Observations on limes, calcareous cements, mortars, stuccos, and concrete : and on puzzolanas, natural and artificial : together with rules deduced from numerous experiments for making an artificial water cement, equal in efficiency to the best natural cements of England, improperly termed Roman cements, and an abstract of the opinions of former authors on the same subject

Front matter

■■iiiiiliiiii^^

OBSERVATIONS I '^'irX

LIMES, CALCAREOUS CEfepJli;

Preface

As the whole of the opinions stated in this Treatise, were deduced from personal observation, or from the successive experiments alluded to, with the exception of those founded on or corroborated by some important facts extracted from a paper of Mr. Timperley, published in the first volume of the Transactions of the Institution of Civil Engineers ; and as these experiments occupied so long a period of time, and the book was printed in portions, during the intervals between successive experiments, it cannot boast of such a methodical arrangement, as might have been adopted, had every experiment recorded in it been tried, before the first sheet was sent to press. Hence it was thought desirable, in order to compensate this want of arrangement by facility of reference, to make the Table of Contents more ample than usual, so as to form a sort of abridgement of tiie work itself, rather than a mere outline of the titles of the subjects discussed.

In this Treatise, the various properties of limes, of calcareous mortars and cements, as well as of puzzolanas, have been discussed in the amplest manner, and reduced to a system, no part of which, however, has been founded on mere hypothesis.

I trust, that a good deal of new information will be found in the following pages, upon a subject of immense importance to mankind, and that the principles developed in it, will prevent such crude notions respecting calcareous mortars and cements, from being adopted in future, as have occasionally caused the gradual and sometimes even the sudden ruin of the locks of canals, wharf and dock walls, and other pieces of brickwork or masonry, exposed to the action of water ; tor although sound principles have been acted upon by writers as well as practical men, how is the young student to decide, when he reads the discordant opinions of Semple, Smeaton and Higgins in this country, and of Belidor, Loriot, Dela Faye, Vicat and Treussartin

PREFACE, I 'V--, '^A

France, all maintained with equal confi^(^e f.^d Avh-en he finds no less discordant opinions maintaiW^ with. nolens confidence by practical men, trusting to whaVthey cslU experience, which may be very limited, ibr unless a m^ir*of business be also a man of research, he cannot know what has been done in foreign countries, or even in distant parts of his own.

To do away this uncertainty, I have endeavoured to point out such modes of experimenting and of personal observation, as will enable an intelligent person, who has no experience of his own, to decide justly between the various sorts of calcareous mortars and cements, that may be held out by their respective partizans, as being the best, or if not absolutely the best, as being the most expedient in an economical point of view ; which last consideration has caused the weaker vs^ater limes and sometimes even common lime, such as the chalk lime of the South of England, to be used for the brickwork or masonry of works of the above mentioned description, than which there cannot be a more mistaken economy, because the mortars of these limes are absolutely unfit to resist the action of water, and cannot insure the stability of walls built with them, and exposed to that action, for any length of time.

Of all the authors, who have investigated the properties of calcareous mortars and cement from time immemorial to the present day, our countryman Smeaton appears to me to have the greatest merit, for although he found out no new cement himself, he was the first who discovered in or soon after the year 1756, that the real cause of the water-setting properties of limes and cements, consisted in a combination of clay with the carbonate of lime ; in consequence of having ascertained by a very simple sort of chemical analysis, that there was a proportion of the former ingredient in all the natural lime stones, which on being calcined, developed that highly important quality, without which

POEFACE.

walls exposed to water go to pieces, and those exposed to air and weather only, are comparatively of inferior strenj;th. By this memorable discovery, Smeaton overset the prejudices of more than 2000 years, adopted by all former writers, from Vitruvius in ancient Rome, to Belidor in France, and Semple in this country, who agreed in maintaining, that the superiority of lime consisted in the hardness and whiteness of the stone, the former of which may or may not be accompanied by water-setting or powerfully cementing properties, and the latter of which is absolutely incompatible with them. The new principle laid down by Smeaton, the truth of which has recently been admitted by the most enlightened Chemists and Engineers of Europe, was the basis of the attempts, made by Dr. John at Berlin and by M. Vicat in France, to form an artificial water lime or hydraulic lime in 1818, and of mine to form an artificial water cement at Chatham in 1826, to which 1 was led by the perusal of Smeaton's observations, without knowing any thing of the previous labours of those gentlemen on the Continent, or of Mr. Frost, the acknowledged imitator of M. Vicat, in this country.

