Question

1- Describe the main differences in HMA mixture preparation between “laboratory prepared” and
“plant produced” specimens.

2- Describe how we determine the number of gyrations to be applied to a specimen for the
purpose of volumetrics determination.

Answer 1

Ans 1 - HMA mixture preparation:

a) As the HMA mixture ages during preparation in the plant, this aging is artificially simulated while preparing in lab.This is done by short term mixture conditioning.

b) Long term aging simulation is done to account for the years of service This is done while we analyse the mixture resistance to low - temperature cracking.

c) Mixture conditioning is done for volumetric mix design.

Ans 2 - 3 types of number of gyrations are used

they are Ni which is initial, Nd which is design and Nm which is mean.

Ni is attributed to the state of mixture once the pavement is built

Nd and Nm is for the compaction phase and long term aging.