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

(1)除冰盐对混凝土抗结垢性能试验方法的研究1)在东北地区，在混凝土冻害中，由除冰盐的影响引起的结垢劣化最为严重。2)在日本，目前还没有一种标准的试验方法来评定混凝土的抗结垢性能。采用ASTM C672法和Rilem CDF法考察了试验条件对结垢发生的影响。两种测试方法之间存在着结垢粒子质量和变异系数的差异。3)实验中氯化物溶液的使用方式不同，会导致结垢量的变化。从结垢速度的角度证实，由于水灰比和试验方法的变化而产生的总剥落颗粒质量几乎受冻融试验早期发展的结垢量的控制。4)从工作性和试验设备的角度来看，Rilem CDF方法被发现作为在日本应用的尺度试验是有用的。(2)混凝土表层抗冻性的评估研究1)改进的拉拔试验方法的可用性被发现是一种很好的测量混凝土表面任意距离的强度的方法2)混凝土表层渗透性快速测试方法的适用性，被认为有希望评估混凝土表面层的密实度和冻融作用导致的劣化程度。

(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.