The minimum thickness for pouring concrete onto concrete is 1.5 inches. In most cases, I don't like pouring new concrete less than 2 inches thick. You can pour up to 1.5 inches over old concrete. Unbonded overlays often have a minimum thickness of 4 to 11 and are suitable for when the base slab has cracks and only serve as structural support of the base.
Cracks will show through a partially adhered or unbonded overlay; thicker overlaps will prevent cracking. Welded wire fabric or armor reinforcement will also hold the overlapping slab and prevent cracking. It is necessary for water to penetrate the old concrete before covering it with new concrete, so that the new one adheres to the old surface. And remember, if your new concrete pour is less than 3 inches thick, you'll want to BOND the new concrete to the old concrete with a bonding agent.
However, before you go out to pour a new layer of concrete on top of the existing layer, you will need to check the condition of the old slab. A concrete screed is a thin concrete cement-based product that is designed to be used for decorative purposes or to repair damage. I recommend pouring new concrete at least 3 inches thick and installing a bond breaker between the old slab and the new slab so that cracks don't transfer through the new concrete. Repaving existing concrete screed is a fantastic way to save money (and resources) instead of pouring a new layer of concrete.
If concrete comes into contact with the eyes, immediately wash them with clean water and consult a doctor. Adding more concrete to wet concrete could affect the mix by getting it too wet, which could cause cracking. You can do this if the concrete is healthy (solid) with small cracks, pits, scale, surface damage or just ugly. When you pour the new concrete on Weld Crete, you activate it and bond the new concrete to the old one.
The same principles above apply to pouring concrete over an existing concrete driveway or sidewalk. While you can pour concrete onto concrete, you'll need to use a bonding agent with new concrete because the cement inside the concrete doesn't have its own. Another way to ensure that a new concrete screed completely adheres to the old concrete surface is with reinforcing bars (reinforcing bars) or steel mesh. Similar to pouring a new layer on top of existing concrete, repaving old concrete will require cleaning and preparing the surface.
The doweled face of the old concrete is treated with a bonding material to facilitate the melting of old and new concrete.