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.     

橡胶颗粒沥青混合料高温稳定性研究

通过在沥青混合料中掺入不同含量的废旧橡胶颗粒进行车辙试验研究,分析了废旧橡胶颗粒沥青混合料抗车辙的路用性能,从而验证了以废旧橡胶颗粒作为骨料的形式掺入沥青混合料中,其高温稳定性比未掺入废旧沥青混合料要好的观点。     

Effect of crumb rubber characteristics on crumb rubber modified (CRM) binder viscosity

Asphalt binder viscosity is of great importance during the production process of hot mix asphalt mixture as typically asphalt plants will store binders between 149 °C and 177 °C. SHRP guidelines state that asphalt binder viscosity must not exceed 3 Pa s. Therefore, given the documented increases in asphalt viscosity when modified with crumb rubber modifier (CRM) it is necessary to produce asphalt binder that fulfills the SHRP criteria while not exceeding plant mixing and storing requirements. This paper reports the results of an investigation of the importance of CRM properties on viscosity of CRM binder. Two binder sources were modified at four concentration levels using four different crumb rubber sources; the viscosities of the produced binders were evaluated by AASHTO T 316. Crumb rubber properties were evaluated by elemental analysis using a scanning electron microscope (SEM) and by determination of glass transition temperature (T_g) using a differential scanning calorimeter (DSC). In general, results indicate that processing procedure and tire type plays an important role in the determination of CRM binder viscosity.     

橡胶集料改性混凝土高温后力学性能试验研究

通过对三种不同橡胶掺量的混凝土试件进行高温试验,研究了橡胶混凝土经历不同高温作用后,试件表观变化现象、质量损失、抗压强度和劈裂抗拉强度,以及弹性模量的衰减规律。试验结果表明,高温作用后,橡胶集料改性混凝土的各项力学指标衰减随橡胶掺量的增加而增大,随受热温度的升高而增大,500℃高温作用后出现陡降。     

Influences of crumb rubber size and type on reclaimed asphalt pavement (RAP) mixtures

Over the years, recycling has become one of the most attractive pavement rehabilitation alternatives, and different recycling methods are now available to address specific pavement distresses and structural needs. The objective of this study was to investigate and evaluate the engineering properties of crumb rubber size and type influences on reclaimed asphalt pavement (RAP) mixtures. The experimental design for this study included the use of three rubber sizes and two rubber types (ambient or cryogenic) in the mixture containing 25% RAP mixtures. In this study, the results of the experiments indicated that the addition of crumb rubber was helpful in increasing the voids in mineral aggregate (VMA) in Superpave mix design and improving rutting resistance of mixture regardless of rubber size and type. On the other hand, indirect tensile strength (ITS) values show no significant difference for mixtures made with three type rubber sizes. However, the increase of rubber size, regardless of rubber type, reduced the resilient modulus values but extended the fatigue life of the modified mixtures.     

高强橡胶混凝土单轴受压力学性能的试验研究

对高强橡胶混凝土进行了单轴受压试验,得到了含不同掺量、不同粒径的高强橡胶混凝土的应力-应变曲线.分析了橡胶掺量、胶粉粒径对高强橡胶混凝土的单轴抗压强度、极限应变、初始弹性模量和破坏形态的影响.研究结果表明:橡胶掺量对高强橡胶混凝土的单轴抗压强度、极限应变、初始弹性模量和破坏形态的影响都比较明显;胶粉粒径对高强橡胶混凝土的强度、初始弹性模量和破坏形态有一定的影响,对极限应变的影响不明显.     

胶粉改性沥青混合料低温特性试验研究

为研究胶粉改性沥青混合料低温抗裂性能,采用沥青混合料小梁弯曲蠕变试验对胶粉改性沥青混合料的低温性能进行检验,并以SBS改性沥青混合料作为参照,结果表明,胶粉改性沥青混合料的感温性较弱,材料力学性能受温度影响较小,与SBS改性沥青混合料相比低温不易开裂。     

高强橡胶混凝土单轴受压本构关系的试验研究

对高强橡胶混凝土进行了单轴受压试验,得到了不同掺量、不同胶粉粒径的高强橡胶混凝土的应力-应变曲线。分析了胶粉掺量及粒径对高强橡胶混凝土本构曲线的影响,提出了高强橡胶混凝土轴心抗压强度的计算公式。根据实测的应力-应变曲线特点,提出了包含上升段本构参数A和下降段本构参数α的高强橡胶混凝土单轴受压本构方程。研究发现,A和α随着胶粉掺量的增加而减小,胶粉的粒径对参数A和α影响不明显,给出了参数A和α的计算公式。     

废胶粉用于防水改性沥青的研究

研究了不同废胶粉及其不同掺量对沥青的改性效果，认为胶粉添加量在18％～24％范围内，沥青性能改善明显；体系中添加配合剂时，性质会发生一系列的变化：软化点升高，低温柔性有所改善。     

胶粉/SBS复合改性高模量沥青混合料性能研究

胶粉/SBS复合改性综合了橡胶沥青和SBS改性沥青的优势,能显著改善混合料的高低温性能。采用残留稳定试验、冻融劈裂试验、低温弯曲试验、车辙试验、四点弯曲疲劳试验和动态模量试验,分析胶粉/SBS复合改性高模量沥青混合料的路用性能及动态力学特性,并与硬质20#高模量沥青混合料及SBS改性沥青混合料进行对比。结果表明,胶粉/SBS复合改性高模量沥青混合料的水稳定性、高低温性能、抗疲劳性能及动态模量值更优,且各项指标满足高模量沥青混合料要求。     

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。     

橡胶集料混凝土梁正截面抗裂性能研究

橡胶集料混凝土塑性较大,普通混凝土的抗裂度公式不再适用.在试验的基础上,对相关参数加以修正,根据正截面受弯承载力计算理论,运用混凝土力学分析方法,导出橡胶集料混凝土梁的开裂弯矩计算公式,计算值与试验值符合良好.     

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。     

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.     

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。     

橡胶集料混凝土的试验研究及工程应用

本文针对橡胶集料混凝土若干力学性能进行了试验研究,结果表明橡胶集料混凝土的强度随着橡胶集料掺量的增加呈下降趋势且强度发展较普通混凝土缓慢,橡胶集料混凝土的弹性模量仅为普通混凝土的38%至88%,峰值轴压应变为普通混凝土的1.2至1.5倍,相应的能量吸收超过普通混凝土10%至30%.试验同时发现橡胶集料混凝土试件破坏前均经历了相当大的变形,表现出很好的延性特征.并根据橡胶集料混凝土的自身材性特点介绍了其在工程方面的应用和展望.     

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.