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International Journal of Civil Engineering and Technology (IJCIET) Volume 7, Issue 3, May–June 2016, pp. 43–55, Article ID: IJCIET_07_03_005 Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=7&IType=3 Journal Impact Factor (2016): 9.7820 (Calculated by GISI) www.jifactor.com ISSN Print: 0976-6308 and ISSN Online: 0976-6316 © IAEME Publication

EFFECT OF CARBON LAMINATION ON THE STRENGTH OF CONCRETE STRUCTURES Gad Vikas V, Desai Ketan S Shivaji University, Kolhapur, India Sawant Vijaykumar S, Sawant Prajakta V Goa University, Goa, India ABSTRACT This work consists of preparation and testing of different structural model like cubes, Beams and Columns. They are tested for Compression test, Flexural test and Split tensile Test. The comparison between Laminated and un-laminated Structural Models was made in order to know how much strength gain after testing of these structural models, so by which the rehabilitation of any structure can be done without demolishing it with less weight to strength ratio. Key words: Compression test, Split Tensile test, Flexural test, FRP composites, strengthening, carbon fiber, Epoxy resin composites, Fiber orientation, laminated polymer composites, Properties Cite this Article: Gad Vikas V, Desai Ketan S, Sawant Vijaykumar S and Sawant Prajakta V, Effect of Carbon Lamination on the Strength of Concrete Structures, International Journal of Civil Engineering and Technology, 7(3), 2016, pp. 43–55. http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=7&IType=3

1. INTRODUCTION The three basic needs of man are Food, Cloth and Shelter Civil engineer has relevance with all basic needs of man directly or indirectly. Man has progressed lot in developing the methods of constructing shelters. Initially man use to stay in huts and as the time passed it developed into house that is load bearing. And nowadays RCC frame structure has dominant share in construction practices. So all this structures were renovated or constructed by using many advanced techniques and materials. And from many advanced materials carbon fibre is also a very good material for construction. Carbon fibre, alternatively graphite fibre, carbon graphite or CF is a material consisting of fibres about 5–10 μm in diameter and composed mostly http://www.iaeme.com/IJCIET/index.asp

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of carbon atoms. The carbon atoms are bonded together in crystals that are more or less aligned parallel to the long axis of the fibre. The properties of carbon fibres, such as high stiffness, high tensile strength, low weight, high chemical resistance, high temperature tolerance and low thermal expansion make them very popular in aerospace, civil engineering, military, and motorsports along with other competition sports. Carbon lamination is a two components composite material consisting of high strength fibers embedded in polymer matrix. Fiber Reinforced Polymers (FRP) sheets are innovative and sustainable building material being developed during last 20-30 years. To achieve objective the work was related to repair and strengthening of engineering structures and it deals with the design for strengthening of concrete structures by carbon fiber composites. [1]R & M international Pvt. Ltd is company which deals with strengthening and retrofitting works. They studied the properties and made use of carbon fiber for their conventional use. The company had carried the rehabilitation of Karal Railway Over Bridge, Navi Mumbai which got functioned in 1991 and the length of bridge is 700m. [2]. The Flexural strengthening of Glued Laminated Timber Beams with Steel and Carbon Fiber Reinforced Polymers. The aim of this thesis is to study the overall behaviour of reinforced Glulam beams loaded in flexure and to study in comparison the strengthening effect of steel and CFRP[3]. Axial testing of columns confined with carbon fiber polymers and also studied the effect of orientation of fiber. Tests were conducted to demonstrate the concrete confinement capability of FRP laminates consisting of carbon fibers with different fiber orientations including ±45-degree direction and different concrete cross section (circular and rectangular). The performance of the ±45-degree FRP laminates is compared to that of unidirectional FRP laminates of different manufacturers and amounts of materials. [4].This study presents a study on the ductility performance of hybrid fibre reinforced concrete. The influence of fibre content on the ductility performance of hybrid fibre reinforced concrete specimens having different fibre volume fractions was investigated. The parameters of investigation included modulus of rupture, ultimate load, service load, ultimate and service load deflection, crack width, energy ductility and deflection ductility. [5]. Wood properties are often inappropriate for heavy loads construction applications. Major drawbacks like durability and high variability among the properties present in timber can be reduced by using glued-laminated timber. A further step to decrease this variability has been widely investigated during the last decades by bonding FRP (carbon, aramid and glass fibres) to timber or glulam beams [6].There is a large world-wide need for simple and reliable methods to repair and strengthen aging infrastructure and buildings. The use of cementitious fibre composites offers several advantages over the existing methods. No other work on strengthening of structural concrete with cementitious composites reinforced with continuous high strength fibres was identified when the present work started in 1998. At present time, 2003, it still is a new technique and very little research has been internationally reported. This work includes a literature survey describing the state of the art of the strengthening of structural concrete with cement based fibre reinforced composites [7]. Fiber-reinforced polymer (FRP) systems for strengthening concrete structures are an alternative to traditional strengthening techniques, such as steel plate bonding, section enlargement, and external posttensioning. FRP strengthening systems use FRP composite materials as supplemental externally bonded reinforcement. FRP systems offer advantages over traditional strengthening techniques: they are lightweight, relatively easy to install, and are noncorrosive. Due to the characteristics of FRP materials as well as the behaviour of

