Geo-polymer Concrete Slab 

Brunswick House 04

This fly ash-based geopolymer concrete slab was poured on a job in Brunswick that is now complete. The slab is made from a cement free mix. Instead of cement, fly ash is used. Fly ash can consist of either a by-product of coal burning at a power station or as a by-product of steel production. As long as the fly ash is sustainably sourced using a fly ash based geopolymer concrete can reduce embodied energy of the concrete (ie the CO2 emissions) as well as have the advantage of absorbing recycled industrial waste. This type of material is still considered to be experimental, but once industry catches up to the science it will see a positive reduction in green house gas emissions.

Our clients in this instance were very keen to ensure their house was as sustainable as possible, and requested the use of this material. Our structural engineer approved the material prior to it being specified. The builder commented that the geopolymer mix was a bit stickier than normal concrete, and did take a bit more work to trowel finish. The initial material was quite green in colour, but once it dried it appeared just like a conventional concrete finish. In this instance we included hydronic coils in the slab, and the slab had a polished finish. The final slab was a bit softer than normal concrete, and a Hiperfloor finish wasn’t thought to be possible. We therefore researched the best applied finish for the slab, and with the concrete polisher’s advice chose a water based product. Overall the final polished concrete finish looked great, and our clients were satisfied that their home has achieved their sustainable objectives.