International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 2, February 2013)
Determination of Structural Properties of Baked Clay as
Replacement of RCC
Dr. Abdul Aziz Ansari1, Nawab Ali Lakho2
1
Professor, Department of Civil Engineering, Quaid-e-awam University College of Engineering Science & Technology,
Larkano, (Sindh)
2
Ph.D Research Scholar, Department of Civil Engineering, Quaid-e-Awam University of Engineering Science & Technology,
Nawabshah, (Sindh), Pakistan
Concrete is suitable for areas where aggregate, both fine
and course are available in plenty. Steel cannot be
produced everywhere but it is to be transported under very
circumstances. However cement needs the input materials,
which could be available, anywhere. Where every clay is
available in abundance could be and should used as chief
material of construction. However there are many problems
to overcome before it could be relied upon for durability,
elegance, strength and long life. Economy is the major
consideration. In developing countries people have very
little choice. They have limited capability to secure a house
of their own. They are hard pressed to make both the ends
meet. Therefore there is a lot of possibility to use clay as
major material of construction to provide houses to the
needy. Keeping this in mind a systematic research has been
carried out to provide a system of construction, which
would be economical, durable, and elegant. No structure
could be termed as safe without reinforcement now a day.
Economy could be achieved only when local materials
casting less are used. Clay is abundantly available in the
area where soil is clayey and alluvial. Clay cost at most
nothing except labor if it is to be dug and used. Clay has
served humanity for the times immemorial. Since the
invention of cement this material has be relegated to
nothingness. It must be mentioned that before first
industrial revolution this was the only major material of
construction for all the people living on the face of this
earth. Lucky were those who could have stone available for
their buildings. But to quarry the stone cut it into pieces,
make their regular shape and then use it for housing was
not that easy. Chiseling, rubbing them smooth, polishing
them was a gigantic task. Great monument of the world
were built from stone with an optical illusion was
something as a pride of nations. The glaring examples are
the Parthenon of Athens and the great pyramids of Egypt.
All the seven wonders of the than known world last except
the pyramids of Egypt. The hanging gardens of Babylon
were constructed from clay. The ziggurats of Mesopotamia
were constructed from clay.
Abstract— Systematic research has been carried out over
past several years to check the suitability of baked clay as
chief material of construction as replacement of Reinforced
concrete, for low-cost housing without sacrificing elegance,
strength and durability of multistory buildings. Initially soil
was dug from 25 sites at a depth of 4 ft. in the vicinity of
Quaid-e-Awam Engineering University, Nawabshah, (Sindh),
Pakistan where the soil is furtile and fit for cultivation. Their
physical properties were determined. The presence of various
salts and their proportion were also found. From test results it
was observed that the salts did not affect the structural
properties of baked clay specimens. A very large number of
cubes were cast with clay as major material and percentage of
pit-sand (silica) as major parameter. The results of
preliminary study in terms of shrinkage, specific gravity,
crushing strength, tensile strength, poison’s ratio, and
modulus of elasticity of baked clay specimen and the best
possible combination of clay and pit-sand were obtained. The
material was then compacted by applying compression and
cube crushing strength as high as 27.61 N/mm2 (3950 psi) was
achieved. Fifty one beams with 70% clay and 30% pit-sand,
20 percent water and 4.5 N/mm2 compacting force were cast,
dried, baked, post-reinforced, grouted with cement and hillsand slurry with the ratio of 1:1 for proper bond between steel
bars and surrounding baked clay were tested with point load,
UDL and various boundary conditions including roller
support, plate support and complete end-fixity. 35 beams were
singly reinforced and 8 contained compression steel as well,
while 8 contained special types of vertical reinforcement to
resist shear. All the beams failed in shear. Cubes were cut
from the body of the beams after testing and structural
properties were determined. The crushing strength as high as
42 N/mm2 (6100 psi) has been achieved. The results are
encouraging and further research is being carried out.
Keywords—Low-Cost housing, Preliminary study, Specific
gravity, Shrinkage, Modulus of Elasticity,
I. INTRODUCTION
Research has been conducted on reinforced concrete
since last almost two centuries. But it all depends upon the
availability of industrially produced materials. These
materials are very expensive. They are to be transported
from distant place to the site. Cast of transportation is very
high due to ever-increasing cast of transportation.
