Chloride Diffusivity of Self-Compacting ConcreteWith Limestone Powder

Supakit SwatekitithamID. 1035011

A Thesis Submitted to
Kochi University of Technology
in Partial Fulfillment of The Requirements for
The Degree of Master of Engineering

Supervisor
Professor Hajime Okamura

Department of Infrastructure System Engineering
Kochi University of Technology
Kochi, Japan

January 2001

Acknowledgement
The intense appreciation would be presented to Prof. Hajime Okamura,
Department of Infrastructure System Engineering, Kochi University of Technology, for
his valuable suggestion, inspection and encouragement all the way through this study.
Thankfulness for the helpfulness of the references’ investigation and solve a
number of intricacies for the period of study would be rewarded to Prof. Hiroshi Shima,
Assist. Prof. Masahiro Ouchi, and Mr. Masaru Ueno.
Grateful acknowledgement is extended to Prof. Mikio Kadota and Assoc. Prof.
Toshio Yoshii for their interests and serving as members of examination committee.
Thanks for all Thai and Japanese friends at Kochi University of Technology for
their heartfelt help to carry on the experiment to accomplish the target all over this study.

Abstract
This paper investigated on the chloride ion movement in self-compacting
concrete. The empirical formulas for chloride diffusion coefficient, which is a functionof water-to-cement ratio, can be examined differently from a conventional concrete. The
mix proportions were separated into two types; self-compacting concrete and normal
concrete blended with limestone powder. The soaking test and fogging test were done inorder to match with the actual structures in the seawater and the seashore area,
respectively. Bleeding was also taken into consideration of chloride content along thedepth of a specimen. In this set of experiment, concrete blended with limestone powder
showed the decrease of chloride diffusivity for the concrete of the same water-cement.
Bleeding effect was shown the different of the chloride concentration at surface between
top and bottom part of a specimen, which is concerned with many parameters. The
concept of total chloride ion concentration at inner surface was formulated with timedependence, which can be obtained an appropriate value for the time of consideration.

Table of Contents
Page
Acknowledgementi

Abstractii

Table of contentsiii

List of tablesiv

List of figuresv

Chapter 1: Introduction

1-3

Chapter 2: Literature Review

4-9-Modeling of chloride ion movement in thesurface layer of hardened concrete
The durability standard specification for concrete
The investigation on minimum maintenance for prestressed
concrete bridge
An integrated computational system of mass/energy generation,transport and mechanics of materials and structures
A Multicomponent composite porous medium

Chapter 3: Experimental Outline
Chapter 4: Experimental Results & Verification- Part 1: Total chloride ion concentration and diffusion coefficient- Part 2: The analysis of chloride ion concentration
at inside surface of concrete.

4
5
6-7
8
8-9
10-12

13-24
25-28

Chapter 5: Conclusion

29

Chapter 6: Further Study30

References

31-32

Acknowledgement:
Appendix A: Tables show the total chloride ion concentration of the specimens
by varying type of concrete, time, w/c and type of testing
Appendix B: Tables show the diffusion coefficient of concrete
Appendix C: The aggregate gradation by sieve test
Appendix D: The total chloride ion concentration at inner surface of concrete
Appendix E: Verification data collected from the references

List of Tables
Page
Table 1. Mix proportion for chloride testing.
Table 2. Material Properties
Table 3. Properties of each mix proportion
Table 4: Void Curve
Table 5: A Mean Constant Diffusion Coefficients from Appendix B

11
11
11
12
25

List of Figures
Page

Fig. 1: Condensation mechanism of chloride ions in the surface layer of concrete
4Fig. 2: The relationship between the surface concentrationand distance from seashore.
6Fig. 3: The comparison of the total chloride concentration curves
between previous assumption and this paper
7
Fig. 4: The diffusion coefficient against w/c curve
7
Fig. 5: The multicomponents of concrete
8Fig. 6: Schematic representation of hard core soft shell model
9
Fig. 7: Computed percolation curves of a composite containing spherical,
equally sized aggregate particles
9
Fig. 8: Void curve used in normal concrete design
12Fig. 9-38: Total chloride ion concentration at time 1, 3 and 5 months of testing 15-23
Fig. 39-42: The average diffusion coefficients of concrete
24
Fig. 43: Comparison between 2 assumptions of chloride concentration at surface
26
Fig. 44-51: The total chloride ion concentration at the inner surface
27-28

Chapter 1
Introduction
In recent times, the design of concrete structure is based on the structural
performance and the environmental conditions. A performance-based design is asolution for new generation of design method. This design method is needed to supply
for any requirement of structural performance in various environmental conditions. The
performance-based design needs the durability index to take in the consideration. Oneof the main indexes is the deterioration of concrete structures by the corrosion of steel,which is affected by chloride ion penetration into concrete. The tests were held on thechloride ion movement in the various types of concrete using self-compacting concreteand normal concrete replaced by limestone powder. From the viewpoint of microscopic
concept, different type of concrete provides a different hydration and microstructuredevelopment. The chloride transport through the depth from open surface of concrete isdifferent. A structure standing on marine atmospheric zone has a different chloride
penetration rate from another submerging in the seawater, thus the experiment had been
done in two cases of soaking and fog tests for supporting those circumstances. For abeam structure, there is a bleeding effect in the longitudinal direction with the chloride
penetration. By this phenomenon, the test was separated by the value of chloride content
occurred along the depth from surface between top part and bottom part of specimens. It
should be noted that the column structure would have the effect perpendicular to thechloride penetrating direction. Therefore this study does not apply to the column
structure subjected to seawater; it’s required a further study on that. Bleeding in anormal concrete is related to properties itself, such as w/c and water content and theapplied force from vibration as well. The bleeding test cannot explain the behavior of
the porosity distribution depending on the depth of a specimen. In the different way,
self-compacting concrete was not required the vibration as applied in normal concrete,
thus the behavior of porosity alignment may be guessed by a proper examination. In thecase of limestone powder blended in concrete, the total chloride ion concentration isdifferent from concrete without it. The reason is on the limestone powder acted as thefilling material to the pore volume in concrete, especially interfacial zone. By the
microstructure concept, compared concrete with limestone powder and without
limestone powder at the same w/c, the diffusion in the case of no limestone powder will
be higher than that with limestone powder. The diffusion coefficients in limestone
powder blended with cement subjected to the chloride ion solution can be solved by thisexperiment. The reason is explained by aggregate influence in chapter 2 that limestone
powder was assumed to be non-reactive material, even though it can be reacted in alittle amount. Once we assumed it as aggregate portion in concrete, both of coarse andfine aggregates is affected on the interfacial pore volume and size. The exception is on avery fine aggregate as cement particle, which does not produce such effects on theinterfacial zone [15], and also act as filler on the porosity in the interfacial zone. The
fineness of limestone powder is very high so it can have very large contacted surface
with water. Limestone powder resists the water move up by segregation and bleeding by
the surface tension or adsorption theory. The bleeding path is decreased by the
replacement of limestone powder compared with conventional concrete at same w/c.
After discussed on the effect of limestone, next there are some influences of the 2 types

