IJERD – International Journal of Environmental and Rural Development (2020) 11-1

Research articleerd

Bending Strength and Toughness Properties of Pavement
Concrete Reinforced with Bamboo Fiber
EIJI MATSUO*
Faculty of Architecture and Civil Engineering, Kyushu Sangyo University, Fukuoka, Japan
Email: ematsuo@ip.kyusan-u.ac.jp

HIROTO SHIMIZU
Yamau Co., Ltd., Fukuoka, Japan

UMI IWANAGA
Sasebo City Office, Nagasaki, Japan

TAKENORI NAGAMATSU
Faculty of Architecture and Civil Engineering, Kyushu Sangyo University, Fukuoka, Japan

MASAKI IIDA
Faculty of Architecture and Civil Engineering, Kyushu Sangyo University, Fukuoka, Japan
Received 16 January 2020

Accepted 10 April 2020(*Corresponding Author)

Abstract The problems of neglected bamboo forest have been actualized in association withthe aging of the people owning bamboo forest in recent years in Japan. Then it becomes
imperative to establish the methods of effective utilization of the bamboo. Some bamboo hasenough tensile strength as construction material, and studies and experiments on bamboo
have been increasing gradually. The purposes of authors are to make short fiber of bamboo(“BF” for short) from Moso- bamboo, one of most popular bamboo in Japan, by ourselves,
and to develop the concrete for pavement which matrix are reinforced with BF. A crosslinked effect between concrete surface on crack by BF had been expected as same as otherkinds of short fibers. The purpose of this paper is to confirm the reinforcement effect by BF,
and cement mortar was the object in order to simplify the experiments, in which the basic
properties were investigated. The experiment factors are the amount of BF, water cement
ratio, fiber length and distribution method of BF. These influence on compressive strength,bending strength and bending toughness was investigated experimentally. As the results, thefollowings were obtained. The strength does not increase only by a cross-linked effect by BF.
The coefficient of toughness can be improved greatly by BF, and this effect is shown even inlittle quantity of fiber. Influence of water cement ratio on the toughness improvement is small.
In case of random mixing of BF, each strength become lower without depending on fiberlength, toughness coefficient can be improved. In case of spreading of BF, the strength andtoughness coefficient can be improved even in little quantity of fiber.
Keywords bamboo fiber, short fiber, bending toughness, strength

INTRODUCTION
In recent years, the problems of neglected bamboo forest have been actualized in association withthe aging of the people owning bamboo forest in Japan. Then it becomes imperative to establish themethods of effective utilization of the bamboo. Actually, bamboo has enough tensile strength asshown in Table 1 and studies and actions about the bamboo has been increasing gradually. Authors
has made short bamboo fiber (see Photo 1, BF for shot) by ourselves from Moso-bamboo, and it is
the final purpose to develop the concrete for pavement which matrix is reinforced by this BF. The
purpose of this study is to confirm the reinforcement effect by BF. Mortar was intended to simplify
the experiments, and its basic properties were investigated. The factors of experiment were fiberⒸ ISERD

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IJERD – International Journal of Environmental and Rural Development (2020) 11-1

amount, water cement ratio, fiber length and casting method of fiber, and the influence of them tocompressive strength, bending strength and bending toughness was acquired experimentally.
Table 1 Tensile strength of Moso-bamboo
No.
1
2
3
4
5
6
7
8
910

width thickness cross section fracture load tensile strength
(mm)
(mm)
(N)
(mm2)
(N/mm2)
10.2
13.5
11.1
12.7
11.9
9.2
9.7
9.5
9.6
11.3

