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

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(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.