ASSESSING THE INFLUENCE OF HUMAN HAIR ON THE MECHANICAL PROPERTIES OF FIBRED REINFORCED CONCRETE MATRIX

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 6, June 2018, pp , Article ID: IJCIET_09_06_053 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed ASSESSING THE INFLUENCE OF HUMAN HAIR ON THE MECHANICAL PROPERTIES OF FIBRED REINFORCED CONCRETE MATRIX Rayed Alyousef Department of Civil Engineering, College of Engineering, Prince Sattam Bin Abdulaziz University, Al Kharj 11942, Kingdom of Saudi Arabia ABSTRACT For many reasons: economic, safety, etc., improvement in the mechanical properties of concrete structures has been an interesting research undertaking. Fibred reinforced concrete has emerged as a candidate that provides useful, practical and economic approach to overcome micro-cracks and other long and short-term shortcomings associated with a concrete matrix. Identifying the weakness of a concrete structure and its associated tension zone and having plastic shrinkage provides a basis to improve the mechanical properties of concrete. This study presents a detailed assessment of the impact of using human hair fibres (HHF) for such purposes. HHF is an alternative non-degradable material, strong in tension, abundantly available at a reasonable price. Typically, when added to concrete structures, fibres help to delay cracking, control shrinkage and reduce permeability of the concrete. Our study is primarily aimed at ascertaining improvements in mechanical properties of fibred reinforced concrete matrix in terms of compressive and flexural strengths as well as cracking patterns and mode of failure. Experiments were conducted on concrete cubes with varying percentage of HHF (up to a maximum of 3%) by weight of cement. Outcomes from the experiments carried out suggest increase in different properties of FRC as the amount human hair fibre reinforcement is increased. Overall, the outcomes validate the immense potentials of using HHF as suitable supplementary material for to improve mechanical properties as well as delay crack patterns in FRC structures. Key words: Human Hair Fibre (HHF), normal concrete, Fibred Reinforced Concrete (FRC), Mechanical properties. Cite this Article: Rayed Alyousef, Assessing the Influence of Human Hair on the Mechanical Properties of Fibred Reinforced Concrete Matrix, International Journal of Civil Engineering and Technology, 9(6), 2018, pp INTRODUCTION Fibred Reinforced Concrete (FRC) is concrete that comprises of fibrous materials used to enhance its structural integrity and serviceability performance [1, 2]. Use of fibres in concrete

2 Assessing the Influence of Human Hair on the Mechanical Properties of Fibred Reinforced Concrete Matrix reinforcement is not a new idea. Since decades ago, horsehair has been used with mortar and straw in mud bricks and blocks [3]. In the early 1900s, asbestos fibres were used in concrete and, since the 1950s, the concept of composite materials in the fields of construction and fibre reinforced concrete have become interesting research undertakings [3, 4]. Scientifically, composite material consists of mixtures of cement, mortar or concrete and discontinuous, i.e. discrete, uniformly dispersed suitable fibres. Whereas fibres are defined to include those from steel, glass, synthetic and natural materials, woven fabrics, continuous meshes, and long wires or rods are not deemed to be discrete fibres [3,5]. FRC encompasses short discrete fibres that are commonly uniformly distributed and randomly oriented [3]. Fibres are available in numerous forms and materials such as steel, glass, and natural fibres and synthetic such as polypropylene fibres. Each fibre is engraved with different properties, such as variable concrete contents, geometries, fibre materials, densities, distribution and orientation, which determine its FRC matrix [4, 5]. Additionally, because of these properties, some fibres exhibit greater impact, abrasion and shatter resistance in FRC than others [3]. Good fibres have decent adhesion within adaptable elasticity modulus and the concrete matrix [3]. As well as being well-matched with the binder (i.e. they should not be destroyed or attacked in the long term), good fibres should be fine, short and flexible to allow mixing, transporting and placing, and have enough strength to resist mixing process [4]. To further enhance the bond and stability between materials, the use of human hair fibre (HHF) can be considered in the design of asphalt cement mixture at a range from 2% to 6% by mass of bitumen [6]. For clarity, it should be emphasized that in this study a fibre is simply described as a small piece of reinforcing material capable of certain characteristics and/or properties. Such fibre is frequently defined by a suitable parameter, called aspect ratio [6, 7, 8-13], which is the ratio of its length to its diameter with typical ranges varying from 30 to 150. [5, 7-11]. Although fibres are generally used in concrete to avoid cracking due to plastic or drying shrinkage and to reduce the permeability of concrete, which leads to less bleeding of water [4, 7, 8-11], studies regarding the nominal percentages of hair imparting maximum strength to concrete is an open research area. Considering the impact of nominal percentage of hair on the different properties of concrete, it was reported in [11-14] that the distribution matrix of hair in concrete and the resultant matrix could affect the properties and the study of admixtures and super plasticizer which could distribute the hairs without affecting the properties of concrete is not studied yet. In this study, we focus on the use of HHF as a fibre reinforcing material in concrete to assess its impacts on the compressive, crushing and flexural strength as well as cracking control to economise concrete and to reduce environmental problems arising with the decomposition of the hair. The remainder of the paper is organised as follows: advances in HHF and FRC are highlighted in the next section. The methodology and experimental framework proposed to ascertain impact of human hair on various mechanical properties of fibred reinforced concrete are presented in Section 4. The outcomes are extensively discussed in Section OVERVIEW ON HUMAN HAIR FIBRE AND INFLUENCES ON FIBRED REINFORCED CONCRETE Hair is used as a fibre reinforcing material in concrete for several reasons for example, it has a high tensile strength which is equal to that of a copper wire with similar diameter, hair, a nondegradable matter is creating an environmental problem so its use as a fibro reinforcing

