Heating aggregates and recycled materials is an energy intensive part of the process of producing asphalt pavement. Sustainability can be improved by increasing the portion of recycled materials while decreasing the energy required to produce the asphalt mixture. A common method to incorporate recycled materials is to mix heated aggregate with cold recycled materials. Interstitial gas conduction is the dominant mode of heat transfer in this process due to the low thermal conductivity of these materials. In this study, a particle-based model that includes the contribution of the interstitial gases was validated with a novel experimental method using infrared (IR) thermography to track the temperature evolution of a mixture of hot and cold aggregates in a flighted, inclined drum. The simulation results showed good agreement with the experiment demonstrating the model's ability to capture the heat transfer and the particle flow in the dynamic system of irregular shaped particles.

This study aimed to evaluate the repeatability of locked-wheel skid trailer (LWST) and sideway-force coefficient routine investigation machine (SCRIM) measurements and investigate the influences of test speed and test temperature on the friction measurements. This study selected 14 test sections from the NCAT Test Track with different surface texture and friction characteristics. The LWST and SCRIM tests were conducted at different test speeds and test times (or temperatures) on the two consecutive days. The repeatability analysis indicates that both LWST skid number (SN) and SCRIM reading (SR) measurements were most repeatable at a test speed of 50 mph and tangent section. The SN measured in the late afternoon and SR measured at noon were more repeatable than those measured at other times. This study recommended an acceptable precision of friction measurement be within 2.5 SN or 3 SR units. In addition, this study concluded that the SN and SR had a good linear correlation. The statistical regression analysis demonstrates that test speed, air temperature, pavement mean profile depth, and pavement type were significant variables affecting asphalt pavement friction. The developed regression models for SN and SR were helpful to correct the friction measurements to a reference speed or temperature.

This study aimed to evaluate the feasibility of using more dolomite aggregates in asphalt surface mixtures that are typically used by West Virginia Division of Highways (WVDOH). The laboratory test results indicated that increasing dolomite content in asphalt surface mixtures resulted in a faster deterioration rate at the early polishing stage. In addition, asphalt surface mixtures containing more than 50% dolomite coarse aggregates would significantly reduce roadway safety. The field test results validated that dolomite shall not exceed 50% of coarse aggregate in asphalt surface mixture if the projected traffic volume is greater than 3.0 million equivalent single axle loads (ESALs).

The objective of this study was to examine the effectiveness of using shotblasting treatment to improve surface friction of asphalt pavements. This study selected six pavement sections with low skid resistance from the National Center for Asphalt Technology Test Track for shotblasting abrasion. These sections included three surface mixture types (open-graded friction course and dense-graded asphalt with and without reclaimed asphalt pavement material) and four coarse aggregate types (limestone, granite, dolomite and sandstone). The dynamic friction tester and lock-wheel skid trailer were used to measure the surface friction of these sections at the different traffic polishing cycles. In addition, the pavement performance including rut depth, cracking and surface roughness were periodically monitored. The test results indicated that shotblasting treatment was effective in improving the friction performance of asphalt pavements and had no detrimental impact on pavement performance in terms of cracking, rutting and surface roughness. The friction improvement by shotblasting treatment was significantly dependent on surface mixture type and coarse aggregate type.

High friction surface treatment (HFST) is commonly used to improve surface friction of asphalt pavements at high crash rate locations, and the objective of this study is to assess the feasibility of using alternative friction aggregates in HFST. Three-wheel polishing device (TWPD) was used to simulate the actual traffic polishing in the laboratory. Firstly, the texture and friction properties of HFSTs with 12 friction aggregates were characterized using circular track meter (CTM) and dynamic friction tester (DFT) after various TWPD polishing cycles (0 k, 70 k, and 140 k). The laboratory results showed that both DFT60 and mean profile depth (MPD) decreased with TWPD polishing cycles, and the DFT60 and MPD results after 70 k TWPD polishing cycles had no significant difference with those values after 140 k TWPD polishing cycles. In addition, a good linear correlation was observed between DFT60 and MPD. Based on the DFT60 results, two bauxite HFSTs showed the best friction performance, and taconite was found to be a suitable alternative aggregate source for HFST. This study also found that slag, silica, and quartz were not good candidates for HSFT application due to the poor texture and friction properties of the corresponding HFSTs. Based on the laboratory evaluation results, eight friction aggregates were selected to pave the HFST sections at the National Center for Asphalt Technology (NCAT) Test Track, which was subjected to 2.6 million equivalent single axle loads (ESALs) in six months. The CTM, DFT, and lock-wheel skid trailer (LWST) were used to characterize the texture and friction properties of field HFST sections, and both DFT and LWST results showed that the bauxite HFST exhibited better friction performance than the granite and flint HFSTs. In addition, there were good linear correlations existing between laboratory DFT60 and MPD results with the corresponding field measurements. Lastly, the influences of aggregate properties (i.e., particle size, durability, angularity, and shape index) on the texture and friction properties of HFST were investigated. The statistical analysis indicated that particle size had significant effects on the MPD and DFT60 of HFST. Meanwhile, only angularity showed a linear relationship with the MPD results of HFST.

