Concrete is the second most consumed item in the world after water and hence it has to be prepared properly so that it doesn’t get deteriorated. As concrete is brittle in nature and hence reinforcement bars are required to take the tensile load experienced by the structural member.
Concrete comprises of various materials mixed in a suitable proportions. Due to heterogeneity in the mix there are voids present in between the materials due to different sizes. Due to the presence of voids, water may ingress into the concrete member and may reach up-to the reinforcement. Due to the presence of moisture around the reinforcement, the bars gets corroded and losses its strength. Also, the volume of the rust in much more than the bars which lead to cracking of concrete and hence the life of the concrete gets reduced.
To determine the permeability of the concrete, Rapid Chloride Permeability Test (RCPT) is performed and the test is covered by ASTM C 1202. The test determines the ability of concrete to resist the chloride ions from penetrating into it.
The test involves passing electrical current through the concrete and measuring the charge passed through it. The lesser the charge that can passed through it, more the resistance of the concrete against chloride ingress or lesser the permeability of the concrete.
Apparatus for the test
Cylindrical Concrete Specimen of 50mm in length and 100mm in diameter.
Two reservoirs; one contains 3.0% NaCl solution and the other contains 0.3M NaOH solution.
DC power source.
Equipment to measure current.
The connection diagram and the actual image for the test is shown below.
PROCEDURE
The concrete specimen is prepared and cured in water for 28 days.
After curing, the concrete specimen is sealed with epoxy coating from all the sides expect its plane surfaces.
After the epoxy is dried, the specimen is placed in the reservoirs filled with the required solutions as stated earlier.
The power source is connected to the reservoirs as per the schematic diagram and 60V is applied through it for 6 hours.
The current passing through the circuit is measured after every 30 minutes and noted.
The total charge passed through the specimen is determined by using the following formula.
Based on the charge passed through the specimen ASTM code has given penetration impact.
