Institute for Transportation

About the research

Soils in Iowa generally rate fair to poor as subgrade soils for paving projects. Select soils for use directly under the pavement are often difficult to find on a project and in many instances are economically unavailable. The objective of this research was to evaluate the use and performance of untreated C-stone as a select fill replacement for Class 1-0 subgrade soils.

A construction project in Wapello County was the site of the research. About 3.1 miles of the project was constructed using 10 in. of reclaimed fly ash as a select fill beneath the PCC slab. The remaining miles were constructed according to the current design and used as a control section.