ITZ between fly ash and cement matrix in HVFA self-compacting
Title: ITZ between fly ash and cement matrix in HVFA self-compacting
Author(s): Y.Q. Jiang, L. Guo, Y.F. Pan, J.G. Chen
Paper category : conference
Book title: International Conference on Microstructure Related Durability of Cementitious Composites
Editor(s): W. Sun, K. van Breugel, C. Miao, G. Ye and H. Chen
Publisher: RILEM Publications
Publication year: 2008
Pages: 575 - 581
Total Pages: 7
Nb references: 10
Abstract: To detect the probability of the interfacial transition zone (ITZ) between fly ash and cement matrix, high volume fly ash self-compacting concrete (HVFA SCC) was prepared.
Microstructures of the ITZ and hydration products of fly ash were investigated by SEM using HVFA SCC specimens conserved for 28d at standard curing conditions. It is found that ITZ between fly ash and cement matrix is distinguished. The width of the ITZ is about 5-10µm, among which about 1µm near fly ash particles is water membrane. Lots of ettringite and portlandite exist in the tinier ITZ. Width of the tinier ITZ becomes smaller and smaller and the ITZ graduates away along with the development of pozzolanic reaction between fly ash and portlandite. Based on the experimental results, it can be explained why high volume fly ash cementitious materials exhibit lower strength and weaker resistance to carbonation and freeze-thaw recycles at early ages. It is necessary to grind or to activate fly ash and to adopt lower water-cementitious materials ratio incorporating strict curing so that the second ITZ in HVFA SCC is able to be mitigated or eliminated, and the durability and resistance to harmful ions attack of HVFA SCC are enhanced.
Online publication: 2009-06-09
Publication type : full_text
Public price (Euros): 0.00