Options for passive long range sensors
Now my question is that are there any alternatives to RFID that would
  reach a range of 2-3m and would be cheaper to implement.


I'm assuming you mean miles and not metres here! Also RFID will never work as you describe it.

Engineer a data collection system (you can buy one of course) and all your temperature sensor voltages are digitized and converted into one big digital frame of data to be sent (via coax or twisted pair) to where you want to receive that data. At that place you would need to recover the data into the individual channels and convert back to analogue.

This type of product is commercially available. You could power the data collection system locally from recoverable batteries or use a regular AC supply if available. You could even  use radio to transmit the frame of data. Given that the cost is in the equipment and not the sensors in the concrete, that cost is re-usable for the next structure you build/test.