The demand for cement, one of the critical materials to satisfy the growing infrastructure and housing needs, is increasing at a significant rate around the world. However, the rising cement demand has contributed to global carbon dioxide emissions and led to a substantial increase in the consumption of energy and material resources for cement production, which has increased the importance of sustainable cement production.
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Importance of Sustainable Cement Production
Sustainable cement is primarily an eco-friendly product that utilizes discarded industrial wastes as raw materials and minimizes the carbon footprint of cement production. Sustainable cement production requires less heat during its production compared to ordinary Portland cement (OPC), leading to less consumption of energy and a substantial reduction in carbon dioxide emissions.
Sustainable cement also has a low shrinkage rate, which makes it more long-lasting compared to OPC. Additionally, the use of industrial waste, such as fly ash and silica fume, in sustainable cement production can prevent large-scale land pollution and reduce the use of virgin material.
Moreover, sustainable cement production requires less water compared to regular cement production, which results in the conservation of a crucial resource, leading to reduced environmental impact of construction.
Less carbon-intensive alternative fuels can be used for heating kilns to significantly reduce the direct carbon dioxide emissions from global cement production. Waste oil, sewage sludges, animal residues, used tires, and lumpy materials can be used as alternative fuel sources for cement clinker production.
Carbon dioxide emissions are directly proportional to the amount of clinker utilized during cement production. Thus, the substitution of clinker with cementitious calcined and natural pozzolans and industrial byproducts such as blast furnace slag and fly ash can decrease the amount of carbon emissions.
Other decarbonization methods that can be used to produce sustainable cement with substantially less carbon emission include improving the energy efficiency during clinker production, improving the grinding efficiency, and using carbon capture, use, and storage technologies.
Types of Sustainable Cement
Magnesium Oxychloride Cement (MOC)
MOC is carbon-neutral cement produced using a concentrated solution of magnesium chloride and magnesium oxide powder, which are byproducts of magnesium mining. Although MOC possesses high compressive strength, water can reduce that strength significantly.
However, this issue can be partially addressed by introducing a small amount of amount of silica lime and fly ash. These additives can fill the MOC pore structure, leading to improvements in durability and strength. Additionally, MOC can lead to corrosion of steel, which is another major disadvantage as the cement cannot be utilized for the construction of reinforced concrete structures.
Ekkomaxx cement consists of 5% renewable liquid additives and 95% fly ash, has almost zero carbon footprint, and can be produced using 95% less virgin material and 50% less water than OPC.
The cement possesses high crack resistance, early strength, resilience, durability, corrosion resistance, sulfate attack resistance, and freezing and thawing resistance compared to conventional cement.
Geopolymer cement is manufactured using aluminosilicates, which are obtained from industrial by-products such as fly ash, in place of environmentally harmful calcium oxide. The geopolymer cement displays a similar performance as OPC based on cost and performance and emits almost 95% less carbon dioxide compared to conventional cement.
Calcium Sulfoaluminate Cement (CSC)
The CSC production requires a temperature of 1232.2 oC in place of 1426.6 oC required during regular cement production, leading to less carbon dioxide emission in the atmosphere. A maximum of 25% energy savings and an approximately 20% carbon dioxide emission reduction can be realized using CSC in place of OPC.
Additionally, the CSC sets rapidly, with the 28-day strength of conventional concrete can be achieved in 24 hours using CSC. Thus, the cement is suitable for projects where rapid setting of concrete is necessary, such as airport runways and bridge decks.
The ferrocrete cement is produced by mixing iron and silica, which are obtained as waste byproducts from the glass and steel industry. The material mixture is then cured using carbon dioxide, which makes the cement a carbon-negative material.
Sequestrated Carbon Cement (SCC)
SCC is manufactured using brine or seawater mixed with carbon dioxide and can be utilized as an OPC substitute. During SCC production, carbon dioxide-rich gases are filtered through seawater. The magnesium and calcium extracted from the seawater react with carbon dioxide to produce white, high-quality cement that is stronger than regular OPC.
Other Cement Types
Sustainable cement produced using the reactive hydrothermal liquid-phase densification method can lower carbon emissions. Although the cement is produced using the same raw materials used for OPC production, its production requires a lower temperature and is based on a different chemical reaction that emits less carbon dioxide compared to regular OPC cement production.
Limestone Calcined Clay Cement (LC3) is a new sustainable cement type based on a blend of calcined clay and limestone, which can be used to decrease the clinker content by half compared to the 95% clinker content present in OPC, resulting in up to 40% reduction in carbon dioxide emissions.
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References and Further Reading
Schneider, M., Romer, M., Tschudin, M., Bolio, H. (2011). Sustainable cement production—Present and future. Cement and Concrete Research, 41(7), 642-650. https://doi.org/10.1016/j.cemconres.2011.03.019
Makul, N. (2020). Modern sustainable cement and concrete composites: Review of current status, challenges and guidelines. Sustainable Materials and Technologies, 25, e00155. https://doi.org/10.1016/j.susmat.2020.e00155
Limestone Calcined Clay Cement. [Online] Available at https://lc3.ch/ (Accessed on 28 September 2023)
Green Cement: Definition, Types, Advantages, and Applications. [Online] Available at https://theconstructor.org/concrete/green-cement-types-applications/5568/ (Accessed on 28 September 2023)
Somers, K., Schulze, P., Reiter, S., C, Zigler, T. (2020). Laying the foundation for zero-carbon cement [Online] (Accessed on 28 September 2023)