Rheological evaluation of ethylene vinyl acetate polymer modified bitumens

The morphological, thermal and fundamental rheological characteristics of ethylene vinyl acetate (EVA) copolymer modified bitumens are studied in this paper. Nine plastomeric EVA polymer modified bitumens (PMBs) have been produced by laboratory mixing bitumen from three sources with an EVA copolymer at three polymer contents. The morphology, thermal properties and rheological characteristics of the EVA PMBs have been analysed using fluorescent microscopy, differential scanning calorometry and dynamic mechanical analysis using a dynamic shear rheometer, respectively. The results of the investigation indicate that EVA polymer modification increases binder stiffness and elasticity at high service temperatures and low loading frequencies with the degree of modification being a function of bitumen source, bitumen–polymer compatibility and polymer concentration. Filler type modification is evident at low temperatures, temperatures above the melting temperature of the semi-crystalline EVA copolymer and for those modified binders that do not exhibit a dominant polymer network.     

Morphology and image analysis of polymer modified bitumens

This paper presents a laboratory study of styrene butadiene styrene (SBS); ethylene vinyl acetate (EVA) and ethylene butyl acrylate (EBA) based polymer modified bitumen samples (PMBs). The PMBs have been produced by mixing a 50/70 penetration grade unmodified (base) bitumen with copolymers at different proportions. The fundamental characteristics of the PMBs have been determined using conventional methods. The morphology of the samples as well as the percent area distribution of polymers throughout the base bitumen have been characterized and determined by means of fluorescent light optic microscopy and Qwin-Plus image analysis software, respectively. The results indicate that the fundamental properties and morphology of the modified bitumens are dependent on the type of polymer and polymer content. Polymer modification improves the conventional properties of the base bitumen such as penetration, softening point, temperature susceptibility. At low polymer contents, the samples reveal the existence of dispersed polymer particles in a continuous bitumen phase, whereas at high polymer contents a continuous polymer phase is observed. Moreover it is found out that a relationship exists between the polymer content and percent area distribution of polymers.     

Evaluation of the improved properties of SBR/weathered coal modified bitumen containing carbon black

One problem of polymer modified bitumens (PMBs) is the poor compatibility between polymer and bitumens. In this paper, the improved properties of bitumen binders containing various kinds of additive including styrene butadiene rubber (SBR), weathered coal (WC) and carbon black (CB) under different concentrations are investigated. To assess the effects of the type and concentration of the additive on classical properties of bitumen binders, the softening points, penetration, penetration index (PI), ductility and Fraass breaking points before and after RTFOT aging are tested. The dynamic mechanical analysis (DMA) of these binders before and after ageing had been characterized by dynamic shear rheometer (DSR) using a combination of temperature and frequency sweeps. With higher polymer concentrations, it produced a highly elastic network which increases the viscosity, complex modulus and elastic response of the PMBs, particularly at high service temperatures. However, ageing of PMBs tended to result in a decrease in the elastic response of the modified bitumens. It also has been confirmed that the morphology observed by optical microscopy and scanning electron microscope (SEM) revealed the compatibility among SBR, WC and bitumen. The storage stability of binder was also improved significantly.     

Laboratory study on the low temperature physical hardening of conventional and polymer modified bitumens

Physical hardening is a reversible process that may influence the long-term performance of a material. In this paper, physical hardening of five unmodified and 35 polymer modified bitumens was studied using a bending beam rheometer (BBR). The modified binders were prepared by mixing 3, 6 or 9% styrene–butadiene–styrene (SBS), styrene–ethylene–butylene–styrene (SEBS), ethylene vinyl acetate (EVA) or ethylene butyl acrylate (EBA) polymers with different base bitumens. The binders were isothermally stored at low temperatures (−15, −25 and −35°C) for different times ranging from 0.5 to 32 h. The results indicated that physical hardening significantly influenced the creep response of the binders, and the hardening index and horizontal shift factor were strong functions of isothermal storage temperature. Unlike the shift factor, the hardening index did not always increase with decreasing storage temperature. At a given storage temperature, a statistical correlation was observed between the two parameters. It was also shown that degree and kinetics of physical hardening were dependent on the base bitumens, and in most cases, the effect of polymer modification was insignificant.     

Storage stability and compatibility of asphalt binder modified by SBS graft copolymer

The performance of styrene–butadiene–styrene (SBS) triblock copolymer modified asphalt binder at high temperature can be improved significantly with the addition of SBS-g-M grafted with vinyl monomer under γ-rays irradiation. The dynamic mechanical properties of SBS modify asphalts binder before and after graft has been characterized by use of dynamic shear rheometer. It has been found that the added content of SBS-g-M 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 with SBS modified asphalts binder. It also has been confirmed that the morphology observed by fluorescence microscopy revealed the compatibility between SBS-g-M and asphalt and the storage stability of binder was improved significantly compared with SBS modified asphalt binder. As a consequence, the use of SBS grafted with polar monomer can be considered a suitable alternative for modification of binder in pavement.     

