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KEYWORDS:
keywords: Endurazyme – Clay – Rice husk ash – Lime -
Cement
Rice Husk Ash
The ash from the
burnt husks of rice is nearly all silica 99%+. I would
suggest a coarse grade of ground silica as a substitute.
The ash has been suggested as a source of silica for
chips computer chips.
Rice husk
ash as cement substitute
Ever wonder what is a cheaper substitute for cement?
The College of Engineering of the Angeles University
Foundation in Angeles City considers the use of rice
husk ash as an alternative for cement and as an additive
to reduce corrosion and increase durability of concrete
structures.
A Memorandum of Agreement has been signed between the
Philippine Council for Industry and Energy Research and
Development as the funding agency and AUF as beneficiary
of the technology transfer project for developing rice
husk ash cement. The rice husk will be sourced from the
V. Del Rosario Rice Mill in San Leonardo, Nueva Ecija.
According to the Biomass Atlas of the Philippines, rice
hull production in Region III exceeded 350,000 metric
tons annually for the period 1990 to 1999, an amount
that virtually goes into agricultural waste.
Tests indicate that rice husk retains 17 to 25 percent
of its weight as ash after burning. This ash has been
proven to be an effective pozzuolana substitute for
ordinary Portland cement, which can cut the average
number of cement bags required by almost half. Silica
contained in the rice husk ash (RHA) reacts with lime
when mixed with water to form calcium silicate hydrates
that effectively binds this kind of cement.
The utilization of RHA, according to PCIERD, holds
promising prospects in the country because it softens
the impact on the environment and capital costs of the
structure. In 1991, preliminary studies on RHA were
undertaken by the UP Building Research Services in
collaboration with the Department of Science and
Technology on its possible use for non-load bearing
blocks for low-income family housing.
The PCIERD-AUF project hopes to target small-scale
contractors, entrepreneurs, and rice mill owners in
Region III. Project leader Lilia Austriaco, PhD, said
that the project is envisioned to provide socio-economic
benefits to potential technology adopters and
environmental rewards in the region. From hereon, the
lowly rice hull ash, for too long consigned as another
unfortunate waste in rice processing, can be a new
source of income for rice mill owners and other
small-scale entrepreneurs.
Expansive soil
has been a problem in Indonesia as in other countries.
Current research found that there is a potential use of
silica waste, resulting from burnt rice husk, as a
pozzolanic material. This paper presents the results of
study on the utilisation of ashes produced from
uncontrolled rice husk burnt in Yogyakarta (Indonesia).
In this research, a series of laboratory tests has been
conducted. The tests were carried out individually or in
a combination in which the Rice Husk Ash (RHA) content
were varied from 7.5, 10, and 12.5 percent, and the lime
content from 2, 4, 6, and 10 percent (by the dry weight
of soil). All the samples have been remoulded at their
optimum moisture content (OMC) and maximum dry density
(MDD). The research shows that lime - rice husk ash
decreased the swell of expansive soil and improved its
strength and bearing capacity.
Blocks or bricks
- Rice husk ash
(RHA) cement blocks
the cement-to-RHA ratio is generally 1: 4, by volume.
Two types of blocks can be produced:
white blocks,
with a compressive strength of 4 N/mm², using ash
(amorphous silica) from field kilns, burnt below
900°C;
black blocks,
with a compressive strength of 1.4 N/mm², using boiler
ash (crystalline silica), burnt up to 1200°C;
Cement research
The first part deals with determining the optimum
grinding time of the RHA in order to produce a highly
reactive product with a minimum energy of grinding. The
performance of the RHA in concrete forms part II of the
study. The results show that the rice-husk ash sample
used in this study is principally composed of SiO2 (90.7
%), contains 4.7% loss on ignition and a relatively high
K2O content of 2.2 %. The RHA ground for the optimum
grinding time (140 seconds in a pulveriser with a
capacity of 30 g) has a median particle size of ~ 8 µm,
a water requirement of ~ 104% and a pozzolanic activity
index of ~ 100% in the mortar used for determining the
pozzolanic activity of the RHA. The results also show
that in general, for similar W/CM (0.40), the
replacement of 7.5 to 12.5% of the Portland cement by
the RHA did not affect significantly the compressive
strength, but improved significantly the resistance to
the chloride-ion penetrability of the concrete with and
without the entrained air.
Add Endurazyme to laterite and black soil fines for
strength.
(
see also black soils and fines)
Copyright
Brian Jackson 2006
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