SPR 2013 Prime KTC: Subgrade Stabilization

The objectives of this project are as follows: 1. Review the current state of practice for subgrade modification of various agencies, including potential cost savings and structural performance. 2. Evaluate, cost, constructability, and strength of various subgrade stabilization techniques, including chemical modification, undercut with aggregate replacement, and geogrid reinforcement. 3. Review current pavement design process to identify potential areas to refine designs to reduce overall pavement cost. 4 Develop project selection guidelines and specifications for subgrade stabilization, based on project type, and potential cost benefit. Kentucky has successfully utilized chemical stabilization of subgrades for more than 20 years. Previous research has indicated that this type of treatment provides a long-term structural benefit to the pavement structure, thus providing an opportunity to reduce the overall pavement thickness and potential pavement cost. Subgrade treatment by undercut and replacement with aggregate has also been utilized for many years. Research has not been completed to understand long-term performance of this treatment. In recent years the use of geogrids as reinforcement for aggregate layers has also been utilized. However, the long-term performance under thick asphalt or concrete pavements has not been documented. Kentucky’s current pavement design procedure is based on a three-layer mechanistic-empirical design philosophy. This method does not provide easy inclusion of stabilized materials as design layers. This research project will evaluate the methodologies which may be available to incorporate stabilization techniques with structural credit into pavement design. Including the recently completed Mechanistic Empirical Pavement Design Guide developed by AASHTO