石油沥青油毡的耐低温性能

讨论了油毡的耐低温性能,石汕沥青改性的技术路线。介绍了丁苯橡胶改性沥青油毡的研究及其技术性能,指出今后在寒冷地医防水工程中应大力推广应用改性沥青油毡。     

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.     

Effect of wax on basic and rheological properties of bitumen with similar Penetration-grades

This paper presents the results of a study on the wax content, the basic and rheological properties of seven unmodified bitumens with Penetration-grades 60–70 and the effect of wax on these bitumens. Among the bitumens, one (currently used in Hong Kong) was supplied by a manufacturer in Singapore while the other six bitumens were obtained from manufacturers in Mainland China. The results of the basic tests show that all bitumens are Penetration-grade 60–70 and have similar basic properties. The test results comply with the Hong Kong bitumen specification. However, the wax contents of some of the bitumens manufactured from crude oil deposited in China are relatively high. The test results obtained by the dynamic shear rheometer further indicate that the bitumens with low wax content performed better than those with high wax content under a high temperature environment. The test results exhibit relatively good correlation between the wax contents and the rheological properties of the bitumens. Therefore, standards and procedures should be established in Hong Kong to specify requirements on wax content or Performance-grade for bitumen used in road paving.     

氰尿酸三聚氰胺与氢氧化镁协效阻燃EVA的研究

通过锥形量热器试验、热重分析、拉曼光谱分析、氧指数、垂直燃烧试验及流变性能测试，研究了氰尿酸三聚氰胺(MCA)和氢氧化镁在无卤阻燃乙烯醋酸乙烯共聚(EVA)混合物中的协效阻燃作用。锥形量热器试验结果表明，一定量的MCA可明显延缓材料的点燃时间，降低热释放速率；垂直燃烧和氧指数试验结果显示，MCA可有效改善材料的熔体滴落性能，增强火焰的自熄能力，但会降低材料的氧指数；流变性能测试结果表明，McA的加入可明显降低材料的熔体粘度，改善材料的可加工性；热重分析结果显示，MCA可延缓EVA树脂的热氧降解并能促进炭层的生成；拉曼光谱证明了阻燃材料形成的炭层具有类石墨结构。MCA与氢氧化镁的协效阻燃效果归因于惰性气体保护层和炭层的形成。     

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.     

Technical study on the Iranian Gilsonite as an additive for modification of asphalt binders used in pavement construction

In this research, effects of the Iranian natural bitumen (gilsonite) on two types of asphalt binders produced in the country with the performance grades of PG58-22 and PG64-22 were studied according to superpave performance grading (PG) system. Results of conducted tests on the modified asphalt binders with 4%, 8% and 12% gilsonite show that although addition of gilsonite to base bitumens can cause improvement in high performance temperature (HT) of mentioned bitumens, it has no positive impact on low performance temperature (LT) of them.     

EVA乳液改性岩棉-砂浆界面及其耐碱侵蚀性研究

使用EVA乳液对岩棉-砂浆界面进行改性以增强其结构稳定性,研究了EVA改性岩棉-砂浆界面的防水性能、EVA乳液对岩棉抹面砂浆水化过程的影响、EVA改性岩棉的耐碱侵蚀性.结果表明:EVA乳液在碱性介质中发生水解反应抑制了前期水化硅酸钙(C-S-H)絮状凝胶的生成,延缓水泥的水化进程.后期C4H6CaO4·2H2O随着时间...     

一种温拌剂对SBS改性沥青性能影响研究

研究了一种自制温拌剂对SBS改性沥青的物理性能和燃烧性能的影响,并通过动态剪切流变仪(DSR)温度扫描试验分析自制温拌剂对SBS改性沥青流变性能的影响。针入度、延度、软化点试验结果表明:自制温拌剂的加入能使沥青的稠度增加,能降低沥青的温度敏感性,提高沥青的高温性能;极限氧指数试验结果表明:温拌剂的加入能提高SBS改性沥青的阻燃性能;温度扫描试验结果表明:与SBS改性沥青相比,掺加6%温拌剂的SBS沥青有更大的复合模量、车辙因子、疲劳因子,更小的相位角,这说明温拌剂的加入提高了SBS改性沥青的车辙性能和疲劳性能。     

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.     

