Concrete Repair & Floor Prep

Prep methods

Shot blast, diamond grind, scarify, scabble

Profile range

CSP 1-5 per ICRI guidelines

Repairs

Spalls, joints, cracks, pits, transitions

Moisture

Testing per ASTM F2170 / F1869

Mechanical profile, not acid etching

Acid etching is a consumer shortcut. It roughens a surface unevenly, leaves salts behind if it is not neutralized and rinsed perfectly, and cannot open a slab that has been power troweled hard.

Shot blasting throws steel shot at the slab and recovers it in a closed loop, leaving a uniform, open profile with the dust captured. It is the standard for large areas.

Diamond grinding is used at edges, in confined areas, on coatings that need removal, and where a smoother profile is called for. Both methods are chosen against the ICRI concrete surface profile the coating manufacturer requires.

Fixing what the prep exposes

Blasting reveals things. Hairline cracks open up, pop-outs become visible, and areas of weak or laitance-heavy surface come off. That is the point: better to find it now than under a finished floor.

Spalls and pits are filled with a resin patching mortar compatible with the coating system. Moving cracks are treated differently from static ones; a static crack gets filled, while a working joint gets a flexible filler that can move without tearing the coating.

Control joints in traffic areas are filled with semi-rigid polyurea so forklift wheels roll across rather than hammering the joint edge.

Moisture: the failure nobody sees coming

Concrete on grade transmits water vapor. If the vapor drive is higher than the coating can handle, the coating blisters and releases, and it does so months after installation when everyone has moved on.

This is why relative humidity probes per ASTM F2170 or calcium chloride tests per ASTM F1869 are run before specifying, particularly on older slabs, slabs without a vapor barrier, and anything below grade.

Where readings are high, a moisture-tolerant primer or a full moisture mitigation membrane goes down first. It adds cost. It costs much less than replacing a failed floor.

Removing a floor that has already failed

Old, delaminating epoxy, glue-down tile mastic, carpet adhesive, thin-set and sealer all have to come off. Depending on the material and the area, that is shot blasting, grinding with PCD tooling, or scarifying.

Removal generates dust and noise, so it is contained, HEPA-collected and scheduled around occupancy. Silica exposure controls follow OSHA 1926.1153.

Once the slab is clean, it is reassessed. Sometimes the discovery is that the original failure was moisture or contamination rather than the coating itself, which changes what should be installed next.

What a proper preparation specification says

A preparation scope worth reading names the method, the target profile and how the result will be verified. Method means shot blasting, diamond grinding, scarifying or a combination. Profile means a specific ICRI concrete surface profile number rather than a description like roughened.

The required profile comes from the coating manufacturer and varies with the system. A thin coating generally calls for a lighter profile than a troweled mortar, and going too aggressive is as much a mistake as not going far enough, because an over-profiled slab consumes material and can telegraph through a thin system.

Verification is straightforward: ICRI produces reference coupons that let the achieved profile be compared directly against the specified one. Where a project matters, that check gets recorded before priming.

The scope should also state what happens to what preparation reveals. Spall repair, joint filling and crack treatment are usually priced provisionally, because the extent is genuinely unknown until the slab is opened up.

Documentation worth keeping

Preparation is invisible once a floor is finished, which is exactly why it should be recorded. Photographs of the blasted slab before priming, moisture test results with dates and locations, and the achieved profile compared against the specification form a short record that is worth having.

If a floor later fails, that record is what distinguishes a product problem from an application problem. Without it, the argument becomes one contractor's account against another's.

Keep the system data sheets and the batch information as well. Manufacturers can trace a product batch, and warranty claims routinely require it.

This documentation costs nothing to produce during the work and is effectively impossible to reconstruct afterwards.

Dust, silica and working in occupied buildings

Preparation is the phase that affects the rest of a building most, and controlling it is largely a matter of equipment and planning rather than luck.

Shot blasting is a closed-loop process. Steel shot is thrown at the slab, recovered magnetically and recirculated, with dust drawn off into a collector. Properly run, it produces remarkably little airborne dust, which is why it is the standard for work in occupied facilities.

Diamond grinding produces more dust and requires vacuum shrouds with HEPA filtration to control it. Respirable crystalline silica is a regulated exposure under OSHA 1926.1153, and the engineering controls that satisfy that standard also happen to be what keeps dust out of the rest of your building.

Containment is the second layer. Poly hoarding at the boundary of the work area, sealed penetrations and negative air pressure inside the zone mean that any dust that does escape the equipment stays where it was generated. Negative air is also what controls coating odour during application.

HVAC needs to be considered explicitly. Shared return air will distribute dust and vapour through a building regardless of how well the work area is sealed, so isolating the affected zone from the system is part of the setup.

None of this is expensive relative to the project, and all of it is far cheaper than cleaning dust out of a facility afterwards.

Choosing between removal methods

When an existing floor covering or coating has to come off, the method chosen affects the cost, the schedule and the condition of the slab underneath.

Shot blasting is fast on large open areas and leaves an even profile, which makes it the default for warehouse-scale work. It is less effective on soft, gummy materials such as some adhesives, where the shot tends to embed rather than fracture the coating.

Diamond grinding is more versatile. With the right tooling it handles adhesives, thin coatings and sealers, and it works in confined areas and along edges where a blaster cannot reach. It is slower per square foot and generates more dust, which means more dependence on vacuum collection.

For thick or tenacious materials, polycrystalline diamond tooling cuts aggressively and is the usual answer for heavy coating removal. Scarifying, which uses rotating cutters to fracture the surface, is used where a substantial thickness has to come off or where a slab needs opening up considerably.

Most real projects use a combination: blasting the open field, grinding the perimeter and detail areas, and switching tooling where the material changes. A quote that names only one method across a varied floor has probably not looked closely at what is there.

Whichever method is used, the slab is reassessed once it is clean, because removal frequently reveals the actual cause of the original failure.

Common questions