Your question omits some specifics. Consequently, this answer may be insufficiently specific, but I'll make a guess or two, and try to give you some ideas to begin with. If you'll edit your question and add some details (e.g. what is it you're trying to do?), then I'll try to edit my answer to be more informative.
Your SCT-013-000 sensor produces a "constant current" output proportional to the current flowing through the coil. But it's an ac current, meaning that it will flow alternately in one direction, then the other, in sync with the ac current that you are measuring. That is, if your measured ac current is 50 Hz, then your sensor output will also be at 50 Hz.
One thing you should understand about a current source: It tries to supply a certain current, and the voltage will vary according to Ohm's law (E = I*R). In other words, if you place a high impedance load across the output of a current source, the voltage across that load will satisfy Ohm's Law, which could be a very high voltage - even a lethally high voltage. Your sensor appears to have a voltage limiting device built in, but I wouldn't depend on this to keep me (or my equipment) safe. Be careful.
As far as using an ADC: This seems like a bad idea based on the fact that you've described your application as "Binary ON/OFF..." in the subject. An ADC would be appropriate if you were trying to measure the amount of current flowing through your sensor instead of an "ON or OFF" state.
As far as using a relay: Again, your objective is not clearly stated, so it's difficult to give you a detailed answer. However, as you mentioned "3.3V" which is the I/O voltage of RPi's GPIO pins, I will hazard a guess that you want to interface your current sensor with your RPi. IF that's the case, you could use a relay, but you might need a rather specialized relay with an ac coil... or a rectifier to convert your ac sensor output to DC, and perhaps a clever interface circuit design to ensure you don't over-drive the relay. This is all "do-able", but it may not be the best or easiest way to do it.
Instead, consider using a 3.3V Zener diode across the output of your current sensor, and then tying that to a GPIO pin as shown in the (grossly simplified) schematic below:
simulate this circuit – Schematic created using CircuitLab
Please note that this is not a "ready to build" schematic! I've included it only to show a design concept. I'll add the details once you've edited your question with some details.
Hope that helps.