令和6年度土木学会全国大会第79回年次学術講演会
第V部門
2024

年9月5日(木) 9:30 ~ 10:50

C306(川内北キャンパス講義棟Ｃ棟)

短繊維補強コンクリート（材料）(1)
座長：岩下 健太郎（名城大学）
10:00 ~ 10:10[V-380] Tensile Characteristics of Fiber-Reinforced Cementitious Composite
with Recycled Carbon Fiber

金久保 利之1、李 思聡1、張 航1 (1. 筑波大学)
キーワード：FRCC、リサイクル炭素繊維、一軸引張試験、架橋則、断面解析*

本研究では，溶媒法によるリサイクル炭素繊維を用いた繊維補強セメント複合材料（FRCC）について，繊維の架橋性能を明らかにするために，FRCCの一軸引張試験を行った．架橋則の評価を通して，引張荷重－ひび割れ幅関係を与えるための単繊維の架橋モデルを提案した．
計算された架橋則を用いた断面解析の結果による最大曲げモーメントは，既存の同材料の曲げ試験で得られた値とよい一致を見た．

© 2024 Japan Society of Civil Engineers- V-380 -V-380

令和6年度土木学会全国大会第79回年次学術講演会

Tensile Characteristics of Fiber-Reinforced Cementitious Composite
with Recycled Carbon Fiber
筑波大学

正会員 ○Toshiyuki Kanakubo

筑波大学

学生会員 Sicong Li

筑波大学

学生会員 Hang Zhang

1. INTRODUCTION

Table 1 Mixture proportion

The authors have focused on the usage of recycledcompressive and bending characteristics of FRCC withUnite weight (kg/m3)
WCFAS
CF-SO-0.5% 0.39
0.30380678291
484
W: water, C: high early strength Portland cement,
FA: fly ash type II, S: silica sandrecycled carbon fiber by the pyrolysis (CF-PY) andTable 2 Mechanical properties of fiberSeries

carbon fiber as a mixed discrete fiber in fiber-reinforced
cementitious

composite(FRCC). The

fundamental

solvolysis (CF-SO) method have been investigated in theprevious study [1], and FRCC with CF-SO have shown
better improvements in bending strength and toughness ofW/B

FA/B

Type

Length(mm)Diameter
( m)

CF-SO

105Tensile
strength(MPa)5800

Elasticmodulus
(GPa)
294

FRCC. This study conducts a uniaxial tension test on
FRCC with CF-SO to clarify the bridging effect of carbon
fiber. An individual fiber bridging model is proposed toexpress the tensile load versus crack width of FRCC via
bridging law calculation.
2. EXPERIMENT OVERVIEWThe mixture proportion of FRCC is shown in Table 1.
Recycled carbon fiber by solvolysis method (CF-SO) isFig. 1 Uniaxial tension test specimen (unit: mm)

used. The length of the fiber is controlled at 10 mm. The
fiber volume fraction is set at 0.5%. Table 2 shows themechanical properties of virgin fiber provided by themanufacturer. The compressive strength and the elastic
modulus of FRCC obtained by 100-200 mm cylinder test
pieces at the loading age of the uniaxial tension test is 41.9
MPa and 16.2 GPa, respectively.
Fig. 1 shows the dimensions of the uniaxial tension

Fig. 2 Specimens after loading

test specimen. The test section is 30 mm long with a crosssectional area of 5 mm × 5 mm. These dimensions of thetest section ensure that the fiber orientation remains

The loading was carried out using an electronic system

consistent, thus eliminating the influence of fiber

universal testing machine with a capacity of 200 N (Fig. 1)

orientation to directly obtain the fiber bridging model.

and a loading speed of 1 mm/min. The tensile load and theThough the total of twenty specimens was prepared, sevenhead displacement were recorded.

specimens were damaged and rendered unusable during

3. TEST RESULTS

the demolding process. Thirteen specimens were tested.
Keywords
AddressFig. 2 shows the photos of specimens after loading.

