Cement powder: water hardness Inorganic cementitious material
. After mixing with water into a paste, in the air Sclerosis
Or in the water and make better hardening, sand and stone material firmly Cemented
In harness。 The word cement comes from the Latin word caementum, meaning is gravel and rubble. Early and lime Ash
A mixture of lime and modern volcano ash cement It is very similar, made of cement stone Concrete
After hardening, not only Strength
High resistance but also fresh water or saline water erode
. For a long time, it is a kind of important Cementitious materials
Widely used in. Civil Engineering
, Water conservancy
, national defense
cement classification According to the purpose and performance for cement:
(1) General cement
General: usually used in civil engineering of cement. General cement mainly refers to six main categories: cement GB175 2007 provisions, i.e. silicate
Cement, ordinary Portland cement, Slag Portland cement
Volcano, marly Portland cement, fly ash
Portland cement and Composite Portland cement
(2): special purpose cement cement. Such as: G Oil well cement
The road, Portland cement.
(3): some outstanding performance characteristics of cement cement. Such as: Rapid hardening portland cement
, low heat slag portland cement
And expansion sulphoaluminate cement
P, aluminate cement and phosphate cement. According to the name of the main hydraulic cement material is divided into:
(1) portland cement
That is, foreign commonly known as Portland cement;
The original state of cement
(6) phosphate cement
(7) to the volcano ash or latent hydraulicity materials and other active materials as the main component of cement. According to the main technical characteristics into cement:
(1): rapidhardening (hydraulic) is divided into two kinds of hard and hard to express;
(2) Hydration heat
: divided into two kinds of heat and heat;
(3) resistance sulfate
: sulfate corrosion and high resistance to sulphate corrosion in two;
(4) expansion: divided into expand
And two kinds of self stress;
(5) high temperature resistance: Aluminate cement
The high temperature resistance to classification of alumina content in cement. Cement named Principle :
According to different categories respectively in the main water cement hard mineral, cement named
For material, purpose and main characteristics, and concise and accurate, the name is too long, allowing a short.
General cement main water cement mixed materials as hard mineral name names or other proper names.
The special cement is named after its specific purposes, and with different types.
The main characteristics of cement water cement as main mineral name named rigid characteristics of cement, and with different types or mixed materials.
The volcano ash or latent hydraulicity materials and other active materials as the main component of cement is the name to name the main components as active materials are named, and also can be called property name, such as Cement gypsum
Lime, volcano ash cement etc.. The definition of the cement type
(1): cement mixing water into a plastic paste, powder can be cemented sand and stone material both in air and in water hardening hardening Hydraulic cementing material
(2): by silicate Portland cement Cement clinker
0%~5%, limestone or granulation Blast furnace slag
The amount of ground water, made of gypsum cementing material, called Portland cement, P.I and P.II, which is known as the Portland foreign cement.
(3): by ordinary portland cement Portland cement clinker, 6%~20% hybrid materials, the amount of gypsum made of ground water cementing material, called Portland cement (the ordinary cement), code: P.O.
(4): Portland cement Portland cement clinker, 20%~70% granulated blast furnace slag made of ground water and the amount of gypsum cementing material, called slag Portland cement, code: P.S.
(5): from the volcano marly Portland cement Portland cement clinker, 20%~40% volcano ash mixed material and the amount of gesso mill made of hydraulic cementitious materials. Known as the volcano marly Portland cement, code: P.P.
(6) fly ash Portland cement by Portland cement clinker, 20%~40% fly ash
And the amount of ground water made of gypsum cementing material, called fly ash Portland cement, code: P.F.
(7) composite Portland cement made from composite Portland cement clinker, 20%~50% two or more than two kinds of provisions and the amount of ground water gypsum cementing material, called composite Portland cement (composite cement), named P.C.
(8) Moderate heat Portland cement
In Portland cement clinker, the appropriate components of gypsum made of ground with moderate heat of hydration of the cement material.
(9) Portland slag cement in Portland cement clinker, the appropriate components of gypsum ground made with low heat of hydration of the cement material.
(10) Rapid hardening portland cement
: consists of Portland cement clinker gypsum, ground made of high strength in early 3 days compressive strength
(11) Sulfate resisting portland cement
: consists of Portland cement clinker with resistance to sulfate corrosion amount of gesso mill made good cement.
Oil well cement
(12): white portland cement Portland cement clinker by iron oxide content less gypsum, pulverized. White cement
(13): Portland cement Portland cement clinker from the road, made of 0%~10% active mixing material and the amount of ground water gypsum cementing material, called Portland cement, (referred to as Cement road
(14): the masonry cement admixture, adding proper amount of Portland cement clinker and gypsum, mainly used for grinding made Masonry mortar
Low grade cement.
(15) Oil well cement
Application: made of Portland cement clinker, composed of appropriate mineral amount of gypsum and mixed materials grinding to a certain temperature under the condition of oil and gas well Well cementing
(16): to cement gypsum granulated blast furnace slag as the main component material, gypsum, clinker of Portland cement or lime ground made of cement.
cement Production process
The production process of Portland cement is representative in cement production, with limestone and clay as the main raw material, crushing, proportioning, grinding raw material and then fed into the cement kiln calcining mature material, then add appropriate amount of clinker gypsum (sometimes mixed with Mixed material
A ground or admixture).
Production of cement raw material with different preparation methods, can be divided into dry (including semi dry) and wet (including semi wet) two.
The dry production. At the same time the raw material drying and grinding, the grinding powder or drying raw meal after feeding Dry kiln
In the method of calcined into clinker. But there are also the raw material powder adding water into Raw meal ball
To stand. Bohr
The method of calcination kiln clinker, called semi dry, dry production is still one of the. The new dry cement
The new dry cement production line with precalcining cement production process. The production in suspension preheater and precalciner technology as the core, using a new type of raw materials, fuel and energy saving grinding technology and equipment, full use of computer control, implementation of cement The production process automation
And efficient, high quality, low consumption, environmental protection. The new dry cement production technology
Is developed in 1950s, Japan Germany and other developed countries, as the core of the new dry process in suspension preheater and precalciner Cement clinker
Production equipment accounted for 95%, the first set of Chinese suspension preheating and precalcining production in 1976. The technology has the advantages of rapid heat transfer, high thermal efficiency, the unit volume is wet cement production, low heat consumption.
The wet production. The raw materials and raw slurry after grinding powder, feed Wet kiln
Methods mature material calcination. There will be a wet preparation of raw slurry dehydration after making method of raw material block into the kiln calcination mature material, called semi wet, wet production is still one of the.
