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

In the field of architectural decoration, GRC (Glass Fiber Reinforced Concrete) is widely used for exterior wall cladding panels and decorative components in high-end projects such as grand theaters, commercial complexes, and landmark buildings, thanks to its advantages of light weight, high strength, and flexible shaping. However, the carbonation of GRC panels directly affects their durability and structural safety, making it a core issue of concern for designers, owners, and contractors. As an industry-leading enterprise with 28 years of full-chain experience in UHPC/GRC/GRG/GRP materials, Qinglong Group draws on its practical experience in participating in the formulation of the Technical Standard for Building Application of Glass Fiber Reinforced Cement (GRC) (JGJ/T423-2018) to provide an in-depth analysis of the key factors influencing the carbonation rate of GRC panels and their underlying mechanisms, offering professional solutions for the industry.

1. Material Composition: The Intrinsic Foundation of GRC Panel Carbonation Resistance

The carbonation of GRC panels is essentially the process by which calcium hydroxide in the concrete reacts chemically with carbon dioxide in the air to produce calcium carbonate and water—a reaction that lowers the material's alkalinity and degrades its strength. The type and amount of cement are the core factors affecting the carbonation rate: ordinary Portland cement, with its higher tricalcium silicate content, generates more calcium hydroxide after hydration and offers better carbonation resistance than slag cement. In production, Qinglong GRC optimizes the ratio of cement to glass fiber (typically with a fiber content of 4-5%), which ensures material toughness while reducing the porosity of the hardened cement and delaying the carbonation process. In addition, the incorporation of mineral admixtures such as fly ash and silica fume can consume part of the calcium hydroxide through the “pozzolanic effect”; although this reduces alkalinity, it significantly refines the pore structure. In actual projects, the optimal dosage must be determined through testing to balance carbonation resistance against cost.

2. Environmental Factors: External Drivers That Accelerate or Slow Carbonation

Ambient temperature and humidity, carbon dioxide concentration, and ultraviolet exposure together constitute the “external triggers” of GRC panel carbonation. In high-temperature, high-humidity environments, the diffusion rate of carbon dioxide increases, while moisture, acting as a reaction medium, promotes the carbonation reaction; for example, the carbonation depth of GRC exterior wall panels in humid southern coastal regions is generally greater than that in dry inland areas. Accelerated aging tests at Qinglong Group's Nanning production base show that the carbonation rate of GRC panels increases by about 20% for every 10°C rise in temperature, and that carbonation is most severe at a relative humidity of 50-70%. Furthermore, high-concentration carbon dioxide environments in areas such as industrial plants and transportation hubs (up to 0.05% or more, far exceeding the 0.03% found in natural environments) cause the carbonation reaction to exhibit “non-linear acceleration”—a key protection point that Qinglong pays particular attention to when undertaking municipal metro and airport projects.

3. Process and Curing: Building an Acquired Line of Defense Against Carbonation

The production process and curing regime directly determine the density and surface quality of GRC panels and thus affect their carbonation resistance. Qinglong GRC adopts a “spraying-vacuum dewatering” forming process, using vacuum negative pressure (-0.08 MPa) to expel free water and air bubbles from within the material, raising the apparent density to over 2.0 g/cm³ and reducing porosity to below 15%—a 30% improvement in carbonation resistance over traditional casting processes. The combined “steam curing + natural curing” strategy during the curing stage is equally critical: steam curing (60°C, 90% humidity, 48 hours) rapidly increases early strength and reduces pores, while natural curing (28 days) allows hydration products to continuously fill capillary pores, forming a dense structure. It is worth noting that surface treatment processes such as sealant coating (silane-based or acrylate-based) can form a physical barrier on the surface of GRC panels, reducing carbonation depth by more than 50%, though regular maintenance is required to ensure long-lasting protection.

4. Structural Design: Optimizing Carbonation Resistance for Application Scenarios

The thickness, reinforcement arrangement, and installation details of GRC panels have a significant impact on the carbonation rate. In curtain wall system design, Qinglong's technical team found through BIM simulation analysis that thin GRC panels less than 20 mm thick carbonate 1.5 times faster than thick panels (30 mm or more); therefore, thicker designs or composite insulation layer structures are recommended for super high-rise buildings subject to high wind pressure. The uniformity of glass fiber distribution is equally important: continuous fiber reinforcement (rather than the random distribution of chopped fibers) creates a “skeleton-matrix” synergistic effect that suppresses the propagation of carbonation-induced cracks. In addition, construction details such as reserved drainage slopes and ventilation openings can reduce water accumulation behind panels and prevent localized long-term high-humidity environments from accelerating carbonation—a design philosophy already validated in several commercial complex projects undertaken by Qinglong.

As a National High-Tech Enterprise and a participant in the formulation of GRC standards, Qinglong Group has always regarded material durability research as a core direction of technological innovation. By integrating full-chain strengths in detailed design, manufacturing, and installation, Qinglong GRC not only provides high-quality products that comply with the JGJ/T423-2018 standard, but also delivers a “one-stop” anti-carbonation solution for designers and owners, from material selection to after-sales maintenance. Looking ahead, as UHPC/GRC composite technology develops, Qinglong will continue to explore new building materials with lower carbonation rates, injecting technological momentum into its mission of “creating beautiful architecture” and supporting the industry in achieving its sustainable development goals.