Sustainability is a developing concern, particularly in the concrete sector. Traditional concrete, which is comprised of Portland cement, is seriously damaging to the environment as it emits vast quantities of carbon dioxide. Moreover, the extraction of concrete materials, such as lime, causes substantial harm to waterways and communities.
To resolve such problems, researchers and industry professionals have investigated ecologically friendly substitutes for concrete production. This article discusses the environmental drawbacks of conventional materials and sustainable alternatives that can be employed to create novel, green concrete.
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Environmental Hazards
It is common knowledge that the Portland cement sector causes environmental destruction and harm. According to research, the manufacture of concrete, specifically the Portland cement industry, is one of the primary contributors to Carbon-Dioxide (CO2) emissions, with estimates spanning between 5% and 7% of global CO2 emissions attributable to Portland cement production. In addition, the extraction of natural resources causes irreparable harm to the planet.
Sustainable Concrete Mixtures
A recent article published in the Journal of Sustainable Construction Materials and Technologies provides a detailed analysis of the sustainable methods to produce concrete via alternative mixture designs.
According to the article, two options to investigate are volcanic ash concrete and pulverized glass pozzotive concrete. Fly ash, which is the byproduct of burning coal, is one of the most commonly used additives in concrete formulation to reduce the quantity of Portland cement, which not only makes concrete firmer but is also environmentally beneficial.
Natural pozzolans, such as volcanic ash, have tremendous potential as a fly ash substitute. The harvesting of this material is considerably less harmful to the environment than the extraction of lime for the production of Portland cement.
Silica Fume is a different kind of concrete mixture that has been shown to increase its durability and strength while reducing carbon emissions by substituting variable amounts of Portland cement. There are disadvantages to this material, including the possibility of price increases or variations in locations where it may not be readily available.
Use of Plastics and Composite Waste
The utilization of plastics and composite wastes as a reinforcement of concrete is not only useful for the substitution of harmful substances but plays a pivotal role in the reduction of land pollution. The Journal of Composites Science has an article focusing on the use of recycled materials for concrete production.
The study investigates the potential for employing recycled resources, such as crushed carbon fibers, plastic debris, rubber agglomerates, and glass particulates, to strengthen concrete. The addition of plastic waste to lightweight concrete produced beneficial results. For the maximum load-carrying capability, a volume fraction of 7.5% was determined to be optimal. Compression and bending experiments were conducted one, seven, and thirty-eight days after treatment, with the extended cure times yielding greater strength.
Reinforcement was provided in the form of Crumbled Rubber Concrete (CRC), which was partially or entirely comprised of shredded waste tires. The results demonstrated that CRCs increased the concrete's resistance to cracking. Rubber aggregates could enhance the power intake and resilience of a material.
As a method for reinforcing concrete, glass particulates are an additional waste material that has been examined. Carbon fiber, which is not truly reusable, is being utilized in greater quantities compared to ever before due to its declining price. Continuous carbon fiber is frequently used as an additive in concrete for enhanced concrete.
Glass-Fiber Reinforced Fiber Aggregates
The class of materials known as fiber-reinforced polymers (FRP) can be used to reinforce concrete. Glass fiber-reinforced plastic (GFRP) rods are now regarded as a viable alternative to conventional steel reinforcement.
As per the latest article in Applied Sciences, particularly owing to superior corrosion resistance, GFRP has gained popularity as a replacement for steel in RCs for meeting endurance and sustainability criteria. GFRP is known to have a high tensile strength, approximately 1100 MPa, compared to steel, which is generally deemed to have a tensile strength of 400 MPa.
Insufficient elasticity is one of the characteristics that calls into doubt the use of GFRP bars in flexure columns, where flexural yield is a critical property for designing secure structures.
Recycled Alccofine Aggregate for Sustainable Concrete Production
The high consumption of organic agglomerates poses a risk of aggregate shortage; therefore, recycled aggregates are employed to circumvent this problem. IOP Conference Series: Earth and Environmental Science has published a research article focusing on the utilization of alccofine.
Alccofine can minimize cement consumption and atmospheric CO2 emissions. Alccofine increases the concrete's resilience and decreases its permeability by partially replacing the binding substance. It enhances weathering and chloride attack resistance. According to the article, up to 10% alccofine supplementation yields optimal results, while further additions result in a decrease in strength due to a boost in pozzolanic concentration.
Implementation of Nanotechnology
Nanofillers have been recommended for the sustainable development of concrete. It has been determined that 2% of nano CaCO3 additives is the optimal amount. Incorporating these additives into cement mortar yields superior compression and flexural durability in comparison to conventional mortar. This mortar's microstructure study indicated the existence of nanostructures with calcite deposition. The existence of nanofillers compacts the cement mortar framework, thereby enhancing the composites' physical characteristics.
Future Perspective
The building material and concrete industries' CO2 emissions pose a grave hazard to people's health and have a devastating effect on the surroundings. Therefore, the United Nations is under pressure to implement green or CO2-free concrete and construction by 2050.
An article focused on carbon emission-free concrete pathways has been published recently in Case Studies in Construction Materials. Sustainable Geopolymer Concrete (GPC) that utilizes industrial byproducts such as with little to no cement content is demonstrating encouraging outcomes that, with future advancements, could pave the way for zero carbon emission concrete that meets structural and other standards.
The use of zero-carbon concretes for the foundation of both residential and business structures is minimal. The mechanical benefits of the aesthetically pleasing smooth slabs created from zero-carbon concrete can be investigated in the laboratory. In addition, very little research has been conducted on the structural, acoustic, and earthquake-resistant properties of zero-carbon concretes.
Long-term testing is required to investigate the use of zero-carbon concrete as pipelines for the transport of exceedingly toxic and acidic substances and as storage containers for biowaste and wastewater.
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References and Further Reading
Wasim, M. (2022). Future directions for the application of zero carbon concrete in civil engineering-A review. Case Studies in Construction Materials, e01318. Available at: https://doi.org/10.1016/j.cscm.2022.e01318
Devaraj, R., Olofinjana, A., & Gerber, C. (2023). Making a Case for Hybrid GFRP-Steel Reinforcement System in Concrete Beams: An Overview. Applied Sciences, 13(3), 1463. Available at: https://doi.org/10.3390/app13031463.
Citation, S. et. al. (2023). Recycling Unrecycled Plastic and Composite Wastes as Concrete Reinforcement. J. Compos. Sci. 7(11). Available at: https://doi.org/10.3390/jcs7010011.
Karthik, C. & Nagaraju, A. (2023). IOP Conf. Ser.: Earth Environ. Sci. 1130 012012. Available at: https://doi.org/10.1088/1755-1315/1130/1/012012
Babcock, R., & Salama, T. (2022). Analysis of alternative sustainable approach to concrete mixture design. Journal of Sustainable Construction Materials and Technologies, 7(2), 40-52. Available at: https://doi.org/10.47481/jscmt.1114597
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