Journal of Transportation Engineering, Part B: Pavements

Dowel bars in concrete pavements can effectively improve the performance of joints as well as the overall performance of pavements. This paper reviewed the mechanical behavior, structural numerical simulation analysis, testing study of doweled joints in concrete pavements, and the research work on the alternative dowel bars. The influences of dowel bar configuration, diameter, spacing, misalignment, rust, and the bonding between the surrounding concrete on the performance of doweled joints were also discussed in this paper. Limitations of theoretical research and test methods were mentioned after reviewing these aspects of dowel bars, indicating the direction for future research on doweled joints in concrete pavements.

Most existing pavement maintenance and rehabilitation (M&R) decision-making approaches ignore the length constraint of preventive maintenance (PM). This study proposed a practical optimization-based decision-making approach that incorporates the length constraint of PM. For the current popular bottom-up decision-making approach, incorporating the length constraint of PM will cause its solution methods (i.e., evolutionary algorithms) to fail. Therefore, this study developed a sliding-window random repair (SWRR) method based on repair methods and sliding-window methods. The SWRR method was inserted into the evolutionary algorithm (i.e., genetic algorithm) of a two-stage bottom-up approach to solve this dilemma. That is, the proposed decision-making approach is composed of the SWRR method and the two-stage bottom-up approach. A parametric study showed that the M&R decision-making plan recommended by the proposed approach was less expensive than the actual engineering plan, but the achieved performance was 5.7% higher. The results prove that the proposed approach can indeed solve the dilemma caused by the length constraint of PM and produce a better decision-making plan.

Permeable concrete pavements are becoming more common as a stormwater management system to mitigate urban flooding. However, they have several well-defined drawbacks including low permeability, high clogging potential, and low strength and durability, notably in cold climates exposed to freezing and thawing. A new generation of high-strength clogging-resistant permeable pavement replacement (CRP) has been developed, through extensive laboratory work, to address these shortcomings and advance the field of permeable pavements. This paper reports on new advances in permeable pavement systems and the performance of a range of conventional permeable concrete and the developed novel CRP (both prepared using Portland cement) of varying porosity exposed to freeze–thaw cycles. This will allow performance evaluations of both systems in a cold climate. The tests involved exposing samples to temperatures varying from $-20°\mathrm{C}$ to $+20°\mathrm{C}$ and measuring changes in mass, area, compressive strength, and ultrasonic pulse velocity after each cycle. These new results show that CRP is highly resistant to degradation caused by freeze–thaw cycles compared to conventional permeable concrete, reducing maintenance requirements and improving service life. This study presents the first high-strength clogging-resistant permeable pavement replacement that is durable under frost action, these findings will support and enable wider use of permeable pavements in cold regions.

Due to the construction method used, the use of conventional rebar is impractical for roller-compacted concrete (RCC) pavement applications, and the use of discrete fibers seems to be the best alternative to this problem. Among the available types, synthetic fibers are commonly employed in pavement applications, due to their advantages such as ease of handling, cost efficiency, and corrosion-free nature. However, studies that numerically examined the extent of synthetic fiber contribution to the mechanical properties and structural requirements of RCC pavements are very limited. To fill this gap in the literature, an experimental study was conducted to examine the effects of synthetic fibers on the fresh and hardened-state properties of RCC. Then, using the material parameters obtained in this study and retrieved (to cover the effect of different material compositions and synthetic fiber types) from the literature, thickness design for a sample pavement was conducted for plain and fiber-reinforced concrete mixtures, to determine the effect of different material compositions and fiber types on the thickness requirement of RCC pavements. Based on the results of the conducted experiments, the amount of change in the fresh- and hardened-state performance of RCC mixtures due to the addition of synthetic fibers were presented. Thickness design results showed that the contribution of fibers may vary in RCC mixtures depending on the type and amount of fibers used, and the properties of RCC mixture in which they are used. For the type and amount of fibers considered in this study, up to 25% reduction in required thickness was observed for synthetic fiber–reinforced RCC mixtures.

