Size Effect on Flexural and Shear Behavior of PVA-ECC
Toshiyuki Kanakubo, Dr.E.
University of Tsukuba, Japan
Katsuyuki Shimizu, Dr.E.
Railway Technical Research Institute, Japan
Tetsushi Kanda, Dr.E.
Kajima Technical Research Institute, Japan

Abstract
High Performance Fiber-Reinforced Cementitious Composites (HPFRCC), which show astrain hardening branch and multiple cracking under uniaxial tensile stress, have been focusedby lots of researchers because of its unique mechanical performance. Engineered Cementitious
Composites (ECC) exhibit a maximum tensile strain of several percent owing to the synergeticeffect of high-performance fiber and specifically designed mortar matrix. Unprecedented highperformance structural members can be expected when ECC is applied to seismic components.
It is considered that the fiber in fiber-reinforced cementitious composite causes scale effectwhich is mainly influenced by fiber orientation. For example, the small size of specimens suchas plate type shows higher tensile strength and deformation capacity because of twodimensional fiber orientation.
This paper describes the test results of bending and shear test of ECC which is reinforced bypolyvinyl alcohol fiber (PVA-ECC). The adopted test methods are 4-point bending test andOhno type shear test to obtain fundamental flexural and shear behaviors of PVA-ECC,respectively. The test parameters are sectional size of specimens and fiber volume fraction of
PVA fiber. Test results are mainly discussed on flexural / shear strength and deformation
capacity influenced by sectional size. The ratio of experimental strength to calculated one isevaluated by volume of specimens.
Keywords: Engineered Cementitious Composite, flexural strength, shear strength, bending test,shear test.
______________________________________
Toshiyuki Kanakubo
Dept. of Engineering Mechanics and Energy, University of Tsukuba
1-1-1, Tennhdai, Tsukuba-city, 305-8573
Japan
Email: kanakubo@kz.tsukuba.ac.jp
Tel: +81 29 853 5045

1.0 Introduction
High Performance Fiber-Reinforced Cementitious Composites (HPFRCC), which show a strain
hardening branch and multiple cracking (Figure 1) under uniaxial tensile stress, have been focusedby lots of researchers because of its unique mechanical performance. Engineered Cementitious
Composites (ECC) exhibit a maximum tensile strain of several percent owing to the synergetic
effect of high-performance fiber and specifically designed mortar matrix. Unprecedented highperformance structural members can be expected when ECC is applied to seismic components [1].
It has been cleared that cementitious materials such as concrete show scale effect on theirmechanical properties due to size of aggregates, existence of air void, and so on. In addition, it isconsidered that the fiber in fiber-reinforced cementitious composite causes scale effect which ismainly influenced by fiber orientation. For example, the small size of specimens such as plate typeshows higher tensile strength and deformation capacity because of two-dimensional fiberorientation [2]. If we use some test pieces to check the mechanical properties of HPFRCC, it isnecessary to have information about the relationships between properties obtained by test pieces
and those in actual structures.
This paper describes the test results of bending and shear test of ECC which is reinforced bypolyvinyl alcohol fiber (PVA-ECC). The adopted test methods are 4-point bending test and Ohno
type shear test to obtain fundamental flexural and shear behaviors of PVA-ECC, respectively. The
test parameters are sectional size of specimens and fiber volume fraction of PVA fiber. Test results
are mainly discussed on flexural / shear strength and deformation capacity influenced by sectional
size. The ratio of experimental strength to calculated one is evaluated by volume of specimens.

Tensile stress (MPa)5432Specimen 1
Specimen 2
Specimen 3
Specimen 4100123
4
Tensile strain (%)

5Figure 1. Strain hardening behavior and multiple cracking of ECC.

2.0 Outline of Loading Test
2.1 Specimen
The dimensions and reinforcing bar arrangements of the specimens are shown in Figure 2 and 3for bending test and shear test, respectively. The lists of specimens are shown in Table 1 and 2.

Main parameters of bending test specimen are height of section (40mm, 100mm and 280mm) andpresence of main bars. All specimens have same ratio of loading span to section height, and mainbar ratio (pt) is also same. 4-point loading is carried out using the universal loading machine.
Measurement items are load and axial deformation between pure bending region along the upperand lower position as shown in Figure 2. The axial deformation is used for calculation of averagecurvature.
Main parameters of shear test specimen are height of section (50mm, 100mm and 280mm) andstirrup ratio (pw). The ratio of shear span to section height is same as 1.25 for all specimens.
Loading was carried out by Ohno method under anti-symmentrical moment with monotoricmanner. LVDTs are set to measure relative displacement between the stubs.

LVDT

S-sizeM-sizeL-sizeFigure 2. Bending test specimen.

S-sizeFigure 3. Shear test specimen.

