If your concrete surface is sinking into the ground, more than likely your sub grade was prepared improperly. It is possible that loose dirt was used used and this will settle as a result of water erosion. It is also possible that the concrete may have been subjected to heavy weight, which caused the sinkage.
Slabjacking is an alternative method of to replacing the sunken floor. This sunken concrete repair could save you a lot of money. Slab jacking where a concrete repair professional drills small holes in the concrete surface, and pumps a mixture of sand, ash, and other materials into the soil below the surface. This process “floats” the floor back up to its proper level. The entire process may take a few hours and will probably be a lot less expensive than the cost of a full replacement.