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members strengthened with FRP, specific guidance on the use of these systems is needed. This document offers general information on the history and use of FRP strengthening systems; a description of the unique material properties of FRP [8]. Beams and slabs externally reinforced with FRP are often in contact with moisture and temperature cycles that reduce the expected durability of the system. Bond degradation is a frequent cause of premature failure of structural elements and environmental conditions are known to relate to such failures. The study shows the effects of cycles of salt fog, temperature and moisture as well as immersion in salt water on the bending response of beams externally reinforced with GFRP or CFRP, especially on bond between FRP reinforcement and concrete. Temperature cycles (10 C; 10 C) and moisture cycles were associated with failure in the concrete substrate, while salt fog cycles originated failure at the interface concrete–adhesive. Immersion in salt water and salt fog caused considerable degradation of bond between the GFRP strips and concrete. However, immersion did not lower the load carrying capacity of beams, unlike temperature cycles (10 C; 10 C) that caused considerable loss. No significant differences were detected on the behaviour of the systems strengthened with GFRP and CFRP [9]. FRP jackets were investigated for their confinement effectiveness on rectangular RC columns. Thirteen reduced-scale short columns were tested to failure in axial compression. Variables investigated include: the type of fibers (AFRP, CFRP or GFRP), the thickness of the jacket, the aspect ratio of the rectangular cross section and the radii of the corners. For square columns, GFRP jackets were observed to increase the ultimate axial stress and strain more effectively than either AFRP or CFRP jackets [10].

2. PROPERTIES OF CARBON FIBER High Strength to weight ratio, Good Rigidity, Corrosion resistant, Fatigue Resistant, Good tensile strength , Fire Resistance/Not flammable, High Thermal Conductivity , Low coefficient of thermal expansion, Non-poisonous, Biologically inert-Ray Permeable, Shelf Life.

2.1. Fiber & Laminate Engineering Properties The values for various engineering properties of carbon fiber and laminate are given below. Table 1 Carbon Fiber Sheet Properties Carbon Fiber Sheet Properties

SI unit

Tensile Strength Tensile Modulus Ultimate Elongation Density

4,900 MPa 230,000 MPa 2.1% 1.8 g/cm3

Table 2 Carbon Fiber Laminate Properties Laminate Properties

SI unit

Tensile Strength

2,750 MPa

Tensile Modulus

16,500 MPa

Ultimate Elongation

1.7%

Density

1.3 g/cm3

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Figure 1 Stress to Strain graph of Various Fibers

2.2. Classification of Carbon Fiber Based on modulus, strength, and final heat treatment temperature, carbon fibers can be classified into the following categories:   

Based on carbon fiber properties. Based on precursor fiber materials. Based on final heat treatment temperature.

3. PROCEDURE OF LAMINATION The execution of strengthening should be carried out according to the following steps. Special care should always be taken to ensure the high quality of work. 

Preparation of concrete surface: Mechanical cleaning of the surface should be carried out (e.g. by sand blasting). Best bond is obtained if the surface is not completely smooth but has a roughness: 0.5-1mmGrinding of surface is carried out and then deep surface holes are levelled.

Figure 2 Grinding of concrete surface

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Figure 3 filling the holes with cement plaster 

Mixing of the two-component glue:

The two component resins used should be properly mixed.

Figure 4 Addition of chemicals

Figure 5 Mixing of chemicals

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Application of glue as well as carbon strips or fabrics:

Resin layer is applied on the surface of the member and the fibres are put into this resin layer in-situ in the form of fabrics. The fabrics are covered again with a resin layer. This procedure can be repeated several times. The successive fabric layers are embedded into the previous resin layer. Fabrics can be unidirectional by running fibres or perpendicular using woven fibres. Resin plays a double role in these applications.

