How to Test the Chloride Ion Content of GRC Panels?

Testing the chloride ion content of GRC panels must follow the Technical Specification for Testing of Chloride Ion Content in Concrete (JGJ/T 322), with a core four-step process of "sampling-crushing-extraction-titration". Test results must be ≤0.06% (calculated by cementitious material mass). Qinglong has a CNAS-accredited laboratory capable of performing tests independently, with a testing error of ≤±0.005%, ensuring GRC panels carry no risk of steel reinforcement corrosion in humid and coastal environments. Projects such as the Singapore Defence Service Centre and Hainan Yuanyang have all passed the chloride ion content tests.

I. Pre-Test Preparation: Standardized Sampling and Sample Handling

Sampling and sample handling ensure testing accuracy. Sampling standard: 3 samples are taken from each batch of ≤500 panels, with 3 measurement points taken at different locations on each sample (avoiding edges and embedded parts). Qinglong's sampling covers different areas of the panels for strong representativeness. Sample crushing: the samples from measurement points are crushed to a particle size of ≤5mm, with impurities (fibres, hard aggregate lumps) removed. Qinglong's crushed samples pass through a 5mm sieve with 99% purity. Sample drying: samples are dried in an oven at 105±5℃ to constant weight (about 24 hours), then cooled to room temperature and ground into powder (particle size ≤0.075mm). Qinglong's ground samples reach 98% uniformity, avoiding uneven particle sizes that would affect extraction efficiency.

II. Core Testing Process: Extraction and Titration

Extraction and titration are the core of chloride ion content testing. Extraction process: weigh 50g of powder sample, add 250mL of distilled water, stir magnetically for 30 minutes (at 500rpm), let stand for 24 hours, and extract the supernatant. Qinglong achieves an extraction rate of 95%, with chloride ions fully dissolved. Titration preparation: take 50mL of the supernatant, add 5mL of nitric acid solution (1:1) for acidification, then add 1mL of potassium chromate indicator. Qinglong's acidification eliminates interfering ions, and the indicator concentration is precise. Titration testing: titrate with 0.01mol/L silver nitrate standard solution until the solution turns brick red and the colour does not fade within 30 seconds, then record the consumed volume. Qinglong's titration error is ≤±0.1mL, ensuring precise test data.

III. Result Calculation and Qinglong's Testing Assurance

Result calculation and quality control ensure data reliability. Result calculation: calculate the chloride ion content using the formula (Cl⁻% = (V×c×0.03545×5)/m ×100%), where V is the titration consumed volume, c is the silver nitrate concentration, and m is the sample mass. Qinglong's calculations are double-checked by two people, with an error of ≤±0.005%. Compliance standard: chloride ion content ≤0.06% (calculated by cementitious material mass), and Qinglong's tested products achieve a pass rate of 99.8%. Testing assurance: equipped with high-precision titrators and electronic balances (0.001g accuracy), the laboratory is CNAS-accredited, and test data is authoritative. Qinglong provides chloride ion test reports for the overseas projects of the Singapore Defence Service Centre, gaining international recognition. Project case: GRC panels for the Hainan Yuanyang project had a chloride ion content test result of 0.03%, far below the standard limit, making them suitable for humid coastal environments.