of concrete between self-compacting concrete and normal concrete blended withlimestone powder acted on the chloride ion penetration. The different between bothtypes are the cement content and aggregate volume fraction. The large aggregatedvolume fraction increases the connectivity among the interfacial pores, so that thechloride ion can easily penetrate into concrete. Moreover the total chloride
concentration is in the unit of % by weight of chloride ion to cement ratio, thus the total
chloride concentration in self-compacting concrete is smaller than normal concrete. In
the opposite, the aggregate can be replaced the capillary and gel porosity in concretealso. The best way is to find the critical aggregate volume fraction to produce the bestchloride ion resistance (see in chapter2 [15]).
In conclusion, the tests show the better resistance against chloride penetration
expressed by diffusion coefficient in the case of self-compacting concrete than normal
concrete. The limestone powder could be improved the resistance of chloride ion
penetration when compared with normal concrete at the same condition. The reductionof chloride penetration is achieved in the case of fog test judged against the soaking test.
The diffusion coefficients between top surface and bottom surface in any w/c wereshown variously.

Proposal of Analysis Method
In the past, there are many analytical models to predict the behavior of chloride
ion ingress for example Ref. [2,3,4]. Their concepts were explained the behavior of ion
absorption that the chloride penetration can be predicted by diffusion theory, ion
adsorption by reactive and non-reactive materials [2,4] and moisture movement [3]together in a specimen. In those references, the diffusion coefficient is assumed a timeindependent value for a type of mix proportion. Some other researchers investigated thechloride ion penetration by applying the concept of Fick’s second law [5,6,7&10] anddisplayed the relationship between diffusion coefficients with time or depth dependentfunction. In fact, the diffusion coefficient for a specimen should be constant for all parts
or higher at the surface level because of skin effect [5], but it decreased with time
because of the development of microstructure and strength (the decrement of porevolume inside a specimen by hydration process). Comparison the Fick’s second law
with the method discussed above, the chloride ion concentration along the depth
computed by Fick’s second law seemed to be covered the behavior of diffusion and ion
adsorption in both reactive and non-reactive materials (excepted on the surface layer) byassumed it as a non-steady condition. The limitation of Fick’s second law is used for thecase of a specimen in a regular environment. Many papers used basically the chloride
ion concentration of solution as the boundary condition at the exposed surface andapplied the Fick’s second law to estimate a diffusion coefficient. In fact, the total
chloride ion at outer surface is the concentration of solution, but inner surface is started
at zero concentration and increased with time by diffusion and ion adsorption. Thus thechloride ion concentration in the solution cannot be applied to the boundary condition.
It is necessary to find the chloride ion concentration at the time of consideration. Some
researchers had already analyzed by assuming the boundary condition with theexponential function of time or square root of time [5,11]. In this paper, theconcentration for the boundary condition was assumed in the logarithm function of time,
because the chloride ion concentration is increased and remained a constant value at along period of time. The experimental results were observed the total chloride ion
concentration at every 5 mm and computed the diffusion coefficients. Referred tochapter 3, the specimens were contained some amount of bleeding, which was affectedto the total chloride ion along the depth. In this paper, it was assumed that the diffusion
coefficient along the depth is constant because of the same properties of concrete. Even
though it was contained a degree of the bleeding effect, it’s assumed to use an averagevalue to define a diffusion coefficient. The diffusion coefficients for various proportionsof cement replaced by limestone powder were observed by Fick’s second law. By theway the first objective is to find the diffusion coefficient for this set of specimens inorder to understand how the types of concrete, the types of test, the amount of cement
replaced with limestone powder, time and bleeding effect affected the chloride ion
penetration. The second is the amount of total chloride ion concentration at innersurface with time dependence. The procedures for both objectives were explained withparticulars in chapter 4.

Chapter 2
Literature Review
Modeling of Chloride Ion Movement in The Surface Layer of Hardened
Concrete. (Maruya, T, Tantermsirikul, S, and Matsuoka, Y)
A model for surface chloride condensation was purposed by the concept of theion adsorption. The model was explained how the surface of concrete could have higher
amount of chloride ion concentration than the submerging solution. The behavior ofchloride penetration cannot be explained by only diffusion theory. The authors had
shown the condensation mechanism at the exposed surface by figure (1).

