What Is the Impermeability Testing Method for GRC Exterior Walls?

The water impermeability of a GRC exterior wall is a key durability indicator of its ability to resist the penetration of liquid water, water vapor, and harmful ions. Its testing must be conducted comprehensively at two levels—"impermeability of the material body" and "overall waterproofing of components/the system"—by combining standardized laboratory test methods with on-site inspection techniques. Based on national standards and with reference to international specifications, Qinglong Group has established a complete testing system covering "water absorption testing, impermeability grade testing, chloride ion diffusion coefficient testing, and on-site water spray testing," ensuring that every batch of GRC products leaving the factory meets the impermeability performance required by the design.

Standardized Laboratory Testing of Material Body Impermeability

1) Water absorption test: This is the most fundamental indirect indicator of impermeability. GRC specimens after standard curing are dried to constant weight, immersed in water for a specified period, then weighed to calculate the percentage of mass gain. The 24-hour water absorption of high-quality GRC should be below 10% (Qinglong's internal control standard often requires below 8%). Low water absorption means the material has low porosity and high density. 2) Impermeability grade (impermeability pressure) test: Using a standard concrete impermeability apparatus, stepwise increasing water pressure is applied to GRC specimens while observing seepage on the back face. The impermeability grade of GRC can usually reach P6-P8 or above, meaning it can withstand water pressure of 0.6-0.8 MPa without penetration, far higher than ordinary concrete. 3) Rapid chloride ion diffusion coefficient test (such as the RCM method): By measuring the migration velocity of chloride ions under an electric field, the ability of GRC to resist chloride penetration can be quickly assessed, which is particularly important for coastal projects. The chloride ion diffusion coefficient of high-quality GRC can be as low as the order of 2.0×10⁻¹² m²/s.

On-Site Verification of Overall Waterproofing of Components and the System

Laboratory tests examine the material itself, whereas in actual projects leakage mostly occurs at weak points such as joints and nodes. On-site inspection is therefore essential: 1) On-site water spray test: Following curtain wall acceptance specifications, dedicated spray equipment is used to continuously spray water on specific areas of the building's exterior wall under simulated storm conditions, checking whether there is any leakage on the interior side. This is the most direct method for verifying the overall watertightness of a GRC exterior wall system (including panels, joints, door and window terminations, etc.). 2) Infrared thermographic inspection: After water spraying or rain, an infrared thermal camera is used to scan the wall surface, and temperature differences can reveal moisture, hollowing, or seepage paths within the wall. This combined testing approach of "laboratory material testing + on-site system verification" provides the scientific basis for comprehensively evaluating the water impermeability of GRC exterior walls.