(18)ĭeviator stress: In triaxial testing the difference between the axial stress applied by the testing apparatus and the confining stress (pressure).ĭowel: A load transfer device across a joint (usually a transverse joint) in a rigid slab, usually consisting of a plain cylindrical steel bar. Such devices may include seismometers, velocity transducers (geophones), or accelerometers. (18)ĭeflection sensor: An electronic device(s) capable of measuring the relative vertical movement of a pavement surface and mounted to reduce angular rotation with respect to its measuring axis at the expected movement.
(73)ĭeflection basin: The bowl shape of the deformed pavement surface caused by a specialized load as depicted from the peak measurements of a series of deflection sensors placed at radial offsets from the center of the load plate. (73)ĭeflection: Vertical deformation of a pavement under an applied load. (72)Ĭurling: Deformation of a PCC slab caused by a temperature difference between the upper and lower surfaces. (72)Ĭrack: A break or disruption in the continuity of the pavement surface that may extend through the entire pavement thickness.Ĭrushed stone: A base (or subbase) course of designed thickness and constructed of graded and mechanically crushed mineral aggregate compacted above the subgrade. Longitudinal joints exist similar to other types of concrete pavements. Transverse reinforcement may or may not exist. Transverse joints exist only for construction purposes and on-grade structures. (71)Ĭontinuously reinforced concrete pavement (CRCP): PCC pavement containing longitudinal reinforcement at or above mid-depth designed to hold shrinkage cracks tightly closed. (4)Ĭhemically stabilized mixtures: Subgrade materials whose plasticity characteristics have been modified using materials such as lime, fly ash, or PCC.Ĭomposite pavement: A pavement structure composed of an asphalt concrete wearing surface and PCC slab, or an asphalt concrete overlay of a PCC slab. The iteration stops once a predetermined level of tolerance has been reached between subsequent calculated estimates. The process begins with a hypothesis of a given layer’s modulus, which is repeatedly compared with the FWD’s output using an iterative mathematical model. (71)īackcalculation: An iterative process by which pavement layer moduli, or other stiffness properties, are estimated from FWD deflection data.
(72)Īxle load: Load exerted by a vehicle on the pavement surface via an axle.īase: The layer or layers of specified or select material of designated thickness placed on a subbase or subgrade to support a surface course layer directly beneath a PCC slab. Also referred to as hot-mix asphalt (HMA). (71)Īsphalt concrete (AC): A controlled mixture of asphalt cement and graded aggregate compacted to a dense mass.
The analysis period should not be confused with the pavement’s design life (performance period). (71)Īnalysis period: The period of time used in making economic comparisons between rehabilitation alternatives. (70)Īlligator cracking: Interconnected or interlaced cracks forming a pattern that resembles an alligators hide. Using Falling Weight Deflectometer Data With Mechanistic-Empirical Design and Analysis, Volume III: Guidelines for Deflection Testing, Analysis, and InterpretationĪggregate: A collective term for the mineral materials such as sand, gravel, and crushed stone that are used with a binding medium (such as water, bitumen, portland cement, lime, etc.) to form compound materials (i.e., asphalt concrete, portland cement concrete, etc.).