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ISSN 0974-5904, Volume 05, No. 04

August 2012, P.P.

#02050418 Copyright ©2012 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.

Experimental Investigation on the Characterization of Solid Clay

Brick Masonry for Lateral Shear Strength Evaluation

QAISAR ALI1, YASIR IRFAN BADRASHI

1, NAVEED AHMAD

1,2, BASHIR ALAM

3,

SHAHZAD REHMAN3 and FARHAT ALI SHAH BANORI

3

1Earthquake Engineering Center, UET, Peshawar, Pakistan

2ROSE School−IUSS Pavia, Pavia, Italy

3Department of Civil Engineering, UET, Peshawar, Pakistan

Email: [email protected], [email protected]

Abstract: The aim of the paper was to carry out the mechanical characterization of solid fired clay brick masonry

through experimental investigation, essential for structural evaluation under lateral loads due to winds and

earthquakes within the context of design and assessment studies. The basic material properties of masonry including

compressive strength, diagonal tensile strength, shear strength, masonry bond strength, Young’s and shear moduli

are obtained through laboratory testing on masonry prisms (48 samples), triplets (96 samples) and wallets (48

samples). Standard brick unit prevalent in Pakistan is considered, similar to units that can be found also in

neighboring countries like India, Iran and Bangladesh amongst others. Three types of mortar ─ cement-sand,

cement-sand-khaka and cement-khaka are used as bonding material for masonry assemblages. Khaka is obtained as

a byproduct of stone crushing process, employed in mortar preparation to produce relatively workable and

economical mortar. The effect of mix proportions of mortar is also investigated. Empirical relationships are

developed herein whereby basic mechanical properties of masonry are correlated with the mortar strength, mortar

type and mix proportions. An attempt is made to correlate mechanical properties between each other and establish

simplified relationships to help facilitate their use in future applications for design and assessment of unreinforced

masonry wall structures under wind and earthquake induced lateral loading.

Keywords: Shear, Diagonal Tensile Strength, Compression, Elastic Moduli, Mortar, Khaka, Unreinforced Brick

Masonry.

Introduction:

Masonry material is largely practiced for construction of

structures and infrastructures e.g. buildings, bridges,

retaining structures, etc., in most of the underdeveloped

and developing parts of the world. It is due to the

traditional construction practices employed in these

countries, motivated also by the regional climatic

conditions . Brick masonry construction employing

solid clay units and cement-mortar can be found in

many urban exposure of Pakistan and so also in

neighbouring countries like India, Iran, Bangladesh

among others. Most of the structures in these urban

exposures are subjected to frequent lateral loads due to

heavy winds and earthquakes that consequently induce

shear stresses in the structural walls. The behavior of

masonry material under lateral loading is dramatically

different than its counterpart materials - concrete and

steel, due to high non-homogeneity and composite

nature of masonry components. The different

mechanical properties of masonry units and mortar and

their interface makes the masonry system behavior

difficult to predict using simple hypotheses as adopted

for concrete and steel. The masonry mechanical

characterization can be best performed through

experimental investigations, which can help facilitate

development of analytical tools for future applications.

Masonry structures are often composed of several load

bearing walls for carrying both gravity and lateral loads.

In building construction, when the connection at wall

intersections and at floor-to-wall is achieved through

proper means, with controlled out-of-plane deflection of

the floors, the building primarily resist lateral loads by

in-plane response of walls (Magenes, 2006; Tomazevic,

1999). The provision of reinforced concrete slab with

deep spandrels, presence of tie rods, ring beams at floor

levels and efficient floor-to-wall connections favours

the integrity of masonry walls. It enables the structure

respond in a box like action to lateral loading with shear

dominated damage in masonry walls. Flexure rocking,

that may result in toe crushing of walls, is also a

possible mechanism to resist lateral loads (Magenes and

Calvi, 1997; Abrams, 2001, among others).

