Geo-Environmental Engineering 2017, Seoul, Korea, May. 19-20, 2017

IMPROVED EFFECT OF CEMENT BENTONITE TYPED FILLINGBY MIXING SODIUM CARBONATE
Ko Hashimoto1, Shinya Inazumi2, Shuichi Kuwahara3, Yukio Uchida 4, Kazuhiro Ishimaru5
1

Advanced Course of Architecture and Civil Engineering, Akashi College, National Institute ofTechnology, Japan, 2Department of Civil Engineering, Shibaura Institute of Technology, Japan,
3
Marushin Co., Ltd., Japan, 4Japan Material Co., Ltd., Japan, 5Department of Civil Engineering, Akashi
College, National Institute of Technology, Japan

ABSTRACT
Cement milk is used as a grout to fill holes which are resulted from pile extraction. Although cement milk has
an advantage of being able to perform blending and placing according to circumstance of work on site, cement
and water cause segregation, so uniform filling is difficult over the entire length of holes. In addition, there is a
disadvantage that cement milk can’t perform a predetermined strength when diluted by groundwater erosion.
Sodium carbonate is a substance expected to suppress the segregation of cement milk and to speed up thedevelopment of strength. In this study, we conducted an indoor mixing test on fillers mixed with sodium carbonate
into cement milk which is a mixture consisting of water, cement and bentonite, and examined various
characteristics from the viewpoint of physical and chemical aspects. (1) By mixing sodium carbonate, bleeding of
cement milk is suppressed. This is considered to be due to increased swelling of bentonite by receiving sodiumions. (2) By mixing sodium carbonate, the strength development time of cement milk is advanced and the longterm strength also increases. This is considered that calcium carbonate is generated at the initial stage of reaction
from the reaction of bentonite and sodium carbonate.
Keywords: cement, bentonite, sodium carbonate, bleeding, early strength1.

exhibits uniform strength without causing material
separation when filling holes generated by pulling out
existing piles. We aim at sophistication of cement
bentonite typed cavity filling since it is possible toadjust blending filling at the construction site. By
mixing sodium carbonate (Na2CO3), it is expected thatthe strength development of the cement bentonite typecavity filling will be promoted and the bleeding will
be suppressed. We will examine the improvement andusefulness as cavity filling by conducting an indoor
blending test on cement bentonite and sodium
carbonate mixed cement bentonite. For examining theimprovement and usefulness, a comparative test is
conducted in view of strength characteristics, fluidity
and material separation.

INTRODUCTION

1.1.

RESEARCH BACKGROUND

In demolition work, it is necessary to remove
existing piles in the ground. If new land use is planned,
existing piles must be removed so as not to interferewith pile foundation of newly built-structures. In
addition, existing piles remaining in the ground areindustrial waste, so troubles often occur in the landsale transaction. Therefore, removal of existing piles
is indispensable. In order to remove an existing piles,
a drawing out method is generally adopted. In thedrawing out method, holes are formed in the ground,which adversely affect the ground environment. In thevicinity of the hole, it may cause problems such as
collapse of earth and sand, subduction of thesurrounding ground, weakening, so it is necessary tofill the filling and stabilize the ground quickly.
Depending on the construction site, the properties
required for the filling are different, but there is no
regulation on filling presently. From the above, there
is a demand for constructing a filler that can reliably
fill and secure stable strength.
1.2.

1.3. OUTLINE OF RESEARCH
In this research, we carried out uniaxial
compression test, penetration test, bleeding test andflow test on cement bentonite and cement bentonite
mixing sodium carbonate, and examine usefulness of
cement bentonite typed filling by mixing sodium
carbonate. In addition, we consider the mechanism of
the development of various properties exerted bymixing sodium carbonate from the physical andchemical point of view (Fig.1).

PURPOSEWe will aim for the development of a filling that1

Geo-Environmental Engineering 2017, Seoul, Korea, May. 19-20, 2017

2.

