Stabilized Mud Blocks
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Transcript of Stabilized Mud Blocks
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By
Raghu.t
DSCE,Bengalooru
Raghu Thyagaraj, Asst Prof.Civil Dept, DSCE
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Concrete masonry is already extensively used in
building construction abroad, It is likely to make
considerable headway in the future in this country due
to following reasons
Durability
Strength
Structural Stability
Good sound absorption and heat insulation.
Fire resistanceRaghu Thyagaraj, Asst Prof.Civil Dept, DSCE
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It is a block made out of cement & aggregates.
The proportion will vary from manufacturer to
manufacturer & ingredients.
Generally it is made of 1:6.
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Concrete Block Technology is based on theprinciple of densi f icat ion of a lean concrete
mix to make a regular shaped, un i form , high
performance mason ry uni t .
It is an effective means of ut i l izing wastes
generated by stone crushers, quarrying and
stone processing units.
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Concrete blocks are of 3 types
Hollow & non-load bearing
Hollow & load bearing
Solid & load bearing.
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Solid
b lock
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IS 2185-1979- Specifications for concrete
masonry units ( hollow & solid concrete block )
IS 2572-1963 code of practice for construction
of hollow concrete masonry.
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The most common sizes are
400x200x200mm,(8 inch)- for load bearing
400x150x200 & (6 inch)- for load bearing
400x100x200.( 4 inch)( for partition walls- non
load bearing)
Other sizes can also be manufactured based on
requirements of clientRaghu Thyagaraj, Asst Prof.Civil Dept, DSCE
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Hollow
block
Cellular
b lock
Corner
b lock
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Hollow Concrete Blocks are an excellent
replacement for clay bricks since they are
energy efficient
Blocks are made of concrete, which absorbs
very little water. At the same time, they have
vertically aligned holes, which do not allow
moisture to seep through.Raghu Thyagaraj, Asst Prof.Civil Dept, DSCE
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Concrete blocks can be used like any other
masonry unit to build foundations, walls, arches
and corbels, etc.
A typical concrete block is equivalent to 4.5
bricks, thus construction is faster than with other
masonry units.
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The mortar is also less which results in cost
saving.
They are also compatible with other materials
like fired bricks, dressed stone and compressed
earth blocks for composite wall construction.
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The strength of concrete blocks depends on its
constituent materials used for its manufacture.
The presences of excessive fine silt in quarrydust & use of low % of cement leads to lower
strengths.
The BIS prescribes a minimum strength of2.0Mpa for concrete blocks.
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Highly Durable.
Low Maintenance, Color and brilliance of
masonry withstands outdoor elements.
Load Bearing, strength can be specified as per
the requirement.
the hollow space in the blocks Provide good
insulation properties against sound , heat &
dampness .Raghu Thyagaraj, Asst Prof.Civil Dept, DSCE
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Good fire resistance
The rough surface of blocks makes plastering
easier.
Concrete blocks permits adoption of thin walls
thereby achieving increased floor area & hence
saving in space.
Do not require formwork.
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Economical & Environment Friendly, flyash
used as one of the raw materials.
Popular for foundation walls.
Blocks are fairly inexpensive.
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Wooden mould & Steel mould
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In India bricks are generally classified as :
Country bricks
table moulded bricks
wire cut bricks.
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Country bricks are made using a simple four
sided mould.
Theses bricks are moulded by the soft mud
process where soil has a high moisture content
facilitating easier pressing.
The moulding is to be done on level ground &
wet brick is left on the ground for drying.
After drying the bricks are burned using
firewood.
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This type of bricks are made by soil with lesser
moisture ,which leads to the improved shape &
strength for the brick.
This bricks generally have frog on one of thebedding faces.
These bricks are dried in shade & then burned in
the kiln.
This bricks are stronger than country bricks &strength ranging from 3.5Mps to 7.0Mpa.
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These bricks are made with very good soil & with
more mechanized operations.
A continuous slab of clay is sliced by a wire
frame into a number of bricks.After drying, the bricks are burnt in the kiln.
A good wire cut brick retains very good shape &
strength ranges from 10Mpa to 20 Mpa.
A wirecut brick with 10Mpa strength can beconveniently used for load bearing masonry upto
5 storeys without RC fames.
