<p><p><div><h2>Project Summary/Scope:</h2>The Washington Dulles International Airport is located in Virginia. In order to continue servicing the needs of the public, new facilities were built at the airport under the project called Dulles Development (d²) Program. As part of the program, 3,048 meters (10,000 feet) of runway was reconstructed with Portland cement concrete. Chemical stabilization for subgrades with cement was adopted.</p><p>Subsurface Conditions: Ground water table varied between 23 and 305 cm (0.75 feet and 10 feet) below the existing pavement surface. Soaked CBR values for natural subgrade soils were found to be between 0.7 and 36.8.</p><p>Portland cement was selected as the additive to treat the top 300 mm (12 inches) of the existing subgrade. Several tests, including mechanical analysis, durability, shrinkage, and unconfined compressive strength test were conducted to select the optimum cement content. Finally, the target cement content of the subgrade was established at 4%.<br><h2>Performance Monitoring:</h2>Heave or differential swelling occurred in several places two months after construction of base courses on two Atmospheric Fluidized Bed Combustion (AFBC)-stabilized sections. The swelling of stabilized subgrades consisted of primary and secondary swelling. The maximum primary swell value ranged from 1.8 to 8.8 cm (0.7 to 3.5 inches). The secondary swell value was very small over a period of 5 years.<br><h2>Project Technical Paper:</h2>Syed, I.M., Fuselier, G.K., and Hewitt, M. (2007). “Innovation in Cement Stabilization of Airfield Subgrades.” 2007 FAA Worldwide Airport Technology Transfer Conference, April, Atlantic City, New Jersey, 1-12.<br><h2>Date Case History Prepared:</h2>November 2012</p><p></div></p></p>