Check your /etc/group file. You will see a few groups you can add your admin user to such as the adm group.
To be honest, it's a bad move. The best method is to use sudo and just grant the commands that your admin user needs to have access to in there.
I have my standard account be able to do things that need root account access on a sudo without the requirement of a password. Such things as chmod, chown and chgrp. I simply do:
sudo chmod .....
Log in to a term as root, then do visudo, you should get enough info in there to sort yourself out, if not give us another shout.