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A CRTTICAL EVALUATION OF ASTM METHOD C 1 14, SECTION19 FOR THE DETERMINATION OF TOTAL CHLORIDE CONTENT OF
CURED CEMENT AND CONCRETE
Shahram Karimi
A thesis submitted in conformity with the requirements for the degree of Maser of Applied Science
Graduate Department of Chernical Engineering and Applied Cherni- University of Toronto
O Copyright by Shahrarn Karimi (300 1 )
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TITLE: A CRInCAL EVALUATION OF ASTM METHOD Cl 14, SECTION19 FOR THE DETERMINATION OF TOTAL CHLOEüDE CONTENT OF CURED CEMENT AND CONCRETE
AUTHOR: SHAHRAM KARiMI
DEGREE OF MASTER OF APPLIED SCIENCE
GRADUATE DEPARTMENT OF CHEMICAL ENGiNEERiNG AND APPLIED CHEMISTRY
üNIVERSITY OF TORONTO (200 1)
An assessrnent was made of the accuracy and precision of ASTM Method C 1 14 for the
anatysis of chlonde in cured cernent paste and concrete.
Cernent pastes with water-to-cement ratios of 0.45. containing known different amounts
of chIoride ranging from 0.0 to 8.0 percent by weight of dry cement. were prepared using
ASTM Type i Ordinary Portland Cement. The samples were alIowed to cure in a
hydrostat for 7 and 28 days with and without rotation and then were analyzed for total
chlonde content using ASTM Method C 114. Complete extraction of chloride fiom the
cernent specirnens was not achieved. showing the inability of the above method to bring
dl the chlorides into solution for analysis. For some of the samples contaîning hi&
chloride content the ASTM method under-reported the true values by as much as 70%.
ACKNOWLEDGMENTS -
1 would like to thank Professor Frank R Foulkes for his time. genuhe interest. and
invaluable guidance throughout this project. 1 wouid also like to thank my family for
their exceptional support and encouragement durùig the course of this study.
iv
TABLE OF CONTENTS
Abstract ................................................................... ................................................................... Ac knowledpents
Table of Contents ................................................................... List of Tables ..... ............................................................... List of Figures .. ................................................................. .
1.0 Introduction .......................................................... 1 . 1 Background .......................................................... 1 . 2 Objective ..........................................................
2.0 Litenture Review ................................................. 2.1 Portland Cernent
2.1.1 Definition ................................................ ........................................ 2.1.2 Manufacturing Process
............................... 2.1.3 Types of Portland Cernent ............. 2.1 -4 Chernical Composition of Portland Cernent
2 . I -5 Cernent Hydration ........................................ ............. 2.2 tntluence of Chloride Ions on Concrete Corrosion
...................................... 2.2.1 Sources of Chloride Ions .................................... 2.2.2 Binding of Chioride Ions
2.3.2.1 Types of Chioride Bonds ..................... ............ 2.2.2.2 Influence of C3A on Chioride Binding
2.2.2.3 Influence of Calcium Silicate Hydrate on Chloride .............................................. Binding
2.2.2.4 Effects of Associated Cation Type on Chloride .............................................. Binding
2.2.2.5 Influence of Sulfates on Chioride Binding ...... 2.3 Analysis of Chloride Content in Cured Cernent Pastes ............
2.3.1 Background ................................................ .... 3 . 2 Analysis of Cernent Pastes and Concrete for Chloride
3.0 Experhental Description ......................................................... 3-1 Overview
3.2 Materiais and Specimens ....................................... 3 2 . 1 Materials ................................................
................................................ 3.22 Cernent Samples 3 2.3 Equiprnent ................................................
3.3 Expecirnental Procedures ............................................. 3 3.1 Bais of Method ................................................ 3.3 2 Description of the Method ..............................
40 ResuIts and Discussion ..................... J . I Evaporable Water in Hydrated Cernent Pastes
4.2 Total Chloride Determination .......................................
. . 11 ... 111
iv vi vii
1 1 3
4 4 4 5 6 7 8 8 8 9 9
13
13 14 15 15 16
19 19 19 20 22 13 .. 22 22
29 29
Determination of the total chioride content of cernent slabs cured for 7 and 28 &ys ............................... 31 influence of Curing T i e on Total Chloride Detennination 36 infiuence of Rotation on Total Chlonde Determination .... 37 A Critical Analysis of the Data ............................... 43 The Influence of Acid Type and Concentration on Total Chloride Determination ...................................... 17 Cornparison of Berman's Method with the ASTM Method Cl14 ........................................................ 48 Effects of Heating, Digestion Time . and Sample Covering 49 Volatilization Losses by Heating ........................... 53
.................................................................. 3.0 Conclusions 54
6.0 Rscommendations ......................................................... 55
7.0 Réferences .............................................................. 56
Appendices Appendix A - General Data ....................................... 59
Appendix B - Tables of Some Measured Data ................. 60
.............................. Appendix C - Sample Calculations 63
LIST OF TABLES
Table f - Portland Cernent Types and Their Applications
Table 2 - Main Chernical Cornpounds of Portland Cernent
Table 2 - Chernical Composiiion of PortIand Cernent Type 1
Table 4 - A Cornparison of ASTM Method C 114 and Berman's Method for Total
ChIoride Analysis
Table 5 - Evaporable Water in Cured Cernent Spheres
Table 6 - Total Chloride Content of Hardened Cernent Slabs Cured for 7 days
Table 7 - Total Chloride Content of Hardened Cernent Slabs Cured for 28 days
Table 8 - Total Chloride Content of Hardened Cernent Spheres Cured for 28 days
Tabte 9 - Etïects of Acid Type and Concentration on Total Chloride Determination in
Cernent Pastes
Table 10 - Cornparison of Berman and ASTM Methods
Table 1 1 - EtTects of Different Parameters on the Total Chloride Extraction of Cernent
Table 12 - EtTects of Heating Tirne on Sodium Chloride Solution
Table AI - Common Vdues of Cornpound Composition of Portland Cements of Different Tges
Table .42 - Main Types of Portland Cernent
Table B 1 - Tables of Sorne Measured Dota
Table B2 - General Date for Cernent Slabs Cured for 28 Days
Table B3 - General Data for Cernent Spheres Cured for 28 Days
LIST OF FlCURES
Figure 1 - Passivated Steel in Concrete
Figure 1 - Corrosion CeIl in Concrete
Figure 3 - Free Chloride Concentration in Pore Solution as a Function of C3A Content
when Sodium Chloride is added at the Tiie of Mixing
Figure 3 - Effect of C3A Content on the Free Chloride Concentration of Pore Soiution in
Cernent Pastes
Figure 5 - Cernent Sampies are kept in Airtight Plastic Containers to Avoid Carbonation
Figure 6 - Fully Automated Titration Machine (QC-Titratem)
Figure 7 - Acid Extraction and Vacuum Apparatus
Figure 8 - Sample Potentiometric Titration Curve for Chloride in Cured Cernent Faste
Figure 9a - Actuai versus Experimental Chloride Content in Cernent Slabs Cured for 7
Days
Figure 9b - Percent Deviation Using ASïM Method versus Actual Chlonde Content for
Cement SIabs Cured for 7 Days
Figure Ion - Actual versus Experimental Chlonde Content in Cernent Stabs Cured t'or 28
Days
Figure [Ob - Percent Deviation Using ASTM Method versus Actual ChIoride Content for
Cernent SIabs Cured for 28 Days
Figure I 1 a - - Actual versus Experimentai Chloride Content in Cernent Spheres Cured
for 28 days
Figure 1 1 b - Percent Deviation Using ASTM Method versus Actual Chloride Content for
Cernent Spheres Cured for 18 Days
Figure 12a - Amal versus ExperimentaI Chioride Content in Different Cernent SampIes
Figure 1% - Percent Deviation Using ASTM Method versus Actual Chloride Content
Figure 13 - Caiibration Curve: Actual Total Chloride Content versus Totai Chloride
According ro ASTM Method for Cernent SIabs Cured for 7 days
Figure 14 - - Calibtation Curve: Actuai Total Chloride Content versus Totd Chloride
According to MTM Method for Cernent SIabs Cured for 28 days
viii
Figure 15 - Calibration Curve: Actuai Total Chioride Content versus Total Chioride
According to ASTM Method for Cernent Spheres Cured for 28 days (rotated for 24 h)
1.0 INTRODUCTION
1.1 Background
Concrete and steel are. by tàr, the most common raw materials used in construction
today, They sometimes compte but usually complernent each other. Reinforced
concrete is a prime example of such a beneficiai coexistence. Concrete is very strong in
compression but cannot withstand high tensile stresses: as a result, steel bars are
embedded within the concrete to produce a composite rnaterial that exhibits desirable
properties under both compression and tension. In r e m concrete provides a suitable
environment for steel by inhibithg the corrosion of embedded steel bars. This is
accomplished through the maintenance of a medium that is highly aikaline. due to the
presence of hydroxyl ions (OH3. This high alkaiinity encourages steel bars to passivate.
which in tum protects them h m comsion. The pH inside concrete is reported to be
around 13.0 and even higher [l?]. In addition. sound. goodquaiity concrete
significantly lowers the rate of dithion of aggressive ions such as chloride and sulfate
ions to the rnetal surface. thereby further reducing the risk of corrosion.
