what is the importance of air void content in bituminous pavements?

Changing Air voids percentage:

We change the air voids percentage to check its effects on the fatigue life and rut depth and plot those results on graph.

1. First of all we open mitch pave

2. Then we go to option no 4 (modify an existing) file menu.

3. After in this menu we press 1 to change the initial settings where we change file name and leave the rest as be then we press f1 key to save.

4. After pressing f1 we are now in the new menu which is shown in the figure 3.4 and here we change the value of air voids. This is highlighted in figure.

5. After that we press f1 again to save our changes and this takes us back to modify and existing file menu.

6. Now we press 2 to modify material type.

7. We do not change anything in this menu and press f1 to go back to modify an existing data file menu.

8. Now we press 3 to go to the next menu which is named as modify material properties here we also do not change anything we just press f1 to go back to modify an existing file menu.

9. Now we press 4 to go to next menu named as modify cross sections for computation we also do not change anything in this menu and just press f1 to go back to modify an existing file menu.

10. There are no 5, 6 and 7 options too but our concern is with no 7 which is go back to main menu so we press no 7 and go back to main menu.

11. In main menu now we press 5 to perform analysis

12. A new menu opens showing results of every data we changed.

13. Then we put this data on excel sheets to make a graphical representation of our results.

One important thing to note is that we cannot see our results on mitchpave again after closing so we have to capture a screen shot.

 

 

Figure: Change in Air Voids Percentage

Air Voids (%) Fatigue Life (ESALs)

3.5 45630000

4 33780000

4.5 25000000

5 25000000

Table 3.3

In case of Fatigue Life the difference between initial and final Air voids is measured as 84.52%. final data shown in diagram.

 

Fig: results Of Air voids On Fatigue Life

Air Voids (%) Rut Depth (in)

3.5 0.1999

4 0.221

4.5 0.2482

5 0.2482

Table 3.4

In case of rut depth the results are shown in the above table when Air Voids are increased from 3 to 5 the rut depth was also increased by about 24.16%. data shown in diagram.

 

 

 Graphs of air Voids vs. Rut depth

Changing AC Modulus:

We change the value of Ac Modulus and check its effect on the results of Fatigue life and rut depth. Then we plot these results on graph and make a trend line.

1. First of all we open mitch pave

2. Then we go to option no 4 (modify an existing) file menu.

3. After in this menu we press 1 to change the initial settings where we change file name and leave the rest as be then we press f1 key to save.

4. After pressing f1 we are now in the new menu we don’t change anything here and press f1to go back..

5. Now we press 2 to modify material type.

6. We do not change anything in this menu and press f1 to go back to modify an existing data file menu.

7. Now we press 3 to go to the next menu which is named as modify material properties

8. In this menu we change the values of Ac Modulus as shown in figure highlighted

9. Now we press f1 to save the changes and go back to modify an existing file menu.

10. Now we press 4 to go to next menu named as modify cross sections for computation we also do not change anything in this menu and just press f1 to go back to modify an existing file menu.

11. There are no 5, 6 and 7 options too but our concern is with no 7 which is go back to main menu so we press no 7 and go back to main menu.

12. In main menu now we press 5 to perform analysis

13. A new menu opens showing results of every data we changed.

14. Then we put this data on excel sheets to make a graphical representation of our results.

One important thing to note is that we cannot see our results on mitchpave again after closing so we have to capture a screen shot.

AC Modulus (psi) Fatigue Life (ESALs)

300000 23320000

350000 25000000

400000 26690000

450000 28320000

Table 3.5

In case of fatigue life the results are shown in the above table when AC Modulus is increased from 300000 to 450000 the fatigue life was also increased by about 1.05%. Final data results in diagram below.

 

Figure Graphical Representation of AC modulus vs fatigue life

Figure Graphical Representation of AC modulus vs fatigue life

 

 

AC Modulus (psi) Rut Depth (in)

300000 0.2493

350000 0.2482

400000 0.2474

450000 0.2467

Table 3.6

In case of rut depth the results are shown in the above table when AC Modulus is increased from 300000 to 450000 the rut depth was decreased by about 21.40%. Final results is look at the diagram below.

 

Graphical Representation of AC modulus vs rut depth

: Graphical Representation of AC modulus vs rut depth