VF21 EXPANSION AGENT

VF-21 is a sulfoaluminate-calcium expansion agent developed for shrinkage-compensating concrete and other high-performance concrete applications. It works by generating controlled expansion during the early hardening stage, which offsets drying shrinkage and reduces the risk of cracking as concrete cures. The product also improves density, impermeability, and long-term durability, while remaining non-corrosive to steel reinforcement and resistant to alkali-aggregate reaction. VF-21 complies with GB23439-2009, the Chinese national standard for concrete expansion agents. Its sulfoaluminate-based expansion mechanism is broadly comparable to ASTM C845 Type K expansive cement systems used internationally, which may help buyers evaluate it against familiar specifications. Luke Chemicals manufactures VF-21 for contractors, ready-mix producers, and distributors sourcing concrete admixtures for export.

Where VF-21 Is Used

VF-21 is suited to projects where crack control and long-term structural integrity matter most. Common applications include underground structures such as basements, subways, tunnels, and civil air defense projects. It is also used in water-retaining structures like pools, water towers, and reservoirs, as well as mass concrete elements including ultra-long slabs and expansion strengthening bands. In infrastructure work, VF-21 is applied in airport runways, highway pavements, bridge decks, marine structures, dams, and spillways. It also performs well in specialty concrete types, including steel tube concrete and large-scale backfill concrete.

Performance Characteristics

VF-21 delivers strong expansion efficiency at low alkali content, supporting stable and predictable concrete performance. It helps refine the concrete microstructure, which increases density and improves overall material quality. Impermeability and frost resistance are both enhanced, extending the service life of finished structures. Because it compensates for shrinkage during hardening and drying, VF-21 lowers the likelihood of cracking in restrained or large-volume pours. The product is also non-corrosive to steel reinforcement and helps suppress alkali-aggregate reactions, which supports long-term structural durability.

Main Technical Indicators

Dosage and Application

Because compatibility between VF-21, cement, other admixtures, and water reducers can vary by mix design, laboratory trial mixes are recommended before full-scale production. This helps confirm the optimal dosage for a given project.

For general shrinkage-compensating concrete, the recommended dosage is 6 to 10 percent of the cementitious material mass. For mass expansion applications such as strengthening bands or self-stressing concrete, the dosage typically increases to 8 to 12 percent. Exact dosage should be adjusted based on cement type, project specification, and performance targets.

Mixing time for ready-mixed concrete matches standard practice. For on-site mixing, extend the mixing time by 60 seconds to ensure even dispersion. Concrete should be fully vibrated during placement, avoiding both under-vibration and over-vibration to maintain density.

Cured concrete should be kept moist for at least 14 days. In winter conditions, apply thermal insulation when ambient temperature drops below 5°C. VF-21 should be used with caution in environments where long-term working temperature exceeds 80°C. For broader project guidance, refer to the Technical Specification for Application of Shrinkage-Compensating Concrete.

Packaging, Storage, and Shelf Life

VF-21 is available in 25kg or 50kg moisture-proof bags, with custom packaging weights available on request. Store the product in a dry, ventilated area and protect it from moisture and physical damage. Do not use if caking has occurred. Shelf life is 12 months under proper storage conditions. VF-21 is non-toxic and non-flammable, and can be transported as general goods.

Luke Chemicals supports export orders with flexible payment terms, worldwide shipping, and a minimum order quantity of 500kg, backed by in-house production and technical guidance for buyers evaluating VF-21 for their mix designs.