Slab & Concrete
It is very normal to be experiencing ongoing minor expansion and shrinkage cracking, as a consequence of environmental changes and from settlement and stabilization of the home. Slab cracking is one of the characteristics of concrete as it shrinks while curing. The cracking is almost inevitable and does not represent failure. Because this cracking appears it does not mean they are necessarily affecting the structural integrity of your home.
These seam like indentations are installed with the intention that the cracks will appear within the joint themselves. You will normally notice these installed in garage or carport floor surfaces. Therefore should cracking be present within the control joint be assured this is quite a normal occurrence. Please note that cracking may also occur out of the control joint & this does not necessarily represent failure either.
Cracking within a control joint