Concrete paving consists of cement, sand, fine rock aggregate and water that has been press formed in a mold. The concrete cures when the water in it has evaporated. Being a medium strength concrete product and depending on your paver choice, it can be as low as a 10mpa strength product, meaning that the paving has the ability to transfer water. Even in the construction of bridges, using 50mpa strength concrete will still require additives to be waterproof, so the weaker paving blocks are never going to be a water-resistant product, basically no concrete is without additives. The constant presence of water will weaken the bond of the surface materials. Once that surface has weakened and begins to wear off, it then allows the concrete to have further rapid failure.
Moisture can transfer from the ground upwards if there was a plumbing or drainage problem. Especially if the rubble base and the coarse river sand bed was not adequately prepared prior to paving being laid, as water can be held by the clay subsoil and then wick up through the paver.
Alternatively simply due to a lack of adequate drainage or fall in the paving surface, can cause water to pool and then be absorbed into the paver.
In the photos attached you can see the concrete paved areas have lost all its durability. The paving surface is crumbling and the paving requires full replacement. Inspection of the base is recommended as the paving may have been installed directly to the soil. No drainage was noted in the area and guttering overflowing issues have also attributed to this issue.
The house slab edge was not adequately protected from the moisture issues and the moisture has transferred into the slab edge causing concrete spalling. The render under the sliding doors has also been damaged due to this moisture transfer.