MethodResearch background

2.1 Materials and mixing conditions
Purpose of research(1)

Cement

The type of cement used in this study is ordinary
portland cement, and one is having a density of 3.16g/cm3 and a specific surface of 3200cm2/g. Cement is amain component which exerts a curing function as a
cement bentonite typed cavity filling because it
reaction with hydration and develops initial and longterm strength by the formation of ettringite andcalcium silicate hydrate(C-S-H).
(2)

Indoor mixing test
Arrangement andconsideration of test results

Investigation of usefulness as
filling
Consideration aboutmechanism of upgrading

Bentonite

The chemical components of the bentonite used on
our test are shown in Table 1. Bentonite has the effectof suppressing material separation of cement andwater by swelling property due to take water into theone 1). Bentonite is a smectite clay mineral containing
montmorillonite as a main component and has alayered structure in which thin plate crystals arestacked. The crystal is negatively charged andelectrical equilibrium is maintained by adsorbing
cations between crystal layers. The interlayer cationsof montmorillonite are mainly composed of sodiumion (Na+), calcium ion (Ca2+), potassium ion (K+),
magnesium ion (Mg2+), and the properties of bentonite
vary depending on the type of the one. The type isdivided into two types, one is called Na type where alarge number of monovalent cations such as Na + andK+ are adsorbed, and the other is called Ca type wherea large number of divalent cations such as Ca2+ andMg2+ are adsorbed 2). The bentonite used in thisexperiment is a Na type bentonite having many Na + ininterlayer cations.
(3)

Fig.1 Procedure of study
Table 1 Chemical components of bentonite
Chemical Components
SiO2
Al2O3
Fe2O3
MgO
CaO
Na2O
K2O
Ignition loss

Table 2 Chemical components of the admixture
Chemical Components
Na2Co3NaCl
Fe2O3
Insoluble matter

Content (%)
99.41
0.35
0.003 or less0.001or lessIgnition loss

0.15

Table 3 Mixing conditions of each material

sodium carbonate

No.

When we mix sodium carbonate as an admixture
into a cement bentonite typed cavity filling in thisexperiment, we use anhydrous salt obtained by heating
at a high temperature of 300°C. Table 2 shows thechemical components of the admixture, and it contains
Na2CO3 of 99.41%. Sodium carbonate is expected topromote the hydration reaction between cement andwater and exert the effect of early strength
development 3).
(4)

Content (%)
67.1
16.8
3.7
3.3
2.7
2.2
1.3
2.9

A-1
A-2
B-1
B-2
C
D
E
F
G

B
(kg/m3)
50
50
50
50
50
50
50
50
50

C
(kg/m3)
240
240
300
300
180
200
220
250
260

S
(kg/m3)
0
20
0
20
20
20
20
20
20

W
(kg/m3)
905
897
886
878
916
910
903
894
891

W/C
(%)
377
374
295
293
509
455
410
358
343

mixing condition
circumferential fixing liquid is set to 0.5N/mm2 at thecompression strength after 28 day material age and isconsidered to be the same as the ground strength, thestrength is generally adopted as a standard. In blend A
and B, cement bentonite and cement bentonite mixing
sodium carbonate whose weight ratios C/B=5, 6 ofTable 3 shows the mixing conditions of eachmaterial used in the series of tests. The target strengthis set to 0.5N/mm2 on the mixing condition. In the
precast pile driving method prescribed in the "Public
Building Standards Manual"4), since the pile2

Geo-Environmental Engineering 2017, Seoul, Korea, May. 19-20, 2017

cement (C) and bentonite (B) were prepared, and weinvestigate the properties of cement bentonite mixing
sodium carbonate perform. In blend C, D, E, F and G,
only the amount of cement (C) is changed to prepare
cement bentonite mixing sodium carbonate and thecorrelation between sodium carbonate and cement is
examined. In the mixing procedure, water (W) andbentonite (B) were added to a stirrer having a rotation
speed of 1,500 rpm/min and stirred for 3 minutes, thenordinary portland cement (C) was added and stir for 3
minutes and sodium carbonate was added and stir for
3 minutes (Fig.2).
2.2.

Strength test

The strength development of cement bentonite
mixing sodium carbonate will be examined according
to the Japanese Industrial Standard (JIS A 1216)"uniaxial compression test". Each material is mixed
according to mixing conditions and it is poured into amold having a diameter of 50mm and a height of
100mm to prepare a sample. Curing is performed for7, 14, 28, 60, 90, 120 days in a thermostatic chamber
at 20°C, and a uniaxial compression test is performedat each curing day (Fig.3).
In order to investigate the change about the actionof cement bentonite due to mix sodium carbonate, we
conduct a simple penetration test on samples of A and
B. Penetration resistance values in immediately after
sample mixing and 30 minutes, 1, 2, 3, 4, 5, 6, 7, 8, 12,
24 hours are measured using a simple measuring
instrument (Fig.4).
2.3.

