Long term strength and durability evaluation of sisal fibre composites

International Journal of Civil JOURNAL OF CIVIL ENGINEERING (Print),
INTERNATIONAL Engineering and Technology (IJCIET), ISSN 0976 – 6308 AND
ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME
TECHNOLOGY (IJCIET)
ISSN 0976 – 6308 (Print)
ISSN 0976 – 6316(Online)
Volume 4, Issue 1, January- February (2013), pp. 71-86
IJCIET
© IAEME: www.iaeme.com/ijciet.asp
Journal Impact Factor (2012): 3.1861 (Calculated by GISI)
www.jifactor.com
© IAEME

LONG-TERM STRENGTH AND DURABILITY EVALUATION OF
SISAL FIBRE COMPOSITES
Part-I: CEMENT MORTAR COMPOSITES

G.Ramakrishna*, T.Sundararajan
Department of Civil Engineering
Pondicherry Engineering College
Pondicherry – 605 014
INDIA
*Corresponding author; E-mail: ramakrishna_grk@rediffmail.com

ABSTRACT

In the first part of a two –part paper, the long-term strength and durability evaluation
of sisal fibre cement mortar composites have been investigated. Strength characteristics of
cement mortar composite (compressive, flexural, split-tensile strength) and that of composite
slabs (flexural and impact strength) were determined at various ages (28-120 days) for 1:3
mix, at a constant flow value (110%) for various fibre contents (0.25%-2.0%, by wt. of
cement). The durability of the composites was evaluated by two methods. It is found that the
strength behaviour of the composites (i.e. compressive, flexural and split- tensile) are similar
over the range of parameters and ages and that there is considerable improvement in the long-
term strength. The two methods of evaluation of durability of the composites can be used to
understand the interaction of the matrix and an alkaline medium considered. The above
results are to serve as a reference to understand the role of a pozzolana used in cementitious
mortar composites, being reported in a companion paper.

Key words: Cement mortar Composite Strength, Durability, Impact Strength, Long-term
studies, Sisal Fibres,

I. INTRODUCTION

Studies on natural fibre reinforced cement/cementitious composites and development
of products for various applications in Civil Engineering, have the twin advantages of
ensuring sustainable development and making available materials/ products at affordable

71

International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),

cost. If the above advantages have to be actually realized, then, two inherent drawbacks
(‘balling effect’ and ‘embrittlement’ of fibres) have to be addressed scientifically and
comprehensively. Gram [1] was the first to recognize the ‘embrittlement of fibres’ in an
alkaline medium and to identify the mechanisms and investigate various measures to improve
the durability of cement composites with sisal and coir fibres. Subsequently several
approaches have been suggested and investigated [2-16]. From a comprehensive review of
literature on the strength characteristics of natural fibre cement composites it is found that
long-term studies on the strength behaviour of the above composites are rare [17]. Further,
studies on the use of flyash in natural fibre composites and its influence on various
characteristics of composites is also rather rare [17]
Hence, a, comprehensive and exhaustive investigations on the long-term strength,
evaluation of durability and durability of sisal fibre cement/ cementitious composites were
undertaken. The first part of the investigation covering the long-term strength characteristics
and evaluation of durability of cement mortar composites is covered in this paper. The results
from the first part of the investigations is expected to serve as a reference to understand the
role of fly ash in influencing the various characteristics of sisal fibre cementitious mortar
composites, which are reported in a companion paper (i.e. part-II of the paper)

II. EXPERIMENTAL INVESTIGATION
2.1 MATERIALS USED
Ordinary Portland cement (OPC – 53 grade) conforming to IS: 12269 - 1987 [25];
good quality river sand, whose gradation corresponds to Zone – II, as stipulated in IS: 383 –
1997 [26], were used. Good quality potable water available in the campus was used both for
mixing and curing the mortar specimens. Sisal fibres are available abundantly in ‘fully
processed form’ in this part of the region. The salient properties of above materials are given
in Tables 1 to 3.
Table 1: Physical Properties of Cement (OPC-53 grade)

Sl. No. Property Value

1 Standard consistency (%) 29%
2 Initial setting time (min.) 55 min
3 Final setting time (min.) 175 min
4 Soundness 1mm
5 Specific gravity 3.14
6 Compressive strength @
i) 3 days 28 MPa
ii) 7 days 38 MPa
iii) 28 days 56.7 MPa
Note: (i)Sand conforming to the gradation stipulated in I.S. specification for ‘standard sand’ was prepared in
the laboratory and used for determining the compressive strength of cement.
(ii)The sample conforms to the requirements of 53 grade as stipulated in IS: 12269-1987

72


Table 2: Physical Properties of Fine Aggregate
Sl. Property Value/
No. description

1 Specific gravity 2.48
2 Water absorption 1.4%
3 Rodded bulk density 1.737 gm/cc
4 Fineness modulus 2.5
Note: Procedure is based on IS: 383 – 1997 [26]

