Direct answer: for resin flooring, quartz must be qualified as a system aggregate
In an industrial resin floor, silica sand or granular quartz may act as a filler in a mortar, aggregate in a filled layer, broadcast material, or a component contributing to anti-slip texture. The right product is therefore not defined by a high SiO₂ content alone.
The buyer should first lock down the role of quartz in the system, then particle-size fraction, cleanliness, dry condition, lot consistency, and compatibility with the resin and application method [1–5].
ISO 3262-21:2023 specifies silica sand - unground natural quartz - as an extender. ASTM C722 covers chemical-resistant resin monolithic surfacings, while ASTM C1486 addresses testing of broadcast and slurry-broadcast systems [1–3]. These references are complementary, but none turns one particle-size range or one composition into a universal grade for every resin floor.
For the broader distinction between quartz flour and graded sand, see our paints and resins guide.
1. Filler, mortar or broadcast: start with the function of quartz
The same flooring system can use several quartz fractions in different layers.
| Quartz function | What the buyer should primarily control | Why |
|---|---|---|
| Resin filler | particle-size distribution, moisture, cleanliness | dosing, wetting and formulation behaviour |
| Resin-mortar aggregate | grading envelope, packing, consistency | mortar structure and repeatability |
| Broadcast onto fresh resin | graded fraction, dust/fines, dry condition | coverage, texture and surface consistency |
| Anti-slip texture | size and distribution suited to the system | surface profile and finish |
This distinction avoids a common mistake: ordering “quartz sand” only from chemical purity when the process first depends on its particle-size form and function.
2. Particle size: reason by layer and process, not a universal value
Particle size influences dosing, particle packing, resin wetting, texture, and the amount of aggregate retained in a broadcast layer. It must therefore be defined against the actual flooring system.
One documented Sikafloor system uses different quartz fractions across its layers, including 0.1–0.3 mm, 0.3–0.8 mm and 0.7–1.2 mm [4]. These ranges are examples specific to that commercial system: they demonstrate functional diversity, not a general standard.
For procurement, a single “D50” is rarely sufficient for graded sand. Depending on the product, the file may include:
- sieve sizes or fraction limits;
- passing or retained percentages;
- oversize control;
- fines control;
- test method and frequency;
- lot-to-lot comparison.
Our guide to silica-sand particle-size distribution extends this analysis when a full grading curve is required.
3. Fines and dust: a process parameter, not just appearance
Uncontrolled fines can change the total specific surface of the mixture and therefore binder wetting. In a broadcast aggregate, they can also change how the material distributes and is recovered.
This relationship should not be converted into a “universal maximum fines content.” The useful limit depends on:
- the resin;
- resin-to-aggregate ratio;
- thickness;
- broadcast or mixing method;
- target final texture.
A good specification defines a repeatable particle-size method and a window accepted by the qualified system.
4. Moisture: qualify the actual delivered condition
For quartz intended to be mixed into resin or broadcast over a fresh layer, moisture condition is a practical procurement parameter. Quartz suppliers for flooring explicitly describe washed and dried products [5].
That does not imply one moisture percentage applies to all epoxy or polyurethane floors. The limit should be set by the formulator or applicator according to the system, packaging and storage conditions.
The control should state:
- measurement method;
- sample condition;
- contractual limit;
- test frequency;
- storage rules after opening.
Our guide to silica-sand moisture explains the difference between an analytical result and lot representativeness.
5. Cleanliness and contamination: protect system compatibility
“Cleanliness” should not remain a vague word on a purchase sheet. The contaminants that matter to the system should be identified: foreign dust, clays, organic matter, process residues, cross-contamination or out-of-fraction particles.
ISO 3262-21 provides a specification and testing framework for silica sand used as an extender [1], but the flooring manufacturer must complement it with its own compatibility criteria.
Robust qualification therefore combines material certificate + test in the actual system.
