Significant Findings from Full-Scale Accelerated Pavement Testing (2004)

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118 GLOSSARY The following are the words and definitions of some com- mon terms used in the field of pavement engineering that may be unknown to some of the readers of this synthesis. Asphalt—A mixture of inert mineral matter, such as ag- gregate, mineral filler (if required), and bituminous binder in predetermined portions. Commonly known in the United States as asphalt concrete (AC) or hot-mix asphalt (HMA). Asphalt, continuously graded—A mechanically mixed asphalt in which the aggregate and filler are distributed in size fractions from coarse to fine within a specified smooth grading envelope. Asphalt, gap-graded—An asphalt mixture composed of mineral particles, with certain intermediate sizes missing from the size range, and filler. Asphalt, LAMBs—Large aggregate mixes for bases con- taining graded large aggregates and meeting prescribed en- gineering properties for use as base course material in South Africa. Asphalt, open-graded—A mechanically mixed asphalt constituted to give a high air void content and rough sur- face texture in the compacted state. Asphalt, semi-gap-graded—An asphalt mixture com- posed of mineral particles, with certain intermediate sizes missing from the size range, and filler. The coarse aggregate fraction is more graded than that of gap-graded asphalt. Asphalt-treated permeable base (ATPB)—Known as a drained pavement in California. Bitumen—A noncrystalline solid or viscous mixture of complex hydrocarbons that possesses characteristic ag- glomerating properties. Bitumen, which is obtained from crude petroleum by refining processes, softens gradually when heated and is substantially soluble in trichloroethyl- ene. Commonly known in the United States as asphalt. Bitumen rubber—A blend of bitumen and approximately 20% by weight of crumb rubber, containing where neces- sary extender oil and/or dilutent. Bituminous-treated base—A layer consisting of granular material mixed with a bituminous binder. Bogie—A mechanical structure designed to enable a wheel carriage to transfer loading to the surface on which it runs, such as a pavement or a rail. Cape seal—A single application of binder and stone fol- lowed by one or two applications of slurry. Cementation—Stabilization with the objective of increas- ing the compressive or tensile strength to a predetermined level. The term “cemented material” is also used. ESAL—Equivalent single-axel load. In the United States, this equates to a load of 80 kN. It is sometimes abbreviated as E80. FORCE Project—An accelerated full-scale pavement test at the Laboratoire Central des Ponts et Chaussées (LCPC, Central Laboratory for Roads and Bridges) circular test track in Nantes, France. The joint test program is known internationally as the FORCE Project (1988–1991). GEMs—Bitumen–emulsion treatment of soils and crushed stone. Commonly known as granular emulsion mixes in South Africa. Macadam—Contains a high-quality aggregate with large, single-sized particles stabilized by filling the voids with a suitable material. Typically the macadam is defined more specifically in relation to the material used for filling the voids; e.g., waterbound macadam (WM) has a filler of natural material with a low plasticity, whereas slurry-bound macadam (SM) has a filling of slurry. Macadam, dense bitumen (DBM)—A very coarse and densely continuously graded asphalt used in the United Kingdom. Macadam, heavy-duty—A variation of macadam. Milled granulated blast furnace slag (MGBS)— Granulated slag, a by-product of the processing of iron ore, milled to a fine powder. Modified material—A material the physical properties of which have been improved by the addition of a stabilizing agent, but in which cementation has not occurred. Pavement behavior—The function of the condition of the pavement with time. Pay adjustment schedule (for quality)—Also called “price adjustment schedule” or “adjusted pay schedule.” A preestablished schedule, in either tabular or equation form, for assigning pay factors associated with estimated quality levels of a given quality characteristic. The pay factors are usually expressed as percentages of the original contract bid price.

119 Pay adjustment system (for quality)—Also called “price adjustment system” or “adjusted pay system.” All pay ad- justment schedules along with the equation or algorithm that is used to determine the overall pay factor for a sub- mitted lot of material or construction. (A pay adjustment system, and each pay adjustment schedule, should yield sufficiently large pay increases/decreases to provide the contractor some incentive/disincentive for high/low qual- ity.) Polymer-modified bitumen—A bitumen with improved physical properties obtained by the addition of a polymer. Precoating—The precoating of the seal stone with a binder to improve the initial adhesion between the stone and the seal binder (precoating of chips). Seal—A term frequently used instead of “reseal” or “sur- face treatment.” Also used in the context of “double seal” and “sand seal” where sand is used instead of stone. Surface treatment—Applications of bituminous materials to a pavement surface with a cover of mineral aggregate. Surface treatment, double—An application of bitumi- nous binder and stone, followed by a second application of binder and stone or sand. A fog spray is sometimes applied on the second layer of aggregate. Surface treatment, single—An application of bituminous binder, followed by a layer of stone or clean sand. The stone is sometimes covered with a fog spray. Standard aggregate base—Known as an undrained pavement in California. Test lane—The track (normally linear) along which a bo- gie travels, applying axle loads to the surface on which it runs. Truck—Set of wheels or a frame mounted on wheels to sup- port a structure. [Synonym for “bogie” and “undercarriage.”] Wheel assembly—May be fixed to an APT device (e.g., a test truck traveling along a test pavement). It may also be a loose assembly that is guided to travel along a pre- planned wheel path. [Synonym for “bogie,” “truck,” and “undercarriage.”] Wheel tracking— Application of wheel load repetitions to a surface. Undercarriage—Supporting framework of a vehicle with a wheel system (United States). [Synonym for “landing gear” (of an aircraft), “truck,” and “bogie.”] UNPG— The aggregate producers union in France.