Modeling viscosity behavior of crumb rubber modified binders

Accurately predicting the viscous properties of crumb rubber modified (CRM) binders has proven difficult, especially as these properties tend to vary with changing crumb rubber concentrations and temperatures. This study explores the utilization of the statistical regression and neural network (NN) approaches in predicting the viscosity values of CRM binder at various temperatures (135 °C and greater). A total of 53 CRM binder combinations were prepared from two different rubber types (ambient and cryogenic), three different binder sources, four rubber concentrations (0%, 5%, 10%, and 15%), and five crumb rubber gradations (ADOT, SCDOT, 0.18 mm, 0.425 mm, and 0.85 mm). The results indicated that the regression model is easy to use and can be used for viscosity prediction, similarly NN-based models also provided accurate for predictions for the viscosity values of CRM binders regardless of rubber type and can easily be implemented in a spreadsheet. In addition, the developed NN model can be used to predict viscosity values of other types of CRM binders efficiently. Furthermore, the sensitivity analysis of input variables indicated that the changes of viscosity are significant as the changes of asphalt binder grade, test temperature, and rubber content. The results also show that these three independent variables are the most important factors in the developed NN models in comparison with other variables.     

胶粉改性沥青黏度影响因素及微观特性研究

将废橡胶粉用于生产胶粉改性沥青(CRMA)是一种节能而又环保的有效途径.在不同条件下制备胶粉改性沥青,并进行黏度测试,分析了胶粉粒径、胶粉掺量、处理温度、处理时间以及微波条件对胶粉改性沥青黏度的影响,采用电子显微照相技术观测胶粉的微观状态变化,进行了胶粉溶胀特性探讨.结果表明,随着处理温度的升高及胶粉掺量的增大,胶粉改性沥青黏度不断增高;而随着胶粉粒径减小,胶粉改性沥青黏度先增后减,其中以60目胶粉改性沥青黏度最大;微波作用可以增强胶粉在沥青介质中的溶胀效果,使胶粉改性沥青黏度增大.在不同条件下胶粉的溶胀程度不同,对胶粉改性沥青黏度的影响也不同.     

Variance analysis and performance evaluation of different crumb rubber modified (CRM) asphalt

In order to sort some important factors affecting the performances of CRM asphalt and evaluate the performances of different CRM asphalt, this study encompassed one kind of base asphalt binder, four kinds of crumb rubber, tread rubber (TR), heavy truck (HT), small truck (ST) and agriculture tire (AT) crumb rubber, two kinds of particle size, 60 mesh and 80 mesh, and three contents. Softening point, low temperature ductility, and penetration index are selected as basic evaluation indicators in analysis. Variance analysis shows that the crumb rubber content is the primary affecting factor in general, followed by the crumb rubber type, and particle size comes last. The greater the crumb rubber content is, the higher the softening point and the penetration index are, and the smaller the low temperature ductility is. Modified effects between 60 mesh and 80 mesh don’t manifest significant difference. The modified effects of TR-crumb rubber and HT-crumb rubber are better while the low temperature ductility of AT-CRM asphalt is the worst. Also according to the results of DSR and BBR test, TR-CRM asphalt has a better and comprehensive performance at the crumb rubber content of 20% by weight of base asphalt binder, and, if the price is also considered, selecting HT-CRM asphalt with the crumb rubber content of 15% is ideal. The study also finds an interesting phenomenon that the rutting factors of CRM asphalt may be remarkably different, although the softening points of them are the same.     

对废橡胶粉改性沥青的认识

从改性沥青用废橡胶粉的有效组成、废橡胶粉改性沥青的制备和性能、影响废橡胶粉改性沥青性能的因素等方面进行了综述,指出当前废橡胶粉改性沥青应用方面所存在的问题及未来的发展策略.     

橡胶粉改性沥青反应过程规律

对3种不同基质沥青原料,分别测定不同反应温度下橡胶粉-沥青体系的黏温曲线,并对特征样品进行红外光谱分析;通过分析橡胶粉改性沥青黏温曲线随反应条件的变化,以及反应过程中官能团的改变,探讨橡胶粉与沥青体系反应规律和作用机制。结果表明:橡胶粉改性沥青反应过程与沥青介质、反应温度和反应时间紧密相关;反应温度越高,溶胀和降解的速度越快;沥青针入度越高,橡胶粉改性沥青黏度变化越大;反应过程并没有生成新的官能团,产品黏度变化主要是受橡胶粉的溶胀和降解过程影响;在实际生产中,橡胶粉改性沥青黏温性能可以通过反应温度和反应时间进行控制。     

国内废橡胶粉改性沥青的研究进展

介绍了国内废橡胶粉改性沥青的应用现状，并对废橡胶粉改性沥青的生产方法、改性机理、改性沥青性能及其主要应用研究的进展情况进行了总结．指出用废橡胶粉对沥青进行改性具有重要的理论和现实意义。     

废橡胶粉改性沥青的低温性能试验研究

通过高速剪切设备在基质沥青中加入一定量的废胎橡胶粉进行改性,得到废橡胶粉改性沥青,采用扫描电镜(SEM)和动态力学的方法(DSR)研究了改性沥青在不同温度下的细观结构和低温流变性能.结果表明,胶粉颗粒的表面网状结构可很好的吸附沥青,改性后的沥青中形成了一种非均相的稳定结构,且在-20℃的低温下仍能保持原状;随温度的降低、动态模量的变化及相位角变化趋于缓和,改性沥青始终保持一定的流动性,从而改善了其柔韧性,提高了抗低温开裂性,该沥青适合北方地区使用.     

