One of my mates works in the warehouse for a computer parts supplier and he bought home some packing foam for me to have a play with. Seeing as I'd been playing a fair amount of Across the Dead Earth lately I decided to get some ruined buildings knocked together as I'm lacking in the terrain department as it is and I can't keep the borrowed bits and pieces from The Uncle forever.
All the foam has been glued together with a hot glue gun. The concrete render was made with a mix of equal quantities of PVA and Polyfill, 1/2 quantity of sand, a squeeze of black paint and a little water to get it to the texture I wanted. Once that was dried I gave it all a going over with a concrete paint and wash via an air brush, and the same with the weathering and rust run offs. The rusted rebar is just gardening wire painted with the same rust. Then the whole lot was finished off with various basing materials.
I'm pretty happy with how they finished up and I'm currently working on a slightly larger compound for the themed competition with the Across the Dead Earth Facebook group.