Effect of Synthetic Hair Fibre Additions on the Strength Characteristics

Adedokun

USEP: Journal of Research Information in Civil Engineering, Vol.13, No.2, 2016

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Effect of Synthetic Hair Fibre Additions on the Strength Characteristics of Concrete 1,2,3

S. I. Adedokun1, S. O. Ajamu2 and H. T. Aderinto3 Department of Civil Engineering, Ladoke Akintola University of Technology, Ogbomoso. Nigeria. 2 Corresponding Author e-mail: [email protected]

Abstract Extensive research has been carried out on the use of different kinds of fibres to improve the characteristics of construction materials. However, literature is scarce on the use of synthetic hair fibre for similar purposes. In this study, effect of synthetic hair fibre addition on the strength of concrete was examined. The synthetic hair fibres were added to the concrete in various percentages by mass of cement from 0% to 6% in intervals of 2%. The impacts of the fibre addition on the workability of concrete were investigated through slump and compacting factor tests. The compressive strength, split tensile strength and density tests were also conducted on each of the test specimens after 7, 14, 21 and 28 days curing, respectively. The results obtained from both the slump and compacting factor tests showed that the workability increased with the addition of fibres with compacting factor and slump increasing from 0.86 to 0.9 and 17 to 25 mm respectively. The fibre additions also increased the compressive and split tensile strengths with increasing days of curing from 0% to 2% but decreased for higher hair fibre contents with days of curing. It was also observed from the results that the density of concrete at 28days decreased with increase in hair contents. Based on this study, addition of 2% hair fibre by weight of the cement is therefore recommended as the optimum value for improving the compressive and tensile strength of the concrete.

Keywords Synthetic hair fibre, concrete, workability, split tensile strength, compressive strength, density.

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1. Introduction The concept of using fibres to improve the characteristics of construction materials is very old. Early applications include addition of straw to mud bricks, horse hair to reinforce plaster and asbestos to reinforce pottery (Balaguru and Shah, 1992). Use of continuous reinforcement in concrete (reinforced concrete) increases strength and ductility, but any presence of crack in concrete leads to corrosion of the steel. Alternatively, the introduction of fibres in discrete form in plain or reinforced concrete may provide a better solution. Hairs are used as fibre reinforcing materials in concrete to study its effects on the compressive, crushing, flexural strength and cracking control to economize concrete and to reduce environmental problems created by the decomposition of hair (Popescu and Hocker, 2007; Jain and Kothari, 2012; Pawar et al, 2015). Ganiron (2014) also stated that human hair is strong in tension and can be used as a fibre reinforcement material. It is an alternate non-degradable matter that is available in abundance at a little or no cost, and it also creates environmental problem for its decompositions. Hair can be used as a fibre material in concrete because of its high tensile strength which is equal to that of a copper wire with similar diameter. Because of the non-biodegradable nature of the hair, they can only be disposed of in an economical way by consigning them to landfill and as such they are relatively environmentally unfriendly (Li, 1998; Ganiron, 2014). Therefore there is need to effectively utilize these hair fibres in an economical and environmentally friendly ways, and one of such ways is to incorporate them into the concrete as admixtures. In addition, it is very obvious that concrete is weak in tension and hence some measures must be adopted to overcome this deficiency. A way of overcoming this is by introducing hair fibre, which is strong in tension and readily available in large quantity, into the concrete. Fibre reinforced concrete has been reported to be convenient, practical and economical method of overcoming microcracks and other deficiencies in concrete (Pawar et al, 2015; Nila et al, 2015). Most of the existing studies (Shakeel et al, 2009; Ahmed et al, 2011; Ganiron, 2014) on the use of hair fibre in concrete are limited to human hair and its effect on compressive strength but this study examined the influence

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of synthetic hair fibre on the workability, compressive strength, split tensile strength and density of concrete. In Nigeria, there are a lot of salon and manicure centres springing up in almost all the shopping complexes throughout the country and the huge waste materials coming from these centres are the used synthetic hairs. This study therefore focused on the reuse of these synthetic hair fibres in concrete production, so as to reduce the waste and at the same time improving the strength of the concrete.

