NUMO-TR-08-01

Release of Superplasticizers andOther Organic Additives from
Altered Cement

Takeshi Yamamoto, Takahiro Nishida, Michihiko Hironaga
Central Research Institute of Electric Power Industry
Satoru Suzuki, Hiroyoshi Ueda
Nuclear Waste Management Organization of Japan

December 2008
Nuclear Waste Management Organization of Japan (NUMO)

2008 年 12 月
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NUMO-TR-08-01

Release of Superplasticizers andOther Organic Additives from
Altered Cement

Takeshi Yamamoto, Takahiro Nishida, Michihiko Hironaga
Central Research Institute of Electric Power Industry
Satoru Suzuki, Hiroyoshi Ueda
Nuclear Waste Management Organization of Japan

December 2008
Nuclear Waste Management Organization of Japan (NUMO)

NUMO-TR-08-01

EXECUTIVE SUMMARY
The behavior of superplasticizers and other organic additives in cementitious materials is an
issue for the long-term safety of high-level radioactive waste disposal. These organic
substances may be leached into groundwater in contact with cementitious material andpossibly affect radionuclide migration behavior in the surrounding rock. To evaluate theimpact of these organics on radionuclide migration, the release properties of organics andleaching alteration properties of cementitious hydrated phases were studied in this project.
The experimental data suggested that the components of superplasticizers (SP) will hardly bereleased from cementitious hydrated phases, even in the case of leaching degradation. Raw
materials of cement powder contained low molecular weight organics and cement grinding
aids and these organics were released from the cementitious hydrated phases during theleaching alteration process. The cementitious hydrated phases altered with enlarged hydraulicpores for the C-S-H phase in specimens examined after immersion experiments. However, theprogression rate of the alteration front was decreased by using low-pH cement in any leachantsolution. SPs possibly decompose into relatively small molecular weight polymers over thelong term. Accelerated experiments were therefore conducted and decomposition phenomena
were detected using several molecular analysis methods.

iNUMO-TR-08-01

CONTENTS1INTRODUCTION .............................................................................................................. 1

2

EXPERIMENTAL PROCEDURE .................................................................................... 2
2.1
2.2

MATERIALS AND SPECIMENS ....................................................................................... 2
LEACHING TEST METHODS ........................................................................................... 3
2.2.1 Fresh leaching test .................................................................................................... 3
2.2.2 Powder leaching tests ................................................................................................ 4
2.2.3 Thin-plate leaching tests ............................................................................................ 4
2.2.4 Block leaching tests .................................................................................................. 4
2.3
ANALYTICAL METHODS ............................................................................................... 4
2.3.1 Liquid phase organic analyses.................................................................................... 5
2.3.2 Liquid phase inorganic analyses ................................................................................. 5
2.3.3 Solid phase analyses (powder, thin-plate and block specimens) .................................... 5
3

RESULTS AND DISCUSSION ........................................................................................ 6
3.1

RELEASE OF ORGANICS AND PH................................................................................... 6
3.1.1 Fresh leaching tests ................................................................................................... 6
3.1.2 Powder leaching tests .............................................................................................. 11
3.2
LEACHING ALTERATION OF THE SOLID PHASE ............................................................ 14
3.2.1 Change in Ca/Si ratio in block leaching tests............................................................. 14
3.2.2 Amount of Ca2+ leached in block leaching tests ......................................................... 15
3.2.3 Amount of Ca2+ and Si leached in thin-plate leaching tests......................................... 16
3.2.4 SEM observations of specimens in thin-plate leaching tests ....................................... 17
3.2.5 Change in hydrate composition in thin-plate leaching tests (XRD analysis)................. 21
3.2.6 Alteration of C-S-H in powder leaching tests ............................................................ 25

4

ORGANIC COMPONENTS IN GROUNDWATER FROM ONKALO BOREHOLES 28
4.1
4.2
4.3
4.4

RESULTS OF TOC ANALYSIS...................................................................................... 28
RESULTS OF GPC ANALYSIS ...................................................................................... 28
RESULTS OF IR ANALYSIS.......................................................................................... 29
RESULTS OF 1H-NMR AND 13C-NMR ANALYSIS ....................................................... 31

5

CONCLUSIONS .............................................................................................................. 34

6

ACKNOWLEDGEMENTS ............................................................................................. 35

7

REFERENCES ................................................................................................................. 36ii

NUMO-TR-08-01

1

INTRODUCTION

Cementitious materials are used widely without any problems in conventional tunnel
construction and excavation. However, if such materials are introduced into radioactive waste
disposal facilities as, for example, concrete liner, grouting material and mechanical plugs, theimpact of the chemical stability of cementitious materials on post-closure safety has to beconsidered. Over the last few decades, this issue has been the subject of frequent study. The
major topics are(1) The chemical impact of leaching alkali and alkaline earth ions (Na, K or Ca) on the
bentonite buffer.
(2) The impact of hyperalkaline solutions following the degradation of ordinary Portland
cement on the bentonite buffer and surrounding rock .
The use of low-pH cement is considered to be an effective measure for reducing the negative
impact of the degradation of cementitious materials on the stability of the host rock and thebentonite buffer. Low-pH cement is used as a substitute for OPC (ordinary Portland cement),
the leachate of which may reach a pH of 12-13. The target pH for the development of low-pH
cement is therefore set at around 11(NUMO, 2004). The material properties of three
representative low-pH cement materials (HFSC, LAC and SAC) have been studied in thelaboratory and it has been concluded that the fundamental mechanical properties of the lowpH mortar are as good as those of OPC mortar (NUMO, 2008).
An effective general method for obtaining low-pH cement is to add fine-grained pozzolanicmaterial, i.e. silica fume, to OPC. On the other hand, incidental problems such as loss ofworkability will be caused by using large amounts of silica fume. In this situation,
superplasticizers (SP) are needed to maintain workability without adding water.
Superplasticizers are effective organic additives for reducing the viscosity of cement
containing fresh mortar, concrete and grout. Although SPs have the advantage of increasing
workability, their long-term behavior and chemical impact on nuclide migration from theviewpoint of long-term safety need to be investigated.
Since 2005, Nagra, SKB, Posiva and NUMO have been conducting a joint project to develop
a fundamental methodology for evaluating the chemical properties of organic compounds
contained in cementitious materials, such as superplasticizers used in cementitious grouting
material. Firstly, as in the last SKB-Posiva-NUMO project on low-pH (pH ≤ 11) injection
grout for deep repositories (Bodén & Sievänen, 2005), the aim in the fabrication of thegrouting materials was to exclude organic additives. The main physical requirement for the
grouting materials is fluidity, i.e. an ability to penetrate, and workability. Although thesemechanical properties could be achieved in the laboratory, there was a significant loss of
fluidity during Posiva’s field injection test. The main reason was thought to be lack ofdispersion in the grouting slurry and Posiva therefore decided to use superplasticizers toachieve sufficient fluidity of the slurry. There are a few major types of superplasticizer and itis necessary to select those with less inhibiting effects on Kd values and high efficiency
options for achieving sufficient fluidity of the grouting slurry. NUMO’s task in the joint
project was to determine the molecular type of organic compounds released from thehardened cement matrix during immersion tests. The immersion tests were based on theaccelerated leaching alteration method to obtain information about the relationship between
release and adsorption of organic compounds from altered hydrates in the cementitious
material.

1

NUMO-TR-08-01

2

EXPERIMENTAL PROCEDURE

2.1

Materials and specimens

Two cementitious grout systems, a low-pH system and a normal pH system as reference, wereused in the experiments. The low-pH system has 3 specimen types, one with no SP and two
with added SP. The ordinary pH system has 2 types, one without and one with SP. The
chemical compositions of the cementitious materials and the mixing proportions for eachspecimen are shown in Table 2.1-1 and Table 2.1-2, respectively.

Table 2.1-1:

Chemical compositions of cement (UF16) and silica fume (Grout Aid) in dry
weight (%).
C

SiO2

Al2O3

CaO

MgO

Na2O

K2O

P2O5

Fe2O3

TiO2

MnO

SO3

Sr

UF16

0.14

22.8

3.65

65.3

0.79

0.08

0.43

0.11

4.39

0.25

0.23

1.76

0.0033Grout Aid

0.31

96.2

1.16

0.48

0.53

<0.03

0.79

0.05

0.28

0.01

0.04

0.09

0.0022

Table 2.1-2:

Mixing proportions for low-pH and normal pH systems (g/g).