Table 3: Physical Properties of Sisal Fibres
Sl. Fibre- Fibre Fibre Tensile Elongation Specific Elastic -
No. type length diameter strength (%) gravity modulus
(mm) (mm) (N/mm2) GPa

1. Sisal 180 -600 0.10– 0.50 31 – 221 14.8 1.4 7.83

2.2 PREPARATION AND TESTING OF MORTAR COMPOSITE
Compressive strength, flexural strength and split-tensile strength of cement mortar
specimens and impact and flexural strength of cement mortar composite slabs of 1:3 mix
were determined at four ages (i.e.28, 56, 90 and 120 days of normal curing) and at six fibre
contents (i.e. ranging from 0% to 2.0%) and at a constant flow value (i.e.112.5%). Details of
the workability studies on the various composites are reported elsewhere [18-20]. From the
‘flow curves’ developed by the workability studies, the required water-binder (W/B) ratio
was selected for preparing the mortar, based on the constant flow value (i.e.112.5). No
adjustment was made for the water absorption-capacity of sisal fibres, as the fibres were pre-
soaked (at least for 5 minutes) in fresh water and then used in the mortar for casting various
test specimens. W/B ratio for each combination of mix for a constant flow value of 112.5% is
summarized in Table 4. Altogether there were 7 combinations (1 combination with OPC; 6
combinations with OPC + sisal fibre). Details of elements cast like size of specimen, number
of specimens, total number of specimens cast for each combination of mix etc. is given in
Table 5, for evaluating the flexural strength of beam specimens of the mortar composites.
After casting the mortar beam specimens, they were cured in water for the specified ages and
at the end of the respective curing period, the specimens were first tested for their flexural
strength as per IS 4031 (Part-8) [21]. Compressive strength of the specimens were determined
by using one of the fractured (broken) pieces of the beam specimens (after determining their
flexural strength) and testing them as per IS 4031-Part-8 [21]. Split- tensile strength of
specimens were determined by using another fractured (broken) piece of the beam specimen
and tested by a ‘novel method’ suggested by Hannant [22]. The slab specimens were tested
by the projectile impact test for evaluating the impact strength characteristics [23]. The
usefulness of the above method has been established based on earlier investigations carried
out on a few natural fibre reinforced cement mortar composites and reported elsewhere [23].
To evaluate quantitatively the improvement in the impact resistance characteristics of
composites, a simple parameter called, ‘residual impact strength (Irs )’ has been defined as

73


given in eqn.(1), which can also be taken as a ‘measure of ductility’ of the composite
imparted by the fibres incorporated in to the matrix. Using the approach the performance of a
few natural fibre composites has been evaluated and reported elsewhere [23].
Energy absorbed upto ultimate failure
Residual impact strength ratio (Irs) = …(1)
Energy absorbed at initiation of first crack

Table 4: W/B Ratio of Mixes Considered for Strength Studies of Sisal Fibre
Reinforced Mortar (1:3; flow value= 112.5%)
Fibre Content 0 0.25% 0.5% 0.75% 1.0% 1.5% 2.0%
Water/Cement 0.64 0.64 0.65 0.68 0.70 0.74 0.76
ratio

Table 5: Details of Elements Cast for Strength and Durability Studies
(1:3; @ 28, 56, 90, and 120 days)
Sl. Type of No. of specimens for No. of Total no. Total no. of
No. element strength studies specimens of specimens
for the specimens cast
durability for the for the
study durability total
A B C D
study no. of
Mixes
(ie.-7)
1. Flexural Beam
(40x40x160mm) 3 3 3 3 - 12 84

2. Slab 2 2 2 2 2 10 70
(300x300x18mm)

Note: (i) ‘A, B, C, D and E’ indicated in the column below ‘strength’ and ‘durability’
studies indicate the curing ages i.e. 28, 56 , 90 and 120 days, respectively .

(ii) The slab specimens of durability studies were immersed in NaOH solution
(0.1N; pH: 12.5) for 28 days, after 120 days of normal curing in water.

Flexural strength of mortar slab specimens were determined by a four-point loading
system and using the 5kN capacity universal tensile testing machine available in the Dept. of
Civil Engineering. The usefulness of the above method has been established and reported
elsewhere [17, 24]. A computerized data-logging system was interfaced to the above test set-
up for acquiring data and processing them, through a software exclusively developed for the
above purpose. For the above test, slab specimens of size 120x90x20 mm were cut and
removed from the fractured slab specimens obtained from the impact test of slab specimens
of size 300x300x18 mm. The load versus deflection values were obtained through LVDT and
logged on to a computer and a plot of load vs. deflection obtained using the specially
developed software, wherein, the load was measured at the loading position of the specimen

74


used in the test. Along with the above plot, the maximum load and deflection at failure as
displayed in the system were logged on to the computer. From the load –deflection curve,
‘flexural toughness’ (FT) of the specimens were evaluated. The various strength tests
conducted on the various specimens are shown in Fig.1 and 2.