Influence of surface area and size of crumb rubber on high temperature properties of crumb rubber modified binders

There are many variables of crumb rubber modifier (CRM) and asphalt binder, affecting the interaction of the CRM with the binder when crumb rubber modified binder (CRM binder) is produced. In this study, the influence of the surface area of CRM blends on the high temperature properties, i.e., the complex modulus (G¹), the phase angle and high temperature grade of the CRM binders was investigated. To this end, the surface areas of CRM particles were measured using the BET (Brunauer, Emmett and Teller) tester, while weighted average particle size of CRM blends was calculated based on their graduations and then used as a size index. High temperature properties of CRM binders were measured using Dynamic Shear Rheometer (DSR) test. A total of 108 CRM binders were produced using different combinations of these variables. Results observed from this study indicated: (1) the surface area of the ambient CRM was twice as large as that of the cryogenic one, leading to a much higher G¹ and phase angle of the CRM binders; (2) the phase angle and G¹ were affected by both the surface area and average size; however, the average size is the predominating factor; and (3) ambient CRM binders were produced about 3 °C in high temperature grade higher than cryogenic CRM binders.     

废胶粉改性沥青应用的若干问题研究

对国内外废胶粉利用的现状进行了综合性评述。介绍了废胶粉的种类、化学成分和多种粉碎工艺以及废胶粉改性沥青的生产方法,分析了胶粉改性沥青的改性机理以及其主要路用性能和主要防水性能。认为,从技术指标而言,胶粉改性沥青的应用应当解决其体系的互溶稳定性;防水用胶粉改性沥青要从假冒SBS改性沥青的阴影里走出来,健全相应的标准,并给胶粉及胶粉改性沥青生产企业相应的扶持政策。     

Microstructure and performance of crumb rubber modified asphalt

Crumb rubber modified asphalt (CRMA) was prepared by matrix asphalt preblending process (MAPP) which uses matrix asphalt as swelling agent in this study. Effects of the proportion of preblending matrix asphalt and properties of crumb rubber on performance of CRMA have been investigated. Scanning electronic microscope (SEM) and fluorescence microscope were adopted to characterize the microstructures of crumb rubber powder and CRMA, respectively. The experimental results indicated that the CRMA have better performance compared with matrix asphalt; the properties of crumb rubber display significant effects on the performance of CRMA, performance of CRMA are improved with the decrease of ash content and the increase of acetone extract. SEM graphs of crumb rubber pre and post preblending demonstrated that the morphological characteristic of preblended crumb rubber powder is obviously different from rubber powder without preblending, and the properties of rubber elastomeric are recovered and improved significantly. Micrographs of CRMB prepared under different conditions showed that compared with CRMB prepared by the traditional preparation process, the scattering state of rubber powder and matrix asphalt in CRMB prepared by MAPP is excellent, even and perfect polymer reticular structure is formed in the sample system.     

Interaction effects of crumb rubber modified asphalt binders

The application of crumb rubber in asphalt mixtures is intended to improve the binder properties by reducing the binder’s inherent temperature susceptibility. This research investigated the interaction effects of CRM binders as a function of various blending treatments in the laboratory. For this study, CRM binders were produced using seven blending times (5, 30, 60, 90, 120, 240, and 480 min), three blending temperatures (177, 200, and 223 °C), and four rubber contents (5%, 10%, 15%, and 20% by weight of asphalt binder). The results from this study showed that (1) The interaction time and interaction temperature for CRM binders were observed to have significant effect on the binder properties; (2) The longer time and higher temperature for interaction of CRM binders resulted in an increase in the high failure temperature and the viscosity. This is thought to be due to the increase in the rubber mass through binder absorption. However, this study found that the control binder of PG 64-22 had little change of the binder properties as a function of interaction conditions; (3) The CRM percentage influence is statistically significant on the viscosity and G^*/sin δ values. Also, the asphalt binder with higher CRM percentage showed a higher large molecular size (LMS) value, and the increase in CRM percentage is considered to result in the additional loss of the low molecular weight in the asphalt binder to the CRM.     

