摘要
Electrical impedance measurements were performed on fine-grained concrete with low volume content of conductive steel and carbon fibres, either as a mono or as a hybrid system. The influences were investigated of the applied frequencies, of fibre combinations and of the age of the composites on the impedance. The results show that when the applied frequency is increased from 0.98 Hz to 1000 Hz, the impedance of the fibre composites significantly decreases. At the same time, impedance difference between plain concrete and fibre-reinforced concrete is enhanced. Dramatic drop of impedance takes place over the low frequency range, i.e. 0.98 to approximately 31 Hz. Impedance also depends on the volume content of hybrid fibres. The cementitious composite with the highest content of hybrid fibres (1.0% steel fibres and 0.2% carbon fibres by volume) has the lowest impedance at all measuring frequencies. 0.6% fibres by volume seem to be a turning point, from which the variation of impedance slows down with the fibre content increases. On the other hand, the impedance increment of the fibre-reinforced composites slows down with the age after 28 days, comparing to plain concrete. (Author abstract) 8 Refs.
Electrical impedance measurements were performed on fine-grained concrete with low volume content of conductive steel and carbon fibres, either as a mono or as a hybrid system. The influences were investigated of the applied frequencies, of fibre combinations and of the age of the composites on the impedance. The results show that when the applied frequency is increased from 0.98 Hz to 1000 Hz, the impedance of the fibre composites significantly decreases. At the same time, impedance difference between plain concrete and fibre-reinforced concrete is enhanced. Dramatic drop of impedance takes place over the low frequency range, i.e. 0.98 to approximately 31 Hz. Impedance also depends on the volume content of hybrid fibres. The cementitious composite with the highest content of hybrid fibres (1.0% steel fibres and 0.2% carbon fibres by volume) has the lowest impedance at all measuring frequencies. 0.6% fibres by volume seem to be a turning point, from which the variation of impedance slows down with the fibre content increases. On the other hand, the impedance increment of the fibre-reinforced composites slows down with the age after 28 days, comparing to plain concrete. (Author abstract) 8 Refs.
