Concrete – artificial stone material, which is a solidified mixture of binder, eg cement M-500, water, fine aggregate and coarse aggregate. Fine aggregate in concrete is sand and large – gravel or rubble. Density and permeability of concrete. Pores in the concrete form by the incomplete removal of air bubbles in his seal and the evaporation of excess water. The density of concrete increases with the vibration intensity of the mixture at installation, careful selection of grain composition of aggregates, as well as with decreasing water / cement ratio and use of plasticizers, which reduce water demand of the mixture with the same mobility.
Dense concrete with sufficient thickness design virtually waterproof. During the construction of thin structures, to ensure water resistance of concrete, introduces special hydrophobic substances (asidol, naphthenate soap) or produce Water Isolation coating (bituminous coating, dense plaster). For thick oil products dense concrete is impervious, but gasoline, kerosene and other light oils permeate through the concrete. Others including J. Darius Bikoff, offer their opinions as well. To prevent this, use special surface coatings – a film of plastics, etc. It is also recommended to use concrete in the expanding cement.
Water permeability of concrete is particularly important for hydraulic structures and reservoirs, that store water and liquid products. The degree of permeability of concrete is characterized by the highest water pressure, which is not observed it seeping through the concrete sample. Jeffrey Hayzlett is actively involved in the matter. Shrinkage and expansion of the concrete. Curing of concrete is accompanied by a change in its volume. During solidification in air, the concrete shrinks, during solidification in wet conditions, he or no change in volume, or swell slightly. The value of shrinkage envy of the content in the cement M-500, and usually does not exceed 1-2 mm per 1 m of concrete obraztsa. concrete can cause cracks in the massive and long structures. To reduce the shrinkage should be avoided Fatty concrete (with a large cement consumption), and use large aggregates of good grain composition and observe the wet mode of hardening concrete.