french institute of science and technology for transport ... - Ifsttar

2_SCIENTIFIC AND TECHNICAL ACTIVITIES
Trapping the CO 2 in demolition
concrete
Changing a defect into a quality
The invention of concrete almost goes hand in hand
with the principle of recycling and the use of recycled
aggregate in new concrete. But this is very much hampered
by the poor quality of aggregate obtained from
demolition. This absorbs a large amount of water in an
hour or so. The fluidity of concrete made with recycled
aggregate therefore diminishes a great deal while it is
being transported to the worksite.
However, although the carbonation reaction is harmful
during the lifetime of a reinforced concrete structure, it can
be put to good use in order to trap CO 2 when the structure
is demolished. The effectiveness of the capture procedure is
assessed by modelling the diffusion of CO 2 through a granular
bed of crushed concrete coupled with the carbonation of each
grain. This modelling makes it possible to optimize waste treatment
conditions.
In connection with this, a 3-year research project (CRAC −
Carbonated Recycled Aggregates for Concrete) was launched
in January 2010. After validating our model in the laboratory,
in 2011 we showed that this type of treatment was capable of
capturing between 20 and 30 kg of CO 2 per cubic metre of
concrete, depending on the quality of the cement paste that
is attached to the aggregate. Our research has also shown that
this process modifies porosity. The aggregate that is obtained
absorbs less water, but does so more rapidly, making it more
suitable for conventional concrete manufacture.
In September 2011, this work won first prize in the Eugène
Freyssinet awards which is given to young engineers who have
made a practical contribution to sustainable development in
the area of construction.
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@ CONTACTS
mickael.thiery@ifsttar.fr & nicolas.roussel@ifsttar.fr
A stockpile of demolished concrete awaiting recycling.
Designing wind turbine
foundations
The standards are at an advanced stage
The recommendations for the design, construction and
testing of wind turbine foundations were published
in 2011. This 113 page document, which is shortly to
be published in English, is the outcome of more than
four years of collective activities that started in 2007.
The work in question, which was undertaken by the
CFMS (French Committee for Soil Mechanics and
Geotechnical Engineering) and directed by Patrick
Berthelot of the Bureau Véritas, brought together a
number of professionals working in the field (technical
supervisor, consultancy firms, foundation contractors,
wind turbine manufacturers) and researchers – including
several from IFSTTAR).
The is a concise reference document for these structures
which have been subject to technical supervision
since 2008 (for towers over 12m) and have been defined
as facilities that are classified on environmental protection
grounds (ICPE) since 2010. It includes a chapter on loading
A stockpile of demolished concrete
awaiting recycling.
ifsttar French Institute of Science and Technology for Transport, Development and Networks