In order to increase thickness of a slab or to build a structural screed it is necessary to lay some rods which connect the new casting to the pre-existing one. The hole of each rod must have a diameter 4 mm wider than the rod and depth equal at least 10 times the diameter.
The rod must be cast ironed with an epoxy adhesive like RESISYSTEM 310 TX or RESISYSTEM 312 which in this case act as anchors. To further improve adhesion between the new casting and the pre-existing one, use RESICOL 122 epoxy cold shut casting, then cast the fresh concrete layer upon layer.