Holdfast Training Services Trial Blog

It is well known that the production of Portland cement (OPC) is highly damaging to the natural environment. It is high in embodied carbon and embodied energy and its production creates noxious waste emissions – globally, production of 1 tonne of OPC produces roughly 1 tonne of CO2. Reducing the OPC content of concrete mixes has been standard practice in construction for many years, through the use of cementitious replacement materials such as blast slag (e.g. GGBS) or fly ash (e.g. PFA) derivatives, but an Australian company is now marketing a geopolymer based concrete which contains no OPC at all.

EFC pavement

Wagner’s Earth Friendly Concrete (EFC) uses an alkali chemical powder to activate other pozzolans – cementitious content (GGBS and PFA) – to achieve the binding effect of cement. If you accept that GGBS and PFA are waste materials (which is a separate topic) then EFC can see 80-90% reductions in carbon carbon emissions when compared to a full OPC mix.

Crucially, this product is now able to match concrete in many applications and appears to be commercially viable. The fine and coarse aggregate content remains the same in terms of performance it shows:

• 30% higher flexural strength
• Very low heat of reaction
• Very low shrinkage
• High sulphate resistance
• High chloride ion ingress resistance
• High acid resistance

There are a number of case studies available (wagner.com.au) which show good performance in pre-casting and pavements in particular (including airports) with an interesting foray into sewer tunnel lining. The low reaction heat, leading to low shrinkage, is an ideal characteristic for pavements (especially I imagine in Oz where curing must be tricky in the heat?) and the high resistance to chemical attack makes it a good choice for sewers or other corrosive environments. It even has a clean white finish.

EFC precast

There certainly seems potential for use in the UK in mass concrete applications at least e.g. piling and ground bearing slabs, but I haven’t seen much evidence yet of it’s use for in-situ superstructure pours. I imagine this is a result of the low reaction heat leading to longer curing times (or vice versa at the chemical level). In a concrete frame longer curing means longer shuttering, more back-propping and slower jumps between floors – i.e. it means money – but this doesn’t apply so strongly to unpropped steel decking (composite) slabs so perhaps there is potential there too.

Has anyone seen this in use yet, especially you guys Down Under?