The durability of concrete means that structures built of it have long life spans, resisting weather, surviving hurricanes and earthquakes, fires, and the many other ravages of time. Concrete structures habitually endure long enough to eventually need refurbishing.
Structure evaluation to determine the extent of the deterioration should begin where the building started with the foundation. From there upward floor by floor, examine the slabs, the walls, the columns and the ceilings. Any cracks, stains, or wear patterns will tell a story about how the building was built and how it was used. Foundation walls frequently are cracked from settlement; there may be leakage through the cracks and/or the joints. The slab on grade may be cracked from heaving of the soil, improper joint construction or design as well as improper compaction. On the upper floors joints that are spalled may have filled with foreign matter. Intermittent cracks may be a reflection of overloading the slab. The cause of stains should also be determined whether from external or internal elements. Are they detrimental to the concrete? Should the stained area be removed?
Materials and methods for repair should offer a balance of needed properties at a reasonable cost. Formed concrete, sometimes of the preplaced aggregate type, is widely used where a great volume of material is to be replaced. If the area is large, but defects are not particularly deep, shotcrete may be the logical choice. Polymer concretes and mortars such as methyl methacrylate and epoxy concretes offer high strength and good bond to properly prepared surfaces. Proper surface preparation is absolutely essential to good bond, but it is equally important to be sure that volume changes of the repair are compatible with the surrounding concrete.