What is the initial setting time of cement, what is the initial setting time of concrete?

The initial setting time of Portland cement shall not be earlier than 45min, and the final setting time shall not be later than 6h30min (390min);

The initial setting time of ordinary Portland cement, slag Portland cement, pozzolana Portland cement, fly ash Portland cement and composite Portland cement shall not be earlier than 45min, and the final setting time shall not be later than 10h (600min).

The initial setting time is the time required from the cement mixing with water to the time when the cement slurry begins to lose its plasticity. The final setting time is from the time when the cement is mixed with water and the time it takes for the cement slurry to completely lose its plasticity and begin to develop strength.

The cement setting time is of great significance in construction, the initial setting time should not be too short, and the final setting time should not be too long. The initial setting time of Portland cement shall not be earlier than 45min, and the final setting time shall not be later than 390min. The initial setting time of ordinary Portland cement shall not be earlier than 45min, and the final setting time shall not be later than 600min.

If the initial setting time of the cement does not meet the requirements, the cement will be scrapped. If the final setting time does not meet the requirements, it will be regarded as unqualified. The initial setting time of concrete is generally determined according to the cement variety, and there is basically no unified time, but there is a general range of 2-3 hours.

If a pre-setting agent is added, the initial setting time can be roughly shortened to half an hour. If a retarder is added, the initial setting time can be extended to 5-10 hours. The specific initial setting time is generally determined by the test, and each batch of cement in each factory must be tested.

The initial setting time refers to the time when the cement is mixed with water and the cement slurry begins to lose its plasticity.

The initial setting time of cement is generally 45 minutes, and the initial setting time refers to the time from adding water to the cement to begin to lose plasticity, the speed of setting time, and the construction method and project progress.

It has a great impact, so it is necessary to measure the setting time.

The setting time of Portland cement is stipulated in the GB standard: the initial setting shall not be less than 45 minutes, and the final setting shall not exceed 6 hours (10 hours for other cements). Under normal circumstances, the initial setting time of cement is basically about 1 1 hour and 30 minutes.

The initial setting time and final setting time of concrete are very important for concrete construction, concrete to the initial setting means that the concrete has reached the thixotropic limit, lose plasticity, can not use vibrating rod, high-frequency vibrator, concrete has been unable to occur plastic deformation, it has reached the limit of concrete construction, the concrete after the initial setting can no longer be constructed, otherwise there will be a serious decrease in strength, honeycomb dog hole. Concrete final setting marks the beginning of the concrete with strength and can withstand a certain load.

According to the normal temperature and humidity, under normal circumstances, the setting time of cement is about half an hour, and the surface will slightly appear in the initial state of solidification.

According to the relevant national regulations, the initial setting time of cement should not be less than 45 minutes, and in the case of Portland cement, the final setting time should not exceed one hour. Generally, the solidification and hardening of cement can be divided into: the initial reaction stage is 5-10 minutes; Incubation period 1 hour; Coagulation period 6 hours; The scleroping period is 6 hours to several years.

2. What are the cement brands?

1. Conch Cement CON (Anhui Conch Cement Co., Ltd.) brand birthplace: Wuhu City, Anhui Province.

2. Southern Cement (China National Building Materials Co., Ltd.).

Brand birthplace: Shanghai.

3. Jidong Cement (Beijing Jinyu Group Co., Ltd.).

Brand birthplace: Tangshan City, Hebei Province.

4. China Resources Cement (China Resources ****).

Brand birthplace: Hong Kong, Macao, Taiwan and Hong Kong, China.

5. Huaxin Cement (Huaxin Cement Co., Ltd.).

Brand birthplace: Huangshi City, Hubei Province.

6. Zoomlion CUCC (China United Cement Group) brand birthplace: Beijing.

7. Taiwan cement cement (Taiwan cement (Yingde) cement****).

Brand birthplace: Hong Kong, Macao, Taiwan and Taiwan.

The initial setting time of concrete depends on the specific temperature situation, the initial setting time is short when the temperature is high, the initial setting time is long when the temperature is low, the initial setting time of concrete is generally 4-10 hours, and the final setting time is 10-15 hours.

The speed of the setting time has a great impact on the construction method and the progress of the project, so the determination of the setting time should be carried out to test whether it meets the requirements of concrete construction. Different retarders, mix ratios, and external temperature will change the initial setting time of cement.

Before measuring the coagulation time, it is necessary to check whether the sliding part of the instrument can slide freely in the bracket, and at the same time check that when the test rod is lowered to the surface of the slurry, the pointer should be the zero point of the calib, otherwise it should be adjusted. Before measuring the setting time, the consistency test rod should be removed and replaced with a test needle, and at the same time, check whether the pointer is zero when the test needle is in contact with the top of the round mold, otherwise it should be adjusted.

Before each measurement, the instrument should first be placed vertically and steady, and it should not be operated in an environment with obvious vibration. After each measurement, the working surface of the instrument should be wiped clean and oiled to prevent rust. The surface of the slide bar should not be bruised or rusted.

Summary. Definition of initial setting time and final setting time of cement.

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Kiss! The definition of initial setting time and final setting time of cement is as follows:

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For Portland cement, its initial setting period shall not be faster than 40 minutes, and the final setting period shall not be less than 395 minutesAnd for conventional Portland cement.

In terms of its initial setting period, it shall not be faster than 40 minutes, and the final setting period shall not be less than 610 minutes. It should be noted that the time of cement setting is very critical in construction, the initial setting period should not be too short, and the end setting period should not be too long.

Precautions for cement solidification

The cement storage method is wrong, and it is easy to be affected by water vapor and agglomerate, so the cement quality should be reviewed after three months from the factory time. Check that the cement will not have the problem of hard lumps or agglomeration, and it can only be used if it is still a fine powder.

Before construction, try to ensure that the base surface is wet, so that the connection with the base surface will be more solid after the cement concrete is poured. In addition, after the pouring is completed, if the sun is relatively strong, it is necessary to carry out watering and curing to avoid the evaporation of concrete water too much, resulting in fatigue. Generally, the watering and curing time is about 7 days to ensure the integrity of the quality of concrete de-pouring.

The initial setting time of cement refers to the time from the time when water is added to the cement to when it begins to lose its plasticity.

Cement is a powdered hydraulic inorganic cementitious material that hardens in air or water. The speed of cement setting time has a great impact on the construction method and project progress. Modern cement was invented in 1824 by Joseph Asputin, an English construction worker.

At that time, it was named Portland Cement, which was of epoch-making significance in the history of cement.

The earliest use of cement was in ancient Rome, where people used a mixture of volcanic ash and lime plus luina water. It was used to glue stones for masonry, but it was not used in large quantities as a building material. In the 20th century, Portland cement properties were constantly being improved.

And successfully developed a number of cement suitable for special construction projects, such as high-alumina cement, special cement and so on.

Type Definition:

Portland cement is a hydraulic cementitious material made of Portland cement clinker, 0% 5% limestone or granulated blast furnace slag, and an appropriate amount of gypsum grinding. It is called Portland cement, which is commonly known as Portland cement abroad. Ordinary Portland cement consists of Portland cement clinker, 6% 20% mixed material.

The hydraulic cementitious material made of an appropriate amount of gypsum grinding is called ordinary Portland cement.

Slag Portland cement is a hydraulic cementitious material made of Portland cement clinker, 20% 70% granulated blast furnace slag and an appropriate amount of gypsum grinding, which is called slag Portland cement. Pozzolana Portland cement is a hydraulic cementitious material made of Portland cement clinker, 20% 40% pozzolana mixture and an appropriate amount of gypsum, and ground finely, which is called pozzolana Portland cement.