Decoration must: Cement knowledge Daquan
Powdered hydraulic inorganic gelling material. After adding water, it becomes a slurry, which can be hardened in air or hardened in water, and can firmly bind sand, stone and other materials together. Cement is an important building material. Mortar or concrete made of cement is strong and durable and is widely used in civil engineering, water conservancy, and national defense projects. The cement production process uses limestone and clay as the main raw materials, and is broken, mixed and ground to make raw materials, fed into cement kiln for calcination of mature materials, and added appropriate amount of gypsum (sometimes also mixed with mixed materials or additives) to grind. Made. Cement is classified into uses and properties: Cement is classified according to its main hydraulic material name: The main technical characteristics are divided into: The principle of cement naming: The nomenclature of the cement is based on different types of cement, the main hydraulic minerals, mixed materials, uses and main characteristics, and strive to be concise and accurate. When the name is too long, abbreviations are allowed. General cement is named after the main hydraulic mineral name of cement under the name of mixed material or other appropriate name. Special cements are named for their specific use and can be modeled differently. Characteristic cement is named after the cement's main characteristics by its cement's main hydraulic mineral name, and may be given different model or mixed material names. Cements based on volcanic ash or latent hydraulic materials and other active materials are named after the name of the main component by the name of the active material, and can also be given the name of the property, such as gypsum slag cement, lime pozzolan cement. Wait. Definition of cement type Production Method <br> The production process of silicate cement is representative in cement production. Limestone and clay are the main raw materials. The raw materials are crushed, mixed and ground, and then fed into a cement kiln for calcination and maturation. Material, then clinker plus appropriate amount of gypsum (sometimes mixed with mixed materials or additives) from grinding. <br> <br> production process of cement production, can be divided into general preparation of raw materials, cement clinker and the like made of three steps. Production process example After the raw materials and fuels are brought into the factory, they are sampled, analyzed and inspected by laboratories, and homogenized according to the quality and stored in raw material sheds. Clay, coal, and pyrite powders are dried by the dryer to the process index value and lifted by the elevator to the corresponding raw material depot. Limestone, fluorspar and gypsum are broken in two stages and sent to their respective depots by hoists. The laboratory calculates the formula based on the quality of limestone, clay, anthracite, fluorite, and pyrite powder. The whole black raw material is dosed through the raw material microcomputer batching system. The raw material mill grinds and the hourly sampling is performed. The percentage of calcium oxide, ferric oxide, and fineness of the raw material was measured, and adjustments were made in time so that the data would meet the requirements of the process formulation. The black raw material that has been milled is pumped into the raw material warehouse through the bucket elevator. The laboratory conducts the homogenization of the raw material through the multi-bank collocation and the mechanical depot method according to the quality condition of the raw material milled. Raw material homogenization warehouse, the raw material is matched by two homogenization warehouses, and the material is lifted to a ball tray silo. The pre-adding water ball control device on the vertical kiln surface is used to match the ratio of material and water. Balls are made into raw balls. The resulting ball is calcined by a vertical kiln distributor at different locations in the kiln. Calcined clinker is sent to the clinker crusher for smashing by the unloading pipe and the squash machine, and is sampled by the laboratory every hour. Chemical and physical analysis of clinker is performed once. According to the clinker quality, the elevator is placed in the corresponding clinker warehouse. At the same time, according to the production and operation requirements and the building materials market conditions, the laboratory will use clinker, gypsum, slag, and cement ratio through the clinker microcomputer batching system. No. 425 and No. 525 ordinary portland cement were respectively ground and sampled once an hour for analysis. The milled cement was put into three cement warehouses via a bucket elevator. The laboratory used the multi-bank collocation and mechanical depot method to homogenize the cement according to the quality of the milled cement. The elevator is sent to two cement homogenization warehouses, and then the two cement homogenization warehouses are used. The cement packaging machine is used for the packaging of cement, and the packed bagged cement is stored in the finished product warehouse, and after passing the test sampling inspection. 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(1) General cement: Cement commonly used in civil engineering. General-purpose cement mainly refers to: GB175-1999, GB1344-1999 and GB12958-1999 provisions of the six major categories of cement, that is, Portland cement, ordinary portland cement, slag Portland cement, pozzolanic Portland cement, powder Coal ash portland cement and composite portland cement.
