De or het betonfundering?

The correct Dutch article is:

de betonfundering

Rule Words ending in -ing: almost always de. See the rule

How to use betonfundering

the betonfunderingde betonfundering
this betonfunderingdeze betonfundering
that betonfunderingdie betonfundering
our betonfunderingonze betonfundering
your betonfunderingjouw betonfundering
every betonfunderingelke betonfundering
which betonfundering?welke betonfundering?
a big betonfundering / the big betonfunderingeen grote betonfundering, de grote betonfundering