Mild steel box section pricing

[cropwell]

I've wondered if foam concrete would do the trick. Less weight and the air component of the mix is relatively inexpensive.

Kit

My late next-door neighbour was a builder. His trick (and I suspect a trick common in the trade) was to give a good squirt of washing-up liquid into the compo mixer. It foamed up the mortar and made it lighter to handle and slippier off the trowel.

Of course for filling beams you really need high density, low elasticity, acoustic decoupling air.