| Portland-Pozzolan Cement (ASTM C 595) | (Concrete Engineering) 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. |
| Pretensioning | (Concrete Engineering) 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. |
| Rebound | (Concrete Engineering) Wet shotcrete or sand and cement which bounces away from a surface again at which pneumatically applied mortar is being projected. |
| Retardation | (Concrete Engineering) Delaying the hardening or strength gain of fresh concrete, mortar or grout. |
| Revibration | (Concrete Engineering) Delayed vibration of concrete that has already been placed and consolidated. Most effective when done at the latest time a running vibrator will sink of its own weight into the concrete and make it plastic and workable again. |
| Rod (tamping) (ASTM C24l) | (Concrete Engineering) A round, straight steel rod, 5/8' in diameter and approximately 24' in length, having the tamping end rounded into a hemispherical tip, the diameter of which is 5/8'. |
| Sack | (Concrete Engineering) A quantity of cement: 94 Ibs. in the United States, 87.5 Ibs. in Canada, for portland or air entraining portland cement, or as indicated on the sack for other kinds of cement. |
| Sand (ASTM C125) | (Concrete Engineering) That portion of an aggregate passing the No. 4 (4.76 mm) sieve and predominantly retained on the No. 200 (74 micron) sieve. |
| Saponification | (Concrete Engineering) The deposit of a gray scum or gray dust on the inside surface of a subgrade wall or floor; as the result of moisture moving through the concrete and washing certain chemicals from the concrete mass. |
| Slip Form | (Concrete Engineering) A form which is raised or pulled as concrete is placed; may move vertically to form wails, stacks, bins or silos, usually of uniform cross section from bottom to top; or a generally horizontal direction to lay concrete evenly for highways, on slopes and inverts of canals, tunnels, and siphons. |