Shot blasting and scarifying for concrete surface preparation

Shot blasting

A shot blaster throws small steel shot at the concrete. It removes laitance, weak surface paste, sealers and thin coatings, and leaves a clean, open texture. The shot and debris are drawn back into the machine, the shot is reused, and the dust goes to a connected dust collector.

Changing the shot size and travel speed changes the depth of the profile. That lets us reach the concrete surface profile (CSP) that a primer, coating or overlay calls for. Shot blasting is fast on large open floors, and its even texture suits thicker systems such as urethane cement and self-levelling toppings.

Scarifying

A scarifier, also called a milling machine, uses rows of rotating cutters that chip into the surface. It removes heavier material than a shot blaster, such as thick coatings, mastics, high spots and built-up layers. It is also used to take down trip edges at heaved slabs and uneven joints, and to cut a deeper profile for thick repairs and toppings. The finish is rough, so it is followed by a coating, overlay or topping.

When to choose these over diamond grinding

Diamond grinding is the right tool for edges, small rooms, thin coatings, polished concrete and floors that need flattening. Shot blasting is often faster on large open areas when an even profile is the goal. Scarifying is the choice for heavy removal. Many projects use both: a shot blaster or scarifier in the open floor and grinders at walls and corners.

One caution: on thin coatings, shot blast patterns can show through the finish. For thin or high-gloss systems, we usually grind instead.