1. MECHANICAL PROPERTIES OF HYBRID STEEL-NYLON FIBERS USED AS
REINFORCEMENT IN CONCRETE
ABDUL KAREEM HASAN
ASHWINI. G
ABSTRACT
This study aims to characterize and quantify the mechanical properties of hybrid steel-nylon fibers used as
reinforcement in concrete. In order to realize the behavior of fiber reinforce concrete, different fiber percentages by
volume of concrete are used in this study with different mixes for each fibers percentage (nylon to steel).
Compressive strength, split tensile strength and modulus of rupture (MOR) tests have been performed in the
hardened state. Super plasticizer and silica fume are used in all the mixes to enhance the fiber reinforce concrete
mechanical properties. When compared to the control sample that contains no fibers, with the increase of fiber
ratio, compression strength, split-tensile strength and flexural strength of concrete increases appreciably. The result
showed that the steel fibers improve the concrete properties better than the nylon fiber due to their higher tensile
strength.
Keywords: Nylon fiber (NF), Steel fiber (SF), Hybrid steel-nylon fibers, Modulus of rupture (M.O.R)
Compressive strength, Flexural strength and Tensile strength.
1. INTRODUCTION AND HISTORICAL
PERESPECTIVE
Concrete the most widely used construction material,
commonly made by mixing Portland cement with
sand, crush rock and water. In many countries the
ratio of concrete consumption to steel consumption
exceeds ten to one or one ton for every living human
being. Today, the rate at which concrete is used is
much higher than it was 40 years ago .It is estimated
that the present consumption of concrete in the world
is of the order of 11 billion metric tons every year.
[1] Concrete is a tension-weak building material,
which is often crack ridden connected to plastic and
hardened states, drying shrinkage, and the like. The
cracks generally develop with time and stress to
penetrate the concrete, thereby impairing the
waterproofing properties and exposing the interior of
the concrete to the destructive substances containing
moisture, acid sulfate, etc. The exposure causes
deterioration concrete due to reinforcing steel
corrosion. To counteract the cracks, a fighting
strategy has come into use, which is, mixing the
concrete discrete fibers. Experimental studies have
shown that fibers improve the mechanical properties
of concrete such as flexural strength, compressive
strength, tensile strength, creep behavior, impact
resistance and toughness. Moreover, the addition of
fibers makes the concrete more homogeneous and
therefore it is transformed from a brittle to a more
ductile material.[2]
The concept of fibre reinforcement used in building
material was first applied in MESOPOTAMIA
using straw of wheat in mud for building houses &
temples (as ziggurat-shaped). These ziggurats are still
standing now with bore hole as ventilation and mats
of reed with tar interval rows. There is evidence that
fibres were used to reinforce clay pots about 5000
years ago.[1]
Researches in the late 1950s and early 1960s by
Romualdi and Batson 1963 and Roulade and
Mandel 1964 on closely spaced random fibers,
primarily steel fibers, heralded the era of using the
fiber composite concretes we know today. In
addition, Shah and Rangan 1971, Swamy 1975.[2]
2. EXPERIMENTAL PROGRAM AND
MATERIALS USED
The properties of materials used in concrete mixtures
are given below:
Cement:
Ordinary Portland cement grade 53 is used
conforming to IS:12269-1987 and IS:4031part 5-
1988.
Fine aggregate:
Natural sand with a 4.75-mm maximum size is used
as fine aggregates. The grading of the sand
conformed to the requirement of IS: 383-1970, Zone
I.
Coarse aggregate:
Coarse aggregate used in this study is 12.5mm
maximum size conforming to IS 383:1970.
Water :
Potable water was used for the experimentation.
Fibers:
Two different types of fibres are used. The first is the
steel fibre having a ‘trough’ shape with hooks at both
ends and glued in bundles of 35 mm long and 0.55 mm
in diameter (aspect ratio = 64), tensile strength 1100
MPa , Youngs modulus 200 GPa, specific gravity 7.8.
The second is nylon fibre of crimped shape and
rectangular cross section of dimension 0.8×0.5 mm
,with length of 45 mm, tensile strength 896 MPa ,
Youngs modulus 5.17GPa , specific gravity 1.16.
Fig.1-(a, b) steel and nylon fibers. In this investigation,
three percentages of fibers by total volume of concrete
0.5%, 1% and 1.5% are used with mix proportion of
100-0%, 70-30 %, 50-50%, 30-70% and 0-100% for
each fibre percentage (nylon to steel).

2. a b
Fig. 1 (a, b) - Steel and Nylon fibers
Silica Fume:
Dry silica fume used which meets the requirements
of IS: 15388-2003.The used weight percentage by
cement weight for all mixes is 10%.