(2) Special cement: special purpose cement. Such as: G-grade oil well cement, road Portland cement.
(3) Characteristic cement: Cement with a certain outstanding performance. Such as: quick-hardening Portland cement, low-heat slag portland cement, expanded sulphoaluminate cement.
(1) Portland cement, commonly known as Portland cement abroad;
(2) Aluminate cement;
(3) sulphoaluminate cement;
(4) Ferroaluminate cement;
(5) Fluoroaluminate cement;
(6) Cements based on volcanic ash or potentially hydraulic materials and other active materials.
(1) Fastness: divided into two categories: fast and fast;
(2) Heat of hydration: divided into medium heat and low heat;
(3) Sulfate resistance: divided into two categories: resistance to sulphate corrosion and high resistance to sulphate corrosion;
(4) Swelling: Divided into two categories: swelling and self-stress;
(5) High temperature resistance: The high temperature resistance of aluminate cement is classified based on alumina content in cement.
(1) Cement: Add water to mix into a plastic slurry that can bind powdered hydraulic binder such as sand, stone and other materials that can both harden in air and harden in water.
(2) Portland cement: hydraulic cementitious material made of Portland cement clinker, 0%~5% limestone or granulated blast furnace slag, and appropriate amount of gypsum ground, known as Portland cement, sub-PI And P.II, commonly known as Portland cement abroad.
(3) Ordinary Portland cement: hydraulic cementitious material made of Portland cement clinker, 6% to 15% of mixed material, and appropriate amount of gypsum ground, known as ordinary Portland cement (referred to as ordinary cement) , code: PO.
(4) Slag Portland cement: hydraulic cementitious material made of Portland cement clinker, granulated blast furnace slag, and appropriate amount of gypsum ground, known as slag Portland cement, code: PS.
(5) Pozzolanic Portland Cement: A hydraulic binder made of Portland cement clinker, a mixture of pozzolanic materials, and a suitable amount of gypsum. Known as pozzolanic Portland cement, code: PP.
(6) Fly ash portland cement: A hydraulic binder made of Portland cement clinker, fly ash and a suitable amount of gypsum ground, known as fly ash portland cement, code: PF.
(7) Composite Portland cement: a hydraulic cementitious material made of Portland cement clinker, two or more specified mixed materials and a suitable amount of gypsum ground, known as composite Portland cement (abbreviated as Composite cement), code PC.
(8) Moderate heat Portland cement: A hydraulic cementitious material with moderate heat of hydration made of an appropriate amount of Portland cement clinker, added with an appropriate amount of gypsum ground.
(9) Low-heat slag portland cement: A hydraulic cementitious material with low heat of hydration made of an appropriate amount of Portland cement clinker by adding a suitable amount of gypsum ground.
(10) Fast-hardening Portland cement: The appropriate amount of gypsum is added from the Portland cement clinker, and the cement is ground to make the cement with the high strength of 3 days compressive strength.
(11) Sulfate-resistant portland cement: Portland cement clinker is prepared by adding appropriate amount of gypsum and finely ground cement with excellent sulfate resistance.
(12) White portland cement: White cement made by adding a proper amount of gypsum into a Portland cement clinker with a small content of iron oxide.
(13) Road Portland cement: hydraulic cementitious material made of road Portland cement, 0%~10% active mixed material and appropriate amount of gypsum ground, called road Portland cement, (abbreviated as road cement).
(14) Masonry cement: From the active mixed material, add appropriate amount of Portland cement clinker and gypsum, and grind it to make low-grade cement that is mainly used for masonry mortar.
(15) Oil well cement: Cement made of Portland cement clinker composed of appropriate minerals, appropriate amount of gypsum, and mixed materials, etc., which is suitable for the cementing of oil and gas wells under certain well temperature conditions.
(16) Gypsum slag cement: granulated blast furnace slag as the main component material, adding proper amount of gypsum, Portland cement clinker or cement made from fine grinding of lime.
Cement production can be divided into dry (including semi-dry) and wet (including semi-wet) methods, depending on the raw material preparation method.
