What Risks Are Posed by Excessive Chloride Ion Content in GRC Materials? How to Control It?

Excessive chloride ion content in GRC materials can trigger serious risks such as metal corrosion and strength degradation, requiring strict control throughout the entire process of raw materials, production, and testing. Qinglong has established a "three-level control system" to ensure chloride ion content complies with national standards and safeguard long-term project safety.

I. Core Risks of Excessive Chloride Ion Content

Excessive chloride ions have far-reaching effects on GRC performance and safety and must not be ignored. Metal connector corrosion: steel connectors and embedded parts commonly used in GRC installation can suffer electrochemical corrosion caused by chloride ions, leading to reduced connector strength and volume expansion, ultimately causing components to loosen and fall off. Qinglong once handled a project where, due to excessive chloride ion content, the corrosion rate of steel connectors reached 40% within 3 years. Material strength degradation: chloride ions destroy the structure of cement hydration products and reduce the compressive and flexural strength of GRC. Experiments show that GRC with excessive chloride ion content can lose more than 25% of its strength over 5 years. Reduced durability: chloride ions accelerate freeze-thaw damage and carbonization, causing GRC surfaces to powder and crack and greatly reducing impermeability, with even more prominent risks in coastal projects.

II. Full-Process Control Measures for Chloride Ion Content

Qinglong has established full-chain control from source to end to ensure content compliance. Raw material control: sea sand is strictly prohibited; low-chlorine quartz sand (chloride ion content ≤0.02%) is selected; cement with chloride ion content ≤0.03% is used; chlorine-free admixtures are preferred; Qinglong requires chloride ion test reports for raw material procurement. Production control: production equipment is cleaned regularly to avoid cross-contamination; mixing water uses drinking water (chloride ion content ≤20mg/L); Qinglong production bases are equipped with water quality testing equipment for real-time monitoring. Testing control: chloride ion content is tested for every batch of raw materials, semi-finished products, and finished products; finished product chloride ion content must be ≤0.06% (by mass), meeting the requirements of the Technical Standard for Application of Glass Fiber Reinforced Cement (GRC) in Buildings; Qinglong's laboratory is capable of rapid chloride ion testing, with results issued within 24 hours. Risk response: non-compliant products are immediately isolated upon discovery, with cause analysis and corrective action; Qinglong has never delivered a product with excessive chloride ion content.

III. Enhanced Control Schemes for Different Scenarios

Special scenarios require targeted elevation of control standards. Coastal high-salt-spray environments: chloride ion content is controlled at ≤0.04%, anti-corrosion coatings are applied to component surfaces, and stainless steel is used for connectors; Qinglong's Ouargla hotel project in Algeria follows this standard. Underground humid environments: testing frequency is increased, with at least 2 groups of samples tested per batch, and sealant is used to seal component joints to reduce chloride ion penetration; a Qinglong underground utility tunnel project using this scheme has shown no corrosion after 4 years of use. Major projects: a "double testing" system is implemented, where in addition to in-house testing, third-party agencies are commissioned for testing to ensure data accuracy; Qinglong's Shenzhen Pingshan High-tech Zone Comprehensive Service Center project (Luban Award) adopts this model.