Proceedings of the 2nd International Seminar on Infrastructure Development
In Cluster Island Eastern Part of Indonesia (ISID 2014)
June 3–4, 2014, Balikpapan, Indonesia
DURABILITY DESIGN FOR INDONESIAN CLIMATE
1)
Rita Irmawaty1, Hidenori Hamada2, Hendra Witanto1
Civil Eng. Dept., Hasanuddin University Department, P. Kemerdekaan KM. 10 Makassar, 90245, Indonesia
2) Civil and Structural Eng. Dept., Kyushu University, 744 Motooka, Nishi-Ku, Fukuoka, Japan
ABSTRACT: Deterioration of concrete structure is directly affected by environmental factors such as
temperature, humidity, chloride ion concentration and CO2 concentration, which will vary depending on the location
and level of exposure to the structures. Increased humidity may increase carbonation. On the other hand, the severity
of marine exposure varies considerable depending on factors such as climate, location related to the sea and structural
consideration. Since durability is a major concern for concrete structures exposed to aggressive environments, where
many environmental factors are known significantly influence the durability of reinforced and/or prestressed concrete
structure. Durability is defined as the ability of concrete to resist weathering action, chemical attack, abrasion, and
other conditions of service (ACI 116R-90). One factor contributing to the deterioration of infrastructure is corrosion
of embedded steel. Corrosion in reinforced/prestressed concrete is mainly caused by the ingress of aggressive agents
such as chloride ion and carbon dioxide (CO2). The main objective of this research is provides recommendations the
optimal strength and adequate cover depth of concrete for Indonesia’s climate as a design consideration for durability,
especially for structure in the marine environment.
Keywords: Durability, concrete cover, carbonated concrete, chloride-rich environment.
1. Introduction
Deterioration of concrete structure is directly affected by environmental factors such as temperature,
humidity, chloride ion concentration and CO 2 concentration, which will vary depending on the location
and level of exposure to the structures.
In the marine environments, the deterioration process is mostly affected by the chloride-induced
corrosion of reinforcement, particularly in the tidal and splash zone. The overall environmental exposure
of concrete structures is affected by both macroclimate and microclimate conditions. Macroclimate
factors include geographical location and, climate-wind, temperature, humidity and precipitation. While
the microclimate is more closely related to the position of a structure in relation to a fluctuating water
level.
Based on researches was conducted by the author in Japan, and discussions of some papers that the
author has published, taking into account the climate of Indonesia, the authors attempted to provide
recommendations regarding the level of strength and concrete cover that is suitable for the environment in
Indonesia.
2. Weather and Climate of Indonesia
Because of its proximity to the equator, Indonesia has a tropical climate characterized by heavy rainfall,
high humidity, high temperature and low winds. Generally, the weather is hot and humid. Indonesian
climate is divided into two distinct seasons: dry and rainy seasons. Most of Indonesia has their rainy
seasons from October through April. The dry season does not mean that there are no rains. In fact tropical
showers in a dry season's afternoon are a regular fair. The average annual precipitation is 1800 mm [1].
The uniformly warm waters that make up 81% of Indonesia's area ensure that temperatures on land
remain fairly constant, with the coastal plains averaging 28°C, the inland and mountain areas averaging
26°C, and the higher mountain regions, 23°C. Temperature varies little from season to season. The main
variable of Indonesia's climate is not temperature or air pressure, but rainfall. The area's relative humidity
ranges between 70 and 90% [2]. Rainfall in lowland areas averages 1800-3200 mm annually, increasing
with elevation to an average of 6100 mm in some mountain areas [3].
