First, what is concrete:
Every wait by gelatinizing material, aggregate and water to cooperate by appropriate proportion mix the mixture that makes, the artificial stone material that gets after moulding harden via pouring again, collectively for concrete.

Two, the classification of concrete
1. Concrete is classified according to strength grade
Strength grade for C10 ~ C60, known as ordinary concrete;
The strength grade is C60 ~ C100, known as high strength concrete;
The strength grade ≥C100 is called ultra high strength concrete.

Concrete is classified by apparent density
Dry apparent density in 2100 ~ 2500 kg/m3 is called ordinary concrete, is made of natural (or artificial) sand, stone aggregate;
The dry apparent density is about 2400 kg/m3, which is the most commonly used concrete in civil engineering.
Dry apparent density is greater than 2600 kg/m3 is called heavy concrete, is made of barite or barium cement, strontium cement, its apparent density can reach 3200 ~ 3400kg/m3, heavy concrete can prevent radiation, radiation, so it is also known as anti-radiation concrete;
Dry apparent density less than 1950 kg/m3 is called light concrete, the use of light porous aggregate or mixed with aeration agent, foam agent and other porous structure of concrete, often used in light structure, thermal insulation engineering.

Concrete is classified according to use or construction method
Such as hydraulic concrete, Marine concrete, road concrete, waterproof concrete, acid resistant concrete, heat resistant concrete, shotcrete, pumping concrete, roller compacted concrete and so on.

Three, the characteristics of concrete
Ordinary concrete is the most widely used structural material in civil engineering. Because concrete has the following advantages:
(1) Local materials, low cost;
(2) It has good plasticity and modelability;
(3) it has strong adhesion with steel bar and can protect steel bar from corrosion;
(4) With high compressive strength;
(5) Good durability, low maintenance and maintenance costs.