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Advances in Materials Science and Engineering
Volume 2016 (2016), Article ID 1650979, 12 pages
http://dx.doi.org/10.1155/2016/1650979
Research Article

An Accelerated Test Method of Simultaneous Carbonation and Chloride Ion Ingress: Durability of Silica Fume Concrete in Severe Environments

1Department of Civil and Environmental Engineering, Purdue University, West Lafayette, IN 47906, USA
2Department of Civil and Environmental Engineering, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran, Iran
3Department of Civil Engineering, University of Tehran, P.O. Box 14155-6619, Tehran, Iran
4Department of Railway Engineering, Iran University of Science and Technology, P.O. Box 16765-163, Tehran, Iran

Received 4 November 2015; Revised 19 April 2016; Accepted 27 April 2016

Academic Editor: Seung-Jun Kwon

Copyright © 2016 S. A. Ghahari et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The effects of simultaneous carbonation and chloride ion attack on mechanical characteristics and durability of concrete containing silica fume have been investigated through an accelerated test method. Specimens containing different amounts of silica fume were maintained in an apparatus in which carbon dioxide pressure and concentration and relative humidity were kept constant, and wetting and drying cycles in saline water were applied. Surface resistivity, sorptivity, CO2 consumption, and carbonation and chloride ion ingress depths measurements were taken. Phase change due to carbonation and chloride ion attack was monitored by XRD analysis, and microstructures and interfacial transition zones were studied by implementing SEM as well as mercury intrusion porosimetry. It was expected to have a synergistic effect in the tidal zone where simultaneous carbonation and chloride ion attack happen. However, the observed reduced surface resistivity, compared to specimens maintained in CO2 gas, could be due to the moisture that is available near the surface, hindering CO2 from penetrating into the pores of the specimens. Moreover, the porosity analysis of the specimens showed that the sample containing silica fume cured in the tidal zone had 50.1% less total porosity than the plain cement paste cured in the same condition.