Title: Effect of Moisture on Electrical Properties of Carbon Black-Filled Cement Composites

Author(s): H. Li, H. Xiao, and J. Ou

Publication: Symposium Paper

Volume: 254

Issue:

Appears on pages(s): 133-144

Keywords: carbon black; cement-based composite; electric properties; moisture; piezoresistance; resistance; self-sensing; strain

DOI: 10.14359/20215

Date: 10/1/2008

Abstract:
The electrical properties of nanophase carbon black-filled cement-based composites are sensitive to moisture content. Previous studies indicate that cementbased composites filled with 120 nm carbon black (CB) in the amounts of 15% (A-15) and 25% (A-25) by weight of cement have promising strain self-sensing properties (that is, piezoresistance properties), thus, this study investigated the effects of moisture on the electrical properties of A-15 and A-25. The results indicate that the initial resistance of composites increases with moisture content. Additionally, the resistance of specimens with certain moisture content increases with measurement time. These two phenomena are mainly attributed to a polarization effect. A waterproof measurement (that is, a specimen encapsulated by epoxy) was developed to insulate the composites from ambient moisture for the composites as strain self-sensing materials. The initial resistance of the specimens encapsulated with epoxy and dipped into water stayed constant during measurement time, and their piezoresistance properties were almost the same as those of the specimens exposed to ambient moisture.