Water-impermeable concrete

WATER-IMPERMEABLE CONCRETE (EN: watertight concrete; DE: wasserdichter Beton; FR: beton hydrofuge, beton etanche; ES: hormigon hidryfugo; RU: водонепроницаемый бетон) is the structural concrete, which does not permit the water to pass under the pressure of 0.2 megapascals and more; this concrete is used for the underground mine construction, hydraulic engineering construction, transport construction, and so on. The water impermeability of the water-impermeable concrete depends on the sizes and quantity of the communicating pores and capillaries; the water impermeability is achieved using the decreasing of the water-cement ratio, the increasing of the consumption and fineness of the milling of the cement, the usage of the special expanding, aluminous, and other cements, the introduction of the additives (finely milled, compacting, plasticizing and air-entraining, complex), the usage of the special methods for the compacting of the concrete mixture, the special conditions for the hardening, which are increasing the degree of the hydration of the cement (for example, using the water-heat processing). The water impermeability of the water-impermeable concrete i s determined according to the maximal pressure of the water at the moment of its seepage onto the opposite surface of the tested sample (the GOST 12730.5-78 standard), or according to the coefficient of the filtration of the water-impermeable concrete, which is evaluated according to the mass of the water, which has flowed under the constant pressure through the unit of the area of the sample with the specified thickness during the unit of the time (the GOST 19426-74 standard). Within the USSR, there are specified for the heavy concretes the following marks (the SNiP 11-21-75 regulations) according to the water impermeability: V2, V4, V6, V8, V10, V12.