Improving subgrade strength and pavement performance by chemical treating subgrade soils

Chemical treatment of subgrade soils to improve unstable soils has historically been done by using lime, cement and other lime/cement by-products. The Michigan Department of Transportation (MDOT) generally uses remove and replace option to treat unsuitable, soft subgrade materials for construction facilitation. Based on the results of preliminary soil investigations and successful use of lime treatment for treating similar soils, a provision was included to construct lime stabilized subgrade for I-96/I-75 reconstruction project in Detroit, Michigan. Later, two test sections using Cement Kiln Dust (CKD) to stabilize subgrade were included to investigate the suitability of CKD. Pavement subgrade strength improvement through lime and CKD stabilization was evaluated using Dynamic Cone Penetrometer (DCP) measurements. As anticipated, the DCP measurements showed substantial strength improvements with both lime and CKD stabilization. Pavement performance improvement due to stabilization was investigated using the new Mechanistic-Empirical Pavement Design Guide (MEPDG). This study concludes, although subgrade stabilization was aimed at providing a stable construction platform, some pavement performance improvements can also be expected in terms of joint faulting and smoothness per MEPDG.