Title: The potential of microwave curing for manufacturing low-carbon concrete
Speaker: Pro. Bai Yun(University of London)
Venue: Room 205, Building No.14, Wushan Campus
Time: November 9, Friday, 14:30
Steam curing is widely adopted by construction industry to facilitate the development of early strength of concrete. Although it can shorten the curing duration and provide economic benefits, it may lead to thermal stress inside the large or thick concrete products due to non-uniform heating. Moreover, it is not environmentally friendly due to its high energy consumption.
Different from steam curing which is dependent on thermal conduction, microwave heating relies on energy conversion, which can result in fast volumetric heating. All the components of concrete are dielectric materials, particularly water. They can absorb microwave effectively and electromagnetic energy can thus be converted into thermal energy. Hence, attempts have been made to apply microwave curing in the manufacture of cement and concrete products since 1980s. Although some pilot studies have proved that microwave curing could be a promising alternative accelerated curing method for the production of precast concrete with shorter curing duration and lower energy consumption, neither curing temperature nor relative humidity was well controlled during microwave curing process in these previous works, which may cause long-term strength loss and durability issues.
In this paper, ongoing research on developing a smart microwave system for manufacturing concrete products is introduced. The key features of this microwave system include using optical fibre Bragg grating (FBG) sensors to control the temperature and the humidity inside concrete and microwave oven cavity, respectively. Using this tailored-made microwave system, research is ongoing in the Advanced and Innovative Materials (AIM) Group at University College London to explore the potential of curing two types of low-carbon cementitious systems, namely high-volume fly ash (HVFA) and alkali-activated fly ash (AAFA). In both systems, thermal curing is essential for the strength development, in particular, early-age strength development. The results indicated that even with 55% of Portland cement (PC) replaced by fly ash, the compressive strength of HVFA concrete can achieve 20MPa after only 8-hour’s microwave curing. In the case of AAFA system where 100% fly ash is activated by NaOH without using PC, a 42MPa compressive strength can be reached within 6 hours’ microwave curing, which compared to the similar compressive strength achieved after 24 hours’ thermal oven curing at 85oC, representing an 18-hour reduction of curing duration and 73% saving of energy consumption. Based on the results obtained so far, the potential of this innovative microwave curing technique for future precast concrete manufacture is then discussed.
Professor Yun Bai is Chair in Construction Materials in the Department of Civil, Environmental & Geomatic Engineering (CEGE) at University College London (UCL). He is also Head of the Advanced and Innovative Materials (AIM) Group, Deputy Head of Civil Engineering Section and Co-Director of UCL-UDM Advanced Infrastructure Research Centre (UUAIR). With over £8 Million funding and some 150 journal and conference publications, Professor Bai has developed a research center in central London to promote industry-driven and interdisciplinary research in material science and engineering in order to provide leading edge sustainable solutions to the challenges facing engineers in today’s changing society and environment. The current research themes covered by his research group include: novel low-carbon cementitious materials, advanced composite materials, rheology of novel cement and concrete, durability of concrete structures, structural health monitoring and nuclear waste immobilisation.
In addition, with more than £1.5 Million funding received over the past 10 years from EPSRC, The Royal Academy of Engineering, Royal Society and British Council (including the most prestigious £1.09 Million EPSRC ‘UK-China Bridge in Sustainable Energy and Built Environment EP/G042594/1’), Professor Bai has established extensive collaborations with both leading academia and industry in China. Professor Bai is a Fellow of The Higher Education Academy (FHEA), Fellow of The Institute of Concrete Technology (FICT) and Fellow of The Institute of Materials, Minerals and Mining (FIMMM).
Announced by School of Materials Science and Engineering