Alkalinity Control in the Application of Sulphoaluminate Cement in GRC: Key Technical Points and Practical Guide

Alkalinity balance is the core issue for the stable service of GRC materials. As a commonly used cementitious material in GRC, sulphoaluminate cement has alkalinity characteristics that relate to product performance and also affect the durability of the reinforcing materials. Qinglong has been deeply engaged in the GRC field for 28 years, accumulating mature experience in sulphoaluminate cement alkalinity control through thousands of project practices, and providing designers and owners with solutions that combine performance and stability.

The core advantages of sulphoaluminate cement in GRC applications lie in its early strength and low shrinkage, but its own alkalinity characteristics require precise control. Hydroxide ions released during cement hydration, if excessively concentrated, will erode alkali-resistant glass fibre, causing fibre strength degradation and ultimately affecting the overall mechanical performance of GRC. In the JC/T940-2022 standard "Glass Fibre Reinforced Cement (GRC) Decorative Products", whose revision Qinglong participated in, it is clearly stipulated that the effective alkali content of GRC cementitious materials must be controlled below 0.6%, an indicator that has become an important basis for industry alkalinity control. In the Panzhihua Third-Front Construction Culture and Tourism Demonstration Project in Sichuan, Qinglong achieved GRC curtain wall panels with no cracking and no strength degradation for more than 20 years through precise control of sulphoaluminate cement alkalinity.

Sulphoaluminate cement alkalinity control must be addressed across the entire process, from raw material selection and mix proportion optimization to production technology. First, select low-alkalinity sulphoaluminate cement, giving priority to products with an effective alkali content of ≤0.5% to reduce the alkalinity base at the source. Second, adjust alkalinity by adding mineral admixtures—in the hyperbolic GRC project of the Nanning New Media Center, Qinglong rationally incorporated active admixtures such as fly ash and slag powder, which both reduced the alkalinity of the system and enhanced the interfacial bond between the cement paste and the glass fibre. Third, control the water-cement ratio to prevent excessive moisture from causing alkali ion migration and enrichment, typically keeping it between 0.35 and 0.45. Finally, optimize the curing regime by combining moisture-retaining curing with low-temperature curing to reduce the likelihood of alkali-aggregate reaction.

Leveraging the R&D strength of its provincial-level engineering technology center, Qinglong has developed a dedicated alkalinity regulator that can precisely adjust the alkalinity of the sulphoaluminate cement system according to the project environment. In the international project of the National Service center in Singapore, addressing the high humidity of the tropical marine environment, Qinglong applied a customized alkalinity control scheme, enabling GRC components to maintain excellent durability even in saline-alkali conditions. For designers, when producing GRC products with sulphoaluminate cement, it is necessary to work with professional suppliers on alkalinity-matching design; for owners, choosing a manufacturer with alkalinity control technology and project experience is key to avoiding later quality risks. Through full-chain technical services, Qinglong ensures that the application of sulphoaluminate cement in GRC both exploits the material's advantages and achieves long-term stable service.