Which of the following materials is NOT used as ballast in a standard railway track permanent way?

The paved area adjacent to and in front of the terminal building is known as the apron, used for loading and unloading aircrafts. The dimensions of the loading apron depend upon: Statement 1: Number of loading positions required Statement 2: Size of the airport and service station for aircrafts

The thickness of the sub-base layer should NOT be less than ____ for a design traffic of less than 10 MSA as per IRC guidelines.