Microbial-induced calcite precipitation (MICP) is a promising, sustainable, and environmentally friendly ground improvement technique. This study examined the effectiveness of molasses (MS) as a broth medium compared to nutrient broth (NB). Sporosarcina pasteurii was used in a 0.5 M cementation solution with pore volumes (PV) of 0.50, 0.75, and 1 PV in biotreatment cycles of 9 and 18 days. Mechanical properties of biotreated samples were assessed through unconfined compressive strength (UCS) and split tensile strength (STS) tests, while calcite content, scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDS) were used to interpret biocementation. NB-treated samples exhibited significantly higher strength and calcite content than MS-treated samples. The durability of biotreated samples under 6, 12, and 18 freeze-thaw (FT) cycles revealed that the FT cyclic process affects the mechanical and physical characteristics of biotreated samples. Samples treated with higher PV and for a longer duration exhibited higher strength and durability. The mass losses in NB and MS samples were 7-14.5% and 15-32%, respectively, after 18 FT cycles. Overall, NB samples exhibit higher strength and durability than MS samples. While MS proved less effective as a broth medium compared to NB for the MICP process, its cost-effectiveness and abundant availability make it a promising choice for the MICP process.

This study examines the effectiveness of the bi-stabilization of clay soils using cane molasses and coconut fiber, focusing on improving the geotechnical and mechanical properties of clay. The performance of the two stabilizers, both individually and in combination for bistabilization, was assessed. The geotechnical properties were determined through sieve analysis, Proctor tests, and Atterberg limit methods, while the mechanical properties were measured using a hydraulic press. The results showed that cane molasses reduced plasticity, enhanced soil cohesion, and increased dry density with molasses content. The Atterberg limits (liquid limit, plastic limit, and consistency index) were maximized at a 4% molasses content, with respective increases of 9.28%, 44.80%, and 37.9% compared to clay without molasses (CB). Coconut fiber improved the flexural strength by 361.9% for CF1, whereas molasses improved the compressive strength by 12.24% compared to plain clay. Bi-stabilization allowed for a maximum improvement in flexural strength of 509.52% compared to CB, 49.42% compared to molasses-stabilized clay bricks (CSM), and 31.96% compared to clay composites with coconut fiber (CF). The compressive strength improved by 22.54% compared with CB, 9.21% compared with CSM8, and 14.94% compared with CF 1/2. In summary, bi-stabilization with sugarcane molasses and coconut fiber provided enhanced performance compared with their individual use.