Abbreviation for asphalt cement.

A person who specializes in the field of acoustics. HMA plant manufacturers may engage acousticians to assist their engineers and customers in noise control. Acousticians may measure complex acoustical characteristics as well as sound pressure levels at a plant site, analyze the measurements and recommend noise control solutions.

Inert material such as sand, gravel, crushed stone and slag used as the chief ingredient of HMA.

    SAND is a fine granular material (usually less than 1/4-inch dia.) produced by natural disintegration of rock or by crushing friable sandstone rock or other suitable rocks.

    GRAVEL is a coarse granular material (usually larger than 1/4- inch dia.) produced by natural erosion and disintegration of rock.

    CRUSHED GRAVEL is produced by artificially crushing gravel, causing most fragments to have at least one fractured face.

    CRUSHED STONE is produced by artificially crushing rocks, boulders or large cobblestones, causing the fragments to have all fractured faces.

    ROCK suitable for making good aggregates is formed all over the world and used to make crushed stone, sand and gravel.

    SLAG, is the air-cooled, non metallic by-product of a blast furnace operation. It consists essentially of silicates and alumino-silicates of lime and other bases.

A device that "shoots" bursts of compressed air into material to loosen it and make it flow better. Commonly used in bins that hold aggregate and RAP.

The numerical ratio of air flow to total filter surface area in a baghouse. Air flow is usually stated in cubic feet per minute (cfm). The total filter surface area is usually stated in square feet, determined by totaling the surface area of all filter bags in the baghouse.

Consider a baghouse with 448 filter bags, each 4-5/8 inches in diameter x 10 feet long, giving a total filter surface area of 5,421 square feet. Assume that the baghouse has an air flow of 29,960 cfm. Thus, the resulting air-to-cloth ratio is 5.5-to-1. This is the optimum air-to-cloth ratio for a baghouse in a HMA facility. The optimum ratio ensures that the baghouse exhaust will meet stringent clean air standards.

An additive often used in HMA to make it less susceptible to stripping. It improves the adhesive bond between the asphalt cement and aggregate. Additives may be in the form of filler or liquid. Lime is the most popular anti-stripping agent and can be used as a filler or as a lime slurry. Liquid anti-stripping agents can also be added to the asphalt cement at the HMA facility. (See stripping.)

A high hardness abrasion resistant steel plate commonly used in HMA production equipment to minimize erosion from aggregate and dust. It has a Brinell hardness of 360.