Strength control method for high strength concrete, should be different from one for ordinary low strength concrete, because strength of high strength concrete grows for longer time, at least till 3300°D・D of maturity due to its high impearmiability. As strength standard deviation varies on its strength growth, only strength gain should not be considered but increasing value of standard deviation should be adopted. Strength control method based on maturity is suitable for high strength concrete, and inspection on ready mixed concrete at construction site should be main for strength control. As far as maturity is concerned, our country is classified in four areas, Sapporo, Sendai : Niigata, western Honsyu of Tokyo, and Naha.