(a) A View of Flexural Testing Machine for Prism Specimens

(b) Test Set –Up for Compressive (c) Test Set –Up for Split- Tensile
Strength of Mortar Strength of Mortar

Fig. 1 : Prism Specimens for Determining the Various Strength Characteristics

75


Shown in (b)

(a) Data Acquisition System

(b)Experimental Set-Up

Fig. 2: A View of Experimental Set-up for Flexure Test of Mortar Slab (broken)
2.3 DURABILITY STUDIES ON SISAL FIBRE CEMENT COMPOSITES
(with Data Acquisition system)

Slab specimens of size 300 x 300 x 18 mm (1:3) were cast under identical conditions
as that of specimens for strength studies. After the specified period of normal curing, the slab
specimens were kept immersed in NaOH solution (prepared at 0.1N) for (another) 28 days.
During the period of exposure in the above alkaline medium, pH of the medium was
maintained constant at (about) 12.0. After 28 days of immersion in the above alkaline
medium, the slab specimens were tested for their impact and flexural strength. To evaluate
the durability of composites identical procedure and experimental set-up used for the case of
normal-cured specimens were used.
‘Irs’ and ‘IT’ of composites before and after exposure in NaOH along with deviation in
the above values computed and expressed as a percentage of relative change in values with
respect to values obtained before exposure, were used to evaluate the durability of the
composites.

76


III. RESULTS AND DISCUSSION

3.1 COMPRESSIVE STRENGTH

Compressive strength of cement mortar composites (1:3; Vf = 0.25% - 2.0%; @ 28,
56, 90 and 120 days of normal curing) are given in Table 6. Based on the above results,
following inferences are drawn:

(i) Compressive strength of cement mortar composites increases, with increase in
fibre content upto 0.5%, beyond which the strength decreases. The above
phenomenon is found to be independent of age of the composite (i.e. from 28 to
120 days).
(ii) Maximum strength is attained when the fibre content in the composite is 0.5%, for
all the ages considered and that the above strength is 25 – 61% higher than the
plain cement mortar strength (at the corresponding ages).
(iii) Moreover, the maximum strength attained increases with increase in age and that
there is about 44%, 104% and 112% increase in the maximum strength, at the ages
of 56 days, 90 days and 120 days, respectively, over the 28 days strength of the
cement mortar composite at 0.5% ( i.e.26 MPa).
(iv) The maximum long – term strength - gain ratio of the composite is about 2.1
i.e. ratio of the compressive strength @ 120 days (i.e. long-term) to that @ 28
days (i.e. at ‘normal age’).

Table 6: Compressive Strength of Sisal Fibre Cement Mortar Composites
(1:3; constant flow value=112%; @ 28, 56, 90 & 120 days)

Sl. Compressive Compressive strength (N/mm2) at fibre contents of
No. Strength at the Age
of 0% 0.25% 0.5% 0.75% 1.00% 1.5% 2.00%
1 28 days 19.5 23.0 26.0 22.5 20.0 12.0 9.0
2 56 days 30.0 32.5 37.5 33.0 28.0 22.5 19.0
3 90 days 33.0 49.0 53.0 44.5 36.0 30.5 25.0
4 120 days 44.0 52.0 55.0 50.0 41.0 35.0 31.0

3.2 FLEXURAL STRENGTH

Flexural strength of cement mortar composites (1:3; Vf = 0.25% - 2.0%; at various
ages 28 -120 days), are presented in Tables 7. Based on the analysis of the above results
and comparing the compressive and flexural strength behaviour of the composites, following
inferences are drawn:

(i) Flexural strength behaviour of cement mortar composites is similar to that of the
compressive strength, within the range of fibre contents and ages considered.
(ii) Flexural strength of cement mortar composites is also maximum when the fibre
content is 0.5%, for all the ages considered and that the maximum strength is
about 34-53% higher than the corresponding plain mortar strength, over the range
of ages considered.

77


(iii) The maximum flexural strength attained (i.e. @ Vf =0.5%) increases with
increase in age and that there is about 16%, 91% and 120% increase in the
strength, at the ages of 56 days, 90 days and 120 days, respectively, over the
maximum strength of the composite (i.e. 4.5 MPa) at 28 days.
(iv) The maximum long-term flexural strength ratio of the cement mortar composite is
2.2, which is nearly the same as that of the compressive strength - ratio of cement
mortar composites under identical conditions.

