The dielectric permittivity of cementitious
materials during 24 hours hydration period at a frequency of 2.45 GHz using a
network analyzer with open-ended probe technique was measured. Influences of
water-to-cementitious ratios, cement types, pozzolans and aggregate types are
taken into consideration. The results show that dielectric permittivity is
strongly affected by initial water-to-cementitious ratio and the rate of
hydration reaction which can be changed by fineness of cement (Types 1 and 3),
pozzolan materials and aggregates (river sand with/without crushed limestone
rock). Dielectric permittivity is relatively high and remains constant during
the dormant period, after that it decreases rapidly when the hydration reaction
resumes and continues to decrease during the acceleratory period.
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