Figure 6 Application of resin layer

Figure 7 Application of carbon fiber material

Protecting layers: Protecting layers can be applied for aesthetic reasons such as sand layer.

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Figure 8 Protecting layer

4. TESTS AND RESULTS 4.1. For evaluation of the engineering properties three tests were conducted viz. Compression test, Split tensile test and Flexural test as described below. Compression Test      

Dimensions of test piece are measured at 3 different places along its height/length to determine the average c/s area. Ends of the specimen should be plane. For that the ends are tested on a bearing plate. The specimen is placed centrally between the two compressions plates, such that the centre of moving head is vertically above the centre of specimen. Load is applied on the specimen by moving the movable head. The load and the corresponding contraction are measured at different intervals. Load is applied until the specimen fails.

Figure 9 compression test

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Split Tensile Test     

Draw diametrical lines on two ends of the specimen so that they are in the same axial plane. Determine the diameter and length of specimen. Place the specimen on the universal testing machine as shown in figure. Apply the load without shock and increase it continuously until nogreater load can be sustained. Record the maximum load applied to specimen. Note the appearance of concrete and any unusual feature in the type of failure.

Figure 10 split tensile test

Flexural Test 

Measure the width and thickness of the specimen including the span length for the calculation of the stress and elastic modulus. Mark on the locations where the load will be applied under three-point bending.

   

Bend testing is carried out using a universal testing machine until failure takes place. Construct the load-extension or load-deflection curve if the dial gauge is used. Calculate the bend strength, yield strength and elastic modulus of the specimen Describe the failure under bending

Figure 11 flexural test

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4.2. Results And Discussion This section deals with the results from the different tests done. The results are plotted as load displacement graphs. Compression Test The compression test was done on cube of dimensions 15cm X 15cm X 15cm.The tests on three cubes of carbon fiber laminated and three cubes of without lamination was done on universal testing machine. The table below shows the obtained results Table 3 Test results of cubes before lamination

Cube 1 Cube 2 Cube 3

c/s Area mm2 22500 22500 22500

MaxForce KN

Max. Displacement

880.5 811.4 860.4

7.80 mm 6.40 mm 7.60 mm

Compressive strength KN/mm2 0.039 0.036 0.038

Table 4 Test results of cubes after lamination

Cube 1

c/s Area mm2 22500

Maximum Force KN 915.90

Maximum Displacement 3.40 mm

Compressive strength KN/mm2 0.041

Cube 2

22500

921.70

3.50 mm

0.040

Cube 3

22500

912.30

3.10 mm

0.040

The compressive strength was increased by about 8% after carbon fiber lamination which is not more but the maximum displacement of laminated cube is much less than unlamented cubes. The decrease in maximum displacement of laminated cubes is about 55% than that of unlamented cubes. The failure of unlamented cube was complete at its maximum load whereas the laminated cubes were still serviceable at its maximum load. Split Tensile Test This test was done on circular column of diameter 15cm and height 30cm.In this test one column with carbon fiber lamination and one without lamination was tested on universal testing machine. The table below shows the obtained results; Table 5 Test results of Column before lamination c/s Area mm2 Circular column

17678.5

Max. Force KN 418.8

Max. Displacement 7.80 mm

Compressive strength KN/mm2 0.024

Table 6 Test results of Column after lamination

Circular column

c/s Area mm2

Max. Force KN

Max. Displacement

Compressive strength KN/mm2

17678.5

921.750

5.60 mm

0.052

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The tensile strength of column was increased by about 55% after carbon fiber lamination. The load carrying capacity of unlamented column was only 418.8 KN whereas load carrying capacity of laminated column was 921.75 KN which is much greater then unlamented column. The decrease in maximum displacement of laminated column is about 28% than that of unlamented columns. The failure pattern is as shown in figure below. The laminated column is still serviceable at the maximum force given to it.

Figure 12 Failure pattern for split tensile test

Flexural Test This test was done on beam of dimensions 15cm x 15cm x 70cm.In this test two beams of carbon fiber lamination and two beams without lamination was tested on universal testing machine. The table below shows the obtained results; Table 7 Test results of Beam before lamination

Beam 1 Beam 2

c/s Area mm2

Maximum Force KN

Maximum Displacement

22500 22500

26.85 29.70

1.00 mm 1.20 mm

Compressive strength KN/mm2 0.0011 0.0013

Table 8 Test results of Beam after lamination

Beam 1 Beam 2

c/s Area mm2 22500 22500

Maximum Force KN 59.3 52.5

Maximum Displacement 1.05 mm 1.10 mm

Compressive strength KN/mm2 0.0026 0.0023

The flexural strength of beam was increased by 55% after carbon fiber lamination. The load carrying capacity of unlamented column was only 28.75KN whereas load carrying capacity of laminated column was 55.9KN which is much greater then unlamented column. The carbon fiber laminated beam was not failed at its given load but the maximum displacement was nearly same as unlamented beam at load greater than 2 times.

