Portland Cement is the most common type of Cement in general use around the World as a basic ingredient of Concrete, Mortar, Stucco & non-specialty Grout. It was developed from other types of Hydraulic Lime in England in the early-19thC by Joseph Aspdin & usually originates from Limestone. It is a fine Powder, produced by heating Limestone & Clay Minerals in a Kiln to form Clinker, Grinding the Clinker & adding 2 to 3% of Gypsum. Several types of Portland Cement are available. The most common, called Ordinary Portland Cement (OPC), is Grey, but White Portland Cement is also available. Its name is derived from its resemblance to Portland Stone which was Quarried on the Isle of Portland in Dorset. It was named by Joseph Aspdin who obtained a Patent for it in 1824. However, his son William Aspdin is regarded as the Inventor of “Modern” Portland Cement due to his Developments in the 1840s England remained the main source of the World’s Cement during the 1850s & 1860s. This Export Market allowed the English Plants to expand Production & mature their Technology & the Home Market for the Product began to take off from 1860 onward, rapidly overtaking that of the earlier Products. Exports all around the Globe remained a major part of the Industry’s Business until the 1890s, when it suddenly became apparent that Foreigners & Colonials could make Portland Cement as well.
The Original “Invention” or “Discovery” of Portland Cement sets the Standard for all subsequent Cement Industry History, in that it cocooned in a web of disinformation, misunderstanding & lies. In this work, the term Portland Cement is applied only in the modern sense. “Portland Cement as we know it” can be simply defined as a Calcareous Cement containing (intentionally!) significant amounts of Alite (“tricalcium silicate”). Portland Cement is one of many materials that can be made by making a finely-ground mixture of Limestone & Clay & burning the mixture at over 1000°C. The properties of the product obtained differ widely depending on the composition of the mixture & the Temperature of Burning.
The most important Industrial undertaking in the Parish has been A large Cement Works was Established as the Chinnor Cement & Lime Co Ltd. It was Founded in 1908, became a Public Company in 1936 & in 1949 a Parent Company, Chinnor Industries Ltd, with 3-Subsidiary Companies. The Founder Mr William Elijah Benton a Mining Engineer from Acton, started a small Business to Manufacture Lime on the Southern edge of Chinnor. This eventually consisted of 5–Beehive Lime Kilns producing Lump Lime for use in both Construction & Agriculture. In 1919 he added a small Cement Plant which used Flare Kilns (that had to be Loaded & Unloaded by hand).
Flare-kiln for Lime Burning. Built 1908. Brick. About 6M Tall, of Bottle or Beehive shape. It is the remaining 1 of 5 similar Kilns, the others having been Demolished. The Dome of the Kiln rises from a Brick Base with a large Semi-Circular Arch on the NW Side within which is a Loading Door. Remains of another Round Arch on the SW side, Blocked Doorway on NE Side & 3-Stoking Holes on SE Side.
Interior: Iron Fire-Grates of 3-Internal Flues in the Floor. Flare Kilns were for the production of Lump Lime for Agriculture & Construction. In 1919 a small Cement Producing Plant was developed Adjacent to the Bank of 5-Flare-Kilns which Produced up to 240-Tons per week. The Kilns continued in Production until 1938.
The Chalk Firing Process was as follows: “The Flare Kiln is filled with about 65-Tons of Chalk & 3-Tons of Coke, introduced in Alternate layers. It was Fired through Fire holes in the Bottom, Coke being used for the 1st-Day & Coal for the next 2-Days. After Burning 10-Days, an average of 25-Tons of Quicklime was Produced. These Lumps of Lime reduced to a fine Powder after Contact with Water“.
By 1928 the Business had grown & the 1st Rotary Kiln was Commissioned & following Progress & Development, the Chinnor Cement & Lime Co Ltd was formed. In 1936 further Investment followed, with Rotary Kiln No.2 being installed in 1938. In 1957 it Employed about 160-men, but the Works were being extended with the object of doubling its Capacity & bringing it to a still higher Degree of Efficiency. Its Market was a comparatively Localised one, the majority of its Customers being in the 7-Counties which were closest to the Works. A further Rotary Kiln No.3 was added in 1958. The Company had also grown, becoming Chinnor Industries Ltd; by 1962, the original Rotary Kiln had been replaced by a New No.1 Inclined Rotary Kiln & the Site extended to almost 200-acres.
![Photograph of cement works in Chinnor, Oxfordshire [c.1930s-1980s] by John Piper 1903-1992](https://astonrowant.files.wordpress.com/2018/06/chinnorcementworks.jpg)
With the Arrival of Rotary Kilns in Britain in 1900, Cement Manufacturing Processes became sharply defined according to the form in which the Raw materials are fed to the Kiln. Raw materials were either Ground with addition of Water, to form a Slurry containing typically 30-45% Water or with 50-80% Water
- In the Wet Process, the Kiln System is fed with Liquid Slurry, the Water then being Evaporated in the Kiln.
- In the Semi-Wet Process, raw material is prepared as a Slurry, but a substantial proportion (50-80%) of the Water is Mechanically removed, usually by Filtration & the resulting “Filter Cake” is fed to the Kiln System.
- In addition to these distinctions, a further Category emerged in the last 40-yrs:
Precalciner Kilns, in which a Proportion of the Kiln Fuel is burned in a Static Preheater before the Feed enters the Rotary Kiln.
The Stored Slurry is contained in 3 x 600–Ton Vertical Steel Tanks, one of which is always Supplying the Kiln with Slurry of the desired composition. The Slurry in all 3-Tanks is Agitated by Compressed Air. The Kiln Slurry-feed is driven by the Kiln so as to regulate the Supply to the Speed of the Kiln. The Kiln (by Edgar Allen & Co Ltd) is 185-ft. long including a 20-ft Cooler on the Discharge end of the Kiln. A Shaker Conveyor by F L Smidth & Co Ltd, carries the Clinker to the Elevators & so to the Mills. The Cement Mill is divided into 4-Compartments & is capable of Grinding 7-Tons per hr to a Residue of rather less than 5% on a 180-Sieve, or finer when making rapid-hardening Portland Cement. The Coal is dried in a Rotary Drier & Ground in the standard type of Combination Mill. The older method of Coal Preparation was deliberately chosen to ensure an Evenly Dried & Ground Fuel to the Kiln.
The so-called ‘Navvies’ were big, crude Machines designed for 1-Purpose: to dig a Ton or more of Chalk in one go. They were powered by basic (pre-1950s) Diesel Engines & Operated via massive Gear Wheels, Cables & Sliding Arms controlled from a Cab that was, to all intents & purposes, Open to the Elements. The Controls were Heavyweight & the Operator’s Job was Physical. This was no Job for a Wimp & the Navvies often worked round-the-clock, on 8-hr Rotating Shifts to match the Cement Production Process & during the Night-time hours, the Machines Operated by Headlights. The noise & sheer size of the ‘Navvies’. The Health & Safety Executive hadn’t been heard of then so there was minimal separation in the Cab between the Driver & the Moving Machinery. You had to rely on simple common sense to keep youself Safe when surrounded by Lethal moving Machinery. There were never any serious Accidents to ‘Navvy‘ Operators, certainly not at the Chinnor Plant.
Aston Rowant & Chilterns Spring Line Villages 