The main advantage of dry production is low heat consumption (such as dry kiln clinker heat consumption with preheater is 3140 ~ 3768 kJ / kg), the disadvantage is not easy even the raw ingredients, workshop dust, high power consumption. The wet production of raw meal composition has the advantages of simple operation, easy control, good product quality, slurry transportation convenience, the advantages of fewer workshop dust, the disadvantage is high heat consumption (heat consumption of clinker is usually 5234 ~ 6490 kJ / kg).
Cement production, generally can be divided into raw material preparation, clinker and cement made of three process, the whole production process can be summarized as " two grinding burn
cement Raw material grinding
Dry and wet two. Dry generally adopts a closed operating system, namely raw materials mill grinded into powder, sorting machine, grinding and grinding operation of coarse powder flowing into, and most of the materiel
In the process of drying and grinding mill at the same time, the equipment used in pipe mill, discharging mill and roller mill etc.. Wet grinding, ball grinding tube usually adopts a backflow through the mill no longer open systems, but also adopts a closed system with the classifier or arc screen.
The main equipment for calcining clinker Kiln
and Rotary kiln
Two types of shaft kiln, suitable for the production of smaller factories, large and medium-sized factory should adopt rotary kiln.
The vertical kiln:
Kiln vertical turning called kiln. Ordinary and mechanized vertical kilns. Ordinary kilns are artificial feeding and artificial feeding or discharging machine, manual unloading; mechanical mechanical shaft kiln feeding and unloading machine. Mechanical shaft kiln is a continuous operation, production, quality and productivity of it are high than ordinary shaft kiln. Most of the foreign kiln rotary kiln has been replaced, but in the current Chinese kiln cement industry, still occupy an important position. According to the policy requirements of small building materials technology, application of mechanical vertical kiln cement plant, gradually replacing the ordinary shaft kiln.
The rotary kiln:
Horizontal kiln (a slope of about 3%), and can be used for the rotary movement known as the rotary kiln. Burning raw powder Dry kiln
Powder and calcined slurry (moisture content is usually around 35%) wet kiln.
A. dry kiln
Dry kiln can be divided into hollow kiln, kiln waste heat boiler, suspension preheater and suspension decomposition furnace. After 70s, the development of a rotary kiln calcining process can improve the yield greatly, kiln decomposition technology. It is characterized by a precalciner kiln, it is based on the suspension preheater kiln, kiln and preheater between added calciner. Add the total fuel amount of 50 to 60% of the fuel in the decomposition furnace, fuel combustion process and raw material preheating and carbonate decomposition process, from the kiln Heat transfer efficiency
The lower zone moved to the decomposition furnace, raw material in suspension or boiling condition and hot air heat exchange, so as to improve the efficiency of heat transfer, the raw in front of the kiln Calcium carbonate
The decomposition rate of more than 80%, to reduce the heat load of kiln, prolong the service life and the kiln kiln operation cycle, in the heating kiln under the condition of maintaining the ability to greatly improve the yield of the objective.
B. wet kiln
For the production of cement kiln wet wet kiln, wet production of raw water is made into slurry 32%~40%. As prepared with liquidity of the mud, so the raw materials mixing and the raw ingredients evenly, make the burning of the clinker of high quality, which is the main advantages of wet production.
Wet kiln can be divided into long wet kiln and with slurry evaporation machine widely used wet kiln, long kiln, kiln has been rarely used. In order to reduce the length of wet kiln heat consumption, heat exchanger is provided with various types of equipment in the kiln, such as chain
The slurry, filtration, or metal preheater Ceramic heat exchanger
cement Cement grinding
Cement clinker grinding usually adopts circle grinding process flow (i.e. closed operating system). In order to prevent dust production, cement factories are equipped with dust collection equipment. electric Dust collector
Bag type dust collector and a cyclone dust collector is commonly used in cement plant dust collection equipment.
Because the raw materials prehomogenizing, raw meal homogenization conveying and dust collecting using new technology and new equipment, especially the kiln decomposition technique, a new dry process production produced. By using this new process the dry production of clinker as the quality of wet production, power consumption is reduced, has become a national cement industry development trend. For example (kiln)
Raw material and fuel into the plant, from the laboratory sampling analysis at the same time averaging collocation according to the quality of raw materials, stored in a shed. Clay, coal, Pyrite
Fly by Dryer
The water drying process to the index value, through the elevator to the corresponding storage of raw materials. Limestone, fluorite, gypsum after two crushed by hoist into their storage.
Laboratory, according to quality of limestone, clay, coal, fluorite, pyrite slag, calculation formula, raw material by Microcomputer Batching system
For the black raw material ingredients from raw mill for grinding, per hour sampling tests a meal calcium oxide
And the content of ferric oxide and fineness, the timely adjustment of the data to meet the strict requirements of the formula. The black meal after grinding Bucket type lifting machine
Put into the raw material base, on the basis of laboratory meal quality, of raw material through multi collocation and mechanical library methods are, by lifting the two raw mealsilo raw materials, two of all of the libraries will be provided to the material collocation, into a ball disc bin, which is on the surface of shaft kiln pre water ball control device of material and water ratio of raw material into a ball by ball disc. A ball from the traditional distributor will Raw meal ball
Distributed in different positions in the calcining kiln, burning a clinker discharge pipe, scale machine sent to the clinker crusher are broken, chemical sampling once per hour by the laboratory of clinker, Physical analysis
According to the quality of clinker by hoist into the corresponding clinker silo, and according to the production requirements and Building materials market
Laboratory, clinker and gypsum, slag
Cement ratio by microcomputer batching system composed of cement clinker, mill No. 425 and No. 525 respectively for Portland cement grinding, once per hour sampling analysis test. Grind the cement by the bucket elevator provided 3 cement base, cement quality on the basis of the laboratory, cement by multi collocation and mechanical homogenization method library. The hoist into 2 cement homogenizing silo, the two cement homogenizing silo collocation, controlled by the microcomputer packaging machine for cement packaging bags of cement packing out stored in the finished goods warehouse, the laboratory sampling qualified after the inspection notice issued by the cement factory.
cement chemical reaction
The main chemical composition of Portland cement: calcium oxide
CaO, Silicon dioxide
SiO2, Ferric oxide
Fe2O3, Three two aluminum oxide
The main minerals of Portland cement: Three calcium silicate
(3CaO, SiO2, short C3S), Two calcium silicate
(2CaO, SiO2, short C2S), Three calcium aluminate
(3CaO, Al2O3, short C3A), Ferritealuminate four calcium
(4CaO - Al2O3 - Fe2O3, short C4AF).
