![]() ![]() As shown below, the spectrographic image of cement is “chemically-locked” and encapsulates the pore structure within the matrix, not allowing free-moving crystal calcium (lime and limestone) to absorb and reabsorb. Studies show that recarbonation accounts for an average of 20 per cent of the carbon dioxide emitted during the production phase of concrete, reducing its whole life CO2 impact. Recarbonation is the reabsorption and release of carbon dioxide (CO2) from the atmosphere during a materials in-use phase. Source: EuLA (European Lime Assoc.) / TU Clausthal, 2008 Quantifying CaCO3 carbon emissions cyclically as kJ/mol Approximately 14% of the lime is used in activities that do not have an explicit reaction with CO2, but it may be possible to engineer this within the life cycle of the material (soda lime glass, soil stabilization). Approximately 20% of lime is used in activities that exploit reactions with CO2 and weathering (e.g., agricultural liming, lime-based building products (bricks/blocks, coatings/finishes). ![]() Of the lime produced in the United States and European Union, 30–40% is used by the steel industry as a fluxing agent, 14% is used in other industries (sugar refining, glass, paper, precipitated calcium carbonate), 10–20% is used in construction and 16–24% is used for environmental remediation/treatment (flue gas desulphurisation, water treatment, acid mine drainage). Like cement, lime is produced by heating limestone (although, solely) at 900° C in a kiln, but is subsequently used in numerous industries besides cement and clinker. Portland Cement) do not repurpose easily in reconstruction and do not reconstitute soundly in landfill. These high-strength products provide solutions for modern architecture and infrastructure, however, they fall short of being environmentally responsible. The clinker is hydrated during construction to produce mortar and concrete. Lime-based building products that have very low-to-no concentrations of Portland cement perform differently than their high cement-based counterparts.Ĭement is produced by heating limestone and a source of silicon (clay/shale) in a kiln at 2000° C to produce metastable calcium silicate minerals (clinker, e.g., Ca2SiO4).Although cement contains lime and limestone (calcium carbonate and calcium hydroxide) – its highly solid, non-crystalline nature traps free moving carbonates, reducing its ability to cyclically ‘recarbonate’ CO2.Cement-based building products absorb only up to 20% of its produced carbon output resulting in partially sustainable end-use materials.Carbonate minerals found in calcium carbonate and calcium hydroxide (limestone & lime) freely exchange CO2 with the environment during production and in the product life cycle. ![]() ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |