United States Department of Transportation
i
Innovative Bio-Mediated Particulate Materials for Sustainable Maritime Transportation Infrastructure
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2017-08-15
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[PDF-1.44 MB]
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Abstract:he mechanical properties of sandy soils in the coastal area and beach sands often do not satisfy construction expectation for maritime transportation infrastructure. The salty, loose sand makes it difficult for quick construction of port, building and roadway. Sometimes the weakness and unpredictability of loose sand properties can lead to unexpected collapse. Such large soil deformations can cause significant damage to constructions in the vicinity and potential loss of human life. With an ever growing demand for quick, safe, and green transportation construction, the need for sustainable construction materials in the coastal area is evident. Traditional construction materials, such as concrete, are not sustainable which have significant impact on the environment (Akiyama et al. 2012). Biomineralization is a promising and environmentally innocuous technology to improve soil engineering properties. It naturally happens and is induced by nonpathogenic organisms that are native to the soil environment (DeJong et al. 2006). One common biomineralization process is microbial induced calcite precipitation (MICP), calcite precipitation act as an agent of cohesion which can bond sand grains together and improve the engineering properties of sand. This innovative field has the potential to meet society’s ever-expanding needs through improving soil properties and perfecting soil durability. Especially, this technology is environmentally friendly. Sporosarcina pasteurii has been widely used for MICP due to its highly active urease enzyme, which catalyzes the reaction network towards precipitation of calcite (DeJong et al. 2006, Chou et al. 2011, Zhao et al. 2014a, Jiang et al. 2016, Pham et al. 2016, Li et al. 2017). This process produces dissolved ammonium and inorganic carbonate. The released ammonia subsequently increases pH, leading to accumulation of insoluble CaCO3 in a calcium rich environment. The precipitated calcite can be used as bio-mediated cohesive material to particulate material. MICP can provide unexplored opportunities for cost-effective, in situ improvement of the engineering properties of soil. As one of the natural process in mineral precipitation, MICP by urea hydrolysis can result in relatively insoluble compounds contributing to soil cementation. Previous research and testing has focused almost exclusively on the standard Ottawa silica sands due to its uniform pore size. As a result, little is known on the more problematic cases of sandy soils in the coastal area and beach sands for the bio-mediated soil improvement. The much finer structure and durability are two unknown factors for the MICP (Li et al. 2017). Strength and durability are two among several key engineering properties of MICP-treated sandsfor using as maritime transportation infrastructure. Durability, which can be defined as the ability of a material to retain stability and integrity over years of exposure to the destructive forces of weathering, is one of the most important properties. MICP-treated sandy soil is a kind of porous brittle material. In moist environment, the repeated wetting and drying cycles should be a main reason for strength reduction of these materials.
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