CORROSION PERFORMANCE OF CONCRETE CONTAINING RICE HUSK-BARK ASH UNDER 5-YEAR EXPOSURE IN MARINE SITE W. CHALEE1 , P. SUWANMANEECHOT2 and C. JATURAPITAKKUL3 1 Department

of Civil Engineering, Faculty of Engineering, Burapha University, Thailand. of Civil Engineering, School of Engineering, Naresuan University Phayao, Thailand. 3 Department of Civil Engineering, Faculty of Engineering, King Mongkut’s University of Technology Thonburi, Bangkok, Thailand.

2 Department

In this study, chloride penetrations and steel corrosion of concrete containing ground rice huskbark ash (GRBA) under 5-year exposure in marine site were investigated. Control concretes were designed using Portland cement type I and V with W/B ratios of 0.45 and 0.65. The GRBA was used as a pozzolanic material to replace Portland cement type I at 0, 15, 25, 35, and 50% by weight of binder with the same W/B ratio of control concrete. The 200 mm concrete cube specimens with steel bar embedded at coverings of 20, 50 and 75 mm were cast. The specimens were cured in water for 28 days and then were exposed to tidal zone of marine environment in the gulf of Thailand. The specimens were tested for compressive strength, chloride penetration and corrosion of embedded steel after being exposed to tidal zone for 5 years. The GRBA concretes continuously gain strength faster than cement concretes, especially in concrete containing GRBA of 15%–35% by weight of binder. The concrete containing GRBA of 15% to 25% (by weight) reduces the chloride diffusion coefficient in concrete together with a low steel corrosion. Keywords: Concrete, rice husk-bark ash, marine environment, chloride penetration, steel corrosion.

1. Introduction Most destructive effect of sea water on concrete structures arises from the action of chloride on the steel reinforcement resulting in the bond breaking between the steel and concrete, and decreases in the steel crosssectional area. In extreme case, the study of chloride content in concrete focuses on the service life of concrete structure, which is seriously damaged by steel corrosion and may face with the high retrofitting and maintenance costs. In long term durability study, it significantly needs the data on corrosion of reinforcing steel related to chloride content. These data are consequently used to analyze the initial corrosion and the service life of concrete structure. Nowadays, the consumption of energy is increased thus the increasing of by-product materials such as ashes from thermal power plants are also increased. Rice husk-bark ash is one of by-products from burning of rice

husk and eucalyptus bark together as a fuel for electricity generating. Previous research had published that the rice husk-bark ash is being utilized as cementitious material in concrete and providing good properties similar to other pozzolan [1–3]. If the rice husk-bark ash can be used in a concrete mixture for improving durability performance, it will reduce the transportation cost, disposal area as well as using a waste material as a valuable in concrete work. Besides, many researchers have obtained the durability data of marine concrete structure in long term exposure [4–7]. However, no research studied the corrosion performance of concrete containing rice husk-bark ash in marine site, especially in long term period. Thus, the purpose of this research is to study the utilization of rice husk-bark ash to improve durability of concrete for marine site, the investigated variables related to compressive strength, steel corrosion and chloride penetration in concrete.

Modern Methods and Advances in Structural Engineering and Construction Edited by Sai On Cheung, Siamak Yazdani, Nader Ghafoori, and Amarjit Singh Local Conference Committee Chair: Gerhard Girmscheid c 2011 by Research Publishing Services :: www.rpsonline.com.sg Copyright  ISBN: 978-981-08-7920-4 :: doi: 10.3850/978-981-08-7920-4 S3-M023-cd

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2. Experimental Program 2.1. Materials Portland cement type I, graded sand, and crushed limestone with maximum size of 19 mm were used in this study. Rice huskbark ash wasobtainedfrom abiomasspower plant, at which a combination of 65% of rice husk and 35% of eucalyptus bark by weight was used as fuel in fluidized bed power plant. The received rice husk-bark ash was ground until the particles retained on a 45µm sieve was 3.0%, having a mean particle size (d50 ) and specific gravity of 10.8 µm and 2.15, respectively. The chemical property of binder materials are listed in Table 1. 2.2. Methods The 200-mm concrete cube specimens were cast and the steel bars (12-mm in diameter and 50-mm in length) were embedded at the corners of concrete specimens with the covering depths of 20, 50, and 75 mm. The ground rice husk-bark ash (GRBA) was used to replace Portland cement type I at 0, 15, 25, 35, and 50% by weight of binder. The W/B ratios of concrete were kept at 0.45 and 0.65. The concrete mixture proportions are shown in Table 2. After casting for 28 days, compressive strength was investigated then the long term specimens were transferred to

Table 1. Chemical composition of Portland cement type I and ground rice husk-bark ash (GRBA).

