Evaluating the Effect of MICP Treatment on Problematic Calcareous Soil of Hormoz Island in Iran

Document Type

Conference Proceeding

Publication Date

1-1-2026

Abstract

The southern regions of Iran such as Hormoz Island feature a vast coastal area dominated by calcareous soils which present significant geotechnical challenges for construction and civil engineering projects due to their unique properties. Selecting an appropriate method to enhance the geotechnical parameters of such soils is crucial from both environmental and economic perspectives. In recent decades, Microbially Induced Calcite Precipitation (MICP) has emerged as a widely recognized and innovative approach for sustainable soil improvement. This study evaluates the effects of MICP treatment, using the ureolysis pathway, on the mechanical behavior of the carbonate soil from Hormoz Island and compares the results to those of Firouzkooh sand, the standard silicate sand of Iran. California Bearing Ratio (CBR) and Unconfined Compression Strength (UCS) tests were carried out on both treated and untreated carbonate and silicate soils under varying bacterial concentrations (OD) and urea-to-calcium chloride ratios (U/C). The results indicated a substantial increase in CBR and UCS values for both soils after treatment. For siliceous sand, the CBR increased from 10.47% to 95.06%, while calcareous sand improved from 49.47% to 161.53%. In UCS tests, siliceous samples reached about 475 kPa at OD = 1 and U/C = 1.5, while calcareous samples achieved about 350 kPa at OD = 1 and U/C = 0.5. SEM images revealed that newly formed calcite crystals effectively bridged soil particle contacts in siliceous samples, facilitating stronger bonding than in calcareous soils, while XRD confirmed the formation of CaCO3 in both soil types. The inherent angular shape of Hormoz Island sands contributed to higher initial bearing capacity, but the pre-existing carbonate reduced the relative efficacy of MICP-induced bonds. Notably, the selection of bacterial concentration and urea-to-calcium chloride ratio proved critical in optimizing strength gains, highlighting the importance of carefully calibrating MICP protocols for varied soil conditions. This study shows that MICP treatment could be a potential solution for improving the geotechnical properties of Hormoz Island’s calcareous soils.

Publication Title

Geo Congress 2026 Geosynthetics Pavements and Soil Improvement Selected Papers from Geo Congress 2026

ISBN

[9780784486764]

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