Building repair: Techniques that can be used to repair buildings and restore their strength effectively

Structural strength is one of the most pivotal factors which affects the strength of any load-bearing structure and even a fine crack can reduce their resistance significantly.

Building repair: Techniques that can be used to repair buildings and restore their strength effectively
India’s 59% land area is prone to earthquakes of which 11% and 18% of the land area falls in zone V (very high-risk zone) and zone IV (high-risk zone) respectively. Next, around 10 major states in the country have been recognized as flood-prone states. Apart from these, the country is prone to several other natural calamities which have had a widespread adverse effect on our buildings in the past. This inevitable scenario not only demands our buildings to be built more strong but also to undergo proper repairing whenever affected by a natural calamity or any other adversity.

Recently, the Delhi government has mandated it for around 32 lakh buildings within the city to obtain earthquake-proof certification. To make the process of building repairs more effective and compliant with government regulations, Dr Anand S. Arya, Professor Emeritus, Dept. of Earthquake Engineering, IIT Roorkee and an advisor to the Ministry of Home Affairs, has defined some techniques that can be used to repair buildings effectively and restore their original strength. These techniques have been published in a document authored by Dr Arya titled “Guidelines for repair, restoration, condition assessment and seismic strengthening of masonry buildings”. These techniques and restoration measures can be used to repair fine cracks as well as cracks which are critical in nature. So, let's take a closer look at these techniques and try to understand them.

Structural strength is one of the most pivotal factors which affects the strength of any load-bearing structure and even a fine crack can reduce their resistance significantly. To maintain the structural integrity of buildings, Dr Arya’s document recommends proper identification and marking of every crack and repairing them either by injecting cement/chemical grout having appropriate strength or by applying an external bandage.


How to structurally repair minor and medium cracks?
Typically, the size of minor and medium cracks vary in the range of 0.5 mm to 5 mm. The tensile strength of structures with such cracks can be restored using pressure injection of non-shrink grout technique. This technique is implemented using the following procedure:

  • First, non-structural materials are removed from the external surface of the structure and plastic or aluminium injection ports are implanted on the surface of the cracks from both sides of the structure. They are fixed in their particular place using polyester putty or 1:3 cement mortar. In some cases, these ports may have a centre-to-centre spacing which is almost equal to the thickness of the structure.
  • Next, a sealant is applied and allowed to dry after which cracks are cleaned using compressed air and/or water.
  • The following process involves injecting the grout. If the crack is vertical, it is injected from the lower part. It can be injected from either end if the crack is horizontal. The injection process is stopped once the grout starts overflowing from the other end.
  • Upon completion of the process, the injection equipment must be removed and the port must be sealed properly before moving on to the next crack.
  • To ensure proper penetration of the grout across the depth and width of the crack, the injection pressure should be higher while the spacing between the ports smaller in case of finer cracks and vice versa in case of larger cracks.

The technique described above is applicable for a wide variety of masonry and concrete structures including beams, columns, walls and floor units. In case the crack to be repaired is in between a reinforcing bar and concrete adjacent to it and the concrete has been reduced to a very fine powder, then the powder should be removed properly using air or water pressure to ensure proper passage of grout during injection.
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How to repair structures having major cracks and crushed concrete?
Cracks which are wider than 5 mm can be categorised as major cracks. Structures having major cracks or structures having areas, where concrete or masonry has been crushed, are treated with a process different from injection. The following steps are followed to execute this process:

  • First, the crack should be cleaned or the crushed material should be removed properly and the void should be filled with expansive cement mortar or quick-setting cement.
  • Supplemental shear or flexural reinforcement should be given in the areas of repairs, if necessary. For further strengthening and protection of the reinforcement applied, it can be coated with a layer of mortar.
  • Severely damaged structures should either be entirely replaced or the affected region of the structure should be substituted.
  • Walls and floor diaphragms can be repaired using steel meshes that could either be nailed or bolted to the exterior surface of the structure and then coated with plaster or micro-concrete.

How to repair structures fractured due to excessive yielding and buckled reinforcements?
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  • Reinforced concrete structures damaged due to buckling, elongation or excessive yielding are generally considered to be severely damaged. To repair such structures, the old or damaged part of steel in them is substituted with either butt welded or lap welded new steel.
  • The right technique to repair a structure without removing the steel present in it should be determined based on the space available in the structure as splicing by overlapping could be unsafe. The damaged portion of the structure should also be provided with additional stirrup ties to confine the concrete and contain the longitudinal bars which would help avoid buckling in the future.
  • To repair some structures, anchoring some extra steel into the existing concrete might be required. This anchorage can be executed using a common technique as per the following procedure: First, drill a hole that is larger than the bar. Then, fill the hole with epoxy expanding cement or with some other high strength grouting material. Finally, push the bar into an appropriate place and maintain its position till the grout sets.

Reach out to Top Cement and Concrete dealers near you and get free quotes
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