Some Mechanical Properties of Ferro-Cement Mortar Modified by Polymer

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Some Mechanical Properties of Ferro
-
Cement Mortar Modified by Polymer


Abdulkader Ismail A. Al
-
Hadithi, Khalil I. Aziz and Mohammed Tarrad N. Al
-
Dulaim


College of Engineering, University of Anbar, Ramadi, Al
-
Anbar, Iraq.



A
A
b
b
s
s
t
t
r
r
a
a
c
c
t
t





The main aim of

this work is to study the effect of adding Styrene Butadine Rubber (SBR) polymer on the
mechanical properties of ferro
-
cement mortar. This kind of polymer was added with different weight ratios of
polymer to cement (P/C), and these percentages were (3%, 7
%, 10%). Reference mix was made for comparative
reason. The following tests were made to investigate ferro
-
cement's mortars mechanical properties as followed:
compressive strength, splitting tensile strength and flexural strength.

Results demonstrated that

in general, there is an improvement in mechanical properties due to adding SBR polymer
and , all cement mortar specimens exhibited continuous increase in these properties with an increase of age
.

In
compressive strength, the increases due to modifying by

polymer in 56 day age were (19.5% to 44.3%). In splitting
tensile strength for the same age , the increases were (19.2% to 42.7%), whereas for flexural strength the increases
were ( 5.9% to 19%).


Keywords
:
mechanical
properties ,cement mortar, SBR polyme
r ,flexural strength



1
-
Introduction

1
-
1
-
Ferro
-
Cement:



Ferro
-
cement has emerged as a viable
structural material for the use in such instance.
Ferro
-
cement is a type of composite construction
material in which a brittle cement
-
sand mortar
matrix is

reinforced with thin wire mesh,
uniformly dispersed throughout the matrix of the
composite.


Ferro
-
cement composite has been widely and
successfully used for the construction of
different structures which include silos, tanks,
folded roofing, shells a
nd bearing walls.

(
Narayanaswamy

et al
, 1981 ; Al
-
Rifaie
et al
,
1994 ;

Al
-
Rifaie
et al

, 2001).
Ferro
-
cement is a
composite material used in building with cement,
sand, water and wire mesh material. It is
fireproof, earthquake safe and does not rust, rot

or blow down in storms. It has a broad range of
applications which include components in a
buildin
g, repair of existing building.



1
-
2
-
Classification
of

Concrete

Polymer
Co
mposites:



Concrete

p
olymer
c
o
mposites are generally
classified into the followin
g types in terms of
process technology.
(Ohama
,1997
)


(a) Polymer Impregnated Concrete

(PIC).

(b) Polymer Mortar and Concrete (PM and PC)

(c) Latex Modified Concrete (LMC).


1
-
2
-
1
-

Polymer Modified Concrete (PMC)



It is produced by incorporating a
monomer,
polymer monomer mixture, or a dispersed
polymer (Latex) into a cement concrete mix. To
affect the polymerization of the monomer or
prepolymer monomer, a catalyst is added to the
mixture. (
Ohama,1996
)


In all cases, the mixing and handling
of
PMC is similar to conventional Portland cement
concrete and mortar materials.


It exhibits excellent bonding to steel
reinforcement and old concrete, good ductility,
resistance to penetration of water and aqueous
salt solutions and resistance t
o freeze
-
thaw
damage. Its flexural strength toughness and
creep are higher than that of plain concrete. The
drying shrinkage is generally lower than that of
conventional concrete. (
Al
-
Qadi et al,1993
)


2
-
Materials and Methods



The experimental program was

planned to
investigate the effect of using polymer on the
mechanical properties of Ferro
-
cement mortar.


