Efficacy of GFRP Wraps on Rehabilitation of Corrosion-Damaged HSC Columns

Dr. J. Revathy, Associate Professor, Department of Civil Engineering, B.S.Abdur Rahman University, Chennai Dr.A.Leema Rose, Associate Professor, Department of Civil Engineering, Adhiparasakthi Engineering College, Melmaruvathur Dr.K.Suguna and Dr.P.N. Raghunath, Professor of Structural Engineering, Department of Structural Engineering, Annamalai University, Annamalai Nagar.

Corrosion of steel reinforcement in concrete is considered to be the major cause of deterioration in civil infrastructure facilities. This article presents the results of a comprehensive experimental investigation carried out to study the effect of Glass Fibre Reinforced Polymer (GFRP) wrapped high strength concrete (HSC) columns subjected to various levels of corrosion. The columns tested for this investigation were 150 mm in diameter and 900 mm in height. The columns were subjected to an accelerated corrosion inducing 10% and 25% corrosion-damaged levels. The corroded columns were wrapped with different configurations of glass fibre reinforced polymer namely Woven Rovings (WR) and Unidirectional Cloth (UDC) of 3 mm and 5 mm thicknesses. The columns were then tested under uni-axial compression till failure. The test results show a marked enhancement in ultimate strength by 39% and ductility by 123%. The strength and ductility of the GFRP confined corrosion-damaged columns increase with increasing wrap thickness.

Introduction

There is a large number of concrete structures around the world that have been damaged by extreme environmental conditions, overloading or simply as a result of normal aging. These structures are unsafe to use and urgently need repair for continued use. In metro cities, the emissions of carbon and nitrogen oxide aggravate the situation further by neutralizing the concrete cover. Typically, a reinforced concrete structure requires major restoration work within 15 years of its construction. Corrosion of reinforcing steel bars is one of the main causes of early deterioration of concrete structures. The important causes of corrosion in steel reinforcement are carbonation and chloride penetration. The formation of rust products lead to cracking and spalling of cover concrete. Reinforced concrete undergoing corrosion give the unpleasant appearance and also the reduction in cross-sectional area of steel bar may lead to a loss in structural integrity of the reinforcing steel. Consequently, the safety and serviceability of the concrete structures is affected. Moreover, bond between the steel and the concrete is reduced. The most common methods for repair and retrofit of reinforced concrete columns are concrete jacketing, steel jacketing, and fibre wrapping. Concrete jacketing requires formwork and considerable increase in the weight and cross-section of the column. Steel jacketing is also labor intensive and costly. Recently, Fibre Reinforced Polymer (FRP) proved to be an efficient material in construction world. It offers a high strength, good fatigue life, low maintenance, lightweight, ease of transportation and handling cost. In addition to strengthening a concrete member, the FRP materials are more resistant to corrosion and provide a protective barrier to concrete from aggressive environment. A number of researchers have been devoted to concrete columns retrofitted with FRP and numerous models were proposed. They reported that FRP confined concrete increased the strength and ductility of the column. A limited number of studies have been carried out on FRP for rehabilitation of corrosion-damaged concrete structures. This research study investigates the effectiveness of using Glass Fibre Reinforced Polymer wrapping on the performance of corrosion-damaged high strength concrete columns.

Experimental Program

Specimen Details of RC Columns
Figure 1: Specimen Details of RC Columns and Reinforcement Cage in Formwork

Specimen Details and Preparation

The diameter of the columns was 150 mm and the height was 900 mm. The concrete used for the specimens had a mean compressive cylinder strength at 28 days of 63.2 MPa. The details of the concrete composition are shown in Table 1. The concrete was cast, compacted, finished, demolded, and cured for 28 days in a standard manner. Deformed reinforcing bars with a diameter of 8 mm of strength 450.6 MPa were used as longitudinal reinforcement. Steel bar with a diameter of 6 mm of strength 300.8 MPa were used as ties at a spacing of 115mm. The longitudinal bars were kept protruding for a length of 75 mm beyond the column face towards inducing accelerated corrosion. Fig.1 presents the specimen details of the RC columns.

