異なる環境条件によるモルタルの細孔構造変化と劣化過程との関係メタデータ

言語: English
出版者:
公開日: 2019-06-25
キーワード (Ja):
キーワード (En): Drying, Environmental condition, Pore
Structure, Maturity, Mortar, Service Life, Frost Damage,
Durability Factor, Carbonation
作成者: グエン, スワン クイ
メールアドレス:所属:

URL

https://doi.org/10.15118/00009909

THE RELATIONSHIP BETWEEN PORE STRUCTURE
CHANGE AND DETERIORATION PROCESS OF CEMENTBASED MORTAR DUE TO THE DIFFERENTENVIRONMENTAL CONDITIONS
異なる環境条件によるモルタルの細孔構造変化と劣化過程との関係

Nguyen Xuan Quy

Doctor of Philosophy

Division of Engineering
MURORAN INSTITUTE OF TECHNOLOGYABSTRACT
Service lifetime refers to the period during which a structure fulfills its performance requirements. Structuresin areas that experience cold temperatures, such as Hokkaido in Japan, are exposed to freeze-thaw cycles
which can cause frost damage, carbonation and reduce service lifetime. The modelling of service lifetime
deterioration is the main aim of this research (Chapter 1). For this purpose (Chapter 2), the experimental
program was designed in the following two series. In Series 1, mortar specimens subjected to drying
conditions in the laboratory as one test set, and exposed to different natural climate conditions at three
outdoor locations in 10 years as another test set. Next, in Series 2 a large tests was performed in thelaboratory by adding not only different temperature but also different relative humidities and curing times.
Mortar specimens were prepared using water, ordinary Portland cement, and sand. Pore structure of mortar
specimens was evaluated using Mercury Intrusion Porosimetry method.

The results indicated that most of the pore structure change in the outdoor exposure test and the laboratory
test showed the same tendency due to drying temperature. Test results confirmed that pore structure ofmortar was coarsened and the pore volume with a diameter range of 40 to 2000 nm and 150-15000 nm wereincreased (Chapter 3, 4). Furthermore, this study reports evidence for the relationship between pore structurechange and maturity, and an improved maturity function is proposed. The change in the pore structure isdetermined by the proposed maturity function, which considers the curing temperature history and therelative humidity. The relative humidity is an additional and novel factor forming the new maturity function
for the prediction of pore structure change. Finally, the experimental results presented are useful information
for understanding the pore structure of mortar changes due to environmental conditions.

In this study, by analyzing the influence of environmental conditions on the change of pore structure,quantifying the relationship of frost damage from pore structure change, conducting laboratory experimentand exposure to real environment, the method for forecasting frost damage deterioration calculated by
ASTM equivalent cycle number including winter environment and dry condition in summer is proposed.
iThe service life of mortar is calculated for each region as forecasting method of frost damage by taking into
consideration the effect of summer pore structure change on frost damage resistance in addition to predictionof frost damage by conventional cycle number corresponding to ASTM using the proposal of environmental
indicator method (Chapter 5).

Keywords: Drying; Environmental condition; Pore Structure; Maturity; Mortar; Service Life; Frost
Damage; Durability Factor; Carbonationii

TABLE OF CONTENTS
ABSTRACT .....................................................................................................................................i
TABLE OF CONTENTS ............................................................................................................. iii
LIST OF FIGURES ........................................................................................................................ v
LIST OF TABLES .........................................................................................................................ix
CHAPTER 1 INTRODUCTION ............................................................................................... 2
1.1. Background ...................................................................................................................... 2
1.2. Service life concept .......................................................................................................... 5
1.3. Problem definition............................................................................................................ 7
1.4. Objective and scope of this thesis .................................................................................... 8
1.5. Outline of this thesis ........................................................................................................ 9
CHAPTER 2 PORE STRUCTURE CHANGE DUE TO ENVIRONMENTAL
CONDITIONS ..............................................................................................................122.1. Introduction ....................................................................................................................122.2. Materials and methods ...................................................................................................142.3. Effect of exposure and curing conditions on the pore size distribution of the mortar ...192.4. Pore structure change in the diameter range of 40 to 2000 nm due to temperature andrelative humidity ............................................................................................................26
2.5. Conclusions ....................................................................................................................31
CHAPTER 3 THE RELATIONSHIP BETWEEN MODIFIED MATURITY AND FROSTRESISTANCE ..............................................................................................................34
3.1. Introduction ....................................................................................................................34
3.2. Materials and methods ...................................................................................................36
3.3. Relationship between the structure change of 40-2000 nm pores and the modified
maturity function ............................................................................................................36
3.4. Effect of pore structure change on frost resistance corresponding to modified
maturity ..........................................................................................................................43
3.5. Conclusions ....................................................................................................................45
CHAPTER 4 CHANGE IN PORE STRUCTURE CHARACTERISTICS OF MORTARON CARBONATION ..................................................................................................47
4.1. Introduction ....................................................................................................................47
4.2. Materials and method .....................................................................................................48
4.3. Pore structure change of 150-15000 nm pores diameter................................................49
4.4. Relationship between pore structure of 150-15000 nm pores diameter and maturity ofcarbonation .....................................................................................................................56
4.5. Service life prediction equation regarding carbonation due to pore structure change ...68
4.6. Conclusions ....................................................................................................................69
CHAPTER 5 SERVICE LIFE PREDICTION BASED ON PORE STRUCTURE
CHANGE ......................................................................................................................71
5.1. Introduction ....................................................................................................................71
5.2. Materials and method .....................................................................................................72
5.3. Frost damage deterioration prediction based on ASTM Equivalent cycles number......73
5.4. Prediction method of service life of mortar by environmental indicator process ..........76iii

5.5. Estimation equation of carbonation speed due to maturity of of 150-15000 nm pores
diameter ..........................................................................................................................86
5.6. Conclusions ....................................................................................................................89
CHAPTER 6 CONCLUSIONS AND FUTURE WORK ......................................................91
6.1. Introduction ....................................................................................................................91
6.2. Pore structure change due to temperature and humidity (Chapter 2) ............................91
6.3. The relationship between modified maturity and frost resistance (Chapter 3) ..............92
6.4. Effect of pore structure change on carbonation (Chapter 4) ..........................................93
6.5. Service life prediction based on pore structure change (Chapter 5) ..............................94
6.6. Future work ....................................................................................................................95
REFERENCES .............................................................................................................................97
ACKNOWLEDGMENTS ..........................................................................................................107
LIST OF PUBLICATIONS .......................................................................................................110iv

LIST OF FIGURES
Figure 1.1 The background of research significance ...................................................................... 2
Figure 1.2 Relationship between the main factors influencing durability and performance,(Comité euro-international du béton. 1992) .................................................................. 3
Figure 1.3 2-D schematic of C-S-H as formed by drying, (Tennis and Jennings 2000) ................. 5
Figure 1.4 Schematic representation of the performance-based approach, (Somerville, Glanville,
and Neville 1997) .......................................................................................................... 6
Figure 1.5 Service life design is based on predictions of future deterioration, (Choo and Newman2003). ............................................................................................................................. 7
Figure 1.6 Objectives of this thesis ................................................................................................. 8
Figure 1.7 Outline of this thesis ....................................................................................................10
Figure 2.1 The sizes of pores in the cement paste range are particularly relevant with regard todurability, (Marchand, Pigeon, and Setzer 1997). .......................................................12
Figure 2.2 The coarsening of pore structure due to environmental conditions .............................13
Figure 2.3 The determination of the critical pore entry diameter and threshold pore entry diameterfrom the cumulative and differential curve, (Scrivener, Snellings, and Lothenbach2016). ...........................................................................................................................14
Figure 2.4 Locations of outdoor exposure test on a map of Japan. ...............................................17
Figure 2.5 Testing equipment: (a) D-drying apparatus (b) Mercury Intrusion Porosimetry (PoreMaster33, U.S. Quantachrome Corp.). ........................................................................19
Figure 2.6 The characteristic curves of the differential pore volume as a function of pore diameterfor cement-based mortars in Series 1. (Note: V is the pore volume and d is theequivalent pore diameter; OPC- identifies the cement type; 0.35 and 0.55 – are thewater-to-cement ratio; M, T and O identify Muroran, Tokyo and Okinawa,
respectively). ................................................................................................................21
Figure 2.7 Influence of the environmental conditions on the pore volume of mortar in Series
1. ..................................................................................................................................23
Figure 2.8 Differential pore size distribution for OPC-0.35 mortar in Series 2............................25v

Figure 2.9 Pore volume change of the 40-2000 nm-diameter pores of mortar after 10 years of
outdoor exposure in Series 1........................................................................................26
Figure 2.10
Change in pore volume of the 40-2000 nm-diameter pores due to (a) temperatureand (b) humidity in Series 1.........................................................................................28
Figure 2.11
Effect of curing temperature on the pore volume of the 40–2000 nm-diameter poresof mortar in Series 2. ...................................................................................................29
Figure 2.12
Effect of relative humidity on the pore volume of the 40–2000 nm-diameter poresof mortar in Series 2. ...................................................................................................31
Figure 3.1 Coefficient of determination of the modified maturity formula for each datum
temperature and datum humidity. ................................................................................39
Figure 3.2 The pore volume of the 40-2000 nm-diameter pores changing as a function of thesquare root of the modified maturity. ..........................................................................41
Figure 3.3 The relationship between the change of pore volume of the 40-2000 nm-diameter poresand the modified maturity of mortar due to laboratory and exposure condition. (Blackdot corresponds to laboratory condition and Color dot corresponds to exposure
condition) .....................................................................................................................42
Figure 3.4 Relationship between maturity and durability index ...................................................45
Figure 4.1 Relationship between pore volume diameter 150-15000 nm and curing period in caseof 60%RH ....................................................................................................................49
Figure 4.2 Relationship between pore volume diameter 150-15000 nm and curing period in caseof OPC0.35 in water ....................................................................................................50
Figure 4.3 Relationship between pore volume diameter 150-15000 nm and curing period in caseof OPC0.45 in water ....................................................................................................50
Figure 4.4 Relationship between pore volume diameter 150-15000 nm and curing period in caseof OPC0.55 in water ....................................................................................................51
Figure 4.5 Relationship between pore volume diameter 150-15000 nm and curing period in caseof OPC0.45 ..................................................................................................................52
Figure 4.6 Relationship between pore volume diameter 150-15000 nm and curing period in caseof OPC0.55 ..................................................................................................................52
Figure 4.7 Relationship between pore structure change of 150-15000 nm pores diameter andrelative humidity in case of OPC0.35 ..........................................................................53vi

Figure 4.8 Relationship between pore structure change of 150-15000 nm pores diameter andrelative humidity in case of OPC0.45 ..........................................................................53
Figure 4.9 Relationship between pore structure change of 150-15000 nm pores diameter andrelative humidity in case of OPC0.55 ..........................................................................54
Figure 4.10

The pore volume due to respective environment curing for each water-cement ratio
55

Figure 4.11
The pore volume due to respective environment curing in water for each watercement ratio in case of 200C ........................................................................................55
Figure 4.12
The pore volume due to respective environment curing in water for each watercement ratio in case of 500C ........................................................................................56
Figure 4.13
Coefficient of determination of regression formula for each datum temperature for
OPC0.35 ......................................................................................................................59
Figure 4.14
Coefficient of determination of regression formula for each datum temperature for
OPC0.45 ......................................................................................................................59
Figure 4.15
Coefficient of determination of regression formula for each datum temperature for
OPC0.55 ......................................................................................................................60
Figure 4.16

Coefficient of determination of regression formula for datum humidity of OPC0.35
62

Figure 4.17

Coefficient of determination of regression formula for datum humidity of OPC0.45
62

Figure 4.18

Coefficient of determination of regression formula for datum humidity of OPC0.55
63

Figure 4.19
Relationship between the pore volume of 150-15000 nm diameter pores and themodified maturity of OPC0.35 ....................................................................................64
Figure 4.20
Relationship between the pore volume of 150-15000 nm diameter pores and themodified maturity of OPC0.45 ....................................................................................64
Figure 4.21
Relationship between the pore volume of 150-15000 nm diameter pores and themodified maturity of OPC0.55 ....................................................................................65
Figure 4.22
Relationship between different reference relative humidities Ht for each water
cement ratio .................................................................................................................67vii

Figure 4.23

Relationship between different initial value for each water cement ratio ............67

Figure 5.1 Examination of meteorological statistical data ............................................................74
Figure 5.2 Overall flowchart of calculation process .....................................................................77
Figure 5.3 Process flowchart .........................................................................................................78
Figure 5.4 Conceptual diagram of relationship between durability index and elapsed years .......80
Figure 5.5 Relative dynamic modulus of elasticity decreasing per cycle .....................................81
Figure 5.6 Relationship between relative dynamic modulus of elasticity and elapsed time.........82
Figure 5.7 Relationship between relative dynamic modulus and elapsed time in Muroran city andYamagata city ..............................................................................................................83
Figure 5.8 Map of service life calculated by ASTM Equivalent cycle number and by FD-CI ....86
Figure 5.9 Pore volume change due to time..................................................................................86
Figure 5.10
Relationship between pore volume of 150-15000nm diameters and carbonation
speed ............................................................................................................................87viii

LIST OF TABLES
Table 1.1

Classification of pore sizes according to the general classification by IUPAC andcement-based materials science terminology, (Aligizaki 2006) ....................................................... 4
Table 2.1

Physical properties and chemical composition of OPC ............................................15

Table 2.2

Mix proportions .........................................................................................................15

Table 2.3

Saturated salt aqueous solution .................................................................................16

Table 2.4

Experimental in-laboratory plan ................................................................................18

Table 2.5

The change of the critical pore entry diameters ........................................................20

Table 4.1

Mix proportions .........................................................................................................48

Table 4.2

Coefficient of determination of reference temperature at reference relative humidityof 80% RH 58
Table 4.3

Coefficient of determination of reference relative humidity at reference

temperature 17 °C ...........................................................................................................................61
Table 5.1

Mix proportions .........................................................................................................73

Table 5.2

Coefficient of ASTM Equivalent cycle formula .......................................................75

Table 5.3

Service life of each region .........................................................................................85

Table 5.4

Carbonation speed coefficients .................................................................................88ix

CHAPTER 1 INTRODUCTION

1CHAPTER 1 INTRODUCTION
1.1.

Background

Cement-based materials, such as mortar, are the most widely used building materials due to their excellent
service performance. In recent years, despite the significant advances made in building material technology,
the frequency of problems caused by the insufficient durability of structures is dramatically increasing.

The service life and long-term behaviour of cement-based materials are controlled by a number of transport
processes in the cement-based materials pore system, (Choo and Newman 2003). Most of the changes anddeterioration that occur in cement-based materials from transport processes in the pore system. The
durability is also influenced or controlled by the number, type and size of pores present in the cement-basedmaterials, (Richardson 2002). Due to the complex nature of environmental effects on cement-basedmaterials, it is believed that controlling the nature and distribution of pores and cracks is essential. The
modelling of these aspects of durability and service life has been in the background in standards and codesof practice, (Soutsos, n.d.).

Figure 1.1

The background of research significanceThe durability of the cement-based materials is basically affected by the processes involved in passing,entering or passing materials, of ions or molecules in the form of liquids and gases. Service life expectancy
will depend on how fast these species can move through the materials. The radius of most ions and gas
2molecules are smaller than the pores in cement-based materials, (Richardson 2002). Adoption of thesepotentially active organisms is primarily affected by the permeability of materials. Osmotic permeability
can be defined as the ease with which an ion, molecule or liquid can move through the materials. The
permeability of cement-based materials, such as carbon dioxide, is a function of the pore structure. However,the capillary pore structure is particularly significant, (P. Kumar Mehta and Paulo J.M. Monteiro 2014).
These mechanisms are characterized by sorptive, permeable, and diffusible material properties, respectively.
Figure 1.1 shows the cause and effect of environmental conditions change that strongly affect the behaviour
and long-term performance of civil infrastructure, (Comité euro-international du béton. 1992).

Figure 1.2

Relationship between the main factors influencing durability and performance, (Comité
euro-international du béton. 1992)

Figure 1.2 shows the relationship between the main factors influencing durability and performance of
cement-based materials.

A classification of pore sizes in cement-based materials is given in Table 1.1; it can be seen that the borderlines between the different classes are not strict and there is an enormous range of pore sizes.

