| Carbonation | (Concrete Engineering) 1) Reaction between the products of portland cement (soluble calcium hydroxides), water and carbon dioxide to produce insoluble calcium carbonate (efflorescence). 2) Soft white, chalky surface dusting of freshly placed, unhardened concrete caused by carbon dioxide from unvented heaters or gasoline powered equipment in an enclosed space. 3) Carbonated, dense, impermeable to absorption, top layer of the surface of concrete caused by surface reaction to carbon dioxide. This carbonated layer becomes denser and deeper over a period of time. 4) Reaction with carbon dioxide which produces a slight shrinkage in concrete. Improves chemical stability. Concrete masonry units during manufacturing may be deliberately exposed to carbon dioxide after reaching 80% strength to induce carbonation shrinkage to make the units more dimensionally stable. Future drying shrinkage is reduced by as much as 30%. |
| Cement Content | (Concrete Engineering) A quantity of cement contained in a unit volume of concrete or mortar, ordinarily expressed as pounds, barrels, or bags per cubic yard. |
| Change of State | (Concrete Engineering) The process whereby liquid is heated to the point of evaporation changing the liquid into a gas the condensation of a gas on a cooler surface returning it from gaseous to liquid form. |
| Condensation | (Concrete Engineering) When a moisture laden gas comes in contact with a cooler surface a change of state from gaseous to liquid occurs. |
| Dry Rodded Weight | (Concrete Engineering) The weight of dry aggregate rodded into a cylindrical container of diameter approximately equal to the height, each of 3 layers rodded 25 times, and the excess aggregate struck off level with the top of the container |
| HRM High Reactivity Metakaolin. | (Concrete Engineering) Refined form of an ASTM C618, Class N (natural) pozzolan. A high performance, mineral admixture, similar in performance to silica fume, additionally comparable in cost. Pure white powdered in form will, not effect the natural color or darken concrete as silica fume does. Suitable for high-performance color matching in architectural concrete. Dosage at 5% to 10%, of cement by weight. No bleed water, better finishability, more creamy, cleanup is easier with slightly higher 28 day strengths and 25% - 35% less plasticizer is required than silica fume. |
| Jacking Equipment | (Concrete Engineering) In prestress concrete, the device used to stress the tendons. |
| Maximum Size Aggregate | (Concrete Engineering) Aggregate whose largest particle size is present in sufficient quantity to affect the physical properties of concrete; generally designated by the sieve size on which the maximum amount permitted to be retained is 5 or 10 percent by weight. |
| Moist Room | (Concrete Engineering) A room used for storing and curing cementitious test specimens. The atmosphere of this room is maintained at a temperature of 73.4 3.0'F or 23.0*1.7'0 and relative humidity of at least 98 percent. These facilities must be adequate to continually maintain free moisture on the exteriors of test specimens. |
| Non-agitating Unit | (Concrete Engineering) A truck-mounted unit for transporting ready-mixed concrete short distances, not equipped to provide agitation (slow mixing) during delivery. |