Journal
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
Volume 109, Issue 1, Pages 265-271Publisher
SPRINGER
DOI: 10.1007/s10973-011-1697-0
Keywords
Fly ash; Dehydration; Rehydration; Blended cement; Compressive strength
Funding
- 973 National Foundational Research of China [2009CB623104]
- National Natural Science Foundation of China [51072058]
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Owing to poor bonding between coarse fly ash particles and hydration products, gap-graded blended cements with fly ash usually show lower compressive strengths than Portland cement. Surface cementitious properties of coarse fly ash were improved by dehydration and rehydration processes in the present study. The results show that during the calcination at 750 degrees C, C-S-H gel is mainly transformed into a new nesosilicate, which is similar to a less crystalline C2S. The formation of melilite from hydration products is also noticed at 900 degrees C, however, this will not contribute to rehydration of calcined fly ash. Rehydration of new generated nesosilicate on the surface of coarse fly ash leads to a better bonding between coarse fly ash particles and hydration products. As a result, both early and late mechanical properties of gap-graded blended cements containing 25% cement clinker and 39% calcined coarse fly ash are higher than those of 100% Portland cements.
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