Fig.2 Mixing and stirring of materials

Bleeding test

A test is carried out according to the JSCE
Standards (JSCE-F522) "Bleeding Rate andExpansion Rate Test Method of grouting Mortar of
Prepacked concreat (Polyethylene Bag Method)" inorder to evaluate material separation of water andcement (Fig.5). The Sample mixing each material put
to a height of 200mm in a polyethylene bag with adiameter of 50mm and the amount of bleeding water
after 1, 3, 24 hours is measured, and the bleeding rate
is obtained using the following formula.

Fig.3 Uniaxial compression test

𝑾𝒃
𝐁𝐫 = () × 𝟏𝟎𝟎𝑽
Br (%) is the bleeding rate, Wb (ml) is the amountof bleeding water at each elapsed time, and V (ml) is
the volume of the whole sample.
2.4.

Fluidity test

The fluidity of cement bentonite mixing sodium
carbonate is evaluated according to JSCE-F521"Fluidity Test Method of grouting Mortar of
Prepacked concreat (Method of P Funnel)". The
Sample mixing each material is filled in a P-funnel
tester having an outflow pipe inner diameter of 13mm,

Fig.4 Simple penetration test3

Geo-Environmental Engineering 2017, Seoul, Korea, May. 19-20, 2017an outflow pipe length of 38mm and a funnel portion
height of 192mm. The sample is allowed to flow by
releasing a finger from the flow pipe, and we measure
the time until the flow of sample is interrupted for the
first time with a stopwatch (Fig.6).

3.
3.1.

Consideration
Consideration on strength test

(1) Initial strength development

From the uniaxial compression test results in Fig.8(a), compare the initial strength of cement bentonite
and cement bentonite mixing sodium carbonate. A-1
has the 7th day strength of 0.09N/mm2, and A-2 has aseven-day strength of 0.30N/mm2, so A-2 is stronger
than A-1. Similarly in the comparison between B-1
and B-2, the 7th day strength of B-1 is 0.37N/mm2 andthe 7th day strength of B-2 is 0.59 N/mm2, so mixing
sodium carbonate makes cement bentonite stronger
than when it does not mix. Therefore, it can be said
that the initial strength of cement bentonite increases
by mixing sodium carbonate. In addition, since nosignificant difference is observed in the strength
development behavior up to the 28th day of age, it isthought that sodium carbonate influence the strength
development before the 7th day of age.
In Fig.7, the results of the penetration test showedthat the resistance values of cement bentonite of A-1
and B-1 rise about 8 hours after mixing and stirring ofeach material, but the values of cement bentonite
mixing sodium carbonate of A-2 and B-2 rise about 1
hour after mixing and stirring. Since the setting
initiation time of cement bentonite is accelerating, it
can be said that mixing sodium carbonate affects thesolidification performance at the one-day of age.
Exercising solidification performance in 1 hour after
filling prevents the invasion of groundwater in the
ground and helps developing stable strength cement
bentonite type cavity filling.
From the above, mixing sodium carbonate into
cement bentonite promotes the solidification
performance immediately after mixing and stirring ofeach material, and exerts a useful effect as a filling.

Fig.5 Bleeding test

Fig.6 fluidity test

resistance value(kgf/cm2)

7(2) long-term strength

From the uniaxial compression test results in Fig.
8(a), compare the long-term strength of cement
bentonite and cement bentonite mixing sodium
carbonate. In comparing A-1 and A-2, B-1 and B-2,
the strength of mixing sodium carbonate is stronger
than not mixing at any age. However, as for thetendency of strength development, there is a tendency
that the strength increases up to about the 28th day of
age in any samples, and the strength hardly increase
after that. In addition, Fig.9 shows the values
normalized by the strength of 28th day of age

A-1

6

A-2

B-1

B-2

5
4
3

2
1
0
0

3

6

9

12

15

18

21

24

elapsed time (h)Fig.7 Result of penetration test
(hereinafter referred to as compression strength ratio).
Comparison of each sample from Fig.9(a) showed nosignificant difference in long-term strength
development behavior after 28th day of age, and thecompressive strength ratio is around 1.0, except for B4

Geo-Environmental Engineering 2017, Seoul, Korea, May. 19-20, 2017

1. There is not effect on the long-term strength
development due to mix sodium carbonate, so thereason why the strength is larger on each age at thetime mixing sodium carbonate is considered that theincrease of the initial strength affects the long-term
strength development.

