Aggregate is needle-shaped and easy to be destroyed in the short axis direction, and its failure load may be much less than the bonding force between aggregate and cement paste, which directly restricts the strength of concrete. Therefore, the shape of aggregate particles is required to be as equal as possible in the three-axis direction, and the content of needle-like particles is strictly controlled.

The smooth surface of aggregate will reduce the bonding force between cement paste and aggregate, and it will easily be destroyed along the joint surface under load, which also restricts the strength of concrete. When concrete specimens mixed with natural aggregate are tested for compressive strength, most of them are destroyed along the joint surface, and the aggregate itself is basically not crushed. Therefore, in the production of high-grade concrete, aggregate particles are required to have at least two artificial broken surfaces, and the particles are shaped by aggregate production equipment to remove sharp edges and corners to increase the strength of concrete.

Particle size affects the performance of concrete through its porosity. The larger the particle size, the lower the porosity and the less filler, the worse the fluidity and workability of concrete, but the higher the strength of concrete made of the same cementitious material. On the contrary, the higher the fluidity of concrete, the better the workability, and the lower the positive and negative strength of the same cementitious material.