Energy and CO2 from high performance recycled aggregate production |
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| Institution: | 1. Technological Center, University Federal of Alagoas, Campus A.C. Simões, BR 104 Tabuleiro do Martins, Maceió, AL 57.072-970, Brazil;2. Department of Mining and Petroleum Engineering, Escola Politécnica, University of São Paulo, Av. Prof. Almeida Prado No. 83, 05508-900, Brazil;3. Department of Construction Engineering, Escola Politécnica, University of São Paulo, Av. Prof. Almeida Prado Travessa 2 No. 83, 05508-070, Brazil;1. Área de Ingeniería de la Construcción, EPS de BELMEZ, Universidad de Córdoba, Córdoba, Spain;2. Área de Química Inorgánica, EPS de BELMEZ, Universidad de Córdoba, Córdoba, Spain;3. ICIST, DECivil, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal;1. College of Civil Engineering, Hunan University, Changsha 410082, China;2. WOWA International Engineering & Consulting Co. Ltd, Shenzhen, Guangzhou, China;3. Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China;4. College of Civil Engineering and Mechanics, Central South University of Forestry and Technology, Changsha 410018, China;1. College of Civil Engineering, Fuzhou University, Fuzhou 350116, China;2. Department of Structural Engineering, Tongji University, Shanghai 200092, China;3. College of Engineering, Fujian Jiangxia University, Fuzhou 350108, China;1. Department of Civil Engineering, University of Salerno, via Giovanni Paolo II 132, 84084 Fisciano, SA, Italy;2. Department of Civil Engineering, COPPE, Federal University of Rio de Janeiro, P.O. Box 68506, CEP: 21945-970 Rio de Janeiro, Brazil;3. Faculty of Civil Engineering and Geosciences, Delft University of Technology, P.O. Box 5048, 2600 GA Delft, The Netherlands |
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| Abstract: | The use of recycled concrete aggregates (RCA) in applications other than road sub-layers is limited by two factors: the high porosity of RCA in comparison with natural aggregates, and the restrictions set forth in standards and building codes. Research efforts aimed at alleviating these restrictions are focused on improving the quality of coarse RCAs by reducing the amount of adhered cement pastes, which is the weakest element in this system and influences the rheological behaviour.This paper presents an analysis of the environmental impacts of the recent mechanical and thermo-mechanical processing techniques which produce high performance RCA by reducing the volume of adhered cement paste. Based on published data, processing scenarios were established. These scenarios permit making rough estimates of energy consumption, CO2 emissions, fines generation and product quality. Using these data and the available emission factors from several countries, an objective comparison was made between these innovating processes and conventional recycling.The production of fines increases from 40% up to as much as 70% as the volume of adhered cement paste on the RCA is reduced. Fuel fed thermo-mechanical process energy consumption, per tonne of recycled aggregate, varies between 36 and 62 times higher than conventional recycling processes. Mechanical processing, combined with microwave heating, increases energy consumption from 3 to a little more than 4 times conventional recycling. Consequently, CO2 emissions released by conventional coarse aggregate production go from 1.5 to 4.5 kgCO2/t, to around 200 kgCO2/t, for that of fossil fuel fed thermo-mechanical treatments.Mechanical and mechanical/microwave treatments appear to have the greatest environmental potential. Notwithstanding, the further development of markets for fines is crucial for reducing environmental loads. |
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| Keywords: | CDW recycling Recycled concrete aggregates (RCA) High quality RCA Energy consumption Environmental impact |
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