Proceedings of the 2nd International Seminar on Infrastructure Development
In Cluster Island Eastern Part of Indonesia (ISID 2014)
June 3–4, 2014, Balikpapan, Indonesia
3. Service Life and Durability-Review of Literature and Code
Concrete is affected by a range of atmospheric variables, which may be affected by climate. The main
variables are carbon dioxide (CO2) level, air temperature and humidity. Increased humidity may increase
carbonation. The optimal relative humidity for carbonation is between 50% and 75%. If the concrete is
very dry (RH < 40%) CO2 cannot dissolve, and no carbonation occurs. If it is very wet (RH > 90%) CO 2
cannot enter the concrete, and the concrete will not carbonate. Table 1 shows deterioration processes
related to relative humidity.
Table 1. Relationship between deterioration processes and relative humidity [11]
Relative severity of deterioration process
Ambient
relative
humidity
Carbonation of
concrete
Frost attack on
concrete
Chemical
attack on
concrete
Risk of steel corrosion
In carbonated
In chloride –
concrete
rich
environment
Very low
(<40%)
Slight
Insignificant
Insignificant
Insignificant
Insignificant
Low
(40-60%)
High
Insignificant
Insignificant
Slight
Slight
Medium
(60-80%)
Medium
Insignificant
Insignificant
High
High
High
(80-98%)
Slight
Medium
Slight
Medium
Very High
Saturated
(>98%)
Insignificant
High
High
Slight
Slight
On the other hand, the severity of marine exposure varies considerable depending on factors such as
climate, location related to the sea and structural consideration. In addition, the transport mechanism is an
aspect that needs to be addressed. The transport mechanism of chloride in different microclimate
conditions is illustrated in Figure1. In the dry zone, chloride ions are transported into the cover zone much
more quickly by the processes of absorption, wick action and hydration suction. The severity rating
according to British Standard 6349-1 for different location relative to seawater on the basis of
macroclimate and microclimate is described in Figure 2. This figure shows that upper tidal and
splash/spray zone are more severe to corrosion than other zone for hot wet climate.
As defined by BS 6349-1 [7], the macroclimate is divided into:
 Cold with freezing
 Temperate
 Hot wet (tropical area)
 Hot dry (arid area)
The potential durability of reinforced concrete greatly enhanced if adequate cover to reinforcement
is specified and monitored for compliance on site. For sufficient protection to reinforcement under marine
conditions, cover should be in the region of 50 to 75 mm. Reduced cover is risky even when using high
quality concrete since defects such as cracks and voids become more significant than they are with
normal cover and may provide a low resistance path to the reinforcement.
Proceedings of the 2nd International Seminar on Infrastructure Development
In Cluster Island Eastern Part of Indonesia (ISID 2014)
June 3–4, 2014, Balikpapan, Indonesia
Based on measurements of chloride ingress within structures it can be demonstrated that levels of
chloride required to cause activation can be achieved at rebar depth in relatively short periods. For
example, with w/c of 0.30 and 50 mm cover depth, the chloride level may exceed 0.4% weight of cement
(the commonly assumed corrosion threshold level) [12] within 30 years in the splash zone [8]. For the
same situation, if cover depth of 60 mm, concrete has a 50 years period of service life [8]. This justifies
the use of large cover (50-70 mm) in the marine environment.
Figure 1. Chloride transport process in a marine structure described by BS 6349-1 [7]
The European standard ENV 1992-1-1 [10] proposed a single exposure class for the marine
environment and minimum cover of 40 mm. However, Costa (1999) [8] found that a cover of 40 mm is
not enough to guarantee a service life of 50 years except in the atmospheric exposure conditions and for
good concrete quality.
Eight year later, the new European Standard (EN 206-1:2000) [9] proposed minimum strength
requirements by applying a maximum w/c ratio for a service life of 50 years in both conditions: carboninduced corrosion and chloride-induced corrosion in seawater as presented in Table 2. Australian
Standard (AS 3600: 2001) [4] also gives the minimum characteristic cylinder compressive strength of
concrete materials and concrete cover needed to maintain adequate durability for a design life of 40-60
years as shown in Table 2.