The objective of this study was to examine the effectiveness of using shotblasting treatment to improve surface friction of asphalt pavements. The National Center for Asphalt Technology (NCAT) Test Track is a 1.7-mile oval where the accelerated loading research is conducted on experimental asphalt pavements. In this study, six pavement sections with low skid resistance were selected for shotblasting abrasion, which included three surface mixture types (open-graded friction course and dense-graded asphalt with and without reclaimed asphalt pavement material) and four aggregate types (limestone, granite, dolomite, and sandstone). The dynamic friction tester and lock-wheel skid trailer were used to measure surface friction of these sections at the different traffic polishing cycles. In addition, the pavement performance including rut depth, cracking, and surface roughness was periodically monitored. The test results indicated that shotblasting treatment was effective in improving the long-term friction performance of asphalt pavements and had no detrimental impact on pavement performance in terms of cracking, rutting, and surface roughness. The friction improvement by shotblasting treatment was significantly dependent on surface mixture type and aggregate type.

Thermal conductivity is an important material parameter that determines the thermal conditions in pavement and influences cracking, rutting, and fatigue. The test standard (ASTM C177) is not suitable for pavement samples. Research at Arizona State University has developed a test method that uses cylindrical samples to measure thermal conductivity. This paper proposes an improved and simplified ASU laboratory test procedure for measuring the thermal conductivity of pavement material using a cylindrical core sample, including a shorter core sample, a smaller hole drilled in the center, rubber retainers to place thermal couples on the outer face of the core and saturated sand to fill the voids in the inner hole. The test generally requires three hours to reach a steady state of heat flow. This test method is verified by more than 50 samples from four different locations across the United States.

The correlations between tire-pavement noises and pavement surface characteristics have been investigated for many decades, but temperature effects on these correlations are not clear yet. The objective of this paper was to investigate temperature effects on correlations between noise levels and surface characteristics correlations. Tire-pavement noises were measured quarterly by on-board sound intensity (OBSI) method on four types of asphalt pavements on the 2009 National Center for Asphalt Technology (NCAT) test track. Air and pavement temperatures were also recorded during those noise measurements. Four pavement surface characteristics (texture, porosity, roughness, and stiffness) were correlated with noise levels using a linear regression method. Temperature effects were established by comparing correlation coefficients between noise levels and surface characteristics with/without temperature correction. The results showed that, air temperature influenced the correlations between noise levels and surface textures, and temperature corrections were necessary to be taken before analysis. It would be benefit to data processing during tire-pavement noise research.

The quality of hot mix asphalt is affected by the quality and consistency of input aggregates and the control of the production process. To improve the quality of hot mix asphalt, both the aggregates gradation and the process variables must be considered. Current practice involves taking samples from actual production and analyzing them in the lab. The entire process can take two hours, which, along with being expensive, is not amenable to real time online process control or even in knowing how much product is actually out of specification. In this paper, an online control system is proposed that can be used to significantly decrease the analysis time and adjust production by using discrete time stochastic simulation combined with algorithmic optimization. Additionally, the system can readily show when a mix is out of specification without lag time or physical experimentation. Results show that this approach can effectively control the production process resulting in improved quality. This is the first known such application in hot mix asphalt online process control.

Pavement surface characteristics are major attributes to tire/pavement interactions and are considered as cost-effective options to mitigate traffic noise. The objective of this paper is to evaluate the effects of single and multiple pavement surface characteristics on tire/pavement noise levels. During the period from August 2009 to August 2011, noise levels and pavement surface characteristics are measured quarterly on impervious and open-graded asphalt pavements at 2009 NCAT test track. The linear regression analysis method and dominance analysis method are used to evaluate the effects of single and multiple pavement surface characteristics on noise levels, respectively. The results show that surface texture increases noise levels at lower frequencies (below 1600Hz) especially on impervious asphalt pavements. Porosity decreases noise levels at every frequency (except at 2500Hz) on open-graded asphalt pavements. These findings will help to design future low-noise asphalt pavements.

cavities airport runway condition assessment. multi-channel, high performance radar This document provides guidelines for using nondestructive testing (NDT) methods that utilize the spectral analysis of surface waves (SASW) and impact echo (IE) technologies to identify delamination in asphalt pavements. This guideline is applicable to all the SASW and IE devices for evaluating delamination in asphalt pavements. Users are advised to understand both SASW and IE because the test equipment may have the ability to measure both. Selection of which data has the highest level of accuracy and confidence will depend on the understanding of each technology and the field-testing conditions.

