Study On Test Method Of Concrete Iodide Ion Diffusion Coefficient

For the moment, the resistance of concrete to chloride permeability is measured using rapid chloride migration(RCM)test. However, RCM test cannot correctly measure the resistance of concrete to chloride permeability if the concrete contains chloride. In this paper, NaCl solution in RCM test is replaced by NaI solution with same molar concentration. The resistance of concrete to chloride permeability is characterized by rapid iodide ion migration coefficient, which named as rapid iodide migration(RIM) test. In this paper, ordinary concrete, carbonated concrete and pre-mixed chloride concrete were tested by both RCM and RIM. The relationship between results of RCM and that of RIM were analyzed. The influence of water-to-binder ratio(W/B), fly ash and curing time on resistance of concrete to chloride and iodide tested by RCM and RIM separately were studied. The mechanism of chloride and iodide migration was investigated through measuring chloride and iodide profile.(1) For the OPC concrete and fly ash concrete without carbonation and chloride,the migration coefficients measured by RIM test present good relationship with that by RCM test. The migration coefficients tested by both RCM and RIM are influenced by the water-binder ratios, fly ash and curing time, and the trends for both tests are the same. Besides, the iodide ion profile in RIM and chloride ion profile present the similar trend.hrough analysis XRD experimental result,it has been found the RCM and RIM test appear chloride and iodide in the similarity place of Angle.(2) The carbonated concrete shows heavier resistance to ion migration in both RIM test and RCM test. The migration coefficients of carbonated concrete measured by RIM test still present good relationship with that by RCM test.(3) In the RCM and RIM test for concrete pre-mixed with chloride, the good relationship between the migration coefficients tested by RCM and that by RIM disappear. RCM test is significantly affected by pre-mixed chloride, while, the pre-mixed chloride only has slightinfluence on the RIM test. The chloride migration coefficient of pre-mixed chloride fly ash concrete cured for 150 d cannot be correctly measured by RCM test, however,the iodide ion migration coefficient of pre-mixed chloride fly ash concrete cured for150 d tested by RIM decreases slightly compared to fly ash concrete without chloride.(4) Compared with RCM test, RIM can be used to measure the resistance of concrete penetrated by chloride ion correctly. The fittings between color depth in RCM and color depth in RIM were carried out for OPC concrete, carbonated concrete and fly ash concrete separately to amend the color depth of concrete tested by RIM. After amend parameters of ????? and ? revision, migration coefficient tested by RIM is0.9 to 1.2 times that tested by RCM. It satisfied engineering's accuracy requirement basically. The amended value tested by RIM can be used as chloride diffusion coefficient and evaluate concrete structure's penetrability.