What Are the Freeze-Thaw Resistance Indicators of GRC Materials and How to Test Them?

The freeze-thaw resistance of GRC material is an important indicator of its durability, especially in cold regions where it determines the material's service life. Qinglong Group evaluates freeze-thaw resistance across three dimensions: "mass loss rate, strength loss rate, and dynamic elastic modulus change". Quality GRC should withstand 300 freeze-thaw cycles with a strength loss of no more than 10%. In a project in Northeast China, our GRC components endured severe cold with their performance fully intact, demonstrating the value of excellent frost resistance. Freeze-thaw resistance is the touchstone of GRC material quality.

Evaluation Standard System for Freeze-Thaw Resistance

According to the JGJ/T 423-2018 standard, the frost resistance grades of GRC material are classified into seven levels: F25, F50, F100, F150, F200, F250, and F300. Qinglong's internal control standards require no lower than F100 for general regions, no lower than F150 for severe cold regions, and F200 or above for key projects. In the Ouargla Hotel project in Algeria, although located in a tropical area, we still produced to the F150 standard, providing redundant protection against possible extreme weather.

Scientific Methods of Freeze-Thaw Testing

Qinglong's laboratory uses the rapid freezing method for frost resistance testing: after standard specimens are soaked in water for 4 days, they are placed in a freeze-thaw test chamber and cycled between -18℃±2℃ and 5℃±2℃, with mass loss and dynamic elastic modulus change measured every 25 cycles. Rigorous standard testing is the only scientific means of evaluating frost resistance; any simplified method may lead to misjudgment.

Analysis of Key Factors Affecting Frost Resistance

The frost resistance of GRC mainly depends on pore structure, water-binder ratio, and fiber distribution. Qinglong significantly improved frost resistance by controlling the water-binder ratio below 0.35, adding air-entraining agents to form uniform closed micro-bubbles, and optimizing fiber distribution to block water seepage channels. In the Yangshengtang Pharmaceutical Hangzhou Industrial Park project, this comprehensive technology enabled GRC panels to perform excellently in freeze-thaw environments.

Correlation Between Frost Resistance and Other Properties

Frost resistance is not an isolated indicator; it is closely related to impermeability and carbonation resistance. Qinglong's research found that GRC with poor frost resistance usually also has a higher chloride ion diffusion coefficient, with durability deteriorating across the board. Therefore, we treat frost resistance as a comprehensive evaluation indicator of material durability, achieving overall performance improvement through systematic optimization.