EARLY STRENGTH DEVELOPMENT OF
CEMENT MIXED SINGAPORE MARINE
CLAY
LU YITAN
NATIONAL UNIVERSITY OF SINGAPORE
2014
EARLY STRENGTH DEVELOPMENT OF
CEMENT MIXED SINGAPORE MARINE CLAY
LU YITAN
(B.Eng. (Hons), NTU )
A THESIS SUBMITTED
FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING
NATIONAL UNIVERSITY OF SINGAPORE
2014
Declaration
I
hereby
declare that
this thesis
is my
original
work
and it has
been
written
by me in its entirety. I have duly acknowledged all
the sources
of infor-
mation which have been used
in

higher curing temperature. The relation between setting time and curing
temperature was found to be governed by the Arrhenius law, and this
relation was validated by literature data of concrete/mortar.
The effect of curing temperature on the long-term strength develop-
ment was also investigated. It was found that cement mixed Singapore
marine clay develops higher ultimate strengths under higher curing tem-
peratures. This behavior is different from the commonly observed “cross-
over” behavior for concrete/mortar or cement mixed granular soils, in which
the ultimate strengths developed under different curing temperatures are
about the same. Due to this difference, the model developed by Chita-
mbira (2004) was modified by introducing a proposed strength enhancing
factor η

T
and adopting a modified shift factor a

T
. By making these mod-
ifications, the effect of curing temperature on both the ultimate strength
and rate of strength gain can be accounted for. Moreover, both ln η

T
and
i
a

T
show Arrhenius-type relation with the curing temperature T. The pro-
posed model in this study was validated by independent tests and literature
data. Thus, the strengths developed under different curing temperatures

Acknowledgment
First and foremost, I would like to express my most sincere and heartfelt
gratitude to Professor Tan Thiam Soon for his invaluable guidance, and
utmost patience throughout the entire course of my PhD study. I would
not have completed this thesis without Prof Tan’s contribution. I wish
to thank Professor Phoon Kok Kwang for his suggestions and continuous
support in various stages of this research. It has always been pleasant
and great learning experience for me to discuss with him various issues in
technical and non-technical fields.
I would like to thank Dr Zhang Rongjun for his help in my laboratory
tests, for the many long and stimulating discussions and for good friendship.
I would also like to thank Dr Surendra Tamrakar for his help in setting up
various laboratory instruments in the initial stage of this research and for
his friendship.
My sincere thanks must go to Dr Darren Chian Siau Chen and Professor
Leung Chun Fai, both of whom are members of my thesis examination com-
mittee, for providing me with in-depth and professional review comments
to improve my thesis. I thank Professor Lee Fook Hou, Dr Goh Siang Huat
and Associate Professor Harry Tan Siew Ann for sharing with me their
expert advices and opinions on my research. I am grateful to my former
mentor, Associate Professor Leong Eng Choon of Nanyang Technological
University, for his concern and encouragement over these years.
Special thanks are due to Dr Muthusamy Karthikeyan, Mr Wong Tsz
Ming and many other engineers from Surbana Consultants Pte Ltd, Sin-
gapore, TOA – JDN (PUT) Joint Venture, Singapore, for their support
during my site visits, and for supplying materials for the laboratory test-
ing. I appreciate the research scholarship and facilities provided by the Na-
tional University of Singapore. The opportunity to work under “Ministry
of National Development (MND) Research Fund for Built Environment” is
acknowledged.

