The construction industry is highly energy intensive and leaves a significant environmental footprint both in terms of carbon emissions and raw material demand. An EU-funded research project was recently launched to address this issue, by investigating the possibility of using waste materials in concrete production. This, researchers believe, could lead to a greener and more sustainable building sector.
© Fotolia, 2012
Concrete is the most widely used construction material in the world, with demand being continually driven through the growth of emerging economies. In fact, concrete is so widely used that global cement production contributes about 5% to annual greenhouse gas emissions, a level comparable to the aviation sector. Greenhouse gases released into the atmosphere, such as carbon dioxide, significantly affect the Earth's temperature.
Concrete production can also contribute to a progressive depletion of natural resources, resulting in serious environmental damage if left unchecked.
Waste not want not
This is why the EnCoRe (Environmentally friendly solutions for Concrete with Recycled and natural components) project was conceived, to bring together a number of research groups capable of injecting innovation into the issue of concrete sustainability. The consortium also aims to stimulate the exchange of ideas and experience on using recycled and renewable constituents to obtain a greener structural concrete.
"Although several possible solutions to improve both the environmental compatibility and sustainability of concrete production in the building industry have already been proposed, further research is still needed to address the potential of recycled and renewable materials," explains project coordinator Dr Enzo Martinelli.
In particular, the EnCoRe project is focusing on three objectives. Firstly, it aims to investigate the physical and mechanical behaviour of concrete with recycled aggregates and cement replacement by-products with 'pozzolanic' properties. A pozzolan is a siliceous material which can be mixed with water and reacts chemically with calcium hydroxide, an inorganic compound obtained when calcium oxide, or lime, is mixed with water. The end result is a compound exhibiting properties very similar to those of cement.
So far the project has found that the current maximum amount of aggregate replacement allowed in cement could be increased, without any sacrifice to quality or safety. Preliminary concrete samples made with up to 30 to 40% of recycled aggregates, for example, have performed just as well as traditional concrete mixes.
Secondly, the project is investigating the possible contribution of recycled fibres, made from steel or plastic, in the field of diffused reinforcement of cement-based mixes. Initial trials in this field are focusing on compressed recycled steel fibres.
Thirdly, the EnCoRe team is looking into the feasibility and possible applications of natural fibre-reinforced cementitious composites (N-FRCC). An examination of the durability of natural fibres under severe climatic conditions is currently under way.
The international aspect of the project is also important. "The relevance of concrete sustainability for emerging countries was a key motivation for gathering both European and non-European partners within this research initiative," acknowledges Dr Martinelli. "This is why European research institutions from Italy and Portugal are currently implementing a staff-exchange programme with non-European counterparts from Argentina and Brazil."
Opening industry opportunities
Dr Martinelli believes that the research being carried out by the EnCoRe consortium will have a significant and positive impact on building and waste-management practices in urban and industrial areas. There is currently a strong demand for both residential and commercial buildings as a result of demographic change and urbanisation. This is occurring on a global basis, but is particularly acute in emerging countries.
There is pressure, too, to meet legislative requirements for sustainable buildings, renewable materials and reduced greenhouse gas emissions. Optimising waste-disposal procedures has also become a government priority.
Lastly, the potential of scaling-up and transferring EnCoRe's research results to field applications is expected to have significant environmental and economic consequences. There is currently a huge amount of construction activity under way among the consortium's Latin American partners.
"Significant emphasis has been placed on sustainable construction practices by Brazilian policy-makers. They are developing structures and infrastructures needed for the organisation of the next Football World Cup and Olympic Games, which will be held in Rio de Janeiro in the coming years," says Dr Martinelli.
Part of this work involves demolishing or improving existing constructions. Here, a 100% recycling target has been set. The work of the EnCoRe consortium could contribute to helping meet this objective.