| The pyroelectric effect, which is useful for temperature sensing, was observed in cement-based materials. The use of short steel fibres (8 micron diameter), together with polyvinyl alcohol ( PVA ), as admixtures greatly enhances the effect, thereby attaining pyroelectric coefficient 6×10-8 C/m2 K (10 kHz). However, due to the high value (2500) of the relative dielectric constant, the pyroelectric voltage is lower than those of plain cement paste or carbon fibre (15 micron diameter) cement paste. Carbon fibre cement paste and plain cement paste are comparable in the pyroelectric voltage, though the pyroelectric coefficient is higher for carbon fibre cement paste than plain cement paste. The pyroelectric effect in cement-based materials is attributed to the increase in mobility of the ions as the temperature increases. 24 refs. |
