### Homeliness, Building

# Bulk and true density of cement

Cement is the main component of dry mixes for construction purposes, which are used in erecting buildings, structures, laying roads, performing reinforced concrete structures or plastering and finishing works. In construction practice, the density of cement (as a ratio of mass to volume) is divided into bulk and true. These two characteristics differ in that the bulk density is measured when the material is in a loose state. It is 1100 - 1600 kg / cubic meter. Meter (1600 kg / cubic meter for the condensed state).

Bulk density of cement is measured on a special device consisting of a funnel and a measuring cylinder. A cement mixture of a certain mass (2 kilograms) is poured into a funnel that delays large inclusions. After that, it gets into the cylinder, it becomes curved, and then it is weighed together with the cylinder. The total weight is subtracted from the weight of the cylinder. Further, the mass is divided by volume and the desired value is obtained. The bulk density value is used when loading concrete components into the concrete mixer .

The true density of cement differs from bulk in that all air components are excluded from cement. This leads to an increase in density to 3000-3200 kg / cc. meter. In construction, the average value of about 1300 kg / cc is used for calculations. meter. It is assumed that cement, whose density varies within such wide limits, the better the quality in the building mix, the closer the density to the average.

The density of cement depends on the degree of grinding of the components, the surface of the grains in the material, and also on how the mixture was dried in the silos. Also among the factors can be noted storage conditions - temperature, humidity and other characteristics. The density of such material as cement further defines parameters such as strength and resistance to water penetration (hydrophobicity).

The cement density of M400 depends on the variety of this type of material. For example, М400-Д0 has no additives (Д = 0), therefore the grade is applied on underground and underwater works, has high water resistance, density and durability. Cement M400-D20 has about 20% of additives, which reduce its density. Therefore, this cement is used for slabs, road works, construction of blind areas, road and paving slabs. But the brand M400-D20-B is similar to the M400-D0 in its strength, but it quickly hardens, which allows it to be used for the production of reinforced concrete structures.

The figure 400 in the marking M400 means how many kilograms of cement can withstand in the solidified state per square centimeter. In our case it is 400 kg. The higher the figure, the higher the load it can take on. Cement is offered to customers in bags or in bulk. In bags, the building material is supplied for finishing operations, and in bulk - for concrete plants for industrial use. However, there are bags of very large capacity, which can hold up to one ton. They are also used for working with building materials in large volumes.

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