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-752] Bending Characteristics of Fiber-Reinforced Cementitious
Composite with Recycled Carbon Fiber
Bending Characteristics of Fiber-Reinforced Cementitious
Composite with Recycled Carbon Fiber*李 思聡1、佐々木 秀人1、金久保 利之1 （1. 筑波大学）*Sicong Li1, Hideto Sasaki1, Toshiyuki Kanakubo1 （1. University of Tsukuba）
キーワード：FRCC、リサイクル炭素繊維、曲げ試験、断面解析
FRCC, Recycled carbon fiber, Bending test, Section analysis
環境負荷の低減と付加価値のある新素材の創出を目的として，リサイクル炭素繊維（ CF）を用いた繊維補強セメント複合材料（ FRCC）に着目した．本研究では，溶媒法によりリサイクル炭素繊維を用いた FRCCの曲げ特性を把握するため，繊維体積混入率を0.5%および0.75%とした FRCC試験体の4点曲げ試験および断面解析を行った．曲げ試験結果に合致するよう断面解析における応力-ひずみモデルを構築した結果，繊維体積混入率の差は認められなかった．溶媒法リサイクル炭素繊維を用いた FRCCの場合，適切な繊維体積混入率は0.5%程度と考えられる．
Bending Characteristics of Fiber-Reinforced Cementitious Composite with Recycled Carbon Fiber
The objective of this study is to investigate the bending characteristics of FRCC with recycled CF bysolvolysis methods. Four-point bending tests are performed on specimens with fiber volume fractions of
0.5% and 0.75%. The section analysis is also conducted to evaluate the bending capacity. As the resultsof the establishment of tensile stress-strain models through section analysis, fiber volume fraction
difference between 0.5% and 0.75% is not observed. The suitable fiber volume fraction is considered to
be around 0.5% for FRCC with solvolysis method recycled carbon fiber.

©公益社団法人土木学会

V-752

Japan Society of Civil Engineers 2023 Annual Meeting

Bending Characteristics of Fiber-Reinforced Cementitious Composite
with Recycled Carbon Fiber
筑波大学大学院

学生会員 ○Sicong Li

筑波大学

学生会員

Hideto Sasaki筑波大学

正会員

Toshiyuki Kanakubo

1. INTRODUCTION

Table 1 List of specimens

The authors have focused on fiber-reinforced cementitious
composites (FRCC) with recycled carbon fiber (CF) for the purpose

Specimen

Dimensions

CF-SO0.5%
CF-SO0.75%

Compression:
100x200mm
Bending:
100x100x400mm

of the reduction of environmental impact and creation of the newmaterials with added value. The previous study [1] has reported theFiber volume
fraction
0.5%
0.75%

Number ofspecimens
Compression:3
Bending:5
Compression:3
Bending:5

fabrication of recycled CF-FRCC and the comparisons of bending
characteristics between the different types of recycled CF. As theresults, recycled CF by the solvolysis method shows better behavior
rather than that by the pyrolysis method.
The objective of this study is to investigate the bending
characteristics of FRCC with recycled CF by solvolysis methods inFig. 1 Dimensions of specimen for bending test

specimens by commonly used dimensions. The section analysis isalso conducted to evaluate the bending capacity.

Table 2 Mix proportion of FRCC

2. EXPERIMENT OVERVIEW

Unit weight(kg/m3)

Specimen

The list of the specimens is shown in Table 1 and illustrated inWCSFA

380

678

484

291

Fig. 1. Total 6 specimens for compression test and 10 specimens for
CF-SO-0.5%

four-point bending test are prepared. The used fiber is recycled

CF-SO-0.75%

carbon fiber by the solvolysis method (CF-SO) as same as that usedCF
913.5

Ad
6W：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

in the previous study [1]. The fiber is cut in 10mm long. Table 2 shows
the mix proportion of FRCC. The fiber volume fraction is set to 0.5%
and 0.75%. In the bending test, axial deformations in constant

Table 3 Results of compression test

bending moment zone are measured to calculate the curvature.

Table 3 shows the results of compression test. FRCC with fiber

CF-SO-0.5%

Averagecompressive strength(MPa)40.8

volume fraction of 0.75% show lower compressive strength than that

CF-SO-0.75%

32.4

Specimen

3. TEST RESULTS

Average elasticmodulus(GPa)
17.2
15.8

The maximum bending stress of CF-SO-0.5% in this study is smallerof 0.5%.
Fig. 2 shows the bending moment-curvature curves obtained inthan that of CF-SO-0.5%[1] due to the scale effect. The maximum

the bending test. The deflection hardening property, in which thebending stress of CF-SO-0.75% is not so different with the result ofbending moment increases after first cracking, can be observed in all

CF-SO-0.5%. It is considered that the fibers are not dispersed evenly

the specimens. After the peak, the curves showed slight softening

in the case of 0.75% volume fraction.

branch, and the crack rapidly opened. Fig. 3 shows the comparison

4. SECTION ANALYSISof the maximum bending stress (maximum bending moment divided

Section analysis is conducted to compare the tensile

by section modulus) including the results of the previous study [1].

