How Do Admixtures Improve GRC Performance? Which Admixtures Are Prohibited? Qinglong's Scientific Guide to GRC Admixture Application

Within the precision material system of GRC, chemical admixtures, though used in minute quantities, play a key role as "performance regulators". High-quality admixtures can significantly improve the workability, mechanical properties, and long-term durability of GRC. However, incorrect selection or misuse of admixtures—especially those containing certain harmful ions—can cause irreversible damage to the glass fibres and the cement matrix. Based on an extensive R&D database and failure case analyses, Qinglong GRC has established a scientific and safe system for admixture selection and management.

In a complex double-curved artistic curtain wall project in Chengdu, the Qinglong GRC technical team faced the dual challenges of extremely high rheological requirements and extra-long operating time. By compounding a self-developed polycarboxylate-based high-performance water reducer (water reduction rate >35%) with a chlorine-free, alkali-free hydroxycarboxylic acid retarder, the team successfully raised the slurry flowability to over 180 mm and extended the workable time from the usual 30 minutes to 90 minutes, perfectly solving the difficulty of casting special-shaped components. More importantly, this admixture system contains no chloride or sulphate ions harmful to glass fibres, ensuring the long-term safety of the product.

Core Admixture Types and Their Beneficial Effects

High-range water reducers (plasticizers): These are the "essentials" of GRC. While maintaining the same flowability, they can substantially reduce the water-cement ratio (typically from above 0.4 down to 0.3-0.35), which is the most critical means of increasing GRC strength, lowering porosity, and improving durability. Qinglong prefers polycarboxylate products with good compatibility with sulphoaluminate cement.
Retarders: Used to adjust setting time to meet the needs of complex component production, summer construction, or long-distance transport. Only types with no negative impact on later-age strength and free of fibre-damaging ions must be selected.
Defoamers: Effectively reduce the harmful large air bubbles introduced during mixing and casting, increase matrix compactness, and are vital for improving surface quality and impermeability.
Fibre dispersants: Special additives that promote the even distribution of glass fibres in the slurry, prevent clumping, and ensure maximum reinforcement efficiency.

Strictly Prohibited Admixture Types and Their Hazards

Chloride-containing admixtures (e.g., CaCl₂, NaCl and other early-strength agents): This is an absolute red line in GRC production. Chloride ions dramatically accelerate glass fibre corrosion and matrix degradation; their use is strictly prohibited under any circumstances and in any proportion.
Admixtures with high sulphate content (e.g., Na₂SO₄): Excessive sulphate ions may react with the aluminium phases to form delayed ettringite, causing later-age expansion and cracking; the total introduced amount must be strictly controlled.
Admixtures with unknown compatibility with glass fibres or cement: Any new admixture must undergo rigorous laboratory compatibility testing and long-term durability evaluation before its application can even be considered.

Principles for Scientific Selection and Compounding of Admixtures

Qinglong GRC adheres to the principle of "test first, then apply". All admixtures must undergo compatibility tests with the specific cement and fibres in the central laboratory, evaluating their effects on workability, strength development, long-term performance, and fibre morphology. Emphasis is placed on the synergistic effects of admixture combinations while avoiding mutual conflicts. All admixtures used must be accompanied by complete testing reports confirming the absence of hazardous substances and be incorporated into the quality management system for batch control.

Admixtures are a catalyst for GRC's technological progress, but also a double-edged sword. With its deep technical expertise and rigorous scientific approach, Qinglong GRC ensures that every application of admixtures enhances performance while firmly safeguarding the bottom line of product safety and durability.