1847.1 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



311 



The success of this process, as a commercial undertakint', though the 

 most expensive of all that were suggested in the First Edition of this 

 work, is therefore peculiarly satisfactory, considering the great importance 

 of good water cement, and the probability ol the natural cement stones of 

 this country, which are only found in certain localities, becoming unequal 

 to the demand, or scarcer than they are at present." 



We will now proceed to give a few extracts froin the treatise, to 

 show its practical character; iirst,as to the qualities of sand and lime, 

 constituting Mortar. 



" The sand used in making mortar should be sharp, that is, angular, not 

 round, and cleim, that is, free from all earthy matter, or other than silicious 

 particles. Hence Road Scraphigs always, as being a mixture of sand and 

 mud, and Pit Sanil generally, as being scarcely ever without a proportion 

 of clay, should be washed before they are used, which is seldom necessary 

 in river sand, this being cleaned by the force of the current which is the 

 cause of its formation. None but clean sharp sand will ever form good 

 mortar, and the intimate mixture of the sand and lime, which should be 

 done wilh a moderate quantity of water, is of no less importance. 



I have ascertained by repeated experiments, that one cubic foot of well- 

 burned chalk lime, fresh from the kiln, weighing 33 lb., when well mixed 

 with 3J cubic feet of good river sand, and about I^ cubic foot of water, 

 produced about 3J- cubic feet of as good mortar as this kind of lime is 

 capable of forming. Some readers may be surprised that this mortar 

 should occupy rather less space than the sand alone originally did, before 

 the lime and water were added lo it. The principal reason is, that dry 

 sand, and all dry loose materials generally, settle into a much smaller space 

 when wetted. Hence the same quantity of sand measured dry, then moist, 

 and aflerwards wet, v\ill occupy unequal spaces. The clean sharp river 

 sand, rather moist, used by us, weighed about 87 lb. per cubic foot. On 

 gradually pouring water upon it in the measure it settled down from 12 to 

 9J inches in htigiit, thus occupying only four-fifths of the space, which it 

 had before filled. 



Pure lime is so little capable of resisting the action of water, that it is 

 unfit even for the external joints of walls exposed to the common vicissi- 

 tudes of the atmosphere. For by degrees the beating rains, to which the 

 outside of such walls is subject, will gradually destroy the mortar of all 

 those joints lo a certain depth, as may be observed by inspecting old walls 

 built with chalk lime mortar, which have not been meddled v/ith for some 



years Walls buiit with the water limes settle less, and those built 



wilh cement are entirely free from this action, because the cement used in 

 the lower courses sets too soon for the weight of brickwork or masonry 

 added above to make any impression on the joints. Now though the dif- 

 ference of settlement, even between those extremes, may be very small, it 

 does not appear prudent to use more than one species of mortar in the 

 same horizontal joints of a building, especially as it would give trouble to 

 the workmen, and occasion loss of time. 



Pure lime mortar has sometimes been used for the backing of wharf 

 walls, the front or facing of which has been protected by water cement, 

 usually lo the depth of about 18 inches, or two bricks thick, from the out- 

 side of the wall. Even this system, though it does not involve the entire 

 ruin of the wall, is highly lo be reprobated. The cement protects the pure 

 lime morlar from the direct action of water in mass, but not against wet or 

 damp, because the moisture penetrates through the pores of the brickwork 

 and of the cement, and although not in sufficient quantity to dissolve the 

 pore lime morlar, it effectually prevents it from setting, so that it always 

 remains in a slate of soft pulp, and is of iio more use towards the consoli- 

 dation of the wall than so much moist clay." 



The next division of the work treats of Piaster q/' Pans, as it is 

 generally called. To test its quality — 



" Mix a small quantity of it wilh water in the form of a ball, and it will 

 set with moderate heat inlo a very hard tine white substance, and will even 

 continue setting under water, but being partially soluble in that liquid in 

 process of time, it is not applicable to the purposes of hydraulic architec- 

 ture." 



The division on Hydraulic Limes desctihes the different limes called 

 in London, "stone limes." 



'* The blue lias lime stones are considered the strongest water limes of 

 this country, and are found on opposite sides of the Bristol Channel, near 

 ■Watchet in Somersetshire, and Aberlhaw in Glamorganshire, and also at 

 Lyme Regis in Dorsetshire. The first of these, mixed wilh puzzolana, 

 was used by Smeaton in building the F^dyslone Lighthouse. The Dorking 

 or Merslham lin)e, and the Hailing lime, so termed from a village on the 

 left bank of Ihe Medway above Rochester, hut which is also found near 

 Burham on Ihe opposite site of the same river, though not possessing such 

 strong hydraulic properties, are also much esteemed ; and these two limes, 

 the former of which is considered rather Ihe best, are more used in the 

 metropolis than the blue lias, probably from the greater proximity of the 

 quarries where they are found, and from very little land carriage being 

 required for either. 