characteristics of CF-FRCC. The analysis is also carried out for theKeywords FRCC, Recycled carbon fiber, Bending test, Section analysis
Address〒305-8573 茨城県つくば市天王台 1-1-1 筑波大学 TEL 029-853-5045

JSCE 令和5年度土木学会全国大会第78回年次学術講演会© Japan Society of Civil Engineers- V-752 -V-752

Bending moment (kN・m)

results of the previous study [1]. The stress–strain models used foranalysis are shown in Fig. 4. The parabolic model is chosen incompression side based on the compression test results. For tensionside, the bi-linear model is established to show the best fitting of theBending moment (kN・m)

Japan Society of Civil Engineers 2023 Annual Meeting

2
CF-SO-0.5%-1
CF-SO-0.5%-2
CF-SO-0.5%-3
CF-SO-0.5%-4
CF-SO-0.5%-51maximum bending moment between the test results and analysis.

00.02

0.04 0.06 0.08
Curvature (1/m)

2CF-SO-0.75%-1
CF-SO-0.75%-2
CF-SO-0.75%-3
CF-SO-0.75%-4
CF-SO-0.75%-5

10.1

00.02

0.04 0.06 0.08
Curvature (1/m)

0.1

Fig. 2 Bending moment-curvature curve

Table 4 lists the analysis results and experimental ones. As the results
25

Maximum bending stress (MPa)of the establishment of tensile stress-strain models, the tensile
strengths for CF-SO range from 5MPa to 8MPa. The large difference
between CF-SO-0.5% and CF-SO-0.75% is not observed.
Comparing the previous results, the tensile strength of CF-SO0.5%[1] is about 0.6 times that of CF-V-0.5%[1]. It is considered to bedue to the difference of the dispersion of fibers as observed in the20151050

previous study [1].

CF-SO-0.5% CF-SO-0.75% CF-PY-2% [1] CF-SO-0.5% [1] CF-V-0.5% [1]Fig. 5 shows stress distributions in cross-sections of theFig. 3 Maximum bending stress
Strain(%)

indicates the stress of FRCC, showing compression in the left-1.5-10-0.5-10-20(negative) and tension in the right (positive). It can be observed that-30

CF-SO-0.5%
CF-SO-0.75%
CF-PY-2% [1]CF-SO-0.5% [1]CF-V-0.5% [1]the tensile stress becomes around two-third of the tensile strength atthe tension edge.

-40

0Stress(MPa)Stress(MPa)specimens at the maximum bending moment. The horizontal axis-50-6014121086420

CF-SO-0.5%
CF-SO-0.75%
CF-PY-2% [1][1]CF-SO-0.5%
CF-V-0.5% [1]00.2

0.60.8Strain(%)(b) Tension side(a) Compression side

5. CONCLUSIONS

0.4Fig. 4 Stress-strain model for section analysis

The deflection hardening property is observed in FRCC withrecycled CF by the solvolysis method. The maximum bending stressof 100mm cross-section specimens is smaller than that of 40mm

Table 4 List of maximum bending moment

specimens. As the results of the establishment of tensile stress-strain

Experimentmodels through section analysis, fiber volume fraction difference

Specimenbetween 0.5% and 0.75% is not observed. The suitable fiber volumeComp.
strength(MPa)Max.
bendingmoment(kN·m)

40.8

1.638

1.639

33.2

32.4

1.761

1.761

35.9

46.4

0.07310.0728

14.6

52.0

0.142

0.146

15.1

48.1

0.220

0.211

15.9

fraction is considered to be around 0.5% for FRCC with solvolysis
CF-SO0.5%
CF-SO0.75%
CF-PY2%[1]CF-SO0.5%[1]CF-V0.5%[1]method recycled carbon fiber.
ACKNOWLEDGEMENTS
The recycled carbon fibers were provided from MIRAI KASEI INC.
REFERENCES[1] Sasaki, H., Li, S.C., Kanakubo, T., Fabrication of FiberReinforced Cementitious Composite with Recycled CarbonSection analysis
NeutralMax.
axis frombendingcomp.
momentedge(kN·m)(mm)6080100Tension-100Stress (MPa)10406080100Tension-100Stress (MPa)1010 Compression
2030Tension
40-100Stress (MPa)

10CF-SO-0.5%[1]0Compression
102030Tension
40-100Stress (MPa)Fig. 5 Stress distribution in cross-section at the maximum moment

JSCE 令和5年度土木学会全国大会第78回年次学術講演会© Japan Society of Civil Engineers- V-752 -10Distance from compressive edge (mm)40Compression
20CF-PY-2%[1]0Distance from compressive edge (mm)Compression
20CF-SO-0.75%
0Distance from compressive edge (mm)CF-SO-0.5%
0Distance from compressive edge (mm)Distance from compressive edge (mm)Fiber, 土木学会年次学術講演会講演概要集, 2023
CF-V-0.5%[1]0Compression
102030Tension40-100Stress (MPa)101