This project was designed to develop and demonstrate the field application of an automated real-time quality control aggregate laser scanning monitoring system. The technical feasibility of the laser scanning, referred to as the Sampling and Laser Targeting System (SLT), consists of a laser, a spectrometer, a fiber optic cable, mirrors and lenses, a housing with a ventilation system, and a laptop computer to monitor aggregate materials introduced into the system. The SLT system works by focusing a high-powered laser at flowing aggregate materials and recovering and analyzing the light generated in this process. The recovered light provides a unique fingerprint of the target material.  Aggregate materials received from several state departments of transportation, including Ohio, New York, Kansas, Oklahoma, and Pennsylvania, were scanned. A special software was developed to analyze spectral data generated during laser scans.  The results suggest that laser scanning and multivariate analysis of spectra generated using the SLT could predict values of acid Insoluble residue, specific gravity, micro-Deval, D-cracking and percent chert in the aggregates tested. A key conclusion of this research is that laser scanning of aggregate is a technology capable of altering the manner in which aggregate quality control procedures are employed by the industry in the future. A draft Standard of Practice or a Test Method on the laser scanning technology was also prepared for consideration by the AASHTO.

The final report is available.