of concrete/mortar . . . . . . . . . . . . . . . . . . . 45
2.5 Early quality control of cement mixed soils . . . . . . . . . . 51
2.5.1 Flow value test . . . . . . . . . . . . . . . . . . . . . 55
2.5.2 Accelerated test of cement mixed soils . . . . . . . . 56
2.5.3 Slump test of concrete/mortar . . . . . . . . . . . . . 59
2.5.4 Accelerated test of concrete/mortar . . . . . . . . . . 60
2.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
v
3 Methodology 67
3.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
3.1.1 Singapore Upper Marine Clay . . . . . . . . . . . . . 67
3.1.2 Portland Blast Furnace Cement . . . . . . . . . . . . 69
3.1.3 Seawater . . . . . . . . . . . . . . . . . . . . . . . . . 71
3.2 Experimental methods . . . . . . . . . . . . . . . . . . . . . 72
3.2.1 Preparation of cement mixed clay mixture . . . . . . 72
3.2.2 Preparation of test specimen . . . . . . . . . . . . . . 73
3.2.3 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . 74
3.2.4 Unconfined compression test . . . . . . . . . . . . . . 75
3.2.5 Laboratory vane shear test . . . . . . . . . . . . . . . 75
3.2.6 Miniature T-bar penetrometer test . . . . . . . . . . 77
3.2.7 Isothermal calorimetry test . . . . . . . . . . . . . . . 79
3.2.8 Proposed accelerated test . . . . . . . . . . . . . . . 81
3.3 Experimental programme . . . . . . . . . . . . . . . . . . . . 82
3.3.1 Experimental investigation on early strength behav-
ior of cement mixed Singapore Marine Clay . . . . . 82
3.3.2 Experimental investigation on effect of temperature
on strength behavior of cement mixed Singapore Ma-
rine Clay . . . . . . . . . . . . . . . . . . . . . . . . . 82
3.3.3 Experimental validation of the proposed early quality
control technique . . . . . . . . . . . . . . . . . . . . 83

6.2.1 Key variables on the accelerated strength q
u
(acc) . . 171
6.2.2 Correlations of q
u
(28day) – q
u
(acc) and q
u
(7day) –
q
u
(acc) . . . . . . . . . . . . . . . . . . . . . . . . . . 172
6.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
7 Conclusions and Recommendations 177
7.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
7.2 Recommendations for future study . . . . . . . . . . . . . . 180
vii
List of Figures
1.1 Extent of reclaimed land in Singapore (based on Ministry of
National Development, 2013 and Schwartz, 2005) . . . . . . 2
1.2 Land area of Singapore from 1960s to 2010s . . . . . . . . . 2
1.3 Operation process of using cement mixed dredged clay as fill
in the reclamation project in Singapore . . . . . . . . . . . . 5
1.4 Operations involved in the use of cement mixed dredged clay
as fill in the reclamation project in Singapore . . . . . . . . 6
1.5 Site unit weight measurement apparatus . . . . . . . . . . . 7
1.6 Site flow value measurement . . . . . . . . . . . . . . . . . . 8
1.7 Sample batching on the mixing barge . . . . . . . . . . . . . 8
1.8 Site temperature monitored by temperature probes . . . . . 10

rized in Table 2.1 versus Actual data [fitting parameters ob-
tained from fitting q
u
(7day) and q
u
(28day) to actual exper-
imental data] . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.5 Strength development with time of a typical mix reported
in TOA Corporation (2009) modelled by models in Table 2.1 25
2.6 Schematic description of setting and hardening of cement
pastes (adapted from Pinto, 1997) . . . . . . . . . . . . . . . 28
2.7 Cement hydration heat evolution with time (adapted from
Nelson, 1990) . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.8 Schematic representation of strength development with time) 30
2.9 Procedures of graph-shifting and the determination of E
a
(reproduced from Chitambira, 2004; original experimental
data from Kawasaki et al., 1984) . . . . . . . . . . . . . . . 35
2.10 Proposal by Chitambira (2004) applied to various literature
data (to be continued) . . . . . . . . . . . . . . . . . . . . 38
2.10 (continued) Proposal by Chitambira (2004) applied to var-
ious literature data (to be continued) . . . . . . . . . . . . 39
2.10 (continued) Proposal by Chitambira (2004) applied to var-
ious literature data (to be continued) . . . . . . . . . . . . 40
2.10 (continued) Proposal by Chitambira (2004) applied to var-
ious literature data (to be continued) . . . . . . . . . . . . 41
2.10 (continued) Proposal by Chitambira (2004) applied to var-
ious literature data . . . . . . . . . . . . . . . . . . . . . . . 42
2.11 Arrhenius plot for the single-stage setting process (t = 0 →
t

