A Novel Utilization of Coal-Derived Material for Pavement

Cement is widely used in pavement construction. A cement-treated base (CTB) with increased strength, stiffness, and water resistance can not only provide good support for surface course but also reduce the in situ water content of soils improving cohesion between bituminous surface and base materials. However, cement production is typically associated with high greenhouse gas emissions and energy consumption. Coal char is a sustainable and eco-friendly byproduct and porous coal-derived material. Recent studies have shown that coal char can be used as a raw construction and building material to improve the engineering performance of cement based products. In this research, the feasibility of using coal char in CTB is evaluated. Coal char, produced from Powder River Basin coal in Wyoming was pyrolyzed at a temperature of 850 °C, resulting in a fixed carbon content of 80%. According to the mix design for CTB of Wyoming Department of Transportation (WYDOT), the total amount of cement in the mix is 1% by weight of material. The effect of different additives (1% cement, 1% char, 0.5% cement, and 1% char with respect to soil weight) on the properties of soils is investigated. Compared to cement-stabilized soils, the char–cement-stabilized soil with 50% less cement use exhibits significantly higher unconfined compressive strength (UCS) and Young’s modulus at 7 days and comparable UCS at 28 days. For uncemented soils, the addition of 1% char leads to 2.3% lower water content. The findings would be beneficial for achieving sustainable pavement construction.