WILLIAM ASPDIN: THE ORIGINS OF PORTLAND CEMENT
EARLY CEMENT PRODUCTION
North West Kent is the cradle of the modern cement industry, but cement is as old as building itself. The very first wattle huts needed a material to bond others which would not of themselves bind together. The first cement was wet clay, and indeed wet clay is still used as a cement in the remoter parts of the world. Five thousand years ago the Egyptians made cement by mixing burnt lime and gypsum and in some cases the stones bound together then are still firmly held today.
The Romans developed the process further and there are examples of their work in Britain today, such as the Pharos at Dover and sections of London Wall. But it was only in the eighteenth century that its properties were scientifically analysed and its use in building became more general. Important names in the development are Smeaton, who built an early Eddystone lighthouse in the 1750s and Parker, who invented 'Roman' cement, with its quick setting properties, at the end of the eighteenth century.
The great milestone was the discovery of Portland cement. Joseph Aspdin, a Leeds bricklayer, took out a patent for his 'Portland' cement in 1824 - though he claimed he had been making it since 1811. Aspdin, whose son worked with him, in fact had little scientific or chemical knowledge and used rule-of-thumb methods.
Some of the vagueness in his patent application could also have stemmed
from his desire for secrecy. He talks of using road scrapings from the
neighbourhood of lime kilns and only using freshly quarried limestone
if these scrapings were not available. Aspdin was also secretive about
his manufacturing process. No-one but the workmen were allowed into his
premises and he personally took part in the loading of every kiln.
It was not clear that he entirely understood what he had discovered. For example, in his patent there is no mention of the need to burn the raw materials to the point of incipient fusion. Indeed this feature was rediscovered with some difficulty by Issac Johnson at Swanscombe in 1847. Be that as it may, Aspdin was granted a patent for "Portland cement" - so called because its colour resembled that of Portland stone.
There has been some argument over whether Joseph Aspdin can actually claim to be the inventor of Portland cement. Sixty years earlier Smeaton had called his cement 'Portland' because of its resemblance to Portland stone and Aspdin's 'Portland' cement was not really like the Portland cement used in the twentieth century.
CEMENT PRODUCTION IN THE 19TH CENTURY
What is certain is that Joseph Aspdin's youngest son William left Wakefield, set up cement works at Rotherhithe, and met Brunel finishing his ill-fated Thames Tunnel. On one occasion when the roof collapsed Brunel dumped tons of Aspdin's cement into the river. This sealed the break in the tunnel roof and Brunel was able to pump the tunnel dry. He then rebuilt it and used Portland cement for the relining. This was probably the first major civil engineering project to use cement. Brunel was obviously aware of the qualities of Portland cement because he could easily have obtained Roman cement locally at half the price.
William teamed up with a Mr Robins and a Mr Maude and built a cement works at Northfleet Creek, Kent trading as Robins, Maude and Aspdin. Aspdin's 'Beehive' kiln, used to make the first genuine Portland Cement, can still be seen at Northfleet. The oldest surviving cement kiln in the world, it has been opened up by Blue Circle for public viewing. A batch of 'bottle' kilns from the 1840s has also survived.
In The Builder of 1848 under the title of Robins, Aspdin and Co, with a wharf at Great Scotland Yard, Whitehall and a depot at Back Grove, Liverpool they advertised:
Portland cement really came to the public's notice in the late 1840s as public rivalry built up between Frost's and Aspdin's. Frost's works at Swanscombe had been bought by J Bazley White in 1834. There had been repeated failures of Roman cement, and Portland cement came to be seen as superior. Even so, by 1850 there were still only four works, producing Portland cement. After 1851 the number producing on the Thames and Medway increased rapidly with White's brand from Bazley White's Frost works being the most prominent.
Around the mid-century, Isaac Charles Johnson, the Manager at Frost's, carried through some important developments of the Portland process.He discovered the importance of the intermixing of chalk and clay in proportion with water and also the clinkering of the mixture. He also modified the kiln so that the chimney was tapered to increase the draught and thus the temperature.
The cement industry established itself in the area rapidly during the latter part of the 1800s. Abundant supplies of chalk and alluvial clay had made it a natural home for the industry. Cement firms sprang up to take advantage of the growing demand for a product whose true potential had become obvious. Competition was keen and in the early years there were no recognised standards of quality. Chalk was dug with picks, shovels and crowbars and grinding was done by windmills. It was a time of trial and error, but a time nonetheless which established a solid reputation for British cement throughout the world.
CEMENT PRODUCTION IN THE 20TH CENTURY
By 1900 nearly 1,000 bottle kilns were clustered along the estuaries of the Thames and Medway, billowing evidence of an industry growing fast. The rivers were alive with sailing barges weaving to and fro as they supplied the cement firms with vital raw materials and carried the finished product off to its customers. In the chalk quarries close to the river steam shovels dug relentlessly. This was the busy North Kent scene in the year in which the Blue Circle group was born.
As the new century dawned there was growing pressure on cement manufacturers to further improve the methods of manufacture and the quality of the product. Small firms could not hope to raise the capital needed to invest in the new efficient rotary kilns and other sophisticated plant. An amalgamation was the answer and in 1900 24 small firms joined forces to create the Associated Portland Cement Manufacturers Limited, known locally as 'the Combine'. Today the company trades as Blue Circle Industries plc. It has grown from its small beginnings in Kent to become Britain's biggest cement manufacturer and one of the industry's world leaders. Through Whitecliff Properties it developed Crossways Business Park, a centre for business innovation, and with Lend-Lease it has developed Bluewater.