Fig1: Condensation mechanism of chloride ions in the surface layer of concrete

Considering both diffusion and condensation of chloride ion adsorption cansimulate the movement of chloride ion in the submerged case, as expressed by Eq.(1).
F’c = Fc + Sc (Cfree)(1)

where F’c : total flux of chloride ion entering the concrete at surface and is the sum andthe sum of the fluxes due to diffusion and ion adsorption (mol/cm2/day), Fc : the flux of
concrete ions due to diffusion only (mol/cm2/day), and Sc : the flux of chloride ion due
to ions adsorption only (mol/cm2/day) and is a function of free chloride content at 1cm.
from the exposed surface. The formula for Sc can be obtained by the chloride
penetration results by Eq.(2).
Sc = (1.4.10-5). exp (-1.15.Cfree(1,t))where Sc : used for 100% cement without blended pozzolanic materials.

(2)

The Durability Standard Specification for Concrete (JSCE, 1999)
The chloride ion penetration was examined in the chapter of ‘Durability
Examination of Concrete Structure’. The code was purposed the steel corrosion
accompanied by ingress of chloride ion, which considered by the limitation of chloride
ion concentration of concrete at the location of steel alignment. The value of 1.2 kg/m3
for chloride ion concentration at steel located was purposed to be a safety forsteel-corrosion generation. The rate of chloride ingress depends on the properties ofconcrete, which can be varied by the mix proportion. The chloride penetration by Fick’
2nd law was used to explain the total chloride along the depth from exposed surface asshown in Eq. (3).
C d = C o (1 − erf (0 .1 ⋅ c))
2 Dd ⋅ t(3)

Where, Cd : the design value of chloride ion concentration in reinforcement steel
position.
Co : the chloride ion concentration in concrete surface (kg/m3)
c : expected value of concrete covering (mm)
Dd : the design value of diffusion coefficient of chloride ion (cm2/year)= Dk.γcDk : diffusion coefficient of the chloride ion in concrete (cm2/year), assumed in
the no crack structure and estimated by eq.(4) as follows:log(D) = [ 4.5(w/c)2 + 0.14(w/c) –8.47 ] + log(3.15 x 107)(4)

Note: the equation is used for the case of 100% OPC as a total powder
and is estimated from the actual structure with non-uniform environment.
t : durable life to ingress of chloride ion (year). In general, 100 year of
durable life is the maximum of the chloride ion concentration in steel position
evaluated by the formula above.
γc : material coefficient of concrete. In general, it is good as 1.0. However, it isbetter as 1.3 concerning top part of concrete generally. If there are no quality
difference for all parts of structure and curing time, it is good to be use as 1.0.
erf. (s) :defined as an error function which is expressed as
erf ( s ) =

2

π

1/ 2

s

∫e

−η 2

dη

(5)

0

This prediction formula is used the thing based on diffusion theory, since thediffusion is the phenomenon that the concentration difference serves as driving force.
However the chloride ion in concrete is fixed and adsorbed in the cement hydrant andconcrete ingredient, which should be added more than diffusion theory only.

The Investigation on Minimum Maintenance for Prestressed Concrete Bridge,(Civil Engineering Research Center, Ministry of Construction, 2000 [16])Referred to The Durability Standard Specification for Concrete (JSCE, 1999),
this paper was investigated on actual structure and improved the new design approachdiffered from previous concept. The investigation was separated the structures location
into the structures along Japan Sea area, along the Pacific Ocean, and Setonaikai area.
The concentrations of salt in those areas are different in concentration for a whole year.
Thus the consideration of chloride ion penetration for a structure depends on thelocation of the structure. The concentration of salt contained in air also differs by the
distance from the seashore. It is meant that the value of the chloride ion concentration at
surface of a structure should be known as the boundary condition. The authors createdthe formula to compute the chloride ion concentration at surface of structure at any
distance from seashore and also compared with the previous reference as shown in fig. 2

Fig. 2: The relationship between the surface concentration and distance from seashore.
From Fig. 2, the formula of Co was proposed by equation 6 & 7 as follows:
Co =1.2 · Cair0.4
Cair = C1 Xb,

and

(6)

b = -0.6 constant(7)

where:
Co: Chloride ion concentration at surface of a structure
Cair: The flux of chloride ion in air (mg/dm2/day, mdd)
C1: The unit flux of chloride ion (mdd)
X: Distance from seashore (km)The different assumption of chloride ion concentration at surface was also
developed more accuracy than the previous approach to the actual value as shown in fig.
3. A long-term structure subjected to chloride ion concentration would have theconcentration at inner surface higher than the outer surface, Co. The appropriate design
value for diffusion coefficient was revised again more precisely.

Fig. 3: The comparison of the total chloride concentration curves between previous
assumption and this paper
The design diffusion coefficient was computed from the total chloride
concentration curve from the actual structures, which can be said that it is absolutely
different from the experimental data obtained from laboratory. The actual structures
were subjected to non-uniformity of the boundary chloride ion concentration, so that the
diffusion coefficient is smaller than the experimental result with the uniform boundary
condition explained by fig. 4.

Fig. 4: The diffusion coefficient against w/c curveAn Integrated Computational System of Mass/Energy Generation, Transport andMechanics of Materials and Structures. (Ishida T., 1999)
This paper purposed the model to explain chloride ion movement phenomenon
in concrete, which separated into 3 mechanism of free chloride, bound chloride and ion
adsorption. The bound chloride and ion adsorption was modified from ref. (2), but freechloride was explained by the mass balance as shown in Eq. (8)∂(φSCcl ) + divJ cl − Qcl = 0∂t(8)where Qcl : the rate of binding or the change of free chloride to bound chloride per unit
volume of concrete (mol/m3/s)
Jcl : flux vector of the ion (mol/m2/s)
φ : porosity of the porous media
S : degree of saturation of the porous medium
Ccl : concentration of ions in the pore solution (mol/l)
For ion adsorption expressed by fig.1, the authors modified the equation from
Eq. (2) to Eq. (9)qads = 6.5 × 10 −3 ⋅ exp(−0.8 ⋅ Ccl )(9)The literatures were led me well understand the chloride ion penetration in
concrete. They were displayed in detail how a chloride ion concentration was differedalong the depth of concrete and a various type of mix.
A Multicomponent Composite Porous Medium, (‘Modeling of Concrete
Performance’, Maekawa K., Chaube R., Kishi T., 1999 [15])There are three basic media, which is referred to as the components of concrete.
These are: (a) the hardened cement paste matrix; (b) the aggregate cement-paste matrix
interface and bleeding paths, called channel; (c) the aggregates. These three basic media
are shown in the fig. 5 given below.

