Stabilization of Thick Fly Ash Slurry Using Alkaline Activators

Abstract

The yearly production of Fly Ash currently in India more than 250 million tons, occupied 65000 acres of land by ash ponds. That much vast amount of fly ash does cause a problem in the form of usage of land, health problems, environmental threats, and disposal. Disposal and utilization maximum care has taken to protect the human life as well as the environment. Fly ash contains some toxic elements, corrosive in nature, therefore, the leachate coming out of the deposits contaminates the surrounding soil and ground water. This can pollute the ground water with toxic metals present occurs in it. So the fly ash disposal is one of the major problems to deal with it. for the disposal of fly ash, a proper solution which would be effective is required to solve the problem. The fly ash is predominantly disposed of adopting wet disposal method into settling tans/ash ponds. This occupies huge valuable land as well as pollutes the ground water. Further, the abandoned ash ponds support no structures due to its inherent low bearing value and high compressibility. To resolve such problems, in the present study, the thick ash slurry is stabilized by mixing with varying percentage of NaOH (0.25%, 0.5%, 1% and 2% by dry weight of fly ash). It is proposed to mix the chemicals in the pipe line during transportation of the slurry to the ash pond. hence, in the first phase, the viscosity of the fly ash slurry mixed with a different percentage of chemicals are evaluated. The viscosity of fly ash at different percentage of water content and sodium hydroxide are evaluated by Marsh funnel test. the viscosity of fly ash increases with increase in the quantity of chemical and it also increases with increase in the time. In this study viscosity of fly ash at 0.25%, 0.5%, 0.6%, 0.7%, 0.8% of NaOH percentage was evaluated. Further, the ash slurry mixed with different doses of alkali is then sedimented in model test tanks having diameter 45 cm and height 60 cm. After curing periods of 15, 30, 60 and 120 days; undisturbed samples were collected and strength parameters, permeability values, and consolidation properties were evaluated. From the test, it is observed that the compressive strength increases with either increase in dose of a chemical or the curing period. The compressibility and permeability decrease with increase in the percentage of NaOH.