You can place new concrete on top of old concrete. However, unresolved issues with old concrete, such as cracks or frost, will carry over to new concrete if left unresolved. In addition, you should pour it at least 2 inches thick. The simple answer is YES, new concrete can be poured over existing 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. The new concrete will fill the pothole completely when cool, but will quickly shrink from the edges as it settles. When adding new concrete over old, dry concrete, the two will not bond together without a binder.
In Maine, where I have been working with concrete for 40 years, and this website is where I can share with you all the knowledge and wisdom I have gained from installing all types of decorative concrete, concrete floors, concrete siding, stained concrete and also fixing cracked or chipped concrete. Screeds are often used to improve the finish of existing concrete for aesthetic purposes or to prepare for other finishing operations. Slab poured onto an existing concrete slab is more prone to frost and crack damage due to the bond between the two layers of concrete. A bonding adhesive is used on the concrete to ensure that the new concrete adheres properly to the existing concrete.
I started this project by pressure washing old concrete to remove all mold, dirt and loose concrete. If necessary, you can end up spraying a curing compound immediately after pouring the topcoat to preserve moisture in the concrete. 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. Whether it's indoor floors or an outdoor concrete deck, concrete surfaces suffer from wear and tear and often need repairs and maintenance.
Although not the best option, adding a new layer of concrete over old concrete is still the next best option. Finish the work by priming the surface and pouring a mixture onto it, giving your concrete base a fresh new layer. Maintain your concrete steps by sweeping and hosing them regularly to remove debris that could wear down the surface of your steps. Your path can gain new life by adding a new layer of concrete on top, with no need to dig up the existing path and start from scratch.
I suggest pouring a minimum of 2 over the old concrete, so you should be able to accommodate the new slab height, whether it's a floor, patio, driveway, or walkway. You can pour new concrete over minor cracks or worn surfaces, but if it's more than that, it'll be worth investigating why the damage occurred and fixing the problem before adding a new layer.