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What are the commonly used cement grades?

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What are the cement grades
what features do they refer to?

1. The main type of Portland cement is pi42 5、PI52. 5、PI62. 5 type of cement, this type of cement is mainly used in projects requiring high cement hardening strength& nbsp;

2. The main model of ordinary portland cement is po32 5、PO42. 5、PO52. 5 type of cement, which is mainly used in ordinary dry environment and can also be used in colder areas

3. The main model of slag Portland cement is ps32 5、PS42. 5、PS52. 5 type of cement, which is mainly used preferentially in high humidity environment, and can not be replaced by other types of cement when used underwater& nbsp; & nbsp;

4. The main model of pozzolanic Portland cement is pp32 5、PP42. 5、PP52. 5 type of cement. This type of cement is generally used in ordinary environment. In addition, this type of cement is strictly prohibited to be used in dry or cold environment& nbsp; & nbsp;

5. The main type of fly ash Portland cement is pf32 5、PF42. 5、PF52. 5 type of cement. The use requirements of this type of cement and pozzolanic Portland cement are basically similar& nbsp; & nbsp;

6. The main model of composite Portland cement is PC32 5、PC42. 5、PC52. 5 type of cement, which shall be selected and used according to the proportion of its mixture& nbsp;

extended data:

cement is divided into:

(1) general cement: Cement commonly used in general civil and Construction Engineering. General purpose cement mainly refers to the six categories of cement specified in GB175-2007, namely Portland cement, ordinary portland cement, slag Portland cement, pozzolanic Portland cement, fly ash Portland cement and composite Portland cement

(2) special purpose cement: cement for special purpose. Such as class G oil well cement and road Portland cement

(3) characteristic cement: a kind of cement with outstanding performance. Such as: fast hardening portland cement, low heat slag Portland cement, expanded sulphoaluminate cement, phosphoaluminate cement and phosphate cement

the main technical properties of cement commonly used in construction engineering include fineness, standard consistency and its water consumption, setting time, volume stability, cement strength, hydration heat, etc

1) fineness. Fineness refers to the fineness of cement particles. It is an important index that affects the water demand, setting time, strength and stability of cement. The finer the particle is, the larger the surface area reacts with water, the faster the hydration reaction speed, the higher the early strength of cement stone, but the larger the shrinkage of hardened body is, and the cement is prone to moisture and reduce its activity during storage and transportation. Therefore, the fineness of cement should be appropriate

2) standard consistency and water consumption. When determining the setting time, volume stability and other properties of cement, in order to make the measured results accurate and comparable, it is stipulated that the cement paste used in the test must be tested by standard method according to the provisions of GB /T l346 inspection methods for water consumption, setting time and stability of cement standard consistency, and reach the uniformly specified slurry plasticity (standard consistency)

water consumption for standard consistency of cement paste refers to the amount of water required to reach the standard consistency when mixing cement paste, which is expressed as a percentage of the weight ratio of water to cement

3) setting time. The time required for cement to lose fluidity from the beginning of adding water is called setting time, which is divided into initial setting time and final setting time. The initial setting time is the time required for the cement from mixing with water to the beginning of the loss of plasticity of the cement slurry; The final setting time refers to the time from the time when the cement is mixed with water to the time when the cement slurry completely loses its plasticity and begins to produce strength

the setting time of cement is of great significance to construction. The initial setting time is too short, and there is not enough time to complete the mixing, transportation, pouring, tamping, masonry and other operations of concrete or mortar during construction; If the final setting time of cement is too late, the construction period will be delayed

the national standard stipulates that the initial setting time of Portland cement shall not be earlier than 45min and the final setting time shall not be later than 6.5h. The initial setting time of other types of general cement is 45min, but the final setting time is 10h. The national standard stipulates that the cement with unqualified initial setting time is waste

4) volume stability. It refers to the stability of volume change after concrete hardening of cement. Cement with poor stability will produce uneven volume expansion during or after slurry hardening, and cause cracking

the main factor of poor cement stability is that the clinker contains too much free calcium oxide and free magnesium oxide or too much gypsum mixed during grinding. The national standard stipulates that the content of free magnesium oxide in cement clinker shall not exceed 5.0%, and the content of sulfur trioxide shall not exceed 3.5%. Cement with unqualified volume stability is waste and cannot be used in the project

5) cement strength. Cement strength is closely related to the mineral composition, cement fineness, water cement ratio, hydration age and ambient temperature of cement. The cement strength shall be made into test blocks, cured and measured according to the provisions of the national standard test method for strength of cement mortar (IS0 method) (GB /T l7671), and the strength grade of cement shall be evaluated accordingly

6) heat of hydration. The heat and heat release rate of cement hydration mainly depend on the mineral composition and fineness of cement. The higher the content of tricalcium aluminate and tricalcium silicate, the finer the particles, the greater the hydration heat

the greater the hydration heat is, the more favorable it is for winter construction, but it is harmful to mass concrete engineering. In order to avoid the cracking of cement stone caused by temperature stress, Portland cement should not be used in the construction of mass concrete engineering, but slag cement with low hydration heat should be used. The hydration heat can be measured according to the method specified in the national standard

reference: Baidu Encyclopedia – cement

common cement grades include: 225, 275, 325, 425, 525, 625, etc. the tensile strength varies according to the variety and grade, and the MPA value is 2.8-4.5 and 3.4

at present, the cement produced in China generally has several grades, such as 225, 325, 425 and 525.

cement grade: cement grade is an important indicator of cement strength, which is based on standard The compressive strength of the test block after curing for 28 days under standard conditions (temperature 20 ℃ + 2 ℃). The label is shown as follows: there are three types of Portland cement: 425525625. Ordinary cement has no. 225275325425525625. Slag, pozzolan and fly ash cement have no. 225275325525.

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