InTrans / Aug 17, 2015
Testing pavement foundation designs at the Central Iowa Expo
You can optimize the pavement mix, placement practices, and finishing techniques, but what’s underneath the pavement can make all the difference between a long-lasting pavement and one that experiences problems prematurely.
The critical characteristics of a pavement foundation are uniformity and stability. The foundation must provide stable support conditions to the pavement throughout the pavement’s service life.
To increase the range of stabilization options for future foundation designs, the Center for Earthworks Engineering Research (CEER) is testing a variety of foundation stabilization technologies and stiffness measurement technologies with a focus on assessing freeze-thaw performance. The project, supported by the Iowa DOT and FHWA, is known as the Central Iowa Expo.
The technologies are being tested on 16 different 700-foot test sections of pavement being reconstructed in Boone County, Iowa:
- Woven and non-woven geosynthetics, as separation layers between the subgrade and subbase, and two different types of geogrids as reinforcement of the subbase layer, plus geocells in the subbase layer for confinement
- Chemical stabilization of subgrade with self-cementing fly ash and portland cement in subgrade and subbase layers
- Two types of fiber reinforcement of subbase, with and without portland cement
- Mechanical stabilization of soil by mixing reclaimed granular subbase material with the subgrade soil on site
- High-energy impact compaction to stabilize existing granular base
- Stiffness-based measurements such as intelligent compaction, falling weight deflectometer, light-weight deflectomer, and dynamic cone penetrometer
- The project is currently under long-term performance evaluation. Seasonal variations in temperature, stiffness, and drainage are being monitored.
An overview of the project is available on YouTube: www.youtube.com/watch?v=qnq4fmRs6so.
Tech briefs have been developed for the different stabilization technologies: https://ceer.iastate.edu/research/completed/boone-county-expo-research-phase-i-granular-road-compaction-and-stabilization/
This article is part of the CTRE EnRoute 2014 Year-at-a-Glance series. Download the full document (.pdf).