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Evaluating Peak Load and Noise Pollution in Different Types of Asphalt

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Note: This project requires the use of materials and equipment found in an engineering laboratory. The student will need to work with a mentor who is a research engineer or graduate student who can assist with performing certain procedures and operating various types of equipment.

Purpose

First, to determine what sort of pavement is suitable for different environments by evaluating the amount of weight the pavement can withstand under varied conditions. Second, to determine whether noise pollution caused by the contact of automobile tires on road pavement can be reduced by the type of pavement used.

Hypothesis

Noise pollution from highways is a large problem in the United States, especially in residential areas. People who live close to busy roads are subjected to not only the annoyance of noise pollution but also its adverse health effects when sounds exceed a certain decibel level. When a vehicle travels at a speed of 25 miles per hour or greater, most of the noise it creates comes from its tires contacting the road surface. Therefore, it is possible that noise pollution from tire contact may be reduced by the use of different types of road surfaces.

Materials Needed

  • 10 different types of commercial asphalt pavement shaped in puck samples (can be obtained from various road paving companies or civil engineering firms)
  • Asphalt Pressure Tester with attached computer containing the program SintechTM (available at some engineering school laboratories)
  • oven
  • temperature gun
  • refrigerator
  • acoustical decibel reader
  • cotton
  • hobby wheel (made of rubber) and axle
  • cordless power drill
  • water
  • vegetable oil

Experiment

The peak load (ITS) that can be withstood by various forms of commercial pavement will be tested using an Asphalt Pressure Tester. Each pavement type will be subjected to different temperatures to see if this change will affect each pavement type’s peak load. The noise pollution will be determined by simulating the relationship between the tire and the pavement using a model tire powered by an electric drill to rotate the tire across the pavement. Various environmental conditions will be added to the surfaces of the samples and tested as well to see how each pavement sample performs.

Procedure

Pressure Experiment
  1. Place the first sample of asphalt to be tested in the Asphalt Pressure Tester by lifting the brace. Let the pavement sample balance in place before replacing the brace on top.
  2. Using the device on the side of the machine, roll the ram so that it is just sitting on top of the brace.
  3. Open the Sintech program on the computer beside the testing machine and check to see that it can record data.
  4. In the program, a screen will appear that shows the amount of pressure on the pavement before starting the test. This is due to the manual moving of the ram. If the screen shows too much pressure, minimize it by moving the ram up. In an ideal situation, the screen should read 0 lb. of pressure. Click "Run." Testing will begin and an equal amount of pressure will be exerted on the pavement.
  5. A graph will appear from the data points received by the computer. Once the pavement sample begins to break apart, the peak pressure will be detailed on the graph and the line will start to move downward. Click "Stop."
  6. A chart will then appear with the peak pressure number included.
  7. Move the ram up along with the brace and take the sample from the machine. Be careful as the sample could create a mess by breaking apart completely.
  8. Repeat steps 1–7 with each pavement type. Accomplishing several trials of the same pavement type is a good way to ensure accurate results.
  9. In a large oven, heat several samples of each specimen type to 55°C. Use a temperature gun to point and capture the accurate temperature of each sample. Place each sample at 55°C in the asphalt pressure tester, repeat steps 1–7, and record your data.
  10. Repeat steps 1–7 with each asphalt sample heated to 45°C and record your data.
  11. Repeat steps 1–7 with each asphalt sample heated to 35°C and record your data.
  12. Cool several samples of each pavement type to –20°C. Place each sample at this temperature in the asphalt pressure tester, repeat steps 1–7, and record your data.
  13. Repeat steps 1–7 with each asphalt sample cooled to –10°C and record your data.
  14. Save all data recorded and graphs for analysis.

Noise Pollution Experiment
  1. On a table, set up the sound decibel reader so that it is at the same height as the road pavement samples being tested. Place it on a platform or even a pile of books if necessary. The sound decibel reader should be set at a rate of 80 and on "slow."
  2. Place a layer of cotton under the platform of books the sound decibel reader is resting on and underneath the asphalt sample that will be tested to help eliminate vibration, if necessary.
  3. Take the model wheel that is attached to an axle and place it into the head of the drill, winding the top until there is a sturdy connection between the drill and the axle. The tire should rotate on its axle on the drill when the drill is turned on.
  4. Place one pavement sample on the cotton in line with the decibel reader.
  5. Bring the tire on the drill to the top of the pavement sample and start the drill so that the tire is riding on the pavement sample and steady the drill with your other hand on top. The drill battery should be resting on top of the table so that there is an equal amount of pressure for every test. Wait for the reading to become steady and record the decibel reading of the noise of the tire on the pavement sample.
  6. Take 10 trials of each pavement type to ensure accurate results.
  7. Repeat steps 4–6 for each pavement type.
  8. Soak the various road pavement samples in a large bucket of water for 12 hours. This is to simulate what pavement would be like on a rainy day.
  9. After 12 hours, take the samples out of the water and repeat steps 4–6 on each of the samples. When spinning the tire on the pavement, it can dry the water on the surface; therefore, for accurate results, rotate the pavement slightly for continuous water on the surface.
  10. After the pavement samples are completely dry, place a layer of vegetable oil on top of every pavement sample. This is to simulate an extremely hot day when oil starts to form at the surface of pavement. Repeat steps 4–6 with all the road pavement samples.
  11. Place the different types of road pavement in a freezer with a temperature of –10°C. This is to simulate what pavement would be like on a cold day.
  12. Once the samples reach –10°C, repeat steps 4–6 on every sample. Save all decibel readings recorded for analysis.

Results

  1. Analyze your results from the pressure part of the experiment. What sample was the strongest with highest peak pressure? What sample was the strongest with highest peak pressure under different temperatures?
  2. Which sample created the most noise? Which created the least? Which sample created the most noise under the various simulated weather conditions? The least?
  3. What may account for the amount of noise caused by a pavement sample?
  4. What types of payment proved to be best for hot or dry conditions? For a relatively cool climate?
  5. Is there any correlation between pavement strength and amount of noise pollution?
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