Rut resistance Properties of a Large stone Flexible Base under Heavy Loads

The rut resistance properties of large stone flexible bases are studied, taking into consideration heavy loads and using computer simulation and numerous indoor tests. In computer simulations of large stone flexible bases, a calculation method was formulated for predicting asphalt pavement rut under dynamic loads. The method was based on the coupling of vehicle dynamic loads and pavement surface unevenness. The results of indoor testing and three dimensional numeric calculation under dynamic loads are confirmed by tracking observation results of a test road. We conclude that the rut resistance properties of large stone flexible base asphalt pavement built using low grade asphalt and low crush value high performance aggregate with reasonable gradation is no worse than that of the semirigid base asphalt pavement, and that ruts mainly are caused by the lateral shear.     

Characteristics of Asphalt Rubber Mortar and Aggregate Gradation Optimization Based on High Temperature Condition

To improve the performance of asphalt rubber mixture under high temperature, an optimal proposal was put forward which selected asphalt rubber mortar and aggregate gradation as the main objects. According to experimental tests, the anti rutting factors and phase angles of asphalt mortar was studied with different rations of filler bitumen. And then, with the characteristics of asphalt rubber, the optimal gradation was presented by means of the adjustment of aggregate gradation which chose dynamic stability and relative deformation as value indexes. The results shew that asphalt rubber mixtures would show an optimal high temperature performance if the following measures can be taken: (1) making an adjustment of ratio of filler bitumen to about 1.2; (2) replacing mineral powder with cement; (3) making an adjustment of aggregate gradation and lower the proportion of mineral powder based on SMA.     

Index of Factors Influencing the Shear Strength of Asphalt Mixtures

Asphalt mixtures with high shear strength have great capability to resist perpetual deformation under high temperatures. We used a single penetration test to analyze the material design indexes for high performance asphalt mixtures. The test results show that the performance of the asphalt binder and the performance of the coarse aggregate, especially the fine aggregate, greatly affect the shear strength of asphalt mixtures. We also suggest that the coarse aggregate with a high aggregate particle index, fine aggregate with high angularity, and asphalt with high viscosity can increase sharply the shear strength of an asphalt mixture. Furthermore, the degree of compaction of an asphalt mixture should be controlled to guarantee excellent long term performance of asphalt pavement.     

浇筑式钢桥面铺装层推挤变形病害机理分析

以贵州省北盘江大桥钢桥面铺装层推挤变形病害为研究背景,采用凝胶渗透色谱法(GPC)和傅里叶变换红外光谱法(FTIR),从沥青分子尺度分析钢桥面铺装产生推挤变形的原因。分析结果表明:沥青老化并不是造成钢桥面铺装层推挤变形的主要原因;从现场调查可知,第2层粘层粘结能力的降低是造成钢桥面铺装层推挤变形病害的次要原因;通过级配分析发现,造成钢桥面铺装层推挤变形的主要原因是浇筑式沥青混合料(GA)级配偏细以及GA中集料颗粒的棱角性较差所致。     

Asphalt pavement structure design of expressway on soft soil foundation

Non homogenous settlement will occur while the expressway is constructed on soft ground. The differential settlement can cause the bigger additional stress inside the asphalt pavement structure accelerating bituminous pavement destruction. Therefore,we must choose reasonable pavement structure when constructing road on soft base in order to reduce the influence on surface layer structure from the differential settlement. Based on ABAQUS finite element method and through analysis, this article draws the conclusion that establishing unbound graded aggregate sandwich structure under the asphalt pavement structure can effectively reduce the horizontal additional stress of the stress controled layer and better prevent crack reflection which is beneficial for constructing the asphalt pavement structure on the soft ground.     

Properties of Steel Fiber Asphalt Concrete and Its Application

To prevent asphalt pavement from cracking under low temperatures and prolong its fatigue life, we tested the properties of a new type of steel fiber asphalt pavement. The tests evaluated Marshall stability, dynamic ruts, and cleavage strength under both low and normal temperature conditions. We also analyzed the anti-corrosion property of steel fiber and the factors affecting the properties of the steel fiber asphalt mixture. The steel fiber asphalt pavement was installed on a highway in Chongqing, P. R. China to investigate the construction art of the steel fiber asphalt mixture and examine its effect in field use. The test results and concrete use in the field show that the cleavage strength and flexibility of steel fiber asphalt concrete increase due to the action of steel fiber. We conclude that the anti-cracking capacity of asphalt pavement under low temperature conditions can be improved by steel fiber. The construction art of steel fiber asphalt pavement is the same as common asphalt pavement without the necessity of anti-corrosion processing for steel fiber. The research results are useful for pavement material selection in low temperature regions and heavy traffic road pavement designs.     

