Mechanical Behavior and Failure Mechanism of Recycled Semi-flexible Pavement Material

The mechanical behavior and failure mechanism of recycled semi-flexible pavement material were investigated by different scales method. The macroscopic mechanical behavior of samples was studied by static and dynamic splitting tensile tests on mechanics testing system(MTS). The mechanical analysis in micro scale was carried out by material image analysis method and finite element analysis system. The strains of recycled semi-flexible pavement material on samples surface and in each phase materials were obtained. The test results reveal that the performance of recovered asphalt binder was the major determinant on the structural stability of recycled semi-flexible pavement material. The asphalt binder with high viscoelasticity could delay the initial cracking time and reduce the residual strain under cyclic loading conditions. The failure possibility order of each phase in recycled semi-flexible pavement material was asphalt binder, reclaimed aggregate, cement paste and virgin aggregate.

The Influential Factors of Semi-Flexible Pavement Cracking Performance

The cracking performance of semi-flexible pavement(SFP) was investigated by using the semi-circular bending(SCB) test in this paper. Thirteen grouting slurries were prepared. The compressive strength of these materials ranges from 3 to 100 MPa. The relationship between the compressive strength of the grouting slurry and the cracking property of SFP was obtained at different loading rates and different temperatures. The peak load, fracture energy(E), flexible index(FI), and cracking resistance index(CRI) were calculated to determine the material performance. The results show that the compressive strength of the grout influences the cracking behavior. With a higher comprehensive strength grouting slurry, the FI value of SFP decreased initially and then increased slightly at 25 ℃ in 50 mm/min. The CRI value decreased at the same time. E values changed just according to the test temperature and loading rate. The damage paths of SFP are different. The damage path of the SFP sample appears as diffuse damage at 1 mm/min at 60 ℃ or clean damage at 50 mm/min at 25 ℃. These findings indicate that there is a correlation between the compressive strength of grouting slurry and SFP cracking behavior. The cracking form is influenced by loading rate and temperature.

Investigation of material composition,design,and performance of open-graded asphalt mixtures for semi-flexible pavement:A comprehensive experimental study

The primary goal of this study is the design and construction of semi-flexible pavement(SFP)mixture in accordance with the engineering and mechanical criteria.This study involves the use of a range of gradation curves,air void contents,cellulose and synthesized fibers,and neat and modified asphalt binders to prepare the open-graded asphalt(OGA)mixtures.To analyze the characteristics of these mixtures,a variety of test,namely binder drainage,semi-circular bending(SCB),Cantabro,wheel tracking,indirect tensile strength(ITS),and permeability tests were conducted.Additionally,to analyze the prepared grouting material,flexural strength,compressive strength,and fluidity tests were conducted.In the final stage,SFP was compared to HMA in terms of engineering characteristics and performance.According to the results,SFP was more resistant to skid,rutting,fire,and moisture damage,while HMA had a better performance in fracture tests,including SCB test.According to the results of the mechanical performance tests conducted on OGA mixtures,the highest and lowest values for air void content to achieve the highest mechanical performance level were 30%-35%and 25%,respectively.Also,based on the laboratory results,it was determined that the required void ratio for constructing OGA mixtures was 24%-26%based on the bitumen type and fibers amount in the mixture.Finally,SFP mixture can be regarded as a viable alternative to common pavements thanks to its high resistance to rutting and moisture damage,long freezing-thawing fatigue life,and adequate fire and skid resistance.

Study on Air-Purifying Performance of Semi-Flexible Asphalt Samples Coated with Titanium Dioxide Using Different Methods

Titanium dioxide(TiO_(2))was recently employed to apply onto road surfaces to degrade the harmful compounds from vehicle emissions.However,it remains a challenging task to find a highly compatible pavement type for TiO_(2)application to achieve durable and efficient air-purifying performance.This study proposed to coat TiO_(2)particles onto semi-flexible pavement surface and tried to investigate an optimum coating method.Three coating methods,including direct mixing TiO_(2)(MT)with asphalt mixture,spraying dry TiO_(2)(ST)coating and watersolution-based TiO_(2)(WT)coating on semi-flexible pavement surface.To achieve this objective,semi-flexible samples were prepared to evaluate and compare the performances of three coating methods by employing resistance to wearing,NO removal efficiency tests and residual texture depth tests.It was found that the ST method not only provided better NO degrading efficiency but also improved the resistance to wearing than the other two methods.

不同养护条件对半柔性路面材料性能的影响

为探究养护条件对半柔性路面材料抗裂性能的影响规律,首先,基于抗压和抗折试验,表征了2种不同强度灌浆料在3种不同养护条件下的强度特性。其次,基于弯拉荷载模式的半圆弯拉试验(SCB)和间接拉伸试验(IDT),研究了灌注后的2种半柔性路面材料在3种不同养护条件下的宏观抗裂力学性能。最后,采用扫描电镜(SEM)分析了不同养护条件和不同养护龄期水泥基灌浆料的微观结构,揭示了养护温度与养护湿度对水泥基灌浆材料的水化产物和分布的影响,并结合宏观力学性能探明了养护条件对抗裂性的作用机理。结果表明:养护条件对浆料强度、断裂特性和微观结构均有明显影响,浆料3 d抗压强度与SCB测试的峰值荷载具有较好的线性相关性;在25℃时,室温养护条件SFP试件的抗裂性能最佳。在-10℃时,普通型浆料的SFP试件在高温养护时性能最佳,早强型浆料的SFP试件则在室温养护条件时性能最佳;浆料微观结构致密程度与其抗压抗折强度有较好的对应性,浆料微观结构致密时SFP试件在25℃具有较好的抗裂性能,而浆料具有微孔结构,与沥青形成良好的界面连接,其SFP试件在-10℃时具有较好的抗裂性能。研究结果对半柔性路面材料的铺筑与应用具有指导意义。

超早强半柔性路面在市政路口的应用研究

针对市政道路交叉路口车辙问题突出且难处置的现状,提出采用超早强半柔性路面技术进行处置的方法。通过对超早强半柔性路面材料进行室内试验研究和实体工程铺筑,结果表明,超早强半柔性路面材料应用在市政道路交叉路口,路面整体承载能力大幅提高,动稳定度可以达到29 930次·mm-1,可以比较彻底地解决其车辙问题,并能满足市政路口改造后需要快开放交通、使用寿命长久的需求,其全寿命周期成本低于4.2元/(m2·cm·年),具有很好的应用前景。

Development of high stability hot mix asphalt concrete with hybrid binder

Cost reduction of public works projects has been desired due to severe financial circumstances. Therefore, asphalt pavement has been requested to extend its life. Semi-flexible pavement or epoxy asphalt pavement, which has high rutting resistance and oil resistance, may be applied to the place where these performances are demanded. However, special technique is required in manufacturing and construction. In addition, these materials have also raised a problem that they cannot be recycled. Meanwhile, conventional asphalt pavement has several drawbacks. It is vulnerable to rutting caused by traffic load and damage caused by petroleum oils such as gasoline or motor oil. The materials used in asphalt mixtures were studied for improving the durability of asphalt mixture. A high stability asphalt concrete was developed which has equal or superior performance to semi-flexible pavement and epoxy asphalt pavement. In this paper, the process of selecting the substance and the characteristics evaluation of the developed mixtures are described. Furthermore, an inspection result as well as follow- up survey of the performance of the developed mixtures obtained from trial and actual construction is shown.