17
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 2, February 2013)
With lot of literature survey regarding housing
pertaining to past several thousand years it has transpired
that clay must be employed to play its due role as the
shelter of human being on the face of this earth as a new
material of construction in its new manifestation in present
times. Reinforcement is the order of the clay. Multistory
buildings are the most common form of present time. Let
us mingle them together to produce new form of
construction using clay for the sake of economy, elegance,
durability and long life. It is a dilemma and irony of the
fate that more than two third of the population of the world
is still living in inhuman conditions and they are not able to
meet their basic needs of life.
Although the modern trend in the field of construction is
framed structure consisting of RCC beams and slabs;
attempt is being made to replace RCC with pre-perforated
post-reinforced baked clay panels. It is more beneficial if
the buildings are to be constructed on mass scale and the
variation of sizes is kept to a minimum.
The plains of our country (Pakistan) where the soil is
alluvial and there is shortage of fine as well as coarse
aggregate, almost every single item i.e. cement, steel bars,
fine & coarse aggregate are to be transported from very
long distances. Being very heavy materials considerable
amounts are to be paid as their cost of transportation. Thus
it is beyond the reach of a common man to opt for RCC
construction.
The universally available materials of construction in the
plain areas are clay and pit sand. At present burnt clay
bricks are being used for masonry construction and for
lintels to span over small openings like those of doors and
windows. If instead of bricks we can produce baked clay
panels of beams, columns, slabs and footing etc. which are
pre-perforated so that the reinforcement bars could later be
placed and grouted with proper bond and if we can attain
the strength properties resembling to those of cement
concrete and if a reasonably good margin of reduction of
prices could be achieved, then the dream of low-cost
housing in its real sense could come true.
In the plains of various parts of the world where the soil
is clayey in nature the baked clay bricks were used as early
as 3000 B.C. in Moen-jo-Daro and Mesopotamia. The
palace of Nebuchadnezzar, the Ishtar gate and the
procession street along with the buildings on both its sides
were constructed with bricks and adorned with glazed
baked clay tile bricks as early as 600 B.C [2]. The hanging
Gardens of Babylon, one of the seven wonders of world
was made up of clay. European monasteries, castles and
mansions were made up with clay and clay was used in the
infill panels of traditional timber frame houses. Many of
these buildings are hundreds of years old and still standing
up proudly today. As building material, clay bricks have
been used in construction since earliest times [3].
The earliest remaining examples of soil reinforcement
are the Ziggurat of the ancient city of Dur-Kurigatzu, now
known as Agar-Quf and the great wall of China. The AgarQuf ziggurat, which stands five kilometers north of
Baghadad was constructed of clay bricks varying in the
thickness between 130-400 mm, reinforced with woven
mats of reed laid horizontally on a layer of sand and gravel
at vertical spacing varying between 0.5 and 2.0 meter.
Reeds were also used to form plated ropes approximately
100 mm in diameter which pass through the structure and
act as reinforcement. The Agar-Quf structure is now 45 m
tall, originally it is believed to have been over 80 m high; it
is thought to be over 3000 years old. The great wall of
China, parts of which were completed in 200 B.C. contains
examples of reinforced soil, in this case it was made of
mixtures of clay and gravel reinforced with tamarisk
branches. New materials like glass fibre and carbon fibre
together with special binding materials are being employed
to repair the damaged structures. But the people of third
world countries can not afford this luxury of using highly
expensive and industrially produced materials of
construction which would have to be imported at the
exorbitant prices. Therefore, these countries must resort to
local materials with minimum possible industrial local
materials with minimum possible industrial processing for
the use of building, the infra-structure and the houses at a
relatively lower cost without compromising on the
durability, strength and elegance.
II. HISTORICAL BACKGROUND GROUND OF CLAY AS A
CHIEF MATERIAL OF CONSTRUCTION
Clay bricks have remained in use as major material of
construction since the known history of mankind on the
earth. Traditional clay architecture is thousands of years
old and even today about one-third of world’s population
lives in homes constructed from clay. Catal Huyuk (present
time Turkey) was the place where glazed tiles were
manufactured as early as 6000 B.C. [1]. Etruscans are
known for their clay statues.
III. STRUCTURAL PROPERTIES OF CLAY
Fine clay particles (in colloidal state) possess the
properties like adsorption and thixotropy [4]. Clay plasters
have been used extensively in buildings in the U.K. and
indeed the world for thousands of years. Although it is not
widely known there are over a million buildings with clay
materials in their structure in the U.K. and a many of these
have clay plasters [5].