The setting and hardening of cement:
1), 3CaO - SiO2+H2O - CaO - SiO2 - YH2O ( Gel: Set & Match
+Ca (OH) 2);
2), 2CaO - SiO2+H2O - CaO - SiO2 - YH2O ( Gel: Set & Match
+Ca (OH) 2);
3), 3CaO - Al2O3+6H2O - 3CaO - Al2O3 - 6H2O (calcium carbonate, hydrated aluminum unstable);
3CaO - Al2O3+3CaSO4 - 2 - 3CaO - Al2O3 - H2O+26H2O - 32H2O (3CaSO4 Ettringite
The three type of water, calcium sulfur aluminum);
3CaO - Al2O3 - 3CaSO4 - 32H2O+2 3CaO - Al2O3 +4 H2O - 3 3CaO - Al2O3 - CaSO4 - 12H2O (single sulfur acid calcium hydrate aluminum);
4), 4CaO - Al2O3 - Fe2O3+7H2O - 3CaO - Al2O3 - 6H2O+CaO - Fe2O3 - H2O.
Quick setting cement cement refers to an abnormal early curing or premature hardening phenomenon. The high temperature makes the water dehydration crystallization of gypsum, into a slurry, thus losing the ability to adjust the setting time. False set is related to many factors, that is mainly due to cement grinding mill in high temperature, the two water gypsum dehydration to hemihydrates sake. When the cement mix water, half water gypsum rapidly reacts with water into two water gypsum, the formation of acicular crystal mesh structure, thereby causing slurry curing. In addition, some high alkali cement, potassium sulfate and potassium gypsum gypsum two generation grew rapidly, can also cause a false set. False coagulation and rapid solidification, the former heat effect, and the intense mixing slurry can restore plasticity, and reach the normal setting, no adverse effect on the strength.
cement Cement history
In 1756, British engineer J. Smeaton characteristics found in water hardening in the research: to get some lime lime water, must be used with clay limestone to prepare for; Underwater construction
The masonry mortar
And the ideal composition is by hydraulic lime and ash into a volcano. This important discovery has laid a theoretical foundation for the research and development of modern cement.
In 1796, the British J. Parke Marl
Burn out of a cement, the appearance of brown, like the era of ancient Rome volcano ash and lime mixture, named Rome cement. Because it is a natural limestone as raw materials, direct firing without ingredients, also known as the natural cement. Good water hardness and rapid solidification characteristics, especially suitable for contact with water engineering.
In 1813, French civil engineers found complete with limestone and clay in three than a blend of the best performance of cement.
In 1824, Britain Construction worker Joseph Aas spectrum Ding
(Joseph Aspdin) invented and made of cement portland
Patent cement. He used limestone and clay as raw materials according to a certain proportion, in similar to the lime burning kiln in calcination
Mature material and cement made by grinding. Because of the Portland local cement hardened color and on the island of England for building stone similar, was named Portland cement. It has the excellent performance of the building, a landmark in the history of cement.
In 1871, Japan began to build cement factory.
In 1877, Britain Auckland
Hampton invented Rotary furnace
And in 1885, after the reform into rotary furnace better langsam.
In 1889, Hebei Tangshan China Kaiping
Near the mine, established by the Tangshan kiln production "fine cotton soil" factory. Established in 1906 in the factory on the basis of new Cement
The company, with an annual output of 40 thousand tons of cement.
In 1893, Endo Hiroyuki in Japan and sea three two people cheer invention is not afraid of the sea of Portland cement.
In 1907, the French billiere using aluminum ore Bauxite
Firing cement. Because the cement contains a large amount of alumina, so called alumina cement".
In twentieth Century, people in the continuous improvement of properties of Portland cement at the same time, the successful development of a number of suitable for special construction projects such as cement. High alumina cement
Special cement, etc.. The whole world has developed more than 100 varieties of cement, cement annual output of about 20 tons in 2007. Chinese establish a unified national standard in 1952, to determine the cement production with many varieties of multi label principle, and according to the content of Portland cement The main mineral
Which was renamed Portland cement, Portland cement has been renamed after.
In 2012, China cement production reached 21.84 tons, production accounted for more than 50% of the world.
cement Classification of production index
cement Decorative cement
Decorative cement commonly used in building decorating surface, simple construction, convenient shape, easy maintenance, low price. There are several varieties:
(1): white portland cement Calcium silicate
As the main ingredient, add a small amount of clinker and the amount of iron
The color of Portland cement
Gypsum and ground.
(2) The color of Portland cement
In white portland cement clinker and high quality white gypsum mixed with pigments, additives and common ground. The commonly used color mixing pigments with iron oxide (red and yellow, brown and black), manganese dioxide (brown and black), chromium oxide (green), blue (blue), ultramarine blue (Dian Lan), blue (Hai Lan), carbon black
(black). The decoration is similar to the cement and Portland cement, construction and maintenance of the same, but relatively easy to pollution, equipment tools must be clean.
cement Use and purchase
In the home decoration, floor tile, wall brick and masonry are used to paste Cement mortar
It can not only enhance the ability of adsorption, surface material and substrate, but also protect the internal structure, and can be used as building hair surface leveling layer, so in the decoration engineering, cement mortar is an indispensable material.
Many customers think that the cement mortar accounted for the larger proportion, the adhesion is stronger, so often in the amount of cement used in the decoration company and disagreement. In fact, in order to paste ceramic tile
For example, if the cement grade is too large, when the setting time of cement mortar, cement absorb a large amount of water, then the water surface of the tile is easy to absorb excessive tension, shorten the service life. According to the general cement mortar cement: sand =1:2 (volume ratio) the proportion of mixing.
Many cement varieties on the market, there are portland cement
Ordinary Portland cement, Composite Portland cement
Portland slag cement, etc., commonly used in home decoration is ordinary portland cement or composite Portland cement.
cement Foam cement
According to the production of foam cement in different ways can be divided into physical foaming and chemical foaming.
A physical foaming cement
The foaming agent prepared by mechanical equipment into the bubble, the bubble add to the cementitious material, aggregate, admixture, admixture and water into slurry, by mixing and pouring molding, curing and thermal insulation board (hereinafter referred to as the foaming cement insulation board).
