Shot Blasting vs. Grinding: Which Is Better for Coatings?
Unsure if you should use shot blasting or grinding for your next concrete project? Here’s everything you need to know.
Key Takeaways:
- Surface preparation is key to the success of any coating or overlay
- Grinding and shot blasting work best in different situations
- Your decision will depend on the job at hand
- Grinding creates a smoother surface, while shot blasting is rougher
Before coating any concrete surface, it’s crucial to ensure the surface is adequately prepared. This includes removing existing coatings, smoothing out imperfections, and creating a nice, even surface. Doing so ensures the new coating will adhere properly and last longer.
Shot blasting and grinding are two of the most common surface preparation techniques. But which one is better for your project? How do you determine which technique to use and when? This comprehensive guide will help you understand the difference between the two, so you can make the best decision for your next coating project.
What is shot blasting?
Shot blasting is a surface preparation technique that involves propelling small pieces of abrasive material (steel shot) at high speeds against a concrete surface. This blasts away existing coatings, dirt, debris, or other contaminants and crushes the top layer of concrete to create a rougher surface.
Abrasive materials used in shot blasters vary in size and style and can be made from steel, copper, or titanium. The size of the shot dictates the degree of surface roughening. The larger the metal abrasive, the more aggressive the shot blasting and the rougher the surface.
Shot blasters have dust containment systems to minimize the shot blast material and dust expelled into the air. After shot blasting, there will be minimal cleanup as most debris will be contained within the machine.
When shot blasting is recommended
Shot blasting isn’t ideal for every surface preparation project. Here are a few instances when shot blasting is the best option:
When a rougher surface is acceptable
Shot blasting is recommended when placing a thick coating or overlay on the concrete. The rougher surface will help the new coating or overlay adhere better. Without proper surface preparation, the new coating or overlay will easily crack, chip, or peel.
When removing thin glue or epoxy paint
Shot blasting is also a quick, efficient way to remove thin layers of glue or epoxy paint from concrete surfaces. As the steel shots hit the surface at high velocity, they dislodge the glue or paint, revealing the bare concrete beneath.
There are other instances when shot blasting can be used, but in most of those cases, grinding is the better option.
What is grinding?
Grinding uses a rotating abrasive wheel with diamond-tipped blades to remove inconsistencies, imperfections, or damaged concrete surfaces. Unlike shot blasting, which is more aggressive, grinding takes a slower, gentler approach. As the abrasive wheel turns, it grinds down the surface of the concrete to create a smooth, even finish ready for polishing, sealing, or coating.
The diamond blades have varying grit levels that dictate the degree of smoothing. A lower grit produces a matte finish, while a higher grit creates a glossy, high-sheen finish. Polished concrete is ground with progressively finer diamond abrasives until the desired level of shine and smoothness is achieved.
Grinding also creates high amounts of silica dust, which can be lethal if inhaled. It’s crucial to have a dust collection system before starting any grinding project. Wet and dry grinding are two common methods for controlling the amount of silica dust expelled into the air.
Wet grinding involves using a water hose to wet the concrete surface and prevent dust particles from becoming airborne. It also helps cool and lubricate the diamond blades. Dry grinding uses a specialized vacuum attachment to suck up the silica dust as it’s created. It’s faster and results in higher-quality polishing.
When grinding is recommended
Grinding is the best surface preparation technique when you’re looking for a smooth, consistent finish. Here are instances when grinding is your best option:
During concrete polishing
Concrete polishing is a popular finishing technique that creates a high-sheen, glossy look. It involves grinding the concrete surface with progressively finer diamond abrasives to remove imperfections until a smooth surface is revealed.
Polished concrete is durable, stain resistant, and easy to maintain, making it a popular choice for residential and commercial applications. Its high reflectivity also makes it an energy-efficient lighting option, as it brightens up a space with natural light, reducing the need for artificial lighting.
Removing rubbery coatings
Rubber coatings can be challenging to remove without damaging the concrete beneath. Grinding is the best way to remove this type of coating, as it won’t cause any damage to the concrete.
The abrasive action of the grinding wheel will slowly and efficiently grind away the rubber coating revealing the clean concrete surface below. Shot blasting is not recommended here, as the steel shots can chip or crack the concrete surface.
Applying thin film coatings
Thin film coatings like urethane or epoxy are designed to be applied to smooth, consistent surfaces. A rough, uneven surface interferes with the adhesion of the coating, resulting in an inferior finish that can fail prematurely. The pits, fractures, and ridges created by shot blasting can mar the aesthetic of the finished coating, as the imperfections will show through.
Grinding creates a smooth, consistent surface perfect for applying thin film coatings. The diamond blades smooth out imperfections on the concrete surface, leaving behind a clean surface ready for coating.
Ultimately, the best surface preparation technique for your project depends on the job. Grinding is the best option for a smooth, consistent finish that is perfect for polishing or applying thin film coatings. Shot blasting is best when you need a rougher surface for thick coatings or when removing thin glue or epoxy paint.
Find it all at Concreate
Whether you need shot blasting or grinding for your next project, Concreate has the surface preparation equipment and expertise to get the job done right. With a decade of experience in the concrete industry, we know what it takes to create a perfect finish that compliments your style.
Visit thisisconcrete.com to learn more about our shot blasting and grinding services, or contact us to speak with a surface preparation specialist. We will be happy to answer any questions and provide a free quote for your project.