6Î æ4P Ô # $å...9Ö É.3 ¿ G# $å5Ô ^ É.3 Ï(» キーワード：農業用コンクリート水路，摩耗機構，促進摩耗試験，セメント系材料，カルシウム溶脱

キーワード：農業用コンクリート水路，摩耗機構，促進摩耗試験，セメント系材料，カルシウム溶脱

Ⅰ 緒言

１研究の背景

Fig. 1 1960

2003 40%2008

41%

1999

5

2000 3

2005 3

20052010 3

2010

2010

a 農業水利施設のストックマネジメント

200225

2002

20022002

2003

2007

Fig. 1 Food self-sufficiency ratio of the major industrial countries based

on calories

0

50

100

150

200

250

300

350

400

1960 1970 1980 1990 2000

(%)

1

農工研報 521～ 57, 2013

2005

b 農業水利施設の性能管理

2003Fig.

2

2001 Fig. 3

Fig. 4

Fig. 2

Concept of management for the performance of facilities

農業水利施設

構造性能

水理性能

水利用性能

管理者

食料・農業・農村基本計画

直接管理

間接管理

2 農村工学研究所報告　第 52号　（2013）

2004 Table 1

2007

20032009

2004Fig. 5

Fig. 3

2001 General maintenance procedures

構造物

点検

劣化予測

評価および判定

対策

対策不要

対策必要

維持管理区分の決定

初期点検

維持管理区分の設定

大規模対策

Fig. 4 Performance based maintenance procedures

構造物

点検

劣化予測

要求性能の設定

現況性能確認

性能低下予測

評価および判定

対策

対策不要

対策必要

農業水利施設性能

対策不可

Table 1 2004 Present state of verification for the performance of concrete structures

3渡嘉敷勝：農業用コンクリート水路における摩耗機構および促進摩耗試験に関する研究

Fig. 6A F

3040

Fig. 6 G

c 農業水利施設における摩耗現象

2007

2008a

Fig. 7

2002

2009

２既往の研究

a 摩耗に関する研究

41993

Fig. 5

2004 Repair and reinforcement design procedures based on the

performance verification

構造物の点検

劣化メカニズムを考慮した劣化進行予測

劣化進行に伴う性能低下予測

補修・補強工法の仮定

供用期間中の構造物の性能＞要求性能

工法と材料への要求性能決定

供用期間中の構造物の性能＞要求性能

工法と材料の仮定

工法と材料の性能＞要求性能

工法と材料の決定

YES

YES

YES

NO

NO

NO

Fig. 6 Performance verification regions of repair and reinforcement

methods

付着性（耐久性）G

既設躯体への追従性G

施工条件への適応性G

凍結融解抵抗性G

耐摩耗性F

耐変質性F

耐候性F

付着性D

躯体表層強度B

平滑性A

水密性A

強度ほか材料特性A

性能試験項目領域

付着性（耐久性）G

既設躯体への追従性G

施工条件への適応性G

凍結融解抵抗性G

耐摩耗性F

耐変質性F

耐候性F

付着性D

躯体表層強度B

平滑性A

水密性A

強度ほか材料特性A

性能試験項目領域

A B

C

D

EFG

補修・補強材料

既設構造物

環境

（温度，日射，乾湿繰り返し，流量，オゾン，塩分，CO2など）

Fig. 7

Erosion state of concrete irrigation canal


2

1

2010

1993

1993 b 水利コンクリート構造物の摩耗に関する研究

1979 ACI Committee 210 1993 Momber Kovacevic1994 Horszczaruk 2009

ACI Committee 210 1993

2001

FEM

Li and Liu 1999 Shimizu et al. 1999 Aquaro 2006Wang and Yang 2009

Hassan and Kosmol 2001Cellular Automata CA

3 CAValette et al. 2006 Chopard

and Dupuis 2002Orbanic and Junkar 2004D'Ambrosio et al. 2001 FEM CA

CA

CA

c 水利コンクリート構造物のカルシウム溶脱に関する

研究

2005 2009EPMA

CaCa

Ca2001 2004

2000 1991

2003Bentz Garboczi 1992

CaCarde et al. 1996

20002001 2002

Ca

d 促進摩耗試験に関する研究

2007JIS

JIS A 1453JIS K 7204

ASTMASTM C 418

ASTM C 1138

1984


19861999

JIS K 7204

ASTM C 418 ASTM C 1138

ASTM C 418ASTM C 1138

Goretta et al. 1999 Momber 2000

Momber and Kovacevic 1994 Hu et al. 20022005 Liu et al. 2006 2010

2010

2006

３研究の目的と論文の構成

6 Fig. 8

EPMA

Ca

４本論文における用語の定義

20012007

2007

2003

Fig. 8 Structure of this paper


Ca

Ca Ca

Ⅱ 農業用コンクリート水路の摩耗状況

１緒論

2005 2008 2009

調査地区および方法

調査地区

F

G

5 32 EPMA

摩耗形状計測

Fig. 92008

0.01 mm 100 mm 0.5 1 mm1000 500 500 mm

Ra RzRa Fig. 10

lx y

y = f(x)

(1)

Rz lRa Rz

Fig. 9

Measuring device for eroded surface profile

Table 2 Summary of field investigations

Gmax (mm)

EPMA

A 40 20

B 51 40

C 35 40

D 38 25

E 38 20

F 30 40

G 2 5

２

a

b

= | ( )|

Table 2 A E 5


(2) B B Fig. 14

Ra Fig. 15 BFig. 14

BA

(3) C C Fig. 16

Ra Fig. 17C1 C6 C7 C6 C1 1,500 m

C7 C6 300 m C1 C6

C760 cm

C7C1 C6

Fig. 11 EPMA EPMA analysis section of the specimen

Table 3 EPMA EPMA analysis conditions

15 kV

300 nA

100 m

100 m

30 msec

800 800

80.0 mm 80.0 mm

Ca Si S Al

y

x

線

RaRz平均線

80mm

80mm

10mm

ｃ粗度係数推定

2008

(2) (3)

(4) n ks Ra

Rz (2) ks(3) (4) 2

Ra Rz ｄ元素分析

EPMA Electron Probe Micro AnalyzerEPMA-1600 D E

36 Fig. 11

EPMA Table 3 EPMA

Ca 2006

Si Al 2

３結果と考察

ａ摩耗状況

(1) A A Fig. 12

Ra Fig. 13 6070 cm 100 110 cm

Fig. 10 Ra Rz Ra

Concepts of arithmetic average roughness Ra and maximum height Rz

= 0.042 = 2 × = 0.26 ×


(4) D D Fig. 18

Ra Fig. 19

20 cm

Fig. 19

(5) E E Fig. 20

Ra Fig. 2130 40 cm

60 70 80 cm100 120 cm

(6)