3

Table 1.1

Classification of pore sizes according to the general classification by IUPAC and cementbased materials science terminology, (Aligizaki 2006)

According to IUPAC,(IUPAC 1971)
Name
Micropores

Diameter<2 nm

Mesopores
22-50 nmMacropores>50 nm

According to Mehta, (P.
Kumar Mehta and PauloJ.M. Monteiro 2014)
Pore type
Size range
Inter-particle
1-3 nmspace
between
C-S-H sheets

Capillarypores (lowwater/cement
ratio)
Capillarypores (highwater/cement
ratio)
Entrained air
voids

10-50 nmAccording to Mindess et al., (Mindess,
Young, and Darwin 2003)
Name
Micropores
inter
layer
Micropores
Smallcapillaries
Mediumcapillaries

3-5 µmLarge
capillaries

50-1 mm

Entrained
air

Gel
pores

Diameter<0.5 nm0.5-2.5 nm
2.5-10 nm
Hollowshell
pores
Capillarypores

10-50 nm

50 nm-10 µm

0.1-1 mm

Cement-based materials may deteriorate with time in an outdoor climate. Degradation can result from theenvironment to which it is exposed, such as carbonation or frost attack. In cold climates, damage tostructures attributable to frost attack is one of the major problems, (Neville 2012). Furthermore, carbonationis the effect of carbon dioxide on cement-based materials and this phenomenon can lead to corrosion on
structures. The causes of deterioration by carbonation or frost attack can be related to the pore structure of
the cement-based materials. The deleterious effect depends not only on characteristics of the cement-basedmaterials but also on the specific environmental conditions. As a result of environmental interactions thepore structure and so the properties change with time. Thus, in this study, the pore structure change byenvironmental conditions including temperature and humidity was carefully investigated and thenestablished the relationship between pore structure change with carbonation and frost damage, and finallythe corresponding prediction formula.

4

Figure 1.3

1.2.

2-D schematic of C-S-H as formed by drying, (Tennis and Jennings 2000)

Service life concept

In 1997, Somerville proposed a quantitative approach to the design of structures for durability, similar tothat adopted in structural design (Somerville, Glanville, and Neville 1997). He described it as an‘engineering approach’ to durability design, and maintained that there were five aspects to be considered:“the predominant deterioration mechanisms which could be quantified using environmental ‘loads’;
performance criteria for a structure, e.g. notional service life or avoidance of deterioration; prediction
models that consider the type and rate of deterioration; factors of safety that consider variability inenvironmental loads and the precision of models; and lastly specifications and quality assurance systems
that verify compliance with the required performance”. Figure 1.4 provides a schematic of the performancebased approach according to Somerville. Somerville was essentially proposing a ‘performance-based’
approach to durability design and specification, which should be based on quantitative predictions fordurability from exposure conditions and measured material parameters. Therefore, quantitative predictions
imply the ability to determine a service life, (Alexander and Thomas 2015).

5

Figure 1.4

Schematic representation of the performance-based approach, (Somerville, Glanville,
and Neville 1997)

Cement-based materials may have durability failures with time in an outdoor climate due to corrosion or
frost attack. In special environment they may suffer from chemical attack by a reaction product absorbing
water. The concept of durability is difficult to quantify because durability is not a property of a cementbased materials and need a proper definition. Service life is a quantitative concept for describing the
durability of cement-based materials in which the performance of the cement-based materials must be
identified and the performance requirements must be defined. The service life is defined as ‘the time during
which a cement-based materials fulfils its performance requirements’, (Choo and Newman 2003). The
definition of service life is shown in Figure 1.5.

6

Figure 1.5

Service life design is based on predictions of future deterioration, (Choo and Newman2003).

1.3.

Problem definition

In the previous study, the volume of 40-2000 nm diameter pores changes depending on the temperature andthe period, and proposes using the maturity temperature-time factor to predict performance. However, it isan empirical formula that does not take into consideration the influence of relative humidity on the maturity
temperature-time factor representing 40-2000 nm diameter pore volume. In addition, the change in thevolume of 40-2000 nm diameter pores differs for each water-cement ratio. Furthermore, the ambientconditions, such as the temperature and humidity during the in-laboratory drying period, might be different
from actual ambient conditions in the outdoor exposure environment. In a real environment, cement-basedmaterials age under various conditions, such as rain, high summer temperatures, and freezing temperaturesin winter. Therefore, it is of great significance to evaluate the pore structure changes in outdoor exposure
tests for mortar samples.

Although there are many studies related to this maturity method, they have mostly focused on strength–
maturity relationships for cement-based materials; little attention has been paid to the pore structure–
maturity relationships for mortar particularly. Literature on the relationship between the maturity and pore
structure change is rare and little evidence is available.

7

Methods for predicting frost damage and change in pore structure have been proposed, but no predictive
method that combines the prediction of frost damage deterioration and that of pore structure change in a realenvironment currently exists.

1.4.

Objective and scope of this thesis

The purpose of this research is to propose an environmental indicator method, which predicts the change indurability factor based on conventional frost damage deterioration, and pore structure change in the summer;
this in turn allows calculation of the service lifetime of cement-based materials. In conjunction with theproposal of environmental indicator method, an experiment that includes the relative humidity factor in theprediction of pore structure change using conventional maturity methods was conducted, and that proposes
use of the modified maturity function.

Figure 1.6

Objectives of this thesis

The main purpose of this thesis is to present a practical model for predicting service life in existing cementbased materials corespond to pore structure change due to environmental conditions. With this aim, the main
objectives of the present thesis are focused on the following aspects:

Pore structure change due to environmental conditions such as temperature, relative humidity.

The pore size range affects the frost damage and carbonation.

Maturity function base on temperature and relative humidity.

The effect of pore structure change on frost resistance.

The effect of pore structure change on carbonation.
8

Cycle equivalent to ASTM using the Japanese climate data Japan Meteorological Agency from 1981 to
2000.



The service life using meteorological indicator FD - CI for frost damage deterioration taking into
consideration the influence of changes in pore structure during the summer on frost damage resistance.

1.5.

Outline of this thesis

The present work is divided in six chapters. The first chapter, CHAPTER 1 is an introduction of the thesis
and it summarizes the background of writing, literature review, the objectives and the aims. The second
chapter, CHAPTER 2 deals primarily with the impact of the environmental conditions on the pore structurechange of mortar. The third chapter, CHAPTER 3 provides the modified maturity function, which included
temperature and relative humidity of environmental conditions that used the results in chapter 2 and shows
the relationship between the pore structure change and frost damage. The fourth chapter, CHAPTER 4
investigates the effect of the pore size range from 150-15000 nm in diameter on carbonation due toenvironmental conditions. The fifth chapter, CHAPTER 5 provides the frost damage prediction method
using ASTM equivalent cycle number and pore structure change, also proposes a meteorological indicatorthat briefly expresses the service life of each area. And the last chapter, CHAPTER 6 outlines the mostimportant conclusions of this thesis.

A summary of the content of each chapter is presented in Figure 1.7.

9

Figure 1.7

Outline of this thesis

10CHAPTER 2
PORE STRUCTURE CHANGE DUE TO ENVIRONMENTAL
CONDITIONS

11

CHAPTER 2 PORE STRUCTURE CHANGE DUE TO ENVIRONMENTAL
CONDITIONS
2.1.

Introduction

For a variety of reasons, pore structure has become the focus of modern building material science and hasreceived much attention for many years. Cement-based materials are porous materials; thus, pore structure
characteristics play a critical role in the engineering properties of cement-based materials [(P. Kumar Mehta
and Paulo J.M. Monteiro 2014)]. Knowledge of the pore structure change is useful for exercising control on
the durability properties and for predicting the deterioration behavior, such as frost damage and carbonation,of cement-based materials [(Neville 2012), (Taylor 1997)]. Figure 2.1 shows the capillary pores andmacropores are particularly are the most relevant with regard to durability of cement-based materials.

Figure 2.1

The sizes of pores in the cement paste range are particularly relevant with regard todurability, (Marchand, Pigeon, and Setzer 1997).

Much research in recent years has focused on the examination of the pore structure change of cement-basedmaterials using the Mercury Intrusion Porosimetry (MIP) method [(Aono et al. 2007), (Atarashi et al. 2009),(Choi, Kim, and Choi 2017), (Diamond 2000), (Gallé 2001), (Gao, Wu, and Jiang 2016), (Nakamura, Hama,
and Zakaria 2015), (Nakamura, Hama, and Taniguchi 2015), (Winslow and Liu 1990), which has become
an important tool for studying pore structure (Aligizaki 2006), (Lamond and Pielert 2006), (Scrivener,
12Snellings, and Lothenbach 2016)]. Changes in the pore structure of cement-based materials such as mortar
can modify the engineering properties [(Marusin 1981), (Maruyama et al. 2017), (Parrott 1992)]. Previous
results showed that the change in the pore structure of hardened cement paste is probably related to thechange in the nanostructure of the C-S-H gel, which is a main constituent of the hardened cement paste [(E.
Kamada et al. 1996), (Powers 1958), (Powers and Brownyard 1946)]. It was pointed out recently that thenanostructure of the C-S-H and the micro-pore structure of cement-based materials are remarkably changedby drying or drying–wetting cycles [(Chang et al. 2017), (Parrott 1981)]. In addition, the change in the
micro-pore structure is due to the polymerization of silicate anions coordinated with a CaO layer developed
when the C-S-H was subjected to drying [(Aono et al. 2007), (Espinosa and Franke 2006)]. In spite of these
efforts, the effects of different environmental conditions on the pore structure change in the mortar are notfully understood. Moreover, the ambient conditions, such as the temperature and humidity during the inlaboratory drying period, might be different from actual ambient conditions in the outdoor exposure
environment. Therefore, it is of great significance to evaluate the pore structure changes in outdoor exposure
tests for mortar samples [(Tonoli et al. 2011), (S. Zhang and Zhang 2006)].

Figure 2.2

The coarsening of pore structure due to environmental conditions

The critical pore entry diameter is one of three important parameters characterizing the pore structure (which
are: total percolated pore volume, threshold pore entry diameter and critical pore entry diameter) can be13determined from cumulative or differential curve of MIP results. Critical pore entry diameter is the pore
diameter where the steepest slope of the cumulative curve is recorded. In the other way, critical pore entry
diameter is the pore diameter corresponds to the highest peak of differential curve (see Figure 2.3).

Figure 2.3

The determination of the critical pore entry diameter and threshold pore entry diameterfrom the cumulative and differential curve, (Scrivener, Snellings, and Lothenbach 2016).

Therefore, in this study, the influence of the environmental conditions, i.e., the temperature and relative
humidity, on the pore structure of mortar is investigated. Mortar specimens were prepared and subjected todrying conditions in the laboratory and exposed to different real natural climate conditions. The
experimental results show that the pore volume changed significantly due to changes in the environmental
conditions.

2.2.

Materials and methods

2.2.1 Materials
Ordinary Portland cement (OPC) in accordance with Japanese Industrial Standard was used to make themortar in Series 1 and 2. The physical properties and mineral compositions are given in Table 2.1. The
14

mineral composition of the OPC was quantified by the X-ray diffraction (XRD) Rietveld method. The sandused as fine aggregate was obtained from a natural origin. The properties of the fine aggregates were
determined as follows: the total water absorption was 1.52%, the density at a saturated and surface-dried
condition (SSD) was 2698 kg/m3, the bulk density was 1487 kg/m3, and the fineness modulus was 2.6.

Table 2.1
Specific gravity(g/cm3)3.16
3.15

Series1
2

Physical properties and chemical composition of OPC
Mineral composition (Rietveld) (%)
C3S
C2S
C3A
C4AF
Others60.2 16.2
4.7
5.4
13.5
68.7 11.7
7.5
5.5
6.6

Specific surface(cm2/g)3460
3510

Table 2.2 shows the proportions to prepare the mortar samples in Series 1 and Series 2. In Series 1, the main
mix variables were the free water-to-cement mass ratio (W/C) of 0.35 and 0.55 and the sand-to-cement ratio(S/C) of 2:1 without any chemical admixture. In Series 2, the main mix variables were W/C of 0.35, 0.45,
and 0.55 and with the same S/C as that of Series 1.

Series1
2

Watercement ratio
(W/C)
0.35
0.55
0.35
0.45
0.55

Table 2.2

Mix proportions

Sandcement ratio(S/C)

Material contents (kg/m3)
Water

Cement

Sand

Flow
(cm)

248
342
247
297
340

709
621
706
660
619

1418
1242
1412
1320
1238

15
28
16
23
29

2.0
2.0

2.2.2 Methods
1/ Preparation and curing of mortar specimens
The materials were mixed in a pan mixer. The cement and fine aggregate were mixed first. After thematerials were uniformly dispersed, water was added and mixed until a consistent mixture was obtained.

For each mortar mixture, 40 × 40 × 160 mm prisms were cast. After casting, all the prisms were left in thecasting room and covered with plastic sheeting for approximately 24 h. They were then demolded and curedin the laboratory and outdoor exposure sites according to the experimental program.
15

2/ Experimental program
The experimental program was designed for the following two series. In Series 1, one test set involved
subjecting the mortar specimens to drying conditions in the laboratory and another test set involved exposing
the specimens to different climate conditions at three outdoor locations. The experiment plan was conductedin the laboratory as shown in Table 2.4. After demolding, the specimens were cut into cubes of 40 × 40 ×
40 mm and subjected to initial curing. First, the initial curing was performed in water at 20 °C for 4 weeks
for all mortar specimens. Next, drying curing and drying–wetting curing were applied at 20 °C and 50 °C,
respectively. In the case of drying at 50 °C in controlled chamber, different relative humidity levels (5%RH
and 60%RH) were used. The 5%RH level set up by controlled chamber. The 60%RH level was performed
using Potassium Iodide (KI) which is saturated salt aqueous solution, and the drying period was varied from
2 and 4 weeks as well.

Saturated
solution
Humidity(%RH)
Target ofhumidity(%RH)
Solubility(g/100g (H2O))

Table 2.3

Saturated salt aqueous solution

20 oC

KI

NaCl

CH3COOK

NaCl

35 oC
CoCl2

50 oC

23.1

75.7

61

59.9

74.9

23

75

60

60

75

269.4

35.89

53

168.8

36.67

Simultaneously, the outdoor exposure test was also performed. After 4 weeks of initial curing, the mortar
specimens were exposed to different natural climate regions for 10 years at three outdoor sites in Japan:
Muroran (M), Tokyo (T), and Okinawa (O) (see Figure 2.4). The latitude and longitude of M, T, and O are(42° N/141° E), (35° N/139° E), and (26° N/127° E), respectively. Muroran (a city is located in thenorthernmost of Japan) has a much cooler climate than Tokyo and Okinawa, long and heavy snowfalls
dominate in winter. Tokyo (the Japanese capital) has the weather is temperate, hot, humid and rainy insummer; the winter is the sunniest and driest season of the year and snowfall is sporadic; sometimes can beaffected by typhoons. The climate of Okinawa (southern island of Japan) is sub-tropical, with no snowfall
16

in winter, and long, hot, moist and rainy summers and especially is the most affected areas by typhoons.
The annual mean temperature (°C) and the annual mean relative humidity (%RH) at the three outdoor sites
were M (8.9 °C, 81%RH), T (16.4 °C, 60%RH), and O (23.4 °C, 71%RH). The total experimental time inSeries 1 was 10 years, after which the experiments in Series 2 were performed.

Figure 2.4

Locations of outdoor exposure test on a map of Japan.

In Series 2, the experiments were only performed in the laboratory (see Table 2.4). After demolding, themortar specimens were cut into 40 mm cubes and subjected to the initial curing for 4 weeks at 20 °C inwater. Next, the specimens were immediately placed in the secondary curing conditions in various
environmental conditions for a period of 2, 4, 8, 13, or 26 weeks. In this stage, drying temperatures of 20 °C,
35 °C, and 50 °C were applied to mortar specimens; the relative humidity setting (%RH) corresponding toeach drying temperature level were as follows: 23%RH, 60%RH, 75%RH, and 100%RH (in case of 20 °C);
13%RH and 60%RH (in case of 35 °C); and 6%RH, 23%RH, 60%RH, 75%RH, and 100%RH (in case 50
of °C). To reach 23%RH, 60%RH and 75%RH level, the saturated salt aqueous solutions were used: for
23%RH using Potassium Acetate (CH3COOK); for 60%RH using Potassium Iodide (KI); for 75%RH using
Sodium Chloride (NaCl). 100%RH condition was in water. The drying–wetting cycle was set at 50 °C and
6%RH for 3 days and then at 50 °C in water for 12 hours.
17Table 2.4

SeriesSymbols

Initialcuring

1

4WK
20D-4W
50DL-2W
50DL-4W
50DH-2W
50DH-4W
50DW-2W
50DW-4W

Water
curing at
20 ℃
for 4
weeks

Experimental in-laboratory plan
Environmental conditions after initial curing
Temperature (°C)
Humidity (%)
20
60
50
5
50
5
50
60
50
60
Dry/Wet cycles (*)

Time interval(weeks)424242 (4cycles)
4 (8cycles)

20oC-23%RH20
2320oC-60%RH
20
60
20oC-75%RH
2075o
20 C-100%RH
20
100
Water
35oC-13%RH
35
13curing at
350C-60%RH
35
60
0, 2, 4, 8, 13,
2
20 ℃
26
50oC-6%RH
50
6
for 4
o
50 C-23%RH
50
23
weeks
50oC-60%RH
50
60
50oC-75%RH
5075o50 C-100%RH
50
100
50oC-DW
Dry/Wet cycles (*)(*)
1 Dry/Wet cycle = Drying at 50 ℃ (5% RH) for 3 days then wetting at 50 ℃ for 0.5 day.