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International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 2, February 2013)
Polymer clay has been in use as man-made modeling
materials just like ceramics. It is being supplied by various
suppliers under the brand name as FIMO which is an easy
to use as extremely versatile plastic based modeling clay
[6]. Attempt has been made by [7] to assess new potential
applications for the Bailen clays, traditionally used for
manufacturing of bricks based on mineralogical, chemical,
particle size, plasticity and firing results. Raw materials and
mixtures used by the local factory were selected and tested
with the addition of some diatomite, feldspar or kaolin.
Based on their properties clay materials from Bailens might
be suitable for making porous red wall tile, clinker, vitrified
red floor tiles and porous light coloured wall tiles by
pressing. The first could be manufactured from the raw
materials and mixtures currently used by the local
manufacturers. On the other hand, stone ware shaped by
extrusion, such as pre-perforated bricks, facing bricks and
roofing tiles also can be manufactured from the mixtures
used at the factory. They must contain 20-25% carbonate
and a small amount of iron oxides. Light-weight bricks
require black and yellow clay with diatomite . Now-a-days
Low Cost Housing (LCH) machinery is being used in
western world to produce Stabilized Earth Brick Machine
for low cost housing. Stabilized Earth Bricks (SEB)
Machine is easily transported onto a construction site and
can immediately produce high quality (as claimed)
interlocking bricks made from the local soil. No mortar is
required to hold the bricks together, made from soil treated
with Road packer Ionic Soil Stabilizer product. The LCH
stabilized Earth Bricks (SEB) can be used within a few
days of production. It is claimed that the homes thus
constructed of production. It is claimed that the homes thus
constructed will be heat resistant, sound proof and
completely stable. A new material of construction called
Grancrete is being developed by scientists at Argonne and
Casa Grande, that may lead to affordable housing (Low
cost) for the world’s poorest, when innovation process
completes up to industry development scale. Ceramic
houses are also being built in USA. Since [8] a resident of
California has remained continuously involved in the
Geltaftan Earth-and Fire System known as Ceramic House,
and of the Super block construction system. He is a U.N.
(UNIDO) consultant for Earth Architecture.
However, if local materials like clay and pit-sand (silica)
can be utilized to construct the house with comparable
structural properties of concrete, the low-cost housing
objective could be achieved without sacrificing the
elegance, durability and structural soundness. Therefore
attempt has been made to study the fundamental structural
properties as well as flexural and shear behaviour of beams
manufactured from baked clay with post-reinforced using
grouting as bonding material consisting of fine hill sand
and cement sullery so that there could be mass scale
production of pre-cast panels for rapid erection of structural
frames along with brick masonry as dividing walls so that
dream of low-cost housing could come true.
V. EQUIPMENTS AND INSTRUMENTATIONS
Since no attempt was made ever before to cast and test
the clay beams, a large number of pieces of devices,
equipment were not available in the market and could not
be purchased. Therefore, all such items were devised
according to specific needs of various operations. They
were designed and fabricated within the premises of
QUEST, Lab: However, standard equipment whatever was
already available in the structures laboratory was
employed. The details of all the device, equipment and
machinery are presented in the following sections as
listed below.
 Stiff steel mould
 Restraining system of mould
 compaction system
 Beam drying system
 Trolley
 Platform Lift
 Grouting system
 Mechanised Compacting Mould System
 Mobile Lift
 Pre-compression system
 End Fixity Attachment
 U.D.L simulator
 Backed clay specimens cutter
 Puller System
VI. MATERIALS
A. Clay and Pit-Sand
Clay is easy to extract and does not require significant
transformation. It is a malleable substance. Clay is one of
the rare matters without intrinsic value, but convertible in
to valuable objects. Clay is also capricious material with
very variable physical properties.
IV. SIGNIFICANCES OF THE STUDY
Basically in third world countries the purchasing power
of common man is very much limited. Therefore to
construct a house using reinforced concrete is not within
the reach of majority.
19
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 2, February 2013)
Clay shrinks during drying and firing. This creates many
problems. Certain clay shrinks more than others. The
finished products of clay crack during cooling.
The clay was obtained from 25 different sources at a
depth of 100mm (4 ft) from the ground level at Quaid-eAwam University of Engineering Science & Technology
Nawabshah. It was dried at a temperature of 105 OC for 24
hours. Then all the samples were sent for chemical analysis
to detect the presence and quantity of various salts. The
clay was then pulverized and pit-sand was mixed with it.
