Analysis of Factors Affecting the Carbonation Rate of GRC Panels and Their Influence Mechanisms

In the field of architectural decorative materials, material durability directly affects a building's safety and aesthetics. Among them, GRC panels (glass fiber reinforced concrete) are a composite material widely used in exterior wall cladding, shading systems, landscape architecture and other scenarios, and their carbonation speed is a key indicator for measuring service life. As an industry expert with 28 years of full-chain experience in UHPC/GRC/GRG/GRP materials, Qinglong Group will provide an in-depth analysis of the core factors influencing the carbonation speed of GRC panels and their mechanisms from three dimensions—material properties, environmental factors, and process control—offering designers and owners scientific guidance on material selection and application.

The Essence of GRC Panel Carbonation: The “Aging Code” of Cement-Based Materials

The carbonation of GRC panels is essentially a chemical reaction in which calcium hydroxide in the concrete reacts with carbon dioxide in the air to produce calcium carbonate and water. This reaction lowers the alkalinity of the material, which in turn affects the interfacial bonding between the glass fibers and the cement matrix, and over the long term may cause problems such as strength loss and surface cracking. While participating in drafting the Technical Standard for Building Application of Glass Fiber Reinforced Cement (GRC) (JGJ/T423-2018), Qinglong Group found that the carbonation depth of high-quality GRC panels should be controlled within 0.5mm per year, whereas in actual projects, differences in material formulations and environmental conditions can cause the carbonation speed to fluctuate by a factor of 3-5.

Material Formulation: The “Genetic Code” That Determines GRC Panels' Carbonation Resistance

1. Cement type and admixture ratio: Using high-alumina cement or sulphoaluminate cement can improve the density of the matrix, reducing the carbonation speed by more than 40% compared with ordinary Portland cement. At its Nanning production base, Qinglong incorporates active admixtures such as silica fume and mineral powder to keep the porosity of GRC panels below 15%, effectively hindering CO₂ penetration.

2. Glass fiber type and content: The addition of alkali-resistant glass fiber (AR glass fiber) not only improves flexural strength (up to over 20MPa); its mesh distribution also forms a physical barrier that delays the carbonation process. Through 28 years of process optimization, Qinglong has established a golden ratio of 5-8% fiber content, maximizing carbonation resistance while ensuring toughness.

3. Water-cement ratio and admixtures: A low water-cement ratio (≤0.45) combined with high-range water reducers can significantly reduce capillary channels. Qinglong's self-developed GRC-specific modifier can increase the material's early strength by 30% and reduce the moisture conditions required for the carbonation reaction.

Environmental Factors: The “External Drivers” That Accelerate or Delay Carbonation

1. Combined effect of temperature and humidity: For every 10℃ rise in temperature, the carbonation reaction rate increases by 1-2 times; carbonation is fastest at a relative humidity of 50-70%. Take, for example, a landmark project in Saudi Arabia undertaken by Qinglong: the hot, dry environment reduced the carbonation speed of GRC panels by about 60% compared with coastal regions in China, confirming the importance of environmental regulation.

2. CO₂ concentration and air pollution: CO₂ concentration in urban industrial areas is 30-50% higher than in suburbs, and the carbonation speed increases accordingly. Meanwhile, acidic gases such as SO₂ and NOx react with the cement matrix to form soluble salts, damaging the dense structure and indirectly accelerating carbonation. In the renovation project of Century Plaza on Nanjing East Road, Qinglong applied surface fluorocarbon coating treatment, improving the pollution resistance of GRC panels by 50%.

3. UV radiation and wet-dry cycles: Long-term UV exposure causes aging of surface resin coatings, aggravating moisture penetration, while frequent wet-dry cycles make the pore structure repeatedly expand and contract, creating channels for CO₂ diffusion. Qinglong's double-curved GRC components adopt a three-layer protection system (primer + intermediate coat + topcoat), achieving 15 years without obvious carbonation in projects such as Canton Tower.

Process Control: The “Quality Control Shield” That Safeguards Carbonation Resistance Across the Whole Chain

1. Density control in production: Qinglong adopts a vacuum extrusion molding process, raising the bulk density of GRC panels to over 2.1g/cm³, combined with steam curing (80℃, 6 hours) to ensure full cement hydration and reduce internal defects.

2. Sealing of installation joints: BIM technology is used to optimize anchor joint design, and elastic sealant is applied for caulking to prevent rainwater infiltration that could cause internal carbonation. In the Dongguan Women and Children's Activity Center project, Qinglong innovatively applied a “breathing curtain wall” system, keeping the cavity behind the GRC panels dry with slight positive pressure.

3. Scientific intervention in later maintenance: A regular inspection mechanism (carbonation depth testing every 3 years) is established, with timely repair of surface damage. Qinglong's after-sales maintenance service includes a dedicated anti-carbonation repair mortar that can restore more than 90% of the protective performance in locally carbonated areas.

As a national “Specialized, Refined, Distinctive, and Innovative” enterprise, Qinglong Group has always made material durability research its technological core. From formulation optimization of GRC panels to full life-cycle management in engineering applications, every step embodies 28 years of accumulated industry experience. Choosing Qinglong GRC means not only choosing a building material, but also choosing a carbonation-resistant solution verified by more than a thousand projects. Looking ahead, Qinglong will continue to uphold its mission of “creating beautiful architecture,” driving technological breakthroughs of UHPC/GRC/GRG/GRP materials in the field of durability, and providing more reliable products and services for the global architectural decoration industry.