Hydraulic characteristics and incubation methods for enhancing durability of Fungi- Mycelium treated silica sand using Rhizopus oligosporus and Rhizopus oryzae combination

Nowadays, the application of Fungi as a bio-mediated soil improvement technique is developing. The hydraulic properties of Rhizopus Fungi-Mycelium Treated Soil are unknown, and the treated sample tends to have low durability. This article presents experimental results on the hydraulic conductivity and shear strength of Fungi-mycelium-treated silica sand. The fungi used in the experiments are a combination of Rhizopus oligosporus and Rhizopus oryzae, which are popular for making Tempeh, a local soybean cuisine from Indonesia. The samples were prepared by mixing the sand with Tempeh inoculum at various treatments and Tempe inoculum and rice flour dosages for enhancing the durability of the treated soil. The results showed that the saturated permeability of the treated soil could be reduced by about 10 times compared to the untreated soil. In addition, the Soil-Water Characteristic Curve of the treated soil also developed. The effect of the fungi appears to fill the void of soil and hence increases the Air Entry Value and residual suction of soil. The curing method outside the mold (O-method) with 10% Tempeh inoculum, and 5% Tempeh inoculum with 5% rice flour is proven can extend the durability of the treated sample, the undrained compressive strength is about 40 kPa on day 14. Scanning electron microscope was performed on the samples, which lasted for 4 months. The mycelium and hyphae are still clearly seen covering all sand particles with different percentages of Tempeh inoculum and rice flour. When the mycelium covered all the sand particles and filled the pores, the water flow was partially blocked. It might be attributed to the strong hydrophobicity of the fungi, which could prevent water from penetrating the soil.