浅谈泡沫沥青冷再生混合料在路面施工中的应用

泡沫沥青厂拌冷再生混合料是指将原沥青混凝土路面铣刨后,将铣刨料运回拌和站,经破碎、筛分并按一定的比例加入石屑、水泥等外掺剂,另外喷入由专用设备对沥青进行发泡后的泡沫沥青,边拌和边喷洒组成的拌和均匀的混合料。然后运送至道路施工现场,使用摊铺设备进行摊铺、经碾压成型后,形成路面结构层的一部分。     

特种陶瓷成型方法

成型技术是制备陶瓷材料的一个重要环节.特种陶瓷成型方法总的来说可分为干法成型和湿法成型两大类,干法成型包括钢模压制成型、等静压成型、超高压成型、粉末电磁成型等;湿法成型大致可分为塑性成型和胶态浇注成型两大类;近些年来固体无模成型技术在特种陶瓷的成型研究中也取得了较为快速的发展.对特种陶瓷的这些成型方法进行了简要介绍,指出了各种成型方法的优缺点,并展望了特种陶瓷成型方法的发展趋势.     

沥青混合料车辙试验机校准方法研究

沥青混合料车辙试验机作为检测设备应用广泛,但目前尚无统一的国家计量技术规范和行业计量技术规范,其检测数据的准确性、有效性大打折扣。文章根据沥青混合料车辙试验机的工作原理,分析其计量特性考察项目,详细探讨了校准方法,为制定统一的沥青混合料车辙试验机校准方法奠定了基础。     

掺生物沥青的乳化沥青冷再生混合料强度特性及路用性能研究

再生剂对老化沥青混合料的改善作用,可使老化沥青混合料的路用性能在一定程度上恢复还原。在进行再生沥青路面混合料设计之前,必须对旧料中沥青的含量及性质、旧料的级配组成及技术指标等进行全面了解,以确定回收的废旧沥青和旧集料性质,为新添集料性质、级配提供掺量依据。本文分析了掺生物沥青的乳化沥青冷再生混合料的概况,对原材料配比和乳化沥青制备情况进行了阐述,接着对不同的生物重油掺量乳化沥青再生混合料力学强度进行实验分析,最后总结了不同生物质重油掺量乳化沥青冷再生混合料路用性能,旨在为提高高速公路的质量以及延长其使用寿命提供保障。     

低温成型抗车辙功能沥青混合料路用性能研究

我国寒冷地区热拌沥青混合料的施工季节短,为了减少低温条件下压实成型对沥青路面使用性能的不利影响,开展掺加低温施工高性能添加剂的沥青混合料路用性能的研究工作。研究了掺加低温高性能添加剂的沥青混合料的压实成型工艺,通过室内车辙实验、水稳定性实验和力学性能实验分析其路用性能特点。结果表明,掺加PRLT添加剂的沥青混合料能够在相对较低的温度条件下成型,提高了沥青混合料的可压实性,可以延长热拌沥青混合料的施工季节,适用于寒冷地区的沥青路面建设;该添加剂显著提高沥青混合料高温抗车辙性能,并一定程度上改善低温抗裂性能、抗水损害性能和力学性能。     

两种粘结料对泡沫沥青冷再生混合料性能的影响

通过加速加载试验、低温弯曲试验、飞散试验研究了泡沫沥青和水泥两种粘结材料对泡沫沥青冷再生混合料(CRMFA)长期高温抗变形能力、低温抗裂性以及抗松散性能的影响。研究结果表明:对CRMFA的长期高温抗变形能力而言,存在一个最佳泡沫沥青用量;增加水泥掺量有助于提高CRMFA的长期高温抗变形能力。CRMFA的低温柔韧性随泡沫沥青用量的增大而提升,但随水泥掺量增加呈抛物线变化规律,为保证CRMFA具有良好的低温抗裂性能,水泥掺量宜小于2wt%。CRMFA的抗松散性能较差,增加泡沫沥青用量可有效降低其松散性;水泥掺量在1.5wt%~2.5wt%时,对CRMFA抗松散性的改善作用不显著。     

冻融循环作用对乳化沥青冷再生混合料抗剪性能的影响

针对乳化沥青冷再生混合料进行反复冻融循环试验,测定不同冻融循环周期后试件的空隙率、贯入剪切强度及无侧限抗压强度,分析冻融循环作用下乳化沥青冷再生混合料力学性能、抗剪强度参数的衰变规律,同时通过扫描电镜(SEM)观察经冻融循环后的混合料微观形貌。结果表明:经过10次冻融循环后,空隙率增大1%,力学强度下降幅度达到20%,而对冷再生混合料粘聚力影响最大,其下降幅度可达到60%;冻融循环过程中产生的膨胀应力及温度应力破坏了混合料内部水泥水化产物形成的立体网状结构,导致冷再生混合料力学性能及抗剪强度参数的衰减。     

纳米陶瓷的成型方法研究进展

简述了纳米陶瓷的各种成型方法,如冷等静压成型、超高压成型、原位成型、离心注浆成型、凝胶直接成型、渗透固化法等等,并列举了若干研究实例,由于各种方法都有其局限性,所以新的成型方法将成为研究的重点.     

