Lab 3 asphalt PDF

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Asphalt Concrete Specimens A complete report detailing the asphalt mix design, the preparation of the asphalt concrete specimens and he asphalt concrete specific gravity and strength properties.

Group 1 Sec B Raul Cervantes 20101357 Joseph Lunn Roy Garza Edwin Pena Objective: Prepare asphalt concrete specimen

March 21, 2018

Asphalt concrete Test

March 28, 2018

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Abstract: Lab 3a consisted of the preparation of the asphalt concrete specimen; by mix and compacting HMA samples prepared with a different binder contents using a gyratory compactor. And Lab 3b consisted of the determination of the bulk specific gravity and the splitting tensile strength of the HMA samples. We found that the load at failure and the tensile stress at failure was less was the binder content by of aggregate percentage increased from 4.5 to 6.0. It’s important because the use of asphalt is for construction and maintenance. Asphalt is used in sealing and waterproofing various structural components, such as roofs and underground foundations. Introduction: There are certain types of asphalts used in pavements. Asphalt cement or asphalt binder used for HMA, patching. The asphalt cement (Binder) adheres well to most rock, is waterproof and fairly durable. It’s is resistant to most acids, alkalis, and salts. But asphalt cement is temperature sensitive. There is Asphalt emulsion and Asphalt cutback which are used for cold mix and maintenance applications. Asphalt binder is a visco-elastic material. Which is viscous at high temperatures and elastic at low temperatures and its charactistics depend on both the temperature and loading rate. The asphalt mixes; asphalt cement alone is used for sealing and water proofing and the asphalt concrete is used for hit mix asphalt pavement surfacing (HMA). Its important to know the requirements for your final sample. The projection of traffic, whether it is going to be used for a surface layer of high stress and rutting, a intermediate layer of high stress and rutting or a base layer of low stress and fatigue. The purpose of the asphalt concrete mix design is to determine the design asphalt content using the available asphalt and aggregates. The design asphalt content varies for different material types, material properties, loading levels, and environmental Page 2 of 7

conditions. Now if the appropriate design asphalt content is not used, the pavement will lack durability or stability, resulting in premature pavement failure. Materials and Equipment: 

Gyratory Compactor

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Compaction molds

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Paper disks for compaction

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Temperature controlled oven

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Flat-bottom metal pans

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Weight scale

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Gloves for handling hot equipment

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Small scoop

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Damp towel

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Water bath

Figure 1 Gyratory compactor

Procedures: Table 1: 3.a-1 Binder Contents by weight of aggregate and by weight of mix for each lab group

Group

Binder content by

Target binder weight (g)

Actual binder weight (g)

weight of aggregate (%) 1

4.5

101.75

102

2

5.0

112.5

112

3

5.5

123.75

124

4

6

135

135

For the mixing and compaction using the gyratory compactor: Page 3 of 7

1. Wearing gloves, remove the large bowl containing the aggregate, and the asphalt container from the oven. 2. Pour the aggregate into the mixing bucket 3. Add the calculated amount of asphalt based off the table 3a.-1 and record the exact amount added 4. Start the mixing process for no longer than 4 minutes, stop as soon as the aggregate coating with asphalt is achieved. 5. Remove the compaction mold from the oven and place it on the compactor 6. Place one paper disk at the bottom of the mold and the funnel on top of it 7. Pour the asphalt mix into the compaction mold, being careful not to lost any material 8. Remove the funnel and place one paper disk at the top of the mix 9. Slide and fix the mold into the compactor and start the compaction 10. Note the height of the sample from the display at the end of the gyrations 11. When the required number of gyrations has been achieved, extract the sample form the mold 12. Handle with care, remove the paper disk We then had to determine the Bulk Specific Gravity 1. Take the cooled specimen in the dry state and weigh it in air. 2. Immerse the specimen in a water bath for 3 to 5 min. and weigh in water 3. Surface-dry the specimen by blotting quickly with a wet towel and then weigh in air Splitting Tensile Test 1. Take the same asphalt sample which was used to determine the specific gravity 2. Place the bottom wooden strip on the testing machine 3. Place the sample horizontally on the wooden strip Page 4 of 7

4. Place the top wooden strip on. The purpose of the wooden strips is to ensure the load is uniformly distributed over the sample 5. Apply load until load failure Results and Discussion Table 2: 3b-1Bulk Specific Gravity (Gmb) (ASTM D2726)

Group

1 2 3 4

The room temperature sample A=Mdry(g)

C=Msubm(g

B=Mssd(g)

Gmb

2015 2330 2300 2215

) 790 612.1 774 574

2025 2335 2305 2220

1.632 1.352 1.502 1.346

Solving for our bulk specific gravity allows us to calculate for other specified parameters such as air voids. Now the bulk specific gravity seems to increase with the lower binder content by weight of aggregate. From 1.346 at a 6.0 binder content by weight of aggregate to a 1.632 at 4.5 binder content by weight of aggregate. Now from the table we can see that the weight of the specimen is less under water and measuring the weight after it had been submerged weighs more than what it did at a dry state, indicating that the asphalt either soaked up some water or more go trapped in the voids.

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Table 3: 3b-2 Splitting Tensile Test data and results

Group

Load at Failure

Initial Length of

1 2 3 4

(lb) 1775 1810 1510 2400

Sample (in) 4.52 5.125 5.25 4.8

Diameter(in)

Tensile stress at

3.93 3.9375 3.9375 3.85

Failure (psi) 63.40 57.21 46.59 82.68

Now from the table we can see the tensile stress at failure absorb more psi as the percentage of the binder content increased. But we also notice the miscues from the other groups. Why would the psi decrease by comparing group 1 and 3 if the binder content was greater for group 3? Even if you look at the load at failure for 1 and 3, group 3 had a far less load capacity than all the others. We also notice that group 4 load at failure and tensile stress at failure we above all the others. Conclusion This lab brought the attention of yet another important topic to light. Asphalt and the application it will be used ultimately determines how the asphalt mix should be designed. This lab brought to light the usage of asphalt, and its importance to construction and maintenance. Asphalt could be used to seal and in fact is waterproof.

Appendix

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Table 4: 3a-2 Height of the compacted samples

Group

1 2 3 4

Total weight of material (g)

Height of the compacted

2352 2374 2362 2385

sample (cm) 11.56 13.31 13.52 12.62

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