Cracking can be the result of one or more factors, such as drying shrinkage, thermal contraction, sub grade settlement, and applied loads. Cracking cannot be prevented but it can be controlled.
Prepare sub grade properly, compact all loose soil underneath the concrete slab. Slope the sub grade for proper drainage. Design a flexible concrete pavement that can accommodate load and movements. Use the proper strength of concrete for the job with properly placed tension control joints. Do not overwork concrete surface. Avoid rapid drying conditions.
Surface scaling occurs when the concrete surface breaks off to a depth of 2 inches and keep spelling away. Causes for scaling vary and are dependent on surface strength, curing procedures, water seepage, air content and air entrainment. Concrete subjected to use of deicing salts combined with freeze-thaw conditions are prone to scaling. Chemicals such as ammonium nitrate and ammonium sulfate, which are components of most fertilizers, can cause scaling as well.
All factors have to be taken into account when designing a concrete mix in order to produce concrete with a workable slump. For best results concrete is finished at the right time, once all water has been evaporated. Cure concrete adequately without using salt or other chemicals durning winter. Don’t overwork the concrete surface. Avoid using a vibrating screed on high slump concrete.
When concrete develops several radio interconnected fine cracks, generally when the slab is damp the day after placement or within the first week. Crazing of concrete is caused by an overly wet mix and poor or inadequate curing and occurs when the cement paste comes up to the surface.
Use a moderate slump concrete without bleeding and segregation. Complete the finishing process when all water has evaporated, do not dust cement on the surface while water is present, and do not sprinkle water over the concrete while finishing it. Use a broom finish instead of using a steel towel. Cure concrete adequately so it can retain the necessary moisture for the hydration process.