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Assessment of durability of Self compacting concrete by use of Steel and

Polypropylene fibres in addition with recycled coarse aggregates.

Mohammed Imran1, Vijayanand M2, Madhu Kumar C A3

1 &3
Assistant professor, Brindavan College of Engineering, Bangalore-560063, India
2
Assistant professor, School of architecture, Ramaiah Institute of Technology, Bangalore-560054, India
ABSTRACT:
The durability of concrete is one of the prominent influencing factor for better serviceability of any
concrete and over the past few decades numerous researches has also been done in order to understand
the behaviour of Self compacting concrete(SCC) with addition of fibres in combination with recycled
aggregates. With development in concrete engineering, waste generated due to demolition of concrete
structures also is a concern. Sustainable development is presently a major issue all over the world. The
use of recycled concrete aggregate (RCA) in concrete as partial and full replacements of natural coarse
aggregate (NCA) is growing interest in the construction industry, as it reduces the demand for virgin
aggregate. Hence recycled coarse aggregates (RCA) can be used as replacement to NCA in order to
reduce the environmental pollution and waste of resources in construction process. In this paper an
attempt has been made to compare the effect of durability properties on SCC by addition of steel fibre
(SF) and polypropylene fibres (PF) in various volume fractions from 0.05% to 0.15% with an interval
of 0.05% and fixed percentage of RCA replaced with natural aggregates. Present work focuses mainly
to evaluate the effect of low percentage fibres and fixed percentage of recycled aggregates on
durability of SCC. In the existing study the mix design for M40 grade SCC is made using Nan Su
method by replacing 25% of natural aggregates with recycled aggregates. Number of durability tests
such as Acid test, Chloride test, Sulphate test and Water absorption test were conducted to understand
the influence of fibres on durability of SCC. Thus the present study highlights to substantiate the
effective usage of fibres to enhance durability properties of SCC.

KEYWORDS: Durability, Fibres, Fresh properties, Polypropylene fibres, Recycled concrete

aggregates, SCC, Steel fibres, Tests

INTRODUCTION
Self- Compacting Concrete (SCC) is a flowing concrete mixture that can consolidate under its
weight. The highly fluid nature of SCC makes it suitable for placing in difficult conditions and sections
with congested reinforcements. The development of Self Compacting Concrete (SCC) is an important
achievement in the construction industry for overcoming problems associated with conventional
concrete. SCC is the improvised concrete that partly replaces the Ordinary Portland Cement (OPC)
with suitable mineral admixtures and filler materials and yet retains qualities of the conventional
cement concrete. The fresh concrete tests done on such SCC have yielded results acceptable to the
EFNARC (2005) standards. The literature pertaining to SFRSCC and PPFRSCC are briefly reviewed.
Al Tamimi et al[1] investigated the resistance of SCC and conventional concrete with w/c ratio of 0.36
and 0.46 subjected to a 1% HCl solution for a period of 18 weeks at 20˚C. After 18 weeks a mass loss
of 9% was observed for SCC compared to 21% for conventional concrete. Liu X[2] investigation
shows that the addition of small amount of polypropylene fibers has shown a positive influence in
reducing the explosive fire spalling of SCC and more significant effect is the increased connectivity of
the pore system after melting of the fibers. Khaloo, et al [3] examined the role of silica fume on
strength of compression and durability of concrete. To attain proper strength use of about 1 to 15% of
silica fume with different trials of W/C ratio varying from 0.3 to 0.6 is carried out, and to achieve high
strength for short and long terms replacement of silica fume of about 5 % to10% by mass proved to be
effective. The above specimens were effectively able to withstand 300 cycles of freezing and thawing.

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Celik ozyildirim[4] pointed out that permeability reduces with time. It can resist high chloride
penetration for concrete with use slag or pozzolono. After 300 cycles of freezing and thawing tests,
there was just 7% reduction in weight of specimen with a factor of durability 60 and more; and a
surface rating 3 hrs. Fly ash specimens had high weight loss than blast furnaces slag concrete. Tarun
Naik,et al[5] investigation showed the role of class ‘C’ of fly ash on permeability of concrete. Different
percentage of fly ash in concrete is replaced with cement varying from 0 to 70%. The Strength of
compression, air permeability, chloride permeability, water permeability was found out for each
concrete mix by replacement of cement with and without fly ash by weight.

