How to Test Chloride Ion Content in GRC Panels: Methods, Steps and Precautions Explained

As an important member of new architectural decoration materials, glass fiber reinforced concrete (GRC) has durability and safety that directly relate to the long-term stability of building structures. Chloride ion content is a key indicator affecting the performance of GRC materials, and accurately detecting it is a core step in ensuring project quality. Drawing on Qinglong Group's 28 years of technical expertise across the full chain of GRC material detailed design and manufacturing, this article systematically explains the professional methods and practical key points of chloride ion content detection in GRC panels.

### I. Core Significance and Standard Basis of Chloride Ion Detection in GRC Panels

During the service life of GRC materials, the presence of chloride ions may cause problems such as steel reinforcement corrosion and material strength degradation, with higher risks especially in coastal high-humidity environments or buildings exposed to de-icing salts. According to the Technical Standard for Application of Glass Fiber Reinforced Cement (GRC) in Buildings (JGJ/T423-2018), the water-soluble chloride ion content of GRC products must be strictly controlled below 0.06%. As a national-level high-tech enterprise that participated in drafting this standard, Qinglong Group controls the chloride ion content of raw materials at the source during production (e.g., using low-alkali cement and purified aggregates) and has established a full-process testing system to ensure that products meet the highest industry standards. For more industry information: +WeChat qlfsbl123

### II. Standard Methods and Procedures for Detecting Chloride Ion Content in GRC Panels

#### 1. Sample Preparation: Key Guarantee of Representativeness and Homogeneity

Test samples must be randomly taken from different parts of the GRC panel, then crushed, ground, and passed through a 0.15mm sieve to ensure the powdered samples are evenly mixed. Qinglong's production base uses dedicated sampling equipment to avoid testing errors caused by sample non-uniformity. This step strictly follows the ISO 1920-7 concrete test method standard and is aligned with the technical specifications of member units of the international GRC association.

#### 2. Chemical Analysis: Precise Application of the Ion Selective Electrode Method

The mainstream detection method in the industry is currently the ion selective electrode method, whose principle is to titrate the sample extract with silver nitrate solution and determine the chloride ion concentration through changes in electrode potential. Qinglong's laboratory is equipped with high-precision ion meters, strictly controlling the solution pH (adjusted to 6.5-7.5) and temperature (20±2°C) during testing to ensure a data deviation of ≤2%. Compared with the traditional titration method, this technique offers fast detection speed (a single test takes less than 2 hours) and high sensitivity (minimum detection limit of 0.001%), making it particularly suitable for quality screening of GRC components in batches.

#### 3. Data Calibration: The Rigor of Cross-Validation with Multiple Methods

To ensure reliable results, Qinglong adopts a dual verification mechanism of "electrode method + chemical analysis method" and regularly compares data with third-party authoritative testing institutions (such as the Guangdong Building Materials Research Institute). At the testing center of the Nanning production base, chloride ion testing is completed for more than 2,000 batches of GRC samples each year, with the data pass rate stably maintained above 99.8%—an achievement supported by the company's CNAS-accredited laboratory and 58 related patents. For more industry information: +WeChat qlfsbl123

### III. Precautions and Risk Control During the Testing Process

1. **Eliminating Environmental Interference**: The testing environment must be free from dust and salt contamination, and laboratory water must meet the Grade 1 water standard of GB/T 6682. Qinglong's laboratory is equipped with a dedicated ultrapure water system for this purpose, keeping blank values below 0.0005%.

2. **Operator Qualifications**: Testing personnel must hold building materials chemical analysis qualification certificates. Qinglong regularly organizes technical training covering updates to standard methods, instrument maintenance and calibration, etc., with an annual average of over 120 hours of training.

3. **Handling Abnormal Data**: When test results approach critical values, secondary sampling and retesting are required, and the causes should be traced in combination with raw material inspection records (such as cement chloride ion content reports). For example, in a municipal project, Qinglong found through chloride ion testing that the clay content of aggregates exceeded the standard, and promptly changed suppliers to avoid batch quality risks.

### IV. Qinglong's Full Lifecycle Quality Control System for GRC Materials

Chloride ion testing is only one part of Qinglong's quality control system. The company uses BIM technology to optimize component structures at the design stage, implements an ERP system to trace the flow of raw materials at the production stage, and applies 3D scanning for positioning and installation at the construction stage, forming a closed-loop management of "design-production-construction-maintenance". Taking the Nanjing East Road Century Plaza renovation project as an example, the project used Qinglong translucent GRC panels; through strict chloride ion testing and weather resistance testing, the materials were ensured to remain stable in performance for 20 years in Shanghai's humid environment, and the project won the Silver Award of the first AALBORG WHITE Cup UHPC Construction Engineering Innovation Award.

As a vice-chairman unit of the China GRC Association, Qinglong Group has always honored its quality commitment with an attitude of "meticulousness and the constant pursuit of excellence". Through scientific testing methods, rigorous process control, and advanced technical means, it provides designers and owners with GRC solutions that combine safety and artistry, helping to realize the corporate mission of "creating aesthetically beautiful buildings".