Table 7: Flexural Tensile Strength of Sisal Fibre Cement Mortar Composites

Sl. Flexural Tensile Flexural Tensile strength (N/mm2) at fibre contents of
No. Strength at the Age
of 0% 0.25% 0.5% 0.75% 1.00% 1.5% 2.00%

1 28 days 3.0 3.5 4.5 3.8 3.0 2.7 2.4
2 56 days 3.4 4.4 5.2 4.6 4.1 3.8 3.3
3 90 days 6.1 7.5 8.6 7.1 6.1 5.6 5.3
4 120 days 7.4 8.8 9.9 9.5 8.6 7.6 6.4

3.3 SPLIT –TENSILE STRENGTH

Split - tensile strength of sisal fibre cement mortar composites (1:3; 28-120 days) are
presented in Tables 8. From the analysis of the above results and on comparing the above
strength behaviour with that of compressive and flexural strengths, following salient
inferences are drawn:

(i) Split - tensile strength behaviour of cement mortar composites is similar to that of
the compressive and flexural strengths, within the range of fibre contents and ages
considered.
(ii) Split-tensile strength of cement mortar composites is also maximum when the
fibre content is 0.5%, for all the ages considered and that the maximum strength is
generally about 20 - 30% higher than the corresponding plain mortar strength,
over the range of ages considered.
(iii) The maximum split – tensile strength increases, with age and that the increase is
about 28%,40% and 54%, over the maximum strength of the composite (i.e.5.0
MPa), at 28 days.
(iv) The maximum long – term split – tensile strength - ratio of cement mortar
composite is 1.6, which is slightly less than that of cement mortar composites in
compression and flexure, under identical conditions.
(v) Ratio of the maximum split-tensile strength to the maximum compressive strength
of the composite under identical conditions, and for various ages, is in the range of
13 to 19%, with an average value of 15.8%. The above (average) ratio indicates
good performance of the composite, under direct tension.

78


Table 8: Split –Tensile Strength of Sisal Fibre Cement Mortar Composites
Sl. Split- Tensile Strength Split - Tensile strength (N/mm2) at fibre contents of
No. at the Age of
0% 0.25% 0.5% 0.75% 1.00% 1.5% 2.00%
1 28 days 3.8 4.8 5.0 4.1 3.5 3.0 2.5
2 56 days 5.7 6.1 6.4 5.5 4.8 4.0 3.9
3 90 days 5.7 6.6 7.0 6.5 5.9 4.9 3.8
4 120 days 6.3 7.2 7.7 7.4 6.6 5.7 4.9

3.4 IMPACT STRENGTH OF CEMENT MORTAR COMPOSITE SLABS
3.4.1 NORMAL –AGE BEHAVIOUR (@28 DAYS)

Impact strength characteristics of cement mortar slabs and cement-mortar composite
slabs (@ 28 days) are presented in Table 9. It can be seen from the above results, that the
energy absorbed after initiation of first crack and upto failure is only nominal (i.e. from 9.25
to 10.0 Joules only). Hence, the inherent ductility of the cement mortar slab, which is
reflected in ‘Irs’ value is very less and is equal to 1.08. The ‘above value is taken as the
reference’, to obtain the relative performance of various mortar slabs / composite slabs.
As the fibre content in the cement mortar slab increases, energy required to cause
‘initiation of crack’ and ‘final failure’ goes on gently increasing and that energy absorbed is
maximum @ 2% fibre content, i.e.18.9 and 35.5 Joules, respectively. This shows the ductility
imposed by the fibres on the composite. In terms of energy absorbed there is an improvement
of 2.04 and 3.56 times than the corresponding energy required for the ‘reference mortar slab’.
Residual impact strength ratio (Irs) which is a measure of ductility inherent in the
material, increases gently with increase in fibre content for the cement mortar composites and
is in the range of 1.27 to 1.88 for the above composite, within the range of fibre contents
considered. However, Irs of cement mortar composites, relative to that of the cement mortar
slab (i.e. reference, with Vf = 0%), denoted by ‘Irs’ , ranges from 1.18 to 1.74. This gives the
range of ductility improvement that could be achieved due to incorporation of sisal fibres
(i.e.0.25% to 2.0% in this study), in cement mortar slabs.
3.4.2 LATER - AGE BEHAVIOUR (i.e.. 56 - 120 DAYS)
Impact strength characteristics of cement-mortar slabs at later-ages (i.e. 56-120 days)
are given in Table 9. Based on critical analysis of the above results and on comparing them
with the early-age behaviour, following inferences are presented:
(i) Later-age behaviour of cement mortar slabs are similar to that of early-age
behaviour, with respect to the energy absorbed. However, increase in energy
absorbed is substantial upto 90 days and that the maximum value is reached @
120 days, within the range of ages considered.

79


(ii) Maximum energy absorbed for initiation of crack and at failure @ 120 days
are,13.8 and 18.0 Joules respectively, @ 120 days, which is about 1.5 and 1.8
times over the corresponding values of the reference mortar slab.
(iii) In terms of Irs, there is only a gentle variation over the various ages considered and
lies with in a narrow range of 1.20 to 1.30. However, ‘Irs’ of the composites is in
the range of 1.11 to 1.20, (i.e.about 20%) indicating only a marginal improvement
in the ductility of the composite slabs, over the early-age behavoiur, within the
range of later-ages considered.

