Change in Flowability of Self-Compacting Concrete due to Pumping
Jiro SaAKUE and Masahiro OUCHI
Kochi University of Technology, JAPANABSTRACT: The mechanism of the reduction in the flowability of self-compacting concrete due to pumping
was clarified. Compressive and shearing force were applied to the mortar of self-compacting concrete.

Theauthors have set up a hypothesis for the mechanism, in which the particles of the cement in the concrete canbe dispersed more resulting in the larger surface area of the particles, and then the repulsing effect by thesuperplasticizer can be reduced.

The chemical analysis was carried out to prove the hypothesis.

surface area and the amount of adsorption of the superplasticizer were measured.
strength was tested.

BETAlso, the compressive

The hypothesis was proved.

KEYWORDS: self-compacting concrete, pumping, external force, dispersion of cement particles
1. INTRODUCTION

pumping may be reappeared.

The concept is shownin Fig.1. Compressive force was applied to theLarge improvement of execution is expected bymortar due to pressurizing bleeding vessel. And

pumping of self-compacting concrete. However there-mixing after the mixing was done for the shearing

change in flowability of self-compacting concrete

stress. As it turned out, the change in flowability candue to pumping has become one problem related tobe reappeared by applying these two types of force 1).

the construction of the concrete. Flowability

Assuming that the dispersed cement particles have

improves or reduces adversely. It is a premise thatan effect, they have an effect on the reduction in theself-compacting concrete fills up formwork only for

flowability due to action of compressive stress andaction of gravity. Therefore the flowability change

shearing stress.

may hinder the construction. Various types of change

from the measurement of the compressive strength,

in the flowability have been reported, but theamount of superplaticizer adsorped to cement

mechanism responsible for this phenomenon has notparticles and the specific surface area of the cement

been clarified.

particles by BET.

The purpose of this research is to clarify themechanism of the change in the flowability of SCC
due to pumping. Above all, the author performed

Pressure

Therefore the authors examined itConcretePipeCompressive &Shear stressPistonmechanism elucidation of a flowability decrease.
Force modelFriction(Shear force)Stress model

It is asuumed that both compressive and shear

Fig. 1 Stress generated in concrete due tostress are generated in the mortar during pumping.

pumping

The authors have set up a new testing method bywhich the stress generated in the mortar due toTable 1 Mix proportions
Unit weight (kg/m3)

W/C

s/m

SP/C

(%)

(%)

(%)

Water

CementFine aggregate

SP

A-1

28.6

450.78

264

922

1224

7.19

A-2

28.6

450.85264922

1224

8.76

B-1

29.8

450.78269904

1224

7.05

C-1

27.0

45

0.78

256

947

1224

7.39

No.

Table 2 Materials
Material

divided into two portions. One portion was subjected

Specifications

Low-heat portland
cementSpecify gravity: 3.22

to pressurization test and re-mixing for compressive
and shear stress. Another portion was kept still.
After that, flow and funnel tests were carried out for

Crushed sandSuperplasticizerSpecify gravity: 2.72;

each portion of the mortar. These tests were carried

FM:3.00

out at almost the same time so that the influence of

Polycarboxylate type

the time may be minimized. And, the flowability ofthe two pars of mortar was compared. The influence

2. METHODOLOGYof the external force was evaluated by comparing thetwo pairs of flowability test results.

2.1 Materials and mix proportions
The mix-proportioning of the mortar is shown in(1) Deformability Gm and Viscosity Rm

Table 1 and the materials are shown in Table 2. The

The mortar flow employed the mortar flow corn

practical(Fig. 2). And the deformability was obtained with (1).

mix-proportioningofself-compacting

concrete’s mortar was assumed.

The discharging time through funnel was measured
using the funnel test (Fig. 3). And the index for theviscosity was obtained with (2). The evaluation of

2.2 Apply of external force to mortar
The pressure to the SCC's mortar was 8.8 MPa with theflowability used two indexes 3).

70mm

stress in the mortar.

60mm

pressurizing bleeding vessel to generate compressive
Also, re-mixing speed was 125rpm on the axis and paddle revolved at 285 rpm tod1
d2

generate shear stress in the mortar. The duration of thepressure and re-mixing was one, three or five minutes
respectively.

2.3 Test method for flowability of mortar
First, mortar was mixed. The mixing speed was 125rpm on the axis and paddle revolved at 285 rpm.
Next, the mortar was kept still afterwards at up to 30
minutes assuming the time between the batchingplant and the casting site. After that the mortar was

d0=100mm
Fig. 2 Mortar flow test

270mm
240mm
60mm

3m0m

30mm
Fig. 3. Mortar funnel test2)
Gm = (d1*d2-do2)/do2(1)

Rm = 10/t(2)

Fig. 4 Molecular structure of superplasticizer

d1,d2: diameter of mortar flow (mm)(4) Specific surface area of cement

do: diameter of flow corn (mm)The specific surface area of the cement was

t: discharging time through funnel (sec)measured by BET method. Firstly hydration reactionof mortar was stopped by the acetone. Secondly it(2) Compressive strength test

was dried in at 40 degrees centigrade for 24 hours.

The compressive strength was tested for theFinally cement of less than 75mm diameter wascylinder of φ 50 * 100 mm at the age of 7 days in thesampled. The specific surface area was measured forstandard curing method.

A-1 and A-2.

(3) Amount of superplasticizer adsorbed to

3 EXPERIMENTAL RESULTS

cementChemical structure of superplasticizer is shown in

3.1 Influence on flowability due to external force

Fig. 4. The amount of superplasticizer adsorbed to

The change in the flowability of the mortar due tocement was measured for per cement 1g by thethe external force is shown in Fig. 5 to 7. The

measurement of the amount of carbon included inchanges in the flowability due to the external force

the fluid phase of the mortar. The fluid phase ofwere different by the dosage of SP or the unit watermortar was triggered with the gravity of about 7000

content of the mortar.