The effect of crumb rubber modifier (CRM) on the performance properties of rubberized binders in HMA pavements

The application of crumb rubber modifier (CRM) in asphalt mixtures is intended to improve the properties of binder by reducing the binder’s inherent temperature susceptibility. During the interaction with asphalt binder, the CRM particles absorb a portion of the oils in asphalt binder and the particles swell; therefore increasing the viscosity and stiffness of the CRM binder. Still, the performance properties of CRM binders in hot mix asphalt (HMA) pavement are considered to be unclear due to the various interaction effects of CRM with asphalt binders, depending on the CRM percentage, source and size. In this study, a laboratory investigation was conducted on the properties of CRM binders as a function of CRM processing method and percentages. A total of twenty-four CRM binders (3 binder sources * 2 CRM processing methods * 4 CRM percentages) were produced and artificially aged through an accelerated aging process. Evaluation of the CRM binders included the following testing procedures: Viscosity at high temperature, performance properties at high and intermediate temperatures, and cracking properties at low temperature. The results from this study indicated that the higher CRM percentages for CRM binders seemed to lead to a higher viscosity, a better rutting resistance and a less chance for low temperature cracking. In general, the ambient CRM was found to be more effective on producing the CRM binders that are more viscous and less susceptible to rutting and cracking.     

Analysis of digestion time and the crumb rubber percentage in dry-process crumb rubber modified hot bituminous mixes

The use of crumb rubber modifier (CRM) in bituminous mixes made by the dry process is not as widely used as the wet process. Nonetheless, this process has advantages, such as the potential to consume larger quantities of crumb rubber, thus resulting in greater savings in energy and natural resources. This research study contributes to the further development and evolution of the dry process through the analysis of the effect of the digestion time (the contact time between the crumb rubber and the bitumen) and the quantity of crumb rubber on the mix design properties. The results of the study showed that the digestion time had no influence on the selection of the optimal binder content or on the compaction of the mixture. In contrast, the digestion time was found to have an impact on the mechanical performance of the mix. In this respect, an increase in the quantity of crumb rubber contributed to a corresponding increase in the amount of bitumen needed, and also caused the mix to become less compact. This study showed that a crumb rubber percentage of less than 1% of the total weight of the mix and a digestion time of 90 min produced the best results.     

橡胶粉改性沥青混凝土配合比设计方法研究

针对采用普通SMA级配设计橡胶粉改性沥青混合料不能满足对SMA沥青混凝土空隙率要求的问题，通过大量室内试验，比较了采用普通SMA级配和间断级配的橡胶粉改性沥青混凝土的物理性能，提出了橡胶粉改性沥青混合料的设计方法。     

废轮胎胶粉改性沥青设计与施工工艺

介绍了使用废轮胎胶粉改性沥青的最新设计和施工工艺，并从原材料的选择、改性沥青加工工艺、混合料设计方法及施工工艺等方面进行了系统的对比研究，为推广和研究改性沥青混合料提供了参考。     

"节约型社会与防水"系列报道之八废胶粉改性沥青在防水材料中的应用前景

介绍了我国近年来橡胶用量与废胶粉产量现状,比较了废胶粉改性沥青在欧美与国内的应用水平;同时介绍了废胶粉改性沥青的基本理论;并通过经济指标的比较,指出此类改性沥青在中国防水材料行业中应用是可行的,但由于目前没有类此改性沥青的标准,使废胶粉改性沥青处于不规范发展的灰色状态,政府应当制定相应的政策予以引导和规范。     

Using two-way ANOVA and hypothesis test in evaluating crumb rubber modification (CRM) agitation effects on rheological properties of bitumen

The effect of CRM aspects on rheological properties of asphalt binder such as improvement in the performance grade (PG) for low, intermediate, and high service temperatures are evaluated and the binder’s dynamic viscosity changes were studied in this research. Enhancement also resulted in the binder’s fatigue and rutting indices. At the same time, the effects of low/high shear blending conditions on the rheological properties were investigated. The effect of interactions between blending conditions and modifier content were studied by utilizing the analysis of variance (ANOVA) method and hypothesis tests.     

橡胶混凝土断裂性能试验研究

开展了橡胶混凝土三点弯曲梁断裂试验,获得了不同试件尺寸和橡胶掺量下的裂缝断裂全过程曲线,对橡胶混凝土断裂能GF及裂缝扩展K-R阻力曲线进行研究。基于数字图像相关方法,获得了橡胶混凝土试件垂直于裂缝扩展方向的全场位移和应变信息,对裂缝扩展的损伤断裂演化过程进行研究。结果表明:随试件尺寸增加和橡胶掺量提高,断裂能均呈现出上升趋势;K-R阻力曲线随试件尺寸变化表现出明显尺寸效应,橡胶掺量在0%~14%设计范围内时,K-R阻力曲线与橡胶掺量无关。     

SBS与废胶粉复合改性沥青性能试验研究

通过SBS与废胶粉沥青复合改性的几种不同配方试验,并以马来酸酐为增溶剂,以SDJ—C1型相容稳定剂来增强改性效果,分析了高温搅拌、剪切熔融的物理改性与接枝反应的化学改性相结合的复合改性机理以及用SBS、废胶粉复合改性后沥青的针入度、软化点、延度等主要性能改善作用,提出SBS、废胶粉复合改性沥青的掺量范围。     

废胶粉改性沥青改性机理及其性能研究

从沥青和废胶粉的化学成分和分子结构入手,介绍了沥青及废胶粉的种类、胶粉多种粉碎工艺以及废胶粉沥青改性的生产方法,分析了废胶粉改性沥青的改性机理,并参考国内外专家的研究结果给出了影响废胶粉改性沥青性能的各种可能因素,最后论述了废胶粉改性沥青的路用性能。