3 Rayed Alyousef material can minimize the problem, it is also available in abundance and at a very low cost, and it reinforces the mortar and prevents it from spalling Human Hair Fibre (HHF) Use of HHF to reinforce structural properties of concrete, enhance designs and performance of concrete is an innovative approach that has continued to gain significance in the world of concrete and modern constructions [3, 4, 8, 10-13]. Chemically, the composition of HHF is about 80% made up of a protein known as keratin, which has a high grade of sulfur created from the amino acid cysteine, characteristics that distinguish it from other proteins [1, 3-5, 10]. Keratin is a laminated complex formed by different structures, which gives the hair a cylindrical structure, strength, flexibility, durability, and functionality [1, 4, 6, 8-11]. Furthermore, most of hair fibres are keratinised and distributed following a very precise and pre-defined design [9, 10]. Hair forms a very stiff structure in the molecular level having the ability to offer the thread both flexibility and mechanical resistance [1-3, 6, 8-13]. Biologically, HHF is consists of three main structures: cortex, cuticle, and medulla [1, 3, 7, 10]. Proteins with α-helix structure that are wound in the hair have long filaments of unknown micro-fibres and are interlinked to one another to form bigger structures, producing cortex cells. This enchained structure provides the capillary fibre more strength and reasonable elasticity. Human hair has about 65-95% of its weight in proteins, while the remaining 35% is composed of water, lipid pigments and other mechanisms [6-9, 11-13]. An important property of the human hair is the high amount of the amino acid cysteine. The amino acid cysteine is may be degraded and afterwards may be re-oxidated under a disulphidic bounding form [10, 13]. Hair is remarkably strong. Cortex keratin is responsible for this chemical propriety and its long chains are composed to create a steady structure and being strong as well as flexible [10-13]. Physically, the proprieties of hair include: resistance to stretching, elasticity and hydrophilic power. On the basis of previous studies, a concrete mix design with HHF limited to 1% and 3% by weight of cement is adopted in this work Influences of different Fibres on the Properties of FRC The addition of fibres to enhance mechanical properties of concrete significantly depends on the type and percentage of fibre [1,6, 8, 9-11]. Fibres with end-anchorage and high aspect ratio were found to have improved effectiveness on the properties and applications of FRC [1, 2, 3-6, 10]. Similarly, splitting tensile strength was reported increase by more than twofold when unreinforced concrete with 3% fibre by volume is added [3, 8-13]. Additionally, the impact strength for FRC is found to be 5 to 10 times that of plain concrete depending on the volume of fibres, while the fatigue strength of FRC increased by around 90% and 70% of the static strength (at 2 x 106 cycles) for non-reverse and full reverse loading, respectively [2-3, 5, 7, 10, 12-13]. However, the compressive strength can be negatively influenced by addition of fibres when its increasing values were limited to 0 to 15%. Nevertheless, modulus of elasticity is observed to increase by 3% for each 1% increase in fibre content by volume, whereas the flexural strength increased by more than twofold when 4% fibre is used [3, 5-7, 10-12]. Also, increase in toughness is observed for increases in FRC by almost 10 to 40 times that of plain concrete [3, 8-13]. Furthermore, properties of concrete are affected by many other factors, such as properties of fine and coarse aggregate as well as cement. Meanwhile, in addition to the stiffness of relative fibre matrix, FRC is usually influenced by types of fibre, aspect ratio, quantity, and orientation of fibre. [1-2, 4, 8-11]

