Stress-Strain Behaviour of Fibre Reinforced Concrete with Different Proportions of Polypropylene and Steel Fibre

This study aims to investigate the stress-strain behaviour, compressive strength, workability, and find the best combination of materials to be used for hybrid fiber reinforced concrete. The best composition of hybrid fiber is 50% polypropylene with 50% steel fiber. Addition of 1.5% of hybrid fiber containing 50% polypropylene and 50% steel fiber improves the axial properties of M20 grade concrete. Addition of hybrid fibers improves the compression strength, flexural tensile strength and split tensile strength.

STRESS-STRAIN BEHAVIOUR OF FIBRE
REINFORCED CONCRETE WITH
DIFFERENT
PROPORTIONS OF POLYPROPYLENE
AND STEEL FIBRE

Necessity of Hybrid Fiber Reinforced
Concrete
 Concrete is brittle in nature and could break easily (Khan and Jafri,
2015).
 Brittleness of concrete should be reduced (Kim, et al., 2016).
 Brittleness could be reduced by adding fibers to concrete (Rai1 and
Joshi, 2014).
 Performance of hybrid fiber reinforced concrete has not been given
much importance.

Objective of the Work
 To study the behaviour of concrete under axial compression due to
the addition of steel fibres (Vairagade and Kene, 2013) and
polypropylene in different proportions.
 To study the use of polypropylene (Dharan and Lal, 2016) and steel
fibres as materials to strengthen reinforced concrete.
 To study the stress-strain behaviour (de-Oliveira Jr. et al., 2010)
compressive strength (Sofi and Phanikumar, 2015), workability and
find the best combination of the materials to be used.

Methodology
 Mix M20 grade concrete (Goyal and Vikram, 2017) with different
percentages (0%, 0.5%, 1.0%, 1.5%, and 2.0%) of the hybrid fibers.
 The ratio of polypropylene and steel fibre would be varied as follows
100:0, 75:25, 50:50 so as to obtain different proportions of hybrid fibres.
 Each proportion of hybrid fibres are cast into 2 cylinders and 2 cubes.
 They are then tested using 200 Tons capacity CTM.
 Aspect ratio of steel fibre used is 55.

Sample preparation
 S1 = 100% polypropylene and 0% Steel fibers
 S2 = 75% polypropylene and 25% Steel fibers
 S3 = 50% polypropylene and 50% Steel fibers
 S1, S2 and S3 are mixed with M20 grade concrete in five
different proportions (0%, 0.5%, 1.0%, 1.5%, and 2.0%)

Results
Samples Compressive
Strength
Flexural
Tensile
Strength
Split Tensile
Strength
Compaction
Factor
M20 20 N/mm2 4 N/mm2 2.5 N/mm2 0.95
M20+ 0.5%S1 22.4 N/mm2 5.2 N/mm2 3.4 N/mm2 0.93
M20 + 1.0%S1 23.6 N/mm2 5.8 N/mm2 3.9 N/mm2 0.92
M20 + 1.5%S1 25.2 N/mm2 7.9 N/mm2 5.2 N/mm2 0.90
M20 + 2.0%S1 24.5 N/mm2 7.1 N/mm2 4.3 N/mm2 0.88
M20 + 0.5%S2 23.7 N/mm2 5.6 N/mm2 3.7 N/mm2 0.94
M20 + 1.0%S2 25.3 N/mm2 6.2 N/mm2 4.3 N/mm2 0.93
M20 + 1.5%S2 27.9 N/mm2 8.3 N/mm2 5.7 N/mm2 0.91
M20 + 2.0%S2 27.6 N/mm2 7.6 N/mm2 4.6 N/mm2 0.90
M20 + 0.5%S3 23.9 N/mm2 5.8 N/mm2 4.2 N/mm2 0.95
M20 + 1.0%S3 26.2 N/mm2 6.6 N/mm2 4.7 N/mm2 0.95
M20 + 1.5%S3 30.5 N/mm2 8.7 N/mm2 6.2 N/mm2 0.96

Stress – Strain Relationship

Discussions
 The results shown in the table indicates that the highest compressive
strength is obtained when M20 grade concrete is mixed with 1.5% of
hybrid fibers made up of 50% polypropylene and 50% steel fibers (Yet,
Hamid and Kasmuri, 2012).
 Both flexural and split tensile strength are also higher for the same
sample (i.e., the sample with 50% polypropylene and 50% steel fibers)
and it occurs when 1.5% of the sample is mixed with M20 grade
concrete.

