What is Concrete?
We like to think of concrete as being “hard as a rock.” And that’s mostly true, except that concrete isn’t just rock. Concrete is a fairly complicated mixture of rock (aggregate), sand, cement, water, and air.
For the most part, the “recipe” for fresh concrete is roughly like this:
■ 6% Air
■ 11% Portland Cement
■ 16% Water
■ 26% Sand (Fine Aggregate)
■ 41% Gravel/Stone (Coarse Aggregate)
Depending on where the concrete is and its intended use, the mixture used can vary greatly. In many cases, steel reinforcing rods (rebar) is placed inside the concrete to strengthen the slab.
So, what can go wrong?
Most commonly, we see:
- Freeze-thaw damage:
- Scaling: A general loss of surface mortar or mortar surrounding the coarse aggregate particles on a concrete.
- Spalling: Concrete which has broken up, flaked, or become pitted. A breakdown of concrete into small pebble-like pieces, resulting in discoloration, pitting and rough surfaces.
- Aggregate pop-outs: Pebbles and small stones loosen from the concrete.
- Delamination: Separation of the top surface of concrete from the subsurface.
- Corrosion of reinforcing rods, sometimes visible by rust-colored staining on the concrete surface. (This is a serious problem and must be dealt with immediately.)
- Efflorescence: Salt and mineral deposits that appear on the surface as white or discolored grains.
These and other concrete problems vary greatly in their causes and repair options. In many cases, the repairs are simply cosmetic. In more severe situations, repairs or replacement of faulty areas are required to prevent catastrophic damage.
3 Kinds of Concrete Surface Repair:
- Full-depth repair, in which the affected section of concrete is removed and replaced.
- Partial-depth repair, in which the affected areas are removed to a “safe depth” and replacing the area with repair mortars.
- Overlays, in which the top surface is ground, cleaned, prepared and replaced with a thin repair material, restoring the floor to a smooth, even surface.
Regardless of the kind of repair needed, a floor audit by The MJA Company will determine the best solution for your floor. The MJA Company’s floor audit is prepared by one of our floor specialists and will present the best options for repairing the floor, the time to repair, and an accurate estimate of costs.
- Concrete Slab Surface Defects: Causes, Prevention, Repair | Portland Cement Ass’n.
- How to Repair a Scaled Surface | Concrete Construction
- Scaled or Spalled Concrete Repair | Chris Sullivan
- Concrete / Aggregate Pop-outs | Concrete Construction
- Corrosion of Embedded Metals | Portland Cement Ass’n.
- Efflorescence and Carbonation | L&M Construction Chemicals