Two, cement chemical foaming
A blowing agent is added by cementitious material, aggregate, admixture, admixture and water into slurry, by mixing and pouring, make it through the chemical reaction in the mold and the slurry generated inside the pores, after curing, cutting into insulation board.
cement Matters needing attention
Silicate cement raw materials
Sealed cement factory quality certificate shall be manufacturer of quality department; the test report should test code, verify the relevant information for verification and test room, and there should be a clear conclusion, signed and sealed complete; manufacturers Cement 28 days strength bubao single is not a lack of valid; use unit must carefully check the cement, for expired the cement, must do the reexamination, and shall carefully check the numerical test report in the field is consistent with the values indicated in the specification standards; for the existence of quality problems of the cement according to the test report, the data can be demoted, but must be after the signature of the person in charge of the approval, and shall indicate the name, the use of the use of Engineering site. If it is a continuous construction project, two cement test the adjacent time shall not exceed the period of validity.
With the cement factory certificate and test report on the construction materials and construction organization design, design changes, negotiation records, technical disclosure, construction log, concrete and mortar mix application notice, concrete and mortar specimens, test pressure test report number, certificate, test report and therefore not only should be used with cement the actual engineering, parts of the cement line, should also correspond with the above construction data consistency. (1) avoid damp hard
With the hard cement will reduce or lose the original strength, so the specification, the cement factory for more than 3 months shall review test according to the test results, the use of. To have damp agglomerate or hard cement should be screened using the screened mass or rub fine grinding after the general engineering or for secondary masonry mortar plastering mortar
. On a touch or a pinch of cement powder mass, may be appropriate to reduce the use of strength. (2) avoid exposure and quick drying
Such as concrete or plaster after operation was exposure, along with the rapid evaporation of water, its strength will be reduced, and even lost completely. Therefore, must be strictly clean and fully wet base construction; after construction should be strictly according to norms and coverage, water conservation. (3) avoid negative temperature freezing Concrete
Mix, if not cold, the cement hydration, and the water is freezing and expansion, concrete or mortar would have been gradually deepened the crisp powder from the outside to the inside, so shall be strictly in accordance with the " Specification for winter construction of building engineering
"(JGJ104 - 97) construction. (4) to avoid
After the solidification of mortar or concrete structures, such as often in hot conditions, there will be a loss of strength, this is because of the high temperatures, cement stone
In addition, some calcium hydroxide decomposition; decomposition of aggregate or under high temperature conditions also Volume expansion
In the high temperature occasion for long, can be used for refractory brick Ordinary mortar
Concrete or isolation door. Have a higher temperature, should adopt special heat-resistant concrete casting, grinding heat resistant materials can also be mixed with a certain amount of concrete. (5) avoid dirty soft base
Cement and hard, clean the base firmly bond together, but the bond bond strength and the smoothness of the base face. In the construction of smooth base, must be pre cut hair hit Ma brushed, can make cement firmly bonded with a substrate.
On the base of dirt, greasy, acid and other substances, will have Isolation effect
That must be carefully removed after the first wash, brush a cement paste, mortar or concrete plastering.
To cement shrinkage in the solidification process, and in the process of wet and dry, hot and cold changes, with loose and weak base can not adapt to the change of volume, inevitable cracks or hollowing and difficult to bond firmly. Therefore, wood, slag
The cushion and lime soil cushion are not with mortar or concrete bonded firmly. (6) avoid impure aggregate
As a concrete or cement mortar aggregate gravel, if there is dust, clay or other organic impurities, will affect the bonding between the cement and sand stone and bond strength, thus reducing the final compressive strength. So, if the impurity content exceeds the standard, must be cleaned before use. (7) avoid water thick ash
People often ignore the effect of water content on the strength of concrete, the construction is easy to cast, sometimes not seriously implement the concrete mix proportion, and very rare. Because about hydration water needed for only 20% of the cement weight, excess water will leave a lot of pores in the concrete, these pores will reduce the strength of concrete. Therefore, under the premise of the protection of pouring and compacting, should minimize mixing water.
Many people think that the plastering cement, the more the more solid dosage of plaster. In fact, the amount of cement mortar is more dense, volume shrinkage plaster layer is greater, which would produce more cracks. In general, the plastering should be the first to use the 1: (3 - 5) sand mortar leveling layer, and then 1: (1.5 - 2.5). Cement mortar
Wipe the surface layer is very thin, do not use too much cement. (8) avoid acid corrosion
Acidic substances in cement and calcium hydroxide neutralization happens, generating object is loose and expansive, water easily hydrolysis powder. The concrete or plaster layer was corroded gradually disintegrated, so avoid acid corrosion of cement.
In contact with acidic substances occasions or container, should use acid resistant mortar and concrete acid. Volcano ash and slag cement, cement Fly ash cement
Have good acid resistance, should give priority to these three kinds of cement mortar and concrete acid. Strict requirements of acid corrosion engineering does not allow the use of ordinary cement.
cement The status of the industry
In 2015 July, cement production 2.12 tons, with the reduction of 4.7%, higher than the growth rate in June rose 1.1%, lower than the same period last year 8.21%1-7 month cement production totaled 12.91 tons, with 5% reduction in slow down growth, higher than June 0.3%, lower than the same period last year 8.69%. The 15 year 1-7 month accumulative total investment in fixed assets 28 trillion and 850 billion yuan, an increase of 11.2%, compared with 6 growth rate slipped 0.2%, is down 5.8% over the same period last year; 15 years 1-7 months of railway transportation investment in fixed assets 336 billion 600 million yuan, an increase of 10.9%, the growth rate 15.1% lower than in June, higher than the same period last year 8.7%. 1-7 month cumulative real estate investment 52562 yuan, an increase of 4.3%, the growth rate 0.3% lower than in June, down 9.4% compared to the same period last year; area of 817 million square meters of new 1-7 month cumulative housing starts fell 16.8%, compared with June growth rate 1% lower than the same period last year fell 4%; 1-6 month accumulative total commercial housing sales area of 599 million square meters, an increase of 6.1%, higher than the growth rate in May rose 2.2%, representing an increase of 13.7%.
The competition pattern and the leading enterprise Chinese cement industry analysis report data show that 1-7 months of cement production to maintain negative growth, a slight decline narrowed. Real estate index data to remain in the doldrums, on the one hand, investment and new construction data QoQ expansion, the investment growth rate is lower than 5%, and may continue to fall, the latter trend is not optimistic. In July the railway transportation chain fell sharply by 15.1%, a 03 year history of the largest decline over the same period, infrastructure and other large projects are still lower than expected.
cement Production index standard 1, the main technical indexes of cement
Volume weight: standard cement proportion is 3.1, the bulk density is usually used 1300 kg / m3.
