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17April 2007-15

AICSGE 6,Structural Engineering Dept.,Faculty of Engineering,Alexandria University

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SELECTION OF APPROPRIATE FIXING AGENT IN CONCRETE

REPAIRS

A. AYOUB, A. KURDI, A. ABDO

* Structural Engineering Department, Faculty of Engineering, Alexandria University-Egypt

A. JAHIN

Civil Engineer

ABSTRACT: Some mechanical properties of commercial fixing agents wereinvestigated to update and complement existing data on these materials.Epoxy and polyester adhesives are the most common adhesives that used to fixsteel reinforcement into hardened concrete. Results obtained in these testsindicated that cured epoxy adhesives posses five to eight times higher tensilestrength and shear strength than Portland cement mortar and much reduces

young's, shear and flexure modulus. Cured polyester adhesives also possesfour to seven times higher tensile strength and shear strength than Portlandcement mortar and much reduces young 's, shear and flexure modulus. Thispaper presents an experimental study to select the appropriate fixing agent inconcrete repair. Compressive strength and flexural strength were carried out

on epoxy and polyester fixing agents, steel reinforcement pull-out test werecarried out on concrete specimens with steel reinforcement fixed into it by epoxyand polyester adhesives, also by cement slurry to compare between materials.Compressive strength is carried out according to ASTM C 109, flexural strengthis carried out according to BS 6319 Part 3 and steel fixing tests is carried outaccording to BS 5080 Part 1/ 1993 and BS 5080 Part 2/1986. Five candidatecommercial epoxy resins and three candidate commercial polyester resins thatare produced by five local companies were selected and tested. Cement mortarcontaining sand cement ratio 3:1 and water cement ratio 0.4 is used as acontrol material in compressive and flexural strength tests, cement slurrycontaining equal weights of cement and water is used as a control material insteel fixing test. Results suggest that most specimens of epoxy and polyesterfixing materials resist approximately the same pull-out loads of specimens that

have steel reinforcement fixed into fresh concrete, and about 20% greater thanthe loads of specimens that have steel reinforcement fixed into concrete bycement slurry. Some other epoxies show a reduction in tension loads about10% of that when steel bars were fixed by cement slurry.


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REINFORCEMENT FIXING MATERIALS

Reinforcement fixing materials or anchorage materials are the materialsused to fix new bars of steel into old concretes that have to repair, the steel bars

are installed into holes drilled into concrete, this system is called post installedsystem as described in ACI 546 R /1996 and ACI 355.1 R /1991. There aretwo types of bonded anchors: grouted anchors and chemical anchors. In thefirst type, the steel bars are bonded in place with cement grout. In the secondtype; the steel bars are bonded in place with two-part chemical compounds ofpolyesters, vinyl esters, or epoxies. The chemicals are available in four forms:glass capsules, plastic cartridges, tubes, or bulk (ACI 355.1 R/ 1991).

Glass capsules are inserted into the drilled hole, and then broken by theanchor rod when it is rotated and hammered into place, thereby mixing twocomponents to cause a chemical reaction.

The plastic cartridges are used with a dispenser and a mixing nozzle, whichmixes the two parts, initiating a chemical reaction while installing thecompound into the drilled hole. The anchor rod is then inserted into the hole

completing the installation. The setting time is dependent on temperature,varying from a few minutes up to several hours.

The tube type contains two components which were mixed and then placedinto the hole, and finally, inserting the anchor rod into the hole.

The bulk systems use epoxies, which are either premixed in a pot and usedimmediately, or pumped through a mixer and injected, into the hole. Theanchor is installed immediately afterward. Epoxies can be formulated to set upquickly or slowly (ACI 355.1 R /1991).

Cement Slurry and Mortar:

Cement slurry containing equal amount of cement and water is the mostcost-effective bonding agent. Cement mortar with 3:1 sand cement ratio and

0.4 water cement ratio is the most cost- effective repairing mortar.

Epoxy Adhesives:

Epoxy resins are gradually becoming some of the most important andversatile polymers in modern civil engineering. Because epoxy have someunique properties, such as toughness, versatility of viscosity and curingconditions, low shrinkage compared to most other thermo- setting resins andconcrete, high adhesive strength and resistance to chemicals.

Epoxies are generally composed of two components: epoxy resin ( the base)and hardener ( the reactor), and some times inorganic filler. These compoundscure by chemical reaction between the resin and the hardener. They are themost common used polymer adhesives.

