Open-graded Friction Course Pavement Research Articles

A multi-gradient analysis of microscopic void characteristics' influence on the mechanical properties of open-graded friction course bituminous pavement

The mechanical properties of the open-graded friction course (OGFC) bituminous pavement are tied to its microscopic void structure, but multiple void parameters influence void formation and distribution. Solely using air voids as an indicator of pavement stability is challenging. Thus, a multi-gradient analysis of void structure factors is vital for advancing OGFC pavement's mechanical property research. This study used computerized tomography (CT) and digital image processing (DIP) to gather data on void structure distribution, size, and complexity in OGFC bituminous mixtures. Mechanical experiments assessed high-temperature deformation, low-temperature cracking, and water damage resistance. Analysis of void parameters' influence led to a predictive model for mechanical property in OGFC mixtures. The study found that as air voids increase within the 18 %–24 % range, both equivalent void diameter and void fractal dimension increase, while void count decreases. Conversely, coarser gradation and a larger nominal maximum aggregate size (NMAS) lead to increased equivalent void diameter but decreased void fractal dimension, reducing void complexity. The mechanical properties of OGFC mixtures decline with rising air voids but improve with coarser gradation and larger NMAS. The predictive model highlights the void fractal dimension and NMAS as critical indicators, with other factors showing weaker influence or multicollinearity issues that are unfit for model fitting. The findings could provide useful references for the structural design, property evaluation, and quality control of OGFC bituminous pavements in actual road construction.

Investigating the Seepage Characteristics of an Open-Graded Friction Course Using Finite Element Modeling

An open-graded friction course (OGFC) is an asphalt mixture designed with a large air void (AV) content that provides enhanced drainage capability at the surface. The main objectives of this study were to investigate the impacts of selected factors (i.e., the OGFC thickness and coefficient of permeability, the permeability of the underlying layer, and traffic loading) on the drainage characteristics of the OGFC, develop a quantitative tool to simulate the deterioration in the functional performance of the OGFC, and propose new guidelines for the AV content of OGFC for optimum functionality. To this end, a three-dimensional finite element (FE) model was developed to evaluate the impacts of OGFC permeability, OGFC layer thickness, underlying layer permeability, rain intensity, and traffic volume on the seepage characteristics of OGFC pavements. The impacts of these factors were evaluated by calculating the time at which the OGFC surface reaches overflow condition ( TC). Statistical analysis of the results showed that all considered factors had a significant impact on OGFC seepage characteristics, except OGFC permeability. In addition, an artificial neural network (ANN) model was developed to predict TC without the need for FE modeling. Results indicated that the ANN model predicted TC accurately with R2 values of 0.99 and 0.98 in the training and validation stages, respectively. The results also indicated that the model accurately predicted TC over time for OGFC pavements with a root-mean-square error of less than 5.0%. Simulation runs were conducted using the developed FE model under different OGFC AV content conditions and rain intensities. Results revealed that an OGFC layer with an AV content of 16% would provide adequate drainage performance while minimizing OGFC durability issues.

Evaluation on Distribution Characteristics of Pore Water Pressure within Saturated Pavement Structure Based on the Proposed Tire-Fluid-Pavement Coupling Model

To investigate the flow characteristics of pore water in asphalt pavement and the variation law of the pore water pressure under vehicle loading, a novel method based on BA network and quartet structure generation set method was proposed to reconstruct the three-dimensional (3D) pavement model with pores. The permeability coefficient and the gradation curve were adopted to evaluate the reliability and stability of the random growth pavement model. Then, the tire-fluid-pavement coupling model was established with FLUENT 3D based on the fluid Mie–Gruneisen state equation. According to the built fluid-solid coupling model, the pressure-velocity coupled finite volume algorithm was applied to study the distribution of the pore water pressure in asphalt pavement. Results show that the pore water pressure in asphalt pavement decays periodically with time under vehicle loading. For different types of asphalt pavement, the pore water pressure in open-graded friction course (OGFC) pavement is the smallest during the whole process. Moreover, the peak values of the pore water pressure decrease in the order of asphalt concrete (AC) pavement, stone mastic asphalt (SMA) pavement, and OGFC pavement. The maximum negative value of the pore water pressure is generally less than 0.3 times the maximum positive values. As for saturated pavement pores, the pore water pressure is hardly affected by the water film thickness. The positive peak value of the pore water pressure increases on an approximate parabolic curve as the vehicle speed improves gradually, while the negative one remains largely unchanged. The results are expected to help reduce tire hydroplaning risk and provide guidance for the selection of asphalt mixtures of drainage asphalt pavement.

