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Green Concrete

       Global warming is one of the major threats to the environment till date. Production of concrete is one of the vital factors for global warming as it accounts for 30% of the total CO2 released in the atmosphere. This can be minimised by eco-friendly substitute known as green concrete. In this post we have discussed about all the raw materials for the substitute of conventional concrete to go green. The Green Concrete is a recycled and light weight substances obtained from demolished site and waste of industries. The other one is green cement like fly ash, silica fume and high reactivity metakaolin(HRM). The widely used is fly ash. These green materials have almost same mechanical properties and fire resistant factor as conventional concrete. It has better thermodynamic, environmental and durability properties. It is also cost effective and the construction is faster. This post also has a clear report of advantages and disadvantages of the green concrete.

 

INTRODUCTION

      Green concrete is a revolutionary topic in the history of concrete industry. This was first invented in Denmark in the year 1998. Green concrete has nothing to do with the colour. It is a concept of thinking environment into concrete considering every aspect from raw materials manufacture over mixture design to structural design, construction and service life. Green concrete is a very cheap to produce, because, for e.g. waste products are used as a partial substitute for concrete materials,  the charges for the disposal of waste are avoided, energy consumption in the production is lower and durability is greater. Green concrete is a type of a concrete which resembles the conventional concrete but the production or usage of such concrete requires minimum amount of energy and causes least harm to the environment.

WHAT IS CONCRETE?

   The word concrete comes from the Latin word “concretus” (meaning compact or condensed). Concrete is a composite construction material made primarily with aggregate, cement, and water. There are many formulations of concrete, which provide varied properties, and concrete is the most used man-made product in the world. The environmental impact of concrete is a complex mixture of not entirely negative effects; while concrete is a major contributor to greenhouse gas emissions and creates problem for the disposal of waste concrete from demolished sites which in turn effects the environment. Therefore recycling of concrete waste is the need of hour.  Concrete is also interesting in relation to other environmental problems than those related to CO2 emission. Due to all these above mentioned reasons civil engineers have come up with a new concept of concrete, named “GREEN CONCRETE”.

WHAT IS GREEN CONCRETE?

   Today the word green is not just limited to color. It represents the environment, which is our surrounding. Concrete which is made from concrete wastes that are eco-friendly are called as “Green concrete”. 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 structural long life cycle with a low maintenance surface. e.g.  Energy saving, CO2 emissions and waste water.

  The central goal of Green Concrete is to reduce the environmental impact of conventional concrete. The Green Concrete satisfies major properties of conventional concrete such as the following:

1) Mechanical properties (strength, shrinkage, creep, static behaviour etc.)

2) Fire resistance ( heat transfer )

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 )

Suitability and advantages of Green Concrete

By adopting green concrete, the dead weight of a structure reduces from 5 tons to 3.5 tons. The panels are large in size and come ready to be installed with a perfect fit. After the concrete is poured the forms stay and the structure is done. Thus reduces the crane age load which allows better handling. These lighter weight structures bring more flexibility in lifting. Green Concrete has good thermal and fire resistance i.e. the structures built with green concrete are safe as the conventional concrete. It has good sound insulation than the traditional granite rock. Also the damping resistance of the building gets improved. So it reduces the amplitude of vibrations. The main suitability is the overall construction period is less as compared to the conventional concrete.

 

The following are the advantages of using green concrete:

  • 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 behaviour of concrete with water cement ratio is similar to conventional concrete.
  • Flexural strength of green concrete is almost equal to that of conventional concrete.

LIMITATIONS

  • Green Concrete has very few limitations. The following are the limitations of using green concrete:
  • The main limitation or disadvantage of using green concrete is that the structures which are constructed using green concrete have less life than the structures constructed by the conventional concrete. As they have less life span they cannot be used for important structures like dams, bridges, etc. For the use in Dams and bridges special air-entraining agents are mixed in the concrete which increases the overall cost of the structures.
  • The split tensile strength of the green concrete is less than the conventional concrete. Thus more reinforcements are needed, which increases the construction cost of the structure.
  • Sometimes corrosion in the steel bars can also occur if the aggregates used are not free from corrosion leading agents.
  • The cost of the reinforcement increases with the use of stainless steel.

 

CONCLUSION

Green concrete having reduced environmental impact with reduction of the concrete industries co2 –emissions by 30%.

  • Green concrete is having good thermal and fire resistant.
  • In this concrete recycling use of waste material such as ceramic wastes, aggregates, so increased concrete industry’s use of waste products by 20%. Hence green concrete consumes less energy and becomes economical.
  • So definitely use of concrete product like green concrete in future will not only reduce the emission of co2 in environment and environmental impact but also economical to produce.
  • Green concrete requires less maintenance and repairs.
  • Green concrete having better workability than conventional concrete.