(545l) Environmental Impacts of Pavement Rejuvenators

The research conducted in this project investigated the potential environmental impacts of three types of pavement rejuvenators: asphalt-based, bio-based, and coal tar-based. Pavement rejuvenators are applied to pavement surfaces to “revitalize” old asphalt pavements and are thereby expected to extend their useful life. Applying rejuvenators may allow municipalities to maintain roadway pavements at a lower cost than completely renovating (removing and repaving) roadways. However, there is little published research on the extent contaminants may be released from rejuvenated pavement materials and as a result, little is known about the impacts of rejuvenators to the environment. This project looked into the environmental concerns of three types of pavement rejuvenators and analyzed the chemicals present to determine any potentially harmful environmental impacts. The three rejuvenators evaluated were an asphalt-based rejuvenator, a coal tar-based rejuvenator and a bio-based rejuvenator.

To conduct this evaluation, a PaveTesting Model Mobile Load Simulator (MMLS) was used to simulate surface challenges that roadway pavements are expected to withstand. Pavement samples coated with the different types of rejuvenators were subjected to testing in the MMLS to simulate roads being driven on through repeated tire-pavement contacts. The MMLS simulation dislodged particulate matter that was subsequently chemically analyzed through gas chromotography analysis. Concentrations of PAHs in each sample were determined.

To assess the environmental impacts, particulate matter detached from pavements treated with each type of rejuvenator was collected, extracted with methylene chloride, and injected into a gas chromatograph with a flame ionization detector (Agilent Technologies) to quantify polycyclic aromatic hydrocarbons (PAHs) present in the particulate matter. Many PAHs are a concern to public health and aquatic life, with some considered carcinogens. With significant quantities of PAHs present in this particulate matter detached during simulation testing, it can be expected that they will be present in particulate matter released from rejuvenated pavements in actual application. The mobilization of this particulate matter could cause problems in the environment because of the presence of PAHs.

Results indicated that the pavement samples treated with coal tar-based rejuvenator produced the least amount of particulate material during MMLS testing (0.2458 g), yet that particulate material had the greatest PAH concentrations, 3,440 ± 380 mg total PAH/kg sample. While the coal tar-based rejuvenator performed best with respect to limiting the mass of particulate that was mobilized from the car tire abrasion, the total amount of PAH mobilized from the pavement was the greatest. The pavement samples treated with asphalt-based rejuvenator resulted in the greatest mass of particulate matter released, 0.8315 g, and the total PAH concentration of that material was found to be 364 ± 26 mg PAH/kg sample. The pavement samples treated with the bio-based rejuvenator contained 582 ± 57 mg total PAH/kg sample, and resulted in 0.5559 g of detached material.
The use of coal tar-based rejuvenator is of concern due to its potential for release of PAH contaminants through detached particulate material. The bio-based rejuvenator appear to have promise due to the low potential for PAH mobilization. It is recommended that additional research be undertaken to evaluate the performance of rejuvenators in extending the useful life of asphalt pavements. Of particular interest is further evaluation of the environmental impact of these products.