Characterization of portland cement concrete using electromagnetic waves over the microwave frequencies

A study was conducted to evaluate the effect of the basic properties of Portland cement concrete (PCC) and chloride presence (in PCC) on its dielectric properties over the microwave frequency range of 0.1 to 1 GHz. PCC specimens were prepared at three w/c ratios, 0.35, 0.45, and 0.55, using three aggregate types, limestone, quartzite, and active-silica, and two types of cement, type I and high alkali. Other PCC mixes were prepared and contaminated with two methods, addition of sodium chloride (NaCI) to the mixing water and immersion of hardened PCC specimens (prepared at a 0.45 w/c ratio) in 6% (by wt) NaCI solution after 28 days of curing. The dielectric properties were evaluated using a coaxial transmission line designed to allow measurements over the frequency range of 0.1 to 1 GHz. The dielectric properties of PCC specimens were eval uated over curing time. Powdered PCC samples were obtained from chloride contaminated specimens and chloride contents were determined using Virginia Tech Procedure. The results showed significant effects of curing time on the dielectric properties of PCC specimens and insignificant effects of w/c ratio, air entranment, and cement type. The dielectric properties showed a significant difference between PCC specimens with different aggregate types. The chloride presence (i n PCC) did not influence significantly the PCC dielectric properties.