Concrete

Grind, Shot Blast or Scarify? Choosing a Prep Method

Diamond grinding, shot blasting and scarifying compared: the surface profile each produces, what each removes, and how to pick one for the job.

Updated · 2 min read

Pick the prep method from the profile you need and what's on the slab. The flooring, patch or coating manufacturer tells you the required concrete surface profile (CSP). The method that reaches it most efficiently, with the least collateral damage, is the right one.

Silica

Grinding, blasting and scarifying concrete release respirable crystalline silica. Follow the controls in OSHA 1926.1153 Table 1 or measure exposures.[3] See Silica dust and respiratory safety.

Quick answer

Each method has a job it does best.

  • Grinding for smooth-to-light profiles, removing thin coatings and adhesive, and flattening high spots. It's the default for flooring prep.
  • Shot blasting for fast, uniform profiles on large open slabs, especially before thicker coatings and toppings.
  • Scarifying for heavy removal: thick coatings, toppings, and deep profiles.

Side-by-side

Here's how the three main methods compare.

Diamond grinding Shot blasting Scarifying
Typical CSP 1 to 3 3 to 7 (the 2013 ICRI guideline lists 2 to 9 depending on setup[1]) 6 to 9
Best at Adhesive and thin coating removal, flattening, light profile Uniform profile on big open areas; removes laitance and thin coatings Thick coatings, toppings, deep texture
Flattens the floor? Yes, can take down highs No, follows the surface No, and leaves grooves
Edges Hand grinder with shroud Needs a grinder at walls Needs a grinder at walls
Debris Fine dust to a collector Dust to a collector; shot is recycled Chips plus dust

CSP ranges are based on ICRI 310.2.[1][2]

How to choose

Work through these steps before you pick a method.

  1. Get the required CSP. It's in the installation instructions for the patch, SLU, adhesive or coating. See ICRI CSP profiles explained.
  2. Identify what's on the slab. Adhesive, thinset, paint, epoxy, curing compound or sealer all change the answer. Test old adhesive for asbestos first: Cutback adhesive and asbestos ID.
  3. Check flatness. If you also need to take down high spots, grinding does both jobs.
  4. Size the job. Shot blasters and big planetary grinders pay off on open floors. Small rooms and corridors favor smaller grinders and floor machines with diamond attachments.
  5. Plan dust and debris. Every method needs a collector matched to the machine.

Common mistakes

Prep problems usually come from overdoing the profile or picking a method that doesn't fix the real issue.

  • Over-profiling for a thin system. Too rough a surface telegraphs through thin coatings and uses more patch and primer.
  • Blasting over flatness problems. A shot blaster profiles high spots; it doesn't remove them.
  • Forgetting the edges. Blasters and scarifiers leave a strip at walls, so budget hand-grinder time.
  • Grinding thick gummy coatings with metal bonds. Use PCD tooling first. See Diamond tooling.

Machines we carry

These are the grinders, blasters and scarifiers we carry.

References

  1. ICRI Concrete Repair Bulletin: ICRI 310.2R-2013 overview
  2. Sika: Surface preparation guide
  3. OSHA: Silica in construction

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