The concrete mix proportion is determined according to the quality and moisture content of cement, stone and sand. The concrete grade is divided into C15, C20, C25, C30, C35, C40, etc. the larger the number, the higher the strength. The general specification requires that the floor concrete should not be lower than C20 and should not be higher than C40, because the higher the concrete strength, the more brittle, I can't answer. You have to decide what grade of concrete to use
Generally, the concrete grade of 2 bags of cement, 4 trucks of stones and 3 trucks of sand is about C20 ~ C30 (the concrete grade varies according to the quality of the materials). The trolley commonly used in the construction site is used for 4 trucks of sand. When building a house at home, this proportion is generally used. When mixing, it should be noted that if the mixer is used, it is generally stirred for about 3 minutes; the mud content of stone and sand should not be too large, Otherwise, the strength of concrete will be seriously affected. The particle size of stone should not be greater than 5cm. Tap water should be used for water. If sewage is used, it contains too much alkali, which is easy to corrode the steel bar
After pouring the concrete, if there is a 5mm depression on the concrete surface, it is better to start two times of plastering and pressing, and fine roughening, and then timely cover (generally covered with plastic film) to prevent exposure to the sun and rapid evaporation of concrete moisture, so as to avoid concrete drying and cracking
During concrete construction, the construction shall be carried out when the temperature reaches above 5 ℃. In summer and autumn, it shall be watered and maintained in time after 24 hours, and 48 hours in spring and winter.
