| you are: Structurally-mechanical properties of the cement test
Porous structure of gel as the most important product of hydration of cement, influences mechanical properties, permeability and frost resistance of a cement stone; thus it is necessary to consider special physical properties of a time of the gel, caused in their small sizes.
A gel Time can be from several angstrem to 1000 And, hence, on the classification given in gl. I, they represent a microtime. The water filling a time of gel (in abbreviated form ' gel water '), has with a firm phase adsorbtsionnuju communication, as adsorbtsionnyj a polymolecular sheet of water (on. V.Derjaginu) has a thickness to 0,15 microns. Gel water freezes at low temperature (according to some information-78°S) and does not pass in ice at the strongest frosts and, hence, a gel time does not affect frost resistance of a cement stone and concrete. The water adsorbed in a time, reduces live section and without that small gelevyh a time, therefore water penetration of cement gel is rather small.
The water Part zatvorenija, not gone in in a gel time, settles down out of gel and forms a capillary time.
The Capillary time has the big effective diameter (more than 1000 and are accessible to water under usual conditions of saturation. At considerable volume of the capillary time penetrating a cement stone, concrete has low frost resistance and the big permeability, badly resists to chemical corrosion and does not protect reliably steel armature.
Water is an active element of structure of the cement stone, participating in formation gidratnyh connections and in formation of a time. Porosity of a cement stone depends not only on the initial water cement relation, but also from forms of communication of water with a firm phase.
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