Operational test of cement initial setting time, test steps of cement setting time

1. Before the measurement, put the round mold on the glass plate, and adjust the instrument so that when the test needle touches the glass plate, the finger is pointed at the zero point of the calibration scale.

2. Weigh 500 grams of cement, add standard consistency water consumption, and mix the net slurry according to the same method as the "standard consistency water consumption test".

3. The mixed net slurry is immediately loaded into the round mold at one time, scraped flat after vibrating several times, and then put it into the curing box.

4. During the measurement, take out the round mold containing the slurry from the curing box, place it under the test needle, make the test needle contact with the slurry surface, and tighten the screw. Then suddenly loosen the screws and let the needle sink freely into the slurry, and observe the pointer reading.

During the initial test, the metal rod should be gently supported and lowered to prevent the needle from bending. However, the initial setting time must still be based on the results measured in free fall. Near the initial setting, test every 5 minutes; Towards final setting, test every 15 minutes.

The needle must not be allowed to fall into the original pinhole for each test. After each test, the round mold containing the slurry must be put back into the curing box and the test needle must be wiped clean.

Steps: 1. Preparation before the test.

The needle used to adjust the setting time is pointed at the zero point when it touches the glass bottom plate.

2. Preparation of specimens.

The cement slurry is made with the standard consistency of water consumption, and immediately put it into the moisture curing box after mold loading and scraping, and the time when all the cement is added to the water is recorded as the starting time of the setting time.

3. Determination of initial setting time.

The first measurement is carried out when the specimen is cured in the humid curing box for 30min, and the test mold is taken out from the moisture curing box and placed under the test needle, the contact between the test needle and the surface of the cement slurry is reduced, and the test needle is suddenly relaxed after tightening the screw for 1-2s and sinks into the cement slurry freely.

Observe the test needle stop falling or reading after 30s, when approaching the initial setting time, measure once every 5min (or less) when the test needle sinks to 1mm away from the bottom plate 4 soil for the cement to reach the initial setting state, from the cement all added to the water to the initial setting state of the initial setting time of the cement.

4. Determination of final setting time.

In order to accurately show the condition of the test needle sinking, a ring attachment is installed on the final setting test needle, and after the initial setting time is determined, the test mold and the slurry are immediately removed from the glass plate in a translational way, and the large end of the diameter of 180 degrees is turned upwards and the small end is downward, placed on the glass plate, and continued to be cured in the moisture curing box.

Towards the final setting time, it is measured every 15 minutes (or less) when the test needle sinks into the test body 0When 5mm, that is, when the annular attachment can not leave traces on the test body, the cement reaches the final setting state, and the time from the cement is all added to the water to the final setting state is the final setting time of the cement.

5. Precautions.

During the measurement, it should be noted that the metal column should be gently supported to lower slowly during the operation of the initial measurement, so as to prevent the test needle from bending, but the result is subject to free fall, and the position of the test needle sinking into the test mold should be at least 10mm away from the inner wall of the test mold during the whole test process, and the test should be repeated immediately when the initial setting state is reached (that is, 2 times) when the conclusion is reached.

The standard test method for cement setting time is as follows:

1. Place the specimen on the base of the penetration resistance meter, and record the total mass of the mortar and the container displayed on the dial.

2. Select the appropriate stylus according to the penetration resistance of the sample.

3. When measuring, the stylus should be at least 25mm away from the edge of the test mold, and the net distance between the points of the stylus through the mortar should be at least twice the diameter of the stylus used. Each of the three test molds is measured at 1 to 2 points, and the arithmetic mean is taken.

is the value of the penetrating resistance at that time.

4. The penetration resistance test of each sample shall not be less than 6 times, and the penetration resistance per unit area of the last one shall not be less than 28MPa. Calculated from the time of adding water to mix, the ordinary concrete at room temperature will be measured after 3 hours, and then measured every lh interval; In the case of fast-hardening concrete or high temperature, it is advisable to start the measurement after 2 hours, and then measure every other time, and in the case of slow-setting concrete or low temperature, it can be measured from 5 hours later, and then every 2 hours.

Cement: Powder sedan carrying form hydraulic inorganic cementitious material.

After adding water and stirring, it forms a slurry, which can be hardened in air or water, and can firmly glue sand, stone and other materials.

Knot together in Bixiang.

Early lime and volcanic ash.

The mixture is similar to modern lime pozzolana cement, which is used to cement concrete made of crushed stone, which is 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.

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. Ordinary Portland cement.

The initial setting time 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 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 retarding differences, mixing ratios, and external temperatures will change the initial setting time of cement.

Before measuring the coagulation time, it should be checked whether the sliding part of the virtual attitude instrument can slide freely in the bracket, and at the same time, when the test rod is lowered to the surface of the slurry, the pointer should be rotten as if aligned with the zero point of the scale, 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.