Eco Efficient Construction Materials
The world’s most favorite construction material is cement. It is used in buildings, roads, runways, tunnels, and many such things. In a way we can say that we are surrounded by concrete, cement being its major component. For the production of cement, a considerable amount of Greenhouse gas, CO2, is released into the atmosphere, highly contributing to the carbon footprint.
Making of Cement:
Pulverized limestone, sand, and clay are heated to about 1,4500C by using either natural gases or coal as fuel. This process not only makes use of the non-renewable natural resources but also releases a good amount of carbon dioxide in the process known as calcination (By heating limestone (calcium carbonate) is converted into quicklime (calcium oxide), that gives off CO2 in the process). It is estimated that about 8 – 10 percent of the total CO2 emitted in the world comes from cement manufacturing. Thus it is very essential to find alternatives to reduce the cement’s carbon footprint for sustainability.
Maximum amount of conventional concrete can be replaced with Eco-efficient material for the betterment of the environment. The term green concrete basically means that one of the components used in making concrete is a waste material and also the production of the concrete does not harm the environment.
Greener and Cleaner Substitutes:
1) FLY ASH:
Fly Ash is the byproduct from burning pulverized (fine particle) coal in power generating plants. Fly ash is collected in the form of fine powder from the exhaust gases either by bag filters or electrostatic precipitators. Since it is a byproduct, a large amount is disposed of in landfills thus polluting the environment. Using this instead of cement not only reduces the CO2 emission but also reduces the load of disposing it.
The property of fly ash is that it is pozzolan, that is, when combined with calcium hydroxide, this material exhibits properties of cement.
The benefits of using fly ash include less CO2 emission along with the reduction in the amount of energy used to produce clay bricks, reduced crack problems, etc.
Usually, only some amount of fly ash is mixed with cement to make it environment-friendly. The reason that it is mixed with cement and not completely use instead of cement is that it requires a large amount of sodium based activators which are expensive. The amount used depends upon the type of fly ash and the level of its reactivity.
Though Fly ash has many benefits, there are some concerns such as seasonal limitations, slower strength gain, etc.
2) Quarry Dust:
Like fly ash, quarry dust is also a by-product and is obtained from the crushing and cutting process of the stone. While crushing rocks, the dust that is generated as a by-product is known as quarry dust.
In the recent years, a lot of research has been carried out on the use of quarry dust. This dust replaces the fine aggregates like natural sand. Nowadays the natural sand that is available has become scarce and also quite costly. Hence alternatives like quarry dust are necessary. Moreover, this quarry dust if not used pollutes the air and is disposed of in the landfills. Therefore, using quarry dust is beneficial for the environment.
3) GGBS Concrete:
Ground Granulated Blast furnace Slag (GGBS) is also a byproduct that is obtained from the steel industry. When pig iron is manufactured, blast furnace slag us obtained as a byproduct. Disposing of this slag is a great concern as it considered as waste. But if this is used instead of cement, both the concerns, that is disposing of the waste and the CO2 emission from the cement manufacturing can be taken care of.
The chemical composition of GGBS is almost the same as that of Portland cement. It contains alumina-silicates of calcium that exhibits the property of cement. Also, for the hydration reaction to take place, it is necessary to activate GGBS. This activation can take place either by any alkali material or by portland cement. Hence, this GGBS is used with cement and can not completely replace cement.
The advantages of including GGBS in cement are, increase in strength and durability, less heat of hydration, reduced CO2 emission, etc.
Conclusion:
These Eco-efficient materials can be considered as a revolutionary idea as these not only help in conserving natural gases used as fuels but also help in reducing the emission of the greenhouse gases. Moreover, all the materials stated above are waste materials that are usually disposed of, thus polluting the environment. Therefore using these materials with cement is not only good for the environment but it also exhibits some advantageous qualities like better tensile strength and improved workability.