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Crushed and Fine Graded Granite Analogue  - Brown Grey
Crushed and Fine Graded Granite Analogue - Brown Grey
4kg
£32.40
Specialist Aggregates Group
Specialist Aggregates Ltd Marine Arts
Strange looking rock
Thursday 27 January, 2011
News Brief

This strange looking rock, was instrumental in the development of modern cements.

Full Story:

I knew that the rock was called a Septarian Nodule, indeed, I had found it in Lias clay in Dorset some years ago, and being an absolute Rock Hound I just had to bring it home.

What I didn't know until researching the background to lime mortar was that these nodules were instrumental in the history of the development of modern Portland cement.

Even today no-one really knows how these strange nodules were formed, however, it was a Clergyman James Parker who discovered and patented a process in 1796 to produce a natural cement by "burning" the stones at just under 1000 degrees and then "slaking" the resultant product with water.

Parker marketed the product as "Roman Cement" although strictly speaking it was nothing like the composition of materials so effectively used some 2000 years earlier, and indeed to confuse further, in modern nomenclature the the product was not a cement at all - we would call it a hydraulic lime.

Regardless of names his "cement" had remarkable properties when mixed with sand to produce a mortar. The mix would set in under 20 minutes and being "hydraulic" the mortar would actually set under water, significantly aiding the construction of buildings, sewers and even lighthouses.

Parkers success led others to experiment with artificial mixes of clays and limestone and to investigate the results of "burning" the mix at temperatures in excess of 1000 degrees, resulting in the first true "Portland" cement as we would recognise it to be produced at the William Aspind Northfleet Works in 1842.

Our images show a Septarian Nodule and one of the resultant applications of the Victorian research on cement products: The stunning light house at La Corbiere on the island of Jersey was first lit in 1874 and was the earliest to be built using reinforced concrete.


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Strange looking rock
Strange looking rock
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