5 Fig. 22A 0.0113 B 0.0192

Fig. 12 A

Canal state in the A district

Fig. 13 A Ra

Arithmetic average roughness Ra versus the height of the canal sidewall from the bottom in the A district

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 20 40 60 80 100 120

Ra

(mm

)

(cm)

Fig. 14 B

Canal state in the B district

Fig. 15 B Ra

Arithmetic average roughness Ra versus the height of the canal sidewall from the bottom in the B district

0.0

1.0

2.0

3.0

4.0

5.0

0 50 100 150 200

Ra

(mm

)

(cm)


BB

0.0113 0.01562001

0.012 0.016 B

0.0136 0.0192B

50

Fig. 23 Ra Rz

B26.4 mm

2 a) Ra Rzb) B 10

mm a) 5

0.93

b)

Fig. 16 C Canal state in the C district

Fig. 17 C Ra

Arithmetic average roughness Ra versus the height of the canal sidewall from the bottom in the C district

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 20 40 60 80 100

Ra

(mm

)

(cm)

C1C6C7

Fig. 18 D

Canal state in the D district

Fig. 19 D Ra

Arithmetic average roughness Ra versus the height of the canal sidewall from the bottom in the D district

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 20 40 60 80 100

Ra

(mm

)

(cm)


20086 mm

4010 mm 6 mm 16 mm

Fig. 24 Ra Rz

1:10.015

0.015

(7)

Fig. 25 F

Fig. 26

Fig. 14

Fig. 20 E

Canal state in the E district

Fig. 21 E Ra

Arithmetic average roughness Ra versus the height of the canal sidewall from the bottom in the E district

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 20 40 60 80 100 120 140

Ra

(mm

)

(cm)

Fig. 22 Estimated roughness coefficient from arithmetic average roughness

Ra versus the height of the canal wall from the bottom

0.010

0.012

0.014

0.016

0.018

0.020

0 50 100 150 200

Ra

n

(cm)

A

B

C

D

E

Fig. 23 Ra Rz Maximum height Rz versus arithmetic average roughness Ra

0

5

10

15

20

25

30

0 1 2 3 4 5

Rz (

mm

)

Ra (mm)

A

B

C

D

E

Fig. 24 Ra Rz

Estimated roughness coefficient from Rz versus that from Ra

0.010

0.012

0.014

0.016

0.018

0.020

0.010 0.012 0.014 0.016 0.018 0.020

Rz

n

Ra n

A

B

C

D

E

1:1


Fig. 27 (8) G Fig. 28

Fig. 26

Macrograph of abraded surface. White circles indicate the desorption pits of coarse aggregate.

Fig. 27 Concepts of weak and strong erosion action, and the results of

eroded states by each action

Fig. 28 G

Eroded canal state after repair in the G district. The polymer cement paste is lost, the fine aggregate remains at the surface.

Fig. 25 F

Apron state of head works in the F district


150 mm

150 mm

200 mm

Fig. 29 D Ca 2 Ca 2

2-dimensional distribution image and concentration profile of Ca in canal concrete specimen in the D district. From the upper: sidewall in the air portion, sidewall in submerged portion, and the bottom.

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30 35

(mm

)

(mass%)

20 mm

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30 35

(mm

)

(mass%)

36 mm

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30 35

(mm

)

(mass%)

15 mm


b 元素分析

D E EPMAFig. 29 Fig. 30

3Ca Si S Al 4 Ca

Ca

1991 1997 2000 2001

150 mm

150 mm

200 mm

Fig. 30 E Ca 2 Ca 2

2-dimensional distribution image and concentration profile of Ca in canal concrete specimen in the E district. From the upper: sidewall in the air portion, sidewall in submerged portion, and the bottom.

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30 35

(mm

)

(mass%)

13 mm

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30 35

(mm

)

(mass%)

18 mm

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30 35

(mm

)

(mass%)

23 mm


2001 20022003 2004

Ca2005 2008

2009 Ca

(1) Ca(2)

13 36 mm (3) Ca18 30% (4) Ca

DCa Ca

Ca

Ca

Ca CaFig. 31

CaCa

Ca

c 実水路における摩耗状況

4016 mm

Ca

EPMA Ca

４結論

Ca

(1)

(2) D

(3) 5

A 0.0113 B 0.0192

(4) B0.0113 0.0156

0.012 0.016

(5) Ra Rz

(6) B 10 mm

(7) 40 16 mm

(8)

(9) EPMA Ca

13 36 mmCa 18 30%

(10)

Fig. 31 Ca

Distance from the specimen surface to the Ca leaching front versus the initial Ca concentration

05

1015

202530

3540

0 10 20 30

(mm

)

Ca (mass%)

D

D

D

E

E

E


(11) Ca

Ca Ca

CaCa

Ⅲ 水噴流摩耗試験

１緒論

2

1993

2007JIS JIS A 1453

JIS K 7204

ASTM ASTM C 418ASTM C

1138

1984 19861999

JIS K 7204



2005

Momber and Kovacevic 1994 Hu et al. 2002 Liu et al. 2006

２水噴流摩耗試験の試験方法

a 水噴流摩耗試験機

Fig. 32

296 14260 mm 70 70 20 mm

6

Fig. 33


1987

b 摩耗量計測

KEYENCE LK-500 10 m Fig. 34

1 mm5

mm 1150 mm 51 11=561

３水噴流摩耗試験における吐出圧力および回転速度

の影響

a 試験方法

(1) 2

Table 42

10 mm

Table 4

Specifications of two types of water jet tester

(MPa)

(MPa)

(L/min)

(m/s)

(m2) (°) d (mm)

x (mm)

x/d

(mm/mm)

A 4.9 3.0 - 4.5 19.1 - 23.4 82.7 - 102 3.8×10-6 40 2.2 70 32

B 20 4.5 - 20.0 11.9 - 25.2 79.4 - 168 2.5×10-6 40 1.8 80 44

Fig. 32

Overview of the water jet erosion tester

Fig. 33 Testing state of water jet

Fig. 34

Measurement domain of the erosion depth of specimen

1

3

4

6

7

5 1

2

3

4

5

6

5

7

2

50m

m

5mm11

50mm


(2)

