Cementitious High-Carbon Fly Ash Used to Stabilize Recycled Pavement Materials as Base Course

Because of the increasingly stringent environment policy stipulated by the U.S. Environmental Protection Agency, local authorities, or both, the power generation industry must take measures to reduce the emission of nitrogen oxides, sulfur oxide, and mercury. These measures increase the amount of residual unburned carbon in fly ash. The increase makes the fly ash unsuitable for concrete production and destines it to become landfill. During roadway construction, existing asphalt pavement is often removed. This paper presents the test results of using cementitious high-carbon fly ash to stabilize recycled asphalt pavement materials in situ as a new base course. A series of laboratory tests was performed, including moisture–unit weight relationship, California bearing ratio, unconfined compressive strength, and freeze–thaw durability. Two high-carbon fly ashes (high-calcium and low-calcium) were used in this study. The test results indicate that using high-calcium, high-carbon fly ash has the potential to be a cost-effective and environmentally friendly technology.