(2): refers to the thickness of the fineness of cement particles. The finer particles, hardening faster, higher early strength.
(3) setting time
Cement mixing with water to condense the time required that the initial setting time began. From mixing with water to condense time required to complete the call final setting time. Portland cement and ordinary portland cement setting time is not earlier than 45 minutes, the final setting time not later than 6.5 hours; volcano ash cement and fly ash cement, composite Portland cement final setting time not later than 10 hours. In fact, the initial setting time in 1~3h, and the final setting for 4~6 hours. The setting time of cement was determined by the special setting time meter
(4) strength: The strength of cement
Should comply with national standards.
In the hardening process of cement: refers to the volume change of uniform performance. With a lot of impurities in cement, will produce uneven deformation.
(6) Hydration heat
Cement and water: effect on exothermic reaction. Hardening of cement
In the process of continuous heat of hydration heat is called.
(7): refers to the standard consistency Cement paste
The bar sink has certain resistance to the consistency of the standard test. Amendment 2, cement standard
The new standard cement China old standards and compared the main changes in two aspects: one is the use of GB/T 17671 - 1999 "cement mortar strength test method (ISO method) to replace the existing" GB177 - 85 "cement mortar strength test method"; two is the strength of ISO based Chinese revised six general cement standard.
(1) GB/T 17671 - 1999 "cement mortar strength test method (ISO method)" standards
GB/T 17671 - 1999 is China With the adoption of international standards
ISO 679 - 1989, released on February 8, 1999, effective May 1, 1999.
17671 GB/T - 1999 and GB177 - 85 belong to the cement mortar strength test "soft training method", which uses plastic sand, 40X40X160mm prism specimens, the specimens were first Flexural strength
Experiment two half after fracture specimens and compressive strength test. The difference lies in the core of the mortar composition are different, ISO methods Water cement ratio
The cement sand ratio is moderate, moderate, especially by gradation Standard sand
Therefore, the strength of numerical ISO test method are more close to the cement in the concrete effect of using the GB-177 method.
(2) the main contents of the six cement standard revision
Test method of A. cement mortar strength to GB/T 17671 - 1999 method
The six cement product standards are cited GB/T 17671 - 1999 methods as the strength of cement mortar, no longer used GB 177 - 85 method. Therefore, GB/T 17671 - 1999 methods rise to a mandatory method, while the GB 177 - 85 decline for the recommended method.
B. The grade of cement
The six old cement standard to implement the Kgf/cm2 representation of the grade of cement, such as 32.5, 42.5, 52.5, 42.5R, 52.5R etc..
Six concrete implementation of the new standard in Mpa's strength, such as 32.5, 32.5R, 42.5, 42.5R, 52.5 and 52.5R
, the strength grade of cement and numerical 28 days compressive strength index of the minimum value of the same.
The new standard also unified the strength grade of China cement, Portland cement is divided into three grades and 6 types, 42.5, 52.5, 62.5, 42.5R, 52.5R, 62.5R, the other five cement can be divided into 3 grades of 6 types: 32.5, 32.5R, 42.5, 42.5R, 52.5, 52.5R
Set the C. strength of age and strength in each age index
The strength of the cement age provisions of the new standard six cement was 3 days, 28 days and two age, every age has the flexural strength and compressive strength index. 3, cement pollution prevention standards
Carbon emissions from the cement industry after the power consumption of resources and ecological industry, the problems of damage to the cement industry will usher in a new round of tide.
The State Environmental Protection Department recently released "cement industrial pollution control technology policy" (Draft) and "pollution prevention and control of the cement industry the best available technology guide" (draft). The two documents the message is that countries through technical standard for pollution control in cement industry to tighten, overall reduction of pollutant emission in cement industry, cement industry at the same time to resolve the problem of excess production capacity; whether technology or technology policy guidelines, should be mandatory.
According to the China Research Academy of Environmental Sciences, China Cement Association, the cement industry is the key polluting industries, its particulate emissions accounted for particulate emissions nationwide from 20 to 30%, sulfur dioxide emissions accounted for 5% of national emissions to 6%, adding some fluorite production in order to reduce the sintering kiln heat consumption, also caused by fluoride pollution of the surrounding area the.
The cement industry is China's iron and steel power, after the third large coal, China's cement clinker burning average heat consumption of 115 kilograms of standard coal / ton, higher than the advanced international level of more than 10%. The existing national scale cement production enterprises around 4000, new dry cement production line more than 1 thousand and 500. The cement industry emissions of carbon dioxide after the electric power industry, the second in the country. Mine resource consumption and ecological damage of cement enterprises is also outstanding issues.
China Institute of environmental science, Hefei cement research and Design Institute of the "pollution prevention and control in cement industry best available technology guide" (Draft) said that the working group in 2010 to conduct research on the 158 cement companies, for each of the 5000 tons / day of dry cement clinker production line, the enterprise required to pay an annual sewage fee of about 90 ~ 1 million yuan.
If through technical transformation and supervision in place, particulate emissions reduced by 50%, nitrogen oxides reduced by 25%, to reduce annual emissions of about 300 thousand yuan, equivalent to an annual tons of cement less to pay 1 thousand and 500 yuan, calculated according to the national cement capacity of 18.6 tons, the next 5 years to reduce sewage charges up to 1 billion 395 million yuan. At the same time to reduce dust, sulfur dioxide, nitrogen dioxide pollution, environmental and social benefits are enormous.
If the cement industry can reach 30% of the raw material / fuel within the next five years the replacement rate, can reduce the annual carbon dioxide emissions of 2.8 tons, at the same time by reducing the use of fossil fuels and the cost savings of $372 billion, generating huge environmental and economic benefits.
Chinese Cement Association Secretary General Kong Xiangzhong said that the cement industry in the process of technological innovation, continuously with overcapacity. State control of cement overcapacity red token has continued, but each stage of major technological innovation, promotion and development for the industry to resolve overcapacity has made a decisive contribution.
According to reports Chinese Cement Association, three years ago, the national investment in new cement production line 463, clinker production capacity of 5.47 tons, which means that at least some backward production capacity of 2 tons of technology was being run out and become overcapacity. But it is the cement industry overcapacity, strengthen the cement enterprises in the pursuit of technological progress and improve the management of power, full market competition, optimize the allocation of resources." Kong Xiangzhong said.
