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

本文主要从面层强度的角度介绍了面层混凝土的抗冻特性。本研究以混凝土表面层强度为强度指标，采用嵌套于混凝土试件侧面的截锥形钢锥进行拉拔试验，对混凝土表面层强度进行了量化。锥体半径为10 mm。表层强度受水泥用量、水灰比、养护龄期和埋入钢锥的深度半径比的影响。试验研究结果如下：1.养护条件对掺混水泥混凝土表层强度的影响大于普通硅酸盐水泥。采用透水板可以有效地降低混凝土表面附近的水灰比。有透水片材的混凝土的面层强度比无透水片材的要大。28d龄期时，混凝土的强度增长在1.2~2.4倍范围内，冻融作用引起的表层劣化程度较大。表面抗拔强度是评价混凝土表层耐久性的一个很好的指标。

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.