7.80
8.00
8.40
7.80
8.13
8.33
8.63
8.43
7.57
8.13
average

79.6
108.0
93.2
99.1
96.7
76.4
83.5
79.8
72.9
91.6

11400
12700
10000
13850
11950
9600
8150
10250
8100
11350
10735

143.3
117.6
107.3
139.8
123.5
125.7
97.7
128.4
111.1
123.9
121.8

Photo 1 Handmade bamboo fiber

METHODOLOGYa) Making of Bamboo Fiber and Materiasls
As a result of trial and error, the bamboo was molded into a fiber form by the next process. (1)split
by circular wedge (2)unfastened by compressor for concrete (3)struck by mallet and unfasted again(4)cut to predetermined length. The moisture state of bamboo was determined as that it had been
dried in laboratory over 1 year after the felling (air-dried state).
The materials were high early strength Portland cement, JIS standard sand, BF and tap water.
Size of specimen was 40×40×160mm and they were taken out of molds on the next day of the casting.
After curing in water, the tests were carried out at 7 days of material age.
b) Series I
The purpose in series I was to find the appropriate mixing ratio of BF which length was 20mm (aspectratio was 13.3). In previous experiment, W/C was 50%, mixing ratio of BF (outer percentage basedon the mass of mortar) was 0, 1, 3 and 5%. As the results, the workability decreased remarkably at5%, so it was concluded that 3% was upper limit. Then, W/C was varied with 50, 55 and 60%, andBF mixing ratio was varied with 0, 1, 2, and 3%. These mix proportions are shown in Table 2 as themixing weight. The compressive strength and bending strength of BF mortar was obtained inaccordance with “Cement Strength Test” to confirm the strength improvement effect by BF.
Furthermore, the bending toughness was calculated based on the JSCE concrete standard
specifications (See Figure1), expecting the toughness improvement effect by BF.
c) Series II and III
In series II, the BF length was changed to 30 and 40mm to increase adhesion. W/C was 55%, and BF
mixing ratio was 0, 1, 2, and 3%. Table 3 shows the mix proportion of series II.
A method to spread BF in tensile domain was adopted in series III. Because when BF is mixed
simply, the placement of BF becomes random in three-dimensionally and the two-thirds waste should
occur in a direction of stress. In actual construction, it will be effective to induce a direction of BF
by a container which has slits (see Photo 2). Firstly, specimens were made in the cover of 0mm,mixing ratio of 0.5%, fiber length of 30, 60 and 90mm and the strength was evaluated by bendingstrength. As the result, fiber length of 60mm, which had increased the bending strength most, wasⒸ ISERD

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adopted, and the specimens with the cover of 5 and 10mm were made in this fiber length. Table 4shows the mix proportion of series III.
Table 2 Mix proportion of series Imixing weight (g)JISWCBF
Sand225450 1350

247.5450 1350

270

450 1350

Load (N)fiber
W/C BF
length（%） (%)(mm)
0150230155
20230160
230
7.7
15.5
23.2
0
7.9
15.9
23.8
0
8.1
16.2
24.4

Tb

δcd
Deflection (mm)Fig. 1 Calculation of Tb

Table 3 Mix proportion of series II

Table 4 Mix proportion of series III

mixing weight (g)fiber
W/C BF
lengthJIS(%) (%)
WC
BF
(mm)
Sand
30
55 0.5 60 247.5 450 1350 4.090

Photo 2 Casting of BF in series III
3000
BF=0%

2500
Bending load (N)mixing weight (g)fiber
W/C BF
lengthJIS（%） (%)
WCBF(mm)
Sand00－1
7.9
55
247.5 450 1350
30215.9
323.8
17.95540 247.5 450 1350 15.9
2323.8

BF=1%
2000

BF=2%

1500

BF=3%

1000

500
00.0

1.0

2.0

3.0

Deflection (mm)Fig.2 Load and deflection curve of series I(W/C=55%)

Calculation of Toughness
Figure 2 shows the load-deflection curve in series I (W/C=55%). Bending toughness could be
evaluated by toughness coefficient, and when this is large, the toughness at destruction could beimproved, which leads the restraint of disasters and accidents.
The spans of beam specimens were 45cm and loads were applied at the 2 points of 3 equal parts.
In order to obtain the details of data for toughness coefficient, the loads were applied slowly until thedeflection became 3mm by the confirmation of data logger. After the measurement, load-deflection
curve was described in the procedure of JIS. The toughness coefficients were calculated by formula(1) using the area from 0 to 1mm of the deflection by the curves.
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=Tb cdL
bd 2

・・・・・・・・・・・（1）Here,σ: bending toughness (N/mm2)
Tb : Area to δcd（N･mm）δcd : deflection (=span/150; mm)
L: span (=120mm)
b: width of section (=40mm)
d: height of section (=40mm)
RESULTS AND DISCUSSIONa) Series 1Figure 3 and 4 show the relationships between BF mixing ratio and compressive strength or bending
strength. Both strength decreased in comparison with non-mixing of BF. According to theobservation of the fractured section of mortar, every BF slipped out without being cut, which meansthat the adhesion of BF and mortar was not enough and the primary tensile strength of BF was notshown.
Figure 5 shows the relationship between BF mixing ratio and toughness. Improve of toughness
coefficient by BF can be confirmed. It is effective even in low BF mixing ratio, and the influence ofW/C on the effect is small. It is estimated that the cross-linked effect by BF increased the toughness
coefficient according to the above-mentioned observation results.