2
-
1
-

Materials
:


2
-
1
-
1
-

Cement:


The cement used through this work was
Ordinary Portland Cement
type I
and it

is
conform to the Iraqi specificat
ion No.
5/1999
.
(
Iraqi specifications

-

No(5)
,

1999
)




2
-
1
-
2
-

Fine Aggregate:



Natural yellow
sand
conforming to the Iraqi
Standard N0.45(
Iraqi specifications

-

No(
4
5)
,
1999
) grading requirements (zone
-
2) was used in
production of concrete specimen
s used in this
study.


2
-
1
-
3
-

Mixing Water:



Ordinary drinking water was used for
mixing and curing for all specimens.



2
-
1
-
4
-

Polymer:



Styrene Butadiene Rubber (SBR) is used as
polymer modifier in this study. Styrene
Butadiene
, an elastomeric polymer, is the
copolymerized product of two monomers,
Styrene and Butadiene. Latex is typically
included in concrete in the form of a colloidal
suspension polymer in water.

The polymer (SBR) was used as a ratio by
weight of cement of 3%,
5% and 10%.


2
-
3
-

Preparation of Mortar Specimens:



Four groups of mixes were used in this
research. All proportions were (1:2) cement:
sand.



2
-
4
-
Mix Preparation:




A mechanical mixer

of the capacity (0.1) m3
operated by electrical power was used, the fine
aggregate and cement were added before adding
polymer and dry mixing were continued until the
dry mix became homogenous, then the polymer
was added until all particles are fully co
ated with
polymer and finally water were added and
mixing continues until uniform mix is obtained,
this procedure is similar to the method used by
Ohama
.
(Ohama
,1997
)


2
-
5
-

Determination of the Workability:



Workability of all types of Mor
tar was
measured by slump test according to the
procedure described in ASTM C143
-
8
9
.

.
(
Annual Book of American Society for Testing
and Materials, 1989
)

The Water/Cementations
materials ratios were adjusted to maintain on
workability.




2
-
6
-
Casting, Compaction and Curing:



The molds were lightly coated with mineral
oil before use according to ASTM C192
-
88 . For
cube
s, cylinders and prisms casting was carried
out in different layers each layer is of 50mm.
Each layer was compacted by using a vibrating
table for (15
-
30) second until no air bubbles
emerged from the surface of the mortar, and the
mortar is leveled off smo
oth to the top of the
molds.


2
-
7
-

Compressive Strength
:




Compressive strength was determined using
of (100
×
100
×
100)mm cubes according to B.S.
1881 ,

Part 116
.

(
British Structural Institute
BSI
,
1983
)


2
-
8
-
Splitting Tensile Strength
:




T
he splitting tensile strength test was
carried out in accordance with ASTM C496
-
86
.
(
Annual Book of American Society for
Testing and Materials, 1986
) Cylinder specimens
of (150*300) mm were subjected to compression
loads along two axial lines which were
dia
metrically opposite. The load is applied
continuously until the specimen failed. The
compressive loading produces a transverse
tensile stress which is uniform along the vertical
diameter
.


2
-
9
-

Flexural Strength
:



According to ASTM (192
-
88)
.
(
Annua
l
Book of American Society for Testing and
Materials,1988
)

concrete prisms of
(100
×
100
×
500) mm were prepared and two
point load test was carried out according to
ASTM (C
-
78
-
84)
.

.
(
Annual Book of American
Society for Testing and Materials, 1984)


3
-
Results
and Discussion


3
.
1
-

Compressive strength
:


The relationship between compressive strength
at different ages and (P/C) ratio is shown in
Figure (1). Results demonstrated that in general
all cement mortar specimens exhibited
continuous increase in compress
ion strength with
increase of curing age and we can notice that


the
compressive strength increases with increase of
(P/C) ratio.


That increase in compressive strength might
be due to three facts; the first is that polymer
-
modified cement mortar has

less W/C ratio,
which gives higher strength. The second is that,
the use of SBR polymer leads to form a
continuous three
-
dimensional network of
polymer molecules throughout cement mortar
which increases the binder system due to good
bond characteristics o
f SBR polymer. The last


is
partial filling of pores with polymer which
reduces the porosity, and hence increases the
strength. (
Ohama,1998
)


The increase at compressive strength with
increase of curing ages can be explained by
completion of polymeriz
ing reaction of SBR
polymer within these ages, in addition to
continued reaction of the hydration process.


