Read the scale from acid etch to breaker
ICRI Guideline 310.2R-2013 shows ten rubber chips, and the chips have been the industry reference since 1997. CSP 1 is an acid etch and CSP 2 is grinding. CSP 3 is a light shotblast, CSP 5 a medium one and CSP 7 a heavy one, with scarifying at CSP 4, 6 and 9. A surface retarder gives CSP 8, and a breaker with abrasive blasting sits at CSP 10.
Look at that list twice. Abrasive blasting shows up at the heavy end of the scale. It shows up again at the top, so the method name alone tells you little, and a crew's promise to blast says nothing about the surface you will get. A crew that promises to sandblast your slab has not promised a CSP number. I'd write the number into the quote.
Match the number to the film thickness
Coating makers usually measure the roughness they need in CSP terms, according to CIM Industries. Their rule of thumb pairs thick epoxy films of 4 to 10 mils with CSP 3, and it pairs overlays thicker than half an inch with CSP 8 or 9. Those are rules of thumb, so the data sheet wins. A trade article in CoatingsPro adds that the right roughness also depends on the concrete's strength, the coating's internal stress and the temperature swings the floor will see.
Say a garage gets a 10-mil epoxy. On that rule it needs about CSP 3, which the ICRI list ties to a light shotblast. A heavy blast to CSP 7 delivers more roughness than that film can use, and the extra work lands on your invoice. I'd treat a profile far rougher than the spec as a cost, not a bonus. concrete surface preparation for a thin film is a game of restraint, and restraint is cheaper than a heavy blast.
Compare the extremes in millimeters
The chips look alike in photos, yet the gap is large. PCTE, a chip distributor, lists CSP 1 and CSP 2 at about 6 mils of depth, roughly 0.15 millimeter. DeFelsko describes CSP 10 as very rough, with amplitude above a quarter inch, which is 6 millimeters, and that puts the top of the scale about 40 times deeper than the bottom.
A thin sealer on a CSP 10 surface would leave peaks poking through. A thick overlay on a CSP 2 surface would have nothing to grip. Either error is a roughness error. No amount of cleaning fixes it afterward, and the redo bill lands on the owner.
Prove the profile with a chip
Inspectors compare the prepared slab with the chip that matches it. ASTM D7682 gives a replica-putty method for the same job, and the putty can be read by eye or measured at 10 spots, as an AMPP article explains. ASTM D8271 covers a depth micrometer for the lower chips.
I'd ask the contractor for a picture of the matching chip held beside the finished slab. Take it before the coating crew arrives. It costs a minute, and it ends the argument about what was promised. That record belongs in the file for your concrete surface preparation, next to the quote.
Works when the spec names a number. Breaks when the spec says only to blast to a rough finish, because nobody can fail a vague promise, and a vague promise is what most disputes start from. I'd insist on a number.
Remember that concrete surface preparation includes more than roughness
Profile is one item on a longer list. Garland says laitance, the fine powder left by alkaline salts on new concrete, has to come off before coating, and so do curing compounds and sealers. New slabs also need time. A Kansas study notes that coating makers recommend at least 28 days of drying, and Garland says moisture can linger well beyond that. I'd check both before paying for any blasting, and I'd have the profile checked at three or four spots across the slab.
The expensive mistake, in my view, is hiring on the word sandblast. You get a rough slab, an undefined roughness and a coating warranty that blames the prep. A single quoted number turns the work into something you can inspect, and an inspected job is cheaper than a redone one.
Put the number in writing
BlastTechs runs mobile abrasive blasting for concrete, metal, wood and pool surfaces around Albuquerque, including Rio Rancho and Los Lunas, and north toward Santa Fe. Send your coating's data sheet and the target CSP number through its services page before booking. Then ask for the chip picture when the work is done, and keep it with your concrete surface preparation paperwork. I'd call before the first pass, not after the last.
Frequently Asked Questions
Q: What CSP do I need for a garage floor epoxy? A: A 4 to 10 mil epoxy film usually calls for CSP 3, according to CIM Industries. Your coating's data sheet overrules that rule of thumb, so read it first and write its number into the quote.
Q: Is sandblasting concrete the same as shotblasting? A: No. Shotblasting hurls steel shot from a machine across the slab, while abrasive blasting drives grit through a hose. ICRI lists both, at different CSP numbers, so ask for the number and not the name.
Q: How rough is CSP 10 compared with CSP 1? A: CSP 10 runs above 6 mm in amplitude, while CSP 1 sits near 0.15 mm. That is roughly 40 times deeper, which is why the wrong number ruins a thin coating.
Q: How can I check the profile after the work? A: Hold ICRI chips against the slab and pick the closest match, or ask for a putty replica read under ASTM D7682. A dated image next to the slab is the cheapest record.