Absorption—Ability of a porous solid material to hold relatively large quantities of gases or liquid.

Addition polymerization—Polymerization in which monomers are linked together without the splitting off of water or other simple molecules.

Adhesion—The state in which two surfaces are held together by interfacial forces which may consist of molecular forces or interlocking action or both. Measured in shear and peel modes.

Adhesive failure—A separation of two bonded surfaces that occurs at the interface between the adhesive and the material being bonded.

Adjusted internal rate-of-return (AIRR)—The compound rate of interest that, when used to discount the terminal values of costs and benefits of a project over a given study period, will make the costs equal the benefits when cash flows are reinvested at a specified rate. (Syn.financialmanagement rate of return [FMRR])
Adsorption—The adhesion of an extremely thin layer of molecules (of gases, or liquids) to the surface of solids or liquids with which they, are in contact.

Aggregate—(1) Crushed stone, crushed slag, or water-worn gravel used for surfacing a built-up roof; (2) Any granular mineral material.

Aging—The effect on materials of exposure to an environment for an interval of time. The process of exposing materials to an environment for an interval of time.

Air lance—A devise used to test, in the field, the integrity of field seams in plastic sheeting. It consists of a wand or tube through which compressed air is blown.

Aliphatic polyurethane coating—Normally used as a top coat, it contains a specific class of isocyanates based on a long straight chain molecular structure. It is noted for its high-tensile strength, high-gloss, color-stable properties and UV resistance.

Alkalinity—The capacity of water to neutralize acids, a property imparted by the water's content of carbonates, bicarbonates, hydroxides, and occasionally borates, silicates, and phosphates. It is expressed in milligrams of calcium carbonate equivalent per litre.

Alligatoring—Shrinkage cracking of the surfacing bitumen on a built-up roof, producing a pattern similar to an alligator's hide.
The cracks may or may not extend through the entire surfacing bitumen thickness.

Alloy, metallic—Material that has metallic properties and which is composed of two or more chemical elements, at least one always being metal.

Alloys, polymeric—A blend of two or more polymers, e.g., a rubber and a plastic to improve a given property, e.g., impact strength.

Aluminum coated steel—Steel coated with aluminum for corrosion protection.

Analysis—The determination of the nature or proportion of one or more constituents of a substance, whether separated out or not.

Anchor bolts—Bolts used to anchor structural members to a foundation or other support. Usually refers to the bolts at the bottom of all columns and door jambs.

Angstroms—(A°) A unit of measurement equal to 10'10 meters (.0000000001 meters). Generally used to measure the wave length of certain types of electromagnetic radiations, i.e., the red line of cadmium is defined as 6438 A°.

Anneal—Heating to and holding at a suitable temperature, then cooling at a suitable rate, for such purposes as reducing hardness, improving machinability, facilitating cold working, producing a desired microstructure, or obtaining other desired mechanical or physical properties.

Annual value—A uniform annual amount equivalent to the project costs or benefits taking into account the time value of money throughout the study period. (Syn. annual worth, equivalent uniform annual value).

Annually recurring costs—Costs incurred in a regular pattern each year throughout the study period, normally for operating and maintenance (O & M).

Anodic metallic coating—Prevents corrosion of exposed areas of the base metal by galvanic protection. The coating becomes the anode and undergoes increased corrosion so that the base metal cathode is protected from further corrosion until all the nearby coating metal is gone.

Anomaly—Something that deviates more than would be expected from normal variations.

Antidegradant—compounding material jscJ to retard deterioration caused by oxidation, ozone, light and combinations of these. Note—antidegradant is a generic term for such additives as antioxidants, antiozonants and waxes.

Antioxidant—A substance which prevents or slows down oxidation of material exposed to air.

Application rate—The quantity (mass, volume or thickness) of material applied per unit area.

Approval drawings—Approval drawings may include framing drawings, elevations and sections through the building as furnished by the manufacturer for approval of the buyer. Approval by the buyer affirms that the manufacturer has correctly interpreted the overall contract requirements for the system and its accessories, and the exact location of accessories in the building.

Architectural drawing—A drawing which shows the plan view and/or elevations of the finished building for the purpose of showing the general appearance of the building, indicating all accessory locations.

Aromatic polyurethane coating—A single or plural component polyurethane coating that is a polymer based on cyclical molecular structure. It is normally used as a base coat for aliphatic top coat systems and also exist as UV-resistant topcoats.

Asbestos—A group of natural fibrous impure silicate materials.
Ash—The incombustible material that remains after a substance has been burned.

Asphalt—A dark brown to black cementitious material in which the predominating constituents are bitumens which occur in nature or are obtained in petroleum processing.

Asphalt felt—An asphalt-saturated felt.

Asphalt, air blown
—An asphalt produced by blowing air through molten asphalt at an elevated temperature to raise its softening point and modify other properties.

Asphalt, steam blown
—An asphalt produced by blowing steam through molten asphalt to modify its properties.

Asphaltene—A high molecular weight hydrocarbon fraction precipitated from asphalt by a designated paraffmic naphtha solvent at a specified temperature and solvent-asphalt ratio.
Note—The asphaltene fraction should be identified by the
temperature and solvent-asphalt ratio used.

ASTM—American Society for Testing and Materials
A tactic—A chain of molecules in which the position of the side methyl groups is more or less random. (Amorphic; Low Crystal-linity)

Atactic Polypropylene (APP)—a group of high molecular weight non-crystalline polymers formed by the polymerization of propylene. These polymers are used as modifiers in asphalt modified roofing membranes.

Atomic number—Defined by the number of protons in the nucleus of a chemical element.

Atomic weight—The mass of an atom of an element, compared to the mass of carbon 12.

Automatic welding—A welding operation utilizing a machine to make a continuous, unbroken weld.

Auxiliary loads—All specified dynamic live loads other than the basic design loads which the building must safely withstand, such as cranes, material handling systems, machinery, elevators, vehicles, and impact loads.

Average—In statistics, the mean average is the sum of the values from a series of tests divided by the number of tests performed. The median average would be the middle value of a series of numbers. The mode would be the most common number of a set of numbers.

AWS—American Welding Society