1, Januari 2009
INTRODUCTION
Masonry can be regarded as an assemblage of structural units which are
bonded together in a particular pattern by
mortar or grout. It is well known as being
strong in compression but weak in tension. It can however be reinforced to carry
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on strength, durability, adhesion, fire resistance, thermal properties, acoustic properties and aesthetics.
Bricks and blocks are produced in
many formats: solid, perforated, and hollow. Clay bricks are obtainable in strength
up to 100 N/mm2 but much lower strength
2040 N/mm2 are generally sufficient for
domestic building and for cladding for
taller building. Where no recent test certificates are available, tests may be carried
out to demonstrate that the units satisfy
the engineering requirements.
The specifications for the sizes of clay
brick and precast concrete masonry units
(concrete block masonry) are given in BS
3921:1985 and BS 6073 Part 1: 1981
respectively. The standard work sizes for
individual clay brick units are 215 mm
length x 102.5 mm width x 65 mm height.
Many varieties are available for the sizes
of concrete block masonry.
Mortar
The primary purpose of mortar in
masonry is to bond masonry units into an
assemblage, which acts as an integral element having particular functional performance characteristics. Its properties
such as compressive strength, flexural
strength, Elastic Youngs Modulus and
Poissons Ratio are all important in determining the strength and quality of masonry. The modern mortar constituents are
cement, lime, sand and water in specified
proportions.
The British Standard of Masonry, BS
5628 Part 1 defines four types of structural mortar which are named as given
designations (i), (ii), (iii) and (iv). Varying
the percentages of the components used to
make the mortar produces the different
types of mortar. The strength of mortar
depends on the proportions of cement and
lime in addition to the water/cement ratio
used in making it.
Of the four structural mortars, designation (i) is the strongest, designation (iv)
is the weakest, with designations (ii) and
(iii) having intermediate strength. The
1 : 0to1/4 : 3
1 : 1/2 : 4to41/2
1 : 1 : 5to6
1 : 2 : 8to9
Masonry
Cement:
Sand
1 : 21/2to31/2
1:4to5
1:51/2to61/2
Mean Compressive
Strength at 28 days
(N/mm2)
Cement:Sand Preliminary Site
with
(Laboratory Test
plasticizer
tests)
1:3
16.0
11.0
1:3to4
6.5
4.5
1:5to6
3.6
2.5
1:7to8
1.5
1.0
70
100
19.2
24.0
15.1
18.2
13.1
15.5
10.8
12.7
least horizontal
35 or greater
22.8
18.8
17.0
14.6
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Table 3. Small specimen sizes for testing the compressive strength of masonry
Face size of unit
Masonry specimen size
lu (mm)
hu (mm)
Length ls
Height hs
Thickness ts
300
150
(2 x lu)
5 hu
3 ts and tu
15 ts and
> 150
3 hu
ls
> 300
150
(1.5 x lu) 5 hu
> 150
3 hu
Note.
(lu), (hu) and (tu) is the length, the height specimen with the distance of the half
and the width of the masonry unit res length. The displacements are measured
pectively. (ls) (hs) (ts) is the length, the whilst applying the compressive force
height and the thickness of the specimen continuously where the maximum force is
respectively.
attained after 25 min to 30 min. The
The
characteristic
compressive modulus of elasticity Ei is calculated as a
strength of masonry is calculated to the secant modulus from the mean of the
nearest 0.1 N/mm2 using the following strains of all four measuring positions
formula (whichever is the smaller):
occurring at a stress equal to one third of
f k = f / 1.2 or f k = f i ,min N/mm2 . (2) the maximum stress archived.
According to Hendry et al. (2004) E = Fi ,max N/mm2 .(3)
i
3 i Ai
some points have been derived from the
compressive test on masonry such as the The individual and mean values for the
compressive strength of masonry is small modulus of elasticity in N/mm2 are
er than the nominal strength of the unit in calculated to the nearest 100 N/mm2.
a compression test and may greatly exceed
BS 5628 (2000) and Eurocode 6
the crushing strength of mortar. Analysis (1996) use the characteristic strength of
of test results shows that the compressive masonry fk which is dependent on the
strength of masonry varies roughly as the masonry units and mortar strength, as the
square root of the unit strength and as the basis for determining modulus of elasthird or fourth root of the mortar cube ticity of masonry in the absence of relestrength.
vant test data. The respective equations
To determine the modulus of elasti for BS 5628 and Eurocode 6 for Em are:
city, the masonry specimens are fitted E = 900 f
N/mm2 ...(4)
m
k
with measuring devices in order to meaE m = 1000 f k N/mm2 ...(5)
sure the change in height. Two devices are
fitted on each side of the length of the
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METHODOLOGY
Masonry units
Compressive strengths of the class B
engineering clay bricks and the dense
aggregate solid concrete blocks were determined. The clay bricks, three cores with
a nominal size of 215 x 102.5 x 65 mm,
were tested for conformity with BS
3921:1985. Ten bricks randomly selected
from each batch of bricks were tested for
determining compressive strength. The
bricks were immersed in a water tank for
24 hours before testing. Each brick was
placed between two 4 mm thick plywood
sheets in the testing machine and tested
with a loading rate of 35 N/mm2/min until
failure.
Compressive strengths of the dense
aggregate solid concrete blocks with nominal dimension of 440 x 100 x 215 mm
were tested in accordance with BS 60731:1981. The concrete blocks were immersed in a water tank for about 16 hours
before capping with 5 mm mortar consisting of 1:1 ordinary cement: sand mixed
by mass. The concrete blocks were covered with damp cloths for at least 16
hours after their first face were capped.
Three cubes of mortar from the capping
mixes were taken to determine the capping compressive strength. The concrete
blocks were immersed in the water after
capping the second face. Compressive
tests of the concrete block were then
carried out after the mortar cubes reached
the compressive strength greater than 28
N/mm2 usually three days after casting.
The rate of the applied load was 10
N/mm2/min.
Mortar
Mortar used to build the prisms was a
designation (iii) mortar mixed with a ratio
1:1:6 of cement:lime:sand, batched by
volume. Tilcon ready mixed limesand
was used. A sufficient amount of water
was added to produce a workable consistency as a designation (iii) mortar. Three
100 x 100 mm mortar cubes were cast for
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Figure 1. Typical rectangular wallettes of clay brick prisms before and after testing
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Figure 2. Typical square hollow of clay brick prisms before and after testing
Figure 3.Typical rectangular wallettes of concrete block prisms before and after testing
CBR1
CBR2
CBR3
CBR4
CBR5
CBR6
CBR7
CBR8
CBR9
CBR10
1286
1131
1244
1539
1199
1622
1468
1422
1590