Proceedings of the 2nd International Seminar on Infrastructure Development
In Cluster Island Eastern Part of Indonesia (ISID 2014)
June 3–4, 2014, Balikpapan, Indonesia
Figure 2. Chloride-induced corrosion severity of a marine structure described by BS 6349-1 [7]
(The higher the rating, the more severe is the durability risk)
Table 2. Limiting values for composition and properties of concrete subject to general structures for 50 years design life
Corrosion induced
Carbonation
Chlorides
Code
XC4 (cyclic wet and
dry)
EN 206-1
XS3 (tidal, splash &
spray zones)
EN 206-1
C (tidal, splash & spray
zones)
AS 3600
Max w/c
0.5
0.45
0.35
Min. f’c (MPa)
Min. cement content
(kg/m3)
30
35
50
300
340
-
45
50
50 (f’c ≥ 50MPa)
70 (f’c = 40 MPa)
Exposure class
Min. cover (mm)
Rather than simply specifying the characteristic compressive strength for environmental exposure
class, BS 6349-1 [7] also specifies limiting values, including permitted pozzolanic addition, in relation to
minimum cover to reinforcement as shown in Table 3 for a service life of 50 and 100 years. An increase
in the proportion of GGBFS or PFA may reduce the requirement for cover to reinforcement.
JSCE (2007) [13] in part 3: Durability design did not explicitly propose a minimum cover in
accordance with w/c ratio and environmental condition for both carbonation-induced corrosion and
chloride-induced corrosion. However, it must be checked whether it meets requirements minimum cover
Proceedings of the 2nd International Seminar on Infrastructure Development
In Cluster Island Eastern Part of Indonesia (ISID 2014)
June 3–4, 2014, Balikpapan, Indonesia
to carbonation depth or diffusion coefficient of chloride ingress on certain environmental condition before
determining the cover thickness and w/c ratio.
Table 3. Limiting values for composition and properties of concrete subject to a marine environment according to BS 6349-1
In frequently wetted, upper tidal, splash, dry internal faces of submerged structures (XS3)
Service life
50 years
Min. f’c (MPa)
100 years
40
30
25
55
40
30
≤ 35
≤ 20
35-80
20-55
50-80
35-55
≤ 35
≤ 20
35-80
20-55
50-80
35-55
Max w/c
0.45
0.5
0.55
0.35
0.4
0.45
Min. cement content (kg/m3)
400
360
360
400
370
370
Min. cover (mm)
60
50
40
80
60
50
Permitted additions proportion
(% by mass)
GGBFS
PFA
On the other hand, many studies have revealed that concrete with very high cement contents and
very low w/cm ratios are extremely hard to place, compact and cure, and highly prone to cracking. With
the new generation of chemical admixtures, it is of course possible to overcome some of these difficulties,
but even then, it is better limiting the total cementitious content and the w/cm ratio of highly durable
concrete (HDC) to a maximum of 400-450 kg/m3 and a minimum/maximum of 0.40 respectively. There is
now conclusive evidence that even when specific code requirements for durability in terms of concrete
quality and concrete cover are achieved in practice, concrete made with only Portland cement as currently
manufactured, are not totally resistant to deterioration when exposed to aggressive salt-laden
environments [20]. In addition, it is well-established that one of the key ways of enhancing the durable
quality of Portland cement concrete in its fresh and hardened states is to ensure that pozzolanic and/or
cementitious industrial by-product form vital and essential constituents of the concrete.
4. Discussions and Recommendations
Design for durability has traditionally been carried out by choosing a concrete mix of sufficient strength
to resist the maximum design stresses, by adopting codified minimal for the depth of cover to the
reinforcement to meet requirements of environmental exposure to suit the strength grade or mix
proportions chosen, and by limiting the width of flexural cracks at the surface. Selection of sufficient
strength of concrete mix using local materials is not difficult, and it can be done by trial mix. The problem
is how to achieve durability through careful design of the cement matrix and its microstructures, and
determine the minimum cover depth for reinforcement that meets the requirements of environmental
exposures.