Laboratory Investigation of an Alternative Permeability Indicator to Determine Optimal Maintenance Timing for Open-Graded Friction Course

Open-graded friction course (OGFC) is a low impact development practice that provides a better pavement drainage solution and safer driving conditions. However, there exists a gap in understanding how internal pores in OGFC mix affect hydraulic conductivity, particularly when OGFC suffers the most rutting damage under the effects of high temperature and heavy traffic loading. There is also a lack of research on determining the optimal maintenance timing for an OGFC pavement. This study aims at characterizing the relationship of volumetric and permeability properties for OGFC slab specimens and quantifying permeability deterioration over time using a developed precipitation simulator and permeability measuring device and rutting test. Seven test temperatures (40, 45, 50, 55, 60, 65, and 70°C) were considered in the rutting test. The effect of clogging material size on permeability was also evaluated. The test results suggested that interconnected air void was lower than total air void, and higher rutting temperature resulted in reduced interconnected air void. The clogging experiment suggested that 0.3–0.6 mm material caused the most clogging while 0.075–0.15 mm material caused the least clogging. Based on this study, it is recommended to use a field measured rut depth as an alternative permeability indicator for determining optimal maintenance timing for an OGFC pavement using the correlation established between permeability and rut depth. A case study of OGFC pavement demonstrated that when the field measured rut depth reached 4.5 mm or higher, timely maintenance is needed.

Adhesion characteristics of graphene oxide modified asphalt unveiled by surface free energy and AFM-scanned micro-morphology

Graphene oxide (GO) is a promising nano-material to modify asphalt used in pavement. This work aimed to evaluate the feasibility of GO modified asphalt for the preparation of a high-viscosity asphalt used in open-graded friction course (OGFC). The adhesion characteristics and micro-morphology of the GO modified asphalt were evaluated using the sessile drop method and atomic force microscope (AFM). The addition of no more than 0.2 wt% GO notably increased the surface free energy of an asphalt and its dispersive and polar components and weakened the aging effects on the surface free energy of the asphalt. GO increased the adhesion work between asphalt and aggregate, with minimal influence on the spalling work. Thus, it remarkably enhances the asphalt-aggregate adhesion to improve moisture resistance of asphalt mixture. Limestone and granite aggregates exhibited the highest and lowest asphalt-aggregate adhesion, respectively, and basalt aggregate lied in between. The AFM observations revealed that GO can change the microstructure of asphalt and enhance the asphalt-aggregate adhesion. The adhesion and moisture resistance of styrene–butadienestyrene copolymer (SBS) + GO modified asphalt reached the requirements of high-viscosity asphalt and can be used in OGFC pavement, whereas the GO modified 70# asphalt requires further modification.