Table 1 – Composition of Concrete Mixture
Material Quantity in Kg/m3
Cement 450
Coarse Aggregate 20 mm 680
10 mm 450
River sand 780
Hyperplasticizer – Glenium B233 0.8 % by weight of binder
Silica Fume 25
Water 160

Test Matrix

The columns were subjected to accelerated corrosion and then tested under uni-axial compression. Three columns were tested without wrapping and the remaining column specimens were wrapped with Woven Roving Glass Fibre Reinforced Polymer (WRGFRP) and Unidirectional Cloth (UDCGFRP) of 3 mm and 5 mm thicknesses. Table 2 summarizes the test program for RC columns.

Table 2 – Test Matrix for RC Columns
Specimen Level of Corrosion (%) Type of GFRP GFRP Thickness (mm)
NC CON No Corrosion --- 0
CD 10 CON 10 --- 0
CD 10 WR 3 10 WR 3
CD 10 WR 5 10 WR 5
CD 10 UDC 3 10 UDC 3
CD 10 UDC 5 10 UDC 5
CD 25 CON 25 --- 0
CD 25WR 3 25 WR 3
CD 25 WR 5 25 WR 5
CD 25 UDC 3 25 UDC 3
CD 25 UDC 5 25 UDC 5

Accelerated Corrosion Process

Each column was subjected to an accelerated corrosion process by applying a direct power supply with an output of 32 V and 11 amps. Fig.2 represents the accelerated corrosion set up.

Accelerated Corrosion Test Set-up
Figure 2: Accelerated Corrosion Test Set-up

The columns were immersed in 3.5% sodium chloride solution in a fiber glass tank such that the reinforcement steel bars were above the NaCl solution. The specimens were kept immersed in the solution for 24 hours, to ensure full saturation condition. The direction of the current was adjusted so that the reinforcing steel bars was connected to the positive terminal of the external DC source to act as anode and negative terminal was connected to a thin stainless steel hollow pipe with perforated holes. This was made to increase surface area and oxygen diffusion. The various levels of corrosion are shown in Table 1. The mass loss due to corrosion is related to the current consumed and time for corrosion can be estimated by using Faraday’s law.

Δw = (Am.I.t) / (Z.F) --------(1)

where Δw = mass loss due to corrosion, Am = atomic mass of iron (55.85 g), I = corrosion current in amps, t = time since corrosion initiation (sec), Z = valency (assuming that most of rust product is due to Fe(OH)2, Z is taken as 2), F = Faraday’s constant [96487coulombs (g/equivalent)]. During the test period, corrosion activity in all the specimens was monitored by measuring the corrosion potential according to the procedures outlined in ASTM C 876-91. The probability of active corrosion is based on specific ranges of potential of steel reinforcement with respect to standard reference electrode.

GFRP Repair Technique

Two types of GFRP materials were used in the present study to repair corrosion-damaged specimens. Woven Roving and Unidirectional Cloth Glass Fibre Reinforced Polymer was used to rehabilitate the corrosion-damaged columns. The Woven Roving has interwoven fibres oriented at 90º to the longitudinal axis of the fabric. The Unidirectional Cloth has fibres oriented in single direction. The GFRP wrap materials were tested according to the ASTM D 638. The tensile strength, elastic modulus of GFRP wrap material are summarized in Table 3.

Table 3 – Mechanical Properties of GFRP
Wrap Material Thickness (mm) Elasticity Modulus (MPa) Tensile Strength (MPa)
WRGFRP 3 6855.81 147.40
5 8994.44 178.09
UDCGFRP 3 13965.63 446.90
5 17365.38 451.50

The column surface was made rough and cleaned with an air blower to remove any dust and loose particles. A high-pressure air jet was then used to clean the surface from dust or any foreign particles after the grinding process. The wet lay-up technique was used to wrap the FRP layers. This technique was started with applying an iso-phthalic polyester resin to the surface of the concrete column. Next, the dry fibrous reinforcement material was wrapped to fully cover the resin. A roller was then used to remove the entrapped air bubbles and press the resin to penetrate into the fabric. The roller was continuously used until the resin was reflected on the surface of the fabric, an indication of fully wetting. On the top of the fabric, another layer of resin was applied. This completed one FRP repair layer. The procedure was repeated to apply the subsequent layers. The wrapped specimens were then left at room temperature to allow curing of the bonded GFRP laminates.

Test Arrangements

All the column specimens were tested in a loading frame of capacity 2000 kN. The column specimens were loaded under a monotonic uni-axial compression up to failure. To measure the axial compression of the specimen, two deflectometers were fitted at top and bottom of the specimen. A lateral extensometer was provided at mid-height of the column to measure the expansion of the column. Fig. 2 shows the test up and instrumentation provided for the test specimens.

