.png)
Compression test
It is the main
and important test. This test only decides the strength of the brick. This test
was carried out by a compression testing machine for both fibrous concrete and
padobe bricks. This test was carried out on the 28th days from the date of
casting for fibrous concrete brick. And padobe bricks were tested after taken
from the kiln. Fig.15 shows the compression test was being done. While testing
the fibrous concrete brick great care must be taken, because fibrous concrete
brick never failed catastrophically, it just compressed like squeezing rubber. So
load was applied up to full compression. When fibrous concrete brick failed at
the higher load, the structure was not fully collapsed. Only the outer faces
cracked and peeled out. But padobe bricks behaved like conventional clay brick
and it collapsed. So the fibrous concrete brick are having elastic behavior
and less brittleness. But padobe bricks are having the physical characteristics
like conventional clay brick. It is having brittleness and less elastic
behavior.
The
following steps were followed for compression testing.
o
First the irregularities in the surface were
removed.
o
Then the fog and other voids in the bed faces
were filled with plaster of Paris to give smooth distribution of load.
o
The brick was placed printing upwards, between
two 3mm thick plywood sheets. This arrangement was placed centrally on the
bottom plate of the compression-testing machine.
o
Then the upper plate of the compression-testing
machine was lowered down up to the brick was holded tightly without any
movement.
o
Then the load was applied axially at a uniform
rate
o
This load was applied till the brick break.
o
The load at the brick failed was noted.
o
Three bricks from same proportion were tested in
every time.
o
And the compressive strength was calculated by
this formula,
Compression strength=(load/surface area)
Compressive strength
of fibrous concrete bricks
S.No
|
Mix
|
No
|
Load
(N)
|
Surface
area (mm2)
|
Compressive
strength
(N/mm2)
|
Average
compressive strength (N/mm2)
|
1
|
M1
|
1
|
75,000
|
23,320
|
3.22
|
3.33
|
2
|
80,000
|
22,984
|
3.48
|
|||
3
|
77,500
|
23,520
|
3.30
|
|||
2
|
M2
|
1
|
55,000
|
22,866
|
2.41
|
2.55
|
2
|
60,000
|
22,826
|
2.63
|
|||
3
|
60,000
|
23,088
|
2.60
|
|||
3
|
M3
|
1
|
97,500
|
22,763
|
4.28
|
4.21
|
2
|
95,000
|
22,523
|
4.22
|
|||
3
|
95,000
|
23,072
|
4.12
|
|||
4
|
M4
|
1
|
85,000
|
23,088
|
3.68
|
3.62
|
2
|
85,000
|
23,415
|
3.63
|
|||
3
|
82,500
|
23,310
|
3.54
|
|||
5
|
M5
|
1
|
75,000
|
21,825
|
3.44
|
3.52
|
2
|
80,000
|
22,321
|
3.58
|
|||
3
|
75,000
|
21,185
|
3.54
|
|||
6
|
M6
|
1
|
92,500
|
23,400
|
3.95
|
3.94
|
2
|
95,000
|
24,062
|
3.94
|
|||
3
|
92,500
|
23,400
|
3.93
|
|||
7
|
M7
|
1
|
60,000
|
23,956
|
2.50
|
2.44
|
2
|
55,000
|
23,608
|
2.33
|
|||
3
|
55,000
|
23,072
|
2.38
|
|||
8
|
M8
|
1
|
85,000
|
23,625
|
3.60
|
3.65
|
2
|
87,500
|
23,744
|
3.69
|
|||
3
|
87,500
|
23,850
|
3.67
|
|||
9
|
M9
|
1
|
40,000
|
21,500
|
1.86
|
2.00
|
2
|
45,000
|
21,917
|
2.05
|
|||
3
|
45,000
|
21,681
|
2.08
|
|||
10
|
M10
|
1
|
65,000
|
24,150
|
2.69
|
2.84
|
2
|
70,000
|
23,850
|
2.94
|
|||
3
|
70,000
|
24,182
|
2.90
|
.png)
Compressive strength chart
A brick that is
used for construction should have compressive strength more than 3.5 N/mm2.
In this above 11 bricks, only 6 type of bricks got compressive strength
more than 3.5 N/mm2. And remaining 5
bricks got compressive strength less than 3.5 N/mm2.
The following types of bricks got
compressive strength more than 3.5 N/mm2 and these bricks are
suitable for building construction.
o
M3
o
M4
o
M5
o
M6
o
M8 and
o
M11
Among these 6 bricks padobe brick
i.e., M11 gave more compressive strength as 6.47 N/mm2. While
considering only the fibrous concrete bricks M3 gave more strength.
The following 5 fibrous concrete
bricks got compressive strength less than 3.5 N/mm2.
o
M1
o
M2
o
M7
o
M9
o
M10
So these bricks are not suitable for
construction, these 5 types of bricks were rejected.
Even
though the 5 types of fibrous concrete bricks got compressive strength more
than 3.5 N/mm2, they are not suitable for load bearing walls.
Because, fibrous concrete bricks are having more elastic behaviour at failure.
It compresses like rubber. So at heavy load, the bricks may compress. Due to
this compression the roof may be collapsed. So these fibrous concrete bricks
are suitable only for non-load bearing partition walls. But the padobe bricks are
not having such type of elastic behavior. So these bricks can be used for load
bearing walls also.
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