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TRIS Online Accession Number:00750977
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NTL Classification:NTL-HIGHWAY/ROAD TRANSPORTATION-Materials;NTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and Performance;
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Abstract:Density is one of the most important parameters in construction of asphalt
mixtures. A mixture that is properly designed and compacted will contain enough
air voids to prevent rutting due to plastic flow but low enough air voids to
prevent permeability of air and water. Since density of an asphalt mixture
varies throughout its life the voids must be low enough initially to prevent
permeability of air and water and high enough after a few years of traffic to
prevent plastic flow.
There are three primary methods of specifying density: percent of control strip,
percent of laboratory density, and percent of theoretical maximum density. All
three methods can be used to obtain satisfactory compaction if used correctly.
The initial in-place air voids must be below approximately eight percent and the
final in-place air voids must be above approximately three percent. The initial
in-place air voids are determined by comparing bulk density to theoretical
maximum density (TMD) and the final in-place air voids are estimated by
comparing bulk density of laboratory compacted sampler to the TMD.
The two methods that have been used to measure bulk density of asphalt mixture
are physical measurements of cores and nuclear gage. The nuclear gage is fast
and non-destructive but is not as accurate as the core method.
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