Hannele Zubeck

Prediction of Low-Temperature Cracking of Asphalt Concrete Mixtures with Thermal Stress Restrained Specimen Test Results

A deterministic model and a probabilistic model were developed to predict low-temperature crack spacing as a function of time using thermal stress restrained specimen test results, pavement thickness and bulk density, pavement restraint conditions, and air temperature. The effect of aging on pavement properties was incorporated in the models by predicting the field aging with long-term oven aging treatment in the laboratory. The calculation of the crack spacing is based on the theory that the pavement slab cracks when the pavement temperature reaches the cracking temperature of the mixture and the slab is fully restrained. The deterministic model predicts crack spacing with time, whereas the probabilistic model predicts crack spacing and its variation with time and yields the reliability of the design with regard to a minimum acceptable crack spacing criterion defined by road authorities. The probabilistic model is recommended for use in predicting the low-temperature cracking of asphalt concrete mixtures.

FIELD VALIDATION OF THERMAL STRESS RESTRAINED SPECIMEN TEST: SIX CASE HISTORIES

Construction histories, cracking observations, and temperature data were collected for five test roads in Alaska, Pennsylvania, and Finland. A full-scale and fully controlled low-temperature cracking test program was conducted at the U.S. Army Cold Regions Research and Engineering Laboratory. Specimens were fabricated in the laboratory with original asphalt cements and aggregates from the test roads. The thermal stress restrained specimen test (TSRST) results obtained for these samples were correlated with the field observations. On the basis of a statistical analysis of the data, the TSRST fracture temperature is associated with the field cracking temperature and crack frequency for the test roads where mixture properties dominated low-temperature cracking. It was concluded that the TSRST can be used to simulate low-temperature cracking of asphalt concrete mixtures.

Workability and Performance of Polymer-modified Asphalt Aggregate Mixtures in Cold Regions

Polymer-modified asphalts have been used in cold regions for about 15 years to address problems with rutting, cracking and premature aging. However, due to the cold climate and remote locations construction problems are sometimes encountered. This paper deals with workability of polymer-modified mixes while assuring that the desired pavement performance is achieved. The construction problems arise with possible poor compatibility of the base asphalt and the polymer, the storage stability of the asphalt–polymer mixture and cold construction temperatures. These properties were tested for several polymer-modified asphalt combinations. A set of products that were compatible, storage stable and had improved temperature susceptibility were selected and further tested in asphalt-aggregate mixtures. A Georgia Wheel rutting test and the Thermal Stress Restrained Specimen Test were performed. A questionnaire study was also conducted to collect experiences and specifications in cold regions. Tests indicate that polymer-modified asphalts should always be the end result of an extensive product development program. The polymer modification improved the performance of all base asphalts in certain polymer–asphalt combinations. However, some otherwise acceptable binders smoked excessively when the temperature was elevated to the recommended mixing temperature. This issue warrants further investigation.

Pavement Preservation Practices in Cold Regions

Pavement preservation is an emerging approach in road upkeep. The State of Alaska Department of Transportation and Public Facilities (AKDOT&PF) aim to spend wisely the funding for its road upkeep by integrating pavement preservation concept into its Pavement Management System. To do this, a literature review was conducted on the performance and cost effectiveness of pavement preservation treatments in cold regions. This paper presents the results of the literature review. The following include the main findings: Pavement preservation treatments, Crack Sealing, Patching, Fog Seals, Chip Seals, Slurry Seals, AST/BST, Microsurfacing, Thin Overlays, Bonded Wearing Courses, Interlayers and In-place Recycling, are all used widely in cold regions. Crack sealing and patching are the most extensively used pavement preservation treatments. Use of chip seals, fog seals, and slurry seals should be considered job specifically. The service life of the treatments varies from about 3 years to 12 years. Microsurfacing and thin overlays have the longest service life. The costs of treatments vary from a region to another as well as from project to another. Other issues despite the cost effectiveness include sustainability and traffic safety.

Development of Enhanced Alaska Pavement Preservation Program and Strategy Selection Guide

The Alaska Department of Transportation and Public Facilities (DOT&PF) wished to enhance its existing pavement preservation management program by using effective pavement preservation treatments for cold regions. This initiative would extend pavement life and defer the need for more costly rehabilitation. By collaborating with the California Pavement Preservation Center and the Alaska University Transportation Center, the Alaska DOT&PF recently completed a pavement preservation research project to improve its pavement preservation program for flexible pavements. Research tasks included conducting an international survey of pavement preservation in cold regions, reviewing literature on cold region pavement preservation treatments, monitoring existing preservation treatments that Alaska used, developing a pavement preservation database, and creating an online computer program for treatment selection. The database for pavement preservation treatment tracking is a web-based online program that includes standard types of pavement preservation strategies used in Alaska; pavement construction, traffic, weather, and other performance-related information; an integrated Google Map function to show the location of pavement preservation projects; and multiple pavement condition survey results with supporting documents. The strategy selection program is integrated within the pavement preservation database. The program sees results of the survey and other information on Alaska treatments to conduct treatment strategy selection and life-cycle cost analysis. Workshops have been given on preservation treatments used in cold regions and use of the database and strategy selection process. Tools developed for the Alaska DOT&PF should be helpful for long-term implementation of an effective pavement preservation program. Other agencies could learn from Alaskas experience.

Evaluation of Pavement Preservation Treatments Used in Alaska

Pavement preservation is recognized as a means to a lower life cycle cost of a road asset; but, possibly not all surface distress data are documented and kept to further enhance a beneficial decision for the best treatment at the proper time. This paper presents a study to identify the types of treatments used in Alaska and how the treatments had performed. Forty-four road sections in Alaska that had received a pavement preservation treatment were surveyed in person along with data available from the Alaska Department of Transportation and Public Facilities (AKDOT&PF). The PASER manual for asphalt roads was used to evaluate the distresses for the road sections. Different treatments provided varied improvement of pavement life, which is also consistent with the findings from parallel research efforts of literature and survey conducted by the research team. In addition, pavement failure modes in different regions of Alaska are different. The same pavement preservation treatments may be applied to different regions but to prevent or mitigate different failure modes. Use of some treatments (for example, chip seals) should be considered job-specifically. There is a need to create a pavement preservation database and keep good records of current and future pavement preservation projects for better evaluating and applying them.

Introduction to Cold Regions Pavement Engineering

Cold Regions Pavement Engineering book by Guy DorE and Hannele Zubeck was recently published by the ASCE Press and McGraw-Hill. It prepares engineers to make right decisions in areas, where freezing temperatures, snow and ice, unstable soils, sparse population, long road mileage and often limited funds dictate design and maintenance actions on pavement structures. The book aimed to practicing Civil Engineers covers the unique environment, performance challenges, testing, design, management and rehabilitation of cold regions pavements including permafrost areas. Combining the latest research and proved techniques from the Northern United States, Canada and the Northern Europe, this is the first complete reference for all pavement projects in cold regions. This invited paper introduces the reader to the issues presented in the book.