JSCE 令和5年度土木学会全国大会第78回年次学術講演会

第V部門

短繊維補強コンクリート（材料）
2023年9月15日(金) 15:10 〜 16:30 V-8 (広島大 東広島キャンパス総合科学部講義棟 Ｋ２０９)[V-751] Fabrication of Fiber-Reinforced Cementitious Composite
with Recycled Carbon Fiber
Fabrication of Fiber-Reinforced Cementitious Composite
with Recycled Carbon Fiber*佐々木 秀人1、李 思聡1、金久保 利之1 （1. 筑波大学）*Hideto Sasaki1, Sicong Li1, Toshiyuki Kanakubo1 （1. University of Tsukuba）
キーワード：FRCC、リサイクル炭素繊維、曲げ強度、曲げ靭性、分散性
FRCC, Recycled carbon fiber, Bending strength, Bending toughness, Dispersion
昨今の環境負荷の低減といった課題に対する一つの提案として，リサイクル繊維を用いた繊維補強セメント複合材料(FRCC)の開発が挙げられる．本研究では，リサイクル炭素繊維を用いた FRCCの作製及び基本性能の調査を目的とし，圧縮試験及び曲げ試験を実施した．圧縮試験の結果より，繊維の種類が圧縮性状に与える影響は少ないことが確認された．曲げ試験の結果より，溶媒法によるリサイクル炭素繊維を用いた FRCCで繊維の架橋効果が確認された．また，走査電子顕微鏡(SEM)を用いた破壊断面の観察により，溶媒法によるリサイクル炭素繊維は十分に分散することが明らかとなった．
The development of fiber-reinforced cementitious composite (FRCC) with recycled fibers provides one
proposal for the reduction of environmental impact. This study aims to fabricate FRCC with recycled CFand investigate its fundamental properties through compression and bending test. From the compression
test results, it is clarified that type of fibers little influence the compressive properties. From thebending test results, bridging effect is confirmed in the FRCC with CF by the solvolysis. It is observed byscanning electron microscope (SEM) that CF by the solvolysis is dispersed.

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Japan Society of Civil Engineers 2023 Annual Meeting

Fabrication of Fiber-Reinforced Cementitious Composite with Recycled Carbon Fiber
学生会員 ○Hideto Sasaki

筑波大学
筑波大学大学院

学生会員

筑波大学

正会員

Sicong Li
Toshiyuki Kanakubo

INTRODUCTION

1.

Fiber-reinforced cementitious composite (FRCC) is mixed withdiscrete fibers. The fibers bridge between cracks and transmit tensileforces. Therefore, cracking and its propagation are inhabited. As aresult, FRCC shows higher tensile performance than that ofCF-V

CF-PY

CF-SO

conventional concrete. Virgin fibers or optimally processed fibers
are usually used for FRCC. On the other hand, the use of recycledmaterials is recently focused on for the purpose of the reduction ofenvironmental impact and creation of the new materials with added

CF-V(SEM x1000) CF-PY(SEM x1000) CF-SO(SEM x1000)

value. The development of FRCC with recycled fibers has possibility

Fig.1 Photo of used fiber

to provide one proposal for this issue.

Table 1 Mix proportion of FRCC

Carbon fiber (CF) is one of the most commonly used fibers asUnit weight（kg/m3）

Specimenfiber-reinforced plastic (FRP). CF has a higher elastic modulus andW
CSFA
CF AdN
CF-V-0.5%9380 678 484 291
6CF-PY-2%
36
CF-SO-0.5%
9
W：Water C：High early strength Portland cement
S：Silica Sand No. 7 FA：Fly ash type II CF：Carbon fiber
Ad：High range water reducing admixture

tensile strength than other fibers. FRCC with CF can be expected tosignificantly improve tensile performance of FRCC. In order toensure the use of FRCC with recycled CF practical, it is necessary toaccumulate the fabrication know-how and clarify its mechanicalperformance. However, there are only a few studies on FRCC withrecycled CF. Sasaki et al. reported that FRCC with CF showed thelow compressive and bending strength [1]. In addition, the conditionsof recycled fibers vary depending on the recycling methods. The
dispersion of recycled fibers in cementitious composite is also
unclear.

Fig.2 Four-point bending test
Table 2 Average compressive strength and elastic modulus

This study aims to fabricate FRCC with recycled CF andinvestigate the fundamental properties of hardened FRCC throughSpecimencompression and bending test. The dispersion of CF in FRCC is alsoN
CF-V-0.5%
CF-PY-2%
CF-SO-0.5%

observed by scanning electron microscope (SEM).

2.

