Road Pavement and Material Characterization, Modeling, and Maintenance

Cold in-place recycling was adopted for a project in China due to the availability of reclaimed asphalt pavement (RAP). Based on the Foshan loop project in Guangdong, the gradation design of cold recycled mixtures (CRM) was optimized by the Bailey Method. Emulsified asphalt and cement were used as additives. Then, the screenings of aggregates in RAP and RAP were analyzed and compared. Additionally, new aggregates and cement were added to dispose the framework structure of the cold recycled mixture, and modified Marshall Tests conducted to determine the optimum amount of emulsified asphalt and water, by which cold recycled mixture was formed and performance experiments of asphalt mixture carried out. Eventually, the results show that the gradation design of cold recycled mixture needs to be adjusted by the screening of aggregates in RAP. Also, cold recycled mixture is suitable for highway sub-grade and pavements of low-grade roads.

The demand to utilize higher percentages of reclaimed asphalt pavement (RAP) in the construction of hot mix asphalt (HMA) pavements continues to rise. Utilization of RAP in HMA is an environmentally friendly and cost effective method of recycling. At high percentage of RAP properties of RAP binder and its interaction with virgin binder plays critical role. Researchers have consistently shown that when RAP is mixed with virgin binder and aggregates, partial blending occurs, that is, something between 100% blending and the "black rock" effect occurs. Impact of partial blending on new virgin binder content is apparent which may cause under-asphalted mixture, resulting in poor pavement performance. Also influence of partial blending on final grade of RAP mix and allowable percentage of RAP has not been evaluated. The purpose of this paper is to develop the blending chart for different degree of blending to study the impact of partial blending on final grade of blended binder. To achieve the objective, blending chart for 100%, 70% and 50% RAP has been developed for PG 70-28 and PG 58-28 binder by carrying out binder study.

The purpose of this paper is to simulate the resilient modulus of asphalt pavement material using support vector machines(SVM).First, selecting 15 training datasets randomly and remaining 9 testing datasets to create model, then radial basis function kernel and polynomial kernel based on support vector machines are used to simulate the resilient modulus. The correlation coefficients values were achieved by radial basis function kernel and polynomial kernel based on support vector machines. The result of sensitive analysis among input parameters such as P_4.75, P_2.36, P_0.075, V_a, P_b shows that the parameter P_b has maximum influence on resilient modulus. The predicting results indicate that the proposed SVM model can gain higher precision than artificial neural network approach and multiple regression, which provides a new way for predicting resilient modulus and other mechanical behaviour index of asphalt pavement material.

Determining pavement serviceability ratings (PSR) for flexible pavement is an important task in pavement management. The PSR is influenced by rutting depth, cracking and patching. In the existing evaluation methods, systematic analysis and regression modeling analysis are often used. However, the first method relies more on experienced judgment and the second method is restrained to use by the territory condition. In this study, a support vector machine (SVM), a new type of learning algorithm based on statistical theory, is developed to estimate the PSR of flexible pavement. The SVM uses a regression technique based on an insensitive loss function. The values predicted by SVM are compared with the values from the AASHO model and the ANN model. The study shows that SVM has better performance in estimating the PSR of flexible pavement than the other models, and it can be a useful and practical tool for estimation of PSR.

Content of attached old mortar, apparent density, water absorption ratio and crushing value are key factors governing the behavior of recycled coarse aggregate (RCA). Relation between water absorption ratio and old mortar content attached to the virgin aggregate part of RCA was investigated. An equation to describe relation of water absorption ratio and old mortar content was then put forward and compared with that in references. Relation between apparent density and water absorption ratio of RCA was investigated. The result indicates that water absorption ratio correlates linearly and negatively with apparent density when the apparent density is lower than 2500 kg/m³. Correlation between water absorption ratio and crushing value was also analyzed. In addition, grading indexes of RCA including apparent density, variation coefficient of apparent density, crushing value, old mortar content, Los Angeles loss and water absorption ratio were determined and specified. Three levels of RCA were recommended for different situations.

