Asphalt Tonnage Calculator for Driveways

Asphalt is designed by thickness but bought by weight, and this calculation performs the conversion. Volume in cubic feet is area times thickness in feet; multiplying by the compacted unit weight of the mix gives pounds, which divided by 2,000 gives short tons. Compacted hot-mix asphalt runs about 140 to 150 pounds per cubic foot, with 145 the usual default, so a 2 inch lift weighs roughly 24 pounds per square foot and a ton covers about 83 square feet. Typical thicknesses are 2 to 3 inches of compacted surface over 4 to 8 inches of crushed aggregate base for a residential driveway, and 3 to 4 inches in two lifts for parking lots. Maximum lift thickness is limited to roughly three to four times the nominal maximum aggregate size, which is why thicker sections are built up in passes. The biggest source of error is confusing loose and compacted material. Mix leaves the truck well below its final density and loses about 20 to 25 percent of its thickness under the rollers, so tonnage must be computed on compacted density. Specifications generally require field density between about 92 and 96 percent of the theoretical maximum specific gravity from the Rice test. Density also varies with aggregate source, since a mix built on heavy trap rock weighs more per cubic foot than one on limestone, so ask the plant for its unit weight. Order 5 to 10 percent extra for edge wedging and truck cleanout, and note that a metric tonne is about 10 percent heavier than a short ton.

Naturally occurring asphalt from the Pitch Lake in Trinidad and from rock asphalt deposits in the Val de Travers region of Switzerland supplied the first modern pavements. In the United States the Belgian-born chemist Edmund J. DeSmedt laid what is generally credited as the first true sheet asphalt pavement in front of the city hall in Newark, New Jersey in 1870, and followed it with Pennsylvania Avenue in Washington in 1876 using imported Trinidad Lake asphalt. As petroleum refining expanded after 1900, refined asphalt cement displaced natural deposits almost entirely, and the growth of automobile traffic turned paving into a large industry needing repeatable mix specifications. Mix design supplied that repeatability. Bruce Marshall of the Mississippi State Highway Department developed a compaction and stability test in the late 1930s that the United States Army Corps of Engineers adopted and refined during the Second World War for military airfields, making the Marshall method the world standard for decades. The AASHO Road Test conducted near Ottawa, Illinois between 1958 and 1960 produced the empirical thickness design relationships that became the AASHTO pavement design guides, formalising the link between traffic loading and required layer depth. The Strategic Highway Research Program, funded from 1987 to 1993, delivered Superpave, which introduced performance-graded binders specified by climate, such as PG 64-22. Quality control still rests on the theoretical maximum specific gravity procedure developed by James Rice, standardised as ASTM D2041 and AASHTO T 209.