The abovementioned passive film can be desuoyed either by carbonation through a
lowering of the pH of the pore solution or by ingress of aggressive ions mrch as chloride
ions into the cernent matrix. Once this passive film is destroyed, corrosion of the steel
can occur. leading to the formation of corrosion products - mostly iron oxides - which
rnay expand to occupy h m two to seven times the voIume of the original steel [3]. Such
expansion can produce intemal forces that can lead to cracking and spalling of the
concrete and, subsequently. to the demise of the whole structure since. it is now exposed
to the surmunding environment
The diffusion of aggressive chlonde ions into concrete structures has been the subjcct of
a great deal of research and debate during the past few decades, A search of the j o d s
Cernent and Concrete Research and American Concrete Institute of Materials Journui by
the author revealed that steel reinforcement corrosion by chloride ions has been cited in
about 30% of the articles since the eady 1980's. This trend wiil probably continue on
account of the ever-increasing use of deicing salts on roadways and bridge decks during
winter. especiaily in North America
To understand the problem and the methods of protecting the reinforcing steel from
chloride anack. it is necessary to study the mechanism of chloride ion d i f i i on into the
concrete. This involves determining the diffusion coetlicient of chioride ions into
hydrated cement pastes [4]. Before conducting such a study. one must be able to measuse
the chloride content of hardened cement paste or concrete with accuacy and certainty.
The most widely used method in North America utilizes ASTM Method C 114. section
19-chloride [SI. which in turn is based on Berman's Method [6] . According to this
method. the total chloride ion content of a sarnple is determined by digesting it in 1+I
nitric acid. filtering. and then canying out a potentiometric titration with silver nitrate
using a chloride-selective electrode. However. surprisingly. it is not clear whether such a
method or any other acid extraction method is capable of determining the me or total
chioride content of the sample [q.
Nevertheless. chIoride analysis is criticai wben conducting duability assessrnent of
exisring concrete structures such as bridge decks and marine strucnues [8]. It is aiso
important to be able to determine the cidoride contents of k h concrete and its
constituents for quality control purposes.
12 Objective
The objective of this research projet was to evaluate the accmcy and consistency of the
standard acid e-utraction method - ASTM Method C I 14. Section 19-chionde - to
determine total chioride content of c d cernent paste specimens.
2.0 LITERATURE REMEW
2.1 Portland Cernent
2.1.1 Definition
According to ASTM C 150. Portland Cernent is defined as "hydraulic cernent produced
by pulverizing clinken consisting essentiaily of hydraulic calcium silicates. usually
containing one or more of the f o m of calcium sulfate as an inter p u n d addition" [9].
2.1.2 Manufacturing Process
Portland cernent is produced by grinding and heating a mixture of calcium and silica
called calcining and sintering respectively. in appropriate forms and proportions up to
about 1500 O C in a rotary cernent kiln. which is a long and sIoping cylinder that rotates
slowly to mix its contents as they move through it. Cement kiIns consist of various zones
with ditkrent temperames to facilitate the occurrence of complex chemicai and physicai
reactions that are required to make the consituents rem with each other.'
The above process cm be done either with or without water. the former being called the
"wet process" and the latter the "dry process". About 70% of al1 plants running in the
United States utilize the dry process. while the remaining 30%. mostly older plants. use
the wet process. in which raw materials are mixed under wet conditions.'
2.13 TypesofPortiaadCement
Ordinary Portiand Cernent (OPC) is by far the most common type in use: in the United
States done. more than 83 million tons were produced in 1998 [IO]. in addition.
' Source: www.uvi.ed/San~hysic~SC13~~WeWSmcnirr/ChemO~ement.hml
4
different types of OPC are produced to meet Merent needs. The American Society for
Testing and Materials Iists eight types of cernent in ASTM C 150. A brief description of
each type and its uses is given in Tables 1 '. Al, and A2.
Table 1 - Portland Cernent Types and Their ~ ~ ~ l i c a t i o n s '
Cernent Type Applications
I Generai purpose cernent. no limits are imposed
II Used when moderate sulfate-resistance is required
[II
IV
v
Used when early high-strength is desired
Used when low heat of hydration is required
Used when high sulfate resistance is critical
Sirnilar to type 1 with an air-enuaining agent
Similar to type II with an air-entraining agent
IIIA Similar to type III with an airentraining agent
According to the US Department of Transportation based on data provided by the U.S.
Department of the tnterior'. more than 92% of the Portiand cernent produced in the
United States consists of types 1 and II. while type III accounts for 3.5%. Ordinary
Portland cement complying with ASTM type 1. supplied by Lafarge Canada was used to
'make the specimens in this work.
2.1.1 Chemical Composition of Portland Cernent
.nie right different types of Portland cernent descnkd in the previous section differ h m
one another in their chernical composition. As discussed earlier. the main constituents of
I Source: www.fhwado~gov/in~cturelmaterials~cemen~htmI
5
Portland cernent are lime, silica, al- and ùon oxide. These react with each other in
the cernent kiln to form more complex compounds. The amount of each cornpound
dictates the type and characteristics of the finished Portland cernent product. Four
complex compounds are considemi to be the major constituents of cernent; and are
denoted by the ASTM as tricalcium silicate, dicalcium silicate. tricalcium aluminate. and
tetracalcium alurninoferrite. and comprise 90% of the cernent by weight These
compounds are listed in Table 2. dong with their chernical fonnulae and abbreviated
symbols [IO].
Table 2 - Main Chemical Compounds of Portland Cernent
Name of Cornpound C hemical Formula Ab breviation
Tricalcium silicate 3Ca0.Si02 c3s
Dicalcium silicate 2Ca0.Si02 CIS
Tticalciurn durninate 3CaO.Ai2O3 C3A
Tetracdciurn alunino ferrite 4Ca0.Alz03.Fez03 C+AF
2.15 Cernent Hydration
Anhydrous Portland cement is a gray powder with particle sizes in the range of
1 ro 50 191. M e n it is disperseci in water. ail the rninerds (CjS. C2S. C j k and
C&F) tsact with the water to produce very insoluble precipitates of Calcium Silicate
Hydrates (C-S-H), calcium aluminate hydrates, and calcium sulfoaiuminate hydrate
(called ettringite). The reactions of the silicates are shown below.
In addition to the above compounds, C3A and C2A also produce calcium hydroxide.
Ca(OH)2. which is slightly soluble in water. Calcium hydroxide reacts with srnaII
amounts of sodium and potassium sulfates that are present s in the cement and results in
the tonnation of potassium and sodium hydroxides. both of which are very soluble in
water.
It cm be seen that during the fmt few hours of hydration. the aikalinity of the pore
solution is mainly due to the formation of calcium hydroxide: but as the hydration
progresses. the pH of the pore solution becomes deterrnined more by the production of
sodium and potassium hydroxides.
23 Influence of Chloride Ions on Concrete Corrosion
2.2.1 Sources of Chloride Ions
As mentioned in section 1.1, the high allralinity of the concrete provides embedded
reinforcement steeI with a corrosion-ke environment as long as the passive layer of
7-Fe203 is not disnirbed. However. it is well documented [ i l . 121 that the intrusion of
chloride ions into concrete can destroy this passive film and initiate corrosion. provided
that water and oxygen also are present, as shown in Figures 1 and 2 [4].
- * . . an- . 0"- . "": t 1 -
Figure 1 - Passivated steel in concreteC41 Figure 2 - Corrosion ce11 in Concrete[J]
Chioride ions can be introduced to the concrete either at the time of mixing. by the
addition of calcium chloride as an accelerator. or they may penetrate into the concrete
from outside sources. such as deicing salts used in winter months.
22.2 Binding of Chloride Ions
ChIorides in cement pastes or concrete are found in three forms: bound with the hydration
products. adsorbed to the surface of the hyâration products. or in the k state within the
pore solution. However, it should be noted that ody the tiee chlorides in cernent pastes
or concrete - water-soluble chlorides - c m contnhte to reinforcement corrosion [7. 131
2 2 3 Types of Chloride Boads
It is well known that chlorides. regardiess of their origin. can be bound to the hydrated
products in cernent pastes or concrete [14]. Many cesearches have shown that the binding
capacity of the hydrated cernent dictates the amount of chloride that can be taken out of
the solution: ix.. be bound to the cernent hydration products. In light of this, two types of
bonds have been identified: physical and chernicd bonds [15].
In a chemical bond. chloride ions are incorporated in the Iattice of the crystalline
hydration products and are held together by a chemical bond. Two such chloride-
containing products are calcium monochloroalurninate and calcium trichloroaluminate
[16]. The arnount of chloride ion that can be chemically bound to the hydration products
depends on tictors such as the type and composition of the cernent or concrete. the
presence of other anions and cations. pH orthe pore soIution. and the temperature.
Chloride ions also can be physicaily adsorbeci at the surface of the hydration products. In
general. it appears that such bonds are weaker than the chemical bonds described above.
However. it is not well known how chloride ions are panitioned within these three States.
223.2 Infiueace of Cd on Cbloride Binding
Many workers have commented on the role of C A in binding of chionde ions in cernent
or concrete [2. 15. 14, As mentioued above. the arnount of Cl- that can be bound
depends on the bidiig capacity of the hydrated cernent. This would translate into the
C A content of the cernent: the higher the C3A content, the higher the Cl- binding
capacity .
The reaction of C3A with water is rapid and exothedc. The litteration of a large arnount
of heat has an adverse effect on the concrete in t enu of workability: consequently. it is
important to retard this reaction by some means. This is usually done by adding gypsum
to the concrete mix prior to hydration in order to slow down the reaction [9].
