Concrete that is made from waster of concrete is called green concrete, the various alternative manufacturing processes can lead to waste of residual product.
The use of this waste materials in concrete reduces the environmental impact e.g. CO2 emissions, energy pollution by dumping waste, energy-saving, etc.
Introduction to green concrete:
Objectives of green concrete:
- To reduce greenhouse gas emissions, i.e., carbon dioxide emissions from the cement industry.
- To reduce the usage of pure resources such as limestone, clay, shale, natural river sand, natural rocks that are being used to making conventional concrete.
- Also, reduce the wastage materials in the concrete leading to air, land and water pollution.
- It has sufficient strength and durability in comparison with standard concrete.
- Also has distinctive resistance to corrosion and also effectively prevents acid rain.
- Buildings made of green concrete use less energy because they are more resistant to temperature changes, thus saving heating and cooling costs.
- Transferring to this concrete for construction reduces the effect of global warming to some extent.
Advantages of green concrete:
- This green concrete reduces shrinkage and creep.
- It produces a very strong and durable concrete.
- This significantly reduces the heat of hydration compared to conventional concrete.
- CO emissions will be reduced by at least 30%.
- At least 20% of the concrete residual products will be used as aggregates.
- This concrete has better work efficiency.
- It has good thermal resistance and fire resistance.
Disadvantages of green concrete:
- The structure constructed with this concrete has a relatively short life compared to the structure with conventional concrete.
- The cement replacements for an inexperienced concrete has fly ash, ground granulated blast-furnace slag (GCBS) blast furnace cement and many others.
- Fly ash is a by product of coal combustion from power plants, with 20% ordinary portland cement linkage by fly ash into concrete with extreme sulfate resistance.
- Ground granulated blast furnace slag (GCBS) will also be raised as a cement substitute for concrete, GGBS is a by-product iron and metal fabrication process from a blast furnace.
- Gross replacement for this concrete is waste materials from concrete manufacturing or might be obtained and reused after the demolition of the structure.
- The main goal of replacement of cement with cement alternatives such as fly-ash, GCBS or slag cement has positive effect on the characteristics of the concrete.
Materials used for green concrete:
Reusable or recycled materials that may be simply decomposed are the materials used within the process of making this concrete.
Examples of such materials are recycled concrete aggregates, recycled demolition waste aggregates, glass aggregates, fly ash, blast furnace slag, manufactured sand, rice husk ash, silica fume and met kaolin.
Uses of green concrete:
It is used in the construction of buildings, dams, columns, bridges and roads.
Green concrete is good thermal and fire resistant.
Within concrete recycling of waste materials such as ceramic waste, aggregates, the use of waste products by the concrete industry has increased by 20%, it consumes less energy and becomes economical.