Cement, which is part of the concrete mix, does not have any natural bonding agent. In many cases, freshly poured concrete will not bond to the other material, but will separate. For weight-bearing surfaces, such as floors and foundations, this problem means the lack of a solid structure. A bonding agent (bonding adhesive) must first be painted over existing concrete to ensure that fresh concrete adheres successfully. Portland cement is not a bonding agent and does not help to create strong concrete.
For this, you need to use other means, such as a chemical binding agent. When gluing wet concrete with dry concrete, it is essential to use an adhesive agent. None of the ingredients in the concrete mix have any natural binding capacity. To bond wet concrete to dry concrete, you must first use a chemical binding agent. Do you remember the elementary school where one of the subjects you were graded in was “play well with others? The concrete would have obtained an F.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. When using a liquid bonding agent, paint the adhesive over existing concrete and allow it to dry until it is sticky. When you pour wet concrete onto dry concrete, it will dry out as an independent layer, but it will not stick. Cover the patch with plastic sheeting as it dries and finish by spraying water on the new concrete for 4 to 7 days. If an existing concrete surface has laitance (a dusty layer of cement and fine aggregates) or has been contaminated with spills such as oil or grease, the bonding agent will not work well. There are a variety of Sakrete concrete repair products available to repair concrete that has begun to deteriorate. However, if there are unresolved problems with your old concrete, including piles of frost and cracks, they can be moved to new concrete. If you need to patch a concrete surface or pour new concrete over old concrete, you should invest in a strong adhesive agent and a concrete patch mixture.
The two pieces of concrete will not make a perfect bond; however, following the instructions correctly and using a suitable bonding agent will make your concrete strong and sufficiently adhered.