The water ingress characteristics of stressed masonry.

Tait, Colin J (1999) The water ingress characteristics of stressed masonry. PhD thesis, Edinburgh Napier University.

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    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.

    Item Type: Thesis (PhD)
    Uncontrolled Keywords: water permeation; masonry structures; absorption rates; bricks; mortar; stress levels;
    University Divisions/Research Centres: Faculty of Engineering, Computing and Creative Industries > School of Engineering and the Built Environment
    Dewey Decimal Subjects: 600 Technology > 690 Building & construction > 691 Building materials
    Library of Congress Subjects: T Technology > TH Building construction
    Item ID: 3672
    Depositing User: Mrs Lyn Gibson
    Date Deposited: 11 Mar 2010 19:31
    Last Modified: 12 Jan 2011 04:54

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