Sandblasting, also known as abrasive blasting, directs highly pressurized air and an abrasive material, such as sand, glass or plastic, onto concrete or another hard surface to clean or roughen it.

It’s a convenient, effective way to strip concrete of paint, adhesive or dirt, sometimes in order to prepare it for new paint or other coatings, including new layers of concrete. It can be used to lightly clean concrete or to cut more deeply into it for non-slip applications or an exposed aggregate finish. It can produce unique textures or patterns or an effective bond for coatings.

Sandblasting is commonly used on parking garages, patios, sidewalks, driveways, roads and bridges.

Benefits of sandblasting include:

• It removes any weak surface layers and opens surface voids, air pockets and other flaws to produce a clean, strong substrate.
• It removes tough stains, layers of paint and even slags of welded materials.
• It’s effective for cleaning or texturizing corners and tight spots.

A related and more aggressive process for heavy-duty surface preparation jobs is shot blasting. A shot blaster propels metal balls contained in a closed chamber of the machine against the surface. A 10-inch ride-on shot blaster can make quick work of open surface areas. For confined spaces, a fume-free electric shot blaster is ideal.

Recommended materials and tools

• Abrasive blaster
• Air compressor
• Abrasive medium
• Dust-collector accessory (optional)
• Dust mask or respirator
• Drop cloths or plastic sheeting
• GFCI or appropriate extension cord
• Wet/dry vacuum
• Knee pads
• Face shield or safety goggles
• Steel-toed boots
• Ear protection
• Gloves

After assembling your tools and materials, follow these steps for the best results.

Choose the right abrasive

Match the abrasive you use to the surface you’re working on and the outcome you want. Use the finest abrasive possible to achieve the desired results. Silica sand or glass beads are often used to remove dirt, grease and paint from concrete. Denser or harder abrasives can achieve a deeper cut. Shape matters, too. Rounder particles cut less deeply than angular media.

Some commonly used abrasives include:

• Silica sand
• Coal slag
• Garnet sand
• Nickel slag
• Copper slag
• Glass beads
• Steel shot
• Steel grit
• Iron ore
• Plastic grit
• Walnut sheet grit
• Baking soda

Observe safety practices

Abrasive blasting may expose workers to crystalline silica or other materials that can cause lung damage, as well as to hazardous levels of dust or toxic metals. Employers should read OSHA’s fact sheet on protecting workers from the hazards of abrasive blasting materials.

Use proper PPE, including safety goggles or face shield, knee pads, gloves, ear protection, steel-toed boots and a complete coverall. To protect your lungs from crystalline silica, wear a dust mask or respirator.

• Ensure the workspace has good ventilation.
• Remove objects that may become damaged and cover exposed areas with drop cloths or plastic sheeting.
• Don’t eat or drink in the blasting area.
• Don’t blast on a windy day.

Use proper technique

1. Start with a small, inconspicuous area to test the results before blasting the entire surface.
2. Set the machine to a lower pressure.
3. Position the nozzle 8 to 16 inches from the body and point the nozzle at the surface. Maintain the same distance from the surface throughout the job for uniform penetration.
4. Increase the pressure setting as needed after a few passes.
5. Use short bursts for corners and tight areas.
6. Use a HEPA filtered vacuum to remove dust and debris or perform cleanup using wet methods.

Browse United Rentals’ full lineup of concrete grinders, planers and abrasive blasters.