Effect of pre-heating duration and temperature conditioning on the rheological properties of bitumen

It is well known that overheating asphalt bitumen can lead to oxidation and stiffening. While heating bitumen is an essential protocol in sample preparation, it is important to identify the oven setting time and temperature for lab testing. Current AASHTO standards do not specify exact oven settings for bitumen sample preparation prior to laboratory testing. This study is evaluating the effect of oven heating duration and pouring temperature during sample preparation in the rheological properties of neat and polymer-modified bitumen (PMB). Rheological properties are measured using Rotational Viscometer, Dynamic Shear Rheometer and Bending Beam Rheometer at grade-specific testing temperatures. A neat bitumen PG64-22 and two PMB PG70-22 and 76-22 in un-aged (original) and aged conditions were tested at two temperatures: 143 °C and 185 °C for 1/2, 2 and 4 h. The effect of short-term aging by rolling thin film oven was also investigated. To investigate the rheological properties over a wide range of temperatures, temperature sweep testing was conducted from 35 °C to 110 °C at a 10 rad/s frequency. The results suggest that there was no significant difference in the viscosity, complex modulus and creep stiffness for the tested bitumen. The RTFO aging index, absolute drop of complex viscosity and temperature aging indices were used to evaluate the bitumen preparation settings. The study recommends using the 143 °C and 2-h heating for proper preparation prior to standard lab testing. The study also investigated the aging influence in rheological properties for neat and PMB using the black diagram, DSR function map, and critical-stiffness temperature.     

Effect of bitumen wax on asphalt mixture performance

This paper mainly deals with waxes which are naturally present in bitumens, and does not include synthetic waxes that sometimes are proposed as bitumen additives. The main objectives were to study the rheological effect of bitumen waxes and the impact of waxy bitumens on asphalt mixture performance, such as rutting, low temperature cracking, and water sensitivity. In the rheological characterisation of bitumens, a dynamic shear rheometer (DSR) and bending beam rheometer (BBR), as well as various conventional methods, were used. For asphalt mixtures, rutting, low temperature cracking and water sensitivity were evaluated by wheel tracking test (WTT), thermal stress restrained specimen test (TSRST), and modified Lottman test, respectively. It was found that, at high service temperatures and within the same bitumen grade, differences in rutting between the asphalt mixtures made with waxy and non-waxy bitumens were relatively small. However, the presence of wax in bitumen resulted in physical hardening at low temperatures. Using waxy bitumens, asphalt mixtures tended to show higher fracture temperature. As regards water sensitivity, no effect of the wax content in bitumen was seen. The water sensitivity was however heavily influenced by type of aggregate and to less extent by bitumen type. The present study implies that the effect of wax on bitumen quality and asphalt mixture performance depends on many factors. Those may include the chemical composition of the bitumen and particularly the nature of the wax.     

Effects of nanoclay on rheological properties of bitumen binder

Nanoclays are the new generation of processed clays of interest in a wide range of high performance composites. In other words, nanoclay is defined as clay that can be modified to make the clay complexes compatible with organic monomers and polymers. Here, it can be said that the polymeric nanocomposites are among the most exciting and promising classes of materials discovered recently. A number of physical properties can be enhanced successfully when as a polymer is modified with small amount of nanoclay on condition that the clay is dispersed at nanoscopic level. This research has accomplished a comparative rheological test on the unmodified and nanoclay modified bitumen. For that matter, so, two types of nanoclay were used: nanofil-15 and cloisite-15A. The nanostructure exfoliation of nanoclay platelets in bitumen has been studied using X-ray diffraction (XRD). In the present research, although the empirical rheological test on bitumen are penetration, softening point, ductility and ageing effect, the fundamental rheological test by dynamic shear rheometer (DSR) is conducted on modified and unmodified bitumen. Test results show that while nanoclay changes rheological properties of bitumen and increases stiffness, it also decreases angle phase and improves ageing resistances, as well.     

