2011 inspection,diagnosis,materials and processing methods to repair the commercial deck in puerto q

Paper No.

'"

11011 INTERNATIONAL

INSPECTION, DIAGNOSIS, MATERIALS ANO PROCESSING METHODS TO REPAIR THE

COMMERCIAL DECK IN PUERTO QUETZAL GUATEMALA

Edgar Maya Corrosión y Protección Ingenería , S.C .

Rio Nazas 6. Cuernavaca, Morelos.

Mexico . 62290.

Lorenzo Martínez(1) Instituto de Ciencias Físicas , Universidad Nacional Autonoma de Mexico, Ave Universidad 1001, Col. Chamilpa, Cuernavaca, Morelos . CP 62210.

Lorenzo M. Martinez-dela-Escalera Corrosión y Protección Ingenería, S.C. Rio Nazas 6. Cuernavaca, Morelos.

Mexico. 62290 .

Marco Vinício Morales Grupo K, Corrosion y Proteccion Guatemala Leonardo De Silva-Munoz Instituto de Investigaciones Eléctricas Reforma 113 Cuerna vaca , Morelos, CP 62490, Mexico

Jorge Canto Corrosión y Protección Ingenería, S.C. Rio Nazas 6. Cuernavaca, Morelos.

Mexico . 62290 .

Jorge A. Ascencio(1)

Instituto de Ciencias Físicas, Universidad

Nacional Autonoma de Mexico,

Ave Universidad 1001, Col. Chamilpa ,

Cuernavaca, Morelos. CP 62210 .

ABSTRACT The corros ion damage in reinforced concrete structures, cause enormous economic losses worldwide.

Concrete structures in oceanic ports and piers are exposed to a series of physical and chemical processes that can cause the rapid deterioration of both concrete and steel rebars . Such structures must receive special attention by performing periodic assessments of their structural integrity and by installing cathodic protection systems. The present paper describes the sequence used to evaluate the corrosion of a reinforced concrete structure that crowned the sheet piling of the commercial pier of Puerto Quetzal in Guatemala. Repair and corrosion protection methods and strategies are also described.

Keywords: Reinforced concrete, coastal environment, concrete corrosion, cathodic protection systems.

INTRODUCTlON Corrosion of steel reinforcing bars (rebars) in concrete structures is one of the most significant maintenance and repair challenges faced by civil engineers. Chloride ion contamination, carbonation , Alkalí-Silíca Reaction, and reaction with sulfate species are the most common forms of concrete (1) Consultants al Corrosíon y Proteccíon Ingenería, S.C.

©2011 by NACE Intemational. Requests for permission to publish this manuscnpl in any fo rm , in pan or in whole. must be in wríling 10 NACE lntemational, Publications Di vision, 1440 South Creek Dri ve. Houston . Texas 77084. The material presented an d the views expressed in this paper are solely those of the aUlhor(s ) an d are nOl necessarily endorsed by the Association.

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deterioration that can increase corrosion risk on reinforcing steel bars inside concrete structures. Using epoxy coated steel rebars, and special concrete mixture compositions can significantly reduce corrosion risks. But when the structures are already built, a common way of protecting the steel rebars is the installation of cathodic protection systems .'

Concrete structures in oceanic ports and piers are especially prone to corrosion. They are exposed to a series of physical and chemical processes that can cause the rapid deterioration of both concrete and steel rebars. Such structures must therefore receive special attention by performing periodic assessments of their structural integrity and by installing cathodic protection systems.

Concerned about visible deterioration of a reinforced concrete structure that crowned the sheet piling of the commercial pier of Puerto Quetzal in Guatemala, Empresa Portuaria Quetzal , responsible for operation and maintenance of the commercial port, asked for engineering services for repairing and protecting the damaged concrete structure.

Following standards from ASTM International (American Society for Testing and Materials),2.3 NACE International (National Association of Corrosion Engineers) and the ICRI (International Concrete Repair Institute),4,5,6 diagnostic and repair procedures were implemented on the damaged concrete structure.

In addition, corrosion protection systems were designed and installed in order to avoid further deterioration of the reinforcing metal bars of the reinforced concrete in question.

