Sequestration of carbon dioxide (CO2) for construction and demolition waste

Orlando Carlos Batista Damin, Deovaldo Moraes Jr, Aldo Ramos Santos

Abstract


The increase of CO2 anthropogenic emissions, such as in burning, the use of fossil fuels and the manufacture of cement, has been indicated as the main cause of global warming. Blamed for the emission of 5 to 7% of carbonic gas in the atmosphere, cement as well as lime trap CO2 during the chemical processes of curing and carbonation. This chemical reaction of carbon dioxide penetration in the moistened cement matrix stands for the rapid healing of products that utilize limestone, where the catalyst is the carbonic acid, which alters the pH of the cement matrix. The main objective of this research is to study the contribution of Construction and Demolition Waste (CDW) to atmospheric carbon mitigation, investigating the ecological impact of its CO2 sequestration capacity and the cement industry initiatives to decrease these gas emissions during the greenhouse effect composition. As a secondary objective, it seeks to quantify in a theoretical and experimental way the contribution of CO2 absorption and adsorption by CDW's unit operations. After that the sample was separated by diameter into three diferent particle sizes and placed on a column of 28cm of height and 3cm in diameter through which were inserted two wires connected to the cylinders with pure CO2 (varying flows) and another air at constant flow rate of 2.99mL/s. Due to time issues CO2 concentrations at the entrance and exit of the column were obtained by titration. CO2 mass experimentally retained in the adsorption samples was approximately 35 times bigger than the amount retained by absorption at the water’s sample – according to Henry’s Law. The results indicate that water at the CDW is responsible for retaining only a small part of CO2. CDW’s CO2 fixation practically results from the unitary operation called adsorption, defined as retention by polarity, molar mass or form of a gas or liquid present in a solid substance, followed or not by a chemical reaction.

Keywords: carbonic gas, carbonation, construction waste, ecology, carbon dioxide.



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