When that water eventually leaves the slab it leaves behind large voids between the solid particles.
Shrinkage cracks in concrete slab.
Concrete slab drying shrinkage cracking can be the unfortunate end.
Concrete and mortar are porous in their structure in the form of inter molecular space.
Some contractors cut or form a grid of small grooves in the slab to keep the shrinkage cracks in an orderly grid which looks better than random cracks but functions the same way.
As the concrete slab dries after placement it shrinks.
Most of the water will eventually evaporate causing shrinkage of the concrete slab.
Plastic shrinkage concrete cracks when concrete is still in its plastic state before hardening it is full of water.
Most of this excess water begins to exit the concrete during placement curing and causes the concrete to shrink.
When the evaporation of the moisture at the surface of concrete is more than the availability of the rising bleed to fill the surface moisture if this process happens before concrete attaining its tensile strength the volume change may cause cracks.
They expand when they absorb the moisture and shrink when they dry.
Shrinkage cracks in concrete occur due to change in moisture of concrete.
In addition to reading about repairing concrete shrinkage cracks if crack repair is needed at all.
This restraint creates tensile stresses in the concrete slab which in turn may produce drying shrinkage cracking.
These cracks are comparatively short cracks.
See details at concrete shrinkage cracks.
Shrinkage cracking can be managed by the use of control joints placed in the slab.
This is the main cause of concrete shrinkage cracks on drying.
When concrete is mixed more water than is needed for hydration is mixed with the dry components such as sand cement and an aggregate.
Shrinkage cracks in a slab photo above are unlikely to be of any structural concern but can be a source of water entry or radon entry in buildings and may form a tripping hazard.
Similar uncontrolled or random cracks sometimes due to poor joint layout meander across the surface.
While the concrete is shrinking many things such as reinforcement or the subgrade restrain the concrete.