"The cement industry pollution prevention and control of best available technology guide" (Draft) writing group pointed out that technical guidelines should be with various emission standards (including local standards) to create the relationship, and want to have some mandatory.
cement National standard
The new cement standard products for " Common portland cement
"(GB 175-2007), the following is the main content of this standard.
The range of 1
This standard specifies the definition and classification of common portland cement, components and materials, strength, technical requirements, test method, inspection rules and signs, packaging, transportation and storage, etc..
This standard is applicable to common Portland cement.
2 normative references
The clauses in the following documents by the standard reference in the provisions of this standard. Fordated documents, subsequent amendments (excluding corrections) or revisions do not apply to this standard, however, encourage the latest version of the parties to agreements based on this standard using these files. For undated references, the latest edition is suitable for this standard.
GB/T176 Cement chemical analysis
Methods (GB/T176-1996, EQV ISO680:1990)
GB/T203 used in cement granulated blast furnace slag
GB/T750 autoclave stability test method
GB/T1345 Cement fineness
Test method (sieve)
GB/T1346 Cement standard consistency
The setting time and soundness of the method of water (GB/T1346-2001, EQV, ISO9597:1989)
GB/T1596 used in cement and concrete fly ash
GB/T2419 Fluidity of cement mortar
GB/T2847 for volcano ash mixed material in cement
GB/T5483 and gypsum Anhydrite
Determination of the specific surface area of GB/T8074 cement (Blaine method)
GB9774 cement packaging bags
Sampling method of cement GB12573
Quantitative determination of GB/T12960 components of cement
Test method of GB/T17671 cement mortar strength (ISO) (GB/T17671-1999, IDT, ISO679:1989)
GB/T18046 used in cement and concrete granulated blast furnace slag powder
Methods for chemical analysis of chloride ions in cement raw materials JC/T420
JC/T667 Cement grinding agent
Incorporation of JC/T742 ash in cement rotary kiln
3 definition and classification
The following terms and definitions apply to this standard.
General Common Portland Cement Portland cement
Made of mixed material of Portland cement clinker and the amount of gypsum, and the provisions of the water hydraulic cementitious materials.
5 components and materials
The 5.1 component
Common portland cement components shall meet the specification in table 1.
Fly ash Portland cement
Code of variety
Clinker and gypsum granulated blast furnace
Gray slag volcano
Mixed materials of fly ash limestone
Portland cement P - I 100 -
P = 95 = 5 - II
More than 95, less than 5
Portland cement P, O = 80 and <95 = 20A - and >5
Portland slag cement S A = 50 P and <80 >20 and 50B -
P - S - B = 30 and <50 and less than 70B - >50
Volcano marly Portland
Cement P P = 60 and <80 = 40C - and - >20
Fly ash Portland cement P, F = 60 and <80 - >20 and 40d -
Composite Portland cement P, C = 50 and <80 >20 and 50E
The a component materials with active mixing material 5.2.3 of this standard, which allows for no more than 8% of cement quality and meet the non active material of this standard 5.2.4 or not more than 5% of cement quality and meet the 5.2.5 standard instead of kiln dust.
The B component materials for active mixing material with GB/T203 or GB/T18046, which allows for no more than 8% of cement quality and in accordance with the active material of this standard article 5.2.3 or with non active material of the standard section 5.2.4 or with any kind of material instead of the standard section 5.2.5 in the kiln ash.
The C component materials for active mixing material with GB/T2847.
The D component materials for active mixing material with GB/T1596.
The e component material is two (inclusive) above with active mixing material of this standard article 5.2.3 or / and with non active material of the standard section 5.2.4, which allows for no more than 8% of cement quality and meet the criteria of article 5.2.5 instead of kiln dust. When the amount of admixture of slag and slag Portland cement shall not repeat.
5.2.1 Portland cement clinker
By SiO2, mainly including CaO, Al2O3, Fe2O3 of the raw materials, according to appropriate proportion into a fine powder burn to partial melting of the calcium silicate as the main mineral composition of cement material. The calcium silicate minerals is not less than 66%, the quality of calcium oxide and silicon oxide is not less than 2.
22.214.171.124: natural gypsum shall comply with GB/T 5483 stipulated in the G or M level two (inclusive) above the gypsum or mixed gypsum.
126.96.36.199: the industrial by-product gypsum calcium sulfate
As the main component of industrial by-products. The former should be proved by experiment on the performance of cement harmless.
The activity of 5.2.3 hybrid materials
With GB/T203, GB/T18046, GB/T1596, GB/T2847 standard of ground granulated blast furnace slag, granulated blast furnace slag, fly ash, volcano ash mixed material.
5.2.4 non active mixing material
The activity index were less than GB/T203, GB/T18046, GB/T1596, GB/T2847 standard of ground granulated blast furnace slag, granulated blast furnace slag, fly ash, volcano ash mixed material; limestone and sandstone, of which three oxidation in limestone two aluminum content should not be greater than 2.5%.
5.2.5 kiln ash
In accordance with the provisions of JC/T742.
5.2.6 grinding agent
Allows adding grinding aids in cement grinding, its content should be less than 0.5% of cement quality, grinding agent shall comply with JC/T667 regulations.
6 strength grade
Strength grade 6.1 Portland cement is divided into 42.5, 52.5, 62.5, 42.5R, 52.5R, 62.5R six grades, R said early strength cement.
The strength grade 6.2 Portland cement, divided into 42.5 42.5R, 52.5 52.5R, four grade.
6.3 Portland slag cement, Volcano gray Portland cement
Fly ash, Portland cement, Portland cement strength grade is divided into 32.5, 42.5, 52.5, 32.5R, 42.5R, 52.5R six grades.
Note: R: early strength type (mainly 3D with the same strength grade cement with high strength
7 technical requirements
7.1 chemical index
The chemical index conforms to the regulations in table 2.
Code of variety
(mass fraction) loss
(mass fraction) three sulfur dioxide
(mass fraction) magnesium oxide
(mass fraction) chloride
Portland cement P - I = 0.75 = 3
Less than or equal to 3.5
Less than 5.0A
Less than 0.06c
P - II = 1.50 = 3.5
Portland cement P - O - 5
Portland slag cement - S - A - P = 4 = 6.0b
P - S - B -
Volcano gray Portland cement P - P - 3.5
Less than 6.0b
Fly ash Portland cement P - F
C - P composite Portland cement
A if the autoclave test qualified, then Magnesium Oxide cement content (mass fraction) allows up to 6%.
If Magnesium Oxide B cement content (mass fraction) is greater than 6%, to cement autoclave stability test and qualification.