783 QAISAR ALI, YASIR IRFAN BADRASHI, NAVEED AHMAD, BASHIR ALAM,

SHAHZAD REHMAN and FARHAT ALI SHAH BANORI

International Journal of Earth Sciences and Engineering

ISSN 0974-5904, Vol. 05, No. 04, August 2012, pp. 782-791

Figure 1 shows typical damages observed in masonry

wall buildings of the above characteristics during the

2005 Kashmir earthquake. Typical damages that may

occur in masonry infill of concrete structures due to

lateral in-plane forces observed during earthquake are

also shown. Local out-of-plane collapse of wall is also

evidenced in earthquakes for deficient structures

(D’Ayala and Paganini, 2011; Javed et al., 2008).

Figure 1: Shear Damages Observed in Load Bearing Walls of Unreinforced Masonry Buildings And Masonry Infill

of Concrete Buildings due to Earthquake Induced Lateral Loads.





A): Diagonal shear cracks in masonry building walls observed during 2005 Kashmir earthquake. A building with

concrete floor slab, deep spandrels and walls with lower vertical aspect ratio (height to thickness). Adopted from

Naseer et al. (2010)

(B): Toe crushing in masonry building walls observed during 2005 Kashmir earthquake. A building with concrete

floor slab, deep spandrels and walls with high vertical aspect ratio. Adopted from Javed et al. (2008)

(C): In-Plane shear cracks observed in masonry infill of concrete structure damaged in 2005 Kashmir earthquake.

A building with reinforced concrete beams and columns provided with concrete floor slab and rigidly connected

masonry infill. Adopted from Javed et al. (2008)

Many available analytical models can be used to

estimate the in-plane strength of masonry walls

(Abrams, 2001; CEN, 1994; FEMA, 2000; Magenes and

Calvi, 1997; Mann and Muller, 1982; Tomazevic, 1999;

Turnsek and Sheppard, 1980, among others). Analytical

models are also available to estimate the strength of

masonry infill panel under lateral loads in concrete

structures (Fardis and Calvi, 1994; Kappos et al., 1998;

Smyrou et al., 2011, among others). All these models

require basic mechanical properties of masonry material

to obtain lateral in-plane strength. This fact makes the

experimental investigation on masonry materials

essential before the assessment of structures can be

performed within the context of existing stock

evaluation and design verification of new construction

schemes (Ahmad et al., 2010, 2011, 2012 among

others).

This paper hence presents an experimental investigation

on solid clay fired-brick masonry material for

mechanical characterization. The experimental work

included laboratory tests under monotonic loading on

masonry prisms: for the estimation of masonry

compressive strength (fmc) and elastic Young modulus

(E), on triplets: for the estimation of bond strength in

shear: cohesion parameter (c) and friction coefficient

(µ) of Mohr-Coulomb model, and on wallets: for the

estimation of diagonal tension strength (ft) and shear

modulus (G), besides tests on constituent materials i.e.

brick units: for unit compression strength, water

absorption and initial rate of absorption and mortar: for

compression strength (fm).

The testing is performed using the standard testing

procedures: ASTM E-519-02 (2002) for wallet tests, EN

1052-3 (2002) for triplet tests, ASTM C-67-06 (2006)

for masonry unit tests, ASTM C109/C109M-08 (2008)

for mortar compression tests and ASTM C-1314-07

(2007) for masonry compression tests. Three types of

mortar are considered; cement-sand mortar (CS),

cement-sand-khaka mortar (CSK), cement-khaka mortar

(CK). The mortars are considered with 12 various mix

proportions (four cases for each mortar type). The

motivation towards investigating masonry in CSK and

CK mortar is that they produce relatively more

workable and economical mortars for masonry

construction (Naeem et al., 1996); It is essential to

understand their impact on the mechanical properties of

masonry. Empirical relationships are developed to relate

the basic mechanical properties of masonry with mortar

strength, mortar constituents and mix ratio. Also, an

attempt is made to correlate the mechanical parameters

with each other. These relationships can provide a

useful means for future applications in the design and

verification studies of masonry construction.

