and analyzed, and the melt apparent viscosity, which describes the rheological behavior of polymer melt in a vibrating force field, was obtained.     

基于室内环境模拟的再生沥青混合料老化影响因素

为了解决不同环境因素对路面工程中未经压实的再生沥青混合料(recycled asphalt mixture,RAP)老化程度影响的问题,以松散的再生沥青混合料为研究对象,利用特制的室内模拟老化试验装置,通过控制温度、湿度、老化时间、氧气浓度等因素,对新制备密级配沥青混合料AC-13进行特定环境条件下模拟老化试验.结果表明:松散RAP混合料的老化程度随试验温度升高而增加,随空气湿度增加和氧气浓度下降而降低;不同试验温度下,沥青老化的成长速度和试验终值均不相同,表明老化过程中的化学反应因温度不同而有所差异;在通入纯氮气的试验中,沥青没有发生任何老化作用,表明沥青的老化只受氧化作用影响;环球法测软化点的试验结果对温度变化较为敏感,动态剪切流变仪(dynamic shear rheometer,DSR)测定的动态复数剪切模量在表征沥青老化程度时存在一定迟滞效应;老化后沥青混合料低温性能出现衰减,主要原因是沥青长期老化作用导致.     

矿浆流变特征对钢球磨损规律的影响

探讨了湿式磨矿过程中矿浆流变特性对钢球磨损的影响规律,研究结果表明,矿浆粘度随矿浆体积分数的增大而增大,当矿浆体积分数大于50％时,矿浆粘度急剧增大,矿浆粘度是影响钢球磨损率的主要流变学因素,当矿浆粘度介于500－1000mPa.s时,钢球的磨损率出现最大值,当矿浆体积分数较高时,添加化学助剂NaNO2,钢球的磨损率降低,磨矿效率提高,控制磨矿条件能改善矿浆的流变学特性,使钢球表现的罩盖层厚度处于最佳值,从而提高磨矿效率,降低钢球的磨损率。     

热流变复杂行为对沥青温度应力计算的影响

为了完善现有沥青胶结料温度应力计算方法,利用弯曲梁流变试验（BBR）得到沥青材料的蠕变柔量,代入线性粘弹性的Burgers模型的应变-应力关系式得到不同温度下的流变参数,再利用Burgers模型的本构状态方程的解析解,计算沥青层下温度应力的数值解（增量法）,并将计算结果与传统Hopkins & Hamming算法的结果进行对比。结果表明:总体来看两种方法大致吻合,但在较低的温度下（-30 ℃左右）,Hopkins & Hamming算法的结果较增量法偏小,低估了热可逆老化的影响;低温养护对沥青的硬化效果与沥青的流变性质相关,流变性质越复杂的沥青,受到低温养护的硬化效果越明显;当处于低温或者长期加载时,热流变复杂沥青的主曲线会偏离时间温度叠加原理。     

基于流变特性的硅藻土与沥青配伍性分析

分别选用不同选矿阶段的硅藻土、不同油源及标号基质沥青制备改性沥青,基于动态剪切流变试验,分析硅藻土品质及基质沥青差异对改性沥青流变性能的影响。研究结果表明:经选矿提纯后所得硅藻精土能有效改善沥青抗变形性能,硅藻原土和尾矿改性效果较差;改性沥青的抗变形性能受基质沥青油源影响,油源不同,改性效果也不同;同时,标号越小的基质沥青,经改性后抗变形能力越好。     

甲基丙烯酸长链酯基氢键缔合型减阻聚合物的合成工艺与流变行为研究

以K2S2O8-Na2SO3为氧化还原引发体系,采用乳液聚合方法合成了一种甲基丙烯酸长链酯基氢键缔合型减阻聚合物。研究了合成温度、氧化剂还原剂摩尔比与减阻率的关系,以及不同极性单体质量分数对剪切稳定性的影响;考察了温度、剪切速率、浓度及极性单体含量对该聚合物体系柴油溶液流变性能的影响。研究结果给出了在实验研究范围内,剪切稳定性最佳时的合成工艺条件;流变行为研究表明,氢键缔合型质子供体聚合物(D)和质子受体聚合物(A)的柴油溶液为典型符合幂律方程的假塑性流体,而两者1∶1混合后形成的氢键缔合型减阻聚合物的柴油溶液在γ.200 s-1时,其流变曲线与幂律方程出现了偏离;同时研究结果也表明,IPC的表观黏度随温度的变化、比浓黏度随浓度的变化规律都与其缔合前身有较大差异;最后对剪切速率与表观黏度的关系进行了实验探讨,得到了一种判断IPC减剪稳定性的可能的量度方法。     

纤维沥青碎石封层结构行为及材料设计研究[D]

为了认识沥青碎石封层的力学行为与破坏机理,采用有限元软件建立沥青碎石封层细观结构二维有限元模型,分析在竖向荷载作用下封层内部细观结构应力、应变和位移的力学行为特性. 分析结果显示:轮迹内侧边缘碎石竖向位移最大,偏转角度最小;相反,轮迹外边缘碎石偏转角度最大,并向两侧逐渐递减. 沥青层内的水平应变主要为压应变,轮迹外侧沥青和胶浆层接触面上剪应变最大. 黏结层的水平变形、剪切变形均不同程度大于沥青层,黏结层与胶浆层交界处具有最大等效Mises应力,易发生剪切破坏. 胶浆层的中心主要为受压变形,胶浆层两侧边缘处主要表现为较高剪切变形.

     

Application research on metal rheological forming of reproducing kernel partial method

The meshless method is a new numerical technology presented in recent years.It uses the moving least square(MLS) approximation as its shape function,and it is determined by the basic function and weight function.The weight function is the mainly determining factor,so it greatly affects the accuracy of the computational results.The process of cylinder compression was analyzed by using rigid-plastic meshless variational principle and programming reproducing kernel partial method(RKPM),the influence of node number,weight functions and size factor on the solution was discussed and the suitable range of size factor was obtained.Compared with the finite element method(FEM),the feasibility and validity of the method were verified,which proves a good supplement of FEM in this field and provides a good guidance for the application of meshless in actual engineering.