When the C is lower when the index is determined by the parties.
Seven point two Alkali content
Alkali content in cement according to the calculated Na2O+0.658K2O said. If the use of Active aggregate
The user is required to provide, low alkali cement, alkali content in cement should be less than 0.60% or determined by the parties.
7.3 physical indicators
The setting time of 7.3.1
The initial setting of Portland cement is not less than 45min, the final setting is not greater than 390min;
Ordinary portland cement, slag Portland cement, Portland cement, volcano ash fly ash Portland cement and Portland cement setting is not less than 45min, the final setting is not greater than 600min.
Boiling is qualified.
The strength of 7.3.3
Different varieties of different strength grades Common portland cement
The different, the strength should be consistent with the provisions of table 3.
Table 3 units for MPa
The compressive strength and flexural strength strength varieties
3D 28d 3D 28d
42.5 = 17 = 42.5 = 3.5 = 6.5
42.5R = 22 = 4
52.5 = 23 = 52.5 = 4 = 7
52.5R = 27 = 5
62.5 = 28 = 62.5 = 5 = 8
62.5R = 32 = 5.5
Portland cement 42.5 = 17 = 42.5 = 3.5 = 6.5
42.5R = 22 = 4
52.5 = 23 = 52.5 = 4 = 7
52.5R = 27 = 5
Slag Portland cement
Volcano ash Portland cement
Fly ash Portland cement
Composite Portland cement 32.5 = 10 = 32.5 = 2.5 = 5.5
32.5R = 15 = 3.5
42.5 = 15 = 42.5 = 3.5 = 6.5
42.5R = 19 = 4
52.5 = 21 = 52.5 = 4 = 7
52.5R = 23 = 4.5
7.3.4 (selective fineness index)
Portland cement and ordinary portland cement with specific surface area of not less than 300m2/kg; Portland slag cement, Portland cement, volcano ash fly ash Portland cement and Portland cement to sieve more than 80 mu m Kong Shai said that the sieve is not greater than 10% or 45 m square hole sieve is not greater than 30%.
8 test methods
The 8.1 component
According to the GB/T12960 or by the producer selection method is more accurate for. In the condition of normal production, producers should at least monthly check on the cement group, the annual average of this standard shall comply with the provisions of Article 5.1, a single test value should not exceed the standard limit of 2%.
In order to ensure the accuracy of the determination of component, the producer should adopt appropriate methods and production procedures to verify the reliability of the suitability of the chosen methods, and validated methods documented.
8.2 insoluble, LOI, Magnesium Oxide three, sulfur dioxide and alkali content
The test in GB/T176.
The test in GB/T750.
8.4 chlorine ion
The test in JC/T420.
8.5 water requirement of normal consistency, setting time and soundness
The test was conducted according to GB/T 1346.
The test in GB/T17671. But the volcano marly Portland cement, fly ash Portland cement, Portland cement and admixture volcano ash mixed material of Portland cement mortar strength in the test, the use of water by 0.50 water cement ratio and cement mortar fluidity is not less than 180mm to determine. When the flow is less than 180mm, required to increase an integral multiple of 0.01 will be adjusted to the ratio of water to cement mortar fluidity is not less than 180mm.
Mortar fluidity test according to GB/T2419, the mortar prepared by GB/T17671.
The specific surface area of 8.7
The test in GB/T8074.
8.880 m and 45 m sieve residue
The test in GB/T1345.
9 inspection rules
The 9.1 number and sampling
Cement factory according to the same species, the same level of intensity and sample number. Bagged cement and bulk cement should be numbered and sampling. Each numbered one sampling unit. Cement factory annual production capacity of the specified number:
More than 200 * 104t, for a number of not more than 4000t;
120 * 104t to 200 * 104t, for a number of not more than 2400t;
60 * 104t to 120 * 104t, for a number of not more than 1000t;
30 * 104t to 60 * 104t, for a number of not more than 600t;
10 * 104t to 30 * 104t, for a number of not more than 400t;
10 * 104t, for a number of not more than 200t.
According to the sampling method of GB12573. Continuously, can also take the same amount of samples from more than 20 different parts, a total of at least 12kg. When the bulk cement transport capacity more than the tonnage plant provides identification numbers, allowing the number of sampling number more than specified tonnage.
9.2 cement factory
Confirmed the cement technical indexes and packaging quality meet the requirements before the factory.
9.3 factory inspection
The inspection items were 7.1, 7.3.1, 7.3.2, 7.3.3.
9.4 decision rules
9.4.1 test results conform to the standard 7.1, 7.3.1, 7.3.2, 7.3.3 for qualified products.
9.4.2 test results do not meet the standards of any 7.1, 7.3.1, 7.3.2, 7.3.3 in the technical requirements for unqualified products.
9.5 inspection report
The inspection report should include the inspection items, fineness, mixed materials and adding other technology, gypsum and grinding varieties and dosage, the agent is Xuanyao or kiln production and contract requirements. When the users need, 7d send in various test results except 28d strength in cement producers outside should be issued from the date, bubao 28d strength test result in 32d.
9.6 delivery and acceptance
9.6.1 delivery of quality inspection of cement can be selected to the real sample test results as the basis, the same number of cement producers can also be the basis of the survey report. What method of acceptance by the buyer and the seller agreed and specified in the contract or agreement. The seller has to inform the acceptance of the responsibility of the buyer. When there is no written contract or agreement, or not in agreement in the contract, the inspection methods stated in the invoice, the Seller shall indicate to the factory with the number of cement test report for approval basis ".
9.6.2 to test the real results for the sample extraction on the basis of acceptance, both parties should be in common sampling before delivery or delivery and seal. According to GB12573 sampling method, sampling quantity is 20kg, and divided into two equal parts. A seller to save 40d, a by the buyer according to the standard of the project and method of inspection.
Within 40d, the test of product quality does not conform to the requirements of this standard, the seller and the objection, both parties should be another sample was saved to send the seller at or above the provincial level approved by the state and the cement for quality supervision and inspection institution for arbitration inspection. Cement stability arbitration inspection, shall be the date of completion of sampling within 10d.
9.6.3 to the same number of cement producers inspection report for approval basis, before shipment or delivery of the buyer in the same number of sampling in cement, jointly signed by the seller after the seller to save 90d, or acceptance sampling, seal and save the 90d with the number of cement sealed sample.
In 90d, the buyer has doubts about the quality of cement, the buyer and the seller is to send the sample should be agreed at or above the provincial level approved by the state and the cement for quality supervision and inspection institution for arbitration inspection.