Chlorides in cernent react with calcium aluminates and, to a lesser extent, calcium
alumino femtes. to tom chloroaluminates and c hloro femte hydrates. The main product
king hnned is chIoroaluminate hydrate known as Friedel's salt.
3 CaO.AI2O3 .CaC12. 1 OH@. A similar reaction with tetracalcium alumino femte (C4AF)
resdts in the formation of calcium chioroferrite. ~C~OEQO;.C~CI~. 1 OHtO [l O]. Bakker
[1 51 has reported that calcium oxychloride. CaO.CaClZ2H20. also will be fonned. but
only at high chloride concentrations.
The generd consensus used to be that cements with high CjA content wodd be Iess
prone to chloride attack. Lambert et al [18] reported a noticeable reduction in chloride in
pore solution wïth increasing C3A content, when chioride is added at the time of mixing
(adrnixed chloride). Figure 3 is a graphical representation of the above study.
Figure 3 - Free chloride concentration in pore solution as a tiuiction of C3A content
when sodium chloride is added at the time of mixing [18]
Rasheeduzzafar et ai [2] has aiso noted a decrease in the arnount of fiee chloride ions in
the pore solution with increased C3A content in cernent paste sampies having a water-to-
cernent ratio ot'0.60 (Figure 4).
However. it should be borne in rnind that if sulphate sdts are present in the cernent mix.
CjA will react preferentially with them to produce trisulph0duItIi~te hydrate. The
remaining C3A will then react with chiorides. Sorne researchers [ 10. 161 have argued that
reaction with CjA is the dominant mechanism for the removal of chiorides fiom the pore
solution when chloride is added at the tirne of rnixing. because of the rapidity of the
reaction. In the case of extemal chloride ingress into cernent or concrete. a smaller
amount of chloroaluminate is fomed because Iess C3A is avaiIable.
Figure 4 - EtTect of C3A content on the t'ree chloride concentration of pore solution in cernent pastes [2]
According to Lambert et ai [18] and Delagrave [16]. other factors also contribute to the
removal of chlotide ions h m the mix water. Lambert et ai [18] have reported that
cements with no C3A have exhibited considerable chloride-binding capacity.
DeIpve [161 has reported on the data provided by other researches [3. 191 showing that
chlorides can also react with tricalcium sikate hydrates as well as with dicalcium silicate
hydrates to form insolubte complexes. These will be briefly discussed in the following
section.
23.23 Influence of Calcium Silicate Hydrate on Chloride Biading
Tricalcium aluminate plays a critical role in the binding of free chiondes in mix water to
fonn insoluble complexes, thereby reducing the risk of reinforcement corrosion-
However. other processes also have k e n found to remove kt: chloride ions h m the
mix water. One important mechanism is suggested by Ramachandran [3]. who states that
fiee chloride ions can interact with the C-S-H phase in three ways: they c m penetrate into
the C-S-H interlayer. bind to the hydrated calcium silicate iayen. or be bound in the C-S-H
layer. He has suggested that substantial arnounts of chloride ion. from the addition of
calcium chioride (CaCI?), can be removed h m the mix water via these- three modes.
However. other researchen have disputed Ramchandran's findings [18.20], Through the
application of high sampling technique. Diamond et al have shown that significant
arnounts of free chloride ions are retained in cernent paste sarnples with water-to-cernent
ratios ot'Od0 to 0.50. even aller long penods of hydration [18J. In general. there is a Iack
of understanding of how chloride ions interact with the C-S-H gel in the cernent paste or
concrete. There is also a limited quantitative knowledge regarding the above
mechanism(s) in the literature: therefore, the me effects of tricalcium and dicalcium
silicate hydrates rernain to be detemiined.
232.4 Effects of Associated Cation Type on Chloride Binding
The environmental conditions influence the cMoride binding capacity of cernent pastes
and concrete in different ways. The type and quanùty of sait that may tie present at the
time of mixing or may peuetrate the cernent matrix Vary from one environment to
another. The deicing sait used on roadways and bridge decks during winter months
consists mainly of sodium chloride, dthough other deicing agents such as calcium-
magnesium acetate (CMA) have shown promise [II]. Calcium chlonde has traditionally
been used as an accelerator in concrete structures to hcilitate setting. Buried concrete
structures might come into contact with subterranean water or soil. which contain
different types and quantities of salts. Marine structufes corne into contact with seawater
that is rich in sodium chloride with Iesser quantifies of KT ~a'*. M~'*. and SO/- [ L 71.
Numerous studies have shown that different cations will have different effects on the
chloride binding capacity of cement pastes or concrete. Arya et al [22] found that calcium
chloride will bind more than sodium chloride when added at the time of mixing. when
identical concentrations of both were used [Iq. Regourd [l3] has suggested that
magnesium sulfate (MgSO4) is the rnost harmful salt in seawater in terms of concrete
corrosion. According to him. magnesium chloride (MgCl>) is more active than sodium
chloride: thereby more h m can be expected from the hrmer saIt as far as attacking
cement is concerned.
2.2.2.5 Influence of Sulfates on Chloride Binding
The addition of sulfates to cernent pastes or concrete will lower the binding capacity of
the system. Hussain et ai [Z]. who measured the chioride uptake in cement pastes with
different C3A content and various sodium sulfate (NatSOa) concentrations, observeci that
a hi& sulfate cement bound less d o n d e than a Iow sulfate cernent. This can be
attributed to the preferential reacbon of suIfate with C;A phase. which will inhibit the
formation of Friedel's salt. Consequently, this wilI increase the concentration of chloride
ions in the pore solution.
In addition. both Hussain et J [23] and Hotden et J [24] have reported an increase in the
pH of the pore solution when sulphate ions were present at the tirne of mixing. An
increase in pH can be explained in terrns of charge neutrality. Hydroxyl ions (OH') will
enter the pore solution to balance the anions rernoved in the forrn of insoluble salt
complexes: this will result in an increase in the pH of the pore solution and.
consequcntly. will have an adverse effect on the chlotide binding [17].
23 Analysis of Cbloride Content in Cured Cernent Pastes
2.3.1 Background
Portland cernent concrete is one of the most versatile and widely used materials in the
constniction industry [9]. Its low cost. abundance. and ease of manufacture has made it
a pert'sct candidate for construction of buildings. pavements, dams. and bridge decks.
amongst others. The use of cementitious materials is very old. dating back to ancient
Egypt [IO]. The demand for concrete has been steadily increasing during the past 100
uears. and this trend will most Iikely continue in the future. However. the chloride-
induced corrosion of reinforcing steel ernbedded in concrete has become the subject of a
great deal of concern and research in the pst few decades. Whether it is a coastai
structure in the Middle East or a highway bridge deck in Canada the main mechanism of
tàilure has most ofien been damage related to reinforcement corrosion caused by the
ingress of chloride ions through the cernent rnatrix to the reinforcing steel [17].
Considerable effort has been devoted to solving this problem. and has created a great
need for developing an accurate and reliable meîhod to determine the chioride content of
hardened cement paste or concrete 1251.
Some anaiytical methods were in use about four decades ago. but there existed some
doubts in regard to their accuracy and precision; in addition, these older methods were
very time-consuming and labour extensive. In 1972. H. A. Berman [6] proposed a
method to determine the chloride content of hardened cernent pastes and concrete. that
cvcntually was adopted by the United States Feded Highwy Administration with some
modifications in 1974. and again in 1977 [251. A S W Method C 1 14. Section 19-
chloride is also based on the above method. with sorne minor moditications.
233 Anabsis of Cernent Pastes and Concrete for Chloride
As discussed earlier. chloride in cernent paste or concrete c m be found in two toms.
water-soluble and water-insoluble chioride. [n addition. water-insoluble or bound
chlorides are further divided into two sub-groups: chemically bound with the hydration
products and physically adsorbed to the calcium silicate hydrates (C-S-H) surface. It is
well established that onIy fixe chiorides can participate in corrosion: therefore. it would
seem logicai that only the amount of free chloride in concrete should be determined,
since onlv these chlorides can conrniute [O reinforcement corrosion. The U.S. Federal
Highway Administration laboratories have reported that 75 CO 80 percent of the total
chloride present in cured concrete is in the fonn of water-soluble chloride [26].
Consequently, nvo methods of chloride ion determination have k e n developed: free
chloride content and water-soluble chloride content.
Up to now. the most accurate method of determining the free chloride content in cernent
pastes or concrete has been the pore solution expression technique in which pore fluid in
the cernent paste or concrete is squeezed out under hi& pressure (300100 MPa) and then
analyzed for chioride content. The second method which determines water-soluble
chloride. involves dissolving or leaching out the fiee chloride in the pore solution.
Standard test methods for the determination of both types of chlonde exist [22].
However. it is recopized that the amount of chioride ions released into the solution
based of the latter method depends on severai factoa. süch as the amount of water added.
the duration of the extraction. the temperature of the system. and the methoci of agitation
[37.28]. tn addition although there are severai leaching techniques in use. none of thern
has produced accurate resuits over the range of chioride additions that was investigated
[271. Furthemore. it is known chat such methods will overestimate the Free chloride
content when applied to concrete exposed to e x t e d chloride such as deicing sdt [Y. 271.
With regard to pore solution expression. it has been found that it is more inaccurate when
appIied to concrete than when applied to cernent pastes [29]. Finally. when coxrete
specimens are dry. it becomes very dficult to obtain enough pare solution to c a q out
the experirnentd work [271.
in view of the above difficuities, it has becorne increasingiy cornmon practice to
determine the totd chioride content of cernent pastes or concrete in order to mess the
need for maintenance of existing concrete structures exposed to salt. and to insure that
new structures do not contain h a d LeveIs of chioride ions. ASTM Method C 114,
Sectionl9-chloride, recommends an acid digestion method in which the total chloride
contents of cernent pastes or concrete are measured.
