Rice milling  generates a by product know as husk  . This surrounds the paddy grain. During milling of paddy  about 78 % of weight is received as rice , broken rice and bran .Rest 22 % of the weight of paddy is received as husk . This husk is used as fuel in the rice mills to generate steam for the parboiling process . This husk contains about 75 % organic volatile matter  and the balance 25 % of the weight of this husk  is converted into ash during the firing process , is  known as rice husk ash ( RHA ).  This RHA in turn  contains around 85 % - 90 %  amorphous silica.

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.

India is a major rice producing country , and the husk generated during milling is mostly used as a fuel in the boilers for processing paddy , producing energy through direct combustion and / or by gasification . About 20 million tones of RHA  is produced annually. This RHA is a great environment threat causing damage to the land and the surrounding area in which it is dumped. Lots of ways are being thought of for disposing them by making commercial use of this RHA.

The particle size of the cement is about 35 microns . There may be formation of void in the concrete mixes , if curing is not done in properly . This reduces the strength and quality of the concrete . Our product Silpozz which is made out of this RHA is finer than cement having  very small particle size of 25 microns ,  so much so that it fills the interstices in between the cement in the aggregate.  That is where the strength and density comes from.  And that is why it can reduce the amount of cement  in the concrete mix .

RHA is a good super-pozzolans . Silpozz can be used in a big way to make special concrete mixes . There is a growing demand for fine amorphous silica in the production of special cement and concrete mixes ,high performance concrete ,high strength, low permeability concrete, for use in bridges, marine environments , nuclear power plants etc. This market is currently filled by silica fume or micro silica , being imported from Norway, China and also from Burma . Due to limited supply of silica fumes in India and the demand being high the price of silica fume has risen to as much as US$ 500 / ton in India

Use of Silpozz

For Strength :

Silpozz has the potential to be used as a substitute silica fumes or micro silica as a much lower cost , without compromising on the quality aspect . Adding Silpozz to the concrete mix even in low replacement will dramatically enhance the workability , strength and impermeability of concrete mixes , while making the concrete durable to chemical attacks , abrasion and reinforcement corrosion , increasing the compressive strength by 10% - 20 % .

For water proofing :

Silpozz has excellent water resistance ( impermeability ) properties and is used in waterproofing compounds to give amazing results. It reduces the water penetration by as much as 60 % .

For Better Concrete in Marine environment:

Adding Silpozz to concrete and paints helps to reduce the chloride ion penetration by as much as 50 % into the structure , thus improving life of the building.

For Lower heat of Hydration :

Adding Silpozz to concrete lowers the heat of hydration by as much as 30 % and prevents formation of cracks during casting .

Technical Specifications :
SiO2 Silica 85 % minimum
Humidity 2 % maximum
Particle size 25 microns
Colour Grey
Loss on ignition at 800C 4 % maximum 
pH value 8

Other Uses of Rice Husk Ash :

RHA acts as a very good insulator . RHA is also used for insulation of molten metal in tundish and ladle in slab caster . The temperature of molten metal in the ladle is around 1400 degrees centigrade and above . When this metal flows from ladle to tundish , the temperature drops to around 1250 degrees . This reduction in temperature leads to choking and causes breakdown in the slab caster.

When this RHA is spread as a coating over the molten metal in the tundish and in ladle , it acts as a very good insulator and the temperature is maintained and does not cool down quickly , hence reducing the breakdown time of the casting. 

Some Definitions :

Amorphous Silica : Rice Husk is burnt in controlled temperatures which is below 700 degrees centigrade . This ash generated is amorphous in nature . The transformation of this amorphous state to crystalline state takes place if the ash is exposed to high temperatures of above 850 degrees centigrade .

Green Concrete : Green Concrete as the name suggests is eco friendly and saves the environment by using waste products generated by industries in various forms like rice husk ash ,micro silicaetc. to make resource-saving concrete structures .Use of green concrete helps in saving energy, emissions, waste water Green concrete is very often also cheap to produce as it uses waste products directly as a partial substitute for cement, thus saving energy consumption in production of per unit of cement . Over and above all green concrete has greater strength and durability than the normal concrete.

High Performance Concrete : Also known as HPC , the name given to mixtures with high workability and very high early strengthsand long term durability .

Silica Fumes : Silica Fumes ( very fine non crystalline silicon dioxide ) or Micro silica is a waste product of induction arc furnace in the ferro silicon industry .

Super Pozzolans : are materials having high silica content of above 85 %

Particle Size , Mesh Size and Grit No.


British Standard

American Standard

Grit No



Specification.ASTM.E 11.79


5.60 mm

3 mesh



4.75 mm

3.5 mesh



4.00 mm

4 mesh



3.35 mm

5 mesh



2.80 mm

6 mesh



2.36 mm

7 mesh



2.00 mm

8 mesh



1.70 mm

10 mesh



1.40 mm

12 mesh



1.18 mm

14 mesh



1.00 mm

16 mesh



850 microns

18 mesh



710 microns

22 mesh



600 microns

25 mesh



500 microns

30 mesh



425 microns

36 mesh



355 microns

44 mesh



300 microns

52 mesh



250 microns

60 mesh



212 microns

72 mesh



180 microns

85 mesh



150 microns

100 mesh



125 microns

120 mesh



106 microns

150 mesh



90 microns

170 mesh



75 microns

200 mesh



63 microns

240 mesh



53 microns

300 mesh



45 microns

350 mesh



38 microns

400 mesh



32 microns

450 mesh



25 microns

500 mesh



20 microns

635 mesh



Articles on our product Rice Husk Ash published on prestigious publication :


ASCE EMD Conference paper

Concretecanoe.org - RHA replaces silica fumes - United States - July 2006

Concrete Canoe - MacInnes - United States - May 2005

Michigan Tech Natural Pozzolan Report - United States - May 2005

Gulf Construction Worldwide - Bahrain - March 2005 Edition

The Institute of Concrete Technology - United Kingdom - Nov. 2004 Edition

National Precast Concrete Association - United States - Sep / Oct 2004 Edition

Institute of Civil Engineers and Surveyors- United Kingdom - May 2004 Edition


Contact  :  info@ricehuskash.com

Disclaimer : All information given to best of belief and knowledge .