In 1927, a reconstruction of the cement works at Swanscombe commenced. This involved replacing the sixteen rotary kilns installed between 1901 and 1905 with three modern rotary kilns capable of producing a combined output of 400,000 tons of cement per year. Additionally, the scheme also included rebuilding the entire railway network within the works and associated chalk pits from narrow to standard gauge, completion coming in 1929. The conversion to standard gauge allowed the cement works to make a physical connection with the North Kent Line through the aforementioned siding on the southern fringes of the original chalk pit. Some isolated sections of narrow gauge track on the Swanscombe Peninsula were retained purely for storing redundant narrow gauge wagons. The wharf on the Thames was completely rebuilt to accommodate three parallel-running standard gauge tracks and a travelling crane.
Naturally, conversion of Swanscombe Cement Works' internal railway network to standard gauge required a new fleet of motive power and rolling stock. As part of the 1927 reconstruction, an order was placed by APCM with R. & W. Hawthorn, Leslie & Co of Newcastle upon Tyne, for the construction of five 25-ton 0-4-0 saddle tank steam locomotives, each with a tractive effort of 21, 425 lbs. Four of these arrived on site in 1928, the fifth in 1929, and a sixth identical engine was ordered and subsequently delivered in 1935. A seventh and final saddle tank, again of 0-4-0 arrangement, but of slightly enlarged cylinder dimensions, arrived new at Swanscombe in 1948. This had also been built in Newcastle, but the railway locomotive construction interests of R. & W. Hawthorn, Leslie & Co had since been taken over by Robert Stephenson & Co. , which subsequently built engines at the same works under the name "Robert Stephenson & Hawthorns".
Perhaps the most difficult aspect of industrial railway history, particularly of cement works, is keeping abreast of track layout changes. Railway lines presented on Ordnance Survey Maps, particularly within the actual chalk pits, quite often have to be assumed to be indicative at best for a specific year. The very nature of the excavation task, where pits grew in size and, eventually, became exhausted, saw frequent realignment of railway lines. Indeed, the regular informal slewing of track to adjust to the changing dimensions of a pit would have been missed between Ordnance Survey editions, but the general extent of a cement operation at a given time, such as the number of connected chalk pits, can still be traced. By 1940, the southern tentacle of Swanscombe Works railway extended for about a mile, terminating within the initial excavation of what we today know as the redundant "Eastern Quarry", on the opposite side of the road to the Bluewater Shopping Centre, Greenhithe. At this time, Eastern Quarry occupied a ground area of about ¼-mile long by as much wide, but by the mid-1950s, this had expanded five-fold in a southern direction. Excavation was undertaken by steam navvies, which were steam-powered machine-driven excavator cranes that used large buckets to scoop up chalk, subsequently swinging these around to deposit their load in adjacent wagons.
Whilst steam traction was formally abolished on British Rail lines in 1968, there still remained hundreds of such locomotives in industrial use around the United Kingdom. However, at least for APCM's Swanscombe Works and the nearby Empire Paper Mills at Greenhithe, the steam locomotive did not reign surpreme for much longer. 1970 was the last full year of service for the Swanscombe's Hawthorn Leslie saddle tanks; in 1971, the locomotives were stored in a line out of use in a siding, their roles having been assumed by a fleet of diesel locomotives. The latter were of the distinctive "Sentinel" type, manufactured by Rolls Royce at Shrewsbury, and comprised a four-wheel base. Happily, of those five saddle tanks delivered from 1928 to 1929, four still remain with us today.
In 1978, APCM renamed itself "Blue Circle Industries PLC", after its market brand name for cement. At this time, the company had two major cement works on the southern bank of the Thames: Swanscombe and Northfleet. The modern works at Northfleet had become fully operational in December 1970, having replaced seven existing APCM works split either side of the river. Sadly, the illustrious works at Swanscombe, having been extant since 1825, had little over a decade left. The 1980s marked a recession in the construction industry and, as a result, it was announced that Blue Circle cement works at Shoreham, West Sussex, and Swanscombe were to close in 1988. Both managed to survived beyond this time, although each had a kiln taken out of use in 1989. Closure of works at Swanscombe and Shoreham was finally enacted in 1990.