Penetration Grading A classification system of asphalt cements based on penetration in 0.1 mm at 25°C (77°F). There are five standard penetration grades for paving: 40-50, 60-70, 85-100, 120-150, and 200-300. Penetration The consistency of a bituminous material expressed as the distance (in tenths of a millimeter) that a standard needle penetrates a sample vertically under specified conditions of loading, time and temperature.

Performance Graded (PG) Asphalt binder grade designation used in Superpave. It is based on the binder's mechanical performance at critical temperatures and aging conditions.

Planned Stage Construction A construction process where stages of the project are performed sequentially according to design and a predetermined time schedule.

Plant Mix (Cold) A mixture of emulsified (or cutback) asphalt and unheated mineral aggregate prepared in a central mixing plant and spread and compacted with conventional paving equipment while the mixture is at or near ambient temperature.

Plant Mix Base A foundation course produced in an asphalt mixing plant, which consists of a mineral aggregate uniformly coated with asphalt cement or emulsified asphalt.

Plant Screens Screens located between the dryer and hot bins, which separate heated aggregates into proper hot bin sizes.

Pneumatic-Tire Roller A compactor with a number of tires spaced so their tracks overlap delivering a kneading type of compaction.

Poise A centimeter-gram-second unit of absolute viscosity equal to the viscosity of a fluid in which a value of stress one dyne per square centimeter is required to maintain a difference of velocity of one centimeter per second between two parallel planes in the fluid that lie in the direction of flow and are separated by a distance of one centimeter.

Polished Aggregate Aggregate particles in a pavement surface that have been worn smooth by traffic.

Polymer-Modified Asphalt (PMA) Binder Conventional asphalt cement to which one or more polymer compounds have been added to improve resistance to deformation at high pavement temperatures and often cracking resistance at low temperatures.

Potholes Bowl-shaped openings in the pavement resulting from localized disintegration.

Power Sweeper A power operated rotary broom used to clean loose material from the pavement surface.

Present Serviceability Index (PSI) A mathematical combination of values obtained from certain physical measurements of a large number of pavements, so formulated as to determine, within prescribed limits, the Present Serviceability Rating (PSR) for those pavements.

Present Serviceability Rating (PSR) The rating assigned to a specific pavement section. Present Serviceability The ability of a specific section of pavement to serve its intended use in its existing condition.

Pumping Slab deflection under passing loads sometimes resulting in the discharge of water and subgrade soils along joints, cracks and pavement edges.

Rapid-Curing (RC) Asphalt Cutback asphalt composed of asphalt cement and a naphtha or gasoline-type diluent of high volatility.

Raveling The progressive separation of aggregate particles in a pavement from the surface downward or from the edges inward.

Reclaimed Asphalt Pavement (RAP) Excavated asphalt pavement that has been pulverized, usually by milling, and is used like an aggregate in the recycling of asphalt pavements.

Reclaiming Machine A self-propelled unit having a transverse cutting and mixing head inside of a closed chamber for the pulverization and mixing of existing pavement materials with asphalt emulsion. Asphalt emulsion (and mixing water) may be added directly through the machine by a liquid additive system and spray bar.

Recycled Asphalt Mix A mixture produced after processing existing asphalt pavement materials. The recycled mix may be produced by hot or cold mixing at a plant, or by processing the materials cold and in-place.

Reflection Cracks Cracks in asphalt overlays (usually over deteriorated PCC pavements) that reflect the crack pattern in the pavement structure below it.

Residue The asphalt binder that remains from an asphalt emulsion after the emulsifying agent has broken and cured, or the remains of a cutback after the volatiles have cured.

Resilient Modulus of Elasticity (MR) A laboratory measurement of the behavior of pavement materials to characterize their stiffness and resiliency (see Soils Manual, MS-10). A confined or unconfined test specimen (core or recompacted) is repeatedly loaded and unloaded at a prescribed rate. The resilient modulus is a function of load duration, load frequency, and number of loading cycles.

Resistance Value (R-value) A test for evaluating bases, subbases, and subgrades for pavement thickness design.

Road Oil Asphalt cement and oils of low volatility, usually similar to one of the slow-curing (SC) grades.

Roadway All facilities on which motor vehicles are intended to travel such as secondary roads, interstate highways, streets and parking lots.

Roughometer An instrumented, single-wheel trailer, which measures the roughness of a pavement surface in accumulated millimeters, or inches, per mile.

Rubblization The pulverization of a portland cement concrete pavement into smaller particles, reducing the existing pavement layer to a sound, structural base that will be compatible to an asphalt overlay.

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