Transforming CO2 into Building Materials

Human-based activities are increasing carbon dioxide (CO₂) in the atmosphere, which, in turn, contributes to various international issues, such as how to tackle climate change and global warming. To combat the challenges caused by the rise of anthropogenic emissions in the environment, new technologies are being created to reduce CO₂ emissions and even transform carbon dioxide into new and useful products.

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Introduction to Polymers as CO₂ Storage

Carbon capture and storage (CCS) is an emerging technology that aims to mitigate CO₂ release into the atmosphere and tackle climate change.

Several existing CO₂ storage systems have proven to be positive. These include geological storage, where CO₂ is injected into deep, porous geological formations. However, this method is limited by the inability to use the stored CO₂. This limitation has led to research seeking new ways to increase the added value of CO₂.

Today, CO₂ has various applications across a range of industrial sectors and products, including food (beverage carbonation, food preservation), metallurgy (welding and cutting), chemicals (fertilizers, urea), and water treatment (pH regulation). Moreover, new applications for CO₂ are emerging, including the production of CO₂-based sustainable fuels, the integration of CO₂ into polymers, and the synthesis of high-value-added chemical compounds.

Applications in Enhancing Construction Materials with Carbon-Derived Polymers

Due to their sustainability properties, carbon-derived polymers have become more popular. The most common polymers are polycarbonates (PCs) and polyurethanes (PUs), which are already widely used.

Polymers in Construction

Polycarbonates are renowned for their properties, such as low weight, high-strength durability, thermal conductivity, and opacity, making them well-suited for roofing, facades, windows, and greenhouses. CO₂ is of particular interest when it comes to finding alternative synthesis pathways for polycarbonates, as it reacts with epoxide-containing molecules to form linear polycarbonates.

Polyurethanes are extremely versatile materials used in foams and coatings. Traditional PU synthesis methods require isocyanates, which pose significant health risks. However, newly developed processes use CO₂ (through the transformation of polycarbonates) in these processes to produce non-isocyanate polyurethanes (NiPUs). Although the NiPU technology demonstrates promise, production remains largely confined to the laboratory, and these materials have not been rolled out on an industrial scale.

Green Concrete

The construction industry is one of the most significant sources of CO₂ emissions, with concrete production alone accounting for 8% of global CO₂ emissions. These facts helped inspire one groundbreaking approach that substitutes the cement in concrete with CO₂-absorbing materials that can transform the greenhouse gas into a useful compound through mineralization.

Traditional mineralization forms carbonates via the reaction between a metal oxide (e.g. CaO, MgO and Ca₃SiO₅) and CO₂. In sustainable concrete, hydrated lime (calcium hydroxide) is incorporated, which absorbs CO₂ to create limestone – an important component as an aggregate in concrete mixtures.

Green concrete achieves strength properties similar to traditional concrete, significantly reducing the curing process from days to hours and increasing cement hardness.

Sustainable Asphalt

There are several avenues of research into applications for CO₂ in asphalt production. Asphalt manufacturing necessitates high temperatures (around 150°C) to lower the viscosity of bitumen. This involves the use of chemical additives that increase production costs. Conventional hot mix asphalt (HMA) and warm mix asphalt (WMA) processes emit greenhouse gases and are, therefore, not sustainable.

Less viscous, more stable bituminous mixtures are being produced via an alternative manufacturing approach that captures CO₂ and combines it with bitumen, water, and natural additives. The stability of these mixtures is contingent on temperature and pressure. It can be further improved with co-surfactants and bio-additives from food waste and animal fats, promoting more sustainable asphalt production processes.

Materials derived from CO₂, such as CO₂-polyurethane, can also be combined with asphalt to improve its properties. Furthermore, special zeolites are being researched and investigated to reduce the asphalt synthesis temperature and lower energy consumption and CO₂ emissions. These zeolites can also adsorb CO₂ to further reduce atmospheric CO₂ levels.

Conclusions on Sustainable Solutions with CO₂

Carbon capture and storage (CCS) is a key tool for combating climate change, but it is also crucial to explore other avenues, such as methods that provide added value to the captured CO₂.

From this perspective, CO₂-derived polymers, including polycarbonates and polyurethanes, can act as sustainable alternatives in the construction industry. While polycarbonates are durable and offer greater resistance, innovative non-isocyanate polyurethanes reduce health risks, although their widespread industrial application remains limited.

Another major advancement is the development of green concrete, which partially replaces cement with CO₂-absorbing compounds via mineralization. This improves concrete's environmental impact and performance while helping reduce construction industry emissions.

While research in sustainable asphalt production is ongoing, it focuses on developing alternative processes incorporating CO₂ to reduce emissions, combining it with bitumen and bio-additives, or using zeolites to reduce synthesis temperatures and adsorb CO₂.

While many of these solutions offer great promise, they remain in experimental stages, which underscores the need for further research to bring about large-scale implementation.

Acknowledgments

Produced from materials originally authored by Javier Ivañez Castellano, Decarbonization Researcher at AIMPLAS.

This information has been sourced, reviewed and adapted from materials provided by AIMPLAS.

For more information on this source, please visit AIMPLAS.