How to Prevent Freeze-Thaw Damage of GRC Exterior Walls in Severe Cold Regions? A Comprehensive Frost-Resistance Strategy for Materials, Design and Construction

Freeze-thaw damage to GRC exterior walls in severe cold regions is one of the most severe challenges to material durability. Its failure mechanism is the accumulation of internal stress caused by repeated frost heave after moisture penetrates the pores. Extensive project experience by Qinglong Group in cold regions such as Northeast China and Northern Europe shows that preventing freeze-thaw damage requires a comprehensive strategy of "material frost resistance as the foundation, structural waterproofing as the key, and designed drainage as the prerequisite." In a border port building in Heihe that we participated in, the GRC curtain wall remained intact after more than 300 freeze-thaw cycles. The key lies in raising the material's frost resistance rating to above F300 and eliminating moisture retention through systematic detailing.

The frost resistance of the material itself is fundamental. We have developed a special frost-resistant GRC mix proportion tailored to severe cold climates. First, the water-binder ratio is strictly controlled below 0.30, with silica fume and high-quality air-entraining agents added. Under a microscope, a uniform system of tiny, non-interconnected air bubbles with an average diameter of less than 50μm can be observed, providing valuable buffer space for the expansion of freezing water. Second, high alkali-resistant glass fiber with a zirconium content of no less than 16.5% is selected, as its strength retention in coupled alkaline and freeze-thaw environments is critical. Finally, a steam curing regime is mandatory to ensure full cement hydration and reduce harmful porosity. Laboratory data show that after 300 rapid freeze-thaw cycles, this GRC mix exhibits a mass loss of less than 0.5% and a relative dynamic elastic modulus maintained above 90%, far exceeding the conventional F100 standard.

Waterproofing and drainage detailing is central to blocking moisture intrusion. In panel joint design, we adopt the "rain screen principle" and a "pressure-equalized cavity" construction, so that even if the outer sealant partially fails, penetrating water can be quickly drained through the designed cavities and drainage holes, preventing accumulation in the back cavity. All horizontal joints are given an outward drainage slope of no less than 5%, with stainless steel drainage vents installed at the lowest points. A coat of crystalline penetrating waterproof coating is applied to the back of the GRC panels, forming redundant protection in addition to the structural waterproofing layer. For areas prone to water accumulation such as window sills and string courses, integral drainage detailing is adopted so that "water basins" never occur.

Anti-icicle and frost-heave-resistant design of detail joints is equally important. At cornices, canopies and similar locations, we install electric heat tracing systems to prevent ice dam formation. All metal connectors are made of low-temperature-resistant stainless steel, and bolted connections are filled with elastic sealant to allow a certain degree of cold-shrinkage movement. During construction, it is strictly required that thermal insulation curing measures be taken whenever the daily average temperature falls below 5℃, ensuring that freshly mixed GRC is protected from freezing before reaching critical strength. Only through this complete closed-loop frost-resistant system—spanning materials, construction details, design and installation—can the long-term safety and aesthetics of GRC exterior walls in severe cold regions be guaranteed.