1 dry production. The raw materials are dried and pulverized at the same time, or they are first dried and then fed into a dry kiln for calcination of the mature materials. However, there is also a method of adding a raw material powder to a raw material ball to make a raw material ball and feeding it into a calcined kiln material in a Libya kiln, which is called a semi-dry method, and is still a kind of dry method production.
2 wet production. After the raw material is pulverized into a raw slurry, it is fed into a wet kiln to calcine the mature material. There is also a method of dehydrating a raw slurry prepared by a wet method to prepare a raw material block and then entering the kiln to calcine a mature material, which is called a semi-wet method and is still a kind of wet method production.
The main advantage of dry production is low heat consumption (such as the heat loss of dry kiln clinker with preheater 3140 ~ 3768 coke / kg), the disadvantage is that the raw material composition is not easy to uniform, the workshop dust, power consumption is high . Wet production has the advantages of simple operation, easy control of raw material composition, good product quality, convenient slurry transportation, and less fugitive dust in the workshop. The disadvantage is high heat consumption (heat consumption of clinker is usually 5234 to 6490 J/kg).
(1) The raw material is milled in dry and wet methods. The dry method generally adopts a closed-circuit operating system, that is, after the raw materials are ground by a mill, they are sorted by a separator, the coarse powder is circulated back to the grinding mill, and most of the materials are simultaneously dried and ground in the mill. The equipment used includes pipe grinding, unloading mill and roller mill. The wet method usually uses an open circuit system such as a tube mill or a baseball mill that once passes through the mill and no longer flows back, but there are also closed systems with a classifier or an arc screen.
(2) The equipment for calcining calcined clinker mainly includes two types of vertical kiln and rotary kiln. The vertical kiln is suitable for small-scale production plants. The large and medium-sized plants should adopt rotary kiln.
1 shaft kiln:
The kiln cylinder is called vertical shaft kiln without turning. Common vertical kiln and mechanized vertical kiln. Ordinary shaft kiln is artificial feeding and manual unloading or mechanical feeding, manual unloading; mechanical shaft kiln is mechanical feeding and mechanical unloading. The mechanical shaft kiln is operated continuously, and its production, quality and labor productivity are all higher than ordinary shaft kiln. In recent years, most of the shaft kiln abroad have been replaced by rotary kiln, but in the current China cement industry, shaft kiln still occupies an important position. According to the requirements of the building materials technology policy, small cement plants use mechanized shaft kiln and gradually replace ordinary shaft kiln.
2 rotary kiln:
The kiln cylinder is placed horizontally (slightly inclined, approximately 3%), and it can be called a rotary kiln. A dry process kiln for calcining raw meal powders and a wet process kiln with a calcined slurry (the moisture content is usually around 35%).
a. Dry kiln dry kiln can be divided into hollow kiln, waste heat boiler kiln, suspension preheater kiln and suspension decomposition kiln. Around the 1970s, a calcination process that can significantly increase the output of rotary kilns was developed. It is characterized by the use of a precalciner kiln, which is based on a suspension preheater kiln, and a precalciner between the preheater and the kiln. Adding 50 to 60% of the total fuel in the precalciner, the combustion process of the fuel and the preheating of the raw material and the decomposition of the carbonate are moved from the zone where the heat transfer efficiency is lower in the kiln to the precalcinator. The raw material is heat-exchanged with the hot air flow in a suspended state or boiling state, thereby improving the heat transfer efficiency, so that the decomposition rate of calcium carbonate in the raw material before entering the kiln is more than 80%, thereby reducing the heat load of the kiln and prolonging the use of the kiln liner. Lifetime and kiln operation cycle, while maintaining the heating capacity of the kiln, significantly increase production.
b. Wet kiln The cement kiln used in wet production is called wet kiln. In the wet production, the raw material is made into slurry with 32%~40% water content. Due to the fluidity of the slurry prepared, the raw materials are well mixed and the raw material components are uniform, so that the quality of the burned clinker is high. This is the main advantage of wet production.
Wet kiln can be divided into wet kiln and wet kiln with slurry evaporator. Long kiln is widely used and short kiln is rarely used. In order to reduce the heat loss of the long wet kilns, various types of heat exchangers such as chains, slurry filter preheaters, metal or ceramic heat exchangers are installed in the kiln.
