| 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. |
| Hydrogenesis | (Concrete Engineering) Another term for condensation. The term is especially applied to base and soil substrates under highway pavements. where the barometric pump causes the inhalation of humid air, which then condenses in those structures, causing an ever increasing moisture content and sometimes instability. |
| Hydrologic Cycle | (Concrete Engineering) The Hydrologic Cycle consists of the evaporation of water from oceans and other bodies of open water; condensation to produce cloud formations; precipitation of rain, snow, sleet or hail upon land surfaces; dissipation of rain or melted solids by direct run-off into lakes and by seepage into the soil. Thereby producing a continuing endless source of water in the sub-grade. |
| Impermeable | (Concrete Engineering) The ability of a material or product to reduce or eliminate gaseous transmissions through it's mass; measured as the rate of Water Vapor Transmission (WVT). Note: Not all materials that are waterproof are vaporproof; all materials that are vaporproof are inherently waterproof. |
| Jacking Force | (Concrete Engineering) The temporary force exerted by the jacking device which introduces tension into the tendons. Jacking Stress In prestress concrete, the maximum stress occurring in a tendon during stressing. |
| Keene's Cement | (Concrete Engineering) A finely ground high density plaster composed of anhydrous, (calcined or "dead burned") gypsum, the set of which is accelerated by the addition of other materials. |
| Mixing Speed | (Concrete Engineering) Rate of mixer drum rotation or that of the paddles in a pan, open-top, or trough type mixer, when mixing a batch; expressed in revolutions per minute (rpm) or in peripheral] feet per minute of A point on the circumference at maximum diameter. |
| 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. |
| Non-evaporable Water | (Concrete Engineering) The water in concrete which is irremovable by oven drying; chemically combined during cement hydration. |
| Overvibration | (Concrete Engineering) Excessive vibration of freshly mixed concrete during placement-causing segregation. |