1843.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



157 



poses. We have observed in tbe walls of many old castles in England, 

 that the stones have been greatly decomposed and eaten away by 

 atmospheric influence, while the mortar joints stand out in relief and 

 indicate what was originally the face of the work. In such cases the 

 mortar has been obviously far superior to the stone, and this supe- 

 riority is further evident, by trying the relative hardness of the two. 

 While the stone will crumble away and yield to any metallic edge 

 applied to it, the mortar can only be impressed with considerable ef- 

 fort. Now we do not hesitate to affirm that the same excellence as 

 that for which the ancient mortar is so celebrated, has never ceased to 

 be within our reach in this country, which is fortunately favoured by 

 an abundance of the materials most proper for the purpose. In works 

 of this kind the ancients had no secret with which we are unac- 

 quainted, but on the other hand, the researches of modern chemistry 

 have brought to light a great deal connected with the subject of mor- 

 tars and cements which in all probability our ancestors knew nothing 

 about. The fabrication of artificial cements and hydraulic limes is 

 entirely a modern discovery, and one of which the Romans were per- 

 fectly ignorant. 



It appears quite clear, from all we can gather on the subject, that 

 the superiority of ancient mortar depended chiefly on a judicious 

 choice of good stone for the purpose of burning into lime, and after- 

 wards upon careful attention to the manipulation of the calcined lime ; 

 and such being the case, there is no reason on earth why modern 

 buildings of every kind should be constructed of materials less im- 

 perishable than those which our Roman and Norman ancestors made 

 use of. 



The great sea wall at Brighton, the dock walls constructed of 

 concrete at Woolwich, and a church said to have been lately built 

 near Brighton entirely of concrete, afford examples of what may 

 be effected by this material. It is quite certain, however, that several 

 circumstances have most unfavourably operated to retard the more 

 general employment of this most valuable substance. Among the 

 foremost of these, we cannot avoid referring to the patent which was 

 taken out a few years since for forming concrete into artificial stones. 

 The signal failure which attended the use of this artificial stone in 

 some government buildings at Woolwich and other places, has too 

 hastily led many engineers and architects to regard as impracticable 

 the employment of concrete or beton for building above the surface 

 of the ground. But let us observe the difference between small 

 blocks of stone formed of concrete and the firm cohesive body which 

 the substance presents when used en masse, as it always should be. 

 The stones which were manufactured of concrete were found, as 

 might have been expected, so tender and brittle at every corner and 

 arris, that it was almost impossible to preserve them with perfect 

 edges up to the time when they were set in the work. Tbe process 

 of setting them by mortar in the same way as ordinary stones, left 

 these tender arises still exposed to injury, and it was no wonder that 

 all along the joints a destruction of the walls took place to a very 

 serious extent. It appears to have been the practice, in forming these 

 artificial stones, to face them with a kind of plastering, which is said 

 to have pealed off in great quantities from the action of frost and 

 other external influences. We. repeat that this absurd project for 

 making concrete into blocks of stone has greatly impeded tbe real 

 advantages of concrete from being properly appreciated. We pro- 

 test, however, most strongly against any inference being drawn un- 

 favourable to a judicious use of concrete from the failure of this at- 

 tempt to form it into artificial stone. 



According to the system of building with concrete, which we pro- 

 pose, the walls should in all cases have coins and coping of stone or 

 brick, so that only a smooth plain face of concrete will be exposed. 

 By adopting this method, no sharp corners or edges will be liable to 

 injury from external violence, and there will be no irregularity or 

 broken roughness in the work to admit the lodgment of moisture 

 and occasion that injury which always takes place when frost ensues. 

 To substitute a pile of separate cubical blocks of concrete for the 

 solid mass of which a building may be at once constructed, appears to 

 us in no respect more rational than the act of a man, who in proceed- 



ing to found upon solid rock, should break the rock in pieces, and join 

 these pieces separately together, instead of founding at once upon 

 the solid material. It may be said that we employ stone and bricks 

 in cubical blocks of small dimensions, but this is a matter of necessity 

 not of choice. Nature furnishes in the quarry blocks of stone, which 

 have a fixed and limited size according to the natural beds, joints and 

 fissures by which the strata have been divided, and in the case of 

 bricks the convenience of manufacture, particularly with reference to 

 the condition of being properly burnt, limits the size to comparatively 

 very small dimensions. In building with concrete, however, no such 

 limits exist, and there can be no comparison between the expediency 

 of fabricating little detached pieces of concrete stone, and that of 

 raising the whole mass of any house, wall, or building, by united and 

 continuous layers extending without a joint over the whole area of the 

 building. 



In seeking for another cause why concrete or beton has not been 

 successfully employed of late years in this country for building above 

 the surface of the ground, we are strongly inclined to the belief that a 

 fair and workmanlike attempt has never been made under judicious 

 superintendence to apply a good hydraulic lime to this purpose. It 

 is indispensable, in constructions of this kind, that the lime should 

 possess some degree of hydraulicity, in order that it may harden 

 before the injurious action of frost comes upon it. It is generally 

 admitted, that mortar which contains no hydraulic principle, that is, 

 mortar made from pure, or as they are technically called, fat limes, 

 require a very long time to set perfectly hard; and it has even been 

 asserted by experimentalists, who are well worthv of credit, that 

 mortar has been found in a soft pasty state several years after it had 

 been used in a building. On the other hand, hydraulic lime will 

 harden in a very short time — requiring, in fact, a period which varies 

 inversely with the strength of its hydraulic principle, this period, 

 in the case of Roman cement, the most hydraulic of all mortars, 

 seldom exceeding a few hours. The readiness with which concrete, 

 composed of strong hydraulic lime, is found to set, confers peculiar 

 value on beton for building purposes, because when once hardened, it 

 is no longer subject to be affected by atmospheric changes, and may 

 safely defy the influence of rain, moisture, frost, and the other des- 

 tructive means by which imperfectly hardened mortar is so speedily 

 destroyed. 



As we have no wish to disguise or conceal what may be called the 

 unfavourable side of this question, it may be as well to refer in this 

 place to the opinions expressed by Lieutenant Denison and other offi- 

 cers of engineers, upon the use of concrete for building purposes. 

 The opinions of these gentlemen are hostile to the employment of 

 concrete, and are founded upon experiments and observations made 

 upon concrete walls at Woolwich and some other places. Now we 

 are perfectly ready to give every possible credit to the officers of en- 

 gineers, for the care with which these experiments were made, and 

 the fidelity with which these results have been recorded. We believe 

 them also to have been free from any prejudice against concrete in the 

 first instance ; but granting all this, we are greatly mistaken if they 

 have made use of the right material. Their experiments appear to 

 have been made upon a simple concrete instead of a true beton, and 

 owing to the long time which the former requires to harden in this 

 climate, it was found to have been dissolved by water, and to have 

 been shattered by frost before it had been allowed time to set. When 

 we look at the undoubted fact, that constructions of beton have actu- 

 ally been practised in France with great success, within the last few 

 years, there are only two ways of reconciling the anomaly which their 

 reputed failure in this country appears to exhibit. Either the expe- 

 riments have not been made with proper care and with good faith, 

 or they have been made upon the wrong substance. At once, without 

 a moment's hesitation, we reject the former supposition, and decide 

 that the latter must have been the case. 



In order that no doubt may remain on the minds of the sceptical 

 with respect to the perfect success which has attended the use of 

 beton for actual building in France, and at the same time to convey 

 some knowledge of the process and style of building adopted, we 



21* 



