IIENG-Singapore_Paper-_March_2014


Abstract—Brick masonry plays an important role in the field of
construction, signifying the need to study the nature of behaviour of
masonry in different conditions and compositions. In this paper,
studies on the experimental investigation of material properties,
compressive and shear behaviour of brick masonry with different
mortar ratios are presented. The material properties are evaluated
from compression testing of brick units, mortar cubes and cylinders.
Bricks are tested in dry and wet conditions in order to make a
comparative study of the material behaviour along all three axes.
Compression and shear tests on brick prism triplets with different
mortar ratios are performed to evaluate and compare their
compressive strength, bond strength and interface behaviour. The
results obtained from the compression and shear tests are then
evaluated and contrasted. The research carried out would facilitate to
evaluate the behavior of unreinforced brick masonry using numerical
simulations under shear and compression loading.
Keywords—Brick masonry, Material properties, Mortar ratios,
Shear
I. INTRODUCTION
N the history of construction, brick masonry contributes the
major portion in the development of eminent historical
masonry structures. Since then, this most economical and
suitable method of construction gained more importance and
huge structures started to emerge all over the world. The
materials required for construction of brick masonry were
easily available in the ancient period.
In later years, Introduction of new technologies in the field
of construction made a great impact in the history of
construction. Advanced construction practices were adopted
using new materials to increase the strength and stability of the
structures. However, this affected the economical factor since
huge investment was required to implement this new method
of construction. New research and developments in this
1
– Final year Civil Engineering, Bannari Amman Institute of
Technology, Sathyamangalam, India.
2
– Principal Scientist, CSIR-Structural Engineering Research
Centre, Chennai, India.
3
– Assistant Professor, Department of Civil Engineering, Bannari
Amman Institute of Technology, Sathyamangalam, India.
*– Corresponding Author. E-mail address: ntp1393@gmail.com
concern have improved the accuracy and hence the developed
countries started to fund for the implementation of new
construction methodologies into practice. Tremendous
improvement was found due to the implementation of these
technologies and this overtook the importance of brick
masonry. Still, masonry buildings were in practice in many
places around the world as this could only satisfy the
economical method of construction of the basic requirements
of the people.
But, many ancient masonry structures failed due to their
inadequate design against structural durability and strength.
This facilitates the importance to study on the brick masonry in
order to predict their behaviour and properties. Many
researches have been carried out in the past to stipulate the
nature of brick masonry and their constituent materials under
different circumstances. But, there are no proper results
published or standard specifications that could meet the
requirements of the engineers. Further research in this field is
necessary to understand their heterogeneous material
properties and to gain an in depth knowledge about their
behaviour.
The present paper deals with the experimental investigations
of the constituent material properties of the brick masonry for
different mortar ratios. Burnt clay bricks of standard size are
used to determine their individual properties. Brick triplet
prisms were cast with different mortar ratios to identify their
composite material properties. The stress-strain curve is
plotted from the experimental data. The flexural strength of
unit brick is found using flexural testing based on the Indian
standard code [1]. The shear bond strength of triplet brick
prisms is also calculated based on the experimental maximum
shear load withstand by the specimen.
The strength of masonry structure mainly depends on the
strength of bonding between the bricks. Interface between the
mortar and brick plays a vital role in enhancing the strength of
masonry. Hence, the interface behaviour of masonry is also
discussed in this paper. Further studies are also proposed to
identify the interface model and bond-slip relation of brick
triplet prism for different mortar ratio based on the
experimental results which is useful for numerical studies on
brick masonry.
As a result of the literature study, few important
Experimental Approach to Investigate the
Behaviour of Brick Masonry for Different
Mortar Ratios
Thanikasalapradeep Nagarajan1*
, Selvakumar Viswanathan1
, Sinthiya Ravi1
, V.Srinivas2
, Premavathi
Narayanan3
I

observations are listed as follows. Palanisamy and Premalatha
[2] studied on the experimental investigation of masonry infill
material properties. Masonry infill walls were constructed
using different types of structural blocks to investigate their
behaviour. Experiments were carried out using fly ash and clay
brick prisms of CM1:4, CM1:5 and CM1:6 for 7 days and 28
days curing period. The stress-strain curve is plotted based on
the experimental results. The fly ash brick prism achieved
maximum strength compared to the clay brick prism.
Nowfer [3] carried out uniaxial compressive test to
determine the mechanical properties of unreinforced masonry
constituent materials. Based on the results, the stress-strain
relationship is defined and a simple numerical model is also
formulated to estimate the elastic modulus. The values are
used as the input for the numerical modeling of masonry which
is used for nonlinear finite element analysis.
