bricks unit 3 bc 5th sem breif notes
UNIT III---BRICKS
• Quality of clay
• Mortar strength
• Strength of brick
• Elasticity
• Water content
• Cure temperature
Failures in bricks are mainly due to
-Water
-Salt
-Use of incompatible adjacent materials
Types of Brick Wall Damage & Defects:
1.Bulging brick above-ground walls:
this is likely to be a bond-brick or bond-course failure - potentially extremely dangerous and very urgent - can presage sudden catastrophic building collapse
2.Cracks and Bulges in brick foundation walls:
frost and earth loading can push a below-grade brick foundation wall inwards. Often the wall is bulged inwards into a basement or crawl area as well as showing horizontal and step cracking and loose bricks over the bulged area.
3.Diagonal or Stair-Stepped Cracks and loose bricks in walls:
these brick wall crack patterns are typically due to frost, settlement, sometimes thermal expansion.
Usually diagonal or stair-stepped occur at building corners where roof spillage is concentrated.
4.Lintel damage over windows or doors due to improper caulking or sealing -
caulking at steel lintels over openings in brick walls can trap moisture leading to exfoliating rust and severe damage, even cracked loose bricks in the wall.
5.Loose bricks and missing or lost mortar:
and movement where mortar is severely washed-out by roof spillage or other water movement against the foundation.Loose and lost bricks may also occur where wood blocks, originally set into a wall to permit nailing of interior components, is damaged by insects or decay.
6.Sand-blasted bricks
which have been "cleaned" of old paint, algae, or stains using high pressure sand blasting or possibly even very high pressure water blasting can be permanently damaged by loss of the harder surface of the bricks
7.Spalling bricks:
brick spalling is caused by water and frost, such as water leaking into a brick structure at any entry point: a crack, a brick which has lost its hard surface, or at openings by window and door penetrations.
8.Exfoliating-
rust damage to brick or other masonry walls occurs when brick walls have been improperly caulked.The most common example of this defect is the damage that occurs to a brick wall when a steel lintel over a window or door is caulked tightly between the brick and the steel.
9.Thermal expansion
Thermal expansion or cracking of brick walls occurs when a long or tall brick wall is built without adequate expansion joints. With age, brick walls "grow" in dimension.
10.Improper repair mortar
Improper repair mortar used during repair work can cause surface spalling of bricks if the mason uses a too-hard mortar high-portland content mortar on soft brick in a climate exposed to freezing weather.
Common causes of brick cracks:
• Expansion or contraction of soil
• Temperature changes
• Failing of house drainage
Deteriorating of brickwork:
Brickwork will deteriorate and decay if not properly maintained.
Such deterioration can be caused by a number of factors and can take various forms. The main signs that brickwork suffer-
• Surface growth
• Efflourescence
• Loose or crumbling mortar
• Cracks appearing through bricks
Causes of deterioration:
1. WATER- one of the most common and serious problems which can affect brickwork is uncontrolled water ingress
The following can be causes of water penetration-
a) rising damp from sub-surface moisture
b) wind blown rain
c) condensation caused by lack of ventilation
d) encroaching vegetation
2. SALT-
they are the major causes of deterioration. Salts enter through contaminated water. It is damaging because it creates a steady expansion of crystals within bricks. This can eventually force the structure of the brick apart.
The most obvious sign of the presence of salt is efflourescence
Precaution in brickwork:
• The rain water and water pipes should be fixed during the brickwork otherwise the brickwork would have to be dismantled to fix the pipes.
• The bricks are to be soaked in water before use otherwise these will absorb water from the mortar and the bonding will be weak.
Maintenance of brickwork:
The following general comments relate to the maintenance and cleaning of brickwork.
1. Mortar
Well-built clay brickwork is virtually maintenance free. The brick colour will not fade and the only obvious reparation maybe that after many years, the joint faces may require re-pointing.
2. Graffiti
Keeping the brickwork free of graffiti can now be accomplished by the use of a range of graffiti removing materials, which will not harm the brick or the joint
3. Efflorescence, Algae, Lichen
• Persistent efflorescence, extensive salt staining from within the brickwork and vegetable growth on the brickwork are due to excessively wet conditions, and, unless the basic problem of water penetration is cured, the staining will repeatedly reappear.
• In such cases, it is necessary to overhaul faulty flashing and damp proof courses, repair leaking rainwater down-pipes, renew copings, etc.
4. General Staining, i.e. dirt
• Staining in brickwork is generally due to external causes but sometimes may result from salts in the brickwork itself.
• Staining can mar the appearance of brickwork but incorrect cleaning techniques can cause permanent damage.
• Where chemicals are to be used, the brickwork should always be wetted, but not saturated, with clean water prior to chemical application, to prevent it absorbing the chemicals.
• After cleaning, the wall should then be rinsed thoroughly with clean water
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