Miscellaneous

Harbury Cement Works: misc_hcw175

A general view of the Harbury Cement Works under the ownership of Associated Portland Cement Manufacturers (APCM) in the early 1930s. APCM bought the Cement Works in 1932 following the financial failure of the Red Triangle Group in the previous year.

Harbury is situated on an outcrop of blue-grey argillaceous limestone and dark blue calcareous clay, which was laid down in alternating bands, each a few inches thick during the Jurassic period. The blue colour was due to pyrite, but this changed to an orange-brown after exposure to air. The natural colour resulted in the limestone being called Blue Lias and this had been hand pick in small quantities at Harbury for centuries. The Blue Lias lime had a reputation for hydraulicity and was produced by burning the raw limestone, but real demand came with the production of Portland Cement from 1860’s onwards. This required greater consistency, which was achieved by grinding the raw limestone into a powder. A slurry was then created by mixing the powder with clay and water, which was then dried and burnt in lime kilns.

As well as advances in kiln technology, other processes were mechanised including the separation of the hard limestone from the softer clay. This was achieved using a rotating cylinder of iron bars called a Rumbler with the waste clay deposited in vast spoil heaps, which can seen on the left of the photograph. The resulting Lias powder usually had insufficient calcium content and this had to be increased by mixing with high grade crushed limestone called sweeteners. At Harbury Cement Works sweetners were initially obtained from the base of the Lias pit on the site, but also imported from Lighthorne Quarry (a 5 mile road journey) and further afield from Ardley Quarry, which was adjacent to the 1910 cut-off main line a few miles south of Anyho junction. This quarry exported 105,260 tons in 1929. Harbury Cement Works also relied on the railway for importing coal for firing the kilns and exporting the final products.

The Service Time Table for Summer 1929 showed that the following freight trains called at Greaves Sidings to attach and detach wagons. Note this included a return Goods service from Leamington Spa:

Robert Ferris

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