What kinds of special cement are there?
Commonly used varieties are white portland cement, colored cement, quick-hardening portland cement, quick-setting quick-hardening portland cement, low-heat cement, medium-heat cement, oil well cement, sulfate-resistant portland cement, masonry cement, refractory cement, expansive cement and radiation-proof cement.
1. Fast hardening cement: also known as early strength cement, the label is usually determined by the compressive strength value of cement 1 day or 3 days. According to different mineral compositions, it can be divided into silicate quick-hardening cement, aluminate quick-hardening cement, sulphoaluminate quick-hardening cement and fluoroaluminate quick-hardening cement. According to the different growth rate of its early strength, it can be divided into fast-hardening cement, and the label is determined by the 3-day compressive strength value; Fast hardening cement, the label is determined by the hourly compressive strength value, and fluoroaluminate fast hardening cement is fast hardening cement.
2. Low-heat and medium-heat cement: This cement has low hydration heat and is suitable for large-volume buildings such as dams. According to the different composition of cement, it can be divided into portland medium-heat cement, ordinary portland medium-heat cement, slag silicate low-heat cement and low-heat micro-expansive cement. Low-heat cement and medium-heat cement are distinguished according to the hydration heat released by cement within 3 or 7 days. According to China standard, the hydration heat of low-heat cement for 3 days and 7 days is lower than 188× 103 and 25 1× 103 coke/kg respectively. The medium heat cement is lower than 230× 103 and 293× 103 coke/kg respectively.
3. Sulfate-resistant cement: cement with strong sulfate corrosion resistance. According to the different mineral composition of cement, it can be divided into sulfate-resistant silicate cement, aluminate belite cement and slag strontium cement. Cement can be divided into sulfate-resistant cement and high sulfate-resistant cement according to its sulfate-resistant performance. Sulfate-resistant portland cement is the main variety of sulfate-resistant cement, which is made of portland cement clinker composed of specific minerals and ground with appropriate amount of gypsum.
4. Oil well cement: cement specially used for cementing oil wells and gas wells, also called plugging cement. It can be divided into ordinary oil well cement and special oil well cement according to the purpose. Ordinary oil well cement is made by grinding silicate cement clinker composed of appropriate minerals and appropriate gypsum. When necessary, active mixed materials (such as slag) or inactive mixed materials (such as quartz sand and limestone) not exceeding 65,438+05% of the cement weight can be added. According to the different depths of oil (gas) wells, ordinary oil well cements in China are divided into four types: 45℃, 75℃, 95℃ and 120℃, which are suitable for cementing ordinary oil (gas) wells.
5. Expansive cement: cement that expands in volume during hardening. According to different mineral compositions, China can be divided into silicate expansive cement, aluminate expansive cement, sulphoaluminate expansive cement and calcium hydroxide expansive cement. Portland expansive cement, alunite expansive cement, iron oxide expansive cement, magnesia expansive cement and K-type expansive cement all belong to portland expansive cement. This kind of cement is generally made of portland cement mixed with various expansive components.
6. Refractory cement: Cement with a refractory limit of not less than 1580℃ can be divided into aluminate refractory cement, low calcium aluminate refractory cement, calcium magnesium aluminate cement and dolomite refractory cement according to different components. Refractory cement can be used to cement various refractory aggregates (such as corundum, calcined bauxite, etc.). ) made into refractory mortar or concrete, which can be used as the lining of cement rotary kiln and other industrial kilns.
7. White cement: White portland cement is the most important variety of white cement. It is a kind of portland cement with low iron oxide and other non-ferrous metal oxides as main raw materials, made of limestone, clay and silica, which is calcined and quenched at high temperature to form cement clinker, and then a proper amount of gypsum (or a small amount of white limestone can be added to replace part of clinker) is ground in a mill equipped with stone (or wear-resistant metal) liner and mill. The physical properties of white portland cement are similar to ordinary portland cement, and it is mainly used as building decoration materials and sculpture products.
8. Colored cement: usually made of white cement clinker, gypsum and pigment. The pigments used are required to be durable, highly dispersible, alkali-resistant, free of soluble salts, and will not damage the composition and performance of cement under the action of light and atmosphere. Commonly used inorganic pigments include iron oxide (red, yellow, brown and black cement), manganese dioxide (black and brown), chromium oxide (green), cobalt blue (blue), ultramarine blue (blue) and carbon black (black); Organic pigments include Kong Quelan (blue) and Tianjin Green (green). Color cement can also be made by adding a small amount of metal oxide into white cement raw meal as colorant, directly calcining it into color cement clinker, and then grinding it into cement. Colored cement is mainly used as building decoration materials, and can also be used as plastering facing for concrete, masonry, etc.
9. Radiation-proof cement: cement that can shield X-rays, γ-rays, fast neutrons and thermal neutrons. The main varieties of this kind of cement are barium cement, strontium cement and boron cement. Barium cement is a clinker with barite clay as the main raw material, which is calcined to obtain barium silicate as the main mineral, and then mixed with appropriate amount of gypsum for grinding. Its specific gravity reaches 4.7 ~ 5.2, and it can be mixed with heavy aggregate (such as barite and section steel). ) to prepare radiation-proof concrete. Barium cement has poor thermal stability and is only suitable for making unheated radiation-proof wall. Strontium cement is made by using strontium carbonate to completely or partially replace limestone in portland cement raw materials, calcining to obtain clinker with tristerium silicate as the main mineral, and adding appropriate amount of gypsum for grinding. Its performance is similar to that of barium cement, but its radiation protection performance is slightly inferior to that of barium cement. Boron-containing cement can be obtained by adding appropriate amount of magnesite and gypsum into high-alumina cement clinker and grinding them together. This kind of cement, boron-containing aggregate and heavy aggregate can be made into concrete with high specific gravity, which is suitable for shielding fast neutrons and thermal neutrons in engineering.
10, antibacterial cement: when grinding portland cement, add a proper amount of antibacterial agents (such as pentachlorophenol and DDT) to make it. Can be used for preparing antibacterial concrete, and can be used in places that need to prevent bacterial reproduction, such as swimming pools, public bathhouses or food industry structures.
1 1. Algae-proof cement: It is made by adding a proper amount of sulfur (or sulfur-containing substances) and a small amount of coagulant (such as hydrated lime) into high-alumina cement clinker and grinding them together. It is mainly used to wet the surface of cool structures, prevent algae from attaching and reduce the damage of algae to structures.
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