3/ Determination of pore structureFirst, after curing under each environmental condition, the mortar specimens were cut into 5 × 5 × 5 mm
cubes, excluding the material within 1 cm of the surface. Next, they were soaked in acetone for 24 hours
immediately to stop the hydration reaction of cement and then kept in D-drying conditions for 24 hours.
Figure 2.5 (a) shows the D-drying apparatus. The temperature of a dry ice–ethanol bath in the trap of thisapparatus was kept at −78 °¬C, the temperature at which the water vapor pressure was about 0.5 µHg.
Finally, the pore size distributions of the mortar specimens were characterized using MIP. The MIP test was
performed using the Pore Master33 (U.S. Quantachrome Corp.) according to Japanese Industrial Standard(JIS R 1655) with operation pressures of up to 228 MPa, corresponding to 6 nm of minimum pore diameter.
Figure 2.5 (b) shows the MIP apparatus. The contact angle between the mercury and pore wall was 140°
and the surface tension of the mercury was 0.4854 N/m.
18

High pressure partTrap

Low pressure partSpecimen chamber(a)Figure 2.5(b)Testing equipment: (a) D-drying apparatus (b) Mercury Intrusion Porosimetry (PoreMaster33, U.S. Quantachrome Corp.).

MIP is a widely-used technique (Abell, Willis, and Lange 1999) for studying the distribution of poresizes in cement-based materials, which applies Washburn’s formula (Washburn 1921):r=−

2σm cos θmPWhere P is the pressure; r is the capillary radius; θm is the contact angle between the mercury and thesurface of the solid material tested; and σm is the surface tension of the mercury.

2.3.

Effect of exposure and curing conditions on the pore size distribution of the mortar

As mentioned previously, the aim of the tests was to determine the pore size distribution using MIP. It waspossible to obtain information about the pore structure change, which is observed in terms of the criticalpore entry diameter of differential curves (Cook and Hover 1999). Figure 2.6 shows the curve of differential
pore size distributions for OPC mortar (OPC-0.35 and OPC-0.55), which were measured at initial curing,
and after 1.5, 5, and 10 years of exposure in Series 1. The pore size distribution curves of OPC-0.35 andOPC-0.55 typically exhibit at least two sharp peaks. The critical pore entry diameter corresponding tohighest peak in differential curve was showed in Table 2.5. These diameter of pore increased with increasing
the W/C ratio. There was a slowdown and downward trend in the increasing of the critical pore entry
diameter after 5 years exposure. A clear difference can be observed for the 1.5-, 5-, and 10-year exposure
testing samples (see Figure 2.6: OPC-0.35-M, OPC-0.35-T, and OPC-0.35-O, respectively). By comparing
the differential curves of OPC-0.35-M and OPC-0.55-M (or OPC-0.35-T and OPC-0.55-T or OPC-0.35-O
19

and OPC-0.55-O, respectively) in Figure 2.6, it can be found that the highest peak is higher with increasing
W/C ratio. Furthermore, the higher the temperature of the exposure area, the sharper the peak of thedifferential pore size distribution curves in case of OPC-0.35. The diameter envelopes and the increased
pore volume show that the exposure samples have a coarser pore size than the initial curing samples. The
coarsened pore structure most probably resulted from the increased temperature, as confirmed by thedifferences in the weather conditions of the exposure sites. The coarsening pore structure results are in
general agreement with previous work (Rostásy, Weiβ, and Wiedemann 1980). The drying process causes
the coarser the pore structure and a significant compression of the cement gel. In addition, the formation oflarge amounts of inkbottle pores due to the drying process reveals the change of the pore structure (Espinosaand Franke 2006). The amount of capillary pores, i.e, the 40-2000 nm pore size range, and the total porevolume increase mention a large coarsening of the pore structure.

Table 2.5
Sample
OPC-0.35-M
OPC-0.35-T
OPC-0.35-O
OPC-0.55-M
OPC-0.55-T
OPC-0.55-O

Initial
32.19
32.19
32.19
62.15
62.15
62.15

The change of the critical pore entry diameters
The critical pore entry diameters (nm)1.5 years
5 years
9.19
9.64
43.2
46.48
85.03
95.22
57.92
155.4165.64
171.81
153.21
195.4120

10 years
9.83
145.5869.2
162.0929.06
205.28

0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
1

10

0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00

100

1000

10000

1000

0.15
0.14
0.13
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
10000 0.00

OPC-0.35-O

1

10

100

OPC-0.35-T

1

10

100

Initial

10

0.15
0.14
0.13
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00

OPC-0.55-T

1

10

1000

10000

1.5 years

100

1000

10000

OPC-0.55-M

1

0.15
0.14
0.13
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00

Figure 2.6

0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00

OPC-0.35-M

100

1000

10000

OPC-0.55-O

1

10

5 years

100

1000

10000

10 years

The characteristic curves of the differential pore volume as a function of pore diameterfor cement-based mortars in Series 1. (Note: V is the pore volume and d is the equivalent pore diameter;
OPC- identifies the cement type; 0.35 and 0.55 – are the water-to-cement ratio; M, T and O identify
Muroran, Tokyo and Okinawa, respectively).

21

Results of the pore volume change for each pore size range are summarized in Figure 2.7. As can be seenin Figure 2.7, the effect of the curing and exposure conditions cause significant changes in the pore volume
of mortar for Series 1. For OPC-0.55 mortar, the pore volumes of the 10-year exposure mortar samples (M,T, and O) are higher than in the case of initial curing only (4WK). On the other hand, the pore volume of
the 10-year exposure mortar samples (M) decreases and is nearly lower than initial curing only (4WK) for
OPC-0.35 mortar. Furthermore, the pore volumes of specimens OPC-0.55 and OPC-0.35, which were cured
at 50 °C in the laboratory, are considerably higher than those of the 10-year exposure specimens (M, T, andO). High curing temperature does affect the pore structure change in a significant way, increasing the porevolume of large capillary pores. This effect is much more important in the range 40–2000 nm. Analysis of
the incremental pore size distribution data shows that the laboratory curing mortar specimen has a muchhigher proportion of pore sizes with diameters in the range of 40–2000 nm than the 10-year exposure
specimens (M, T, and O). The volume of these pores apparently increased with increasing W/C ratio.
Previous studies [(Atarashi et al. 2009), (E. Kamada et al. 1996), (Nakamura, Hama, and Zakaria 2015),(Nakamura, Hama, and Taniguchi 2015)] have shown that the volume of pores of diameter 40–2000 nm
significantly affects the mechanism of frost damage in cement-based materials. Therefore, pore sizes in thisrange must be taken into account when analyzing the pore structure change of cement-based materials. Thechange in volume of the aforementioned pores is presented in Section 3.4.

22

Pore volume of 40–2000 nm pore diameters （cc/g）

0.10

0.10

OPC-0.35

OPC-0.55

40-2000 nm
6-40 nm

0.08

6-40 nm40-2000 nm

2000-10000 nm

0.08> 10000 nm

2000-10000 nm
0.06> 10000 nm

0.06

0.04

0.04

0.02

0.02

0.00

0.00

Mortar specimens

Mortar specimens

Figure 2.7

Influence of the environmental conditions on the pore volume of mortar in Series 1.

In Series 2, the effect of the relative humidity on the pore structure change was examined. Figure 2.8 shows
the differential pore size distribution of mortar at 50 °C corresponding to the increase of the relative humidity.
In general, the curves show the envelope of differential pore size distributions for OPC-0.35 mortars, whichwere measured at 0, 4, 8, 13, and 26 weeks. From the differential pore size distribution shown in Figure 2.8,
the 26-w mortar presents the highest derivative peak with a pore diameter of approximately 100 nm (except
for 75%RH and 100 %RH). By observing the pore size distribution, the critical pore entry diameter is foundto be obviously larger, expanding from 10 nm at initial curing to 100 nm at 26-w curing. A larger criticalpore entry diameter indicates that the pore is coarser. Furthermore, it is clear that the highest derivative peakstrongly decreases as the relative humidity increases, especially for the 50 °C and 100%RH mortar. The
results in Figure 2.8 clearly show that the highest derivative peak dropped sharply when the relative
humidity reached 75%RH and it could not observe in case of in water (100%RH). It is interesting that thedifferential pore volume does not change in water. Based on these observations, it can be concluded that therelative humidity has a significant effect on the pore structure change of mortar. In other words, the pore
structure change is a function of relative humidity. This conclusion agrees with that of other investigations(Adolphs, Setzer, and Heine 2002). The gel pores remain continuously water-filled. Furthermore, atintermediate and low relative humidity, the capillary pressure works in the water-filled pulling the pore23

walls together. Beaudoin and Tamtsia (2004) pointed out that the microstructural change of C-S-H isinfluenced by drying at a low and intermediate humidity and the collapse of the C-S-H structure due todrying may occur (Beaudoin and Tamtsia 2004). This is the reason for the coarsening of the pore structure
at lower relative humidity.

24

50℃-6%RH
4w
13w

0ｗ
8ｗ
26ｗ

1

10

100

1000

Differential pore volume(dV/d(logd)) (cc/g)

Differential pore volume(dV/d(logd)) (cc/g)

0.14
0.13
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00

0.14
0.13
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00

10000

50℃-23%RH

1

10

4w

8w

13w

Differential pore volume(dV/d(logd)) (cc/g)

Differential pore volume(dV/d(logd)) (cc/g)

0ｗ
26ｗ

10

100

1000

0.14
0.13
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00

10000

1

10

10

1000

Differential pore volume(dV/d(logd)) (cc/g)

Differential pore volume(dV/d(logd)) (cc/g)
10000

1000

0.14
0.13
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00

10000

50℃-DW

1

0ｗ

4w

13w

26ｗ

10

100

8w

1000

Pore diameter (nm)Pore diameter (nm)Figure 2.8

100
Pore diameter (nm)

4w
13ｗ

100

10000

4w
13w

0ｗ
8w
26ｗ

1

50℃-100%RH
0ｗ
8ｗ
26ｗ

1000

50℃-75%RH

Pore diameter (nm)
0.14
0.13
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00

100
Pore diameter (nm)50℃-60%RH

1

13w

26ｗ

Pore diameter (nm)
0.14
0.13
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00

4w

0ｗ
8w

Differential pore size distribution for OPC-0.35 mortar in Series 2.

25

10000

2.4.

Pore structure change in the diameter range of 40 to 2000 nm due to temperatureand relative humidity

First, comparing the volume of the pores of diameter 40–2000 nm in environmental conditions (PVd) andthe volume of the pores of diameter 40–2000 nm in initial curing (PVi) in Series 1 shows that the change ofthe pore volume in the 40–2000 nm range tends to reach an upper limit due to exposure time in case of
OPC-0.55 (see Figure 2.9 (b)). The significant increase rate of the changes in the pore volume for the O site
samples are particularly faster than for the M and T climate exposure sites. A clear difference in the rate ofvolume change can be observed in the case of OPC-0.35 (see Figure 2.9 (a)). Figure 2.9 (a) shows an
obviously faster rate of increase in volume change during the first 5 years of exposure, whereas the rate ofincrease slowed down for the following 5 years. For OPC-0.55 mortar, the pore volume of mortar in the 40–
2000 nm diameter range at the O site increased by a factor of approximately 2 during the first 5 years of
exposure, after which the increase significantly slowed down with almost no change for the subsequent 5
years. As such, it can be concluded that the higher the temperature, the greater the rate of pore volume
change for the pore size range of 40–2000 nm. Furthermore, the pore volume in this range can reach alimiting value after long-term exposure.

5

The pore volume change(PVd / PVi)

The pore volume change(PVd / PVi)

5

OPC-0.35

4
3
2
1

M

T

OPC-0.55

4
3
2
1

M

O

0

T

O

0
0

Figure 2.9246Time（year）

8

10

0

2

4
6
Time（year）

8

10

(b)
(a)
Pore volume change of the 40-2000 nm-diameter pores of mortar after 10 years of
outdoor exposure in Series 1.

In addition, our results in Series 1 provide compelling evidence for the pore structure change of 40-2000
nm pore size range due to long-term exposure but they may still not be sufficient. An increase in26

environmental temperature highly influences the deterioration processes of cement-based materials [(E.
Bastidas-Arteaga et al. 2010), (Emilio Bastidas-Arteaga et al. 2013), (Stewart, Wang, and Nguyen 2011),(Yoon, Çopuroğlu, and Park 2007)]. The deterioration such as frost damage can be affected by the pore
structure change of 40-2000 nm pore size range. The frost resistance is higher with lower amount of pore in
the 40-2000 nm pore size range (E. Kamada et al. 1996). Therefore, this study provides a framework for
future studies. Future work should therefore include a follow-up designed to evaluate the influence of thepore structure change of 40-2000 nm pore size range on frost resistance in the long term for different climate
regions.

27

Pore volume of 40–2000 nm pore
diameters （cc/g）

4WK

M

T

O

0.07

20D-4W

50DH-4W

0.07

OPC-0.35

0.06
0.05
0.04

OPC-0.55

0.06

0.07
0.06
0.05
0.04
0.03
0.02
0.01
0

0.05
0.04

0.03

0R2＝0.984
10 20 30 40 50 60 0.03

0.02

0.02

0.01

0.01

R2＝0.537

0

0

0

10

20

30

40

60 0

50

10

20

30

40

50

60

80

100

Temperature (o C)(a)Pore volume of 40–2000 nm pore
diameters （cc/g）

4WK

M

T

O

0.07

OPC-0.35

0.06

0.04

0.03

0.05
0.04
0

R ＝0.673

0.02

0.01

0.01

0

0

20

40

60

R2＝0.781

0.03

10 20 30 40
2 50 60

0.02

050DH-4W

OPC-0.55

0.06

0.07
0.06
0.05
0.04
0.03
0.02
0.01
0

0.05

50DL-4W

0.07

100 0

80

20

40

60

Relative humidity (%)(b)
Figure 2.10

Change in pore volume of the 40-2000 nm-diameter pores due to (a) temperatureand (b) humidity in Series 1.

Figure 2.10 shows the linear correlation between the change in the pore volume for 40–2000 nm pore
diameters and the environmental conditions in Series 1, i.e., the temperature and relative humidity foroutdoor exposure and for in-laboratory curing. Figure 2.10 also shows that there exists a meaningfulcorrelation between the volume of pores in the 40–2000 nm diameter range and the temperature as well as
between the same pore volume and the relative humidity. The tendency is clearly illustrated in Figure 2.10(a) and (b). The linear correlation in Figure 2.10 (a) has the best fit for the experimental data. For the caseof the OPC-0.35 mortar specimens, Figure 2.10 (a) indicates that the pore volume of the pores of diameter
40–2000 nm exhibits the highest correlation with the temperature, with a coefficient of determination R 2
28reaching 0.984. For both OPC-0.35 and OPC-0.55, there is an upward trend in the volume of the pores ofdiameter 40–2000 nm with increasing temperature and increasing W/C (see Figure 2.10 (a), except for 20D4W), which is in agreement with similar experiments performed by Nakamura et al. (2015), (Nakamura,Hama, and Zakaria 2015). However, unlike previous investigations that were only concerned about theeffect of the temperature, in this study, the effect of the relative humidity on the volume of the pores ofdiameter 40–2000 nm is also observed. The results illustrated in Figure 2.10 (b) highlight that the porevolume decreases with an increase in the relative humidity. Alternatively, it can be anticipated that the linear
correlation line may meet the 4WK line at 100%RH. Meanwhile, the volume of 40–2000 nm diameter pores

Pore volume of 40-2000 nm
diameter (cc/g)

does not change in water.

0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00

0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00

OPC-0.35

0

10

20

30

0

10
20
30
Curing period (week)
20℃

Figure 2.11

0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00

OPC-0.45

35℃

OPC-0.55

0

10

20

30

50℃

Effect of curing temperature on the pore volume of the 40–2000 nm-diameter poresof mortar in Series 2.

