What does coarse aggregate of concrete mean?

In reinforced concrete engineering, the particle size of coarse aggregate shall not be greater than 1/4 of the minimum size of the cross section of concrete structure, and shall not be greater than 3/4 of the minimum clear distance of steel bars.

For concrete solid slab, its maximum particle size should not be greater than the thickness of 1/3 and should not exceed 40 mm ... Gravel for pumping concrete should not be larger than 1/3 of the inner diameter of the conveying pipe, and pebbles should not be larger than 1/2.5 of the inner diameter of the conveying pipe.

Classification of concrete aggregate

Concrete aggregate is usually divided into fine aggregate and coarse aggregate. In concrete, the particle size between 0. 155 ~ 5 mm is generally called fine aggregate; Particle size greater than 5mm is called coarse aggregate.

Coarse aggregate is divided into pebbles, gravels, crushed pebbles, and mixtures of pebbles and gravels. According to the particle size, it can be divided into small stones (5~20mm), medium stones (20 ~ 40~80mm), large stones (40~80mm) and extra-large stones (80 ~ 150 mm), which are called Grade I, Grade II, Grade III and Grade IV in turn.

When these four gradations are included in the concrete mixture ratio, it is called fully graded concrete, and concrete with only one or two gradations is called small aggregate concrete. The ratio of pebbles: medium pebbles: large pebbles: extra-large pebbles is 2: 2: 3: 3 in the commonly used fourth-grade aggregate, 3: 3: 4 in the third-grade aggregate, and 5.5 in the second-grade aggregate.

Refer to Baidu Encyclopedia-Coarse Aggregate for the above contents.