DETERMINATION OF CHLORIDE CONTENTS IN FLOOR LAYERS OF BATHROOMS –
RIYADH
By:
Mahmoud M. Idris
College of Architecture and Planning -King Saud University, Riyadh, Saudi Arabia
KEYWORDS: Floor Layers, GI Pipes, Corrosion, Chloride Ions, Dextrin Suspension, end
point.
ABSTRACT
Corrosion attack occurs as a result of chemical interaction of a metal with its
surrounding. The prime cause of corrosion of metals embedded in the building fabric
(i.e., GI water pipes, steel reinforcement…etc.) is the presence of high level of
chloride contents in the building materials and water. Results of chemical analysis
have shown that the level of chloride contents in the various floor layers of bathroom
and tap water are very high, compared with the recommended limits by different
codes and organizations. Eventually, this creates a favorable environment for the
corrosion of water pipes embedded within floor layers of bathrooms and kitchens.
Solutions for such a problem have to be worked out in this study.
‫ والمسبب الرئيس لتآكل معادن‬.‫تحدث هجمات التآكل في المعدن نتيجة لتفاعلها مع الوسط المحيط بها‬
:‫الملخص‬
‫الخ) هو وجود نسبة عالية من‬...‫العناصر المدفونة في جسم المبنى (مثل أنابيب المياه الصرف وقضبان التسليح‬
‫ كما‬،ً‫الكلوريد في المواد المستخدمة في طبقات أرضيات الحمامات والمياه مقارنة بالنسب المسموح بها عالميا‬
‫دلت بذلك نتائج التحليل الكيميائي الذي أجري لبعض العينات المجمعة من طبقات األرضيات والماء لعدد من‬
‫ وبالتالي تكون طبقات المواد المستخدمة في أرضيات الحمامات باإلضافة إلى المياه المستخدمة‬.‫الحمامات‬
‫ لذا كان من الضروري البحث في‬.‫لألغراض المختلفة قد ساهمت في خلق البيئة المناسبة لحدوث عملية التآكل‬
.‫هذا الموضوع بغرض الوصول لمعالجة هذه المشكلة‬
INTRODUCTION
Agents with whom metal comes in contact may define corrosion as the
destructive chemical attack of metal. In fact, the destruction occurs as a result of the
interaction of metal with its surrounding environment (Addleson and Rice, 1991).
Under certain conditions related to water, temperature and composition, the contact of
natural water with inorganic materials–metallic or non-metallic–may lead to
formation of mineral deposits at the solid-liquid surface (Halleux, 1982).
Also, if the materials are wetted, metals embedded inside components of
building may corrode and may be brought into aqueous contact with other metals or
materials which may lead to electrolytic attack (Ransaw 1980). The agencies
responsible for the attack vary from material to material and from one location to
another. According to (Addleson and Rice 1991), whether the attack is likely to occur
depends on the chemical properties of the material, its exposure to dampness and the
nature and composition of the particular agency within the material.
In practice, different metals may be in contact with moisture so as to behave
like small battery (galvanic cell). However, current and thus corrosion may also be set
up in single metals when one part becomes anode and another the cathode. In both cases,
the moisture involved may contain air or other dissolved chemical substances, which
conduct electricity. Variations in physical conditions, which may give rise to the setting
up of currents, include differences in temperature, stray currents, and water flow.
(Buenfeld et al., 1998) reported that chloride ion is the main cause of
Corrosion of steel reinforcements in concrete. Chloride may penetrate through
concrete cover from the external environment or be present in the original mixmaterials. They explained that the process in the propagation of corrosion is the
migration of chloride ions from the cathode to the anode in the electric field generated
by the corrosion cell. Chloride ions are highly aggressive and capable of breaking
down, or preventing the formation of protecting film.