M-sizeL-size2.2 Material Properties of PVA-ECC
PVA fiber shown in Table 3 was utilized in this research. Fiber volume fraction was set to 1.0, 1.5and 2%. Water / binder ratio was 42.7%. Compressive strength at the testing age ranges from 40.3
to 44.4MPa by using 100 -200mm cylinder test piece. Hereafter, PVA-ECC with 1.0%, 1.5% and2.0% volume fraction is identified as PVA10, PVA15 and PVA20, respectively.

Table 1. List of bending test specimen.
Fiber volume
Sectional sizeSpecimen
fraction Vf (%)
b×D (mm)
PVA10-F-S
1.0
PVA15-F-S
1.5
PVA20-F-S
2.0
40×40
PVA10-FR-S
1.0
PVA15-FR-S
1.5
PVA20-FR-S
2.0
PVA10-F-M
1.0
PVA15-F-M
1.5
PVA20-F-M
2.0
100×100
PVA10-FR-M
1.0
PVA15-FR-M
1.5
PVA20-FR-M
2.0
PVA10-F-L
1.0
PVA15-F-L
1.5
PVA20-F-L
2.0
280×280
PVA10-FR-L
1.0
PVA15-FR-L
1.5
PVA20-FR-L
2.0Main bar
Arrangement Yeild strength (MPa)--2-D3pt=1.04%

222--3-D6
pt=1.04%

382--5-D13
pt=1.04%

363

Table 2. List of shear test specimen.
Fiber
Main bar
Stirrup
Sectionvolumeb×D
Specimen
Yld.
Yld.
fraction
Arrangement
Arrangement
(mm)
(MPa)
(MPa)
Vf (%)
PVA10-00-S
32×50
1-D6 pt =2.41%
729
PVA10-00-M
64×100
4-D6 pt =2.43%729
1.0
PVA10-89-M
2-D3@25
222
PVA10-89-L
2-D6@40382
180×280 8-D13 pt =2.43% 722
PVA10-120-L
4-D6@59
382
PVA15-00-S
32×50
1-D6 pt =2.41%
729
PVA15-00-M
729
64×100
4-D6 pt =2.43%
1.5
2-D3@25
222
PVA15-89-M
PVA15-89-L
2-D6@40382
180×280 8-D13 pt=2.43% 722
4-D6@59
382
PVA15-120-L
PVA20-00-S
32×50
1-D6 pt =2.41%
729
PVA20-00-M
729
64×100
4-D6 pt =2.43%
2.0
2-D3@25
222
PVA20-89-M
PVA20-89-L
2-D6@40382
180×280 8-D13 pt =2.43% 722
PVA20-120-L
4-D6@59382

pw (%)
0.00
0.89
0.89
1.20
0.00
0.89
0.89
1.20
0.00
0.89
0.89
1.20

Lots of uniaxial tension test methods for cementitious composites have been proposed andinvestigated by the numbers of researchers. In actual fact, however, uniaxial tension test requires

special loading equipment, mold and much time to perform. In this research, the bending test
which is specified as Japan Concrete Institute Standard (JCI-S-003-2005) [3] is adopted (Figure 4).
Evaluation method for tensile strength and ultimate tensile strain of fiber reinforced cementitious
composites has been introduced as the Appendix of JCI-S-003-2005. The evaluation method isintroduced based on the following assumptions for stress distribution under the maximum bending
moment as shown in Figure 4.
i)
The stress distribution on the compression side is triangular.
ii)
The stress distribution on the tension side is uniform (ft,b).
These assumptions represent a state in which the strain on the tension edge has reached theultimate strain (εtu,b) but the stress on the compression edge has not reached the compressive
strength under the maximum bending moment. It is considered that these assumptions generally
agree with actual strain and stress distributions of ECC. Table 4 summarized compression test andbending test results. Bending test results are obtained by the specimens PVA10-F-M, PVA15-F-M
and PVA20-F-M.
Table 3. Mechanical properties of PVA fiber.
Fiber length
Fiber diameter Tensile strength
(mm)
(mm)
(MPa)
120.040
1600

Elastic modulus
(GPa)
40

xnεtu,bφu

M max

f t,b

Strain distribution
Stress distribution
Figure 4. Bending test setup and evaluation method by JCI-S-003-2005.
Table 4. Mechanical properties of PVA-ECC.
Compression
Compressive
ElasticID
strengthmodulus
(MPa)
(GPa)
PVA2016.7
42.5
PVA15
17.4
42.0
PVA10
18.1
40.2

Strain atmax.
(%)
0.53
0.42
0.40

Tension
UltimateTensile
strainstrength
(%)
(MPa)
4.76
1.07
2.39
0.42
2.83
0.58

3.0 Test Results
3.1 Bending Test
Examples of crack patterns after loading are shown in Figure 5 and 6. As shown in Figure 5, in thespecimens without main bars, cracks took place over the pure bending region uniformly in S-size
specimens, while multiple cracks concentrated in the certain region in M and L-size specimens.
While the number of cracks is larger in L-size specimens, crack spacing is smaller in S-size
specimens. As shown in Figure 6, in the specimens with main bars, fine cracks took place
uniformly with the crack spacing as almost 4mm.

