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

本文主要从表面层强度的角度介绍了表面层混凝土的抗冻特性。本研究采用表面层强度作为强度指标进行试验研究，量化混凝土表面层的改善程度。表层强度是通过拉拔试验测量的，使用一个截锥形钢锥嵌入混凝土试件的侧面。圆锥体半径为10mm。水泥、水灰比、养护龄期和预埋钢锥深度半径比对表层强度有影响。此外，还研究了冻融作用对混凝土强度的影响。本实验研究的结果总结如下：1。掺混水泥混凝土的养护条件对表层强度的影响高于普通硅酸盐水泥。采用透水薄板可有效降低混凝土表面附近的水灰比。掺入透水薄板的混凝土表层强度大于未掺入透水薄板的混凝土表层强度。28日龄时，强度增加幅度为未加布时的1.2 ~ 2.4倍。冻融作用对混凝土表层的影响较大。但是，透水薄板的使用被证实对改善混凝土的表层是有效的。研究发现，表面层抗拉强度是评价混凝土表面层耐久性的优良指标。

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.