3.0 EXPERlMENTAL DESCRIPTION
3.1 Overview
The experimental program consisteci of two phases:
Phase 1 - sample preparation
Phase II - determination of the chioride content of each specimen
Phase 1 involved the preparation of hÿo sets of samples: cement spheres (30 mm in
diameter) and cement slabs ( 3 7 x 3 7 ~ 7 mm). The cernent spheres were prepared in such a
manner as to minimize segregation by slowly rotating thern (2 revolutions per minute) for
34 hours after casting.
Phase 11 included analysis of al1 the specimens containine different amounts of chloride.
utilizïng either Berman's Method [6] or ASTM Method C I 1 4 Section 19-chloride [j].
A great deai of effort went into analyzing the samples and interpreting the results. The
objective of this phase was to determine the accuracy and precision of the above
methods. particularly the latter.
3.2 Materials and Specimens
3.2.1 Materials
The raw materials were obmined at the start of the program and were used throughout the
course of the work. The ordinaq Portland cernent (OPC) was supplied by Lafarge
Canada ( meeting ASTM Type 1 specifications)- The chernical composition of the above
material is shown in Table 3.
Analyticd reagent grade sodium chloride (NaCl, 99.9%) and silver nitrate (AgNO3.
mrets A.C.S. specifications) and deionized water ( 4 0 MSLm) were used to prepare
aqueous solutions for testing and to add to the mix water to prepare cernent samples.
Sodium chloride was dried at LOS O C for 24 hours prior to making solutions.
Table 3 - Chernical composition of Portland cement Type 1 (suppiied by Lafarge Canada)
Comwnent Weieht ( O h )
Compound Composition C S (tricalcium silicate) CLS (dicalcium silicate) C:A (tricalcium aluminate) CaA F (tetracalcium aluminot'emte)
3 2 2 Preparation of Cement Samples
For a pure OPC sampIe. 10 g of PortIand cernent was mixed with 4.5 g of deionized
water. to create a sample with a water-to-cernent ratio of 0.45. The cernent paste was
mixed thoroughly to produce a uniform sample, and then placed h i d e plastic molds.
Three sets of cement pastes were prepared:
1. The tint set was cast in plastic rnolds (37x37~7 mm) with the tnix water
containing chlorides at each of the concentrations given in Table 5 (page 30).
This set was used to evaluate the influence of the chioride concentration and
curing time in the determination of the fiee chloride content. A11 the samples
were cured in a hydrostat (100% relative humidity) for seven days at room
temperature (about 22 O C ) .
2. The second set was prepared in the same manner as the above set but they was
cured for 28 days.
3. The third set consisted of a senes of cernent pastes identical to the previous set
but was cast in 30 mm diameter plastic molds and rotated at about 3 rpm for 14
hours to minimize segregation. This series was used to evaiuate the influence
of rotation in the determination of the free chlonde content in addition to the
goals stated above.
The cernent sarnples were dried at 105 O C for 24 hours and were weighed to the nearest
0.001 g using a - Acculab VI mode1 - balance. The sarnples were cnished in an
enclosed metal box using a hammer and then were finely ground using a mortar and
pstle. Al1 powder cernent samples were stored in airtight plastic containers to avoid
carbonation (Figure 5 on page 23).
3 3 3 Equipment
The potentiometric titrations were performed using a computer-controlled burette -
Burivar 12, model MS-9A9 - with an Orion silver/sulfide combination electrode -
model 90-06. The accuracy of the instrument is + 0.01 mV and has an automatic
temperature compensation probe (Figwe 6 on page 23).
33 Experimental Procedures
33.1 Basis of the method
ASTM Method C 114. Section 19-chlotide involves the extraction of chloride ions
through an acid digestion process from c m d cement pastes or concrete. The total
chloride content of the sample is determined fiom analyzing the obtained aqueous
solution and is cxpressed as a percentage by weight of the dry sample: Le., cement or
concrete. This is based on the assumption that al1 chloride complexes (mainly
chloroalurninates) present in the sample wilI decompose upon the addition of nitric acid
and readily will come into the solution as k e chloride ions.
33.2 Description of the method
The method used for the determination of the total chloride contents of various ground
powders was similar to that outIined in ASTM Method Cl 14. Section 19-chloride. A
bnef description of this method is provided here. as weH as a comparison of the above
-
Figure 5 - Cernent samples kept in airtight plastic containers to avoid carbonation
Figure 6 - Fully Automateci Titration Apparatus (QC-Titrate?
method with its predecessor. Berman's method (Table 4). Complete descriptions of the
above methods have been given elsewhere [5,6].
After adequate grindimg, the samples were first dried at 105 OC to constant mass and
allowed to cool in a desiccator. They were then sieved through a 3 1 5-micron sieve and
only material passing the sieve was kept for analysis. Five grams of sample was placed
in a 250 mL beaker and dispersed with 75 mL of deionized water.' Twenty-five
milliliten of dilute (I+I) nitric acid was immediately and slowly poured into the beaker
and the solution was stirred with a glass-stining rod to break up any lumps. Three
milliliters of hydrogen peroxide (30% solution) then was added to the mixture if the smell
of hydrogen sulfide was strong. The beaker was covered with a watch glass and allowed
to stand for 1 to 2 minutes. after which it was placed on a preheated hot plate and brou@
just to a boil. The covered sample then was removed from the hot plate and was allowed
to cool until it was saîè to handle for filtering,
A 500-mL Büchner funne1 and fiItration Rask was used to tilter the solution: vacuum was
applied to facilitate the filtration (Figure 7). The filtering procedure was as follows:
Ali the glassware was rinsed with deionized water prior to filtration.
A 9-cm coarse filter paper was placed inside the h e l and was washed with four
25-mL doses of deionized water.
The washings were discarded and the flask was rinsed with a srnail portion of
deionized water.
I ASTM CI 14 requires 5 g samples for marerials having an expected chloride content of l e s than about 0.15% chloride and propomonally smaller samples for materials having higher chloride contents.
Table 4 - A cornparison of ASTM Method C 1 14 and Berman's Method for total chloride analysis
1 to 3 gram samples.
Add 10 mL distilled water and stir.
Add 3 mL o f concenaated HN03 and air.
Dilute with hot water to 50 mL.
If necessary. add more acid:
Methy l oranse indicator -. red solution
Heat the solution at medium heat and boil for ont
minute (to avoid losing volatile chlorine).
Filter into a 150-mL beaker. Use double filterç:
medium and hi& pomsity.
Decant the clear solution and wrtsh
the tilter paper with hot distilled water 5 to 10 tirnes
and allow the tiltrate to cool to room tempefanue.
Titrate potentiomemcally with
0.0 i M or 0.025 M AgN03 solution.
10. %CI is calculated using:
V: Volume o f AgNO; added
M: Moralin o f AgNO: solution
W: Weight o f the sarnple (3)
ASTM Method C 114 -Seetion 19. chloride (1997)
5g cement or log concrete.
Add 75 mL water.
Add 75 mL o f dilute (Itl) HNOl and stir.
If can srnet1 H2S. add 3 ml H a .
Add 3 dmps o f methyl orange indicator and stir. Covcr the
beaker and allow to stand for 1 to 2 minutes. If solution
turns yellow or yellow-orange, add more ( l+ 1) acid until
solution is faint pink or red. Then add 10 more drops.
Heat the solution rapidly. while covered to boiling. Do mot
boil for more than few seconds.
Wash a corne-textured tilter four times with 25-mL
increments o f watcr into a flask under suction.
Wash the tlask and filter the sample solution. Rinse the
beaker and the filter paper twice with small ponions of
water. Transfer the f i l m e to a 150-mL beaker and rime the
flask once with water. Cool the filmte to roorn temprnrurr
The volume should not exceed 175 mL. To the cooIed
sample add 1.00 mL o f standard 0.05 M NaCI.
Titrate potentiometrically with 0.05 M AgN03 solution.
IO. Use the formula k l o w to calculate %CI:
V,: Volume o f AgNOl used for sample titrarion V?; Volume o f AgN03 used for blank litration* M: Morality o f AgNO3 solution W: Wcight o f the sample (g) 0.10: milliequivalents o f NaCl added
(O2mL x 0.05 N)
* refer to ASTM C I 14 for biank prepmion [SI.
Figure 7 - Acid Extraction and Vacuum Apparatus
0 The suction apparatus was assembleci and the solution was filtered under vacuum.
Once the solution went through, the residue was rinsed twice with small portions
of distilled water.
0 The tiltrate was poured back into the original beaker and the flask was rinsed hto
the beaker. The final volume was 160-180 mi..
a The beaker was covered with a watch glas and was placed in a 25 OC water bath
to cool.
Two milliliters of standard 0.0500 M NaCl solution was added CO the cooled sample.
which then was titrated potentiometrically with standardized 0.0500 M silver nitrate
iA2NOI) solution using the automaleci titracor. QC-Titratorr\'. The titration set un is
shown in Figure 7 and a sample titration cuve is presented in Figure 8. The end point of
the titration was reached when the change in mV pet volume of titrant added was at the
ma~imum.
It should be noted that two standard samples containing 0.0500 M chloride solutions were
used to calibrate the instrument every time rneasurements were taken.
