How do I pour new concrete over old concrete?

How do I pour new concrete over old concrete?

Depends if your pouring a veneer or a new slab. not specific enough so I’ll just give you a general answer, when pour new over old. The old surface must be cleaned and scarified. If it were a slab you would treat the old concrete as the foundation and simply pour over it. If it were grade beams and structural work , your going to have to remove all old concrete and work the soil per specification on the structural sheet per the structural engineer

So my advice is:-

1. Identify the old concrete see if there is structural cracks or settlement.(sacking or depression of concrete surface)
2. Repair it first.
3. To pour concrete over the old slab needs an expert like structural contractor who know how to do it. As it requires reinforcement or rebar with proper spacers at a minimum of every 600 mm both ways (hope you understand the meaning).

The idea is the new concrete slab you are pour it over must be rienforced (R.C) not a ‘mass concrete’ to be effective.

It’s best to get a specialist to do the job.