Lime mortar

“ In certain places mortar, when well made, becomes with age as hard as flint. In American towns, where anthracite coal is burned, it rots away in chimneys under the influence of sulphurous acid with great rapidity. In the Pacific Islands, where lime is made from delicate small sea-shells or coral, and mortar is like a paint or enamel, a missionary has recorded that, when he taught the natives how to make it, they whitewashed everything, even to the children, who thus became white people. ”

“ Roman cement mortar should consist of one or one and a half parts of cement to one part of sand. Selenitic lime mortar is usually in the proportions of one to four or five, and must be mixed in a particular manner, the lime being first ground in water in the mortar mill, and the sand gradually added. Blue or black mortar contains equal parts of foundry ashes and lime; but is improved by the addition of a proportion of cement. For setting fire-bricks fire-clay is always used. ”

“ The mortar, used in laying bricks and common stone, has a greater proportion of sand, which is generally of an inferior quality. Besides, the materials are incorporated with less care. Lime for the purposes of building is procured chiefly by calcining limestone in a kiln, with wood, coal, or some other combustible substance. It is also obtained by burning chalk, marble, and marine shells. Water poured upon newly-burnt or quick lime, causes it to swell, and fall to pieces into a fine powder. ”

“ The adhesion of common lime mortar varies enormously, with the nature of its materials, the sort of stone or brick which it is used to cement, the thickness of the joints, the care taken to fill them effectually and solidly, the degree of wetness or dryness of the mortar itself and of the stone or brick to which it has been applied, and the rate at which the mortar has been dried during its setting, and the amount of moisture and of air to which it has been subsequently exposed. ”

“ Mortar of hydraulic lime, cement mortar, or mortar gauged with cement, must be mixed up in quantities sufficient only for immediate use. Any material not used at the time, or at least the same day, will be wasted; cement cannot be reworked after it has begun to set as its setting properties are destroyed.
Slaking is a most important part in the process of making mortar. There are three methods of slaking lump lime—the first by immersion, the second by sprinkling with water, and the third by exposing the lime to the atmosphere and leaving it to absorb moisture. ”

“ The Pozzuolanic cement.setting of the mortar is due to the drying of the lime (a purely physical phenomenon, no chemical action occurring between the lime and the sand) . The function of the sand is simply that of a diluent to prevent undue shrinkage and cracking in drying. Subsequent hardening of the mortar is caused by the gradual absorption of carbonic acid from the air by the lime, a skin of carbonate of lime being formed; but the action is superficial. Mortar made from pure or “fat” lime cannot withstand the action of water, and is only used for work done above water-level. ”

“ To a casual observer mortar is mud, but to a builder who understands the chemistry of mortar it is a compound of water, lime and sand, and when properly prepared forms an indestructible cement. Fresh slacked lime, when brought in contact with clean, sharp sand, adheres strongly to the surface of each grain, and forms the silicate of lime. ”

“ The presence of limestone quarries so close to the station offered a great advantage for the solid construction of their walls and buildings, it made them practically indestructible. No lime was used at Veratinum (Wilderspool) ; at Ribchester a little was used in one of the foundation walls for grouting; at Melandra I found some mortar, made of lime and gravel, adhering yet to some blocks of millstone grit, none in the foundations or walls; while, on the other hand, I picked up pieces of mortar, composed of pounded brick and lime, in Castle Hill, Northwich, Cheshire. ”

“ If the sand is not thoroughly dried, or the lime has got damp from the air, the quantity of water must be less than the above proportion; and, on the contrary, when the lime is used as soon as slaked, it may require more; so that the proper stiffness of the mortar, under those circumstances, will regulate the making of the composition. ”

“ And even then it is reckoned a hot and forcing manure, chiefly fit for cold and wet lands. The principal use of lime, however, is as an ingredient in mortar. This, you know, is the cement by which bricks and stones are held together in building. It is made of fresh slacked lime and a proportion of sand well mixed together; and, when used for plastering walls, some chopped hair is put into it. The lime binds with the other ingredients; and in length of time, the mortar, if well made, becomes as hard, or harder, than stone itself. ”

“ In some of the cheap common buildings of the present day, mortar is too often made from lime which has been so long from the kiln, that it is nearly reconverted into a hydrate, and has lost the chemical quality which renders it valuable; the sand, too, is taken from the road with all its impurities, and the water from the nearest kennel. ”

“ The heat that is generated comes from the violence with which the two substances rush together. Before absorbing water lime is called quicklime; after this absorption, which has reduced it to powder, it is called slaked lime. This slaked lime is reduced to a paste with water, and then well mixed and kneaded with sand. The result is the mortar used in laying stone and brick in order to hold the courses firmly together and give solidity to the building. ”

“ Different qualities of lime require varying amounts of water, but the average quantity is about a gallon and a half to Slaking. every bushel of lime. It should be all added at one time and the mass then left to slake undisturbed. Hot limes are often used for mortar. These are unsuitable for plastering unless slaked for a long period. It will at once be seen that when mortars composed of these limes are used immediately after mixing, slaking must continue for a long time, drying up the moisture necessary for setting, and causing the mortar to crumble to dust in the joints of the brickwork. ”

“ The lime, in the state in which it comes from the kiln, is first ground to powder, and is then mixed with sand and gravel, and chippings of stone. The purposes for which the mortar is required indicate the coarseness and quantity of the intermingling gravel. When wanted as concrete, to form, independently of other materials, the foundation of some heavy structure, stony fragments of larger size are mingled with the lime than when the mortar is to be used to cement chiselled stones, or even than when wanted to constitute with rubble the interior of a wall. ”