The natural cements of Fngland, most improperly and absurdly termed Roman cement, though the discovery of their properties and use, is as much a modern discovery as the steam engine, and of more recent date, possess an infinite superiority over all other hydraulic mortars, not excepting puzzolana, which in combination with lime formed the strongest cement that the Romans were acquainted with. First discovered by Parker in 1796, our English cements are now prepared for use by a great number of manufacturers, some of whom may be depended upon as never offering a bad article for sale, and any individual who applies to them, will be sure to have it good ; but in the public Departments, it is so common to advertise for tenders for building materials and to accept the lowest, that it

PREFACE.

tempts unprincipled men, who gain such contracts by offering to supply them at a lower price than would compensate the fair dealer, to endeavour to pass off not merely an inferior but an adulterated article upon the receiving Officers, of which I have known an instance at Chatham. This induced me to endeavour to lay down rules for judging of the quality of cement offered for sale, and for ascertaining whether it has been adulterated or not, by attending to which, the most unexperienced person may easily detect such frauds, in 24 hours or even less.

Instructions have also been given, by which Officers of Engineers or others, stationed in the Colonies, or employed in exploring some new country, will be enabled to judge, whether a calcareous stone, whose properties have not before been ascertained, is a water cement, a water lime, or a common lime.

Moreover, as it is very difficult to decide upon the value of different calcareous cements and mortars, by building portions of walls with them, which would not only require an inconvenient length of time to compare them, but would be liable to great uncertainty ; rules have been laid down, by which their comparative strength may be judged of experimentally, in a short space of time such as ten days, with very little trouble and with the greatest accuracy ; tha'. is, if I am right in the opinion formed by me after the continual experiments of many years, namely that those cements and mortars, which set the soonest under water, and which are found to possess the greatest resistance and adhesiveness at the end of that period, will also prove the most durable, and will retain the same comparative superiority for any length of time. These rules, if correct, as I trust they are, will obviously be of the greatest importance, by enabling an Engineer to make a judicious choice between two sorts of cement or of mortar, both apparently good ; but between which there may in reality be a considerable

PREFACE.

difference, which no other mode of comparison can detect so conveniently, or wi'ih so much accuracy.

Tlie properties of cements first attracted my notice most particularly, so that when after many previous failures I succeeded in forming an efficient artificial cement on a great scale in 18;10, I took very little notice of limes and none of puzzolana, in a Pamphlet printed by me in that same year, which contained my Observations on the Natural Water Cements of England, with a description of ray Artificial Cement made in imitation of them. This pamphlet was sent by authority of the Master-General and Board of Ordnance to all the Royal Engineer Stations at home and abroad, and by the Court of Directors of the East India Company to all their Engineer Stations in India ; and copies of it were presented by me to various Scientific Societies, as well as to several private friends. I discovered, however, on resuming the same subject six years afterwards, thatmy artificial water cementof 1830 was not the strongest, that could have been made of the same ingredients, as will be seen by a perusal of the present Treatise.

That the artificial cement, more recently made at the Royal Engineer Establishment in the years 1836, 1837 and 1838, is equal in efficiency to the best natural water cements of England, as set forth in the title page of this work, has been fully proved by numerous experiments* tried not only in presence of all the Royal and Honourable East India Company's Engineer Officers attending this Establishment, but also of Officers of other Regiments and Corps in the Garrison of Chatham, as well as of other Gentlemen, and of Clerks of Works, Builders and Artificers, whom 1 made a point of inviting to attend, as I wished to make my experiments as public as possible. The natural English cements were either supplied by Messrs. Francis and Co. of Vauxhall, or from her Majesty's Dockyard at Sheerness, both of excellent quality, and made.

PREFACE.

according to custom, of a mixtnre of calcined Harwich and Sheppy stones, which are better than either of those cements used singly. In such experiments, as were not tried for the purpose of ascertaining comparative strength, but for investigating the general properties of water cements, whenever the particular sort experimented upon is not specified, let it be understood, that Messrs. Francis's cement was used.

Other experiments recorded in the following Treatise have established an important fact before considered doubtful, namely that cement is no less suitable lor masonry composed of the hardest and heaviest stones, than for brickwork ; as was proved by the remarkable circumstance of a Bramley-fall stone breaking before the cement joint, which united it to another large stone of the same kind, gave way.

That a few courses of brickwork and cement bond, aided by hoop iron in the joints may supersede the necessity of chain timbers and bond timbers of all descriptions in the walls of buildings, as well as of wooden lintels over the openings of doors and windows and of bressummers over shop fronts, had been fully proved by the experimental brick beams of Mr, Brunei and of Messrs. Francis & Co, but as their experiments left the comparative importance of the cement and of the hoop-iron bond doubtful, I was induced to build three experimental brick beams, one with cement alone, another with cement and hoop-iron bond, and a third with Hailing lime mortar and hoop iron bond, which on being all broken down fifty days al'terwards, proved the vast importance of the hoop-iron bond, without which the brick and cement beam had comparatively very little resistance, and the brick and mortar beam would have had none. The practicability of executing domes or roofs with brickwork and cement, in forms absolutely impossible with the best lime mortar, was also proved by an interesting experiment.

i ^ . \ PREFACE.

