Natt Makul and Dinesh Kumar Agrawal

pp. 693 - 703

Abstract

Portland-pozzolan cement pastes at a very early stage subjecting to microwave heating were investigated. Microwave
with a 2.45 GHz and multimode cavity was used for the experiments. The pastes containing pozzolan materials (pulverized
fuel ash, metakaolin and silica fume) were proportioned with a 0.38 water/solid mass ratio and a 20% by weight replacement of
total solid content. It was observed that the temperature increased continuously during microwave heating. Some ettringite
rods and amorphous C-S-H fibers appear at 4 hrs. The metakaolin-cement paste exhibited little difference between the watercured and microwave-cured pastes. For the silica fume-cement paste the SF particles under microwave curing had dispersed
more than with the 4 hr–cement paste. The produced phases included calcium silicate hydrate, calcium hydroxide and
xenotile. The pastes can be developed in compressive strength quite rapidly and also consumed more Ca(OH)₂
 in the
pozzolan reaction to produce more C-S-H.

Keywords

• microwave
• microstructure
• Portland cement
• paste
• pozzolan