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日本建築学会大会学術講演梗概集（中国） 2017 年 8 月

Influence of Notch on Bending and Tensile Characteristics of FRCC
Regular Member
Regular Member
Bending test
Polypropylene

Uniaxial tension testBridging stress○Yu MU*
Toshiyuki KANAKUBO**AramidNotch

1. INTRODUCTION
Fiber-reinforced cementitious composites (FRCCs) are a groupof cement composites with the mixture of short fibers toincrease their ductility and strength by the effect of fiber
bridging after first cracking. Though the bending test anduniaxial tension test are usually carried out to characterize theirperformance, both notched specimens and un-notched
specimens have been used for these test. The objective of thisstudy is to make clear the influence of the notch on bending andtensile performance of FRCC by the bending test and uniaxial
tension test.
2. BENDING TEST
Aramid and polypropylene (PP) fibers (Fig. 1) were used with 1%
volume fraction for all experiments. The characteristics of thefibers are listed in Table 1. The mix proportion for base mortar
is shown in Table 2. The compressive properties are listed inTable. 3.
2.1 Three-point bending test with notchThe notched beam specimens with 100mm square section (Fig.
2) specified in JCI-S-002-2003 were used. The notch was cut inthe middle of specimen with a depth of 30mm. One LVDT wasset to measure the load point deflection (LPD).
2.2 Four-point bending test without notch
The four-point bending test (Fig. 3) based on JCI-S-003-2007
was carried out. Three LVDTs were set to measure the load
point deflections (D1, D2) and the deflection at the center of thespecimen.
2.3 Bending stress vs. rotation angle
For three-point bending test specimen, the rotation angle isdefined as load point deflection (LPD) divided by half of span
(150mm). In case of four-point bending test specimen, therotation angle is defined as the average of load point deflections(D1, D2) divided by shear span (100mm). In order to compare
the difference of specimens with or without notch, the bending
stress is also defined as bending moment at the load point
divided by section modulus. The relationships of bending stressand rotation angle for aramid and PP specimens are shown inFig. 4. In case of Aramid specimens, the load was increased
significantly after first cracking to maximum for both types ofFig. 1 Used fibers
Table 1 Characteristics of used fiber
Diame- Tensile Elastic
Density LengthterStrength Modulus
Fiber(g/cm3)
(mm)
(mm)
(MPa)
（GPa）
Aramid1.39
30
0.53432
73
PP
0.91
30
0.7
580
4.9

Influence of Notch on Bending and Tensile Characteristics ofFRCC― 171 ―

Table 2 Mix proportion of base mortar
Unit weight (kg/m3)
Water cementratioWCS
FA
0.56
380678484
291
Table 3 Compressive properties
FiberAramidPP

Compressive
Strength (MPa)
51.3
51.5

Elastic Modulus(GPa)
17.7
17.2

Fig. 2 Three-point bending test

Fig. 3 Four-point bending test
MU Yu, KANAKUBO Toshiyuki

* 筑波大学大学院博士後期課程・修士(工学)**筑波大学システム情報系教授・博士(工学)Bending Stress（MPa）

64
2000.025 0.05 0.075 0.1
Rotation angle

8PP 3-point
Second peak
Avg. 2.13MPa

64
2008
Aramid 4-point
Second peak
Avg. 5.48MPa

64200.025 0.05 0.075 0.1
Rotation angle

00.025 0.05 0.075 0.1
Rotation angle

8PP 4-point
Second peak
Avg. 2.44MPa

642000.025 0.05 0.075 0.1
Rotation angle

8Aramid with notch
Second peak
Avg. 3.02MPa

642Tensile Stress（MPa）

081234Crack width (mm)5PP with notch
Second peak
Avg. 1.61MPa

642001234
Crack width (mm)85Aramid without notch
Second peak
Avg. 3.31MPa

64
20Tensile Stress（MPa）

0Fig. 6 Cross-section
Tensile Stress（MPa）

Fig. 5 Tension test specimen

4. CONCLUSIONSThe notch on bending test specimen nor uniaxial tension test
specimen does not largely affect the peak stress after first
cracking in case of FRCCs tested in this study.
REFERENCES1)Kanakubo, T., Miyaguchi, M. and Asano, K. (2016)“Influence of Fiber Orientation on Bridging Performance of
Polyvinyl Alcohol Fiber - Reinforced Cementitious Composite”,
ACI Materials Journal, Vol.133, No.2, pp.131- 141.

Aramid 3-point
Second peak
Avg. 4.37MPa

Bending Stress（MPa）

Bending Stress（MPa）
Bending Stress（MPa）

8Fig.4 Bending stress – rotation angle curve

Tensile Stress（MPa）

bending test. For PP specimens, the load dropped after themaximum load and increased gradually again showing secondpeak load. The average of bending stresses at the maximum load
after the sudden drop of the load (second peak) is 4.37MPa and5.48MPa for Aramid three-point and four-point specimen. The
bending stress of PP specimen at second peak is 2.13MPa and2.44MPa.
3. UNIAXIAL TENSION TEST
3.1 Specimens with and without notch
The uniaxial tension test was conducted for same FRCCs withbending test specimens. The specimens are divided into twoseries, i.e., without notch or with notch. The method of theuniaxial tension test is same one performed in the previous
study1). The dimensions of the specimen and cross section ofnotch are shown in Fig. 5 and Fig. 6. The test region of crosssection are 50mm × 50mm and 40mm × 40mm for thespecimens without and with notch, respectively. The total
length of the specimen is 510mm. Pin-fix ends were adopted at
the boundaries to minimize possible effects of external moment.
Tensile load and deformation in the test region were obtained
directly from the experiment.
3.2 Tensile stress vs. crack with or axial deformation
Tensile stress is calculated by considering the different section
area of two types of specimens. Tensile stress versus crack width(with notch specimen) or axial deformation (without notchspecimen) are shown in Fig. 7. The tensile behavior after first
cracking differs by types of fiber. Except the PP specimen
without notch, the tensile stress showed a significant drop after
first cracking. Due to the fiber bridging effect, the tensile stressincreased until to the second peak and then decreased gradually.
For the Aramid specimen without notch, multiple cracks wereobserved after first cracking which leads to the several increase
and decrease of tensile stress. In case of the PP specimen
without notch, the second peaks could not be measured due tosudden opening over 1mm crack width. The average tensilestress of Aramid specimen with and without notch at second
peak is 3.02MPa and 3.31MPa, of that for PP specimen is
1.61MPa and 1.33MPa, respectively.

012345
Axial deformation (mm)86PP without notch
Second peakAvg. 1.33MPa

420012345Axial deformation (mm)Fig. 7 Tensile stress – crack with or axial deformation curve*Doctoral Program in GSSIE, University of Tsukuba, M. Eng.
**Professor, FEIS, University of Tsukuba, Dr. Eng― 172 ―