Study on the assessment of scaling resistance of concrete exposed to deicing salts and the test method in Japan

(1)1）在东北地区，除冰盐的影响导致的混凝土结垢恶化是混凝土冻害中最严重的一种。2）在日本，混凝土的抗结垢性评价没有标准的试验方法。使用ASTM C672方法和RILEM CDF方法检查了测试条件对结垢发生的影响。两种方法的结垢量和变异系数存在差异。3）氯化物溶液的使用方式也会导致结垢量的变化。从结垢率的观点来看，水灰比和试验方法的变化所引起的结垢颗粒的总质量几乎取决于冻融试验初期的结垢量。4）从可操作性和试验设备的观点来看，RILEM CDF法作为结垢试验在日本是有用的。(2)混凝土表层抗冻性评价方法的研究1）改进的拔出试验方法可以测量混凝土表层任意距离处的强度，是混凝土冻融弱化部位强度的一种很好的测量方法; 2）混凝土表层渗透性快速测试方法的适用性，被认为有希望评估的紧密性和混凝土表层的退化程度，由于冻融作用。

(1) Study on the test method for scaling resistance of concrete exposed to deicing salts1) In Tohoku district, the scaling deterioration caused by influence of deicing salts was detected most seriously recognized among frost damage of concrete.2) In Japan, however, there is no standard test method for assessing the scaling resistance of concrete. The influences in testing conditions exerting the occurrence of scaling were examined using ASTM C672 method and RILEM CDF method. Between both test methods, there existed the differences of the mass-of-scaled-off particles and the coefficient of variations.3) Also, the ways how to apply the chloride solution in test, resulted in the change of the amount of scaling. It was confirmed, from the viewpoint of scaling rate, the total mass-of-scaled-off particles due to change of the water cement ratio and the test method were found to be almost governed by the amount of scaling developed at the early cycle of the freeze-thaw test.4) RILEM CDF method was found to be useful as the scaling test to apply in Japan from the viewpoint of work-ability and test equipment.(2) Study on the assessment of frost resistance of surface layer of concrete1) Availability of modified pull-off test method which enabled the measurement of strength at an arbitrary distance from concrete surface was found to be an excellent measure of the concrete strength in the weakened portion due to freeze-thaw action.2) The applicability of rapid testing methods for permeability of surface layer of concrete, were judged promising to assess the tightness and the degree of deterioration of concrete surface layer due to freeze-thaw action.