Leaching Assessment of Eco-Friendly Rubberized Chip Seal Pavement

Abstract

Companies in the United States need to mine billions of tons of raw natural aggregate each year. At the same time, billions of scrap tires are stockpiled every year. As a result, replacing the natural aggregate with recycled aggregate is beneficial to the construction industry and the environment. This paper is part of a comprehensive project that developed, and field implemented, a new eco-friendly rubberized chip seal where the mineral aggregate in chip seal is partially or totally replaced with crumb rubber made of recycled tires. This paper presents an extensive study of the environmental impact of using rubber aggregate in chip seal pavement in terms of leaching under different pH conditions, including simulated acid rain. The results are compared with those of conventional chip seal. Leaching from the constituents of chip seal, that is, rubber aggregate and emulsion, was investigated. Two types of rubber and two types of asphalt emulsions were studied. The leaching performance of rubberized chip seal was also investigated. This study revealed that the toxic heavy metals leached from the rubberized chip seal, for pH ranging from 4 to 10, were below that of the EPA drinking water standards. In addition, a significant reduction of heavy metal leaching was recorded when rubber was used with emulsion in the form of chip seal pavement under different pH conditions. Finally, the metal leaching in all types of samples (including rubber, asphalt emulsion, and chip seal) decreased with the increase in pH value.