Iowa Department of Transportation
Iowa Highway Research Board
Peter Taylorptaylor@iastate.edu email >
Director, CP Tech Center
Halil Ceylanhceylan@iastate.edu email >
About the research
The aim of the work described in this report was to investigate the impacts of internally cured (IC) concrete paving on warping in test pavements built in Iowa. The study involved both laboratory investigations and field implementation of internally cured concrete for Iowa pavement systems.
The primary objective of this research was to perform a full-scale field demonstration using IC technology and to investigate its performance in rural roadways. Two overlay construction projects were identified for the field demonstration. Samples of the mixtures were taken at the time of placement and sent to the laboratory for parallel testing with laboratory prepared mixtures.
A number of sensors were embedded in the concrete slabs to monitor moisture and temperature over time. Periodic measurements were taken throughout the year to observe and evaluate the dimensional stability of the slabs.
To assess the value proposition of using internal curing in concrete overlays, life-cycle cost analyses were conducted using reported costs from the projects. Because little structural benefit is expected from the IC mixtures, the assessment was based on a predicted reduction in maintenance costs of the sections due to improved permeability determined in the laboratory tests. Both the net present value (NPV) and equivalent annual annuity (EAA) calculation results indicate a net savings over time with the use of IC technology.
Based on the field and laboratory results, using lightweight fine aggregate (LWFA) improved the concrete hydration for about one month after placing. The biggest challenge appears to be related to obtaining and preconditioning the LWFA.
In summary, the technique does appear to be of benefit for reducing the potential for early-age cracking, improving ride and increasing the longevity of relatively thin overlays. Assuming that the challenges of transportation and storage can be overcome, this is a viable technique to help improve the performance of such pavements.