My stack coming out of my boiler was leaking I inquired what to use at the local home depot to repair it and the guy suggested using high temp furnace cement around it. I built it up in layers now its freezing out and i guess the heat changes cracked it all, below are some pics. What is the best thing to fix this? I dont know if i should just tar around the base or put some roofing paper and tar and pitch it a little away. If anyone has some ideas for me that would be great thanks for any help.