Ground Calcium Carbonate (Coarse, d50 20µm)

Ground calcium carbonate (GCC), also known as natural calcium carbonate or heavy calcium carbonate, is produced by mechanical grinding of limestone, chalk, or marble. This coarse grade with a median particle size of approximately 20 µm is one of the most widely used and cost-effective mineral fillers in the composites industry.

Coarse GCC is primarily used for bulk volume extension of resin systems at low cost. In UPR and gelcoat formulations, it reduces raw material cost while maintaining adequate mechanical properties. The coarse particle size produces low surface area (1–2 m²/g), resulting in minimal viscosity increase even at high loading levels (up to 200 phr), making it ideal for thick section composites, artificial stone, and cast polymer products.

White coarse GCC also serves as a pigment extender and opacity contributor in gelcoats and filled resins. It is chemically inert to most resin systems and cure packages. For improved performance in wet environments or where mechanical properties must be retained, surface-treated grades (stearic acid or silane coated) are available. Coarse GCC should be thoroughly dried before use to avoid moisture-related processing defects.