RE:aggregate....Siempre:
Rail track ballast is a subset of aggregate - and that material has its own specific properties.
Rhyolite is a typical material that can be used for track ballast.
Aggregate subsets:
- concrete stone or 57's - used in RMX mixes
- rip rap - big chunky stuff used in road stabilization sidings and major silt traps
- asphalt rock - material - normally smaller than 57's used in HMA road surfaces
- base material - a bigger size used in foundations and road bases, and prep on heavy civils
- sand - used in RMX and HMA mixes
- Track ballast - larger, see Rhyolite
- Poorer quality rock can be used in haul roads, pads and bases in energy fields (it usually sells for a good prices - because the demand is so strong - but this material may not necessarily have good properties suited to an RMX mix