Cement is the main component of dry mixtures for construction purposes, which are used in the construction of buildings, structures, laying roads, performing reinforced concrete structures or plastering and finishing works. In construction practice, the density of cement (as the ratio of mass to volume) is divided into bulk and true. The two characteristics differ in that the bulk density is measured when the material is in a loose state. It is 1100 - 1600 kg / cu. meter (1600 kg/cu.m. for compacted condition).
The 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, which traps large inclusions. After that, it enters the cylinder, trimmed, and then weighed together with the cylinder. The weight of the cylinder is subtracted from the total weight obtained. Next, the mass is divided by the volume and the desired value is obtained. The bulk density value is used when loading components into the concrete mixer forconcrete preparation.
The true density of cement differs from bulk cement in that all air components are excluded from the cement. This leads to an increase in density up to 3000 - 3200 kg / cu. meter. In construction, an average value of about 1300 kg / cubic meter is used for calculations. meter. It is assumed that cement, the density of which varies within such a wide range, the better the quality in the building mix, the closer the density value is 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 silos. Also among the factors can be noted storage conditions - temperature, humidity level and other characteristics. The density of a material such as cement further determines parameters such as strength and resistance to water penetration (hydrophobicity).
The density of M400 cement depends on the variety of this type of material. For example, M400-D0 has no additives (D=0), so the brand is used in underground and underwater works, has high water resistance, density and strength. Cement M400-D20 has about 20% additives that reduce its density. Therefore, this cement is used for floor slabs, road works, blind area construction, road and paving slabs. But the M400-D20-B grade is similar to the M400-D0 in terms of its strength, but it hardens very quickly, which allows it to be used for the production of reinforced concrete structures.
The number 400 in the markingM400 means how many kilograms of cement can withstand in a hardened state per square centimeter. In our case, this is 400 kg. The higher the number, the higher the load it can take on. Cement is offered to customers in bags or in bulk. Building material is supplied in bags for finishing operations, and in bulk - to concrete plants for industrial use. However, there are very large capacity bags that can hold up to one ton. They are also used to work with building materials in large volumes.
