WHAT
IS GREEN CONCRETE?
Today the word green is not just
limited to color, it represents the environment, which is surrounding us.
Concrete which is made from concrete
wastes that are eco-friendly are called as “Green concrete”.
The other name for green concrete is
resource saving Structure with reduced environmental impact for e.g. Energy
saving ,co2 emissions, waste water.
“Green concrete” is a revolutionary
topic in the history of concrete industry. This was first invented in Denmark
in the year 1998 by Dr.WG.
Concrete wastes like slag, power
plant wastes, recycled concrete, mining and quarrying wastes, waste glass,
incinerator residue, red mud, burnt clay, sawdust, combustor ash and foundry
sand.
Green Concrete is a term given to a
concrete that has had extra steps taken in the mix design and placement to
insure a sustainable Structure and a long life cycle with a low maintenance
surface. e.g. Energy saving, CO2 emissions, waste water.
The goal of the Centre for Green
Concrete is to reduce the environmental impact of concrete. To enable this, new
technology is developed. The technology considers all phases of a concrete
construction’s life cycle, i.e. structural design, specification, manufacturing
and maintenance, and it includes all aspects of performance, i.e.
1) Mechanical properties (strength,
shrinkage, creep, static behavior etc.)
2) Fire resistance (spelling, heat
transfer etc.)
3) Workmanship (Workability,
strength development, curing etc.)
4) Durability
(corrosion protection, frost, new
deterioration mechanisms etc.)
5) Thermodynamic properties (input
to the other properties)
6) Environmental aspects
(CO2-emission, energy, recycling etc.)
There are a number of alternative
environmental requirements with which green concrete structures must comply:
- CO2 emissions shall be reduced
by at least 30 %.
- At least 20 % of the concrete
shall be residual products used as aggregate.
- Use of concrete industries own
residual products.
- Use of new types of residual
products, previously land filled or disposed of in other ways.
- CO2-neutral, waste-derived
fuels shall substitute fossil fuels in the cement production by at least
10 %.
In
addition to the environmental goals there are a number of environmental
intentions. Most important are:
To avoid the use of materials which
contain substances on the Environmental Protection Agency’s list of unwanted
materials, not to reduce the recycling ability of green concrete compared with
conventional concrete and not to increase the content of hazardous substances
in the wastewater from concrete production compared with wastewater from
production of existing concrete types.
Different concrete types are tested
for workability, changes in workability after 30 min., air-content, compressive
strength development, E-modulus, heat development, homogeneity, water
separation, setting time, density and pumpability. Furthermore, frost testing,
chloride penetration and an air void Analysis are carried out for the concretes
in the aggressive environmental class.
The Water/cement ratio, water/binder
ratio and the chloride content are calculated from the mixing report of the
precise mixture proportions and from the chloride content in the different raw
materials.
ADVANTAGES
- Reduction of the concrete
industry’s CO2-emmision by 30 %.
- Increased concrete industry’s
use of waste products by 20%.
- NO environmental pollution and
sustainable development.
- Green concrete requires less
maintenance and repairs.
- Green concrete having better
workability than conventional concrete.
- Good thermal resistant and fire
resistant.
- Compressive strength behavior
of concrete with Water/cement ratio is similar to conventional concrete.
- Flexural strength of green
concrete is almost equal to that of conventional concrete.
LIMITATION
- By using stainless steel, cost
of reinforcement increases.
- Structures constructed with
green concrete have comparatively less life than structures with
conventional concrete.
- Split tension of green concrete
is less than that of conventional concrete.
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