Load transfer efficiency (LTE) is commonly used to evaluate degree of load transfer in case of jointed concrete pavements. The concept of load transfer is very important and fundamental to Federal Aviation Administration's (FAA) rigid pavement thickness design procedures. The FAA procedure assumes 25% of stress applied to the edge is transferred across a joint to the adjoining slab. Degree of load transfer across a joint was found to be different under a static and moving aircraft gear. Moreover, as an aircraft traverses a joint, the wheels might be oriented perpendicular or parallel to the joint. The slab bending phenomenon tends to be different under different gear configuration in various positions with respect to the joint. The effect of differential stress distribution along the joint under various modern day aircraft gear configurations in different positions was studied using a 3D-Finite Element analysis program FEAFAA. It was found that load transfer across a joint is a function of number of loaded areas along the joint edge. Overall the differences in LTE were insignificant for similar aircraft in different positions along the joint.

It is well-known that the properties of bituminous materials that are exposed to external environmental conditions such as solar radiation, diurnal temperature fluctuations and rain changes during its service life. Surfacing seals consist of a combination of bitumen and aggregate, and are used to provide a all-weather surfacing to protect underlying layers and provide safe access to vehicles traveling on a road. Analysis of a number of sections in Gauteng, South Africa, has shown that surfacing seals lost a large proportion of their aggregate where the road was crossed by a bridge. As all original properties of the seal components as well as the traffic on the road were similar, it was deduced that the micro-climate where the road traveled underneath the bridge should have caused this localized failure condition. In this paper the phenomenon is investigated through analysis of the material properties of the surfacing seal, the micro-climate underneath the bridge and the combined effect of these factors on the performance of the seal. It is shown that the micro-climate can affect the performance of a otherwise suitable surfacing seal to such an extent that the performance of the seal is severely compromised.

The texture of the pavement surface and its ability to resist the polishing effect of traffic is of prime importance in providing skidding resistance. Skid resistance is a measure of the resistance of pavement surface to sliding or skidding of the vehicle. Road surface texture is essential for pavement skid-resistance. However, its measurement is only possible in the laboratory on cores taken from trafficked roads, and is time consuming. Now it is necessary to develop new methods of monitoring road on-site efficiently. In this dissertation, a system has been developed for measuring the road texture, form and angularity of aggregate based on image analysis, which consists of a line-laser, CCD and a computer. The line-laser can scan a field of 100mm for each time. The form and angularity of aggregate and microtexture of pavement surface is measured by analyzing image of laser. And the character of road microtexture can be recognized by pattern recognition. Thus the methods which were used to measure the shape characteristics of aggregates are unified. Basing on the principles set for the sand patch method, the mathematic model and hardware designing were given. A comparative study was performed to find the British Pendulum Skid Resistance Number for a number of mixes. The experimental results show that the vision measurement system can efficiently improve the testing speed and the accuracy on-site.

In recent years, the national highway system in Taiwan has tried to advance its service performance based on adaptation to the geographical and climatical environment in the Taiwan area. To do so, porous asphalt concrete has been introduced into Taiwan. This material has been used for years, in other places, in order to make pavement construction durable and extend the life cycles of highways and to improve safety in driving, rapid drainage and skid-proofing of paving. The study collects proper influence factors for consideration with the Factor Analysis Method and the questionnaire survey method, and verifies the relevant factors obtained from this research and the drainage-type relevant factors in an attempt to obtain the weight and influences of factors. With the establishment of the performance evaluation model for asphalt concrete pavement, this research can provide the national highways construction service with a useful decision making model for evaluation.

The research effort documented in this paper is directed toward identifying an analytical model that can be used to predict the resistance of HMA overlays to reflective cracking and predict their long-term performance. Various models were identified and three models were studied and compared in this research effort: 1) Virginia Tech Simplified Overlay Design Model, 2) Rubber Pavements Association (RPA) Overlay Design Model, 3) the New AASHTO model for Reflective Cracking. The identified models were assessed by the research team based on their ability to predict the performance of HMA overlays subjected to reflective cracking. An overlay design was conducted for three different HMA overlay mixes using the three identified overlay design methods. The overlay mixes were manufactured using different aggregate gradations from the Sloan pit in Southern Nevada and a PG76-22 polymer modified asphalt binder. The overlay was designed for 7,000,000 ESALs over the 20 years analysis period. Finally, a comparison was exerted among the various HMA overlay thicknesses required by each method and the material properties associated to such determination to accomplish the design traffic.

