​ASTM C1202: Rapid Chloride Permeability (Coulombs Passed)

The ASTM C1202 rapid chloride permeability test, which is widely used, quickly determines how resistant your concrete is to chloride ingress.

How we conduct the concrete permeability test

ASTM C1202 testing
Photo credit: Mary Vancura, Cutting 1202 samples

This test begins with a couple days of sample preparation and conditioning. After the sample is cut to 2 inches thick, it is coated in a waterproof epoxy, which is allowed to dry. With the epoxy dry, the sample is conditioned for approximately 24 hours in a dry vacuum, a vacuum filled with boiled water, and, then soaking in boiled water. Once conditioning is complete, the sample is placed into a test cell. One side of the cell is filled with sodium chloride solution and the other side with sodium hydroxide solution. A potential difference of 60 Volts is maintained across the sample for 6 hours. The test apparatus measures the total charge passed through the concrete sample during this time. The ASTM provides a correlation between charge passed and chloride ion penetrability in the following form:

rcp test
Photo credit: Mary Vancura, 1202 samples w/out epoxy

(From the ASTM standard):

Charge passed (coulombs) Chloride Ion Penetrability

> 4,000 High

2,000-4,000 Moderate

1,000-2,000 Low

100-1,000 Very Low

<100 Negligible

What works about the ASTM C1202 test:

It is popular because, after a 28-day standard cure, this test requires only three days to complete. This test is best used as a general assessment of the chloride ion penetrability of a specific concrete mixture and as a quality control test.

What doesn’t work about this test:

ASTM C1202 is criticized for being influenced by heat created by the applied current, being a measure of all ions (not just chloride ions), and for not achieving steady-state migration. It is not a great test for concrete mixtures that include steel fibers or admixtures that influence the conductivity of the pore solution (corrosion inhibitor) because the presence of either of these will increase the current, giving artificially high results.