Electrical property of cement-based composites filled with carbon black under long-term wet and loading condition

Cement-based composite filled with 120 nm carbon black (CBCC) in the amount of 15% by weight of cement was a promising strain sensor material candidate, of which the resistance was sensitive to strain. This paper showed that the initial resistance of CBCC not only increased with water content but also, increased with the measurement time. These two phenomena were mainly attributed to a polarization effect which strengthened with water content. A waterproof measurement, i.e. a specimen encapsulated by epoxy resin, was developed to insulate the composite from ambient moisture. The effects of full water absorbing capacity of epoxy, creep behavior of CBCC and environmental temperature on the waterproof efficiency were studied. The results indicated that the effects of creep strain and temperature on resistance could be compensated and an epoxy with full water absorbing capacity less than 1.83% could meet the waterproof requirement of CBCC that guaranteed the accuracy of the resistance measurement. (c) 2008 Elsevier Ltd. All rights reserved.