Discussion on Alkalinity Issues and Countermeasures When Using Sulphoaluminate Cement in GRC

In the field of modern architectural decoration, material performance and durability have always been a core concern for designers and engineering parties. Sulphoaluminate cement, as a key cementitious material for GRC (Glass Fiber Reinforced Concrete), has its alkalinity issue directly affecting the long-term stability and safety of components. Qinglong Group, a national high-tech enterprise with 28 years of full-chain experience in UHPC/GRC/GRG/GRP, drawing on its practical experience of participating in the formulation of the Technical Standard for Building Application of Glass Fiber Reinforced Cement (GRC) (JGJ/T423-2018), provides an in-depth analysis of the key points of alkalinity control and systematic solutions for sulphoaluminate cement in GRC applications.

I. Potential Impact of Sulphoaluminate Cement Alkalinity on GRC

Sulphoaluminate cement is widely used in GRC components for its characteristics such as rapid hardening, early strength gain, and low hydration heat. However, a high-alkali environment may trigger two major core problems: one is alkali corrosion of glass fibers, leading to the deterioration of the material's mechanical properties; the other is the alkali-aggregate reaction (AAR), which causes component cracking. A landmark project once saw a 30% loss of glass fiber strength due to uncontrolled alkalinity, highlighting the importance of scientific control. Verified through more than 2,000 sets of experimental data by Qinglong's technical team, when cement alkalinity (measured as Na₂O equivalent) exceeds 3.5%, the flexural strength of GRC will decrease significantly — this is also a widely recognized safety threshold in the industry.

II. Key Technical Approaches to Alkalinity Control in GRC Production

In response to the alkalinity characteristics of sulphoaluminate cement, Qinglong has established a three-dimensional solution of “source control – process optimization – later-stage monitoring”. On the raw material side, adopting a golden ratio of low-alkali sulphoaluminate cement (alkali content ≤2.5%) and highly alkali-resistant glass fibers (ZrO₂ content ≥16%), combined with independently developed mineral admixtures (such as silica fume and fly ash), can reduce the alkalinity of the system by more than 40%. During production, a pH online monitoring system regulates the acidity and alkalinity of the slurry in real time, ensuring that the pH value remains stable in the range of 10-11 during molding — this technology has been applied in award-winning projects such as the light-transmitting concrete at Nanjing East Road Century Plaza.

III. Strategies for Addressing Alkalinity Issues in Engineering Practice

Facing complex working conditions, Qinglong has innovatively proposed the concept of “graded protection”: for long-term exposed components such as dry-hanging exterior walls, a double-coating protection system is adopted — an alkali inhibitor is applied on the inner layer, and the outer layer is covered with a silane impregnation agent, improving impermeability by 50%; for humid environments (such as swimming pools and underground utility corridors), an alkali-aggregate reaction inhibitor has been developed, which blocks harmful expansion reactions through the principle of ion exchange. After a coastal project applied this technology, following 5 years of sea wind erosion, no alkali precipitation appeared on the component surfaces, and the strength retention rate reached 92%, confirming the effectiveness of the solution.

IV. Full-Chain Services Ensuring GRC Project Quality

As an industry leader integrating detailed design, manufacturing, construction, and installation, Qinglong engages in alkalinity control from the initial stage of each project: at the design stage, BIM technology is used to simulate the impact of the alkaline environment on the structure and optimize the reinforcement scheme; in production, an RFID chip traceability system is activated to record the alkalinity data of each batch of materials; during construction, 3D laser positioning technology is used to ensure installation precision; after sales, a 5-year alkalinity testing service is provided, forming closed-loop management. This full life-cycle service model has helped Qinglong become a strategic partner of top real estate developers such as Poly and China Overseas.

Alkalinity control of sulphoaluminate cement in GRC is essentially a deep integration of materials science and engineering experience. Supported by 58 patented technologies, Qinglong Group applies the philosophy of “meticulousness and the pursuit of excellence” throughout every project, not only providing designers with broader creative space but also injecting lasting safeguards into building safety. In the future, with the innovative development of UHPC/GRC composite systems, alkalinity control technology will become a key engine driving the high-quality development of the industry.