PROBLEM TO BE SOLVED: To provide civil engineering materials made from steel slag, by forming a stable coating on the steel slag surface, capable of effectively preventing the pH rise in the surrounding environment, with a reduced amount of alkali elution.SOLUTION: A chitosan solution with a pH of 5.0 or more and less than 7.0 is applied to a steel slag in a granular or massive form, so that a chitosan coating is formed on the particle surface of the steel slag. Due to the effect of alkali eluting from the steel slag, a stable chitosan coating capable of effectively suppressing the alkali elution is formed on the steel slag surface. Furthermore, a carbonization processing is performed after the processing by the chitosan solution, so that defective parts of the coating can be filled (coated) with calcium carbonate or the like. As a result, a still more stable organic-inorganic composite coating can be formed.SELECTED DRAWING: Figure 3