Rheological properties and storage stability of bitumen/SBS/montmorillonite composites

Styrene–Butadiene–Styrene triblock copolymer is commonly used for modifying physical, mechanical and rheological properties of bitumen. Because of the poor compatibility between SBS and bitumen, SBS modified bitumen is not storage stable at high temperature. To obtain more compatibility between SBS and bitumen, several methods have been suggested. In this study, organophilic montmorillonite/SBS modified bitumen mixtures were prepared by melt intercalated blending. Physical and rheological properties of polymer modified bitumen were compared before and after adding nanoclay to the bitumen. Results showed that the presence of nanoclay improves the storage stability of PMB significantly without adverse effect on other properties of it. The structure of OMMT/SBS/bitumen blend was characterized by XRD. The spectra indicated that proper dispersion of OMMT in SBS led to a homogenous blend which is named exfoliated structure. The result of storage stability test showed that the difference in softening point was in good accordance with ASTM standard limitation which means that OMMT can improve the storage stability of PMB. Also morphological analysis confirmed storage stability results.     

Chemical interaction between EVA and Portland cement hydration at early-age

Ethylene/vinyl acetate (EVA) copolymer, as latex or redispersable powder, is added to mortars and concrete to improve the fracture toughness, impermeability and bond strength to various substrates. The physical and chemical interactions were already proved after one day of hydration but during the first hour just the physical interaction was identified and some evidences of a chemical interaction. The aim of this paper was to evaluate the chemical interaction between EVA and Portland cement during the first hours of hydration in the thermogravimetric analysis. The results confirmed that the EVA hydrolyses in pH alkaline and consumes calcium ions from the solution, forming an organic salt (calcium acetate), reducing the calcium hydroxide content. And, its interaction occurred in the first 15 min of hydration.     

废轮胎媒介-A2/O工艺的脱氮性能研究

将废轮胎切碎后与乙烯-乙酸乙烯酯共聚物(EVA)及沸石按一定比例混合制成一种辅助媒介,并添加至A2/O工艺的好氧段,考察了对脱氮效果的影响.试验结果表明,投加该媒介后可在好氧段内产生大量的微缺氧区,当维持污泥浓度为3～4 g/L、DO为1.6～2.4 mg/L以及进水C/N值为9～11、pH值为7.7～8.1的条件下,取得了较好的同步硝化反硝化效果,使脱氮能力提高了约13%.     

Laboratory comparison of the crumb-rubber and SBS modified bitumen and hot mix asphalt

The use of crumb rubber (CR) recycled from waste tires using an ambient grinding process was evaluated at two stages in asphalt formulation. First, bitumen modified with crumb rubber was evaluated by rotational viscometery (RV), dynamic shear rheometry (DSR) and conventional binder tests. Hot asphalt mixtures including crumb-rubber-modified bitumen were then evaluated by determining the permanent and fatigue characteristics and stiffness moduli of control and modified mixtures. The properties of the crumb-rubber-modified bitumen and asphalt mixtures were compared to different contents of styrene–butadiene–styrene (SBS) modified-bitumen and asphalt mixtures. The tests showed that to achieve the same performance, as with SBS-modification, the CR-content must be used at much higher than SBS. 8%-CR modification was determined as the most suitable content according to both binder and mixture tests.     

岩沥青改性沥青及混合料性能研究

介绍了天然沥青的种类与天然岩沥青的特点。对三种天然岩沥青改性沥青进行了沥青的技术性能试验、沥青混合料的马歇尔试验、高温车辙试验、低温弯曲试验和残留稳定度试验等,结果表明：在沥青中掺入5%的岩沥青,可使沥青及沥青混合料的高温性能得到明显的改善,且掺加工艺简单方便、价格低廉,值得推广应用。     

Preparation and properties of an environment friendly polymer-modified waterproof mortar

A new type of environment friendly polymer-modified waterproof mortar (PMWM) was developed through adding ethylene vinyl acetate (EVA)/vinyl acetate–vinyl ester of versatic acid (Va–VeoVa) mixture (re-dispersible emulsion powder), mine tailings, quartz sand and additives to the eco-cement, which was prepared by grinding the mixture of steel slag, blast-furnace slag, fly ash and activator. The optimal material proportioning of PMWM was obtained based on the Orthogonal experiment: re-dispersible emulsion powder, 11 wt.%; cement–sand ratio, 1:3.5 (tailings/quartz sand = 1:3); EVA/Va–VeoVa ratio, 1:1; water reducing agent (based on the cement weight), 1.5 wt.%. The product conforms to JC/T 984-2005 (China professional standard: Polymer–cement waterproof mortar). Some factors influencing the characteristics of the mortar were discussed.