Sustainable Soil Stabilization Using Garden Waste Ash as a Partial Replacement for Lime in Silt Soils

This study investigates the effectiveness of partial substitution of vegetable garden waste ash (VGA), an agricultural waste, as an alternative to traditional lime additive within the scope of sustainable soil improvement applications in soil stabilization. In the experimental program, mixtures containing VGA at rates varying between 0–8% were prepared using low plasticity silty soil obtained from Kastamonu province, and a constant binder content of 4% was maintained. The engineering performances of the mixtures were evaluated with unconfined compressive strength (UCS) tests; carbon footprint and carbon efficiency (CI) were also analyzed as environmental sustainability indicators. The results show that VGA additive significantly increases UCS values, and the highest strength is obtained in the mixture containing 4% VGA. When the compaction properties are examined, it is observed that the maximum dry unit volume weight decreases with the increase in VGA ratio, and the optimum water content increases. Carbon emission analyses emphasize the environmental burden of traditional lime use, while VGA additive reduces this burden and provides an environmentally friendly alternative. The inverted U-shaped relationship between UCS and CI highlights the importance of determining optimum additive ratios. In particular, the 4% VGA ratio provided the most favorable results from both technical and environmental perspectives.