نوع مقاله : پژوهشی
1 دانشگاه بوعلی سینا، عضو هیئت علمی، دانشگاه تهران، عضو هیئت علمی وابسته
2 دانشجوی دکتری مکانیک خاک و پی
3 گروه عمران، دانشکده مهندسی، دانشگاه بوعبی سینا، همدان، ایران
عنوان مقاله [English]
Cement-based stabilization/solidification is one of the common methods to prevent the transportation of heavy metal ions in soils. The main objective of this paper is to investigate the controlling mechanism in cement-based stabilization/solidification of Pb ion-contaminated bentonite in two different curing conditions of closed and open systems. Curing an open system is defined as a curing condition in which the stabilized/solidified sample has continued access to free water. In contrast, in the close curing process, the stabilized/solidified sample has been prevented to have access to any external water after initial mixing. To achieve the above-mentioned objective, a series of geo-environmental experiments, including pH, solubility measurement, TCLP, and XRD, were performed. In the first step, the bentonite sample was contaminated with 100 cmol/kg-soil of lead nitrate. After achieving equilibrium, the contaminated sample was stabilized/solidified with 15% cement. The results indicate that with application of 15% cement on the contaminated bentonite, the pH takes place on the range of 10.5 to 11.5 which is a safe domain for lead precipitation. In other words, the minimum required percentage of cement for stabilization/solidification is the quantity in which the pH of system comes about in the necessary range for heavy metal precipitation. This quantity is generally a function of the type and concentration of heavy metal contaminant. According to the experimental results of this research, it is shown that the method of curing does not have any noticeable impact upon the stabilization process of stabilized/solidified contaminated bentonite. On the other hand, according to the XRD results it is shown that in close system more pozzolanic components have formed. Therefore, the achievement of EPA criteria for TCLP experiments in cured samples at close system is attributed to the more progress in pozzolanic interaction and more formation of C-S-H and C-A-S-H components at 28 days for cured samples at close condition.