| EPSRC Reference: |
EP/J016055/1 |
| Title: |
Increasing the early age strength of High Volume Fly Ash (HVFA) concrete |
| Principal Investigator: |
Coakley, Dr E F |
| Other Investigators: |
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| Researcher Co-Investigators: |
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| Project Partners: |
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| Department: |
Engineering and Computing |
| Organisation: |
Coventry University |
| Scheme: |
First Grant - Revised 2009 |
| Starts: |
10 September 2012 |
Ends: |
09 March 2015 |
Value (£): |
97,757
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| EPSRC Research Topic Classifications: |
| Civil Engineering Materials |
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| EPSRC Industrial Sector Classifications: |
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| Related Grants: |
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| Panel History: |
| Panel Date | Panel Name | Outcome |
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03 Feb 2012
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Engineering Prioritisation Meeting - 3 Feb 2012
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Announced
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Summary on Grant Application Form |
The construction industry is heavily reliant on production of Portland cement and, in the UK alone, 12 MT of cement is produced per annum. Depending on the specific production processes used, manufacture of 1 kg of Portland cement produces 0.7 kg - 1.0 kg of CO2. Many sources suggest that cement manufacture accounts for up to 5% of the world's CO2 emissions. There is an urgent need for a step change in technology to achieve the radical reductions in carbon emissions necessary to stabilise climate change.
Many different approaches can be used to mitigate the effects of cement production. Considerable improvements have been made with kiln efficiency and waste fuels are now commonly used. However, during the production process, calcium carbonate decomposes into calcium oxide and carbon dioxide. This calcination reaction causes over half the CO2 emissions from the production process so there is limited scope for improvement. A number of initiatives have examined cement alternatives or replacement materials to reduce the Portland cement requirement of concrete. "Novacem" is an innovation from Imperial College London that made significant progress on a radical alternative to calcium-silica based cements based on magnesium oxide produced from magnesium silicates. Although these developments are encouraging, this process would require entirely new plant and with world production of cement at 2.5 billion tonnes per annum, this technology will take a long time to make a significant impact. Other initiatives such as "Ecocem" in Australia are based on cement replacement materials. A considerable amount of research and development of cement replacement materials has been carried out but replacement levels have specified maximum limits in current standards to ensure concrete behaviour does not differ significantly from Portland cement concrete.
Fly ash is a by-product from coal-fired power stations which can be used as a partial cement replacement in concrete. It reacts with calcium hydroxide (produced during hydration of Portland cement) to form stable calcium silicate and aluminate hydrates - the pozzolanic reaction. Fly ash typically replaces 20% - 35% of the cement content within a concrete mix but there are obvious environmental benefits for incorporating higher proportions of cement replacement. However, the pozzolanic reaction between the fly ash and calcium hydroxide occurs quite slowly, which increases setting times and reduces the rate of strength gain of the concrete. This can cause problems associated with surface finishing, delayed removal of formwork etc. which can increase the cost and duration of a construction project. Researchers have consistently found that the higher the proportion of fly ash, the lower the early age strength of the concrete. Therefore, improvement of early age strength of fly ash concrete, particularly when incorporating high volumes of fly ash, warrants investigation.
This project has been developed by Coventry University after detailed discussions with key industry figures representing cement, fly ash and admixture suppliers and concrete users. A comprehensive experimental programme will investigate the use of mineral activators to reduce setting times and enhance early age strengths of HVFA concretes. Cement kiln dust is a by-product of the cement manufacture process and its high alkalinity makes it a suitable activator of fly ash. Waste gypsum is also available in abundance and has been shown to increase the rate of strength gain of fly ash concrete. The aim of this study is to incorporate these by-products into HVFA concrete mixes to give comparable early age performance to equivalent Portland cement concretes. The effect of intergrinding the cementitious materials and activators will also be assessed. Also, a range of fly ash sources will be investigated to account for variations in chemical composition of the fly ash, which have been shown to affect concrete strength.
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Key Findings |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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Potential use in non-academic contexts |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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Impacts |
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| Description |
This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk |
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Sectors submitted by the Researcher |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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| Project URL: |
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| Further Information: |
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| Organisation Website: |
http://www.cov.ac.uk |