Table 9: Impact Strength of Sisal Fibre Cement Mortar Composites

Sl. Fibre Impact Strength/ Residual Impact strength Ratio at
No. content
(%)
@28 days 56 days 90 days @120 days

A B C A B C A B C A B C

1 0 9.25 10 1.08 12.5 15 1.20 13.49 17.0 1.26 13.84 18.0 1.22

2 0.25 11.02 14 1.27 15.4 18.8 1.22 16.01 20.5 1.28 16.91 22.5 1.70

3 0.50 13.43 18 1.34 16.01 24.5 1.53 17.18 27.5 1.60 17.35 29.5 2.0

4 0.75 16.19 23 1.42 16.38 29.0 1.77 17.37 32.5 1.87 17.76 35 2.25

5 1.00 17.41 27 1.55 16.66 33.50 2.01 17.61 37 2.10 18.18 40.0 2.53

6 1.50 18.00 31.5 1.75 17.51 38.0 2.17 18.69 41.5 2.22 19.39 45.0 2.68

7 2.00 18.88 35.5 1.88 18.55 42.5 2.29 19.23 45.2 2.35 21.34 54.0 2.88

3.5 FLEXURAL STRENGTH OF CEMENT MORTAR COMPOSITES SLABS

Results of flexural strength evaluated by the four - point loading method using the
broken pieces after conducting the impact test , are given in Table 10, for various ages and
other parameters considered. Based on the above and also comparing the flexural strength of
the composites (i.e. standard specimens), following inferences are drawn:

(i) Behaviour of composite mortar slabs are generally similar to that of flexural
strength of standard specimens of mortar and composites, within the range of
parameters and ages considered.
(ii) Flexural strength of reference mortar slabs (CM 1:3, fibre content = fly ash,
content= 0%) is found to be 3.93 MPa, (at 28 days), which is comparable to the
strength of reference mortar specimens under flexure. However, the strengths are
always lower, at all later-ages. Moreover, the later-age strength of slabs (@120
days) are about 30% lower than the strength of flexural specimens.

80


(iii) Flexural strength of cement mortar composite slabs are maximum at the fibre
content of 0.5% and at all ages, which is also similar to the flexural behaviour of
composite specimens (evaluated by the standard procedure). However, the
maximum strength obtained by the composite slabs are always less than the
maximum strength attained by the specimens (in flexure) at all ages considered.
The above phenomenon may be due to the ‘residual stress’ present in the slab
specimens due to the impact test, conducted earlier.

The primary objective of the above test is to obtain the ‘reference data’ for determining the
‘flexural toughness factor’ (IT) of the composite slabs after exposing them in NaOH and,
hence, to evaluate the ‘durability of the composite’.

Table 10: Flexural Strength of Sisal Fibre Cement Mortar Composite Slabs

Sl. Flexural Strength at Flexural strength (N/mm2) at fibre contents of
No. the Age of
0% 0.25% 0.5% 0.75% 1.00% 1.5% 2.00%
1 28 days 3.93 4.11 3.98 3.41 3.08 2.93 2.29
2 56 days 4.55 4.67 4.77 4.47 4.10 3.57 2.40
3 90 days 4.80 5.10 5.76 5.55 5.25 4.32 3.97
4 120 days 5.26 5.40 5.41 5.34 5.00 4.73 4.40

3.6 DURABILITY OF SISAL FIBRE CEMENT MORTAR COMPOSITE SLABS

3.6.1 EVALUATION OF DURABILITY BASED ON ‘IRS’

Impact strength of cement mortar slabs, cement mortar composite slabs, before and
after exposing them in NaOH medium, are given in Table 11, for various fibre contents.
From a critical evaluation of the above experimental data, following observations are
obtained:

(i) ‘Irs’ values of cement mortar composite slabs increases with increase in fibre content,
after exposure in the alkaline medium, when compared to the Irs value before
exposure and it is found to be independent of the fibre content. ‘Irs’ values of the
above composite slabs after exposure have the same trend as that of slabs before
exposure in the alkaline medium and that it is maximum when the fibre content is
maximum i.e. 2.0% in the cement mortar composite slabs.
(ii) A closer look at the deviation in Irs values above results presents an interesting
scenario, i.e. (i) The deviation in Irs values of all plain mortar slabs, are all negative,
indicating nearly failure of matrix, due to exposure in the alkaline medium; (ii) the
deviation in ‘Irs’ values of all composite mortar slabs are all positive as ‘Irs’ values of
composite slabs after exposure are higher than the corresponding values before
exposure.

