Cracks in concrete slabs may be caused by various reasons, as we saw in the previous section. In some cases, the crack or cracks are cut across the slab and cause damage both in itself and in the substrates such as plaster and paint. The moisture penetrating through the crack is likely to erode the steel reinforcement (rebars) and to become a passage for air or industrial pollutants that cause carbonation and deterioration. The plastered and painted surface (usually white ceilings) on the bottom surface of the slab then shows moisture absorption and subsequent decay with a characteristic color (reddish or ochre) derived from the corroded steel reinforcement. If you encounter such a problem, the actions you should take are: Check the top of the concrete slab to identify possible cracking. If on the slab there is a layer of screed installed, it may be necessary to remove it and reinstall another one. If there is an extra layer with tile or some other lining material, ideally it should be removed and reinstalled (if desired) after dealing with and curing the problem completely. If this is not possible, at least after the repairs of the cracks are complete, make sure to waterproof the lining or the exposed slab, after first allowing enough time for the moisture trapped in the slab or its substrates to evaporate (the warm period of the year is ideal for such tasks). Strip and remove the deteriorated and weak parts of the slab and the area around the crack location. Open slightly with a cold chisel or another tool (small trowel) the crack along its length. Then check the bottom of the concrete slab (usually the ceiling beneath this floor). Remove the loosened or deteriorated plaster from the surface until the concrete slab is made visible. We identify the areas where the plaster has hollowed by knocking it slightly. The sound of hollowed plaster is different compared to a solid surface without serious damage. We identify this crack or cracks that have allowed moisture from the top to seep to the bottom, and after cleaning, we remove the deteriorated parts and slightly open the crack. Seal the entire length of the crack with the epoxy putty D-38 (p. 235). From the upper part of the slab, we inject into the crack liquid injectable epoxy resin D-33 (p. 235) CRACKS special subjects CRACKS IN CONCRETE SLAB CRACK THICKNESS MEASUREMENT RULER (in mm) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.4 1.6 1.8 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Cut here
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