1.40

unconfined cimpression
strength(N/mm2)

1.20(3) Increase Mechanism of Initial and Long-term
Strength

A-1

B-1

B-2

0.80

0.60
0.40
0.20

0.00
0

20

40

60

80

100

120

140

material age (day）The amount of cement is changed in C, D, E, F,
and G of cement bentonite mixing sodium carbonate.
From Fig.8(b), there is a trend that the smaller thewater-cement ratio is, the stronger the strength is ateach age. In addition, from Fig.9(b), there is no clear
difference in the tendency of strength development inany samples except for C, and the compressive
strength ratio at 90th day of age is about 1.15. There isno difference in behavior of initial and long-term
strength development of cement bentonite mixing
sodium carbonate by difference in cement amount, so
it can be said that sodium carbonate has no effect on
cement. Therefore, the initial strength increase of
cement bentonite by mixing sodium carbonate does
not promote the hydration reaction between cement
and water, and it is considered that forms a cured bodydifferent from cement hydrate.
Here, attention is paid to sodium carbonate andbentonite. Bentonite has different properties
depending on the type of interlayer cation ofmontmorillonite, but bentonite easily changes its
properties by ion exchange with other types of cations
since it has ion exchange properties. The interlayer
cation exchangeability increases in the following
order5).
𝑵+ < 𝑲+ < 𝑪𝒂𝟐+ < 𝑴𝒈𝟐+
When sodium carbonate (Na2CO3) dissolve in water,
it ionizes to sodium ion (2Na+) and carbonate ion(CO32-).Therefore, Ca2+ contained in the interlayer
cations in the bentonite and Na+ ionized from thesodium carbonate perform ion-exchange, and Ca2+ andCO32- are bonded to form calcium carbonate (CaCO3).
Calcium carbonate is a water-insoluble substance, andforms a cured body by binding molecules with eachother. The early strength development of cement
bentonite by mixing sodium carbonate and theincrease in long-term strength are attributed to theformation of a cured body of calcium carbonate
immediately after mixing of materials.

(a) Comparison by mixing sodium carbonate
unconfined compression
strength(N/mm2)

0.60

C

D

E

F

G

0.50
0.40

0.30
0.20

0.10
0.00

0

20

40

60

80

100

material age (day)(b) Comparison by changing cement amountFig.8 Result of uniaxial compression test

compressibe strength ratio( σ/σ28)

1.400
1.200
1.000
0.800
0.600
0.400
0.200

A-1

A-2

B-1

B-2

0.000
0

20

40

60

80

100

120

140

material age (day)(a) Comparison by mixing sodium carbonate
compressive strength ratio(σ/σ28)

1.400
1.200
1.000
0.800
0.600

0.400
0.200

C

D

E

F

G

0.000
0

3.2.

A-2

1.00

20

40

60

80

100

material age (day)Consideration on breathing test(b) Comparison by changing cement amount

Table 4 shows the results of the bleeding test. In
Cement bentonite of A-1 and B-1, the bleeding rateincrease with the passage of time, but in cement
bentonite mixing sodium carbonate of A-2 and B-2,
about 0.5% bleeding is only confirmed after 1 hour,
and there is no moisture on the surface of the specimen.
Similarly, in C, D, E, F, and G, it can be confirmed thatFig.9 Compressive strength ratio
the bleeding rate becomes 0% within 24 hours fromthe mixing of the materials. The decrease in the
bleeding rate of cement bentonite due to the mixing
sodium carbonate is attributed to the increase in the5Geo-Environmental Engineering 2017, Seoul, Korea, May. 19-20, 2017

