Electrical Indication of Concrete’s Ability to Resist Chloride Ion Penetration

Electrical Indication of Concrete’s Ability to Resist Chloride Ion Penetration

[ASTM C 1202: 2012]

·         Specimen: (100mm ø Casting Cylinder) or (cores from 150mm cubes and slabs) or (Cores from Site Structures)

·         Test Age: 28 or 56 days

·         Curing: Keep in water tank at (23 ± 2) °C and then remove from tank 2 days before testing.

·         Preparation of solutions:

3% NaCl = 970mL distilled water + 30g NaCl

0.3N NaOH = 1L distilled water + 12g NaOH Pellets

·         Preparation of specimen:

-          Extract core of 100mm ø from casting face of specimen

-          Trim the casting face (Top Surface) up to 5mm & cut slice of (50±3) mm thickness

-          Apply rapid setting coating (as insulator) to side surfaces of specimen and leave for dry 1day

·         Conditioning:

-          Place the specimen into vacuum desiccator and start vacuum pump.

-          Set pressure to be less than 50 mm Hg and maintain for 3 h.

-          Fill the vacuum desiccator by de-aerated water without stopping the vacuum pump and maintain for 1 h

-          Stop the vacuum pump and allow the air to re-enter the desiccator

-          Soak the specimen for (18±2)h and then remove from water for testing

·         Testing:

1.       Fix the specimen in the cell & Fill the side of the top surface with 3.0% NaCl solution which will be connected to the negative terminal of power supply. Fill the other side which will be connected to the positive terminal of the power supply with 0.3N NaOH solution

2.       Turn on the power supply and set to (60±0.1)V

3.       Record the initial reading of Current (mA) and Temperature (°C) (from NaOH Solution Side)

4.       During the test, the air temperature should be maintained in the range 20 to 25 °C

5.       Read and record current and temperature every 30 minutes until 6h (13 readings)

6.       Terminate the test if the temperature of solution exceeds 90°C before 6h

·           Calculation:

-          Total (mA) = I₀ +2(I₃₀ + I₆₀+ I₉₀+ I₁₂₀+ I₁₅₀+ I₁₈₀+ I₂₁₀+ I₂₄₀+ I₂₇₀+ I₃₀₀+ I₃₃₀) + I₃₆₀

-          Charge Passed (coulombs): Qx = (Total/1000)*900

-          Corrected Charge Passed (coulombs): Qs = Qx*(95/Ø)²

-          Indicate the Chloride Ion Penetrability based on the Charge Passed values as in table:

Charge Passed (coulombs)	Chloride Ion Penetrability
> 4000	High
2000 – 4000	Moderate
1000 – 2000	Low
< 1000	Very Low
< 100	Negligible