Hi. The end post of a fence Im installing was too large in diameter so the fence supplier advised me to cut it down and install a smaller diameter pipe inside. Problem is, theres concrete in the larger pipe and the smaller pipe can only sit inside about 6€� deep.

Can anyone suggest a specific product for what to put into the larger pipe to secure the smaller one? I was thinking epoxy or even squirt a whole tube of Liquid Nails in there, but really not sure what to put.

See photos:
https://photos.app.goo.gl/6TdBDsGyhUmCsiFq7
https://photos.app.goo.gl/McL2smxvQA1b5Uqo7

Thanks for advice.
Theodore