Rocket Mass Heater Batch Burner Chamber Refractory Casting

I'm building a batchbox rocket burner cast from refractory concrete. The design is taken from the magnificent work of Peter van den Berg and colleagues who have generously made design details available at their web site http://batchrocket.eu. I intend to develop the basic burner into a water-heating boiler over the coming weeks and will post update when I have time. This video concentrates on casting the burn chamber. The mix used for this casting was: 2 parts 'ciment fondu' high-alumina cement 2 parts powdered fire clay 1 part fine sand 4 parts perlite 4 parts clay pebbles Thanks for watching.