Use of Dielectric Constant for Determination of Water-to-Cement Ratio (W/C) in Plastic Concrete: Part 2: Comparison Determined W/C Values by Ground Penetrating Radar (GPR) and Microwave Oven Drying Measurements
Abstract
This paper series includes two parts: (1) volumetric water content modeling, and (2) comparison w/c characterization results from two methods. In part (2), the dielectric constant values of freshly mixed concrete were measured by an 800 MHz GPR in plastic stage from 10 min age to 70 min age. The volumetric water contents of plastic concrete were calculated by the theoretical model from part 1 and the w/c values of plastic concrete were further determined. The microwave oven drying measurement has also been used to determine gravimetric water contents of plastic concrete and further been used to calculate the w/c. The calculated w/c results based on the GPR measurement had an average coefficient of variation (COV) of 1.28%, while the microwave oven drying measurement results calculated w/c values had an average COV of 4.34%. The p-value of the t-test of calculated w/c errors (w/c) of these two methods were 0.3353 and 0.7833, respectively. The results indicate the dielectric constant measurement can be a potential method to determine the w/c of plastic concrete.