4 Assessing the Influence of Human Hair on the Mechanical Properties of Fibred Reinforced Concrete Matrix 3. METHODOLOGY AND EXPERIMENTAL LAYOUT The influence of HHF on the mechanical properties and strength of fibred reinforced concrete is assessed in terms of compressive, flexural and splitting tensile strength. This assessment is based on one hundred eighty concrete cubes. This section highlights the methodology and experimental frameworks adopted for the tests Properties of materials used In general, a mix design ratio of 1: 2.1: 3.85 for water, cement and sand: was used, while the water cement ratio is The remainder of this subsection enumerates details of the materials used Cement The typical cement used consists of mixture of siliceous, calcareous, aluminous substances and crushed clinkers of a fine powder. For this, ordinary Grade 40 Portland cement is used in this study. Its specific gravity is 3.15 with an initial setting time of about 45 minutes and final setting time of around 600 minutes Fine aggregate In the experiments presented in this study, sand having properties specified by the ASTM standards was sourced locally. Following that, the sand was sieved through 4.75 mm sieve holes, which removes any particles greater than the required value. This was subsequently washed to further remove dust particles. Overall, fine aggregates with fineness modulus and specific gravity of 3.35 and 2.65 kg/m 3 respectively was used Coarse aggregate Based on ACI 221 specification, the particles size of coarse aggregate should be greater than 4.75 mm [14]. Nevertheless, this is allowed to vary depending on nature of work. The coarse aggregate used in this experiment varies in size ranging from 20 mm, 16 mm and 12 mm; it is crushed and lanky in shape. Furthermore, dust particles were removed and the resulting coarse aggregates were used in the normal concrete with specific gravity of 2.74 kg/m Human hair fibres Earlier in Section 2, the general properties of HHF were highlighted. The specific properties of the human hair used in our experiments are tabulated in Table 1. The HHF was added at percentage differences of 1%, 2% and 3% by weight of cement in 40 grade concrete blocks. Then, the compressive, tensile and flexural strengths were compared with blocks from plain cement concrete. To clarify, throughout this study, 70 mm hair length is chosen because it provides mechanical interlinking and joining the hair lengths by the means of adhering lengths of hair together and treating the hair lengths so that they naturally tend to inter-engage with one another. This further helps to improve the desired tensile strength of hardened FRC matrix. Table 1 The properties of HHF Property Value Hair diameter 95 to 130 µm Hair length ~ 70 mm Aspect ratio Tensile strength of Human Hair fibre ~ 390 MPa Ultimate Tensile Strain 50.2%

5 Rayed Alyousef Water Based on ACI 523.3R-93 specification [15], it is recommended that the water used to make concrete should be clean, fresh and absolutely drinkable. Consequently, in keeping with this stipulation, water used in the experiments reported here conform to this and other ASTM standards for mixing and curing of concrete cubes FRC Mix Design Specifications The objective of setting limits to the proportion of constituent materials used in concrete mix design is determined based on their relative volumes to ensure strength, durability and workability of the concrete structure, within acceptable economic standards. In this study, concrete mix was designed in conformity with ACI [16] to achieve the required compressive strength of 40 MPa. Therefore, the design mix proportions of 40 grade concrete used in the study is presented in Table 2: Table 2 Example of concrete mix proportions Constituents Water Cement Fine aggregate Coarse aggregate Water-Cement Ratio Weight 100 kg/m kg/m kg/m kg/m Preparation of concrete cube specimens Casting and testing of cubic and beam specimens of standard size for compressive, flexural, and splitting tensile strength analysis were prepared and tested as per stipulations ASTM C39 [17], ASTM C78, and ASTM C496, respectively. Furthermore, all the test specimens were demodulated after 24 hours of casting Fresh and harden tests Workability Test The most general standard workability tests employed in fresh concrete are slump test and compaction factor tests that are carried out according to specifications provided in ASTM C143 [18]. These stipulations are aimed at assessing the workability of fresh concrete. However, it has been observed that the workability of concrete is reduced steadily with the increase in the percentage of HHF in concrete mix. In such instances, the compaction factor was found to be 0.82 and 90 mm slump value for concrete mix prepared. This further reduced until 1.5% volume (by weight) of cement of HHF was added into FRC. This then dropped unexpectedly after 3% volume of HHF was added into FRC was found to be unworkable. Therefore, for the purpose of our study, it was deemed that concrete reinforced with 1.5% of HHF was within acceptable workable conditions in comparison to the other higher values Compressive strength test As stipulated in ASTM C39, compressive strength of FRC is influenced by the wet-mixing time, curing time, temperature and the addition of the fibre additives. Cube specimens of standard size 150 mm 300 mm were used to study the compressive strength of our concrete samples. The cubes were positioned on the bearing surface of UTM testing machine of 100 tonnes capacity as demonstrated in Fig. 1. A uniform loading rate of 550 kg/cm 2 per minute was applied until final failure of the cube was observed. This was recorded as the maximum load and, using it, the compressive strength was experimentally determined (or computed theoretically using Eq. (1)). Cube compressive strength (f ck ), MPa, σ = (1)

