Under ideal conditions of normal exposure or dry service, cracks with a width of less than 0.3 mm on the concrete surface do not pose any risk of corrosion of steel reinforcement. However, in highly aggressive or corrosive environments, the safety limit is considered to be 0.2 mm or less. When it comes to concrete, strength is measured in pounds per square inch (PSI). A concrete mix with a strength of 2000, 3000, 4000, or more than 5000 PSI indicates the amount of pressure it would take to crush the concrete slab.
When it comes to determining what is considered acceptable cracking in concrete, there are no set standards. However, Australia does have some standards when it comes to deciding whether cracks are due to defects or not. In general, cracks that are wider than a credit card and go through the depth of concrete are structural in nature and could be a sign of more serious problems. Proper site preparation, quality mixing and good concrete finishing practices can go a long way in minimizing the appearance of cracks and producing a more aesthetically pleasing concrete project.
Consult an engineer or concrete repair professional to determine the cause of the crack and recommend the best repair solution. In most cases when cracks appear in concrete, the crack can be identified and the cause of cracking established. This category covers the performance of concrete whose shape can no longer be altered without damage. It includes cracks caused by drying shrinkage, as well as those resulting from temperature movements that occur in all materials exposed to the elements.
Inclined cracks sometimes appear when coarse particles of aggregate near the surface form a skeleton in which the cement paste can settle and separate. Vibration and revibration will reduce or prevent cracking. After heavy rain or melting snow when the ground below is soft and damp, excessive weight on the slab can press the concrete down and cause cracking.