Improvement of Surface layer Strength of Concrete by Using a Special Curing Sheet


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Title: Improvement of Surface layer Strength of Concrete by Using a Special Curing Sheet

Author(s): T. Sugawara, M. Shoya, and N. Saeki

Publication: Special Publication

Volume: 128


Appears on pages(s): 625-636

Keywords: air-entrained concretes; curing films and sheets; pullout tests; freeze-thaw durability; strength; water-cement ratio; Materials Research

Date: 11/1/1991

This paper presents the characteristics of the surface-layer strength of concrete produced using a special curing sheet to improve the surface layer. The curing sheet is attached to the interior of the forms and has the ability to absorb water from the concrete surface and to retain the absorbed water for curing. The surface layer strength was measured by a pullout test that was carried out by modifying the Michaelis test machine and using truncated conical steel cones embedded in the concrete. The 14-day surface layer strength obtained by using the special curing sheet increased by 1.2 to 1.5 times of that obtained without using the sheet. The improved strength is attributed to the lowering of the water cement ratio in the surface layers produced by using the sheet. After freeze-thaw tests, the surface layer strength of air-entrained concrete showed less decrease independent of the use of special curing sheet. The surface layer strength might be a useful index for the evaluation of the quality of the surface layer of concrete.