Depressions are a type of distress that cause whole-body vibration (WBV) on people traveling in vehicles, adversely affecting traffic safety, especially at high driving speeds. The study investigated the WBV levels of people traveling in the vehicle during the passage of passenger cars over depressions at the depths defined in the standard. In this context, vibration measurements were made in the vehicle at various driving speeds on some road sections with a known vertical profile with a passenger car. The road sections have been selected with a speed control hump in the middle of the section to consider extreme changes while riding. Vehicle responses were digitized by calibrating a half-vehicle dynamic model with the help of profile data of known geometry and vibration data. WBV values occurring in the seats of vehicles caused by depression type distress in nine different sizes, three different depths defined in low (L), medium (M), and high (H) severity levels and three different widths at each depth, were dynamically simulated. The evaluations were repeated for road profiles expressing A and B classes according to ISO 8608. In the simulation, vibration values were produced by changing ten units to see the change in vibration parameters in the range of vehicle speeds between 10 and $100\mathrm{km}/\mathrm{h}$, and the effects of driving speed on WBV were also taken into account. Vibration data were analyzed using vertical weighted root-mean-square acceleration (${\mathrm{a}}_{\mathrm{w}}$), vibration dose value (VDV), and equivalent static compressive stress (${\mathrm{S}}_{\mathrm{e}}$) parameters defined in the ISO 2631 standard. The analysis shows that with the increase in driving speed, the discomfort increased by 16% in depressions of 0.5 m width, 26% in depressions of 1 m width, and 79% in depressions of 3 m width.

Pavement grooving is an accepted remedial measure to improve skid resistance and reduce crash rates on horizontal curves. However, besides experience-based guidelines, currently no mechanistic procedure is available for quantitative evaluation of the effectiveness of a pavement grooving design in skidding prevention on horizontal curves. To ensure driving safety on wet horizontal curves in particular, there is a practical need for a reliable procedure to determine the effectiveness of a pavement grooving design in increasing tire–pavement skid resistance and the maximum safe driving speed. With the aim to bridge the knowledge gap, this paper presents a computer simulation procedure based on the finite-element method to evaluate the effectiveness of a pavement grooving design in terms of its ability to increase the maximum safe vehicle speed and reduce skidding potential on a wet horizontal curve. For illustration, three common grooving designs were considered, each having a different groove width, depth, and spacing. For each grooving design, two orientations of grooving, namely longitudinal and transverse grooves, were studied. The simulation model allowed different operating conditions to be analyzed, including different geometric dimensions of a horizontal curve, pavement surface properties, and pavement surface water film thicknesses. The analysis not only confirmed past observations and measurements that longitudinal grooving was significantly more effective than transverse grooving in raising pavement skid resistance and the maximum safe driving speed on horizontal curves, but also quantitatively provided their respective magnitudes of improvement.

In this paper, a micro-macro evaluation method of rejuvenator diffusion extent into aged asphalt in hot in-place recycling was put forward considering the cooling process of the recycled layer after paving. The material parameters were back-calculated by the backward regression method, and the temperature field of the recycled layer after paving was obtained by finite-element simulation and verified by the onsite measured data. The time-domain inverse method of the temperature field was proposed to exert the cooling process in a laboratory diffusion experiment of the rejuvenator. The macroviscosity index and micro-fourier transform infrared reflection-attenuated total reflection (FTIR-ATR) spectrum of aged asphalt before and after rejuvenator diffusion were compared, and the rejuvenator diffusion extents on the surface and inside the recycled asphalt layer in hot in-place recycling were studied. It was shown that the thermophysical parameters of recycling and original asphalt mixtures have an obvious influence on the cooling process of the recycled layer, which influence the rejuvenator diffusion process. Considering the actual temperature field of the hot in-place recycled layer is necessary, and the rejuvenator diffusion extent obtained from macro-micro methods showed high consistency. The unevenness of rejuvenator diffusion on the surface and inner recycled layer can be caused by their different cooling processes after paving, and it needs a long period to be eliminated in the environment temperature, which could bring nonuniformity to the properties of recycled mixtures. Increasing the mixing time of recycled mixtures appropriately and changing the thermophysical parameters of recycled mixtures to extend the cooling process are the keys to promote the diffusion of rejuvenator into aged asphalt.

