I am 99% finished a small wall/patio and firepit and just need to cap it and install firebrick on the inside of the firepit area. The customer wants it done ASAP but we are (finally) getting very cold weather for the next several days. I really need to finish this so I can get paid, but I am afraid the cold will not let the mortar set up right. any ideas on what I should do? I also have to PL the caps on and I can wait on that, but the bricks need to get in there.