Researchers at CalPortland Co. have released a paper of peer-reviewed scientific studies entitled ‘Incorporating the Effect of Carbonation in Concrete Life Cycle Assessment’. The paper states that concrete buildings, pavements, and structures are silently absorbing CO2 from the atmosphere, apparently to such a degree that the built environment represents one of the world’s largest storehouses of carbon. However, the company has stated that this information is currently excluded from global, national, and regional greenhouse gas accounting methods.
The company notes that concrete, the world’s most popular building material, constitutes a large portion of the global built environment. The production of portland cement, which is an ingredient of concrete, is commonly identified as a major contributor to greenhouse gas emissions. Often, the story ends there. CO2 emissions occur when calcium carbonate, the main component of limestone, is exposed to intense heat as part of the cement production process. These emissions come from both the burning of fuels used to heat the cement kiln and from the CO2 released from the raw carbonates used to make cement. This process is called calcination.
The process of calcination is not chemically stable and is, therefore, reversible. CO2 in the atmosphere reacts with the hydrated cement in concrete and carbonates are regenerated. Exposed concrete in the built environment absorbs carbon dioxide through the reaction of CO2 with concrete compounds, resulting in CaCO3, the main component of limestone. This reaction permanently removes CO2 from the atmosphere and binds it in a stable state within concrete. This process is called carbonation.
According to CalPortland, considerable attention has been paid to quantify the industrial process emissions from cement production. However, the natural reversal process of the uptake of CO2 during concrete’s complete material life phases is just beginning to receive the consideration that CalPortland believes it deserves.
Many organisations and companies are actively working on measures to reduce greenhouse gas emissions. Having a better appreciation of the level of CO2 uptake by concrete can help with the better development of strategies to mitigate the impact of climate change. CalPortland’s paper and several noted studies show that carbonation in cement products represents a substantial carbon sink that is not currently considered in emissions calculations.
The company has stated that the efforts of its researchers illustrate that, to understand the effects of greenhouse gases associated with the built environment, focused studies on CO2 uptake in concrete within the context of its overall Life Cycle Assessment are necessary.
Read the article online at: https://www.worldcement.com/the-americas/28062019/calportland-releases-scientific-paper/
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