Table 4 – Summary of Test Results
Specimen Ultimate Load (kN) Ultimate Axial Deformation (mm) Ultimate Lateral Deformation (mm)
NC CON 1025 3.38 0.39
CD 10 CON 1000 3.30 0.36
CD 10 WR 3 1075 3.87 0.46
CD 10 WR 5 1150 4.24 0.50
CD 10 UDC 3 1220 4.26 0.54
CD 10 UDC 5 1300 4.53 0.61
CD 25 CON 900 3.21 0.31
CD 25 WR 3 1040 3.74 0.43
CD 25 WR 5 1090 4.00 0.46
CD 25 UDC 3 1190 4.13 0.51
CD 25 UDC 5 1250 4.36 0.59

Results and Discussions

Overall Behavior

The experimental values obtained from tests were summarized in Table 4. From this table, it is seen that the load carried by the corroded columns was significantly reduced due to corrosion damage such as cracking and reduction in cross sectional area of steel reinforcement. The corroded columns lost about 3% and 12% of its load carrying capacity for 10% and 25% degrees of corrosion damage respectively. However, the ultimate axial compression capacity of corrosion-damaged columns was enhanced by GFRP wrapping. The axial compression capacity of corrosion-damaged columns was found to restore the ultimate strength by GFRP wrapping. On overall observations the corroded and then repaired columns were about 40% stronger than the non-corroded un-strengthened columns. It is also to be noted that the UDCGFRP wrapped corrosion-damaged columns resulted in higher ultimate load, this is because fibers in the hoop direction result in the highest hoop tensile strength. The concrete columns wrapped with 3 mm thick WRGFRP and UDCGFRP showed an increase in ultimate axial load by 8% and 22% respectively and those with 5 mm thick WRGFRP and UDCGFRP wrap column exhibited an increase of 15% and 30% respectively for 10% level of corrosion damage. For columns subjected to 25% level of corrosion damage, WRGFRP and UDCGFRP of 3 mm thickness increased the strength level by 18% and 32% respectively and 5 mm thick WRGFRP increased the load capacity by 22% and for 5 mm thick UDCGFRP exhibited an increase of 39%. These results clearly indicate that the effect of GFRP on corrosion damage remarkably improved with increasing wrap thickness.

Failure Modes

The failure of unwrapped corroded columns occurred due to the cracking and reduction in cross sectional area of steel reinforcement. The failure of wrapped specimens was typically marked by rupture of the fibre at or near the mid-height of the specimen. Although it was sudden, the failure could be predicted by the appearance of white patches at the top of the column as the result of the fibre stretching.

Stress-Strain Response

Typical stress-strain curves for corrosion damaged specimens wrapped with WRGFRP and UDCGFRP are shown in Fig.3.

The curves to the right represent the plots of axial compressive stress versus axial strains whereas the curves to the left show the plots of axial compressive stress versus lateral strain. The curve indicates a significant enhancement in strength and ductility of corrosion damaged concrete. Recent studies by Toutanji (1999), Chaallal et al (2000), Bae et al (2009) have shown a similar bilinear trend for FRP wrapped columns with no descending branch. The response in the first region of the curves was similar to that of control columns. The point corresponding to the abrupt change in slope of the curves represents the onset of unstable crack propagation. Beyond this point, concrete volume expansion was observed due to extensive propagation of crack. At this stage, the fibre wrap was fully activated and provides an effective confinement to the cracked concrete and thus increased its axial compressive strength. The response in the plastic region was dependent on the stiffness of FRP sheet wrapping. The lateral strain response was almost closer to a straight line as compared to the axial strain response. This may be due to excessive cracking of the concrete core and hence the column directly depends on the fiber wrap, which is linear-elastic. The curves clearly show that confinement with GFRP enhanced the performance of concrete, both its strength and ductility, under axial load. It can also be inferred that the wrapped columns have more energy absorption capacity before failure.

