CHARACTERIZATION OF PORTLAND-CEMENT CONCRETE USING ELECTROMAGNETIC-WAVES OVER THE MICROWAVE-FREQUENCIES

A study was conducted to evaluate the effect of the basic properties o f 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-si lica, and two types of cement, type I and high alkali. Other PCC mixes were prepared and contaminated with two methods, addition of sodium c hloride (NaCl) to the mixing water and immersion of hardened PCC speci mens (prepared at a 0.45 w/c ratio) in 6% (by wt) NaCl solution after 28 days of curing. The dielectric properties were evaluated using a co axial transmission line designed to allow measurements over the freque ncy range of 0.1 to 1 GHz. The dielectric properties of PCC specimens were evaluated over curing time. Powdered PCC samples were obtained fr om chloride contaminated specimens and chloride contents were determin ed using Virginia Tech Procedure. The results showed significant effec ts of curing time on the dielectric properties of PCC specimens and in significant effects of w/c ratio, air entrainment, and cement type. Th e dielectric properties showed a significant difference between PCC sp ecimens with different aggregate types. The chloride presence (in PCC) did not influence significantly the PCC dielectric properties. (C) 19 98 Elsevier Science Ltd.