JIS R 5201

W/C=50%W/C=40% 2

296 142 60 mm 120 14

Table 5

(3) Table 6 9 A3.0 4.5 MPa B 4.5

20.0 MPa AW/C=50% 40% 2

B 330 rpm A04560 B2006060 rpm B20060

1 5 146 10 24

b 結果と考察

(1) Fig. 35

A B4.5 MPa A B

1.9 Fig. 36

Bernoulli

(5)

p

(5) v

(6)

Table 5 Water-cement ratio and compressive strength of specimen

W/C (%)

(N/mm2)

7 14 21 28

WC50 50 37.0 43.9 45.9 47.1

WC40 40 58.5 62.8 66.9 66.7

Fig. 36

Comparison of water jet flow velocity as a function of the discharge pressure with device A and B

0 5 10 15 20 250

50

100

150

200

(MPa)

(m/s

)

A━━A Cv

B━━B Cv− − Bernoulli

Fig. 35

Comparison of discharge flow rate as a function of the discharge pressure with the device A and B

0 5 10 15 20 250

5

10

15

20

25

30

(MPa)

(L/m

in)

AB

Table 6 Test cases

(MPa)

(rpm)

(hour) (hour)

A03030 A 3.0 30 260 20

A04030 A 4.0 30 140 20

A04530 A 4.5 30 140 20*1

A04560 A 4.5 60 140 20

B04530 B 4.5 30 140 20

B10030 B 10.0 30 10 1

B15030 B 15.0 30 10 1

B20030 B 20.0 30 10 1

B20060 B 20.0 60 10*2 1

= 2

= 2


cv 1996 Fig. 36 (6)

cv A1.06 B 0.836

A cv 1 (5)v

B vl < v

A

(2)

Fig. 37Fig. 34

AA04530 0 mm

B B04530 B2003015 mm

B

B

25 +25 mm35 +33 mm 74%

Fig. 37

Examples of the eroded cross-sectional shape

-50 -40 -30 -20 -10 0 10 20 30 40 50-25

-20

-15

-10

-5

0

(mm) (m

m)

A04530 140hB04530 140hB20030 10h

Fig. 38 A

Erosion depth and rate at each discharge pressure using the device A. From the upper: 3.0, 4.0, 4.5 MPa.

0 50 100 150 200 250 3000

2

4

6

8

10

(mm

)

WC50-1WC50-2WC40-1WC40-2

A03030

0 50 100 150 200 250 3000.00

0.02

0.04

0.06

0.08

0.10

(mm

/h)

WC50-1WC50-2WC40-1WC40-2

A03030

0 20 40 60 80 100 120 140 1600

2

4

6

8

10

(mm

)

A04030

0 20 40 60 80 100 120 140 1600.00

0.02

0.04

0.06

0.08

0.10

(mm

/h)

A04030

0 20 40 60 80 100 120 140 1600

2

4

6

8

10

(h)

(mm

)

A04530

0 20 40 60 80 100 120 140 1600.00

0.02

0.04

0.06

0.08

0.10

(h)

(mm

/h)

A04530


(3)

AFig. 38

3.0 MPa4.0

MPa W/C=50% 40%

20

W/C=50% 4.5 MPa100

B

Fig. 39 B A

Fig. 39 B

Erosion depth and rate at each discharge pressure using the device B. From the upper: 4.5, 10.0, 15.0, 20.0 MPa.

0 20 40 60 80 100 120 140 1600

2

4

6

8

10

(mm

)

WC50-1WC50-2WC50-3WC40-1WC40-2WC40-3

B04530

0 20 40 60 80 100 120 140 1600.00

0.02

0.04

0.06

0.08

0.10

(mm

/h)

WC50-1WC50-2WC50-3WC40-1WC40-2WC40-3

B04530

0 2 4 6 8 10 120

2

4

6

8

10

(mm

)

B10030

0 2 4 6 8 10 120.0

0.2

0.4

0.6

0.8

1.0

1.2

(mm

/h)

B10030

0 2 4 6 8 10 120

2

4

6

8

10

(mm

)

B15030

0 2 4 6 8 10 120.0

0.2

0.4

0.6

0.8

1.0

1.2

(mm

/h)

B15030

0 2 4 6 8 10 120

2

4

6

8

10

(h)

(mm

)

B20030

0 2 4 6 8 10 120.0

0.2

0.4

0.6

0.8

1.0

1.2

(h)

(mm

/h)

B20030


W/C=50% 40%4.5

MPa 20 10 MPa 1 2

A B 4.5 MPa

A B BW/C=50% 148% W/C=40% 114%

A B1.9

10 mm Fig. 40

(7)

ER Xa, b

Table 7

Fig. 40

Erosion rate versus the discharge pressure and the water jet flow velocity

A, WC50B, WC50

A, WC40B, WC40

1 10 1000.001

0.01

0.1

1

(MPa)

(mm

/h)

A, W/C=50%B, W/C=50%

A, W/C=40%B, W/C=40%

10 100 10000.001

0.01

0.1

1

(m/s)

(mm

/h)

Table 7 Regression parameters of the test results by power function

W/C (%)

a b

A 50 6E-06 5.74 0.988

B 50 5E-04 2.55 0.987

A 40 1E-04 2.81 0.957

B 40 1E-04 2.78 0.967

A 50 4E-25 11.48 0.988

B 50 5E-12 5.10 0.987

A 40 5E-14 5.62 0.957

B 40 2E-13 5.56 0.967

Fig. 41 30 rpm 60 rpm

Comparison of the erosion rate with the test drum rotation at 30 and 60 rpm with discharge pressure 4.5 and 20.0 MPa

0 20 40 60 80 100 120 140 1600.00

0.01

0.02

0.03

0.04

0.05

(h)

(mm

/h)

A, 4.5MPa 30rpm-50 30rpm-4060rpm-50 60rpm-40

0 2 4 6 8 10 120.00.20.40.60.81.01.21.41.6

(h)

(mm

/h)

B, 20.0MPa 30rpm-50 30rpm-4060rpm-50 60rpm-40

=


22

W/C = 40% AB

A B

(4)