Silicon dioxide, SiO2 Aluminum oxide, Al2 O3 Iron oxide, Fe2 O3 Calcium oxide, CaO Magnesium oxide, MgO Sodium oxide, Na2 O Potassium oxide, K2 O Sulfur trioxide, SO3 Loss On Ignition, LOI

b) Compressive strength test

Fig. 1. Specimen preparation for durability test.

the tidal zone of the marine site in Chonburi Province (the Gulf of Thailand). The ranges of annual temperature at this site are between 26 and 35◦ C, and the chemical analysis of seawater, chloride and sulfate compositions are ranging from 16,000 to 18,000 and 2,200 to 2,600 mg/l, respectively. After being exposed to seawater for 5 years, compressive strength was investigated. Besides, the concrete cube specimen was broken and then the embedded steel bars were removed. The corrosions of embedded steel bars were measured in terms of the percentage of rusted area and image recording. Also, water soluble chloride in concrete was investigated, in accordance with ASTM C1218 [8]. The prepared specimens in this study are shown in Fig. 1. 3. Results and Discussion 3.1. Compressive strength

Sample Chemical Composition (%)

a) Chloride penetration and steel corrosion tests

Cement Type I

GRBA

20.80 5.50 3.16 64.97 1.06 0.08 0.55 2.96 2.89

87.0 1.08 2.58 1.25 0.5 0.08 1.0 0.09 5.71

Compressive strength of concretes were determined at 28 days of curing then, cylindrical specimen with 100-mm in diameter and 200-mm in height were also performed for the strength test after 5-year exposure in marine site. The results are shown in Table 3 and found that the compressive strength at 28 days decreases with the increase of GRBA replacement and the lowest compressive strength was founded in 50%-GRBA concrete (for each W/B ratio). Between

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Modern Methods and Advances in Structural Engineering and Construction Table 2. Compressive strength of concretes at 28-day and 5-year exposure in tidal zone of marine environment. Compressive strength (MPa) Mix

28-day curing

5-year exposure

45.1 42.9 40.8 39.4 39.3 30.9 33.8 32.9 31.1 28.6

44.5 46.3 44.1 43.2 40.5 29.5 35.3 34.6 34.0 29.1

120

No strength loss

115 110 105

50%-GRBA

35%-GRBA

25%-GRBA

Cement

15%-GRBA

50%-GRBA

85

35%-GRBA

90

Cement

95

25%-GRBA

100 15%-GRBA

Compressive Strength Ratio at 5-year to 28-day (%)

I45 I45GRBA15 I45GRBA25 I45GRBA35 I45GRBA50 I65 I65GRBA15 I65GRBA25 I65GRBA35 I65GRBA50

3.2. Chloride penetration in concrete In orderto evaluate chloride behaviorin concrete, the water soluble chloride in exposed concrete was investigated and presented in term of chloride penetration profiles. Moreover, the chloride diffusion coefficient (Dc ), basedon measuredchloride penetration values was also calculated by fitting the general solution of Fick’s second law [10] on chloride penetration profile. Figure 3 shows the chloride penetration profiles of GRBA concretes at 5-year exposure in marine environment. The results showed that GRBA concretes provided lower chloride penetration than concretes without GRBA at the same W/B ratio and the same distance from surface of concrete. In addition, the use of 15%–25% of GRBA in concrete significantly reduces the chloride penetration or increases its durability. However, the use of high volume GRBA

28 days and 5 year-exposure, GRBA concretes continuously gain strength faster than Portland cement type I concretes, especially in concrete containing GRBA of 15%–35% by weight of binder. During 5-year exposure, the seawater did not seem to influence the strength of the concrete containing GRBA, no strength loss found in GRBA concrete (as shown in Fig. 2). This result was agreed with the investigation by Thomas (2004) [5] that the strength loss between 2 to 10 year exposure in marine environment of concrete containing pozzolanic material was less than that cement concrete. The strength loss of pozzolan concrete in sea water is lower than the cement concretes due to the good properties of pozzolan concrete such as lower permeability, higher strength at long term, and chemical paste composition [9].

I45GRBA15 I45GRBA50

I45GRBA25

7.00 6.00 5.00 4.00 3.00 2.00

-

Fig. 2. Percentage compressive strength of GRBA concrete at 5-year exposure as compared with 28day curing.

I45 I45GRBA35

8.00

1.00 0.00 0

10

20 30 40 Distance from surface(mm)

50

60

a) W/B of 0.45 I65 I65GRBA35

8.00

I65GRBA15 I65GRBA50

I65GRBA25

7.00 6.00 5.00 4.00 3.00 2.00

-

0.65

W/B Ratio

Cl (% by wieght of binder))

0.45

Cl (% by wieght of binder))

80

1.00 0.00 0

10

20 30 40 Distance from surface(mm)

50

60

b) W/B of 0.65 Fig. 3. Chloride penetration profiles of concretes containing GRBA at 5-year exposure in marine environment.

-

-6

2

Cl Diffusion coefficient (D cx10 mm /s)

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Sai On Cheung, Siamak Yazdani, Nader Ghafoori, and Amarjit Singh (Eds.)

