Calcium formate (CAS 544-17-2) is the calcium salt of formic acid, Ca(HCOO)2, a white free-flowing powder with a molecular weight of 130.11. It is bought for two very different jobs: as a chloride-free set accelerator for concrete, mortar and tile adhesives, and as a buffered acidifier in animal feed. The same plant makes both, which is why one CAS number appears on three separate specification sheets.
We hold three commercial grades – concrete accelerator, feed additive and general industrial – and the table below is the honest answer to what actually separates them.
Specification by grade
| Parameter | Concrete accelerator grade | Feed additive grade | Industrial grade | Why it matters |
|---|---|---|---|---|
| Assay (as Ca(HCOO)2) | Min 98% | Min 98% | Min 98% | Purity is identical across the three grades. If a supplier quotes a materially lower assay for a “technical” grade, ask what the balance is – usually moisture and calcium carbonate |
| Calcium content | Min 30.1% | Min 30.1% | Min 30.1% | The single most useful line on the sheet: it is a cross-check on assay, not a separate property (see below) |
| Moisture | Max 0.5% | Max 0.5% | Max 0.5% | Drives caking in storage and dust in handling; also protects the assay figure |
| Arsenic | Max 5 ppm | Max 5 ppm | Not normally specified | The only chemical test that differs between the sheets – it exists because feed and construction markets audit it |
| Particle size | Typically 40-60 mesh as agreed | Typically 60-80 mesh as agreed | 50 mesh | Controls dissolution rate and dust. Coarse accelerates less aggressively in mortar; fine dissolves faster in feed premix |
| Chloride | Declared chloride-free on request | Not relevant | Not relevant | Decides whether the material may be used in reinforced and prestressed concrete at all |
Reading the 30.1% calcium figure
The theoretical calcium content of pure calcium formate is 30.80% (40.078 / 130.11). At 98% assay the calculated calcium content is 30.80% x 98% = 30.18%, which is exactly where the “min 30.1%” limit sits. The two numbers are therefore not independent specifications – calcium content is a convenient proxy for assay that a buyer can verify with a simple EDTA titration instead of an ion chromatography method.
The practical consequence is a one-line acceptance test: if a delivered lot titrates below 30.1% calcium, either the assay is under 98% or the lot has picked up moisture or carbonate filler. You do not need to run the full assay to know something is wrong.
A second useful conversion for formulators: the formic acid equivalent of calcium formate is 70.75% (2 x 46.03 / 130.11). One kilogram of calcium formate delivers the same acid load as about 0.71 kg of pure formic acid, but buffered by the calcium salt and therefore far less aggressive on equipment and on the feed pellet.
How it is made
The dominant industrial route is direct neutralisation: formic acid is charged to a reactor and neutralised with calcium hydroxide or calcium carbonate, then the solution is filtered, concentrated and crystallised, and the crystals are centrifuged and dried to the 0.5% moisture limit. The cleaner the neutralisation, the lower the residual carbonate – which is what shows up as a low calcium titration or as effervescence when an acid is added to the sample.
A second route – sodium formate plus calcium chloride metathesis – also produces calcium formate, but it carries a chloride residue that must be washed out before the material can be sold into reinforced concrete. That is why a credible concrete-grade supplier will state the chloride route explicitly rather than just claiming “chloride-free”.
Where each grade is used
| Grade | Applications |
|---|---|
| Concrete accelerator | Set accelerator in ready-mix, precast, shotcrete and repair mortars; accelerator in tile adhesives and self-levelling compounds; used where an accelerator is needed but chlorides are forbidden because of embedded steel |
| Feed additive | Buffered acidifier in piglet, poultry and aqua feed; acidifier in silage and in drinking-water lines; calcium source in mineral premixes |
| Industrial | Leather deliming and bating auxiliaries; drilling and workover fluids; dry-mix mortar and grout packages; intermediate in formate and oxalate chemistry; de-icing blends |
Why the concrete market pays for calcium formate rather than calcium chloride
Calcium chloride is the cheaper accelerator and it works faster, but the chloride ion migrates to the steel and initiates pitting corrosion once the passivating layer breaks down. Calcium formate accelerates the hydration of tricalcium silicate by supplying calcium ions and a weakly acidic anion that raises the early heat of hydration, without introducing chloride. For reinforced and prestressed elements, in repair mortars over existing rebar, and in specifications that cap acid-soluble chloride, this is the difference between an admissible admixture and a rejected one.
The trade-off is dose and cost. Calcium formate is used at higher addition levels than calcium chloride to reach the same early strength, so the purchasing decision is really a cost-per-unit-strength calculation against a chloride limit – not a straight price comparison per tonne.
Packaging, storage and documentation
| Item | Detail |
|---|---|
| Packaging | 25 kg net bags (paper with PE liner, or woven PP for industrial grade), 1000 kg jumbo bags, 25 kg fibre drums for feed grade |
| Storage | Dry, sealed, below 30 deg C. The material is hygroscopic – opened bags should be resealed, and stacks should not sit directly on a concrete floor |
| Documentation | Batch COA (assay, calcium, moisture, arsenic, particle size); SDS; for feed grade a feed-additive registration statement and GMP+ or FAMI-QS certification where applicable; for concrete grade a chloride declaration |
| Regulatory | Feed use: authorised as a feed additive in the EU (E238) and listed in national feed-additive catalogues; concrete use: assess against the chloride and alkali limits of the relevant admixture standard in your market |
Related products: sodium gluconate (CAS 527-07-1) as a set retarder and water-reducing aid, calcium chloride 94% (CAS 10043-52-4) for the chloride-based comparison, and calcium chloride 74% flakes (CAS 10035-04-8).
Contact PolyBlueChem for a current COA for any of the three grades, a 1 kg sample for trial pours or premix work, and pricing on 25 kg and jumbo-bag quantities.
