Demonstration Project for Enhanced Durability of Asphalt Pavements through Increased In-Place Pavement Density

2020PDFTech ReportAschenbrener, TimBrown, E RayTran, Nam H.Blankenship, Phillip BAuburn University. National Center for Asphalt TechnologyUnited States. Department of Transportation. Federal Highway AdministrationAuburn University. National Center for Asphalt TechnologyUnited StatesAsphalt pavementsBest practicesCompactionDemonstration projectsDurabilityIn place densityLiterature reviewsMix designStatesEvothermFHWA/LA.17/628LTRC Project Number: 18-4BSIO Number: DOTLT 1000214Final Report; Enter Date: 10/2018 \u2013 9/2019Recognizing the importance of in-place density in building cost effective asphalt pavements, a Federal Highway Administration (FHWA) Demonstration Project was created for \u201cEnhanced Durability of Asphalt Pavements through Increased In-place Pavement Density.\u201d Based on prior studies, a one-percent decrease in air voids achieved through improved compaction was estimated to improve the fatigue performance of asphalt pavements between 8 and 44 percent and improve rutting resistance by 7 to 66 percent. A one-percent decrease in air voids through improved compaction was estimated to extend the service life by 10 percent, conservatively. The objective of this demonstration project was to determine the benefit of additional compaction and show that additional density could be obtained through improved techniques. Many states also added additional compaction equipment and showed that this allowed for obtaining additional density. This project effort included two major components: (1) a literature search to serve as an educational component regarding the best practices for increasing density, and (2) the construction of 10 field demonstration projects. The literature search identified best practices and new technologies that can help achieve higher densities. These included mixture design factors, field compaction techniques, best practices such as longitudinal joints and tack coats, measurement and payment, and the use of warm-mix asphalt. Two success stories of the many identified were highlighted. Eight of the ten states improved densities by at least one percent compared to a control section on their demonstration projects. There were at least two pavement sections constructed within each of the 10 states that participated in this demonstration project. Many of the states constructed more than two pavement sections for a total of 38 sections. There were many variables including mixture type, construction equipment, and procedures between states and within states. A summary of the methods that states used to obtain increased density generally fell into one of five categories: (1) improving the agency\u2019s specification by including or increasing incentives and increasing the minimum percent density requirements; (2) making engineering adjustments to the asphalt mixture design to obtain slightly higher optimum asphalt content (although not part of the original goal of the demonstration project); (3) improving consistency as measured by the standard deviation; (4) following best practices; and (5) using new technologies.131