How long does cement take to harden, and how long does it take for ordinary cement to harden complet

Hello, cement itself will not be hard. The place where it is stored must be moisture-proof, and it is best to have something to isolate the contact between the cement and the ground. If it is wet, it will quickly solidify and harden.

Usually, the strength of national standard cement in 3 days is more than 16 points. In other words, when exposed to water, it will harden quickly. There is no water, moisture-proof is done well, and it is no problem to store it for a month.

The standard Favicat instrument is a judgment method for determining the initial and final setting time of cement. When the standard needle penetrates into the mold test 4 1mm away from the bottom of the mold test, it is the initial setting time of the cement, and when the standard needle penetrates into the surface of the mold test, that is, only the standard needle traces are left on the surface of the mold test) is the final setting time of the cement. National regulations:

Ordinary Portland cement.

The initial setting time is not more than 45 minutes, and the final setting time is not later than 10 hours. The initial setting time of Portland cement is not earlier than 45 minutes, and the final setting time is not later than the hour. In the bulk cement sampling of the factory, the cement of the same cement plant and the same grade shall not exceed 400t as a sampling unit.

Cement samples should be drawn from 20 bags of cement in different stacking parts about 1kg, a total of 20kg. It is not necessary to open the bag when sampling, and the sampler can be inserted through the slit in the corner of the bag and then pulled out. The mixed specimen is divided into two equal parts.

One copy is tested, and the other copy is sealed and stored in a clean and moisture-proof container for 3 months, so that it can be submitted to the state-designated inspection agency for re-inspection or arbitration in case of doubt.

The cement test conditions are specified as follows: the temperature of the laboratory should be 17 25, and the relative humidity.

greater than 50; The temperature of the curing chamber is 20 1; The temperature of cement sample, standard sand, mixing water and mold testing should be the same as that of the laboratory; The test water shall be clean fresh water.

1) The national standard stipulates that the initial setting time of cement shall not be earlier than 45min, generally 1 3h; The final setting time shall not be later than 12h, generally 5 8h.

2) The test method is to add the water consumption of standard consistency to the cement to make the slurry test mold, from the time of adding water to the setting time, the time when the test needle of the tester sinks into the slurry from the bottom plate is the initial setting time, and the time when the test needle sinks into the slurry does not exceed the time of final setting.

Generally, it will not be hard after a month.

Ordinary cementIt takes 28 days to completely harden the finch to get acacmodalized.

It takes 28 days for the cement to harden completely. The hardening of cement is divided into two stages, one is the solidification stage, and the other is the strength growth stage. The initial setting time of Portland cement shall not be earlier than 45min, and the final setting time shall not be later than 6h30min; Ordinary Portland cement.

The initial setting time shall not be earlier than 45min, and the final setting time shall not be later than 10h.

After the final setting, the cement begins to increase in strength, and the design strength can be basically reached 28 days after pouring. The cement strength test and evaluation is based on this. However, the growth of cement strength has not ended, but is still growing slowly, and after half a year or even a year, the strength is still increasing.

Precautions for cement purchase

1. Whether the paper bag packaging of the main cement is intact and whether the identification is complete.

2. Twist the cement powder with your fingers, and feel a little sand, fine, and powder, indicating that the cement fineness is normal.

3. Observe the color, yellowing indicates that the clinker is raw burning, and the amount of whitish slag is too much, so the cement strength is relatively low.

4. Be sure to see the production date of cement, cement also has a use date. The performance of cement beyond the expiration date of 30 days has decreased. The strength of cement decreases by 10%-20% after three months of storage, 15%-30% after six months, and 25%-40% after one year.

The cement can not be used for more than 3 months after the factory period of the spine, and the brand of cement is different.

You can't use it indiscriminately.

In the case of good ventilation, when the indoor temperature exceeds 10 degrees, the setting time of cement takes about 3-4 days.

It usually takes 3-5 days for the concrete floor to dry thoroughly, and about a week if the weather is wet. In the current winter climate, it takes about 4 days for cement to reach the strength that people can walk, and the indoor temperature cannot be lower than 5 degrees Celsius. The setting time of cement is divided into initial setting and final setting.

When the concrete first loses its plasticity, it is called initial setting, and when the concrete completely loses plasticity, it is called final setting. Generally speaking, the setting time of concrete is related to the setting time of cement.

If the temperature is higher, the cement will dry faster. When the temperature is around 20 degrees, the cement can dry within 5-8 hours. If the temperature has reached more than 35 degrees in the hot summer, the cement will dry in less than two hours.

Notes:

In the process of hardening, if the cement does not produce uneven volume deformation, cracks, bending, etc., it is called qualified volume stability; If the volume of cement hardens unevenly, causing harmful expansion, which will cause the building to crack or even collapse, it is called unqualified stability.

If the cement contains too much free calcium oxide or magnesium oxide, especially if the particles are coarse, and the storage time in the factory is short, the stability will be unsatisfactory. Because the overheated calcium oxide and magnesium oxide have not been fully matured, the hydration of Bensun Lu's body is very slow, and the hydration will begin early after the cement is condensed, that is, under the condition of cement stone constraints, and the cracking phenomenon will be formed after the volume expansion.

It takes about 3 to 4 days for the cement to solidify.

There are two stages of cement solidification, namely initial setting and final setting. At the time of initial setting, the surface should be hardened within about 3 to 4 hours after the pouring is completed. And the final coagulation, that is, to achieve the effect of complete coagulation, basically takes 3 to 4 days.

Introduction to cement

Cement: powdered hydraulic inorganic cementitious material. After adding water and stirring, it forms a slurry, which can be hardened in air or water, and can firmly cement sand, stone and other materials together.

The mixture of early lime and pozzolana was similar to that of modern lime pozzolana cement, and the concrete made from cemented crushed stone was not only strong when hardened, but also resistant to the erosion of fresh or salt water. For a long time, as an important cementitious material, it has been widely used in civil construction, water conservancy, national defense and other projects.

In the 20th century, while continuously improving the performance of Portland cement, people successfully developed a number of cements suitable for special construction projects, such as high-alumina cement, special cement, etc.

There are more than 100 types of cement in the world, and the annual output of cement in 2007 was about 2 billion tons. In 1952, China formulated the first national unified standard, which determined that cement production should be based on the principle of multiple varieties and multiple labels, and renamed Portland cement according to the main mineral composition it contained, and later changed to Portland cement.