Which of the following statements is/ are correct?
1
Concrete sleepers can generally be mass-produced using local resources and are better for packing of ballast through machine due to its flat base.
2
Composite Sleeper Index' is employed to determine the number of fixtures required for a certain type of sleeper.
3
Concrete sleepers have a very long lifespan and have no scrap value and can be used in track-circuited areas.
4
Composite Sleeper Index' is employed to determine Mechanical strength of wooden sleeper whereby its suitability for use is assessed.