Introduction to cement knowledge

2022-07-22
  • Detail

Main technical performance indicators of cement: (1) specific gravity and unit weight: the specific gravity of ordinary cement is 3:1, and the unit weight is usually 1300 kg/cubic meter (2) fineness: refers to the thickness of cement particles. The finer the particles, the faster the hardening, and the higher the early strength. (3) Setting time: add water to mix the cement until it starts

the main technical performance indicators of cement:

(1) specific gravity and unit weight: the specific gravity of ordinary cement is 3:1, and the unit weight is usually 1300 kg/cubic meter

(2) fineness: refers to the thickness of cement particles. The finer the particles, the faster the hardening, and the higher the early strength

(3) setting time: the time required for cement mixing with water to start setting is called initial setting time. The time required from mixing with water to the completion of coagulation is called the final setting time. The initial setting time of Portland cement shall not be earlier than 45 minutes, and the final setting time shall not be later than 12 hours

(4) strength: the cement strength should meet the national standard

(5) volume stability: refers to the uniformity of volume change of cement during hardening. Cement contains many impurities, which will produce uneven deformation

(6) heat of hydration: the interaction between cement and water will produce exothermic reaction. During the hardening process of cement, the heat constantly released is called heat of hydration

commonly used cement grades: 25, 275, 325, 425, 525, 625, etc. their tensile strength varies with different varieties and grades, and the MPA value is between 2.8-4.5 and 3.4-8.0

varieties of decorative cement: decorative cement is often used to decorate the surface of buildings. It has the advantages of simple construction, convenient modeling, easy maintenance and low price

application and purchase of cement mortar

in home decoration, cement mortar is used in floor tile, wall tile pasting and masonry. It can not only enhance the adsorption capacity between surface materials and base, but also protect the internal structure. At the same time, it can be used as the leveling layer of building gross surface. Therefore, cement mortar is an essential material in decoration engineering

many customers believe that the greater the proportion of cement in the whole mortar, the stronger its adhesion. Therefore, they often disagree with decoration companies on the amount of cement used. In fact, it's not true. Take sticking ceramic tiles as an example. If the cement grade is too large, when the cement mortar is set, the cement absorbs a lot of water. At this time, the water of the ceramic tiles on the surface layer is absorbed too much, which is easy to crack and shorten the service life. Generally, cement mortar shall be mixed in the proportion of cement: sand =1:2 (volume ratio)

purchase principle of cement and sand:

in order to ensure the quality of cement mortar, attention must be paid to whether 425# Portland cement produced by large manufacturers is selected. Sand should be selected. The particle size of medium sand is very suitable for use in cement mortar. Many customers think that the finer the sand, the better the mortar, which is actually a misunderstanding. The adsorption capacity of too fine sand is not strong, so it cannot produce large friction and stick the ceramic tile

沈阳男科医院

杭州耳鼻喉医院

济南肿瘤医院

Copyright © 2011 JIN SHI