Christy et al. [4] studied the bond strength of brick masonry
triplet and found that it varies with difference in the mortar or
masonry unit combination. The bond strength of triplet clay
and fly ash brick prism was determined using mortar with and
without pozzolanas. The result showed that the presence of fly
ash increased the bond strength.
Meghashree and Satish [5] deals with the experimental
identification of shear strength of brick masonry by 100%
replacement of pond ash in place of cement mortar.
Experiments are carried on brick triplets and masonry wall
panels for determining the shear bond strength and diagonal
split tension respectively. The author has recommended further
studies by using pond ash to increase the strength of masonry.
II.PROPERTIES OF MATERIAL
A.General
Brick masonry exhibits heterogeneous property due to
different constituent materials. Hence, it is important to
identify the individual properties of brick and mortar to
understand the overall behaviour of masonry. Experiments
were carried out using the compression testing machine and
the compressive strength is determined. The maximum strain
values for individual material are also tabulated from the
experimental results.
B.Brick
The bricks used in the research are the handmade burnt clay
bricks of uniform shape and size. The dimension of the bricks
is measured using measuring scale. The average dimension
was found to be 220mmx100mmx75mm. The quality of brick
is ensured by its appearance and the good bricks are selected
from the brick stack as per the requirements.
C.Cement
The 53 grade ordinary Portland cement is used in this
research to cast mortar cubes and cylinders. The cement
mortar is prepared using this OPC and fine aggregate with
suitable water-cement ratio which is further used to cast triplet
brick prisms.
D.Sand
The river sand is used to prepare the cement mortar as per
the mix proportion. The sand is sieved using 1.2mm sieve to
prepare a fine mix of the cement mortar.
III. TEST ON BRICK UNIT
A.General
Tests on individual brick units includes the determination of
water absorption capacity and compressive strength. Since, the
burnt clay bricks are porous in nature, the absorption capacity
is found using the water absorption test as per IS 3495 (Part
2): 1992 [6].
Totally three brick specimens are weighed and their
individual weight is noted (M1). These specimens are
immersed in water for 24 hours. After 24 hours the specimens
are removed from water and wiped to determine their weight
(M2). The water absorption after 24 hours immersed in water is
given by the formula (1),
M2 – M1
× 100 (1)
M1
The water absorption values of bricks used in the present
study are given in Table I from which the water absorption of
the bricks are found to be around 14%.
TABLE I
WATER ABSORPTION
Specimen
No
Brick
Dimension (mm)
Water
Absorption (%)
1 220×100×74 10.71
2 220×100×75 13.33
3 220×105×75 18.52
B.Compression Test on Brick Units
The maximum load that the burnt clay brick can withstand is
determined using the compressive strength test as per IS 3495
(Part 2): 1992 [6]. Compressive strength of brick depends
upon the composition of clay, method of brick manufacturing
and degree of firing. The bricks are tested along three axes
both in wet and dry conditions as shown in Fig 1. The test is
carried out using the compression testing machine of
maximum 300 tonnes capacity. The test is progressed with a
constant rate of loading of 50 N/s. The frog of the brick is
filled with mortar and the level of bed surface is also ensured
before testing.
Compressive Strength = in N/mm2
(2)
The load at which the brick fails in (N) is noted and the
maximum compressive strength of individual brick is
evaluated by the above mentioned equation (2) and the values

are given in Table II. The average compressive strength of
bricks used is found to be 3.57MPa in the x-axis direction.
TABLE II
COMPRESSIVE STRENGTH OF BRICK UNIT
S.No Axis of
Testing
(Refer Fig.1)
No of
Specimens
Average
Compressive
Strength of Brick
( N/mm2
)
Dry
Brick
Wet
Brick
Dry
Brick
Wet
Brick
1 X-Axis 3 3 3.93 3.57
2 Y-Axis 3 3 2.67 2.49
3 Z-Axis 3 3 1.64 1.27
From the experimental data, the stress-strain graphs are
plotted for dry and wet bricks for the three different axes of
testing. A comparative study is made by plotting the combined
stress-strain graph for the dry and wet bricks for each axis as
shown in Fig 2-4.
(a) (b)
(c)
Fig 1 Compression Test on Brick Unit (a) Along X-axis,
(b) Along Y-axis and (c) Along Z-axis
Fig 2 Stress-Strain Curve for Dry and Wet Brick along X-axis
Fig 3 Stress-Strain Curve for Dry and Wet Brick along Y-axis
Fig 4 Stress-Strain Curve for Dry and Wet Brick along Z-axis
Dry bricks is found to be giving more compressive strength
than the wet bricks. The value of young’s modulus obtained
from the stress-strain curve plotted from the experimental
results of the compression testing on brick is found to be
3070MPa.
