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International Journal of Civil Engineering and Technology (IJCIET)

Volume 9, Issue 6, June 2018, pp. 459–471, Article ID: IJCIET_09_06_053

Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=9&IType=6

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

© 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. 459–471.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=9&IType=6

1. 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

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 5.

2. 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 non-

degradable matter is creating an environmental problem so its use as a fibro reinforcing

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.

2.1. 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.

2.2. 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].


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.

3.1. 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 0.47. The remainder of this subsection enumerates details of the

materials used.

3.1.1. 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.

3.1.2. 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/m3 respectively was used.

3.1.3. 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/m3.

3.1.4. 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 550 – 650

Tensile strength of Human Hair fibre ~ 390 MPa

Ultimate Tensile Strain 50.2%

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3.1.5. 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.

3.2. 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 211.1 [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/m3 210 kg/m

3 135 kg/m

3 250 kg/m

3 0.47

3.3. 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.

3.4. Fresh and harden tests

3.4.1. 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.

3.4.2. 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/cm2 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 (fck ), MPa, σ =

(1)


Concrete Matrix


where; P is the cube compression load in N and A is the area of the side of cube in mm2.

Figure 1 The 100 tonnes kN UTM compressive machine

3.4.3. 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/mm2/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, σb =

(2)

3.4.4. 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

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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).

σb =

(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.

4.1. 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.

4.1.1. 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


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/mm2)

Time

(days)

Compressive strength (in N/mm2)*

Control 1% HHF 2% HHF 3% HHF

Experiments [*] Experiments [*] Experiments [*] Experiments [*]

1 11.4 - 13.3 - 13.7 - 12.8 -

3 24.5 - 29.4 - 27.6 - 25.1 -

7 35.4 14.46 40.3 14.53 38.8 14.77 36.2 14.85

28 43.1 17.50 48.1 17.54 46.4 17.85 44.3 21.67

Figure 4 Compressive strength at different curing time (in N/mm2)

4.1.2. 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

0

10

20

30

40

50

0 3.5 7 10.5 14 17.5 21 24.5 28

Com

pre

ssiv

e st

rength

(in

MP

a)

Curing time (in days)

Compressive Strength vs Time

Control

1% HHF added

2% HHF added

3% HHF added

Agrawal-Control

Agrawal - 1%

Agrawal - 2%

Agrawal - 3%

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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)

Time

(days)




1 - - - - - - - -

3 - - - - - - - -

7 3.9 3.52 4.2 3.58 4.6 3.6 4.4 3.64

28 4.8 5.19 4.9 5.27 5.1 5.34 5.2 5.40

Figure 5 Flexural strength at different curing time (in kN)

4.1.3. 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

0

1

2

3

4

5

6

0 3.5 7 10.5 14 17.5 21 24.5 28

Fle

xura

l st

rength

(in

kN

)


Flexural Strength vs Time

Control

1% HHF added

2% HHF added

3% HHF added

Agrawal - control

Agrawal - 1%

Agrawal - 2%

Agrawal - 3%


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)

Time

(days)




1 1.2 - 1.4 - 1.4 - 1.4 -

3 2.5 2.1 2.8 2.17 2.9 2.25 3.2 2.34

7 3.7 3.11 3.8 3.19 4.2 3.27 4.6 3.33

28 4.4 3.69 4.7 3.71 5.2 3.76 5.6 3.82

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,

0

1

2

3

4

5

6

0 3.5 7 10.5 14 17.5 21 24.5 28

Spli

ttin

g t

ensi

le s

tren

gth

(in

kN

)


Splitting Tensile Strength vs Time

Control

1% HHF added

2% HHF added

3% HHF added

Kumana - control

Kumana - 1%

Kumana - 2%

Kumana - 3%

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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.


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.

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concept of improving strength of concrete using human hair as fiber reinforcement.

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[3] T. Naveen Kumar, Komershetty Goutami, Jinna Aditya, Kuppala Kavya, V.Raja

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[4] and Shweta kaushik. An experimental study on mechanical properties of human hair fibre

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