This research investigated the effect of reactant concentrations, reaction medium, urease enzyme source, and calcium source on the precipitation rate of calcium carbonate (CaCO3). This project is aiming to develop a biochemical reaction by using Enzyme Induced Calcite Precipitation (EICP) technique. This new technique would help in replacing the traditional cementation for the dune sand stabilization and promise an environmentally friendly and sustainable approach in the field of construction materials. Jack beans and soybeans were employed as a substrate to catalyze the urea hydrolysis in the study. The sources of calcium used in the experiments were calcium chloride (CaCl2), eggshell and sesame. In addition, both seawater and distilled water were used as a reaction medium to distinguish the effect on calcium carbonate precipitation. The experiments showed that using sesame at a concentration of 4.5 g, 5 g of urea and 6 g of jack bean at 60 mL of distilled water, is the best reaction conditions to precipitate 100.288 g of calcium carbonate. Further, the results indicated that the calcium carbonate precipitation enhanced by using 5 g of urea, 5 g of CaCl2 and 5 g of soybean at 50 mL of seawater. The precipitation amount was 25.593 g. These results provide a useful way for the bio cementation by following the EICP technique to address the issues of environment friendly practice of ground improvement.
Dune sands are poorly graded collapsible soils lacking fines. This experimental study explored the possibility of sustainable invigoration of fine waste materials in dune sand to improve the geotechnical properties. The fine wastes used in this study are reservoir sediments and marble waste powder. The fine waste powder was mixed with dune sand at different percentages (5, 10, 25, 50%) to study the gradation, void ratio and, compaction characteristics. A machine has been manufactured to elucidate the maximum void ratio using a developed and manufactured linear-axis 3D clay printer arm. The geotechnical properties of sand-waste mixes delineated in this study reveals the enhancement in compaction and gradation characteristics of dune sand. According to the results, the binary mixture of dune sand with 25% of marble waste and 50% of reservoir sediment gives the highest maximum dry density. Thus, for improving dune sand’s geotechnical characteristics, the addition of fine marble waste and reservoir sediment to the dune sand is an environment-friendly solution.
This study investigates the use of wadi sediments as a potential source for the core of rock-fill dams. The current practice utilizes clay and silty materials for the core of the rock-fill dam. In Oman, clay is not abundantly available, so there is a need to propose a local alternative material as a potential source for the core of the rock-fill dam. Dredged sediment is believed to have properties like clay but is a waste material deposited in reservoirs. The samples of wadi sediments were grouped from the reservoir of Wadi Jizzi Dam, located a few kilometers away from the city of Sohar. A detailed laboratory-testing program investigates the physical characteristics, grain size distribution, liquid and plastic limits, specific gravity, compaction, hydraulic conductivity (permeability), swelling potential, and unconfined compressive strength. All the tests were performed following the British Standard. The pure dredged sediment has a hydraulic conductivity of 7.11x10-6 cm/s, which is comparable to the requirements of the core of the dam. To improve the other properties of the dredged sediment, it is mixed in different proportions with dune sand collected from the Al-Sharqia Desert of Oman. The test results suggest that a mixture ratio of 50% of sediment to the dune sand gives optimal strength, durability, and permeability. On the other hand, for the comparison purposes, bentonite was mixed with sand by various percentage. The microscopic investigation and X-ray diffraction (XRD) analysis tests on dredged sediments suggest that the material can be utilized without causing any environmental concerns. The outcomes of this study is expected to assist the practitioners in achieving cost-effectiveness and sustainability in the design.
Managing sediments dredged from reservoirs of recharge dams is an environmental issue, however, these sediments can be an abundant and economical source of fine-grained fill soil. This experimental investigation quantifies the geotechnical properties of a reservoir sediment used to improve engineering properties of a poorly graded dune sand in Oman. The binary mixes were prepared with different percentages (5, 10, 20, 50, 75, 90, 95%) of sediment with sand. Laboratory tests such as gradation, consistency limits, compaction, and unconfined compression tests were performed to measure the engineering characteristics of the binary mixtures. The results showed that the maximum dry density increases up to a sediment content of 50% and then decreases with further increase in the sediment content. The optimum water content increases with the increase in sediment content from 17% for pure sand to 22.5% for pure sediment. The optimum moisture content shows a good correlation with the plastic limit of the binary mixture of sand and sediment. The unconfined compressive strength substantially increases with sediment content up to 75% and then decreases with further increase in the sediment content. The binary mixture of sand sediment is sensitive to moisture, however, the order of strength stability against moisture is dune sand mixed with 75, 50, and 20% sediments. The addition of sediment to dune sand improved the uniformity coefficient to some extent with an increase in the maximum and minimum void ratios as well. The elemental analysis of the sediment confirms that the material is non-contaminated and can be employed in geotechnical engineering applications as a sustainable and environmentally friendly solution.
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