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(i) Bricks should be table moulded, well burnt in kilns,copper coloured, free from cracks and with sharp and
square edges.
(ii) Bricks should be uniform shape and should be of
standard size.(iii) Bricks should give clear ringing sound when struck each
other.
(iv) Bricks when broken should show a bright homogeneous
and compact structure free from voids.
(v) Bricks should not absorb water more than 20 percent by
weight for first class bricks and 22 percent by weight for
second class bricks, when soaked in coldwater for a
period of 24 hours.Raghu Thyagaraj, Asst Prof.Civil Dept, DSCE
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(vi) Bricks should be sufficiently hard no impression,
should be left on brick surface, when it is scratched
with finger nail.
(vii) Bricks should be low thermal conductivity and they
should be sound proof.
(viii) Bricks should not break when dropped flat on hardground from a height of about one meter.
(ix) Bricks, when soaked in water for 24hours, should not
show deposits of white salts when allowed to dry inshade.
(x) No brick should have crushing strength below 55kg/cm2
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The clay fired bricks are lighter than the cement
hollow blocks. They are not porous, absorb lesswater and therefore do not require plastering.
These blocks are equal to six handmade bricks
and hence would save cost for the buyers.
Different sizes of burnt hollow clay bricks are:
Length mm Width mm Height mm
190 190 90
290 190 90290 140 90
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The minimum average crushing strength of
the bricks should be 3-5 N/mm2 according
to the IS 3952-1988.
The average water absorption of the bricks
by mass when shaIl be not more than 20
percent.
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Here, the soil available locally are made use for
production of blocks.
These blocks can be manufactured @ construction
sites by a manual press;
Transportation cost is not incurred;
No burning process is done ( which is a must for
bricks); so no wood used here, thereby being eco-
friendly.
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These are dense solid blocks compacted using a machine
with a mixture of soil, sand, stabilizer (cement/lime) and
water. OR
Stabilized mud block can be manufactured from a mixture
of suitable soil-sand and stabilizers such as Portland
cement or a combination of lime and Portland cement. A
uniform mixture of soil-sand-stabilizer is compacted into a
high density block at optimum moisture content using a
machine.
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Soils contain particles of different sizes such as gravel,
sand, silt and clay minerals (soils containing 10-15%
clay and 60-75% sand are satisfactory )
Classify the soils into 2 broad categories:
(a) Expansive soils and
(b) Non-expansive soils depending upon whether
the soil contains an expansive clay mineral or not.
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Soils containing non-expansive clay minerals can be
utilized for stabilized mud blocks using Portland cement
as a binder.
Whereas expansive soils need hydrated lime to
stabilize the swell-shrink properties and hence use of
lime is essential for producing stabilized mud blocks
with expansive soils.
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The following steps are involved in the stabilizedmud block production process:
a)Sieving the soil through 5mm sieve.
b) Mixing of soil and sand (or crusher dust) in therequisite proportion.
In case of higher clay %, the sand fraction in the
soil should be increased to bring down the clay
content.
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c) Adding stabilizer (cement/lime) to soil-sand mixture
and mixing with optimum quantity of water.
The proportion of soil and stabilizer depends on the
strength and performance requirements and the type
and amount of clay in the soil.Cement stabilization is best for sandy soils in which
cement is generally added to the tune of 6 to 8% by
weight of soil.A sandy soil will need about 10-12% water for Optimum
Moisture Content.
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d) Pressing the block in a machine to the
required density.
e) Ejecting the block, stacking and curing.
The blocks must be stacked in a shaded area to
prevent quick loss of moisture on exposure to sun
which can cause shrinkage cracks.
Curing has to be done for 28 days.
If the blocks cannot be cured for 28 days due to
time constraints, then ensure that they are cured
for at least 14 days, with the remaining curing
carried out by keeping the masonry wet.
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SMB roduction at construction siteRaghu Thyagaraj, Asst Prof.Civil Dept, DSCE
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Compacting the blockRaghu Thyagaraj, Asst Prof.Civil Dept, DSCE
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Machine with mould lid openRaghu Thyagaraj, Asst Prof.Civil Dept, DSCE
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Block ejectionRaghu Thyagaraj, Asst Prof.Civil Dept, DSCE
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Stacking and curingRaghu Thyagaraj, Asst Prof.Civil Dept, DSCE
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Blocks of different shapes
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SMB block corbel
Rounded corner and Corbelled
SMB blocks
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Stabilized mud blocks can be manufactured in differentsizes and shapes. Maximum size of the block is limited by
the capacity of the machine to supply required compaction
force or energy during the block production process.