6 Assessing the Influence of Human Hair on the Mechanical Properties of Fibred Reinforced Concrete Matrix where; P is the cube compression load in N and A is the area of the side of cube in mm 2. Figure 1 The 100 tonnes kn UTM compressive machine Flexural strength test ASTM C78 stipulates that flexural strength of FRC can be greatly enhanced by incorporating different types of short synthetic fibers such as polypropylene, and fibers through a bridging effect. This can be done during the micro- and macro-cracking of the FRC matrix under flexure. However, it was/has been observed that any further addition of fibers tends to reduce flexural strength. Normal concrete beams and human hair reinforced concrete beams of size 150 mm 150 mm 700 mm were tested using a flexure testing machine. The specimen was simply supported on two rollers separated 600 mm apart and a bearing of 50 mm from each support as shown in Fig. 2. Figure 2 Typical flexure test frame and setup of the one-way slab The flexure loads were applied as two-line lateral loads, while a hydraulic jack was applied on a load cell activated by a manually operated pump. The applied load was transferred from the jack as a one-point load, which was then distributed into a two-line load across the specimen width using a spender beam (I-beams). The load is applied at a uniform rate of 4 KN/min with the extreme fibres stress increasing at 0.7 N/mm 2 /min until the specimen failure is observed. At this point, the modulus of rupture can be calculated using Eq. (2). The modulus of rupture is calculated using the formula, MPa, σ b = (2) Splitting tensile strength test The splitting tensile strength (ASTM C496) is among the basic and important properties where the concrete is very weak in tension due to its brittle nature and is not expected to resist the direct tension. Normal cylinder specimens and human hair reinforced concrete cylinders

7 Rayed Alyousef of size 300 mm (height) 150 mm (dia) are cast, cured and tested. The test is carried out by positioning a cylindrical specimen in horizontal direction between the loading surface of a compression testing machine and the load applied until the failure of the cylinder is observed. This experimental set up is presented in Fig. 3. However, when the load is applied along the matrix of the cylinder; the horizontal stress is generated, as shown in the equation (3). σ b = (3) where P is the compressive load on the cylinder in N, Lis the length of the cylinder in mm and d is the diameter of the cylinder also in mm. Figure 3 Splitting tensile strength test 4. DISCUSSION AND ANALYSIS OF RESULTS Based on the outline of the experimental framework discussed in the preceding section, here we present a discussion on the results obtained and conclude by presenting a few insights into possible applications and improvements to use human hair fibre. First, we present a summary of the results obtained. Table 3 presents the results of the tests performed on cubes for the compressive, flexural and splitting tensile strength analysis respectively, using the same mix design proportions of concrete, but varying percentages of HHF by the weight of cement used Mechanical properties tests As mentioned earlier, the mechanical properties included in the study are compressive, flexural, and splitting tensile strength which are tested on cubes cast using Grade 40 concrete - with and without HHF as fibre reinforcement. However, the percentage of HHF is varied from 1% to 3% over 1% increments in each batch. Furthermore, tests were conducted at different curing periods of 1, 3, 7, 14 and 28 days to ascertain the influence of such variations in curing periods on the mechanical properties of test cubes Compressive strength test The quantity of HHF is evenly added into the concrete mix manually. From the analysis of the results, it can be observed that mixing of human hair in the concrete to accomplish similarity is a problem at concentration above 2% of HHF in comparison to using control samples which causes lumping and balling of HHFs (Table 3]. It is found an ultimate influence on the mechanical properties of the concrete that is basically meant in this study. However, a gradual increase in the mechanical properties was observed as up to 3% of human hair was added. Unlike curing times reported in Table 3 and Fig. 4, beyond this point, not much declining trend was observed. This decreasing phenomenon may be attributed to lumping and balling on