Finally, an interesting observation in this study is that the pore volume changes due to both temperature andrelative humidity in Series 2, as shown in Figure 2.11 and Figure 2.12. The results in Figure 2.11 show thatthe temperature increases with increasing pore volume. In most cases, the 40–2000 nm pore volume started
to increase after 2 weeks, then dramatically increased and reached the highest value, close to the upper limit,
after about 13 weeks. This is similar to the trends seen in Nakamura et al. (2015), (Nakamura, Hama, andZakaria 2015). These observations are important since they refine findings in the literature concerning theinfluence of temperature on the 40–2000 nm diameter pore volume. Previous studies [(Nakamura, Hama,
and Taniguchi 2015), (Nakamura, Hama, and Zakaria 2015)] have identified the high drying temperature asa reason for the coarsening of pore structures. However, the results presented in this study show that the29relative humidity is another factor contributing to the coarseness of the pore structure, and as shown in
Figure 2.12, this contribution can be significant. A significant difference in the pore volume change isobserved, as seen in Figure 2.12, where the volume of the pores of diameter 40–2000 nm increases withdecreasing relative humidity. For the 6%RH, 23%RH, 60%RH, and DW mortars, there was a very rapid
increase in the pore volume after 2 weeks; the pore volume then slowly increased after 4 weeks and remained
constant after about 13 weeks. The volume of the pores of diameter 40–2000 nm increased slightly for the
75%RH mortar for case OPC-0.35-50 °C. Interestingly, the pore volume does not change in most cases forthe 100%RH mortar during the curing period. Therefore, the results in Figure 2.11 and Figure 2.12 show
the need to consider both of relative humidity and temperature for predicting the change of pore volume ofdiameter 40–2000 nm pores in mortar. Based on the temperature and humidity dependency of the pore
structure change, the datum humidity and datum temperature were considered.

30

0.06

Pore volume of 40-2000 nm
diameter (cc/g)

OPC-0.55-50℃
0.05
0.04
0.03
0.02
0.01
0.00
0

5

10

15

20

25

30

20

25

30

20

25

30

Pore volume of 40-2000 nm
diameter (cc/g)

0.06

OPC-0.45-50℃

0.05
0.04
0.03
0.02
0.01
0.00
0

5

10

15

Pore volume of 40-2000 nm
diameter (cc/g)

0.06

OPC-0.35-50℃

0.05
0.04
0.03
0.02
0.01
0.00
0

5

10

15

Curing period (week)

Figure 2.12

6%RH

23%RH

60%RH

75%RH

100%RH

DW

Effect of relative humidity on the pore volume of the 40–2000 nm-diameter poresof mortar in Series 2.

2.5.

Conclusions

1. Both the laboratory and outdoor exposure tests revealed that the pore structure of mortar was coarsened
due to temperature and relative humidity; the volume of the pores of diameter 40–2000 nm increased
and reached an upper limit value.
2. The drying temperature was more critical to the coarsening of the pore structure. The influence of drying
on the pore structure change at 50 °C was more severe than the effects of the outdoor exposure test on
the mortar specimens.
31

3. The relative humidity had a significant effect on the pore structure change of mortar. The pore volumeof the 40–2000 nm diameter pores increased with decreasing relative humidity. The pore volume after
initial curing did not change in water content.

32

CHAPTER 3
THE RELATIONSHIP BETWEEN MODIFIED MATURITY ANDFROST RESISTANCE

33

CHAPTER 3 THE RELATIONSHIP BETWEEN MODIFIED MATURITY ANDFROST RESISTANCE
3.1.

Introduction

The main factors affecting the pore structure change of mortar are age, relative humidity, mix proportion
parameters, and curing temperature. Espinosa and Franke (2006) showed that the surface area of hardened
Portland cement paste reduces after chemical aging while the pore structure becomes coarser due to thedrying process, (Espinosa and Franke 2006). Adolphs et al. (2002) found that the changes in the mesoporous
range (10 nm to 100 nm) of hardened cement paste exhibits a strong dependency on relative humidity (RH),(Adolphs, Setzer, and Heine 2002). Hamami et al. (2012) determined that the water-to-cement mass ratio
and paste volume fraction were the main mix parameters affecting porosity, (Hamami, Turcry, and AïtMokhtar 2012). Moukwa and Aītcin (1998) pointed out that the oven-drying temperature affects the pore
structure of hardened cement paste by opening pores in the range of 0.02 and 0.1 µm, (Moukwa and Aītcin
1988). The influence of heat curing on the pore structure was also identified by Reinhardt and Stegmaier(2006) and Galan et al. (2016), [(Reinhardt and Stegmaier 2006), (Galan et al. 2016)]. Furthermore, amaturity function is defined in ASTM C1074 - 11 as follows: “a mathematical expression that uses themeasured temperature history of a cementitious mixture during the curing period to calculate an index thatis indicative of the maturity at the end of that period”, (“ASTM C1074 - 11 Standard Practice for Estimating
Cement-based materials Strength by the Maturity Method,” n.d.). In addition, the maturity is a function of
the product of the temperature multiplied by time (ACI 116R, n.d.). As a result, it is believed that the pore
structure change is closely related to the maturity function [(Nakamura, Hama, and Taniguchi 2015),(Nakamura, Hama, and Zakaria 2015)].
The term “maturity” was introduced for the first time in 1951 (Saul 1951), and is calculated from thetemperature history according to the Nurse-Saul maturity function shown in Equation (1):tM    T  T0 t
0

34

(1)

where M is the maturity index (°C-days), T is the average cement-based materials temperature (°C), To isthe datum temperature (°C), t is the elapsed time (days), and Δt is the time interval (days).

This equation also called the Nurse-Saul function. This function takes only the effect of temperature on thestrength development of cement-based materials into account and has mostly been used with the cold
weather concreting.

Although there are many studies related to this maturity method [(Abdel-Jawad 2006), (Carino and Tank
1992), (Galobardes et al. 2015), (Jin et al. 2017), (Liao, Lee, and Kang 2008), (Malhotra and Carino 2004),(Meneghetti and Meneghetti 1985), (Topçu and Toprak 2005), (Voigt, Sun, and Shah 2006), (Volz et al.
1981), (Xuan, Zhan, and Poon 2018), (Yikici and Chen 2015)], they have mostly focused on strength–
maturity relationships for cement-based materials; little attention has been paid to the pore structure–
maturity relationships for mortar particularly (Nakamura, Hama, and Zakaria 2015). Moreover, literatureon the relationship between the maturity and pore structure change is rare and little evidence is available.

Based on the pore volume change of the pores of diameter 40–2000 nm, a modified maturity function thatis able to predict the change in the mortar pore structure caused by environmental conditions is proposed.
The results of this study strongly confirm previous predictions about the relationship between maturity andpore structure change.

Frost damage is the most serious durability issue to affect structures. This phenomenon can occur whenmoisture within the material freezes and expands causing deep cracks in a structure. Many studies on the
frost damage deterioration of cement-based materials in real environments have been conducted. Hama etal. [(Hama, Y., Senbu, O., Tomosawa 2002), (Hama et al. 1999), (Hama, Y., Aono, Y., and Shibata 2004),(Hama, Y., Kamada, E., Han 1997)] showed that the frost resistance of high performance cement-basedmaterials without an air-entraining admixture decreased after several years of outdoor exposure. Hasegawa
et al. (Hasegawa, K. 1979) classified the risk map by calculating the frost damage risk based on external

35

factors (weather conditions such as freezing and thawing temperatures, freeze and thaw speed, andprecipitation).

Conversely, frost damage deterioration of cement-based materials is known to depend on pore structure.
According to Kamada et al. (E. Kamada et al. 1996), the greater the volume of 40-2000 nm diameter pores,
the lower the frost resistance of the cement-based materials for various water-cement ratios and curing
temperatures.

3.2.

Materials and methods

Ordinary Portland cement (OPC) was used to make the mortar. The sand used as fine aggregate was obtained
from a natural origin. The proportions to prepare the mortar samples in Series 1 and Series 2 are given in
Table 2.2. In Series 1, the main mix variables were the free water-to-cement mass ratio (W/C) of 0.35 and0.55 and the sand-to-cement ratio (S/C) of 2:1 without any chemical admixture. In Series 2, the main mix
variables were W/C of 0.35, 0.45, and 0.55 and with the same S/C as that of Series 1.

3.3.

Relationship between the structure change of 40-2000 nm pores and the modified
maturity function

As is well known, according to the origins of the maturity method [(Nurse 1949), (Saul 1951)], maturity is
calculated using the Nurse-Saul maturity equation (see Equation (1); nevertheless, this equation is only
applied for the strength prediction of cement-based materials. It was suggested in the introduction that thepore structure change is closely related to the maturity function. There are very few results in the scientific
literature about this relation. Nakamura et al. (2015) found an empirical formula expressing the relation
between the pore structure change and the maturity, [(Nakamura, Hama, and Taniguchi 2015), (Nakamura,Hama, and Zakaria 2015)]:Pd  0.0012 Mp  0.0097 0  M p  598

Pd  0.0391 M  598
p

36





(2)

where Pd is the pore volume of pores with 40–2000 nm diameters after drying (cc/g) and M p is the maturity(°C∙days). M p , which is a function of the drying temperature corresponding to the pore structure change, isgiven as:M p    d,t  31t
n

(3)

t 1

where d,t is the curing temperature (°C) and t is the time (days).

The function in Equation (2) shows a strong correlation between the drying temperature and the pore
structure change. Nonetheless, the maturity in Equations (2) and (3) does not include the relative humidity,as Equation (3) considers time and temperature as the only main factors. It is clear that the environmental
conditions, including both temperature and humidity, strongly affect the pore structure change. The resultsin this study point to the need to consider the effect of relative humidity on the pore structure change as anequally major factor. This is in agreement with a study by Liao et al. (2008) in which it was concluded thatthe relative humidity needs to be accounted for when using a maturity function for cement-based materials
strength prediction, (Liao, Lee, and Kang 2008). Therefore, it is necessary to improve these equations toestablish proper and complete expressions of the pore structure change.

The correlation between the change in the volume of the pores of diameter 40–2000 nm and the modified
maturity can be illustrated in general by the following formula:

PVd   Mph   0  Mph  a
Pd  

M ph  a

(4)

where α is the slope of a straight line to the upper limit, β is the initial pore volume (cc/g) value before
drying, γ is the upper limit of the pore volume (cc/g), and a is an empirical constant. Based on theexperimental results in Series 2, all of these parameters can be expressed by a linear equation from a linear
correlation with the W/C ratio:37

W)  0.0005
CW  0.027( )  0.0076
CW  0.0695( )  0.0062
CWa  372.4( )  307.67
C  0.002(

(5)
(6)
(7)
(8)

In this study, the modified maturity function ( M ph ) based on the results in Series 2 was propose, which isa function of temperature and humidity, expressed as the following equation:

Mph   RH t  d,t  Dt t
n

t 1

(9)

where d,t is the curing environment temperature (°C), Dt is the datum temperature at which the further
increase of the volume of the pores of diameter 40–2000 nm does not occur (°C), t is the time (days), andRH t is the added humidity factor. RH t is:RHt   H t  d,t (10)where d,t is the curing environment humidity and H t is the datum humidity at which the further increase of
the volume of the pores of diameter 40–2000 nm does not occur (%RH).

The datum temperature and datum humidity in Equations (9) and (10) were obtained based on Figure 3.1.
The datum temperature in Equation (9) is the temperature corresponding to the highest coefficient ofdetermination at which the further increase of the volume of the pores of diameter 40–2000 nm does notoccur, as shown in Figure 3.1 (a). The coefficient of determination was obtained by the correlation between
the change in the volume of the pores of diameter 40–2000 nm and the modified maturity. It is interesting
to see that the datum temperature in Equation (9) is 16 °C for all W/C cases (see Figure 3.1 (a)). Similarly,
the datum humidity in Equation (10) is the humidity corresponding to the highest coefficient ofdetermination at which the further increase of the volume of the pores of diameter 40–2000 nm does not38

occur was determined for each W/C. For W/C = 0.35, 0.45, and 0.55, the datum humidity was 76%RH,

1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10

0.35
15

16

0.45
17

0.55

18

19

20

Coefficient of determination

Coefficient of determination

80%RH, and 83%RH, respectively (see Figure 3.1 (b)).

1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.70

Datum temperature (° C)

Figure 3.1

0.35
0.75

0.45
0.80

0.85

0.55
0.90

0.95

1.00

Datum humidity (%)(a)(b)
Coefficient of determination of the modified maturity formula for each datum
temperature and datum humidity.

Figure 3.2 indicates the relationship between the volume of the pores of diameter 40–2000 nm and themodified maturity which as a function of temperature and relative humidity. It can be clearly seen that theline has a steep slope, which was measured over the square root of the modified maturity. An empiricalformula can be obtained from the initial slope of the line, which shows a good correlation between the porevolume and the modified maturity of each W/C ratio (see Equation (4)). The volume of the pores of diameter
40–2000 nm soon reached a maximal value (the so-called upper limit), at which most of the data converges
to a straight line with a different upper limit value. The higher the W/C ratio, the larger the upper limit. As
can be seen from Figure 3.2, it is clear that the coefficient of determination R2 reached a higher value withincreasing W/C ratio. It can be concluded that the W/C ratio has a significant impact on the volume of thepores of diameter 40–2000 nm. In agreement with the literature [(Nakamura, Hama, and Taniguchi 2015),(Nakamura, Hama, and Zakaria 2015)], this study found that the modified maturity has a close relationshipwith the pore structure of mortar. The relationship between the change of volume of the pores of diameter
40–2000 nm and the modified maturity due to laboratory and exposure condition is shown in Figure 3.3. It
can be seen that the correlation is good in both case of laboratory and exposure condition. The change ofvolume of the pores of diameter 40–2000 nm due to laboratory is higher than the change of volume of thepores of diameter 40–2000 nm due to exposure condition. Similar upward trends of the change of volume39

of the pores of diameter 40–2000 nm are observed here for OPC-0.35 and OPC-0.55. Therefore, it can beunderstood that the pores of diameter 40–2000 nm was coarsened due to environment condition.

To sum up, the application of Equation (4) to predict the change of volume of the pores of diameter 40–
2000 nm based on modified maturity and the limits of this work open new perspectives for the future work.
The prediction equation of the current study investigated pore structure with only 40 – 2000 nm range.
However, this pore size range strongly affects the frost resistance of cement-based materials according toKamada (1996). Therefore, the application of Equation (4) to predict frost damage needs to be taken into
consideration.

40

Pore volume of 40-2000 nm diameter (cc/g)

0.06
0.05

y=0.0448

0.04

W/C=0.55

0.03

y = 0.0017x + 0.0075
R² = 0.953

0.02
0.01
0
0

20

40

60

80

60

80

60

80

Pore volume of 40-2000 nm diameter (cc/g)

0.06
0.05
y=0.0368

0.04
0.03

W/C=0.45
y = 0.0013 x + 0.004
R² = 0.932

0.02
0.01
0
0

20

40

Pore volume of 40-2000 nm diameter (cc/g)

0.06
0.05
0.04

y=0.031

0.03
W/C=0.35

0.02

y = 0.0013x + 0.002
R² = 0.899

0.01
0
0

20

40

The square root of maturity of time-temperatureand humidity √Mph

Figure 3.2

The pore volume of the 40-2000 nm-diameter pores changing as a function of thesquare root of the modified maturity.

41

Figure 3.3

The relationship between the change of pore volume of the 40-2000 nm-diameter poresand the modified maturity of mortar due to laboratory and exposure condition. (Black dot corresponds
to laboratory condition and Color dot corresponds to exposure condition)

42

3.4.

Effect of pore structure change on frost resistance corresponding to modified
maturityIn this study, the modified maturity function, that is a function of temperature and humidity, can be
expressed as in Equation (11):nMph = ∑( θd,t − Dt )(Ht − φd,t )∆t

(11)

t=1

Where Mph is the modified maturity function using temperature and humidity (℃.days); θ d,t is the curing
temperature (℃); Dt is the datum temperature at which an increase in volume of 40-2000 nm diameter pores
does not occur (℃); Ht is the humidity of the curing environment (% RH); and φd,t is the datum humidity at
which an increase in pore volume does not occur.

The characteristic of pore structure change (PVd/PVi) is expressed as the ratio of the volume of 40-2000 nm
diameter micro pore in drying condition, PVd, to its volume after initial curing condition, PVi, (in water at
20 0C for 4weeks). The relationship between the pore structure change (PVd/PVi) and the modified maturity(Mph) can be shown by a linear regression. The correlation was good in the case of the square root ofmodified maturity (√Mph) and natural logarithm of pore structure change (Ln(PVd/PVi)). It was found thatthe line of regression corresponds well to the experimental data in Figure 3.2.
PVdln () = w√Mph (0 ≤ √Mph < √b)
PVi
=m

(12)

(√Mph ≥ √b)

where, (PVd/PVi) is the pore structure change in drying condition, b is constant value.

The relationship between the volume of 40-2000 nm diameter pores, the air content-paste ratio and the
durability index are represented in Equation (13); while the relationship between drying conditions and thechange in pore structure is calculated with Equation (14) using the parameters obtained from the exposure
test results. If the initial durability factor is DFi, and the durability factor after drying is DFd, the ratio of the43durability factor before and after changing the pore structure calculated from Equations (13), (14), and (15)can also be expressed as Equation (16).
A
log(DF) = −0.317 − 1.209 log(PV) + 1.799
PPVdW= 0.99Temp. −0.151 + 1.564FB + 6.81
PVi
B
DFd
PVd −1.209
=(
)
DFi
PVi

(13)
(14)
(15)

Where: DF is the durability factor; DFd is the durability factor after drying; DFi is the durability factor at
initial conditions (water curing at 20°C for 4 weeks is the standard); PV is the 40 to 2000 nm diameter porevolume (cc/g); A/P is the air content-paste ratio (%); PVi is the volume of 40-2000 nm diameter pores after
initial curing (cc/g); PVd is the volume of 40-2000 nm diameter pores after drying (cc/g); Temp. is the
maximum temperature reached during the drying period (°C); W/B is the water-binder ratio (%); and FB isthe cement type (N = 0, FB = 1).