PC-TitratlON PLUS
Sample Name ~aport D a k W û 3 2 ~ 1 7:18 PM Operator: A
GO.OS-SL28-2 Sample Number: 3926 Run Number 223
Equation Name Equation ResuR Un&
C 1 vel lcon~5.453'1000/svol 40.6048 ppm
prcnt (vel'tcon35.453'100)1(1000'swght) 0.0001 %CI
eP vel 4.00W mL
svol 5voI
tmn tcon
175.0000 mL Figure 8 - Sample Potentiometric
0.0500 Titration Curve and Output Data
4.0 RESULTS AND DISCUSSION
1.1 Evaporable Water in Hydrated Cernent Pastes
Water can be found in two foms in hydrated cernent pastes: evaporable water in the pore
solution and non-evaporable water as part of the hydrated cement products.
Hardened cement spheres were dned in an oven at IO5 "C for 24 hours after a 28-day
cure to determine their evaporable water content. It was found that evaporable water
comprised about 17% of the total mass of the specimens. Therrnogravimemc analysis is
required to detennine the percent of non-evaporable water of the cured cement samples
through loss on ignition. in which samples are heated at a rate of 35 OC per minute up to a
temperature of 1000 "C [30]. i-iowever. this was beyond the scope of this thesis. The
results are summarized in Table 5.
4.2 Total Chloride Determination
There is no doubt that the corrosion of reinforcing steel bars embedded in concrete
structures such as bridges. pavements. and marine structures has become a costly problem
in North Amerka. To address this. much work has been done throughout the wodd to
find solutions to prevent concrete deterioration in new structures and to mitigate the
problem in existing ones. The high performance concretes currently k ing recommended
for structures in which the presence of chloride is expected are characterized by low
permeability and diffisivity. The fim step to rneaswe the permeability and diffiisivity of
such concrete systerns is to determine their chioride dimision coefficients. To do this
successfully. a fast and reliabte rnethod is needed to determine the total chloride content
Table 5 - Evaporable Water in Cured Cernent Spheres
Set NaCl in Rotation Curing Weight (g) mixiraccr Tirne P d Before Afier A h After % Evaporablr ?/o Loss due
[Ml (hour) (day) Curing Drying Crushing Powderdrying water to cmhing
of the specirnens. Berman's method has traditionaily been used to do this: more recentiy.
ASTM has introduced a procedure for the detemination of the total chloride content of
cernent pastes and concrete which is based on Berman's method, with few rninor
modifications ( t ek to Table 4). Bot. rnethods chirn to achieve cornplete extraction of
chlorides h m cernent pastes and concrete to an accuracy of 0.5 percent of the arnount
present in the original sample [6].
A series o f cernent samples was prepared and chIoride ions were introduced into the mix
by dissolving known quantities of NaCl in the mix water. After pteparing the samples
according to the procedure outlined in section 3-22, their totai chloride contents were
determineci usine ASTM Method C 114. Section 19-chloride. as described in section
3.3.2. The results are presented in Tables 6 through 8.
4.2.1 Determinaiion of Total Chloride Content o f Cernent Specimens Cured for 7
and 28 Days
The tirst set of samples consisteci of 14 cernent slabs ( 3 7 x 2 7 ~ 7 mm) containing different
arnounts of chloride. ranging fnim 0.00 to 5-00 M. added at the time of mixing into the
mix water as NaCI. Afier wet curing in a 100% relative hurnidity container for 7 days.
total chloride contents were determined following the standard method de~cnbed in
section 3.3.2. The results are presented graphically in Figures 9a and 9b and nurnerically
in Table 6.
From Figure 9a. it is apparent that cornplete extraction of chlorides From the cernent
pastes was not achieved, The first trend that c m be seen is a _mdud reduction in the
percentage of r'ctracted chloride as the chloride content of the sarnple increases. The
tiltered extracts contained ody 4l to 97 percent of the total chloride; this signifies a
chloride loss of more than 55% at the highest concentration of 5 M NaCl. or 8% chloride
by weight of dry cernent. [t c m be hypothesized that an incomplete decornposition of
chloride-complexes such as chIoroaIuminate hydrates (Friedel's salt) has led to such
deviations from actuai vdues: this will be discussed in more detail in the fol~owing
sections. The second mnd (Figure 9b) is a very sharp increase in the rate of chloride loss
at iower concentrations, which is benveen 0.006 to 0.012 g CYg dry cernent. rhere is no
obvious explmation for this trend but it may be due to the formation of complexes that
-*-Adual Values
Slabs - 7 days
Figure 9a - Actual versus Experirnental Chloride Content in Cernent Slabs cured for 7 days
0.00 0.01 0.02 0.03 0.U 0.05 0.06 0.07 0.08 0.09
Actual Chloride Content {g Cri g dry cernent)
Figure 9b- Percent Deviation Ushg ASTM Method versus ActuaI Chioride Content for
Cernent Slabs Cured for 7 days (Error bars represent 1 standard deviation)
Table 6 - Total Chloride Content of Hardened Cernent Slabs Cured for 7 Days
Sam pie NaCl Chlofide Content (g) Name Concentraion (M) Acîuai Experïrnenîal %Deviation Avg. %Deviation %Chloride
NO.OO-SL07-1 NO.OOSL07-2 NO.OOSL07-3
F0.02-SLO7-1 F0.02-SLO7-2 F0.02-SLO7-3
G0.05SL07-1 GO.05-SLO7-2 G0.05SL07-3
H0.10-SL07-1 HO. 1 O-SL07-2 HO. 1 O-SLO7-3
10.20-SL07-1 10.20-SL07-2 t0.20-SLO7-3
J0.30-SLOf -1 J0.30-SL07-2 J0.30-SL07-3
K0.40-SL07-1 K0.40-SLO7-2 K0.40-SL07-3
LO.50-SL07-1 LO.50-SL07-2 LO.50-SLO7-3
M0.70-SL07-1 MO. 70-SL07-2 M0.70-SLO7-3
Al .00-SL07-1 Al .00-SL07-2 Al .00-SL07-3
62.00-SL07-1 82.00-SL07-2 82.00-SLO7-3
C3.00-SL07-1 C3.00-SL07-2 C3.OOSLO7-3
04.00SLO7-1 04.00-SLO7-2 04.00-SL07-3
€5.00-SL07-1 E5.00-SLO7-2 ES.W-SL07-3
O 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09
Actual Chloride Content (g CI 1 g dry cernent)
Figure I Oa - Actual versus Experimental Chtoride Content in Cernent Slabs Cured for 18 Days
slabs - 28 days
1
4.0 6 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09
Actual Chloride Content (g Cïlg cernent)
Figure IOb - Penient Deviation Using ASTM Method versus Actual Chloride Content for Cernent
Slabs Cured for 28 Days
Table 7 - Total Chloride Content of Hardened Cernent Slabs Cured for 28 Days
Sampie NaCl WMde Content (g) Name Concentraian [MI Achat Enierimental %Deviaion Ava. %Deviation %Chloride
N0.00.SL28-1 NO.OO-SL28-2 NO.OO-SL28-3
FO.02-SL20-1 FO.02-SL28-2 FO.02-SL28-3
G0.05SL28-1 G0.05-SL28-2 G0.05SL28-3
HO.lO-SL28-1 HO. 10-sua-2 HO. 10-SL28-3
10.20-SU81 10.20-sL28-2 10.20-SL07-3
J0.30-SU81 J0.30-SL28-2 J0.30-SL28-3
K0.40-SL28-1 K0.40-SL28-2 K0.40-SL28-3
LO.50-SL28- 1 L0.50-SL28-2 L0.50-SL28-3
M0.70-SL28-1 M0.70-SUC2 M0.70-SL28-3
A l .MISL28-1 A l .o@SL28-2 A l .00-SL28-3
B2.00-SL28-1 BZOO-SU82 B2.MISL28-3
C3.00-SL2&1 c3.00-SL28-2 c3.00-sL28-3
D4.00-sua-1 D4.00-sua2 D4.00-SL28-3
E5.OO-SL28-1 E5.MISL28-2 ES.OOSL28-3
are v e l hard to decompose, even with nitric acid, when the chloride concentration is
low. but more readily decornposable when chloride ions are abundant within the cernent
mauix.
The second series of tests was conducted on cernent slabs similar to the first series but
cured for 28 days, Figures 10a and lob and Table 7. respectively. present the -mphical
and numerical data for these slabs. The trends are similar to those observed for 74.
curing timss.
Figures 12a and 1Zb show the intluence of curing time on chloride extraction and
recovep fiom spheres cured for 28 days. It can be seen that. as in the case of slabs. as the
curing period increases. the percent chloride recovery decreases.
4.23 Influence of Curiag Time on Total Chloride Determination
Figures 9a and 10a show the percent deviation of the total chloride using the ASTM
method versus the actual chloride content for the above-mentioned series. As mentioned
above. the percent chloride extraction decreases as the actuai chloride content increases.
