Rice husk ash

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1. RICE HUSK ASH PRESENTED BY AGLAIA

2. Rice husk They are the hard protecting coverings of grains of rice. It is used as fuel in the boilers for processing of paddy producing energy through direct combustion and / or by gasification . for every 1000 kgs of paddy milled , about 220 kgs ( 22 %) of husk is produced.

3. Rice hull ash/Rice husk ash Combustion of rice hulls affords rice husk ash (RHA). Concrete made with RHA as a partial cement substitute to levels of 10% to 20% by weight of cement has superior performance characteristics compared to normal concrete . The fineness of the ash also makes it a very good candidate for sealing fine cracks in civil structures, where it can penetrate deeper than the conventional cement sand mixture.

4. When burnt completely, the ash can have a Blaine no. of as much as 3,600 compared to the Blaine no. of cement between 2,800 to 3,000, meaning it is finer than cement. RHA is about 25% by weight of rice husk when burnt in boilers.  It is estimated that about 70 million tones of RHA is produced annually worldwide. So for every 1000 kgs of paddy milled , about 220 kgs ( 22 % ) of husk is produced , and when this husk is burnt in the boilers , about 55 kgs ( 25 % ) of RHA is generated.  

5. X-ray spectrum of RHA

6. Chemical composition The rice husk ash possesses a chemical composition similar to many of the organic fibre. Cellulose Lignin Hemi cellulose SiO2 holocellulose

7. Production Winnowing It used to separate the rice from hulls, is to put the whole rice into a pan and throw it into the air while the wind blows. The light hulls are blown away while the heavy rice fall back into the pan. Burning Rice husk is produced by burning rice husk between 600-700 0c temperatures for 2 hours.

8. Winnowing Procedure

9. Types of burning process On field burning Produce poor quality of rice hush ash and also it has low reactivity. Fluidized -bed furnace burning This is a controlled method of burning the rice husk. The combustion heat of rice husk is used for the generation of electricity.

10. Industrial furnace This is more environmental and economical method of burning The efficient combustion will give a silica content of 90-95%.

11. When Mixed with concrete… The heat of hydration is reduced this results in drying shrinkage and durability of concrete. Reduction in permeability of concrete results in the disintegration of concrete structure. Resistance against chloride and sulphate attack. Reduce the failure of RCC beam.

12. Applications High performance concrete Insulator Green concrete Bathroom floors Industrial factory flooring Concreting the foundation Swimming pools Water proofing and rehabilitation

13. TECHNICAL SPECIFICATIONS : SiO2 – Silica 85 % minimum Humidity 2 % maximum Particle size 25 microns Color Grey Loss on ignition at 800°C 4 % maximum pH value 8 Properties

14. Advantages Improves compressive strength ,flexural strength and split tensile strength of concrete when mixed with RHA. RHA mixed with concrete shows better bond strength as compared to OPC concrete. RHA makes a role to increase resistance to chemical reactions. RHA would result in a reduction of the cost of concrete construction, Reduction of the environmental greenhouse effects.

15. Disadvantages Suitable incinerator /Furner as well as grinding method is required for burning and grding rice husk in order to obtain good quality ash Transportation problem Unburnt RHA is not suitable for concrete production.

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