Study on The Quality of Surface Layr Concrete Due to Frost Damage

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This report presents the characteristics of frost resistance of the surface layr concrete, mainly from viewpoint of surface layr strength. In this study, experimental studies were carried out using the surface layr strength as a strength index to quantify the improvement in the surface layr of concrete.The surface layr strength was measured by a pullout test using a truncated conical steel cone embedded in the side of concrete specimens. The radius of the cone was 10mm. The surface layr strength was affected by the cements, water cement ratios, curing age and depth radius ratio of the embedded steel cone. In addition, the change in strength of concrete due to freeze thaw action was studied.The results obtained in this experimental study are summarized as follows :1. The effect of curing condition on the surface layr strength was higher in concrete containing blended cement than normal portland cement.2. The permeable sheet used is effective in reducing the water cement ratio near the surface of concrete.3. The surface layr strength of concrete with the permeable sheet is greater than that without the sheet. The increase was within the range of 1.2-2.4 times the strength obtained without the sheet at the age of 28 days.The surface layr deterioration due to freezing and thawing action was large near the surface of concrete. But, the use of the permeable sheet was confirmed to be effective to improve the surface layr of concretes.5.The surface layr pullout strength was found to be an excellent index to evaluate the durability of the surface layr of concrete.