The Washington herald., 1912-03-20

hardened, which shaking is accompanied
by expansion. causing disintegration OF
the mortar and popping.
Third-Agtng, that Is, storage Tor con-
siderable period after the lime Is siaked.
otherwise IL will not attain Its full hard-
hess.
er OF the last two requirements that
lime owes any disrepute into which II
has fallen. and not to the fault OF the
lime-burner in furnishing an inferior
Vitruvius. writing Is B. c., stated that
lime should be tempered Il. e., slaked).
lcng time before IL is used, so that the
bring the whole mass to the same con-
sistency The Greeks not only made
their stueco hard by long storage: 3Ht
many men with wooden stayes- While
the reason for this Is not given. II is
not unreasonable TO suppose that the pur-
pose was to partially pulvertze and thor
oughly Incorporate any puZzolanic ma
teTial that might be added. Phny states
that the ancient Roman laws forbade the
| for three years Gilmore speaks of the
custom in South Europe of shaking the
\ lime the season before II Is to be used,
and the modern building codes Of Europe
require storage of the lime after shaking
! for considerable periods. For example, the
| city of Berlin prohibits the use of any
1 lime in buildings that has not been slaked
with that existing in the city of New
/ York. where the better grade of master
plasterers congratulate themselves on
having secured recently the passage Of
/ a law making Il necessary that all limo
used in wall plastering shall be slaked
| for forty-elght hours before used, and
and stone masonry object to the pro-
posed requirement that the lines shall
be slaked for twenty-four hours before
| think no lime should be used that has
not been slakad for at least three weeks
| and storage for three months would be
effect of storage in preventing the pop
ping of the lime after being placed on
the wall, the cause for the gain in
strength of the mortar through storage
that the soaking Of the lime for lorg
periods causes rearrangement OF the
molecules so as to facilitate what may
| be termed the initial stage Of crystalliza-
ton. It Is recognized that crystals OF
carbonate of lime adhere more firmly TO
the sand and will stand greater de,
when they are thrown out Of solution
in water. It is not unreasonable TO as
sumo that during storage the water pres
ent becomes supeTsaturstseo' @ c,se "a ENC -Snic %nen
acid the crystals are larger and the bind
i ing action more complete. This view
is supported by the fact that when dry
hydrated lime is exposed to the atmos-
phere 1t recarbonates without any bind
ling or cohering of the particles together,
the material still retaining Its poWdery
form. The first hardening Of lime NOR
tars Is due to desiccation. which. unlese
sufficient sand is added, is accompanied
with considerable shrinkage in volume
and consequent cracking. The lime IN
the mortar is present partly in solid
condition between the grains as calcium
hydrate and partly In solution in the
Idjoxide Is absorbed by this solution, form.
ing crystalline calcium carbonate, ano
az. calcium carbonate is less soluble than
calcium hydr9te, the carbonate carbonate OF lime lime
taken into solution by the water present
and the action continues. Under certain
conditions tse calcium carbonate may
form a film on the outer surface ano
prevent the absorption Of further guam
titiee of carbon dioxide. Frequent In
stances are on record Of lime mortar
in The interior % OF heavy walls in ad.
solutely the same condition as when u
!, was first used; this condition being due
! either to the formation & Of an impSrvioni
: which prevented the access OF the air. ar1c
the further absorption of carbon dtoxide
and also the drying out o. the mortar s
wall, preventing access Of air to the NOR
tar In a closed chamber, for instance
! the absorption Of carbon dioxide by fresf
, ltion of carbon uioxide Is also dependen'
on the amount of moisture present Al
lines hardan thrugh the absorption Of
. carbonic acid, and the strength OF tn,
lime mortars depend on the cohesion oi
crystalline compounds formed during car
donation and their adhesion to the par
ticies OF sand with which they are mixed
r lime mortars are not suited for use undel
water or in positions where the air can
. not come In contact with them. In spit.
of this fact, however. they constituted
with the exception of isolated Instances
of the use OF mortars formed from
caicined gypsum. or of hydraulic lime
: Ii the chief cement OF the builder UP q
: the beginning of the nineteenth century
? and are pre-eminently the -cementtiou
: material OF the past. net
Believed Maenesia Important.
III Among the studsIs y cementitious ma
. terial during the early part Of the nine
: teenth century Il was generally assumes
that masnesia had sn Important part d
: the hardening ef naortarss Viyat. Ger
Gilmore, Chatoaeg. valiant. Scorgic. Pas
I II ley, and others stating positively tina
= the prefencf OF 1aeneIr1 improved NOR
: tars and cements. sf1ee recently, as q re
suit principally n the ftuoy OF Portian
!: icement In ssa-va4ez. conclusions wer
; reached that nlasrefz was detrimental
3 and these couclusic-s Here applied TO a