20-03-2014, 02:14 PM
Green Concrete in Denmark
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Synopsis:
Cement and concrete may have an important role to play in enabling Denmark to fulfil its
obligation, agreed at the Kyoto conference, to reduce the total CO2 emission by 21 % compared to the 1990-
level before 2012. This is because approximately 2 % of Denmark’s total CO2 emission stems from cement
and concrete production.
There is considerable knowledge about how to produce concrete with a reduced environmental impact.
However, it is not known to a sufficient degree - neither in Denmark nor internationally - on what scale, and
with what technology, this “green” concrete can be applied in practice in buildings and structures. For
instance, there is not enough information about how the properties of green concrete, such as compressive
strength, durability, fire performance, casting and execution, hardening, and curing are affected by the
measures to reduce the environmental impact of concrete.
This paper gives an overview of the present state of affairs in Denmark of concrete types that have reduced
environmental impact, including the use of low energy cement, recycling of crushed concrete as aggregate,
the use of fly ash and micro silica, etc. There is a description of among other things the possibilities of using
“green” concrete within the existing standards and specifications, and Danish and European research
projects about green concrete, life cycle assessments, etc. A special focus will be on a large Danish centre
running from 1998-2002, involving leading universities, institutes, building owners, contractors,
consultancies, and cement and concrete manufacturers.
CEMENT AND CONCRETE’S ROLE IN MEETING THE ENVIRON-
MENTAL OBLIGATIONSCement and concrete may have an important role to play in enabling Denmark to fulfil its obligation to reduce
the total CO2 emission by 21 % compared to the 1990-level before 2012, as agreed at the Kyoto conference.
This is because the volume of concrete consumption is large in Denmark. Approx. 1.5 tonnes of concrete per
capita are produced annually. The CO2 emission related to concrete production, inclusive of cement production,
is between 0.1-0.2 tons per ton produced concrete. This corresponds to a total quantity of CO2 emission of 0.6 -
1.2 m tons per year. Approximately 2 % of Denmark’s total CO2 emission stems from cement and concrete
production.
The potential environmental benefit to society of being able to build with green concrete is huge. It is realistic to
assume that technology can be developed which can halve the CO2 emission related to concrete production.
With the large consumption of concrete this will potentially reduce Denmark’s total CO2 emission by 0.5 %.
The somewhat soft demands in the form of environmental obligations result in rather specific technical
requirements for the industry - including the concrete industry. These technical requirements include among
others new concrete mix designs, new raw materials, and new knowledge (practical experience and technical
models) about the properties of the new raw materials and concrete mix designs.
State of affairs of concrete with reduced environmental impact
There is considerable knowledge in Denmark about how to produce concrete with lower environmental impact,
so-called green concrete.
The concrete industry in Denmark has considerable experience in dealing with environmental aspects. The
concrete industry realised at an early stage that it is a good idea to be in front with regard to documenting the
actual environmental aspects and working on improving the environment, rather than being forced to deal with
environmental aspects due to demands from authorities, customers and economic effects such as imposed taxes,
etc.
Furthermore, some companies in the Danish concrete industry have recognised that reduction in production costs
often go hand in hand with reduction in environmental impacts. A Danish concrete element manufacturer has
achieved significant economic savings by dividing the waste into different fractions and thereby increasing the
recyclability. Thus, environmental aspects are not only interesting from an ideological point of view, but also
from an economic aspect.
Cement and concrete production
It is also possible to reduce a concrete’s environmental impact by reducing the environmental impacts in cement
and concrete production. The Danish cement manufacturer has many activities concerned with the reduction of
environmental impacts (6).
As regards concrete production, experience with reductions of primarily water consumption, energy
consumption and waste production is available. Even though the contribution of concrete production to a
concrete type’s environmental profile is minor, it does give a contribution, and it is important - environmentally
and economically - to the single concrete producer.
In a large Danish project, “Environmental management in the building and construction industry”, a guide to
environmental reading, environmental management based on the ISO 14001 standard, and a “get-started” guide
are under preparation. The guide can help the concrete producers reduce environmental impacts from their
production (11), (12), and (13).
DANISH CENTRE FOR GREEN CONCRETE
In Denmark, there is considerable knowledge about how to produce concrete with a reduced environmental
impact. However, it is not known to a sufficient degree - neither in Denmark nor internationally - on what scale,
and with what technology, this “green” concrete can be applied in practice in buildings and structures. For
instance, there is not enough information about how the properties of green concrete, such as compressive
strength, durability, fire performance, casting and execution, hardening, and curing, are affected by the measures
to reduce the environmental impact of concrete. This is the background for the large Danish centre called Green
Concrete.