set (something) in concrete
To establish something firmly or permanently; to make something unalterable or not subject to change. The healthcare law looks promising, but we'll have to wait until Congress sets it in concrete before we know exactly what it will do.
set in concrete
If a plan is set in concrete, it is fixed and cannot be changed. With expenditure plans now set in concrete for three years, slower growth would mean higher taxes. Note: You can also say that a plan is cast in concrete. But the sale conditions must be cast in concrete.