Fig.5: The multicomponents of concrete

The amount of aggregate volume fraction plays an important role in deciding theoverall transport behavior. It had been reported that the porosity within the interfacialzone near aggregate surface could be up to 3 times the porosity of bulk matrix. The
water to cement ratio near aggregate surfaces is usually larger than the wall effect,
which means that cement powder particles near a wall-like surface cannot packefficiently as in the bulk medium. It leads to coarse microstructure and high porosity
near aggregate surface, whose thickness depends on the size of aggregate. The
aggregate volume fraction also plays on the effect of bleeding path of water movement
modeled by hard core soft shell theory as shown in fig. 6

Fig. 6: Schematic representation of hard core soft shell model
The volume fraction of aggregate at which such a percolation of interface occurs
can be called the critical volume fraction of the aggregate. When the aggregate volume
fraction is increased, a larger amount of interfaces contacts occur. This leads to a largerof the interfaces becoming connected together. Then the model can be predicted theamount of interfacial volume fraction percolated related with the aggregate size and theaggregate volume fraction. The minimum value of interfacial volume fraction
percolated can explain the critical aggregate volume fraction as shown in fig.7

Fig. 7: Computed percolation curves of a composite containing spherical,
equally sized aggregate particles

Chapter3
Experimental Outlines
The test was held 10 mix proportions as shown in table (1) for testing chloride
movement in 2 different types of soaking and fog test. First 5 mixes are designed as
self-compacting concrete blended with limestone powder at w/c = 0.3, 0.4, 0.5, 0.6 and0.7. Other 5 mixes are normal concrete blended with limestone powder at equal of w/cvalues as above. The coarse aggregate was used at 53% by solid volume and fineaggregate was used at 45% by mortar volume. The large size gravel and small size
gravel were used as coarse aggregate in the proportion of 1: 2.333 by weight. The
material properties were shown in table (2) and the test for gradation (Appendix C) andsolid volume were shown in table 4. The deionized water was utilized for mixing waterto prevent the effect of some reactive ions. The mixing procedure had been separated
between self-compacting concrete and normal concrete. Firstly for self-compacting
concrete, the order is cement+sand (30sec)!water equal to 70% by volume powder(90sec) !rest of water+SP (30sec) !coarse aggregate (60sec). By this method, it canbe obtained some improvement of the concrete properties in fresh state. For selfcompacting concrete, the slump flow, box test and V-shape funnel speed were measured
just after mixing as the properties during the fresh state as shown in table (3). Secondly
for normal concrete, the order is cement+sand (30sec)!water equal to 74% by volume
powder (90sec) ! !coarse aggregate (60sec) ! rest of water+SP (60sec). This method
is aimed to have concrete at very low w/c surrounding the aggregate particles andincrement of slump value as shown in table (3). The cylindrical concrete specimens of
10 x 20 cm. were cast just after mix and leave for 24 hours under sealed condition, andthen removed into the curing pond at constant temperature 20°C for 28 days. The
specimens were needed to coat all surface excepted top and bottom sides with the
purpose of exposing to the control environment. The aim of study is for understanding
the bleeding effect by the inequality of data from both sides. The specimens after 28
days curing will be transferred to 2 testing conditions: soaking test and fog test. The
important caution is that before putting a specimen into the test, it should be provided
the water absorption for a while in order to fill up porosity with water and to protect thesuddenly sucking of chloride solution at the surface of specimens. The condition ofsoaking test is 20°C and chloride ion concentration of 5% (NaCl = 8.24%)[9]. The
fogging test is supposed to be similar to the offshore neighborhood with the averagetemperature of 25°C. The fog test was used the same concentration of chloride ion
concentration with the rate of 0.6 m3/sec. The test results were procured at time of 1
month, 3 months and 5 months. The specimens were removed from the test at testingtime and wait until it had been dried before cutting. The specimens were cut in every 5mm from opened surface, and crushed to be very fine. The titration machine using
AgNO3 as titration solution were used to tritrate the total chloride content from a sample.
The testing procedure was referred to ASTM C114, 1997[8].

Table 1. Mix proportion for chloride testing.
NO. Type w/p w/c % replacement cementLswater sand gravel
SP





(kg/m3) (kg/m3) (kg/m3) (kg/m3) (kg/m3) (kg/m3)
1 Normal 0.94 0.3
0.5
485
2
146
768
1039 4.877
2 Normal 0.94 0.4
22.6
364
106
146
768
1039 4.703
3 Normal 0.94 0.5
36.7
291
169
146
768
1039 4.599
4 Normal 0.94 0.6
46.4
243
210
146
768
1039 4.530
5 Normal 0.94 0.7
53.6
208
240
146
768
1039 4.480
6 SCC 0.94 0.3
0.5
597
3
179
774
848
9.295
7 SCC 0.94 0.4
22.6
448
131
179
774
848
6.940
8 SCC 0.94 0.5
36.7
358
207
179
774
848
5.938
9 SCC 0.94 0.6
46.4
298
259
179
774
848
5.570
10 SCC 0.94 0.7
53.6
256
295
179
774
848
4.958
Table 2. Material Properties
Material
type
CementLs
Sea SandCrushed sandBig gravel
Small gravelSpecific
gravity
3.15
2.7
2.57
2.55
2.68
2.66