In addition, Ashar (2010) [6] found that the statistical characteristics of compressive strength of
ready-mixed concrete produced by a single company in both Indonesia and Japan show lower coefficient
of variations than those of the concrete produced by several companies. Hence, quality control of readymixed concrete in Indonesia, which is a developing country, is quite comparable to that in Japan. This
finding is understandable since practically the same level of technology for producing normal concrete in
major ready-mixed concrete factory is applied in those countries. However, for HSC or HPC, concrete
quality in Indonesia is slightly lower compared to Japan for the same grade [14] as described in Figure 3.
Proceedings of the 2nd International Seminar on Infrastructure Development
In Cluster Island Eastern Part of Indonesia (ISID 2014)
June 3–4, 2014, Balikpapan, Indonesia
Figure 3. Compressive strength of concrete [14]
Since using material and testing results from Japan to propose the durability standard for Indonesia,
the requirements should be raised one level higher (or up to twice of the real value) due to differences in
the concrete quality. For instance, by using the rate of carbonation on PC-O beams (y = 0.845year) [18],
for a service life of 50 years and w/c ratio of 0.407, the minimum requirement cover depth is 6 mm.
Meanwhile, if accelerated conditions with higher CO2-concentration, for example, 4%-volume, to speed
up process is used. Four weeks of accelerated carbonation in 4%-volume is often considered as equivalent
to approximately 4 years in natural conditions [19]. Based on this assumption, for w/c of 0.45, the depth
of carbonation was measured to be 1.458 mm at the fourth week in accelerated chamber with 5%- CO2concentration (source: data N45-J-J [14]) which can be considered equal to 5 years in natural condition.
From this data, we can determine the constant y = 0.652 mmyear. This means, for 50 years’ service life,
a minimum cover concrete of 5 mm is needed in carbonated concrete.
By considering the Indonesian climate (RH ranges between 70 and 90%), classification in Table 1
where the risk of corrosion in carbonated concrete is classified as medium to high, and unexpected
aspects, the concrete cover of 25 mm for normal conditions and minimum of 35 mm for cyclic wet and
dry conditions with water/cement ratio of 0.45 for 50 years’ service life are recommended.
In view point of chloride-rich environment such as tidal and splash zones, the risk of steel corrosion
become more severe in high relative humidity as presented in Table 1. Moreover, based on the JSCE
Guideline (2007) [13] by plotting the value of Dd for 50 years’ life time and minimum design concrete
cover of 60 mm (Table 4), a maximum w/c for condition without cracking in the splash zone is equal to
0.30 (Figure 4). Similarly, for 70 mm concrete cover, a water/cement ratio is 0.40.
By using N35 specimen data [14]: effective diffusion coefficient (De) and total chloride ion
concentration at the surface of concrete (Co), the concrete cover and service life is determined based on
Fick’s second law. The apparent diffusion coefficient (Dap) is calculated by convert from De. If Co = 16
kg/m3 and limit concentration for occurrence of corrosion (Clim) = 1.2 kg/m3, for a service life of 50 years;
it takes a minimum concrete cover of 50 mm.
The other case is exhibited by PC sheet pile with w/c of 0.32, which it is estimated to be only 20year service life in splash zone for 30 mm cover depth. For cover depth of 50 mm, the use of GGBFS as
cement replacement showed service periode longer than without GGBFS [15]. Similarly, a 35-year old
PC beam (w/c = 0.407) with cover depth of 30 mm showed a very severe reinforcement corrosion after 20
years exposed in real marine tidal environment and then stored in the laboratorium with a constant
temperature over than 15 years [18].
