Most cracks in concrete occur within 2-3 days of being laid. However, it takes a full month for the concrete to fully settle and for fine cracks to disappear. Shrinkage cracks can appear on the surface within hours of pouring the concrete, and this is often due to the freeze-thaw cycle of the ground. This ground movement can cause the concrete to crack if it cannot move freely with the ground.
Concrete provides structures with strength, rigidity, and resilience against deformation, but these characteristics can also lead to concrete structures that lack flexibility to move in response to environmental or volume changes. Cracking is often the first sign of distress in concrete, but deterioration may occur before any cracks appear. Cracking can occur in both hardened and fresh concrete due to volume changes and repeated loading. The most common reason for early cracking in concrete is plastic shrinkage.
When the concrete is still in its plastic state, it is filled with water which takes up space and makes the slab a certain size. As the tile loses moisture during curing, it becomes a little smaller and this shrinkage creates stress on the slab. The stress can become too great for the now-hardened concrete, causing it to crack and relieve stress. A construction joint is a break or space between two concrete slabs where two successive slabs are joined together in a structure.
Corrosion of reinforcing steel and other embedded metals is a major cause of premature aging, deterioration, and durability issues in concrete. Alkali-Silica Reactivity (ASR) is another durability problem that can cause premature deterioration of concrete structures. When choosing between pavers and a concrete slab, you'll need to consider your budget for both installation and long-term repairs. The expansion process of concrete can take 5-20 years before cracking eventually leads to failure of the structure.
Quick drying of the surface causes it to shrink and crack, so it's important to cover the concrete with an insulating plastic sheet or straw to trap moisture and help it cure at an even rate. Concrete is one of the most durable building materials out there, but it's important to appoint qualified corrective repair contractors to properly repair any cracks as soon as possible in order to extend its life. To minimize drying shrinkage, the total water content of the mix should be kept as low as possible for the intended application. Sealing the surface can also help control shrinkage, while properly spaced shrink joints and suitable steel details allow shrinkage to occur in a controlled manner.