How to sand the cement floor?

The design strength of concrete ground is generally C20-C25 fine stone concrete, which is generally used as the leveling base and covered with 1: 2.5 cement mortar for secondary survival. In order to effectively control the common faults of cement floor, we adopted the construction method of one-time survival of hard cement mortar. Control of raw materials for construction preparation: ordinary portland cement or slag cement with cement grade not less than 32.5 (expired caking cement shall not be mixed, and pozzolanic cement shall not be used). Pay special attention to whether the cement varieties used in the surface layer are consistent with the cement label varieties used in the bottom fine stone concrete. When using yellow sand and stones, coarse sand should be used, with a particle size greater than 2.5 mm and a silt content less than 3%. The stone particle size should not be greater than 15mm, and should not be greater than 2/3 of the pouring thickness. The silt content should be controlled below 2%, and the water should meet the standard of concrete mixing water.

Construction steps Before pouring the floor, the base must be cleaned up. It is best to use special machinery to clean up, and the internal corners and surrounding parts that are not cleaned are cleaned manually. Mechanical cleaning should pay attention to the hidden conduit not to break. After cleaning, water should be sprayed 2-3 days in advance to wet the base. Before measuring the surrounding ash cake (screed), 500mm horizontal line should be popped up on the indoor wall, and expansion joints should be set at about 5m-6m on the ground. Those protruding from the base should be removed, and the concavity and convexity should not be greater than10 mm. When pouring concrete, use pure cement to set the slurry first (sprinkle the cement evenly at the grass-roots level, then sprinkle water, and at the same time use a broom to evenly open the plain cement slurry). While sweeping, one-sided The slump of concrete should be strictly controlled. Slump should be controlled in 30-50 mm, and should be evenly mixed. Label cannot be lower than C20. When concrete is poured, it should be slightly raised, the ash cake should be spread evenly, then leveled with a ruler, then rolled with a roller and rubbed flat with a wooden crab or vibrated with a flat vibrator until it floats.

Grasp the upper hard cement mortar correctly, use coarse sand for yellow sand, and mix the mortar evenly according to the specified proportion. Cement and stones should be dry-stirred. After being evenly stirred, add a proper amount of water to stir, so that the mortar can feel a mass of moisture in your hand (called dry cement mortar), and then use it for spare level construction. The important link to ensure that the dry cement floor is free of sand, peeling and pits is to flatten the mortar floor with wooden crabs until it is slightly dry. The second calendering control time should be that there are a few footprints when people step on it (where there is a small amount of Shui Ze, it can be calendered for three times). After 24-48 hours of natural curing, start to spread sacks and spray water for curing, and the curing time shall not be less than 7 days (the curing time of slag silicate cement shall not be less than 10 day).

Another method is to use highway shot blasting machine. The road shot blasting machine throws the shot at the working face at a high speed and a certain angle by mechanical means, so that the shot impacts the road surface, makes the road surface rough and removes the residue. At the same time, the negative pressure generated by the vacuum cleaner will recover the pellets and the impurity dust after cleaning, and the intact pellets will be automatically recovered after being cleaned by airflow, and the impurities and dust will also fall into the dust box.

Highway shot blasting machine uses motor-driven shot blasting wheel to generate centrifugal force and wind force during high-speed rotation. When the pellets with a certain particle size flow into the pellet feed pipe (the velocity of the pellets can be controlled), they are accelerated and brought into the high-speed rotating pellet distributor. Under the action of centrifugal force, the projectile is thrown into the directional sleeve through the window of the directional sleeve (controlling the shot blasting direction), picked up by the high-speed rotating blade, and accelerated continuously along the length direction of the blade until it is thrown out. Then the projectiles, dust and impurities pass through the rebound chamber and reach the top of the storage hopper. The high-power dust collector separates particles from dust through the separation device above the storage hopper, and the particles enter the storage hopper for further recovery, and the dust enters the dust collector through the connecting pipe. After the dust enters the dust collector, it stays on the surface of the ash storage hopper and the filter element through the separation of the filter element. The automatic blowback dust collector cleans each filter element automatically and regularly through blowback air provided by the compressor. Finally, in the machine, the particles and the cleaned impurities are recovered separately through the air flow cleaning by the supporting vacuum cleaner, and the particles can be reused. Shot blasting machine is equipped with dust remover, which can realize dust-free and pollution-free construction, which not only improves efficiency, but also protects the environment.

Cause analysis of sand formation on cement floor;

1. When concrete and mortar are mixed, excessive water is added, or the mixing is uneven, and the mortar is separated until the surface is sanded and peeled.

2. The number of surface calendering is not enough, and the pressure is not real, resulting in water separation and sanding.

3, calendering time is not good, or after the final set of calendering, the mortar surface is damaged and sand.

4, the use of cement strength grade is too low, resulting in can not meet the requirements of strength grade.

5, the use of sand and gravel aggregate gradation is too fine, resulting in failure to meet the required strength grade.

6, improper maintenance, cement concrete in the maintenance period due to moisture or external factors affect the normal maintenance of cement.