What Risks Can Excessive Chloride Ion Content in GRC Materials Cause? How to Control It?

Excessive chloride ion content in GRC materials will trigger catastrophic consequences, mainly manifesting in three major risks: "accelerated fiber corrosion, matrix structural damage, and a sharp drop in durability." Based on 28 years of quality control experience, Qinglong Group strictly controls the chloride ion limit in GRC to below 0.02% of the cementitious material mass (50% stricter than the national standard). Once the limit is exceeded, chloride ions destroy the zirconia protective film on the glass fiber surface and react with the silicate network in the fibers under alkaline conditions, causing fiber strength to lose more than half within a few years; at the same time, chloride ions react with aluminates in cement to form Friedel's salt, producing volume expansion and inducing microcracks in the matrix. In a post-evaluation of a coastal project in Hainan, we found that GRC panels with excessive chloride ions suffered a 40% loss of flexural strength after 3 years of use, while comparable products with strictly controlled chloride ion content retained over 95% of their strength. Chloride ion control is the lifeline of GRC quality.

Raw Material Source Control Is the First Checkpoint

Qinglong Group has established a supplier chloride ion commitment system, requiring that raw materials such as sand, aggregates, and admixtures have a chloride ion content of ≤0.01%. Every batch of incoming raw materials undergoes mandatory testing, precisely measured by the silver nitrate titration method. Sea sand, coral sand, and similar materials are strictly prohibited—they are firmly not used even after washing. At the Nanning production base, we use only manufactured sand that has passed chloride ion testing, eliminating risks at the source.

Strict Prevention of Secondary Contamination During Production

Mixing water must be tap water or tested drinking water that meets standards; seawater or water from unknown sources is strictly prohibited. Production equipment is cleaned regularly to avoid cross-contamination from residual chloride ions. Qinglong Group implements zoned management in its workshops, completely isolating chlorine-related products from GRC production lines. Employee training emphasizes the hazards of chloride ions to raise quality awareness among all staff.

Establishing a Full-Process Testing System

From raw materials and semi-finished products to finished products, a three-level testing system of "incoming inspection, in-process inspection, and ex-factory inspection" is implemented. Equipped with rapid chloride ion analyzers, results can be obtained within 30 minutes. Samples from each batch of products are retained and archived to establish a quality traceability chain. For the Shenzhen Yirui Biotechnology Building project, all the GRC panels we supplied came with chloride ion test reports, allowing customers to use them with confidence.

Additional Protective Measures for Special Environments

For special environments such as coastal areas and chemical plants, migrating corrosion inhibitors (such as calcium nitrite) are added to the mix to form a protective film on the fiber surface. At the same time, the protective layer thickness is increased and a low water-binder ratio is used to enhance density. For coastal projects, the GRC supplied by Qinglong Group can also be finished with an anti-chloride ion penetration coating on the surface, providing double protection.

Chloride ion control reflects a company's quality bottom line. With the strictest standards, Qinglong Group builds a solid line of defense for GRC durability for its customers.