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

Admixtures are the "performance regulators" of GRC materials; when used scientifically, they can significantly improve workability, mechanical properties, and durability. Qinglong Group classifies GRC admixtures into four major categories—water-reducing, setting-controlling, toughening, and functional—achieving performance optimization through precise compounding. However, certain admixtures can react adversely with the GRC system and must be strictly prohibited. In the Shanghai Astronomy Museum artistic components project, we successfully solved the cracking problem of super-large artistic components through composite admixture technology, demonstrating the value of the scientific use of admixtures.

The Key Role of Water-Reducing Admixtures

High-range water reducers are the core admixtures for GRC, capable of substantially lowering the water-binder ratio without affecting flowability. Qinglong prefers polycarboxylate-based water reducers, with a water reduction rate of 25%-35%, lowering the GRC water-binder ratio from the conventional level of above 0.4 to 0.3-0.35. This not only improves early and ultimate strength but also significantly reduces drying shrinkage and permeability. In the curtain wall project of the Yirui Biotech Building in Shenzhen, the low water-binder ratio mix increased the compressive strength of GRC panels by more than 30%.

Time Control with Setting-Controlling Admixtures

For different construction processes, Qinglong uses setting-controlling agents to precisely control the setting time of GRC. Spray-up forming requires extended operating time, so retarders are added; precast production seeks higher mold turnover, so accelerators are used. We determine the optimal dosage through extensive testing, avoiding slow strength development caused by excessive retardation, or impaired fiber dispersion caused by overly rapid acceleration.

The Crack-Resistance Contribution of Toughening Admixtures

Although glass fibers already provide good toughness, Qinglong also incorporates polymer emulsions (such as acrylic emulsion and styrene-butadiene latex) into critical components for further toughening. Polymers form continuous films in the cement matrix, mitigating brittleness and improving impact resistance and durability. In the large roof project of the Hainan International Convention and Exhibition Center, polymer-modified GRC demonstrated excellent resistance to thermal deformation.

Blacklist of Strictly Prohibited Admixtures

Qinglong explicitly prohibits admixtures containing chlorides (such as calcium chloride early-strength agents), as chloride ions can cause steel reinforcement corrosion and fiber degradation; admixtures with excessively strong air-entraining properties are prohibited to avoid the formation of harmful pores; admixtures containing ammonium salts or nitrates should be used with caution, as they may trigger alkali-aggregate reaction. All admixtures must pass rigorous compatibility testing before use.