By substituting Equation (12) into Equation (15), it is possible to obtain the durability factor ratio given in
Equation (16).
−1.209DFd
PVd −1.209=()= (𝑒𝑥𝑝 (α√Mph ))
DFi
PVi

(16)

On the other hand, frost resistance is evaluated by durability factor. The durability factor of CIF test wascalculated by the modified ASTM C666 Equation (17):

DF =

P×N
M

(17)

where, DF durability factor of the test specimen, P relative dynamic modulus of elasticity at N cycles, %, N
number of cycles at which P reaches the specified minimum value for discontinuing the test or the specified
number of cycles at which the exposure is to be terminated, whichever is less and M specified number ofcycles at which the exposure is to be terminated.

44

As a result, it is clear that can predict the frost damage by the modified maturity function. In addition to therisk of frost damage in cold regions, in the high temperature dry condition mainly in summer, the initial
durability index as shown in Equation (16), drops sharply as shown in Figure 3.4 as the amount of poreswith a diameter of 40-2000 nm increases. Therefore, in addition to the conventional number of cycles
Equivalent to ASTM, the influence of maturity is also considered as an important factor. The slope w of theequation representing the pore structure change is a linear Equation concerning the water cement ratio.

Figure 3.4

3.5.

Relationship between maturity and durability index

Conclusions

Based on the experimental results of this work, the following conclusions can be drawn:

1. It was confirmed that as the drying temperature was higher, the amount of pores with diameters of 402000 nm increased. Regardless of the water cement ratio, the tendency of the pore structure to coarsen
with the age in all curing conditions except 20 ℃ 100% RH and 50 ℃ 100% RH was confirmed.
2. The modified maturity can be use for proper and complete expression of pore struture change. Using
the Equation expressing the temperature-humidity time product, it is possible to predict the amount ofpores with a diameter of 40-2000 nm corresponding to the temperature, humidity and the water cement
ratio.
3. Frost damage can be predicted by modified maturity corresponding to durability factor.
45

CHAPTER 4CHANGE IN PORE STRUCTURE CHARACTERISTICS OF
MORTAR ON CARBONATION

46

CHAPTER 4 CHANGE IN PORE STRUCTURE CHARACTERISTICS OF
MORTAR ON CARBONATION
4.1.

Introduction

Carbonation is one of the most well-discussed research topics and a common type of attack in cement-basedmaterials, (Šavija and Luković 2016). Cement-based materials have to undergo a certain extent ofcarbonation reaction during their service life. The process begins when cement-based materials exposed tothe environment, atmospheric carbon dioxide penetrates into the cement matrix, dissolving in the poresolution to precipitate as various forms of calcium carbonate. This reaction affects both the pore structureand durability of cement-based materials. Carbonation reaction reduces the alkalinity of cement-basedmaterials and thus the reinforcement initiates to corrosion. Carbonation of portlandite and the C-S-H phasecan result in a significant reduction of pH and in the increase of volume of calcium carbonate in the pore
network. Therefore, at a certain level the the protective oxide film on the steel bars surface can be destroyed,(Ashraf 2016).

According to Borges et al., when the porosity in cement pastes is high hence the atmospheric carbon dioxide
diffusion can happen, the portlandite is further depleted and the interlayer calcium from C-S-H phase also
reacts with atmospheric carbon dioxide. Therefore, atmospheric carbon dioxide attack causes
polymerisation in C–S–H phase, cracking and coarsening the porosity. And Borges conluded that thecoarsening of the pore structure of cement-based materials related with the formation of silica gel, (Borges
et al. 2010).

The pore-size distributions of cement-based materials can compare before and after carbonation by using
MIP results. Ngala et al. showed that carbonation reaction changes the pore size distribution by increasing
the proportion of capillary pores in the pore sizes greater than 30 nm, (Ngala and Page 1997). Temperature
increase led to a significant reduction in the water retained at equilibrium and the “monomolecular layer
edification of capillary condensation within a meso-porous medium” is clearly visible (Henriksen 1993) .

47

Therefore, carbonation of cement-based materials is one of the principal causes of deterioration can lead tocorrosion of the steel bars in cement-based materials. Many studies have attempted to investigate the effectof carbonation on microstructure of cement-based materials. Moreover, in many studies the pore size rangethat affect the carbonation is unknown. This study aimed to investigate the variation of pore size 150-15000
nm in diameter and carbonation resistance in mortar subjected to environmental conditions and exposure
times. This pore size range is within the capillary pores types.

4.2.

Materials and method

Ordinary Portland cement (OPC) and the sand used as fine aggregate was obtained from a natural origin
were used to make the mortar. The properties of the fine aggregates were determined as follows: the total
water absorption was 1.52%, the density at a saturated and surface-dried condition (SSD) was 2698 kg/m3,
the bulk density was 1487 kg/m3, and the fineness modulus was 2.6. Table 4.1 shows the proportions to
prepare the mortar samples. The main mix variables were W/C of 0.35, 0.45, and 0.55 and the sand-tocement ratio (S/C) of 2:1 without any chemical admixture.

Table 4.1
Watercement ratio
(W/C)
0.35
0.45
0.55

Sandcement ratio
(S/C)
2.0

Mix proportions
Material contents (kg/m3)
Water

Cement

Sand

Flow
(cm)

247
297
340

706
660
619

1412
1320
1238

16
23
29

The pore size distributions of the mortar specimens were characterized using the Mercury Intrusion
Porosimetry. The Mercury Intrusion Porosimetry test was performed using the Pore Master33 with operationpressures of up to 228 MPa, corresponding to 6 nm of minimum pore diameter.

48

4.3.

Pore structure change of 150-15000 nm pores diameter4.3.1 Effect of temperature on the pore structure change of 150-15000 nm pores diameter
Figure 4.1, Figure 4.2, Figure 4.3, Figure 4.4 show the relationship between the diameter of 150-15000 nm
for each water-cement ratio and the curing period in different temperature conditions.

The influence of the temperature on the relationship between the diameter of 150-15000 nm pore and thecuring period was confirmed. The overall tendency is that the higher the temperature, the larger the diameterof pore diameter 150-15000 nm. In underwater curing, the amount of pores with a diameter of 150-15000
nm has not changed due to period, regardless of temperature (see Figure 4.2, Figure 4.3, Figure 4.4).

150-15000nm (W/C=0.55-60%RH)
Pore volume, cc/g

0.05
0.04
0.03
0.02
0.01
0
0

2

4

8

13

26

Time, week
20°C

Figure 4.1

35°C

50°C

Relationship between pore volume diameter 150-15000 nm and curing period in case of
60%RH

49

150-15000nm (W/C=0.35-100%RH)
0.05

Pore Volume, cc/g

0.04
0.03
0.02
0.01
0
0

2

4

8

13

26

Time, week
20°C

Figure 4.2

50°C

Relationship between pore volume diameter 150-15000 nm and curing period in case of
OPC0.35 in water

150-15000nm (W/C=0.45-100%RH)
Pore Volume, cc/g

0.05
0.04
0.03
0.02
0.01
0
0

2

4

8

13

26

Time, week
20°C

Figure 4.3

50°C

Relationship between pore volume diameter 150-15000 nm and curing period in case of
OPC0.45 in water50

150-15000nm (W/C=0.55-100%RH)
Pore Volume, cc/g

0.05
0.04
0.03
0.02
0.01
0
0

2

4

8

13

26

Time, week
20°C

Figure 4.4

50°C

Relationship between pore volume diameter 150-15000 nm and curing period in case of
OPC0.55 in water

4.3.2 Effect of relative humidity on the pore structure change of 150-15000 nm pores
diameterFigure 4.5, Figure 4.6, show the relationship between the diameter of 150-15000 nm for each water cement
ratio and the period in different relative humidity conditions. For each temperature, as a whole trend, theslope of increase increases as the humidity decreases. In addition, the amount of pores with a diameter of
150-15000 nm also increases. At 50 oC and 60%RH and 75% RH, the amount of pores with a diameter of
150-15000 nm significantly increased due to the curing period increased. In underwater curing, the amountof pores with a diameter of 150-15000 nm has not changed due to period, regardless of temperature.

51

150-15000nm (W/C=0.45-500C)
0.04

Pore volume, cc/g

0.035
0.03
0.025
0.02
0.015
0.01
0.005
0
0

2

4

8

13

75%RH

100%RH

26

Time, week
6%RH

Figure 4.5

23%RH

60%RH

Dry/WetRelationship between pore volume diameter 150-15000 nm and curing period in case of
OPC0.45

Pore volume, cc/g

150-15000nm (W/C=0.55-500C)
0.05
0.045
0.04
0.035
0.03
0.025
0.02
0.015
0.01
0.005
0
0

2

4

8

13

75%RH

100%RH

26

Time, week
6%RH

Figure 4.6

23%RH

60%RH

Dry/WetRelationship between pore volume diameter 150-15000 nm and curing period in case of
OPC0.55

Figure 4.7, Figure 4.8 and Figure 4.9 show the pore structure change strongly in the range of relative
humidity of 60-70% in most cases.

52

W/C=0.3530

PVd/PVi

25
20
15
10
5
0
0

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Relative Humidity, %2w

Figure 4.7

4w

8w

13w

26w

Relationship between pore structure change of 150-15000 nm pores diameter andrelative humidity in case of OPC0.35

W/C=0.45
40
35

PVd/PVi

30
25
20
15
10
5
0
0

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Relative Humidity, %2w

Figure 4.8

4w

8w

13w

26w

Relationship between pore structure change of 150-15000 nm pores diameter andrelative humidity in case of OPC0.45

53

W/C=0.55
12

PVd/PVi

10
8
6
4
2
0
0

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Relative Humidity, %2w

Figure 4.9

4w

8w

13w

26w

Relationship between pore structure change of 150-15000 nm pores diameter andrelative humidity in case of OPC0.55

4.3.3 Effect of water-cement ratio on the pore structure change of 150-15000 nm pores
diameterComparing each temperature and humidity with water cement ratio, it was confirmed that the initial value
becomes larger as the water cement ratio is higher. Also, as the water cement ratio is higher, the increase in
the amount of pores with a diameter of 150-15000 nm tends to be larger. Thus, it is considered that thehigher the water cement ratio, the coarsening of the pore diameter of the diameter of 150-15000 nm due tothe period tends to be increased.

54

150-15000nm (500C-75%RH)
Pore Volume, cc/g

0.05
0.04
0.03
0.02
0.01
0
0

2

4

8

13

26

Time, week
w/c=0.35

Figure 4.10

w/c=0.45

w/c=0.55

The pore volume due to respective environment curing for each water-cement ratio

In the case of underwater curing, there is almost no change in the amount of pores with a diameter of 15015000 nm regardless of the water cement ratio.

150-15000nm (200C-100%RH)
Pore Volume, cc/g

0.05
0.04
0.03
0.02
0.01
0
0

2

4

8

13

26

Time, week
w/c=0.35

Figure 4.11

w/c=0.45

w/c=0.55

The pore volume due to respective environment curing in water for each water-cement
ratio in case of 200C

55

150-15000nm (500C-100%RH)
Pore Volume, cc/g

0.05
0.04
0.03
0.02
0.01
0
0

2

4

8

13

26

Time, week
w/c=0.35

Figure 4.12

w/c=0.45

w/c=0.55

The pore volume due to respective environment curing in water for each water-cement
ratio in case of 500C

4.4.

Relationship between pore structure of 150-15000 nm pores diameter and maturityof carbonation

Previous study have shown that the temperature, humidity and time is related to pore structure change. In
addition, in this study, it is shown in Chapter 3 that water cement ratio and relative humidity are also related.
Here, it can be considered that an empirical formula of the change in pore volume (PVd) can be derived asshown in Equation (18) using these as elements.

PVd = f(Temp. , Time, W⁄C , RH)(18)

Where，PVd: Diameter 150 - 15000 nm pore volume after drying; Temp.: Curing temperature (℃); Time:Time (days); W/C: Water cement ratio; RH: Relative humidity.

Moreover, the modified maturity is proposed in chapter 3, it is clarified that temperature and time are related
to pore structure change and it can be expressed by the Equation (19), in which Mphc is the modified maturity
function of time-temperature and humidity relating the pore size from 150 to 15000nm in diametercorresponding carbonation.

56

Mphc = f(Temp. , Time, RH)(19)

Therefore, the pore structure change using Equations (18) and (19) obtained above is shown in Equation(20):

PVd = f(Mphc , W/C)

(20)

4.4.1 Datum temperature
The height of the coefficient of determination is investigated by a linear equation using the square root of
the time-temperature-humidity time product and the pore volume (PVd) with a diameter of 150 to 15000
nm. Here, it is conceivable that those which do not correctly indicate the slope of the straight line due to thevariation of the measurement result. Data is selected and the reference temperature and the reference relative
humidity are examined. For the selection method, only curing conditions with two or more data are used
between the initial value.

Firstly, from the result of Section 4.3, at 20 ° C and 50 ° C, the amount of pores with a diameter of 150 to15000 nm does not increase in water, and increases at a relative humidity of 75% RH, so the reference
relative humidity is 75%. It is assumed that the semi-relative humidity is 85% RH, and the temperature withthe highest coefficient of determination is taken as the reference temperature and indicated by a yellow
frame. Based on the above results, the reference temperature was not dependent on water cement ratio, andthe coefficient of determination was high at 17 ° C. Table 4.2 and Figure 4.13, Figure 4.14, Figure 4.15
show the coefficient of determination of the reference temperature when the reference relative humidity is
assumed.

57

Table 4.2

Coefficient of determination of reference temperature at reference relative humidity of
80% RH
Temperature (℃)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

OPC0.35
0.908845421
0.909560333
0.910219754
0.910933587
0.911592014
0.912304774
0.913016977
0.913728625
0.914385039
0.915040983
0.915696456
0.916351461
0.916896941
0.917387595
0.917823512
0.918095856
0.918259223
0.918095856
0.917551088
0.914658406

58

OPC0.450.892244361
0.893028555
0.893867999
0.89465077
0.895488693
0.896325834
0.897162193
0.897997773
0.898832576
0.899666605
0.900444335
0.901221393
0.901942348
0.902607334
0.903161115
0.90354856
0.903714557
0.903493221
0.902551938
0.897217922

OPC0.55
0.890730038
0.891852006
0.892972564
0.894147639
0.895265324
0.896493168
0.897663634
0.898888202
0.900055554
0.901276872
0.902441134
0.90354856
0.90465463
0.905593728
0.906476696
0.907083238
0.907358804
0.907138358
0.905869748
0.898721314

Figure 4.13

Coefficient of determination of regression formula for each datum temperature for
OPC0.35

Figure 4.14

Coefficient of determination of regression formula for each datum temperature for
OPC0.4559

Figure 4.15

Coefficient of determination of regression formula for each datum temperature for
OPC0.55

4.4.2 Datum humidity
Table 4.3 and Figure 4.16, Figure 4.17, Figure 4.18 show the coefficient of determination of the reference
relative humidity. The reference temperature was set to 17 ° C and the coefficient of determination of thereference relative humidity was calculated. As for the reference relative humidity, W / C = 35% is (Ht =85% RH), W / C = 45% is (Ht = 95% RH), W / C = 55% is (Ht = 95% RH) and the result with highcorrelation coefficient was obtained.

From this, it is found that the minimum temperature (Dt) at which the pore structure occurs is constant at
17 ° C regardless of the water cement ratio, and the reference relative humidity (Ht) at which the pore
structure occurs differs depending on the water cement ratio.