Initially the ratio of pit-sand was a variable to find the best
composition.
The salts were also one of the parameters to determine
their effect on the compressive strength and other material
properties of baked clay specimens. The third parameter
was the water content to get the best results and the fourth
parameter was the pre-compression for compaction. For the
best results it is recommended that the clay should be in a
very fine state of division commonly known as colloidal
state of particles. For a dense and compact mass of clay the
free sand present in it should be graded from the finest
particle of less than 0.002 mm to the coarsest size of 1
mm. Pit-sand used this study passing through standard
sieve No. 3
The concrete ingredients were mixed by weight for the
characteristic strength of 20 N/mm2 (3000 psi) at 28 days.
The size of coarse aggregates was 10 mm (0.375inch).
Ordinary Portland cement manufactured by Zeal Pak
Cement factory Hyderabad was used. The value of slump
was in the range of 10-30mm.
E. Reinforcement
Tor steel bars of 9.53 mm (3/8 inch) diameter, 12.7 mm
(½ inch) diameter and 15.87 mm (5/8 inch) diameter were
used. In Pakistan for the sake of economy 74% of
reinforcing steel bars are produced from scrap. The
manufacturing processes also vary considerably. Therefore,
their strength properties are not uniform. These bars
showed limited ductitlty. The batch of steel bars procured
for our research did not show distinct yield point therefore
the average 0.2% proof stress was calculated for three bars
and was found to be 554.2 N/mm2 (80360psi) and average
ultimate stress was 652 N/mm2 (94540 psi). The percentage
elongation was quite low when compared with the codal
value, where as ACI suggests elongation of 12 %., it is to
be mentioned here that the extensometer was removed at
this point and the failure of bar occurred just one stage of
loading after this point.
B. Mixing Water
Potable water was mixed in the mixer of clay and pitsand to the extent of 18 to 20%. In fact samples of under
ground water from a large number of sites were tested for
various properties and salts. It was found that presence of
salts had no appreciable effect on the compressive strength
of baked clay. However, underground water that
was
found fit for agricultural purpose by Fuji Fertilizers
Company Nawabshah.
VII. METHODOLOGY
Initially pH value, Electric Conductivity, Exchangeable
Sodium and Gypsm, Total salts content in solution (PPM),
Moisture Contents, Specific Gravity, Liquid Limit, Plastic
Limit, Flow Index, Liquidity Index, Plasticity Index,
Consistency Index, Toughness Index, Density of wet and
dry soil are to obtain from twenty five different sites is
determined. Preliminary studies are performed in terms of
shrinkage, specific gravity, compressive strength, tensile
strength, Poisson’s ratio and modulus of elasticity of baked
clay specimens consisting of hundreds of specimens
including cubes, cylinders and briquettes.
C. Cement Slurry
Ordinary Portland Cement and fine hill sand passing
through standard sieve No 16 were mixed in the ratio 1:1
and the slurry was produced by adding water five times the
weight of cement. This slurry was forced into the holes
where steel bars had been housed by grouting system. The
slurry was developed during this study based on
experimentation in terms of proper flow, complete filling of
the space in the holes and proper bond between steel and
surrounding baked clay.
D. Concrete
Four concrete beams were cast, cured and tested for the
sake of comparison of results. For this purpose concrete
mix design in accordance with the recommendations of the
Department of Environment, London, HMSO, 1975 were
followed.
Fig. I & II: Photograph showing further strengthening of the system
to top bulging and puller system that was designed for pulling the
shaft out.
20
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The major parameter is clay and pit-sand ratio. A large
number of baked clay specimens is compacted by applying
compacting force of 6 N/mm2 to improve the structural
properties. Substantial equipment and testing arrangements
required are also fabricated to like; Stiff steel mould are
fabricated for casting the models of beam panels as shown
in Fig I & II.
The design of these moulds is accomplished on the basis
of stress analysis performed by using computer software
using Finite Element Analysis. The analysis is particularly
aimed at finding the lateral deformation of the mould due
to applied compression for compaction. Elastic out-ward
displacement is determined in order to ensure that bulging
of the beam resulting in the expansion of the sections
should not occur. Special arrangement for applying the precompression manually (so that density could be improved
and compaction to the desired degree could be achieved), is
designed.
Fig III: Isometric and side view
of the kiln.
Fig IV: Dimensional sketch
of the kiln.
