If you are going to fill the cells anyway than it's no big deal to through some reinforcement in there. #4 - 24" O.C. horizontal and vertical. Call a masonry Contractor and see what spacing gets expensive. In California #4 - 16" O.C. is common
I am designing a roof with a 24' span using 4x15 beams (nominal-3-1/2" x 14" actual dimensions). The beams are exposed to elevated temperatures 100-120 deg F throughout the entire year.
Which wood product is the best for elevated temperatures: Parallam (PSL), Glulam or regular sawn lumber...