C E M

132

CEM

With respect to the water used in the preparation ofaquatic cements, that of rivers or ponds, where it can beprocured, is to be preferred to spring water: but for worksexposed to the action of the sea, it is usually more convenient,and equally advantageous in other respects, to use salt water.

The Loriot-mortar is a composition which at one time hadobtained considerable celebrity in France , and was employedin many large works. It was invented, about seventy yearsago, by M. Loriot, who imagined that he had discovered theprocess used by the Romans. The principle of the inventionconsisted in adding to any quantity of mortar, made in theusual way with lime and sand, but prepared rather thinnerthan usual, a certain portion of quick-lime in powder. Thelime-powder being well incorporated with the mortar, themass heated, and in a few minutes acquired a consistenceequal to the best plaster-of-Paris ; at the end of two daysit became as dry as an ordinary cement at the end of severalmonths; and when the ingredients were well proportioned,it set without any cracking. The quantity of powder variedfrom £ to £ of the other materials, according to the qualityof the lime: too much, burning and drying up the mass ; andwith too little, its peculiar advantages being lost. The pro-portions are essential, but can only be determined by actualexperiment.

Loriot’s process was at one time, as we have observed,very much in vogue, but has now fallen into disuse. Foundedon the false conception that the induration of mortars wasthe mere result of a more or less rapid desiccation, andpresuming it to be possible to obtain this end by the intro-duction of a powerful absorbent, it met with the usual fateof error, and sunk into disrepute.

Mr. Smeaton says of this composition—“ I have madetrial of this method, both in small and in large; for howeverlittle likelihood of advantage a proposition may contain, yet,when this concerns a physical process, nothing can be safelyconcluded but from actual trial; and I must candidly ownthat the effect was much better than I had expected; forI found the composition not only set more readily than mortaras commonly made up, but much less liable to crack, andconsequently, if this cement was made use of in water-build-ing, it was less apt to re-dissolve, because it would morespeedily get set to a firmer consistence, and so as more ablyto resist the water from entering its pores ; but when thewater was brought upon it, in whatever state of hardnessit was at the time, it at best remained in that state withoutany further induration, while the water remained upon it ;and, as I expect, would so remain, till it had some opportunityof acquiring hardness by further drying.”

Indeed, for the purpose of quick concretion, variousmaterials are recommended to be added, such as brick andtile powder, and forge scales. The following is an approvedreceipt: one measure of bricks, finely pounded ; two mea-sures of fine river-sand; old slacked lime in sufficient quan-tity to make a mortar in the usual manner, and sufficientlyliquid to quench the lime powder, which is added to the samequantity as that of the pulverized bricks.

It is somewhat extraordinary, that a process similar to thecomposition of the Loriot-mortar is described in A Treatiseon Building in Water, by George Semple , printed in Dublin,1776. In discoursing on the good qualities of the roach-lime of Ireland, Mr. Semple remarks, that “it has someuseful qualities, not much known among the generality ofworkmen. As for instance, our lime-stone will makeexceeding good terras for water-works, for which purposeyou are to prepare it thus : get your roach-lime brought toyou hot from the kiln, and immediately pound, or grind itwith a wooden maul, on a smooth large stone, on a dry

boarded floor, till you make it as fine as flour; then, witho°loss of time, sift it through a coarse hair or wire sieve, aI Vto the quantity of a hod of your setting mortar (whichthis account should be poorer than ordinary) put in twothree shovelfuls of this fine flour of the roach-lime, andtwo men, for expedition’s sake, beat them together, wisuch beaters as the plasterers make use of, and then uit immediately. This, I can assure you, will not only staI1 .as well, but is really preferable to any terras.” The memof M. Loriot -was published in 1774, only two years previoto this treatise of Semple, who appears to have been a 111rather of practice and experience than of reading> ar> ^besides, in the book quoted from, he expressly, th° u °incidentally, mentions his ignorance of the French langufoWe are justified, therefore, in stating that the knowleof the advantages of mixing quick-lime powder in mot ‘was not confined to M. Loriot, though it might have ban original invention in him, and that he was the firs* " ydrew the public attention to the process, and used it inconsiderable works. . ^

We have now to notice the valuable Treatise of M- *the celebrated French engineer, on the Composition 0 ^ j ia 3tars and Cements . This scientific and elaborate work ^been made extensively known in this country, by the a ^manner in which it has been translated by Captain "•Smith , of the Madras Engineers. The labours of this S ^tleman have given increased value to M. Yicat’s woi tI a tothe numerous notes, tables, and other information, a< *° e uS e-the original work by Captain Smith , will be found most jful to the professional man, and well worth his carefnlattentive study. 0 gil

In this place we shall briefly describe the mode Pby M. Yicat in the manufacture of the Artificial Jdya r - o0Limes , he so strongly recommends. We shall have oc° a 0 fto return to his work hereafter, when on the subj eCConcrete. . .„ a iiy

:pO e

The practice of M. Yicat seems to have been p

irincip'

•eferei

directed to the adoption of the hydraulic limes, in p re ‘“ , r y,to the more energetic cements so generally used in this c0 p re'but his investigations have been conducted on so c ®hensive a scale, that the processes laid down by him ofmanufacture of artificial hydraulic compounds are ca P a t ofapplication to almost every requirement of the Arcln

Engineer, or to almost every situation.

th at

th«

The opinion so decidedly expressed by M. Vicat, IW 7 ta i)l/superior adhesion of the hydraulic limes, must ’ ne j-, r en celead to their general adoption in this country, in p reto our (so-called) Roman cements, has been much .c 0111 jjs*by practical men. It may be said, without entering ' nt0 j,jcl*

> n c e .!,

cussion of the question, that it appears to be one on ' ^ of

a contrariety of opinion may be occasioned by a diff e *situation and circumstances. Thus, in comparing *of the two systems, it is important to consider,

the m<

that,

in

ef * 1oi' e !

esse» ti: ''

the means of minute mechanical division are an th ,=element, in the other that it is unnecessary; and t 1 ^ e i>Velement, which in one situation may be obtained atrate, in another may be expensive and unattainable- h eThe hydraulic limes, therefore, which do not re( l ’! 1 \ ) ]0 f ° lground previous to use, are at all events most sui ‘ c£l ii'those situations where the facilities of mechanical agennot be resorted to, while the ground cements ai ^.jjttl®adapted to the vicinity of a large capital, where it lS 0 {iief simportance that the builder becomes dependent up°for his supply. St ° al> ,

The difference, in fact, consists in this, that th®cements, of whatever kind, will ever be furnished V

facturers, whereas the hydraulic limes may at all