Effects of Silane Coupling Agent on Road Performances of Composite Asphalt Mixtures

Aiming at the influence of mastics to aggregate adhesion on the performances of asphalt mixtures, three modeling techniques were adopted to prepare composite asphalt mixtures specimens. The influences of silane coupling agent on their road performances were studied and coupling mechanism was analyzed with Infrared Spectroscopy (IR) and Scanning Electron Microscope (SEM). The results indicated that the road performances at 7 day and 28 day curing age increased in the beginning and then decreased with the increase of silane coupling agent dosages. The road performances, such as freeze thaw splitting strength ratio, Marshall stability and compression modulus would be enhanced 10%~30% at 0.6% in asphalt emulsion mass. There was Si O Si chemical bond on interface between mastics and modified granite aggregate by Si O chemical bond of silane coupling agent. Surface of cement asphalt emulsion mastics was rough and its structure was dense. The cement asphalt emulsion mastics can be adhered to granite aggregate surface and mastics to aggregate interface structure is improved with silane coupling agent addition.     

Space-time Distribution Characteristics of Temperature Field During Asphalt Pavement Paving

The temperature of hot asphalt mixture and environment has a significant effect on the quality of asphalt pavement while paving.Influenced by various kinds of factors, the temperature of the hot asphalt mixture and environment are complicate and changeable while paving.The temperature of different space and time around asphalt pavement are measured while paving hot asphalt mixture on Hou-Yun expressway.The space-time distribution characteristics of temperature field while paving through analysis are given.     

Study on Influence of Fiber to Stability of Asphalt Concrete Pavement

The effect of fiber in asphalt mixtures has attracted general concern. For study of this problem, four kinds of fibers are chosen in this test. Asphalt and modified asphalt are adopted in asphalt mixtures AC-16I. The road performance influenced by additional fiber was analyzed impersonally,i, e. the stability of asphalt concrete under high temperature condition, anti-crack ability under low temperature condition, the water resistance and fatigue performance. It was shown through the research that the optimum asphalt content, air void rate, clearance rate of the mineral powder, saturation degree, and the flow value were increased and the density was decreased after adding the fiber. The road performance, such as the stability of asphalt concrete under high temperature condition, anti-crack ability under low temperature condition, water resistance and fatigue performance, was obviously improved,and the high temperature stability and fatigue performance improved most evidently. The fiber asphalt mixture performance reached and even exceeded the modified asphalt mixture performance. The modified asphalt performance after adding fiber would be improved more greatly.     

Principle and Application of the Asphalt Pavement Recycling Technology

With the coming maintenance period of the aging road in China, the old asphalt pavement's recycling has become an important issue.By introducing the principle of the asphalt pavement recycling technology and the status quo of the application, this paper calls for a strengthened relational research and a heavy concern with the issues, so as to gain the optimum economical and social benefit.     

Experiments on the asphalt fume suppression agents and properties of asphalt concrete with fume suppression agent

Through lots of screening tests, two fume suppression agents, i.e. SBS and nanometer CaCO3, which can reduce the asphalt fume without affecting the properties of asphalt, are screened from seven additives. The best ratio of two agents for suppressing fume is presented by contrast tests of fume suppression effect, and the fume can be reduced about 30%. The properties of asphalt concrete with fume suppression agents and the mechanism of SBS and nanometer CaCO3 reducing the asphalt fume are investigated. The research findings are useful for reducing the asphalt fume in bad ventilation condition of channel pavement and urban road pavement construction.     

Test Method of Indoor Noise for Micro-surfacing Mix

Micro-surfacing mix has been wildly used in the pavement maintenance for its water proofing, anti-skidding and wear resistance. However, micro-surfacing pavement has higher noise than the common asphalt pavement and its noise can not be measured effectively and accurately. Therefore, the indoor noise test method of micro-surfacing mix based on wet track abrasion test was explored. The micro-surfacing mix specimens were used to imitate the micro-surfacing pavement. The wet track abrasion tester was used to provide the vehicle loads. The sound level meter was used to measure the noise between tire and pavement. Furthermore, the indoor noise of nine kinds of micro-surfacing mixes with different gradation was examined. The results show that the equivalent sound level in the second time period has good relationship with the surface texture depth by sad patch method. Then the test method and test procedure for the indoor noise of micro-surfacing mix based on wet track abrasion test were given. Finally, two micro-surfacing mixtures with different gradations were made to validate the test method. The results show that the evaluation method can effectively distinguish the difference of micro-surfacing mixes with different gradation and can supplement the mix design method of micro-surfacing mixes.     

Predicting Damage Rate of Asphalt Pavement for the Fatigue Performance Cracking with Axial Loading

The damage rate of asphalt pavement for the fatigue performance cracking is studied with axial loading by the relationshi Pof surface cueved index with Falling Weight Deflection basin, bottom pulling strain of asphalt surface and aumbers of axial loading. The predicting result of standard axial loading and more-classified loading is very different, so as its increasing rate with the time going. It fits real circumstance to predict the fatigue character of asphalt pavement according to more-classified loading and could be an effective measurement for predicting fatigue life of asphalt pavement ruder axial loading.     

Recycling Technology of Aged Asphalt Pavement

Firstly,the current development of the technologies for recycling of reclaimed asphalt pavement(RAP) in China and abroad is introduced in this study.The theoretic evidence is supplied for the feasibility and means of the recycling technology for RAP by analyzing the aged asphalt recycling mechanism.On the basis of it,a series of recycling processes for RAP are stated in detail,including the performance assessment of RAP,mix design and construction techniques of recycling asphalt mixture.The traits and actual example of different construction techniques for RAP supplied a good consultation for its reasonable choice.All of them would play a role in the research,application and spread of the recycling technologies for RAP in China.     

