Cement composition using alpha type calcined gypsum and constructing method thereof

A cement composition is provided to inhibit the crack generation by using alpha type calcined gypsum as a cement additive to lower the contraction expansion rate, induce an initial coagulation time and decrease the hydration heat of the cement, improve the resistance against the volume change in accordance with drying and wetting and the freezing and thawing resistance, and improve the tolerance and the crack inhibitory capability by adding a hydrophilic polyvinyl alcohol fiber. A cement composition comprises cement, polymer powder, polyvinyl alcohol cut fiber, silica fume and alpha type calcined gypsum for decreasing the contraction expansion rate. The composition further comprises at least one selected from the group consisting of fly ash, a fluidizing agent and blast furnace slag. A method for repairing and reinforcing using a cement mortar composition comprises the steps of: (a) mixing the cement, alpha type calcined gypsum, silica fume, fly ash, polyvinylalcohol cut fiber, polymer powder, fluidizing agent, and blast furnace slag to prepare the cement composition; (b) mixing the cement composition with heavy sands, fine sands and water to prepare the cement mortar composition; (c) after arranging an object side to be constructed, spraying water thereto to maintain the wet state; and (d) applying the cement mortar composition to the object side.