2. Material and Method 2.1 Materials The materials used in this study were coarse aggregate, fine aggregate, cement and synthetic hair fibre. The coarse aggregate (Granite) was obtained from a quarry site located at Gambari, Ogbomoso while fine aggregate was collected from Oba River along Oyo road, Oyo State. The synthetic hair fibre shown in Figure 1 was taken from dumping sites and hair dressing shops in Ogbomoso. The cement was Dangote cement purchased from a local retail marketer in Ogbomoso metropolis.

Figure 1 Synthetic hair fibre used in this study

2.2 Experimental tests Experimental tests on the aggregates, fresh and hardened concretes were conducted at the Structural Laboratory of the department of Civil

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Engineering, LAUTECH, Ogbomoso, Nigeria. The various tests conducted are discussed below. Sieve analysis: Sieve analysis was carried out for both coarse and fine aggregates. For fine aggregates, the sample was sundried for twenty four hours to prevent clogging which might occur as a result of the presence of moisture. 500 grams of the dried sample was measured using weighing balance and was transferred through sets of sieves that had already been arranged in order of aperture sizes, with the biggest aperture size at the top. The sieves were covered and mounted directly on the mechanical shaker. The power was switched on for five minutes so as to allow the sand of different grain sizes to pass through and retain on the sieves. The samples retained on each sieve were collected and recorded. The procedure was also repeated for coarse aggregates except that sieving was carried out for ten minutes. Batching and mixing: Batching by weight was used in this study because of its simplicity and accuracy as compared to batching by volume, and this was carried out for design mix of 1:2:4. The hair fibres were cut into 10mm lengths, and were batched in percentage by weight of the cement. The percentages of hair adopted are 0, 2, 4 and 6%, and were thoroughly mixed with the concrete. For 0%, fine aggregate was first mixed with cement on a concrete platform until there was a uniform mixing; coarse aggregate was then added and mixed until a uniform distribution of particles was attained. After this, water cement ratio of 0.6 was added and mixed until there was a uniform distribution of aggregate and a desired consistency was attained. However for 2 and more percentages of fibre additions, fine aggregate and hair fibre were first mixed with cement on a mixing platform until there was a uniform mixing; coarse aggregate was then added and mixed until a uniform distribution of particles was attained. After this, water cement ratio of 0.6 was added and mixed until there was a uniform distribution of aggregate and a desired consistency was attained. Workability tests: Slump and compacting factor tests were conducted on fresh concrete to investigate the effect of synthetic hair fibre on the workability of concrete (Figure 2). Slump test was carried out by filling the truncated cone to one-fourth of its height and compacted with tapping rod twenty five times. The force with which the compaction was carried out is such that the rod penetrates the full depth to be compacted. The other three layers were compacted in the same manner. After compaction of the top

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layer, the cone was filled up to the top and levelled using hand trowel then it was removed, the vertical settlement of the cone is the slump of the mix. For compaction test, the cylindrical mould was weighed and then placed under the hopper. The top hopper was filled and the hinged bottom was released to let the concrete fall from the specific height to the lower hopper. The door of the lower hopper was then released to allow the concrete falls on the cylindrical mould placed below it. The surplus concrete from the mould was removed and levelled using hand trowel. The concrete was then weighed as the partial compaction weight. After this, the cylindrical mould was filled with concrete and compacted in three layers after which it was levelled. The concrete was then weighed as the full compaction value. The compacting factor value was then obtained as the ratio the partially compacted weight to that of fully compacted weight.

(a) (b) Figure 2 Slump cone (a) and compacting factor apparatus used for workability test (b) Casting and curing: The concrete specimen were cast into the 150 mm x 300 mm cylindrical moulds (Figure 3) and compacted for thirty five strokes using a standard compacting rod. The top layer was levelled with hand trowel and smoothened for some time and then labelled accordingly. The cylinders were left undisturbed for 24 hours. After this period, the moulds were stripped and the curing of the concrete which is an exercise of complete hydration of cement in the hardened concrete was done after 24 hours of

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casting for each sample. The operation was done using curing tank at the structural Laboratory in accordance with BS 1881 and curing periods of 7, 14, 21 and 28 days were adopted. Split tensile and compressive strength tests: The mass and dimensions of the specimen were noted before testing, the sides of the specimen lying in the plane of the pre-marked lines were measured near the ends and middle of the specimen. The bearing surface of the testing machine was wiped clean and the test specimen was placed in the centering jig. The jig which comprises of two packing strips and a steel loading plate which was used between the platen of the machine and the hardboard packing strip, with loading pieces carefully positioned along the top and bottom of the plane of the cylinder. The steel loading strip was of a rectangular cross section. The load was applied on the loading strip in such a way that the fracture plane will cross the trowelled surface.