Discussions Continued
 Compaction factor which indicates the workability of concrete is
also highest for the sample with 1.5% hybrid fiber and a percentage
of 50% steel fiber (Song and Yin, 2016) and 50% polypropylene.
 It could be seen from the graph that the stress-strain relationship is
also improved when 1.5% of hybrid fiber with a mixture of 50%
steel fiber and 50% polypropylene is used.

Discussions Continued
 Due to the addition of hybrid fibers there is a maximum
improvement of about 52.5% in the Compression Strength.
 The Flexural Tensile Strength has improved by a maximum of
117.5% due to the addition of hybrid fibers.
 The Split Tensile Strength has improved by a maximum of 148%
due to the addition of hybrid fibers.

Discussions Continued
 The workability of concrete decreases due to the addition of
polypropylene but improves due to the addition of steel fibers
(Razzak, and Ali, 2011).
 Addition of hybrid fibers improves the stress-strain characteristics
(Rizzuti and Bencardino, 2014). of M20 grade concrete.

Conclusion
 The best composition of hybrid fiber is 50% polypropylene with 50%
steel fiber as seen from the results shown above.
 Addition of 1.5% of hybrid fiber containing 50% polypropylene and
50% steel fiber improves the axial properties of M20 grade
concrete.
 Addition of hybrid fibers improves the compression strength,
flexural tensile strength and split tensile strength.

References
 de-Oliveira Jr., L.A. et al., (2010, July). Stress-strain curves for steel fiber-reinforced concrete in
compression. Matéria (Rio J.), 15(2), 1-4.
 Dharan, D.S. and Lal, A. (2016, June). Study The Effect of Polypropylene Fiber in Concrete.
International Research Journal of Engineering and Technology, 6(3), 616-619.
 Goyal, H. and Vikram, Er. (2017, March). An Experimental Study on Mechanical Properties of M20 &
M25 Grade Concrete with Addition of Glass Fiber. International Journal For Technological Research In
Engineering, 4(7), 1051-1056.
 Khan, I.K. and Jafri, M.S. (2015, January). Behaviour of SFRC with Varying Mixes and Percentages of
Fibres. International Journal of Research in Chemical, Metallurgical and Civil Engg., 2(1), 42-44.
 Kim, W., Kim, J. and Kwak, Y-K. (2016, November). Evaluation of flexural strength prediction of
reinforced concrete beams with steel fibres. Journal od Structural Integrity and Maintenance,
1(4), 156-166.
 Rai1, A. and Joshi, Y.P. (2014, May). Applications and Properties of Fibre Reinforced Concrete.
International Journal of Engineering Research and Applications, 4(5), 123-131.

References Continued
 Razzak, A.A.A. and Ali, A.A.M. (2011, June). Modelling and numerical simulation of high strength
fibre reinforced concrete corbels. Applied Mathematical Modelling, 35(6), 2901-2915.
 Rizzuti, L. and Bencardino, F. (2014, October). Effects of Fibre Volume Fraction on the Compressive
and Flexural Experimental Behaviour of SFRC. Contemporary Engineering Sciences, 7(8),
379- 390.
 Sofi, A. and Phanikumar, B.R. (2015, December). An experimental investigation on flexural
behaviour of fibre-reinforced pond ash-modified concrete. Ain Shams Engineering Journal,
6(4), 1133- 1142.
 Song, W. and Yin, J. (2016, August). Hybrid Effect Evaluation of Steel Fiber and Carbon Fiber on the
Performance of the Fiber Reinforced Concrete. Materials, 9(8), 1-8.
 Vairagade, V.S. and Kene, K.S. (2013). Strength of Normal Concrete using Metallic and Synthetic
Fibres. Procedia Engineering, 51, 132-140.
 Yet, T.C., Hamid, R. and Kasmuri, M. (2012, October). Dynamic Stress-Strain Behaviour of Steel
Fiber Reinforced High-Performance Concrete with Fly Ash. Advances in Civil Engineering.
Retrieved from http://dx.doi.org/10.1155/2012/907431 .