Polyester adhesives

Polyester adhesivesare less sensitive to inaccuracies in proportioning thanepoxies. They posses a number of desirable qualities such as good resistance to


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a wide range of chemicals, high resistance to abrasion and water penetrationand high bond strength with most building materials.

The amount of heat involved during curing is greater than with epoxies.Shrinkage of polyesters during curing is more than with epoxies, it ranged

between 4% and 8% by volume and may continue over a long time (JackVinson/1975).Most polyester do not bond well to damp surfaces like epoxies, they have

little resistance to fire.

COMPRESSIVE STRENGTH TEST

ASTM C l09/1980 specified the compressive strength test method. 50mmcubes were prepared from epoxy and polyester adhesives and tested, the controlspecimens were made of cement mortar with the same dimensions, suchspecimens were cured 7 days in fresh water, stored in the laboratorytemperature for 28 days then tested.

FLEXURAL STRENGTH TEST

Flexural strength test has been carried out according to BS 6319 Part3/1990 to determine the flexural strength of specimens of polymer-basedmortars and cement based mortars.

The principle of the flexural strength test is the subjection of a testspecimen of a defined geometry and in the form of a simple beam to four pointsloading until failure. Measurement of the apparent surface stresses in bendingis carried out to determine flexural strength.

The dimensions of the specimens and the four points loading test asspecified in BS 6319 Part 3/ 1990 are shown in Fig. 1

Fig.1. Dimensions of the four points loading test.

A deflection transducer or a dial gauge - capable of continuously monitoringthe central deflection of the beam to an accuracy of 0.01 mm- was used.

Four specimens were tested at a time from each batch, the test specimenswas maintained at the test temperature for not less than 16 hours before

testing. The test was carried out at 20C.When testing specimens, the two moulded faces was placed to beperpendicular to the upper face that contact with the metal rollers.

The flexural strength f (in N/mm2) of each specimen is calculated using thefollowing equation:


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f=FL/BD2 whereF is the maximum load recorded prior to fracture in Newton.L is the span of the specimen in mmB is the breadth of the specimen at its point of fracture in mm

D is the depth of the specimen at its point of fracture in mmThe mean flexural strength obtained for a minimum of four specimensoriginating from the same batch was calculated and expressed to the nearesto.2 N/mm.

STRUCTURAL FIXINGS TEST

BS 5080 Part 1/1993 and BS 5080 Part 2/1986 specify a method forconducting tests under tensile and shear forces respectively on structuralfixings installed in concrete used in civil engineering, the tests apply to thebonded fixings held in drilled holes by grouts or other bonding materials. Thedistinct situation in which the test can be applied is for comparative purposes,to compare fixings installed in drilled holes using bonding agents with fixings

cast in concrete or to compare between different bonding agents.The specimens size is based on a characteristic dimension A that is equal to

the maximum diameter of the fixing or of the embedded length, whichever isgreater. The minimum distance of 12A between the center of any fixing and afree edge, and the minimum depth of 4A below the maximum depth of the fixingor of the hole into which it is inserted (BS 5080). The dimensions shown in Fig.2 were used.

Fig.2. Dimensions of structural fixings specimens .

Concrete specimens was cast, compacted by mechanical vibration and curedat least 7 days in water before drilling and the fixing was located in thespecimen on any cast face, i.e. not on the top, trowel led face as shown in Fig. 3.

The reinforcement in the standard specimen shall be so positioned as tooffer no additional strength in the zone of interaction between the concrete and

the fixings.BS 5080 Part 1/1993 and BS 5080 Part 2/1986 state that the diameter of

the drill bit used shall be specified either by the supplier of the fixing materialsor by the user. In this study it was chosen (16mm), the hole shall be normal


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to the surface of concrete, the fixing shall be secured so that the axis of thethreaded portion remains normal to the surface of the concrete.

Fig.3. Structural fixing test specimens.

Tension and shear forces were applied as shown in Fig.4 using the universaltesting machine.

Fig.4. Tension and shear forces

Five samples of each patch of fixing materials were tested using pull outtest, also five samples of control specimens (SC) were tested. The steel bars ofcontrol specimens are stitched into the mould before casting fresh concreteusing a wooden tie as can be seen in Fig. 5.

Fig. 5. The wooden tie for control specimens.


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Fig.6. Steel shear test machine.

