9.8What are the engineering applications of each of these tests?

a. Flash point test: (ASTM D92) It is a safety test that measures the temperature at which the asphalt flashes; asphalt cement may be heated to temperature below this without becoming a fire hazard. It is the temperature of the asphalt when the volatile fumes coming off the sample will sustain a flame for a short period of time.

b. RTFO procedure: (ASTM D2872) used to simulate the short-term aging that occurs in the asphalt during production asphalt. Used to prepare samples for evaluation for rutting potential with the dynamic shear rheometer and prior to conditioning with the pressure-aging vessel.

c. Rotational viscometer test: (ASTM D4402) it consists of rotational coaxial cylinder viscometer and a temperature control unit. It performs on unaged binders. Also tests are performed at higher temperatures to establish the temperature susceptibility relationship used to determine the compaction and mixing temperatures required for the mix design process.

d. Dynamic shear rheometer test: (AASHTO T315) used to measure three specification requirements in the performance grading system.

e. Penetration test: (ASTM D5) measures asphalt cement consistency. An asphalt sample is prepared and brought to a temperature of 25 Celsius and a needle is continuously penetrating the viscosity.

9.11Define the four methods used to grade asphalt binders. Which method is used in your state?

1. Performance Grading: Is conducted by testing the temperature at the lower and upper layer of the asphalt concrete. Lower temperature is the pavement surface while the higher temperature is the lower layer. The binder can be suitably selected for various temperatures.

2. Penetration Grading: by using the penetration test, the grade of the binder will depend on extend of penetration measured in mm per 5 seconds.

3. Viscosity Grading: by using the viscometer the binder is poured into the thermocell and a spindle is carefully inserted. The viscosity of the binder is determined by the ease of the spindle turning at a specific temperature.

4. Viscosity of Aged Residue Grading: similar to the viscosity grading the binder is aged in a laboratory condition. Then the binder is poured into bottled and kept in an oven and made to rotate vertically. To speed up the aging process a jet of air is made to pass through the bottle.

9.20Why is it important to have optimum binder content in HMA? What would happen if a les-than-optimum binder content is used? What would happen if more than the optimum value is used? What is the typical range of binder content in HMA?

It is important to have optimum binder content because the binder is used to keep the aggregate together. The aggregates are the parts that hold the load acting on the pavement. If a less-tan-optimum binder content is used the aggregate will not

be bound very well. Aggregates won’t be fully covered by the binder and so will cause displacement of the aggregates and there will be freedom of movement, causing failure to the pavements. There will be failure of the pavements if more than optimum binder is used. There will be an increase of lubrication of the aggregates and will skid inside the layer, thus leading to a smaller ability of loading. The typical range of binder content in HMA is 4%-7%.