u
versus Normalized flow diameter D/D
mold
. . . . . . . . . 91
3.14 q
u
(7day) versus Cement-to-Solid ratio C/S at different Water-
to-Solid ratio W/S . . . . . . . . . . . . . . . . . . . . . . . 92
3.15 D/D
mold
and τ at t = 0 versus C/S at different W/S . . . . 93
3.16 Later-age q
u
versus Yield stress obtained from vane rheome-
ter test at t = 0 (replotted from TOA Corporation, , 2007) . 94
3.17 Normalized flow diameter D/D
mold
versus Time . . . . . . . 97
3.18 Yield stress τ versus Time . . . . . . . . . . . . . . . . . . . 98
3.19 D/D
mold
and τ versus C/S at t = 1, 2 and 3 hour . . . . . . 99
4.1 Vane shear strength versus Time (to be continued) . . . . 103
4.1 (continued) Vane shear strength versus Time . . . . . . . . 104
4.2 Vane shear strength versus time in logarithmic scale (to be
continued) . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
4.2 (continued) Vane shear strength versus time in logarithmic
scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
4.3 Normalized strength development with time in logarithmic
scale at 23 ± 2

◦
C
and 48
◦
C . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
4.9 Normalized strength developments with time in logarithmic
scale at 37
◦
C (by 20-hour strength) . . . . . . . . . . . . . 117
4.10 Normalized strength developments with time in logarithmic
scale at 48
◦
C (by 10-hour or 20-hour strength) . . . . . . . 117
4.11 Test of repeatability for VST on mix E4 at 48
◦
C . . . . . . 118
4.12 Heat evolution profile at 30
◦
C isothermal condition com-
pared with the strength development at 23 ± 2
◦
C and 37
◦
C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
4.13 Vane shear strength versus time in logarithmic scale at 37
◦
C (to be continued) . . . . . . . . . . . . . . . . . . . . 123
4.13 (continued) Vane shear strength versus time in logarithmic
scale at 37
◦

5.1 Long-term strength developments over time under different
curing temperatures (to be continued) . . . . . . . . . . . 136
xi
5.1 (continued) Long-term strength developments over time
under different curing temperatures . . . . . . . . . . . . . . 137
5.2 Normalized strength developments under different curing tem-
peratures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
5.3 Long-term strength developments fitted by Equation 2.7 (to
be continued) . . . . . . . . . . . . . . . . . . . . . . . . . 141
5.3 (continued) Long-term strength developments fitted by Equa-
tion 2.7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
5.4 Graphical illustration of the effects of a

T
and η

T
on strength
development modelled by Equation 5.1 . . . . . . . . . . . . 144
5.5 Strength developments under different temperatures mod-
elled by the proposed model in Equation 5.1 (to be con-
tinued) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
5.5 (continued) Strength developments under different temper-
atures modelled by the proposed model in Equation 5.1 . . . 147
5.6 Dependence of a

T
on curing temperature T . . . . . . . . . . 148
5.7 Dependence of η



T
— T and η

T
— T
obtained from database in Table 5.1 by the application of
the proposed model in Equation 5.1 . . . . . . . . . . . . . . 158
5.9 Comparison between the experimental data and the strength
developments modelled by the proposed model in Equation
5.1 (to be continued) . . . . . . . . . . . . . . . . . . . . . 160
xii
5.9 (continued) Comparison between the experimental data
and the strength developments modelled by the proposed
model in Equation 5.1 . . . . . . . . . . . . . . . . . . . . . 161
6.1 Apparatus used in the accelerated curing and the associated
cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
6.2 Temperature-time history of the cooling regime from 5 inde-
pendent measurements . . . . . . . . . . . . . . . . . . . . . 166
6.3 Reduction in t
f,set
with increasing temperature . . . . . . . . 167
6.4 Specimens swelled significantly after 1 to 2 hours of curing
at 90
◦
C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
6.5 A disintegrated specimen after 1 to 2 hours of curing at 90
◦
C168
6.6 Strength predicted from Equation 6.2 versus Actual test data 172