bentonite typed cavity filling mixing sodium
carbonate was examined from the viewpoint ofstrength characteristics, material separation andfluidity. The obtained results are shown below.
(1) From the uniaxial compression test, mixing
sodium carbonate increases the initial and longterm strength of cement bentonite. The earlystrength development helps stabilizing the groundas soon as possible.
(2) From the penetration test, by mixing sodium
carbonate, cement bentonite exerts curingperformance from about 1 hour after mixing
materials. The rapid gelation prevents invasion ofgroundwater into the filling in the ground, and thefilling can stably exhibit the predetermined
strength.
(3) From the bleeding test, bleeding of cement
bentonite is suppressed by mixing sodium
carbonate. When it fills into the hole made bypulling out piles in the ground, the materials is
kept homogeneous and the strength is not differ
depending on the depth direction.
(4) From the fluidity test, the fluidity of cement
bentonite is not lost by mixing sodium carbonate.
Workability is assured in filling holes in the
ground.
In the future, it is necessary to clarify themechanism of various characteristics development byverifying from a physicochemical point of view.

Table 4 Results of bleeding and fluidity test
No.

A-1
A-2
B-1
B-2
C
D
E
F
G

flowing
downtime (s)

1hour

7.7
7.6
7.8
7.6
7.7
7.7
7.7
7.7
7.7

3.6
0.5
4.0
0.4
0.9
0.7
0.5
0.5
0.5

bleeding rate (%)
3hour
24hour
9.3
0.0
9.5
0.0
0.8
0.5
0.0
0.0
0.0

9.5
0.0
9.8
0.0
0.0
0.0
0.0
0.0
0.0

swellability of bentonite and the initial strength
development of cement bentonite. Bentonite exerts
swellability by interlayer cations of montmorillonite
adsorbing water molecules. As compared with Ca typebentonite, the Na type bentonite has a weak electricalattraction between the unit layers, and so it is likely toswell when adsorbing water molecules. As describedabove, sodium carbonate in water is ionized togenerate Na+, which is exchanged with Ca2+ contained
in interlayer cations in bentonite. It is considered thatthe swelling property of bentonite is improved,
because the interlayer cations become more inclusiveof Na+. In addition, a hardened body is formed quickly
since calcium carbonate is produced, and movement ofwater molecules in cement bentonite is inhibited.
There is also a decrease of the amount of water due tothe hydration reaction with cement. Therefore, it isconsidered that various phenomena such as increase ofswellability with bentonite due to mixing of sodium
carbonate, early strength development of cement
bentonite, and hydration reaction of cement and water
are involved, and the bleeding does not occur after
several hours from mixing.
3.3.

5.

[1] Kouken Horii, Masaaki Nishi, Tsutomu
Yamazaki, Junichi Sakamoto, Michimae Taizou,
Yasushi Utaka, “Development of cement
bentonite complex solidified bodies using
concrete recycled materials”, Summaries of the
Academic Lectures of the Japanese Association ofArchitectural Conferences, 2007.
[2] Yashima Takashi, “Estimation of smectite
exchangeable cations by powder X-ray regression
method”, JGCA Technical Forum 2011 lecturecollection, No. 40, 2011.
[3] Kiyoshi Kato, Naoki Kato, Toshio Yuzawa, Isao
Masukawa, “A Study on Rapid Evaluation ofLong-term Strength and Unit Cement Volume by
Ultimate Initial Strength of Rapid HardeningPromoted Concrete”, Report of ConcreteEngineering Annual Papers Report, pp. 343 - 346,
1990.
[4] Ministry of Land, Infrastructure and Transport,“Public
Building
Construction
Standard
Specification (Building Construction), Heisei
20th edition, Ministry of Land, Infrastructure andTransport, 2014.
[5] Masanobu Ogata, “Characteristics of bentonite
and its application”, Clay science vol. 46, No.2,
pp.131-138, 2007.

Consideration on fluidity test

Table 4 shows the results of the fluidity test. In
each sample, the flowing down time is about 7.7s, andno decrease in fluidity of cement bentonite due tomixing sodium carbonate is observed. As describedabove, since curing started in about one hour after
mixing the materials, the early strength development
performance does not affect the fluidity at the time offilling. Although there is a possibility that material
separation may occur due to flowing down, since
bleeding hardly occurs, it can be said that the samples
are having moderate fluidity. Therefore, it is able tosay that the cement bentonite mixing sodium
carbonate has ensured workability as a cavity filling.

4.

REFERENCES

CONCLUSIONSIn this study, the usefulness of the cement
6