6. Chemical purity: important, but rarely sufficient alone
Chemical analysis can confirm the siliceous nature of the product and track selected impurities. It does not predict particle-size distribution, moisture, cleanliness or application behaviour.
Also distinguish:
- bulk chemistry, for example measured by XRF;
- mineralogy, identifying crystalline phases;
- particle size, describing grain dimensions;
- system performance, which must be tested with the relevant resin and process.
Our silica-sand XRF/XRD guide explains why these data are not interchangeable.
7. Performance belongs to the resin + aggregate system
ASTM C722 and ASTM C1486 are particularly useful in preventing a commercial misunderstanding: they concern resin surfacings and their testing, not a universal purity or particle-size threshold for sand [2–3].
A study on quartz-powder-filled epoxy coatings also shows that quartz particle size and loading can modify coating properties [6]. This supports a qualification principle - test size and loading in the formulation - but should not be converted into a recipe for a granular broadcast floor.
A good quartz certificate does not replace flooring-system validation.
8. Procurement table: what data should the supplier provide?
| Data | Why it matters | Avoid |
|---|---|---|
| Material designation / origin | traceability | generic name only |
| Fraction or grading curve | filler/broadcast behaviour | nominal size without method |
| Fines and oversize | fraction consistency | no tolerance |
| Moisture | delivered condition | “dry” without method or limit |
| Cleanliness / contamination | compatibility | undefined declaration |
| Chemistry/mineralogy when relevant | identity and impurities | confusing SiO₂ with quartz % |
| Lot number | traceability | certificate not linked to lot |
| Test methods | comparability | results without protocol |
| Packaging | protection until use | ignoring moisture pickup/contamination |
9. Supplier qualification in six steps
Step 1 - Define the system
State resin, layer, thickness, quartz function and application method.
Step 2 - Define the fraction
Turn “fine sand” or “medium quartz” into measurable criteria: sieves, passing/retained percentages, fines and oversize.
Step 3 - Define material condition
Set useful drying, cleanliness, contamination and packaging criteria.
Step 4 - Check the certificate
Verify that each value is tied to a method, unit and identifiable lot.
Step 5 - Test in the actual system
Validate mixing, wetting, application, broadcast, texture and relevant performance for the process. System testing should follow appropriate contractual or normative methods [2–3].
Step 6 - Lock down consistency
After approval, monitor the same parameters on subsequent lots. Representative sampling is essential: a precise result from an unrepresentative sample remains insufficient.
10. Safety: do not confuse product quality with dust exposure
Crystalline quartz can generate respirable dust during handling of dry material. NIOSH treats respirable crystalline silica as an occupational hazard [7].
This should be managed through risk assessment, dust control, handling procedures and appropriate protective measures. It is separate from the commercial particle-size or purity specification of quartz.
11. The most common purchasing mistakes
- buying on SiO₂ percentage alone;
- copying a particle-size fraction from another system;
- confusing micronized flour with granular aggregate;
- asking for “dry” without a method or limit;
- ignoring fines and oversize;
- accepting a certificate without a lot number;
- assuming quartz suitable as a filler automatically suits broadcast use;
- treating a supplier datasheet value as a universal standard;
- approving material without testing it in the actual resin system.
12. Information to provide for a quotation
For a technically usable offer, state:
- use: filler, resin mortar, broadcast or anti-slip;
- resin or system type;
- required particle-size fraction and tolerances;
- fines/oversize criteria;
- moisture requirement and method if defined;
- cleanliness or contamination requirements;
- chemistry/mineralogy if genuinely required;
- lot quantity and annual volume;
- bags, big bags or other packaging;
- destination and delivery frequency;
- required tests or quality documents.
Conclusion
For an industrial resin floor, the right silica sand is not “the purest” in absolute terms. It is the quartz whose function, particle-size fraction, dry condition, cleanliness and consistency are compatible with the validated system.
Standards and test methods help structure control, but they do not replace the formulator’s specification. Procurement should therefore connect three levels: material characterization, lot traceability, and validation of the resin + aggregate system.