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Investigations of anhydrite in circulating fluidized bed combustion ash as cement retarders



Author(s): Jueshi Qian, Yan Shen, Zhiwei Zhang, Zhi Wang
Paper category: Conference
Book title: 2nd International conference on Microstructural-related Durability of Cementitious Composites
Editor(s): Guang Ye, K. Van Breugel, Wei Sun, Changwen Miao
Print ISBN: 978-2-35158-129-2
e-ISBN: 978-2-35158-123-0
Publisher: RILEM Publications SARL
Pages: 1478- 1490
Total Pages: 12
Language: English


Abstract: 
CFBC ashes are different from most conventional coal ashes for good pozzolanic and hydraulic properties, but the ashes with high SO₃ content are undesirable for active admixture for cement due to some harmful effects. This study has investigated if anhydrite in CFBC ashes can replace natural gypsum to act as a setting retarder by means of setting time, strength development, volume stability, hydration rate and hydration products. Experimental results have indicated that anhydrite in CFBC ashes can be an efficient retarder of the setting of cement but lead to lower mortar strength. The effect is not harmful to volume stability of cement paste in the case of appropriate anhydrite addition. Compared with natural gypsum, anhydrite in CFBC ashes makes ettringite formation slower and more transformable. Additionally, the long-term behavior of anhydrite in CFBC ashes in the hardening process of cement also remains to be studied. Consequently, this paper has raised some future work on this topic.


Online publication: 2013
Publication Type: full_text
Public price (Euros): 0.00