The hydration of cement is responsible of
strength at early and latest age in reference
mixes. The hydration operation is responsible for
this

strength; therefore, the difference between
compressive strength of reference mixes and
other mixes is smaller at early ages and becomes
larger at latest ages. Whereas, for cement mortar
mixes containing polymer both the cement
hydration and production of

polymer film by
polymerization are responsible for strength
gain.(

Al
-
Hadithi,2005
)


So at early ages for (PMM), the
polymerization operation is at the beginning with
low hydration development, after that both
hydration and polymer film production
will
develop causing increasing compressive strength
and then increasing the difference between
polymer modified mortar and reference mixes.
The polymer film will behave as a container of
water needed for reaching cement hydration at
advanced steps.(
Al
-
Had
ithi,2001
)


The specimens made from mixes containing
polymer with different percentage seem to be
less damaged at failure when compared with
these made from reference mixes. This might be
due to the effect of increasing the bond among
particles by pol
ymer film.


The highest magnitude of compressive
strength at (7) days
age

is (43.5 MPa) for
concrete specimens and the highest magnitude of
compressive strength at (28) days
age

is (50.2
MPa), while at (56) days
age
, the respective
highest magnitude is (53
.4 MPa) , all these
magnitudes occurred with P/C ratio of (10%).


The histogram of the development of
compressive strength with age for various P/C
ratio is shown in fi
gure (2).



Fig
ure
1
.
Relationship between Compressive
Strength and Age for Various

P/C
Ratios

Fig
ure
2
.

Development of Compressive Strength
with Age for Various P/C Ratios.


3
-
2
-
Splitting Tensile strength:



The value of splitting tensile strength
obtained from tests on (100×200) mm cylindrical
cement mortar specimens after curing

age of
7,28
,56 days
.
Figure (3)

shows

the development
in splitting tensile strength of cement mortar
specimens with and without polymer. The results
indicated that all types of cement mortar
specimens exhibited continued increase in
splitting tensile stre
ngth with development of
curing ages.


From Figure (3), it can be seen that the
splitting tensile strength increases with

an
increase

in (P/C) ratio for all specimens at
different ages. This increase may be due to the
reduction in W/C ratio, contrib
ution of high
tensile strength by the polymer itself and the
increase may be ascribed to the reduction in
capillary porosity of the cement matrix because
of using the SBR polymer which fills the voids
in concrete. (
Letif
,
1998 ; Folic,1998
)

At (7) days
age

the highest magnitude of splitting tensile
strength is (5.64 MPa) for

cement mortar
specimens with (10%) P/C ratio, and at (28)
days
age

the highest magnitude of splitting
tensile strength is (6.85 MPa) for cement mortar
specimens with (10%) P/C ratio whi
le at (56)
days
age
the highest respective magnitude is
(6.88 MPa) for cement mortar.


The histogram of the development of
splitting tensile strength with age for various P/C
ratios is shown in Figure (4).




Fig
ure
3
.
Relationship between Splittin
g Tensile
Strength and Age for Various P/C
.


Fig
ure

4.

The Development of Splitting Tensile
Strength
with Age for Various P/C
Ratios


3
-
3
-

Flexural strength



Th
e

flexural
strength was determined at ages
of (7), (28) and (56) days for moist cured ceme
nt
mortar prisms of (100×100×500) mm
dimensions. The results indicated that flexural
strength increased with development of curing
ages, also the flexural strength increased with the
increase in P/C ratio at all ages for different
types of mortar mixes. Fr
om Figure (5), it can be
seen that, this increase in flexural strength is
attributed to the reduced capillary porosity
caused by the reduction of water content of the
mix because of adding the polymer to that mix in
addition to dispersion of the cement
agg
lomerates

into primary particles. Further, the
dispersion system will include particles spaced at
more uniform distance from one another.
Thereby on continuing hydration there is a
greater statistical chance of intermeshing of
hydration product with fine a
ggregates surface to
produce a system of higher internal
.













