Factors Influencing the Leaching of Asphalt Components

The main applications of asphalt involve the coating of surfaces, e.g., in roads, roofs, pipes, and linings of water basins. in all of these applications, asphalt has the possibility of coming in contact with water. Such contact can lead to the leaching of components from the asphalt into the environment. Chemical oxygen demand (COD) is a method useful in evaluating the leachability of asphalt components. The leaching conditions (leaching time and temperature) and leaching medium (content of chloride and pH value) influence the COD of leachate. These were studied using the COD leaching test. For the five asphalt binders, the COD of the leachate increased with an increase in leaching time. The COD data also showed that the concentrations of components leached from styrene-butadiene-styrene (SBS) modified asphalt and oxidized asphalt were more than from neat asphalt binders. The influencing data showed that the COD of leachate increased with the increasing of temperature, but the temperature had less influence on the leachability of lower penetration grade asphalt than higher penetration grade asphalt. The leaching of asphalt binders coming from different oil sources was influenced differently by chloride. The amounts of components leached from SBS modified asphalt and oxidized asphalt were less than from neat asphalt. The influence of chloride is attributed to the salting out effect. By investigating the influence of the leachate pH on COD, it was proven that acidic conditions had the most influence on asphalt leachability, and the COD of leachate from oxidized asphalt decreased comparing to the neat asphalt. SBS modified asphalt, was best for resisting leachability by strong acid compared with neat asphalt neat asphalt.