Specimen

Water UF16/DM/DM

Grout Aid
/DM

SP/DM

Type ofsuperplasticizer

XREF52

1.21

0.930

0.070

-

-

REF52

1.21

0.930

0.070

0.01

SP40

XP308B

1.40

0.592

0.408

-

-

P308B

1.40

0.592

0.408

0.04

Mighty 150

NormalSystemLow-pH
System

P379G
1.20
0.592 0.408
0.015
Glenium 51*DM : weight of binder in dry material base, SP40: less water reducing effect than other SPs, used in REF52 tokeep the same level of water/DM ratio as in other cases.

The component materials of the grouts were as follows:•••

Ultrafine 16 (UF16): Sulfate-resistant Portland cement
Grout Aid (GA): Silica fume slurry (solid content: 50 mass%)
SP40: Poly melamine sulfonate (PMS)-based superplasticizer••

Mighty 150: Poly naphthalene sulfonate (PNS)-based superplasticizer
Glenium 51: Polycarboxylate (PC)-based superplasticizer

All initial hardened specimens and raw materials were provide to CRIEPI by Posiva. Groutspecimens were mixed and cast in a plastic tube around 1.5 m long and 50 mm in diameter.
Both tube ends were sealed and cured at room temperature (12oC) for four weeks untildelivery to CRIEPI. The hardened specimens were processed into several different shapes as
discussed below after two additional months of curing at room temperature (20oC). The
hardened pastes were thus cured at room temperature for a total of three months. One type of
hardened paste, i.e. XP308B, was mixed without using SP and showed numerous voids and2

NUMO-TR-08-01

microcracks as seen in Figure 2.1-1. This initial defect caused difficulties for the minutecutting needed for shaping the immersion specimens, so XP308B was recast using a 4x4x16
cm mold to allow vibrating compaction. This hardened paste was cured under 20oC humid air
conditions for three months before processing into the shapes used for testing.

a) P308B
Figure 2.1-1:

2.2b) XP308B

Tomographic images of delivered specimens: a) P308B, b) XP308B. Images
were photographed using X-ray computer tomography. Several cracks areapparent in the XP308B hardened paste, compared with P308B.

Leaching test methods

Leaching tests were conducted for both uncured fresh grouts and cured hardened grouts. The
fresh grouts were placed directly in leachants, while the cured hardened grout specimens were
immersed in leachants in the form of powders, thin-plates and block-shapes. In all theexperiments, three types of leachant, namely synthetic fresh groundwater (ALL-MR),synthetic saline groundwater (OL-SR) and deionized water, were used. Table 2.2-1 shows theion concentrations in the leachants ALL-MR and OL-SR. ALL-MR and OL-SR wereprepared by mixing suitable reagents into deionized water. The leachants were prepared bymixing chemical reagents in an N2-filled glove box following the method outlined by
Vuorinen et al. (2004).
-3

Table 2.2-1:

Ion concentrations of ALL-MR and OL-SR (mg•dm ).

Na

Ca

K

Mg

HCO3-

ALL-MR
OL-SR

55.2 5.14 3.91 0.71 65.04800 4000 21.0 54.6 -2.2.1

Fresh leaching test

SO42-

B

Sr
Cl
Si
48.9
2.39
35.0
0.92 1.19 105
14726 -

4.20
9.60

F

Br

Fresh grouts were mixed at a temperature of 20°C in accordance with the mixing proportions
shown in Table 2.1-2 and were cast into polypropylene vessels immediately after mixing. The
leachants were poured slowly into the grout-embedded vessels one hour after the beginning of
mixing. The leachant/grout volume ratio was fixed at 4.0. The cross-section of the vessel was
33.1 cm2. After pouring in the leachant, the vessels were sealed and kept in N2 gas-filled
glove boxes at 20°C. The fresh leaching test is a batch-type test and the specimens were set
for each sampling period. The sampling periods were set at 1, 3, 7, 28 and 56 days.
3

NUMO-TR-08-01

2.2.2

Powder leaching tests

Hardened grouts were ground into a powder with a grain size less than 100 μm and the groundpowder specimens were dried for 24 hours using an aspirator. The particle size distribution of
all the powdered samples was confirmed to be almost the same. After drying, the powder
specimens were immersed in each leachant at 20°C. The leachant/powder ratios were fixed as
10, 50, 100 and 1000 cm3 •g-1. The powder leaching test is a batch-type test aimed at
obtaining quantitative data on the liquid and solid phases under ionic equilibrium conditions
between the solid and liquid phases for various leachant/powder ratios. All leachingprocedures except grinding and drying were performed in N2 gas-filled glove boxes to avoid
carbonation. The sealed vessels were mixed well at the start of the immersion test; afterwards
the specimens were maintained under static conditions for a total of 38 weeks. The solid
phase in each vessel was confirmed not to be in a concretion condition at the end of theimmersion test.
2.2.3

Thin-plate leaching tests

These tests were performed to determine the physical and chemical properties of uniformly
altered mass specimens and the plates therefore had to be as thin as possible. The thickness ofthe specimens was determined to be 0.5 mm with 20 mm sides based on the required stiffness
during handling. Thin-plate specimens were cut from blocks of hardened paste as mentioned
above using a fine cutting machine. During the slicing procedure, ethanol was used as acooling agent for the blade. The ethanol was dried and removed from the specimens using anaspirator for 24 hours after slicing. The prepared thin-plate specimens were immersed in eachleachant at 20°C, with 16 pieces of specimen being placed in one vessel containing 2 liters ofleachant. The liquid to solid ratio for leachant volume to contacted surface area of thespecimen is 14.9 cm3 •cm-2. The leachants were exchanged every 6 weeks to accelerateleaching by maintaining a high ionic concentration gradient between the leachant and theporewater in the solid phase. The leachants were thus exchanged 4 times during the 30-week
immersion period. All experimental procedures except for specimen preparation were carriedout in N2 gas-filled glove boxes to prevent carbonation.
2.2.4

Block leaching tests

Block leaching tests were performed to evaluate the progression rate of the leaching alteration
front in each cement system. The hardened paste was cut into 20 mm cubic blocks. During the
cutting procedure, deionized water was used as a cooling agent for the blade. The blockshaped specimens were dried using an aspirator for 24 hours after slicing. The preparedspecimens were immersed in vessels filled with 2 liters of leachant at 20°C and the liquid tosolid ratio for leachant volume to contacted surface area of specimen was 83.3 cm3•cm-2. The
leachant was exchanged every 4 weeks during the immersion period, from 1 to 53 weeks, toaccelerate leaching alteration by maintaining a high ionic concentration gradient between theleachant and the porewater in the solid phases. All leaching procedures except for specimen
preparation were done in N2 gas-filled glove boxes to prevent carbonation.

2.3

Analytical methods

Liquid phase analyses for both the organic and inorganic cases were carried out for all
experiments. In the case of the solid phase analyses, element concentration mapping analyses
were performed only for the block-shaped specimens with the aim of estimating the relative4

NUMO-TR-08-01

differences in progression rates of the leaching alteration front. Structural analysis of the Si
ion in Si-containing compounds was performed only for powder specimens that were
sufficiently homogeneously altered to estimate the state of C-S-H during the immersion
period. Pore size distribution analysis was applied to the thin-plate specimens and 5 mm
thickness of surface area for the block-shaped specimens. Observational shape analysis ofhydrates and other compounds was carried out on thin-plate and block-shaped specimens,
particularly focusing on the surface of the altered phases and immediately beneath the alteredphases to estimate the difference in shape of hydrates and pore size. The other solid phaseanalyses, i.e. qualitative and quantitative analyses of crystal components and hydrates, wereapplied to all specimens. The aims of detection for each analytical method are as follows:
2.3.1

Liquid phase organic analyses

Total organic carbon (TOC) was measured using a TOC analyzer. The molecular weight ofdissolved organics was determined by gel permeation chromatography (GPC).
2.3.2

Liquid phase inorganic analyses

The pH of the leachate was measured using a pH meter and the concentration of the mainelements was analyzed using Inductively Coupled Plasma –Atomic Emission Spectrometry(ICP-AES).
2.3.3

Solid phase analyses (powder, thin-plate and block specimens)

The physico-chemical properties of the solid phases altered by leaching were analyzed by:a; XRD (qualitative analysis of crystal components, X-Ray Diffraction) .
b; TG-DTA and DSC (quantitative and qualitative estimation of hydrates, ThermoGravimetry with Differential Thermal Analysis and Differential Scanning Calorimetry).
c; EPMA (element concentration mapping, Electron Probe Micro Analyzer).
d; SEM (observational shape analysis of hydrates and other compounds, Scanning Electron
Microscope).
e; MIP (pore size distribution analysis, Mercury Intrusion Porosimetry).
f; 29Si-NMR (structural analysis of Si ion in Si-containing compounds, especially C-S-H
phases, Nuclear Magnetic Resonance).