Experimental Investigation of Clay Fired Brick

Masonry:

1.1 Experimental Tests Program:

The experimental program for mechanical

characterization of masonry included tests on masonry

units, mortar, masonry prisms, masonry triplets and

masonry wallets. The tests are performed at the Material

Testing Laboratory of Civil Engineering Department of

UET Peshawar, Pakistan. The following sections briefly

elaborate each of the tests.

1.2 Tests on Masonry Constituents Material:

1.2.1 Masonry Unit Tests Per ASTM C-67-06:

The present study has focused on investigating masonry

of solid clay fired brick masonry units, common in

various parts of Pakistan, which can also be found in

other South Asian countries like India, Iran,

Bangladesh, among others. The tests on brick units

included water absorption test (on nine samples), initial

rate of absorption (IRA) test (on five samples),

compressive strength test (on nine samples). The results

of the experiments showed unit water absorption of

19.3% (COV 4.23%); IRA of 82.20 gm/min/30inch2

(COV 18.21%); compressive strength of 16.91 Mpa

(COV 22.89%).

The water absorption capacity which is less than 20%

indicates a good quality of the unit. The IRA of unit

which is greater than 30gm/min/30inch2

indicates that it

must be wetted well before employing in the

construction of masonry works.

1.2.2 Mortar Tests Per ASTM C109/C109M-08:

Various types of mortars investigated in the present

study included CS, CSK and CK mortars. The addition

of khaka to the ordinary CS mortar produces more

workable and economical mortar for brick masonry

construction (Naeem et al., 1996). Chemical analysis on

khaka shows 95% of CaCo3 content (Naeem et al.,

http://www.springerlink.com/content/?Author=E.+Smyrou

784 Experimental Investigation on the Characterization of Solid Clay




1996). In the present study, the mix proportions of

mortar constituents as found in most of the construction

works are investigated. Four cases for each mortar type

are considered with mix proportions of 1:4, 1:6, 1:8 and

1:10 for CS and CK mortars; and 1:2:2, 1:3:3, 1:4:4 and

1:5:5 for CSK mortar. Gradation tests are performed on

both sand and khaka constituents, see

Figure 2 which revealed a relatively fine graded

aggregate contents of khaka.

Figure 2: Gradation Profile of Sand and Khaka

Constituent Employed For Mortar Preparation

Figure 3: Mean Compressive Strength of Mortar Cubes,

28-days. CS Represents Cement-Sand Mortar, CSK

Represents Cement-Sand-Khaka Mortar and CK

Represents Cement-Khaka Mortar

Mortar cubes of size 50mmx50mm were prepared for

the aforementioned mortar types and tested after 28

days for compression strength. A total of 108 mortar

cubes (nine samples for each mix proportion) were

tested. Figure 3 shows the mean estimated compressive

strength of each mortar cubes (four cases for each

mortar types).

Generally, the strength of mortar decreased with

increasing the mix-ratio. The experiments indicated that

the addition of khaka to ordinary mortar increases the

strength of mortar. On an average the strength is

increased by 72 percent for CK mortar and 50 percent

for CSK mortar.

1.3 Tests on Masonry Assemblages:

1.3.1 Masonry Triplets Tests Per EN-1052-3:

The triplet tests were performed on masonry

assemblages composed of three bricks using the EN-

1052-3 testing setup (Figure 4). The top and bottom

brick units were clamped whereas the central unit was

subjected to horizontal loading. Two cases for pre-

compression (250kg and 500kg) were considered

whereby the prism is loaded at the top.

The testing provides estimates of the shear strength

(bond strength) and friction coefficient of the masonry:

parameters employed in the Mohr-Coulomb shear

strength model.

Figure 4: Triplet Test Specimen and Loading Setup per

EN-1052-3

where τ represents the in-plane shear stress, c represents

the shear strength at zero pre-compression; µ represents

the coefficient of friction; σ represents the pre-

compression stress on the prism. A total of 96 prism

samples (eight samples prepared for each mix

proportion of each mortar type) were tested.





