Hydromechanical Response of Moderately Calcareous Clayey-Sand Treated with Nutrient Additive or Cementation Solution

This study examines the effects of organic and chemical amendments on the moisture retention, evaporation, and cracking behavior of carbonate-rich clayey sand under drying conditions. Two treatments were evaluated: a microbial growth medium (Potato Dextrose Broth, PDB) and a biocementation precursor solution containing calcium chloride and urea. These were compared to an untreated control condition to assess their influence on drying dynamics, cracking evolution, and carbonate stability. Both treatments delayed crack initiation, reduced crack width, and lowered the crack length intensity factor (CLIF) relative to the control condition. Soil water retention curves (SWRC), modeled using the Fredlund and Xing equation, showed improved water-holding capacity in treated soils, particularly at higher suction levels. Evaporation rates were also reduced and were noted to be more stable over time. Despite a notable reduction in native carbonate content (from 7.7% down to ~4%) in the treated specimens, they exhibited a more stable drying trend. This suggests that microbial growth, byproducts, and secondary cementation may offset the loss of natural bonding (provided by natural carbonates). These findings provide insights on and highlight the potential of targeted organic and chemical amendments to enhance the performance of naturally cemented unsaturated soils, with applications in climate-resilient geotechnical design and sustainable land management.