Commonwealth of Pennsylvania PA Test Method No. 634Department of Transportation March 2017 5 Pages

LABORATORY TESTING SECTION

Method of Test for

UNBONDED AREA OF ANCHOR MATERIAL AND COATED DOWEL BAR FOR CONCRETE PAVEMENT APPLICATIONS

This PTM references AASHTO R 39, AASHTO T 22, and AASHTO T 198. These full AASHTO standards are available from American Association of State Highway and Transportation Officials, 444 N. Capitol Street, N.W., Suite 249, Washington, D.C. 20001 (www.transportation.org).

INTRODUCTION

This method provides a procedure for evaluating adhesive anchoring material used to anchor force-transfer coated dowel bars employed in concrete pavement patching in accordance with Pennsylvania Department of Transportation (PennDOT) Specification Publication 408, Section 516.2(k) only. This is not intended for miscellaneous or temporary concrete barrier (Publication 408, Section 643) applications.

1. SCOPE

1.1. This test method covers the determination of the percentage of unbonded area for a fusion-bonded epoxy coated dowel bar embedded in a cylindrical cement concrete specimen using an adhesive anchoring material between the coated dowel bar and the cement concrete cylinder.

2. REFERENCED DOCUMENTS

2.1. AASHTO R 39, Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory

2.2. AASHTO T 22, Standard Method of Test for Compressive Strength of Cylindrical Concrete Specimens

2.3. AASHTO T 198, Standard Method of Test for Splitting Tensile Strength of Cylindrical Concrete Specimens

3. SIGNIFICANCE AND USE

3.1. A higher adhesive bonding percentage is generally indicative of greater structural integrity.

3.2. The adhesive bonding percentage is used in the evaluation of the structural integrity of the bonds formed between the concrete, anchoring adhesive, and the embedded fusion-bonded epoxy coated dowel bar.

4. APPARATUS

4.1. Testing Machine—The testing machine shall conform to the requirements of AASHTO T 22 and be of a type with sufficient capacity to provide a loading

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rate of 2.0 inches per minute and accommodate a 6 x 12 inch concrete cylinder oriented horizontally.

4.2. Supplementary Bearing Bar or Plate – If required, the supplementary bearing bar or plate shall conform to the requirements of AASHTO T 198, Section 5.2.

4.3. Bearing Strips - The two wood bearing strips, each 1/8 x 1 x 12 inch nominal, shall conform to the requirements of AASHTO T 198, Section 5.3.

4.4. Rotary Hammer Drill – The rotary hammer drill shall be capable of producing a 1 3/8 inch diameter by 9 inch depth hole in hardened cement concrete.

4.5. Drill Bit – The drill bit shall be suitable for drilling a 1 3/8 inch diameter by 9 inch depth hole in hardened cement concrete.

4.6. Equipment for cleaning drilled hole - compressed air and wire brush.

4.7. Caulking gun for adhesive application with mixing nozzle meeting requirements of the adhesive manufacturer.

5. TEST UNIT ASSEMBLIES

5.1. A total of three test unit assemblies shall be fabricated and each test unit assembly shall include the following components:

5.1.1. One 6 inch diameter x 12 inch long cement concrete cylinder (> 28 days old) conforming to the molding and curing requirements of AASHTO R 39. Cylinders shall have a minimum mix design compressive strength of 3,000 psi or meet the requirements of Pub. 408, Section 704, Class AA Cement Concrete,

5.1.2. One 1 ¼ inch diameter x 18 inch length epoxy coated dowel bar conforming to Pub 408, Section 705.3(b), and

5.1.3. Adhesive anchoring material.

5.2. The assembly instructions shall be in accordance with Section 6.

6. PROCEDURE

6.1. Cement concrete cylinder preparation

6.1.1. Drill a 1 3/8 diameter x 9 inch depth hole along the longitudinal axis of the cement concrete cylinder. Use a rotary hammer drill unless otherwise directed by the adhesive manufacturer.

6.1.2. Clean the hole per the adhesive manufacturer’s directions.

6.1.3. Measure the depth of the drilled hole from the top surface of the cement concrete cylinder to the bottom of the drilled hole to the nearest 0.1 inch and record this measurement as L.

6.2. Dowel bar insertion

6.2.1. Clean the epoxy coated dowel bar with acetone or solvent.

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6.2.2. Orient the cement concrete cylinder horizontally on Kraft paper and place in a chemical fume hood and turn on fume hood.

6.2.3. Mix & place adhesive anchoring material in the drilled hole of the cement concrete cylinder per manufacturer’s directions.

6.2.4. Note the runout characteristics of the adhesive anchoring material for each test unit assembly. Adhesive anchoring material that runs out of the hole prior to dowel bar insertion is unacceptable. The adhesive anchoring material must have sufficient viscosity so that it does not run out of the horizontal drilled hole.

