Bulk Use of Biomass and Co-fired Ash in Novel Binders

This research project will investigate biomass and other renewable ash (including ash from paper recycling waste) in high volume construction applications. These ashes are currently only available in very limited quantities but are predicted to increase substantially over the next 20 years. As the UK moves from coal towards biomass and co-firing in many power stations, there will be an increase in biomass ash which is not suitable for use with Portland cement, the largest current use of coal fly ash. Unless a use for this new ash is found, the UK will develop an increasing waste problem. It is important that this research is undertaken now, before the waste problem develops.

Geopolymers are a promising alternative to Portland cement based concretes because of the very low embodied CO2 compared with Portland cement, the ability to use both geologically abundant minerals and wastes in their formulation, and the low capital outlay required for production. Commercial activities in the UK are just starting with only one company actively marketing geopolymer construction products. Most current geopolymers are based on industrial by-products such as fly ash from coal power stations and slags from steel manufacture, and these require mixing with high energy alkali activators before use.

Biomass ash is high in natural alkalis and by using these natural alkalis along with the other natural properties of the ashes, it should be possible to produce concretes with much lower environmental impact than that of Portland cement concrete or existing geopolymer concretes with comparable performance. It will also will reduce material going to landfill in the UK, and help the UK in meeting climate change targets.

The project will benefit the global population in different ways. All will benefit from reduced CO2 emissions and the effect this will have on the global environment.

The reduced waste to landfill will benefit the UK population and reduce landfill taxes. The UK population will benefit economically from reduced cement imports which increase the UK trade deficit. International experience has shown that commercial uptake is most likely to be led by small and medium enterprises (SMEs) which contribute significantly to economic growth in the UK.

Ash yield and properties depend on the source material and processing conditions (particularly temperature), and it is important for the most desirable properties of biomass and paper sludge ashes for use in geopolymer synthesis to be available, particularly in the area of biomass energy generation where conversion and construction of new plants is ongoing. This information will enable informed decision-making by plant designers and operators, where the efficiency of the power generation can be considered alongside the value of the ash as a by-product.

Companies involved in the commercialisation of geopolymers will benefit from the increased knowledge base and the likely reduced costs of this technology compared with current methods. Impact activities by the research staff would increase awareness of the technology and would assist marketing.

Along with the areas in the academic beneficiaries section, hygrothermal behaviour and the influence on occupant health and in-service energy use is an area which requires investigation for a number of different construction materials, including geopolymers. The potential for geopolymers to inhibit bacterial, mould and other biological growth through their higher natural pH than Portland cement is an area requiring scientific investigation. If geopolymers can be designed to buffer humidity and inhibit biological growth, it will be an important breakthrough in design and maintenance of buildings. This will result in improved health and reduced energy consumption which would benefit occupants of buildings containing geopolymers.