7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0

W/B= 0.65

W/B= 0.45

0

10

20 30 40 GRBA replacement (%)

50

Fig. 4. Effect of GRBA on chloride diffusion coefficient of concretes at 5-year exposure in marine environment.

in concrete (50% replacement) provided a low resistance of chloride penetration when compare to the concrete containing low volume GRBA. The similar trend was also foundin both W/Bratio of0.45and0.65. This result is confirmed by several researches that the pozzolanic reaction of GRBA in concrete performs lower permeability, thus leads to lower chloride ingress than normal concrete [2, 3]. The effect of GRBA and W/B ratio on chloride diffusion coefficient (Dc ) of concrete at 5-year exposure in marine site is showed in Fig. 4. In both concrete with W/B of 0.45 and 0.65, the chloride diffusion coefficient of concrete decrease with GRBA replacement level but they were found to increase when the substitution ratios of GRBA up to 50% by weight of binder. This result was also confirmed the chloride penetration that the use of high volume GRBA is lower chloride resistance than that concrete with the low volume GRBA. This is because the high replacement of GRBA will result in lower cement content in the concrete mixture, thus the amount of cement is not enough to react with GRBA to form additional calcium silicate hydrate.

Fig. 5. Effect of GRBA on steel corrosion in concretes at 50-mm covering depth for 5-year exposure in marine environment.

at 5-year exposure. The results indicated that the higher is the chloride content in concrete, the higher is the corroded steel. The concrete containing GRBA of 15% to 25% (by weight) reduces the free chloride content (at the position of embedded steel bar) together with a low steel corrosion. The steel corrosion was evidently increased with the increase of W/B ratio, especially at the high volume of GRBA concrete (35–50% GRBA). It was found that the use of GRBA in concrete up to 50% replacement shows the lowest corrosion resistance, highest of steel corrosion was found at each W/B ratio. However, the use of 15–35% of GRBA can be significantly enhanced the corrosion resistance of embedded steel bars and presents a better corrosion resistance as compare to cement concrete. Since, the pozzolanic reaction of GRBA in concrete can improve the physical characteristics of paste (low permeability), which results in enhancing the corrosion resistance as well. For instance, concretes containing GRBA 0%, 15%, 25%, 35%, and 50% by weight of binder with W/B ratio of 0.45 had percentages of rusted area at 50-mm covering depths of 22%, 2%, 3%, 8%, and 57%, respectively. 4. Conclusions

3.3. Corrosion embedded steel in concrete Figure 5 shows the percentages of rusted area relating to free chloride content at the position of the embedded steel in concrete

(1) During 5-year exposure in sea water, GRBA concretes continuously gain strength faster than cement concretes, especially in concrete containing GRBA of 15%–35% by weight of binder.

Modern Methods and Advances in Structural Engineering and Construction

(2) The chloride diffusion coefficient of concrete decrease with GRBA replacement level, however it were found to increase when the substitution ratios of GRBA up to 50% by weight of binder. (3) The use of 15%–25% GRBA in concrete with W/B ratio of 0.45 produces a high compressive strength together with a low embedded steel corrosion and low chloride ingress into concrete. Acknowledgements The authors gratefully acknowledge the financial supports from the Research and Development Funds, Faculty of Engineering, Burapha University, Thailand contact No. 7/2554. References ASTM C1218, Standard Test Method for WaterSoluble Chloride in Mortar and Concrete, Annual Book of ASTM Standards, USA, 04(1), 1997. Chalee, W. and Jaturapitakkul, C., Effect of W/B Ratios and Fly Ash Finenesses on Chloride Diffusion Coefficient of Concrete in Marine Environment, Mater. Struct. 42, 505–515, 2009. Chalee, W., Ausapanit, P. and Jaturapitakkul, C., Utilization of Fly Ash Concrete in Marine Environment for Long Term Design Life Analysis, Materials and Design, 31, 1242–1249, 2010.

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Chindaprasirt, P., Homwuttiwong, S. and Jaturapitakkul, C., Strength and Water Permeability of Concrete Containing Palm Oil Fuel Ash and Rice Husk–Bark Ash, Constr. Build. Mater., 21, 1492–1499, 2007. Crank, J., The Mathematics of Diffusion, 2nd edn. Oxford Press, London, 1975. Naik, T. R., Singh, S. S. and Hossain, M. M., Permeability of Concrete Containing Large Amounts of Fly Ash, Cement and Concrete Research, 24, 913–922, 2004. Sata, V., Jaturapitakkul, C. and Kiattikomol, K., Influence of Pozzolan From Various by-Product Materials on Mechanical Properties of HighStrength Concrete, Constr. Build. Mater., 21, 1589–1598, 2007. Tangchirapat, W., Buranasing, R., Jaturapitakkul, C. and Chindaprasirt, P., Inuence of Rice Husk Bark Ash on Mechanical Properties of Concrete Containing High Amount of Recycled Aggregates, Constr. Build. Mater., 22, 1812–1819, 2008. Thomas, M. D. A. and Matthews, J. D., Performance of Pfa Concrete in a Marine Environment-10year Results, Cement and Concrete Composites, 26, 5–20, 2004. Troconis de Rincon, O., Castro, P., Moreno, E. I., Torres-Acosta, A. A., Moron de Bravo, O., Arrieta, I., Garcia, C., Garcia, D. and MartinezMadrid, M., Chloride Penetration Profile in Two Marine Structures-Meaning and Some Predictions, Building and Environment, 39, 1065–1070, 2004.