Grinding stones are the consumable that decides how a concrete floor job goes. Put a coarse stone on a slab that only needs the trowel marks knocked down and you will spend the rest of the day chasing scratches. Put a fine stone on a slab with a real high spot and you will be there until dark. The C24 is the medium grit in the Edco range, and it is the stone most contractors reach for first, because it removes material at a usable rate without leaving a pattern that takes three more passes to clean up. This pack contains 24 stones.
Use Cases
- Knocking down trowel marks. The most common reason a stone goes on the machine at all - taking a poorly finished slab back to flat before coating or covering.
- Rain spots and surface defects. Pour that got caught by weather and set with a pocked face.
- Excess concrete and high spots. Anything under about 1/16 inch of proud material, including slab edges and joints that will catch a floor covering.
- Surface prep before coating. Opening up a slab so an epoxy, urethane or sealer bonds instead of peeling.
- Terrazzo and decorative work. Where a medium stone is the intermediate step between the coarse cut and the fine finish.
Where C24 sits in the grit range
Edco runs the stones from super coarse through super fine: C10S super coarse, C10 coarse, C24 medium, C80 fine and C120 super fine. Most work is a sequence rather than a single grit. Heavy removal starts coarse, and the passes step finer until the surface matches the specification. C24 is the workhorse in the middle. It is aggressive enough to take down trowel marks and rough finishes in a reasonable number of passes, and fine enough that the scratch pattern it leaves can be cleaned up by a single finer pass rather than two.
How fast material comes off
Edco publishes that its grinder will remove up to 1/16 inch of concrete at a rate of approximately 500 square feet per hour when running C10S super coarse stones. A medium C24 will remove less material per pass than that, since removal rate falls as the grit gets finer - use the published figure as a ceiling for the coarsest setup rather than as an expectation for this stone.
Rate on any given slab depends on things nobody controls from a catalog: the hardness of the surface, the size of the aggregate, the age of the slab, and any additives or sealers that have to be cut through to meet the surface specification. Adding weight to the grinder increases the grinding speed, which is the standard adjustment when a slab is harder than expected.
Getting the life out of a set
Stones wear as a set, so replace them as a set - mixing a fresh stone with worn ones puts the load on the new one and takes the machine off flat. Keep the head level and let the weight of the machine do the cutting rather than leaning on it, which glazes the stone rather than cutting. On a hard, dense slab, stones can glaze over and stop cutting; a short pass on a more abrasive area will usually open them back up. Buying 24 at a time is the practical way to run this, because a job that needs stones needs a full set and a spare set.
Specifications
- Manufacturer part number: 11024-24
- Brand: Edco
- Grit: C24, medium
- Pack quantity: 24 stones
- Application: Edco floor grinder accessory
- Materials worked: concrete and terrazzo
Frequently asked questions
Which grit should I start with?
If the slab has real high spots or heavy trowel marks, start coarse and step down. If it is reasonably flat and you are prepping for a coating, C24 medium is usually the first stone on the machine. Finish grits are C80 and C120.
How much concrete will these take off?
Edco publishes up to 1/16 inch of removal at roughly 500 square feet per hour with the coarsest C10S stones. A medium C24 removes less per pass. Hardness, aggregate size, slab age and any sealers present all change the number on your job.
Can I fit a few new stones alongside my old ones?
It is not recommended. Stones wear together, and a fresh stone in a worn set carries a disproportionate share of the load, cuts unevenly and wears out quickly. Change them as a set.
My stones stopped cutting - are they worn out?
Not necessarily. On hard, dense concrete stones can glaze over, which feels like the machine stopped working. Running over a more abrasive section usually reopens the face. If the stone is genuinely down to its usable limit, it needs replacing.
Will these work on terrazzo?
Yes. Grinding stones of this type are used on concrete and terrazzo. Match the grit to how much material you need to remove and to the finish the job specifies.
Discount Cleaning Products supplies Edco floor grinder accessories and consumables and supports the account from the United States. If you are not sure which grit sequence your slab needs, tell us what the surface looks like and what is going down on top of it and we will help you work it out.
