How can we prevent cracking, or at least keep it down to acceptable levels? Because of the many causes there is no simple or sure formula. We should attack all along the line, not merely at one point or on a single factor or against one selected member of the construction team. First of all, though, we need some standards of acceptability. The acceptability of a crack depends on what standard is to be applied and the circumstances of the concrete use. This article discusses several considerations, which include: visual tests, leakage, material collection, indicator of concrete deterioration, and tensile face of structural members. For example, if the crack causes water to come through a roof, wall, or floor that would otherwise be relatively watertight, the crack is usually objectionable.
One excellent way to prevent cracking is by using prestressed concrete. Cracking is a tensile phenomenon, and prestressing puts the concrete in compression. Thereafter, any contraction due to lowering of moisture or temperature, and any strain due to elastic loads, merely relieve part of the compression. Prestressing gives the designer control of cracking caused by applied load. Wall panels have been cast with light prestressing in both directions not at all because of structural requirements but to compress the concrete lightly and prevent cracks.