5

NUMO-TR-08-01

3

RESULTS AND DISCUSSION

3.1

Release of organics and pH

3.1.1

Fresh leaching tests

Figure 3.1-1 shows the amount of organic carbon elution (TOC) from fresh grout leachates.
The elution of organic substances was identified for both XREF52 and XP308B, both ofwhich are SP-free compositions. The sample XREF52 showed higher TOC than XP308B. As
the amount of cement (UF16) in the cementitious material in dry weight ratio is 93.0 % for
XREF52 and 59.2 % for XP308B (Table 2.1-2), the difference in the amount of TOC isconsidered to be dependent on the amount of cement. Based on the above result, TOC elutionof solution leached with XP308B and XREF52 is understood to be caused by the grinding aid(CGA) contained in the cement.
Addition of SP increased the amount of TOC in both the normal and low-pH systems and theinfluence of SP on elution was clearly recognizable. TOC amounts eluted from the low-pH
cement system were confirmed to be smaller compared with the normal pH system. In
addition, when P308B (with Mighty 150 added) was immersed in the synthetic saline
groundwater system (OL-SR), the amount of TOC elution was higher than in the cases where
it was immersed in other leachates.
To interpret the influence of SP on TOC values, the initial content of TOC was calculated
numerically for each grout material to estimate the amount of grout remaining after the
immersion period. Table 3.1-1 shows the density and TOC for each raw material. TOC foreach grout was calculated using the following equation (3-1)
XREF52
REF52
XP308B
P308B
P379G

TOC /mg dm -3

80
70
60
50
40

100

Solution: All-MR

90

XREF52
REF52
XP308B
P308B
P379G

80
70
60
50
40

80
70

50
40

30

30

20

20

20

10

10

10

0

0

20
40
60
Immersing period /days

Figure 3.1-1:

TOCini =

Where

80

XREF52
REF52
XP308B
P308B
P379G

60

30

0

Solution: OL-SR

90

TOC /mg dm -3

100

Solution: Deionized90

TOC /mg dm -3

100

0
0

20
40
60
Immersing period /days

80

0

20
40
60
Immersing period /days

Change with time in TOC in the leachate (fresh leaching test).

C × TOCC + S × TOC S + SP × TOC SP
C + S + SP + W(3-1)

TOCini: initial TOC of grout (weight %)TOCc, TOCS, TOCSP : TOC of cement, Grout Aid, SP (weight %)C: mixing proportion of cement (weight %)S: mixing proportion of Grout Aid (weight %)SP: mixing proportion of superplasticizer (weight %)W: mixing proportion of water without water from Grout Aid (weight %)680

NUMO-TR-08-01

The TOC values for weight per unit volume were calculated by multiplying TOC (weightratio) by the density of the grout. The calculated results are shown in Table 3.1-2. The TOC
values for the low-pH system are higher than for the normal pH system, mainly because of thehigh TOC in Grout Aid. However, the amount of TOC released in the case of the low-pH
system was lower than that for the normal pH system. Therefore, organic compounds were
thought to be hard to elute, with most of them remaining in the hardened grout as shown in
Figure 3.1-2.

Table 3.1-1:

Density and TOC of raw materials.

Density TOC*
/kg m-3 /weight%
CementUltrafine 16 3150
0.14
SilicaGrout Aid
1390
0.31
SP40
7.98
Superplasticizer Mighty 150 22.4
Glenium 51 24.4
*TOC values were measured by TOC-SSM (Solid Sample Combustion Unit).
Material

Table 3.1-2:

Calculated initial TOC for each grout paste.

Calculated TOC
Mass Unit /weight%
Volume Unit /g dm-3
Items
Items
Total
Total
UF16
GA
SP
UF16
GA
SP
XREF521439
0.08010.0607 0.0195
0.00001.153
0.873 0.280
0.000
REF52
1439
0.11620.0607 0.0195
0.0361
1.672
0.873 0.280
0.519
XP308B1358
0.14040.0355 0.1049
0.00001.907
0.483 1.424
0.000
P308B
1358
0.54710.0355 0.1049
0.40687.431
0.483 1.424
5.525
P379G
1404
0.30580.0388 0.1144
0.15264.293
0.544 1.606
2.143*Density was calculated using the densities of component materials and mixing proportions.
Density*/g dm-3

7

1.8

1.6

1.6

ref52 (81.1%)

1.4
1.2

xref52 (78.6%)

1
0.8
0.6
0.4

Deionized water

0.2

1.8
1.6
ref52 (81.2%)

1.4
1.2

xref52 (78.5%)

1
0.8
0.6
0.4

ALL-MR

0.2

0
40

60

0

Immersing period /days
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m-�
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1.8
Remaining TOC / g dm-3

Remaining TOC / g dm-3

NUMO-TR-08-01

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*The values adjacent to the specimen name indicate the TOC remaining at 56 days. It is noted that the range ofthe vertical axis in the low-pH system (bottom figures) is about 5 times greater than for the normal pH system(upper figures).
Figure 3.1-2:

Remaining TOC in hardened grouts for the immersion period.

Based on the TOC results, most of the eluted organic substances were attributed to the cement
grinding aid. In order to examine the increase in the amount of TOC due to addition of SP, gelpermeation chromatography (GPC) analyses were carried out on leachates at 56 days. Figure
3.1-3 shows examples of GPC analysis profiles and their interpretation. Figure 3.1-3-A shows
the profile for Mighty 150 and Figure 3.1-3-B shows the result for leachate in the P308B freshleaching test. The main component in Mighty 150 constituted by ten naphthalene skeletons
corresponding to the peak at 19 – 23 minutes was detected as shown Figure 3.1-3-A; there
was also an occurrence of raw material with naphthalene dimer corresponding to the 24
minute peak in the figure. On the other hand, there was no appearance of large molecularweight organics in the leachate as shown in Figure 3.1-3-B, but the occurrence of low
molecular weight organics that would be derived from cement grinding aid (CGA) was
detected in the figure. GPC analyses of fresh leaching test results are shown in Table 3.1-3. It
was confirmed that cement grinding aid is present in all the solutions. While melamine was
not found in REF52 (SP40) with added SP40, MS transmutation substances such as methylol
amine or a homologue of methylol amine (H2N-CH2-OH), which is a homologue of its dimer,
were recognized. A homologue of methylol amine is a constituent of melamine and wasconsidered to represent decomposed melamine substances or melamine foreign substances. In
P308B with added Mighty150, the NS dimer of naphthalene sulfonate acid (NS) was
recognized using a KS type column in GPC. For P379G with added Glenium51, when leachedin deionized water and the synthetic fresh groundwater system (ALL-MR), the methacrylicacid M-PEG monomer (MAA-M-PEG) was recognized and this is considered to be an
unreacted monomer of Glenium 51. Similarly, it was understood that, when immersed in thesaline groundwater system (OL-SR), the unreacted monomer MAA-M-PEG was also eluted.
8

NUMO-TR-08-01

When SP was added, in each case no high molecular weight polymers, which are the major
ingredients of SP, were recognized. It was clear that the elution of organic components islimited to low molecular weight substances such as monomers and dimers.

Figure 3.1-3:

Results of GPC analysis and interpretation.

Table 3.1-3:

Results of GPC analysis (fresh leaching test).

