When it comes to surface preparation of concrete floors, there a four key elements that should be top of mind:
Is it SOUND?
“Drumminess” is caused by inadequate adhesion to the steel reinforcement, there can be many other signs of ‘unsound’ concrete. A simple tap test with a hammer, or even dragging a chain over the over the surface can quickly reveal the dreaded drummy sound of delamination.
Is it CLEAN?
Abrasive blasting or grinding will not remove contamination, it may drive it in deeper. Instead, detergent washing and degreasing gives you a better chance of success and should be done BEFORE you abrade or blast.
Concrete cleaning fact:
Did you know that efflorescence is best removed with a stiff brush, and mildew is best killed and removed with a diluted bleach solution?
Is it DRY?
Moisture level measurement in concrete has recently become a contentious topic, although it’s fair to say there has been a move away from reliance on simple surface reading methods, like the Tramex style of devices that rely on electrical conductivity through any moisture that be on the surface to the more involved drill in probe type of relative humidity measurement device, with many manufacturers and specifiers now requiring the ASTM F2170 standard
The ASTM F2170 standard represents a fundamental change in how moisture is measured and to what degree of accuracy is to be obtained. ASTM recognizes that floor coverings often fail due to unsuitable concrete moisture levels beneath them or arising out of the concrete substrate.
This topic is complex and probably requires another blog entirely. That’s for another day.
Why PROFILE matters and how do you assess it
Anchor profile is the distance from peak to valley, or ‘roughness’ of the surface.
Anchor Profile is critical for a successful coating project. By providing more contact area for the coating to attach to and creating a more complex plane on which the coating can resist removal from, you greatly increase the adhesion of the coating to the substrate.
International Concrete Repair Institute or ICRI 310.2 provides an outline of assessing the ‘roughness’ of the prepared concrete substrate by means of a visual replication through rubber comparator chips. They range from CSP1 through to CSP 10 ( Concrete Surface Profile)
COMMON CONCRETE FLOORING PREPARATION METHODS
- Most common, but not always the best choice.
- Lower cost of equipment.
- Uses different grades and configurations of diamonds to grind the concrete surface
- Versatile and ideal for roll coat applications and up, it can also be used for polishing concrete.
- Relatively fast and efficient with big machines, but small machines are more popular due to their lower cost and ease of transport.
- Can achieve CSP 1, 2 and 3 or higher but commonly only results in CSP 1 or 2 when it should be higher.
2. Shot Blasting
- Generally faster and cleaner than grinding
- Generally leaves a greater surface profile on the substrate.
- Propels steel shots against the concrete and recirculates the steel shot after separating it magnetically from the concrete dust.
- Leaves track marks, which aren’t visible if it’s more than a roll coat system.
- Can achieve CSP 1 through to 9
3. Scarifiers, Scabblers, Water Jetting
Sometimes, you need to bring in the heavy hitters, especially if you are trying to remove previous coatings that are very thick or stubbornly adhering to the substrate.
- Scarifiers use rotating cutting wheels, which are usually very noisy and dusty usually, but are very effective
- Scabblers are air-powered pistons that smash the surface with great force, literally pounding the coating
- Waterjetting operates at 5,000-10,000 psi; extreme caution is required in their use, but they are extremely effective in the right hands of a specialised operator.
In essence, surface preparation is the single most important step to a successful coating application. Determining the proper method for surface preparation requires an understanding of the coating system to be applied and the condition of the existing surface to be coated.
Ascoat’s experience, equipment and expertise allows us to provide the best outcome on your next commercial and industrial flooring project.