(a) (b) Figure 3: The concrete specimen (a) and its failure pattern on the compression machine (b) The load was applied without shock and increased continuously at a nominal rate. The failure pattern of the concrete specimen is shown in Figure 3. The compressive strength test was done along with the split tensile strength. Density test: The effect of the hair fibre on the density of concrete was also investigated by determining the ratio of the mass of the concrete specimen to its volume.

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3. Results and Discussion 3.1 Sieve analysis Figure 4 shows the particle size distribution curve for both coarse and fine aggregates. The coefficient of uniformity, coefficient of curvature and fineness modulus for the fine aggregate was 3.15, 1.09 and 3.97 whereas those of coarse aggregate were 1.86, 1.00 and 4.34 respectively.

(a)

(b) Figure 4 Sieve analysis fine aggregate (sand) (a) and coarse aggregate (granite) (b) It can be observed from the Figure 4 that the fine aggregates were sandy soil with the presence of fine gravel size which provides strong affinity for gripping with lesser binding materials. The particle size of the fine materials

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falling within the final limit of grading zone 2 (BS 882: Part 3) is also an indication that the material is sandy soil. In the grading of the coarse aggregate, particle size of 13.2 mm was seen to dominate the aggregate type and it was used for the study. 3.2 Aggregate impact test The results of the aggregate impact test conducted showed that the coarse aggregate is tough and suitable for the purpose of this study. The average aggregate impact value was 20.96. This value fell between 0 and 35, which is an indication of a normal aggregate. 3.3 Workability test Workability of the fresh hair fibre concrete was investigated using slump and compacting factor tests (Table 1). For slump test, the result showed that the slump value increased from 17 mm to 25 mm for 0% - 4% fibre but decreased to 20 mm for 6% hair fibre content. It can also be inferred that 0% - 6% fibre additions gave true slumps, which is an indication of adequate cohesion in the mix. Workability of the concrete increased with increasing hair fibre contents from 0% - 4% because the higher the slump the higher the workability (Neville, 1990). The results of compacting factor test revealed that the compacting factor increased (0.86-0.9) with the addition of hair fibre though the value was 0.9 for all hair fibre modified concretes.

Hair percentage 0 2 4 6

Table 1 - Results of slump and compacting factor tests Slump (mm) Partial Full Compacting compaction compaction factor 17 15 17.5 0.86 18 16.2 18 0.9 25 15.4 17.2 0.9 20 15.8 17.6 0.9

3.4 Compressive strength test Figure 5 shows the relationship between the compressive strength and percentage of hair fibre at different curing ages. For 0% - 2% fibre additions, the compressive strength of concrete increased with increasing age of curing and hair fibre content. However for hair fibre additions above 2%, the compressive strength of the concrete decreased with increase in both curing age and hair contents. This is an indication that addition of synthetic hair

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fibre to concrete can improve its compressive strength up to 2% by weight of cement but reduced the strength of concrete beyond this limit.

Figure 5 Relationship between compressive strength and curing days of concrete 3.5 Split tensile strength test Figure 6 presents the relationship between the split tensile strength and percentage of hair fibre at different curing ages of concrete. Similar to that of compressive strength test, the split tensile strength of concrete for 0% - 2% fibre additions increased with increasing age of curing and hair fibre content. But for hair fibre additions above 2%, the tensile strength of the concrete decreased with increase in both curing age and hair contents. This also shows that addition of synthetic hair fibre to concrete can increase its tensile strength up to 2% by weight of cement but reduced the strength of concrete beyond this limit. It can be clearly seen from this study that synthetic hair fibre has significant effect on both the compressive and tensile strengths of concrete.

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Figure 6 Relationship between split tensile strength and curing days of concrete 3.6 Density test The effect of hair fibre on the density of the concrete was also investigated after 28days of curing. The ratio of the mass of concrete cylindrical specimen to its volume was determined and presented as shown in Figure 7.

