Stabilized Mud Blocks

8/12/2019 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.


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

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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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Documents

Stabilized Mud Blocks