Proceedings of the 2nd International Seminar on Infrastructure Development
In Cluster Island Eastern Part of Indonesia (ISID 2014)
June 3–4, 2014, Balikpapan, Indonesia
Table 4. Maximum design diffusion coefficient for chloride ingress Dd [13]
Figure 4. Effect of water/cement ratio and crack width on diffusion coefficient [13]
Table 5 describes the minimum requirements concrete cover for 50-year service life. The value in
the table are based on the literature review in Section 3, approach method by JSCE (2007) and calculating
concrete cover by Fick’s second law. As can be seen that the JSCE provide a minimum concrete cover is
quite large with high level strength concrete compared to other standards. However, overall, the values in
this table justify the use of large cover (50-70 mm) in the marine environment.
Table 5. Summary of a minimum concrete cover for 50 years’ service life
(tidal and splash zone)
Max w/c
Min f’c
(MPa)
Min cement
content
(kg/m3)
Min cover
(mm)
Ref. (6.2)
EN 206-1
AS 3600
BS 6349-1
JSCE
Calculation
0.30
0.45
0.35
0.45
0.30
0.40
0.35
-
35
≥ 50
40
60
50
60
-
340
-
400
-
-
-
60
50
50
60
60
70
50
Proceedings of the 2nd International Seminar on Infrastructure Development
In Cluster Island Eastern Part of Indonesia (ISID 2014)
June 3–4, 2014, Balikpapan, Indonesia
Currently, a popular cement type in Indonesia is Portland pozzolan cement (PPC); for general
structures and structures that require sulfate resistance and moderate heat of hydration. PPC is
manufactured by inter grinding well-burnt OPC clinker with 15 to 35% Pozzolana and required
percentage Gypsum to the fineness not less than 300 m2/kg. It contains high reactive silica (HRS) to
enhance ultimate performance of concrete and suitable for marine work and mass concrete work. In view
point of strength, the strength of PPC is similar to OPC type I of Indonesia’s cement. Furthermore, from
compressive strength testing of mortar using OPC (w/c = 0.35), Japanese cement showed 5% higher than
Indonesia’s cement [14].
By considering the Indonesian climate which is located in tropical area with high relative humidity,
and facing a potential high risk of corrosion of steel in the chloride-rich environment, so it needs to be
carefully considered when determining the requirement of maximum w/c and minimum cover. For 50
years’ service life in tidal and splash zones, using PPC, it seems reasonable to require a maximum w/c of
0.35 and a minimum strength of 50 MPa. Referring to the JSCE Standard in Table 5, for compressive
strength of 50 MPa, minimum concrete cover of 70 mm is recommended for Indonesian climate.
5. Conclusion
Concrete structures in Indonesia have a high risk of steel corrosion in carbonated concrete and chloriderich environment because of its proximity to the equator, which has a tropical climate with high humidity
and high temperature. Based on the evaluations and consideration of current codes and standards from
some countries, the optimal durability design to Indonesian climate for a service life of 50 years is
recommended as follows:
1. By considering high relative humidity (70-90%), where the risk of corrosion in carbonated
concrete is medium to high, the concrete cover of 25 mm for normal conditions and minimum of
35 mm for cyclic wet and dry conditions with water to cement ratio of 0.45 is recommended.
2. For tidal and splash zone, where mostly affected by the chloride-induced corrosion of
reinforcement, a concrete cover of at least 70 mm is required, with maximum w/c of 0.35 and
minimum strength of 50 MPa if using Portland pozzolan cement, which contains 15 to 35%
pozzolana.
3. In the implementation of construction practices, many problems are attributed to the design and
construction process such as poor detailing, low cover and inadequate curing, due to a lack in
experienced supervision and workmanship which does not understand the need for cover to
reinforcement, adequate compaction and curing for the various exposure conditions and concrete
grades, therefore, sufficient durability is often not achieved.
4. All the requirements such as cover, compaction and curing are achievable properly only when
diligent work practices in place.
References
[1]. http://www.indonesiapoint.com/weather-of-indonesia.html, “Weather of Indonesia”, 2012.
[2]. http://en.wikipedia.org/wiki/Climate_of_Indonesia, Wikipedia, “Climate of Indonesia”, 2012.
