Impact of curing time on UCS-electrical resistivity relation of cement grouted sands

As the curing process proceeds, both the strength and electrical resistivity (rho(mix)) of cement-based (or cement-grouted) materials increase, leading to the nondestructive rho(mix) measurement technique is very appealing in the assessment/monitoring of the quality of cement-grouted materials. However, the strength gain of cement-grouted sands with time differs from the increase in rho(mix) with time. Thus, the relationship between unconfined compressive strength (UCS) and rho(mix) can be affected by the curing time. This study evaluated the effect of curing time on the relationship between rho(mix) and UCS of sands grouted with microcement. The ultimate goal of this study is to estimate UCS over time of cement-grouted sands based on rho(mix). Three silica sands with different median particle sizes were grouted with microcement at different water-to-cement ratios (wc) of 1.0, 1.5, and 2.0. Both unconfined compression test and electrical resistivity measurement test were conducted. Results demonstrate that curing time, particle size, and wc influenced both rho(mix) and UCS of tested grouted sands in a similar manner; therefore, a direct relationship between rho(mix) and UCS can be established. However, the complex impact of curing time on the relation between UCS and rho(mix) and the nonlinear increase in UCS with time hinder the capture of adequate interplay between UCS, rho(mix), and curing time. Because a nonlinear increase in UCS with time can be represented by hyperbolic model, an estimation method for hyperbolic model parameters is newly suggested in this study based on rho(mix) at early curing days.