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The use of carbon dioxide directly i.e. without chemical modification, or after chemical conversion processes for the production of building construction materials is a key strategy to mitigate climate change and use resources efficiently.
Researchers have been relentlessly conducting investigations to implement this strategy in the production of building materials, and the results have been very fruitful. Some of the examples demonstrating this are:
- CO2 is now used for manufacturing resins, foams, and plastics.
- CO2 can be used to cure fresh concrete.
- CO2 can be used for the production of carbon-negative aggregate which is a sustainable building material.
- Nanofibers can be manufactured by converting carbon dioxide, which has the potential to be used as a constituent for the production of blocks in the future.
CO2 emissions act like a blanket in the atmosphere and trap heat in the air. They prevent the earth from cooling and are one of the major causes of global warming. These developments are promising and have made material production and building construction more sustainable and environmentally friendly.
How to Use Embodied Carbon to Reduce Global Warming?
1. Curing Concrete using Carbon Dioxide
Ready-mix concrete can be set and hardened by the carbonation process instead of hydration. The chemical reactions that occur during this process include the reaction between calcium silicate in cement and carbon dioxide in the presence of water to produce calcium carbonate and calcium silicate hydrate gel.
Moreover, the carbonation reactions speed up the curing process and consequently enhance early compressive strength. The curing process does not require any special chamber or devices. It has been observed that one cubic meter of concrete consumes approximately 3.5 kg of carbon dioxide.
Curing concrete with carbon dioxide is an effective way to bring down the percentage of embodied carbon. This is because it consumes carbon dioxide and subsequently reduces global warming, and the properties of CO2-cured concrete are similar and sometimes better than that of concrete cured using other conventional techniques.
2. Producing Carbon Negative Aggregate
Carbon dioxide is used to treat industrial wastes like cement dust, steel slag, oil-shale ash, incinerator ash, and contaminated soil to produce carbon-negative aggregate. These waste materials, if not treated, would be disposed of into landfills or emitted into the atmosphere, causing environmental pollution. The production of carbon-negative aggregate is essential from an economic and environmental perspective.
As illustrated in the figure, accelerated carbonization technology is used to produce carbon-negative aggregate. The process does not require heat and only electricity is needed to move materials through the system. The production of aggregate consumes more carbon dioxide than the quantity released; that is why the aggregate is carbon negative.
3. Manufacturing Polymers
Carbon dioxide can be used as a principal constituent or partial replacement material in the production of many polymers. For instance, it replaces part of fossil fuel-based raw materials to produce polymers that are used to make resins, foams, and plastics.
4. Cleaning Concrete Surfaces
Carbon dioxide can be utilized to produce dry ice pellets. The dry ice pellets can replace sandblasting to remove paint from concrete surfaces.
5. Production of Sustainable Materials
The construction industry releases a significant amount of carbon dioxide and cement production is responsible for half of that. Carbon dioxide emissions can be cut down using low-carbon cement that demands lesser energy during production and has magnesia as the major constituent. The magnesia in concrete absorbs carbon dioxide during the curing process.
The low-carbon cement is manufactured from a mix of magnesium oxychloride and fly ash. Magnesium oxychloride is a byproduct of magnesium mining, whereas fly ash is a byproduct of coal combustion.
6. Conversion of Carbon Dioxide into Nanofibers
Nanofibers, which are produced from converting carbon dioxide, could be building blocks of the future. Researchers have found that the strength, flexibility, and conductivity of nanofibers are superior to that of steel. As a result, it can be employed as a lightweight and high-strength material in building construction.
Nanofibers can be grown into a stronger formation called carbon nanotube. The carbon dioxide emitted from natural gas power plants can be segregated and converted to a carbon nanotube. Carbon nanotubes (CNTs) can be added to cement-based materials to nucleate hydration products, control microcrack formation, enhance mechanical behavior, and reduce deformation.
The use of carbon dioxide directly or indirectly in the chemical conversion process in material production and building construction is a key strategy to mitigate climate change and use resources efficiently.
Carbon dioxide works as a blanket in the atmosphere and traps heat in the air. The CO2 blanket in the air prevents the earth from cooling and causes global warming. So, it is one of the major causes of global warming.
Several construction materials can be produced from carbon dioxide in combination with other materials. For instance, carbon dioxide has been used to manufacture resins, foams, and plastics. Moreover, fresh concrete can be cured using carbon dioxide. The curing process uses 3.5 Kg carbon dioxide per cubic meter of concrete
The production of carbon-negative aggregate is another application of carbon dioxide in building materials. Additionally, nanofibers are manufactured by converting carbon dioxide. This material has the potential to blocks in the future.
Can a net-zero carbon concrete replaces the conventional one?
Embodied Carbon in Construction: High Time to Reduce it