EXPERIMENTAL PROGRAMME

Compressive strength test was carried out on three specimens preparedfrom each of the fives selected epoxy adhesives and the three selected polyesteradhesives and three specimens prepared from cement mortar. The specimenswere cubes of 50 mm side length.

Flexural strength test was carried on four specimens prepared from each ofthe fives selected epoxy adhesives and the three selected polyester adhesives

and four specimens prepared from cement mortar. The specimens were prismsof 2525320 mm dimensions.

Pull-out test and steel shear test were carried out on steel fixed intoconcrete by the five selected epoxy adhesives, the three selected polyesteradhesives and cement slurry (SS). Five samples of each patch of fixingmaterials were tested, also five samples of control specimens were tested (SC).

Materials and Mix Proportions

Five epoxy adhesives and three polyesters commercially available in theEgyptian market were examined throughout the program. List of the chemicalproducts and some of their characteristics are given in Table 1. Coded keys areassigned to the products, such coded keys are EA, EB, EC, ED, EF, PB, PC, and

PF, the first litter is referred to the product epoxy or polyester, the second litteris referred to the company.

Portland cement Type 1 (Amerria) meets BS 12/1989 requirements wasused in the tests, the physical properties of cement are given in Table 2.


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Table 1 Description of the adhesives

Codedname

Description and density of contents Classification Mixing ratioBy weight

content Description Densitygm/cm

EA

Threecomponents.FillerBaseHardenerAfter mixing

White with yellow grainsYellow liquidLight brown liquidEasy workable lightbrown dough

1.821.31.11.25

Polymerconcrete

PC

Filler: base:hardener

17 : 2 : 1

EB

Three componentsFillerBaseHardenerAfter mixing

Gray fine cementitiouspowderLight green liquidYellow liquidVery viscose, badworkable black dough

2.031.151.0

2.0

Polymerconcrete

PC


40 : 7 : 2

EC

Three componentsFillerBaseHardenerAfter mixing

White powderHeavy white liquidBlack doughVery viscose, badworkable gray dough

2.21.251.45

1.75

Polymerconcrete

PC


21 : 4 : 3

ED

Two componentsBaseHardenerAfter mixing

White heavy liquidOpaque gray doughHeavy light gray slurry

1.71.81.8

Epoxybondingagent

Base:hardener

2 : 1

EF

ThreecomponentsFillerBaseHardenerAfter mixing

Gray fine powderLight amber yellowliquidAmber yellow liquidLight brown dough

1.841.31.151.6

Polymerconcrete PC


70 : 7 : 2

PB

Two componentsComp. 1Comp. 2After mixing

Light green powderHeavy pink liquidLight green dough

1.71.032.04

Polyesterpolymerconcrete

PC

3 : 1

PC


Fine green powderHeavy pink liquidDark green dough

1.951.232.04


PC

3 : 1

PF


Light pink powderDark pink liquidPink dough

1.781.261.96


PC

3 : 1

Natural siliceous sand from (Katatba) has been used as fine aggregate in allmixes. This natural sand has a fineness modulus about 2.5, Sieve analysistest results of fine sand according to ASTM C33/2003 are given in Table 3. "N.M.S. crushed pink limestone delivered from sixty kilometer, Alexandria Cairo desert road has been used as coarse aggregate in producing concreteprisms for structural fixing test. The results of sieve analysis test for coarseaggregate are given in Table 4.

Tap water was used for mixing and curing concrete and one type of

admixtures was used in producing concrete; it was super-plasticizer. Thequantities of concrete constituents were designed to achieve 28 days cubecompressive strength more than 500 Kg/cm. The mix design for 1m of


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concrete is as follows: P.L.S. coarse aggregate = 1140 Kg, sand = 664 Kg,cement = 450 Kg, water = 157 liters and super-plasticizer = 6 liters

28 days cube compressive strength was 550 kg/cm

Table 2 Physical properties of ordinary Portland cement (Amerria)

Description of Test Specification LimitBS 12/1989

Test Data

Percentage of water required to give a paste ofstandard consistency 25%Setting time (Vicat test)

InitialFinal

Not less than 45 minNot more than 10 hours

hr : min1 : 302 : 40

Soundness of cement( Le Chatelier test) Not more than 10mm 7.7 mmFineness of cement

% Retained on B.S. sieve No.(170) by weight Not more than 10% 4%

Compressive strength of mortar cube (50mm)( 3 sand: 1cement)

3 days, N/mm7 days, N/mm

Not less than 18Not less than 27

19.7329.24

Table 3 Sieve analysis of fine aggregate (sand)

Sieve No. " No.4 No.8 No.16 No.30 No.50 No.100

ASTM C 33-Limits

Upper limits 100 100 100 85 60 10 10

Lower limits 100 95 80 50 25 0 0

% Passing 100 99 96 84 56 10 4

Table 4 Sieve analysis of coarse aggregate (pink lime stone).