Range of actual block dimensions shall be as follows.
Length: 200mm to 305mm,Width: 100mm to 200mm,
Height: 75mm to 100mm.
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Some typical sizes for the stabilized mud blocks are
given in Table.
Blocks of special shapes such as rounded corner,corbelled or any other shape for the purposes of
enhancing aesthetic appearance of masonry and the
building can be manufactured with special attachments
to the machines.
Sl No. Dimensions (mm)Length Width Thickness
1 230 105 75 or 90 or 100
2 230 190 90 or 1003 200 200 75 or 90 or 100
4 305 143 90 or 100
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The wet compressive strength of the stabilized mud blocksshould be determined in saturated condition. The blocks have tobe soaked in water for at least 48 hours prior to the strengthtest.
The minimum wet compressive strength of blocks should be 3
N/mm2or 30 kg/cm2for a double storeyed house construction.
Using a higher percentage of cement more than 8% cement -higher strengths in the range of 4 to 6 N/mm2 can be achieved. Ablock of 7 N/mm2 stength is suitable for four-storeyed load
bearing construction.
Blocks of strength 2.5 3 N/mm2can be used for load bearingwalls in framed buildings and for single storied houses in ruralareas.
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Strength and water absorption values of SMB
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Strength and water absorption values of SMB
collected from different construction sites are
given Table-3.
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Composite mortars such as cement-lime-sand or
cement-pozzolana-sand or cement soil-sand mortars are
best suited for stabilized mud block masonry.
The mortar selection shall be based on masonry designand the nature of application such as plastering,
pointing, etc.
Cement-soil-sand mortars of 1:2:5 or 1:1:6 give better
bond strength for the masonry when compared to 1:6
cement-sand mortar.
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Stone masonry in lower part of a wall rural housingRaghu Thyagaraj, Asst Prof.Civil Dept, DSCE
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SMB wall exposed to 10 years of natural
weatheringRaghu Thyagaraj, Asst Prof.Civil Dept, DSCE
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Two storeyed load bearing seminar hall (6.2m span designed for one more storey)
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Residential building with SMB walls and vault
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Cost of SMB mainly depends upon:
(a) cost of soil and sand or quarry dust,(b) cost of stabilizer (cement/lime),
(c) labour cost of block making and
(d) depreciation cost of machine.
Range of costs for a block of size: 230 X 190 X 100 mm (2.7 timesbrick volume) is as follows.
1) Cost of soil: Rs. 0.40 1.40
2) Cost of sand/quarry dust: Rs. 0.50 1.50
3) Labour cost: Rs. 1.50 2.00
4) Cement (7%) cost: Rs. 2.50 2.75
5) Machine depreciation: Rs. 0.50 0.50
---------------------
Total cost Rs. 5.40 8.15
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Cost can be drastically reduced by the use of local
materials and self-help labour.
Number of blocks (of size 230 X 190 X 100 mm) requiredfor 1 m of SMB masonry = 180-190 and
volume of mortar in 230 mm thick wall = 20%.
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Stabilized mud blocks having strength and performance
equivalent to or better than that of burnt clay bricks are
being produced and used.
Load bearing masonry buildings of up to 4 storey heighthave been built using SMB.
Properly prepared SMB blocks do not disintegrate upon
soaking in water for any length of time and the exposedbuildings can perform satisfactorily over ones life time.
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e) The walls do not require plastering and offer scope for
exposed natural finish with aesthetically pleasing
appearance.
f) The block strength can be adjusted by proper selection of
stabilizer content.
g) Provides good thermal comfort
h)Creates additional local employment in block production
Can be made with locally available earth which makes itcost effective.
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Requires a good understanding of the type of soil
available for block production and how it can be
improved/ stabilized.
Availability of soil in adequate quantity from a singlesource, can be a limitation
Needs careful design and detailing of the building to
ensure that the walls are not damaged by rain.
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