60

Table 4.3

Coefficient of determination of reference relative humidity at reference temperature 17 °C
Relative
Humidity
0.75
0.76
0.77
0.78
0.79
0.8
0.81
0.82
0.83
0.84
0.85
0.86
0.87
0.88
0.89
0.9
0.91
0.92
0.93
0.94
0.95
0.96
0.97
0.98
0.99

Coefficient of determination
OPC0.35
OPC0.45
OPC0.55
0.82176639
0.896548939 0.882043083
0.86844689
0.901387819 0.889381808
0.884985876 0.903050386 0.892412461
0.895767827 0.904157066
0.89465077
0.903382532 0.904930937 0.896493168
0.908845421 0.905593728 0.898053451
0.912743118 0.906090503 0.899444273
0.915368778 0.906531853
0.90066642
0.917005998 0.906862724 0.901776025
0.917932459 0.907138358 0.902773504
0.918150314 0.907358804 0.903714557
0.917877988 0.907579198 0.904599359
0.917224073 0.907689374 0.905372851
0.916133178 0.907799537 0.906090503
0.914822387 0.907909687 0.906752447
0.913181253 0.907964757 0.907413908
0.911427452 0.908019824 0.907964757
0.909450383 0.908019824 0.908515272
0.907358804 0.908019824 0.909010451
0.905151921 0.908019824
0.90950536
0.902884267 0.908019824 0.909945053
0.900555384 0.907964757 0.910384534
0.898164796 0.907909687 0.910823803
0.895712007 0.907854614 0.911153116
0.893252484 0.907799537 0.911537163

61

Figure 4.16

Coefficient of determination of regression formula for datum humidity of OPC0.35

Figure 4.17

Coefficient of determination of regression formula for datum humidity of OPC0.45

62

Figure 4.18

Coefficient of determination of regression formula for datum humidity of OPC0.55

4.4.3 Relationship between the pore volume of 150-15000 nm diameter pores and themodified maturity
The relationship between the square root of the temperature and humidity time product calculated using thereference temperature (170C) obtained from the above results and each reference relative humidity and thepore volume PVd with a diameter of 150 to 15000 nm is shown in Figure 4.19, Figure 4.20, Figure 4.21. It
can be confirmed that considering the water cement ratio, temperature and humidity, the pore volume PVd
with a diameter of 150 to 15000 nm. A good correlation was obtained for each water cement ratio for eachstraight line. The proposed function was fitted with the experimental data.

63

Pore volume of 150-15000nm diameterPV 150-15000nm
0.01800
0.01600
0.01400
0.01200
0.01000
0.00800
0.00600
0.00400
0.00200
0.00000

y = 0.0003x + 0.0005
R² = 0.9024

0

10

20

30

40

50

The square root of maturity of time-temperature and humidity, sqt
of Mphc, OPC0.35

Figure 4.19

Relationship between the pore volume of 150-15000 nm diameter pores and thePore volume of 150-15000nm diameter

modified maturity of OPC0.35

PV 150-15000nm
0.016
0.014
0.012
0.01
y = 0.0003x + 0.0013
R² = 0.9405

0.008
0.006
0.004
0.002
0
0

10

20

30

40

50

60

The square root of maturity of time-temperature and humidity, sqt
of Mphc OPC0.45

Figure 4.20

Relationship between the pore volume of 150-15000 nm diameter pores and themodified maturity of OPC0.45

64

Pore volume of 150-15000nm
diameterPV 150-15000nm
0.03
0.025
0.02
y = 0.0003x + 0.0034
R² = 0.8891

0.015
0.01
0.005
0
0

10

20

30

40

50

60

70

80

The square root of maturity of time-temperature and humidity, sqt
of Mphc, OPC0.55

Figure 4.21

Relationship between the pore volume of 150-15000 nm diameter pores and themodified maturity of OPC0.55

Experimental equation (21), (22) and (23) represent the relationship between the time-temperature-humidity
product and the diameter of the pores with a diameter of 150-15000 nm obtained. Figure 4.22 shows therelationship between different reference relative humidities Ht for each water cement ratio. The reference
humidity is in a linear relationship with the water cement ratio, and as the water cement ratio increases, theamount of pores with a diameter of 150-15000 nm increases at a high relative humidity.

W/C=35%：PVdc = 0.0003 × √∑(θd,t − 17) × (0.85 − φd,t ) × t + β(21)

W/C=45%：PVdc = 0.0003 × √∑(θd,t − 17) × (0.95 − φd,t ) × t + β(22)

W/C=55%：PVdc = 0.0003 × √∑(θd,t − 17) × (0.99 − φd,t ) × t + β(23)From equation (21), (22), (23) and Figure 4.22, Figure 4.23, the relationship between pore volume of 150 –
15000 nm in pore diameter can be expressed by equation (35):

PVdc = 0.0003 × √∑(θd,t − 17) × (Ht − φd,t ) × t + β(24)

The modified maturity function that expressing the relationship between pore volume of 150-15000nm indiameter and the environmental conditions in which affect carbonation, is:65Mphc = ∑(θd,t − 17) × (Ht − φd,t ) × t(25)W
Ht = 0.7 × ( ) + 0.615
C

(26)

W
β = 0.0145 × ( ) − 0.0048
C(27)

Where:The datum humidity Ht is:

And the initial value is:

W/C is water-cement ratio. Therefore, in general, the pore structrure change regarding carbonation can be
expressed by equation (33):

PVdc = 0.0003 × √Mphc + β
Where, Mphc is the modified maturity of 150-15000 nm pore size regarding carbonation.

66

(28)

Figure 4.22

Relationship between different reference relative humidities Ht for each water cement
ratio

Figure 4.23

Relationship between different initial value for each water cement ratio

67

4.5.

Service life prediction equation regarding carbonation due to pore structure change

The pore structure change can be predicted regarding temperature and relative humidity is give by equation(28).

In terms of carbonation exposure, a non-linear differential equation is developed by Papadakis et al.
(Papadakis, Fardis, and Vayenas 1992), (Demis, Efstathiou, and Papadakis 2014). This equation permits thecalculation of the carbonation depth according to the following equation (29):𝐶𝑂2√ 2𝐷𝑒,𝐶𝑂2 (100) 𝑡
X𝑐 =0.33𝐶𝐻 + 0.214𝐶𝑆𝐻(29)

where CO2 is the CO2-content in the ambient air at the cement-based materials surface (%), CH and CSH
are the contents of calcium hydroxide and calcium–silicate–hydrate in cement-based materials volume(kg/m3), the effective diffusivity of CO2 in carbonated part (m2/s), is calculated as:

𝐷𝑒,𝐶𝑂2 = (1.64 × 10

−6 )

×

(𝑃𝑉)1.8

𝑅𝐻 2.2× [1 − (
)]
100

(30)

where RH is an ambient relative humidity, RH (%), and PV is the pore volume of cement-based materials
is calculated from equation (28)

In addition, Henriksen, (Henriksen 1993), presents a service life model due to the deterioration ofcarbonation as shown in equation (34):

√𝑇𝑎
T=(
× 𝐶)
𝑋𝑐

2

(31)

Where, T is service life (years); Ta is age at time of inspection (years); Xc is measured carbonation depth attime of inspection (mm) and C is cover (mm).

Therefore, by combining equation (28), (29) and (31), the service life prediction equation regarding
carbonation due to pore structure change can be obtained.
68

4.6.

Conclusions

As a result, the reference humidity and the reference relative humidity were reset and an empirical formula
was obtained. The reference temperature at which the pore structure change occurs is 17 °C regardless of
the water cement ratio. In addition, it was revealed that the pore volume increases as the humidity decreases
and the pore volume increases as the water cement ratio increases. The pore structure changes strongly at
60%RH and 75%RH. A pore volume of 150 to 15000 nm in diameter and a time-product of temperatureand humidity were in good relation.

69

CHAPTER 5SERVICE LIFE PREDICTION BASED ON PORE STRUCTURE
CHANGE70

CHAPTER 5 SERVICE LIFE PREDICTION BASED ON PORE STRUCTURE
CHANGE
5.1.

Introduction

Frost damage of cement-based materials is an important issue for cement-based materials structures in cold
climates, up to now, some frost damage deterioration prediction methods have been proposed. Among them,
the number of cycles Equivalent to ASTM is treated as an index considering a relatively large number ofparameters such as weather conditions and curing conditions. It is well known that the frost damage
resistance of cement-based materials depends on the pore structure, and the amount of pores with a diameterof 40 to 2000 nm has a large influence on frost damage resistance.

On the other hand, as also in Chapter 2 and Chapter 3, it is known that the amount of pores with a diameterof 40-2000 nm coarsens the amount of pores under high-temperature drying conditions. Here, if the frost
damage resistance is reduced by coarsening the pores under high temperature drying conditions, there is arisk that frost damage will occur not only in cold area, which is a representative of cold districts, but also in
all areas. For example, in regions where dry conditions tend to be high in summer, the amount of pores withdiameters of 40 to 2000 nm increases in the summer and the risk of frost damage may be higher than in cold
region such as Hokkaido in Japan due to freezing and thawing in winter.

Many different mathematical methods for service life prediction have been presented. The mathematicalmodel expressed in this study is based on pore structure change, combined with previous laboratory tests
and empirical results from existing exposure mortar samples. The model can be used to predict service life
in practical situations. In the previous study, the volume of 40-2000 nm diameter pores changes dependingon the temperature and the period, and proposes using the maturity temperature-time factor to predict
performance. However, it is an empirical formula that does not take into consideration the influence ofrelative humidity on the maturity temperature-time factor representing 40-2000 nm diameter pore volume.
In addition, the change in the volume of 40-2000 nm diameter pores differs for each water-cement ratio.
Methods for predicting frost damage and change in pore structure have been proposed, but no predictive
71

method that combines the prediction of frost damage deterioration and that of pore structure change in a realenvironment currently exists.

In this chapter, a method that adds the potential change of frost damage of cement-based materials by
maturity function proposed in Chapter 3, in order to predict frost damage deterioration, to the risk of frost
damage by the region in winter by ASTM Equivalent cycle number. In addition, The ASTM Equivalent
cycle number is the index proposed in 1999 that calculation based on Japan climate in 1982. This study will
reexamine it using the daily average year value of the Meteorological Agency of 1981 to 2010 with thestandard year extended AMeDAS weather data from 2000 to 2010.

Furthermore, the purpose of this research is to propose an environmental indicator method, which predicts
the change in durability factor based on conventional frost damage deterioration, and pore structure change
in the summer; this allows calculation of the service lifetime of cement-based materials. In conjunction withthe proposal of environmental indicator method, an experiment that includes the relative humidity factor in
the prediction of pore structure change using conventional maturity methods was conducted, and that
proposes use of the modified maturity function. A theory is presented for the estimation of the service lifeof mortar exposed to frost action.

5.2.

Materials and method

The physical properties and mineral compositions are given in Table 2.1. The mineral composition of the
OPC was quantified by the X-ray diffraction (XRD) Rietveld method. The main mix was water-cement ratio(W/C) of 0.45 and the sand-to-cement ratio (S/C) of 2:1 without any chemical admixture.

72

Table 5.1

5.3.

Watercement ratio(W/C)

Sandcement ratio
(S/C)

0.45

2.0

Mix proportions
Material contents (kg/m3)
Water

Cement

Sand

Flow
(cm)

297

660

1320

23

Frost damage deterioration prediction based on ASTM Equivalent cycles number

ASTM Equivalent cycle number (Y.Hama et al. 1993) is a method to estimate the effect of freezing
temperatures on the extent of frost damage, and the effective number of freeze/thaw cycles corrected to
ASTM Equivalent cycles, was proposed as shown in Equation (32) and Table 5.2.

CyASTM−sp = C. F. s. p. Ra90

(32)

Where, CyASTM-sp is the number of ASTM Equivalent cycles (cycle/year); C is the coefficient of the curingcondition; F is the coefficient of the freeze-thaw condition; s is the coefficient of the sunlight condition; pis the coefficient of the degradation process; Ra90 is the effective number of ASTM Equivalent cycles by air
temperature (cycles/year).

The number of cycles corresponding to ASTM Ra90 by air temperature is calculated using the region
coefficient, T (Equation (33) and (34)). Furthermore, it is shown in Equation (35) that there is a relationshipbetween the Equivalent ASTM cycles of Ra60 and Ra90.

T = −t a min (1 −

Df
)
Dw

ta β
Ra90 = ∑ (− ) = 4.2T − 5.4
18
Ra60 = 1.64Ra90

(33)
(34)
(35)

Where, tamin is the annual minimum freezing temperature (°C); Df is the freeze duration in days; Dw is thetotal number of freezing and thawing days; ta is the freezing temperature (°C); and β is a constant.

73

Regional coefficient T used for ASTM Equivalent cycle number was calculated from the Japanese climate
data in 1982. Therefore, this study will reconsider using the daily average value of Japan Meteorological
Agency in 1981 to 2010.

In calculating ASTM Equivalent cycle number CyASTM-sp shown in Equation (32), it is necessary to
determine C, F, s, P, Ra90. Ra90 can be expressed by the region coefficient T and can be obtained by knowing
the annual extreme of day minimum temperature, freezing duration (number of days), freezing and thawing(total days).

Figure 5.1

Examination of meteorological statistical data

The annual extreme value tamin of the day minimum temperature was set to the lowest value in every hourof the year. In addition, the freezing temperature of concrete is generally slightly lower than 0 °C, as thelowest temperature ranges from -0.1 °C to -0.9 °C, the effect on frost damage is small. So, the minimum
day temperature is -1.0 or less and the maximum day temperature is equal to or higher than 0 °C is definedas one freeze-thaw cycle; and the freeze duration Df, the freezing and thawing total number of days Dw were
calculated.

The ASTM Equivalent cycle number uses the relative dynamic elastic modulus as an index showing theprocess of deterioration of concrete in the freeze-thaw test. The process of frost damage deterioration is74

thought separately into two stages, the process in which signs of deterioration appear at a relative dynamic
elastic modulus of 90% and the process in which the deterioration after that appears clearly.

As a result of examining correspondence between deterioration prediction using ASTM Equivalent cycle
number and deterioration of actual structure, it became clear that the temperature and humidity in concrete
varies depending on environmental conditions such as snow cover and site. Regarding the humidity, thehorizontal member was higher in humidity than the vertical member, and it was found that the humidity inthe concrete correlated with the deepest snow; although, there was variation. In addition, due to differences
in moisture supply conditions, there is a difference in damage amount due to freezing and thawing between
indoor acceleration test and actual structure.

By studying the correspondence between the prediction of degradation using ASTM Equivalent cycles, andthe deterioration of an actual structure, with differences in the level of moisture supply, the indoor
acceleration test and actual structure show different extents of damage due to freeze-thaw cycles. It was
found that the deterioration speed in the ASTM Equivalent cycle is faster than the actual degradation speed.

Table 5.2

Coefficient of ASTM Equivalent cycle formula
Process of frost damage
SignalClear 90%≥Ed>60%100%≥Ed>90%
1.00
1.64
1.00
1.00
1.45
1.45
1.00
1.00
0.66
1.41
0.26
0.80
0.14
0.45
1.00
1.00
0.21
0.23

ASTM Equivalent cycle CyASTM=C.F.s.p.Ra90
Degradation coefficient, pConditions
Coefficient

Solar radiation, sCuring and Drying, C
C
Freeze-thaw, F

North face
South face
In waterIn airDrying at 200C
Drying at 300C
In waterIn airFurthermore, if the accelerated test result of the targeted cement-based material is known, it is possible topredict deterioration and estimate the service lifetime using Equation (36) with ASTM Equivalent cycles
and considering the effect of weather conditions using the coefficients in Table 5.2.

X Ed =

NEd
CyASTM−sp
75(36)

Where, XEd and NEd are the number of years or cycles, respectively, that pass before the relative dynamic
modulus of elasticity decreases to 90 or 60% of its initial value in an accelerated test; and X90 and X60 are
the number of years in which the relative dynamic modulus of elasticity is 90% or between 90 and 60%,
respectively, of its initial value in a natural environment.

Further, if CyASTM-sp which is annual number of freezing-thawing cycles and the number of cycles at which
the relative dynamic modulus in the freezing-thawing test of the target cement-based materials become 90%
and 60% are known, the service life for frost damage deterioration can be calculated. Therefore, service life
for frost damage deterioration in this study has been defined as the number of years until the relative dynamic
modulus falls below 60%. Although it is possible to estimate the service life depending on the number ofcycles Equivalent to ASTM, it is considered that cement-based materials does not change the frost hazard
as potential, so consideration should be given to the frost resistance accompanying the change in pore
structure due to drying is an issue.

5.4.

Prediction method of service life of mortar by environmental indicator process

5.4.1 Proposal of environmental indicator for frost damage of mortar considering theeffect of drying
One of degradation phenomena of cement-based materials in cold areas is frost damage due to freeze-thaw
action. In order to extend the life of cement-based materials structures, it is necessary to properly predict
deterioration due to frost damage. Regarding the influence of external factors on the frost damage
deterioration of cement-based materials, Hasegawa et al. calculated the frost damage risks in various partsof the country from the weather conditions such as temperature, solar radiation, precipitation, and snow
melting amount, and the regional difference of the occurrence probability of freezing damage. It is done byclassification of frost damage risk map. Hama et al. have proposed a method to estimate frost damage ofactual structures, proposing "ASTM Equivalent cycle number" representing the freeze-thaw action of thecement-based materials structure under regional coefficient and real environment as an index showing theseverity of freezing and thawing action in the cold region, (Y.Hama et al. 1993).
76

Figure 5.2

Overall flowchart of calculation process

On the other hand, relating to the pore structure that affects the frost resistance, Kamata et al. analyzed theresults of the freeze-thaw test and the measurement of the pore structure of hardened cement paste and foundthat the good correlation between the pore volume of 40-2000 nm in diameter and the frost resistance. Aonoet al. found that the structure of C - S - H of the paste with low water cement ratio changed due to the effectof drying, it is revealed that the pores become coarse so that the amount of pores having a diameter from 40
to 2000 nm increases and the frost resistance decreases. In addition, Nakamura et al. proposed a temperaturetime product representing the change in the pore volume of 40 to 2000 nm in diameter due to the drying
temperature and period. Conventional frost damage deterioration prediction method has been shown that
cement-based materials has no change in potential frost damage, but it seems to be necessary to consider
deterioration of frost process relating to pore structure change due to drying. Therefore, in this research,
proposing environmental indicator method, which is a frost damage environment index which can take into
consideration changes in freezing hazard due to drying; also is a frost damage prediction method considering
the influence of pore structure change by drying and aim to calculate the service life of each region.