6.2.5. Insert a coated dowel bar slowly into the drilled hole containing the adhesive anchoring material to avoid creating air pockets in the adhesive anchoring material which will result in unbonded areas. Twist the coated dowel bar during insertion to ensure the full perimeter wetting of the coated dowel bar with the adhesive anchoring material. Ensure the coated dowel bar is fully inserted to the bottom of the drilled hole. Adhesive anchoring material displaced by coated dowel bar insertion is not cause for rejection. (See Figure 1)

6.2.6. Wipe off excess adhesive anchoring material outside the drilled hole.

6.2.7. Record time, temperature, & humidity at completion of coated dowel bar insertion.

6.2.8. Allow each test assembly to set undisturbed. Record the tack free time which is the elapsed time from initial placing of the adhesive anchoring material until it is no longer sticky to the touch.

6.3. Horizontal splitting of test unit assembly.

6.3.1. Perform split test 22 +/- 0.5 hours after completion of coated dowel bar insertion.

6.3.2. Center cylinder horizontally in compression machine.

6.3.3. Place the wood strips lengthwise along the top and bottom of the cement concrete cylinder.

6.3.4. If required, place the loading plate between the top wood strip and the crosshead. (Figure 2)

Note: Specific instructions on splitting the cylinder will vary with the compression machine used. A Nominal test speed of 2.0 inches per minute has proved to be convenient.

6.3.5. Apply load continuously and without shock until dowel can be separated from cylinder.

6.4. Section 6.1 to Section 6.3 shall be conducted for each of the three test unit assemblies.

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(Figure 1) (Figure 2)

7. CALCULATION OF UNBONDED AREA FOR INDIVIDUAL TEST UNIT ASSEMBLY

7.1. Areas of exposed coated dowel bar indicate no bond to the epoxy coating. See Figure 3.

7.2. Areas of exposed cured adhesive anchoring material with no concrete indicate no bond to the cement concrete. See Figure 4.

7.3. Measure the maximum length and maximum width of each unbonded area to the nearest 0.1 inch.

7.4. Calculate the rectangular area of each unbonded area (Area = length x width), to the nearest 0.1 in2.

7.5. Add or sum all individual unbonded areas for each test unit assembly to determine the total unbonded area, AUBi, for a test unit assembly to the nearest 0.1 in².

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(Figure 3 – Exposed epoxy coated dowel bar indicating no bond to epoxy coated dowel bar)

(Figure 4 – Exposed adhesive anchoring material indicating no bond to cement concrete)

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(Figure 5 – Examples of samples showing minimal unbonded areas)

8. CALCULATION OF PERCENTAGE OF UNBONDED AREA FOR INDIVIDUAL TEST UNIT ASSEMBLY

8.1. Calculate the total embedded surface area of each individual coated dowel bar, ESAD, using Equation 1.

ESAD = π d L (1)

where:

ESAD = Embedded Surface Area of individual coated dowel bar, nearest 0.1 in2.

π = 3.14

d = diameter of coated dowel bar, in.

L = embedded length of coated dowel bar in each test unit assembly (depth of drilled hole in the cement concrete cylinder), in.

8.2. Calculate the percentage of unbonded area of individual test unit assembly, AUBi, using Equation 2.

P UBi , %= A UBiESA D

×100 (2)

where:

PUBi, % = Percentage of unbonded area of the individual test unit assembly to the nearest 1%.

AUBi = Total unbonded area of the individual test unit assembly, in2.

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ESAD = Embedded surface area of the individual coated dowel bar, in2.

9. CALCULATION OF THE AVERAGE PERCENTAGE OF UNBONDED AREA OF ALL TEST UNIT ASSEMBLIES

9.1. Calculate the average percentage of unbonded area of the three test unit assemblies, Avg. PUB, %, using Equation 3.

Avg . P UB , %=(P UB1,%+P UB2, %+P UB3 , %)3

(3)

where:

Avg. PUB, % = Average percentage of unbonded area of the three test unit assemblies.

PUBi, % = Percentage of unbonded area of the individual test unit assembly.

10. REPORT

10.1.Report the following information:

10.1.1. Mix design of the cement concrete used.

10.1.2. Total area of exposed epoxy coated dowel bar for each test unit assembly.

10.1.3. Total area of exposed adhesive anchoring material for each test unit assembly.

10.1.4. Total percentage of unbonded area for each test unit assembly.

10.1.5. The average percentage of unbonded area of the three test unit assemblies.

11. Precision and Bias

11.1.Precision - The precision of this test method has not been determined.

11.2.Bias - The bias of this test method cannot be determined since no standard reference material is available.