RESEARCH SIGNIFICANCE
To keep the concrete more cohesive and achieve high flow ability, a proper design of Self
Compacting Concrete possesses high powder content when compared to the conventional concrete. Use
of high volume of cement remarkably increases the cost of the concrete and also it is more vulnerable
to drying shrinkage. Hence, the SCC can be replaced for conventional concrete, but it should not be
very expensive. One of the alternatives to overcome these drawbacks is to use industrial by-products or
waste materials which are finely divided materials added to the concrete as partial replacement material
in SCC. As these additives replace part of the OPC, the cost of SCC will be reduced. Addition of these
materials will increase the workability, strength, and durability properties of SCC. Utilizing the waste
mineral admixtures and filler materials as the substitute for cement in SCC will fulfill the expectations
of providing greater sustainability in the construction industry. The scope of the work consists of
i)Collection of sample ii)Detailed characterization of fly ash and all other materials used for the
investigation. iii) Design of concrete mix for the materials selected and calculation of design mix for
SCC using Nan-Su method. iv) To assess its properties in fresh state and casting of specimens. v)
Investigating durability properties such as Acid attack, Chloride attack, Sulphate attack and Water
absorption.

MIX PROPORTIONS
Controlled Concrete mixes were designed having a constant water/binder ratio of 0.35, fine
aggregate content of 782 kg/m3, coarse aggregate content of 720 kg/m3 and total binder content of 520
kg/m3.Cementitious materials used in mix are cement 285kg/m3 and fly ash 282 kg/m3 in a fixed
proportions. The other mixes were designed with varying quantities of SF and PF but keeping the RCA
replacement with coarse aggregates as constant at 25% as shown in table 3. The percentage of SF and
PF were varied as, 0.05%,0.10% and 0.15% by volume of concrete mass. Since the specific surface
area of different binders varies, the water requirements in SCC will not be the same for all types of
binders .Therefore, the requirement of Superplasticizer (SP) varies slightly from one mix to another to
improve the workability of SCC. The EFNARC (2005) guidelines and the arrived mix proportion for
the control mix are listed in Table 2.

SIGNIFICANCE OF DURABILITY STUDIES

The need for the present study arises from the requirement to improve the overall utilization of
the mineral admixtures and filler materials in correct proportions in SCC particularly to structures in
the aggressive environment depending upon the requirements. The effect of those mineral admixtures
and filler materials towards the enhancement of the strength and durability of SCC needs to be
researched. Additionally use of sustainable materials in concrete in the form of RCA was also one of
the prime motives of this research. A simple mix design procedure is also needed to be developed for
SCC with fly ash content. The main aim of this study is to investigate the durability properties for all
mixes by conducting various durability tests.

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METHODOLOGY
In the current work, design mix adopted for development of SCC is Nan Su Method. Various
trail mix were prepared to produce SCC based on European guidelines (EFNARC)[8]. The control mix
of M40 grade SCC thus produced consists of 568kg/m3 of cementitious material of proportion
1:1.38:1.27 with a water cement ratio of 0.35. The PF is taken as 1.05 for a volume ratio of fine
aggregate to total aggregate(s/a) which is 50%. In our existing research 53 Grade Birla Super ordinary
Portland cement is used and was tested for codal specifications as per IS 12269-1897 to determine its
properties. Table 1 and table 2 represents all the test results performed on the materials and fresh
properties of SCC. The steel fibers used in the course of action are crimped steel fibers of aspect ratio
60 and thickness of ± 0.5mm triangular polypropylene fibers of 12mm length is used. The volume
fraction of fibers ranges from 0% to 0.15% to an equal interval of 0.05%. Master Glenium 8233 has a
recommended dosage range of 0.5% - 2% or trial starts from 750ml-1500ml for 100 kg of
cementations material for most concrete mixes. As per our trial mix for producing SCC recommended
dosage fulfilling all fresh properties of EFNARC is1400ml of chemical dosage for 100kg of cement
refer table 2. In order to proceed with the following tests various different size samples were used with
specimen dimensions of [LxBxD] 150x150x150mm cubes for Acid, Sulphate ,Chloride and Water
absorption testThese present study highlights the substantiate usage of fibres to enhance durability
properties.