Figure 5: Shows the Mean Shear Strength and the Corresponding Friction Coefficient Observed for each Mortar

Type. On Average, the addition of Khaka to the Ordinary Mortar Increased the Strength by 40 Percent for CK

Mortar type and 22 Percent for CSK Mortar Type whereas the Friction Coefficient is Increased by 20 Percent for

CK Mortar Type and 2 Percent for CSK Mortar Type.

Figure 5: Observations made from the Triplet Tests. From Left to Right: Masonry Bond Strength (Shear Strength

at Zero Pre-Compression) and Friction Coefficient. CS Represents Cement-Sand Mortar, CSK Represents Cement-

Sand-Khaka Mortar and CK Represents Cement-Khaka Mortar.

It is worth to mention that for the estimation of lateral in-plane shear strength of wall a correction factor is employed

to the Mohr-Coulomb parameters i.e. c & µ. It is due to the fact that these parameters are obtained from tests at local

level. Their correction for strength evaluation of walls is essential (Magenes and Calvi, 1997).





where k represents the correction factor; ∆x represents the length of the brick unit, 230mm in the present study; ∆y

represents the height of the brick unit, 70mm in the present study; µ represents the friction coefficient. The new

parameters can be calculated then as follow: cnew = c×k & µnew = µ×k.

1.3.2 Masonry Wallets Tests Per ASTM E-519-2:

Tests on masonry panels (wallets) of size 690mmx690mm with 230mm thickness were prepared in English masonry

bond pattern. Tests were performed on panels for the estimation of diagonal tension strength of masonry. The testing

setup was designed as per the ASTM E-519-2 recommendations (see

Figure 6). Linear variable displacement transducers (LVDTs) were installed, both on each horizontal and vertical

directions to measure the mean horizontal and mean vertical deformation of the specimen during loading.

Figure 6: Diagonal Tension Test Setup per ASTM E-519-2

This test setup is generally interpreted for diagonal tensile strength evaluation based on the consideration that the

specimen is subjected to pure shear, the specimen is cracked when the principal stress at the center of the panel

becomes equal to the tensile strength of masonry (ASTM E519-02; RILEM, 1994). However, it is urged based on

numerical and analytical studies that the specimen in reality is not subjected to uniform and homogenous state of

stresses. Because of this the specimen is not under pure shear (Brignola et al., 2009; Frocht, 1931; Magenes et al.,

2010).

The analytical formula recently proposed and employed by Magenes et al. (2010) is used in the present study to

estimate the diagonal tensile strength of tested wallets.

where ft represents the diagonal tensile strength; P represents the peak vertical loading; t represents the thickness of

the specimen; l1 and l2 represent the length of sides of the specimen. A total of 48 wallet samples (four samples

prepared for each mix proportion of each mortar type) were tested.





The diagonal tension strength is also interpreted to estimate the shear rigidity i.e. shear modulus, of masonry

material using the ASTM procedure, which is employed and recommended for shear modulus estimation (Magenes

et al., 2010).

where G represents the shear modulus; τ represents the shear stress; γ represents the corresponding shear strain; Pmax

represents the peak vertical load at failure; ∆V & ∆H represent the vertical and horizontal deformation in the vertical

and horizontal LVDT’s, respectively; g represents the gauge length of either of the LVDTs.

The above equation (4) is meant to obtain the shear modulus as the slope of the shear stress-strain curve between the

two specified points when the loading reaches 5 percent of the peak load and 33 percent of peak load i.e. the slope of

stress-strain curve between 5 percent and 33 percent of peak load. Other parameters are defined earlier.

Figure 8 reports the mean shear modulus of the

masonry wallets obtained for each mortar types.

Figure 7 reports the mean diagonal tensile strength of tested masonry wallets for each mortar type. It can be

observed from the typical damage pattern that the crack developed upon failure follows bed and head joints of

masonry. It is an indication that the strength is largely contributed by the masonry mortar and mortar-brick interface

bond strength. Thus, the use of various mortar types will affect the tensile strength of masonry wallets.