Abstract

Presently, the application of cold-mix asphalt (CMA) in structural layers of pavement is limited due to the slow curing rate and low early-life strength. This study attempts to achieve the reduction in curing period and improvement in strength development of CMA by using nonconventional fillers (NCFs) such as fly ash, ground granulated blast-furnace slag (GGBS), rice husk ash (RHA), and fly ash and GGBS activated with RHA. Curing rate was evaluated using moisture loss monitoring of mixture and compacted specimens of CMA. Strength development was evaluated using indirect tensile strength testing and wheel tracking testing. Laboratory investigations revealed that curing period and temperature have a significant impact on the rate of moisture loss and strength gain. Mechanical strength increased with the increase in curing period and temperature for cold mixes with NCFs. CMA with GGBS activated using RHA exhibited higher curing rates than conventional CMA and substantially higher early-strength development among all the mixes considered. This is due to the combined effect of moisture loss and accelerated hydration process. Statistical analysis also indicated that the improvement was significant. Thus, the use of GGBS with RHA as activator by partial replacement of mineral filler is a potential solution to prolonged curing period and weak early-life strength of CMA.

Practical Applications

Cold-mix asphalt is a sustainable paving mix with economic and environmental advantages. All the steps involved in the construction of the road using a cold mix are done at ambient temperature. Increasing the application of cold-mix asphalt is highly essential. The long time required for curing and the low early strength deter the extensive use of cold mixing in the field. This study suggests that the use of cold mixes in which ground granulated blast-furnace slag with rice husk ash are incorporated as filler helps in resolving these issues by increasing the curing rate and early strength of cold mixes. The study recommends using 25% stone dust, 50% ground granulated blast-furnace slag, and 25% rice husk ash as filler. Because ground granulated blast-furnace slag and rice husk ash are industrial and agricultural waste materials, respectively, using these materials is a sustainable way of resolving the problems of cold mixing. Also, as these materials are easily available, and the modified mix can be easily produced; this can be conveniently implemented in the field. This can pave the way to the use of cold mixing in the top layer of heavily trafficked roads as well.

This study assessed the cracking performance of warm-mix asphalt (WMA) and reclaimed asphalt pavement (RAP) mixtures for airfield pavements and explored performance-based airfield asphalt mix specifications. Fundamental properties of these mixtures were investigated through performance-based laboratory tests such as complex modulus, semicircular bend (SCB), and direct tension cyclic fatigue (DTCF) tests. Performance prediction software was utilized to evaluate mixture performance during the design period. Based on the complex modulus and SCB tests results, it was found that organic additive and RAP tend to increase mixture susceptibility to fracture. Results of the DTCF test showed that fatigue indexes ranked mixtures in different ways, which emphasizes the importance of using performance prediction programs to investigate mixture fatigue performance. The results of performance prediction indicated that utilization of hybrid WMA additive and RAP would increase airfield pavement fatigue damage. The contradictory results of laboratory tests and pavement performance simulation showed that the airfield current asphalt pavement thickness design procedure lacks a usable model of fatigue cracking in its standard design program.

Treatment records are among the most frequently underreported data items in pavement management systems (PMSs), which negatively affects various PMS analysis tools, such as pavement performance and deterioration models. Disregarding unreported treatments may lead to inaccurate pavement age and condition estimates, resulting in erroneous and nonoptimal maintenance and rehabilitation decisions. Nevertheless, the unreported and frequently missing pavement treatment data has received limited attention. Hence, this paper contributes to the body of knowledge by introducing a methodology for detecting unreported treatment actions and their occurrence probabilities over pavement age using a machine learning classification algorithm. Logistic regression models were developed using historical pavement condition data and validated on two levels: (1) split validation; and (2) manual validation using video logs of the pavement condition before and after treatment application. The results show that the developed models can detect unreported pavement treatments with accuracy, precision, and F1 scores ranging from 89% to 96%, 82% to 91%, and 70% to 85%, respectively. The presented methodology and developed models will help highway agencies identify unreported and missing pavement treatments, contributing to more cost-effective maintenance and rehabilitation decisions.