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5. COST COMPARISON OF STEEL JACKETING AND CARBON FIBER LAMINATION For comparison of cost of carbon fiber lamination with conventional retrofitting work that is steel jacketing, the column of size 900mm x 900mm and height having 3.3m was considered.

5.1. Cost required for Steel Jacketing Table 9 costs required for steel jacketing Sr. No.

Description of Items

Unit

Qty.

Om shanti enterprises Rate

Amount

1

Providing and fixing 12mm dia. anchor fasteners at 350c/c horizontally & 400c/c vertically staggered on both adjoining faces with anchorage of 125mm.

PER/ NOS

132

475

62700

2

Providing and fixing 20mm dia. anchor fasteners- at top & bottom with anchorage of 200 mm in beams & through bolting in slabs of 150 thick.

PER/ NOS

24

875

21000

3

Providing fabrication and erecting structural steel like plates, angles etc., of various sizes as per drawing including cutting, grinding etc. Complete. (Please note vertical angles to be 150 x 150 x 6 instead of 75x75x6 as mentioned drawing.) Including marking of points on steel plate up to 16mm thick for fixing of anchor fasteners, drilling the same, providing stiffner plates as per drawding. Provided.

KG

2250

120

270000

4

Levelling the column /beam/ slab to be strengthened prior to steel plate jacketing using epoxy putty, roughening of existing column surface for proper bonding between old concrete 7 plate including providing 7 applying high performance adhesive agent for providing a bond betn column & steel plates as per manufacturers specification as recommended.

SQM

15

1000

15000

SQM

16

350

5600

5

Providing & applying two coats of rust preventing & fire retardant paint to the exposed steel plate area. 1) Berger prtectmastic or equivalent. Total amount

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Rs 374300 /-

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5.2. Cost required for Carbon Fiber Wrap Table 10 Cost required for carbon fiber lamination Sr. No.

Description of Items

1

Erection of scaffolding Breaking of column surface using Chipper machine Applying polymer skim coat

2 3

UNIT

QTY

ARYABHATT ENTERPRISES RATE

AMOUNT

-

500

500

SQM

12

550

6600

SQM

12

750

9000

12

4000

48000

-

435

-

12

700

8400

LUMP.

4

Carbon fibre wraps system including all taxes.

SQM

5

Fibre anchor (For Beam Only)

PER NOS

6

Sand sprinkling

SQM

TOTAL AMOUNT

Rs. 72500 /-

Therefore, the cost involved for carbon fiber wrapping is only 20 to 25 % that of using steel jacketing.

6. CONCLUSION The compressive strength of the carbon fiber wrap is 8% more as compared to unlamented cubes. The tensile strength of carbon fiber wrap to column is 55% more as compared to unlamented column. The flexural strength of carbon fiber wrap made to beam is 55% more as compared to unlamented beam. The carbon fiber wraps increases tensile and flexural strength then that of compressive strength. The maximum displacement of carbon fiber wrap is about 30 to 50 % less than that of unlamented concrete cube, column and beam. The use of carbon fiber wrap saves 70 to 75 % cost associated with using steel jacketing. Further investigation should be carried out to check the use of carbon fiber as partial replacement for steel.

REFERENCES [1] [2] [3] [4] [5] [6]

Amelie Gresille (2009), Carbon fiber strengthening and jackting of engineering structures Dr. Gopal Lalji Rai, Kulvinder Singh, Yogesh Singh R & M international Pvt. Ltd. External Pre-Stressing Using Carbon Fibre Laminate JOBIN JACOB & OLGA LUCIA(2007) Flexural strengthening of glued laminated timbers with steel and carbon fiber reinforced polymers” Renato Parretti and Antonio Nanni Axial Testing of concrete columns with carbon FRP: Effect of Fiber Orientation S. Eswari, P.N. Raghunath and K. Suguna (2008) Ductility Performance of Hybrid Fibre Reinforced Concrete Alann Andre (2006) Fibres for Strengthening of Timber Structures

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