visual signs of weak concrete


Being able to pick the signs of a weak slab is not always easy. There are various mechanical means for testing the integrity concrete, like rebound hammer tests or tensile pull off adhesion tests, but you don't always have the ability to conduct these types of physical tests.

In this post, I want to share some photos to demonstrate a few quick and easy ways to pick if you're dealing with a weak slab.

In the first photo you'll see how easily a screwdriver was able to gouge the surface of this slab. If you're able to gouge the concrete as easily as this then it's a good sign you've got a weak slab.


In the second photo you'll note the weathering on one side of the roller door line compared to the other. In this case the house was less than 12 months old and to see this amount of deterioration is something that would set off a few alarm bells.




The third image shows a divot in the floor that has easily popped out down to the larger aggregate layer.


The fourth photo shows the rapid wear and tear of the floor directly outside the entrance. Even though it's only foot traffic in this case, the twisting of footwear was enough to cause significant damage.


The final photo shows a degraded area of a slab where the fine trowelled finish has quickly worn through and begun to pit the surface. The rate of deterioration is much quicker once you have loose aggregates and sand that tend to contribute to the grinding of the surface.


A special thanks to Tough Floors for sending me these great photos!

If you're asked to install a resin floor on a slab that's showing any of the signs of weakness above, take care to carefully analyse the concrete and determine the best way to prepare the slab and build some integrity back into the surface first.