[3]. http://www.nationsencyclopedia.com/Asia-and-Oceania/Indonesia-CLIMATE.html#b, Encyclopedia
of the nation, “Indonesia-Climate”, 2012.
[4]. AS 3600, “Concrete Structures”, Australian Standard, 2001.
[5]. AS 4997, “Guidelines for the Design of Maritime Structures”, Australian Standard, 2005.
[6]. Ashar, S., Limsuwan, E., and Ueda, T., “Characteristics of Material and Fabrication for Concrete
Structures in Indonesia”, Engineering Journal, Vol. 14 (4), 2010.
[7]. BS 6349-1:2000, “Maritime Structures, Part 1: Code of practice for general criteria”, British
Standard.
Proceedings of the 2nd International Seminar on Infrastructure Development
In Cluster Island Eastern Part of Indonesia (ISID 2014)
June 3–4, 2014, Balikpapan, Indonesia
[8]. Costa, A. and Appleton, J., “Chloride Penetration into Concrete in marine Environment- Part II:
Prediction of Long Term Chloride Penetration”, Materials and Structures, Vol.32, June 1999, pp.
354-359.
[9]. EN 206-1, “Concrete-Part 1: Specification, Performance, Production and Conformity”, European
Standard, 2000.
[10]. ENV 1992-1-1: Euro code 2. Design of concrete structures. Part I-General rules and rules for
buildings.
[11]. George Somerville, 2008, “Management of Deteriorating Concrete Structures”, Tailor & Francis.
[12]. Glass, G.K. and Buenfeld, N.R., “The Presentation of the Chloride Threshold Level for Corrosion of
Steel in Concrete”, Corrosion Science, Vol.39, No.5, 1997, pp. 1001-1013.
[13]. JSCE Guidelines for Concrete No. 15, “Standard Specifications for Concrete Structures-JSCE (Part:
Design)”, 2007.
[14]. Rita Irmawaty, H. Hamada, Y. Sagawa, S. Yamatoki, “A Discussion on Durability of High Strength
Concrete (HSC) in View Point of Micro Pore Structure”, The 3 rd International Conference of
European Asian Civil Eng. Forum (EACEF), Yogyakarta-Indonesia, Sept 2011.
[15]. Rita Irmawaty, H. Hamada, Y. Sagawa, D. Yamamoto, “Performances of Pre-stressed Concrete
Sheet Pile after 12 Years Exposure in the Marine Tidal Environment”, JCI-Annual Conference
2012, Hiroshima, Japan, July 2012.
[16]. Rita Irmawaty, H. Hamada, Y. Sagawa, T. Ikeda, “Enhancement of Chloride Resistance of Prestressed Concrete Sheet Pile by Blast Furnace Slag”, JSCE 14 th International Summer Symposium,
Nagoya, Japan, Sept 2012.
[17]. Rita Irmawaty, H. Hamada, Y. Sagawa, Load Bearing Capacity of 35-Year-Old Prestressed
Concrete Beams due to Combined Effects of Carbonation and Chloride Attack, Proceedings of
JSCE-Annual Conference Kyushu Branch, Kumamoto, Japan, March 2013.
[18]. Rita Irmawaty, D. Yamamoto, H. Hamada, Y. Sagawa, “Deterioration of Prestressed Concrete
Beams Due Combined Effects of Carbonation and Chloride Attack”, Proceedings of 3 rd International
Conference on Sustainable Construction Materials and Technologies-SCMT3, Kyoto, Japan, August
2013.
[19]. Saija, V., “Accelerated carbonated Concrete as Corrosion Environment”, in Dunster, A.M.,
Accelerated carbonation Testing of Concrete”, BRE, Information Paper, 2000.
[20]. Swamy, R.N., “Sustainable Concrete for 21st Century Concept of Strength through Durability”,
JSCE Concrete Committee Newsletter, 13, 2008.