10 signs, packaging, transportation and storage
Bulk cement can or bag, cement bag net weight per bag is 50kg, and shall not be less than the quality mark of 99%; the total mass of 20 random bags (including packing bags) should be not less than 1000kg. Other forms of packaging is negotiated by the parties, but the bags of quality requirements, should comply with the above provisions. Cement packaging bags shall comply with the provisions of GB9774.
Cement packaging bags shall be clearly marked: the implementation of standards, cement, code, strength, the name of the producer, the symbol of the production license (QS) and serial number, serial number, packing date, net content. Bags on both sides should be based on the varieties of cement with different cement strength grade and color printing, portland cement
and Portland cement
The red, Slag Portland cement
The use of green; volcano marly Portland cement, Portland cement and fly ash Composite Portland cement
Using black or blue.
Shipped in bulk and bagged marks should be submitted to the same content card.
10.3 transport and storage
The cement shall not damp and mixed with debris in the transport and storage of different varieties, and the strength grade of cement to avoid confounding during storage.
The concrete, referred to as "concrete (t ng): refers to the cementitious materials will aggregate cement into the whole project Compound material
Collectively. Generally speaking Concrete
The term refers to the use of cement as cementitious material, sand and stone as aggregate; and water (with or without admixtures and additives) according to a certain proportion, concrete mixing, molding, curing and, also known as ordinary concrete
It is widely used in civil engineering.
cement The setting time of cement
Cement and water will become semi fluid with plasticity, when after a period of time, the cement slurry gradually lose plasticity, and keep the original shape, this phenomenon is called condensation (divided into initial setting and final setting). In the hardening period, the strength of the cement is increased gradually.
The construction requirements of the cement setting time is within a certain range. If the setting is too fast, the concrete will soon lose liquidity, thus affecting the vibration; on the contrary, if the setting is too slow, it will affect the speed of construction. Therefore, the standard provisions of the initial setting time of cement and the final setting time should be within a certain range.
Determination of setting time is the standard consistency of cement paste, in a certain temperature and humidity condition. By adding water to date, it sank in the slurry needle net from the bottom of 0.5 ~ 1 Omm, the time required for the initial setting time, the paste begins to lose its plasticity; try to sink into the needle paste does not exceed 1 Omm, the time required for the final setting time, then paste completely lost and entered the hardening period of plasticity.
Cement in the hardening process, if you do not have uneven volume deformation, no cracks, bending and other phenomena, called qualified volume stability; if the hardened cement volume produced uneven changes caused by harmful expansion, will make the building crack, even collapse, it is called stability unqualified. This kind of cement can not be used in the project.
If excessive amounts of free calcium oxide in cement or Magnesium Oxide, especially coarse particles, and in the factory and storage time is short, will produce stability unqualified phenomenon. Because of the fire (more than 1000 DEG C) of calcium oxide and Magnesium Oxide did not fully cooked, water itself is very slow, in the cement setting with cement after constraints began hydration, volume expansion, it will form a cracking phenomenon. In addition, if the three sulfur content in cement is excessive, will generate acid calcium, sulfur aluminum volume expansion, but also will cause poor stability.
Test the stability of cement, according to GB/T 750-1992. The inspection process is using the standard consistency of cement paste, made into a certain shape (diameter 70 ~ 80mm, the center is about lOmm thick and thin edge gradually) try the cake, put in boiling boiling 4h, such as bread and boiled by naked eye found no crack, no check with a ruler the bending phenomenon, called qualified stability; conversely, it is not qualified.
Test method for stability in the pat method, and the Rayleigh clamp method and measuring method. After the two methods have quantitative numerical limits, but the method is complicated, complex play is poor; and the pat rule has simple equipment, convenient operation, sensitive, and visual observation, of good repeatability and a series of advantages, so still listed as the national standard method.
Boiling method can only check verification free damage of calcium oxide. Because Magnesium Oxide burned more slowly than excessive calcium oxide hydration, so boiling can be found caused by Magnesium Oxide's instability, only through high temperature and high pressure autoclave test, in order to determine this phenomenon. While three of sulfur dioxide caused by the instability, only by cold cake method and immersion method to test the upcoming trial cake on the 20 C + water conservation 28d 3 DEG C, check whether there is unstable phenomenon. Because when the temperature is over 60 ~ 70 degrees, will not be formed calcium sulphoaluminate volume expansion.
The national standard has been on Magnesium Oxide and three sulfur were limited, so the autoclave method and immersion method two tests generally can not do.
cement Quality identification
The first one: "Hope" know the pros and cons of mud
First, see from the appearance of the packaging quality. To see whether the damage proof performance after laminating woven bag, see the sign is clear and complete. Usually, the regular factory production of cement should be marked with the following contents: registered trademark, origin, production license number, standard, packing date, bag net weight, factory number, cement etc.. The inferior cement often did not elaborate on. Secondly, carefully observe the color of cement. Generally speaking, the normal color of cement should be grayish white, the color is too deep or change there may be other impurities too much.
Second: "smell" mud quality analysis
Here the "smell" is not the smell, smell after all cement for consumers is not safe here, "smell" is to listen, listen to businesses about cement ingredients, thus to infer the cement quality. Some domestic small cement plant in order to sell at a low price, in violation of the cement standard, using too much cement blending material
No, in strict accordance with the national standards of raw material ratio, the performance of its products as can be imagined. The formal manufacturers in the cement raw material selection is very strict, the produced cement has high bonding strength, the setting time is moderate, Durability
Third: "ask" the source of mud
The main is to ask the manufacturers and the cement production process, see the "origin" is normal, the production process is advanced. At present, illegal decoration materials on the market products for the production of small cement kiln process are not only the product quality is not stable, environmental protection is the enemy; and some professional manufacturers with new dry kiln production, the use of computer technology to control the advanced management, to ensure product quality and stability of cement.
Fourth: "cut" mud know life
This step is mainly used to cement the finger pulse, the length of time to identify its factory. Cement also has a shelf life, in general, more than 30 days of the date of The strength of cement
Drop. After three months of storage of the cement strength decreased 10%-20%, 25%-40% decreased after one year. Can the normal use of the cement should be no damp agglomerate phenomenon, high quality cement cement powder with the fingers, feel the feeling of fine particles. The packaging of inferior cement, opening inspection will have wetting and caking phenomenon; inferior cement cement powder with the fingers, a rough sense of the fineness of cement, coarse is not normal, when using low strength, viscosity is poor.