Dielectric Properties of Cement-based Materials

Abstract

The objective of this research was to study the influence of moisture and temperature on the dielectric properties of cementitious materials (cement paste, mortar and concrete). The mix proportions including Portland cement Types 1 and 3, sand, coarse aggregate and admixtures (fly ash, silica fume, superplasticizer and air-entraining agent) were studied to investigate the dielectric properties. The results of this study were used as the data base of curing cementitious materials with microwave energy. The Network analyzer was used for measuring of the dielectric properties with opened ended coaxial probe technique.

From the tested results of the dielectric properties of cementitious material, it was found that temperature did not affect the dielectric properties of solid proportions but it had an effect on the dielectric properties of liquid proportions. In the case of  the dielectric properties of cementitious materials,  it was observed that the dielectric properties of all specimens  showed the highest values in initial period after mixing (0-3 hours) but these values were rapidly decreased in next period (3-18 hours), and at 24 hours after mixing the dielectric properties yield comparable values. The dielectric properties of cementing materials increased with increasing the water-to-binder ratios. For cementitious materials with Portland cement Type 3, it was found that the dielectric properties were higher than that of Portland cement Type 1. In case of the admixtures, it was observed that the cementitious materials with fly ash showed the highest dielectric properties and the dielectric properties of the cementitious materials with silica fume were less than that mixed with fly ash. The cementitious materials without admixtures showed the lowest dielectric properties