C.Flexural Strength Test on Brick Unit
The flexural strength of brick is obtained experimentally as
shown in Fig 5 based on the Indian standard code IS: 4860-
1968[1]. The flexural breaking load (P) for individual brick is
noted for three different specimens. The flexural strength of
brick specimen with breadth (B) and depth (D) is calculated
using the formula,
Where, (L) is the intermediate span between the supports.
Fig 5 Flexural Test on Brick Unit
x
y
z

The value of flexural strength of brick is given in Table III.
The average flexural strength of brick is found to be 1.12MPa.
TABLE III
FLEXURAL STRENGTH OF BRICK UNIT
Specimen No Failure Load (kN)
Flexural Strength
(N/mm2
)
1 2.72 1.137
2 2.62 1.095
3 2.70 1.128
IV. TEST ON CEMENT MORTAR
A.General
The cement mortar plays a vital role in the construction of
brick masonry as its property greatly influences the strength of
masonry. The strength of masonry bond depends on the type of
mortar used and the thickness of mortar joint between the
brick units. Hence, this specifies the importance of cement
mortar and their properties. In order to know their behaviour
and properties, cubes and cylinders were cast using standard
moulds for different mortar proportions of 1:2, 1:3 and 1:4 to
determine their strength experimentally. The moulds are
removed after 24 hours and the cubes are allowed for curing
for a period of 15 days.
B.Determination of compressive strength of mortar cubes and
cylinders
The cement mortar cubes and cylinders of standard size
were cast for 1:2, 1:3 and 1:4 mix proportions and cured for 15
days. Totally twelve cubes are tested using the compression
testing machine as shown in Fig 6 to calculate the maximum
compressive strength as stipulated by IS 2250-1981 [8] and the
values of compressive strength are given in Table IV . From
the experimental data, stress-strain curve is plotted as shown in
Fig 7 and the Young’s modulus of cement mortar obtained is
given in Table V. The compressive stress obtained from the
test on cubes and cylinders is compared and is shown in Fig 8.
(a) (b)
(c)
Fig 6 Compressive Strength Test (a) CM Curing (b) CM Cube and
(c) CM Cylinder
TABLE IV COMPRESSIVE STRENGTH OF CEMENT MORTAR CUBE
S.No
Mortar
Proportion
Average Compressive
Strength (N/mm2
)
1 1:2 18.19
2 1:3 15.47
3 1:4 11.81
Fig 7 Stress-Strain Curve for Mortar Cube for Different Mortar
Proportions
TABLE V
MODULUS OF ELASTICITY AND MAXIMUM STRAIN VALUES OF MORTAR
S.No
Mortar
Ratio
Modulus of
Elasticity
(MPa)
Maximum
Compressive
Strain (mm)
1 1:2 5385 0.0083
2 1:3 4075 0.0078
3 1:4 3600 0.0076
Fig 8 Comparison of Cube and Cylinder Strength for Different
Mortar Proportions
V.TEST ON TRIPLET BRICK PRISM
A.General
Along with the individual properties of the constituent
materials of brick masonry, the composite behaviour is also
studied by different experimental tests on triplet brick prism

[9]-[16]. The behaviour of constituent materials of brick
masonry varies in individual and composite state. In order to
understand their behaviour, a total of 24 brick triplet prisms
were cast for different mortar mix proportions to identify their
compressive strength, shear bond strength and their interface
behaviour. Based on the experiment results, the values
obtained are used as the input to numerical models for finite
element analysis of the same in order to establish a
comparitive study.
B.Determination of compressive strength of triplet brick prism
Ganapathi, et al [11] found that the compressive strength of
brick prisms vary based on the failure pattern, Water
absorption, mortar proportion and individual compressive
strength of bricks. In this research, triplet brick prisms were
cast using different cement mortar proportions 1:2, 1:3 and 1:4
with bond thickness of 10mm and cured for 15 days. The
compressive strength of brick prisms are obtained from the test
as shown in Fig 9 and the average of three test specimen
results for respective mortar proportions are given in Table VI.
Corresponding stress-strain curves is shown in Fig 10 and the
values of elastic modulus are identified as given in Table VII
for further analysis.