Chloride is usually found to be contaminated with the original mix ingredients
(aggregates and water) (Matta, 1993). In addition, laden soil and water may come in
contact with concrete allowing penetration of salts into even high quality concrete. On
the other hand, moisture plays an important role in promoting corrosion especially in
areas like bathrooms and kitchens, where the major source of water found in
buildings. Inspection of a number of defective bathrooms under maintenance in the
King Saud University (KSU) staff flats, have shown serious deterioration of water
pipes buried within the bathrooms floors (Fig. 1). Galvanized steel pipes (  1525mm) are used for both cold and hot water supply. UPVC pipes of sizes  50 and
110mm are used for waste water and soil disposal respectively. Both water supply and
disposal pipes are buried in the sand filling below the terrazzo floor finish. Samples of
sand filling concrete screed, terrazzo tiles from 13 bathrooms together with samples
of water from 4 different locations were collected. The materials of these layers and
water samples are tested to determine the level of chloride contents.
Fig. (1): Corroded Pipes
Concentration limits of chloride-ions vary widely from place to
place. Many national codes and publications from various countries give different
limits of chloride-ions by weight of cement. According to (Matta 1992), ACI
committees differ somewhat on their recommendations for maximum chloride
concentrations. While the ACI committee 201 recommends a limit of 0.10% watersoluble chloride ions by weight of cement, the ACI 318-83 requires a maximum of
0.15%, and the ACI 222 allows a maximum of 0.20%. He added that other national
codes and publications give more liberal limits, as the Norwegian code N5 3474,
Chloride Ion Limits:
which allows 0.6% and the CIRIA publication No. 31 that recommends 0.3% chloride
ions by weight of cement. These limits largely based on studies carried out in foreign
countries. These limits, beside the (CIRIA 1984) limits are used widely in the Gulf
region. (Table 1) summarizes the limits for total chloride and sulphates in concrete as
recommended by (CIRIA 1984).
Table (1): Recommended Limits for Total Chloride and Sulphates Content in Concrete
Type of Concrete
Reinforced concrete made
with Portland cement
containing less than 4%
C3A (e.g. sulphate resisting
Portland cement)
Reinforced concrete made
with Portland cement
containing 4% or more
C3A (OPC and ASTM type
I & II usually contain more
than 4% C3A)
Un-reinforced concrete
Max. Chloride (C1) Contents
(% by Weight of Cement)
Max. Sulphate (SO3) Content
(% by Weight of Cement)
All cases 4.0 including the
sulphate ions in the cement
0.15
0.30
0.60
Source: CIRIA Guide to concrete construction in the Gulf Region Publication # 31 (ref. # 7)
According to CIRIA, experience in the Gulf region (and elsewhere) has shown
that the maximum chloride contents which is unlikely to cause corrosion at a serious
rate in uncarbonated concrete is about 0.5% C1 by weight of cement. Where concrete
has partly carbonated, the amount of chloride needed to promote corrosion is even
lower. It is therefore extremely important that the concrete cover to the reinforcement
should be impermeable.
Conditions in Riyadh: According to (Hanson 1992), corrosion problems in Saudi Arabia
of embedded steel frequently occurred at or near ground level. It appears that
chloride-laden soils or water come in contact with the concrete, or chloride-laden
water may be applied to concrete, allowing penetration of chlorides into even highquality concrete. Capillary action may also draw the chlorides up the near-surface
region of the concrete. Intermittent wetting and drying of moisture condensation on
concrete floor–as in case of bathrooms or kitchens–also supports corrosion process.
Water and Aggregate: The water in the Gulf region has usually high chloride ion
concentration, about 30000 ppm (Hanson 1992). The main source of water in Riyadh
comes from desalination plants in Jubail 400 Km to the East of Riyadh. The water is
fed into the city network via cast iron pipes, and then to the buildings network and
appliances via galvanized steel pipes and chrome-plated steel or brass/copper fittings
(Fig. 2). Both cold and hot water pipes are buried within the building fabric (walls and
floors) (Figs. 3 and 4). Because of the permeable nature of the building materials, i.e.
sand filling concrete...etc., which may also contain some oxygen and the chemical
nature of the infilling material, corrosion, is likely to start by the electrochemical
process. This may take place, as the infilling material gets wet from leaking pipes and
water coming from above and through the finishing material creating a favorable
environment for corrosion.