30 rpm 60 rpmFig. 41 W/C=40%

4.5 MPa 20.0 MPaW/C=50%

4.5 MPa 30 rpm 60 rpm 20.0 MPa60 rpm 30 rpm

４セメントペースト試験体およびモルタル試験体の

摩耗特性

a 試験方法

(1) 2 1 3

Table 8JIS R 5201 M40 S/C

M50296 142 60 mm

2 128

(2) Table 9 A

28 672

1 2 3 4 7 14 21 28

b 結果と考察

(1) Fig. 42

Fig. 43

Fig. 44Fig. 45 Fig. 46

M50 Fig. 47 C50 Fig. 48

M50

Table 8 Mix proportion and compressive strength of specimen

W/C (%) S/C

28 (N/mm2)

M50 50 3.0 39.1

M40 40 2.6 51.1

C50 50 0 40.7

Table 9 Conditions of water jet erosion test

4.5 MPa

24.1 l/min

30 rpm

40

296 142 60 mm

Fig. 42 M40

Surface state of the specimen after erosion test (M40)


C50

(2)

Fig. 49 77

7

Fig. 43

Comparison of the erosion weight of mortar and cement paste specimen

0 7 14 21 280

50

100

150

200

250 (g

)M50-1M50-2M40-1M40-2C50-1C50-2

Fig. 44

Comparison of the erosion volume of mortar and cement paste

0 7 14 21 280

20

40

60

80

100

120

140

(cm

3 )

M50-1M50-2M40-1M40-2C50-1C50-2

Fig. 45

Comparison of the average erosion depth of mortar and cement paste specimen

0 7 14 21 280

5

10

15

20

(mm

)

M50-1M50-2M40-1M40-2C50-1C50-2

Fig. 46

Comparison of the maximum erosion depth of mortar and cement paste specimen

0 7 14 21 280

5

10

15

20

(mm

)

M50-1M50-2M40-1M40-2C50-1C50-2

Fig. 47 M50 28 Eroded surface state of specimen M50 after test (28 days)

Fig. 48 C50 28

Eroded surface state of specimen C50 after test (28 days)


M50 M40 7M40 M50 1.2 2

(3)

Fig. 50 X-X Y-YFig. 51 Fig. 52

C50-2 Y-Y -40 mm

X-X

40

Y-Y

Fig. 53

Fig. 49

Comparison of the average erosion rate of mortar and cement paste

0 7 14 21 280

0.5

1.0

1.5

2.0 (m

m/

) M50-1M50-2M40-1M40-2C50-1C50-2

Fig. 51 X-X 28 Cross-sectional erosion shape at X-X’ (28 days)

-60 -40 -20 0 20 40 60-20

-15

-10

-5

0

X-X' (mm)

(mm

)

M50-1 M50-2 M40-1 M40-2 C50-1 C50-2

Fig. 52 Y-Y 28 Cross-sectional erosion shape at Y-Y’ (28 days)

-80 -60 -40 -20 0 20 40 60 80-20

-15

-10

-5

0

Y-Y' (mm)

(mm

)

M50-1 M50-2 M40-1 M40-2 C50-1 C50-2

Fig. 50

Measurement position of erosion surface shape at the specimen

Ｙ’

Ｘ

(5mm )

Ｘ’

Ｙ


9070 mm

63.4 87 mm63.4

90 87 70 mm

Fig. 52

63.4 90

５コンクリート試験体の摩耗特性

a 試験方法

(1)

3 40%, 50%, 60%

296 142 60 mm

2 128 28

(2)

1 2 3 5 1030 50 100 200

50 50 mm

b 結果と考察

0 3050

10 10

3a

Table 10 Mix proportion of concrete specimen

(mm)

(%)

(%)

(kg/m3)

W C

S

G

A

20 40 43.0 155 387 746 1050 0.968

20 50 43.0 170 340 746 1050 0.850

20 60 43.0 182 303 746 1050 0.757

Table 11 Compressive strength of specimen

W/C (%) 28 (N/mm2)

W/C40 40 41.4

W/C50 50 35.4

W/C60 60 25.1

Table 12 Conditions of water jet erosion test

15 MPa

22.0 l/min

30 rpm

40

296 142 60 mm

Fig. 53

Water jet impact angle and the distance from the nozzle to the specimen

試験体

63.4° 63.4°

70m

m

Table 10

Table 11

Table 12 B

40% Fig. 54

Fig. 55


(1)

(2)

Fig. 560.5 mm 0.22 0.33

mm/h 2 mm0.003 0.004 mm/h 1.1 1.9%

0.5 mm

６コンクリートブロック試験体の摩耗特性

Fig. 57

Fig. 54 W/C40-1

Changes of eroded surface state of specimen versus test time

Fig. 55

Average erosion depth versus test time

0 50 100 150 2000.0

0.5

1.0

1.5

2.0

2.5

3.0

(hour)

(mm

)

W/C40-1W/C40-2W/C50-1W/C50-2W/C60-1W/C60-2

Fig. 57

Eroded state of concrete blocks in an actual canal

Fig. 56 Average erosion rate versus the erosion depth

0.0 0.5 1.0 1.5 2.0 2.5 3.00.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

(mm)

(mm

/h)

W/C40-1W/C40-2W/C50-1W/C50-2W/C60-1W/C60-2

0h 1h 2h 3h 5h

10h 30h 50h 100h 200h


a 試験方法

(1) 2 Table 13

4 18N 40

30N

20 mm

Table 14 Table 15 (2)

B10 MPa

0.018 m3/min 2 318N-1 3 30N-1 3 0

20 40 60 80 102

21 18N-0 30N-0 0 1 3 6

10 15 20

b 結果と考察

(1) Fig. 58

18N 30N20 20

Fig. 59 40

102 18N0.0024 mm/h 30N 0.0025 mm/h

20 18N

Table 13 Mix proportion of concrete specimen

(N/mm2)

(%)

(%)

(kg/m3)

W

C

S

G

A

18N 18 70 39.0 165 236 745 1165 3.54

30N 30 47 39.0 165 351 708 1108 3.51

Table 14 Steam curing conditions of concrete block specimen

(h) 1 2 4 7

( ) 20 20 20/h 60

Table 15 Compressive strength of specimen

(N/mm2)

1 7 14

18N 11.6 20.7 23.8

30N 23.2 41.2 43.5

Fig. 58

Average erosion depth versus test time

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 20 40 60 80 100 120

(mm

)

(h)

18N-1 18N-2 18N-330N-1 30N-2 30N-318N-0 30N-0

Fig. 59 Average erosion rate versus test time

0.00

0.05

0.10

0.15

0.20

0.25

0 20 40 60 80 100 120

(mm

/h)

(h)