% Absorption Surface area(cm2/g)
3280
4000
2.62
2.67



Table 3. Properties of each mix
proportion
NO. Type w/p w/c Slump flow
(mm. X mm.)
1 Normal 0.94 0.3
2 Normal 0.94 0.4
3 Normal 0.94 0.5
4 Normal 0.94 0.6
5 Normal 0.94 0.7
6 SCC 0.94 0.3
650*640
7 SCC 0.94 0.4
645*663
8 SCC 0.94 0.5
680*680
9 SCC 0.94 0.6
685*665
10 SCC 0.94 0.7
669*668

Funnel speed Box test Temp. Slump height Strength(sec.)(cm.)(celcius)(cm.)
28-d (MPa)
23.7
12.6
85.6
24
16.7
73.4
24.2
19
60.6
23.6
20.3
49.8
23.5
21.9
39.6
11.47
32.2
22.8
83.9
13.6
31.5
23.6
70.6
19.14
33
23.1
62.1
14.34
32.4
22.3
52.6
14
31.5
22.7
42.7

Table 4 Void Curve
Crushed sand: Sea sand = 1.02:1 by volume (1:1 by weight)
Large-size gravel: Small-size gravel = 1:2.333 by weight% void of sand =

35.14

s/a

% void% void of gravel =

42.18

0

39.06

0.275

27.26

0.3

25.67

0.325

24.88

0.4

23.68

0.425

23.12

0.45

23.41

0.55

24.63

0.575

25.44

0.6

25.96

1

35.14

Chapter 4
Experimental Results & Verification
The specimens were mixed with the replacement of limestone powder blended
with cement, which was designed by varying the weight ratio of water to cement from
0.3-0.7 at the constant volume ratio of water to powder at 0.94 and constant aggregate
volume fraction. The total chloride ion concentrations along the depth of a specimen
from both soaking and fog test were examined with the time of 1, 3 and 5 months inorder to estimate the specimens’ diffusion coefficient. The diffusion coefficient was
explained in Part 1, and the surface chloride ion concentration was discussed in Part 2.
The overall steps of calculation for the experimental data were expressed as follows:
1.
2.
3.
4.

5.

Computed the average total chloride ion concentrations in every 5 mm depth
in the unit of % by weight of cement.
Set the total chloride ion concentration at 0-5 mm as a boundary condition,
because the real boundary condition at inner surface was still unknown.
Computed an average value of the diffusion coefficients obtained from latter
depth using equations (3 & 5) for 3 different periods of test.
After got an average value of diffusion coefficient, used the equation 3 tocompute the inner surface (Co) by assumed Cd = the total chloride ion
concentration at 0-5mm, c is 2.5 mm and Dd = computed diffusion
coefficient from step 3.
Created the empirical formula for the total chloride ion concentration at
inner surface as expressed in equation 13.

Part1: Total chloride ion concentration and diffusion coefficient
On the figure 9-38, the experimental results (see in Appendix A.) were shown
the total chloride ion concentration varied by type of test, penetrated depth, w/c andtime in the unit of % by weight of cement. The total chloride ion concentration curves
were shown with included top and bottom surface and 2 types of concrete curves in agraph. These results are shown the high concentration at the surface and the decrementof total chloride ion concentration along the depth inside concrete. The higher diffusion
coefficient, the higher total chloride ion concentration is basically observed. The total
chloride between top and bottom surface of each type of mix are shown differently. The
reason is that the rich of paste volume were contained on the top part but the rich of
aggregate were contained on the bottom part. After casting concrete, the specimens
were affected by bleeding in theirs, then the water was moved up and aggregates were
sunk to the bottom part. Thus concrete was not uniformed and a new formation along
the depth was taken place. The top part became increasing of paste volume and also w/c
in paste matrix, but decreasing of aggregate’s volume. In the other part, the getting
higher of aggregate’s volume covered with low w/c paste matrix was observed. Whenthe chloride ion was penetrated it was stored in the pores of concrete specimen, thus theamount of total chloride in a specimen was related to the pore volume and theconnection of pore paths. The aggregate effect is on the reduction of capillary pores andgel pores by replacing of paste volume, but the induction of the interfacial pores andpath connection was become apparent. The unit of total chloride was used by thepercentage of weight of cement per 1m3 of volume, thus the computed total chloride ion
concentration was overestimated on the top part and underestimated on the bottom part.
Therefore the difference was turned out to be decreasing at inside depth. In conclusion,
it was revealed that the top part of a specimen had a chloride penetration curve higher
than that of the bottom part and those curves became narrow through the depth.
The observation was conducted to the difference between self-compacting
concrete and normal concrete with the same water to cement ratio. On the figures,chloride penetration paths of self-compacting concrete were under those of normal
concrete. They could be concluded that the durability on chloride penetration in case of
self-compacting concrete was higher than normal concrete in any water to cement ratio
even though the 28-day compressive strengths of self-compacting concrete were lower
than normal concrete in some mix proportions. By the figures, they can be explained inaddition that the longer time of test, the larger deviation of total chloride ion
concentration curve between 2 types was investigated. The reason is that selfcompacting concrete was used aggregate volume fraction less than in case of normal
concrete, so among the pores in the interfacial zone were not connected continuously,
and then the chloride ions were slowly penetrated through a specimen (see in Chapter2).
Moreover the inconsistency of total chloride ion concentration at a depth from exposed
surface between top and bottom part of self-compacting concrete was narrower thanthose of normal concrete caused by bleeding effect. Thus, It was found that the bleedingin case of self-compacting concrete is lower than in case of normal concrete due to theneedless of a vibration force and the viscosity of the paste to prevent the elevation ofwater is also higher. It is the advantage to use self-compacting concrete for an actual
structure not only no vibration is required, but also durability concerned.
From the total chloride ion concentration curves, the depth at 2.5 mm was set tobe the initial condition to compute the diffusion coefficient in order to avoid someeffects that were discussed in Part 2. The equations of Fick’s second law and error
function shown in chapter 2 [1] were applied to calculate the average diffusion
coefficients for each w/c. A specimen is contained some amount of bleeding which is
caused by w/c, water content, % replacement of limestone powder and vibration energy.
Thus, the new alignment of aggregate and also real w/c along the depth is unclear. After
bleeding was happened, the top part of the specimen was contained less of aggregate
content but higher in w/c, and then the diffusion coefficient would be differed between
top and bottom. Therefore it is still unclear about it, so the average value for diffusion
coefficient along the depth of a specimen was assumed to present at this time (seeAppendix B). Moreover the verification of diffusion coefficients with conventional
concrete from the references (see in Appendix E) was done in fig (39-42). After all, thediffusion coefficient for a mix was used in the analysis of the chloride ion concentration
at surface of the same concrete specimen (see in Part 2).

