Asphaltic Plug Joints for Bridges: Material Requirement, Construction, and Testing

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Asphaltic plug joint (APJ) is a type of bridge expansion joint that is a simple general-purpose expansion device for bridges having a total motion of less than 50 mm (2 in).

These joints are used in joint expansion sealing on asphalt concrete overlay and portland cement concrete decks. It should not be used for movement applications exceeding ±50 mm from the installation width. 

Materials Required for Asphaltic Plug Joints

1. The asphaltic binder used in the asphaltic plug joints shall be a thermoplastic polymeric-modified asphalt.
2. The physical properties of the asphaltic binder shall be in accordance with the values given in the table below.
3. The specified aggregate shall be crushed, washed, and dried. The aggregate shall be weighed and packaged to avoid confusion on the job site. 
4. The closed-cell foam expansion joint filler shall be non-gassing and capable of withstanding the elevated installation temperature (199 °C) of the asphaltic binder.

Dimensions and Tolerances 

The shape, size, and dimensional tolerance shall be as per the design requirements. These tolerances shall comply with the field construction specifications. The standard minimum blockout dimensions are 50 x 500 mm; however, it should be noted that these values fluctuate depending on existing field conditions.

Construction Procedure of Asphaltic Plug Joints

1. The asphaltic binder shall be heated to a temperature as specified by the manufacturer. The melter must be supplied with a continuous agitation system and calibrated thermometers. 
2. The specified aggregate shall be heated to the manufacturer's prescribed temperature in a manufacturer's recommended mixer. A digital temperature sensor shall control the temperature of the specified aggregate.
3. The asphaltic binder shall be blended with the heated aggregate at an aggregate ratio to the asphaltic binder as specified by the manufacturer.
4. The asphaltic binder and specified aggregate can be pre-measured and pre-packaged, heated on-site in a manufacturer's recommended mixing unit.
5. The specified aggregate shall be coated completely with a binder before placement in the blackout.
6. The closed-cell foam expansion joint filler shall be placed into the expansion gap at a depth not greater than the width of the gap.
7. To guarantee a water-tight junction below the bridging plate, fill the joint aperture with an asphaltic binder until it flows into the matching blockout.
8. The bridging plate shall be aluminum or mild steel, a minimum of 6-mm thick and 200-mm wide, cut in a minimum of 1.2 m lengths, centered over the entire length of the expansion joint gap when specified. When specified, the bridging plate shall have pre-drilled holes at 300-mm on the center for the locating pins.
9. The blended, heated asphaltic binder and heated specified aggregate shall be placed in a prepared blockout.
10. When specified, the locating spikes used to position the bridging plate, shall be galvanized 16 d column nails or larger. 
11. The blended, heated asphaltic binder and heated coated specified aggregate shall be compacted longitudinal and transverse to the joints using a roller or plate compactor, which delivers a minimum centrifugal force of 15 kN.
12. Where an antiskid surface is required, the surface of the asphaltic plug joint shall be heated before broadcasting the antiskid material in accordance with the manufacturer's written instructions.

Test Material Sampling

1. A batch of thermoplastic polymeric modified asphalt must include a maximum of 19,100 kg. Prior to transporting the material, random samples of the batch must be obtained. If there are many batches in the shipment, a sample from each batch must be obtained.
2. One sample for testing should consist of a minimum of 1.4 kg of thermoplastic polymeric modified asphalt obtained from the manufacturer's facility.
3. A batch must include no more than 20,000 kg of the specified aggregate. Each material shipment will have a sample of the batch picked at random.
4. A minimum of 23 kg of the specified aggregate shall constitute one sample for size and gradation analysis. 
5. A lot shall consist of a maximum of 305 m for the closed-cell foam expansion joint filler.
6. A minimum of 300 mm of the closed-cell foam expansion joint filler constitutes one sample for testing purposes.

Test Methods Low-Temperature Cone Penetration-Nonimmersed 

Apparatus 

1. Penetrometer/Cone

The total moving weight of the cone and attachments must be 150.0 +/- 0.1 g.

2. Cold Chamber

The cold chamber shall be capable of maintaining the required cold test temperature within 61.1 °C.

Specimen Preparation

1. Pour a portion of the asphaltic binder prepared into three 177-mL tins measuring approximately 69-mm in diameter and 44 mm in depth and fill flush to the rim of each tin. 
2. Allow the test specimens to cure according to their material specifications.

Procedure

1. Place the three test specimens and three cones in the cold chamber at 18°C 6 0°C for no less than 4h. 
2. One sample and core are removed from the cold chamber, and the location on 120° radii is determined immediately, halfway between the center and outside the test specimen. 
3. Ascertain that the cone point is positioned on the spot in the test specimen that accurately represents the material and is free of dust, water, bubbles, or other foreign material.
4. For the second and third samples, repeat the process described above.

Test Report

The average of the three results is calculated and recorded as the value of the specimens' penetration in millimeter units.

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