Influence of morphology on high-temperature rheological properties of bitumen modified with styrene-butadiene-styrene (SBS) copolymer

Different microstructures of the same polymer-modified bitumen (PMB) were obtained by subjecting the bitumen modified with styrene-butadiene-styrene (SBS) copolymer to isothermal annealing at various temperatures. The effects of the morphology on the rheological properties of SBS-modified bitumen were investigated within the high-temperature range. The PMB microstructures were quantitatively evaluated using image analysis. A dynamic shear rheometer was used to measure the rheological parameters of the PMB samples and perform the multiple stress creep and recovery (MSCR) test. A quantitative basis could be established on which to discuss the relationship between the PMB morphology and rheology. The image analysis indicated that conditioning by isothermal annealing evidently led to a difference in the microstructure of the samples. Variation of the thermal history is demonstrated to be a practical way to vary the morphology of the PMB with the same raw materials and formulation. Compared with the two-phase morphology, the single-phase microstructure tended to have a narrower linear viscoelastic (LVE) region of the PMB. Within the LVE region, especially at low frequencies, the homogenous PMB can store more energy when experiencing loadings and is more elastic. Outside the LVE region, based on the MSCR test results, the homogenous morphology could assist in reaching a higher percentage of strain recovery after the creep period.     

改性沥青的流变性和储存稳定性研究

以高富AH-50为基质沥青分别制备SBS、胶粉和EVA改性沥青,利用动态剪切流变仪(DSR)分析不同种类改性沥青动态黏弹参数(储存模量G'和损失模量G″)随频率和温度的变化,结合60℃稳态流动试验和Carreau模型表征沥青的流变性能,并用储存稳定指数IS表征不同改性剂与沥青的相容性能。结果表明:试验范围内,随频率的增加G'和G″逐渐变大,相同频率下G'明显小于G″,改性沥青以黏性成分为主,且两者的差值在低频和高温下较大;与基质沥青相比,SBS和胶粉改性沥青的临界剪切速率γc降低幅度远大于EVA改性沥青的γc,SBS和胶粉的掺加使沥青偏离牛顿流体的程度更大,对剪切的敏感性更高;SBS和胶粉与沥青的相容性较差,在相分离时SBS迁移至上段,胶粉迁移至下段,而EVA与沥青的相容性较好,体系不易发生相分离。     

Analysis of the effect of wax content on bitumen under performance grade classification

This paper describes an analysis of the effect of wax content on bitumen under performance grade (PG) classification. Wax content affects the performance and rheological behavior of bitumen. Bituminous mixtures with bitumen of high wax content tend to become very soft at high temperatures leading to rutting problem on pavement. Also the rheological behavior of bitumen has a great influence on the behavior of bituminous mixtures.To address the potential adverse effect of wax on bitumen, countries in Europe limit the wax content to 2.2% (BS EN 12606-1). In Mainland China, the standard (JTG F40-2004) classifies bitumen into three grades (Grades A, B and C). Grade A, with wax content below 2.2%, is used for highway pavement construction. Grades B and C, with wax content limits of 3.0% and 4.5% respectively, can only be used on roads with relatively lower traffic. The current binder specifications in Hong Kong Special Administration Region is based on penetration testing, which does not properly account for pavement performance. This paper assesses the effects of wax content and the rheological properties of seven types of bitumens and provides the basis for a performance grading binder standard for Hong Kong.     

引气剂对砂浆流变性的影响

采用砂浆扭矩转速测试仪研究了4种引气剂对砂浆流变性能及恒定剪切速率下扭矩经时变化关系的影响.结果表明:引气剂不改变砂浆的流变特性,即砂浆均表征为线性Bingham流体;在低流态时,引气剂大幅提高了砂浆的流动度,而在高流态时,引气剂却略微降低了砂浆的流动度;随引气剂掺量的提高,砂浆塑性黏度相应提高,低流态时屈服应力降低,高流态时屈服应力有先增后减的趋势;在恒定剪切速率下,扭矩随时间逐渐降低最后趋于稳定,且恒定剪切速率愈大,扭矩愈大.     

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.     

浅析缓凝剂对建筑石膏基本性能影响

通过在建筑石膏中应用不同类型的缓凝剂进行试验,探讨了缓凝剂对建筑石膏基本性能的影响.研究表明,缓凝剂在掺量较低的条件下可较大幅度延缓建筑石膏凝结时间,同一种缓凝剂随掺量增加其凝结时间延长.试验发现,不同缓凝剂对各种建筑石膏的适应性差别较大.同时,适量的缓凝剂对建筑石膏流动性能有一定改善作用.过量的缓凝剂会损失石膏基材硬...     

