Use of Processed Tear-off Roof Shingles to Improve Performance of Roadbase Materials

This paper presents the results of a research project that focused on evaluating the potential use of processed tear-off shingles in road works. The project was conducted in attempts to promote construction sustainability through recycling more construction wastes into roads. The targeted applications were road base and unpaved gravel roads. Two different sizes of tear-off shingles were investigated: ground shingles with 100% of the particles passing sieve 4.75 mm and processed shingles with a maximum size of 75 mm and 40% passing 4.75 mm. Petrogrpahic examination confirmed that the investigated shingles did not contain asbestos. Five types of granular materials were investigated to determine the type of material that benefits the most from using the shingles. The five types of materials were quarried crushed limestone, crushed natural gravel with 72% crushed particles, and three recycled concrete aggregates (RCA). California Bearing Ratio (CBR) results showed that ground shingles provided better results compared to processed shingles. The use of an optimum amount of shingles (5%) increased the stability of the granular materials. This was the case for two of the RCAs and the natural gravel material investigated in this study. On the other hand, one of the tested RCA and the crushed limestone were adversely affected by the addition of shingles. The response of a granular material to shingle modification was found to be related to the amount and quality of fines in the materials. In terms of permeability, the addition of shingles did not have a significant impact on the drainage characteristics of the tested materials.