Concrete Overlays for Airports (by Dave Sethre)

Larry Engbrecht from the SD ACPA and I partnered to do a 50 minute presentation February 27th for the SD Airports annual workshop in Aberdeen.  Our topic was a technical coverage of concrete overlays for airports.  Larry did a real nice job in the first part introducing the concept and some discussion on design, and I finished with some examples and design/construction considerations.  We must have hit a resonant note, as we had some very nice comments afterwards and some good questions, indicating significant interest from airport owners/managers As part of my presentation, I used the New Smyrna Beach, Florida overlay project which used a 3” overlay for an apron.  This project was constructed in 1996 with private funds and is working great.  We don’t see a lot of airport construction money outside FAA funding in SD (or ND), so we are limited by FAA rules to a minimum of 5” thickness for any concrete pavement.  However, it was beneficial to show the success of very thin concrete applications and success stories.      We can live with the 5” thickness limitation, but need to continue to convince everyone that our soils will not limit us in success with this.  It seems like a no-brainer, if the asphalt in place has been performing adequately for a number of years.  But there is this perception that asphalt is flexible, so performance is better when the subgrades move around with frost heave.  I introduced the concept of shortening joints spacing in areas where low to moderate subgrade issues occur on a spot basis.  For instance, for a 5” overlay, we can use 9’ joint spacing on the good soil, and shorten to 6’ spacing where the soil will expand a little.  The concept is to provide more control joints to catch a crack, if one happens.  Of course, if we have major subgrade issue, we should reconstruct; preferably in concrete. Latest News: Interstate Engineering together with the Airport Commission at Ft. Yates have changed materials for their new runway construction from asphalt to concrete. Congratulations on a great choice!      With the seeming success of this presentation, I am going to offer the same presentation for the ND Airports workshop.   Submitted by Dave Sethre.