The cover itself is made up of clay. After the burning is
over, the cover is partly removed for gradual cooling of the
baked items. The temperature was maintained and
measured with the help of thermo-couple. Four flues were
provided opposite to each other to create draught.
VIII. BAKING SYSTEM
For baking the cubes, cylinders and beams during this
experimental work, a kiln as shown in Fig. III, was
constructed. Dimensional sketch of the kiln and its top
view & front view are presented in Fig. IV. The kiln was
heated by burning fire wood. Each time for complete cycle
of burning, approximately 800 to 900 kg of fire wood is
consumed.
The temperature was controlled and maintained carefully
by adding or abating the fire wood as per the requirement.
Initially the lower temperature of 250 oC was maintained
for six hours. The temperature was then raised gradually to
950 oC and was maintained at this level for 16 hours. Then
the temperature was lowered slowly and the fire was
stopped and the kiln was allowed to cool down over next
two days. The temperature and time period were selected
after preliminary study trying a large number of
temperature and duration combinations to achieve the
best possible results. The inner space of the kiln was
enough to burn six beams at a time. The beams were placed
inside through rectangular opening on the opposite side of
the burning wood. There is an opening at the top which is
covered at the time of burning.
IX. PRESENT STUDY
It may be re-iterated here that the total research work has
been divided into two series i.e. Preliminary Test Series
and Main Test Series. The latter is further sub-divided into
five phases. The effective span of all the beams was 1670
mm (65.75 inch). Apart from baked clay beams four
concrete beams were also cast, cured and tested for the sake
of comparison.
Altogether Fifty One beams were tested out of which
Fourteen were rectangular and Nine were I-shaped. Six
beams were cast baked with an increased compaction force
to the level of 4.7 N/mm2 from 3.5 N/mm2. Two beams
were reinforced with horizontal steel only while an other
two contained vertical steel as well. A number of beams
were tested with various boundary condition i.e. roller
support, plate support and fixed ends.
21
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 2, February 2013)
X. EXPERIMENTAL RESULTS AND DISCUSSIONS
In this paper detailed discussion is presented
regardingthe experimental results which have been
obtained after testing a large number of specimens. Here
the true picture of the structural behaviour of baked clay
has been presented. It would be proved consequently that
the baked clay is if not superior can’t be relegated as
inferior material of construction.
A. Compressive Strength
Cubical strength as well as cylindrical strength of the
specimens cut from the beams themselves was determined.
the details of which are presented in Table I. From this
tables it is apparent that the cubical strength as high as 37.6
N/mm2 is reached which is quite reasonable. Table II
compares cubical strength of concrete with that of
baked clay for respective beams. From this table it is
obvious that the average cubical strength of baked clay is
approximately 12% more than that of concrete. It may be
mentioned here that the clay was compacted with a
compressive force of 4.75 N/mm2. From this table it can be
concluded that even with a very small compressive strength
of baked clay is comparable with ordinary port-land cement
concrete used for residential buildings can easily be
achieved.
Fig V & VI: Mechanized System of Compaction
It may be mentioned here that all the work the details of
which is presented here pertains only to the short term
loading. However, the effect of long term loading and other
related aspects is being taken care of by Nawab Ali Lakho
as part of his own research programme, which is being
carried out at Quaid-e-awam University of Engineering
Science & Technology, Nawabshah, Sindh, pakistan.
Whereas the compaction of baked clay moulds was
accomplished by manual method of simple rectangular
steel box where wing nuts were tightened to compact the
mould as shown in Fig. I & II.
TABLE I
CUBICAL STRENGTH, MODULUS OF ELASTICITY AND POISSON'S RATIO
OF BAKED CLAY SPECIMENS
S. #.
Fig VII: Beam Mould for Mechanized System
Further research of long term loading is being carried
out by Nawab Ali lakho by employing mechanized system,
the details of which will be presented elsewhere. The
mechanized system devised, designed and manufactured by
Nawab Ali Lakho is presented in figure V, VI & VII.
It was observed that mechanized system of Nawab Ali
Lakho was more effective and produced better results
regarding compaction than manual compaction.
Description
Modulus
of
Elasticity
Poisson's
Ratio
01.
BCRRPE-1
35.8
34.90
0.165
02.
BCRRPE-2
33.5
33.83
0.167
03.
BCRRUDE-1
37.4
35.63
0.169
04.
BCRRUDE-2
37.6
35.71
0.170
05.
BCRPUDE-1
37.3
35.60
0.165
06.
