Browsing by Author "Yuksekdag, Zehra Nur"
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Article Citation Count: 10Bacteria-Induced Cementation in Sandy Soils(Taylor & Francis inc, 2015) Gürbüz, Ayhan; Sarı, Yasin Dursun; Yuksekdag, Zehra Nur; Department of Civil EngineeringBacteria-induced calcite precipitation (BICP) is a promising technique that utilizes bacteria to form calcite precipitates throughout the soil matrix, leading to an increase in soil strength and stiffness. This research investigated BICP in two types of sands under sterile and nonsterile conditions. Bacteria formation and BICP in the sterilized sand specimens are higher than those in the nonsterilized sand specimens. The development of calcite with time is initially greater for the sand specimens containing calcite. Scanning electron microscope imaging allowed the detection of cementation from calcite precipitation on the surface and pores of the sand matrix. The effects of injecting nutrient mediums and bacteria into the specimens, as well as pH of soil samples on BICP were investigated. The bearing capacity of biologically treated vs. untreated sand specimens were determined especially by laboratory foundation loading tests.Article Citation Count: 11Cementation in a matrix of loose sandy soil using biological treatment method(Academic Journals, 2011) Gürbüz, Ayhan; Sarı, Yasin Dursun; Yuksekdag, Zehra Nur; Cinar, Berat; Department of Civil EngineeringMan-made materials varying from cement-based to chemical-based have been injected into soils to improve their engineering properties (shear strength, compressibility, permeability, bearing capacity etc.). Soil type in general plays important role in determination of treatment material and method. Materials used for soil treatment might have side effects in terms of air pollution, soil or water contamination etc. during manufacturing or application. An alternative, environmentally friendly soil treatment method that is based on the use of bacteria present in soils and named Biological Treatment Method (BTM) has been used by researchers to bond particles of loose sandy soils via creation of calcite (CaCO3) generated by bacteria using urea to influence the precipitation of calcium carbonate. This study presents the results of bacterial induced cementation (BIC) in matrix of loose sandy soil. A bacterium used in this study is Sporosarcina pasteurii that is naturally present in soils and is aerobic type. The bacteria grown in laboratory environment were injected to the matrix of loose sandy soil. Subsequent nutrient mediums were introduced to specimens to accelerate the development of cementation level. Number of bacteria, pH level, temperature and amount of CaCO3 were measured during the duration of testing. Images of Scanning Electron Microscope (SEM) showed that creation of cementation from precipitation of CaCO3 on the surface and pores of soil matrix were observed for only sand samples into which nutrient was flushed on sequence of arbitrary time.