Assessment of Sulfate-Induced Heave in Chemically Treated Soils Using a Novel Hybrid Sensor

Highway agencies frequently encounter problems caused by sulfate-induced heave in lime- and cement-treated subgrades. A thorough evaluation of sulfate-related risks for subgrades involves time-consuming laboratory tests. A real-time monitoring of the sulfate heaving phenomenon in the test section in the real field environment would provide a quick performance evaluation of sulfate soils treated with chemical additives. This would help transportation agencies in producing resilient pavements with low maintenance issues. This article presents an innovative hybrid sensor comprising a bender element and time domain reflectometry that can evaluate sulfate-related heave in real time. The new sensor was calibrated in the laboratory by studying the strength and stiffness behavior of three chemically treated high-sulfate soils. Following laboratory calibration, the sensor was embedded in lime-treated field sections, where the changes in moisture and stiffness were monitored simultaneously in real time. Field testing proved that the sensor was able to provide data to assess sulfate-induced heaving in the field. This article details the development of this sensor that can save millions of dollars for transportation agencies in the better stabilization design for sulfate soils.