H. Susanto, J. Supardi and S. Fonna
Keywords: Corrosion Degradation, ASTM C876, V-Isit 2.7.3, Coastal Building, Tsunami 2004
Abstract:
In the aftermath of the Tsunami in 2004, some infrastructure that was submerged by tsunami water was rehabilitated, reconstructed, and reused. Infrastructure that has been submerged by a tsunami can cause a decrease in strength due to corrosion attacks and can collapse suddenly when an earthquake on a small scale occurs. The impact of decreasing the strength of this infrastructure has been examined by the ASTM C876 Half-cell Potential Technique Method and mapped using V-Isit 2.7.3 software. The results show that there is a decrease in strength in the column of buildings that have been submerged by the tsunami (-250mV) - (- 400 mV) (vs.Cu/CuSO4) and higher when compared to buildings that are not submerged by the tsunami (-200mV) - (- 300mV) that were built after the tsunami occurred. Visual observations were made on one tsunami submerged building in 3 building columns and one tsunami building which was not submerged in 4 columns. Visual observations of the column surface of buildings submerged by the tsunami showed that the steel reinforcement in the column had been actively corroded. It is seen that in all columns there have been cracks that have been increasing every year, visible corrosion products in the form of rust continue to produce, in 2018 the surface of the building column that cracked and peeled has been repaired, but in 2019 the surface of the column has cracked again. The condition of the building column that was not submerged by the tsunami was visually visible and showed that the corrosion attack was higher in the column facing the seashore.
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Degradation of Reinforced Concrete Corrosion on Coast After The 2004 Tsunami Herdi Susanto1*, Joli Supardi2, Syarizal Fonna3 1,2Department of Mechanical Engineering, Faculty of Engineering, Teuku Umar University Meulaboh 23681, Indonesia 3Department of Mechanical and Industrial Engineering, Faculty of Engineering, Syiah Kuala University, Banda Aceh 23111, Indonesia *Corresponding author : herdisusanto@utu.ac.id Abstract In the aftermath of the Tsunami in 2004, some infrastructure that was submerged by tsunami water was rehabilitated, reconstructed, and reused. Infrastructure that has been submerged by a tsunami can cause a decrease in strength due to corrosion attacks and can collapse suddenly when an earthquake on a small scale occurs. The impact of decreasing the strength of this infrastructure has been examined by the ASTM C876 Half-cell Potential Technique Method and mapped using V-Isit 2.7.3 software. The results show that there is a decrease in strength in the column of buildings that have been submerged by the tsunami (-250mV) - (400 mV) (vs.Cu/CuSO4) and higher when compared to buildings that are not submerged by the tsunami (-200mV) - (- 300mV) that were built after the tsunami occurred. Visual observations were made on one tsunami submerged building in 3 building columns and one tsunami building which was not submerged in 4 columns. Visual observations of the column surface of buildings submerged by the tsunami showed that the steel reinforcement in the column had been actively corroded. It is seen that in all columns there have been cracks that have been increasing every year, visible corrosion products in the form of rust continue to produce, in 2018 the surface of the building column that cracked and peeled has been repaired, but in 2019 the surface of the column has cracked again. The condition of the building column that was not submerged by the tsunami was visually visible and showed that the corrosion attack was higher in the column facing the seashore. Keywords : Corrosion Degradation, ASTM C876, V-Isit 2.7.3, Coastal Building, Tsunami 2004 Introduction After the earthquake and tsunami struck Aceh in 2004, some infrastructure in West Aceh was repaired and reused [1], This condition is very vulnerable because buildings submerged by the tsunami are very risky [1,2,3]. Considering that Aceh is an area prone to earthquake disasters [4], this causes the phenomenon of corrosion in tsunami-submerged infrastructure that will be reused by local communities is important to monitor. Infrastructure that has been submerged by a tsunami, if repaired while still using a structure that has been submerged in sea water, is vulnerable to corrosion [5,6] and can cause a decrease in strength [6] This is certainly not desirable because it can cause material losses and result in casualties to the community due to falling debris from infrastructure. To avoid the possibility of sudden failure of infrastructure, especially those located in the 2004 tsunami affected area in West Aceh, monitoring of corrosion potential has been carried out to determine the level of corrosion risk in reinforced concrete in 2014 [7] and 2015 [8] by using the half-cell potential technique method [9]. Visual monitoring is carried out on the surface conditions of reinforced concrete building columns. Observations were made on tsunami-submerged buildings and non-tsunami submerged buildings on the coast. Growth in crack levels occurring on the surface of building columns was observed in 2014, 2015 and 2019. The observations were studied to determine the level of infrastructure degradation in seashore after the 2004 tsunami. Research Methods This research will be carried out in the 2004 tsunami affected area of West Aceh in Padang Seurahet and Ujong Kalak villages. Measurement of the corrosion