Filling basement pit - which building material?

Hello! I need your help, I am having my old house with a basement demolished and refilled. My company wants to backfill with RC 0/20 and compact it in layers while damp. Is the material good, or should they use filling sand? I would be very grateful if you could give me advice. Regards Sandro and Merry Christmas

... what is the final result supposed to be?

Build a house without a basement so that the load-bearing capacity is optimal. Or what do you think about the result

Why not build a house with a basement? The hole is already there. Filling it costs money too, so the final additional costs for the basement should not be that significant.