The test results were very similar for both curing times at lower chloride contents (up to
0.036 g Cl ! g dry cernent). but started to deviate from each other when the chioride
content increased to 0.044 g Cl 1 g dry cernent and beyond. Acid extraction of cernent
specimrns cured for 7 days were recovered 44 to 97 percent of the actuai chloride. while
those that were cured for 28 days only recovered 29 to 94 percent of the actuai chioride
added at the time of mixing. This signifies a chloride l o s of about 71% at the highest
chloride content of 0.403 g CI 1 g dry cernent. while the corresponding figure for the
7day cured samples is about 56%. This m be attributed to the reaction of k e chloride
ions in the pore solution with the cement hydration pmducts. particularly tncalcium
aluminate. to form chlorocomplexes such as Friedel's sait. It is generally accepted that
concrete or cernent continues to cure well after hydration kgins and may take years to
cornplete. Therefore. it is possible that the above reactions continue to occur atier 7 days.
consequently immobilizing more chioride ions h m the pore solution. If the acid
extraction is not successtùl in recovering al1 the chtonde ions. a p a t e r error will be
associated with the cernent samples that were cured for a longer period; i.e. 28 days.
4.23 Influence o f Rotation on Total Chloride Determination
The third set consisted of a series of cernent pastes identical to the second set but cast in
30 mm diameter plastic molds and rotated at about 2 rpm for 24 hours to minimize
segregation. This series was used to evaluate the intluence of rotation on the
determination of the total chloride content. in addition ro assessing the accuracy and
precision of .ASTM Method C 1 14. Section 19-chIoride.
.A cornparison of the results obtained for this set of samples with those of the previous
sets - cernent slabs cured for 7 and 28 days - indicates similatities in terms of
extracted chloride over the whoIe range of chloride content of 0.0 to 8.0%.
O 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09
A-1 Chknd. Content (g CI 1 g dry cernent)
Figure I l a - .4ctual versus hperimental Chloride Content in Cernent Spheres Cured for 28 Days
0.00 0.01 0.02 0.03 0.M 0.05 0.M 0.07 0.08 0.M Acanl Chloride Content (g CI 1 g dry cement)
Figure I I b - Percent Deviation Using ASTM Method versus Actual Chlonde Content for Cernent
Spheres Cured For 28 Days
Table 8 - Total Chloride Content of Hardeneci Cernent Spheres Cured for 28 Days
NO.00-SP28-1 N0.00-SF'28-2 NO.OMP28-3
F0.02-SP28- 1 FO.02-SP28-2 FO.02-SP28-3
G0.05SP28-1 G0.05-SP28-2 G0.05-SP28-3
Ho.10-SP28-1 Ho. 10-SF'28-2 HO. 10-SPZ8-3
10.20-SP28-1 10.20-SP28-2 10.20-SP28-3
J0.30-SP28-1 J0.30-SP2ô-2 J0.30-SP28-3
K0.40-SP28-1 K0.40-SP28-2 KO.GSP28-3
LO.50-SP28-1 L0.50-SP28-2 LO.50-SP28-3
M0.70-SLO7-1 M0.70-SLO7-2 M0.70-SLO7-3
A1.OO-SL07-1 Al .00SLO7-2 A1 .OGSL07-3
02.004 ~ 0 7 - 1 B2.00-SLO7-2 82.00-SL07-3
C3.00-SLO7-1 (3.00-SLO7-2 C3.00-SL07-3
04.00SL07-1 04.00-SL07-2 û4.00-SL07-3
E5.WL07-1 E5.00SL07-2 E5.OITSL07-3
Acid extraction of cement spheres cured for 28 days recovered 34 to 96 percent of the
total chloride that was added to the rnix at the tirne of mixing.
The agreement found between results obtained for this series and the previous two series
indicates the inability of ASTM Method C 114, Section 19-chloride to extract al1 the
chloride from hardened cernent samples. The decomposition in niuic acid is the most
widely used rnethod for chloride extraction for several reasons: it is very fast compared
with other methods. the procedure is very simple to follow. it is economical. and it has
been claimed to be very accurate and precise [6]. The main objective of this part of the
study was to examine this l a s claim. which the results have show to be invalid.
The results presented in Figures 12a and 12b and in Tables 7 and 8 show that the amount
of acid-soluble chloride extracted fiom cernent samples rotated h r 24 hour exceeds the
arnount of acid-soluble chloride extracted h m cernent samples that have not k e n
rotated. This cm be clearIy seen especially in sarnples with chloride contents greater than
about 1 .O%. There is no obvious explanation for this trend. but the results ernphasize the
complexity of the hydration and chioroaIuminate and other chloro-complex formation
mechanisms within the cernent rnatrix. The fact that the amount of acid-soluble chlorides
increases when cernent specirnens are mtated tends to emphosize the significance of the
pore structure of the cernent matrix. which controls the accessibility of chioride ions to
the reaction sites. If the marked reduction of acid-sduble chloride is due to insoluble
chloro-complex rormation, then by rotating the specirnens. chioride ions are restricted in
their movements since pore structures are formed differently than when the specirnens are
not rotated. When cernent samples are not rotated, segregation will occur. in which
mixture components separate and different phases wiII be formed within the cernent
matrix. As a result, pore structure geornetry will be affecteci and larger pores and
capillary voids tend to be formed. Chloride ions. in tum. will have more access to
reaction sites and. thecefore. cm be bound more easily and freely to the cement hydration
products. Furthemore, the above results show that chloride binding capacity and other
important characteristics of the cement are not soleIy based on cernent composition but
also can be affected by other factors, such as the pore structure of the cernent.
Segrcgation is defined "as separation of the constituents of a heterogeneous mixture so
that their distribution is no longer uniforrn". in wet cernent. this is rnanifested by the
separation of grout (cernent and water) h m the mix [IO]. This will directly influence the
formation of pore structures within the cernent matrix and. consequently. will affect other
cernent characteristics, such as pore solution chemistry.
-*-Actual Chloride Content- -*Cement slabs, aired for 7 days, not rotated
O 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09
ActuaI Chloride Content (g CI 1 g dry cernent)
Figure 13a - Actual versus Expen'rnental Chioride Content in different Cernent Sarnples
+ Cement siabs. cured for 7 days. n u faakd
8 Cernent shbs. curad for 28 days. n u rUatecl
Cement spheres. cured far 28 W. mrated for 24
0.0 0.M 0.01 0.02 0.03 0.01 0.05 0.08 0.07 0.M 0.09
k tua l Chloride Content (g CI 1 g dry cernent)
Figure 1 Zb - Percent Deviation Using ASTM Method versus Actual Chloride Content
Total Chloride According to ASTM Method for Cernent Spheres
42.4 Critical Analysis of the Data
The fact that the total quantity of chloride was not extracted in al1 the above experiments,
even at the lowest chioride content of 0.006 g Cl 1 g dry cernent. shows the inability of
ASTM Method Cl 14, Section 19-chloride to bring al1 the chlorides into solution for
analysis. Three graphs (Figures 13 -15) have been constmcted based on the results
obtained in the previous sections. These graphs can be used as caiibration curves when
the actual total chloride content in a cured sample of Type 1 OPC is not known. The
ASTM Method is relatively accurate when the chloride ievel is low: Le.. less than 0.02 g
CI / g cernent. However. the results deviate from actual levels when chloride levels start
to rise beyond 0.02 g Cl'/g cement.
tt is worth noting that the above rnethod or any other chloride extraction method.
consists of two distinct parts: complete extraction of chlorides fiom the sample and
accurate determination of the total quantity of the extracted chloride. The latter step is
usually pert'ormed with an autornated titrator. as in this research project. or a pH meter
and an appropriate chloride ion-selective electrode. It is the former step that requires an
understanding of the complexity of the problem. According to Berman [6], Lolivier [3 11
and Koelbel et al [32] both reported low results (low chloride extraction) even aller
several hours of heating with 1+8 and 1+4 iiN03. respectively. when using a method
similar to ASTM C IM. This has been mainiy attributed to the Iow concentrations of
HN03 used to digest the cernent samples. although several factors can be responsible for
this. The iniluences of a number of such factors have k e n investigated and the results
are presented in the following sections.
0.000 0.005 0.010 0.015 0.020 0.025 0.OM 0.035 0.010
Total Chloride Content Based on ASTM Method (g CI 1 g dry cernent)
Figure 13 - Calibration Curve: Actual Total Chioride Content versus Total Chloride Accordhg to ASTM Method for Cernent Slabs Cureci for 7 Days
0.000 0.005 0.010 0.0 15 0.020 0.025
Total Chloride Content Bosed on ASTM Method (g Cl / g dry cernent)
Figure 14 - Cdibration Curve: Actual Total Chioride Content versus Totd Chloride According to ASTM Method for Cernent SIabs Cured for 28 Days
0.000 0.005 0.010 0.015 0.020 0.025 0.030
Total Chloride Content Ba& on ASTM Method (g CI 1 g dry cernent)
Figure 15 - Calibration Curve: Actuai Total ChIoride Content versus Total Chloride
According to ASTM Method for Cernent Spheres Rotated for 24 h and Cured for 28 Days
42.5 The Influence o f Acid Concentration on Total Chloride Detemination
A series of tests was conducted on identical cernent samples containing known amounts
of chloride (added to the mix water) folIowing Berman's method. Al1 the parameters
were kept constant. but the type and quantity of the acid used for digestion were varied to
evaluate their intluence on the total chloride determination.
Table 9 presents the results of the above test perfomed on samples containing 1.1%
chloride ions (0.01 1 g Cïlg sample). Complete chloride recovery fiom the above
samples was not achieved by doubling, or even. tripling the amount of ni& acid.
Similar results were obtained when nimc acid was replaced by suifùric acid. It is
concluded that the specitied amount of acid required by the method is suficient. and that
the addition of more acid will not bring more chlorides into the solution.