8 Compressive strength (in MPa) Assessing the Influence of Human Hair on the Mechanical Properties of Fibred Reinforced Concrete Matrix the compressive strength as seen from the results obtained. In addition to impacting numerous properties of concrete, such as compressive and splitting tensile strength, addition of HHFs to the concrete not only improves the binding properties, controls micro-cracks and also enhances spalling resistance. Furthermore, width of the cracking patterns is seen to decrease as does the rate of compressive strength (which decreases by between 5 to 8.5%) in comparison with splitting tensile strength (which decreases from 12 to 25%) and flexural strength (from 18 to 26%). This observation could be attributed to the change in the behavior of the concrete with the addition of HHF as reinforcement fibres. As reported in Agrawal et al. (2016) [19], adding human hair with different precentage. To provide a common platform for comparison with such studies, human hair was added to the mix the compressive strength increased compared with conventional concrete. For example, at 7 and 28 days curing period 6.29% and 9.18% compressive strength increment were observed when compared with conventional mix. Nevertheless, an improvement in strength of concrete was observed by adding human hair as fiber reinforcement in concrete mix. Table 3 Compressive strength at different curing time (in N/mm 2 ) Compressive strength (in N/mm 2 )* Time Control 1% HHF 2% HHF 3% HHF (days) Experiments [*] Experiments [*] Experiments [*] Experiments [*] Compressive Strength vs Time Curing time (in days) Control 1% HHF added 2% HHF added 3% HHF added Agrawal-Control Agrawal - 1% Agrawal - 2% Agrawal - 3% Figure 4 Compressive strength at different curing time (in N/mm 2 ) Flexural strength test Based on the results of flexural strength test in Table 4 or Fig. 5, it is observed that after the maximum load is reached, the beam specimens failed due to bending compression. From this test, significant increase in properties of concrete based on the percentages of HHFs by weight of cement in concrete can be inferred. However, it instructed ductility to a positive extent that can be seen in experimental testing of beams. The beam tends to bend, thereby providing a warning well before failure, which helps to enhance the safety of users. As the percentage of

9 Flexural strength (in kn) Rayed Alyousef HHF increases, an increase of up to 2% in strength is observed, after which a decline sets in. This suggests the onset of absorption of water by human hair, which can go as much as 30% of its own weight and even as high as 40-45% of its weight if impure. Therefore, when addition of HHFs to concrete is not sufficiently used by the cement it rapidly increases the ratio of unhydrated cement. This leads to a decline in strength and the structure becomes weak. For cubes that proportion of concrete with 2% HHF increases of 16% and 6% in flexural strength are obtained for such samples and the control specimens, which outperforms similar specimens of concrete mixture without HHFs and the control concrete specimens whose flexural strength is 2% and 3%, respectively. However, for concrete specimens with 1% HHF, it is observed that there is little increase in flexural strength at both 7 and 28 days from the date of casting in comparison with the control specimens. Interestingly, however, an increase of about 4% in flexural strength is observed as the volume of HHF is increased from 1% to 2% and from 2% to 3%. Therefore, it could be inferred that the addition of HHF as reinforcement fibres does not significantly impact on the flexural strength except in terms of delaying the initial cracking along the beam span under three points load testing condition. The study in [19] reported a 3% increase when hair was added to the mix the flexural strength compared with conventional concrete. For comparison sake, at 7 and 28 days curing period we observed 6.82% and 6.55% increases in flexural strength for our proposed approach in comparison with conventional concrete mix. However, it should be noted that strength of concrete was improved by adding human hair as fiber reinforcement in concrete mix. Table 4 Flexural strength at different curing time (in kn) Compressive strength (in N/mm 2 )* Time Control 1% HHF 2% HHF 3% HHF (days) Experiments [*] Experiments [*] Experiments [*] Experiments [*] Flexural Strength vs Time Curing time (in days) Control 1% HHF added 2% HHF added 3% HHF added Agrawal - control Agrawal - 1% Agrawal - 2% Agrawal - 3% Figure 5 Flexural strength at different curing time (in kn) Splitting tensile strength test To assess further assess the influence of human hair in mechanical properties of reinforced concrete, in this subsection we present tests on splitting tensile strength as well as investigations into the impact of curing periods on the test samples. As highlighted in previous sections, our test specimens consist of Grade 40 concrete with and without addition