45Bending strength (N/mm2)

W/C=50%
W/C=55%
W/C=60%403530250%

1%
2%
BF mixing ratio (%)

1%
2%
BF mixing ratio (%)

Toughness coefficient (N/mm2)

Fig. 5 Relationship between BF mixing ratio
and toughness coefficient in series I

1%
2%
BF mixing ratio (%)

3%

Fig. 4 Relationship between BF mixing ratio
and bending strength in series I

W/C=50%
W/C=55%
W/C=60%0%

W/C50%
W/C55%
W/C60%

0%3%

Fig. 3 Relationship between BF mixing ratio
and compressive strength in series I4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0

8.5
8.0
7.5
7.0
6.5
6.0
5.5
5.0
4.5

Compressive stgrength (N/mm2)

Compressive strength（N/mm2）

503%

50
40
3020

BF30mm
BF40mm

1000%

1%
2%
BF mixing ratio (%)

3%

Fig. 6 Relationship between BF mixing ratio
and compressive strength in series IIⒸ ISERD84

IJERD – International Journal of Environmental and Rural Development (2020) 11-1b) Series II and III

8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0

8
Bending strength (N/mm2)

Bending strength (N/mm2)

Figures 6 and 7 show the relationships between BF mixing ratio and compressive strength or bending
strength. Figure 8 shows the relationship between cover and bending strength in series III. Bending
strength and compressive strength decreased by mixing BF. However, in the case that BF was spreadwith little cover and the fiber length was 60mm, the effect of BF was shown most, and the bending
strength was stronger than non-mixing, nevertheless the mixing amount was only 0.5%. When BF ismixed at random, it is estimated that the effect as the fiber cannot be shown, even if fiber length andmixing amount are changed, because the adhesion between fiber and mortar are not enough.
Figure 9 shows the relationship between the mixing ratio and toughness coefficient with various
fiber length. The toughness coefficient improved with the increase of mixing ratio generally in seriesII, however, the effect by the change of fiber length could not be confirmed. Figure 10 shows therelationship between cover and toughness coefficient in series III. The toughness coefficient of themix proportion with the fiber length of 60mm and the cover of 5mm improved most even the mixing
amount was only 0.5%.

BF30mm
BF40mm0%

1%
2%
BF mixing ratio (%)

3%

76Bending strength offiberless (6.7N/mm2)

543

30mm
60mm
90mm

2
10046cover (mm)810Fig. 8 Relationship between cover andbending strength in series III
2.0

2.0

Toughness coefficient (N/mm2)

Toughness coefficient (N/mm2)

Fig. 7 Relationship between BF mixing ratio
and bending strength in series II21.6
1.2
0.8
BF40mm
BF30mm

0.40.00%

1%
2%
BF mixing ratio (%)

3%

1.5

Toughness of fiberless(0.62N/mm2)

1.0
0.5
0.00Fig. 9 Relationship between BF mixing ratioand toughness coefficient in series II5Cover (mm)10Fig. 10 Relationship between cover andtoughness coefficient in series IIICONCLUSION
The summary of this study on the concrete for pavement which short bamboo fiber was mixed withis as follows:(1) The strength does not improve only by a cross-linked effect.
(2) Toughness coefficient greatly improves, and the effect is shown even if the amount of fiber islittle.
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(3) The influence of W/C on the effect of toughness improvement is small.
(4) When bamboo fiber is mixed at random, each strength decreases, and toughness coefficientincreases regardless of fiber length.
(5) In case of spreading construction of bamboo fiber, both strength and toughness coefficient
improves even by little amount of fiber.
(6) As a contrivance to align the same direction of bamboo fiber easily in large scale on actual road,the sieve with slit in one direction could be effective, practicable and economical.
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Suzuki, M., Hasegawa, H., Mutsunobu, K. and Yamamoto, T. 2006. Spreading and ecology of bamboo groves
distributed in Yamaguchi prefecture. Journal of JSCE-G, 62 (4), 445-451.
Matsuo, E. and Takami, K. 2009. Applicability of bamboo as reinforcement for concrete. Journal of JSCE-F,
65 (2), 190-195.
Terai, M. and Minami, K. 2012. Experimental study on mechanical properties of bamboo fiber reinforced
concrete. Proceeding of the Japan Concrete Institute, 34 (2), 1279-1284.
Kimura, S., Saito T. and Demura, K. 2012. Flexural behavior of bamboo-reinforced cement mortars using
emulsion treated reinforcement. Proceeding of the Japan Concrete Institute, 34 (1), 1456-1461.
Yagi, S., Saito, T. and Demura, K. 2014. Effect of emulsion treatment for bamboo reinforcement on freezing
and thawing resistance of bamboo-reinforced cement mortars. Cement Science and Concrete Technology,Vol. 67, Japan Cement Association, 501-506.
Japan Society of Civil Engineers. 2017. Standard specifications for concrete structures, Materials andConstruction, 265-275.
Matsuo, E., Suenaga S., Terasaki A. and Nagamatsu, T. 2019. Treating method and bond properties of thebamboo in BRC beam. Proceeding of the Japan Concrete Institute, 41 (1), 1523-1528.

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