Table 9 - Effects of Acid Type and Concentration on Total Chloride Determination in Cement Pastes
Sample Sample Weight Nitric Acid Sulfuric Acid Digestion tirne* Unrecovered Chloride Number (g) ( m u (mu (min) (%)
3716 1 .OO** 0.04 5717 1 .OO** 0.09
3 733 1 .O0 3 .O0 10 28.86
5734 1 .O0 3 .O0 1 O 28.57 * Digestion time refea to the t h e that the sample was digested by the acid before heating. ** These m p l e s consisteci of 1.00 mL of 0.70 M NaCl in water (no cernent) and were used as references.
4.2.6 Cornparison of Berman's Method with the ASTM Method Cl14
Many workers have attributed low chloride determinations to the incomplete recovery of
chlorides fiom hardened cement paste and concrete or chloride loss through chlorine
volatilization upon heating the mixture [6, 8, 3 1. 321. A series of experiments was
pertbrmed on identical tiardened cement pastes with a known quantity of chioride to
evaluate the influence of severai factors involved in the chloride extraction process.
Cement spheres. 30 mm in diameter. containing 0.3 1% chloride ions were cast according
to the method outiined in section 3 . 2 2 The spheres were rotated for 24 hours at about 2
rpm and then were cured for 27 days in a hydrostat, AAer drying in an oven at 105 O C for
24 hours. their total acid-soluble chloride contents were detennined as described by
ASTM C 1 14. Section 19-chloride and Berman with several modifications.
The acid-soluble content of the first series of sarnples was determined according to the
above methods: i.e. ASTM Method C 114. Section 19-chloride and Berman's method.
without any modifications, The chloride content measured through these methods served
nvo purposes: to compare the two methods in terms of their accuracy and precision, and
also to serve as a guide and reference for future studies. The Results of the chloride
analyses perhrmed on these sarnptes are shown in Table 10. A good agreement was
observed between the results obtained with both techniques. The average amount of
unrecovered or lost chloride was found to be 15.2% and 15.3% for the Berman and the
ASTM C 144 methods. ~spectively.
Table 10 - Comparison of Berman and ASTM Metfiods
Sample Method Digestion Filtered Convered Heated Unrecovered Standard Number Time (min.) Chloride (%) Deviation
64 Benrian - 3 Yes Yes Yes 15.09 65 Bennan 2 Yes Yes Yes 14.39 84 Benrian - 7 Yes Yes Yes 16.01 0.8 1
Average 15.16
66 ASTM 2 Yeç Yes Y s 15.18 67 ASTM - 3 Yes Yes Y s 15.12 85 ASTM 2 Yes Y a Y= 15-58 0.25 Average 15.29
1.2.7 Effixts of Heatiag, Digestion Time, and Sample Covering
As mentioned above. if the container is not properly covered, volatile chlorine can be lost
when the mixture is heated. The next set of experiments was designed to investigate the
influence of heating. digestion time. and proper cover on total chloride recovery.
The results tiom this part of the study are surnrnarized in TabIe I I . It can be seen that
digestion time has Iittle effect on the total chloride extraction. provided the mixture is
digested for at least two hours. Ln addition. a cornparison of the above results with those
presented in Table 10 shows that if the mixtures are allowed to digest for at least two
hours. the influence of heating wiil be minimal.
Some workers have claimed that the elimination of the filtration step in the total chIoride
extraction wilI not significantly affect the outcorne [8]. The elimination of this step is
desirable for several reasons. First. it simplifies the procedure. since filtering requires not
only extra time but a h extra care to perform. Second. it reduces the risk of producing
Table 1 1 - Effects of Different Parameters on the Total Chloride Extraction o f Cernent Pastes
Sample Methcd Digestion Filtered Covered Heated Unrecovwed Nurnber T h e Chlori& (%)
ASTM 2 days Yes ASTM Z ~ Y S _ Yes
, , - 7 .
- - .,.+ :-
h a n 2 d a ~ Yes Berman 2 days Yes
Berman 2 hours Yes Berman 2 hours Y s
GSTM i h w r s Yes ASTM l h m Yes
Bennan 1 hours No &man 2 hotus No
ASTM 2 hours No ASTM 2 hours No
&man* 2 min Yes Berman* 3 min Yes
ASTM* 1 min Yes ASTM* 1 min Yes
Yes Y s
Yes Ys
Y s Y e
Yes Yes
Y 6 Yes
Y 6 Yes
Y s Y s
Yes Yes
No No
, - -
No No
No No
No No
Y s Ys
Yes Y s
Yes Yes
Yes Yes
A- -Y= Is.64 * ReBus used to colIect any condensate that may have formai.
erroneous results by insuflicient washing of precipitates or incomplete filtration OP the
mixture [a]. However. it is important to remember that the soiid residue present in the
digested concrete mixture cm affect the outcome of the titration; i.e.. the end point
determination. It has been suggested that the solid matter can affect the ionic activity in
solution by ionic adsorption [8]. However. the titration cm proceed if the solution
contains only a srna11 amount of solid residue- [SI.
A series of tests was conducted to determine the effects of the elimination of the filtration
step on the total chioride extraction pmess outiined by the two test methods. The results
fiom this part of the mdy (Table I l . sample numbers 82.83.86, and 87) confumed the
ASTM's tinding that a smail arnount of solid residue will not interfere with the titration.
The amot.int of chloride loss was found to be 15.7% for both rnethods. These are in good
agreement with the results of the previous determinations for which the solutions were
tiltered.
Berman [6] and ASTM [5J both have suggested that chloride can be lost through
volatilization during the extraction process if the beaker containing the solution is not
pmperly covered: a watch glas is ofien used to minimize loss of chlonne.
In the next series of experiments, the chloride extraction process was canied out in a
closed system (Figure 7). This set up served two purposes: it significantiy reduced the
risk of Iosing volatile compounds during digestion with nitric. and also was helpful in
condensing some of the vapours formed during the heating stage. However. it is worth
mentioning that if chloride is lost due to formation of chlorine upon cernent digestion. the
latter cannot be condensed back into liquid form. This is due to the fact that the boiling
point of liquid chlorine is about 34.6 'T at atmospheric pressure [33]. The arnount of
unrecovered chioride was found to be 15.2% and 15.6% for the Berman and ASTM C
1 14 methods. respectively (sample numbers 92-97). It was concluded that the original set
up is sukEcient in recovering and trapping the chloride in cernent upon digestion, and that
any losses must be accounted for elsewhere.
As discussed above. chiorides, regardless of their origùi. can be bound to the hydrated
products in cement pastes or concrete 1141. Tricaicium aluminate (C3A) is. by far. the
best candidate to irnmobilize aggressive chioride ions that are present in the cement
matrix at the tirne of mi.xing or when they diffuse into it at a later stage. Although severai
chloride complexes are known to be produced the main product k ing formed is
chloroalurninatr: hydrate known as Friedel's sait. The assumption is that upon the
addition of nitric acid and heating the mixture. ail these complexes will decornpose and
chloride ions will pass into solution. if that were the case. the total chloride content of
any cernent sarnple couid be deterrnined by a simple titration. However. chioride losses
have been known to occur. and many workers [6.25] have commented on the inaccuracy
of the most available methods for determining chloride content in cernent pastes or
concrete. They have amibuted the above problem to either chloride l o s h o u &
formation of volatile chlorine upon acid digestion or incomplete extraction-
.& series of 5.0 M aqueous NaCl solutions (Portland cernent not present) were prepared
and heated (90-100 O C ) for varying pends OF time to determine the eKects of heating
time on volatilization losses when no cernent is present and. rherefore- no ~hloride
complexes are forrned, This eliminated one of the sources of e m r - incomplete
chloride emaction due to chloride cornplex formation. Identicai 2.0 M aqueous sodium
chioride solutions were heated for 5 seconds and 5 minutes and then were titrated
following the ASTM Method. It was found that upon heating the solutions for 5 seconds
and 5 minutes. the chionde losses were about 0.23% and 0.66%. respectively. A set of
siniilar samples also was prepared and titrated sithout heating and the chioride loss was
found to be mund 038%. The resdts are summatized in Table 12 and it c m be seen
that the amount of chloride that wilI be Iost upon heating the solution is insignificant.
Therefore. it can be hypothesized that the main source of 2rror observed in these
experiments is attributable to an incompIere chioride extraction. and chis is, most Iikety.
due to chloride cornplex formation.
Table II - Effects of Heating Time on Sodium Chioride Solution
Sample Method Fittered Covered Heated Unrecovwed Average N u m k Chloride (?id Unrec. Chloride (KI
3899 ASTM No Yes No 3899 ASTM No Yes No
3 897 ASTM 30 Yes Yes-5 seconds 0.1 3903 ASTM No Yes Ys-Ssecorids 0.44 0.23
3898 ASTM No Yes Yes - 5 minutes I .O4
3904 ASTM No Ys Yes - 5 minutes 0.28
5.0 CONCLUSIONS
1. The potentiometric titration procedures - ASTM Method C 1 14. Section 19-chloride
and Berman's Method -are precise but not accurate. particularly when the chlonde
concentration is higher than 0.01 g Cl-/g dry cement.
2. Although chloride wili be lost as volatile chiorine upon acid digestion and heating.
the main source of error is an incomplete chlonde extraction. The latter is. most
likely. due to compkex formations that will not compktely decompose in nitric or
sulfuric acids.
3. When chlonde is added to the mix water. the higher the concentration in the mix
water. the higber the final amount of unrecovered chioride.
4. The addition of more niaic acid does not bring more chloride ions into solution.
5. Elimination of the filtration step does not affect the titration, provided as the solution
contains only a small amount of solid residue.
