What happens if you send tether (USDT) to a bitcoin address? I have both a GDAX and a Binance account. I chose to withdraw my tether and move them into GDAX into the bitcoin address. After about an hour of the transaction, it said it was complete with "10 confirmations"(the number of confirmations keep increasing). I have checked into my GDAX account however and it still shows no BTC or transaction history, whereas it shows that it is complete within Binance. 

Is this transaction valid (will it work)? 
If so, how much time does such a transaction normally take?
USDT is part of the omni layer on top of Bitcoin.

While the transaction will go through (since any omni transaction is a valid Bitcoin transaction), you will not be credited for the USDT as GDAX is a USD exchange. They don't support USDT, and hence won't be trying to detect omni transactions for it.

You should contact GDAX support about how to recover your USDT.