Density (kg/m3)

2700 2600 2500 2400 2300 2200 2100 Figure 7 Relationship between density and hair fibre on concrete

0% after 28days 2%curing.

4%

Hair fibre content 937

6%

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The results showed that concrete density decreased with increase in the percentage of synthetic hair fibre, which gives an indication that the higher hair content the lower the density. This suggests that hair fibre can be effectively used to produce light weight concretes with increased strength.

4. Conclusion The effect of synthetic hair fibre on the strength characteristics of concrete was investigated with the following conclusions drawn from the study. 1. The results of the investigation showed that synthetic hair fibre had significant effect on workability, compressive strength, split tensile strength and density of concrete. The slump value of the concrete increased from 17 mm to 25 mm for 0% - 6% fibre additions with 4% fibre showing the highest slump. The compacting factor of concrete also increased from 0.86 for 0% hair fibre to 0.9 for all hair fibre contents. The two tests indicated that workability of concrete increased with the addition of synthetic hair fibre. 2. The compressive and split tensile strengths of concrete increased with increasing hair fibre content from 0% - 2% but decreased beyond this value. This shows that the optimum compressive and split tensile strengths in concrete were achieved with 2% synthetic hair fibre additions. 3. The study also showed that density of concrete after 28days curing decreased with increase in the percentage of synthetic hair fibre, which gives an indication that the higher the hair content the lower the density. This suggests that hair fibre can be effectively used to produce light weight concretes with increased strength. 4. Based on this study, synthetic hair fibre up to 2% addition by weight of cement is therefore recommended for improving the workability, compressive and split tensile strengths, and to reduce density of concrete. The concrete produced with this fibre can thereby be utilized as light weight concrete with increased strength.

References Ahmed, S., Ghani, F. and Hasan, M. (2011) Use of Waste Human Hair as Fibre Reinforcement in Concrete, IEL Journal, 91, pp.43. Available from: https://www.tib.eu.

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Balaguru, P. N. and Shah, S. P. (1992), Fibre Reinforced Cement Composites, Mc Graw Hill International Editions. British Standard Institution (1983), Testing concrete: Method for making test cubes from fresh concrete (BS 1881 -108), British Standard Institution, London, United Kingdom. British Standard Institution (1992), Specification for aggregates from natural sources for concrete (BS 882 -3), British Standard Institution, London, United Kingdom. Ganiron, T. U. (2014), Effects of Human Hair Additives in Compressive Strength of Asphalt Cement Mixture, International Journal of Advanced Science and Technology, 67, 11- 22. www.sersc.org/journals/IJAST/vol67/2. Jain, D. and Kothari, A. (2012), Hair Fibre Reinforced Concrete, Research Journal of Recent Sciences, 1, 128-133. Available from: www.isca.in/rjrs/archive/iscsi/21.ISCAISC-2011-7EngS-12. Li, G. (1998), Experimental Study of Cement – Asphat Mortar Emulsion Composite, Cement and Concrete Research, 28(5), 635-640. lejpt.academicdirect.org/A17/047_058.htm. Neville, A.M. (1990) Properties of Concrete, Longman Scientific and Technical, London. Nila, V. M., Raijan, K. J., Susmitha, A., Riya, B. M. and Neena, R. D. (2015), Hair Fibre Reinforced Concrete, International Journal of Advent Technology, Special Issue, pp 60-67. Available from: www.ijrat.org/downloads/tasc15/TASC%2015-205. Pawar, L. B., Bhirud, Y. L. and Yeole, P. M. (2015), Effect of Natural and Artificial Fiber on Concrete, International Journal of Modern Trends in Engineering and Research, 2 (7), 594 – 597. Available from: www.ijettjournal.org. Popescu, C. and Hocker, H. (2007), Hair the Most Sophisticated Biological Composite Material, Chemical Society Reviews, 37 (8), 1282-1291. Available from: https://pschemistry.files.wordpress.com/2011/06/group1hairchemistry1.pdf. Shakeel, A. Farrukh, G. J., Akhthar, N. and Hasan, M. (2009), Use of Waste Human Hair as Fibre Reinforcement in Concrete, International Symposium on innovation and sustainability of structures in Civil Engineering, Guangzhou, China.

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