STONE CONSTRUCTION - Ancient Building Technology - page 164

interstices of random rubble masonry require a great quantity of mortar, thus the
cheapest serviceable substance is mud. Gypsum (or lime) based mortar however
is relatively expensive and therefore only to be used when the quantity required
per masonry unit is relatively slight.
From Early Neolithic times, mud mortar has always been used in connection with
rubble masonry construction (Vol. 2, p. 95; O. Aurenche, La Maison Orientale I ,
p. 72). Mud is very glutinous and adhesive when plastic, however thereat er time
appears to deal dif erently with dif erent mud mortared masonry. In some the
plastic mud at er drying out remains compact so that the construction is stable
well bedded masonry. On the other hand, in some instances, the mud mortar
becomes dessicated and loses all adhesive virtue. Not only this, but it loses its
cohesion as well and trickles away from the interstices of the masonry. Deprived
of i xing and also of adequate bedding the units of rubble collapse or are easily
displaced and the building becomes ruinous—a convenient source of supply for
later building in rubble. Presumably the root of this diversity is the composition
of the soil used for the mud.
h e traditional preference for gypsum based mortar in i ne stone masonry is
unfortunately not elucidated in manuals of building construction or building
materials. Some physics or chemistry should stand behind this, but there is no
consideration of the matter conveniently available for the study of ancient building
construction. Also ground up stone dust, a favoured ingredient for mortar used
in modern i ne stone masonry, is likewise rarely mentioned in connection with
ancient building, but cf the use at Karnak in New Kingdom Egypt of gypsum and
stone dust (Arnold, p. 291).
For long reference in archaeological reports on ancient building to gypsum or
lime were worthless since the observer lacked the capacity to discriminate between
traces of the two materials. In more recent times scientii c understanding has been
applied to this question with the result that regional zones have been postulated in
the ancient world where one of the materials was much more commonly used than
the other (O. Aurenche, La Maison Orientale , Vol. 2, pt 2, ill 198; O. Aurenche, I,
p. 28, Cartes 1 & 2). However it is not generally appreciated that this analysis is
based almost entirely on the use of the materials in plaster (Vol. 2, pp. 159-74),
not in mortar (Vol. 2, pp. 174-77).
h e primary question is the i eld of use of cementitious mortar in ancient i ne
stone masonry. It is not used with large block masonry ( grand appareil ) such as
Pharaonic Egyptian (Clarke & Engelbach, p. 78; Arnold, pp. 291-92) or Classical
Greek ashlar masonry since the dead weight of the individual block provides its
own i xing. Hence the i eld should be i nely dressed small block masonry ( petit
appareil ). h is, in ef ect, should equate with ancient “bastard ashlar” where it may
be imagined that gypsum based mortar was employed at the i nely jointed faces of

Fixa-
tion of
blocks by
cementi-
tious
mortar

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