How to Test Chloride Ion Content in GRC Panels? Key Durability Indicators and Qinglong Group's Laboratory Control Standards

Testing the chloride ion content in GRC panels is a critical control step for evaluating their durability, particularly the risk of corrosion to embedded steel reinforcement, and must employ scientific and precise chemical analysis methods. The Qinglong Group laboratory strictly follows standards such as the Standard for Durability Design of Concrete Structures (GB/T 50476), using the silver nitrate titration method or potentiometric titration for quantitative analysis, ensuring testing precision reaches 0.001% (by mass). We require that the acid-soluble chloride ion content of all GRC panels leaving the factory must not exceed 0.06% of the cementitious material mass, tightened to 0.04% for projects in coastal areas. Before supplying materials for coastal projects such as the Hainan International Convention and Exhibition Center, we provide authoritative third-party chloride ion content test reports, eliminating durability disasters caused by chloride salt attack at the source.

Standard Sampling and Sample Preparation

The first step in testing is scientific sampling. Powder samples are typically drilled from GRC panels after 28 days of curing, with sampling points avoiding edges and special areas. The collected samples must be immediately ground until all of the material passes through a 0.16mm square-hole sieve, then dried at 105±5℃ to constant weight to eliminate moisture interference.

Detailed Explanation of the Silver Nitrate Titration Method (Volhard Method)

This is currently the most commonly used method. The sample is dissolved in nitric acid, and an excess of silver nitrate standard solution is added to completely precipitate the chloride ions as silver chloride. Then, with ferric ammonium sulfate as an indicator, the excess silver nitrate is back-titrated with ammonium thiocyanate standard solution. The chloride ion content can be precisely determined by calculating the amount of silver nitrate consumed. This method is rigorously operated and delivers reliable results.

Rapid Testing and Process Control

In addition to final inspection of finished products, Qinglong Group also screens incoming raw materials (especially sand and admixtures) for chloride ions. We are equipped with rapid chloride ion testers for monitoring during the production process. Meanwhile, through strict control measures such as never using sea sand and selecting high-quality water reducers, the risk of chloride ion introduction is reduced at the source. Strict chloride ion control is the chemical cornerstone of GRC achieving a long service life.