浅析沥青混合料配合比设计方法

沥青混合料的配合比设计直接关系到沥青混合料的路用性能,对于沥青路面的使用性能也有重要的影响,因此必须加强沥青混合料配合比设计研究。本文首先论述了沥青混合料配合比设计的原则,进而提出了沥青混合料的配合比设计方法,以期为相关从业人员提供合理的参考。     

热态沥青混合料路面振动压实过程ANSYS模拟研究

为研究热态沥青混合料压实过程的力学行为和变形特征,通过分析沥青混合料的振动压实机理,建立三自由度压路机非线性力学模型和运动方程,用ANSYS软件建立路面振动压实过程的力学模型。考虑混合料的变形是与率相关的应力-应变的非线性蠕变行为,运用Origin软件非线性回归来分析MTS压实试验的复杂蠕变参数,得到0.6MPa不同荷载循环下的蠕变参数值;混合料塑性流动非常显著,成为不可逆的流动变形,c1越大,蠕变越明显,塑性变形就大,c3越小,蠕变越小,塑性流动变小。结果表明:热态沥青混合料在振动冲击的作用下,塑性变形增加得很快,卸载后的永久变形使得混合料压实,形成"骨架-密实"结构;一定荷载作用次数后,混合料处于无法压实的状态。可见,混合料必须在一定的温度范围和压实功的作用下才能获得有效压实。     

Influence of asphalt compaction procedure on 3D deformation properties

In this study, the effect of various laboratory procedures for compacting hot-mix asphalt to form test specimens is investigated. Based on the triaxial cyclic compression test (TCCT) according to the European specification EN 12697-25, the resistance to permanent deformation of the specimen obtained from different types of laboratory compaction is studied. The deformation behaviour of the laboratory-compacted specimens is always compared with the deformation properties stated in TCCT for the asphalt mix specimen taken from on-site roller-compacted road pavement. As a result, the effect of the choice of laboratory compaction procedure on the resulting deformation behaviour in TCCT is assessed.     

Effect of laboratory foamer on asphalt foaming characteristics and foamed mixture properties

In the United States, mechanical foaming is the most popular method for producing warm mix asphalt, which is the latest technology implemented to reduce the production temperature and/or enhance the compactability of asphalt mixtures. Three commonly used commercially available laboratory foamers to produce asphalt foams include the Wirtgen WLB 10S (Wirtgen foamer), the InstroTek Accufoamer (InstroTek foamer) and the Pavement Technology Inc. Foamer (PTI foamer). Though these foamers have been widely used in research studies and construction practice, it is still unknown whether they produce asphalt foams with the same quality and quantity. In this study, asphalt foaming characteristics produced by these three laboratory foamers were measured using a non-contact test set-up consisting of a laser device and a digital camera, and compared in terms of instantaneous volume expansion, foam stability and surface area evolution of foam bubbles. Additionally, the workability, coatability and mechanical performance of foamed mixtures prepared using these same laboratory foamers were compared against the conventional hot mix asphalt (HMA). Test results indicated that foamed asphalts produced by the Wirtgen foamer had the largest volume expansion and greatest foam stability, followed by those produced by the InstroTek foamer and the PTI foamer. The optimum foaming water content (W_opt) was determined for each laboratory foamer based on the workability and coatability results of the corresponding foamed mixtures. In addition, the performance evaluation of the foamed mixtures produced at W_opt values indicated equivalent mixture stiffness but greater moisture susceptibility as compared to the conventional HMA.     

Influence of different roller compaction modes on asphalt mix performance

This study aims to investigate the relationship between different roller compaction modes and resulting mechanical performance. In order to accomplish these objectives, a trial asphalt pavement section was observed and monitored both during the paving and compaction processes. Asphalt mix was sampled from the paver to be used later in laboratory and evaluate the differences between compaction in-field and laboratory. Asphalt concrete mixes were prepared and compacted in the laboratory using a steel roller compactor, with varying factors that influence compaction in terms of compaction modes (static, vibratory and a combination of both), as well as effort and temperatures in order to attempt to simulate field compaction conditions. The identification of a harmonised compaction procedure for specimen fabrication able to produce mixtures with stiffness properties resembling field compacted mixtures was also investigated based on the performance-based test results.     

Algorithm development for the application of ground-penetrating radar on asphalt pavement compaction monitoring

Ground-penetrating radar (GPR) is a promising non-destructive technique to be applied on monitoring the density change during asphalt pavement compaction. The utmost challenge of this application is the unknown effect of surface moisture, sprayed by the compactor during compaction, on GPR signals. To extract density information without the effect of surface moisture, a correction algorithm based on reference scan approach was developed. To evaluate the performance of the algorithm, a full-scale test site was constructed with compaction pass number from 0 to 10, and a large amount of GPR data were collected from the pavement with different surface moisture contents. A total of 22 cores were extracted for validation purposes. After applying the algorithm, it was found that the average density prediction error was reduced significantly. By using correction algorithm together with the density model, the density of asphalt pavement was obtained with high accuracy.     

