Question

4. Consider the PG 70-28 and PG 64-22 asphalt binders: (a) Which do you think would be the more expensive binder to specify, and why? (b) You are preparing a set of project plans for a routine maintenance overlay in the city of Sioux Falls, SD. Not considering cost, which binder (PG70-28 or PG 64-22) do think will provide better performance in terms of rut resistance? Why? (c) You are preparing a different set of plans for a project to construct a section of new roadway on new alignment in north eastern South Dakota. Which binder (PG 70-28 or 64-22) do you think will provide an asphalt pavement that is less likely to develop low temperature cracking? Why? Do you suggest any other asphalt binder which may work better?

Answer 1

we decide the PG (performance grade) asphalt binder on the basis of three things;

1-Rutting

2-Fatigue

3-Cracking

(a) PG 70-28 means its can resist max temp as 70 and min temp as -28 while PG 64-22 can withstand temp as max 64 and min -22 hence to make PG 70-28 we need more temp resistant admixture and chemicals which will make this more expensive as compared to the PG 64-22 .

(b) If we are not bound by the cost factor then obviously we will go for PG 70-28 binder because is has more rutting    resistance.

(c) PG 70-28 will be less likely to develop low temp cracking and it will have confidence limit upto 98%.

   other asphalt binders may be AC-15P, CRS-2P, MC-2400L, etc.