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Chủ Nhật, ngày 20 tháng 11 năm 2011

Importance of Classification of Cracks


Cracks in a building are like ailments in human body. The building gets weaker and weaker if the cracks are not treated properly. The cracks give an impression of faulty and poor quality work. Moisture penetrates through the cracks and deteriorates the external facade as well as the internal facade. For determining a treatment procedure for the cracks, cracks have to be classified depending on its cause and nature. Different types of cracks have to be treated in different ways depending on its nature of occurrence.

Cracks in Buildings
In my earlier articles, I have discussed major and minor causes of cracks. Studying these causes also help in the classification of cracks.

The classification of cracks is based on various factors:

  1. Direction of the cracks
  2. Extent of the cracks
  3. Width of the cracks (if tapers)
  4. Width of the cracks
  5. Depth of the cracks
  6. Alignment of the cracks
  7. Sharpness of the edges
  8. Cleanliness
  9. General

Direction of the cracks

  1. Vertical
  2. Horizontal
  3. Diagonal
  4. Straight
  5. Toothed
  6. Variable and irregular
The materials trough which crack passes should be recorded.

Extent of the cracks

The cracks usually occur at starting and finishing points i.e. across the openings, passes round the edges of the materials or cracks close to the ground – passing through dpc (damp proof course) or confined above or below.

Width of the cracks (if tapers)

Mark the end of the crack
Direction of taper
(It is important to note the humidity of the day. Some cracks widen and close during the day due to thermal changes)
This is necessary for remedial work.

Width of the cracks

It can be measured through instruments and tell-tale signs. The changes in the length of the cracks should be noted.

Depth of the cracks

Figuring out or measuring the actual depth of the crack is irrelevant, but how many of the materials of the wall have cracked is important to detect.
For example, Just point film may have cracked which is not a very serious crack. A piece of very fine wire may be used to detect the fine crack.

Alignment of the cracks

A note should be taken of the levels of the materials on the two sides of the crack, one side sometimes being forward of the other can be done by feeling with the finger tip, passing it across the crack in both direction, when any direction in the level is readily apparent.
Alignment indicated whether the crack has been produced by a straight pull, or with a tensile force or as with a diagonal pull as with a shear action.

Sharpness of Edges

Most cracks have sharp edges but they may be rounded or roughened if the sides of the cracks have been brought together by compressive forces or by vibrations. Badly broken edges will often be indicative of initial compressive forces.

Cleanliness

Examine the cracks with magnifying glass for the following reasons:
  • Brightness of the sides of the cracks
  • The presence of dust, algae, insects etc
  • The presence of decorative materials (example, Paint on the sides of the crack)

General

Observe the crack over a period of time to know whether it is static or altering in size and if bows are there, measure the extent of bow.

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