Microbial induced calcite precipitation (MICP) is one of the potential methods for improvement of engineering properties of soil. A laboratory study was conducted to investigate the influence of various factors on engineering properties of MICP-treated soil catalyzed by bacteria and ureases. Some of these factors include bacteria concentration, urease concentration, cementation media concentration, reaction time, type of sand, and curing conditions. The experiments of MICP catalyzed by Sporosarcina pasteurii and urease were conducted in similar conditions. The soil samples were prepared with full contact flexible molds (FCFMs). The results of unconfined compression test show that the experimental factors (bacteria/urease concentration, cementation media concentration, reaction time, and type of sand) have a significant impact on the MICP process and engineering properties of sand treated by both bacteria and urease, whereas the curing conditions has a small effect. The unconfined compression strength (approximately 1.76–2.04 MPa) of bacteria treated samples is almost $5\times$ (approximately 0.33–0.43 MPa) that of urease treated samples under similar urease activity. The MICP process catalyzed by bacteria is much more effective than the process catalyzed by urease in terms of engineering soil properties improvement.

Aeolian sand is widely distributed in the desert. It is susceptible to wind erosion because it consists of fine particles that lack cohesion between them. Wind erosion of Aeolian sand, dune migration, and dust storms in deserts affect the environment and infrastructure severely. Conventional chemical methods for lessening the effect of wind erosion are environmentally unfriendly. This paper examines Aeolian sand bio-remediated by microbially induced calcite precipitations (MICPs). The geomechanical properties of the Aeolian sand remediated by MICP were tested to explore its behavior as a desert bio-crust. The results indicated that a bio-crust of Aeolian sand with suitable strength required 7 days for formation. The remediated Aeolian sand had an average unconfined compression strength of 0.66 MPa and an average inner friction angle of 36° at a bacterial concentration in the OD₆₀₀ range of 0.5–0.8. These findings indicate that formation of bio-crust could serve as protection against desert erosion. The particle characteristics and the porosity of Aeolian sand play an important role in the formation of the bio-crust. Crust from bio-remediated well-graded, high-porosity soil is stronger than crust from bio-remediated, poorly graded, low-porosity soil, given that both soils have the same bacteria concentration.