Large-scale comprehensive utilization of industrial solid waste is a worldwide problem. The application than the fly ash and the carbide slag are used as road construction materials is a comprehensive utilization method of large amount consumption of industrial solid waste. Combined the physical and chemical properties of fly ash and carbide slag, the changes of compressive strength, flexural strength and elasticity modulus of different cement content are studied. Considered the climatic conditions and traffic conditions of rural road in Three Gorges reservoir area, the impermeability, the frost resistance, the wear resistance, the dry shrinkage and the thermal shrinkage of fly ash-carbide slag residue concrete are analyzed. The results indicate that the fly ash-carbide slag residue concrete has good road performance and can meet the requirements of road construction in Three Gorges reservoir area; It provides a new method for the solid waste disposal, the environmental protection and rural road construction in Three Gorges reservoir region.

The "Shapiro-Wilk test method (W-test)" was applied to analyze the probability distribution of the wheel tracking test result of asphalt mixture. The wheel tracking tests were executed on samples made in lab and samples obtained from mixture plant. f The results indicated that the dynamic stability and relative deformation partly fitted normal distribution and totally fitted lognormal distribution. According to the theory of stress-strength interference, the reliability coefficients of high temperature performance indexes under different reliability and different variation were calculated, and on basis of corresponding specification, control criterions of high temperature performance for various highway grades were present.

This paper investigates the impact of compaction methods on the performance of quiet (porous) asphalt mixes. Four different compaction methods are included: Marshall impact compaction, Hveem kneading compaction, Superpave gyratory compaction, and rolling wheel compaction. The rolling wheel compaction was selected as a surrogate for field compaction. Specimens of four different porous mixes with the nominal maximum aggregate size (NMAS) varying from 4.75 mm to 19 mm were compacted by the four methods, and were tested for various performance indices, including permeability, sound absorption, friction, surface macrotexture, moisture sensitivity, resistance to raveling and aging, and rutting resistance. It is found that difference exists among performances of a porous asphalt mixture compacted by different methods. The compaction effect varies with aggregate gradation and the performance being evaluated. Recommendations are given in the paper on selection of compaction methods based on the nominal maximum aggregate size.

With its unique characteristics (such as anti-leaking, fatigue crack resistance, durability), Gussasphalt has been widely used in projects of steel deck pavement. However, its limitation is the overloading abilities in high temperature condition. In China, around Yangtze River and southward, the environmental temperature in summer usually exceeds 36 □, along with high traffic volume and heavy-loaded vehicle. It's necessary to improve the high temperature stability of Gussasphalt to meet the severe application requirements of steel deck pavement, for solving the technical problems on steel deck pavement in high temperature and heavy load conditions. This study, which served the increase of anti-overloading ability of Gussasphalt in high temperature condition as the purpose, by adjusting the structures and construction technology of Gussasphalt, introduced a new type of Gussasphalt—Embedded Gussasphalt. Embedded Gussasphalt has a higher interlocking rate of aggregates framework, lower asphalt content and lower construction temperature. Test results of fluidity, rutting and fatigue life showed that the high temperature stability and fatigue performance of embedded Gussasphalt got remarkably improved without fluidity decreased.

In this paper, the additive was adopted to activate crumb rubber powder to prepare a compound modified asphalt, and its mechanism of activating crumb rubber modified asphalt is studied. Mechanical testing was adopted to study the activation mechanism of additive to crumb rubber powder. Differential Scanning Calorimetry was used to analyze the performance improvement mechanism of the activated rubber to the modified asphalt. Physical models were then constructed to explain the mechanism. The results indicate that: The crumb rubber powder is dissolved totally by the additive which contains lots of oil and aromatics, then the crumb rubber powder release more solubilizer with the action of cutting at high speed, so that the crumb rubber powder can be compatible with the asphalt more steadily, and the performance of the compound modified asphalt is more superior.