6. The arnount of acid-soluble chIorides increases when cernent specimens are rotated.
This emphasizes the significance of the pore structure of the cernent rnatrix, which
controls the accessibility of chloride ions to the reaction sites.
7. As curing time increases. the amount ofacid-soiubk chIorides will decrease.
1. ASTM Method C 114. Section 19-chloride must be corrected by the use of a
calibration factor for cured OPC sarnples containing greater than 0.08 g Cl-lg dry
cement.
2. Csments with different mcalcium aluminate (C;A) content should be tested to
evaluate the effets of C;A content on chloride binding.
3 The role of calcium silicate hydrate (CSH) on chloride binding should be
investigatcd.
4. The efTects of various cement extenders such as silica fume and fly ash on chloride
binding should be studied.
5. The use of calcium chloride instead of sodium chloride. as well as the use of different
watsr-to-cernent ratios should be investigated.
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h h e e d d a r . Hussain. S.. and Al-Saadoun. S.. "Effect of Tricalcium Aluminate Content of cement on Chloride Bindiig and Comsion of Reinforcing Steel in Concreten. ACI A4aterial.s journal, 89. 1992. pp. 3-1 2
Ramachanduran. V. S.. M&erials and Structure. 6 197 1
Karimi. S.. -'Development of a Rapid Method to Determine Chioride Diffusion Coetticient in Cured Cernent Pastes-. B.A.Sc. Thesis. University of Toronto. 1997
'-Standard Test Methods for Chemical Analysis of Hydnuiic Cernent (CI L4-97). section 1 9-Chloride". .4nnual Book of .-fST.bf SrandarciS. 01.01. ASTM. Philadelphia. 1997. pp. 1 1 1 - 1 12
Berman. H. A.. "Determination of Chionde in Hardened PortIand Crment Pas~e. Monar. and Concrete". Journal of Materials. JMLSA. f. 1972. pp. 330-335
Dhir. R. K.. Jones. M. R.. and Ahmed. E. H.. "Determination ofTotal and Soluble C hlorides in Concrete". Cernent and Concrete Reseurch. 20. 1990. pp. 579-590
Climen~ M. A., Viqueira. E., de Vera. G.. and Lopez-Atalaya M. M.. ".halysis of Acid-soluble Chiotide in Cernent. Mom. and Concrete by Potentiomevic Titration without Filtration Steps". Cernent und Concrete Research. z. 1999. pp. 893.889
Mehta. P. K.. foncrete: Structure. Properties, and Materials". Second Edition, Prentice Hall. New Jersey. 1993. pp. 180-194
Neville. A. M.. "Properties of Concrete". Founh Edition. Prentice Hall- Essex- England. 2000. pp. 68-75
Lem. J.. -'Effects of Chlonde Ion in Cernent Paste Solution on the Comsion of Embedded Iron. MASc. Thesis, University of Toronto. 1993.
Locke. C. E.. -Proceedings of 8" International Congres on Metallic Corrosion-. NRC. Toronto. 1984
"Pertbrmance of Concrete in Marine Environment". -4merican Concrete Insfitute. Publication SP-65. Detroit. 1980- pp. 226-240
14. Luping. T., and NiIsson, L., Thloride Binding Capacity and Binding [sotherms of OPC Pastes and Mortars". Cernent and Concrere Research. U, i 993, pp. 247- 353
SchiessI. P.. "Corrosion of Steel in Concrete", 1" Edition. New York. 1988. pp. 22-49
Delagrave. A.. Marchand, J., Ollivier. J.. and Julien. S.. Thloride Bindmg Capacity of Various Hydrated Cement Paste Systems". .-ithtanced Cemenr Based .Llu~eriais. 0 1997. pp. 28-35
McGrath. P., Private Communications. 1996
Lambert. P.. Page. C. L.. and Short, N. R.. "Pore Solution Chernisl of the Hydrated System TricaIcium Silicate/Sodium ChloriddWatef'. Cernent and CBnCrert! Research. IS, 1985. pp. 675-680
Beaudoin. J. J. and Ramachandran. V. S.. -Interaction of Chlonde and C-S-W. Cémenf und Concrere Research. 20.1990. pp.875-883
Diarnond, S.. "Chloride Concentrations in Concrete Pore Solutions Resulting h m Catciurn and Sodium Chloride Admixtures". Crmenr, Concrefe, und .-lggregutt~.~. & 1986
Santagata. M. C. and Collepardi. M., "The Effect of CMA Deicers on Concrete Properties". Cemenr and Concrete Research, 30.2000. pp. 1389-1 394
.-a. C.. BuenfeId. N. R. and Newman. J.. B.. "Factors Influencing Chloride- Binding in Concrete". Cernent and Concrere Reseurch. a. 1 990. pp. 29 1-300
Hussain. S. E.. R a s h e e d d a r . and Al-Gahtani. A. S.. -influence of Sulfates on Chioride Binding in Cernent". Cemenr and Concrere Reseurch. 24- 1994. pp. 8-24
Holden, W. R., Page. C. L.. and Short. N. R.. 'The Inheuce of Chiorides and Sulphates on Durabiïitf. Corrosion of Reinforcement in Concrete Construction. 1983
Clear. K. C. and Hanigan. E. T,, "Sampling and Testing for Chloride Ion in Concrete". FederaI Highway Administration Washington. D. C.. Matexiais Division. 1997. pp. 1-22
B i s h m S. W.. "Rapid, Accurate Method for Determining Water-Sotuble Chionde in Concrete, Cernent. Mortar. and Aggregate: Application to Quantitative Study of Chloride Ion Distribution in Aged Concrete". ACI .tlaterials Jownal. 88.1991, pp. 165-270
Haque. M. N. and Kayyali, O. A., " F m and Water Soluble Chloride in Concrete", Cernent and Concrere Research, 25- 1995. pp. 53 1-542
Cox. T. R. G., The Distniution of Chioride in Concrete". Conc., 20- 1986, pp. 9- I 1
Sandberg. P.. "Studies of Chloride Binding in Concrete Exposed in a Marine Environment". Cernent and Concrere Research. 29, 1999. pp. 473-477
Chan. G. W.. T h e Use of Rapid Scan Voltammeûy to Study the Effects of Adding Silica Fume and Commercial Corrosion inhibitors to Cured Cernent Pastes Containhg Embedded Iron Exposed to Chloride". M.A.Sc. Thesis. University of Toronto, 1996
Lolivier. J.. -Determination of Chloride in Hardened Concrete" (in French). International Symposium on Admixtures in Mortars and Concrete. Brusseb. 1967. RILEM-.ABEM. Report VI1 1. x. pp. 197-21 1
Koelbel. G.. Louvrier. J., and Voinovitch. 1.- Chimie =Inafytique. 50. 1968. pp. 1 78-1 86
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APPENDIX A - General Data
Table Al - Common Values of Compound Composition of Portland Cements of Different Types [IO]
Cernent Value Compound Composition (%) No. of
CiS CzS C3A CAF CaSOa Free Ca0 Me0 Ignition Los Samoles
Mau. T p e 1 Min.
M a n
Mau. Type II Min.
M m
Mau. Type Ill Min.
Mean
Mau. Tye IV Min.
M a n
Max. T'pe V Min.
M a n
Table .42 - Main Types of Portland Cernent [1 01
Rapid-hardeiing Putland E . . rapi&hardening Pbrtland Ultra high carly strength Partland Low h a Putland Maiifid canait
S u i f e-resisting Putland
Portland blastthaœ
Tye III
White Putland -
Table B 1 - Generai Date For Cernent Slabs Cured for 7 Days NaCl m e n t Valurne Average vol. Standard Theoreücaf Adual Con'n Weight of AgN03 of AgN03 Dviation A m 3 Amount of NaCl
Pl (mg) Added (ml) added (ml) Volume (mL) in sample (g)
Table BZ - General Date for Cernent SIabs Cured for 28 Days NaCl cernent Vdume Aveiage vol. Standard Theoretical Adual Con'n Weight of AgN03 of &NO3 Dviation AgN03 Amount of NaCl
Pl (mg) Added (ml) added (ml) Volume (ml) in sample (g)
Table B3 - General Data for Cernent Spheres Cured for 28 Days NaCl cernent Vdume Average vol. Standard Theoretical Actual Con'n Weight of A@03 of &NO J hnation W O s Arnount of NaCl
[M] (mg) Added (rnL) added (ml) Volume (mL) in sarnple (g)
APPENDIX C - S a m ~ l e Calculations
Determination of Evapourrtble Water
Frorn Table 5: Weight of the cement sphere before drying = 21.957 g
Weight of the cernent sphere f i e r dqing = 20.745 g
% Evapourable water = r(24.957-20.745)/(24-95n]x 1 00% = 16.88%
Calibration of ASTM Metbod C 114
Consider Cernent samples that have been prepared by mixing 4.45 g of cernent with 2 mL of 2 M NaCl solution. The arnount of chloride is therefore:
This is the known (actud) value of chloride in the sample.
After curing for 28 days. the saniples were titrated with 0.05 M A g O 3 solution:
moles Cl- = moIes AgCl= C x V C = Concentration of AgN03 (M) V = Volume of AgN03 (mL)
Volume of silver nitrate added = 67.3 mL
Concentration of Silver nitrate = 0.05 M
Moles CI- = (0.0672 L)x(0.05 mol.&) = 0.003360 mol Cl'
Chioride content = (0.003360 mol Cl-)x(35.453 @mol) = 0.1 i24 g Cl-
Recommended