Non-Destructive Evaluation of Cement-Mixed Soil

This paper describes how electrical resistivity (ER) and time-domain reflectometry (TDR) were used to determine the electromagnetic (EM) properties, electrical resistivity (ρ) and apparent dielectric constant (K_a), of soil-cement mixtures. Laboratory tests simulating cement-mixed soil were performed on large-size specimens (286-mm diameter and 305-mm height) of different soil, cement, and water proportions at regular time intervals up to 56-days. Soil, cement, and water have measurably different EM properties, and as cement consumes water during hydration and bond formation continues during hardening the EM properties change over time. Water content and unconfined compressive strength (UCS) were also measured at 7-, 14-, 28-, and 56-days. For soil-cement samples K_a decreased and ρ increased with time. ρ was found to be directly related to strength gain. Increasing cement content increased strength but decreased electrical resistivity.