A multi-structure multi-run range (MSMRR) approach for using machine learning with constrained data in pavement engineering

In pavement engineering, the data sets that are typically obtained from experiments are small and cannot be classified as big data. The effective use of machine learning techniques such as artificial neural networks (ANN) for small data is a challenge because of poor accuracy of models. This paper presents a method of multiple structure multiple run and ranging to optimize ANN to produce models with small data sets with high accuracy. In this method, a large number of data fitting ANNs, with different number of neurons, layers, training and validation ratios, and randomized layer weights and biases are run in parallel, and the most accurate ANN is filtered out on the basis of the lowest MSE or highest R. The process is demonstrated with weather and pavement temperature data for a hot mix asphalt (HMA) and an open graded friction course (OGFC) pavement. Models are generated to predict the temperature at a depth of 12.5 mm below the surface. For the HMA pavement, an accuracy of 99.73% was obtained and an optimum structure was found to be with 4 layers, 11 neurons, 70% training ratio, 15% validation ratio. In the case of the OGFC pavement, an accuracy of 99.75% was obtained for an optimum structure with 3 layers, 11 neurons, 75% training ratio, 15% validation ratio. Furthermore, the fitting/regression problem was converted to a classification problem with different ranges, and then ANNs were utilized to develop very accurate classification models with small datasets.

Five-Year Performance of Improved Open-Graded Friction Course on the NCAT Pavement Test Track

Open Graded Friction Course (OGFC) mixtures are used as the final riding surface on roadways as they offer many benefits, such as reducing hydroplaning, reducing splash and spray behind vehicles for improved driver visibility, improving wet-pavement friction, and reducing surface reflectivity during wet-weather conditions. Despite these benefits, the use of OGFC has diminished over the years due to durability and service-life issues. The typical OGFC pavements in Alabama have exhibited premature distresses (e.g., raveling) after approximately six or seven years in service. Therefore, there is a need to change the current OGFC mix design procedure to improve the mix durability. In this study, three modified OGFC mixtures were designed based on a 12.5-mm OGFC mix design previously approved by the Alabama Department of Transportation (ALDOT) and paved in three test sections (E9A, E9B, and E10) on the National Center for Asphalt Technology pavement test track to evaluate possible changes to ALDOT’s OGFC mix design procedure. The ALDOT-approved mix design lasted less than 20 million equivalent single-axle loads (ESALs) on I-85, a few miles from the test track, whereas the three modified OGFC mixtures lasted more than 20 million ESALs and remained in place for another research cycle (10 millions ESALs) on the test track. The three modified OGFC mixtures also showed improved laboratory performance characteristics compared with those of the ALDOT-approved OGFC mixture. Based on the field and laboratory test results, adjustments made in the three modified OGFC mixtures can potentially improve the long-term field performance of OGFC mixtures in Alabama.

Adhesion Characteristics of Tire-Asphalt Pavement Interface Based on a Proposed Tire Hydroplaning Model

In order to study the adhesion between tire and asphalt pavement, we established a finite element model of a hydroplaning, inflatable, patterned tire based on the coupled Eulerian–Lagrangian method and then validated the model’s applicability. We numerically calculated tire-pavement adhesion curves for three types of pavement: asphalt concrete (AC), stone mastic asphalt (SMA), and open-graded friction course (OGFC). In accordance with adhesion characteristic theory with regard to tires and asphalt pavements, we analyzed the influential factors that affect the adhesion characteristics of the tire-asphalt pavement interface in an antilock braking system and under damp conditions. The results show that the adhesion between tire and pavement is related to the movement of the tire. In this study, the longitudinal adhesion coefficient for the tire-pavement interface initially increased with an increase in the slip rate and then decreased. Once the slip rate was about 20 percent, the longitudinal adhesion reached its maximum value. In addition, we found that a deep surface macrotexture improved the hydroplaning speed of the tire when the water film was not too thick and the inflation pressure was high. Also, dry pavement led to better adhesion than a wet state in terms of specific mean profile depth. With the same water film thickness, the adhesion coefficient decreased with an increase in driving velocity. The OGFC pavement offered better skid resistance than both AC pavement and SMA pavement.

