Yes, you can put new concrete on top of old concrete, provided there are no problems such as significant cracks or frost elevations with existing concrete. A new layer of concrete should measure approximately two inches to ensure even and strong coverage. The simple answer is YES, you can pour new concrete over existing concrete. Unbonded overlays often have a minimum thickness of 4 to 11 and are suitable for when the base slab has cracks and will only serve as a structural base support.
Cracks will show through partially adhered or unbonded layer; thicker overlays will prevent cracking. The reinforcement of armor or welded wire cloth will also hold the facing slab and prevent it from cracking. You can pour a new layer of concrete onto an existing concrete surface. You may want to upgrade or expand a surface, or repair minor problems such as cracks, chips, nicks, or surface discoloration.
Adding a new layer over the old one can save time, money and resources. Hopefully, you will better understand how to pour concrete over old concrete. You can add new concrete to an existing concrete slab if the old concrete is in good condition. You will need to thoroughly clean the old concrete surface and use a suitable concrete bonding agent before pouring the new concrete to meet all structural requirements.
Unfortunately, there are some disadvantages to pouring new concrete over old concrete. A big problem would be that it can reduce the useful life of the area. For example, a new concrete building on a new gravel base will ensure that the structure is robust and can last up to 40 years. However, if old concrete is not in good condition, it will significantly reduce the life of your floors over time.
The fluctuation of temperatures will cause the concrete to rise, which will cause cracks and separations. Finally, if you are going to add any texture with tools or a broom, dye or stamp, you will need to do so before the concrete sets completely or add a curing compound to form a protective layer on the surface. It is advisable to repair them as soon as they appear to prevent them from spreading or letting too much water into the concrete. You can find several commercial adhesive agents that you can apply to your existing concrete with a rag or brush before pouring the new layer of concrete.
That said, you should know what you are doing before dealing with new concrete that joins existing concrete. A fully bonded coating (BCO - bonded concrete coating) is placed on an existing textured concrete surface and forms a bond, adhering the two layers of concrete together. Problems such as cracking, discoloration, frost, deterioration (crumbling), or a slab that sits at different uneven levels cannot be solved by pouring a new concrete slab on top. You will need coarse-grained aggregate concrete if you intend to make a coarse-grained slab and fine sand or crushed stone for minor floor repairs.
You may need to ask some helpers for help with the process of laying the new concrete and its stamping. Pouring the old concrete instead of having to do a demo and remove it, ended up saving the customer hundreds of dollars. If you are able to pour new concrete over old concrete, you probably want to know the risks you would take in doing so. You can pour new concrete over existing slabs in the case of floor slabs, provided you do it correctly.
More on this later. New concrete will likely shrink at a different rate than existing concrete if mix designs are not carefully blended. When pouring concrete onto concrete, if the new concrete is less than 3 inches thick, it is best to bond the new concrete to the old concrete. But if you're building a small part of your yard or just want to try DIY construction, this is the process you need to follow for a solid and reliable bond between old and new concrete.
Pouring concrete onto old concrete instead of directly onto a new gravel base limits your ability to maximize slab life. . .