Composition of the cement
|Composition of the cement||Preparation of a clay mixture||Preparation of cement mixture||Preparation of concrete mixes|
Building mixtureBuilding mixturecan be lime, clay, clay-lime, lime-gypsolite and clay-cement. Before you add the clay in mixture, it is necessary to pre-soften and pass through a dense sieve
Building mixture should be absolutely uniform, to impossible to distinguish individual ingredients in it. This is achieved by continuous stirring with a suitable tool. Critical for building mixture is a quantitative ratio of the components. It depends on the purpose of the mixture (masonry, plaster, sealing cracks, etc.).
Preparation of lime building mixturePreparation of lime building mixture get as: sand evenly poured on a solid surface and cover the necessary amount of lime. The mixture is shoveled a few times, then carefully mix with a hoe. In the middle do the crater, into which is poured water. The mixture is again stirred so that the crater gradually filled with the mixture, and the edges were constantly above the mixture to avoid overflow. The ready mixrute must be a sufficiently dense homogeneous mixture.
Preparation of a clay mixtureThe clay mixture can be used for masonry and plaster only in auxiliary and secondary buildings. This solution is prepared as lime, but it is weaker than lime. To increase strength the hydrated lime (gypsum or cement) added in the clay mixture. For clay-lime mixture to one part clay take 0,3...0,4 parts of hydrated lime and 3...6 parts of sand. The amount of sand depends on the function of the mixture (masonry, plaster). For preparation of clay-plaster mixture to one part clay take 0.25 parts of gypsum and 3...5 parts of sand. To clay-cement mixture needs a one part clay, 0.15...0.2 part of cement and 3 ... 5 parts of sand.
Composition of the cementCement is the main material for construction. The composition of cement is a mixture of limestone and clay. The mixture is subjected to sintering and the sintered mass is milled and get a grey powder consisting of CaO, Al2O3 and SiO2. If this mixture mix with water, then the mass hardens. If added sand to cement, then concrete is produced. If armature inside in concrete products - skeleton of steel rods or mesh, then got very durable material - ferroconcrete.
Unlike other binders (lime, plaster, sand, liquid glass) it may continue to harden after mixing with water and pre-curing in air. It is resistant to water in the solid state.
Required 24...28% water to do the cement paste. Deviation both downward and upward lower quality of cement.
Grappling cement occurs one hour after mixing it with water and stops when hardening the mass loses its plasticity - usually after 12 h.The higher the temperature, the faster cement setting. So in the summer the cement hardens faster. The process can be accelerated by using various additives.
How to destroy hardened cement.
Hardened cement (cement stone) is destroyed soft water, containing carbonic acid, acidic waters (discharges of industrial production), water containing sulphates and chlorides (seawater).
Keeping the concrete wet during curing is essential to achieve the design strength. The surface begin to pour with water immediately after establishing that it is not damaged by water (24 hours after the getting concrete) .
Solutions. Colloidal solutions
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