CONCRETE: WHY DOES IT FAIL?

Posted by Tom Martino at 1:21 pm 48 Comments Print

So many times residential concrete fails! Why? There are three main reasons: The wrong material, the wrong installation or the wrong curing.

I recommend that you go to my Referral List to find the best when it comes to concrete contractors. However, I also believe you should know a little bit about the subject.

MATERIAL. You need the proper concrete mixture.
- WEIGHT – I recommend at least 4000 PSI (that means it will hold 4000 pounds per square inch – if installed properly).
- SLUMP – I also recommend no more than a 5-inch “slump”. That is a very specific measurement to see how much concrete settles (concrete is put into a cone shape, with the pointy side up. When the cone is removed you measure how far the concrete settles). NOTE: The wetter it is the more it will slump. Too much water is NOT good! But many contractors add water to make the concrete go farther or to make the finishing easier.
- THICKNESS – 4-inch minimum, 6-inches is better.
- REINFORCEMENT – The keep the concrete together you need proper reinforcement. There are three basic methods of reinforcement: Rebar, Fiber mesh or steel mesh.
  - Rebar are steel rods placed horizontally thru the concrete. If rebar is used there should be at lease 2-inches of concrete below it and 2-inches of concrete above it (in addition to the width of the rebar itself). Rebar must be installed on “stand-offs” to keep it off the ground. Rebard is necessary for all structural purposes like self supporting floors and bridges and self-supported walk-ways.
  - Fiber mesh is the easiest to work with. It is mixed into the concrete and is good for most general purpose residential installations – but it is not structural.
  - Steel mesh is the best all-around reinforcement. But it must be installed properly! It must be pulled up off the ground so it lies in the middle of the concrete.
INSTALLATION. Concrete must be worked properly. The reinforcement has to be placed properly (except for fiber) and the top coat needs to be “finished” properly. Avoid workers who add a lot of water to extend curing time and working time. It is a shortcut used by inexperienced concrete finishers.
CURING. If concrete cures too quickly there will be problems down the road. You also don’t want it to cure too slowly – for practical reasons. Curing can be assisted by chemicals, sprays and water.
EXPERIENCE. There is no substitute for experience! Count on the Referral List @ Referralist.com.