Effect of warm mix additives on the interfacial bonding characteristics of asphalt binders

The quality of the interfacial bonding between asphalt binder and aggregates plays a significant role in determining the durability of asphalt mixtures. Warm mix asphalt (WMA) modifiers have been used extensively in the last decade primarily to reduce production and compaction temperatures as well as to improve workability of asphalt mixtures. This study aimed to provide better understanding of the effects of these WMA modifiers on the interfacial bonding between asphalt binders and aggregates. The evaluation focused on measuring surface energy of binders in unaged and aged states and aggregates and then calculating energy parameters that describe the potential of a given asphalt-aggregate combination to resist fatigue cracking and moisture damage. Results show that the combination of asphalt-WMA additive, as well as the content applied of WMA additive has a significant impact on the fatigue cracking and moisture damage resistance. The results suggest that it is poor practice to use a given type and percentage of WMA modifier without regard for binder type. Instead, test methods are recommended to evaluate the compatibility of asphalt binder, WMA additive type/content, and aggregates for improved performance at different conditions.     

Linear and nonlinear viscoelastic and viscoplastic analysis of asphalt binders with warm mix asphalt additives

Warm-Mix Asphalt (WMA) is a widely used product, which proved a contribution to the reduction in asphalt mixing and compaction temperatures. This reduction leads to lower fuel consumption and smoke emission in asphalt plants. Most of the characterisation of binders used in WMA has focused in the past on measuring linear viscoelastic properties and associated Superpave parameters. Several studies have shown that the average stresses and strains of the asphalt mixture remain mostly within the linear viscoelastic response. However, localised strains in the binder phase of the mixture could reach values high enough to induce nonlinear viscoelastic and viscoplastic deformations. Therefore, this study focuses on an experimental and analytical evaluation of linear, nonlinear viscoelastic and viscoplastic responses of selected binders modified for use in WMA. The first part of the paper analyses the linear viscoelastic material properties and their ability to evaluate permanent deformation resistance. Then, the non-recoverable creep compliance parameter obtained from the Multiple Stress Creep Recovery (MSCR) test is analysed to assess the nonlinear response and permanent deformation of asphalt binders. The paper utilises a nonlinear plasto-viscoelastic (NPVE) approach to assess and quantify the nonlinear plasto-viscoelastic response of binders by separating the recoverable and irrecoverable strains measured in the MSCR test. Two WMA additives were included in this study by mixing them with polymer-modified and unmodified asphalt binders. Analysis of results showed that the NPVE approach captured a higher percentage of recovery than the NLVE approach. However, binder’s performance evaluation and ranking did not change by adopting the NPVE approach. The nonlinear viscoelastic parameters provided insight on the behaviour of asphalt binders mixed with WMA additives during loading cycles. Sasobit showed higher influence than Advera on binders in resisting permanent deformation by increasing the recoverable strain during the unloading phase.     

表面活性类温拌混合料施工在隧道工程中的应用

对表面活性温拌沥青混合料在隧道工程中的应用进行了介绍,主要阐述了温拌混合料的施工要点,并结合项目特点,指出施工单位采用的温拌沥青技术既可提高混合料的压实性能,又能显著降低沥青混合料有害气体的排放,值得推广应用。     

Java手机短信平台研究

无线消息传递的实现扩展了J2ME应用程序的联网及I／O能力,使得通过用GSM网络上的消息传递服务如短信服务(SMS)进行发送与接收消息成为可能。文章通过对手机短信互发与从网站向手机发送短信这两部分,对手机短信的原理进行分析,并分别对短信的发送程序进行了编程及实现。该应用在电子商务领域具有较广的应用前景。     

Moisture susceptibility of warm mixed-reclaimed asphalt pavement containing Sasobit and Zycotherm additives

In this research, the influence of Sasobit and Zycotherm on the properties of reclaimed asphalt pavement (RAP)-warm mix asphalt (WMA) was investigated. Moisture susceptibility was evaluated applying the resilient modulus ratio, the indirect tensile strength ratio, and the fracture energy ratio. Laboratory testing results indicated that Zycotherm mixtures had more resistance to moisture damage than Sasobit WMA and hot mix asphalt (HMA) mixtures. The stiffness of mixtures increased dramatically by increasing the amount of RAP and using Sasobit exacerbated this problem.     

Use of Fourier transform infrared spectroscopy to study ageing characteristics of asphalt binders

The present study aims at studying ageing characteristics of conventional bitumen, polymer modified bitumen (PMB) and warm mix asphalt (WMA) by using FTIR. Results of obtained FTIR spectrum were quantified by calculating different indices and finally based on these indices ageing index of the binders for short- and long-term ageing were calculated. Results showed ageing increased amount of complex and high molecular weight components of the binders. PMB was found to have greater ageing resistance than conventional asphalt binders. In case of WMA, results found to be inconclusive, requiring further investigation.     

Field performance of top-down fatigue cracking for warm mix asphalt pavements

As a result of repeated rehabilitation efforts over the past few decades, often asphalt pavements have become deep-strength pavements. Consequently, top-down cracking has become a primary distress type. In particular, the top-down cracking performance of warm mix asphalt (WMA) pavements, i.e. how does it compare with similar hot mix asphalt (HMA) pavements is largely unclear mainly due to the lack of field performance data. This paper presents an effort of monitoring the top-down cracking performance of 28 pavement projects including WMA pavements and their corresponding HMA control pavements with service lives ranging between 4 and 10 years. These pavements cover different climate zones, WMA technologies, service years, pavement structures and traffic volume levels. Two rounds of distress surveys were conducted at a two-year interval, and the material (asphalt binder and mixture) properties of the pavements were determined using field cores. The top-down cracking performance of the HMA and WMA pavements was compared based on the first and second round distress surveys. It was found that the HMA and WMA pavement in general exhibited comparable performance. The significant determinants (material properties) for top-down cracking were determined, which were vertical failure deformation of mixes measured at 20 °C from indirect tension test.     

基于微观特性的温拌沥青老化特性研究

选用两种不同温拌剂(Sasobit和Evotherm),分别对三种基质沥青进行改性,并采用布氏粘度、渗透凝胶色谱(HP-GPC)及原子力显微镜(AFM)对其老化特性进行研究.结果表明:相对于基质沥青,温拌沥青(WMA)在老化前后粘度都相对降低,老化时间越长,粘度越大;老化后沥青的GPC曲线左端明显凸起,且老化时间越长,曲线左端凸起越高,LMS值越大,且LMS值与粘度具有良好的相关性,沥青中大分子含量(LMS)增加,沥青粘度也相应增大.通过老化前后沥青的AFM形貌图观测可知,在相同条件下,相对于基质沥青,温拌沥青可有效防止沥青老化;Sasobit温拌剂对沥青的改性作用明显优于Evotherm温拌剂.     

能实现音频检测的数字音频码流保护系统

随着数字技术在广播电视领域的广泛应用,多路数字音频编码复用技术也得到普遍使用,本文介绍了综合应用多种监测技术,实现对数字音频码流内每一套音频节目的实时监测,并可以根据监测结果自动实现主备切换的数字音频码流保护系统．     

在线音乐网站的设计与实现

探讨了基于ASP技术和Access数据库实现在线播放WMA音乐文件的方法,对其中的关键技术进行了详细分析。通过使用ASP的数据库存取组件ADO的内部对象实现了对网站后台数据库中音乐文件的显示和播放。