FRCC, Recycled carbon fiber, Uniaxial tension test, Bridging law, Section analysis〒305-8573 茨城県つくば市天王台 1-1-1
筑波大学構造エネルギー工学域 TEL 029-853-5045© Japan Society of Civil Engineers- V-380 -V-380

令和6年度土木学会全国大会第79回年次学術講演会

During the loading process, a crack formed in the central
Tensile load per fiber (N)0.02

position of the specimens. Most of the fibers were ruptured.
The average value of the maximum load is 108.2 N. The
tensile strength ranging from 2.32 MPa to 6.64 MPa, andthe average tensile strength is 4.32 MPa.
4. FIBER BRIDGING MODEL

0.01

0The bridging law (tensile stress vs. crack widthrelationship) is calculated by the summation of forces

12
34
Crack width (mm)56Fig. 3 Individual fiber bridging model

carried by individual bridging fibers. Since the uniaxial

20 0tension test specimens exclude the influence of fiber

Load (N)orientation, the only factor affecting fiber bridging
behavior is the embedded length of the individual fibers.

10 0

The calculated bridging force can be obtained by Eq. (1).

Pbridgelb l f /2

P (lb )

(1)
0Where, Pbridge: bridging force, P(lb): pullout force of

123
C ra c k w id th (m m)

45Fig. 4 Calculation result of bridging law

individual fiber, lb: embedded length, lf: fiber length.

Table 3 Result of section analysis

According to the experimental results, the individual
fiber bridging model can be obtained reversibly using Eq.

Series(1). Fig. 3 illustrates the individual fiber bridging model,

CF-SO-0.5%

Maximum moment (kN･m)
SectionExperiment
analysis
1.638
1.561

Experiment/ Analysis
0.95

which is the bi-linear model. Based on the average valueof the maximum load, Pbridge has been determined to bepreviously reported [2]. Table 3 shows the list of maximum

108.2 N. The crack width at the maximum is determined

bending moment by experiment [2] and calculated values.

from the average experimental data and has been measured

The calculated maximum bending moment is 0.95 times

to be 0.25 mm. The spreadsheet software (Excel)

the experimental data, showing a close agreement.

procedure is used to calculate the bridging law. As a result

6. CONCLUSIONSof finding the characteristic points, the maximum tensile1) The bridging law, derived from the uniaxial tension

load of the individual fiber is determined as 0.0177 N andtest, serves as the subject for further exploration of thethe corresponding crack width is 0.25 mm as shown in Fig.

tensile characteristics of FRCC by solvolysis method

3. The calculation result of bridging law is shown in Fig. 4.

recycled carbon fiber.

The load becomes to zero when crack width becomes equal

2) The calculated maximum bending moment by section

to half of fiber length.

analysis is 0.95 times the experimental data,

5. SECTION ANALYSIS

demonstrating a close agreement.

Section analysis is conducted to evaluate theACKNOWLEDGEMENTS

Recycled carbon fiber

adaptability of calculated bridging law of FRCC. The

was provided by MIRAI KASEI INC.

stress-strain model in tension side is derived based on theREFERENCES

bridging law depicted in Fig. 4 by bi-linear model, and the[1] Sasaki, H., Li, S., Kanakubo, T., Fabrication of FiberReinforced Cementitious Composite with RecycledCarbon Fiber, JSCE 2023 Annual Meeting, V-751, 2023.
[2] Li, S., Sasaki, H., Kanakubo, T., Bending Characteristics of Fiber-Reinforced Cementitious Composite with
Recycled Carbon Fiber, JSCE 2023 Annual Meeting, V752, 2023.

data from compression test are used in compression sideby the parabolic model. For tension side, stress is obtainedby dividing the load by the cross-sectional area, while
strain is determined by dividing the crack width from thebridging law by the pure bending length of 100 mm, as© Japan Society of Civil Engineers- V-380 -