G for five minutes with a centrifuge to extract it, andit was measured by the total organic carbon
measurement.

Rm

The relationship between the duration of applying
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0

the external force and the rate of change in the5 minExternal force
1 minute

3 min

was reduced due to the external force. When thewater to cement ratio or the dosage of SP was high,still

1 min
3 min

the reduction in the deformability was small. It was5 min

found from the result that when Gm was large, theA-1

0.0

deformability is shown in (Fig. 8). The deformability

2.0

4.0

influence of external force was small. If the viscosity

A-2

6.0

before applying external force was low, the change
8.0in Gm was also small.

Gm

Fig. 5 Change in flowability due to external

The rate of change of Rm is shown in Fig. 9. Rm

force: difference in SP dosageof C-1 was reduced remarkably after one minute as

2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.60.4
0.2
0.0

1 min

.

5 min
3 min
20still
1 min
3 min
5 min

A-1

0.0

2.0

4.0

B-1

6.0

8.0

Rate of change of Gm (%)

Rmwell as Gm.

Gm0

A-1

A-2

B-1

C-1

4

5-20
-40
-60
-80
-100

Fig. 6 Change in flowability due to external

0force: difference in water to cement ratio

123

6Action time of external force (min)

2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0

external force

1 min
3 min

still

5 min

still

1 min
A-1

3 and 5 min
0.0

2.0

4.0C-1

6.0

8.0

Gm

Fig. 7 Change in flowability due to external
force: difference in water to cement ratio

Rate of change of Rm (%)

Rm

Fig. 8 Rate of change in deformability due to60
50
40
30
20
100-10-20-30
-40
0

1

2

3

A-1

A-2

B-1

C-1

4

5

Action time of external force (min)Fig. 9 Rate of change in viscosity due toexternal force

6

SP adsorbed amount (mg/g)

6.5

3.2 Influence on compressive strength
The relationship between the duration of applying
the external force and the compressive strength isshown (Fig. 10). The compressive strength wasincreased with the increase of the duration ofapplying the external force despite of the type of themix-proportioning. It is assumed that the external

A-1

A-2

B-1

6.0

5.5

5.0

4.5

force dispersed the coagulated cement particles and0

1

2

3

4

5

6

Action time of external force (min)it promoted the hydarion of the cement particles,4)

which resulted in the higher compressive strength .

Fig. 11 External force increased
adsorption of superplasticizer to cement

75
73
71
69
67
65
63
61
59
57
55

A-1

A-2

B-1

C-1was measured for A-1 and A-2 (Fig 12) by BET
method. The specific surface were increased greatly
due to the external force.

It was found from theresult that the cement particles were dispersed due tothe external force. That is, it is possible that thedispersion of cement particles influenced the change
in the flowability.
123

45

2.0

6Action time of external force (min)Fig. 10 External force increased
compressive strength
3.3 Specific surface area of a cement particle dueto action of external force

20Specific surface area (m /g)2

Compressive strength (N/mm )Also, the specific surface area of cement particle

The external force increased the amount of

1.8
1.6
1.4
1.2
A-1

A-2

4

5

1.0

superplasticizer adsorbed to cement (Fig. 11).

012

36

Action time of external force (min)However, the deformability was reduced although
the deformability was reduced.

Fig. 12 External force increased surface
area of cement particles
Therelationshipbetweentheamountof

superplasticizer adsorped to the cement particles andthe specific surface area was examined (Fig. 13).
Increased total surface area of the cement particles

reduced the amount of the superplasticizer adsorbed(3) It was concluded that dispersion of cement

to cement particles per unit surface area. It wasparticles decreased the effect of superplasticizer due

concluded that dispersion of cement particles

to the decrease in the amount of superplasticizer

decreased the effect of superplasticizer.

adsorbed to cement particles per unit surface area

According to the previous research, the reduced

and that it resulted in the reduction in the flowability

amount of superplasticizer adsorped to cement perof mortar in SCC.

unit surface also reduced the flowablity of the mortar. ,which corresponded to the result in this study.

Rate of change of SP adsorption
amount per surface area (%)

5)

0A-1

-5

5 REFERENCES
1) Sakue J, Ouchi M: Reappearance of Change ofA-2

Flowability of Self-Compacting Concrete due to-10

Pumping, fib, 2006-152) Okamura H, Maekawa H, Ozawa K: High-20

performance concrete, Gihodoshuppan, 1993.9-25

3) Ouchi M, Hibino M, Sugamata T, Okamura H:-30

Quantitative evaluation method for the effect of-35superplasticizer in self-compacting concrete,-40020406080

Rate of change of specific surface area (%)

Proceedings of the Japan Concrete Institute,Vol.21, No.1, pp.129-134, 1998
4) Fukaya Y, Tuyuki N: Cement Concrete Materials

Fig. 13 Reduction in adsorption ofsuperplaticizer to unit surface area ofcementScience, The House of technical book, pp.68-99,
2003.105) Sugamata T, Edamatu Y, Ouchi M: Quantitativeevaluation for retaining in diepsersing effect bysuperplasticizer,

4 CONCLUSIONS

ProceedingsoftheJapan

Concrete Institute, Vol.22, No.2, pp.163-168, 2000
The purpose of this research is to clarify themechanism of the change in the flowability of SCC
due to pumping. The results were summarized asfollows:(1) If deformability of the mortar was high, theinfluence of the external force was reduced.
(2) Compressive strength of the mortar, the amount ofsuperplasticizer adsorped to cement and the BET
surface area were measured.

The dispersion ofcement particles was increased due to the externalforce.