/t-In l$^6,„^^|ien the first sheets of this work were sent to pres&^'h s(J^ |f enthusiasm prevailed in favour of concrete, * ; espedaU^l^en moulded into artificial stone, which induced iji'e to experiment upon the resistance of small square • prisms of artificial stone, made of various limes and cements mixed with different proportions of sand and gravel, after allowing them sufficient time to set. The extreme weakness of these experimental prisms convinced me, that concrete was of very inferior importance, except when used in mass for foundations or for backing, to which Sir Robert Smirke, who first introduced the use of it in this country, very judiciously confined it. The unfavorable impression as to the value of artificial stone, produced by our experiments at Chatham has been confirmed on a great scale by the failure of the external surface of the concrete docks and wharf walls in her Majesty's Dock-yards at this place and at Woolwich; and even for foundations it requires to be used with judgment, and ought greatly to exceed in area the base of the walls to be supported by it ; otherwise it may settle unequally and crack, as was the case in the experimental concrete casemate built at Woolwich, or it may sink to a considerable depth in soft soil, as was the case with the concrete wharf wall built by Mr. Ranger by direction of the then Admiralty Architect at the north extremity of Chatham Dock-yard, which has sunk about one foot deep in the mud, since it was first built, and which from the nature of its profile, combined with this deficiency of base, would have capsized and fallen into the Medway, if it had not been afterwards secured by iron bars and pieces of chain cable, acting as land ties, and fixed to piles driven at some distance in rear of it.*

In respect to water-limes, and water-mortars, or hydraulic

* This wall escaped my observation, until the whole of my Treatise was printed ; otherwise I should have noticed it in the body of the worii. The concrete casemate at Woolwich was described in Article 32 and its note and its failure from unequal settlement, in the note to Article 33. '

PREFACE. / ^ Pjg^v

limes or hydraulic mortars as the French ternn^r^^ ^^^^^ tried fewer experiments, the results of which^igpve^avt; \ convinced me, that the opinion of Smeaton, s^ejgen^r^jly'^ adopted, that the Aberthaw or blue lias is far the^^^jgest oj^ our EnglishlimeSjis perfectly correct. Indeed itseerhs t(dt.]^oJ^>' sess rather greater strength than he gave it credit for, when he considered it necessary to mix it with puzzolana, for 1 have found, in confirmation of the efficiency of the system, since adopted for the masonry of several important works, and amongst others for that of the celebrated Menai bridge, that the mortar of this lime will set on being immersed, whereas the mortars of all the other English limes, that I have experimented upon remain in a state of pulp under water, unless improved by the addition of a proportion of puzzolana. But this substance, as imported from Italy, being too expensive to compete with the blue lias lime mortar ; the only resource for making the other limes of England available for works exposed to the action of water, at a moderate expense, appears to be the use of artificial puzzolana, made by calcining the blue clay of the Medway or any other impalpable clay, whether alluvial or fossile. My own experiments induce me to put great confidence in this expedient, in which however, there is nothing original ; because puzzolanas both natural and artificial have been in common use in the south of Europe since the time of the Romans, though the latter has been little used in this country, and the former I believe not at all, until Smeaton first introduced it about 80 years ago.

The subject of cements having frequently been discussed within the last 10 years at the Institution of Civil Engineers, where Mr. Frost and I, when present on those occasions, always explained our respective proceedings to the members, it was suggested to me that if the Treatise, which I then announced my intention of publishing, should take a comprehensive view of the whole subject of limes and

PREFACE.

mortars also, it would be more useful to practical men, than if confined to observations on natural and artificial water cements only, like my pamphlet of 1830. In compliance therefore with what appeared to be the wish of several members of that excellent and most liberal Institution, I have enlarged more upon limes, mortars and puzzolanas in the body of my Treatise than I had at first intended to do ; and in deference also to their opinion, I have added in the Appendix an abstract of the writings and proceedings of the most eminent British and Foreign authors on the same subjects, that is of the more modern ones, for every author on limes and mortars, that I have met with, followed the authority of Vilruvius, until after the middle of the last century, when Smeaton came into the field, and pointed out the inaccuracy of his doctrines, in the same manner as Lord Bacon had set aside the implicit belief in the doctrines of Aristotle in matters of Philosophy.