77

Figure 5.3

Process flowchart

In this study, the environmental indicator method, which is a frost damage deterioration prediction method
considering the influence of pore structure change due to summer high temperature drying condition on
frost resistance and ASTM Equivalent cycle number as an index of prediction of frost damage of cementbased materials was proposed. Calculation of the service life of cement-based materials by environmental
indicator method revealed that the number of years is shorter than the service life calculated by ASTM
Equivalent cycle number, even in areas where the influence of winter seasons was small and the risk of frost
damage deterioration was underestimated. It was confirmed that there is the risk of frost damage
deterioration by considering the influence of pore structure change during the summer season.

In order to predict frost damage deterioration, this study proposes a method which adds the potential changeof frost damage of cement-based materials by the maturity formula proposed in Chapter 3 to the risk of frost
damage by the winter region according to ASTM Equivalent cycle number. In order to calculate regionality
by environmental indicator method, need to consider fixed water cement ratio. In the experiment conducted
in Chapter 2, water cement ratio is 0.35, 0.45, 0.55, but in calculation of Chapter 5 water cement ratio of0.45 is used.

As described in Equation (16), it is considered that the service life of concrete structures can be estimatedby using the number of cycles equivalent to ASTM if the antifreeze property of cement-based materials isknown. On the other hand, the durability index is generally calculated by the Equation (17). Next, in
Equation (16), if the initial durability DFi is known, the durability index when the pore structure is changed78

by drying can be expressed as DFd by the Equation (16). In addition, when the temperature-humidity time
product exceeds the upper limit, it is calculated using the upper limit value.

Therefore, even if do not know the frost harmfulness of concrete, it still can calculate the service life if N is
known. Examination is made using Equations (16) and (17). The durability index DFd changed by the pore
structure change differs in the calculation formula between both case of when the relative dynamic elastic
modulus is greater than or equal to 60 at 300 cycles and when the relative dynamic elastic modulus is lessthan 60. In addition, in ASTM Equivalent cycle number, it is considered that the slope is different in theprocess of signs of deterioration with a relative dynamic elastic modulus of 90% or more, and clear
deterioration of 90% to 60% is observed. However, general concrete structures are unlikely to have small
initial durability index. Therefore, in this research, consider the gradient of degradation as constant.

As forecast of frost damage deterioration taking into consideration change of pore structure in summer,
prediction of change of potential against frost damage by cement-based materials by temperature / humidity
time product. In addition to forecasting method of frost damage by region in winter by ASTM Equivalent
cycle number, it is possible to calculate the service life. In the actual environment, under freezing andthawing calculated from the ASTM Equivalent cycle number in winter as it in summer, the durability index
decreases due to the pore structure change, so the relative dynamic modulus of cement-based materials can
not be represented by a simple straight line. Therefore, from the ratio of the durability index, the decreasein the durability index for each year is calculated. Because the temperature and humidity time productincreases every year, the evaluation of the durability index changes year by year as the 1st year, 2nd year,
nth year and years increase. Therefore, as shown in Figure 5.4, a process which changes with aging is
calculated as a ratio k to the previous year. Since the initial durability index is maintained, the axis deviates
as it is reevaluated the following year. Therefore, considering the ratio k for each year, it is possible topredict the current future as shown by the broken line in Figure 5.4. The ratio k (n) to the previous year in
the nth year is expressed by the Equation (37), and the durability index in the year is represented by the
Equation (38) by using k (n).
79

𝑘𝑛 =

𝐷𝐹𝑑(𝑛) ⁄𝐷𝐹𝑖
𝐷𝐹𝑑(𝑛−1) ⁄𝐷𝐹𝑖

(37)

𝑛

𝐷𝐹𝑑(𝑛) = 𝐷𝐹𝑖 ∙ ∏

𝑗=1

𝑘(𝑗)

(38)

Where, kn represents the ratio of the durability index to the previous year at the nth year, and DFd(n) represents
the durability index of the nth year.

Next, the reduction amount of the relative dynamic elastic modulus for each cycle is calculated. With relate
to the durability index DF, since the calculation method is different when DF ≧ 60 and DF <60, thereduction amounts are respectively calculated by Equations (39) and (40) separately for the case.
100 − 𝐷𝐹𝑑(𝑛−1)(𝐷𝐹 ≥ 60)300
100 − 60
∆𝐸(𝑛) =(𝐷𝐹 < 60)𝑁

∆𝐸(𝑛) =

(39)
(40)

Where, ΔE (n) represents the decrease amount of 1 cycle relative dynamic elastic modulus in the nth year.

Figure 5.4

Conceptual diagram of relationship between durability index and elapsed years

As shown in Figure 5.5, ΔE (n) represents the slope of the relative dynamic elastic modulus with respect
to the number of cycles, and the way is different when DF ≧ 60 and DF <60. Moreover, considering theprocess of actual frost damage deterioration, it seems that the relative dynamic modulus coefficient does notdecrease with a certain value as shown in Figure 5.5. In this study, however, cement-based materials is
supposed to deteriorate constantly every cycle in order to simplify calculation.
80

Equations (40) can be rewritten to Equation (42) by substituting Equation (17) into Equation (41) andsubstituting into Equations (40).
𝑀 ∙ 𝐷𝐹(𝑛−1)𝑁=𝑃
100 − 60
8∆𝐸(𝑛) ==
𝑀 ∙ 𝐷𝐹(𝑛−1)𝐷𝐹(𝑛−1)𝑃

Figure 5.5

(41)
(42)

Relative dynamic modulus of elasticity decreasing per cycle

Using the calculated amount of decrease in relative dynamic elastic modulus per cycle and the number ofcycles Equivalent to ASTM, the amount of decrease in the relative dynamic elastic modulus at each year is
calculated. The relative dynamic elastic modulus is calculated in each year from the decrease amount of therelative dynamic elastic modulus by the Equation (43). By integrating the relative dynamic elastic modulus
which decreases every year in real environments, it is possible to express the relationship between elapsed
years and relative dynamic elastic modulus. The service life is the number of years until the relative dynamic
elastic modulus falls below 60%. If the relative dynamic elastic modulus falls below 60% in a certain
number of years, the number of years before that year is the service life.
𝑛

𝑅𝐷𝑀(𝑛) = 100 − ∑𝑗=1

𝐶𝑦𝐴𝑆𝑇𝑀−𝑠𝑝 ∙ ∆𝐸(𝑗)where, RDM (n) represents the relative dynamic elastic modulus at the nth year.

81

(43)

5.4.2 Service life of each region
Regarding the weather data used for the calculation, the number of cycles Equivalent to ASTM proposed in
the past research is the Japan climate data in 1982). In this study, the temperature-humidity time productusing the Japan Meteorological Agency's day-to-day flat average value from 1981 to 2010 for ASTM
Equivalent cycle number, calculated from the standard year extended AMeDAS weather data from 2000 to2010. Figure 5.6 shows the relationship between the relative dynamic modulus of elasticity and the elapsed
years in each temperature / humidity time product, ASTM Equivalent cycle number.

Figure 5.6

Relationship between relative dynamic modulus of elasticity and elapsed time

If the number of years in which the relative dynamic elastic modulus is 60% is taken as the service life,in the case of the same weather condition in winter, the service life is shorter as the influence of summer
becomes larger. In the case where the influence of summer is the same, it can be confirmed that the severe
weather condition in winter becomes tolerable and the number of years becomes shorter. Therefore, it ispossible to calculate the service life by using the environmental indicator method (FD-CI).

ASTM Equivalent cycle number, the value obtained by substituting each coefficient necessary for eacharea used for temperature and humidity time product, and the relative dynamic elastic modulus
respectively calculated from the calculation method using environmental indicator method. The service
life up to 60% is shown in Table 5.3. Regarding the number of cycles equivalent to ASTM, the solar82radiation condition s is the north surface, the curing / drying condition C is 20 ° C, drying, the freezing
and melting condition F is the melting in air frozen water.

The service life was calculated as cement-based materials in which the number of cycles at which therelative dynamic elastic modulus in the accelerated test was 90% was 300 cycles and the number of cycles
at which the relative dynamic modulus coefficient became 60% was 600 cycles.

Figure 5.7

Relationship between relative dynamic modulus and elapsed time in Muroran city andYamagata city

For the temperature-humidity time product, the service life was calculated with the water binder ratio 45%
and the initial durability index 90. Compared with the service life calculated from the conventional numberof cycles Equivalent to ASTM, the service life calculated using environmental indicator method proposedin this research is found to be shorter. This is thought to be due to a decrease in durability index due to pore
structure change during the summer season.

Here, as an example, comparing the two areas of Muroran City in Hokkaido and Yamagata City in Honshu,
the ASTM Equivalent cycle number shows almost the same value in both areas, but the temperature /humidity time product of Yamagata city is higher than Muroran city. As shown in Figure 5.7, by the
relationship between relative elastic modulus and elapsed years, the service life of Yamagata city is shorter
than that of Muroran City. Since Yamagata city, which has a large temperature-humidity time product,83

shows a small value of service life, it can be seen that even if the same ASTM Equivalent cycle number istaken into consideration, the service life is shortened.

Also, the service life of each place calculated using environmental index is mapped. Figure 5.8 shows a map
calculated from the number of cycles Equivalent to ASTM and by environmental indicator method.

Although the service life is 100 years or more regardless of Hokkaido and Honshu at ASTM Equivalent
cycle number, it can be seen that the service life is shortened in most areas by environmental indicatormethod. Although the risk of frost damage deterioration has been evaluated solely by the influence of winter,from the environmental indicator method, considering the influence of the summer seems to be necessary
for anti - freezing measures even in temperate areas.

84

Table 5.3

Service life of each region

Number of cycles Equivalent
to ASTM (times / year)
CyASTM-90
CyASTM-60

Hokkaido

Modified
Number of cycles
According tomaturity
Equivalent to ASTM
FD-CI
RegionMphService life
Service life (years)※1(° D · day)(years)※2
Wakkanai
0.3
1.4
14.2
510
62
Kitami
0.6
3.2
37.7
222
27
Asahikawa
1.1
6.2
81.9
115
13
Abashiri
0.8
4.2
35.3
171
22
Sapporo
0.9
4.8
76.2
147
17
Obihiro
1.7
9.3
62.8
76
11
Nemuro
0.7
3.8
6.9
186
43
Suttsu
0.5
3.0
34.6
238
29
Muroran
0.6
3.3
10.3
216
38
Urakawa
1.2
6.9
5.3
104
35
Hakodate
1.3
7.0
57.7
102
13
Aomori
0.7
4.1
71.0
175
19
Hachinohe
0.8
4.5
50.1
160
20
Akita
0.4
2.0
100.7
349
36
Morioka
1.1
6.2
85.4
114
13
Miyako
0.7
4.1
46.8
175
21
Sendai
0.2
1.2
85.6
616
62
Yamagata
0.6
3.3
131.6
215
23
Fukushima
0.2
1.2
155.8
616
61
Tochigi
1.3
7.0
25.4
102
17
Utsunomiya
0.4
2.2
133.5
328
34
Karuizawa
1.9
10.5
22.4
67
14
Matsumoto
1.1
5.8
154.0
122
14
Kofu
0.3
1.7
218.7
428
43
Takayama
1.1
6.0
119.1
119
13
Okayama
0.2
1.2
158.5
616
61
Asozan
0.9
5.1
14.0
140
26
Yufuin
0.4
2.0
107.3
349
36
※1 The solar radiation condition is calculated as the service life as cement-based materials with North face,

Honshudrying at 20 ° C, melting in air in frozen water, the number of cycles at which the RDM becomes 90% is
300 cycles, and the number of cycles at which the RDM becomes 60% is 600 cycles.
※2 Service life is calculated as cement-based materials with water cement ratio of 45% and initial durability
index of 90.

85

Figure 5.8

Estimation equation of carbonation speed due to maturity of of 150-15000 nm pores
diameter

W/C=0.45
Pore volume of 150–15000 nm pore
diameters （cc/g）

5.5.

Map of service life calculated by ASTM Equivalent cycle number and by FD-CI

0.04

0.03
y = 0.0013x + 0.0035
R² = 0.9685

0.02

0.01

0
0

5

10

15

20

Time (week)

Figure 5.9

Pore volume change due to time

86

25

30

Figure 5.9 shows the relationship between pore volume of 150-15000 nm pore diameters and curing time.
The pore volume increases with time duration. Figure 5.10 shows the relationship between pore volume of150-15000nm diameters and carbonation speed. From Figure 5.10, the formula for estimating thecarbonation speed due to pore structure change is obtained:

Ne𝑑𝑐 = 41.064𝑃𝑉𝑑𝑐 + 1.9799(44)

Combining equation (43) and equation (28) in Chapter 4, the estimation value of carbonation speed can beobtained as in Table 5.4.

Carboantion speed, mm/sqrt(week)32

y = 41.064x + 1.9799
R² = 0.925

1

0
0

0.005

0.01

0.015

0.02

Pore volume of 150-15000nm diameters, cc/g

Figure 5.10

Relationship between pore volume of 150-15000nm diameters and carbonation speed

87

Table 5.4

RegionHokkaido
HonshuWakkanai
Kitami
Asahikawa
Abashiri
SapporoObihiroNemuroSuttsuMuroranUrakawa
Hakodate
Aomori
Hachinohe
Akita
Morioka
MiyakoSendai
Yamagata
Fukushima
Tochigi
Utsunomiya
Karuizawa
Matsumoto
Kofu
Takayama
OkayamaCarbonation speed coefficients
Sqrt ofMph(° D · day)
3.77
6.14
9.05
5.94
8.73
7.92
2.63
5.88
3.21
2.31
7.60
8.42
7.08
10.03
9.24
6.84
9.25
11.47
12.48
5.04
11.55
4.73
12.41
14.79
10.91
12.59

88

Estimation
carbonation
speed
mm/sqrt(week)
2.08
2.12
2.19
2.11
2.18
2.16
2.06
2.11
2.07
2.06
2.15
2.18
2.14
2.23
2.20
2.13
2.20
2.28
2.32
2.10
2.29
2.09
2.32
2.44
2.26
2.33

5.6.

Conclusions

In this study, the environmental indicator method has been used to as a forecasting method of frost damage
degradation taking into consideration the influence of changes in pore structure during the summer on frost
damage resistance and calculated the service life of cement-based materials for each region. Whencalculating the service life using environmental indicator method, the number of years is shorter than theservice life calculated by ASTM Equivalent cycle number. It was found that there is a danger of frost damage
deterioration and that it is necessary to take measures against freezing damage even in areas where theinfluence of winter season is small and the risk of frost damage deterioration was underestimated. In addition,
the carbonation speed can be estimated due to pore structure change from the relationship between the porevolume of 150-15000 nm pore diameters and carbonation speed.

89CHAPTER 6
CONCLUSIONS AND FUTURE WORK

90

CHAPTER 6 CONCLUSIONS AND FUTURE WORK
6.1.

Introduction

In this study, by analyzing the influence of environmental conditions on the change of pore structure,quantifying the relationship of frost damage from pore structure change, conducting laboratory experimentand exposure to real environment, the environmental indicator method for forecasting frost damage
deterioration calculated by ASTM Equivalent cycle number including winter environment and dry conditionin summer is proposed.

6.2.

Pore structure change due to temperature and humidity (Chapter 2)

In this chapter, in order to clarify the influence of curing conditions (temperature, curing period, moisture,
water cement ratio) on pore structure change, coarsening by drying and densification by hydration reaction,
the relations with the pore structure change of dry and wet repetition assuming an actual environment werearranged.

Under the condition where the relative humidity is low, the peak of pore size distribution shifts to larger
diameter as the curing period progresses. It was confirmed that as the drying temperature was higher, theamount of pores with diameters of 40-2000 nm increased. Regardless of the water cement ratio, the tendencyof the pore structure to coarsen with the age in all curing conditions except 20 ℃ 100% RH and 50 ℃ 100%
RH was confirmed. Also, in underwater curing, since the amount of pores is small, it is considered to bedensified.

