| 摘要 |
PURPOSE:To improve the surface smoothness, surface strength and durability of concrete, by using a sheet having a porous plastic film layer having specific air-permeability and water-permeability as a sheet to be placed in a mold. CONSTITUTION:A concrete curing film composed of a porous plastic film layer (or its laminate with a reinforcing layer) having a gas permeability of 10<0>-10<3> sec/100cc and a water-permeability of 10<1>-10<4>l/m<2>.hr under a pressure of 0.2kg/cm<2> is placed in a mold and concrete is cured in the mold. If the air- permeability of the film is <10<0>sec/100cc, fine particle of cement enters into the void of the film layer to deteriorate the surface smoothness of the concrete and the releasability of the film layer. If the air-permeability is >10<3>sec/100cc, the degassing becomes insufficient to generate craters caused by water bubble and air bubble. When the water-permeability is lower than the lower limit, craters are liable to generate in a concrete having high water content similar to the above case and when it exceeds the upper limit, the strength of the concrete is frequency lowered by the generation of cavities caused by the excessive dehydration beyond the necessary level.
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