Effect of ageing on bitumen chemistry and rheology

Effect of ageing on bitumen chemistry and rheology was studied. Seven bitumens were aged according to the thin film oven test (TFOT) and the rolling thin film oven test (RTFOT). The binders were characterised using infrared spectroscopy, chromatography and dynamic mechanical analysis. Statistical correlation between different chemical parameters, as well as between chemical and rheological parameters, was examined. The relationship between TFOT and RTFOT was also investigated. It was observed that ageing influenced bitumen chemistry and rheology significantly. However, chemical and rheological changes were generally not consistent, and consequently, ageing susceptibility of bitumens may be ranked differently when different evaluation methods are used. Regardless of the type of the parameters measured, a strong correlation was observed between TFOT and RTFOT, and the two ageing procedures show similar severity.     

破乳剂对预交联颗粒凝胶界面扩张流变的影响

利用界面扩张流变方法研究星型(PES)、梳型(PEC)和支链型(PEB)非离子聚醚类破乳剂以及阳离子反相破乳剂(HY01)对预交联颗粒凝胶(PPG)界面膜性质的影响。结果表明:聚醚类非离子破乳剂通过竞争吸附,顶替界面上的PPG分子,能够降低界面扩张模量,破坏界面膜强度;星型的分子结构对界面层结构的影响效果最强;反相破乳剂通过静电相互作用影响PPG界面膜的性质,在适宜浓度形成界面复合物,界面膜强度较大,而高浓度的反相破乳剂仍然对界面膜产生破坏作用。     

Effect of different high viscosity modifiers on rheological properties of high viscosity asphalt

High viscosity asphalt (HVA) has been a great success as a drainage pavement material. However, the larger porosity of drainage asphalt mixtures weakens the cohesion and adhesion and leads to premature rutting, water damage, spalling and cracking. The purpose of this study was to investigate the rheological properties of HVA prepared using different high viscosity modifiers through conventional tests, Brookfield viscosity tests, dynamic shear rheometer tests and bending beam rheometer tests. The conventional performance results demonstrated SBS + rubber asphalt (SRA-1/2) exhibited excellent elastic recovery and low-temperature flexibility. The 60°C dynamic viscosity results indicated TPS + rubber asphalt (TRA) had the excellent adhesion. The rotational viscosity results and rheological results indicated that SRA-2 not only exhibited excellent temperature stability and workability, as well as excellent resistance to deformation and rutting resistance, but also exhibited excellent low-temperature cracking resistance and relaxation performance. Based on rheological results, the PG classification of HVA was 16% rubber + asphalt for PG76-22, 20% rubber + asphalt for PG88-22, TRA and SRA-1/2 for PG88-28. From comprehensive evaluation of the viscosity, temperature stability and sensitivity, as well as high/low temperature performance of HVA, SRA-2 was found to be more suited to the requirements of drainage asphalt pavement materials.     

石粉对3D打印白水泥基材料流变性能与力学性能的影响

3D打印水泥基材料的结构不稳定性和难于调控的流变性能制约其在建筑材料领域的发展.本文通过使用0～3％石粉取代胶凝材料调控3D打印白水泥基材料的流变性能来改善其3D结构和力学性能.研究发现:石粉的掺入会提高3D打印白水泥基材料的静态和动态屈服应力,同时使得其线性粘弹区范围增大,并显著提高浆体的弹性模量,3D打印白水泥基材...     

添加石蜡的复合充填材料流变性能实验研究

以相变温度30℃的石蜡微胶囊作为相变材料,对蓄热充填料浆的流变性能进行实验测试。研究表明:充填料浆的屈服应力随石蜡添加量和料浆浓度的增加而增大,但石蜡添加量对充填料浆屈服应力的影响更加明显;充填料浆的黏度随料浆浓度的增加而增大,减小料浆浓度有利于改善充填料浆流变性能的负面影响;充填料浆的剪切应力随石蜡添加量和料浆浓度的增加而增大,石蜡添加量对剪切应力的影响要大于料浆浓度对剪切应力的影响。     

超细循环流化床粉煤灰对碱式硫酸镁水泥力学性能的影响

针对传统碱式硫酸镁(BMS)水泥制备工艺中硫酸镁需加热溶解及粉煤灰添加后相容性差的问题,采用硫酸、超细循环流化床粉煤灰(UCFA)、氧化镁为原料制备BMS水泥,主要研究了UCFA及其掺量对BMS水泥力学性能的影响。结果表明,BMS水泥的抗压强度随养护时间的延长而提高,随UCFA掺量的增加而降低。掺10%UCFA的BMS水泥抗压强度与不掺UCFA的相近,28 d抗压强度分别达到了79.1、79.5 MPa,且具有优异的早强性能。将UCFA与硫酸反应后加入氧化镁制备BMS水泥,优先酸浸可以对UCFA进行刻蚀,通过增加UCFA表面粗糙度来促进其反应,从而改善水泥性能,并且降低生产成本,而且掺入一定量的UCFA可以增加水泥的密实度,从而提高抗压强度。     

