21AA On Steroids!You may have read how the construction crews installed the Traverse City Cherry Capital Airport improvements during a short but intense reconstruction schedule. Do you know what they used to build it? How do you support passenger jet airplanes and their payload that can weigh up to 240,000 lbs.? P209 is not some cleaning formula your grandma used. It is 100% dense grade aggregate that is specified to hold up to the wear and tear of airport traffic. On typical Michigan Department of Transportation (MDOT) highways, an aggregate base called 21-AA is typically specified. Some engineers call P209, 21-AA on steroids. All crushed stone creates fines during the crushing process. This material collects in the P200 sieve in the testing process. The mix design on a typical 21-AA mix design produces 8%-12% of P200 material during production. P209 specifications during the Cherry Capital Airport project only allowed 0%-5% P200 fines. An incredibly difficult standard to meet for a mix design and the crushing crew making it. Persistence (and a lot of hours) allowed crews to meet the standard and exceed expectations. |
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P-Four-O What? You've heard about the long hours and 24/7 construction schedule (see TEU: Episode 38 above right). You know the structure underneath the runway to hold up to the 240,000 lb airplanes landing at the Traverse City Cherry Capital Airport (see GALOT 19: P209 above left). Now what material do you use to keep the landing gear on those heavy planes happy? P401 and P403 - and a little 3D magic combined. P401 and P403 is an asphalt mix design that utilizes a self-healing polymer modified oil to keep the 10 inch thick asphalt runway as smooth as possible. How do you ensure you are meeting the required runway surface elevation above sea level set by the contract? 3D milling and paving. By using a 3-dimensional tin loaded into global positioning system satellites or total robotic stations on-site, Team Elmer's was able to ensure that all milled surfaces removed the exact amount of material to meet future elevations. (Think more material removed in a high spot and less material removed from a dip in the runway.) This 3-D milling and paving process was able to maintain elevations during the 115 ft addition, 800 ft reconstruction, and over 7,000 ft. resurfacing. Why not use grade stakes from a survey crew? Placing stakes on an existing asphalt runway 150 ft wide (18 car lanes) was not a viable option. Using robotic grade control, Team Elmer's ensured extremely accurate grades - within a tolerance of 0.25 inch or less of final elevation over the entire 7,000+ ft. runway length. We are thankful indeed! |