Sandblasting Concrete: A Guide to CMUs

Sandblasting is a fast and reliable way to remove paint and signs of weathering on concrete, and recondition its surface. Unfortunately, while it is tempting to DIY, concrete sandblasting is not something that property owners find easy to do.

Here in this article, you’ll learn the essential bits of information about sandblasting, particularly CMU sandblasting. Let’s get right to it as we improve your knowledge about this excellent surface preparation method.

CMU sandblasting overview

brick_wall_sandblastingConcrete Masonry Unit or CMU sandblasting requires knowledge and experience. So, it is best to hire a reliable sandblasting company to do the job. But, choose those who did well on their previous projects.

Concrete sandblasting is usually noisy and messy. Therefore, the sandblasting equipment operator wears protective gear to avoid inhaling debris and getting abrasive particles in their eyes.

If you are sandblasting CMU blocks around windows, you must carry out extensive preparation. Also, clean up the mess after the task. It will help you avoid contaminating the sewers or ground.

What is a CMU block?

Before we discuss how CMU sandblasting is done, allow us first to discuss what a CMU block is. This concrete block is a building material that is safe for the environment as it is made from:

  • Water
  • Portland cement
  • Aggregates like grave, sand, bottom ash, fly ash

Some CMU blocks also contain recycled materials like recycled glass or slag cement. While the integrity of the blocks is not affected by mixing these materials, they can slightly change the overall look of the CMU.

For decades, CMU blocks have been an essential component of masonry structures. They have several advantages over other materials, such as:

  • Fire resistance
  • High durability
  • Easy maintenance
  • Easy installation

Why choose sandblasting concrete over pressure wash?

concrete SandblastingPressure washing might also be effective in cleaning surfaces. But, sandblasting provides a better result for concrete. It can remove paint on concrete, grime, dirt, and other hard-to-remove surface contaminants. These are possible because it has a harder contact approach than pressure washing. In concrete sandblasting, tiny sand particles are blasted into a surface under high air pressure to eliminate a thin layer of the surface being worked on.

How to sandblast concrete

 1.   Clear your work area

When working on CMU sandblasting, you first need to clear your working area of stuff you don’t wish to be covered with debris. Then, cover them with 6 mil plastic sheeting or move them temporarily.

2.   Cover windows

Use 6 mil plastic to mask windows where the sandblaster is heading. Use two layers of polyethylene-coated cloth duct tape to secure the plastic to the window frame. Also, don’t use masking tape. This type of tape can come off and ruin the window while the sandblaster is nearby.

3.   Set up the sandblaster

Set up a sandblaster at the tip of the spray equipment that mixes the sandblasting media and water. It is known as “wet abrasive blasting.” This method is slower than dry blasting, but it prevents dust clouds from blowing about the neighborhood.

Having technical knowledge of sandblasting is essential for this part. It is best to hire an experienced sandblasting contractor if you do not have experience using a sandblaster.

4.   Choose abrasive medium

Choosing a suitable abrasive medium is vital to acquire the best result for a particular surface. After placing the medium on the tank, cover the valves on the machine.

5.   Get the compressor working

Switch the compressor on, then set the pressure to 40-50 psi. Make sure to position the nozzle 8-16 inches away from you while directing it at the concrete. Begin sandblasting by pressing the machine’s trigger.

6.   Sweep in a horizontal motion

Like spraying paint, spray on the concrete by sweeping the nozzle into a horizontal motion. The difference is that you have to speed up by half. Spray longer on hard to remove stains or areas where dirt is thick.

7.   Blow off the concrete’s surface

Finish cleaning the concrete by blowing off residues using compressed air. Afterward, collect the abrasive media using a wheelbarrow and store it away.


To conclude, aside from the noise and mess, it needs experience and knowledge to use the sandblasting equipment. Choosing the right type of abrasive medium and setting the right air pressure on the compressor are also important. Isn’t it best to assign the task to a professional sandblasting contractor?