22 research outputs found
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