1855. 



NEW ENGLAND FARMER. 



281 



^ For the New England Farmer. 



GRAVEL WALLS. 



Mr. Editor : — The point at which the remarks 

 I heretofore offered you stopped, was, a suitable 

 adhesive mixture for gravel buildings. 



Mortar, as a building material, is a cement 

 made of quick-lime and sand, for the purpose of 

 holding stone, brick and other matter together. 



Limestone is sufficiently firm and compact for 

 building, and is doubtless safe and durable. The 

 process, as is well known, in producing quick-lime, 

 is to expose this stone to a powerful heat. This 

 process destroys its peculiar qualities as stone by 

 driving off the carbonic acid, yet is in a state 

 which with suitable additions or absorptions of 

 carbonic acid, it will become stone again. An 

 English writer, Jennings, (nota very modern one, 

 it is true,) says, "That it is well known that quick- 

 lime alone and water will not make good mortar. 

 Various substances have been used for the pur- 

 pose, as finely sifted coal ashes, and gravelly sand 

 from the neighborhood of spring water." He 

 says further, "that equal parts of quick-lime and 

 the article which is to supply the carbonic acid, 

 whether sand, fine gravel, coal ashes, or other 

 matter, will be a fair proportion of each ingredi- 

 ent, but it may happen from peculiar circum- 

 stances that this general rule ought to be depart- 

 ed from." It must not be overlooked too that wa- 

 ter is a necessary ingredient in the composition 

 of mortar, and from our theory, he says, "it fol- 

 lows that that which contains the greatest quan- 

 tity of carbonic acid unmixed with substances 

 not congenial to the composition of mortar, such 

 as clay and vegetable, matter must be the best. 

 Besides the carbonic acid and lime, which are the 

 most important parts in the formation of mortar, 

 there is reason for concluding that the water it- 

 self is more than a medium fur the formation of 

 the carbonate of lime ; but what its precise oper- 

 ation is, we are not prepared to say." 



A writer, (Gregg,) in the tenth number of the 

 fourth volume of The Plouyh, the Loom and the 

 Anvil, on the subject of slaking lime and prepar- 

 ing mortar, says, "To bring caustic or quick-lime 

 into a fit state to be mixed with other ingredients 

 to form mortar, it must be reduced to a hydrate, 

 when it is called slaked lime, and the process of 

 reducing it is called slaking. It is pretty gener- 

 ally admitted that the induration of mortars de- 

 pends upon theirabsorption of carbonic acid /rom 

 the atmosfhere ; and it seems to be essential to 

 this reunion of carbonic acid with the lime, that 

 the latter should have previously combined with 

 its equivalent, or about one-third of its weight 

 of water. Stuccoes made with hastily prepared 

 lime remain soft and powdery for a long period ; 

 but those prepared with well-slaked and tempered 

 lime soon absorb carbonic acid, and become hard 

 often to a considerable depth from the surface. 

 The presence of water being necessary, is further 

 confirmed by the fact, that if dry quick-lime be 

 placed in a jar of carbonic acid, no absorption 

 whatever takes place. 



"Quick-lime slaked by the addition of water, is 

 the mode usually used in practice. * * * In this 

 mode of slaking, care must be taken to throw on 

 the necessary quantity at once ; none must Ijc ad- 

 ded during the effervescence, or the lime will be 

 numbed, fall in powder imperfectly, and continue 



gritty. Equal care must be ta^([ti not to drown 

 the lime with too much water. Thus drowned it 

 loses the grtater fart of its binding qualities, and 

 this is especially the case with rich limes. 



"The substances mixed with lime to form mor- 

 tar are sand, ashes and burnt clay. To enable 

 lime to harden by the absorption of carbonic 

 acid, it is necessary to divide it as minutely as pos- 

 sible, or so as to expose as much surface as pos- 

 sible to the action of the air. The addition of 

 any of the al)ove substances effects their division, 

 and their action is simply mechanical.'''' The same 

 writer says, "that if a greater proportion of sand 

 is used than 3| of sand to 1 of lime, (chalk lime 

 is here spoken of) the mortar is not plastic enough 

 for use, and causes it to be too friable, for excess 

 of sand prevents mortar from setting into a com- 

 pact adhesive mass. But different limes require 

 different proportions." 



The theories of these authors differ seriously in 

 reference to the process by which quick-lime be- 

 comes stone again, and the settlement of this 

 question is very essential in reference especially 

 to concrete or gravel buildings. 



O. S. Fowler, who first built on this mode in 

 this section of the country, and who pu1)lished a 

 book on this subject, seems to have proceeded 

 without much attention to the proportion or 

 principles of mortar-making ; and, so fiir as I am 

 informed, those generally who have built in this 

 manner have followed too closely his directions. 

 On the 24th page, of his book, after a description 

 of the materials for his walls, is the following : 

 "These materials now require to be mixed with 

 lime, and any easy mode of commingling these 

 stones, gravel and sand with the lime, will serve 

 the purpose. I have never tried mixing them in 

 a dry state, but am certain this will answer a 

 good purpose, but it will probably take some 

 more time ; yet I think it better to wet the lime 

 first, because it incorporates itself with these 

 stones better wet than dry ; at least, I think the 

 lime can be wet more easily by itself, than after 

 mixing with the stones." On the 28th page he 

 says, "I deposited my lime" and "I then poured 

 in my water, not merely enough to wet the lime, 

 but so that the whole mass would be as thin as 

 milk, and stirred it up completely, so as to amal- 

 gamate the water and the lime together." He 

 then put into this lime-water sixteen to eighteen 

 barrows of sand to eight barrows of lime. "If it 

 was too thick to be worked easily, more water 

 was put in, and as it was worked water was still 

 added, until the mass ivas so thin that it would 

 follow the men about as fast as they worked 

 backward and forward." "I speak of this thin- 

 ness," he says, "because lime mixes so much bet- 

 ter when a large amount of water is used than 

 when it is rather dry." He further says, "that 

 he mixed a1)out one hundred barrows of stone 

 and sand, to eight barrows of lime ; and the pro- 

 portionate value of the lime is to good stone- 

 lime as 2i to 8, making from thirty to forty parts 

 of gravel and stone to one of stone-lime." But 

 this ho admits is too little lime, and recommends 

 one part stone-lime to twenty, twenty-five or thir- 

 ty parts sand and stone; and finally "recommends 

 to those who are timid and cautious, one part of 

 good stone-lime to twenty of sand and gravel." 



This mass of lime and water, sand, gravel and 

 stones, was mixed with the shovel and still wa- 



