Degree Type


Date of Award


Degree Name

Master of Science


Civil, Construction, and Environmental Engineering


Civil Engineering

First Advisor

Jeramy C. Ashlock

Second Advisor

Bora Cetin


Granular-surfaced roadways in Iowa rural area frequently experience damage and degradation from the effect of rainfall, flooding, seasonal freeze-thaw cycles, heavy agricultural machinery and steadily increasing traffic loads. Rutting, potholes and frost boil problems appeared usually and leading these granular roads to unpassable. As a result, many counties have to close damaged roads for repairs and spend significant portions of their budgets on maintenance and rehabilitation of granular roads. Several stabilization methods for granular roads were examined for improving the performance and minimizing damages in Iowa by the previous completed Phase II Iowa Highway Research Board Project TR-664 “Low-Cost Rural Surface Alternatives: Demonstration Project”. To investigate additional stabilization methods suitable for use in Iowa, six mechanical and five chemical stabilization methods employing different types of virgin and recycled materials were examined and used to build test sections in this study. Comprehensive construction procedures were developed and 31 test sections were built in four counties distributed geographically around the state of Iowa in August through October 2018. Extensive laboratory, field tests, and photographic surveys were performed prior to construction, as well as after construction to monitor the performance of the demonstration sections. The shear strength and elastic modulus of granular roads surface course were obviously improved by one of the chemical method, cement treated surface, and three of the mechanical methods, optimized gradation with clay slurry and two slag stabilization methods. The composite elastic modulus was improved by two cement treated methods and two mechanically methods, optimize gradation with clay slurry and aggregate columns. Several equipment was also found that can shorten the construction time and stabilize the soil more efficiently.

Copyright Owner

Yijun Wu



File Format


File Size

141 pages