Removal of Binder from Asphalt Mixture Using High Temperature and High Pressure Water

Abstract

A new recycling technology is proposed for separating and recovering aggregate and binder from asphalt pavement waste to develop a sustainable asphalt pavement recycling system. Investigation of the system used water as the solvent, which is the most convenient, economic and safe solvent for humans and the environment. Hightemperature and high-pressure water was evaluated for removing the binder from the asphalt mixture and recovering the aggregate. The study found that high-temperature and high-pressure water could remove the binder, particularly in the supercritical region, and that water was effective for removing binder and recovering aggregate from Type II modified asphalt as well as straight asphalt. Further removal of the remaining binder was achieved by repeating the tests in the sub-critical region where adequate effects were not achieved in a single test, suggesting the potential for an iterative approach under low-temperature and low-pressure conditions that would be more suited to commercialization. The present high-temperature and high-pressure water method of separation and reclaiming technology can recover and recycle valuable natural aggregate and oil resources from asphalt pavement waste.

Separation and Recovery of Aggregate from Asphalt Pavement Wastes Using High-temperature and High-pressure Water

“…Past research has confirmed that high-temperature and high-pressure water can effectively remove virgin binders and efficiently recover aggregate 5) . Here we discuss the relationship between the infl uence of binder property deterioration on the conditions required for removal of binders by high-temperature and high-pressure water, and the results of high-temperature and high-pressure water reaction tests on deteriorated binders.…”

“…Aggregate samples after reaction were recovered by fi ltering (glass fiber filter paper with particulate retention of 1.6 µm). Solids adhering to the surface of the filter paper were removed with hexane, and the residuals and the samples were dried in a furnace (110 C for 8 h) 5) . The binder removal rate was calculated from the change in the mass of the sample before and after fi lming and reaction using Eq.…”

“…For reference, the removal rates of virgin binders are shown in parentheses 5) . High-temperature and high-pressure water removed deteriorated binders equal to that of the virgin binder under all reaction conditions.…”

“…This suggests the need to review methods of aggregate recovery, particularly the solid-liquid separation method. For samples recovered under the same conditions, globularization was successfully eliminated by cleansing the aggregate after the reaction 5) . The grain size of the recovered aggregate after supercritical water reaction measured as passing mass percentage was +0.4% for 0.3 mm and −1.3% for 0.075 mm, which indicates sufficient retention of the grain composition of fine and very fine aggregate components and extremely small variation in sample mass before and after reaction.…”

“…Our research focuses on the separation and recovery of aggregate from RAP using high-temperature and highpressure water. Firstly we evaluated the infl uence that deterioration of asphalt binders to ability for separation of high-temperature and high-pressure water to assess feasibility of this process as recycling technique for RAP 5) . We then conducted property and quality evaluation tests on the recovered aggregate, and evaluated the suitability of the recovered aggregate as pavement aggregate.…”