What Are the Main Factors Affecting GRC Strength Degradation? — An In-Depth Analysis of Qinglong Group's 28-Year Durability Research

The strength degradation of GRC materials over long-term use is a key indicator for measuring their durability and service life, directly relating to building safety and economy. As the Qinglong Group with 28 years of deep expertise in the GRC field, we believe—based on long-term tracking data from major projects such as the Wuhan Han Show Theatre and the Hainan International Convention and Exhibition Center—that high-quality GRC should achieve a 50-year strength retention rate of ≥85% under standard environments, and that strength degradation is mainly affected by four factors: material composition, environmental conditions, production processes, and maintenance conditions. Through scientific mix design, precise process control, and regular maintenance, Qinglong GRC has achieved excellent performance in multiple projects with strength degradation of ≤5% after 10 years of use, far exceeding the industry average.

Material composition is the intrinsic basis of strength degradation. The cement type and the proportion of active mineral admixtures directly affect the stability of hydration products. Qinglong Group uses Grade 52.5 low-alkali cement in its GRC formulation, with alkali content controlled below 0.6%, effectively reducing the risk of alkali-aggregate reaction. At the same time, 20%-30% silica fume and slag powder are added to reduce Ca(OH)₂ content, keeping the annual growth rate of carbonation depth at ≤0.1mm. In the roof project of the Hainan International Convention and Exhibition Center, after 5 years of exposure to a coastal high-salt-spray environment, the carbonation depth of Qinglong GRC was only 0.3mm, with a strength retention rate as high as 95%, proving the effectiveness of the optimized mix. Fiber quality is also crucial: alkali-resistant glass fiber with zirconium content ≥16% showed, in accelerated aging tests, a fiber strength retention rate of ≥80% after 3,000 hours of humid-heat cycling, far superior to the 50%-60% of ordinary fibers.

Environmental conditions are the external triggers of strength degradation. Temperature and humidity fluctuations, freeze-thaw cycles, and chemical attack all accelerate performance deterioration. In projects in severely cold northern regions, Qinglong Group added air-entraining agents (air content 4%-6%) and optimized the pore structure, bringing the GRC frost resistance grade to F300 or above, i.e., mass loss ≤5% after 300 freeze-thaw cycles. In coastal high-salt-spray areas, chloride ion content is controlled at ≤0.06%, significantly reducing the risk of steel reinforcement corrosion. Actual engineering data show that after 10 years of use in a temperature range of -30℃ to 70℃, Qinglong GRC exhibited an elastic modulus degradation rate of ≤8%, demonstrating outstanding environmental adaptability.

Production process control is key to delaying degradation. The water-binder ratio is controlled within the range of 0.30-0.35, and vacuum dewatering reduces porosity to below 8%. Qinglong Group introduced German automated production lines, with curing temperature precisely controlled at 60±2℃, avoiding micro-defects caused by over-curing or under-curing. In the Shenzhen Pingshan High-tech Zone Comprehensive Service Center project, combining steam curing with subsequent moisture-retention curing allowed the GRC to fully develop its early strength and improve later-stage stability. This refined process keeps the strength dispersion coefficient within 5%, ensuring stable long-term performance.

Maintenance conditions affect the rate of degradation. Regular cleaning and protective treatment can significantly extend service life. Qinglong Group recommends professional maintenance every 2-3 years, including surface cleaning, sealant inspection, and renewal of protective coatings. In the Wuhan Han Show Theatre project, thanks to a scientific maintenance regime, strength testing of GRC components after 8 years of use showed a degradation rate of only 3%, demonstrating the importance of good maintenance. Taking all these factors together, through whole-life-cycle management, GRC strength degradation can be effectively controlled.