81


Table 11 : Impact Strength of Sisal Fibre Cement Mortar Composite Slabs Before and
After Exposure in NaOH
(1:3; Constant flow value =112%; r=200)

Sl. Fibre Impact Strength/ Residual Impact strength Ratio Deviation in
No. content Before Exposure After Exposure Irs
(%)
A B C A B C
1 0 13.84 18.0 1.30 8.91 10.89 1.22 -6.15
2 0.25 16.91 22.5 1.33 9.9 16.83 1.70 +27.81
3 0.50 17.35 29.5 1.7 10.89 21.78 2.0 +22.35
4 0.75 17.76 35 1.97 11.88 26.73 2.25 +14.21
5 1.00 18.18 40.0 2.20 12.87 32.67 2.53 +20.00
6 1.50 19.39 45.0 2.32 15.84 42.57 2.68 +18.96
7 2.00 21.34 54.0 2.53 16.83 48.51 2.88 +13.83

Note: (i) Energy for one blow = 0.99J (Height of fall = 21cm)
(ii) A- Impact strength at initiation of crack (in Joules)
B – Impact strength at final crack (in Joules)
C- Residual impact strength (Irs)

3.6.2 EVALUATION OF DURABILITY BASED IN FLEXURAL TOUGHNESS INDEX (IT)

Flexural toughness of cement mortar slabs, cement mortar composite slabs, before
and after exposure in NaOH medium are presented in Tables 12, for various fibre contents.
From a closer look of the above, it is seen that IT values of various mortars / composites
exhibit the same trend as that of ‘Irs’ values, with respect to the range of parameters
considered.

Table 12 : Flexural Toughness Index of Sisal Fibre Cement Mortar Composite Slabs
(1:3; Constant flow value = 112% ; r = 200 ; @ 120 days)

Sl. Fibre Toughness Energy/Toughness index = {A2/(A1+A2)} Deviation in
No. content IT
(%) Before Exposure After Exposure
A B C A B C
1 0 1322 700 0.346 1006.5 368.5 0.268 -22.54
2 0.25 1557 432.5 0.217 790.8 701.2 0.470 +116.58
3 0.50 998.5 434 0.302 198.6 846.7 0.810 +168.21
4 0.75 1361 2388.4 0.637 629.5 1887.5 0.750 +17.73
5 1.00 1319.5 471.2 0.263 848.1 498.1 0.370 +40.68
6 1.50 2413.8 1788 0.425 885.4 2392.0 0.730 +71.76
7 2.00 1347 1846 0.578 325.0 1084.0 0.770 +33.21

Note: (i (A) – Area of the load-displacement diagram upto the pre-cracking stage- (A1)
(B)- Area of the load-displacement diagram after the post-cracking stage-(A2)
(C)- Flexural toughness index –( IT )= {A2/ (A1+A2)}

82


IV. CONCLUSIONS

4.1 STRENGTH BEHAVIOUR OF CEMENT MORTAR COMPOSITES

(i) Compressive, flexural and split-tensile strength behaviour of sisal fibre cement mortar
composites (1:3) are similar over the range of parameters and ages (normal age i.e. at
28 days, and at later – ages upto 120 days), considered. All the above strengths attain
the maximum at identical fibre content in the mortar composite (i.e. sisal fibre content
= 0.50%).
(ii) Maximum compressive strength attained by the cement mortar composite is about 26
MPa [@ sisal fibre content (Vf) = 0.5%), at the normal – age], which is about 25 –
61%, higher than the plain cement mortar strength, for the range of ages considered.
The maximum long-term strength-gain ratio of the cement mortar composite (i.e. ratio
of compressive strength @ 120 days to that at normal age) is about 2.1.
(iii)Maximum flexural strength attained by the cement mortar composite is 4.5 MPa (at Vf
= 0.5), at the normal – age, which is about 30 – 50% higher than the reference mortar
strength and for the range of ages considered. It is found that the long – term
(maximum) flexural strength - ratio is nearly the same as that of the compressive
strength - ratio.
(iv) Maximum split – tensile strength attained by the cement mortar composite is 5.0 MPa
(@ Vf =0.5, at the normal – age), which is about 20 – 30% higher than the reference
mortar strength and for the range of ages, considered. It is found that the long- term
(maximum) split- tensile strength ratio is about 1.6, which is slightly less than the
other two strengths considered.

4.2 IMPACT STRENGTH OF CEMENT MORTAR COMPOSITES

(i) Residual impact strength ratio (Irs) which is measure of ductility inherent in the
material ranges from 1.18 to 1.74, for the cement mortar composite slabs relative to
that of the reference cement mortar slab, at normal-age and the range of sisal fibre
contents considered.

(ii) There is only a marginal improvement in the ductility (as measured by Irs) of the
cement mortar composite slabs, over the early – age behaviour, within the range of
later – ages considered.

4.3 FLEXURAL STRENGTH OF CEMENT MORTAR COMPOSITES

1. Flexural strength behaviour of composite mortar slabs are generally similar to that of
standard specimens (of mortar and composites), within the range of parameters and
ages considered.

2. However, the maximum strength obtained by the composite slabs are always less (
by 30% - average) than that attained by the specimens (under flexure), at all ages
considered, which may be attributed to the ‘residual stress’ present in the slab
specimens by virtue of the earlier impact load subjected on them.

