Concrete is a building material composed of a mixture of aggregates, sand, and water agglomerated by a hydraulic binder (most often cement) which serves as "glue". It is possible to add adjuvants and other ingredients to modify its characteristics. Mixed with water, we obtain a paste, with variable homogeneity, which can, depending on the material, be molded in the workshop (artificial stone), or cast on site. The concrete then "sets", that is to say it solidifies.