Part 2: The analysis of chloride ion concentration at inside surface of concrete.
As discussed, many researchers assumed the condition of chloride ion
concentration in the submerged solution as follows:
t=0&x=0!

Co(0,0) = CsolutionandCo(x,t) = Csolution x f(t)(10)

Co(x,t) = Csolution + Cion adsorption

(11)

or

where Cion adsorption is the ion adsorption of chloride ion concentration at surface layer[2,3]
Table 5:Shows a Mean Constant Diffusion Coefficients from Appendix B

Soaking TestTop Surface
w/c Normal SCC
0.3
0.886 0.784
0.4
1.432 1.194
0.5
2.459 1.990
0.6
3.607 2.821
0.7
5.602 4.395

Fog Test
Bottom Surface 
Top Surface
NormalSCC
w/c
Normal
SCC
0.897
0.648
0.3
0.735
0.490
1.328
1.375
0.4
1.063
0.836
2.316
1.905
0.5
2.081
1.796
3.528
3.064
0.6
3.402
2.875
4.794
4.352
0.7
5.076
4.085

Bottom Surface
Normal
SCC
0.631
0.490
0.933
0.831
2.019
1.722
3.193
2.738
4.541
4.152

From the data table in Appendix D, the chloride ion in solution is constant at 5%of water, and was converted into % by weight of cement in each mix proportion. The
test was observed that the total chloride content at the inside surface was started at zeroand increase with time. Then the total chloride at surface was higher than theconcentration of solution at a certain time, because of diffusion and ion adsorption
theory. Thus it seems to be concluded that the assumption of chloride ion in solution as
the boundary condition was not exacted. For example, the total chloride ion
concentration of w/c = 0.3 at top part of 28-day test data is 4.17 % for soaking testcompared with 25.18 % of the solution. If the 25.18 % were used as boundary conditionin order to compute a diffusion coefficient by Fick’s second law, the computed
diffusion coefficient would be shown a diffusion coefficient at surface lower than insideconcrete. It was cleared to explain the example by fig.43 that shows large difference atsurface layer, and this thing was also recommended by the literature, fig. 4.
In fact, the diffusion coefficient is one of the material properties, which should
be constant along the depth proved by this figure. Some researchers used both 1. The
chloride ion concentration of solution is the boundary condition and 2. The equation for
diffusion coefficient was referred to Fick’s second law; then at surface 0-5mm thecoefficient is low. When the coefficient at 5-10mm was computed, the apparent
coefficient was a mean between 2 different values from 0-5mm and 5-10mm. Thus thecomputed diffusion coefficient from Fick’s second law was shown in the function of
depth. On the other hand, in case of high w/c and long time, the coefficient could beshown inversely compared with the example.

Cl (% by weight of
cement)Fig. 43: Comparison between 2 assumptions of chloride
concentration at surface

30
25
20
15
10
5
0

Computed Surface
Cl ion from paper
5% of cl in solution
assumed to be
surfaceconcentration

0

10

20

30

depth

It can be said that the outer surface contained 5% of chloride ion concentration
as the salt solution was not equaled the inner surface of concrete at any time. This paper
was aimed to create the formula of chloride ion concentration at inner surface with thefunction of time, chloride ion concentration of the solution, cement content, relative
humidity and diffusion coefficient as follows:
Cinner = Couter ·Unit weight· f(t, D, RH)
Wcement(12)

Where Couter : Chloride ion concentration in the submerge solution (% in water)
Wcement: Weight of cement content (kg/m3)
Cinner : Chloride ion concentration at inner surface of concrete (% by Wcement)t: Required structure’s life (year)
D: Diffusion coefficient (cm2/year)
RH : Relative humidity of testing environment, ( for soaking test, RH =1 andfor fog test RH = ≈ 0.8)
The regression method was used to identify the equation for f (t, D), which isfunctioned as follows,f(t, D, RH) = {{[(0.0930 ⋅ D) + 0.1287] ⋅ LN(t)} + (0.3330 ⋅ D) + 0.4002} ⋅ RH (13)The curves for chloride ion concentration at inner surface and empirical formulawere shown in the fig. (44-51). Finally, the design mix proportions for a structure wasassumed the service life (t), mix proportion (w/c) and location of structure (Couter), andthen Cinner can be obtained. Then Fick’s second law can also compute the total chloride
ion concentration along the depth of covering. After all, the limitation of chloride ion
concentration at the position of steel (= 1.2 kg/m3 recommended by ref. [1]) can bechecked easily.

