Costs for cleaning the concrete mixer truck

Actually a minor matter. Nevertheless, I wonder who has to bear the costs mentioned above?

I am building with the free allocation of the individual trades. I obtain the building materials from a regional wholesaler. Today, the concrete for the floor slab was poured. Now it was said that I have to bear the cost for cleaning the concrete mixer. However, this is not included in the offer. It states "ready-mixed concrete" price X, "concrete pump base price" price X, "concrete delivery performance" price X/CBM. Nothing else.

For delivered but ultimately unused concrete that remains in the mixer truck, the concrete plants charge a significant fee and also specify this in the [AGB] or delivery conditions.

However, I expect the cleaning of the concrete pump to be included or clearly stated in the offer from the outset. I would not accept this as a surprising additional charge.

Ok, thank you very much for this information! There was still a remainder in the concrete mixer… I think I did quite well with 60 €.