High-efficiency CSA Expansive Agent is obtained by blending suitable natural anhydrite with a specially manufactured clinker which consists essentially of calcium sulphoaluminate and CaO. High-efficiency CSA expansive agent is always mixed with ordinary cement. When mixed in the proper proportions with ordinary cement and hydrated, cement mortar or concrete expands during the early stages of hydration. This expansion, when restrained, makes it possible to minimize drying shrinkage. Moreover, when the ratio of High-efficiency CSA Expansive Agent to ordinary cement is increased its high expansion qualities make it ideal for use in prestressed concrete.