Cinner (% by weight of
cement)Fig. 44: T he chloride concentration at the top part of normal
concrete at inner surface for soaking test
100.00
80.00
60.00
40.00
20.00
0.00
0

0.2

0.4

0.6

0.8

1-month3-monthw/c

5-monthCinner (% by weight of
cement)Fig. 45: T he chloride concentration at the top part of normal
concrete at inner surface for fog test
100.00
80.00
60.00
40.00
20.00
0.00
0

0.2

0.4

0.6

0.8

1-month3-monthw/c

5-monthCinner (% by weight of
cement)Fig 46: T he chloride concentration at the bottom part ofnormal concrete at inner surface for soaking test
100.00
80.00
60.00
40.00
20.00
0.00
0

0.2

0.4

0.6

0.8

1-month3-monthw/c

Cinner (% by weight of
cement)5-monthFig 47: T he chloride concentration at the bottom part ofnormal concrete at inner surface for fog test
100.00
80.00
60.00
40.00
20.00
0.00
0

0.2

0.4
w/c

0.6

0.8

1-month3-month5-monthCinner (% by weight of
cement)Fig 48: T he chloride concentration at the top part of SCC atinner surface for soaking test
100.00
80.00
60.00
40.00
20.00
0.00
0

0.2

0.4

0.6

0.8

1-month3-monthw/c

Cinner (% by weight of
cement)5-monthFig 49: T he chloride concentration at the top part of SCC atinner surface for fog test
100.00
80.00
60.00
40.00
20.00
0.00
0

0.2

0.4

0.6

0.8

1-month3-monthw/c

5-monthCinner (% by weight of
cement)Fig 50: T he chloride concentration at the bottom part of SCC
at inner surface for soaking test
100.00
80.00
60.00
40.00
20.00
0.00
0

0.2

0.4

0.6

0.8

1-month3-monthw/c

Cinner (% by weight of
cement)5-monthFig 51: T he chloride concentration at the bottom part of SCC
at inner surface for fog test
100.00
80.00
60.00
40.00
20.00
0.00
0

0.2

0.4
w/c

0.6

0.8

1-month3-month5-monthChapter5
Conclusion
1. The limestone blended with cement can reduce the diffusion coefficient forchloride ion penetration at same w/c as conventional concrete.
2. The diffusion coefficient for self-compacting concrete showed the value lower
than that of normal concrete therefore self-compacting concrete clarified better
durable concrete in chloride resistance.
3. The outer solution cannot be applied as the boundary condition in thedetermination of chloride ion penetration by Fick’s second law.
4. The effect of bleeding affects the difference in chloride ion penetration between
top part and bottom part caused by many parameters such as w/c, watercontent, % replacement of limestone powder, paste volume, SP and vibration,etc.
5. The fog test provided less the diffusion coefficient than the soaking test because
the relative humidity inside pore was not fulfilled with water or solution.
6. By this test, the bleeding effect is in according with chloride ion concentration,
which is the same as in the case of a beam or a girder structure. Thus the test
will be suitable to be used in design of a specific type of structure only. In thecase of column, the bleeding effect is perpendicular to the chloride penetrationroute, the test of specimen that same as column will lead us to understand theeffect of bleeding along the depth or a new alignment between paste andaggregate after bleeding took place.

Chapter 6
Further Study
1. The test should be prolonged into concrete made from cement replaced with fly
ash and slag.
2. The test specimen should be changed into a prism, which contains some of
bleeding effect by controlling vibration energy.
3. The model for understanding of a new formation of paste property andsegregation of aggregate.
4. The criteria to match the experimental result with the actual application ordesign purpose.

References

1. Japan Society of Civil Engineers, Standard specification for durability ofconcrete, 1999 (in Japanese)
2. Maruya T., Tangtermsirikul S. and Matsuoka Y., Modeling of Chloride Ion
Movement in The Surface Layer of Hardened Concrete, Concrete library of
JSCE, No. 32, December 1998, pp. 69-84
3. Ishida T., An Integrated Computational System of Mass/Energy Generation,
Transport and Mechanics of Materials and Structures, The doctoral thesis
submitted to University of Tokyo, March 1999, pp 36-41
4. Plang-ngern S. Chloride Binding Capacity in Fly Ash Concrete, The masterthesis submitted to International Institute of Technology Thammasat University,
1999
5. Carmen A., Jose M. D., and Cruz A., Mathematical Modeling of a Concrete
Surface “Skin Effect” on Diffusion in Chloride Contaminated Media, Elsevier
Science Ltd., 1997
6. Yamamoto A., Motohashi K., Misra S., and Tsutsumi T., Proposed Durability
Design for RC Marine Structures, Concrete Under Severe Conditions:
Environment and Loading (volume one), published by E&FN Spon, 1995
7. Gjorv O.E., Sakai K., Testing of Chloride Diffusion For Concrete, Concrete
Under Severe Conditions: Environment and Loading (volume one), publishedby E&FN Spon.,1995
8. ASTM C 114-97a, Standard Test Methods for Chemical Analysis of Hydraulic
Cement, 1997, pp 111-112
9. Maruya T., Matsuoka Y., and Tangtermsirikul S., Simulation of Chloride
Movement in Hardened Concrete, Concrete Library of JSCE, No.20, 1992,
pp.57-70
10. Chatterji S., On The Applicability of Fick’s second law to Chloride Ion
Migration Through Portland Cement Concrete, Cement and concrete research,
Vol. 25, No. 2, 1995, pp.299-303
11. Weyers E. R., Service Life Model for Concrete Structures in Chloride Laden
Environment, ACI Materials Journal, Vol. 95, No.4, 1
12. Tang L., Andalen A., Johansson J. -O., Hjelm S., Chloride Diffusion Coefficientof Self-compacting Concrete, Self-compacting concrete, Edited by Skarendahl
and Peterson, Rilem Proceedings Pro7, Sep. 13-14, 1999
13. Chan Y.N. S., Ji X., Comparative Study of The Initial Surface Absorption and
Chloride Diffusion of High Performance Zeolite, Silica fume and Pfa Concretes,
Cement and Concrete Composites, Vol. 21, 1999, pp. 293-300
14. Leng F.,Feng N.,Lu X., An Experimental Study on The Properties of Resistanceto Diffusion of Chloride Ions of Fly ASH and Blast Furnace Slag Concrete,
Cement and concrete research 30,No. 989-992, 2000
15. Maekawa K., Chaube R. and Kishi T., Modeling of Concrete Performance, by E
& FN Spon, 1st Edition, 1999, pp. 107-117
16. The Civil Engineering Research Center, Ministry of Construction, The
Investigation for Minimum Maintenance for Prestressed Concrete Bridge,
December 2000, (in Japanese)17. Sandberge P., Studies of Chloride Binding in Concrete exposed in a marine
Environment, Cement and Concrete Research, Vol. 29, 1999, pp. 473-477

