Monitoring hydration process and quality of sand grouted with microfine-cement using shear wave velocity and electrical conductivity measurements

This study aims at monitoring the grouting status such as hydration process and quality of sand grouted with microfine-cement using shear wave velocity (V_s) and electrical conductivity (EC) measurement techniques. The microfine-cement with the maximum particle size < 15 μm and the three angular sands with median particle sizes ranging from 0.47 mm to 1.01 mm were used in this study. The testing specimens were prepared at relative density ~ 70% and water to cement ratio = 1.0, 1.5, and 2.0 in a split plastic mold for the real time continuous measurements of V_s and EC, and for the unconfined compression tests at the end of curing time of 3, 7, 14, and 28 days. The results demonstrate that both unconfined compressive strength (UCS) and V_s show almost constant values after the curing period of 20-28 days; while, the variation of EC is negligible after the curing period of 10-20 days. Therefore, the shear wave velocity measurement technique can be superior to electrical conductivity measurement in terms of monitoring of hydration process of tested sands grouted with microfine-cement. However, both V_s and EC show strong linear relationship with UCS of tested materials, reflecting both non-destructive testing methods can be beneficially used for the quality evaluation of grouted materials.