Concrete slabs that have moved because of age or improper placement can have areas of height inequality. The variation in height can cause trip hazards, excessive wear on rolling equipment, and be areas of premature concrete breakdown.
In severe cases, slab replacement may be necessary, but in most instances, moderate height inequalities can be flattened using a scarifier. Good examples of inequalities that should be corrected are: sidewalk joints, slab joints where settling may have occurred, and movement cracks. In all cases, the difference in height presents a problem for any floor treatment to be applied, for longevity of the product, and traffic safety.
A Scarifier Provides a Great Solution
A scarifier uses a drum style cutting assembly which impacts the concrete surface from a vertical angle. The same way a hammer could be swung down on a concrete surface, a scarifier does this with multiple cutters that have specialized tips to break the concrete into dust.
The damage done by a properly operated scarifier is superficial and should never undermine the structural slab’s integrity. The machine is meant to attack the high spots and barely disturb the low spots. Similar to planing down wood on a deck, the scarifier is meant to reduce the high spot to the low spot’s level. The result is a flat condition where the previously high spot now is similar or close to the height of the adjacent low spot.
The profile left by the scarifier can be varied but #4-#5 is the typical profile produced by the machine. In cases where the floor coating or covering needs a CSP of #2, as an example, then subsequent grinding would be needed to achieve that profile.
Operating the scarifier is fairly straightforward in that it runs at one speed and is moved manually or by self-propulsion. The depth of the cut is adjustable and controlled by the operator based upon the inequality that needs to be removed. Adjustment can be done by crank, spring handle, or hydraulic action.
Steps for Operating a Scarifier
Using the AIRTEC ES200 8-inch scarifier, as an example, the operation procedure is as follows:
- Adjust the drum to its non-cutting depth. This holds the drum above the floor and allows full rotation without actually impacting the floor.
- Depress the power button to start the motor.
- Walk forward as you adjust the drum depth using coarse or fine controls depending on the cutting depth required. The noise of the drum contacting the floor will be heard and the machine will begin to pull itself forward (away from the operator).
- Walk backward (opposite to the pull of the drum) maintaining a pace that allows the cutters to remove as much as possible without making rust or oddly placed gouges.
- Repeat the passes until the floor inequality is removed to the specified flatness.
- Return drum to its neutral position above the floor.
- Depress the stop button to stop the motor rotation.
The AIRTEC scarifier is relatively basic in its design but very effective to do the flattening work. Practice will help the operator to achieve a consistent profile and flatness that requires little work to reach the final spec.
Avoid Potential Problems with These Practical Tips
- One possible mistake is to run the machine in a stationary position while the drum is impacting the concrete. This will cause a rut or groove which will require repair since it would be a low spot (reverse inequality). Therefore, always keep the machine in motion — forward or backward — to avoid this.
- Another mistake is operating the machine in the direction the drum pulls the machine. Dust capture will be reduced and the machine will not attack the surface consistently. In this case, the operator should move the machine against the “pull” in order to get a proper cut.
- A final possible mistake is adjusting the drum too low which can cause the motor to overload or the machine to bounce across the concrete instead of planing it. Make sure the drum is only low enough to catch the tops of the higher areas.
In the case of small flattening needs, a single phase, 8-inch machine works fine for spot treatment. In the case of whole floor flattening, self-propelled, three-phase machinery is the more practical choice.
Final tip: with any concrete preparation activity, size and power directly affects the work’s productivity — the bigger a machine, the faster the work’s completion.