There are many reasons for damage to the screed – these can be external or internal impacts.
Changes in the soil can have a negative impact on screeds that are poured directly onto the soil base. Deformations are possible due to poor compaction of the base. The reason may be the lack or insufficiency of thermal insulation – with the onset of cold weather, the effect of winter heaving of the soil is possible. Another reason is that the screed was poured without regard for the very close location of groundwater.
All these factors can lead to instability of the soil layers, which is reflected in the concrete slab. And this is without taking into account possible seismic shocks.
Internal impacts. This point most often includes the use of low-quality mortar for the screed, as well as pouring carried out in violation of technological requirements. Another factor is the completely natural shrinkage of the building, which can create very significant internal stresses in the concrete slab, leading to its cracking.
External impact. This group includes mechanical damage due to falling of various heavy objects, violation of operating rules (exceeding the permissible load), or exposure to moisture for a long time.
As you can see, some factors can be foreseen, and you can try to minimize the likelihood of their negative impact. But there are also natural causes, as well as natural aging processes of building structures. So repairing a concrete floor can become an urgent need for any home or apartment owner.