10 Splitting tensile strength (in kn) Assessing the Influence of Human Hair on the Mechanical Properties of Fibred Reinforced Concrete Matrix of human hair as fibre reinforcement. For the former, we further varied the amount of hair fibre from 1% to 3%. These samples indicate that the presence (1% and 3%) of HHFs by volume of cement increased the splitting tensile strength of mortar by about 7% and 22% compared to the control (unreinforced) specimen at 28 days. Furthermore, it was observed that, when compared with the control specimens, Grade 40 concrete with 2% HHF presents an increase of 14%, 12% and 15% in flexural strength over 3 days, 7 days and 28 days curing periods, respectively (Fig. 6). Similarly, 14% improvement in splitting tensile strength due to the fibre addition was observed with increase in HHF from 1% to 3%. Meanwhile, the optimum fibre volume fracture was seen to vary between 0.6 to 0.8% with ductility factor as fibre content was increased. Thus, suggesting that addition of HHFs could be helpful in curtailing the effects of seismic forces on building structures. Additionally, by comparing the results obtained alongside those in [20] (which reported increase in the split tensile strength that when human hair was added to the mix compared with conventional concrete), we observe 6.76% and 6.98% increase in flexural strength at 7 and 28 days curing period in comparison with conventional (control) mix respectively. Based on these results, it can be further established that improvement in strength of concrete is achievable by adding human hair as fiber reinforcement in concrete mix. Table 5 Splitting tensile strength at different curing time (in kn) Compressive strength (in N/mm 2 )* Time Control 1% HHF 2% HHF 3% HHF (days) Experiments [*] Experiments [*] Experiments [*] Experiments [*] Splitting Tensile Strength vs Time Curing time (in days) Control 1% HHF added 2% HHF added 3% HHF added Kumana - control Kumana - 1% Kumana - 2% Kumana - 3% Figure 6 Splitting tensile strength at different curing time (in kn) 5.2. Type of cracking and mode of failure A crack on a concrete structure, also known as a break, split, fissure, fracture, separation, joint or cleavage, is an elongated, narrow opening observable to the normal human eye and is extended from the surface into another zone. For load bearing reinforced concrete member,

11 Rayed Alyousef cracks are classified according to the extent of damage. Cracks with a width of 5 mm can be repaired either by cement grouting or use of steel wire meshes that could be inserted into the cracks. Fig. 7 presents different cracks when fibre reinforced concrete is used. As seen therein, crack formation and propagation decrease because fibres can form a strong bond with the concrete mix and also bridge the cracks to some extent. Based on these results (Fig. 7), and other tests presented in earlier parts of this study, it can be observed that severity of cracks was significantly reduced in cubes with reinforced with HHF than those without HHF reinforcement. (a) Splitting tensile test failure (b) Compressive test failure (c) Flexural test failure Figure 7 Cracking patterns and mode of failure at different testing condition 5. CONCLUDING REMARKS An assessment of the impact of reinforcing concrete structures with human hair fibre (HHF) is presented in this study. Specifically, the impact of adding these fibres on the mechanical properties of concrete matrix was assessed from different perspectives. Results of tests undertaken suggest remarkable increment in compressive, flexural, and splitting tensile strength as the percentages of human hair fibres added by weight of cement was increased to the mixture. Further investigations also show an impact on curing times for specimens of Grade 40 concrete specimens with HHF gradually varied from 1% to 3% as well as without human hair as fibre reinforcement. However, declines in compressive strength (about 5 to 8.5%) were observed in comparison to 12 to 25% in splitting tensile strength and 18 to 26% in flexural strength. This could be attributed to changes in the behavior of the concrete as HHF is added as reinforcement fibres. Additionally, it was observed that the size (by width) of cracking patterns in the specimens decreased towards the final failure of the test sample, i.e. loss of its ultimate strength capacity. Among others, the study validates earlier claims suggesting use of human hair fibres as suitable supplementary material for FRC for enhanced mechanical properties as well as delaying problems related to cracking patterns in concrete structures. Additionally, the study establishes that improvements in strength of concrete structures is achievable by adding human hair as fiber reinforcement

