8/13/2019 Identification and Repair of Cracks in Buildings

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126 NBM&CW FEBRUARY 2010

Repairs

A fter few years of construction,many structures startshowing the cracks. Thoughfew minor and other distress.Cracks in any building are acommon occurrence but it is

important to understand the causesand the measures needed to betaken for their prevention. Buildingsthat have developed cracks in their RCC parts may pose a greatdanger to the life and propertybecause the process of corrosionprogresses very fast and couldcause even the collapse of thestructure. Therefore, it is advisablethat proper repairs andrehabilitations are carried out faster.In this process identification andremoval of the cause of cracking isof prime importance and this mustbe removed in the first step.

There are many reasons whichcan cause cracks in the buildingsas for example chemical reactionsin concrete construction, changesin temperature and climate,movements and settlement infoundation of buildings, shrinkage,environmental stresses, corrosionetc.

Identificationand Repair of Cracks inBuildings

Identification of

CracksMulti storied buildings are more of dynamic structures rather thanstatic. They go through the normal

phenomenon of settlement,deflections, vibrations andmovement because of themovements of loads and wind.With time this dynamism causessome stresses, which can showup in the form of cracks in manystructures in the walls, slabs, ceilingetc. At times these types of cracksare only plaster deep and can betreated by, chasing them into Vshaped groves and filling them upwith good quality cement basedcrack filler. Surface cracks in theplaster, and those, at the junctionof the soffit of the beam and thetop of brick work in a wall or those,at the junction of column and thebrick work, are mostly plaster cracksand can be treated easily.

In the reinforced concretestructures (RCC), if the concrete ishaving porosity or the section is notproperly reinforced, cracks candevelop and water/moisture reaches

the steel by leakage. This water inthe presence of carbon dioxideoxidizes the steel and causesrusting or corrosion. The volumeof corroded steel is much largethan the volume of steel hence

exerts a lot of pressure on theneighboring concrete and theconcrete develops cracks. Thecracks due to corrosion can appear on slabs, columns and beams.These cracks are larger andgenerally associated with browncolored stains. Thus, it is easy toidentify that building has developeda structural problem and needfurther investigations and physicalexamination of the steel by acompetent structural repair Consultant. After removal of thecover concrete the degree of theproblem can be established.

Causes for CorrosionCorrosion is caused by theoxidation of steel. Reinforcing steelwhen comes in contact withatmospheric carbon dioxide in thepresence of moisture the corrosionprocess starts and spreads fastlike cancer. Ground water