The physical properties and hydration of concrete that contains an inorganic waterproof additive were evaluated.The inorganic waterproof additive consists mainly of CaO, A12O3, SiO2, and SO3.The dosage of inorganic waterproof additive was varied from 0 to 8 kg/m3.The water/cement ratio of the control concrete was 0.6.The slumping, air content, and concrete temperature with inorganic waterproof additive were almost equal to that of the control.The concrete setting time was almost equivalent to the control concrete.Water permeability tests were conducted using standard ASTM C 666 and commenced at day 28 at a water pressure of 0.5 MPa.The extent of water permeability was improved by the amount of inorganic waterproof additive added.Hydraulic conductivity was reduced by ~10 for an inorganic waterproof additive of 8 kg/m3.The concrete compressive strength was evaluated according to standard JIS A 1108 at days 7 and 28.The compressive strength was increased slightly according to the amount of inorganic waterproof additive added.Bleeding tests were conducted using standard JIS A 1123.The amount of bleeding before setting was controlled by the inorganic waterproof additive.Hydration analysis indicated that the inorganic waterproof additive generated ettringite,which combines large amounts of water compared with Portland cement, and contributed to the reduction in bleeding and the formation of a dense matrix.Bleeding resulted in the formation of water channels in the concrete after setting.We assume that the channels influence water permeability.The reduction in bleeding and the formation of a dense matrix by an inorganic waterproof additive improved the water permeability and concrete compressive strength.Improvements in water permeability by an inorganic waterproof additive will contribute to the sustainability of concrete structures.