12 Assessing the Influence of Human Hair on the Mechanical Properties of Fibred Reinforced Concrete Matrix ACKNOWLEDGMENTS The author gratefully acknowledges contributions from technical staff of the Structure s Laboratory at the Department of Civil Engineering, Prince Sattam Bin Abdulaziz University, Al Kharj, Kingdom of Saudi Arabia. REFERENCES [1] Majumdar A.J. Fibre cement and concrete -a review garston. Building research establishment, (1975). [2] Achal Agrawal, Abhishek Shrivastava, Siddharth Pastariya, and Anant Bhardwaj. A concept of improving strength of concrete using human hair as fiber reinforcement. International Journal of Innovative Research in Science, Engineering and Technology, 5(5), (2016) [3] T. Naveen Kumar, Komershetty Goutami, Jinna Aditya, Kuppala Kavya, V.Raja Mahendar, R.C.Reddy [4] and Shweta kaushik. An experimental study on mechanical properties of human hair fibre reinforced concrete (M-40 Grade). Journal of Mechanical and Civil Engineering (IOSR- JMCE), 12(4), (2015) [5] Sinan Abdulkhaleq Yaseen. An experimental investigation into the mechanical properties of new natural fibre reinforced mortar. Eng. and Tech. Journal, Vol. 31, Part (A), No.10, (2013). [6] Jain D. and Kothari A. Hair fibre reinforced concrete. Research Journal of Recent Sciences, Vol. 1, (2012) [7] Tomas U. Ganiron Jr. Australian Institute of Geoscientists. Effects of human hair additives in compressive strength of asphalt cement mixture. International Journal of Advanced Science and Technology, Vol.67, (2014) [8] A.S.Balaji and D.Mohan Kumar. Laboratory investigation of partial replacement of coarse aggregate by plastic chips and cement by human hair. International Journal of Engineering Research and Applications, 4(4), (2014) [9] Mishra, Shubham. Nanoindentaion and tensile testing of human hair fibres. Journal of Materials Science (2016): [10] Sen, Tara, and HN Jagannatha Reddy. Various industrial applications of hemp, kinaf, flax and ramie natural fibres. International Journal of Innovation, Management and Technology 2.3 (2011): 192. [11] Verma, A., V. K. Singh, S. K. Verma, and A. Sharma. Human Hair: A Biodegradable Composite Fiber A Review. Int J Waste Resour 6, no. 206 (2016): 2. [12] Ahmad, S., Ghani, F., Akhtar, J. N., and Hasan, M. (2009). Use of waste of human hair as fibres reinforcement in concrete. IEI Journal, 91. [13] Bore, Pierre, Jean-Claude Arnaud, and Gregoire Kalopissis. Process for improving the quality of living, human hair by lanthionization. U.S. Patent No. 3,971, Jul [14] Formanek, F., De Wilde, Y., Luengo, G. S., & Querleux, B. (2006). Investigation of dyed human hair fibres using apertureless near field scanning optical microscopy. Journal of microscopy, 224(2), [15] The ACI committee 221. Guide for use of normal weight aggregate in concrete. ACI 221R.89, reapproved 1994, ACI, Farmington Hills, Michigan, (1994)

13 Rayed Alyousef [16] ACI Committee 523. Guide for cellular concretes above 50 pcf, and for aggregate concretes above 50 pcf with compressive strengths less than 2500 psi. ACI Journal Proceedings; Vol. 72, No. 2 (1975). [17] The ACI committee Recommended practice for selecting proportions for normal and lightweight concrete. ACI standard, Farmington Hills, Michigan, (1977). [18] ASTM C39/ C39M 17b. Standard test method for compressive strength of cylindrical concrete specimens. ASTM international, (2017). [19] ASTM C143/ C143M 15a. Standard test method for slump of hydraulic-cement concrete. ASTM international, (1959). [20] Achal Agrawal, Abhishek Shrivastava, Siddharth Pastariya,Anant Bhardwaj. A Concept of Improving Strength of Concrete using Human Hair as Fiber Reinforcement. International Journal of Innovative Research in Science, Engineering and Technology. Vol. 5, Issue 5, (2016). [21] M. Kumanachakravarthi and M.Sivaraja. Human Hair as Fiber Reinforcement in Concrete. Advances in Natural and Applied Sciences. 11(8);