Shot Blasting Pressure Calibration
Two pneumatic valves that look identical on a control panel can provide vastly different output velocities. The technical notes at epoxy floors allen tx vbittech publishes on this cover the mechanics of shot blasting for preparing a concrete slab in Allen, TX, where the epoxy bond depends entirely on a specific surface profile.
Calibrating Air Pressure for Impact Control
High pressure increases the velocity of the abrasive, but too much force causes spall on the concrete. You need to balance the PSI against the weight of the media. If the pressure is set too high, you will strip the aggregate out of the cement paste rather than cleaning the surface. If it is too low, the media will just bounce off the substrate without creating the necessary profile. Start at a low setting and increase the pressure in five PSI increments while observing the texture of the stone. This ensures the surface is ready for a primer without compromising the structural integrity of the slab.
Managing Media Flow Rates
The volume of shot or grit flowing through the nozzle determines the density of the impact. A heavy flow rate creates a deep profile, which is useful for high build systems like a thick quartz sand broadcast. However, a flow that is too heavy can lead to uneven coverage or "slugs" of media that clog the lines. You must adjust the metering valve to maintain a steady stream. A consistent flow prevents patches of smooth concrete that would later cause the polyurea or urethane layers to delaminate. Watch the hopper level to ensure the media is feeding at a constant rate throughout the entire area.
Matching Media to Substrate Strength
Not every floor in Allen, TX, requires the same intensity. An old, soft slab might require a lighter touch to prevent deep pitting. In these cases, using a smaller shot size with moderate pressure is better than using large grit at high velocity. If you are prepping for a metallic pigment finish, you need a very uniform profile. Too much aggression will create craters that ruin the aesthetic of the metallic pour. Test a small section first to see how the concrete reacts to the impact before moving to the main floor area.
Verifying the Surface Profile
After the shot blasting is complete, you must inspect the texture. The goal is a sandpaper-like feel that is consistent across every square inch. Check the joints and any area where you previously applied joint filler to ensure the blasting has integrated the repair with the surrounding concrete. If the profile is too shallow, the bond between the base coat and the slab will fail under heavy foot traffic. A mechanical profile is the only way to guarantee the longevity of the system.