Fig. (2): Salt from Water Leak through Pipe Joint
The level of the ground water in Riyadh is rising at an average rate of 1m
annually. The total amount of excess water penetrating into the soil in Riyadh is
estimated about 64000m3 per day (Al-Shaikh et. al., 1992). The soil and ground
already contaminated with high levels of sulphates (between 284 – 1733 mg/L) and
chlorides (between 221 – 1841 mg/L) (Al-Towegri and Al-Tabba, 1992). Hence, any
additional water will dissolve more of the salts and raise the risk of corrosion of
embedded pipes.
FLOOR FINISH
SAND FILLING
DISPOSAL PIPE
SUPPLY PIPES
FLOOR SLAB
FLOOR FINISH
SAND FILLING
DISPOSAL PIPE
SUPPLY PIPES
FLOOR SLAB
Fig. (3): Typical Details of Floor Layers in Bathrooms
According to (Al-Idi and Al Mehthl 1995), concrete deterioration in Saudi
Arabia is mainly due to the presence of chlorides and sulphates. Samples obtained from
batch plants in the Eastern and Central Provinces of Saudi Arabia were tested. The
results have shown that the inability of the local aggregates to meet the limits
established by the industry standards. The aggregates in the Central Province (where
Riyadh is situated) have 70% acid soluble chlorides (C1) and 55% acid soluble
sulphates (SO4), compared to 3% and 40% British Standard (BS 1881) limits,
respectively, (Table 2).
Fig. (4): Pipe Buried Within Floor Layers of Bathrooms
Table (2): Local Aggregate
Property
Eastern
Province
Central
Province
I.S. Limits
Absorption
100 %
100 %
2.5 (BS 5337)
Abrasion
100 %
100 %
50 (ASTM
C33)
Acid Soluble chlorides
95 %
70 %
0.03 (BS
1881)
Acid soluble chlorides
Sulphates(SO 3 )
55 %
55 %
0.4 (BS 1881)
90 % (20
mm)
37 % (10
mm)
100 % (20
mm)
74 % (10
mm)
18 (ASTM
C33)
Soundness
Source: Al-Idi and Al-Mehthl, Application of available technologies for production of Durable concrete,
4th Saudi Engineering Conference, 1995. (ref. # 3).
The climate of Riyadh is characterized by the extreme variations
of temperature (between 43oC in summer and 8oC in winter), humidity, and radiation
(MDA, 1990). Coupled with this, the high levels of carbon monoxide (10-20 ppm),
sulpher dioxide (15-30 ppm) and hydrogen sulphide (0.02ppm) present in the
atmosphere (Al-Awat and Ba Sahby 1985). In addition, the sulphate and nitrates were
found in the dust-fall in Riyadh at low levels of 0.3 and 0.09 tons/Km2 per month
respectively. Lead particles were also found at higher levels between 4.0-9.0 µg/m3,
which exceed that of 1.5 µg/m3 in the EEC (El Shobokshy et al., 1990). Eventually,
these high levels of concentration of gases in the atmosphere coupled with extreme
variations of temperatures will speed the rate of deterioration of building materials.
Physical Environment:
MATERIALS AND METHODS
Samples of building materials from
different floor layers i.e., sand filling, concrete screed and terrazzo tiles, together with
pieces of GI water pipes from 13 defective bathrooms under maintenance in King
Saud University (KSU) staff flats were collected. Each sample is kept in polythene
bag, firmly tied and labeled. The labels indicate the number of building and flat floor
level, and the name of the layer.
The samples are ground into a very fine powder to ensure homog-eneity and to
have a true representation of the sample. Samples of tap water from four different
flats were also prepared for chemical analysis. A list of the required chemical tests is
prepared and submitted to the KSU Department of Chemistry.
Chemical Analysis Procedure: The chemical analysis for the samples is carried out
following the procedure described below.
Materials of the Layers: Weigh out in weighing dish 5gm of each samples; then transfer
to 250ml Erlenmeyer flasks, and dissolve in 50ml distilled water, add 10ml 1%
dextrin suspension, close tightly and shake well for one hour before using. Add 10
drops of dichlorofluorescien indicator solution. The dextrin prevents excessive
coagulation of the precipitate at the end point. This keeps a larger surface area for
absorption of the indicator, which enhance the sharpness of the end point.
