Curing process monitoring of cementitious grout using time domain reflectometry (TDR) system

Abstract

Curing process monitoring of the cementitious grout is necessary for its successful use and to ensure the serviceability of the constructed, repaired, and stabilized infrastructures using that material. In this study, time domain reflectometry (TDR) system is applied to monitor the curing process of the cementitious grout based on the changes in relative permittivity (εr). To utilize the TDR system to electrically conductive cementitious grout, a TDR probe with coated core electrode (coated probe) is manufactured, and a calibration is performed to evaluate the formal εr by using the coated probe. The coated probes are installed in the middle and at the bottom of the cementitious grouts with a length of 950 mm, and the εr have been evaluated with curing time using both middle probe (εr(middle)) and bottom probe (εr(bottom)). In addition, compressive strength tests are performed on separately prepared specimens for comparative analyses. Experimental results show that the εr(middle) and εr(bottom) decrease with curing time and converge from the fully cured time, and the curing process of cementitious grout monitored by the TDR system is consistent with the compressive strength developments of the specimens tested with curing time. Therefore, the TDR system with a coated probe may effectively be used for monitoring the curing process of the cementitious grouts based on the changes in electromagnetic property.