83


4.4 DURABILITY OF SISAL FIBRE CEMENT MORTAR COMPOSITES

(i) Irs and IT values could reflect the changes in the strength due to the interaction
between the matrix and the medium considered (i.e. NaOH) and hence can be used
with confidence to evaluate the durability of the mortar composites.

V. ACKNOWLEDGEMENT

This work reported herein forms a part of comprehensive investigations on the
rheology, strength and durability characteristics of sisal fibre cement and cementitious
composites, carried out by the authors in the Dept. of Civil Engg., Pondicherry Engineering
College, Pondicherry , India. The kind support and co-operation extended by the Principal,
and the Head of Civil Engg. Dept., PEC , in all the endeavors of the authors is recorded with
a deep sense of gratitude. The financial assistance received from Dept. of Science and
Technology, (DST), Govt. of India, has greatly helped to carry out the experimental
investigations reported in this paper, which is gratefully acknowledged

REFERENCES

(1) Gram, H - E., ‘Durability of Natural Fibres in Concrete’, Report No 1, 1983, Swedish
Cement And Concrete Research Institute, Stockholm, ISSN 0346-6906, 255pp.
(2) Castro, J. Naaman, A.E., ‘Cement Mortar Reinforced With Natural Fibres,’ Jl. of
Ferrocement, Vol,11, No.4, Oct. 1981, pp. 285-301.
(3) Ramaswamy, H.S., Ahuja, B.M., Krishnamoorthy, S., ‘Behaviour of Concrete
Reinforced With Jute, Coir And Bamboo Fibres,’ The Intl. Jl. of Cement Compotes and
Light Weight Concrte, 1983. pp.3-12.
(4) Toledo Filho, R.D., Ghavami, K., England, G.L., Scrivener, K., ‘Development of
Vegetable Fibre-Mortar Composites of Improved Workability’, Cement & Concrete
Composites, Vol.25, 2003, pp.185-196.
(5) Berhance, Z., ‘Performance of Natural Fibre Reinforced Mortar Roofing Tiles’,
Materials and Structures, Vol.27, 1994, pp.347-352.
(6) Canovas, M.R., Selva, N.H., Kawiche, G.M. ‘New Economical Solutions For
Improvement of Durability of Portland Cement Mortar Reinforced With Sisal Fibres’,
Materials and Structures, Vol.25, 1992, pp. 417-422.
(7) Gram.H.E. and Nimityoungskul.P, Durability of natural fibres in cement-based roofing
sheets, Proc. of the Symp. on Building Materials for Low-income Housing: Asia and
Pacific Region, Bangkok, Thailand, Jan.20-26,1987, Oxford & IBH Publ.Co.(P) Ltd.,
NewDelhi,pp.328-334.
(8) John.V.M, Agopyan.V. and Derolle.A., Durability of blast furnace slag-based cement
mortar reinforced with coir fibres, Proc. of the Second Intl. Symp. on Vegetable Plants
and their Fibres as Building Materials, Salvador, Brazil, Sep.17-21 , 1990, Sobral.H.S
(Ed.).,Chapman & Hall, London, pp.87-97.
(9) Canovas, M.E., Kawiche, G.M., Selva, N.H., ‘Possible Ways of Preventing
Deterioration of Vegetable Fibres In Cement Mortars’ Proc. of Second Intl. Symp. of
RILEM on Vegetable Plants and their Fibres As Building Materials Sobral, H.S. (Ed.),
Salvador, Brazil , Sep. 17-21, 1990, Chapman & Hall, London, pp. 120-129