EXPERIMENT OVERVIEW

2.1

Tested recycled CF

Compressive strength(MPa)
44.9
48.1
46.4
52.0

Elastic modulus(GPa)
16.0
17.2
17.2
17.1

The pyrolysis (CF-PY) and the solvolysis (CF-SO) are major

fibers are not dispersed due to residual resin. The fibers cut in 10mm

methods for recycling CF [2]. In this study, CF recycled by these twolength are used for fabrication of FRCC in the case of CF-V and CF-

methods are used. Virgin fiber (CF-V) is also used for comparisonSO.

with recycled fibers. Fig.1 shows fibers by ordinary photograph and2.2

SEM. In CF-V, individual fibers are dispersed. In CF-PY and CF-SO,Compression and bending test of FRCC

Table 1 shows the mix proportion of FRCC. The specimen "N"

Keywords FRCC，Recycled carbon fiber，Bending strength，Bending toughness，Dispersion
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Japan Society of Civil Engineers 2023 Annual Meeting

Bending moment (kN・m)indicates mortar without fiber. The other specimens’ identifications
correspond to FRCC using each type of CF. The fiber volume
fraction was set to 0.5% in the case of CF-V and CF-SO, and 2% in
CF-PY.

Bending moment (kN・m)

measured to calculate the curvature as shown in Fig.2.

0.1

0modulus. The average compressive strength and elastic modulus of
the four types of specimens are similar. The type of fibers has little

CF-SO-0.5%
Fig.3 Bending specimen
after bending test

effect on the compressive properties.
Bending test

Fig.3 shows a typical example of test pieces after bending test. In

0.2
0.4
Curvature (1/m)

CF-PY-2%

CF-PY-2%

Table 2 shows a list of average compressive strength and elastic

3.2

CF-PY-2%-1
CF-PY-2%-2
CF-PY-2%-3
CF-PY-2%-4CF-PY-2%-5
CF-PY-2%-6

0.2

0Bendimg moment (kN・m)

Compression test

0.2
0.4
Curvature (1/m)

CF-V-0.5%

test pieces, respectively. In the bending test, axial deformations are

3.1

0

CF-V-0.5%

carried out by 50x100mm cylinder and 40x40x160mm rectangle

TEST RESULTS

0.1

0The uniaxial compression test and four-point bending test are

3.

CF-V-0.5%-1
CF-V-0.5%-2
CF-V-0.5%-3
CF-V-0.5%-4
CF-V-0.5%-5
CF-V-0.5%-60.2

CF-SO-0.5%-1
CF-SO-0.5%-2
CF-SO-0.5%-3
CF-SO-0.5%-5
CF-SO-0.5%-6

0.20.1000.2
0.4
Curvature (1/m)

CF-SO-0.5%
Fig.4 Bending momentcurvature curve

Table 3 Average maximum bending moment

all test pieces, one crack took place and failed by opening the crack.

Specimen

Bending moment (kN・m)

In CF-V-0.5% and CF-SO-0.5%, the fibers bridging the crack were

CF-V-0.5%

0.220

observed.

CF-PY-2%

0.073

CF-SO-0.5%

0.142

Fig.4 shows the bending moment-curvature curves. In CF-PY-2%,
the bending moment increases linearly to the peak. Then the bending
moment decreases rapidly. In CF-V-0.5% and CF-SO-0.5%, thebending moment gradually increases after cracking to the peakshowing deflection hardening property. After the peak, the bending

CF-V (x100)

CF-PY (x100)

CF-SO (x100)

moment decreases rapidly.
Table 3 shows the list of average maximum bending moment. Theaverage maximum bending moment of CF-PY-2% is 0.332 times thatof CF-V-0.5%. The average maximum bending moment of CF-SO-

CF-V (x150)
CF-PY (x180)
CF-SO (x150)
Fig.5 Photo of fractured cross-section

0.5% is 0.645 times that of CF-V-0.5%. It is recognized that bridging
effect of fibers improves the bending strength and toughness in case(2) Improvements in bending strength and toughness were observedof CF-V-0.5% and CF-SO-0.5%.

4.

in FRCC using recycled fiber by the solvolysis method.

OVSERVATION OF FIBER IN FRCC
Fractured cross-sections of test pieces after bending test wereACKNOWLEGEMENTS
The recycled carbon fibers were provided from MIRAI KASEI

observed by SEM to observe the dispersion of fibers as shown Fig.5.
In CF-PY-2%, most of the fibers are not dispersed even in FRCC. In

INC. and Toray Industries, Inc.

CF-V-0.5%, the packs of 2~4 fibers are scattered at intervals ofREFERENCES

300~500µm. In CF-SO-0.5%, packs of 3~4 fibers are scattered at[1]佐々木隆ほか，超臨界水処理による炭素繊維補強樹脂材

intervals of 300~600µm. These scattered fibers are observed over

料のリサイクルに関する研究,コンクリート工学年次論文集，

the entire cross-section.

Vol.28,No.1,pp.1553-1558,2006

5.

[2] 株 式 会 社 ミ ラ イ 化 成 ， 再 生 炭 素 繊 維 事 業 の ご 紹 介 ，CONCLUTIONS(1) Fiber type has little effect on compressive properties.

https://www.miraikasei.com/pdf/sale_carbon.pdf(2023/03/16 閲覧)

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