Regardless of drying temperature and water cement ratio, the lower the relative humidity and the more thetendency of increasing the pore volume of the diameter of 40-2000 nm with the material age was confirmed.
However, no increase in pore volume was observed at 20 °C. 75% RH, 20 °C. 100% RH, 50 °C. 100%RH.
It was confirmed that as the water cement ratio was higher, the amount of pores with diameters of 40 to2000 nm increased. Regardless of the water cement ratio, it was revealed that the upper limit of the diameterof 40 - 2000 nm pores reached the upper limit at 8 weeks of 35 ℃ 13%RH, and the upper limit value for91each water cement ratio is different. No increase in pore size of 40-2000 nm in diameter was observed inwater curing, so it is considered that there is a maximum relative humidity at which pore structure change
occurs.

6.3.

The relationship between modified maturity and frost resistance (Chapter 3)

Chapter 3 formulates the pore structure change for each using curing conditions (temperature, curing period,
water cement ratio) as elements, formulation of change in freezing harmfulness from the pore structurechange which is the object of this research was carried out. Furthermore, using the proposed prediction
formula, laboratory experiments and application of real environments were verified.

It was considered that there was a maximum humidity at which pore structure change occurred since no
increase in pore size of 40-2000 nm in diameter was observed at relative humidity of 100% RH (underwater
curing), regardless of the drying temperature. A prediction formula of pore structure change considering
curing conditions (drying temperature, drying period, relative humidity, water cement ratio) proposed withthe high correlation result was obtained.

The reference temperature at which the pore structure change occurs is a constant value regardless of thewater cement ratio. However, at the reference humidity where the pore structure change occurs, results
showing different values depending on the water cement ratio were obtained.

Based on experimental results with widely varying water cement ratio and temperature and humidity
conditions, with the aim of expanding the application range of maturity function, which represents the pore
structure change of mortar by drying, based on the equation of temperature and humidity time product.

Experimental results of increasing the humidity condition of this study revealed that it is not possible torepresent the change in the pore volume of diameter from 40 to 2000 nm even with the temperature timefunction equation. Therefore the temperature humidity time product by multiplying the temperature time
product by the element of the reference relative humidity was proposed. As a result, the datum temperature92

and the datum relative humidity were reset and an empirical formula was obtained. The datum temperature
at which the pore structure change occurs is 16 ° C regardless of the water cement ratio. In addition, it was
revealed that the pore volume increases as the humidity decreases and the pore volume increases as thewater cement ratio increases. A pore volume of 40 to 2000 nm in diameter and a time product of temperatureand humidity were in good relation.

By using the equation expressing the temperature-humidity time product, it is possible to predict the amountof pores with a diameter of 40-2000 nm corresponding to the temperature, humidity and the water cement
ratio. The datum humidity and the upper limit value were in a linear relationship with the water cement ratio,
and could be expressed by a linear equation. Due to the pore structure change due to high-temperature drying
in the summer, it was confirmed that the decrease in the durability index becomes larger as the annual
temperature humidity time product is larger.

6.4.

Effect of pore structure change on carbonation (Chapter 4)

In this chapter, in order to clarify the effect of curing conditions on pore structure change, the pore size
range in which affect carbonation is investigated. It was confirmed that as the drying temperature was higher,
the amount of pores with diameters of 150-15000 nm increased. Regardless of the water cement ratio, thetendency of the pore structure to coarsen with the age in all curing conditions.

No increase in pore volume was observed at 20 °C. 100% RH and 50 °C. 100%RH. It was confirmed thatas the water cement ratio was higher, the amount of pores with diameters of 150-15000 nm increased.

It was considered that there was a maximum humidity at which pore structure change occurred since no
increase in pore size of 150-15000 nm in diameter was observed at relative humidity of 100% RH(underwater curing), regardless of the drying temperature. A prediction formula of pore structure change
considering curing conditions proposed with the high correlation result was obtained.

93

6.5.

Service life prediction based on pore structure change (Chapter 5)

In this chapter, in predicting frost damage deterioration, the ASTM Equivalent cycle number representing
the regional frost damage deterioration is used as meteorological conditions for frost damage deteriorationof cement-based materials. In this study, the service life of cement-based materials is calculated for eachregion as forecasting method of frost damage by taking into consideration the effect of summer pore
structure change on frost damage resistance; in addition to prediction of frost damage by conventional cycle
number corresponding to ASTM using the proposal of environmental indicator method.

In the cycle Equivalent to ASTM, the Japanese climate data which was used in the previous research waschanged and re-examination was carried out using the average month value of the Japan Meteorological
Agency from 1981 to 2010. Regarding the pore structure change, the regional nature was examined by using
the time product of temperature and humidity (the modified maturity function). In addition, a meteorologicalindicator to show the length of service life was proposed.

The relation between the annual extreme lowest temperature of the day in each region and the region
coefficient shows a very good correlation in various parts of Honshu without the freezing duration, but thecorrespondence between them was bad. From these, it was confirmed that the regionality of the severity of
the freezing and thawing action can be easily represented by the annual extreme of the daily lowest
temperature.

In Hokkaido, Honshu, the higher the daily maximum temperature, the higher the temperature and humidity
time product tended to be. In Hokkaido in particular, the relationship was a good result. From this, it isconsidered that the temperature in winter season in Hokkaido is low and outside the datum temperature andhumidity of time humidity time product, the temperature in the summer seems to have influenced as it is.

It was confirmed that the decrease of the durability index was larger as the annual temperature and humidity
time product was larger as the pore structure change due to high temperature drying in summer.

94

The service life using environmental indicator method for frost damage deterioration taking into
consideration the influence of changes in pore structure during the summer on frost damage resistance wascalculated. As a result, when comparing the conventional ASTM Equivalent cycle number and theenvironmental indicator method to service life, even in the area where influence of winter season has beensmall and the risk of frost damage deterioration was underestimated in the past, the service life becomesshorter considering the influence of summer has been found.

6.6.

Future work

In this study, the environmental indicator method as a forecasting method of frost damage degradation was
proposed and the service life of cement-based materials for each region was calculated. When calculating
the service life using environmental indicator method, it was found that the number of years is shorter than
the service life calculated by ASTM Equivalent cycle number. It is confirmed that there is a danger of frost
damage deterioration and that it is necessary to take measures against frost damage even in areas where theinfluence of winter season is small and the risk of frost damage deterioration was underestimated.

The service life according to the number of cycles Equivalent to ASTM is more than 100 years in all areas,
but considering drying by environmental indicator method, it will be less than 30 years in most areas. For
this reason, it is important to consider the effect of drying in summer. Prediction formula of change infreezing resistance is influenced by humidity and difference of each freeze-thaw test method in laboratory
experiment, micro cracks caused by drying shrinkage and frost damage deterioration in the actual
environment may affect the change in frost resistance. Furthermore, it is necessary to consider the influenceof the air amount on the change in frost resistance.

Since the number of cycles equivalent to ASTM and the calculation conditions of environmental indicatormethod are strict conditions as compared with actual conditions, it is necessary to study the correction
method in the future.

95

Service life of cement-based materials is typically based on deterioration. In reality, existing cement-basedmaterials are subjected to numerous of deterioration in their environments. Therefore, laboratory
simulations and deterioration predictions should take into account these multiple deterioration mechanisms,
when modelling service life, such as combining of both frost damage and carbonation.

96

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ACKNOWLEDGMENTS
It seems like just yesterday that I came to Muroran Institute of Technology when Sakura was blooming. I
would like to call some people by name, without whose contributions, help and support I could not havefinalised the research presented in this thesis. It is to them that I owe my deepest gratitude.

All of the experimental work was completed in the laboratory of the construction and building materials
within the Department of Architecture, Civil and Environmental Engineering at Muroran Institute ofTechnology. I am gratefully acknowledged Muroran Institute of Technology for the financial support andthe opportunity offered to me for pursuing a PhD degree.

The first person I am indebted massive thanks is Professor Hama. I would like to give my sincerest
acknowledgement to him for his excellent guidance, patience, and providing me with an excellent
atmosphere for doing research. He taught me to be patient, be logic, and pay more attention to the details
during the research. His tireless efforts and constructive comments on this thesis are highly appreciated. In
these three years, his suggestions, patience and encouragement supported me to pursue a doctorate. My
thesis will not be finished without his sparkling ideas, mental support, fruitful discussions and patiently
correction.

I also wished to express my appreciation to the vice supervisors, Prof. Mizoguchi and Prof. Sugata, whoprovided me their time, important opinions and valuable feedback for the revision of my doctoral thesis andthe doctoral thesis defense presentation.

For the critical discussion on building materials topics, I would like to express my deep gratitude to Assist.
Prof. Choi and Assoc. Prof. Kishimoto for the useful discussions, suggestions, guidance, support, andencouragement we had during seminar presentation in our laboratory. I am thankful to the post-doctor Kim
from Korea for his suggestions and friendship.

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I would also like to express a word of thankfulness to all Hama’s laboratory members, Dr. Zhang,
Dr.Hasegawa, Mr. Akio, Ms. Midori, Mr. Van, Mr. Yamagishi, Mr. Gota, Mr. Miwa, Mr. Shimakage, Mr.
Kawamura, Mr. Matsumoto, Mr. Noguchi, Mr. Satou, Mr. Tamura, Ms. Kanako, my dear Vietnamese
friends, especially to Otokoyama-Team (Mr. Ha) and all international friends, Dr. Reddy, Dr Madhu, Mrs.
Shun, Dr. Owolabi, Ms. Wiwi, Dr. Guochin, Mr. Ding, Mr. Sha, Dr. Mona, Dr. Boom, Mr. Odd, Mr. Andrey,
Mr. Rikky for their friendship, kindness, timely help and encouragement, especially to Miss Midori, mytutor and also my best friend; she helps every time I needed! Their friendship made my journey to finishing
my study easier and my daily life rich and colorful. My warm thanks to PoreTeam members, Mr. Akio and
Mr. Matsumoto for their help, technical and funny discussions, amusing talks, encouragement, and strong
support.

I would like to thank Dr. Wakasugi, Dr. Kanazawa, Mr. Abe, Mr. Ao, Mr. Yamaguchi, Dr. Na, Mr. Hirata
and Ms Nishikawa in Nippon Steel and Sumikin Cement Company, who provided me an opportunity to join
their team as intern and gave me a lot of their guiding about SEM, XRD test, whom I have great regard andhonour to work with.

I am really beholden beyond words to express my sense of gratitude to all the staffs of the centre forinternational relations at Muroran Institute of Technology, Mr. Endo, Ms. Noda, Ms. Chiba, Mr. Tajima,
Mr. Baek, Ms. Ikeda and Japanese teacher, Assoc. Prof Ono and Assoc. Prof Yamaji for help and patiently
teaching to make my life of studying abroad more perfect and make my doctoral study journey colorful andunforgettable forever.

I am grateful to my home university, Hanoi Architectural University in Vietnam, for allowing me to pursue
my Ph.D. degree abroad. I would like to thank Assoc. Prof. Vương Ngọc Lưu, Assoc. Prof. Lê Quân, Assoc.
Prof. Phạm Minh Hà, Assoc. Prof. Vũ Ngọc Anh, Assoc. Prof. Vũ Hoàng Hiệp, Assoc. Prof. Vũ Quốc Anh,Dr. Hoàng Văn Tùng, Dr. Nguyễn Việt Cường, Dr. Nguyễn Công Giang, Dr. Dương Quang Hùng, Dr. Đào
Minh Hiếu for their introduction and recommendation and supported me to apply this PhD position in MIT.

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Last but not least, I wish to acknowledge the love, support and understanding of my family, my parents, myparents-in-law, my brother-in-law and my younger sister and their son. I owe my loving thanks to my wifeNguyễn Thị Hiền and my daughter Nguyễn Thanh Hòa with her encouragement and understanding during
the hard period of the PhD. We shared our joy, happiness, stress, and depression together. For being whothey are, I love them so much!

Nguyễn Xuân Qúy(Muroran, Hokkaido, Japan, March 2019)109

LIST OF PUBLICATIONSJournal papers:
1. Nguyen Xuan Quy, Junho Kim, Yukio Hama, Effect of 10-year outdoor exposure and curing conditions
on the pore structure characteristics of hardened cement mortar, Journal of Advanced Concrete
Technology, Vol. 16 (9), p.461-475, 2018. https://doi.org/10.3151/jact.16.461

Proceedings and International Conferences:
2. Nguyen Xuan Quy, Akio Sakaguchi, Hyeonggil Choi, Yukio Hama, Modelling the effects of Maturity
on the change of Pore Structure of Mortar due to Drying Temperature and Humidity, Joint Seminar on
Environmental Science and Disaster Mitigation Research (JSED 2017), Section B, p.111, Japan, 2017.
(Written and Poster English Presentation)
3. Akio Sakaguchi, Yukio Hama, Shota Nagai, Nguyen Xuan Quy, Hyeonggil Choi, Maturity of
Temperature and Humidity that presents the change of Pore Structure of Mortar by Drying condition,
Proceedings of 10th International Symposium Between Korea, China and Japan on Performance
Improvement of Conrete for Long Life Span Structure (PICLS 2016), Part 2, p.99, Korea, 2016.
4. Nguyen Xuan Quy, A study on Pore Structure Change and Carbonation of Mortar due to DryingWetting Cycles, Dokukon 2016 Muroran Institute of Technology Graduate School of Engineering
Doctoral Student Research Presentation, Tokyo, Japan, 2016. (Poster English Presentation)
5. Nguyen Xuan Quy, Akio Sakaguchi, Kouta Matsumoto, Hyeonggil Choi, Yukio Hama, The Modified
Maturity Function in Frost Damage Prediction of Cement-based Materials due to Environmental
Conditions, Proceedings of AIJ Hokkaido Architectural Research Conference, No.90, p.17, Japan, 2017.
(Written and Oral English Presentation)
6. Nguyen Xuan Quy, Akio Sakaguchi, Hyeonggil Choi, Yukio Hama, Service Lifetime Prediction of
Cement-Based Materials in Cold Weather Regions, Proceedings of 11th International Symposium
Between Korea, China and Japan on Performance Improvement of Conrete for Long Life Span Structure(PICLS 2017), Part 4, p.189, Japan, 2017. (Written and Oral English Presentation Award)
7. Kouta Matsumoto, Nguyen Xuan Quy, Hyeonggil Choi, Yukio Hama, A study on the proposal ofclimate index for frost damage of concrete, Proceedings of the 13th Korea-Japan Joint Symposium on
Building Materials and Construction, Vol.13, p.103-108, Korea, Aug. 2017, (Moohan Kim Award Best
Paper in Japanese)
8. Nguyen Xuan Quy, Kouta Matsumoto, Yukio Hama, The effect of Environmental Conditions on
Service Life of Mortar corresponding Meteorological Index, Joint Seminar on Environmental Science

110and Disaster Mitigation Research (JSED 2018), Section B, p.151, Japan, 2018. (Written and Poster
English Presentation)
9. Kouta Matsumoto, Nguyen Xuan Quy, Hyeonggil Choi, Yukio Hama, Study on maturity of temperatureand humidity describe the change of pore structure by drying condition of mortar using different typeof cement, Joint Seminar on Environmental Science and Disaster Mitigation Research (JSED 2018),
Section A, p.83, Japan, 2018.
10. Kouta Matsumoto, Nguyen Xuan Quy, Yukio Hama, Pore structure and properties of mortar specimens
using different types of cement exposed outdoor for 10 years, Proceedings of 12th International
Symposium Between Korea, China and Japan on Performance Improvement of Conrete for Long Life
Span Structure (PICLS 2018), Part 1, p.95, China, 2018. (Written and Oral English Presentation Award)
11. Takumi Noguchi, Kouta Matsumoto, Nguyen Xuan Quy, Yukio Hama, Mapping of FRPST damage
climate indexes using mesh climate value, Proceedings of 12th International Symposium Between
Korea, China and Japan on Performance Improvement of Conrete for Long Life Span Structure (PICLS2018), Part 2, p.272, China, 2018.
12. 松本皓太, Nguyen Xuan Quy, 崔

亨吉, 濱 幸雄, 各種セメントに対応した乾燥によるモルタ

ルの細孔構造変化を表す温湿度時間積, 日本建築学会北海道支部 第 90 回研究発表会、室蘭，
北海道、日本、2017.
13. 松本 皓太, 野口 巧巳, Nguyen Xuan Quy, 濱 幸雄, コンクリートの凍害劣化を対象とした環境指標の提案: その 1 乾燥の影響を考慮したコンクリートの凍害劣化予測, 自然環境下のコンク
リート劣化に関するシンポジウムソンホソ, 自然環境下のコンクリート劣化研究委員会, JCI –C95, p.235-240, 日本、 2018.
14. 野口 巧巳, 松本 皓太, Nguyen Xuan Quy, 濱 幸雄, コンクリートの凍害劣化を対象とした環境指標の提案その 2 メッシュ気候値を用いた凍害環境指標のマップ化, 自然環境下のコンクリート劣化に関するシンポジウム, 自然環境下のコンクリート劣化研究委員会 , JCI –C95, p. 241248, 日本、 2018.

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