I purchased a historic home that has the original concrete basement floors. However, recently the house was sinking and has since been deconstructed, raised and rebuilt on only on the necessary areas- the south/ south east corner. So less than half of the concrete basement is newer. My issue is the other part of the basement that is not new is cracked and if one were to "knock" on sections it would sound hollow. Also, close to the limestone foundation walls the concrete dips down about 2 or 3 inches. There are also large areas about 3 ft in diameter where spalling has occurred. My question is: Without removing the old concrete and entirely replacing it with new concrete what are some fixes that would resolve the issue? and perhaps slow further deterioration, level out the surface and get that awesome smoothed industrial look? I was thinking there might be a semi "flexible" concrete material that would stick to the original, but be strong enough to hold back deterioration and perhaps give a little. Please, if you have experience with this type of problem your solutions are welcomed! I tried to include photos, but not sure the best way to do this... I don't have a URL.