Filter the solution in 250ml volumetric flask. The whole solution is filtered and
the residue is washed with distilled water, filtered in the same flask, and diluted to the
mark. Take 25 ml of the sample for the determination of chloride ions concentration in
the sample materials. Titrate with standard silver nitrate (AgNO 3 ) solution to the end
point. A blank containing distilled water, dextrin, and dichlorofluorescien were titrated
with standard silver nitrate (Ag NO 3 ) solution for calibration.
Fajans method is used for the determination of chloride as soluble chloride
(Christian 1994 The chemical analysis is done in collaboration with the Department of
Chemistry, College of Science, King Saud University). The principle is that: the sample
is titrated with standard Ag NO 3 (silver nitrate) solution, using dischlorofluorescin
adsorption indicator end point.
The analytical procedure is based on the following reactions:


Ag + C1  AgC1 
Ag  + SCN   AgSCN  (brick-red suspension)
Where; Ag: Silver, Cl: Chloride, AgCl: Silver Chloride, SCN: Thiocynate, AgSCN:
Silver Thiocynate
If the color of the suspension (AgSCN) turns to brick-red this means that the
solution has reached the end point. When finished, put all silver-containing solutions
in a jar provided for this purpose. Then calculate and report the percent C1 for each
portion titrated in the sample.
Water Samples: The analytical procedure for the determination of chloride (Cl-) in tap
water is based on the following reactions:
Preparation of Samples for Chemical Analysis:
Hg (SCN)2 + 2 Cl- → HgCl2 + 2SCN2SCN- + Fe3+ → Fe (SCN)+
Where; Hg: Mercury, HgCl: Mercuric chloride, Fe3:
Iron 3 (Ferric), Fe SCN: Iron
Thiocynate.
The chloride contents of the water samples react with Hg (SCN-)2 liberating
SCN-, which in turn forms with Fe (III) the red–colored complex ion (Fe SCN)+ 2 . This
is measured spectrophotometrically at 480nm.
RESULTS
The results of the chemical analysis for the determination of chloride
concentration in the samples of the various floor layers in 13 bathrooms and water
samples are summarized in (Table 3 and 4).
The results have shown very high concentration of chloride (ranging from 814
ppm to 822 ppm) in the sand filling, where GI water and drainage pipes are buried. On
the other hand, the chloride contents are very high in the screed layer and the terrazzo
tiles (ranging from 1195 ppm to 1912 ppm). These values approach the maximum
allowable limit recommended by the various codes; 200 ppm (0.02%) of ACI 318-83,
600 ppm (0.06%) of the Norwegian code N5 3474 and the CIRIA limit of 300 ppm
(0.03%).
Table (3): Chloride Concentration in Samples of Various Floors Layers of Bathroom
Chloride Concentration (ppm) in Samples
No.
Label
Location
Sand Filling
Concrete Screed
Terrazzo Tiles
1.
B22F10 2nd Floor
820
1412
1220
2.
B38F09 2nd Floor
822
1459
1441
3.
B27F09 2nd Floor
817
1445
1315
4.
B42F03 Ground Floor
819
1382
1278
st
5.
B05F06 1 Floor
821
1395
1312
6.
B37F01 Ground Floor
822
1425
1399
7.
B19F02 Ground Floor
821
1225
1195
8.
B38F03 Ground Floor
821
1422
1325
9.
B39F04 Ground Floor
814
1435
1412
10.
B29F03 Ground Floor
815
1912
1622
11.
B21F14 3rd Floor
822
1432
1325
12.
B21F04 Ground Floor
817
1412
1325
13.
B42F09 2nd Floor
814
1416
1389
The histograms in (Fig. 5) represent the variations in the levels of chloride
contents in the different layers forming bathrooms floors.
Results of the water analysis have shown higher values of chloride contents in
the range of 360 ppm to 365 ppm which exceed the limits of 350 ppm and
recommended by the (WHO1984) and adopted by The Saudi Arabian Standards
Organization (SASO 1984). This means that water inside pipes is the main cause of
corrosion to the material of the pipe than the external layers of the floor. Eventually,
this may weaken pipes walls causing holes allowing for water leak.