PVA20-F-S
PVA20-F-M
PVA20-F-L
Figure 5. Crack patterns of bending test specimen without main bars after loading.

PVA20-FR-M
Figure 6. Crack patterns of bending test specimen with main bars after loading.

Near
Origin0点近傍1510S-size
サイズS試験体
M-size
サイズM試験体
L-size
サイズL試験体
First crack○ 初期ひび割れ点Maximum moment□ 最大モーメント点

5000.1

Bendingstrain (%)
曲げ歪(%)40

PVA20-Fseries
PVA20Fシリーズ
Bending
stress (MPa)
曲げ応力(MPa)

Bending
stress (MPa)
曲げ応力(MPa)

Relationships between bending stress and bending strain are shown in Figure 7. Bending stress iscalculated by bending moment divided by modulus of section. Bending strain is defined ascurvature at pure bending region multiplied by half of section height. Deflection hardening
behavior which means that load increases after first cracking is observed in all the specimens. Inthe specimens with main bars, maximum bending stress is obtained by the compressive failure atthe compression side. The maximum bending stress and deformation capacity of the specimen ofPVA20 is larger than those of specimens of PVA15 and PVA10. The differences in bending stressand bending strain between L, M and S-size specimens without main bars are recognizedremarkably. It is assumed that theses differences are due to fiber orientation that fiber direction

01

2

Bendingstrain (%)
曲げ歪(%)

3Figure 7. Bending stress - bending strain curve.

4NearOrigin0点近傍

PVA20-FR
seriesPVA20FRシリーズ

3020
サイズS試験体
S-size
サイズM試験体
M-sizeL-size
サイズL試験体
First crack○ 初期ひび割れ点Maximum moment□ 最大モーメント点

10000.2 0

Bending
strain (%)
曲げ歪(%)

123

曲げ歪(%)
Bending
strain (%)

45

shows the tendency of placing along the axial direction in case of smaller specimens. In thespecimens with main bars, maximum stress of M-size specimen shows higher value rather than Ssize specimen. It is considered that this phenomenon is due to the difference of yield strength ofmain bars.
3.2 Shear Test
Examples of crack patterns after loading are shown in Figure 8. All specimens failed by shear with
opening certain crack at the ultimate stage. Fine cracks were observed along the major crack. The
difference of crack patterns by specimen size was not recognized. Relationships between shear
stress and translational angle are shown in Figure 9. The shear stress is calculated from shear force
divided by sectional area between tension and compression main bars. S-size specimens show
higher shear strength rather than that of M-size specimen in case of no stirrup (pw=0%). On theother hand, the shear strength of M-size specimen with stirrup (pw=0.89%) is smaller than one ofL-size specimen. The reason of this is considered that yield strength of stirrup of M-size specimen
is smaller than that of L-size specimen.

PVA20-00-S

PVA20-00-M

PVA20-89-M
PVA20-89-L
Figure 8. Crack patterns of shear test specimen after loading.

PVA20 pw=0.00%

5432

サイズS試験体
S-size
サイズM試験体
M-size
最大せん断応力点
Maximum load

100204060-380

Shear stressせん断応力τs(MPa)(MPa)Shear stress
せん断応力
τs(MPa)(MPa)

6PVA20 pw=0.89%

1050-3

Translational
angle (x10部材角 (x10rad) rad)Figure 9. Shear stress - translational angle curve.

M-size
サイズM試験体
サイズL試験体
L-size
最大せん断応力点
Maximum load

020406080-3
Translational
angle-3(x10部材角 (x10rad) rad)

4.0 Evaluation of Flexural and Shear Strength
4.1 Flexural Strength
It has been reported that the flexural strength considering scale effect can be evaluated by highstress volume of the specimen [4]. In this paper, tensile strength obtained by the method of theAppendix of JCI-S-003-2005 is evaluated using bending test specimens without main bars. Thehigh-stress volume is assumed to be same as the volume of pure bending region. The relationshipbetween high-stress volume (V) and tensile strength is shown in Figure 10. The tensile strength(ft,b) is standardized by the tensile strength obtained by M-size specimen (ft,b-M). In this figure, thetest results of bending test specimen with steel fiber reinforced ultra high-strength concrete [5] arealso indicated with the identification of DCT. The same tendency that small specimens show
higher tensile strength can be recognized in spite of the differences of fiber volume fraction andfiber types. The following equation is obtained by regression analysis.

f t ,b / f t ,b − M = 6.72 ⋅V −0.144(1)

The tensile strength can be evaluated by Eq. (1) for any size specimen using tensile strength of Msize (section: 100x100mm) specimen. Using this relationship, flexural strength of the specimen
with main bars is calculated by section analysis. The tensile stress – strain relationship of PVAECC is assumed to be perfect elastic-plastic model with the yield strength of ft,b. Figure 11 shows
the comparisons of flexural strength between experimental values and calculated ones. The
average of the ratio of experimental values to calculated ones is 1.33.