Evaluation on the Damage Evolution of the CRCP+AC Composite Pavement by the Concrete Dameged Plasticity Material Model

In the study on the CRCP+AC composite pavement, the form and distribution pattern of cracks are two important factors influencing the performance and the lifetime of the pavement. The concrete damaged plasticity material model incorporated in the general purpose finite element software named ABAUQS was adopted to describe the mechanical characteristics of the CRC slab. Combining with the temperature field database drawn from the three-dimensional transient heat transfer analysis, the structural damage under the condition of temperature changing is analyzed. The structural damage evolution and the crack behavior of the CRC slab subjected to the thermal-mechanical coupling condition are further analyzed, which suggests that the role of the asphalt concrete surface is not confined only to the scope of improving the performance of the road, its capacity for improving the stress state of CRCP slab is worthwhile to be affirmed. And the reasonable thickness of AC layer should be designed in consideration of the thermal contraction and damage properties of the CRC slab comprehensively.     

Index System of Sub-Microstructure Analysis System of Asphalt Concrete(MASAC)

Based on the study of image processing algorithm,the Sub-Microstructure Analysis System of Asphalt Concrete(MASAC) suitable for Windows Operating System was specially programmed.In this paper the index system of MASAC is chiefly illustrated and the functions of a part of indexes are briefly introduced.The index system is classified into 5 types,i.e.characteristics of aggregate particles,arrangement of aggregate particles,contact among aggregate particles,air voids between aggregate particles and distribution of aggregate particles.By analysis for the microstructure of asphalt concrete,it can be used to investigate the internal relationship between asphalt concrete microstructure and macro-performance,and evaluate the asphalt mixture homogeneity.     

The influence of the filler-asphalt ratio on the high-and-low-temperature performance of gussasphalt mortar

Asphalt mortar is an important component of gussasphalt mixture, a mixture of asphalt and mineral filler. Five filler-asphalt ratios are used. The high and low temperature performance changes of gussasphalt mortars with different filler-asphalt     

苏州中国花卉植物园温湿效应及其对人体舒适度的影响

探讨苏州城市景观公园不同群落温湿效应及其对人体舒适感的影响,为公园内部绿地系统的布局和植物种植规划提供参考。以苏州市中国花卉植物园园外道路和园内的道路、香樟林、栀子花林、槐树林、复合林6种不同样地为研究对象,测量分析各样地温湿度变化以及对人体舒适度的影响。结果表明：将园外沥青道路作为对照,在降温强度方面,园内不同样地的降温幅度0~4.2℃,依次为乔草>乔灌草>灌草>园内沥青道路;在增湿强度方面,园内不同样地的增湿幅度0~11.7%,香樟林、槐树林、复合林在白天的增湿效果十分明显。在不同季节,整个植物园相比于园外沥青道路有降温增湿的作用,人体舒适感增加,为人们户外活动提供了一个良好的选择。今后在公园的经营管理过程中,在植物配植方面,可以考虑以乔木为主体,选择单一或复合混交结构,合理建设游憩林等林下休闲场所,以最大限度改善生态环境,吸引更多游客。     

A Cold Recycling Technique for Foamed Bitumen Mix

Based on the latest research, we introduce asphalt foaming principles and their characteristics and analyze the influencing factors from macro and micro perspectives. The methods of designing foamed bitumen mixture, the optimum mixing water content, the influence of curing conditions, laboratory testing methods, mechanical characteristics, and the influencing factors of foamed bitumen mixture are discussed. We outline some new asphalt foaming technologies used in warm mix asphalt. Viewpoints regarding the development of foamed bitumen are put forward by analyzing the design and the evaluation methods of foamed bitumen mixture, the development and the selection of asphalt foaming additive, the improvement of the manufacture techniques of foamed asphalt, and the technology of modified asphalt foaming.     

Cementation Effect with Cement during Cold In Place Recycling System of Asphalt Pavement

Different kinds of structures of RAP and different contents of cement were prepared. By means of standard compaction test, unconfined compressive strength, water stability, modulus and SEM test, the cementation effect with cement was studied. It was shown that the maximum dry density of RAP mixture rose from 1.91g/cm3 to 2.00g/cm3 with the increase of cement content when A/S was 0.4. The maximum dry density of RAP mixture would rise when adding more asphalt. The unconfined compressive strength rose from 1.48MPa to 2.63 MPa and then down to 2.28MPa when cement content was 6%. The best property could be got when A/S was 0.4 and the cement content was 6% with 9.5% water. The compressive strength of RAP mixture declined after it was cured in water for 24 h, but it had the same tendency with those of which had not been maintained in water. And it is also found that RAP does not obtain better stabilities in high temperature with modular test. From SEM test, it is shown that ettringite and C S H interlace and form the netted structure, and the aggregate would be enwrapped to increase the strength.