In contrast to a quite good understanding of the hysteretic effects in tire-road contact, there is limited knowledge about the adhesive part of the friction, especially concerning its relevance under wet conditions. In this paper the test apparatus of the German Institute of Rubber Technology is used to investigate the friction coefficient in process of sliding, in particular the adhesion. The adhesion is quantified through the difference between the cases with pure water and with soap water as lubricant. The derived curves of friction over the sliding time are characterized by different parameters in the sliding stages. Results reveal that adhesion amounts to 10% of the total friction even in wet conditions, which means that adhesion is not negligible in predicting the friction. The adhesion in the process of the contact shows a decreasing tendency during the sliding process. Its development over the sliding time varies to a certain degree with the sliding speed and the asphalt type.

This paper investigates the behaviors of typical mineral components of the aggregates due to tire-polishing. Four kinds of granitic aggregates were polished and tested. The friction and surface texture in polishing process were monitored. The wearing behaviors of typical mineral components were analyzed by spectrum approach. It was found that a fine mineral structure for granite brings an overall high friction level. The alkali feldspars group contributes to almost constant skid resistance and these crystals experiences a unique increase on all wave lengths in the polish process. The work here may be helpful for an active design of a high friction level all through the service years for pavement surfaces.

This paper aims to examine the effect of the unsaturated flow in the drainage layer of highways and approximately modified the saturated model as well. We compared the 1-D Boussinesq equation-based model against the 2-D models based on Laplace and Richards equations. By analyzing the simulations results, we investigated the role played by the unsaturated flow in draining water from the pavement system under different conditions. For the cases considered presently (drainage layers built with the materials with the hydraulic properties close to the sand and gravel which are fine graded and coarse-graded material respectively), horizontal flow was dominant. Nevertheless, those models for simulating saturated flow overestimated, to some extent, the groundwater table, which can be physically captured by Richards equation-based model. Particularly for fine-graded material, the capillary zone is relatively thick. As long as the saturated soil layer below the groundwater table is relatively narrow, the flow in unsaturated zone is significant which cannot be neglected. Then we adopted the Gardner water retention curve to improve the Boussinesq equation- based model (saturated model). The result shows that the groundwater table predicted by the modified model matches well with that predicted by Richards equation-based model (unsaturated model).

High calcium fly ash and fly ash are two kinds of industrial waste residue. By analyzing their chemical compositions, the mechanism in strength of the high calcium fly ash and fly ash mixture is expounded in this paper. Based on the method in Test Methods of Materials Stabilized with Inorganic Binders for Highway Engineering, the technical performances of the mixture of high calcium fly ash and fly ash in highway application, which include the strength, modulus and water stability, were studied by systematic experiments. And, the influence factors of the mixture strength were analyzed, too. The results indicate that the mixture has higher strength, modulus and good water stability. The technical performances of high calcium fly ash and fly ash mixture conform to the current specifications for design of highway asphalt pavement, so it can be used as sub-base course or base course construction material.

In the paper Sweden slice method is employed to carry on pavement foundation stability analysis of Anhui Bozhou-fuyang expressway. The program named expressway slope stability analysis program is compiled with Visual Basic (VB) language based on the practice conditions of the expressway, and then the safety stability coefficients of the pavement foundation in various working conditions are obtained by the program. The results show that the program established here can be used to carry on highway pavement foundation stability analysis easily and precisely and Bozhou-fuyang expressway pavement foundation is safe.

Selection of slab size plays an important role in the construction of airport concrete pavements with an expected high performance at a low cost. Many countries including the United States have expressed differing opinions for decades about what constitutes the correct slab size. Many airport engineers and owners favor the larger slabs (7.62 by 7.62 meters) because of the low cost in construction and maintenance during their service life. Others prefer smaller slabs (5 by 5 meters) because of the better performance and longer life based on survey data. Although the current FAA advisory circular AC150-5320/6E does not recommend a slab size larger than 6.1 by 6.1 meters, some experienced field engineers still design and build concrete runways utilizing 7.62- by 7.62 -meter slabs. The detailed survey data analyses presented in this paper find the pavement condition is very sensitive to slab size for aprons but not for runways. Therefore, the use of small slabs is more important in aprons than in runways. A simple analysis-based probability theory can also provide information for different levels of administration to determine their budget in pavement management for a given threshold value of pavement condition index (PCI) or to determine the threshold value of PCI based on the available budget.