Of the Foreign Writers, that I have met with, M. Vicat and his countryman General Treussart of the French Engineers are far the most distinguished, as they have both carried their experimental researches in(o the properties and use of hydraulic and common limes, and of the various mortars that may be made, by mixing them with sand alone, or with puzzolana or trass natural or artificial, with and without sand, in numerous combinations, to a far greater extent than any former writers or practical men had ever done ; and therefore it must be acknowledged, how much not only their own countrymen but other nations are indebted to them, for the information contained in their respective works. But of the two, M.Vicat's writings appear to have made the greatest impression in France, probably from the circumstance of his having been prior to General Treussart, so that he was the first to draw general attention to the great importance of hydraulic limes and mortars in that country. They are both equally satisfactory in their experiments as to

PREFACE.

the hydraulic powers of diflerent mortars, which they estimate by the same mode ; but neither of them has attempted to ascertain the adhesiveness of their experimental mortars to stones or bricks, which as I said before is of much more importance than their resistance. Upon this last property, however, both M.Vicatand General Treussart have founded their opinions of the comparative strength of different mortars, possessed of the same water-setting powers. On perusing their proceedings with attention, M. Vicat's experiments on this point appear to me so very unsatisfactory, that I cannot help giving the preference to those of the General, which carry conviction along with them, being simple in their nature, and all described in the clearest manner, and perfectly congruous and consistent with each other. Whenever the opinions of these two gentlemen, or of any other authors native or foreign, noticed in the Appendix, differ essentially from mine, I have not failed to remark upon them ; always stating however, whether I dissented in consequence of their being contradicted by the results of my own experiments, or merely as a matter of doubt, or of private opinion.

There seems reason to believe, that the proper mode of preparing and of using cement could not have been understood in France, when M. Vicat and General Treussart published, otherwise they never would have undervalued it, in the extraordinary manner they have both done, by declaring that they considered it much inferior to the hydraulic limes, which they experimented upon. This error, for I do not scruple to pronounce it such, can only have arisen from their having treated their cement and their limes in the same manner, which could not fail to spoil the former, as will be acknowledged by every English builder or workman, who has been in the habit of working with both. M. Vicat in particular goes so far in depreciation of cement, as to say, that although a vast quantity of it is now

PREFACE.

employed in and near London, it will gradually be disused as soon as the hydraulic limes shall be better knovvin and appreciated in England. Nothing appears to me to be more unlikely than that this prediction shall ever be verified. The Aberthaw or blue lias lime, one of the strongest limes in the world, was and is well known in England, but as hydraulic mortar, it was immediately superseded by cement, for all private works of importance, as soon as the latter came into the London Market, although cement was then sold under Parker's patent, at a much higher price in comparison with lime, than has been customary since. Now as there was in those days a much greater difficulty in prevailing on the public to adopt any thing new, than there is at present, nothing can be more conclusive than the above fact ; for it must be evident that private individuals, who had occasion to build a wharf on their premises, would never have put themselves to a great additional expense, by using this new cement in preference to the limes formerly in use, unless it had possessed a most decided superiority over the latter. In the public works of this country, on the contrary, whether executed by Government or by great commercial companies, cement has be#n less employed even for brickwork, by the Engineers intrusted with the direction of them : and in masonry it has never been used at all, in consequence of a strong prejudice prevailing against it, as being altogether unfit for connecting large stones, which I feel confident that our experiments at Chatham will tend to remove. In the mean time the wharf or dock walls, of the great public works alluded to, have either been built with the mortar of what was considered the best water lime, that could most conveniently be procured near the spot, or with mortar improved by the addition of puzzolana, in imitation of Smeaton's example, though not of the principle he acted upon, which was to use the best hydraulic mortar that he was

PREFACE.

able to form by a combination of the most suitable ingredients, known in his time. He found, that this consisted in a mixture of puzzolana, with blue lias lime ; because the admirable properties of the English cements had not yet been discovered. If they had, I have no doubt that he would have used them for the construction of the Edystone Lighthouse, in preference to every other sort of mortar ; and by so doing, he might have dispensed with some of the very ingenious but expensive expedients adopted by him for bonding all his stones together. To conclude, so far from assenting to M. Vicat's opinion, I am persuaded that the use of cement is not only increasing in England ; but that it will in time supersede the most approved hydraulic mortars in other countries also, for works of importance exposed to the violent action of water.

C. W. PASLEY,

Royal Engineer Establishment, Chatham, the I7th of September, 1838.

Table Of Contents

PRELIMINARY OBSERVATIONS, &C. Pag^

Circumstances, which ioduced the author to endeavour to make an artificial cement in 1826. His repeated failures, and abandonment of the pursuit (Article 1) 1

Accidental success in 1828 (2). That this eventually led to final success on a great scale, in 1830 (3) 2