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• Particle-Size Distribution - Particle distribution of granular materials among various sizes; for concrete material normally designated as gradation. Usually expressed in terms of cumulative percentages smaller or larger than each of a series of sieve openings or percentages between certain ranges of sieve openings.

• Pea Gravel - Portion of concrete aggregate passing the 3/8' sieve and retained on a No.4 sieve.
• Peeling - A process in which thin flakes of matrix or mortar are broken away from concrete surface; caused by adherence of surface mortar-to forms as forms are removed, or to trowel or float in portland cement plaster.
• Pining - Development of relatively small cavities in a concrete surface, due to phenomena such as cavitation or corrosion.
• Plane of Weakness - The plane along which a structure under stress will tend to fracture; may exist because of the nature of the structure and its loading, by accident, or by design.
• Plastic - A condition of freshly mixed concrete. mortar or cement -paste indicating that it is workable and readily re-moldable, is cohesive, and has an ample content of fines and cement but is not over wet.
• Plastic Consistency - Condition in which concrete, mortar, or cement paste will sustain deformation continuously in any direction without rupture.
• Plasticity - Property of freshly mixed concrete, cement paste or mortar which determines its ease of molding or resistance to deformation.
• Plasticizer - A material that increases the workability or consistency of a concrete mixture, mortar or cement paste.
• Porosity - The ratio of the volume of voids in the material to the total volume of the material, including the voids, usually expressed as a percentage.
• Portland Blast- slag Cement Furnace (ASTM C 595) - The product obtained by intimately intergrinding or an intimate and uniform blending a mixture of granulated blast furnace slag and portland-cement clinker.
• Portland Cement (ASTM C 150) - The product obtained by pulverizing clinker consisting essentially of hydraulic calcium silicates.
• Portland-Pozzolan Cement (ASTM C 595) - The product obtained by intimately intergrinding a mixture of portland-cement clinker and pozzolan, or an intimate and uniform blend of portland cement and fine pozzolan.
• Post-tensioning - A method of prestressing concrete in which the tendons are tensioned after the concrete has hardened.
• Pozzolan (ASTM C 618) - A siliceous, or siliceous and aluminous material, which in itself possesses little or no cementitious value but will, in a finely divided form, such as a powder or liquid and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form permanent, insoluble compounds possessing cementitious properties.
• Precast - A concrete unit, structure or member that is cast and cured in an area other than its final position or place.
• Preplaced Concrete - Concrete manufactured by placing clean, graded coarse aggregate in a form and later injecting a portland cement-sand grout under pressure, to fill the voids.
• Proportioning - Selection of proportions of material for concrete to make the most economical use of available materials to manufacture concrete of the required strength, placeability, and durability.
• Prestressed Concrete - Concrete in which stresses have been introduced which are opposite in sense to those that the structural member will be expected to carry during its use.
• Pretensioning - A method of prestressing reinforced concrete in which the steel is stressed before the concrete has hardened and restrained from gaining its unstressed position by bond to the concrete.
• Pumping (of Pavements) - The ejection of a mixture of water and solid materials such as clay or silt along cracks, transverse or longitudinal joints, and along pavement edges caused by downward slab movement due to the passage of heavy loads, machinery or equipment over the pavement after free water has accumulated in or on the subbase, subgrade or basecourse.

Contributions: Kaiser Cement, Portland Cement Association, Concrete Manual, Bureau of Reclamation, U. S. Department of the Interior and many other publications, with special thanks to Bob Cameron of W. R. Meadows. © 2008 Moxie International, Inc. All Rights Reserved.

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