The main objective of this paper is to present a probabilistic approach for estimating asphalt concrete (AC) pavement damage–associated costs (PDAC) attributed to overweight (OW) vehicles. The approach is based on mechanistic-empirical analyses considering statistical distributions of critical factors influencing pavement damage. Monte Carlo simulation was used to generate OW vehicle cases for a wide range of conditions observed in Nevada. The cases were based on Nevada Department of Transportation (NDOT) 10-year overdimensional permit database containing more than 340,000 entries. The database was analyzed to generate PDAC distributions for different flexible pavement structures and temperature profiles. PDAC values were found to be particularly sensitive to environmental conditions and AC layer thickness. In the case of AC permanent deformation analysis, PDAC increased exponentially as pavement temperature increased. In an AC fatigue cracking analysis, high PDAC values were observed at intermediate temperatures. The probabilistic nature of the presented approach allows for PDAC evaluation over a variety of OW vehicle configurations and environmental conditions. It provides a meaningful, yet practical method of determining PDAC from OW vehicles without the need to conduct detailed and prohibitive individual deterministic assessments.

Download a PDF of "Proposed AASHTO Practice and Tests for Process Control and Product Acceptance of Asphalt-Treated Cold Recycled Pavements" by the National Academies of Sciences, Engineering, and Medicine for free.

Construction techniques and mix design methods are subjected to continuous development along with new inventions, technologies, and related implementation strategies. Due to recent materials introduced into asphalt mixtures such as modified asphalt binders, high percentages of Reclaimed Asphalt Pavement (RAP), warm mix technologies, recycling agents, and others, the asphalt industry is rapidly moving toward the Balanced Mix Design (BMD) method. Current asphalt mixture design methods are structured around meeting a range of volumetric requirements and sometimes other properties such as stability and/or moisture sensitivity. Although this allows for volumetric parameters to be monitored and controlled during production, it does not give much engineering insight as to how the mixture will perform under field conditions. The objective of this research was to assist the local agencies in Nevada with the transition from the Marshall method to the BMD, the latest methodology for designing asphalt mixtures, using the Superpave gyratory compactor and performance tests. Based on experimental data, the research team aimed to create an approach for an optimised, and high-performing mix designs with the use of 15% RAP along with an implementation plan that could be adopted by local agencies and serve as an example for other agencies.

Growing interest in reducing the environmental impacts of pavement preservation materials has increased the need for evaluations of emulsified asphalt. This study applies a cradle-to-gate Life Cycle Assessment (LCA) to quantify and compare the environmental profiles of four widely used cationic emulsions in the United States: CSS 1, CSS 1H, CRS 2, and CRS 2P. The assessment incorporates primary data collected from 17 manufacturing plants across different regions, supported by information from suppliers and secondary datasets from the 2023 GaBi database. Impact calculations were performed using GaBi software, and sensitivity analyses were conducted to determine which formulation components most influence the results. Environmental impact categories in the study include global warming potential (GWP), particulate matter (PM_2.5), photochemical ozone creation potential (POCP), and renewable and nonrenewable primary energy demand. The findings show that rapid-setting emulsions (CRS 2 and CRS 2P) generally exhibit lower environmental burdens than slow-setting emulsions (CSS 1 and CSS 1H). Differences in asphalt binder content, emulsifier dosage, and latex additions were identified as major contributors to environmental performance. By identifying key drivers of environmental impact, this study supports more sustainable material choices in pavement preservation. The results provide updated industry-specific LCA benchmarks for emulsified asphalt and highlight opportunities for environmental improvement through targeted adjustments to product formulations.

The sustainability of roadway construction has rapidly been gaining attention within the pavement industry. The pavements examined in this study are in a Northern Nevada county with many of the roadways categorized as low volume roads. The county began surfacing rural roads with 100% Reclaimed Asphalt Pavement (RAP) millings, without any design considerations for decades. These pavements have provided satisfactory performance with little to no maintenance for their intended purpose for 25–30 years. The presented research revealed RAP milling surfaced roads with layer coefficients between 0.18 and 0.30, and design thicknesses ranging from 5 to 11 inches.

Asphalt-treated cold recycled pavements, including cold in place recycling, full depth reclamation, and cold central plant recycling, are becoming popular rehabilitation options because they are economical, sustainable, and provide good performance. Because asphalt-treated cold recycled pavements use foamed or emulsified binder, they require a curing period post-construction before being opened to traffic or surfaced. Uniform guidelines on when an asphalt-treated cold recycled roadway can be opened to traffic or surfaced are not widely established, many are based on time or moisture content, and extreme ranges exist among agency specifications. Mixture designs also vary widely among agencies with regard to active filler use and asphalt recycling agents, further complicating the determination of necessary curing time. NCHRP Project 09-62 investigated a variety of test methods for determining when a recycled roadway could be opened to traffic or surfaced. This included extensive laboratory and field evaluations. New shear strength and raveling test methods were developed. For each test method a ruggedness study and inter-laboratory study were performed. The ruggedness study revealed critical test fixture and operation parameters. Six asphalt-treated cold recycled pavement process/material combinations were tested by three entities to develop precision estimates and statements (i.e., repeatability and reproducibility) for the new test methods. Tools and information from this study provide a rational basis for establishing specifications, which will help reduce pavement damage from early traffic and minimize roadway closures and delays.