Table 1: Material properties

Sl No Materials Test Result

Standard consistency 33%
1. Cement Fineness test 4%
Specific gravity 3.22
2. Fine Aggregate Specific gravity 2.64
Sieve analysis Zone I IS 383 (1970)
Specific gravity 2.65
3. Water absorption 0.5%
Coarse Aggregate
Sieve analysis Zone I IS 383 (1970)
Aggregate impact 24.86%

Fibers Steel Fibres Aspect ratio 60

4.
Polypropylene 12mmlength,0.5mmØ

Table 2: Fresh properties

J ring Slump flow L- Box V funnel U Box

Chemical
Trial Height (Tr) Flow at Left Right Diff in
dosage per Horizontal T50 cm Blocking ratio
100 kg Difference Flow T5 min Limb Limb height
(mm) (sec) (H2/H1)
(mm) (sec) (sec) (mm) (mm) (mm)
1 1200 ml 13.50 685 5.6 0.83 30 32 280.5 276.0 45

2 1300 ml 11.00 710 3.2 0.84 18 20 282.0 278.5 35

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3 1400ml 8.00 730 2.4 0.86 10 12 272.0 270.0 20

Permissible values 6-12 Max 30

10 mm 600-800 2-5 sec 0.8-1 ≤ Tr+3
as per EFNRC[8] sec mm

Table 3: Compressive strength variation with RCA replacement.

Sl. Specimen Id Cement Flyash FA CA RCA Compressive

No kg/m3 kg/m3 kg/m3 kg/m3 kg/m3 strength 28
days(N/mm2)
1 SCC-0%RCA 285 282 782 720 0 47.58
2 SCC-25%RCA 285 282 782 540 180 48.12
3 SCC-50%RCA 285 282 782 360 360 38.25
4 SCC-100%RCA 285 282 782 0 720 36.75

Experimental Programme

Results and Discussions

1. Acid Resistance Test

The specimen cubes were weighed and immersed in water diluted with 2N, 10% by weight of HCl
acid for 8 weeks. From the acid test it can be noticed that in comparison with series of various
proportions of Steel fibers and polypropylene fibers, the effect of 0.05% of Steel fibers and 0.10% of
Polypropylene are offering better resistance against strength and weight loss. Overall the performance
of SFRSCC with 0.05% of Steel fibers has offered better resistance against loss of compressive
strength and weight. The effect of acid on compressive strength is shown in Fig 1 & Fig 2.

Fig. 1.Results of SFRCC cubes immersed in HCl Fig. 2.Results of PPFRSCC cubes immersed in HCl

2. Sulphate Resistance Test

Then the specimen cubes were weighed and immersed in water diluted with 5% by weight of
MgSO4 for 8 weeks. Existing study from Sulphate resistant test reveals that the SCC without fibers are
offering resistance against the loss in compressive strength but not weight. It is seen that SFRSCC with
0.10% and 0.05% PPFRSCC offered better resistance against loss in compressive strength and weight.

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When compared the values of 0.10% SFRSCC and 0.05% PPFRSCC, SFRSCC with 0.10% offered
better results. The effect of acid on compressive strength is shown in Fig3 and Fig4.

Fig. 3. Results of SFRCC cubes immersed in MgSo4 Fig. 4.Results of PPFRCC cubes immersed in MgSo4

3. Chloride Resistance Test

The specimen cubes were weighed and immersed in water diluted with 5% by weight of NaCl for 8
weeks. Comparative notes of the test results examined from the Chloride resistant test shows that the
effect of 0.10% of SFRSCC and PPFRSCC seen to have better resistance against loss in weight and
compressive strength. On the other hand SCC is offering poor resistance against weight loss but the
effect on compressive strength is negligible. Overall the effect of 0.10% of Steel fibers is predominant
when compared with 0.10% of Polypropylene fibers in resisting Chloride attack. The effect of acid on
compressive strength is noted in fig5 and fig6.

Fig. 5.Results of SFRCC cubes immersed in Nacl Fig. 6. Results of PPFRCC cubes immersed in Nacl

4. Water Absorption Test

After 28 days of curing, specimens were dried for 24 hrs and placed in oven at 1050C. The
specimens were immersed in water after cooling it to room temperature and variation of gain in mass is
noted .Later the percentage of water absorption was calculated. It is ascertained from the water
absorption test that water absorption of SCC when compared to SFRSCC and PPFRSCC is
approximately around 11% more except 0.10% of PPFRSCC which resembles same water absorption
behavior as exhibited by SCC. As observed from the test results the resistance of 0.10% of SFRSCC
and 0.15% of PPFRSCC has better effect against water absorption. In comparison PPFRSCC is 2%
more resistant against water absorption than SFRSCC.
The results are depicted in fig7 and fig8.

