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Globally the rice producing countries, rice husks are one of the most available agriculture wastes. Annually it is estimated that 600 million tons of rice paddies are produced. Averagely 20% of the total rice paddy is husks. Which gives a total of approximately 120million tones annually. If poorly managed rice husks is a great threat to the marketing environment as it can easily cause a lot of damages to the land and the surrounding Areas[CITATION NPC16 \p 235 \l 1033 ]. Hence he commercial use of the husks and its ash is the alternate solution to the disposal problem.
Rice husks is an agricultural byproduct or residue of rice milling industry. Different rice samples have different chemical composition this is due to the varying climatic conditions on which the rice was grown. The current conditions of the world greatly demand for the use of durable materials which are also very strong. Rice husks are known to be good example of such materials. The husks are produced under controlled conditions at a temperature that is below 800 produced silica in an amorphous form. The produced silica can be utilized for the purpose of construction works.
Landfill cover refers to a layer of compressed earth or soil which is laid on top on deposition of an operational landfill site. The covers assist in preventing the interactions between the air and the wastes. This greatly reduces odor and offers a stable base upon which machinery and vehicles may operate[CITATION Wal16 \p 184 \l 1033 ].
The rice husks have been accepted as green supplementary material that has many applications ranging from small scale to large scale. It can be used as a cover in landfill sites and water proofing. In other situations, it is also used as an admixture to make the concrete resistance against the chemical penetration.
Due to the large amounts of rice husks that are produce in various countries it has been a great challenge on how to dispose them. This calls for studies to come up with ways on how the husks can be used commercially. The current conditions of the world greatly demand for the use of durable materials which are also very strong. Rice husks are known to be good example of such materials[CITATION Ami14 \p 338 \l 1033 ].
This report focuses on the use of bentonite added rice husk as impervious barriers of landfill covers. From the studies that have been carried out by many scholars regarding to this subject. It has been concluded that rice husks can be commercially used in various industries such as the processing of cement, steel, refinery industries among many more. The sustainability of rice husks ash mainly depends on the chemical composition of the ash, predominantly the silica content available. Due to its properties rice husks have been found to be more superior to other supplementary materials such as silica, slag, fly ash and fume.
Project aims and objectives
The main aim of this study was to find out how bentonite added rice husk as impervious barriers of is used as landfill covers. With that many other objectives were set to aid in achieving the main aim of the study. The specific objectives in this study included.
To carry out a detailed literature survey regarding to bentonite added rice husk as impervious barriers of landfill covers, in order to get a deep understanding of this topic.
1. To find out what are the properties of rice husks ashes
2. To determine the application of rice husks ashes in various industries su8ch as construction
3. To understand the various burning process of rice husks and the quality of ashes obtained from them.
The significance of the research
This study is carefully crafted to find out how bentonite added rice husk as impervious barriers of can be used as landfill covers. The findings of this study will be of great importance to the conservation of the environment since the disposal of rice husks has been a great challenge in many countries globally considering that rice is a stable food in many countries.
Delimitations and limitations
The study will mainly focus on how the bentonite added husks can be used as landfill covers. With that the research will be tied strictly to the topic of study. Any other information not related to the topic of research will not be looked into. Various sources both primary and secondary sources that contain information relevant to this topic will be reviewed.
[CITATION Gré13 \p 563 \l 1033 ]conducted some experiments to study the impact of mixing rice husks ash together with bentonite in an effort to upgrade it as a construction material. The outcome of that study enabled him to conclude that stress strain behavior of the unconfined compressive strength indicated that failure strain and stress increased by 50% and 106% respectively, the moment the rice husks ash content was increased from 0% to 25%. when the rice husks content was increased from 0% to 12%.
According to [CITATION Bre16 \p 149 \l 1033 ] carried out the research on the behavior of the clay soil, which was stabilized with the rice husks ash that was mixed with the soil to study the enhancement of the weak subgrade in terms of the strength and compaction characteristics. The silica produced from the rice husks ash was found to be successful as a pozzolainc material in the soil stabilization.
[CITATION Fra13 \p 382 \l 1033 ]carried pout a research on the impacts of the rice husks ashes on the engineering properties of black cotton soil. The findings of the research concluded that with the increase in the rice husks percentage the optimum moisture content in the soil increased from 18.25 to 22 percent. The maximum dry density also decreased from 1.68 to 1.51gm/cm3. There was a great increase in the values of California bearing ration and the unconfirmed comprehensive strength.
