Analysis of Alkalinity Issues and Countermeasures When Using Sulphoaluminate Cement in GRC

In the application of GRC materials, alkalinity control is a core element in ensuring the durability and safety of components; only by scientifically addressing alkalinity issues can the perfect unity of architectural art and engineering quality be achieved.

As an industry leader with 28 years of deep expertise in the UHPC/GRC/GRG/GRP materials field, Qinglong Group fully understands the decisive role of material performance in building quality. In the production and application of GRC (Glass Fiber Reinforced Concrete), sulfoaluminate cement is widely adopted for its rapid hardening and early strength characteristics, but alkalinity has always been a key factor affecting the long-term stability of components. This article analyzes the causes, hazards, and systematic solutions of the alkalinity problem, providing professional technical reference for designers and owners.

I. Alkalinity Characteristics and Potential Risks of Sulfoaluminate Cement in GRC

During the hydration of sulfoaluminate cement, hydroxide ions are released, maintaining the slurry in a highly alkaline environment with a pH of 12-13. While this strongly alkaline medium can activate supplementary materials such as slag to enhance early strength, it may also cause "alkali corrosion" of glass fibers, manifesting as fiber strength degradation and cracking in the interfacial transition zone, ultimately affecting the flexural performance and durability of GRC components. A landmark project that failed to control alkalinity once suffered surface efflorescence and localized cracking on decorative moldings, significantly increasing later maintenance costs.

II. Three Key Factors Affecting Alkalinity Problems in GRC Components

1. Cement Type and Dosage Control: Pure sulfoaluminate cement can have an alkali content exceeding 3.0%, which must be neutralized by blending with composite Portland cement (recommended ratio 1:1-3:1). At its Nanning production base, Qinglong determined the optimal mix ratio through orthogonal tests, keeping the alkali content stably below 1.5%.

2. Selection of Alkali-Resistant Glass Fibers: Alkali-resistant glass fibers with a zirconia content ≥16% (such as ECR fibers) achieve an alkali resistance retention rate of over 85%, far higher than the 30% of ordinary glass fibers. The Technical Standard for Building Application of Glass Fiber Reinforced Cement (GRC) (JGJ/T423-2018), in whose drafting Qinglong participated, explicitly specifies fiber alkali resistance performance indicators.

3. Curing Process Parameter Optimization: Steam curing temperatures above 80°C accelerate the alkali-aggregate reaction. Qinglong innovatively adopts a "stepped cooling curing method", keeping the maximum internal temperature of components within 65°C to effectively reduce the precipitation of alkali-active substances.

III. Qinglong's Full-Chain Alkalinity Control Solution for GRC

As a national high-tech enterprise, Qinglong has established a full-process control system from raw material screening to finished product testing: at the detailed design stage, BIM technology is used to simulate alkali stress distribution; in production, an automated batching system ensures alkalinity fluctuation ≤0.2%; during construction and installation, on-site pH detection equipment (accuracy ±0.1pH) monitors interface treatment quality in real time. Through this system, the translucent concrete project at Century Plaza on Nanjing East Road undertaken by Qinglong achieved a record of zero alkali corrosion cracking and won the AALBORG WHITE Cup UHPC Construction Engineering Innovation Award.

IV. Summary of Alkalinity Management Experience in Industry Practice

Comparing the technical solutions of peer companies such as Guangdong Shiji Shangpin and Shantaixin Industrial, Qinglong believes that alkalinity control must balance material cost and performance. For ordinary components such as European classical moldings, a "cement blending + conventional curing" approach is recommended, while for high-end projects such as the hyperbolic curtain walls of grand theaters, a combined strategy of "low-alkali cement + alkali-resistant fibers + intelligent curing" should be implemented. Of Qinglong's current annual capacity of 600,000 square meters, 85% of GRC products use customized alkalinity control solutions, with customer satisfaction consistently maintained above 98%.

Alkalinity management is the "invisible lifeline" of GRC material applications. Backed by 28 years of full-chain experience, Qinglong Group deeply integrates materials science with engineering practice, providing reliable technical support for designers to realize their creative visions. Choosing a GRC manufacturer with systematic solution capabilities is a key decision to ensure both the decorative effect and structural safety of a building.