Concrete construction is generally expected to give trouble free service through out its intended design life. However, these expectations are not realized in many constructions because of structural deficiency, material deterioration, unanticipated over loadings or physical damage.
Premature material deterioration can arise from a number of causes, the most common being when the construction specifications are violated or when the facility is exposed to harsher service environment than those expected during the planning and design stages.
Physical damage can also arise from fire, explosion – as well as from restraints, both internal and external, against structural movement. Except in extreme cases, most of the structures require restoration to meet its functional requirements by appropriate repair techniques.
Buildings and other structures have a certain useful life, which depends on the specifications adopted. The large number of monuments, which are cherished heritage structures have stood well over a period of time. But some of these have shown signs of distress due to age, aggressive natural environment industrial pollution etc. Further, distress gets aggravated due to overloading/ misuse of buildings. A few buildings have also failed due to faulty design / construction. Thus, Repairs & Rehabilitation of buildings are of vital importance.
The Scope is:
- To identify the causes of Repairs of Residential buildings
- To select and plan the effective remedy using appropriate methodology.
Before attempting any repair procedure it is necessary to have a planned approach to investigate the condition of concrete and reinforcement. While the diagnosis of damage or deterioration in some cases is reasonably straightforward, it may not be so in many cases. Particularly difficult are cases in which the cause and effect phenomenon cannot be readily explained.
This will require a thorough technical inspection and an understanding of the behaviour of the structural component, which is being repaired. Inspection calls for detailed mapping of affected areas, documentation of type and location of symptoms and their history and photographic evidences. It may also include the environmental factors which are likely to accelerate the damage process. Existence of concealed ducts, water lines, wet areas require special attention. A comprehensive inspection data helps in making an effective strategy for repair and rehabilitation.
Three distinct stages are to be recognized while taking up a repair job.
Stage 1: The first stage involves documentation of damage, its type and extent, prognosis of repaired structure and recommendations on repair methodology. For major jobs it will be worth while to engage an independent consultant to do this job.
Stage 2: The second stage requires preparation of detailed drawings, sketches, execution guidelines and notes, material and works specifications and tender document. The tender document should adequately cover various elements to the extent possible. Specific provisions in terms of material specifications should be included. It should clearly define modalities of payment, works measurements and records. This will facilitate in receiving a fair and competitive proposal for the repair works. Guidelines prepared for executing the job should be practical and flexible so as to encourage the ingenuity of the contractor executing the job.
Stage 3: The third stage is actual execution of repairs. This is a specialized job and those who have the necessary expertise and resources in terms of tools and plants should be engaged. The supervising engineer should have a good understanding of the procedures and give an attentive supervision. In some cases it may become necessary to monitor the effectiveness of repairs by various tests before and after the repairs have been executed.
Selecting a most appropriate material and repair methodology is very important to achieve durable, effective and economic repairs. Matching the response of repaired sections with the main structure is an important task. Compatibility of materials and matching specifications are essential in any repair job.
Just as building durable construction requires understanding of structural engineering, material science, and environment/ exposure conditions, repair jobs also require the same level of attention in these areas. The buildings taken up for repair may have structural deficiency and in such cases it is necessary to consider provisions for strengthening through bracing and creating alternative load transfer framing to give additional reserve strength to the structure for adequate safety and serviceability response. If this aspect is overlooked, the symptoms are likely to reappear even after repairs have been carried out.