Rheological behavior and properties of bitumen modified with polymeric coated precipitated calcium carbonate

Precipitated calcium carbonate coated by a thin layer of a polymeric compound has been used to modify bitumen and its effects on bitumen performance were studied by completing common tests. Rheological behaviors of the prepared mixtures were also investigated. The obtained results showed that using of modifier, especially in the amount of 5%, lead to increase in rutting resistance which was indicated by stiffness factor. Fourier Transform Infra Red studies emphasized the interaction between modifier and bitumen. Scanning Electron Microscopy showed no agglomeration of modifier in the mixtures. Meanwhile the results showed good storage stability for the modified bitumen.     

A comparative study on properties of porous friction course mixes with neat bitumen and modified binders

This paper summarises details of the laboratory investigation on the effect of various binders on the performance and durability of porous friction course (PFC) mixes. Three different modified binders and neat bitumen were investigated for three different aggregate gradations at two predetermined binder contents. The performance was evaluated in terms of stone-on-stone contact condition, air voids, and hydraulic-conductivity of compacted PFC mixes. The structural durability was investigated based on aged abrasion loss and moisture susceptibility. The findings provide a better understanding of the effect of each binder type on the performance and durability of PFC mixes.     

Preparation and properties of bitumen modified by EVA graft copolymer

This paper presents a laboratory study of modified bitumen containing ethylene vinyl acetate (EVA) and ethylene vinyl acetate grafted maleic anhydride (EVA-g-MAH) copolymers. When the different polymers were added, the physical properties of modified bitumens, such as softening point, ductility at low temperature and storage stability at high temperature are changed. The polymer modified bitumens (PMBs) were analyzed by thermogravimetry (TG), derivative thermogravimetry (DTG) and fourier transform infrared spectroscopy (FTIR). Thermal characterizations showed that the main decomposition stage refers to samples with modifiers exhibited a slight increase in thermal stability and the sample with the highest stability was EVA-g-MAH PMBs. FTIR analysis suggested that it is difficult to prove the EVA-g-MAH has reacted with the functional group in bitumen by FTIR spectrum. The dynamic shear rheometer (DSR) tests reported that added content of EVA-g-MAH has great effect on the rheological properties of the binder and its high temperature performance was improved while its temperature susceptibility was reduced in compare to EVA modified bitumens binder.     

双掺粉煤灰和粉状高炉矿渣的自密实混凝土流变性能的研究

研究了以水泥,粉煤灰和粉状高炉矿渣为胶凝材料的自密实混凝土的工作性参数和流变参数,并分析了它们之间的关系。结果表明,掺入10%粉煤灰和矿粉的自密实混凝土的扩展度和T50分别为625 mm和6.4 s,此时混凝土流动性最小。掺入粉煤灰和矿粉均能提高混凝土的扩展度、L仪充填比、屈服应力和塑性黏度,其中粉煤灰对混凝土体系流动性的提高更为显著。随着扩展度的升高,混凝土屈服应力呈下降趋势,而T50与塑性黏度则呈正向的变化关系。     

Effect of filler on low temperature physical hardening of bitumen

Laboratory investigations of low temperature physical hardening of bitumen using a Bending Beam Rheometer (BBR) are described. The study encompasses five bitumens, three conditions with regard to additives and three testing temperatures (−15, −25 and −30°C). As additives, two fillers, hydrated lime and calcium carbonate, were used. The effect of the fillers on the isothermal low temperature hardening was evaluated with the aid of a physical hardening index. The viscoelastic nature of the bitumens and bitumen/filler mixtures was investigated utilising the Burger model, and the Burger parameters were used to calculate dissipation energy ratios (dissipated energy over stored energy) in each BBR test. The results obtained did not indicate any significant effect of the fillers on low temperature physical hardening. Analyses of the dissipation energy ratio showed a considerable capacity for energy dissipation, even at a temperature as low as −30°C. With few exceptions, more energy was dissipated than stored during a BBR test. It appears that the dissipation energy ratio is not necessarily related to the stiffness of the binder.