18N-1 18N-2 18N-330N-1 30N-2 30N-318N-0 30N-0


Fig. 60

(2)

102 18N-130N-2 18N-0 30N-0 4

(2) (3)Fig. 61

20

102 18N0.0156 30N 0.0145

７カルシウム溶脱試験体の摩耗特性

Ca2005 2009

Ca

Ca Ca

Ca

a 試験方法

(1)

40 50 60% 370 70 20 mm

1 20 28

(2) Ca Ca

3

Ca2+

1993 2001

2002Fig. 62

9 72 72 mm70 70 mm Ca

Ca

(a) (b) 102 h

Fig. 60

Comparison of erosion state of surface at an actual canal and at the specimen after accelerated erosion test (102h)

Fig. 61

Estimated roughness coefficient versus test time

0.008 0.009 0.010 0.011 0.012 0.013 0.014 0.015 0.016

0 20 40 60 80 100 120

n

(h)

18N-1 30N-218N-0 30N-0

Fig. 62 Overview of accelerated Ca leaching test

オン水

定圧装置

試験体

スンレスメッシュ

仕切り板

(a) 試験装置の概要

(b) 仕切り板に設置した試験体

(c) 試験状況


60 V 0.273 V/mm

28 1 1

(3) 28 B

5610 MPa 102

Fig.

630 10 20

30 1 1.5 2 2.5 3 3.5 4 5 10 20 40 6080 102 18

10 mm

40 mm 5 mm9

1 mm 41 369 41 9

(4)

SEM-EDSJSM-5600LV JED-2200

70 20 5 mmSEM-EDS 20 20 5 mm

3.6 mm2.8 mm

Ca Si S Al C Cl FeK Mg Mn Na O P 13

(5)

M2.942 N

15 (8)

HV F N dvmm

SEM-EDS1 2 3 4 5 7

10 mm 10

b 結果と考察

(1)

Fig. 64

10 22 4

10

Fig. 65

Fig. 63

Overview of eroded state, erosion depth measurement position and collection position of specimen for SEM-EDS

Fig. 64

10 Average erosion depth versus test time

0 20 40 60 80 100 1200

5

10

15

20

25

(h)

(mm

)

W/C40W/C50W/C60

W/C40W/C50W/C60

0 2 4 6 8 1001234

70mm

70m

m20

mm

SEM-EDS

40mm

40m

m

= 0.1891


2 3 mm3 mm

Fig. 66 3 mm

40 50 60%19.4 20.1 27.6 3 mm

3 mm 1 3

mm3 mm 3 mm

3 mm

19.4 27.6

(2) Ca SEM-EDS Ca Si X

Fig. 672 mm Ca

Fig. 65

Erosion rate versus erosion depth

0 2 4 6 80

1

2

3

4

5

6

(mm)

(mm

/h)

W/C40W/C50W/C60W/C40W/C50W/C60

Fig. 66

Erosion rate ratio versus erosion depth

0 2 4 6 80

5

10

15

20

25

30

(mm)

W/C40W/C50W/C60

W/C = 40 % W/C = 50 % W/C = 60 %

W/C = 40 % W/C = 50 % W/C = 60 %

Fig. 67 Ca Si X (cps)

K X K Characteristic X-ray intensity distribution of Ca and Si in Ca leached specimens


８補修材料の摩耗特性および推定粗度係数

Fig. 70

Table 16 Estimated chemical alteration depth from specimen surface

(mm)

W/C40 W/C50 W/C60

Ca 2.06 1.93 1.86

2.10 2.41 2.43

Fig. 68 Vickers hardness versus the depth from surface

0 2 4 6 8 10 120

20

40

60

80

100

120

(mm)

W/C40W/C50W/C60

Fig. 69

Erosion rate ratio versus erosion depth near the minimum point

1.5 2 2.5 3 3.5 4 4.50.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

(mm)

W/C40W/C50W/C60

(a) (b)

Fig. 70 Surface states of repair materials. (a) Canal sidewall after repair

construction, (b) canal sidewall after 1 year.

Ca Ca CaCa

Fig. 61 Ca

Fig. 67 Ca

Ca/Si

(3) Si Fig. 67 Si X Ca

CaSi Ca

Si Si2002

SiO2

Ca(OH)2

Ca/Si C-S-HSi

X Si

(4) Table 16

Fig. 67 CaSEM-EDS

Fig. 66 1

Ca

(5)

Fig. 68 40% 50%

3 mm 2 mm

60%3 mm

Fig. 66Fig. 69 2.2 2.7 mm


a 試験方法

5 A E4 1

C50 2 M40 M50

A4.5 MPa 0.023 m3/min

5 0 2040 60 80 100 120 140 160 180 200 300 400500 600 672

0 24 48 7296 168 336 504 672

(2) (3)

b 結果と考察

672 Fig. 71

Fig. 72

M50 M40 A DE B C

B C

200

100

Fig.

73 2

1

A B C

D E C50 Fig. 71

Surface states of specimen after accelerated erosion test

Fig. 72

Average erosion depth versus test time with repair materials

0 100 200 300 400 500 600 7000

5

10

15

20

(h)

(m

m)

AB

CD

EC50

M50M40


22

Fig. 74M50, M40

0.011 0.0152001

M50 M40

Fig. 75

９水噴流摩耗試験機の改良

Fig. 32

4

a 新型試験機の概要

Fig. 76

0 901

4 Fig. 77 b 試験方法

W/C = 50% JIS 12

PCM-AHigh Performance Fiber

Reinforced Cement Composites HPFRCC

15 MPa 0.022 m3/min

Fig. 76

Overview of the new water jet erosion tester

Fig. 73

Examples of surface profile of specimen and the fitted curve for the correction

-20

-18

-16

-14

-12

-10

-8

-6

-4

-2

0

-25 -15 -5 5 15 25

(mm

)

(mm)

ABCDE

C50M50M40

Fig. 74 Estimated roughness coefficient versus test time

0.007

0.008

0.009

0.010

0.011

0.012

0.013

0.014

0.015

0.016

0 200 400 600 800

n

(h)

A

B

C

D

E

C50

M50

M40

Fig. 75

Estimated roughness coefficient versus the average erosion depth

0.007

0.008

0.009

0.010

0.011

0.012

0.013

0.014

0.015

0.016

0 5 10 15 20

n

(mm)

A

B

C

D

E

C50

M50

M40

1

34

6

1

2

3

4

5

6

5

2

65

43

7

7


30 rpm50 mm

30 45 60 75 90 5

0 1 2 3 4 5 (2)

c 結果と考察

JISFig. 78 530 45 2.5 60 75

90 HPFRCCPCM-A 30 90

Fig. 79 1 = 0

Fig. 80 HPFRCCPCM-A

75 90

JIS 45 6075 90

Bitter 1963a 1963b

0 903

JIS

Fig. 81 JIS 7590

JISFig.

