Clinker manufacture operational: 1872-5/1945
Approximate total clinker production: 1.83 million tonnes
Raw materials: Blue Lias Limestone and Clay (Rugby Limestone Member: 195-200 Ma) from quarry at 444250,264250, upgraded by rumbling. The Lias was 60% clay of around 35% CaCO3, and 40% limestone of around 78% CaCO3, and most of the clay was sidecast. The Lias was of too low a grade for modern cement, and from 1919, supplementary high-grade sweetener limestone (4-11% of dry rawmix) was bought:
Sometimes called Nelson’s Works. The site made lime from early times and like Southam had its own dock on the Grand Union Canal. The manufacture of “cement” dates from 1857, but as with the other Warwickshire plants, true Portland cement was not made until later: around 1872 in this case, when two small dry process bottle kilns were employed. The number of small bottle kilns was gradually increased, and a set of chamber kilns may have been added, perhaps around 1889.
A historical account of this plant is hampered by lack of data, and particularly by lack of maps. As with many rural areas, there is no map edition between the 2nd edition County Series of 1909 and the late 1960s revision. This means that no map shows the rotary kilns, and the only evidence for their location are a few poor quality aerial photographs of the 1930s. The fact (if it is a fact) that there were chamber kilns originates from a statement in a valuation document drawn up by a law firm in 1910 (Rugby Archive RS/9/1/5/6) which says “there are several old slurry drying Kilns, no longer required as such, which we understand will be converted into, and used as Clinker Stores.” The 1909 map does not depict anything that can be unambiguously identified as a chamber kiln block. The 1930s aerial photography shows an area where clinker is being stacked, with little indication that it might once have accommodated chamber kilns, but if it did, then a rectangle 98’ × 80’ can be identified, and, as it happens, there is a tall brick stack at one corner. This, depending on orientation, could contain six 22 tonne or four 30 tonne kilns. This information could be regarded as tenuous enough to ignore, were it not for the fact that the maps show the bottle kilns to be very small – the twenty-three amounting to only 302 t/week capacity. With the three Schneider kilns making 240 t/week, some 160 t/week extra capacity is needed to make the 700 quoted by Davis. (Davis is generally very reliable, using his own objective expert assessments of the plants rather than “declared” capacities.) I therefore go for the 6×22 tonne arrangement. Further circumstantial justification is the fact that wet process rotary kilns were chosen. All the Warwickshire manufacturers were watching each other closely at this time, and collaborating to a significant extent. Both Rugby and Harbury had chamber kilns and chose the wet process. Southam had dry process bottle kilns and chose the dry process. Previous experience of making slurry was evidently decisive, and without chamber kilns, Stockton would have had no need to make slurry.
Around 1902, three of the later bottle kilns were converted into Schneider kilns. By 1907 there were 8 lime kilns and 23 cement bottle kilns (305 t/week), six chamber kilns (135 t/week) and three Schneider kilns (240 t/week), totalling 680 t/week, corresponding to Davis’ estimate of 700 t/week. The Schneider kilns were converted to forced-draught (together 450 t/week) in 1908. These used dry-ground briquetted rawmix. The use of static kilns ceased in 1913. New continuous lime kilns were installed at the same time as the rotary kilns, and the plant continued to make a significant amount of Lias lime.
The plant did not expand up to the depression, and Rugby took a share in the near-bankrupt company in 1937. Following complete takeover in 1945, it became clear that there was no point in keeping it as a separate unit alongside the newly modernised Southam, and production ceased immediately, with the plant continuing to function as a depot until it closed in 1949. In addition to the canal, the plant also had a railway connection through the L&NWR Weedon-Leamington branch from 1895. The plant site remained derelict for many years, and was finally cleared of structures in 1968. The canal spur was filled in and the site has remained waste land, with foundations still visible. The quarries are partially back-filled, but mainly flooded.
Although this was the most important Warwickshire plant at the start of the twentieth century, information is hard to come by, and this account is far from satisfactory. Please contact me with any relevant information or corrections. I am particularly interested in firmer dates and statistics, pictures and plans.
Originally Collis and flat stone mills were used, grinding stone brought from the quarry by tramway. By 1905, they had 3 tube mills (size unknown) for wet grinding. In 1919, a wet "combination" tube mill was installed at the quarry, and the Lias was pumped to the plant as a slurry. At the plant, a second combination mill ground the slurry with added bought-in sweetener limestone.
Two rotary kilns were installed:
Supplier: Edgar Allen
© Dylan Moore 2011: commenced 7/8/2011: last edit 30/07/16.
Picture: ©English Heritage - NMR Aerofilms Collection. Catalogue number R2841. A high-definition version can be obtained from English Heritage. This was taken in 1937, looking southeastward. At the bottom left is the canal, with the plant spur branching off. At the top right is the main lias quarry, with large piles of clay spoil. The building with a sloping awning, was probably the Schneider kilns. In front of the tall stacks is a building - presumably a clinker store - connected by conveyor to the kiln house. The power plant (front left) was operating. The finish mills were presumably behind this, and three cement silos are beyond these. The ruinous buildings at the left rear of the plant seem to have contained earlier rawmills.