Civil Engineering Reference
In-Depth Information
In any event it may be possible to say that speaking generally i ne stone masonry
(
opus quadratum
) under Roman rule tended to develop away from the sophisti-
cated pattern bonding of Hellenistic ashlar towards a simple stretcher bond which
continued into Byzantine times. With this development (indeed as part of it)
opus
quadratum
construction developed away from uniform i nely jointed masonry
throughout the thickness of a structure towards a facing to other material—and
thus to an element in mixed construction. But this i eld is too extensive to survey
here (cf supra, p. 155).
Fixation
of blocks
204
399
b.
Fixing
During antiquity two dissimilar means of i xing stone masonry were practiced. h ey
and the manner of their application both were constant throughout the ancient
world (and indeed remained so in at er times). h ey were:
(i) Cementitious mortar
(ii) Inset couplings (of wood or metal)
Cementitious mortar not only provides the desired adhesion between units of
masonry, it also provides the bed on which the units rest stably. h e inner cou-
plings between blocks secure them one to another where the form of the blocks
themselves provides the necessary bedding. Cementitious mortar can be prepared
from several substances and its composition is characteristic of the type of masonry
where it is employed. h e material (wood, metal) of the couplings and their form
imports both geographical and historical distinctions, and is of considerable
archaeological signii cance.
(i) Cementitious Mortar
In connection with building the term mortar is used loosely for any plastic earthy
substance employed in masonry in conjunction with the masonry units (stone,
brick). It may serve two distinct functions—ot en both combined, but not neces-
sarily so: as a lubricant to facilitate the setting in position of masonry units, and
as an adhesive to i x the units together when it has “set”. h e following remarks
are concerned with the latter function—hence the term cementitious mortar. h e
uniformity in the manner of use of such mortar is striking.
In brief, cementitious mortar is used with rubble masonry, not with i nely dressed
(hair line jointed) ashlar masonry which is set dry-stone (Orlandos II, pp. 99-100).
More specii cally when rubble masonry is random, irregular and little shaped
the type of cementitious mortar employed is “mud mortar”. On the other hand
where another type of mortar is used with stone masonry, gypsum based mortar
is strongly preferred to lime based mortar (which is always used with burnt brick
masonry). A reason for this distribution (as is obvious) is economic: to i ll the
164-166
149
