How Do Admixtures Improve GRC Performance? Which Admixtures Are Prohibited?

Admixtures are an essential component of GRC materials. Proper selection of admixtures can significantly optimize product performance and improve production efficiency and application results. However, some admixtures can negatively affect GRC and must be strictly prohibited to ensure product quality and long-term stability.

I. Core Improvement Effects of Admixtures on GRC Performance

High-range water reducers are the most commonly used admixtures in GRC production. They lower the water-binder ratio while maintaining workability, improving the density and strength of components. The polycarboxylate-based water reducer selected by Qinglong achieves a water reduction rate of over 25%, increasing GRC compressive strength by 15%-20%. Retarders adjust cement setting time, preventing surface defects caused by overly rapid setting during construction in high-temperature environments; they are particularly suitable for summer construction or the production of components with complex shapes, ensuring casting and forming quality. Waterproofing agents enhance the impermeability of GRC and reduce water absorption. Qinglong's specialized waterproofing agent can raise the impermeability grade of components to P8 or above, making them suitable for humid environment projects such as exterior walls and waterscapes. In addition, defoamers reduce air bubbles in the slurry, preventing pore defects on component surfaces; water-retaining agents improve curing effectiveness and reduce early-age shrinkage cracking. The proper combination of these admixtures is key to ensuring GRC product quality.

II. Types of Admixtures Prohibited in GRC Production

Chloride-containing admixtures are the primary prohibited category, such as calcium chloride and ferric chloride. Chloride ions corrode glass fibres and steel reinforcement (where present), causing strength degradation and reduced durability in components, and in severe cases creating structural safety hazards; industry standards explicitly prohibit their use. High-alkali admixtures are likewise prohibited, such as certain accelerators and antifreeze agents. Excessive alkalinity accelerates the erosion of alkali-resistant glass fibres, reduces the bond strength between fibres and the cement matrix, and shortens product service life. Admixtures containing harmful volatile substances are prohibited; these release harmful substances during curing, polluting the environment and potentially forming voids within components, reducing density. In addition, some inferior retarders and air-entraining agents affect GRC strength development and result in substandard strength, and must also be included in the prohibited scope. Qinglong explicitly requires that all admixtures pass compatibility testing and environmental testing before they may be used.

III. Key Principles for Selecting and Using Admixtures

Admixture selection must follow the principle of compatibility to ensure suitability with raw materials such as cement and fibres. Qinglong conducts small-batch trials before use to verify the effects of admixtures on slurry workability and strength development. Controlling admixture dosage is essential; excessive use can easily cause side effects—for example, too high a water reducer dosage may cause excessive retardation, and too high a waterproofing agent dosage may affect bonding performance. Qinglong uses precision metering equipment to keep dosage errors within ±0.5%. Environmentally friendly admixtures that comply with national environmental standards are preferred, avoiding harm to human health and the environment, and are especially suitable for interior decoration and public building projects. In addition, admixtures from reputable brands with stable quality should be selected, avoiding inferior products of unknown origin to reduce quality risks.

IV. Qinglong's Admixture Application and Control Practices

Qinglong has established a comprehensive admixture selection and control system, maintaining long-term partnerships with well-known admixture enterprises at home and abroad to ensure stable product quality. Combined admixture solutions are customized for different project requirements—for example, in the UHPC/GRC composite project at Century Plaza on Nanjing East Road in Shanghai, the combination of a high-range water reducer and a defoamer enabled precise forming of components with complex shapes; for the high-salt-mist environment project in Hainan, specialized anti-corrosion and waterproofing admixtures were selected to enhance product weather resistance. A dedicated admixture testing procedure has been established: each incoming batch is tested for performance indicators and harmful substance content, dosage is monitored in real time during production, and performance effects are tested at the finished product stage to ensure admixtures deliver positive results. Relying on 58 related patented technologies, Qinglong continuously optimizes admixture application solutions, providing technical support for GRC product performance improvement.