Aggregate Image Measurement System 2 (AIMS2): Final Report

INTRODUCTION

The Federal Highway Administration partially funded this project through the Highways for LIFE Technology Partnerships Program Grant DTFH61-08-G-00003. The purpose of the Technology Partnerships Program is to work with the highway construction industry to accelerate the adoption of promising innovations. The overall scope of this project, undertaken by Pine Instrument Company, was to take a system developed for research applications investigating aggregate shape characteristics and reconfigure it into an industry-viable tool. This technology utilizes digital imaging technology to capture and analyze images of aggregate particles to provide particle shape information. The goals of this grant were to improve the design, simplify the operation, establish the system and methodology as sound, perform an interlaboratory study to evaluate the precision of the results, and evaluate the commercial viability of the technology.

This Introduction provides a brief background into the importance of aggregate shape properties and how that importance led to this work and covers the scope and goals of the project. The Equipment section provides an overview of the technology concept and the initial research equipment in which the technology had been established. This section also discusses the new technology platform. The Experimental Plan section discusses the calibration of the new system to the original, the ruggedness testing, and the interlaboratory study (ILS) that was completed within this project. The Material Testing Procedures section discusses the test and practice procedures that have been developed as part of this effort, which have been adopted as Provisional Standards by the American Association of State Highway and Transportation Officials (AASHTO). The Commercialization section outlines Pine Instrument Company's plans and project observations regarding the viability of this technology platform. The Conclusion provides a concise summary of this project grant and the targeted path forward.

Background

Aggregate shape characteristics are well known to be important in influencing the structural performance of hot-mix asphalt (HMA), hydraulic cement concrete, and unbound aggregate pavement layers. Aggregate shape characteristics also influence the skid resistance of pavement surfaces. As such, accurate and consistent characterization of these properties will contribute to the enhancement of pavement performance and public road safety.

Current methods utilized for evaluating aggregate shape characteristics have proven to be time-consuming and subjective. There has been an identified industry need for a system to evaluate these properties utilizing a consistent, repeatable, and objective methodology. Measuring the shape properties of aggregates with an objective system will yield significant and immediate benefits to the transportation industry that can be realized by incorporating the improved aggregate shape characterizations into the design of pavement structures. A technology platform that can offer an objective means of qualifying aggregate shape properties to meet specifications will help ensure consistent pavement performance.

In addition to improving pavement structural performance, a technology platform that provides automated, consistent, repeatable, and objective outcomes has the potential for increasing public safety by providing a means for qualifying aggregate shape and surface texture, which are related to pavement friction properties, sometimes referred to as skid resistance. Furthermore, as the development of warm-mix technology continues in pavement applications due to its reduced energy footprint, aggregate properties will continue to be a critical parameter in pavement design. Consequently, a system of this sort has the potential to contribute significantly to the design of safe, high-quality, and long-lasting pavements. Large savings due to reduced requirements for maintenance and rehabilitation can also be realized.

It is also believed that the lack of accurate characterization of aggregates can lead to specifications that either overemphasize the need for superior aggregate characteristics or, in contrast, allow for the use of marginal aggregates. The delivery of a technology platform as an industry tool that provides accurate and objective aggregate characterization will contribute to the improvement of pavement material specifications. This improvement in material characterization will allow highway engineers to accurately select locally available materials that can be used in pavement construction while maintaining, and potentially improving, pavement performance. The use of local materials is highly favorable given the cost and logistical issues associated with transporting aggregates long distances.

Objective

The objective of this project undertaken by Pine Instrument Company in conjunction with the Federal Highway Administration was to design, develop, and fabricate a viable industry instrument to characterize aggregate shape properties utilizing digital imaging technology. This system would include hardware to capture the images and software capable of analyzing those images and to provide useful and meaningful data. As part of achieving this overall objective, a technology platform needed to be developed that would also withstand the tests of repeatability, reproducibility, objectivity, and ruggedness for both within-laboratory and between-laboratory situations. Finally, this technology platform needed to be evaluated against standard marketability thresholds and commercial viability expectations. The remainder of this report covers these areas in full detail.