Studies on Frost Resistance of Concrete by Making Dense Surface Layr Using Permeable Sheets and Surface Coating

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(1) Making dense surface layr and its estimation.A total of four permeable sheets, mainly composed of high density and span bond fabric of polyester were examined to make tight surface layr of concrete. When using these sheets, the pits on concrete surface deceased and the surface appearance was greatly improved because of discharge of free water and large air void. Then, the rebound number and the surface layr strength also increased by lowering the water cement ratio.(2) Effect of permeable sheet and surface coating to improvefreeze-thaw resistance of concrete.Using permeable sheets and surface coating, the freeze-thaw resistance and surface layr strenth were greatly improved. A high relationship between the surface layr strength and relative dynamic modulus of elasticity was found, and the strongest correlation was observed between ratio of surface layr strength to initial value and relative dynamic modulus of elasticity. Therefore, the surface layr pull out strength was found to be an excellent index to evaluate the degree of surface layr of concrete due to frost damage.From the facts described above, It was found that the surface treatment such as coating and the use of permeable sheet could greatly improve the damage of the surface layr of concrete due to frost action.