Effect of particle size distribution on green properties during high velocity compaction

Iron powders with two different particle size distributions were compacted by high velocity compaction. The influences of particle size distribution and impact velocity on green properties, including green density, springback, tensile strength and bending strength etc., were studied with scanning electron microscopy (SEM) and a computer controlled universal testing machine. The results show that the particle size distribution and the impact velocity strongly affect its properties. Wider size distribution results in green compact with higher density and better strength. Furthermore, springback of compacts is lower produced by the powder with wider size distribution, especially for radial springback. As impact velocity increases, its green density and green strength gradually increases, but the increasing rate of density decreases gradually. No special relation is found between springback and impact velocity. In addition, the axial springback and the bending strength are higher than the radial springback and the tensile strength, respectively.     

国产环氧沥青混合料固化强度增长规律研究

研究了环氧沥青混合料的强度形成机理,在此基础上对影响环氧沥青混合料强度的两个重要因素即混合料的容留时间、养生温度进行了研究,确定了不同温度下环氧沥青混合料的容留时间范围及强度增长规律;采用差示扫描量热法（DSC）测得环氧沥青结合料在不同升温速率下的动态DSC曲线,通过非线性回归求得固化动力学关键参数,建立环氧沥青结合料的固化反应模型。研究结果可以指导环氧沥青混合料的生产与施工,同时对铺装层开放交通时间的确定有参考意义。     

高温持续荷载作用下复合纤维对沥青混合料稳定性的影响

为了研究复合纤维沥青混合料在高温持续荷载作用下的稳定性,根据工程中常用纤维和已有研究成果,选用了三种复合纤维,对沥青混合料的变形发展规律及内部空隙结构特征开展试验研究。首先采用加速加载试验,对不掺加纤维和掺加复合纤维的沥青混合料在高温持续荷载作用下的横断面变化和车辙深度进行分析;再利用X-CT扫描技术与VG软件三维重构功能,研究不同纤维沥青混合料的空隙组成及形态特征演变规律。结果表明:高温持续荷载作用下,掺加纤维混合料横断面变形呈现"W"字型,不同纤维在沥青混合料中发挥"加筋"、"增黏"、"吸油"的协同作用,能显著减小沥青混合料的流动变形,且掺加复合纤维III的混合料流动变形最小;掺加不同复合纤维的沥青混合料可采用y=a-b·ln(x+c)进行车辙深度预估。加速加载试验后,掺加三种复合纤维的沥青混合料空隙率最大仅增加7%,分形维数仅降低不到0.5%,表明掺加三种复合纤维基本不改变沥青混合料的空隙结构特征,而且在高温持续荷载作用下,可较好地保持沥青混合料内部空隙的三维形态特征,进而改善沥青混合料的抗变形能力。     

Influence of compaction direction on performance characteristics of roller-compacted HMA specimens

Hot mix asphalt (HMA) slabs produced by roller compaction can be used to core and cut specimens for further testing. The relation between the direction of compaction and testing in the laboratory is not always the same relation as it is between the direction of compaction and actual loading in the field. This paper presents outcomes of a study analysing the influence of the compaction direction on performance characteristics of roller-compacted HMA specimens. Performance parameters of a base layer mix are obtained from performance-based test methods, including high-temperature, stiffness, fatigue and low-temperature tests. The relation between direction of compaction and specimen testing is varied in all three dimensions to find relevant influences. From the results, it can be concluded that all obtained performance parameters are sensitive to the anisotropy of the material due to compaction, especially for stiffness and fatigue performance. For the high-temperature performance, specimens from path- and force-controlled compaction were compared. The applied compaction work rather than the compaction method is linked to the difference in the corresponding results. The uniformity of the compaction in terms of the variation of bulk density of the specimens reflects on the scattering of test results.     

Estimation of optimum binder content of recycled asphalt incorporating a wax warm additive using response surface method

This paper presents a new approach to estimate the optimum binder content (OBC) of recycled asphalts (RAs) incorporating a warm mix additive based on the interaction effects of compaction temperature, RA content and binder content using volumetric and strength characterisation. The experimental design was developed using response surface method (RSM) based on central composite design for various compaction temperatures (130–160 °C), RA contents (30–50%) and binder contents (4.9–6.0%). Laboratory tests were performed and analysed to meet the desired volumetric and strength properties according to the Malaysian specifications for the design of dense asphalt mixtures. Statistical analysis and mathematical models proposed by RSM were used to determine the OBC. The results showed that compaction temperature is the most significant factor in determining the OBC. There are minimum differences in the OBC variation of samples incorporating different dosage of RA. The developed model can be used for quick estimation of OBC for various levels of compaction temperature and RA content.