Sieve No. 1" " " " No. 4 No. 8

ASTM C33 -Limits Upper limits 100 100 77 55 10 5Lower limits 100 95 55 20 0 0% Passing 100 96 55 30 6 0

TEST RESULTS AND DISCUSSION

Cube compressive strength

Fig. 7 shows the cube compressive strength results of the epoxy andpolyester adhesives and the percentage increase of the compressive strength ofcement mortar.

Polyester adhesives have greater compressive strength than epoxyadhesives and cement mortar, the compressive strength of polyester adhesives

is 125% greater than that of cement mortar, the compressive strength of epoxyadhesives is ranged between 30% and 120% greater than that of cementmortar according to the kind of epoxy used.


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Fig . 7. Compressive strength of adhesives and cement mortar

Flexural Strength

Fig. 8. Flexural strength of adhesives and cement mortar

Fig. 8 represents the flexural strength results of the epoxy and polyester

adhesives and the percentage increase of the flexure strength of cementmortar.

Polyester and epoxy adhesives have greater flexural strength than cementmortar, the flexural strength of polyester adhesives is ranged between 109%and 370% greater than that of cement mortar according to the type of polyesterused, the flexural strength of epoxy adhesives is ranged between 165% and375% greater than that of cement mortar according to the kind of epoxy used.

Pull out test

Fig. 9 illustrates the test results of the pull out test of steel fixed intoconcrete by adhesives and cement slurry SS together with the control SC (steelbars fixed into fresh concrete).

Most specimens of epoxy and polyester fixing materials resist approximatelythe same pull-out loads of specimens that have steel reinforcement fixed intofresh concrete SC and about 20% greater than the loads of specimens that havesteel reinforcement fixed into concrete by cement slurry SS while EA and ED


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resist approximately the same loads of SS and show a reduction in tensionloads about 10% of SC load.

Fig. 9. Steel tension failure loads.

The maximum value of pull out loads is attained by polyester adhesives, it isabout 24% greater than the loads attained by cement slurry.

Fig.10 shows the pull-out test modes of failure. SC specimens followconcrete cone failure CF. SS, EA and ED specimens follow bond slip failure BF,while the other specimens follow the three modes of failure.

Fig. 10. Pull-out test modes of failure.Shear test

Fig. 11 illustrates the test results of the shear test of steel fixed intoconcrete by adhesives and cement slurry SS together with the control SC.

Fig.11. Steel shear test results.


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Most Epoxy and polyester fixing materials resist approximately the sameloads of SC and about 10% greater than the loads of SS while EA and ED resistapproximately the same loads of SS and show a reduction in shear loads about10% of SC load.

Taking to consideration that the price of epoxy or polyester steel fixingagents is approximately forty times the price of the same weight of cementslurry, it can deduced that the cement slurry is a good choice for fixing steelinto concrete.

Fig. 12 shows the shear test modes of failure. SS, EA and ED specimensfollow concrete sliding failure CF, while the other specimens follow steel shearfailure SF.

Fig.12. Shear test modes of failure.

CONCLUSIONS

Five candidate commercial epoxy resins and three candidate commercialpolyester resins that are produced by five local companies were selected andtested. Compressive strength and flexural strength were carried out onepoxy and polyester fixing agents, steel reinforcement pull-out test werecarried out on concrete specimens with steel reinforcement fixed into it byepoxy and polyester adhesives, also by cement slurry to compare betweenthese different materials and the control SC (steel bars are stitched into the

mould before casting fresh concrete)..

Polyester adhesives have greater compressive strength than epoxy adhesivesand cement mortar, the compressive strength of polyester adhesives is 125%greater than that of cement mortar. The compressive strength of epoxyadhesives is ranged between 30% and 120% greater than that of cementmortar according to the kind of epoxy used.

Polyester and epoxy adhesives have greater flexural strength than cementmortar. The flexural strength of polyester adhesives is ranged between109% and 365% greater than that of cement mortar according to the kind ofpolyester used, the flexural strength of epoxy adhesives is ranged between165% and 375% greater than that of cement mortar according to the kind ofepoxy used.

