Technical requirements of coarse aggregate for concrete

1. Particle grading

When the aggregate particle size increases, its specific surface area decreases, the amount of cement in concrete is also reduced, in order to meet the technical requirements, the coarse aggregate particle size should be selected as large as possible; in reinforced concrete projects, the particle size shall not be larger than the smaller size of the cross-section of the concrete structure 1/4, shall not be larger than the smaller net distance between the steel bars 3/4.

2. Harmful impurities

Coarse aggregate contained in the mud, silt, fines, sulfates, sulfides and organic matter are harmful impurities, the content should be in line with the “construction pebbles, gravel,” the provisions of the other is strictly prohibited to mix with calcined dolomite or limestone blocks.

3. Needle, flaky particles

Too much needle and flake particles in coarse aggregate will make the concrete easy to deteriorate and reduce the strength, the content of needle and flake particles should be controlled within a certain range.

Concrete strength grade ≥C60 C55-C30 ≤C25

Needle, flaky particles content ≤8% ≤15% ≤25

Mud content ≤0.5% ≤1.0% ≤2.0

Mud content ≤0.2% ≤0.5% ≤0.7

Water Absorption ≤1.0% ≤2.0% ≤2.5%

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