The cement company says the freight connection will open in February 2012
Lafarge Cement is building a rail connection to the main north Kent line at its former cement works in Northfleet.
Crossrail will be the first main user of the restored line, and will use it to transport excavated material from the western tunnel bore at Royal Oak, near Paddington, to Northfleet, for onward transportation to Wallasea Island by ship.
The company expects the rail sidings to be operational from the middle of February next year.
The sidings and connection to the main line are being designed and constructed by Balfour Beatty Rail, while Chunnel Group have carried out the siding preparation works within the main site.
The rail link is around 2.25km long overall, and 4.75km of new track will be provided.
Lafarge developed proposals for the site in association with Kent and Gravesham councils.