Microwave heating on cement-pozzolan pastes: Dielectric permittivity, physical properties and numerical heat transfer characteristics
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Abstract
Cement-pozzolan pastes at a very early stage subjecting to microwave heating were investigated. Microwave at an operating frequency of 2.45 GHz associated with a multi-mode cavity was used. The pastes containing pulverized fuel ash (PFA) or silica fume (SF) were proportioned with a 0.22-water/solid mass ratio (w/s). Test results showed that the temperature increased continuously during microwave heating. Some small fibers appear in the paste but none appear in the microwave-heated PFAcement paste. For the SF-cement paste the SF particles under microwave heating had dispersed. The pastes can be consumed more Ca(OH)2 in the pozzolan reaction to produce more C-S-H. The calculated temperature rise of the paste containing PFA without loss of moisture and steady heat transfer conduction consistently agreed with the proposed mathematical model.
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