On average the addition of khaka to the ordinary mortar increases the diagonal tension strength by 110 percent for

CK mortar type and 93 percent for CSK mortar type.

The diagonal tension strength is also interpreted to estimate the shear rigidity i.e. shear modulus, of masonry

material using the ASTM procedure, which is employed and recommended for shear modulus estimation (Magenes

et al., 2010).





where G represents the shear modulus; τ represents the shear stress; γ represents the corresponding shear strain; Pmax

represents the peak vertical load at failure; ∆V & ∆H represent the vertical and horizontal deformation in the vertical

and horizontal LVDT’s, respectively; g represents the gauge length of either of the LVDTs.

The above equation (4) is meant to obtain the shear modulus as the slope of the shear stress-strain curve between the

two specified points when the loading reaches 5 percent of the peak load and 33 percent of peak load i.e. the slope of

stress-strain curve between 5 percent and 33 percent of peak load. Other parameters are defined earlier.

Figure 8 reports the mean shear modulus of the

masonry wallets obtained for each mortar types.

Figure 7: Diagonal Tension Strength of Masonry Wallets. From Left to Right: Typical Damage Mechanism of one

of the Representative Samples and Mean Estimates of Masonry Diagonal Tensile Strength for Each Mortar Type. CS

Represents Cement-Sand Mortar, CSK Represents Cement-Sand-Khaka Mortar and CK Represents Cement-Khaka

Mortar.

Figure 8: Shear Modulus of the Wallets obtained

through Diagonal Tension Test on Masonry Wallets. CS

Represents Cement-Sand Mortar, CSK Represents

Cement-Sand-Khaka Mortar and CK Represents

Cement-Khaka Mortar.





Figure 9: Masonry Bond Strength (Shear Strength) to

Mortar Compression Strength.

On average, the addition of khaka to the ordinary mortar

increases the shear stiffness (shear modulus) by 91

percent for CK mortar type and 90 percent for CSK

mortar type.

2 Simplified Empirical Relationships for Masonry

Mechanical Properties:

The basic mechanical properties (masonry bond strength

and diagonal tensile strength) obtained experimentally

for each mortar types are correlated with the mortar

compressive strength to establish simplified

relationships for future applications. Furthermore,

correlation is performed between the mechanical

properties (bond strength and coefficient of friction) and

mortar types and mix proportion.

Additionally, correlation is performed between various

mechanical properties (bond strength to tension

strength, compressive strength to tensile strength,

Young modulus to shear modulus) to provide easy

means for estimation and conversion of masonry

mechanical properties. These relationships can be used

for future applications given either of the information on

the mortar strength or type and constituents.

2.1 Mortar Strength to Masonry Mechanical

Properties:

2.1.1 Mortar Strength to Masonry Bond

Strength:

For each mortar type, the mean bond strength obtained

is correlated with the mean compressive strength of

mortar. Nonlinear regression analysis is performed and

empirical relationship is established between mortar

strength and masonry bond strength through best fitting.

The following relationship is developed.

where fm (MPa) represents the compressive strength of

mortar, Additionally, constrained regression analysis is

performed whereby the power of fm is kept 0.60 and 1.0,

in order to possibly further simplify the above equation.

Either of the above equation may be employed, for most

of the practical cases, to obtain the masonry bond

strength given the mortar compressive strength.

shows the experimentally obtained data employed for

correlating the bond strength to mortar strength and

possible best fitting through regression (unconstrained

and constrained) analysis.

2.1.2 Mortar Strength to Masonry Diagonal

Tension Strength:

For each mortar type, the mean masonry diagonal

tension strength is correlated with the mean

compressive strength of mortar. Nonlinear regression

analysis is performed and empirical relationship is

established between the mortar compressive strength

and diagonal tensile strength through best fitting. The

following relationship is developed.

