| Pumping (of Pavements) | (Concrete Engineering) 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. |
| Rebound | (Concrete Engineering) Wet shotcrete or sand and cement which bounces away from a surface again at which pneumatically applied mortar is being projected. |
| Reinforced Concrete (RC) | |
| Retardation | (Concrete Engineering) Delaying the hardening or strength gain of fresh concrete, mortar or grout. |
| Retempering | (Concrete Engineering) The addition of water and remixing of concrete which has started to stiffen: usually not allowed as it may affect the ultimate strength. |
| 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. |
| Rock Pocket | (Concrete Engineering) Area or portion of hardened concrete which is deficient in mortar and consisting primarily of coarse aggregate and open voids; caused by insufficient consolidation or separation during placement, or both; by leakage from form. |
| 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. |
| Sacking | (Concrete Engineering) Removing or alleviating defects on a concrete surface by applying a mixture of sand and cement to the moistened surface and rubbing with a coarse material such as burlap. |