Masonry Structures

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Masonry Structures
Crack and repairs
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What is a defect?
An imperfection, deficiency or fault in a
building component is termed as a defect.
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Causes of a defect

• It is useful to classify the possible causes
  into four categories, each of which has a group
  of relevant investigation methods associated with
  it. The categories of causes considered here are
• Construction
• Long-term loading
• Transient loading
• Environment

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Deterioration Characteristics

• Deterioration of Materials
• Defects originating in the ground
• Defects due to Wear Tear
• Defects due to Water
• Defects due to Vegetation

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Deterioration of MaterialsCharacteristics and
Countermeasures

• Brickwork
• A characteristic of brick as a material is its
  long-term expansion
• Movement joints in clay brickwork incorporated at
  10-12 m centres and the width of the joint should
  be assessed, allowing 1 mm of movement per metre
  run.
• Elimination of total saturation by the use of
  details which minimise the amount of wetting,
  even in positions of extreme exposure.
• Reinforced and prestressed brickwork

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• Stonework
• Effect of porosity
• Effect of surrounding stonework
• Effect of Leaching
• Effect of Bed Stone
• Effect of Nitrogen
• Efffect of Sulphate Attack

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Defects originating in the ground

• Settlement and ground strain
• Consolidation and expansion
• Earth pressure
• Mining subsidence
• Uncontrolled water

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Defects due to Wear Tear

• natural deterioration of a structure due to
  time-related effects of climatic and
  environmental conditions,
• adverse effects of normal use, particularly the
  loading to which it may be subjected.
• Remedial Action
• Grouting
• Stitching
• Face patching
• Reinforcement
• Saddle/relieving slab

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Defects due to Water

• Groundwater
• Structural instability
• Piping Hydrostatic pressure can cause water
  seepage under pressure from the increased head of
  water, resulting in undermining of the foundation
  
• Loss of jointing material
• Environmental effects
• Groundwater penetration of the structure can lead
  
• Preventive measures
• The groundwater-table can be effectively
  controlled by drains installed at formation level
  in conjunction with a rear wall drainage system
  which is positively connected to an outfall
• Installing a system of well pointing and pumping
  the water to an outfall
• Protecting the structure against the ingress of
  water using mastic asphalt tanking or a
  waterproofing system

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• Corrective Measures
• Pressure pointing and grouting for preventing the
  ingress of water into a brick or stone masonry
  structure
• Well pointing and pumping corrective solution
  inasmuch as the groundwater can be quickly
  lowered, but continual pumping of the water is
  required.
• Relieving drains can effectively lower the
  groundwater but have a limited application for
  deep foundations.
• Waterproofing is cost effective for the
  superstructure of masonry arch structures but is
  impractical to install for existing substructures
  

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Defects due to Vegetation

• Large plants creepers, shrubs and trees can have
  deep-seated disruptive effect on masonry.
  Vegetation growth on and around structures is
  often considered to enhance their appearance,
  softening their lines and setting them in an
  attractive environment of ever-changing colour.
  However, the physical effects of the growths of
  roots and suckers, as they penetrate joints and
  cracks or withdraw moisture from the soil under
  foundations, may be major contributors to the
  disintegration of those structures
• Preventive Action
• proper control of vegetation on, over and
  adjacent to structures
• Single trees should be located no nearer to an
  existing structure than their mature height
• For groups or rows of trees competing for water
  over a limited area, the distance should be
  increased to some 1.5 times the mature height