Evaluation of the benefits of open graded friction course: Case study

This study evaluated the benefits of Open Graded Friction Course (OGFC) via two field projects constructed by the Nevada Department of Transportation: one project was in Elko, and the other was in Las Vegas. Each project included both the OGFC and Dense-Graded Hot Mix Asphalt (DGHMA) sections. The Elko project was located in the town area of Elko while the Las Vegas project was constructed in a rural area on I-15 interstate highway. Laboratory tests were performed to evaluate the durability, rutting, and moisture-susceptibility of OGFC mixtures. The selected test methods included the Cantabro test, Tensile Strength Ratio test, and Hamburg Wheel-Track test (HWTT). The laboratory test results showed that the Las Vegas OGFC mixture passed all the performance criteria, but the Elko Mixture failed to satisfy the HWTT criterion.The field performance tests were conducted to assess the permeability, friction, and noise functionality over time. The selected test methods included the NCAT falling head permeameter test, locked-wheel skid trailer test, and On-Board Sound Intensity test. The field performance results demonstrated that the Las Vegas OGFC pavement exhibited benefits in permeability, friction, and noise reduction compared to the DGHMA pavement, while the Elko OGFC pavement showed comparable performance with the DGHMA pavement after 2-years of service. Finally, a cost-benefit analysis was conducted to monetize the advantages and disadvantages of OGFC pavements. As demonstrated in the economic analysis, the OGFC pavement in Las Vegas reduced the net present value of OGFC costs by 36%, while the OGFC pavement in Elko increased the net present value of costs by 86%. This indicates that the implementation of OGFC is cost-effective in rural highways but impractical in urban or town areas. High speed traffic is generally needed to help keep the interconnected voids of an OGFC pavement from becoming clogged over time. As a result of the reduced speed on the Elko project, the permeability functionality was lost after one year and the noise reduction benefit was lost after thirty two months.

Performance Modeling of Open-Graded Friction Course Pavements

An open-graded friction course (OGFC) is a special-purpose surface layer of hot-mix asphalt (HMA) pavement that is increasingly being used around the world. Owing to its numerous benefits, OGFC is being regularly used as a final riding surface on interstate and high-traffic expressways by different highway agencies in the United States. However, some OGFC sections have experienced premature failure due to ravelling only after 6-8 years of service life. The major problems associated with OGFC can be classified into three categories: design, maintenance and premature failures. Permeability is an important performance measure of OGFC mixtures in design phase. Regression models developed in this research paper will be helpful in getting estimate of permeability values during the design phase of OGFC pavement layer. This estimated permeability values will be helpful in improving the design procedure based on laboratory permeability data

Clogging evaluation of open graded friction course pavements tested under rainfall and heavy vehicle simulators

In this study a new procedure is developed to obtain core samples from field sections to assess clogging mechanisms of open graded friction course (OGFC) pavements using X-ray computed tomography (CT) imaging. The approach compared X-ray computed tomography (CT) images taken before and after: (1) rainfall simulations without trafficking to investigate particle-related clogging and (2) full-scale accelerated pavement rutting tests (APT) to investigate deformation related clogging of OGFC layers. Rainfall simulations were performed with runoff water of known total suspended solids (TSS) and particle size distributions (PSDs). Full-scale accelerated rutting tests were performed under controlled temperature and loads. Both investigations were performed for three different OGFC pavements with different layer thicknesses and mix types. The clogging of rutting test sections were also evaluated by comparing the surface permeability measurements performed before and after APT testing.The results of X-ray CT image processing revealed a significant reduction in air-void content of core samples after APT rutting tests. The highest air-void reduction was concentrated at the bottom of the OGFC layers. Permeability measurements also showed a 40%–90% reduction in permeability after APT trafficking. X-ray CT image processing of core samples tested under simulated rainfall showed that air void content reduction is concentrated in the lower part (2–6 mm from the bottom) of the OGFC layers as a result of particle accumulation. Small changes in air void contents were observed in the upper part of the OGFC layers (10–15 mm) while these reductions in air void contents were not significant to cause surface overflow and hence it is expected that the tested OGFC pavements will have sufficient permeability to infiltrate water during most average storm events.