Effect of Moisture and Chloride Content on the Direct and Reflected Ground Penetrating Radar Waves Amplitude Ratio in Concrete Slab

Abstract

This paper focused on the effect of various moisture and chloride content on the direct and reflected waves (DW and RW) of Ground Penetrating Radar (GPR) amplitude ratio of concrete slab. The GPR is used in detecting both corrosion agents of 13 numbers of concrete (water/cement ratio= 0.7) slab samples. Radar measurement is employed on a fixed point of the samples to measure two signals referred to as the direct and reflected radar waves amplitudes. Simple signal processing on the collected time domain signal plots is executed by MATLAB® software to compute the attenuation of peak-to-peak amplitude of DW and RW which are normalized with respect to the peak-to-peak amplitude of DW recorded in air. From the analysis, strong linear relationships (R² = 0.82 and 0.96) for water content variation of DW and RW are found. However, a very weak linear relationship with R² of 0.31 for chloride content variation of DW but a strong linear relationship (R² = 0.95) for the RW are established. These findings showed that both moisture and chloride content have a measurable influence on both GPR signals, which enable the GPR utitilisation on detecting the amount of both corrosion agents in concrete. The DW and RW amplitude ratio have the potential usage in mapping problematic zone by moisture and chloride contamination in concrete.