How can I prevent our IT admins with sysadmin to read data stored inside an encrypted database? I built a web application that stores sensitive data into a SQL Enterprise 2014 database with TDE encryption. My key is safe; I know if someone steals the database file from disk the data is protected. However, if you run SQL Management Studio on the database server, you can query and read the database.

I believe this is because the SQL database loads the database with the masterkey, thus decrypting the DB and making queries readable. But at the same time, I cant prevent an IT admin with sysadmin rights to run queries on the data. If I remove their access to a database table, they could easily re-grant themselves the rights they need to read the data.

Is there anything I can do to prevent this from happening? I thought of saving the text itself in an encrypted format but that will affect my queries to run efficiently.
Per the other comments, one way to block them is to NOT have the IT Admins in the sysadmin role.  Sysadmin can override anything pretty much.  

If they really need a high level of access and you dont want to out right encrypt your data, you could try a combination of a custom server role and/or database roles.  As long as you are on at least SQL server 2012 (for the server roles piece), this would allow you to grant them a more controlled level of access to the sql instance.  

The real question is "Do they need SysAdmin?"  If the answer is yes, you'll have to encrypt the data.