(a) (b)
Fig 9 Compression Test on Triplet Brick Prism (a) During Test
and (b) At Failure
TABLE VI
MAXIMUM COMPRESSIVE STRENGTH OF BRICK PRISM
S.No
Mortar
Ratio
Mortar
Thickness
(mm)
Compressive
Strength of
Prism (MPa)
1 1:2 10 2.43
2 1:3 10 2.03
3 1:4 10 1.92
From the results, the average compressive strength of triplet
brick prism is found to be around 2.15MPa. The brick prism
with mortar ratio of 1:2 exhibits higher strength than other two
mortar ratios. This shows that the mortar ratio plays important
role in the strength of the brick masonry. The average modulus
of elasticity of the masonry is found to be 3570, 3155 and
3125 MPa for three mortar ratios of 1:2, 1:3 and 1:4
respectively at almost the same compressive strain values.
Fig 10 Stress-Strain Curve for Brick Prism for Different Mortar
Proportions
TABLE VII
MODULUS OF ELASTICITY AND MAXIMUM STRAIN VALUES OF
BRICK PRISM
C.Calculation of Shear Bond Strength of Triplet Brick Prism
Masonry is a combination of brick and cement mortar which
need to exhibit homogeneous material property. The
homogeneity of masonry depends on the level of bond
strength. But, in most of the cases this is not applicable due to
variation in the property of the materials [17]-[22]. The bond
strength between brick units is greatly influenced by the
characteristics of cement mortar. Sometimes, the property of
brick also affects the bonding due to high water absorption
capacity. Kishi et al. [19] carried out shear strength tests with
triplet brick prisms to obtain the shear strength of interface
between brick and mortar by immersing them in water for 24
hours before casting the prisms. Samarasinghe and Lawrence
[20] performed shear tests on masonry triplets and found that
the shear bond strength of brick prisms cast with pre-wetted
bricks is high compared to dry bricks. There are no proper
code specifications for testing shear bond strength. Hence, a
setup is made as shown in Fig 12 particularly to test the shear
bond strength of triplet brick prisms according to the required
setup as shown in Fig 11. The shear bond strength of triplet
clay brick prisms cast using 1:2, 1:3 and 1:4 cement mortar
proportions are experimentally determined. The average bond
strength values of triplet brick prism is shown in Table VIII.
S.No Mortar Ratio
Modulus of
Elasticity
(MPa)
Maximum
Compressive
Strain (mm)
1
1:2 3570 0.00098
2
1:3 3155 0.00088
3
1:4 3125 0.00085

Fig 11 Shear Test Setup for Triplet Brick Prism
Fig 12 Experiment Setup for Shear Testing
TABLE 8
SHEAR BOND STRENGTH OF TRIPLET BRICK PRISM
S.No Mortar Ratio
Average Shear
Bond Strength
(MPa)
1 1:2 0.139
2 1:3 0.087
3 1:4 0.072
Fig 13 Comparison of Shear Stress and Displacement of Triplet Brick
Prism for Different Mortar Ratio
From the experimental data, a graph is plotted between the
shear bond strength and displacement as shown in Fig 13. The
average bond strength of brick triplet is found to be 0.139MPa,
0.087MPa and 0.072MPa for CM1:2, CM1:3 and CM 1:4
respectively as shown in Table VIII.
D.Interface Behaviour of Brick Masonry
Interface is a thin layer between the brick and mortar which
greatly influences the strength of bonding [23]. In order to
understand their behaviour, an interface model is derived and
the experimental results are compared with the proposed
model. Based on the experimental results of this paper, various
studies are to be carried out in the future to propose an
interface model which predicts the exact failure mode of brick
masonry.
VI. CONCLUSION
The experimental research work carried out to investigate
the material properties of brick masonry constituent helps in
gaining an in depth knowledge about the difference in
individual and composite behaviour of masonry.
1. The Young’s Modulus and the Stress-Strain values of the
constituent materials of brick masonry are determined
under compressive load.
2. The flexural strength of brick is also identified from the
experimental result which is used as an input for finite
element analysis.
3. The shear bond strength of triplet brick prism for
different mortar proportions is experimentally found and
future studies are recommended to identify the bond slip
relation and interface model.
This research paper can also be used as a reference for
numerical modeling and analysis. Using the prescribed
Young’s modulus value of different materials of brick
masonry, the finite element model can be created and
analyzed.
ACKNOWLEDGMENT
This paper is being published with kind permission of the
Director, CSIR-SERC, Chennai. The Scientists, Project
Assistants of Bridge Engineering Division, Technical Staff of
Structural Testing Laboratory are highly acknowledged for
their kind support in this research work. We thank the Dean,
Head of Department and faculty members of Civil Engineering
department of Bannari Amman Institute of Technology for
their support and encouragement.
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