(3) The fine grinding of grinding cement clinker is usually performed by a loop-flow grinding process (ie, a closed circuit operation system). In order to prevent dust from flying in production, cement plants are equipped with dust collection equipment. Electrostatic precipitators, baghouse precipitators and cyclone precipitators are commonly used dust collectors in cement plants.
In recent years, due to the adoption of new technologies and new equipment in the areas of pre-homogenization of raw materials, homogenization of raw meal, and dust collection, especially the appearance of decomposing technologies outside the kiln, a new dry process technology has emerged. With this new process, the quality of the clinker produced by the dry process is no less than that of the wet process, and the electricity consumption has also been reduced. This has become the trend of the cement industry in various countries.
Main technical indicators of cement (1) Specific gravity and bulk density: The proportion of ordinary cement is 3:1, and the bulk density is usually 1300 kg/m3.
(2) Fineness: refers to the thickness of cement particles. The finer the particles, the faster the hardening and the higher the early strength.
(3) Condensation time: The time required for cement to add water to start coagulation is referred to as the initial setting time. The time required to complete the stirring from the addition of water is called the final setting time. The initial setting time of Portland cement is not earlier than 45 minutes and the final setting time is not later than 12 hours.
(4) Strength: Cement strength should meet national standards.
(5) Volume stability: refers to the uniform performance of cement volume change in the hardening process. The cement contains many impurities and will produce uneven deformation.
(6) Heat of hydration: The effect of cement and water will produce an exothermic reaction. In the process of cement hardening, the constant release of heat is called heat of hydration.
(7) Standard Consistency: refers to the consistency of a cement paste with certain resistance to the sinking of a standard test rod.
The revision of the cement standard There are two main changes in the new cement standard in China compared with the old standard. The first is the use of GB/T 17671-1999 "Cement mortar strength test method (ISO method)" instead of the current GB177-85 "cement glue." "Sand Strength Test Method"; Second, based on ISO strength, China revised six general cement standards.
(1) Standard GB/T 17671-1999 GB/T 17671-1999 Standard for Testing the Strength of Cement Mortar (ISO Method) was formulated in accordance with ISO 679-1989, which was adopted in China and published on February 8, 1999. , effective from May 1, 1999.
GB/T 17671-1999 and GB 177-85 belong to the same "soft practice method" for testing the strength of cement mortar, that is, using plastic sand, 4X4X160cm prism test body, the test body is first subjected to the flexural strength test, and the two half tests after breaking are performed. The body is then subjected to a compressive strength test. The core difference between the two is that the composition of the glue sand is different, the water-cement ratio adopted by the ISO method is moderate, the sand-sand ratio is moderate, and the grading standard sand is used in particular. Therefore, the strength value obtained by the ISO method is closer to that of the GB-177 method. The effect of cement in concrete.
(2) The main contents of the revision of the six cement standards a. The cement mortar strength test method is changed to GB/T 17671-1999. The six cement product standards all refer to the GB/T 17671-1999 method as the cement mortar strength test method, and the GB 177-85 method is no longer used. Therefore, the GB/T 17671-1999 method has become mandatory, and the GB 177-85 method has declined to the recommended method.
b. The cement label is changed to the strength grade of the six old cement standards. The cement number in terms of Kgf/cm2 is used, such as 32.5, 42.5, 42.5R, 52.5, 52.5R.
The new six cement standards adopt the strength grade represented by Mpa, such as 32.5, 32.5R, 42.5, 42.5R, 52.5, 52.5R, etc., so that the value of the strength grade is the same as the lowest value of the 28-day compressive strength index of cement.
The new standard also unifies the strength grade of China's cement. Portland cement is divided into 6 grades of 3 grades, 42.5, 42.5R, 52.5, 52.5R, 62.5, 62.5R. The other five cements are also divided into 3 grades 6 The type is 32.5, 32.5R, 42.5, 42.5R, 52.5, 52.5R
c. Intensity age and intensity of each age setting Six cement standards The cement ages specified in the new standard are 3 days and 28 days. Each age has the index requirements of the flexural and compressive strength.