Concrete surface preparation succeeds when you specify the profile the coating needs, prove the slab is sound and dry, and stop blasting there. ICRI’s CSP scale runs from 1 to 10, abrasive blasting covers CSP 2 to 7, and a 4 to 10 mil epoxy calls for CSP 3. More profile is not better.
ICRI Guideline 310.2R describes surface preparation as the work that leaves concrete sound, clean and roughened to suit the product, with oil, dirt, old paint, films and laitance removed. It grades roughness with ten Concrete Surface Profile chips, from CSP 1, nearly flat, to CSP 10, rougher than a quarter inch. A quote that says only sandblast tells you nothing about which chip you will get.
For concrete surface preparation I’d write the target as a number in the contract, CSP 3 for example, and let the method follow. Inspectors compare the finished slab with the same chips, so one number serves both sides.
A coatings contractor’s guide lists thick films such as 4 to 10 mil epoxies at CSP 3 and concrete overlays thicker than half an inch at CSP 8 or 9. A Sika epoxy data sheet asks for CSP 3 to 4 by shot blasting or equivalent. Thin films need less profile, and thick overlays need more to key into.
A repair mortar wants more, since Sika’s sheet for one asks for an exposed-aggregate profile of at least one eighth inch, equal to CSP 6 to 7. I’d confirm with the product’s own data sheet, since manufacturers differ.
A Graco guide says abrasive blasting spans CSP 2 to 7 and, unlike many methods, works on vertical and overhead surfaces. It recommends vapor abrasive blasting for removing laitance and efflorescence and for gently abrading delicate surfaces. That explains why blasting suits walls, pool shells and tight corners.
BlastTechs says its pool work strips old coatings, plaster, mineral scale and stains ahead of resurfacing, and its mobile service covers Albuquerque, Santa Fe, Rio Rancho and Los Lunas. For a pool shell or a patio, ask which CSP the crew will aim for and how it will confirm it.
Sika’s primer instructions warn that over-blasting reduces the coverage rate of the primer and topcoats. They also warn that a shot-blast pattern can show through the last coat, a defect they call tracking. The goal is uniform texture at the specified CSP.
Measure what you made, since ASTM D8271 uses a depth micrometer, ASTM D7682 uses replica tape or putty, and the CSP chips give a visual match. Pick one method before the job and use it everywhere.
A USG technical answer says concrete that looks strong may still carry laitance, a weak layer that can be visible or invisible, and that anything weak at the surface has to be removed by mechanical means. It also says tensile strength should be assessed in the surface’s existing state. Appearance proves little.
In concrete surface preparation, ASTM C1583 measures tensile strength near the prepared surface by direct pull-off, and its abstract calls the result an indicator of how adequate the preparation was. Tremco’s bulletin pairs 4,000 psi concrete with CSP 3 to 4 and uses a pull-off test with its primer to expose hidden laitance.
Tnemec’s guide describes three tests, an 18-inch plastic sheet taped down for at least 24 hours, a calcium chloride test under ASTM F1869 and in-situ probes under ASTM F2170. Its rule of thumb for most floor primers is 3 pounds per 1,000 square feet per day or 75 to 80 percent RH. Your coating’s data sheet sets the real limit.
Waiting 28 days does not guarantee dryness, according to a roofing trade article that found no known correlation between the two. A flooring-trade case showed RH readings well above 75 percent while calcium chloride results sat near the 3-pound limit, because a sealed surface slows vapor.
OSHA’s construction silica standard, 29 CFR 1926.1153, sets a permissible exposure limit of 50 micrograms per cubic meter as an 8-hour average and an action level of 25. Abrasive blasting jobs must also comply with 29 CFR 1926.57, the ventilation rule. Concrete contains silica, so the dust from blasting it counts.
A manufacturer’s OSHA summary adds that dry sweeping of silica dust is not allowed, so cleanup needs wet sweeping or a HEPA vacuum. I’d ask any crew for its dust plan, covering enclosure, wet methods and cleanup, before the first pass.
Photograph the finished surface beside the CSP chip you specified. Record the moisture results, the pull-off readings and the date, then hand the sheet to whoever applies the coating. A coating failure two years later is far easier to resolve when the file shows what the concrete was at the start.
I’d keep the file for the life of the coating. It costs a page and may save a re-do.
Before you hire anyone for concrete surface preparation, ask for the target CSP, the moisture test and its result, the pull-off method and the dust plan in writing. In Albuquerque, Santa Fe, Rio Rancho or Los Lunas, BlastTechs offers mobile abrasive blasting, so ask for those four items with the quote.
Q: What CSP do I need for an epoxy floor coating?
A: A coatings contractor’s guide puts 4 to 10 mil epoxies at CSP 3, and manufacturer sheets often ask for CSP 3 to 4. Check the data sheet for your product and write that number into the contract.
Q: Can abrasive blasting prepare concrete?
A: Yes. A Graco guide says it covers CSP 2 to 7 and works on vertical and overhead surfaces, and it recommends vapor blasting for laitance and delicate surfaces.
Q: How long should new concrete cure before coating?
A: Manufacturers usually ask for 28 days, though some systems accept 14, according to AMPP. A roofing trade article found no known link between 28 days and dryness, so test moisture instead of counting days.
Q: Does blasting concrete create silica dust?
A: Yes. OSHA’s construction standard sets 50 micrograms per cubic meter as the 8-hour limit and expects abrasive blasting to also meet 29 CFR 1926.57. Ask the crew for its enclosure, wet-method and cleanup plan.
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