BCRPUDE-2
36.6
35.29
0.166
36.31
35.16
0.167
Average
22
Cubical
Strength
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B. Poisson’s Ratio and Modulus of Elasticity
Table I, show the value of Poisson's ratio and the
modulus of elasticity which were determined by adopting
the procedure recommended by BS CP 1881-1970 [9] for
different phase of experimental study separately.
It can therefore be inferred that the modulus of elasticity
of baked clay is well within the range of that of concrete
(grade-20).
C. Modulus of Rupture
Apart from the properties mentioned above experimental
study was carried out to determine the modulus of rupture
of baked clay by testing plain beams without
reinforcement. The beams were 1000 mm long 143 mm
wide and 286 mm deep subjected to two point loads at one
thirds of the span with an effective span of 900 mm.
The loads were applied gradually and for every load
increment displacement was measured. Universal Load
Testing Machine of Forney from U.S.A. along with its two
point load kit was used for this test. The failure was
sudden, brittle and without impending warning. From
ultimate load using the well known elastic equation the
ultimate stress was found to be 3.3 N/mm2. This seems
quite reasonable. From this result it can be concluded that
this material, if not superior, cannot be considered as
inferior than cement concrete.
TABLE II
COMPARISION OF COMPRESSIVE STRENGTH, MODULUS OF
ELASTICITY AND POISSON'S RATIO OF CONCRETE AND BAKED CLAY
SPECIMENS
Cube Crushing
Strength
Modulud of
Elasticity
Poisson's Ratio
Concrete
Backed
Clay
Concrete
Backed
Clay
Concrete
Backed
Clay
0.69
4.65
32.46
35.67
0.177
0.169
34.06
37.05
35.09
35.11
0.169
0.164
32.97
37.65
33.58
34.95
0.168
0.166
32.57
6.44
33.71
35.24
0.171
0.166
XI. FLEXURE AND SHEAR BEHAVIOUR
The flexural strength of the beams in terms of
tension and compression was calculated by using the
equations of BS CP 8110 [11] and ACI-318 [12] after
removing all partial safety factors. The shear strength of the
beams was also estimated in accordance with the above
codes. For the phase-I of the Main Test Series. It was
expected that the failure would be dominated by shear
strength of the beams. The failure of the beams did occur
due to shear. The failure occurred due to diagonal cracks as
IXshown in Fig. VIII & IX.
It can be observed, that although the failure was
dominated by shear, the strain in baked clay at the level of
flexural steel is an indication that the yielding point had
already in the beams which were tested by applying UDL.
Although maximum shear is at the supports and if the shear
alone is responsible for the failure such an increase of
ultimate load could not have been achieved. It may be
mentioned here that the UDL was applied by the system so
that the friction could be minimized in order to let the
baked clay material undergo compression without being
deterred by the load application system. However, since
this was a relatively stiff steel beam transferring load
through a number of circular bar pieces welded with it, this
might have affected the behaviour of the beams and their
ultimate load to some extent. Perhaps a system consisting
of smaller separate hydraulic jacks or a multi-point
electrically operated hydraulics load applying machine
would have worked better.
From this table it can be found that the average value of
Poisson’s ratio for all the baked clay beams is 0.167. Few
selected cases for which concrete beams were tested,
comparison is shown in Table II. From this table it can be
seen that the average value of Poisson’s ratio for all the
three cases is 0.171, while the average value for the
respective baked clay beams it is 0.166. The average
difference is insignificant. Hence it can be concluded that
the Poisson’s ratio of baked clay is also within the same
range as that of concrete. It may be mentioned here that
from literature it is apparent that the value of Poisson’s
ratio of ordinary concrete ranges between 0.15 to 0.2. It can
be observed that the Poisson’s ratio of baked clay also falls
within this range.
The modulus of elasticity of ordinary concrete as
reported in the literature ranges between 21 to 28 N/mm 2.
For High Strength Concrete it is as high as 40 N/mm2.
The average value of modulus of elasticity for all baked
clay beams is 35.24 N/mm2. From Table II, it is apparent
that the average modulus of elasticity of concrete is 33.71
N/mm2 and for respective baked clay beams it is 35.24
kN/mm2 which is averagely 4.6% higher than that of
concrete grade-20. It may be mentioned here that modulus
of elasticity for concrete of grade-20 as given in [10] is 25
N/mm2.
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International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 2, February 2013)
1) It was observed that the best results could be
achieved when the clay is 70% and pit-sand 30%.