Site Characteristics

Quetzal Marine Terminal, located on the pacific coast of Guatemala (13 0 55" N, 90 0 47" W), was built from 1980 to 1984 in order to satisfy the urgent need of a modern port for importlexport activities at the Pacific Ocean route . The terminal is managed by the state owned company "Empresa Portuaria Quetzal" and it is considered one of the main ports in Guatemala due to the large import-export volumes. The whole complex has 835.15 hectares, divided into 10 zones involving general port activities, cargo storage, commercial and industrial development areas, administration buildings, and other services. Its strategic geographic localization allows it to serve the Pacific Basin and the West Coast of the American Continent, and because its nearness to the Panama channel, it can be accessed from any place around the world .

At the eastern part of the terminal, lies the principal dock destined for general national and international commerce (Figure 1a). Its principal structural element is a steel sheet piling crowned by a reinforced concrete beam. The concrete beam is a continuous structure 1,050.00 m long, 4.50 m high and 1 m wide. Being directly exposed to the Pacific Ocean waters and ship collisions, the concrete beam has been subject to chemical and physical stress that has resulted in visible deterioration of the structure .

Maintenance records indicate that on 2007, the front part of the pier was repaired, but according to the staff of the port, the repair works were incomplete leaving several areas with exposed steel rebars (Figure 1b,c) . Apparently, repair works limited to the substitution of steel parts in the concrete structure, but neglected to restore the damaged or demolished concrete. The exposed steel structure was considerably deteriorated due to corrosion .

Figure 1: .

a) Aerial view of Puerto Quetzal.

b), c) Examples of damage on the concrete sheet piling crowning beam .

EVALUATION METHOOS ANO RESULTS

In order to properly diagnose the concrete structures integrity, jt was necessary to gather existing information about the site such as construction technical and historical information about the site operation such as and repair reports, and previous integríty studies of the last 12 months. all information for starting the studies on the concrete structure, a series tests were in order to assess the extent of the damage upon the concrete and the steel rebars.

Mechanical Strength Tests The mechanical strength of the studied concrete was evaluated using procedures described in the ASTM Ca05 standard. Physical were made upon the concrete structure using a sclerometer as illustrated in figure 2a. Resuas showed that the strength of the concrete was acceptable, since of the showed impact values higher than 300Kg/Cm2, while only 3% of the readings had unacceptable values (Table 1).

Table 1

Concrete Core Sample Test Cylindrical concrete core were taken from the concrete beam of the pier using a pedestal drill machine (Figure 2b), The core served as specimens for the study of pH, carbonation and of chloride The samples had between 5 to 7.5 cm in diameter and different depths, and were taken from damaged sections and from areas where concrete appeared in conditions. In order to retrieve the concrete cores as near as possible to the internal steel rebars, a metal detector was used. The specimen cutting, preparation and analysis were performed according to ASTM C42.

Chemical analysis of the concrete indicated that there was no significant amount of carbonate but the chloride content was aboye the recommended limit of 0.025 % by weight in almost aH of the core samples (Table 2). This indicated that active corrosion of metal rebars was most Iikely

Table 2

Free Corrosion Potential Measurements Free corrosíon potential (Ecorr) values of reinforced concrete are related to the probability of corrosion of its steel reinforcing bars. Ecorr measurements were carried out using a standard COIJPElr/cODIJer sulfate (CU/CUS04) reference electrode connected to a high impedance input multimeter to ASTM C876 standard 2c). Table 3 presents the percent of the tested concrete surface with low, moderate high probability of corrosíon. Results show that less than the half of the testing points presented potentials aboye the low corrosion risk límit.

Table 3

p ercent ofC oncrete Surf ace Wlt' h Low , Moderate and High p robablltyof T Corroslon Corrosion probability according to ASTM C876 Lowprobability of corrosion (Ecorr > -200mV vs. CU/CUS04) Moderate probabili!y of corrosion (-200mV < Ecorr < -350mV vs . CU/CUS04) High probability of corrosion (Ecorr < -350mV vs. Cu/CuSO,J

Area (%) 40% 35% 25%

Evaluation of Hidden Corros ion Zones by Acoustics Tests Steel rebar corrosion in reinforced concrete is sometimes not visible from the surface of the concrete.

When carbonate or chloride species and water penetrate the structure and reach the metal rebars , corros ion processes take place without any visible man ifestation on the surface of the structure .