6.72
V -0.133
5.9Vft,b/σ/ ft,b-M
σmax
M max

-0.144

3PVA10
PVA15
PVA20
DCT

Flexural strength
曲げ強度
Test / cal
実験値／計算値

1.5

10.5
104105106107
23High-stressvolume) (mm )
体積(mm108

Figure 10. Relation between high-stressvolume and tensile strength.

○ PVA10△ PVA15□ PVA20▽ DCT210SMLSpecimen size
試験体サイズFigure 11. Comparison of flexural strength
between experiment and calculation.

4.2 Shear Strength
The shear strength is evaluated by Japan Society of Civil Engineers (JSCE) Method [6] shown in
the following equations. Tensile strength of PVA-ECC for each size of specimen is calculatedusing Eq. (1).

Q = Qc + Qs + Q fQc: shear strength of member without stirrup (equal to ordinary RC member)

(2)

()

Qc = 4 1 / d ⋅ 3 100 pt ⋅ 0.7 × 0.203 f c ⋅ b ⋅ dQs: shear strength by stirrup (equal to ordinary RC member)

Qs = p w ⋅ f wy ⋅ b ⋅ (d / 1.15)
Qf: shear strength by HPFRCC (ECC)

Q f = f t ,b ⋅ b ⋅ (d / 1.15)
where,dpt
fcpw
fwy
bft,b

: effective height of member: main bar ratio: compressive strength: stirrup ratio: yield strength of stirrup: width of member: tensile strength of HPFRCC (ECC)

Figure 12 shows the comparisons of shear strength between experimental values and calculated
ones. The average of the ratio of experimental values to calculated ones is 1.28.
3Test / cal
実験値／計算値

Shear strength
せん断強度

2○ PVA10△ PVA15PVA10□ PVA20
PVA15▽ DCTPVA20
void mark:DCT
no stirrup
中白：肋筋なし
solidmark:
中塗：肋筋ありwith stirrup

10S

MSpecimen size
試験体サイズ

LFigure 12. Comparison of shear strength between experiment and calculation.

5.0 Conclusions
This paper described the test results of bending and shear test of PVA-ECC. The test parameters
were sectional size of specimens, presence of steel reinforcements and fiber volume fraction of
PVA fiber. The size effect was observed that smaller specimen show higher strength anddeformation capacity both for flexural and shear performance. Tensile strength of PVA-ECC wasevaluated by 4-point bending test specified by JCI-S-003-2005 Method. Scale effect for the tensile
strength was expressed by the high-stress volume of the specimen. The flexural strength and shear
strength of the specimens show good agreements with calculated ones using evaluated tensile
strength of PVA-ECC.

6.0 References
1. Kanda, T., Tomoe, S., Nagai, S., Maruta, M., Kanakubo, T. and Shimizu, K., “Full Scale
Processing Investigation for ECC Pre-cast Structural Element,” Journal of Asian Architecture andBuilding Engineering, Vol.5, No.2, Architectural Institute of Japan, 2006, pp.333-340.
2. Kanakubo, T., “Tensile Characteristics Evaluation Method for Ductile Fiber-Reinforced
Cementitious Composites,” Journal of Advanced Concrete Technology, Vol.4, No.1, Japan
Concrete Institute, 2006, pp.3-17.
3. Japan Concrete Institute, “Method of test for bending moment – curvature curve of fiberreinforced cementitious composites (JCI-S-003-2005),” Journal of Advanced Concrete
Technology, Vol.4, No.1, Japan Concrete Institute, 2006, pp.73-78.
4. Urano, T., Murakami, K., Mitsui, Y. and Shigaki, T., “Studies on Application to FlexuralAnalysis of Tension-Softening and Its Size Effect of Steel Fiber Reinforced Concrete,” Journal ofStructural and Construction Engineering, No.463, Architectural Institute of Japan, 1994, pp.1-7(in Japanese).
5. Shimizu, K., Kudoh, S. and Kanakubo, T., “Size Effect on Flexural and Shear Behavior ofDFRCC,” Proceedings of the Japan Concrete Institute, Vol.28, Japan Concrete Institute, 2007 (inJapanese).
6. Japan Society of Civil Engineers, “Recommendations for Design and Construction of High
Performance Fiber Reinforced Cement Composite with Multiple Fine Cracks,” Concrete Library
127, Japan Society of Civil Engineers, 2007, pp.30-31.