“ Even if fresh lime and sharp sand are used, in accordance with the usual specifications in building contracts, the mortar bond may still be weak by reason of careless or imperfect mixing. All mortar, even that used for laying stones and bricks, should be mixed until a lime film surrounds every particle of sand. Plastering the outside of the wall below the grade line and pointing the wall above cannot make a firm, good wall out of one which has been carelessly laid or one bedded in inferior mortar. ”

“ Mortar made with what are called fat or rich limes--that is to say, nearly pure lime, such as is got by calcining marble or pure chalk--sets slowly, with difficulty, and is rarely tenacious. Burnt clay or brick reduced to powder improves the setting of such lime, especially if the two materials be calcined together; so will an admixture of cement. Mortar made with what is known as slightly hydraulic lime, that is to say, lime containing a small proportion of clay, such as the gray stone lime of Dorking, Merstham, and that neighborhood, sets well, and is tenacious and strong. ”

“ It is well known that earth which is not too argillaceous, with only the moisture it has when fresh dug, on being rammed between frames of wood till the rammer will no longer impress it, makes eternal walls; but a mass as hard as stone may be made with a little lime added to sand, horse-dung, or ox blood. The more the lime is beaten, the moister it becomes, and it must contain so much moisture as to become by beating a solid mass, adhering in all its parts, and not remain crumbling, that will properly set as a mortar. ”

“ Even the cements deteriorate somewhat with age, and the common stone lime is often used after it is partially or entirely air-slaked. If the binding material be inferior and the sand have quantities of fine earth or vegetable matter mixed with it, it will be seen how impossible it is to secure a strong and binding mortar. ”

“ If there be too little moisture at first, it will remain a powder; if there be too much it will become a soft mortar. Lime is of no use mixed with clay or vegetable earths, which, if well beaten, are stronger without it. ”

“ If required to be very fine, take for the next layer finely-sifted lime, with about a tenth part of rye-flour, and a little ox-blood; beat it till it becomes a very stiff mortar, and then smooth it with a trowel. The next day, again smooth it with a trowel; and so continue to do, daily, till it be entirely dry. When it is quite dry and hard, rub it over with fresh ox-blood, taking off all which it will not imbibe. No wet will penetrate this composition, which, however, after some time, is often painted with oil-colors. The whole floor appears as a single stone, and nothing will affect it. ”

“ Metallic surfaces, as well as various kinds of stone, are there corroded, while the mortar of walls may often be observed to be slowly swelling out and dropping off, owing to the conversion of the lime into sulphate. Great injury is likewise done from a similar cause to marble monuments in exposed graveyards. ”

“ The lime is covered with the sand and left undisturbed for a day or two to slake, and the whole mass is then turned over and well mixed with the larry. The mortar is often used immediately the materials are thoroughly incorporated, but it should rather be kept covered over with sacks until well tempered. For large works a mortar mill working by hand, steam, or other power effects a considerable economy. ”

“ Sand and its sources having been thus treated, next with regard to lime we must be careful that it is burned from a stone which, whether soft or hard, is in any case white. Lime made of close-grained stone of the harder sort will be good in structural parts; lime of porous stone, in stucco. After slaking it, mix your mortar, if using pitsand, in the proportions of three parts of sand to one of lime; if using river or sea-sand, mix two parts of sand with one of lime. These will be the right proportions for the composition of the mixture. ”

“ Dens of Death.
That time he had forgotten to put lime in the mortar. It was just sand. When the houses fell in the sight of men, the law was at last able to make him responsible. It failed in the matter of the soil pipe. It does sometimes to this very day. ”

“ A common iron mortar, such as is used by druggists and apothecaries, is found to answer very well for grinding or pounding the brimstone, charcoal, salt-petre, &c. separately; and apothecary’s close sieves, fitted with wire-cloth, are the best possible implements for obtaining the fire powder; but when corn gunpowder is to be mealed, or the various ingredients are to be mixed together, such mortars cannot be used, as the heat generated by the continued action of the pestle might inflame the mixture, and thereby place the life of the operator in imminent danger. ”

“ The practice of our masons of putting the blood of oxen into mortar was no doubt in the first instance associated with the idea of a sacrifice; however this may be, the blood had no doubt a real effect in hardening the mortar, just the same as treacle, which has been known to be used in our days. The use of cement when any extra strength is needed has put aside the use of either blood or treacle in the mixing of mortar. ”

“ Only the chimney remains as its monument. Slowly, little by little, the patient solvents that find nothing too hard for their chemistry pick out the mortar from between the bricks; at last a mighty wind roars around it and rushes against it, and the monumental relic crashes down among the wrecks it has long survived. ”

“ But I must return, and tell my readers, in a few words, the chemical history of mortar. If limestone be burnt, or rather roasted, in a kiln, the carbonic acid is given off—as you may discover by your own nose; as many a poor tramp has discovered too late, when, on a cold winter night, he has lain down by the side of the burning kiln to keep himself warm, and woke in the other world, stifled to death by the poisonous fumes. ”

“ There is also a kind of land-mortars, mounted on travelling carriages, invented by count Buckeburg, which may be elevated to any degree; whereas the British as we have already stated, are fixed to an angle of 45 degrees, and are firmly lashed with ropes.
Partridge Mortar, is a common mortar, surrounded by 13 other little mortars, bored round its circumference in the body of its metal. The centre one is loaded with a shell, and the others with grenades. The vent of the large mortar being fired, communicates its fire to the small ones; so that both shell and grenades go off at once. ”

“ But, perhaps, the worst of all mortar is that wherein very fine pit-sand, containing a portion of earthy matters, is used, and when the whole is mixed up with impure water. So little attention is often paid to the quality of mortar, in common buildings, that one would imagine it were applied, as if intended more to prevent the sifting winds from penetrating the walls, than as the medium by which they were ultimately to be bound or formed into a compact fabric. ”