3.7 Experimental programme for the investigation of the strength
development in the long term under different temperatures . 84
3.8 Assessment programme for FVT with corresponding UCTs . 88
3.9 Assessment of strength behavior at t = 0, 1 hour, 2 hour and
3 hour using FVT . . . . . . . . . . . . . . . . . . . . . . . . 89
5.1 Database for the validation of the proposed Arrhenius-type
relations in Equation 5.2 and Equation 5.3 . . . . . . . . . . 152
xiv
5.2 Database for the validation of the proposed model in Equa-
tion 5.4 by comparing the modelled strength development
with the actual strength development . . . . . . . . . . . . . 153
6.1 Basic properties of the two different types of Singapore UMC
in the accelerated test . . . . . . . . . . . . . . . . . . . . . 169
6.2 Experimental programme for the validation of the proposed
accelerated test . . . . . . . . . . . . . . . . . . . . . . . . . 170
xv
Nomenclature
A, B, a, b, m Back fitting constants
a
T
Shift factor
a

T
Modified shift factor
β Characteristic constant for a convective heat transfer
system
C
m
Cement amount or cement dosage per unit volume

k
T
Reaction rate constant at temperature T
k
i
T
Reaction rate constant for the early hydration from end
of mixing to initial set at temperature T
xvi
k
i→f
T
Reaction rate constant for the early hydration from ini-
tial set till final set is completed at temperature T
K
f,set
Extent of reaction at final set
K
i,set
Extent of reaction at initial set
M Maturity index
p

c
Preconsolidation pressure in the e – log(p) plot usually
obtained from the oedometer consolidation test
q
u
(acc) Unconfined compressive strength obtained in the accel-
erated test

T
i
Initial temperature
T
0
Reference curing temperature
t Curing time
t
0
Reference curing age
t
f,set
Time of final set
t
i,set
Time of initial set
xvii
t
i→f,set
Time taken from initial set to final set
τ Yield stress of fresh mixture
W/C Water-to-Cement ratio by mass
W/S Water-to-Solid ratio by mass
w Water content
ABBREVIATIONS
C–A–H Calcium Aluminate Hydrate
C–S–H Calcium Silicate Hydrate
DSM Deep Soil Mixing
FVT Flow Value Test
MRT Mass Rapid Transit

last decade (Koh, 2005). Therefore, there is a need to use alternate fill
materials to continue land reclamation works.
1
Figure 1.1: Extent of reclaimed land in Singapore (based on Ministry of
National Development, 2013 and Schwartz, 2005)
Figure 1.2: Land area of Singapore from 1960s to 2010s
Another consequence of the increasing shortage of land is that there is
no more landfill in Singapore since 1998 because of the highly built up urban
environment in the whole country. Nowadays, wastes are first incinerated
2
and the incinerated ash are contained in an offshore dumping site that
is engineered to hold the wastes without contaminating the surrounding
water.
Meanwhile to raise the productivity of the limited land space, the past
two decades saw the increasing exploitation of subterranean space. In re-
cent years in particular, the extensive underground construction for the
Mass Rapid Transit (MRT) system as well as the construction for under-
ground oil cavern has generated massive amount of unwanted soils. These
excavated earth arising from underground exploitation, together with the
dredged soils arising from regular dredging works for the maintenance of
the navigation channels and port waterways have posed a major challenge
to their disposal, as it is too expensive to dump these unwanted soils in the
offshore dumping site. Therefore, it is a very attractive proposition if the
unwanted dredged soils are used for land reclamation. In doing so, not only
the shortage of reclamation fill is resolved, the unwanted soils also find a
way to be disposed with economical value.
3