Acoustic tests can be used to detect hidden metal corrosion zones . Acoustic tests were performed according to ASTM 04580 standard (Figure 2c). Combined with Ecorr and resistivity measurements, hidden corrosion zones were indentified (Table 4) .

Table 4

oegree of Interna ICorros lon on t he InspectedConcrete S urface Degree of deterioration by_ corrosion Severely damaged zones . (Urgent attention) Moderately damaged zones . (Short term maintenance) Minimal corrosion problem zones . (Long term maintenance)

Inspected surface area (%) I 20 % I I 73 % 7%

I

Figure 2: IIlustrations of the corrosion evaluation methods applied : a) strength tests, b) concrete cores removal , c) potential measurements , and d) acoustic tests.

REHABILlTATION STRATEGIES In order to avoid further deterioration by corrosion of the concrete crowning beam of the pOrt sheet piling the following actions were recommended : â&#x20AC;˘ Replacement of fragile or contaminated concrete. â&#x20AC;˘ Cleaning and rehabilitation of damaged or contaminated reinforcing steel.

â&#x20AC;˘ Installation of zinc sacrificial anodes . â&#x20AC;˘ Application of a protective coating on the concrete surface .

Photographic evidence and amounts of replaced concrete , rehabilitated steel rebars and installed zinc anodes are presented in Figure 3 and Table 5.

Table 5

Amoun s ofReplacedConcrete , Rehabilitated Steel Rebars and Installed Zinc Anodes

I Quantity

Rehabilitation activity

Replacement of damaged or contam inated concrete Clean and rehabilitation of damaged or contaminated reinforcing steel Installation of zinc sacrificial anodes Application of a polymer coating to protect the entire surface of the concrete beam .

Top face

Front face

I

1,050 m 2

4,725 m 2

I

1,800 kg .

2,100 kg.

4,116 anodes

13,967 anodes

I

5,775.00 m 2

Figure 3: Rehabilitation process photographs . a) Removing and cleaning concrete , b) and c) Installation of zinc anodes .

CONCLUSIONS

The concrete crowning of the commercial dock sheet piling in Quetzal Marine Terminal, Guatemala, had visible signs of deterioration including the corrosion of exposed steel reinforcing bars . A team of engineers performed historical background research executed a complete diagnosis of the integrity of the structure including chemical analysis and the localization of corroded internal steel rebars , and carried out rehabilitation activities. In addition to concrete and steel rebars repair, a cathodic protection system was installed using zinc sacrificial anodes and a protective coating was applied on the reinforced concrete structure . Rehabilitation activities were still ongoing to the date this paper was written. With the applied measures , further corrosion of the reinforcing bars will be stopped , and the useful life of the repaired concrete structure will be considerably extended.

ACKNOWLEDGMENTS

Authors thank Eduardo Gonzalez of Vector Corrosion Technologies for his valuable assistance during the technical evaluation.

REFERENCES

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2. C. Andrade , V. Castelo, M.C. Alonso, JA Gonzalez, "The Determination of the Corrosion Rate in Steel Embedded rn Concrete by the Polarization Resistance and A. C. Impedance", ASTM STP 906 , Ed . V Chaker , ASTM, Philadelphia, 1986.

3. M. Hannson, B. Sorensen, "The Threshold Concentratíon of Chlorides in for the Initiation Reínforcement Corrosion", ASTM STP 1065, N.S. Berke, V. Chaker and D. Whiting, American Society of Testing and Materials, Philadelphia, pp. 3, 1990.

4.

Manual de Inspección, Evaluación y Armado, DURAR (Durabilidad de la armadura),

5.

Millard, JA Harríson, A.J. Eduards, "Measurement of the Electrical Resistivity of Reinforced Concrete Structures for the Assessment of Corrosion Risk", Br. J. of Nondestructive Testing. Vol. 31, pp. 616,1989.

6.

W. Morrís, M. "Evaluacíón del Avance de la Corrosión de en Estructuras de Hormigón" División Corrosión, INTEMA Facultad de Ingeniería, Universidad Nacional de Mar del Plata Juan B. Justo 4302 B7608FDQ Mar del Plata - Argentina.

7. David W. Whitmore, Concrete Bridge

de Corrosión en Estructuras de Hormigón ISBN 980-296-541- 3,1

and J. Chrístopher Ball "Galvanic Corrosion Protection Systems for Vector