What is the difference between Portland cement and ordinary cement?
Composite Portland cement main features: early low strength, good heat resistance, acid resistance is poor.Using fly ash and coal gangue as a mixture, the Department of green building materials, enjoy the national tax incentives, early and late strength and stability, water Low heat, suitable for general industrial and civil construction, is a kind of economic cement.
Ordinary Portland cement Main features: high early strength, high hydration heat, good resistance to freezing, poor heat resistance, poor corrosion resistance, less dry shrinkage. Scope: manufacturing ground, underground and water concrete, reinforced concrete And prestressed concrete structures, which are subjected to cyclic freezing and thawing structure and high strength requirements. They are not suitable for large volume concrete engineering and chemical and seawater erosion engineering.
Where the cement cement clinker, 6% -15% of the mixed material and the amount of gypsum made of hydraulic cementitious material, known as ordinary Portland cement, referred to as ordinary cement. National standards for ordinary silicate The technical requirements for cement are:
(1) the size of the mesh size of 80μm square hole screen sieve should not exceed 10%, otherwise unqualified.
(2) coagulation time of the initial setting time shall not be more than 45 minutes, the final setting time no later than 10 hours.
(3) According to the compression and flexural strength, Portland cement is divided into 325,425,525,625 four labels.
Ordinary Portland cement due to the mixed material less content, its nature and Portland cement is basically the same, slightly different, mainly as follows:
(1) early strength slightly lower
(2) slightly better corrosion resistance
(3) hydration heat slightly lower
(4) good frost resistance and impermeability
(5) slightly less resistant to carbonization
(6) slightly less wear resistance
Composite Portland cement by the Portland cement clinker, two or more than the provisions of the mixed material, the amount of gypsum made of hydraulic cementitious material, known as composite portland cement (referred to as composite cement) . The total amount of mixed material in the cement should be greater than 15% by mass and not more than 50%. No more than 8% kiln dust is allowed to replace part of the mixed material in the cement. The content of the mixed material shall not be mixed with the slag Salt cement repeated.
Cement is generally divided into ordinary Portland cement, mixed with Portland cement and special cement. Ordinary Portland cement: by limestone, clay, iron ore powder in proportion to the mixture, this time the mixture called raw material. Calcined, the general temperature of about 1450 degrees, calcined product called clinker.Then clinker and gypsum together with the grinding, according to the proportion of mixed, known as the cement.
The silicate cement mixed with the mixture is added to other substances in a conventional portland cement in proportion to a certain amount of processing to achieve special effects such as slag cement, pozzolanic silicate cement, fly ash Portland cement, Composite portland cement, etc. These cement raw materials than the original ordinary Portland cement to more active mixed material or non-active mixed material.
Special cement in the material stage and the production process is somewhat different, such as high alumina cement (aluminate cement) material is bauxite, limestone after calcination to get clinker, and then ground into aluminate cement.
Others have some characteristics of cement used less, such as white cement, mainly used for decorative works, the material is pure kaolin, pure quartz sand, pure limestone, calcined at the appropriate temperature of the raw material.
China will implement a new cement standard from June 1, 2008, the new standard provides the original ordinary Portland cement in the maximum content of mixed material from 15% to 20%. This is equivalent to Germany (Europe the same) The details of the ten varieties of cement, in our country referred to as "ordinary portland cement"