Andrew Wimsatt

Test Method and Model Development of Subbase Erosion for Concrete Pavement Design

The erosion of material beneath a concrete slab is an important performance-related factor. If applied to the selection of base materials, this factor can enhance the overall design process for concrete pavement systems. However, erosion of the subbase has not been included explicitly in analysis and design procedures because there is no well-accepted laboratory test or related erosion model suitable for design. Therefore, this paper focuses on advancing a simple laboratory test method to evaluate erodibility of a subbase material and then introducing and validating an erosion model that incorporates the results from the new laboratory test method. Erosion-related design procedures were reviewed relative to previous test methods. Erosion models were evaluated for their utility to characterize the erosion resistance of subbase materials. With this information, a new test configuration was devised; it used a rapid triaxial test and a Hamburg wheel-tracking device for evaluating erodibility in relation to the degree of stabilization, base type, and cement content. Test devices, procedures, and results are explained and summarized for application in mechanistic design processes. A proposed erosion model is validated by comparing erosion predictions to erosion results.

DIRECT ANALYSIS METHODS FOR FALLING WEIGHT DEFLECTOMETER DEFLECTION DATA

Two direct methods of analyzing falling weight deflectometer deflection data are presented. One method, which involves dividing the deflection 1828.8 mm (72 in.) away from the load plate by the deflection underneath the load plate, relates directly to the ratio between the pavement modulus and subgrade modulus for a two-layer system. The other method described in the paper gives a qualitative evaluation of the stiffness of the base material as it relates to the pavement surface. Examples of using these methods are described and compared with results from the Modulus Version 5.0 computer program developed by the Texas Transportation Institute.

Quality Assurance for Automated and Semi-Automated Pavement Condition Surveys

Automated and semi-automated pavement distress surveys are being used increasingly to collect pavement condition data. This data, along with other information, is used to measure pavement performance and support pavement maintenance, preservation, and rehabilitation decisions. Generally, these automated and semi-automated systems consist of image capturing technology (i.e., hardware) and image processing and analysis algorithms (i.e., software). This paper provides a review of quality assurance practices for automated and semi-automated pavement condition surveys, including quality of images, accuracy and repeatability of measurements, data delivery requirements, equipment calibration, and control and verification sites. The information on these practices was obtained through a review of seven request for proposals (RFPs) issued by seven state departments of transportation (DOTs) between 2010 and 2015, and supplemented by a review of three manuals for these surveys.