potential of reinforced concrete infrastructure was carried out in August 2014 [7] and the second year in June 2015 [8]. Two buildings that were submerged by the tsunami and two buildings that were not submerged by the tsunami were selected in previous studies [1]. In this study, observations were made on tsunami-submerged and non-submerged infrastructures on the coast, each of which was a tsunami-submerged building and one that was not submerged. Observations were made on building columns that have been measured corrosion potential in previous years [1,7,8]. The location of the building that is the object of research in this study is shown in Figure 1. Measurement of the distance between the location of the research object to the shoreline is measured using the Google Earth-based online web application. And observations of cracks that occur on column surfaces are documented using a digital camera. Figure 1. Location of Research Objects Measurement of the corrosion potential of reinforced concrete infrastructure in previous studies [1,7,8] with the half-cell potential technique [9] method was measured in three columns of reinforced concrete. Before being measured, the reinforcement location is determined using a rebar locator first. Then, making a grid on the column surface in accordance with the location of reinforcement. Measurement of corrosion potential using a half-cell meter. The measurement results in the contour column plot using V-Isit 2.7.3 software [8]. Figure 2. Location of Research Object I The object of study I that was the target of observation in this study was public facilities (Baitul Atiq Mosque). The location is approximately 50 meters from the beach on the right side of the mosque and is 4 meters from the river mouth on the left side of the mosque. This is still used by the local community to worship and every year on December 24 is also used as a location for prayer and dikir as a tsunami warning that struck Aceh in 2004, the location of the object of study I is shown in Figure 2. The object II of research is a mushalla (Mushalla Teuku Umar Batee Puteh) which was built after the earthquake and tsunami struck Aceh in 2004, this building was built in early 2014 which is located in Ujong Kalak village in Johan Pahlawan sub-district and is 100 meters from the coastline, location Research object II is shown in Figure 3. Figure 3: Location of Research Objects II Visual observations of column surfaces were conducted in 2014, 2015 and 2019, so that corrosion degradation that can occur on the surface of reinforced concrete columns can be studied, taking observational data with visual photographs of column surfaces using a digital camera, then the degree of degradation of the columns was studied. Results and Discussion Corrosion Degradation of Buildings Submerged by the Tsunami Visual building infrastructure which is the object of research I is shown in Figure 4. Figure 4: Tsunami submerged buildings as research object I The three building columns of the research object I have been measured in the corrosion potential of reinforced concrete surfaces in 2014 [7] and 2015 [8]. Monitoring the level of corrosion in each column has been analyzed using V-Isit 2.7.3 software [1], in this study observations were made on the three surfaces of reinforced concrete columns, where data collection on the column surface was taken in 2014, 2015 and 2019. For a schematic of a column plan that is the object of observation of reinforced concrete column surfaces in buildings submerged by the tsunami, shown in Figure 5. Figure 5: Schematic Column position of Object I [1] The results of measuring the corrosion potential of reinforced concrete surfaces on research object II (Padang Seurahet village) in 2014 [7] and 2015 [8]. The results of the column contour plots are shown in Figure 6. Figure 6: Contour column surface potential of research object I [7,8] Figure 6. shows that for column 1, the condition of the column facing towards the sea is in a high corrosion level with a column surface potential level of 250-400 mV and evenly distributed on the column surface and very susceptible to early failure. The measurement results in 2015 showed that there was passivation on the reinforcement and it was feared that the majority of the reinforcement had rust, while columns 2 and 3 were at the intermediate level, except that the lower and upper columns had been at a high corrosion level and there was an increase in corrosion potential at 2015. Therefore, early response to this building column needs to be done. Observation of the column surface was carried out in column 2 of the tsunami inundated building. Photographs of column surfaces for buildings submerged in tsunami are shown in Figure 7. Where in some parts of the column cracks have occurred in the column and the rust has begun to push concretely until some parts of the column have peeled off and the steel reinforcement has largely turned into rust [1]. (a) Column 2014 (b) Column 2015 Figure 7. Condition of columns in buildings submerged by the tsunami Figure 7 shows the condition of the column where the reinforced steel has been corroded, so that the column volume increases with the appearance of rust and causes cracks in the concrete [9], the damage continues to occur and day after day the level of degradation will continue to occur on the reinforcing steel until the column loses strength. Figure 8: Condition of columns in buildings submerged by the 2019 tsunami The condition of the building column which was submerged by the tsunami has been improved in 