Development of Engineered Cementitious Composites with Conductive Inclusions for Use in Self-sensing Applications

The mechanical and a.c. electrical properties of a new varietal of engineered cementitious composite (ECC) incorporating conductive inclusions are presented. Electrical measurements were undertaken over a wide frequency range while curing and when under uniaxial tensile loading to study the influence of ongoing hydration and multiple microcrack formation on the composite electrical impedance. When presented in Nyquist format, the work shows that conductive inclusions reduce the bulk resistance of the composite while enhancing its polarizability, transforming the classic, single-arc bulk response of typical cement-based materials to a two-arc response. The bulk resistance was shown to increase with time and damage, the former being due to refinement of pore-structure during hydration. Conductive inclusions smaller than the average microcrack width of ECC were shown to improve the sensitivity of the composite to cracking, while those with high aspect ratio resulted in better electrical continuity at low volume fractions