Northeast Corridor schedules effected.

[BT CPSO 266]

I got a new Amtrak Timetables book that does not feature any schedule on the Northeast Corridor. It mentioned the reason was upgrades to the route from the $8 Billion stimulus; and the schedules were constantly fluctuating. What exactly are they doing? making the route faster for the Acela?

[RudyRockvilleMD]

They are replacing defective concrete ties so it is necessary to close tracks at different times which affects schedules. I doubt if  it will make the line faster for the Acela Express.