82HPFRCC PCM-A

30 75

1

Fig. 77 Conditions of the new water jet erosion tester

Fig. 78 JIS Average erosion depth of JIS mortar at different impact angle of

water jet

0

2

4

6

8

10

0 1 2 3 4 5 6

(mm

)

(h)

30°

45°

60°

75°

90°

Fig. 79 HPFRCC PCM-A

Average erosion depth of HPFRCC and PCM-A at different impact

angle of water jet

0

2

4

6

8

10

0 1 2 3 4 5 6

(mm

)

(h)

HPFRCC(30°)

HPFRCC(45°)

HPFRCC(60°)

HPFRCC(75°)

HPFRCC(90°)

PCM-A(30°)

PCM-A(45°)

PCM-A(60°)

PCM-A(75°)

PCM-A(90°)

Fig. 80 Average erosion rate versus the impact angle of water jet

0.0

0.5

1.0

1.5

2.0

2.5

15 30 45 60 75 90 105

(mm

/h)

( )

JIS

HPFRCC

PCM-A


Fig. 81 JIS

Eroded surface states of the specimens after test

Fig. 84 Specimen preparation methods for accelerated erosion test using collected cores from an actual canal

Fig. 82 JIS Arithmetic average roughness versus the average erosion depth of

JIS mortar

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0 2 4 6 8

Ra

(mm

)

(mm)

30°

45°

60°

75°

90°

(a) D (b) E

Fig. 83 Eroded surface states of the collected cores from the actual canal in

the D and E district

70 70 20 mm

Ca

00 mm

d 水噴流の衝突角度の選定

HPFRCC PCM-A Fig. 8075 90

JIS 75 90

Fig. 83

JISJIS

45

10 現地水路試験体の摩耗特性

2010

1.10 1.72 year/h

a 試験方法

D E100 mm Fig.

84 70 70 20 mmFig. 29

Fig. 30 Ca Ca


Ca D 35 55 mmE 25 45 mm 35 mm

25 mm

15 MPa 0.022 m3/min30 rpm50 mm

45 0 15 30

1 2 4 6 8 10

5a 95%

b 結果と考察

95 Fig. 85Fig. 86 D

15 1.1 mm 24

1 mmD Ca

15 2.7 mm6

E 15 4.6 mm

8

4 mmE Ca

15 1.2 mm8

Ca

D E

CaFig. 86 E

7 CaFig.

87

Ca

Fig. 88 Erosion rate versus the erosion depth using actual canal specimens

0

5

10

15

20

0 2 4 6 8 10 (m

m/h

)

(mm)

D

D Ca

E

E Ca

Fig. 85 95% 95th percentile erosion depth versus test time using actual canal

specimens

0

2

4

6

8

10

0 2 4 6 8 10 12

95%

(mm

)

(h)

D

D Ca

E

E Ca D E

Fig. 86 Eroded surface states of actual canals and accelerated erosion test. A sample in the back is eroded by actual canal and two specimens

in the front are eroded by accelerated erosion test.

Fig. 87 E

Back surface state of collected core in the E district


6

Fig. 88

E5 mm

5 mm E Ca2 mm

11 結論

(1)

(2)

(3)

4.5 MPa 20.0 MPa

(4)

(5)

(6)

(7)

(8) 20

(9) 102

18N-1 0.0156 30N-2 0.0145

(10) Ca19.4 27.6

Ca Ca

(11) Ca

(12) Ca

(13)

(14) 5

(15) 0.011

0.015

(16)

(17)

JIS45

(18)

(19) E Ca


Ⅳ 農業用コンクリート水路における摩耗機構

１緒論

２摩耗機構

2

Ca

Table 17

6 mm 2008

1180

0.31 0.63 mm/year 1.7 3.5 m/day0.43 mm/year 2.4 m/day

Table 18

Table 197.50 1.85 mm 0.90

0.08 mm 50%1.38 mm

0.43 mm/year

Table 18 2008b

Standard grading of the fine aggregate

(mm) 10 5 2.5 1.2 0.6 0.3 0.15

(%) 100 90 100 80 100 50 90 25 65 10 35 2 10

Table 17

Estimated erosion rate in actual canal

(year) Rz (mm)

Rz + 6 (mm) (mm/year) ( m/day)

A 40 6.3 12.3 0.31 1.7

B 51 26.4 32.4 0.63 3.5

C 35 11.2 17.2 0.49 2.7

D 38 8.2 14.2 0.37 2.1

E 38 6.8 12.8 0.34 1.9

Table 19 Typical diameter of the fine aggregate

(mm)

(mm)

(%)

10

5 7.50 10

2.5 3.75 10

1.2 1.85 30

0.6 0.90 25

0.3 0.45 15

0.15 0.23 8

0.08 2


3.2 1.38 mm3.2

D EFig. 89

2

1986Heuer and Walter 1998

3 m/sec

1992

3b 7 Ca 3b Ca

7

Ca20

Ca

Ca

Ca

Carde 1996

Ca

Ca

３摩耗モデル

CaCA

Ca

D

E

Fig. 89 1 1 mm

Eroded surface of collected cores from submerged sidewall in actual canal


a セルオートマトン

CA J. Neumann 1940

1998 1970 J.H. Conwaygame of life

1998 S. Wolfram 1983 CA 1CA

Packard Wolfram 1985 2 CA

S. Wolfram 1986 CA LGALattice Gas Automata

CA Frisch et al. 1986 CA

CA

CA 2

CASudjono 2002

k

2 CAFig. 90

b 摩耗のモデル化

2 CA Fig. 91

0 1 38

100 30 mm

(a) (b)

Fig. 90 2 CA Two types of neighboring cells used in two-dimensional cellular

automata model

Fig. 91

Discretization of the model domain

Fig. 92

Arrangement of the aggregate in the model domain

100 mm

24 m

m6

mm

20 mm10 mm mm

(a) (b) (c)

Fig. 93

Examples of the erosion action values from neighboring water cells toward central cement paste cell

8

16

8

4

4

2

1

2

5

5

5

5

5

5

5

5

2

4

8

1

16

2

4

8


0.2 0.2 mm 500 15024 mm 6

mm 20 mm2 10 mm 3 3 mm 10 Fig.