2) When cubes and cylinders were cut from the body of
the beams themselves after testing the Poisson’s ratio
was found to be 0.167 as compared with that of
concrete which ranges between 0.15 to 0.21.
3) The average value of modulus of elasticity for all
tested beams was found to be 35.24 KN/mm2 as
compared with 25 KN/mm2 for concrete of grade20.
4) Cubical strength as high as 37.4 N/mm2 was reached
when cube were cut from the beam cost with a
compacting force of 4.75 N/mm2. An average value
was found to be 33.52 N/mm2.
5) The modulus of rupture of this baked clay material is
also in good agreement with that of concrete of
grade-20.
6) It is quite apparent that the failure of beams is
dominated by shear rather than flexure, therefore,
shear strength must be improved to ensure ductile
failure due to yielding of steel in tensile zone.
7) Split of bottom cover, slipping of bars or
destruction of bond between steel and surrounding
material did not take place, showing that the system
of grouting worked well and was adequate.
8) The presence of vertical steel bars as shear
reinforcement did not show any improvement of
strength rather it acted as an intruder.
9) Presence of longitudinal steel in compression zone
proved to be beneficial causing substantial
improvement of shear strength.
10) Beams subjected to Uniformly Distributed Load
and fixed at both ends showed a very good strength
which is averagely 5 times more than the calculated
strength when estimated by using CP8110
recommendation for beams containing top and
bottom steel without but no vertical steel. Where as it
is 2.91 times when compared to the calculated value
by using ACI-318.
11) Pre-perforated and post-reinforced system of
construction consisting of pre-cast panels of baked
clay holds promise as an alternative of cement
concrete at a reduced cost without compromising on
the quality, durability and elegance of multistory
buildings.
12) It was observed that mechanized system of Nawab
Ali Lakho was more effective and produced better
results regarding compaction than manual
compaction.
Fig VIII: Baked Clay Rectangular beam tested by applying point
load with roller supports.
However, due to practical difficulties and unavailability of required gadgets this system could not be
developed / tried. After testing the beams the bottom cover
of a few beams was removed to ensure that bond failure
between steel and surrounding concrete did not occur.
Thus it can be deduced that if buildings are to be
constructed in the rural areas where hill sand, coarse
aggregate and cement are not available locally this material
can also serve the local population well within affordable
prices. This material could prove suitable for multistory
buildings of reasonable height.
Fig IX: Baked Clay I-Section beam tested by applying point load
with roller supports
Therefore we shall stick to the original idea of
producing structural panels on large scale with minimum
quantity of reinforcement, no cement, no aggregate of hill
origin but clay and pit-sand, dune-sand and river bed sand;
all available locally and cheaply.
XII. CONCLUSIONS
The conclusion of the work reported in this thesis can be
summarized as under:
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International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 2, February 2013)
[6]
Garic, S. 2005. Polymer Clay and Elastic Clay. Creative Clay for
Creative People, 1-7.
[7] Gonzalez, I. Galan, E. Miras, A. & Paricio, P. A. 1998. New Use
for Brick-Making Clay Materials from the Bailen area (Southern
Spain), Clay Minerals, GSW, Geo-Science World, Mineralogical
Society of Great New Use for Brick-Making Clay Materials from the
Britain and Ireland. Vol. 33, No. 3, 453-465
[8] Khalili, N. 1984. Alternative Building Materials for Pre- Fabricated
Low-Cost Housing”, U.N. (UNIDO), Consultant for Earth
Architecture, California Council of the American Institute of
Architectures (CCAIA).
[9] British Standard Code of Practice. 1970. B. S. 1881, Method of
testing of Concrete, Part V, 1970
[10] Astill, A. W. & Martin, L. H. 1981. Materials and Load, Value of
Modulus of Elasticity of Concrete, 1-8, Elementary Structural
Design of Concrete to CP-110, Printed in Great Britian by the
Pitman press, Bath. 7
[11] British Standard Institution. 1972. CP-110, The Structural use of
Concrete, Part-I, Design Materials and Workmanship.
[12] ACI-318. 2001. Building Code Requirement for Reinforced
Concrete, American Concrete Institute.
Acknowledgement
The authors wants to express the deepest sense of
gratitude for the support of Quaid-e-Awam University of
Engineering Science & Technology, Nawabshah and
Higher Education Commission for providing Financial
Assistance to carry out this research.
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