Fig
ure
5
.

Relationship between Flexural Strength
and Age for Various P/C Ratios.



At (7) days
age

the highest magnitude of
flexural strength is (5.63MPa) for specimens
with (10%) P/C r
atio, at (28) days
age

the
highest magnitude of
flexural

strength is
(5.77MPa) for specimens with (10%) P/C ratio
while at (56) days
age
, the highest respective
magnitude is (5.81MPa) for specimens with
(10%) P/C ratio. The histogram of the
development of
flexural strength with age for
various P/C ratios is shown in figure (6).


Fig
ure

6.

The Development of
Flexural Strength
with Age for Various P/C Ratios



4
-
Conclusions
:



Based on the extensive research works the
following conclusions can be drawn
:

1
-

The mechanical properties of polymer
modified cement mortar had shown a
clear increase in general due to the
inclusion of SBR latex for specimens.
The increase of P/C ratio from 3% to
10% had resulted in:
-


A
-

For Compressive, Splitting Tensile and
Flexu
ral Tests:

(a) An increase in the 7 day compressive
strength from 31.6 N/mm
2

for reference mix to
37.8 N/mm
2

(P/C = 3%), to 40.2 N/mm
2

(P/C =
5%) and to 43.5 N/mm
2

(P/C = 10%).

(b) An increase in the 28 day compressive
strength from 35.2 N/mm
2
for referen
ce mix to
42.5 N/mm
2

(P/C = 3%), to 49.8 N/mm
2

(P/C =
5%) and to 50.2 N/mm
2

(P/C = 10%).

(c) An increase in the 56 day compressive
strength from 37 N/mm
2

for reference mix to
44.2 N/mm
2

(P/C = 3%), to 51.7 N/mm
2

(P/C =
5%) and to 53.4 N/mm
2

(P/C = 10%).

(e
) An increase in the 7 day splitting tensile
strength from 4.61 N/mm
2

for reference mix to
5.36 N/mm
2

(P/C = 3%), to 5.4 N/mm
2

(P/C =
5%) and to 5.64 N/mm
2

(P/C = 10%).

(f) An increase in the 28 day splitting tensile
strength from 4.74 N/mm
2

for reference
mix to
5.55 N/mm
2

(P/C = 3%), to 6.32 N/mm
2

(P/C =
5%) and to 6.85 N/mm
2

(P/C = 10%).

(g) An increase in the 56 day splitting tensile
strength from 4.82 N/mm
2

for reference mix to
5.78 N/mm
2

(P/C = 3%), to 6.56 N/mm
2

(P/C =
5%) and to 6.88 N/mm
2

(P/C = 10%
)..

(h) An increase in the 7 day flexural strength
from 4.56 N/mm
2

for reference mix to 5.03
N/mm
2

(P/C = 3%), to 5.12 N/mm
2

(P/C = 5%)
and to 5.63 N/mm
2

(P/C = 10%).

(i) An increase in the 28 day flexural strength
from 4.6 N/mm
2

for reference mix to 5.1
1
N/mm
2

(P/C = 3%), to 5.14 N/mm
2

(P/C = 5%)
and to 5.77 N/mm
2

(P/C = 10%).

(j) An increase in the 56 day flexural strength
from 4.88 N/mm
2

for reference mix to 5.17
N/mm
2

(P/C = 3%), to 5.24 N/mm
2

(P/C = 5%)
and to 5.81 N/mm
2

(P/C = 10%).


2
-

This increase i
n mechanical properties
may be attributed to continuous polymer
network formed within the mortar body,
the improved bond between hydration
products and polymer


5
-
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:


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-
Hadithi
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-
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-
Hadithi
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-
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,

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