Ductility Response

Table 5 – Ductility Indices
Specimen Deflection Ductility Energy Ductility
NC CON 1.92 3.07
CD 10 CON 1.90 3.01
CD 10 WR 3 2.73 4.03
CD 10 WR 5 2.88 4.08
CD 10 UDC 3 3.74 5.75
CD 10 UDC 5 3.97 5.82
CD 25 CON 1.74 3.04
CD 25 WR 3 2.67 4.13
CD 25 WR 5 2.88 4.21
CD 25 UDC 3 3.72 5.43
CD 25 UDC 5 3.89 5.61
Table 5 summarizes the ductility indices of tested columns. GFRP wrapping increased not only the strength but also the ductility considerably. In addition, it is clear that confinement with GFRP wrap greatly improved the corrosion-damaged column’s ductility. The ductility of the columns increased as the number of layers of wrapping increased. For test specimens subjected to 10% corrosion damage level, 3 mm thick WRGFRP and UDCGFRP increased the ductility by 44% and 97% respectively and 5 mm thick WRGFRP enhanced the ductility by 53% and for 5 mm thick UDCGFRP exhibit an increase in ductility by 109%. The increase in ductility was found to be 54% and 65% for 3 mm and 5 mm thick WRGFRP for test specimens subjected to 25% corrosion damage level. The columns with 3 mm and 5mm thick UDCGFRP showed an increase in ductility by 114% and 123% respectively for 25% level of corrosion damage.

Conclusion

In this study, the effect of GFRP sheet wrapping on rehabilitation of HSC columns from corrosion of steel reinforcement was investigated and the following conclusions were made.
  1. GFRP wrapped corrosion- damaged concrete columns enhanced its load carrying capacity of the columns.
  2. GFRP wrapped corrosion-damaged concrete columns exhibited higher axial and lateral strains at the ultimate stage.
  3. The corrosion–damaged-strengthened columns possess enhanced ductility in comparison to corroded-unwrapped columns.
  4. UDCGFRP wrapped corrosion-damaged concrete column exhibit a better performance when compared to WRGFRP.
  5. The maximum increase in ductility was found by 65% and 123% for respectively for WRGFRP and UDCFRP wrapped corrosion-damaged concrete columns.
  6. The failure mode in all the wrapped columns consisted of rupture of fibres.

Acknowledgment

The authors acknowledge the financial assistances of the University Grants Commission, New Delhi through its Grant scheme, which enabled for conducting this research. The experimental work was carried out in the structures laboratories of the Annamalai University, Chidambaram.

References

  • Almusallam, T.H. (2007), Behaviour of Normal and High-Strength Concrete Cylinders Confined with E-glass/epoxy Composite Laminates, Composites, Part B-Engg, 38, 629-639.
  • ASTM (1991), Standard Test Method for Half-Cell Potentials of Uncoated Reinforcing Steel in Concrete, C 876-87.
  • ASTM D 638, Standard Test Method for Tensile Properties of Plastics.
  • Belarbi,A., and Bae, S.W. (2007), An Experimental Study on the Effect of Environmental Exposures and Corrosion on RC columns with FRP Composite Jackets. Composites, Part (B), 38, 674-684.
  • Chaallal, O., Shahawy, M. and Hassan,M. (2003), Performance of axially loaded short rectangular columns strengthened with carbon fiber-reinforced polymer wrapping, ASCE, Journal of Composites for Construction, 7(3), 200-208.
  • Debaiky,A., Green, M., and Hope,B. (2002), Carbon Fiber-Reinforced Polymer Wraps for Corrosion Control and Rehabilitation of Reinforced Concrete Columns, ACI Materials Journal, 99(2), 129-137
  • Matthys, S., Toutanji, H., Audenaert, K. and Taerwe, L. (2005), Axial Load Behaviour of Large-Scale Column Confined with Fiber-Reinforced Polymer Composites, ACI Structural Journal, 102(2), 258-267.
  • Mirmiran, A. and Shahawy, M. (1997), Behavior of Concrete Columns Confined by Fiber Composites, ASCE, Journal of Structural Engineering, 123(5), 583-590.
  • Toutanji, H. (1999), Stress–Strain Characteristics of Concrete Columns Externally Confined with Advanced Fiber Composite Sheets. ACI Materials Journal, 96(3), 397-404.
  • Pantazopoulou, S. J., Bonacci, J. F., Sheikh, S., Thomas, M. D. A., and Hearn, N. (2001), Repair of Corrosion-damaged Columns with FRP wraps, ASCE, Journal of Composite Constructions, 5(1), 3–11.
Click Here
To Know More or to Contact the Manufacturer
Please let us know your name.
Invalid Input
Please let us know your Designation.
Please let us know your Contact Number.
Please let us know your email address.
Please brief your query.
Our other Value-Added Services:

To receive updates through e-mail on Products, New Technologies & Equipment, please select the Product Category(s) you are interested in and click 'Submit'. This will help you save time plus you will get the best price quotations from many manufacturers, which you can then evaluate and negotiate.