92

Fig. 93

20% c Ca 溶脱のモデル化

Ca Ca1

(9)

u Ca D CAD

1998

(10)

0.2 mm0.02

CaCa Fig. 94

Ca

Ca

d 摩耗・Ca溶脱統合モデル

7 Ca

Ca

Ca

Fig. 95

e シミュレーション

Mathematica 7 Fig. 93Fig. 96

Fig. 97 Fig. 98

Ca CaFig. 99

Ca 40Fig. 100

Ca

Fig. 101

4 9

Fig. 94 Ca Direction and allocation of Ca particles diffusion

Fig. 95 Simulation flow diagram

Start

Ca

End

Yes

No

1/4

1/4

1/4

1/4 1/3

1/3

1/3

1/2

1/2

=

= 2 ×


t = 0 year

t = 2 year

t = 5 year

t = 10 year

t = 15 year

t = 20 year

t = 25 year

t = 30 year

t = 35 year

Fig. 96 Erosion progress by the isotropic action

Ca


t = 0 year

t = 2 year

t = 5 year

t = 10 year

t = 15 year

t = 20 year

t = 25 year

t = 30 year

t = 35 year

Fig. 97 Erosion progress by the left dominant action

Ca


t = 0 year

t = 2 year

t = 5 year

t = 10 year

t = 15 year

t = 20 year

t = 25 year

t = 30 year

t = 35 year

Fig. 98 Erosion progress by the upper dominant action

Ca


４結論

(1)

(2)

2

(3)

Ca Ca

(4)

Ca

(5) CA

Ca

(6)

Ⅴ 水路構造材料の促進摩耗試験

１緒論

ASTM C 1138

Fig. 102 E

1 1 mm Comparison of eroded surface states of actual canal surface and

accelerated erosion surface from the collected cores from the actual canal

Fig. 99 Ca Weakening of cement cells above the aggregate along with Ca

leaching

材

水

メンメン

(a) Ca (b) Ca

Fig. 100 40

Eroded states after 40 years by the isotropic action with and without Ca leaching

(a) 20 (b)

Fig. 101 Eroded state after 20 years by the upper dominant jet flow

5

10

20

2

100

5

10

20


Liu 1981 2007 2009 ASTM C 1138

3 13 mm 19mm 25 mm

20052010

２水噴流摩耗試験機の摩耗機構

Fig. 32Fig. 76

Fig. 102

３標準試験条件

JIS R 1645

Table 20 990

45 ４標準試験体

JIS R 52011

3 0.50 JIS

70 70 20 mm

70 70 mm

Table 20 Test conditions for water jet erosion test (draft)

JIS R 1645

200 5

17 0.5 MPa 15 0.1 MPa

1.5% 0.022 0.001 m3/min

45

10 mm 50 mm

0.3 mm 1.0 mm 50 50 mm

48

4

4 15 30 1 2


70 70 20 mm100 mm

70 70 mm

470 70 20 mm JIS A 1171

Fig. 103 JIS 28 94

20 2.4 mm94

2828

５評価指標

a 摩耗深さ

Fig. 104

Table 21Table 22

62.3%71.1% 66.9%

70%

70% 30%

85% E

Fig. 10595%

Fig. 103 JIS 28 94

Average erosion depth versus test time using material age 28 and

94 days of JIS mortar

0

1

2

3

4

5

6

7

8

0 5 10 15 20 25

(mm

)

(h)

28

94

Fig. 104 Concepts of the erosion front position and the measurement region

of true erosion depth


100%

85% 2.1 2.4 95% 2.7 3.4

8595% 85 95%

10

85 95%

Table 21 Aggregate area ratio to concrete cross-sectional area with standard specified mix proportions

(mm) (%) W/C (%)

s/a (%)

(kg/m3) (m3/m3)

(%)W C S G s g

AE

15 7.0 55 47 180 327 796 907 0.304 0.342 64.6

15 7.0 50 46 180 360 766 910 0.292 0.343 63.6

15 7.0 45 45 180 400 735 908 0.280 0.343 62.3

20 6.0 55 44 175 318 765 985 0.292 0.372 66.4

20 6.0 50 43 175 350 737 988 0.281 0.373 65.4

20 6.0 45 42 175 389 706 986 0.269 0.372 64.2

25 5.0 55 42 170 309 750 1048 0.286 0.395 68.2

25 5.0 50 41 170 340 722 1051 0.276 0.397 67.2

25 5.0 45 40 170 378 692 1050 0.264 0.396 66.0

40 4.5 55 39 165 300 710 1123 0.271 0.424 69.5

40 4.5 50 38 165 330 682 1126 0.260 0.425 68.5

40 4.5 45 37 165 367 653 1125 0.249 0.424 67.4

AE

15 7.0 55 48 170 309 832 912 0.318 0.344 66.2

15 7.0 50 47 170 340 803 916 0.306 0.346 65.2

15 7.0 45 46 170 378 771 916 0.294 0.346 64.0

20 6.0 55 45 165 300 801 991 0.306 0.374 68.0

20 6.0 50 44 165 330 773 995 0.295 0.375 67.0

20 6.0 45 43 165 367 742 995 0.283 0.375 65.9

25 5.0 55 43 160 291 786 1054 0.300 0.398 69.8

25 5.0 50 42 160 320 758 1058 0.289 0.399 68.8

25 5.0 45 41 160 356 727 1059 0.278 0.400 67.7

40 4.5 55 40 155 282 745 1130 0.284 0.426 71.1

40 4.5 50 39 155 310 717 1134 0.274 0.428 70.2

40 4.5 45 38 155 344 688 1135 0.262 0.428 69.1

Fig. 105 E

Comparison of each percentile erosion depth using collected core specimen in the E district

0

1

2

3

4

5

6

0 2 4 6 8 10 12

(mm

)

(h)

70%

85%

95%

Table 22 Densities of materials

(kg/m3)