Leachant

Deionized water

ALL-MR(freshwater)

OL-SR(saline water)
1)
2)

Specimen

GPC column1)

XREF52
REF52
XP308B
P308B
P379G
XREF52
REF52
XP308B
P308B
P379G
XREF52
REF52
XP308B
P308B
P379G

SB
SB
SB
SB, KSSB
SB
SB
SB
SB, KSSB
SB
SB
SB
SB, KSSB

Detected organics2)

Odor

CGA
CGA, MS transmutation
CGA
CGA, NS dimer
CGA, M-PEG monomer
CGA
CGA, MS transmutation
CGA
CGA, NS dimer
CGA, M-PEG monomer
CGA
CGA, MS transmutation
CGA
CGA, NS dimer
CGA, M-PEG monomer

Odorless
Amic
Odorless
NS
Odorless
Odorless
Amic
Odorless
NS
Odorless
Odorless
Amic
Odorless
NS
Odorless

SB: Shodex OHpak SB804x2, KS: Shodex KS804x2
CGA: Cement Grinding Aid

Figure 3.1-4 shows the pH changes in the leachate. When immersed in deionized water, in
XREF52 and REF52 (SP40) (normal pH systems), pH will increase with the progression of
the immersion period, suggesting elution of e.g. Ca2+, Na+, K+ and OH-. On the other hand, inXP308B, P308B and P379G (low-pH cement systems) independent of the type of SP, pH
increased up to 7 days and decreased thereafter (Figure 3.1-5, Figure 3.1-6). It was consideredthat ions such as Ca2+, Na+, K+ and OH- in the liquid phase were released from hydrates up to
9

NUMO-TR-08-01

7 days but that, in accordance with the progression of the pozzolanic reaction, these ions wereconsumed and/or adsorbed on the produced C-S-H phase.
14

13

13

12

12

12

pH

XREF52
REF52
XP308B
P308B
P379G

10
9

pH

13

11

11
10

10

9

XP308BP308B

9XP308B

8

P308B
P379G
60

8

20

40

60

0

20

Immersing period /days

Figure 3.1-4:

R�E�F
2
5
�
X�P�3�
B
8
�
0

8�0
0
�

P�3�0
B
8
�
P�3�7
G
9
�

7�0
0
�
6�0
0
�
5�0
0
�
4�0
0
�
3�0
0
�
2�0
0
�

1�, �00�S�o�l�u�t�i �o�n �
R
-M
L
:A

9�0
0
�
�
3
C�a� �c
� o�
n�c�
e�n�
t �r�a
d -�
g
/m
n
tio
�

-�
�
3

0

60

8�0
0
�

X�R�E�
25�F5�, �0
0
�

R�E�F
2
5
�

4�, �50�

X�P�3�
B8�04�, �0
0
�

P�3�0
B
8
�

7�0
0
�

P�3�7
G
9
�

6�0
0
�
5�0
0
�
4�0
0
�
3�0
0
�
2�0
0
�

2�, �50�
2�, �00�

X�R�E�
25
�
F

1�, �5
0
�

R�E�F
2
5
�

1�, �00�X�P�3�
B
8
�
0

5�0
0
�

�
0

�
0

�
0

2�
�
0

4�
�
0

6�
�
0

�
0

I�m�m
�e�r �s�i�n�g� �p�
ys
/a
d
rio
�
e

Figure 3.1-5:

2�
�
0

4�
�
0

6�
�
0

P�3�7
G
9
�
�
0

2�
�
0

4�
�
0

6�
�
0

I�m�m
�e�r �s�i�n�g� �p�
ys
/a
d
rio
�
e

Change with time of Ca concentration in leachates (fresh leaching test).

1,000
XREF52

Solution: Deionized

700

XP308B
P308B

600

P379G

500
400
300
200

Na concentration /mg dm-3

800

5,000

Solution: ALL-MR

900

REF52

XREF52
REF52

800
700

XP308B
P308B

600

P379G

500
400
300
200
100

100
20

40

Immersing period /days

60

Solution: OL-SR

4,500
4,000
3,500
3,000
2,500

XREF52

2,000

REF52
XP308B

1,500

P308B

1,000

P379G

500

0

0

Figure 3.1-6:

P�3�0
B
8
�

I�m�m
�e�r �s�i�n�g� �p�
ys
/a
d
rio
�
e

1,000

0

S�o�l�u�t�i �o�n
R
-S
L
:O
�

3�, �0
0
�

1�0
0
�

900

40

3�, �5
0
�

1�0
0
�
�
0

20

Immersing period /days

Change with time of pH in leachates (fresh leaching test) .

S�o�l�u�t�i �o�n�:��
zd
n
io
e
D

9�0
0
�

XREF52
REF52

Immersing period /days

X�R�E�
25
�
F

1�, �00�

40�
3C�a� �c
� o�
n�c�
e�n�
t �r�a
d -�
g
/m
n
tio
�

0

C�a� �c
� o�
n�c�
e�n�
t �r�a
d
g
/m
n
tio
�

11

XREF52
REF52

P379G

8

Na concentration /mg dm-3

Solution: OL-SR

Solution: ALL-MR

Na concentration /mg dm-3

pH

14

14

Solution: Deionized

0

0

20

40

Immersing period /days

60

0

20

40

Immersing period /days

Change with time of Na concentration in leachates (fresh leaching test).

1060

NUMO-TR-08-01

3.1.2

Powder leaching tests

Figure 3.1-7 shows the amount of total organic carbon elution (TOC) in powder leaching tests.
TOC was eluted from both XREF52 and XP308B (no SP added). For all solutions (with aleachate to powder ratio of 10), TOC after 38 weeks in XREF52 was around 30 mg/dm3,
indicating TOC around 1.5 times higher than that of XP308B. As the amounts of cement in
XREF52 and XP308B are equivalent to 93.0 % and 59.2 % of dry weight ratio respectively,
the amounts of TOC are considered to be dependent on the amount of cement. Accordingly,
TOC elution of XP308B and XREF52 is understood to be caused by the grinding aid
contained in the cement. SP addition caused an increase in TOC, suggesting elution of SP
ingredients. When P308B (Mighty150 added) was immersed in any leachant, the amount of
TOC elution was larger than that of P379G (Glenium 51 added). The difference can be
explained by the different dosage of each SP. PC-based SPs, i.e. Glenium 51, have theadvantage of a high water-reducing effect with low dosage compared to PNS-based SPs, i.e.
Mighty150.

XREF52
REF52

4.0

XP308B
P308B
P379G

3.5
3.0
2.5
2.0
1.5
1.0
0.5

Leaching organic carbon /mg g-1

0.0

4.0
3.5

XP308B
P308B

3.0

P379G

2.5
2.0
1.5
1.0
0.5

5.0

0.0
1

10

100

1000

10000

10

100

1000
3

50

40

XP308B
P308B

40

P379G
30
20
10

TOC /mg dm-3

REF52

10

100

1000

Leachate powder ratio /cm3 g

10000
-1

2.0
1.5
1.0
0.5
1

10

100

1000
3

XREF52
REF52
XP308B
P308B
P379G

30
20

10000
-1

Solution: OL-SR

XREF52
REF52

50

XP308B
P308B
P379G

40
30
20
10

0
1

2.5

Leachate powder ratio /cm g

10

0

3.0

60
Solution: ALL-MR

XREF52

50

3.5

-1

60
Solution: Deionized

XREF52
REF52
XP308B
P308B
P389G

4.0

10000

Leachate powder ratio /cm g

60

Solution: OL-SR

4.5

0.0
1

Leachate powder ratio /cm3 g-1

TOC /mg dm-3

XREF52
REF52

Solution: ALL-MR

4.5

TOC /mg dm-3

Leaching organic carbon /mg g-1

Solution: Deionized

4.5

Leaching organic carbon /mg g-1

5.0

5.0

0
1

10

100

1000
3

Leachate powder ratio /cm g

10000
-1

1

10

100

1000
3

Leachate powder ratio /cm g

10000
-1

*Upper figures: in unit volume of leachate, lower figures: in unit mass of immersed powder
Figure 3.1-7:

TOC concentrations in leachate (powder leaching test).

Table 3.1-4 to Table 3.1-6 show identification results for eluted organic substances analyzed
by GPC. Similarly to the results for fresh grout leaching tests, cement grinding aid (CGA)
was eluted from the hardened hydrated phase and low molecular weight organic substances
contained in SP together with CGA were eluted from the hardened hydrated phase withaddition of SP. With a high liquid to solid ratio, the eluted TOC concentration was very small
and it was hard to obtain sufficient TOC for detection by GPC despite concentrating theamount obtained.

