Conductivity/activation energy relationships for cement-based materials undergoing cyclic thermal excursions

The electrical conductivity of a range of concrete

mixes, with and without supplementary cementitious

materials (SCM), is studied through multiple cycles of

heating and cooling over the extended temperature range

-30/?70 C. When presented in an Arrhenius format, the

experimental results display hysteresis effects at the lowtemperature

end of the thermal cycle and, in those concretes

containing supplementary cementitious materials at

higher water/binder ratios, hysteresis effects were evident

over the entire temperature range becoming more discernible

with increasing number of thermal cycles. The

depression in both the freezing and thawing point could be

clearly identified and was used to estimate pore-neck and

pore-cavity radii. A simplified approach is presented to

evaluate the volumetric ratio of frozen pore water in terms

of conductivity measurements. The results also show that

the conductivity and activation energy of the concrete

specimens were related to the water/binder ratio, type of

SCM, physical state of the pore water and the thermal

cycling regime.