One of the major
challenges of our present society is the protection of environment. Some of the
important elements in this respect are the reduction of the consumption of
energy and natural raw materials and consumption of waste materials. These
topics are getting considerable attention under sustainable development
nowadays.
Today engineers and
architects have choices of the material and products they use to design
projects – when it comes to a building frame the choice is typically between
concrete, steel and wood; for paving applications the choice is generally
between concrete and asphalt. For its suitability and adaptability with respect
to the changing environment, the concrete must be such that it can conserve
resources, protect the environment, economize and lead to proper utilization of
energy. To achieve this, major emphasis must be laid on the use of wastes and
byproducts in cement and concrete used for new constructions.
Material choice depends on several factors
including first cost, life cycle cost and performance for a specific
application. Due to growing interest in sustainable development engineers and
architects are motivated more than ever before to choose materials that are
more sustainable. On what “measurement” basis can engineers and architects
compare materials and choose one that is more sustainable or specify a material
in such a way as to minimize environmental impact?
Life Cycle Assessment
(LCA) seems to offer a solution. LCA considers materials over the course of
their entire life cycle including material extraction, manufacturing,
construction, operations, and finally reuse/recycling. LCA takes into account a
full range of environmental impact indicators—including embodied energy, air
and water pollution (including greenhouse gases), potable water consumption,
solid waste and recycled content. just to name a few. Building rating systems
such as LEED and Green Globes, are in various stages of incorporating LCA so
that they can help engineers and architects select materials based on their
environmental performance or specify materials in such a way as to minimize
environmental impact.
Recent focus on
climate change and the impact of greenhouse gas emissions on our environment
has caused many to focus on CO2 emissions as the most critical environmental
impact indicator. The problem with this approach is that it forces engineers,
architects and product manufacturers to focus their efforts on reducing
greenhouse gas emissions without regard to other sustainable practices. Even a
small reduction of the environmental impact per tonne of concrete will result
in large environmental benefits because of the vast amount of concrete produced
today.
Concrete is also
interesting in relation to other environmental problems than those related to
CO2 emission. It may be possible to use residual products from other industries
in the concrete production while still maintaining a high concrete quality.
During the last few decades, society has become aware of the problems
associated with landfilling of residual products, and limits, restrictions and
taxes have been imposed. As several residual products have properties suited
for concrete production, there is a large potential to increase material recycling
by investigating the possible use of these for concrete production.
When assessing the
environmental compatibility of concrete it is essential to consider all life
cycle phases. This means that it is no longer sufficient to address
environmental issues associated with the production of the individual building
materials. The environmental impacts associated with the use and disposal of a
structure has to be considered. The energy consumption and CO2 emission
associated with the use of a structure are generally in the same magnitude or
larger than the energy consumption and CO2 emission associated with production
of the individual construction materials. Use, maintenance and durability are
therefore important aspects, which have to be considered. A result of this is
new qualifications are needed for the actors in the concrete construction
sector. It is not enough for the individual producers to know the environmental
performance of their own materials. Knowledge of the total environmental
performance from cradle to grave is needed. Furthermore, a united business
effort involving the relevant actors is needed in order to achieve real
environmental improvements.
With this background
it is important to reduce the environmental impact of the materials themselves
not least because environmental improvement is a competitive parameter.
Building materials with reduced environmental impact are often less expensive
to produce. Furthermore, environmental performance is increasingly taken into
account in tenders. The material with the best environmental parameters is most
likely to be used.
According to the
World Business Council for Sustainable Development, concrete is the most widely
used substance on Earth apart from water. Approximately 2.35 billion tons of
concrete are produced each year. That works out to a cubic meter, or about a
35- by 35- by 35-foot cube of concrete for each person on Earth every.
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