Most specimens of epoxy and polyester fixing materials resist approximatelythe same pull-out loads of control specimens (that have steel reinforcementfixed into fresh concrete), and about 20% greater than the loads of specimensthat have steel reinforcement fixed into concrete by cement slurry. Whilesome specimens with steel reinforcement fixed by some epoxies resist


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approximately the same pull-out loads of specimens that have steelreinforcement fixed into fresh concrete and show a reduction in loads about10% of specimens fixed by cement slurry load.

Most specimens of epoxy and polyester fixing materials resist approximatelythe same shear loads of control specimens (that have steel reinforcementfixed into fresh concrete), and about 10% greater than the loads of specimensthat have steel reinforcement fixed into concrete by cement slurry. Whilesome specimens with steel reinforcement fixed by some epoxies resistapproximately the same shear loads of specimens that have steelreinforcement fixed into fresh concrete and show a reduction in shear loadsabout 10% of specimens fixed by cement slurry load.

The maximum value of pull out loads is attained by polyester adhesive, it isabout 24% greater than the loads attained by cement slurry. Taking intoconsideration that the price of epoxy or polyester steel fixing agents isapproximately forty times the price of the same weight of cement slurry, itcan deduced that the cement slurry is a good choice for fixing steel intoconcrete.

Compression and flexural strengths that the usual data specified in datasheets introduced by the producing companies are less important data thanthat must be specified in the function of steel fixing agents, the mostimportant data are the pull-out test and shear test loads sustained by eachmaterial.

AcknowledgementThe work presented in this paper was carried out at the material

laboratories of the Faculty of Engineering of Alexandria University. Thanks aredue to the director of the material laboratories. Thanks are also due to thematerial stuff.

REFERENCE

[1] ACI Committee 355.1R 91 State of the art report on anchorage toconcrete. ACI Manual of Concrete Practice, Farmington Hills, Michigan.

[2] ACI Committee 548 .1 R 97 Guide for use of polymers in concrete .ACI Manual of Concrete Practice, Farmington Hills, Michigan.

[3] ASTM C 109 80 Standard Test Method for Compressive Strength ofHydraulic Cement Mortars (Using 2-in Cube Specimens) Annual Bookof ASTM Standers, American Society for Testing and materials.

[4] ASTM C 881 90 Standard Specification for Epoxy Resin BaseBonding systems For Concrete Annual Book of ASTM Standards,American Society for Testing and Materials.

[5] ASTM E 488 - 96 Standard test method for strength and anchors in

concrete and masonry elements Annual Book of ASTM Standards,American Society for Testing and Materials.

[6] ASTM C33-03 Standard Specification for Concrete Aggregates, AnnualBook of ASTM Standards, American Society for Testing and Materials


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[7] British Standard Institution BS 5080 part 1 Structural fixings inconcrete and masonry method of test for tensile loading .

[8] British Standard Institution BS 6319 part 3, Testing of resin andpolymer / cement compositions for use in construction, methods for

measurement of modulus of elasticity in flexural and flexural strength [9] Lee How son and George C.S. Yuen Building maintenance technology Building department, Ngee a polytechnic, Singapore.

[10] N. Jackson Civil engineering materials English language book society[11] Neville, A.M. Properties of concrete. Pitman, London (1983).[12] Y.L. Mo, Member, ASCE and J. Chan Bond and slip of plain Re-bars in

Concrete Journal of Materials in Civil engineering November 1996.[13] ASTM E 1512-01 Standard test method for testing bond performance of

bonded Anchors Annual Book of ASTM Standards, American Societyfor Testing and Materials.

[14] ACI Committee 546 R -96 Concrete repair guide . ACI Manual ofConcrete Practice, Farmington Hills, Michigan.

[15] ASTM C136-04 Standard Test Method for Sieve Analysis of Fine andCoarse Aggregates, Annual Book of ASTM Standards, American Societyfor Testing and Materials.

[16] Jack R. Vinson, Tsu Wei Chou Composite materials and their use instructure London 1975.

[17] Alaa El-Din M.Jahien, .New Repairing Materials And its Applications"M.Sc thesis, Structural Engineering Department, Faculty of Engineering,Alexandria University, 2004.

[18] Tawfic Ayoub, Adel el Kurdi, A. Ali Abdo, and Alaa El-Din Jahien,"Selection of Optimum Bonding Properties in Concrete Repairing Work"under submission to ASCE 6, 2007.

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