11

NUMO-TR-08-01

Table 3.1-4:
Specimen
XREF52

REF52

XP308B

P308B

P379G

Table 3.1-5:
Specimen
XREF52

REF52

XP308B

P308B

P379G

Results for GPC analysis (powder in deionized water).
L/S ratio
10
50
100
1000
10
50
100
1000
10
50
100
1000
10
50
100
1000
10
50
100
1000

Detected Organics
CGA
CGA
CGA
CGA
CGA, MS transmutation
CGA, MS transmutation
CGA
CGA
CGA
CGA
CGA
CGA
CGA, NS dimer
CGA, NS dimer
CGA
CGA
CGA, M-PEG monomer
CGA
CGA
CGA

Odor
Odorless
Odorless
Odorless
Odorless
Amic
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless
Faint
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless

Results for GPC analysis (powder in ALL-MR).
L/S ratio
10
50
100
1000
10
50
100
1000
10
50
100
1000
10
50
100
1000
10
50
100
1000

Detected Organics
CGA
CGA
CGA
CGA
CGA, MS transmutation
CGA, MS transmutation
CGA
CGA
CGA
CGA
CGA
CGA
CGA, NS dimer
CGA, NS dimer
CGA
CGA
CGA, M-PEG monomer
CGA, M-PEG monomer
CGA
CGA

12

Odor
Odorless
Odorless
Odorless
Odorless
Amic
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless
Faint
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless

NUMO-TR-08-01

Table 3.1-6:
Specimen
XREF52

REF52

XP308B

P308B

P379G

Results for GPC analysis (powder in OL-SR).
L/S ratio
10
50
100
1000
10
50
100
1000
10
50
100
1000
10
50
100
1000

Detected Organics
CGA
CGA
CGA
CGA
CGA, MS transmutation
CGA, MS transmutation
CGA
CGA
CGA
CGA
CGA
CGA
CGA, NS dimer
CGA, NS dimer
CGA
CGA

Odor
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless
Odorless

10

CGA, M-PEG monomer

Odorless

50
100
1000

CGA
CGA
CGA

Odorless
Odorless
Odorless

Figure 3.1-8 shows pH changes during powder leaching tests. For all leachate/solid weightratios, the resulting pH was always lowest in the saline water system and there was not muchdifference between the deionized and ALL-MR waters. In the case of the normal pH grouts(XREF52 and REF52(SP40)) immersed in deionized water, in the range 10 cm3•g-1 to 100
cm3•g-1 for the liquid-solid ratio, the decrease in pH along with the increase in liquid-solid
ratio was relatively small, with around 12.7 in both cases. However, when the liquid-solid
ratio increased from 100 cm3•g-1 to 1000 cm3•g-1, the pH decreased by about 1.0. It wasconsidered that, with a liquid-solid ratio of 1000 cm3•g-1, all the CH (portlandite) that acts asa pH buffer dissolves with dilution of the solution and pH becomes lower. On the other hand,in the low-pH cement systems (XP308B, P308B, and P379G), the pH was around 10.9 for all
liquid-solid ratios. This difference can be explained by the different hydrates in each type of
cementitious material. The low-pH cement system containing no CH does not have a pH
buffering effect such as REF52 and there is only leaching degradation of the C-S-H phase.
However, in such a case, C-S-H with a low Ca/Si ratio in the low-pH cement systems may
have a strong absorption effect on Na+ and K+. Also, when immersed in the freshwater
system (ALL-MR), the same level of pH was indicated in both the case of the low-pH and thenormal pH cement systems. However, when immersed in the saline water system (OL-SR),
the pH of the leachate of all grout types was lower compared to immersion in deionized waterand the freshwater system (ALL-MR). Due to an excess of electrolytic ingredients, the OHconcentration leached from the hardened hydrated cement was relatively lower.

13

NUMO-TR-08-01

14

13

11

10

9

8
1:10
1:50
1:100
1:1000
1:10
1:50
1:100
1:1000
1:10
1:50
1:100
1:1000
1:10
1:50
1:100
1:1000
1:10
1:50
1:100
1:1000
1:10
1:50
1:100
1:1000
1:10
1:50
1:100
1:1000
1:10
1:50
1:100
1:1000
1:10
1:50
1:100
1:1000
1:10
1:50
1:100
1:1000
1:10
1:50
1:100
1:1000
1:10
1:50
1:100
1:1000
1:10
1:50
1:100
1:1000
1:10
1:50
1:100
1:1000
1:10
1:50
1:100
1:1000

pH

12

XREF52

REF52

XP308B
Deionized

P308B

P379G

XREF52

REF52

XP308B

P308B

P379G

XREF52

ALL-MR

REF52

XP308B

P308B

P379G

OL-SR

*pH was measured after 38 weeks of immersion and monitored in a glove box.
Figure 3.1-8

Difference in pH for different leachate/solid weight ratios and leachate types(powder leaching test) REF52 (SP40).

3.2

Leaching alteration of the solid phase

3.2.1

Change in Ca/Si ratio in block leaching tests

EPMA analysis was carried out for the normal pH cement system (REF52 (SP40)) and the
low-pH cement system (P308B) immersed in all leachant solutions for 52 weeks. Figure 3.2-1
shows the distribution of the Ca/Si molar ratio for a polished surface created by cutting acrossthe center of altered block specimens immersed in all leachant solutions for 52 weeks. For thenormal pH cement system (REF52(SP40)) immersed in deionized water, the Ca/Si ratio
decreased from 1.9 to 1.0 within 6.0 mm of the contacting water surface. When the Ca/Si ratio
decreases to around 1.5 to 1.6, this would suggest the disappearance of calcium hydroxide(CH). When the Ca/Si ratio near the contacting water surface was around 0.8 to 1.5, leachingalteration of C-S-H had also occurred following the disappearance of CH. On the other hand,when the low-pH cement (P308B) was immersed in deionized water, it was verified that the
Ca/Si ratio decreased in a range around 1.5 mm from the surface and leaching alteration of CS-H occurred near the contacting water surface. In the normal pH cement system immersed in
the freshwater system (ALL-MR), no lowering of the Ca/Si ratio was observed. The results of
the liquid phase analysis also showed almost no release of Ca2+ (Figure 3.2-2). In the low-pH
cement system immersed in ALL-MR, the Ca/Si ratio was lowered around 0.5 mm from thecontacting water surface. When immersed in ALL-MR, the inhibiting effect on the
progression of the leaching alteration front was remarkable for the normal pH cement system.
The reason was assumed to be a rapid release of Ca2+ due to disappearance of CH, resulting in
the production of calcite as a secondary mineral on the contacting water surface when
encountering HCO3-. In the normal pH cement system immersed in the saline water system(OL-SR), it was noted that the Ca/Si ratio was lowered to 1.2 to 1.3 over the entire crosssection and leaching of calcium hydroxide reached the central part of the specimen. On theother hand, in the low-pH cement system immersed in OL-SR, the Ca/Si ratio was lowered to

14

NUMO-TR-08-01

around 0.5 only at the surface and the decrease is believed to be due to the leaching alterationof C-S-H releasing much more Ca2+ than Si.

*analyzed area: 2.5 x 10 mm for immersed specimens and 2.5 x 5 mm for initial specimens*upper row: contacting surface, lower row: inside block specimen
Figure 3.2-1:

3.2.2

Distribution of Ca/Si molar ratio in REF52(SP40) and P308B block specimens.

Amount of Ca2+ leached in block leaching tests

Figure 3.2-2 shows the amount of Ca2+ accumulated in leachates measured at the time ofsolution replacement. When immersed in deionized water, low-pH systems showed a small
amount of leached Ca2+ while the normal pH system showed a trend for increasing leaching of
Ca2+. On the other hand, when immersed in the freshwater system (ALL-MR), for the normal
pH cement system Ca2+ leaching was not observed; this is different from the test results in the15

NUMO-TR-08-01

other leachants. When immersed in the saline water system (OL-SR), there was significant
leaching of Ca2+, with no notable difference being observed between the normal and low-pH
cement systems.
40

REF52

Cumulative difference amont of
Ca concentration / /mg dm-3

Cumulative amont of-3
Ca concentration /mg dm

900

Solution: Deionized

XP308B

800

P308B

700

P379G

600
500
400
300
200
100

35

5,000

XREF52
Solution: All-MR

REF52
XP308B

30

P308B
P379G

25
20
15
10
5
0
-5

0
20

40

60

REF52

4,000

XP308B
P308B

3,000

P379G
2,000
1,000
0
-1,000-2,000-10
0

XREF52

Solution: OL-SR
Cumulative difference amont of
Ca concentration /mg dm-3

XREF521,000

0Immersing period /weeks

20

40

0

60

20

40

60

Immersing period /weeks

Immersing period /weeks*The scale of the y-axis is in a suitable range for each immersion system
Figure 3.2-2:

2+Change in Caconcentration in leachant with time (block leaching test).

