Layering new concrete over old isn t a durable option only when the materials used are of poor quality or if one skips the binding procedure.
How to concrete over old concrete.
As mentioned earlier concrete in itself doesn t have any binding properties to take the load of an additional new layer.
Smooth the surface using a two by four or float then add texture as desired using tools or a broom.
So if you pour new concrete over the old surface without preparing the one.
Brush the slurry over the damp concrete to form an even layer.
Pouring concrete over old concrete instead of directly over a new gravel foundation limits your ability to maximize the slab s lifespan.
For this to be feasible the contractor needs to pour at least 2 inches thick use smaller aggregate and incorporate reinforcement such as welded wire mesh or fiber mixed into the concrete.
This old concrete patio was a perfect candidate for pouring new concrete right.
Make sure all of the old concrete has a layer of slurry on top of it before you move on.
When i say bond the concrete you are lying on top off needs to be a rough finish like scabbled.
The form shall extend above existing concrete surface based on the designated thickness of the new concrete.
Before you add your new concrete take a large brush and dip it into the bonding slurry.
Get the old concrete slab completely wet making sure any cleaning chemicals you used get rinsed off in the process.
Pouring over old concrete need similar basic formworks that employed with fresh pours.
Make sure that the height of the formwork is even.
The old concrete was over 20 years old.
A well poured concrete slab with a deep sturdy foundation can last for 30 to 40 years.
Install the form usually wood form around the perimeter of old concrete surface.
Concrete is porous so it can absorb liquid.
The surface was badly worn and pitted but the slab was sound and there was ample height to pour a new slab right over the old one.
Dry up any water pooled over the concrete before continuing.
When pouring new mix over old concrete make the mixture stiffer than usual by adding less water.
If you are laying pouring concrete over existing concrete there needs to be a bond.
If done properly new concrete can often be poured right over an existing slab.
It was originally poured in multiple sections so it had some seams that looked like cracks.
Brush a thin layer of the slurry mixture onto the old concrete.
Keep spraying it until the moisture runs off the sides instead of being absorbed.