In May 2000, the Colorado Department of Transportation (CDOT) requested a forensic study of a project located on I-24 north of Denver. The request was made because, within a year of the 1997 overlay, longitudinal cracking appeared in the surface. Transverse cracks were attributed to reflective cracking. However, the longitudinal cracks appeared to be surface initiated. In October 2000, a forensic team reviewed the project and established a sampling and testing plan to take cores from the roadway. Based on data analysis of the cores, the higher than expected in-place air voids, the low effective asphalt, and segregation within the mat, all contributed to the early cracking.

Asphalt is a complex but popular civil engineering material. Design engineers must understand these complexities in order to optimize its use. Whether or not it is used to pave a busy highway, waterproof a rooftop or smooth out an airport runway, Asphalt Materials Science and Technology acquaints engineers with the issues and technologies surrounding the proper selection and uses of asphalts. With this book in hand, researchers and engineering will find a valuable guide to the production, use and environmental aspect of asphalt. - Covers the Nomenclature and Terminology for Asphalt including: Performance Graded (PG) Binders, Asphalt Cement (AC), Asphalt-Rubber (A-R) Binder, Asphalt Emulsion and Cutback Asphalt - Includes Material Selection Considerations, Testing, and applications - Biodegradation of Asphalt and environmental aspects of asphalt use

This reports document research that was performed to (1) determine causes of variability and tolerances for volumetric and mechanical properties of dense-graded asphalt mixtures measured within and among the three specimen types; and (2) propose a practice for state departments of transportation to incorporate these results in specifications and criteria for quality assurance, mix design verification or validation, and structural design and forensic studies. The research was conducted in two phases. In Phase I, datasets of laboratory and field test data were collected and pooled in a meta-analysis in an attempt to determine levels of variability in asphalt mixtures and the factors causing variability among and between the three specimen types. Despite the inclusion of 25 extensive datasets representing roughly 8,000 individual mixtures in the meta-analysis, the results of the analysis were inconclusive. Phase II was then undertaken--a program testing specimens from paving projects across the United States to quantify the effects of process-based factors on the variability of volumetric and mechanical properties of the specimen types. The key outcome of the research is a proposed practice for evaluating the cause and magnitude of variability within and among the three specimen types. In addition, tolerances of volumetric and conversion factors between the three specimen types of mechanical properties evaluated are proposed based on the average difference between specimen comparisons for the mixtures evaluated in Phase II. Agencies may use these proposed values to evaluate and adjust their current tolerances.

Structural Behavior of Asphalt Pavements provides engineers and researchers with a detailed guide to the structural behavioral dynamics of asphalt pavement including: pavement temperature distribution, mechanistic response of pavement structure under the application of heavy vehicles, distress mechanism of pavement, and pavement deterioration performance and dynamic equations. An authoritative guide for understanding the key mechanisms for creating longer lasting pavements, Structural Behavior of Asphalt Pavements describes the intrinsic consistency between macroscopic performance and microscopic response, structure and material, as well as global and local performances, and demonstrates the process of pavement analyses and designs, approaching science from empirical analyses. - Analyzes the external and internal factors influencing pavement temperature field, and provide a review of existing pavement temperature prediction models - Introduces a "Bridge Principle through which pavement performance and fatigue properties are consolidated - Defines the intrinsic consistency between macroscopic performance and microscopic response, structure and material, as well as global and local performance - Summaries the mechanistic response of pavement structure under the application of heavy vehicle, distress mechanism of pavement, pavement deterioration performance and dynamic equations, and life cycle analysis of pavement