Q. Asphalt mix design - durability vs. stability?

The main aim of asphalt mix design is to achieve a mix with economical blending of aggregates with asphalt to achieve the following: 

(i) Workability to facilitate easy placement of bituminous materials without experiencing segregation;

(ii) Sufficient stability so that under traffic loads the pavement won't undergo distortion and displacement

(iii) Durability by having sufficient asphalt

(iv)  Sufficient air voids

In asphalt mix design, high durability is generally attained at the expense of low stability. Therefore a balance has to be stricken between durability and stability requirements.