2000
1500
Sand Filling
Concrete Screed
1000
Terrazzo Tiles
500
B42F09
B21F04
B21F14
B29F03
B39F04
B38F03
B38F03
B19F02
B37F01
B05F06
B42F03
B27F09
B38F09
0
B22F10
Level of Chloride (C1) in ppm
2500
Number of Flats
Fig. (5): Level of Chloride Contents in Various Floors Layers
Table (4): Chloride (Cl-) Contents in Tap Water
Item
1
2
3
4
Water Sample
Sample No. 1
Sample No. 2
Sample No. 3
Sample No. 4
Chloride Content (ppm)
360
362
365
362
DISCUSSION
Results of the chemical analysis of the raw materials of the samples (before
grinding), gave a very high chloride contents in the range of ⋍ 6250 to ⋍ 7000 ppm.
This indicates that these results are not typical of a representative sample. Samples are
then ground into fine powder to ensure homogeneity of the materials and consistency
of values. Even though the average values of chloride contents in the various layers
are still high compared with the maximum levels recommended by many codes and
organizations. The only justification for such high values could be resulting of
chloride accumulation over a period of time, i.e., water tends to evaporate leaving the
chloride ions to deposit within the materials of the layers.
The source of chloride is usually found to be contaminated in the original mix
ingredient (Matta, 1993). Aggregates in the Central Province, where Riyadh is
situated, have 70% acid soluble chlorides (Al Idi and Al Mehthl, 1995). In addition to
high chloride contents in the water and the soil.
A geotechnical test prepared by
Saudi Labs Ltd., (1992) for the staff flats, indicates high water salinity (TDS = 3885
ppm), with high chloride contents (865 ppm) and high sulphate contents (1580 ppm);
and higher concentrations of sulphates (1774-2185 ppm) and moderate concentration
of chloride (113-149 ppm) in the soil.
All cement products are characterized by their comparatively large initial
drying shrinkage, which makes them move widely (Addlesonands and Rice, 1991),
creating cracks. In addition to their permeable nature, the concrete layers (screed and
terrazzo tiles) allow chlorides to penetrate through them from external environment and
raise the level of chloride already exists in the material. More-over, chloride ions may
transport in concrete by diffusion due to concentration gradient or by water flow due to
difference of pressure (capillarity) or absorption (Bunfeld et. al.,1998), and draw
chloride up the surface of the material.
Moisture plays an important role in promoting corrosion, and in most cases,
moisture passing through concrete contains dissolved salts including chlorides
depositing them within the floor layers. This is aggravated by the high rate of
evaporation in Riyadh, and because of the high fluctuation in the annual rates of
relative humidity (between 7% to 71%, Sharif 1975) and the daily variation between
the early morning high rate and lower rates at mid-day. Also, the flats are left empty
of occupants and dry of water during the summer vacation (June–August), after a long
period of intensive use of water (from May to the end of September). According to
(Ransaw 1980), water has high heat of vapourization and it is therefore slow to
evaporate. Hence, in the bathrooms where plenty of water is used, it is possible that
the excess water would penetrate through the porous materials of the floor finish.
CONCLUSIONS
Results from the chemical analysis have shown the presence of high levels of
chloride contents in the different floor layers of bathrooms. Since chloride is the
major agent causing corrosion of steel, then GI water pipes and other steel elements
buried within any of these layers will be subjected to serious attacks of corrosion.
Corrosion of embedded water pipes may take place internally (drinking water
contains high contents of chloride) as well as externally where the pipes are surrounded
by material (filling or concrete) with high chloride contents. Water leaking from these
pipes may penetrate through the R.C. floor slabs leading to corrosion of steel
reinforcement and GI pipes. Also causing damage to furniture, equipment and the
interior decorations of upper spaces as well as causing damage to foundations at
ground level.
Solutions for such a problem may be in the following:
1-Using pipes made of materials other than steel-not affected by chloride.
2-Coat the GI pipes with protecting material against chloride (i.e., epoxy).
3-Using filling material, which is not affected by chloride.
4-Avoid, if possible, burying GI water pipes within building structure.
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