A new system can be used for assessing the condition of hot-mix asphalt (HMA) pavements to detect debonding between HMA layers. The study was partly funded by a SHRP 2 project through the National Center for Asphalt Technology. The objective was to develop a reliable technique for determining the internal condition of HMA pavements that included debonding conditions between each layer. A prototype of an impact echo and spectral analysis of surface waves scanner (originally developed for assessment of bridge deck condition) with up to three pairs of transducer wheels was used in the project. Background on the development of the scanner and a case study performed on HMA pavements of known conditions at the National Center for Asphalt Technology's pavement test track are presented. The research investigation was performed as a blind study, and the actual pavement conditions were revealed to the research team after the initial data analysis and reporting of detected delamination conditions were completed.

Asphalt pavements with delamination problems experience considerable early damage because delaminations provide paths for moisture damage and the development of damage such as stripping, slippage cracks, and pavement deformation. Early detection of the existence, extent, and depth of delaminations in asphalt pavements is key for determining the appropriate rehabilitation strategy and thus extending the life of the given pavement. This report presents the findings of the first two phases of Strategic Highway Research Program 2 (SHRP 2) Renewal Project R06D, Nondestructive Testing to Identify Delaminations Between HMA Layers. The main objective of the project was to develop nondestructive testing (NDT) techniques capable of detecting and quantifying delaminations in hot-mix asphalt (HMA) pavements. The NDT techniques should be applicable to construction, project design, and network-level assessments. During Phase 1 of the project, the research team evaluated NDT methods that could potentially detect the most typical delaminations in asphalt pavements. Both laboratory and field testing were conducted during this task. Based on the findings from this testing, the manufacturers of two promising technologies conducted further development of their products to meet the goals of this project in Phase 2. The two technologies advanced in this research were ground penetrating radar and impact echo/spectral analysis of surface waves. Additionally, the project developed guidelines and piloted both NDT technologies in collaboration with highway agencies. Once completed, the results from this additional scope of work will be published as an addendum to this report. This volume describes the uncontrolled evaluations used in the development of NDT techniques capable of detecting and quantifying delaminations in HMA pavements.

A number of state agencies, consultants, and research centers are using a dynamic friction tester (DFT) as a quick, relatively simple, lightweight device for spot-­testing pavement surface friction. Based on the experience of these users, a number of issues with the equipment and test standard have been noted. The scope of this workshop is to bring DFT users together to discuss these issues and collectively outline areas that should be addressed. The objectives of the workshop are to: 1. provide an open forum for discussion; 2. develop a list of concerns; 3. provide direction for further development of the equipment and test method; 4. provide an opportunity for side-­‐by-­‐side testing of DFT devices.

Asphalt pavements with delamination problems experience considerable early damage because delaminations provide paths for moisture damage and the development of damage such as stripping, slippage cracks, and pavement deformation. Early detection of the existence, extent, and depth of delaminations in asphalt pavements is key for determining the appropriate rehabilitation strategy and thus extending the life of the given pavement. This report presents the findings of the first two phases of Strategic Highway Research Program 2 Renewal Project R06D, Nondestructive Testing to Identify Delaminations Between HMA Layers. The main objective of the project was to develop nondestructive testing (NDT) techniques capable of detecting and quantifying delaminations in hot-mix asphalt (HMA) pavements. The NDT techniques should be applicable to construction, project design, and network-level assessments. During Phase 1 of the project, the research team evaluated NDT methods that could potentially detect the most typical delaminations in asphalt pavements. Both laboratory and field testing were conducted during this task. Based on the findings from this testing, the manufacturers of two promising technologies conducted further development of their products to meet the goals of this project in Phase 2. The two technologies advanced in this research were ground-penetrating radar (GPR) and impact echo/spectral analysis of surface waves (IE/SASW). Additionally, the project developed guidelines and piloted both NDT technologies in collaboration with highway agencies. Once completed, the results from this additional scope of work will be published as an addendum to this report.