2018 by covering the surface of the column that has been peeled off using cement, but in 2019 the repaired surface has cracked on its column surface, this condition show in Figure 8. Corrosion Degradation of Buildings Not Submerged by the Tsunami The building which is the object of research II is shown in Figure 9. Figure 9: Buildings not submerged by tsunami (objects II) The schematic of a non-tsunami submerged building plan that is the object of measurement is shown in Figure 10. Figure 10: Schematic Column position of Object II [1] The results of measuring the corrosion potential of reinforced concrete surfaces in 2014 [7] and 2015 on research object II (Ujong Kalak village). With the condition of the building not submerged by the tsunami. The results of the column contour plots are shown in Figure 11. Figure 11: Contour column contour surface of research object II [1,7,8] Figure 11 shows the condition of the Mushalla column in Ujong Kalak village, where columns 1 and 2 with the column position on the part of the building facing the sea, show that the corrosion rate has been distributed evenly on the surface of the column. This is caused by the vapor and humidity contained in chloride ions in this section is very high and the splash of the waves is large enough to cause chloride ions from ocean waves to be carried by winds from the sea [1] on average NaCl in the air for coastal areas within 50 yards from the coast 11.1 msd and corrosion rates 0.950 mm / yr 3 m / s [10], so that the building column in the morning until noon receives a fairly high chloride ion content with an average wind speed of 9 km / h and a relative humidity of 78-94% [11], this condition is depicted in a sketch of the corrosion phenomenon of a beachside building, shown in Figure 12. This condition causes the column facing the sea to have a higher level of corrosion. In 2015, this shows an increase in corrosion potential on reinforced concrete surfaces for columns 1 and for columns 2 which are at the corner of the building. This corrosion potential decreases due to the passivation phase of reinforcing steel and after passing through this phase it is likely that an increase in potential rate very fast. Figure 12: Condition of columns in buildings facing to the sea Figure 13: Condition of columns in buildings not submerged by the tsunami Buildings that are not submerged by the tsunami, the case in research object II visually shows the difference between the column facing the sea and the mountain where the column facing the sea has experienced a crack in the column due to pressure from rust which is a product of reinforcing steel corrosion in concrete. In addtion, the appearance of rust causes the volume of the concrete to increase and also pushes the concrete surface, causing the column surface to crack, the cracks on the surface of column 2 are shown in Figure 13. Visual column surface on the mushalla wall facing towards the mountain, it shows that there are no cracks that occur on the surface of the column, also the potential for corrosion is still at a low level, so it is still safe against reinforced concrete corrosion. Then, Figure 14 shows that the corrosion attack starts from the bottom side of the column, different when compared to the side of the wall facing the sea which is more actively corroded with the initial symptoms of corrosion starting from 2/3 of the column surface from the top of the reinforced concrete column. It is estimated, the condition of the column facing towards the sea will be very actively corroded compared to the side facing towards the mountain. The condition of the columns directly facing the mountain direction is shown in Figure 14. Figure 14. Condition of columns in buildings facing towards to the mountain Conclution Observations on buildings that were submerged by the tsunami showed that the reinforcing steel in the column had been actively corroded. So that the corrosion product in the form of rust continues to produce and causes the surface of the column to continue being pushed by rust, this causes cracks that continue to occur on the surface of the column. Improvements to the column surface by patching cement on the column surface do not make the structure conditions good, cracks on the column surface will continue to increase with time. Building columns facing the sea for the case of buildings built after the tsunami show symptoms of increasing corrosion rates that are higher when compared to the condition of the columns that are on the side facing the mountain which are more passive from corrosion attacks. References [1] Herdi Susanto, Syifaul Huzni, and Syarizal Fonna, Corrosion of Reinforced Concrete Structures Submerged by the 2004 Tsunami in West Aceh, Indonesia, International Journal of Corrosion, vol. 2018, Article ID 4318434, 9 pages, 2018. [2] M. Ridha, S. Fonna, S. Huzni and A.K. Arifin, 2013, Corrosion Risk Assessment of Public Buildings Affected by the 2004 Tsunami in Banda Aceh, Journal of Earthquake and Tsunami Vol. 7 No. 1, World Scientific Publishing Company [3] M. Ridha, et.al, 2010, Corrosion Risk Assessment of Existing and New Reinforced Concrete Buildings after six years Tsunami Aceh 2004, Proceding 5th Annual International Workshop & Expo on Sumatera Tsunami Disaster & Recovery, TDMRC Unsyiah. [4] BAPPEDA Aceh, 2010, Rencana Pembangunan Jangka Panjang Aceh (RPJP Aceh) Tahun 2005-2025, http://bappeda.acehprov.go.id/v2/index.php?option=com_content&view=article&id=1 09&Itemid=57 (diakses pada tanggal 2 April 2012). 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