The above Equation 8 is found to provide higher

estimate of diagonal tension strength for CS mortar type

(see

Figure 10). Thus additionally constraint regression

analysis is performed for CS mortar type only whereby

the power of mortar compression strength fm is kept

0.80, in order to establish relationship between CS

mortar strength and masonry diagonal tension strength.





Figure 10: Masonry Diagonal Tension Strength to

Mortar Compression Strength. CS Represents Cement-

Sand Mortar, CSK Represents Cement-Sand-Khaka

Mortar and CK Represents Cement-Khaka Mortar.

The above equation (8) may be employed for CK and

CSK mortar type to obtain the masonry diagonal tensile

strength given the mortar compressive strength.

Equation (9) can be employed for masonry in case when

CS mortar is used in the construction work.

Figure 10 reports the experimentally obtained data

employed for correlating the masonry diagonal tension

strength to mortar compressive strength and possible

best fitting through regression (unconstrained and

constraint) analysis.

2.2 Mortar Type and Mix Proportion to Masonry

Mechanical Properties

2.2.1 Mortar Type and Mix Proportion to Masonry

Bond Strength and Friction Coefficient:

For each mortar type, the mean masonry bond strength

and friction coefficient, parameters c & µ employed in

Equation (1), are correlated with the mortar constituents

proportion (mainly sand, khaka, and sand-khaka).

Linear regression analysis is performed and empirical

relationships are established between the mortar

constituents proportion and shear strength parameters of

masonry. Each mortar type is considered separately.

The following relationships are developed for c & µ of

the Mohr-Coulomb strength law for considered mortar

types.

Bond Strength:

Friction Coefficient:

In the above equations, S represents the proportion of

sand for unit cement proportion in CS mortar; K

represents the proportion of khaka for unit cement

proportion in CK mortar; SK represents the combined

proportion of sand-khaka for unit cement proportion in

CSK mortar considering that sand and khaka are

employed in equal proportion.





Figure 11 reports the experimentally obtained data

employed for correlating the masonry shear strength

parameters to mortar constituent for considered mortar

types and possible best fitting through linear regression

analysis. The horizontal axis of the Figure 11 represents

the proportion of sand to cement for CS mortar; khaka

to cement for CK mortar and combined khaka-sand

(added being equally) proportion to cement for CSK

mortar.

Figure 11: Masonry Shear Strength Parameters to Mortar Types and Mix Proportion.

From Left to Right: Masonry Bond Strength and Friction Coefficient Employed in Mohr-Coulomb Strength Model.

CS Represents Cement-Sand Mortar, CSK Represents Cement-Sand-Khaka Mortar and CK Represents Cement-

Khaka Mortar.

The above equations may be employed to estimate the

masonry shear strength given the type of mortar (i.e.

mortar constituents), and mix proportion. It is worth to

mention that these parameters are obtained at local level

and will require to be modified by the Mann and Muller

(1982) correction factor k i.e. Equation (2) before

employing them in shear strength evaluation of masonry

wall (Magenes and Calvi, 1997).

2.3 Correlating Masonry Mechanical Properties:

2.3.1 Masonry Compressive Strength to Masonry

Diagonal Tension Strength:

The mean masonry compressive strength is correlated

with the mean masonry diagonal tensile strength as

elsewhere (Ali, 2006). Nonlinear regression analysis is

performed and an empirical relationship is established

between the masonry compressive strength and diagonal

tensile strength through best fitting. The following

relationship is developed.

where fmc represents the masonry compressive strength.

The model can be employed to estimate the masonry

compressive strength given the masonry diagonal tensile

strength and vise versa.

reports the experimentally obtained data employed for

correlating the masonry diagonal tensile strength to

masonry compressive strength and possible best fitting

through nonlinear unconstrained regression analysis.

2.3.2 Masonry Young Modulus to Shear Modulus:

For each mortar type used herein, the mean masonry

Young modulus is correlated with the mean shear

modulus of masonry, in order to provide an easy means

of converting elastic moduli of masonry. Linear

regression analysis is performed and an empirical

relationship is established between the masonry Young





modulus and masonry shear modulus through best

fitting. The following relationship is developed.

