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New introduction to the 1997 edition of

Mortars and Cements

L J Vicat

In 1812 L. J. Vicat, as an engineer in the France of the Napoleonic wars, began research into the nature and use of limes, particularly their use in hydraulic engineering works. By 1818 he had made sense of a complex subject and he presented a publication Recherches Expérimentales sur les Chaux de Construction, les Bétons et les Mortiers Ordinaires to the Institut de France – Académie Royale de Sciences. On the title page he is described as Ingenieur du Corps Royal des Ponts et Chaussées de France, and that may have been a recent appointment arising from this work. Ten years later, in 1828, he reworked that text to include notes on further major investigations, particularly those of other French engineers. However, these further investigations all served to support the conclusions he had already reached and the body of the text has much in common with the earlier book. The 1828 book was titled Résumé des Connaissances Positives Actuelles sur les Qualités, le Choix et la Convenance Reciproque des Matériaux Propres et la Fabrication des Mortiers et Ciments Calcaires and by this time Vicat was Ingenieur en Chef des Ponts et Chaussés. He again reworked the text in 1856 when it was published as Traité pratique et théoretique de la Compositition des Mortiers, Ciments et Gangues à Pouzzolanas. In the intervening years there had been a massive development in the production of hydraulic limes in France and Vicat noted that there were now nine hundred producers.

It was the 1828 book which Captain J. T. Smith of the Madras Engineers translated into English for publication in 1837. Smith's translation adds a new dimension to the text with extensive notes on developments in England and on his own experiences in India. He clearly admired Vicat greatly, but had originally found the text hard to follow, so much so that he repeated many of the experiments. Occasionally he points out where Vicat is mistaken.

Whilst the book covers a wide range of topics and is of immense importance, not many of Vicat's works were wholly original. His strength is in drawing together earlier notions and sifting the good ones from the bad by careful experiment. In 1846 Vicat was awarded a state pension for his work on artificial Pozzolans, but similar materials were well known in classical Roman times and well published. By 1818, he had assisted Messrs Brian and St Leger to establish a cement works (in Vicat's terms 'an artificial hydraulic lime works') at Meudon near Paris, predating any of the known English cement makers, but later than the 1810 English Patent by Edgar Dobbs (which Vicat is unlikely to have seen) and the successful experiments of M. Guyton de Morveau published in France in 1800 or 1801. His work on slaking of limes has strong echoes of de la Faye's work said to have been published in 1777 and based on concepts in Vitruvius. The existence of hydraulic limes (that is, limes which can develop strength under water) had been noted by Pailadio in 1570 and explained by John Smeaton in 1791.

Smeaton's experiments had overturned a very long held series of prejudices which Vitruvius had set out in his Ten Books on Architecture. These embodied the conventional wisdom of the eighteen hundred years from their writing, in about 25 BC, and very probably from the Greeks before the Romans, until the publication in 1791 of John Smeaton's experiments which had been carried out in preparation for his building of the Eddystone lighthouse in 1756. The conventional wisdom had been that hard durable mortars came from lime prepared from the hardest limestones and preferably from moist, shady quarries. In contrast soft stones, such as chalk, should only produce soft mortars. Over all of those years craftsmen must have been biting their tongues because the facts simply do not support the theory. Although the moisture in the limestone and the hardness of the stone do have some beneficial effects these are far less significant than another property which had not been explained. In his kitchen sink tests Smeaton showed that the limes which worked well for 'water building' were those made from limestones or chalks which contained a suitable proportion of clay. Vicat took all of this much further until he was able to describe some very simple procedures to allow an engineer in the field to assess the nature of lime from any deposit encountered. He prepared a classification which is still valid today and enables the best possible use to be made of any lime, particularly for hydraulic works. He explains how even the least promising may be modified with special sands or with pozzolans to give any performance which could reasonably be required.

Although he had helped with the early production of cement he could not imagine that it would be very widely used as he could not believe that cements, which had to be ground in a mill, could ever supplant hydraulic limes which could be prepared by the common work-man without machinery.

Many early texts on lime can be treacherous to read because the use of words has varied significantly over time. For example in other texts where stone limes and chalk limes are compared we may need to bear in mind that 'stone lime' might actually mean lime from grey chalk. Similarly before Vicat a 'lean lime' in France (chaux maigre) was the common term for a hydraulic lime, whilst in England it means a lime with a significant proportion of inert material. However, both Vicat and Smith have been very careful in the use of words. The words psammites and arénes for types of sand were so unfamiliar to Smith (and, indeed, to us today) that he left them in their French form and the reader should see the explanations on pages 46 and 47. The only other tricky word for us is 'cement'. To us the immediate image is ordinary Portland Cement, or perhaps white cement, and neither of those had been developed in 1837. Perhaps the simplest interpretation of the word in this text would be 'hydraulic binder'.

A few words on the structure of the book may also be helpful. Looking up references could hardly be simpler with an excellent table of contents and an excellent index. The book is also very readable in small bites at any point in the work, however the logical structure is less clear. The main text runs from pages 1 to 139 and this is closely based on the 1818 book. Both Vicat and the translator have added wonderful footnotes. The majority of these are from Smith whose footnotes are all suffixed '–TR.'. Vicat's own footnotes are marked '–Original note'. Most of Vicat's further comments are set out in the Appendix from pages 141 to 231. There is a reference forward to each such note at the end of the appropriate paragraph in the main text. Very occasionally Smith also includes a section in the appendix and these are prefixed '*' and suffixed '–TR.'. After the Appendix, from pages 234 to 256, is a sequence of sixteen tables by Vicat and a further one from the translator. These set out the results of various experiments and analyses.

This book is perhaps the most important text ever published on limes. Whilst much of the subject matter may seem comfortingly familiar a few parts will make the reader blink; for example the excellent results achieved with non hydraulic lime slaked 'spontaneously'. In Britain today 'spontaneously' slaked lime would simply be discarded.

Michael Wingate
Hindolveston

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