Super plasticizer:
A commercially available super-plasticizer
(Sikament® FFN) conforming to the specification in
IS: 9103-1999 is used throughout this work in all
mixtures. The weight percentage according to cement
weight is the same for all mixes and is 3%,
3. MIX PROPORTIONS
1) Control mix (without fibers) is designed in
accordance with the provisions of standard
practice for selecting proportions and
workability according to IS: 10262- 2009 and
IS: 456 -2000.
2) Mix proportion 1: 1.90: 3.35, cement, fine
aggregate and coarse aggregate respectively.
3) For normal mass concrete to have a 28-day
cube compressive strength of M20 MPa.
4) Three percentages of fibers by total volume
of concrete 0.5%, 1% and 1.5% are used with
five mix proportion of 100-0%, 70-30%, 50-
50%, 30-70% and 0-100% for each fibers
percentage (nylon to steel).
5) The water/cement ratio is maintained at 0.35
± 0.02.
6) Super plasticizer/cement ratio is kept around
3%.
7) The silica fume/cement is kept at 10%.
8) Concrete mixed were made by hand
(manually).
4. MIXING, CASTING, CURING
The procedures for mixing the fiber-reinforced
concrete involved the following:
1) The coarse aggregate and fine aggregate
were placed in a concrete pan and dry mixed
for 1 min.
2) The cement in addition to silica fume are
spread and dry mixed for 1 min.
3) About the half of the mixing water in
addition to the total amount of the super
plasticizer is slowly added and mixed for 2
min. After that, the specified amount of
fibers is distributed and mixed for 3 minutes.
4) The remaining water is added and the mixing
is done until good homogeneous mixture.
5) The freshly mixed fiber-reinforced concrete
is fed into the molds .The cubic molds for the
compressive strength measuring 15×15×15
cm, prism molds for the flexural specimens
measuring 10×10×50 cm and cylinder molds
for the tensile strength specimens 15×30 cm.
Three specimens are cast for each mentioned
test. After the feeding operation, each of the
specimens is allowed to stand for 24 hrs
before de molding, stored in water at 24±3C0
for 27 days, and then removed and kept at
room temperature until the time of testing.
We intend to test 144 specimens, plus 12 for
slumps and mix proportion equal to 156 test
specimens, divided in three groups , cubes,
cylinders, and beams to investigated
compression, tension , and flexibility. Each
groups 48 specimens (cubes, cylinders, and
beams).
5. EXPERIMENTAL METHODOLOGY
5.1 Compressive Strength Test
Compressive strength of concrete is measured on 150
mm cubes in conformity with the test procedure was
carried out in accordance with IS:516-1959.
The average of the compressive strength of three
cubes is adopted for each test, and the test was
conducted at age of 28 days. Table1 and fig.2 showed
Compressive strength test results.

3. Table1-Compressive strengthtest results
Fig.2-Compressive strength test results
5.2 Split Tensile Strength
The split tensile strength is determined as per the procedure outlined in IS: 5816-1999. To assess the split tensile
strength of concrete cylinder specimens of 150×300 mm for each mix. The average results are adopted as in table
2, and fig.3 The tests was conducted at age of 28 days.
Table 2- Split tensile strength test results
Fig.3- Split tensile strength test results
5.3Flexural Strength (Modulus ofRupture M.O.R)
The 100×100×500mm prisms are tested according to IS: 10086-1982. Two points load are applied at the specimen.
The specimen is tested at the age of 28 days and the averages of three specimens to a mix are accepted as the
flexure tensile strength of that mix. Table3and fig.4
20.52
33.45
30.8
46.5
39.5
34.7
20.52
36.2
27.5
43.3
29.3
33.2
20.52
26.526.6
40
31
35.5
0
5
10
15
20
25
30
35
40
45
50
Normalconcrete
100%NF-0%SF
70%NF-30%SF
50%NF-50%SF
30%NF-70%SF
0%NF-100%SF
Normalconcrete
100%NF-0%SF
70%NF-30%SF
50%NF-50%SF
30%NF-70%SF
0%NF-100%SF
Normalconcrete
100%NF-0%SF
70%NF-30%SF
50%NF-50%SF
30%NF-70%SF
0%NF-100%SF
CompressiveStrength(MPa)
Hybidization ratio
2.58
2.92.87
3.33.5
4.2