84


(10) Oliveria, M.J., Agopyan, V., ‘Effect of Simple Treatments of Malva Fibres for the
Reinforcement of Portland Cement Mortar, Proc. of Fourth Intl. Symp. on RILEM
Fibre Reinforced Cement and Concrete, Jul. 20-23, 1992, Swamy R.N. (Ed.), E & FN
SPON, London, pp 1073 – 1079.
(11) Gram, H.E., ‘Durability Studies of Natural Organic Fibres in Concrete Mortar or
Cement,’ RILEM Symposium – FRC 86: Development In Fibre Reinforced Cement And
Concrete, Swamy, R.N. And Others (Eds.) Sheffield, England, Jul. 13-17, 1986, Vol. II,
Paper No. 7.1.
(12) DelvastoS., Botache,C.A., Alban, F., Gutierrez, R.M., Perdomo,F., Segovia, F.,
Amigo,V’., ‘Effect of Fique Fiber Surface Chemical Treatments on the Physical and
Mechanical Properties of the Fiber Subjected to Aggressive Mediums’, Brazil
NOCMAT 2004, Pirassununga,SP,Brazil, Oct.29 – Nov 3, 2004, pp. 54-163.
(13) Singh, S.M., ‘Studies on the Durability of Plant Fibres Reinforced Concrete Products’,
Joint Symposium RILEM / CIB/ NCCL., on Use of Vegetable Plants and Fibres as
Building Materials, Baghdad, Oct.1986, pp. C- 127 to C- 138.
(14) Ramakrishna, G., Sundararajan , T., ‘Effect of a Few Pozzolanic Materials on The
Strength of Treated/Untreated Sisal Fibre Reinforced Concrete’, Natl. Sem. on
Concrete Technology For 21st Century, Feb. 9 -10, 2001, Annamalainagar, India,
pp.79 -85.
(15) Ramakrishna, G., Sundararajan,T., ‘Effect of Yeast – Blended Water on The
Workability and Strength Characteristics of Sisal Fibre Reinforced Concrete’, Natl.
Sem. on Advances in Construction Materials, Feb. 14 – 15, 2003, Ahmedabad, India,
pp.201-208.
(16) Ramskrishna, G. Sundararajan, T., ‘Effect of Yeast – Blended Water on Some Physical
and Strength Characteristics of San Fibre Reinforced Concrete’, Natl. Conf. on
Advances in Concrete Technology, Sep. 21 – 22 , 2000, Patiala, India, pp.28 – 39.
(17) Ramskrishna, G. Sundararajan, T., ‘Rheological, Strength and Durability
Characteristics of Sisal Fibre Reinforced Cementitious Composites’, Ph.D Thesis
Submitted to the Pondicherry University, Pondicherry, India, Apr.2005 (Degree
awarded in Aug.2005), 389pp.
(18) Ramakrishna, G., Sundararajan , T., ‘Influence of Water-Binder Ratio and Fibre
Content on the Workability and Rheological Characteristics of Sisal Fibre Cement
Mortar Composites’, (unpublished).
(19) Ramakrishna, G., Sundararajan , T., ‘Influence of Water-Binder Ratio and Fibre
Content on the Workability and Rheological Characteristics of Sisal Fibre Cementitious
Mortar Composites’, (unpublished).
(20) Ramakrishna, G., Sundararajan , T., ‘Influence of Fibre Content and Aspect Ratio of
Sisal fibres on the Workability and Rheological Characteristics of Cement Mortar
Composites’, Journal of Structural Engineering,(accepted for publication).
(21) IS: 4031 (Part 8) – 2000, ‘Method of Tests for Hydraulic Cement & Part 8:
Determination of Transverse and, Compressive Strength of Plastic Mortar Using
Prism’, BIS , India
(22) Hannant, D.J. ‘The Tensile Strength of Concrete: A Review Paper’, The Structural
Engineer, Vol. 50, No.7, July 1972, pp. 253 – 258.
(23) Ramakrishna, G., Sundararajan , T., ‘Impact Strength of a Few Natural Fibre
Reinforced Cement Mortar Slabs: A Comparative Study’, Cement & Concrete
Composites, Vol.27, No.5.2005, pp.554-564.

85


(24) Ramakrishna, G., Sundararajan , T., ‘New methods of testing for studying the rheology
and strength of low modulus fibre reinforced cement/cementitious mortar composites’,
(unpublished).
(25) IS: 12269 – 199, ‘Specification for 53 Grade Ordinary Portland Cement’, BIS, India
(26) IS: 383- 1997, ‘Specification for Coarse and Fine Aggragates from Natural Sources for
Concrete’, BIS, India.
(27)M. Vijaya Sekhar Reddy, Dr.I.V. Ramana Reddy and N.Krishna Murthy, “Durability
Of Standard Concrete Incorporating Supplementary Cementing Materials Using Rapid
Chloride Permeability Test” International Journal of Civil Engineering & Technology
(IJCIET), Volume 3, Issue 2, 2012, pp. 373 - 379, Published by IAEME.
(28)Dr. Prahallada. M.C., Dr. Shanthappa B.C. and Dr. Prakash. K.B., “Effect Of Redmud
On The Properties Of Waste Plastic Fibre Reinforced Concrete An Experimental
Investigation” International Journal of Civil Engineering & Technology (IJCIET),
Volume 2, Issue 1, 2011, pp. 25 - 34, Published by IAEME.
(29)N.Ganesan, Bharati Raj, A.P.Shashikala and Nandini S.Nair, “Effect Of Steel Fibres On
The Strength And Behaviour Of Self Compacting Rubberised Concrete” International
Journal of Civil Engineering & Technology (IJCIET), Volume 3, Issue 2, 2012,
pp. 94 - 107, Published by IAEME.

86

Long term strength and durability evaluation of sisal fibre composites

Recommandé

Recommandé

Contenu connexe

Tendances

Tendances (18)

En vedette

En vedette (6)

Similaire à Long term strength and durability evaluation of sisal fibre composites

Similaire à Long term strength and durability evaluation of sisal fibre composites (20)

Plus de IAEME Publication

Plus de IAEME Publication (20)

Long term strength and durability evaluation of sisal fibre composites