Amount of Ca2+ and Si leached in thin-plate leaching tests

3.2.3

Figure 3.2-3 shows the cumulative amount of Ca2+ in the leachate for each time of solution
replacement. When the normal pH cement system was immersed in deionized water and the
freshwater system (ALL-MR), the amount of leached Ca2+ increased at the time of initialsolution replacement (6th week); after this the leaching rate stabilized. On the other hand,when the low-pH cement system was immersed in deionized water and ALL-MR, almost noleaching of Ca2+ was observed. It was assumed that secondary minerals such as calcite wereformed. When immersed in the saline water system (OL-SR), there was the same tendency asin the block leaching test, i.e. leaching of a significant amount of Ca2+ without any clear
difference between the normal and low-pH cement systems.

Solution: Deionized

XP308B

800

P308B

700

P379G

600
500
400
300
200

900

700
600
500
400
300
200
100

0

0
10

20

30

40

2+

900

Solution: OL-SR

800
700
600
500
400
300
200

0
10

20

30

Immersing period /weeks

Change in Ca

XREF52
REF52
XP308B
P308B
P379G

1,000

100
0

Immersing period /weeks

Figure 3.2-3:

Solution: All-MR

800

100
0

XREF52
REF52
XP308B
P308B
P379G

1,000

REF52

Cumulative difference amont of
Ca concentration / /mg dm-3

Cumulative amont of-3
Ca concentration /mg dm

900

Cumulative difference amont of
Ca concentration /mg dm-3

XREF52

1,000

40

0

10

20

30

40

Immersing period /weeks

concentration in leachant with time (thin-plate leaching test).

Figure 3.2-4 shows the cumulative amount of Si in the leachate for each time of solution
replacement. When the normal pH cement system was immersed in deionized water and the
freshwater system (ALL-MR), the amount of leached Si increased continuously and it wasverified that leaching alteration of C-S-H occurred at the first solution replacement time (6thweek). Also, when the low-pH cement system was immersed in the leachates of these systems,
16

NUMO-TR-08-01

fairly high leaching of Si was observed at the time of initial solution replacement (6th week)
and the amount of leaching increased for all immersion periods compared with the case of
immersion of the normal pH cement system. This suggests that the leaching alteration of C-SH is larger in the low-pH cement system under the same test conditions compared with thenormal pH cement system. On the other hand, when any cement system was immersed in thesaline water system (OL-SR), the amount of leached Si was less than for the cases of the othertwo types of immersing solutions. It was considered that secondary minerals such as smectite
were being produced.

160

XP308B
P308B

140

P379G

120
100
80
60
40

Cumulative difference amont of
Si concentration / /mg dm-3

Cumulative amont of-3
Si concentration /mg dm

180

200

REF52

Solution: Deionized

180
160

Immersing period /weeks

Figure 3.2-4:

3.2.4

40

160

80
60
40

0

30

180

XP308B

100

0
20

200

REF52

120

20

10

XREF52

P308B
P379G

140

20
0

Solution: All-MR

Cumulative amont of
Si concentration /mg dm-3

XREF52200

XREF52
Solution: OL-SR

REF52
XP308B
P308B

140

P379G

120
100
80
60
40
20
0

0

10

20

30

Immersing period /weeks

40

0

10

20

30

40

Immersing period /weeks

Change in Si concentration in leachant with time (thin-plate leaching test).

SEM observations of specimens in thin-plate leaching tests

The initial states of hydration were observed on fractured sections of the specimens and theleaching alteration was observed on the surface of each thin-plate specimen. The initial statesof hydration for REF52 (SP40) are shown in Figure 3.2-5-I and Figure 3.2-5-II. For the initialstate of C-S-H colloids, there are numerous pores with sizes from several tens of nm to 10 µm.
Almost the same trend was observed for the initial state of P308B (Figure 3.2-6-i and Figure
3.2-6-ii), but the small pores of the C-S-H colloids were observed to be much morecompacted. In the case of immersion in deionized water, based on the leaching alteration at
the surface, the volume of C-S-H colloids in REF52(SP40) was reduced slightly (Figure
3.2-5-IV), resulting in very rugged surface conditions and also some formation of gel
products (Figure 3.2-5-III). The main components of the gel products were determined to be
Ca and Si using EDX elemental analysis. On the other hand, in the deionized water P308B
maintained fairly smooth surface conditions with generation of pores around 10 µm in
diameter (Figure 3.2-6-iii); shrinkage of C-S-H colloids was also observed (Figure 3.2-6-iv).
In ALL-MR, significantly more polyhedral shaped crystals of calcite precipitated on thesurface of REF52 (SP40) (Figure 3.2-5-V) compared to P308B (Figure 3.2-6-v). The reason
was assumed to be the difference in the leaching ratio of Ca2+; much more Ca2+ had leachedfrom the surface of REF52 (SP40) that contains a lot of CH. In contact with HCO3- in theleachant, this then leads to calcite precipitation on the surface of specimen. However, despite
significant precipitation of calcite, the C-S-H phase just below the calcite layer was altered,with generation of numerous pores with diameters of several tens of nm to 10 µm (Figure
3.2-5-VI, Figure 3.2-6-vi). In OL-SR, many round crystals with small plates were precipitatedon the surface of both types of specimen (Figure 3.2-5-VII, Figure 3.2-6-vii). The crystals
were identified as a kind of smectite, because of the indication from EDX elemental analysis
that the main components were Mg and Si with small amounts of Cl and Ca. The XRD results
17

NUMO-TR-08-01

discussed below also support this interpretation. However, despite its coating effect on thesurface of the specimen, the C-S-H phase beneath the smectite layer had been altered withgeneration of different pore sizes, resulting in a very irregular C-S-H phase (Figure 3.2-5-VIII,
Figure 3.2-6-viii).

18

NUMO-TR-08-01

150nm

15µm
I) initial/REF52 : initial C-S-H phaseII) initial/REF52 : C-S-H colloids

Gelformatio

15µm

150nm

III) deionized/REF52 : leached C-S-H phase 1IV) deionized/REF52 : shrunk colloids

15µm

15µm
V) ALL-MR/REF52 : calcite precipitation on surfaceVI) ALL-MR/REF52 : leached C-S-H beneath calcite phase

15µm

15µm

Ⅷ) OL-SR/REF52:leached C-S-H beneath smectite phaseⅦ) OL-SR/REF52 : smectite precipitation on surface

Figure 3.2-5:

Morphogenic change in hydrates and pores (REF52 (SP40)).

19

NUMO-TR-08-01

150nm

15µm

ⅱ) initial/P308B : SF and pozzolanic reacted phasei) initial/P308B : initial C-S-H phase

15µm

150nm

ⅲ) deionized/P308B : leached C-S-H phaseⅳ) deionized/P308B : shrunk colloids

15µm

15µm
ⅴ) ALL-MR/P308B : calcite precipitation on surfaceⅵ) ALL-MR/P308B : leached C-S-H beneath calcite phase

1.5µm

1.5µm

ⅷ) OL-SR/P308B:leached C-S-H beneath smectite phaseⅶ) OL-SR/P308B : smectite precipitation on surface

Figure 3.2-6:

Morphogenic changein hydrates and pores (P308B).

20

NUMO-TR-08-01

3.2.5

Change in hydrate composition in thin-plate leaching tests (XRD
analysis)

In deionized water, loss of CH (portlandite) and ettringite was observed for the alteredspecimens of the normal pH cement system (XREF52 and REF52 (SP40)) (Figure 3.2-7).
Ettringite also disappeared in the low-pH cement system (P308B, P308B and P379G).
Disappearance of hydrates was also observed (Figure 3.2-8). In addition, broad peaks
appeared in all cement systems at around 2 θ=40o and 43o (Figure 3.2-7, Figure 3.2-8). Thesepeaks may indicate generation of amorphous substances as a result of alteration of C-S-H as
shown in Figure 3.2-5-III. There was no evidence suggesting peaks of talc and/or hydrotalcite.

Figure 3.2-7:

Hydrate composition in REF52 thin-plate specimens in deionized water.

Figure 3.2-8:

Hydrate composition in P308B thin-plate specimens in deionized water.

