Prof. Chi Sun Poon is currently the Michael Anson Professor of Engineering, Chair Professor of Sustainable Construction Materials and Head of the Civil and Environmental Engineering Department of The Hong Kong Polytechnic University. He is also Director of the recently established Research Centre for Resources Engineering towards Carbon Neutrality. He specializes in the teaching and research of eco-friendly construction materials, concrete technology and waste management. He is a Fellow of the Hong Kong Institution of Engineers and has been serving actively on various professional and government committees. He is a pioneer in the research on valorizing different types of wastes as construction materials. His extensive publications in the area make him one of the leading scholars in this field. He was appointed as a Changjiang Scholar Chair Professor in 2017 and was awarded the State Technological Innovation Award 2017 (2nd Class).
Total Recycling of Concrete Waste using Accelerated Carbonation
Our world is facing critical environmental challenges due to the extensive release of CO2 and the production and use of concrete contribute a significant portion of the carbon emission. Meanwhile, with accelerated urbanization and redevelopment, huge amounts of concrete waste are generated. Carbonation of waste concrete can utilize concrete as a carbon sink due to the rapid chemical reaction between CO2 and the hydration products of cement, which can not only address the CO2 emission issue but also provide means to effective utilization of waste resources.
This paper focuses on the application of carbonation technologies to achieve the total recycling of concrete waste. Different approaches and technologies including standard gas-solid carbonation, pressurized gas-solid carbonation, flow-through gas-solid carbonation, and wet carbonation methods will be introduced and their mechanisms will be discussed. Furthermore, the application of the carbonation products obtained from concrete waste with different particle sizes will be addressed.
The study results indicate that carbonation of waste concrete with different particle sizes can generate carbonated coarse aggregate, carbonated fine aggregate, and high-value products (nano-silica gel, micro-fiber and superfine powders), achieving the total recycling of concrete waste. The accelerated carbonation processes cannot only enhance the properties and values of the recycled concrete waste, but also sequestrate a large amount of CO2. Furthermore, the performance of new concrete incorporating these carbonation products can be significantly improved. Therefore, the developed carbonation technologies of concrete waste provide significant contribution to construction waste recycling and reduction of CO2 emission of the construction sector.