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Rice Hull Ash (RHA)

Thursday 23 June 2011, by Owen Geiger

Rice Hull Ash (RHA)

Rice Hull Ash (RHA)

Rice hulls, the outer covering on rice grain, are used as fuel for electrical power generation and in rice mills to generate steam for the parboiling process through direct combustion and/or by gasification. The hulls contain about 75% organic volatile matter and the balance 25% of the weight is converted into ash during the firing process, is known as rice hull ash (RHA). This RHA contains around 85% – 90% amorphous silica. It is estimated that about 70 million tones of RHA is produced annually worldwide. This RHA is a great environment threat causing damage to the land and the surrounding area in which it is dumped.
The particle size of cement is about 35 microns. There may be formation of voids in concrete mixes if curing is not done properly. Voids reduce the strength and quality of concrete. Our product – Silpozz (pozzolanic micro-silica) – 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-pozzolan. 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, etc.

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 waterproofing:
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 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.

Some defintions:
Amorphous Silica: Rice Hulls are 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 hull ash, micro silica, etc. 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 strength and 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 above 85%.

Source: http://www.ricehuskash.com/details.htm
Silpozz website

Image source: http://www.ricehuskashthailand.com/rice-husk-ash-products/

Note: Contact rice hull ash producers in your area. You can order different kinds for different purposes. Some ash is specially ground for use in cement/geopolymer. You even have a choice of packaging.


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