Density of Asphalt Concrete - How Much is Needed?

00750977https://doi.org/10.21949/14044941990PDFTech ReportAsphalt mixturesInstruments for measuring densityCores (Specimens)Nuclear gagesasphaltdeformationnuclear metersphyscial propertiesAlabama;United StatesNational Center for Asphalt Technology (U.S.)Brown, E.RayNTL-HIGHWAY/ROAD TRANSPORTATION-MaterialsNTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and PerformanceUS Transportation CollectionDensity is one of the most important parameters in construction of asphaltmixtures. A mixture that is properly designed and compacted will contain enoughair voids to prevent rutting due to plastic flow but low enough air voids toprevent permeability of air and water. Since density of an asphalt mixturevaries throughout its life the voids must be low enough initially to preventpermeability of air and water and high enough after a few years of traffic toprevent plastic flow.There are three primary methods of specifying density: percent of control strip,percent of laboratory density, and percent of theoretical maximum density. Allthree methods can be used to obtain satisfactory compaction if used correctly.The initial in-place air voids must be below approximately eight percent and thefinal in-place air voids must be above approximately three percent. The initialin-place air voids are determined by comparing bulk density to theoreticalmaximum density (TMD) and the final in-place air voids are estimated bycomparing bulk density of laboratory compacted sampler to the TMD.The two methods that have been used to measure bulk density of asphalt mixtureare physical measurements of cores and nuclear gage. The nuclear gage is fastand non-destructive but is not as accurate as the core method.84