Hardened concrete has a number of properties, including:

Mechanical strength, in particular compressive strength.
The strength of normal concrete varies between 25 and 40 MPa. Above 50 MPa, the term High Performance Concrete is used (50 MPa corresponds to a force of 50 tonnes acting on a square with sides of ten centimetres).

Durability.
Concrete is extremely resistant to the physico-chemical attack emanating from the environment (frost, rain atmospheric pollution, etc…) It is particularly well-suited for structures exposed to demanding and extreme conditions.

Porosity and density.
These properties are responsible for the first two. The denser (or the less porous) the concrete the better its performance and the greater its durability.
The density of concrete is increased by optimizing the dimensions and packing of the aggregate and reducing the water content.

Fire resistance.

Thermal and acoustic insulation properties.

Impact resistance.