Posted on July 18, 2019
Concrete is a mixture of cement, gravel, sand, water and a range of aggregates. With about 10 billion tons of concrete produced every year, it is the most consumed substance in the world, second only to water.
It is also the world’s most widely used material for construction – from bridges to large buildings, concrete forms the very foundation of our infrastructure. Over 70% of the world’s population lives in a concrete structure.
Due to the durability and strength of concrete, it is used to build various types of structures like buildings, pavements, pipes, floor slabs, beams and pillars.
However, despite the massive production and consumption of concrete around the globe, there has been a lot of speculation about the fact that it might be an active contributor to greenhouse gas emissions.
Keeping in mind the current climate condition and the phenomena of global warming, there is a pressing need for the construction and other industries to go through a green revolution - in other words, industries need to adopt and introduce environmental friendly materials.
With this understanding, the concrete industry has, fortunately, found some sustainable and eco-friendly alternatives to concrete.
Green concrete is a form of eco-friendly concrete that is manufactured using waste or residual materials from different industries, and requires less amount of energy for production. Compared to traditional concrete, it produces less carbon dioxide, and is considered cheap and more durable.
The aim of using green concrete is to lessen the burden on natural resources, and increase dependency on recyclable materials. Of the multiple strategies being utilized to achieve sustainability through eco-friendly concrete, re-using wash water to reduce water consumption is a good technique.
Partial replacement of energy-consuming cement with reusable materials is among the best strategies used to achieve eco-friendly construction material. For example, cement can be replaced with Fly Ash, Silica Fume, and Wood Ash, etc.
Fly Ash is a byproduct of combustion of coal which was previously discarded in the landfill, but is now used for manufacturing green concrete.
AshCrete is a substitute for traditional concrete that heavily utilizes recycled fly ash. Fly Ash is mixed with lime and water to make it strong and durable, similar to conventional cement.
Use of fly ash in Ashcrete makes it an environment friendly alternative, since it can replace cement which in turn leads to reduced CO2 emissions. Moreover, 25% of cement can be replaced using high-volume fly ash concrete.
Other benefits of fly ash include reduced bleeding, increased strength of concrete, and reduced shrinkage, when compared to traditional concrete.
Apart from making it environmentally friendly, fly ash also makes concrete resistant to alkali-silica reactivity.
Blast Furnace Slag
Just like fly ash, blast furnace slag is a byproduct that can be recycled and used to make an environmentally friendly alternative to concrete. This glassy granular material is produced by quenching molten iron slag from the blast furnace into water or steam.
This material can replace about 70% to 80% cement, and improves the durability of the concrete. Another advantage of blast furnace slag is that the production process emits less amount of heat for hydration.
Also known as “Silica Fumes,” micro silica is an ultrafine powder which is a by-product of ferrosilicon alloy and silicon production, from the condensation of Silicon dioxide. It can displace around 7% - 12% cement in concrete.
Microsilica is known to improve the durability of concrete by making it less permeable, and increasing its compressive strength.
Concrete made with silica fumes is specifically used for structures that are exposed to harsh chemicals. Compared to traditional concrete, it is a much eco-friendlier material.
Other than finding substitutes for cement, replacing aggregate materials with recyclable and reusable resources is an effective strategy used to minimize greenhouse emissions caused by traditional concrete.
Some aggregate alternatives include paper/fiber, waste plastic, post-consumer glass, and concrete debris.
Papercrete Or Fibrous Concrete
Papercrete is made using waste paper, which is recycled and reused as an aggregate material in concrete manufacturing. While it does not entirely replace cement in the mixture, even small quantities of papercrete is enough to combat some of the ill effects of concrete production.
Use of concrete debris is a clever way to utilize waste concrete material and cut down on resource consumption from the process of concrete production. This process saves valuable landfill space and the reuse of debris reduces the use of virgin raw materials.
Glass, being a versatile inert material, is a suitable aggregate replacement for concrete. Since it can be recycled and reused many times without any changes in its chemical properties, post-consumer glass increases the durability of concrete and helps in reducing consumer landfill waste.
Utilizing waste plastic is a smart move, as it is a non-biodegradable material. Plastic waste is easily recycled, and can easily replace up to 20% traditional aggregate material. Although concrete produced using plastic waste provides strength within a specific limit, it is unarguably an eco-friendly alternative to traditional concrete.
With the use of composite materials and foam beads, the Buatex wall system is a strong and less energy requiring alternative to traditional concrete. This is an improved method of constructing walls that can be fireproof, storm resistant, and sound absorbing.
Potential Alternatives To CO2 Emitting Concrete
Despite the availability of various alternatives to traditional concrete, researchers are still working on manufacturing better, eco-friendlier concrete.
A British manufacturer, “Novacem” claims to have developed a carbon dioxide absorbing concrete, using magnesium sulfate. According to the manufacturer, this new kind of concrete can absorb up to 0.6 tons of carbon dioxide, compared to a ton of traditional concrete which emits around 0.4 tons of C02.
While this concrete is still in its trial stages, it is expected to have a significant impact on the construction industry, once it is out in the market.
The need for environmentally friendly concrete is growing by the day – this is important, as it not only protects the earth and our health, but it can also yield a stronger and more durable alternative to traditional concrete.