Summary

A 19th century downdraught kiln known as Aspdin’s Kiln 224m NNW of Chaplains House.

Source: Historic England

Details

This record was the subject of a minor enhancement on 17 March 2015. This record has been generated from an "old county number" (OCN) scheduling record. These are monuments that were not reviewed under the Monuments Protection Programme and are some of our oldest designation records.

The monument includes a mid-19th century downdraught kiln, known as Aspdin’s Kiln, surviving as upstanding and below-ground remains. It is situated on low lying ground near the south bank of the River Thames, south of Grove Road at Northfleet.

The circular, beehive-shaped kiln is built of brick and set on a base about 7.5m square. It is surmounted by a short cylindrical brick chimney and has three arched openings; two in the south face of the base and one in the south-west face of the circular chamber. An underground opening leads off to the north.

The downdrought kiln was built by William Aspdin in about 1846, to the patented design of his father, Joseph Aspdin. It is thought to be the oldest Portland cement kiln in the world. Joseph, a Leeds builder or bricklayer, had gained a patent for what he described as ‘Portland Cement’ on 21st October 1824. This was a calcined mixture of limestone and clay. The choice of name was due to its resemblance in colour to Portland stone. In actual fact its mineralogy and hydraulic activity was quite different from modern Portland cement. However William Aspden improved the manufacturing process; introducing a higher firing temperature allowing the formation of alite crystals, a key characteristic of modern Portland cement. This new form of cement was substantially stronger then existing ‘Roman’ cement. The benefits were recognised by Marc Isambard Brunel who employed it in the construction of the Thames Tunnel. Having left his fathers’ business in 1841, William set up a cement firm at Northfleet in 1846.

The surviving kiln is part of a much larger 19th century cement works which extended along the south bank of the River Thames. During the 1850s the works had nine bottle kilns and produced a Portland cement called ‘Nine Bottle Cement’. The works closed in the early 20th century.

Source: Historic England

Reasons for Scheduling

A downdraught kiln is a type of kiln in which air rises up inside the oven to be forced back down and out through the base of the oven. It was commonly used in the production of pottery during the post medieval period and was often termed ‘Beehive Kiln’ given its domed shape in resemblance to a beehive.

Aspdin’s Kiln produced an early form of Portland cement, essentially a calcined mixture of limestone and clay. Technical progress in the manufacture of cement in the later 19th century, specifically; the development of rotary kilns, the addition of gypsum to control setting and the use of ball mills to grind the raw materials, led to widespread production of Portland cement used by the modern construction industry. This is made by heating limestone with other material, such as clay, to 1450 degrees centigrade in a kiln. The resulting substance, ‘clinker’ is then ground with a small amount of gypsum into a powder to make the cement. Portland cement is a basic ingredient of modern concrete, mortar and grout, and a major component in the construction of buildings, dams, tunnels and other infrastructure.

The 19th century example at Northfleet is a well-preserved example of a downdrought kiln used in the production of cement. It is thought to be the oldest Portland cement kiln in the world and as such is of considerable historic interest. The site will contain below-ground archaeological information relating to the construction of the kiln, as well as deposits of the material it produced.

Source: Historic England

Sources

Websites
Portland Cement Online, ‘Cement History’, accessed 30 March 2010 from http://www.portlandcement.net/cement%20History.htm
Other
Kent HER TQ67SW77. NMR TQ67SW77. PastScape 413989.

Source: Historic England