In ASTM C1202, it is mentioned that concretes with dissociating admixtures may produce high values of RCPT cumulative charge passed due to the high ionic concentration of the concrete pore solution. But, equilibrium calculations indicate that the anions in these admixtures will replace more conductivie hydroxide ions in the pore solution, as calcium hydroxide precipitates for example. Then, the increase in RCPT charge passed would not be due to a more conductive pore solution but rather due to a more open pore structure, with a higher conductivity for the concrete (and also a higher chloride ion diffusivity). Does anyone have some measured conductivity data on such solutions with and without these admixtures, for example?
Though I don't have any measured conductivity comparing those variables mentioned, based on the experience I have using the test; I believe the conductivity measured by RCPT is based on the conductivity of the pore solution of the concrete.
Therefore, the use of some admixtures may affect the RCPT results has they are capable of altering the conductivity of the pore solution. An experience I can use to justify this is using RCPT for alkali activated materials(AAMs). Though AAMs shows better permeability results in other tests compared to that of OPC concrete, they exhibited a very high coulomb values. The conclusions that were drawn from the higher column values for the AAMs was that there is presence of more conductive ions in AAMs compared to that of OPC concrete
Hii Prof. D. P. Bentz
Article A short-term test method to determine the chloride threshold...
This work was done by one of my former colleague Jayachandran K during his PhD, they have confirmed the movement of nitrate ions along with chloride in test conducted on corrosion inhibitor admixed specimens.
Hope this will be useful.
Regards
Yuvaraj
- Badges
- Science topic