About GCC Standard Grade Calcium Carbonate
GCC standard grade is ground calcium carbonate milled from high-purity calcite and classified to a medium particle size, with a median typically in the 8–15 µm range. It is the workhorse of the range: bright, inert, easy to handle and economical at high loadings. It is intended for formulations where volume, whiteness and processability matter more than an ultra-fine particle size.
The largest uses are in construction chemicals and general fillers. In wall putty, tile adhesives, grouts and skim coats it builds body and improves trowelling. In rubber goods such as footwear soles, mats, hoses and profiles, it extends the compound and helps mould flow without adding significant reinforcement. Economy emulsion paints, primers and distempers use it as their primary extender. Because calcite is soft, the grade causes little wear on mixers, pumps and extrusion equipment, which keeps maintenance costs down in high-throughput plants.
Obsidian Minerals produces the standard grade from selected calcite and uses air classification to keep the top cut and the residue on the 45 µm sieve under control, so customers avoid grit and surface defects in thin coats. The grade is supplied uncoated; finer and stearic-coated grades are offered separately in the range for polymer and premium paint applications.
Typical specifications
| Parameter | Typical Value | Test Method |
|---|---|---|
| CaCO₃ | ≥ 97.0 % | ASTM C25 |
| Brightness (GE) | ≥ 92 | Internal method |
| Median particle size (D50) | 8–15 µm | Laser diffraction (ISO 13320) |
| Residue on 45 µm (325 mesh) | ≤ 1.0 % | ASTM D185 |
| Oil absorption | 16–22 g/100 g | ASTM D281 |
| Moisture | ≤ 0.3 % | Internal method (105 °C) |
| Fe₂O₃ | ≤ 0.10 % | ASTM C25 |
| MgO | ≤ 1.0 % | ASTM C25 |
Typical values for guidance. Guaranteed limits are stated on the Technical Data Sheet and batch CoA.
Key features & benefits
Cost-effective volume filler
A medium particle size and moderate binder demand allow GCC standard grade to be used at high loadings in putties, adhesives and economy paints, lowering cost while keeping a workable viscosity.
Controlled top size
Residue on the 45 µm sieve is typically kept to 1 % or less, which limits grit, pinholes and scratch marks in skim coats, putties and thin paint films.
Clean white base
Brightness of 92 or higher on typical batches gives a neutral white base, which can reduce the tinting or titanium dioxide needed to reach a target shade in light-coloured products.
Low abrasion
With a Mohs hardness of about 3, ground calcite causes little wear on mixers, pumps, screw conveyors and extruder barrels compared with harder fillers such as silica.
Stable in alkaline systems
The grade is inert in cement, lime and alkaline emulsion systems, so it does not interfere with setting in putties and adhesives or upset the pH of water-based paints.
Applications
Wall putty and skim coats
The main filler in cement-based and polymer-modified wall putty, where it provides body, smooth trowelling, easy sanding and a white surface ready for priming and painting.
Tile adhesives and grouts
Used as a fine aggregate and filler in cementitious tile adhesives and grouts to improve workability, control density and help reduce cost per bag of finished product.
Rubber compounds
A non-reinforcing extender for footwear, mats, hoses, cables and moulded goods, helping mould flow, extrusion and dimensional stability while lowering compound cost at practical loadings.
Economy paints and primers
A primary extender in interior emulsions, distempers and primers, where it builds solids and contributes to opacity in matt finishes at a competitive raw material cost.
Usage & handling
- In wall putty the grade is commonly the main filler, with its share set by the white cement and polymer content of the formulation.
- Rubber compounds typically take about 20–100 phr, depending on hardness and cost targets.
- Add during dry blending or at the mill-base stage; no pre-treatment is required.
- GCC is not hygroscopic, but bagged material should be stored dry and protected from rain and condensation.
Packaging & supply
- 25 kg and 50 kg HDPE or paper bags for construction chemical and paint plants
- 1 MT and 1.2 MT jumbo bags for high-volume and silo-fed users
- Custom bag sizes and private labelling available on request
Frequently asked questions
What is GCC standard grade used for?
GCC standard grade is a general-purpose filler for wall putty, skim coats, tile adhesives and grouts, rubber goods, and economy paints, primers and distempers. It is selected where a bright, inert, low-cost filler is needed in large volumes and where the finished product does not require the smoothness or mechanical performance of a fine grade.
What particle size is the GCC standard grade?
The median particle size (D50) is typically 8–15 µm, measured by laser diffraction, with residue on the 45 µm (325 mesh) sieve of 1 % or less. This gives a good balance between low binder demand and smooth application. The guaranteed particle size limits for your order are given on the Technical Data Sheet.
Is the standard grade suitable for PVC?
It can be used in some economy flexible PVC and rubber-like compounds, but for rigid PVC pipes and profiles the coated grade is the better match. Its stearic acid treatment improves dispersion and reduces moisture pick-up, which helps surface finish and impact strength. Customers should confirm suitability through compound trials.
How does the standard grade differ from the fine GCC grade?
The standard grade has a median size of about 8–15 µm and is optimised for volume and cost. The fine grade is classified to a median below 5 µm with a much tighter top cut, giving smoother films, better gloss retention and less effect on polymer properties. The fine grade is used where finish quality justifies its higher binder demand.
Can the standard grade be supplied with a different top cut?
Yes. Residue limits and median size can be adjusted within the capability of the grinding and classification circuit to suit a particular putty, adhesive or rubber formulation. Share your target values and a trial sample can be prepared. Agreed limits are then fixed on a grade-specific Technical Data Sheet.