21

NUMO-TR-08-01

In leaching altered specimens of the normal pH cement system (XREF52 and REF52 (SP40))
in freshwater (ALL-MR), ettringite and CH disappeared and calcite was produced (Figure
3.2-9). Also, for the specimens of the low-pH cement system (XP308B, P308B, and P379G),
it was verified that ettringite was lost and calcite was produced (Figure 3.2-10). In addition, in
all the cement systems, as was the case when immersed in deionized water, broad peaks
indicating amorphous substances were generated in the range 2 θ = 40° to 50o.

Figure 3.2-9:

Hydrate composition in REF52 thin-plate specimens in ALL-MR.

Figure 3.2-10:

Hydrate composition in P308B thin-plate specimens in ALL-MR.

22

NUMO-TR-08-01

In the leaching altered specimens of the normal pH cement system in saline water (OL-SR), it
was verified that calcium hydroxide (portlandite) and ettringite were lost, while Friedel salt
(Ca2Al(OH)6Cl2H2O) was produced (Figure 3.2-11). In the leaching altered specimens of the
low-pH cement system (XP308B, P308B and P379G), ettringite disappeared and a type ofsmectite such as stevensite was produced (Figure 3.2-12). In addition, in all the cement
systems, broad peaks indicating amorphous substances were generated in the range 2 θ = 40°
to 50o.

Figure 3.2-11:

Hydrate composition in REF52 thin-plate specimens in OL-SR.

Figure 3.2-12:

Hydrate composition in P308B thin-plate specimens in deionized water.

23

NUMO-TR-08-01

25

25
REF52 Sheet
Solution: Deionized

P308B Sheet
Solution: DeionizedInitial （60.3%）
Immersed (74.2%)

Porosity /vol.%Porosity /vol.%

15

10

15

10

5

5

0
0.001

0.01

0.1

1

10

100

0
0.001

1000

0.01

0.1

1

10

100

1000

Pore diameter /μm

Pore diameter /μmI) deionized/REF52

II) deionized/P308B
25

25
REF52 Sheet
Solution: ALL-MR

Initial （63.0%）

P308B Sheet
Solution: ALL-MR

Initial （60.3%）
Immersed (80.5%)

Immersed (74.6%)

20

Porosity /vol.%20

Porosity /vol.%Immersed (74.7%)

20

20

15

10

15

10

5

5

0
0.001

0.01

0.1

1

10

100

0
0.001

1000

0.01

Pore diameter /μm

0.1

1

10

100

1000

Pore diameter /μm

III) ALL-MR/REF52

IV) ALL-MR/P308B
25

25
REF52 Sheet
Solution: OL-SR

P308B Sheet
Solution: OL-SR

Initial （60.3%）
Immersed (69.8%)

15

10

0.01

0.1

1

10

100

15

10

0
0.001

1000

Pore diameter /μm

0.01

0.1

1

10

100

Pore diameter /μmV) OL-SR/REF52
Figure 3.2-13:

Immersed (67.2%)

5

5

0
0.001

Initial （63.0%）

20

Porosity /vol.%20

Porosity /vol.%Initial （63.0%）

VI) OL-SR/P308B

Change in pore size distribution (thin-plate leaching test).

24

1000

NUMO-TR-08-01

Ettringite that was initially contained in all specimens disappeared during leaching tests
irrespective of the type of solution, as shown in Figure 3.2-7 to Figure 3.2-12. From theseresults, it was concluded that all parts of every specimen were altered. When the normal pH
cement system (XREF52 and REF52 (SP40)) was immersed in deionized water, a decrease inporosity for a pore diameter range of 0.01 to 0.04 µm and an increase in porosity for a pore
diameter range of 0.1 to 2 µm were observed (Figure 3.2-13-I). In the low-pH cement system(XP308B, P308B and P379G), a decrease in porosity for a pore diameter range of 0.003 to
0.03 µm and an increase in porosity for a pore diameter range of 0.04 to 0.5 µm wereobserved (Figure 3.2-13-II). Porosity changes in the low-pH cement system in the pore size
range of 0.03 µm or less were considered to be equivalent to voids among C-S-H colloids.
The pore size of C-S-H colloids was confirmed by SEM images. The observed tendency forincreasing porosity in the range 0.04 to 0.5 µm and the porosity decrease in the range 0.003 to
0.03 µm were attributed to expansion of the fine pores among C-S-H colloids due toshrinkage and/or a decrease in the number of C-S-H colloids along with leaching alteration.
The increase in porosity of the normal pH cement system was larger than for the low-pH
cement system and the increase in porosity around a pore diameter of 1µm was attributed toleaching of calcium hydroxide. When ALL-MR and OL-SR were used as leachants, theporosity for a pore diameter of greater than 10 µm increased much more than for the case ofdeionized water (Figure 3.2-13-III, -IV, -V and -VI). In addition, a notable decrease inporosity with a pore diameter of 0.03 µm or less and an increase in porosity for a pore
diameter of 0.03 to 1 µm was observed in case of low-pH cement. Leaching alteration of the
C-S-H phase for the thin-plate samples was more extensive in the case of ALL-MR and OLSR than in the case of deionized water.

3.2.6

Alteration of C-S-H in powder leaching tests

Figure 3.2-14 and Figure 3.2-15 show the amount of leached Ca2+ and Si converted into unit
mass of initial powder specimen, respectively. When the normal pH cement systems were
immersed in deionized water and freshwater (ALL-MR), leaching of Ca2+ was clearlyobserved and the amount of leached Ca2+ increased with increasing liquid-solid ratio. For the1000 cm3•g-1 case, Si leached only slightly due to alteration of C-S-H. On the other hand,when the low-pH cement systems were immersed in deionized and freshwater, in the range up
to 100 cm3•g-1 for the liquid-solid ratio, the leached amount of Ca2+ was small. For the 1000
cm3•g-1 case, however, there was an indication of an excess amount of leached Ca2+ that had
not precipitated as calcite. As in the case of thin-plate immersion, the low-pH cement systems
showed much more leaching of Si than the normal pH system. When immersed in saline
water (OL-SR), leaching of Ca2+ was clearly observed, but Si did not leach significantly as inother immersion cases. Particularly in the low-pH cement system, it was understood that C-SH had altered into secondary minerals, e.g. smectite, as determined by XRD analysis, byexchanging Ca2+ and Mg+ of the ionic layer in C-S-H.
Figure 3.2-16 shows 29Si-NMR spectra of the initial and altered states of powder specimens(REF52(SP40) and P308B) for the case of a liquid-solid ratio of 1000cm3•g-1. The value on
the horizontal axis in the figure indicates a chemical shift of the peak and the magnetic field
increases towards the origin of the horizontal axis. In the initial state of the normal pH cement
system, it was verified that the hydration of cement grains had progressed continuously. In thecase containing unhydrated cement grains, the Q0 peak indicating the monomer state of the Si
tetrahedron would be larger. The Q1 peak indicates one end of the dimer where another Si
25

NUMO-TR-08-01

tetrahedron bonded in one direction only; the Q2 peak indicates the center of the trimer whereanother Si tetrahedron bonded in 2 directions. As Q1 and Q2 show the end and mid-section ofa chain respectively, the Si tetrahedron comprising C-S-H in the initial specimen of thenormal pH cement system was verified as having a chain structure. In the normal pH cement
systems, the Q2/Q1 ratio of the initial specimen was low, but in the leaching alteredspecimens immersed in any type of solution, the Q2/Q1 ratio increased as an indication of an
expansion in the chain structure of the Si tetrahedron (connection made by leaching Ca2+ fromthe C-S-H phase, resulting in a low Ca/Si ratio of C-S-H). In all leaching altered specimens,
the Q1 and Q2 peaks shifted to the right side of the horizontal axis (low magnetic field side),suggesting that Al was taken up in the altered C-S-H. In the initial specimens of the low pH
cement system, the Q2/Q1 ratio is larger than the normal pH cement system and a weak Q3
peak is generated. This was understood to be due to the low Ca/Si ratio of the C-S-H structure.
In the case of immersing low-pH cement in deionized water and freshwater (ALL-MR), theQ2/Q1 ratio and the peak positions were almost the same. This could be explained as almost
no change having occurred in the chain structure of the Si tetrahedron comprising C-S-H
during the leaching alteration of C-S-H. It was understood that Ca2+ and Si leachedsimultaneously, but the rather high rate of Ca2+ leaching from the C-S-H colloids of the lowpH cement system and the alteration of C-S-H would result in a decrease of C-S-H colloid
volume with enlarging pore space among C-S-H colloids (Figure 3.2-13). When the low-pH
cement system was immersed in saline water (OL-SR), it was concluded from the fact that theQ3 peak, which indicates the status of three-directional bonding of the Si tetrahedron withother Si, had generated.that alteration of C-S-H into smectite as shown in the results of XRD
analysis had occurred.

