Cracks are a result of a clash between two different materials. The clash could be due to chemical reaction between two or more materials, such as corrosion in metals (rusting) and hydration in concrete. It can also be caused due to physical factors such as overloading, vibrations, temperature variations, inferior materials used, faulty construction, insufficient curing, and moisture content in certain materials.
Two types
Cracks in buildings are broadly classified as structural and non-structural. Structural cracks are those that may occur due to deficient designs, overloading, abnormal vibrations, use of inferior quality materials, failure of foundations that are placed on loose soils, adopting of incorrect construction methods, poor workmanship, etc.
Construction works executed by persons who have no technical knowledge of structural behaviour of buildings, is also one of the major causes for such cracks to appear.
Non-structural cracks are those which are caused due to temperature-induced movement of materials. They are not dangerous to the safety of the building. However, they are an eyesore and hence have to be addressed.
Effect of temperature
Effect of temperature on materials in a new building is more, as increased moisture content in materials used need to evaporate which takes place over a period of about three to four years after construction. Hence, in several cases, owners defer final painting of their building until such a period is completed.
Such cracks can be reduced or nullified through good engineering practices during design and construction of a building. Provision of expansion joints at crucial locations of a building will help in releasing the stresses induced by structural members.
Foundation matters
It is also very important to rest the foundations on hard and firm soil structure. Soil testing should be carried out to ascertain the type of foundation, width & depth of foundation, level of resting the foundation to safely transmit the forces, etc.
Employing qualified structural engineers, experienced civil engineers and appropriate skilled labour force for construction are the most important steps to be taken by the owners of the building.
Quality of materials used shall be checked and ensured by the engineer in charge. Correct methodologies and sequence of construction shall be followed. Curing all items of work, done with cement, should be ensured for the prescribed period of time.
Good quality of formwork materials and supporting structure is essential. Reinforcements in RCC members should be properly detailed and executed, giving appropriate cover for the concrete. Extreme care and caution must be exercised in mixing materials for concrete as well as placement, compaction and curing of concrete.
(The author is a consulting structural engineer and GC Member, ACCE-I)
