Structural masonry is an assembly of masonry
units of bricks or concrete or stone blocks, bonded together
with mortar, used in buildings and civil engineering structures.
Like concrete, masonry is good in compression but brittle and
weak in tension. Hence, their use is restricted to use in situations
where they largely remain in compression. An exception is when
large wall panels are subject to horizontal wind loads, which
produce bending and small tensile stress to the masonry.
It is noteworthy to distinguish between bricks
and brickwork. Bricks are the individual units whereas brickwork
refers to the complete product including the mortar. The compressive
strength of brickwork is significantly less than that of the
Table 1 summaries the common types of masonry
units and mortars. It is noteworthy that the
stone units are excluded in here.
Fire resistance of masonry constructions is
always measured on structural elements, such as block or brickwork
walls and columns, and there are no requirements for individual
units or the bonding mortar. Historically, masonry walls have
demonstrated excellent fire resistance, provided that the foundations
and supporting structure can keep the wall in place during the
fire. However, thermal bowing of very tall unreinforced cantilever
masonry walls due to a severe fire on one side of the wall can
lead to collapse (Buchanan 2001).
British codes currently do not give a calculation
method for masonry, and design is on the basis of experimentally
determined resistance levels for walls (Vekey 2002). Guideline
on fire resistance is stated as the minimum thickness of masonry
walls of various types of construction to give a stated fire
resistance period ranging from 30 minutes up to 6 hours.
In general, for a given material type, fire
resistance increases with:
- Thermal resistance of the body material
- Absorbed or combined water content
- Any non-combustible applied finishes, especially insulating
plasters and renders