Converting Waste Agricultural Biomass into a Resource - UNEP

Rice Hull Ash Cement (RHAC) Hollow Blocks 122
Philippines, Research
Crop
Residue
Process
Equipment
Main Product
Rice
Hull Ash
Densification
Mold
Hollow blocks
Technical Description of Technology
Ricehull-ash-cement (RHAC) hollow block is a combination of refined ricehull
ash, cement and sand. These blocks are as durable as the concrete hollow
blocks yet much cheaper. Rice hull contains high temperature forms of silica,
which in amorphous state (burned between 700 to 750oC) is pozzolanic or
possesses binding property. But at very high temperatures (beyond 750oC),
the amorphous silica turns crystalline, thus losing its binding property. Since
natural pozzolanas are usually of volcanic origin and occur in only a few
regions of the world, artificial pozzolanas such as rice hull ash cement are
needed to serve as cement substitutes.
Detailed Process Description
Hollow Blocks From Rice Hull Ash
Procedure 123 :
1. Burn rice hull into ashes.
2. Refine the ashes.
3. Mix the following:
o 60 parts of cement
o 40 parts of rice hull ash
o water
4. Put in a wooden mold.
5. Let it dry.
Specific Considerations for Developing Countries
RHAC blocks can be mass-produced for low-cost housing projects, while at
the same time ease the disposal of rice hull waste. The raw materials are
readily available and inexpensive, while the processing equipment can be
made locally. Ash from incinerated rice hull can replace considerably the
Portland cement used in construction.
122 http://www.uplb.edu.ph/community/fprdi/commtech/rhac.htm
123 http://entrepinoys.blogspot.com/2007/09/clay-bricks-hollow-blocks-from-cheap.html
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