P308B
P379G

150
100

250

200
150
100

200
150
100
50

50

50

0

0

0

-50

1

10

100

1000

10000

1

Leachate powder ratio /cm3 g-1

100

1000

10000

1

90
XREF52
REF52
XP308B

70
60

P308B
P379G

50
40
30
20

Solution: ALL-MR

80

XREF52
REF52
XP308B
P308B
P379G

70

Leaching Si /mg g-1

Solution: Deionized

60

10000

50
40
30
20

60
50
40
30
20

0

0

-10

-10

-10
100

1000
3

Leachate powder ratio /cm g

10000
-1

XREF52
REF52
XP308B
P308B
P379G

70

0

Figure 3.2-15:

1000

Solution: OL-SR

80

10

10

100

90

10

1

10

Leachate powder ratio /cm3 g-1

Ca concentration for different leachate/solid mass ratios (powder leachingtest).

90
80

10

Leachate powder ratio /cm3 g-1

2+

Figure 3.2-14 :

-1

P308B
P379G

250

Leaching Si /mg g-1

Leaching Ca /mg g-1

200

300

XREF52
REF52
XP308B
P308B
P379G

Solution: OL-SR
300
-1

250

XREF52
REF52
XP308B

Solution: ALL-MR
350

Leaching Ca /mg g

300

XREF52
REF52
XP308B

Leaching Ca /mg g-1

Solution: Deionized350

Leaching Si /mg g

350

400

400

10

1

10

100

1000

Leachate powder ratio /cm3 g-1

10000

1

10

100

1000

10000

Leachate powder ratio /cm3 g-1

Si concentration for different leachate/solid mass ratios (powder leachingtest).

26

NUMO-TR-08-01

Figure 3.2-16:

Comparison ofleaching test).

29

Si-NMR signals for REF52 (SP40) and P308B (powder

27

NUMO-TR-08-01

4

ORGANIC COMPONENTS IN
FROM ONKALO BOREHOLESGROUNDWATER

The following analyses were additionally conducted for three groundwater samples takenfrom the boreholes ONK-PVA1, ONK-KR4 and ONK-KR3 and supplied by POSIVA Oy.
These liquid samples contain organics that leached in a low-pH cement grouting experiment.
Organic components were analyzed using the methods listed below:•••

TOC: after visual observation to check for floating material, a TOC analysis was
carried out after filtration.
GPC: samples were analyzed after vacuum concentration and filtration.
Infrared spectroscopy (IR) and 1H/13C-NMR: analyses were carried out after vacuum
concentration.

4.1

Results of TOC analysis

The TOC in each sample is shown in Table 4.1-1. KR4 showed a lower TOC content than
PVA1 and KR3.
Table 4.1-1:

4.2

TOC in ONKALO groundwater samples.

SampleTOC (mg/L)

ONK-PVA1

14.4

ONK-KR3

14.4

ONK-KR4

10.8

Results of GPC analysis

The GPC results are shown in Figure 4.2-1. No polymers indicating the main components of
SP were present and only low molecular weight substances were detected. The main SP
components would show a large peak around 20 minutes (Figure 3.1-3). This was thought tobe due to humic substances in the groundwater and/or low molecular weight organics, i.e.
cement grinding aid, from cements.

28

NUMO-TR-08-01

Figure 4.2-1:

4.3

GPC profiles of samples ONK-PVA1, ONK-KR3 and ONK-KR4 (molecularweight distributions).

Results of IR analysis

The IR profiles are shown in Figure 4.3-1. The only chemical bonds detected were H2O
and/or CO32-. The precipitates in each sample were composed mainly of inorganic salts, e.g.
calcium chloride or calcium carbonate.

29

NUMO-TR-08-01

Figure 4.3-1:

IR profiles of samples ONK-PVA1, ONK-KR3 and ONK-KR4 (chemical bonds).

30

NUMO-TR-08-01

4.4

Results of 1H-NMR and 13C-NMR analysis

The 1H-NMR profiles are shown in Figure 4.4-1 and the analytical results of both detections
are shown in Table 4.4-1. In each sample, ethoxy, hydroxy, acetyl, ethyl and methyl silene
groups were detected, indicating the possible existence of some type of surface-active agent.
In KR4 (in addition to the possibility of a surface-active agent), it is also possible that somekind of chemical additive is released from the cementitious material, e.g. tri-ethanol-amine asa cement grinding aid, because of the detection of aromatic compounds, amino-methylenegroup and oxy-methylene group. It is also possible that eluted SP40 compounds are present,
i.e. MS transmutation substances such as methylol amine or a group of methylol amine that isa homologue of its dimer.

31

NUMO-TR-08-01

Figure 4.4-1:

1

H-NMR profiles (chemical bonds).

32

NUMO-TR-08-01

Table 4.4-1:

Chemical bonding groups in ONKALO samples ONK-PVA1, ONK-KR3 and
ONK-KR4, detected by NMR analysis.

33

NUMO-TR-08-01

5

CONCLUSIONS

The release of organics from hardened cementitious materials and the physico-chemical
properties of cementitious materials altered by leaching were examined using powder, thinplate and block-shaped specimens immersed in deionized, fresh and saline water. The main
findings of this study can be summarized as follows:•

Cement grinding aid and some low molecular weight raw materials ofsuperplasticizers, e.g. naphthalene dimer, melamines and M-PEG, were detected in theleachant from hardened cementitious grout materials. Elution of the main SP
components was not detected in any leaching test.

•

Low-pH cements are highly durable in terms of the progress rate of the leachingalteration front, but the degree of alteration of the C-S-H phase in a thin surface layer
in contact with the leachant is strong and results in a layer of porous hydrates throughextensive leaching of Si.

•

To some extent, calcite and smectite will have a protective coating effect on thesurface of cementitious materials in contact with freshwater and saline water, but
beneath this layer there will be alteration damage due to gradual leaching of Ca2+ andSi from the C-S-H phase.

TOC, GPC, IR and NMR analyses were carried out on ONKALO groundwater samples todetermine the possibility of SP elution from cementitious grouting materials. The main
findings of this study can be summarized as follows:•

Each groundwater sample that had been in contact with the normal pH cement/ SP40
system and the low-pH cement/Mighty 150 system or that had not been in contact withany cementitious materials showed evidence of some surface-active agent, e.g.
lubricating oil for the drill bit.

•

In the normal pH cement/ SP40 system, there was possible elution of cement grinding
aid and/or some SP40 compounds.

34

NUMO-TR-08-01

6

ACKNOWLEDGEMENTS

Dr. Imoto, previously of CRIEPI, was extensively involved in this SKB-Posiva-NagraNUMO international project. He played a very important role in the experimental study on
investigating alteration phenomena of cementitious materials. He is now with the BASF
research center. His contribution is gratefully acknowledged.
Dr. Tanaka (of BASF and a Hachiyo consultant) played an important role in the interpretationof the analyzed data for organic compounds and his contribution is also gratefully
acknowledged.

35

NUMO-TR-08-01

7

REFERENCES

Bodén, A., Sievänen, U. (2005): Low-pH injection grout for deep repositories, Summary
report from a co-operation project between NUMO(Japan), Posiva(Finland) andSKB(Sweden), SKB Report R-05-40, Swedish Nuclear Fuel and Waste Management
Co., Stockholm Sweden.
NUMO (2004): Proceedings of the international workshop on bentonite-cement interaction in
repository environments, NUMO Technical Report NUMO-TR-04-05, Nuclear Waste
Management Organization of Japan, Tokyo Japan.

NUMO (2008): Study on long term applicability of low alkaline cement for repository
environments, NUMO Technical Report NUMO-TR-08-02, Nuclear Waste Management
Organization of Japan, Tokyo Japan (in Japanese).
Vuorinen, U., Lehikoinen, J., Imoto, H., Yamamoto, T., Alonso, M.C. (2004): Injection Groutfor Deep Repositories, Subproject 1: Low-pH Cementitious Grout for Larger
Fractures, Leaching Testing of Grout Mixes and Evaluation of the Long –Term
Safety, Posiva working report 2004-46, Posiva Oy, Helsinki Finland.

36