forth laterally with a grader before being spread andcompacted. This action speeds up setting or curing.Always round your answer to the next highernumber. In this case, 1478.4 is rounded to 1479 gallons.TYPES OF ASPHALT PAVEMENTCONSTRUCTIONTwo major types of asphalt pavement constructionare in use today: plant mix construction (so-calledbecause the mixture is prepared in a central mixingplant) and mixed-in-place construction (so-calledbecause the mixture is mixed on the area to be paved).PLANT MIX CONSTRUCTIONL =Asphalt-paving mixtures, prepared in a asphaltmixing plant, are known as plant mixes. Plant mixasphalt concrete is considered the highest quality plantmix. It consists of well-graded, high-quality aggregateand asphalt cement.The asphalt and aggregate areheated separately from 250°F to 325°F, carefullymeasured and proportioned, then mixed until theaggregate particles are coated with asphalt. The hotmixture, kept hot during transit, is hauled to theconstruction site where it is spread on the roadway withan asphalt-paving machine. The smooth layer from thepaver is compacted by rollers to proper density beforethe asphalt cools.W =D =146 =Asphalt concrete is but one of a variety ofhot-asphalt plant mixes.Other mixes, such as sandasphalt and coarse-graded mixes, are prepared andplaced in a similar manner; however, each has onecommon ingredient, which is asphalt cement.Asphalt mixes, containing emulsified or cutbackasphalt, may also be prepared in asphalt mixing plants.The aggregate may be partially dried and heated ormixed as it is withdrawn from the stockpile. Thesemixes are usually refered to as cold mixes, even thoughheated aggregate may have been used in the mixingWF =2,000 =process.Both asphalt mixtures, made with emulsifiedasphalt and some cutback asphalts, can be spread andcompacted on the roadway while quite cool. Suchmixtures are called cold-laid asphalt plant mixesThey are hauled and placed in normal warm weathertemperatures. These mixtures, after being placed on theroadway, are sometimes processed or worked back andCompute Plant-Mix MaterialsSeveral methods are used to calculate the amount ofhot-mix material, required for paving projects; however,when the weight of a hot mix per square yard or cubicfoot is not known, two equations are used in the NCF tocompute the number of tons of asphalt, required for aproject. These equations are as follows:length of project in feet.width of project in feet.depth or thickness of compacted mat. Youmust change inches into feet by dividing thenumber of inches by 12 (inches in 1 foot).For paver screed height, add 1/8 inch foreach inch of the mat to be paved. (Example:For a 2-inch mat, two blocks of wood 2 1/4inches thick will be required to set under thescreed.) The blocks must be thicker thanthe finished compacted mat to allow foradditional compaction by rollers.This number represents the approximateweight of 1 cubic foot of compactedhot-mix asphalt.This number can varyfrom 140 to 160 pounds; however,146 pounds equals the 110 pounds persquare yard per l-inch depth of asphalt usedin the second equation for figuring tonsrequire for asphalt. (See table 16-2.)Waste factor equals 5% or .05, or 10% or.10, depending on the experience of thescreed operators and handwork required onthe project.2,000 pounds is equal to one ton; therefore,you must divide the total weight of materialby 2,000, giving tons required.16-9
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