The water ingress characteristics of stressed masonry.

Tait, Colin J.

Abstract

Water ingress, usually by wind-driven rain, is the main cause of premature
deterioration in masonry structures. Water acts as a transport mechanism for
aggressive chemicals and can also undergo freeze/thaw cycles leading to bursting of
the masonry microstructure.
Factors such as the absorption rates of brick, water/cement ratio of the mortar,
workmanship of the mason and poor design detail have all been identified as
influencing the amount of water likely to penetrate a structure. It is also recognized
that the majority of water ingress occurs at the brick unit/mortar joint interface,
where interstices are present that allow access to the masonry interior.
The size, extent and influence that the brick/mortar interface has in governing water
ingress is likely to be controlled by both the applied stress level and bed orientation
of the main mortar beds relative to the direction of loading. Very little research has
investigated these parameters in detail.
By using a new ingress measurement technique, the effect of the applied stress level
and bed orientation was quantified. The main mortar beds of concentrically loaded
masonry panels were found to deteriorate in their resistance to water ingress as they
were orientated from perpendicular to parallel relative to the direction of loading.
Poisson's ratio effects, which generated differential expansion between brick and
mortar were believed to control water ingress at mortarjoints orthogonal to the main
beds. Water ingress at these mortarjoints was also found greatly influenced by both
applied stress level and bed orientation.
Factors such as the applied pressure head of water impinging onto the panel, the
variability of the brick type used, eccentricity of applied loads and the pre-wetting of
panels were also found to have some controlling influence on the water ingress
characteristics of masonry.
Empirical modelling of water ingress dependent upon time, stress level, bed
orientation and pressure head of water, was also undertaken. This enabled the
volume of water ingress to be mathematically generated, with these models
exhibiting good agreement with experimental data.
Suggestions for future work include assessing the effect of higher applied stress
levels on water ingress, verification of the laboratory work with on-site tests and the
introduction of freeze/thaw testing on loaded panels to simulate an abrasive external
environment. Numerical analysis using finite element modelling was also identified.

Thesis Type	Thesis
Deposit Date	Mar 11, 2010
Peer Reviewed	Not Peer Reviewed
Keywords	water permeation; masonry structures; absorption rates; bricks; mortar; stress levels;
Public URL	http://researchrepository.napier.ac.uk/id/eprint/3672
Contract Date	Mar 11, 2010
Award Date	1999-05

The water ingress characteristics of stressed masonry.

Tait, Colin J.

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Abstract

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