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Fig. 7. Results for water absorption for SFRCC cubes Fig. 8. Results for water absorption for PPFRCC cubes

Conclusions
The main motive behind conducting this research work is to study the influence of low volume
fractions of fibers in enhancing durability properties of SCC. With respect to the same objective
following conclusions are drawn from the present study. It can be clearly seen from the results that
even low volume fractions of fibers when used considerable effect in enhancing durability properties
can be achieved. Definitely the performance of steel crimped fibers is efficient at such low volume
fractions as well and also resulted considerable improvement in offering better resistance towards
disintegration of cubes when immersed in various chemicals. On the contrary it is really difficult to
compare steel fibers and polypropylene fibers performances among each other considering a fact that
material property varies in them. Especially in aspects where strength parameter is seen the
performance of steel fibers are better compared to polypropylene fibers and in few categories like
resistance offered towards water absorption and Rapid chloride penetration test performance of
polypropylene fibers produced effective results.

1) From the acid resistant test it can be noticed that in comparison with series of various proportions of
Steel fibres and polypropylene fibres, the effect of 0.05% of Steel fibres and 0.10% of Polypropylene
are offering better resistance against strength and weight loss. Overall the performance of SFRSCC
with 0.05% of Steel fibres has offered better resistance against loss of compressive strength and
weight.

2) Existing study from Sulphate resistant test reveals that the SCC without fibers are offering resistance
against the loss in compressive strength but not weight. Whereas the effect of Steel fibers and
Polypropylene fibers in various proportions is different. It is seen that SFRSCC with 0.10% and 0.05%
PPFRSCC offered better resistance against loss in compressive strength and weight. When compared
the values of 0.10% SFRSCC and 0.05% PPFRSCC, SFRSCC with 0.10% offered better results.

3) Comparative notes of the test results examined from the Chloride resistant test shows that the effect
of 0.10% of SFRSCC and PPFRSCC seen to have better resistance against loss in weight and
compressive strength. On the other hand SCC is offering poor resistance against weight loss but the
effect on compressive strength is negligible. Overall the effect of 0.10% of Steel fibres is predominant
when compared with 0.10% of Polypropylene fibres in resisting Chloride attack.

4) It is ascertained from the water absorption test that Water absorption of SCC when compared to
SFRSCC and PPFRSCC is approximately around 11% more except 0.10% of PPFRSCC which
resembles same water absorption behavior as exhibited by SCC. As observed from the test results the

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resistance of 0.10% of SFRSCC and 0.15% of PPFRSCC has better effect against water absorption. In
comparison PPFRSCC is 2% more resistant against water absorption than SFRSCC.

5) RCA is useful as a substitute for NCA to produce concrete with acceptable properties and durability.
However, the main problem of using RCA in new concrete is its inconsistent quality, particularly when
it is obtained through demolition of old concrete structures. In the present study use of 25% RCA is
possible to produce SCC with acceptable quality.

References

1. Al-Tamimi A and Sonebi M. “Assessment of self-compacting concrete immersed in acidic

solution”, ASCE Journal of materials in civil engineering, 15(4) ,2003, pp 354-357.
2. Liu X. “Microstuctural investigation of self-compacting concrete and high performance concrete
during hydration and after exposure to high temperatures”, Ph.D. thesis, University of Ghent,
Belgium, 2006.
3. Khaloo,et al “Evaluation of properties of Silica fume for use in concrete”, International conference ,
Dundee, Scotland,1999, pp167-173.
4. Celik Ozyildirim “Evaluation of High performance Concrete pavements in Newport News,
Virgina”, 2001, Paper No.1-3173.
5. Tarun Naik, et al “Permeability of concrete containing large amounts of fly ash”. Reference: CBU-
1933-2002.
6. Ray,et al,” Effect of silica fume on Super plasticizer concrete”. International Conference on
concrete, Dundee, Scotland, 1997, pp 457-465.
7. Nan-Su,et al, “A simple mix design method for self-compacting concrete”, Cement and concrete
research paper,2001,pp 1799-1807.
8. EFNARC, “Specification and guidelines for self-compacting concrete”, European federation of
producers and applications of specialist products for structures, 2002.
9. Geert De Schutter, Peter J. M. Bartos, Peter Domone and John Gibbs,” Self-Compacting Concrete”,
Whittles publication, UK, 2008.

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