Method of preparing building materials

In a method of making a building material by activation of latently hydraulic ground granulated amorphous basic blast-furnace slag to form a direct acting hydraulic binder, wherein the method comprises mixing the slag, with water, sand, gravel, and an activator, said slag, water, sand, gravel and activator being present in amounts effective to enable the slag to react chemically with the water, in combination with the sand and gravel, to produce a concrete of desired strength, the improvement comprising forming the activator as a combination of an acidic component and a basic component, said acidic component being a phosphate or mixture of phosphates in an amount of 2 to 40% by weight based on the amount of the slag, said phosphate or mixture of phosphates having surface tension reducing action or said method further comprising adding a detergent or mixture of detergents to said slag, sand, gravel, and activator, said basic component being magnesium oxide, or magnesium oxide in combination with aluminum oxide, titanium oxide, zirconium oxide, or zinc oxide, said basic component being present in an amount of 2 to 20% by weight based on the amount of the slag, said improvement causing the formation of a concrete of great mechanical strength and high chemical resistance with the magnesium oxide and phosphate or mixture of phosphates incorporated into the concrete without the need for heating at a high temperature.