In order to reduce the harm caused by traffic noise, porous asphalt pavement was widely used in the world. For single-layer porous asphalt pavement easy blocking, double-layer porous asphalt pavement structure was brought out. With the top-layer has smaller porosity, bottom-layer porosity slight greater, this structure has formed an effective dispersed space for noise absorption. The top-layer has a filter effect on large particles. Dust falling into the surface pore was water out due to the bottom-layer porosity was greater. So the double-layer porous asphalt pavement has self-cleaning effect on pore clogging. The numerical simulation for acoustic absorption properties of porous asphalt pavement structure was made with application of finite element method and acoustic-solid coupling model by large-scale commercial software ABAQUS. The noise-reducing feature was analyzed for the double-layer porous asphalt pavement in porosity and thickness combinations and then structural parameters suitable for double-layer porous pavement was proposed. The result indicated that double-layer porous asphalt pavement has better sound absorption for top-layer porosity of 10%, bottom-layer porosity of 25%, top-layer thickness of 2cm and bottom-layer thickness of 4cm.

With the on-site measured pavement temperature from some section on Jing-Zhu expressway, the rule of maximum tensile stress, maximum shear stress and the maximum flexure of surface at different slope and different stress field were presented by FEM, under the composite effect of horizontal loading and vertical load. It turns out that the degree of slope affects the stress of surface course more, and the tensile stress appears within the range of 2cm-deep from surface. The high temperature field did not make tensile stress and shear stress of upslope pavement increase, but it made the flexure of surface rise. Then efforts were made in this study to investigate rutting failures on Jing-Zhu expressway in China, a long and steep slope expressway, to determine the cause and the source of the rutting. The features of the rutting on each asphalt pavement layer were analyzed by surveying the rutting depth, excavating transverse profile section, and boring samples in the typical sections of expressways where different degree of rutting damages were observed. It was found that 60% of rutting is generated by asphalt middle course and the remaining 40% comes from the other surfaces, which means that middle course is the most important surface course to resist rutting disease. Finally, according to the results, some suggestion for the design of the upslope pavement structure was put forward. According to it, the mixture of the surface was designed and test road was built. The detected data from the test road turns out the asphalt pavement has a good performance.

In order to promote the technological element in decision-making of pavement maintenance management, a quantitative evaluation method for treatment effectiveness of maintenance activities on jointed concrete pavement was proposed through analyzing historic maintenance data in pavement maintenance management system. In order to verify the correctness of the method, the historic maintenance data of Xiangtan-Leiyang Expressway were analyzed to calculate the treatment effectiveness of void beneath pavement can be repaired by slab undersealing with different injected materials. After a series of statistical analysis, the treatment effectiveness of slab undersealing using cement grout was 75.8%, and the treatment effectiveness of slab undersealing using emulsified asphalt was 84.4%. According to this quantitative analyzing result, the current unit price of slab undersealing using emulsified asphalt grout is too high to popularize, its reasonable unit price is recommended as 21.4 yuan/m².

In developed countries, the determining of location to apply preventive maintenance treatments relies on analyzing the data of pavement inspection. However, due to funds shortage and obsolete inspection equipment, pavement inspection is not an effective method to determine the preventive maintenance location in China. According to this situation, a new method is developed to determine the preventive maintenance location by analyzing historical maintenance data in pavement maintenance manage system. In order to verify the effectiveness of the method, the historic maintenance data of Xiangtan-Leiyang Expressway were analyzed. Some pavement sections were determined as the location of preventive maintenance by using this method, and correctness of analysis results were validated by field investigation.

The differential settlement and pavement cracking along the joint between an old and new embankment often appear for an embankment widening, which will deteriorate the riding performance of the widened road greatly. Centrifuge model test and numerical analysis using ABAQUS have been carried out for the geosynthetic-reinforced embankment of a road widening. Tensile strain in the geogrid was measured in the centrifuge model test and a sensitivity analysis was carried out with numerical analysis. It was found that the geogrid in the new embankment not only reduces the differential settlement between the new and old embankments, but also limits the horizontal deformation of the new embankment. The effect of geosynthetic-reinforcement in the widening embankments is enhanced with the increase of the geogrid modulus.