|#||Class of concrete||Concrete grade||Concrete strenght||Slump retention|
Concrete is an artificial stone material, which is produced by cement, inert aggregates, water and chemical admixtures. It has a very strong grip with steel rebar, both have approximately the same longitudinal expansion factors and it keeps the bar from corrosion. Nowadays concrete is the most widely spread building material. First trace of concrete-like product is discovered BC 6500 years.