Engineers will be on site for two months, working inside the viaduct and also suspended from its ten arches as they repair stone and steelwork on the structure, which carries the main Edinburgh-Glasgow train line over the M80.
As well as these repairs, all metal elements within the structure will be cleaned, repaired and coated for protection from weather and pollution.
To ease future inspection and maintenance, numerous stairs, walkways and platforms will be created inside the viaduct.
Work begins on Monday, August 31 and the project is part of the Edinburgh-Glasgow Improvement Programme (EGIP), which will see the main train route between the cities electrified by 2016.
Network Rail project manager Owen Ferry said: “Working on the viaduct represents an unusual engineering challenge in that it is both working at height and in confined spaces where there are deep voids which represent different hazards.
“We rely on experienced specialist engineers to make sure this work is delivered safely and to a high standard, Given their experience working across similar structures, we are confident that they will fully meet this challenge.
“As Castlecary Viaduct is listed, we are working with the relevant local authorities to make sure the work is planned and delivered sympathetically with minimal impact on this superb Victorian structure and minimal disruption for local residents and motorists.”
The electrification is part of a £742m Scottish Government investment in Central Scotland’s rail network.
The nature of this work means road closures are inevitable and these are detailed below. On occasions when the road is completely closed, motorists should exit the M80 at Haggs, divert through Kilsyth and rejoin at Auchenkilns.
The closures timetable is as follows. All closures are during the night shift hours of 8pm to 6am only, unless otherwise stated.
September 14-18: M80 Northbound emergency lane closed.
September 16 and 17 - Northbound full closure.
September 18 and 19 - Northbound lane 1 closed.
September 28 and 29 - Northbound and southbound lane 2 closed
September 30 and October 1 - Southbound lane 1 closed
October 2 and 3 - M80 southbound full closure
October 5 to 9 - M80 southbound 5 to 9
October 12 to 16 - Castlecary East private road under traffic light control
9pm October 31 to 5.30am November 1 - southbound road closure
7pm November 7 to 5.30am November 8 - B816 and M80 Northbound emergency lane closed.