2.58
3.353.57
3.9
4.3
4.9
2.582.62.8 3
3.6
3.3
0
1
2
3
4
5
6
Normalconcrete
100%NF-0%SF
70%NF-30%SF
50%NF-50%SF
30%NF-70%SF
0%NF-100%SF
Normalconcrete
100%NF-0%SF
70%NF-30%SF
50%NF-50%SF
30%NF-70%SF
0%NF-100%SF
Normalconcrete
100%NF-0%SF
70%NF-30%SF
50%NF-50%SF
30%NF-70%SF
0%NF-100%SF
SplitTensileStrength(MPa)
Hybidization ratio
Sl.No. % of fibers in
totalvolume
of mix
concrete
Mix proportion
for each
fibers(nylon-
steel)
Average
compressive
strength
(MPa)
1
0 Normal concrete 20.52
0.5
100%NF-0%SF 33.45
70%NF-30%SF 30.8
50%NF-50%SF 46.5
30%NF-70%SF 39.5
0%NF-100%SF 34.7
2
0 Normal concrete 20.52
1
100%NF-0%SF 36.2
70%NF-30%SF 27.5
50%NF-50%SF 43.3
30%NF-70%SF 29.3
0%NF-100%SF 33.2
3
0 Normal concrete 20.52
1.5
100%NF-0%SF 26.5
70%NF-30%SF 26.6
50%NF-50%SF 40
30%NF-70%SF 31
0%NF-100%SF 35.5
Sl.No. Percentage
Of fibers in
total
volume of
mix
concrete
Mix proportion
for each
fibers(nylon-
steel)
Average
split
tensile
strength
MPa
1
0 Normal concrete 2.58
0.5
100%NF-0%SF 2.9
70%NF-30%SF 2.87
50%NF-50%SF 3.3
30%NF-70%SF 3.5
0%NF-100%SF 4.2
2
0 Normal concrete 2.58
1
100%NF-0%SF 3.35
70%NF-30%SF 3.57
50%NF-50%SF 3.9
30%NF-70%SF 4.3
0%NF-100%SF 4.9
3
0 Normal concrete 2.58
1.5
100%NF-0%SF 2.6
70%NF-30%SF 2.8
50%NF-50%SF 3.
30%NF-70%SF 3.6
0%NF-100%SF 3.3

4. Table3- Flexure tensile strength (M.O.R ) MPa
Fig. 4- Flexure tensile strength (M.O.R ) MPa
6. CONCLUSIONS
1. The following conclusions are driven from the present study:
1) Inclusion of steel and nylon fibers to the concrete mix strongly increased the compressive strength.
The strength increased up to 226.6% for a fiber volume fraction equal to 0.5%.
2) The use of hybrid steel-nylon fibers will increase the split tensile strength of concrete. The
maximum raise is for the fiber ratio 1% and reaches to 189.9%. However, the nylon fiber seems to
have a slight effect on the split tensile strength and the effect of steel fiber alone is larger than that
of nylon fiber.
3) When compared to the control mix which contain no fiber, increase of fiber volume fraction
provides an enhancement in the flexural strength for all hybridization ratio, and the maximum
increase reaches to 187.5% for fiber volume fraction 1.5%. Here too, the inclusion of nylon fiber
seems to have a slight effect on the flexure strength.
7.REFERENCES
1. P.Kumar Mehta (2013)- Concrete ,microstructure, properties, and materials
2. Rafat Siddigue( 2000)- Special structural concrete.
3. IS:8112-1989:Specification for 53 grade ordinary Portland cement.
4. IS:383-1970 : Specification for coarse aggregate and fine aggregate from natural sources for concrete.
5. IS:456-2000 :Plain and reinforced concrete code of practice.
6. IS: 2386(part-I, II, III, and IV) -1963: Method of tests for aggregates for concrete.
7. IS:516-1959:Method of test for strength of concrete
8. P.S. Song and S. Hwang, B.C. Sheu, (2005)- Strength properties of nylon- and polypropylene – fiber –
reinforced concretes. Cement and concrete research. 35: 1546–1550.
9. Faisal Fouad Wafa- Properties and applications of fiber reinforced Concrete JKAU:Eng. Sci .,Vol.2,pp
.49-63 (1410A.H./1990A.D.).
10. IS:5816-1999:Splitting tensile strength of concrete method test .
11. IS:15388-2003: Specification for silica fume
12. Yao, W., Li, J., and Wu, K- "Mechanical properties of hybrid fiber-reinforced concrete at Low fiber
volume fraction," Cem. Concr. Res., "Vol. 33, No. 1, pp. 27-30, 2003.
13. Dr. Mazin Burhan Adeen- Determination of mechanical properties of hybrid steel-nylon fiber reinforced
concrete modern applied science Vol. 4, No. 12; December 2010.
Sl.No. % Of
fibers in
total
volume
of mix
concrete
Mix proportion
for each
fibers(nylon-
steel)
Average flexure
tensile
strength(M.O.R)
MPa
1
0 Normal concrete 4
0.5
100%NF-0%SF 4.85
70%NF-30%SF 5
50%NF-50%SF 5.3
30%NF-70%SF 6.5
0%NF-100%SF 6
2
0 Normal concrete 4
1
100%NF-0%SF 3.65
70%NF-30%SF 4.2
50%NF-50%SF 5.5
30%NF-70%SF 5.62
0%NF-100%SF 6.2
3
0 Normal concrete 4
1.5
100%NF-0%SF 3.55
70%NF-30%SF 5.4
50%NF-50%SF 5.8
30%NF-70%SF 6
0%NF-100%SF 7.5