1,000

3,150

2,620

2,650


b 比摩耗速度および耐摩耗性

JIS

3

Table 20

9HPFRCC PCM-N

Fig. 106 Fig. 107 1 JIS

1 JIS

６実構造物の供用時間に対する促進倍率

10

CaEPMA

Fig. 85 Fig. 88 Ca

Fig. 108 Fig. 109

5 6

5a

2

1

2 mm

Fig. 106 JIS HPFRCC PCM-A

Erosion rate ratio of HPFRCC and PCM-A to JIS mortar

0.66

1.04

0.52

1.10

0.0

0.2

0.4

0.6

0.8

1.0

1.2

HPFRCC PCM-A

JIS

30°

45°

Fig. 107 HPFRCC PCM-A

Erosion resistance of HPFRCC and PCM-A

1.51

0.96

1.92

0.91

0.0

0.5

1.0

1.5

2.0

2.5

HPFRCC PCM-A

30°

45°

Fig. 108 95%

Comparison of 95th percentile erosion depth of collected cores from the D and E district

0

2

4

6

8

10

0 2 4 6 8 10 12

95%

(mm

)

(h)

D Ca

E Ca

Fig. 109

Comparison of the erosion rate versus the erosion depth of collected cores from the D and E district

0

5

10

15

0 2 4 6 8 10

(mm

/h)

(mm)

D Ca

E Ca


1 22 mm 4 mm

Table 230

Fig. 110

3

７複合摩耗試験

2

20 40

7 Ca

20

８結論

(1) JIS R 1645

(2) JIS R 5201

JIS70 70 20 mm

(3)

85% 95% (4) JIS

(5)

(6)

Ⅵ 結言

Table 23 D E

Calculation conditions of accelerating magnification in the D and E districts

D E

(year) 38 38

Rz (mm) 7.05 4.48

Rz+6 (mm) 13.05 10.48

[Rz+6] (mm/year) 0.344 0.276

[1 ] (mm/h) 5.41 2.26

[2 ] (mm/h) 3.54 1.49

[2 mm ] (mm/h) 10.75 1.49

[4 mm ] (mm/h) 5.41 0.64

Fig. 110

Comparison of the accelerating magnification at the each threshold

15.8

10.3

31.3

15.8

8.2 5.4 5.4

2.3

0

5

10

15

20

25

30

35

1 h 2 h 2 mm 4 mm

(yea

r/h) D

E


１研究の総括

35 51 53

EPMA 2 21

1

5 0.0113 0.0192

51

0.0113 0.0156

0.0120.016

Ra Rz

40 10 mm16 mm

Ca

19.4 27.6

Ca CaCa

Ca

5

0.011 0.015

JIS

45

Ca

2


Ca

CA

Ca

JIS R 1645

JIS R 5201 JIS70 70 20 mm

85% 95%JIS

２今後の展望

2008

1993

2006

謝辞：

参考文献

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607 15-22. 3) Aquaro, D. 2006 Erosion due to the impact of solid

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・

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TOKASHIKI Masaru

Summary Knowledge of the mechanisms of erosion and a method for testing accelerated erosion of the cementitious

materials of a concrete irrigation canal are of major importance for maintaining the performance of a canal over the long term. Most previous studies of erosion of concrete in hydraulic structures have examined the effect of high-velocity water flow or the impact intensity of rocks transported in the water flow on erodibility, whereas the long-term effects of low-velocity water flow and calcium leaching on the erodibility of such structures has rarely been examined. Therefore, field investigations, water jet erosion tests, and cellular automata simulations were performed to investigate these phenomena.

The first objective of this study was to explain the mechanisms of erosion of concrete irrigation canals. The following results were obtained:

(1) Erosion of a concrete irrigation canal results from the complex degradation of the hardened cement paste (hcp) component of the concrete by both chemical and mechanical processes;

(2) Calcium hydroxide is leached from the hcp into the water; (3) The microstructure of the hcp is thereby coarsened; (4) Hcp with coarse microstructure has low strength; (5) Collision of flowing water or waterborne sand with the low-strength hcp causes fatigue or abrasive failure,

detaching it from the concrete body; (6) Detachment of the hcp from the concrete causes detachment of aggregate that is no longer supported by the

hcp matrix from the concrete. These results are based on the following observations. Field measurements of arithmetic surface roughness of concrete irrigation canals in five districts indicate that

erosion progressed as the exposure time of hcp to water increased. Moreover, observations of eroded concrete surfaces show that the surfaces of the aggregate did not erode; rather, the hcp around the aggregate was detached from the concrete body. Furthermore, electron probe microanalysis of specimens of concrete from the canals shows that calcium was leached from the surface hcp to a greater depth than the depth of erosion, indicating that leaching, a chemical process preceded mechanical erosion. Despite the occurrence of calcium leaching, no volume loss was observed from the concrete surfaces in contact with water with zero or very slow velocity, indicating that a volume loss of concrete, defined as erosion, requires not only chemical but also mechanical processes.

Water jet erosion test results of experimentally leached hcp specimens showed that the maximum erosion rate in leached portions of the specimens was 19.4 to 27.6 times that in non-leached portions. This result indicates that the erosion resistance of leached portions is remarkably deteriorated.

Two-dimensional cellular automata simulations were performed to evaluate the contributions of chemical and mechanical processes to the erosion process. The results show that hcp was eroded at nearly the same rate regardless of the diameter or the arrangement of aggregate in the concrete. This finding may indicate that the erosion of hcp is not affected by the presence of aggregate.

The second objective of the study was to establish an accelerated erosion test method for the cementitious materials of concrete irrigation canals. As a result, the following method was proposed:

(1) The parameters of the accelerated erosion test consisted of nozzle entrance pressure, water jet flow rate, impingement angle of the water jet, distance from nozzle to specimen, nozzle shape, rotation rate of the specimen, water quality, exposure time, and replacement of nozzle;

(2) The control specimen was a rectangular solid composed of mortar meeting the JIS R 5201 standard with the

Studies on Erosion Mechanism and Accelerated Erosion Test of Concrete Irrigation Canal


dimensions 70 x 70 x 20 mm; (3) The 85th to 95th percentile of measured erosion depth was adopted as the index for determining the erosion

front depth; (4) The ratio of the erosion rate of the cementitious materials to that of the control specimen mortar was adopted

as the erodibility index of the materials; (5) The reciprocal of the erodibility index was adopted as the erosion resistance index of the cementitious

materials; (6) The accelerated rate of erosion of a sound specimen from a concrete canal was estimated as the correlation

between the water jet erosion test time and the service time of real concrete canals; (7) A combined test incorporating both chemical and mechanical processes is required to evaluate the erosion

resistance of cementitious materials, because in the real environment such materials are affected by both chemical reactions and mechanical actions.

Keywords : concrete irrigation canal, erosion mechanism, accelerated erosion test, cementitious materials, calcium

leaching


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