All die water lime stones are of a bluish grey or brown colour, which is 

 communicated to them by Ihe oxide of iron. They are usually termed 

 ' stone lime' by the builders of the metropolis, to distinguish them from 

 common chalk lime, but so far improperly, that the Dorking lime stone is 

 not much harder thau chalk, and the Hailing lime stone is actually a 



chalk, and not harder than the pure chalk of the same neighbourhood, 

 from which it is only distinguished in appearance by being a little darker. 

 In fact, all the coloured chalks found in various parts of England, com- 

 monly termed Grey Chalks, which are the Lower Chalks of the geologists, 

 and generally free from flints, are possessed of hydraulic properties more 

 or less powerful." 



The chapter on Concrete contains some useful directions for mixing 

 the ingredients, which is followed by some observations on "grouting." 

 Among architects and builders there is a difference of opinion as to its 

 advantages; our author's opinion appears to be favourable to its use. 



" Upon this subject, I may be permitted to remark, that unless every 

 course be grouted, it appears to me that there is a risk of the grouting not 

 penetrating lower than Ihe single course immediately under it, for the beds 

 of plastic morlar iu Ihe next courses below that, have sufficient consistency 

 to intercept the grouting, unless those beds themselves should have been 

 imperfectly laid, which seldom or never happens, even when middling or 

 indifferent bricklayers are employed. For this reason, one can scarcely 

 expect sound brickwork, unless every course be grouted, especially ia 

 thick walls, although the more general custom is to work with mortar 

 only. When one of the massy walls of the new British Museum, after 

 being grouted in Ihe manner before described, was cut through for some 

 temporary purpose, it was remarked that the brickwork resisted the tools 

 of the workmen quite as much, and appeared equally firm in the joints, as 

 if the latter had been filled with plastic mortar instead of grouting. Tlie 

 same risk of part of the vertical joints being left dry may occur also in 

 masonry, and there can be no method of guarding against it more elfectual 

 than to grout each course." 



Water cemertt, or what is called "Roman cement," comes next. This 

 material, we consider, has been abused in its use more than any other con- 

 nected with building, and from its repeated failures in exposed situa- 

 tions, and particularly when used near the ground for stucco and on the 

 top of projections, such as cornices, make one doubt its boasted 

 durability for such works ; but whether its failure be owing to the im- 

 proper mixing of too much sand, or the cement being of bad quality, 

 it is difficult to say : we may instance as a failure the balustrade en- 

 closure on the east side of Regent's-park, which has been frequently 

 repaired. In the construction of brick-walls, cement appears to have 

 stood well, and might be advantageously used to a greater extent than 

 what it is; when all circumstances are taken into consideration, the 

 expense is not very much more than lime-mortar. General Pasley 

 observes, that " cement" is always weakened by the addition of sand, 

 whereas every kind of lime is improved by it. For concrete founda- 

 tions it is requisite to use double the quantity of cement than is required 

 when lime is used, consequently it is not recommended for that pur- 

 pose; but for the lower parts of a wharf-wall or pier under water, one 

 measure of cement mixed with three, and not more than four, of gravel 

 or sand, may be advantageously used. 



The valuable information communicated by the General on the 

 manufacture of Artificial cement made from chalk and clay, form the 

 most useful part of the treatise, and deserves the attentive study 

 of all parties connected with building. We will select one or two of 

 the author's successful experiments, detailing the process of making 

 the artificial cement, which we here suggest should be called Pas/et/'s 

 Cement, in contra-distinction to the numerous cements which are in 

 the market ; none of which, however, appear to be superior, if equal, 

 to the one recommended in this tre.itise, and which the General found 

 to be the best after a long series of trials and experiments. The first 

 experiment on a large scale is thus described : — 



" Having, towards the close of the year 1828 and in the beginning of 

 1829, tried as many experimeuts on a small scale as I then considered 

 necessary, I determined lo prepare a considerable quantity of artificial 

 cement composed of chalk and blue clay, with a view of applying it on a 

 larger scale, lo those purposes for which the natural cements have been 

 used in architecture. 



The chalk, after having been broken small and dried in the air, was 

 pounded in small quantities at a time, in iron troughs mat had belonged to 

 a forge, with iron rammers made for ihe purpose, and was passed through 

 sieves with brass wires, having 25 meshes to Ihe inch, being the finest used 

 in the Ordnance gunpowder v\orks. A large mass of dry pulverised 

 chalk being thus provided, 5 cubic feet of it were laid on a wooden plat- 

 form, and made into a paste with a moderate quantity of water, alter 

 which 2 cubic feet of Ihe blue clay were added, and the whole iutinialelj 

 mixed together on the same platform by shovels. When a sufficient quan- 

 tity was prepaied, ihe mixture was next moulded in the same manner as 

 common bricks, excepting that water was used instead of fine sand to 

 prevent adhesion. After these bricks of raw cement, which were twelve 

 inches long, became drier, they were cut into five equal parts, each form- 

 ing a cube of rather less than 2^ inches side, this being the average size of 

 the lumps into which chalk is usually biokeu, before it is burned, iu the 

 common open lime-kilus in Rent. 1 made my moulds exactly 12 inches 

 lung, and 2fL inches wide by 2^% inches deep, in order that 25 bricks, or 

 125 cubes, should be exactly equal to one cubic foot. Thus, by merely 