Applications of rice husk ash
The ash obtained from rice husks has a wide range of applications in many industries such as the processing of cement, steel, refinery industries among many more. The sustainability of rice husks ash mainly depends on the chemical composition of the ash, predominantly the silica content available. Rice husks ash has been found to be a superior to other supplementary materials such as silica, slag, fly ash and fume.
The rice husks have been accepted as green supplementary material that has many applications ranging from small scale to large scale. It can be used as a cover in landfill sites and water proofing. In other situations, it is also used as an admixture to make the concrete resistance against the chemical penetration[CITATION Joh161 \p 43 \l 1033 ].
The rice husks ash as wide applications in the construction industry such as;
2. Green concrete
3. Industrial factory flooring
4. Swimming pools concreting the foundations
5. Rehabilitation and water proofing
Burning process of the rice husks
As initially mentioned the quality of the rice husks greatly depends on the type of burning process which they undergo. Various type of burning is usually carried out such as,
Open Field Burning method
This technique of open burning of the rice husks usually produces ash of poor quality. These usually produce a highly crystalline form structure which has lower rates of reactivity.
Fluidized -Bed Furnace Burning method
In this technique the burning of the rice husks is controlled. The heat that is produced during the combustion process is used to generate electricity. The operations management that are controlled are carried out by controlling the time and temperature. The combustion is carried out at temperatures between 500 and 700 degrees Celsius. The process is carried out for a longer period to ensure that carbon is completely removed or the same is achieved by increasing the temperature from 700 to 800 degrees Celsius for a period of 1 minute[CITATION NPC16 \p 670 \l 1033 ].
The husk ashes produced from 6his method contains 80% to 95 % silicon dioxide, 3-18% of unburned carbon and 1-2% of K2O. The ash produced by this method has a higher cellular structure.
This technique is mainly used to facilitate economic and environmental reason. The ashes produced by this method have amorphous silica and cellular structure. The ashes also obtained from this method are highly pozzolainc.
Material and method
The sample soil that were used for this study will be collected from a local dumping site and the rice husks will be collected from the local rice mills. The rice husks will be burnt on an open field in order to convert them to rice husks ash. The Bentonite that was used will be sodium bentonite. Standard procedures will be followed while various laboratory experiments were carried out.
Data collection strategies
Data for this study will be collected by use of various methods. Both primary and secondary sources will be used. For the secondary all the books, journal and other publications that contain information related to the topic of research will be reviewed while for the primary sources various practical sessions will be organized where by experiments will be done.
Role of the researcher
The role of the researcher will be to collect data regarding to the topic of research, it will be the responsibility of the researcher to come up with the most appropriate techniques of collecting data. It will also be the responsibility of the researcher to organize the research according to the timeframe.
From the experiments that were carried out the hydraulic conductivity of soil when it was tested alone was high. This clearly indicates that soil was highly permeable which cannot be used as covers for land fill. The addition of bentonite and rice husks ashes reduced the permeability of the soil by reducing the amount of water passing through it. That was attributed to the facts that the fine particles of bentonite filled the voids in the soil and therefore reducing the amount of water passing through it. From the experiments carried out it can be concluded that additional of 20% bentonite and 20% rice husks ashes greatly reduced the permeability of soil and there for making it better to be used for landfill covers.
The addition of bentonite added rice husks ashes greatly contributes to the improvement of the soil strength. The rice husks ashes have the ability to stabilize the soil and therefore the addition of it together with bentonite to the soil improves the strength. Bentonite being a clay mineral greatly contributes to the transformation of the shear strength of soil[CITATION Ind16 \p 665 \l 1033 ].
Additional of bentonite added rice husks to the soil increase the plastic limit of the soil and at the same time reduces the shrinkage limit of soli, this makes that soil to be ideal for landfill covers.
In conclusion, the challenge of how to dispose the rice husks that are produced in pretty in rice producing countries has called for research to come up with ways on how the rice husks can be used commercially. For this study ways on which ways on which the bentonite added husks can be used as land fil covers have been discussed.
From the literature review that has been conducted it can be conducted that the addition of bentonite added rice husks ashes greatly contributes to the improvement of the soil strength. The rice husks ashes have the ability to stabilize the soil and therefore the addition of it together with bentonite to the soil improves the strength. Bentonite being a clay mineral greatly contributes to the transformation of the shear strength of soil.
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