Exploring the impact of temperature in valorising digestate as a strength enhancer of the expansive soil

In engineering projects involving expansive clay, its mechanical and chemical properties are enhanced through soil stabilization using various admixtures such as fly ash, lime, and cement. Considering the admixture’s limitation in recent years, the employment of waste materials in stabilizing such soils is highly encouraged. This study investigates the efficacy of digestate ash as a soil stabilizer under diverse temperature conditions (100°C to 800°C) through an unconfined compressive strength test at an optimal stabilizer content. The Atterberg’s limits and compressive strength test were performed on the clay with and without additives at room temperature through various curing times (0 and 28 days). The digestate ash was used at 0 to 25% (by dry clay weight) as an additive along with the initial consumption of lime as an activator at 4.5% (by dry soil weight). The maximum unconfined compressive strength value of 336 kPa was observed when using 15% digestate ash obtained at 560°C for a curing period of 28-days. The significant alteration in mineralogical and chemical composition was identified when the DA-modified clay underwent X-ray diffraction and fourier transform infrared examinations. This research facilitates better understanding of digestate ash-based soil stabilization in different thermal conditions, aiding sustainable soil improvement in civil engineering and environmental remediation.