The above equation may be employed for most practical

cases to obtain the masonry shear modulus given the

masonry Young modulus. The condition, E>1000 (MPa)

given alongside the equation is again essential to avoid

any unrealistic estimate of shear modulus.

Figure 12: Masonry Diagonal Tension Strength to

Masonry Compression Strength.

Figure 13 report the experimentally obtained data

employed for correlating the masonry shear modulus to

masonry Young modulus and possible best fitting

through linear unconstraint regression analysis. The

figure also shows the code specified relationships e.g.

the EC6 specified like most of the building codes, for

masonry which in the present case seems to provide a

very higher estimate of the shear modulus for a

specified value of masonry Young modulus.

Figure 13: Masonry Young Modulus to Shear Modulus.

3 Conclusions:

The paper presented the mechanical characterization of

solid fired clay brick masonry through experimental

investigation. Laboratory tests were performed on 108

mortar cubes, 96 masonry prisms for triplet tests, 48

masonry prisms for compression tests and 48 masonry

wallets for diagonal tension tests. The effect of various

mortar types (cement-sand CS, cement-khaka CK and

cement-sand-khaka CSK) and mix proportion on the

mechanical properties are investigated.

Simplified relationships are developed to relate the

mortar strength, mortar types and mix proportion with

the masonry basic mechanical properties. The study

provided tools essential within the context of

assessment and design verification of masonry walls

subjected to lateral loads. The relationships: mortar type

and mix proportion to masonry bond strength and

friction coefficient are first of its kind and of a great

importance for practical applications. Masonry

constructions common in Pakistan and which can also

be found in neighboring countries (like India, Iran,

Bangladesh among others) are considered in the present

study. The following conclusions are drawn based on

the experimental study.

Given the mortar compression strength, the basic

mechanical properties of masonry can be found as

follow:

Bond Strength = 0.0326×Mortar Strength0.6633

Diagonal Tension Strength = 0.11×Mortar Strength0.8281

,

for CK and CSK mortar

Diagonal Tension Strength = 0.07×Mortar Strength0.80

,

for CS mortar

Masonry Compression Strength = 4.57×Diagonal

Tension Strength0.30

Masonry Young Modulus = 1790×Diagonal Tension

Strength0.30

Masonry Shear Modulus = 175.06× Diagonal Tension

Strength0.70





Given the mortar composition and mix ratio, the

basic mechanical properties of masonry for Mohr-

Coulomb relationship can be found as follow:

Bond Strength:

Friction Coefficient:

where S represents the proportion of sand, K represents

the proportion of khaka and SK represents the combined

proportion of sand-khaka per unit cement.

Masonry bond strength, compression strength,

diagonal tension strength and elastic moduli decreases

with increasing the relatively proportion of sand and

khaka constituent in mortar.

Masonry friction coefficient increases with

increasing the relatively proportion of sand and khaka

constituent in mortar for CS and CSK mortar type

whereas it decreases with increasing the relatively

proportion of khaka constituent in mortar for CK mortar

type.

The relationship between shear modulus and Young

modulus as specified by the Code appears to provide an

over-conservative estimate for shear modulus for the

considered masonry type.

The research study revealed that mortars with

khaka either alone as the fine aggregate or in

combination with sand, provide relatively high shear

strength and stiffness as compared to mortars with only

sand as fine aggregate. The positive aspects of use of

khaka as a masonry constituent are the good mechanical

characteristics besides being economical and more

workable in construction work.

Acknowledgements

The authors acknowledge the reviewers for kindly

providing constructive remarks which improved the

presentation of the research work significantly. The first

author gratefully acknowledges the support and

financial assistance provided by the University of

Engineering & Technology in the form of three years of

study leave. He also wishes to place on record his

gratitude to the Higher Education Commission (HEC)

of Pakistan for providing the funds for this research

under its Merit Scholarship scheme for PhD studies in

Science and Technology.

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http://www.springerlink.com/content/5x523331ug6v3k7n/



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