Appendix A: Tables show the total chloride ion concentration of the specimens
by varying type of concrete, time, w/c and type of testingAppendix B: Tables show the diffusion coefficientof concrete

Appendix B: Shows Diffusion Coefficients of concrete for 1,3 and 5 months
Testing

1-month
w/c
0.3
0.4
0.5
0.6
0.7
3-month
w/c
0.3
0.4
0.5
0.6
0.7
5-month
w/c
0.3
0.4
0.5
0.6
0.7

Soaking Test
Top Surface
Bottom Surface
Normal SCC Normal SCC
1.296 1.149 1.168 0.902
2.155 1.516 1.787 1.733
3.435 2.764 2.970 2.245
4.202 3.399 3.932 3.515
6.111 4.833 5.307 4.451
Top Surface
Bottom Surface
Normal SCC Normal SCC
0.724 0.642 0.872 0.526
1.273 1.181 1.335 1.253
2.159 1.653 2.150 1.872
3.467 2.662 3.377 2.914
5.585 4.578 4.600 4.341
Top Surface
Bottom Surface
Normal SCC Normal SCC
0.637 0.560 0.652 0.515
0.869 0.886 0.862 1.137
1.782 1.554 1.828 1.597
3.151 2.404 3.276 2.762
5.110 3.773 4.477 4.266

1-month
w/c
0.3
0.4
0.5
0.6
0.7
3-month
w/c
0.3
0.4
0.5
0.6
0.7
5-month
w/c
0.3
0.4
0.5
0.6
0.7

Fog Test
Top Surface
Bottom Surface
Normal SCC Normal
SCC
1.082 0.700 0.920
0.683
1.359 0.873 1.239
0.971
2.704 2.461 2.762
2.173
4.095 3.825 3.308
3.081
5.424 4.624 5.137
4.333
Top Surface
Bottom Surface
Normal SCC Normal
SCC
0.618 0.468 0.543
0.484
1.047 0.825 0.864
0.765
1.867 1.495 1.655
1.586
3.393 2.486 3.261
2.717
5.159 3.969 4.365
4.125
Top Surface
Bottom Surface
Normal SCC Normal
SCC
0.506 0.301 0.430
0.304
0.784 0.810 0.695
0.758
1.670 1.431 1.640
1.407
2.717 2.315 3.012
2.417
4.646 3.663 4.121
3.997

Appendix C: The aggregate gradation by sieve test

Table C-1: Crushed sand gradation

Table C-2: Sea sand gradation

sieve size W sand % retained % retained % passing



(mm)
acc.
10 0.00
0.00
0.00
100.005 0.70
0.12
0.12
99.88
2.5 166.00
27.67
27.78
72.22
1.2 331.50
55.25
83.03
16.97
0.6 36.30
6.05
89.08
10.92
0.3 28.80
4.80
93.88
6.12
0.15 20.20
3.37
97.25
2.75
0 16.502.75
100.000.00
total 600.00 100.00

sieve size W sand % retained % retained % passing



(mm)
acc.
10
0.00
0.00
0.00
100.00
5
49.20
8.20
8.20
91.80
2.5
161.60 26.93
35.13
64.87
1.2
275.20 45.87
81.00
19.00
0.6
39.70
6.62
87.62
12.38
0.3
31.70
5.28
92.90
7.10
0.15
24.00
4.00
96.90
3.10
0
18.60
3.10
100.00
0.00


total
600.00 100.00

Table C-3: Large size gravel
Table C-4: Small size gravel
Gmax = 20 mm.
Gmax = 10 mm.
sieve size W gravel % retained % retained % passing sieve size W sand % retained % retained % passing






(mm)
acc.
(mm)
acc.
80 0.00
0.00
0.00
100.00
80
0.00
0.00
0.00
100.0040 0.00
0.00
0.00
100.00
40
0.00
0.00
0.00
100.0020 151.00
2.95
2.95
97.05
20
0.00
0.00
0.00
100.0013.2 3112.00 60.86
63.82
36.18
10
628.12 20.94
20.94
79.06
10 1774.00 34.70
98.51
1.49
5
2371.88 79.06
100.000.00
5 58.00
1.13
99.65
0.35
2.5
0.00
0.00
100.000.00

2.5 18.00
0.35
100.000.00
total 3000.00 100.00

total 5113.00 100.00

Appendix D: The total chloride ion concentration at inner surface of concrete(kg/m3)

Appendix E: Verification data collected from the references

Mix proportion

Name
Ref. 13
Ref. 13
Ref. 13
Ref. 13
Ref.14
Ref.14
Ref.14
Ref. 2(28d)Ref. 2(98d)
Ref. 2(182d)
Ref. 2(378d)
Ref. 2(588d)
Ref. 17w/c cement water 20mm agg. 10mm agg. sandsp
Average D
 (kg/m3) (kg/m3) (kg/m3)(kg/m3) (kg/m3) (kg/m3) (cm2/yr)
0.27
500
135
426
851
548
7.3
4.85
0.33
500
165
419
837
539
4.7
9.88
0.39
500
195
410
819
527
2.7
28.53
0.45
500
225
403
805
518
0
38.56
0.26
660
156
1100
620
1.8
2.40
0.3
550
165
1120
640
1.5
2.60
0.34
500
170
1150
640
1
5.50
0.5
350
175
481
475
866
2.59
0.5
350
175
481
475
866
2.32
0.5
350
175
481
475
866
1.84
0.5
350
175
481
475
866
1.99
0.5
350
175
481
475
866
1.72
0.5
390
195
787
876
1.15

Note: The average D was computed from the total chloride concentration curve fromthe references by the concept used in this paper.