58.4
51.3
56.4
69.8
54.4
73.6
66.6
64.5
72.1

63.0
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Table 5. Compressive
concrete block unit
strength
of
Mean
Specimen Failure Compressive
Strength Compressive
Load
N/mm2
Strength
(kN)
N/mm2
CBL1
CBL2
CBL3
CBL4
CBL5
CBL6
CBL7
CBL8
CBL9
CBL10
475
508
637
672
587
423
663
551
553

10.8
11.5
14.5
15.3
13.3
9.6
15.1
12.5
12.6

12.8
Compressive
strength
of
M1
45.0
4.5
M2
42.1
4.2
M3
41.0
4.1
M4
39.5
3.9
M5
40.7
4.0
M6
40.2
4.0
M7
42.0
4.2
M8
42.1
4.3
M9
42.2
4.3
Mean compressive strength of
mortar
4.3
4.0
4.2
4.2
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Clay brick
rectangular
wallettes
Clay brick
square
hollow
prisms
Concrete
block
rectangular
wallettes
Dimensions (mm)
Compressive
strength
(N/mm2)
9.7
14.7
16.0
13.5
19.5
19.9
20.8
20.0
7.0
9.3
9.7
8.7
Characteristic
Compressive
strength (N/mm2)
Modulus of
elasticity, E
(N/mm2)
Mean
Modulus of
elasticity, E
(N/mm2)
11800
12700
15400
11.2
13500
17800
13600
16300
16.7
15900
6900
7500
7500
7.2
7300
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Stress (N/mm2)
8
6
4
3
2
1
2
0
0.000
0.001
0.002
0.003
Strain
Conclusion
From the research conducted, the
following conclusion can be drawn.
The compressive strength of masonry
units was 63.0 N/mm2 for clay brick
and 12.8 N/mm2 for concrete block.
The brick is classified as Engineering
B.
The compressive strength of mortar
was 4.2 N/mm2. The compressive
strength of mortar (iii) determined
experimentally fulfils the requirement
defined.
The compressive strength of clay brick
and concrete rectangular wallettes was
11.2 N/mm2 and 7.2 N/mm2 respectively. By using the same material but
forming different shape of specimen
gave the compressive strength value of
the square hollow clay brick 50 %
bigger than clay brick rectangular
wallettes. The values were in general
smaller than those given in BS 5628
Pt.1 : 1992.
The failure of the masonry tested in
compression was due to development
of tensile cracks parallel to the axis of
the loading
Overall, the modulus of elasticity of
masonry was 1000 fk which is close to
Recommendation
It is recommended that when testing
modulus of elasticity of masonry
strains in transverse direction should
be measured in order to determine the
Poissons Ratio of masonry.
The research conducted was in the UK
and using the British and European
Standards. It is of important to carry
out the experimental in Indonesia as
the development of masonry as structural masonry has not well known.
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ACKNOWLEDGEMENT
The author would like to thank to
everyone who helped the experiment in
the laboratory and also who helped to
make this paper done.
REFERENCES
British Standards Institution. BS EN
10521:1999 Methods of Test for
Masonry  Part 1: Determination of
Compressive Strength.
British Standards Institution. BS 3921:1985 Specification for Clay Bricks.
British Standards Institution. BS 60731:1981 Precast Concrete Masonry
Units  Part 1: Specification for Precast Concrete Masonry Units.
British Standards Institution. BS 4551:Part 1:1998 Methods of Testing Mortars, Screeds and Plasters Part 1: Physical Testing.
British Standards Institution. BS 56281:1992 Code of Practice for Use of
Masonry: Part 1: Structural Use of Unreinforced Masonry.
British Standards Institution. BS 56282:2000 Code of Practice for the Use of
Masonry: Part 2: Structural Use of
Reinforced and Prestressed Masonry.
British Standards Institution. DD ENV
199611:1996 Eurocode 6: Design of
Masonry Structures. Part 11: General
Rules for Buildings Rules for Reinforced and Unreinforced Masonry.
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