The structural filler
The cavity between the infill panels is filled with structural material. The type of high strength material used is determined by the purpose of the structure and by the choice of locally available materials. Both high and light density concrete is frequently employed. Reinforcement can be added when required by local building codes.
The concrete filling is done with a pump device, or a tipper.
Thesize of gap to fill up with concrete will determine the plasticity of the fresh concrete and the maximum size of aggregates.