Invalid Input
Invalid Input
Invalid Input
Equipment with cutting edge technologies is making tunneling smoother at RVNL’s mega railway project and helping contractors overcome geological complexities. Sandvik’s DT 821 C and DT 922i advanced automatic

Read more ...

The Metro-Rail segment in India is growing at a frantic pace with positive long-term prospects, supported by the impetus provided by the government by way of business-friendly policies and financial support. Use of advanced

Read more ...

Lucknow Metro has achieved the distinction of becoming the fastest built metro rail project in the country - both in terms of completion of construction work and execution. On 25th November 2013, LMRCL

Read more ...

India received its first mode of modern transportation in 1853 when the first railway line was laid from Bombay to Thane to boost industrial activities and ensure easy accessibility to heavy raw materials. In the following

Read more ...

The growth of the tunnel construction in the country has been driven by a robust pipeline of projects and investments in setting up hydropower projects, developing urban mass rapid transit systems, improving road

Read more ...

Stoked by their debut success with the timely completion of Kajang Line’s underground section, Gamuda Engineering found themselves pitted once more against the unique challenges of tunnelling in Kuala Lumpur

Read more ...

A tunnelling project is a race against time and costs. Getting it right from the very beginning requires knowledge, skill and experience, as well as a proper range of equipment that fulfils the customer’s tunnelling

Read more ...

The Mumbai-Nagpur Expressway is delayed until 2022. In the meantime, a machine ‘GHH IS26’ with remarkable reliability has been specially flown in from the supplier and is in operation to help complete the project

Read more ...

The project, located at the riverside of the Moscow River, passes under heavy traffic and crowded buildings. It includes two sections of a total length of 2947m. One is from Maple Avenue Station to No.2 Working Shaft

Read more ...

Pull Force is the force that a truck or prime mover can exert onto a transporter or any type of trailer. It has been a subject of much controversy and misunderstandings as truck manufacturers and end-users often do not talk

Read more ...

The first Sandvik DT922i, a computer controlled fully automatic tunneling jumbo, has been introduced by Sandvik Mining and Rock Technology in India with a vision to achieve high levels of safety, productivity and

Read more ...

Horizontal Directional Drilling is a technology in pipe and utility installation that allows greater accuracy and flexibility in placement and ends the need for costly digging, large crews, road closures and other

Read more ...

Special knowledge is required for building tunnels and wind energy plants in order to implement demanding projects. The facilities and manufacturing processes required for such projects can be adjusted well in advance for

Read more ...

The Large Hadron Collider (LHC) at CERN is the biggest particle accelerator in the world – and growing. To equip the LHC for new, more ambitious experiments in the next decade, the accelerator is currently

Read more ...

The river has its source at over 3000 meters high in the snow-covered Andes. It reaches the Pacific Ocean after 250 km. On its way, it overcomes a considerable gradient and is, therefore, ideally suited to generate electricity

Read more ...

Tan Shunhui, Chairman, CREG, discusses the competitive advantages of the company’s tunneling equipment and solutions, emerging opportunities in developing countries, factors driving its growth and success across

Read more ...

15-meter mega Slurry TBM rolled off the assembly line at CRCHI. The excavation diameter of the equipment is 15.01 m, its total length is about 130 m, total weight is about 4300 t, installed power is about 9755 kW, rated

Read more ...

Being the longest water delivery line in the history of Jilin province, transferring water from Songhua River into Central Jilin Province will transfer the largest capacity of water and cover the largest areas. The water diversion

Read more ...

Amit Kaul, BASF India Limited (Construction Chemicals Division), India, tells about the innovative tunnel lining system and related design aspects, and also describes the main advantages of this lining system in comparison

Read more ...

Underground infrastructures are an integral part of modern cities as they serve to counter problems of surface congestion and environmental degradation. The problems of ground vibrations, vibration induced noise and ground

Read more ...

×
Sign-up for Free Subscription
'India Construction Week'
Weekly e-Newsletter on Construction Industry
Get the latest news, product launches, projects announced / awarded, government policies, investments, and expert views.