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Concrete Repair and Rehabilitation

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While the use of simple concrete mixes dates back to the Roman times, over the last hundred years, the use of concrete in building construction has grown by leaps and bounds. Alongside it, a greater scientific understanding of the material, it’s properties, interactions and uses have likewise grown. Despite this rapid increase in our understanding, across the world we are encountering significant deterioration as well as, unfortunately, failure of concrete structures. Most serious failures are structural and durability failures. It is estimated that about a fourth are structural failures and three-fourths are durability problems. New, scientifically advanced materials and technologies exist today that can help concrete retain or regain it’s strength and durability. Like most newer technologies, the advantages they bring to the construction industry need to gain better recognition and understanding.

Cracks and spalling of concrete caused by corrisionMany materials and methods exist in the market to repair concrete.  Some experts estimate that up to half of all concrete repairs fail. To understand the role advanced technologies can confer to concrete and other natural building materials, the factors that can cause premature deterioration should be reviewed in a site specific manner.  What is important from the perspective of Tech Dry India, as a manufacturer of waterproofing and building rehabilitation products, is that concrete failure can commonly be traced to a water problem that initiated the damage.  It is time, therefore, that waterproofing chemicals must be viewed under a broader umbrella that encompasses a role in concrete protection, concrete rehabilitation and concrete repair.

Original design faults, use of unsuitable materials, untrained or poor workmanship and lack of routine maintenance all and more can affect the durability of a concrete structure. Serious breakdown occurs when concrete is permeable or concrete cover to reinforcement is deficient, leading to corrosion of steel and other embedded metals and non-uniform volume change.

When water and salt get into concrete, the reinforcing steel corrodes.  That’s why the concrete cover over the reinforcing steel has to be dense and of low permeability.  Water brings with it pollutants such as carbon dioxide which dissolves to form a weak acid, carbonic acid that can reduce the pH of the concrete causing it to deteriorate.  Chloride ions, sulphuric acid and numerous other environmental factors continuously must be encountered by the concrete structure.  Most problems with concrete can be solved by figuring out a way to keep the water from getting in.  This is where waterproofing products and methods that can deliver results become key participants in the protection or repair process.

We have written often about the role of protecting new construction materials from ingress of water.  A key difference between repairs and new construction is that in new construction both the quality of the work done, techniques and products used are known.   On the other hand, with rehabilitation and repair jobs, the underlying causes of defect are not exactly known. Surface examination doesn’t take away the high likelihood that surprises will occur when the site is opened up for repairs.  Surprises of this type are generally not pleasant and typically more problematic and expensive.

Generally, by the time there is visible damage, significant deterioration has already occurred.  The longer the delay in remedial efforts, the higher the expense and lower the certainty that the problem can be fixed.   Indeed, De Sitters Law of Five describes 4 stages of deterioration, Phase A, B, C & D, with A being early stage and D being later/advanced stage.  The Law of 5 pertains to the estimated increase of cost of repair by 5x, as each phase is crossed so Phase A: $1 spent is as effective as $5 spent in Phase B, $25 in Phase C  $125 in Phase D.

The unknown nature of the underlying structure as well as the damage that has already occurred makes it important to treat for the various issues that could potentially be presenting at the site.  Tech Dry India’s mission has long been to bring technologically advanced, quality products as innovative solutions to the market.  Tech Dry manufactures the Protekta range of products (For more information, please review at www.techdryindia.com) Since our beginning in 1992, led by our Founder, the late Dr. Surendra P. Bhatnagar, our R&D worked hard to find optimal solutions which has been central to our competence.  We offer a very large number of products, each of which has been designed to address specific factors related to strength and durability of the construction material used in the structure. We have successful methodologies for the treatment of problems from the top of the building to several feet below ground.  As an example, we have routinely performed highly successful repair of leakage from terraces.  The surface is likely to have natural expansion and contraction stresses, wind and rain stresses, the impact on the surface, particularly the damaged surfaces such as cracks, popouts, settling etc. means that there are a multitude of issues that the surface would need to be protected against. Each unique to the given situation.

In old terraces such as buildings at the Bangalore Club, Mount St. Joseph’s Church and the Deccan Herald or newer construction where for example cracks have occurred, treatment includes products to reduce hollowness, voids, porosity and such defects as cracks or gaps filled with high elongation and bonding polymers. Protekta Base and Protekta Flexjoint and Protekta 500 are some of the products that can be used in these situations. Where the diversity of our product lines becomes really useful however, is when it is a specific type of bonding, or a particular degree of flexibility that is needed, the method can be modified to suit the surface needs. Each Protekta product is designed to complement the others and so multistep processes are possible.  Each building had it’s own history and structure so devising the appropriate treatment along with having the range of products to select from becomes essential in conducting repair work. Exposed surfaces may have high traffic and need abrasion resistant coatings or surfaces may require coatings that can reduce the impact of the sun or need repellency products, all of which can be found within our product range.  It should be pointed out that the mixing of products from different manufacturers is not a smart thing to do as the products were not designed to work in a synchronized manner and may reduce or null their effect.

Another interesting example of repair with Protekta products is a project where the problematic area was the basement. Having a very high water table water infiltration was difficult to stop. The positive side of the structure also was not available.  By designing a process using a combination of flexible polymers, fast acting grouting techniques, soil stabilizing and treated mortar, we were able to resolve this issue.  It is evident, that different situations of basement water leakage will require different approaches. While many will require grouting from the negative side, having the requisite products available to work alone or in partnership with other products is a hallmark of our repair and rehabilitation successes. Where possible, retaining walls should be treated from the positive side.  In the repair market this is often limited due to the extent of the excavation that would require, or by lack of access to that portion.

In conclusion, there are numerous options that can be used to enhance the structural strength and durability.  Our products are environmentally friendly, water based, and can scientifically offer real solutions to problems that exist. These can help in the repair and rehabilitation process of concrete structures and the repair industry can enhance it’s success but understanding these newer technologies better and adopting them.

Acknowledgements for their assistance in preparation of this article:

–    Mr. Nagesh V. Hanagodu
–    Mr. K. P. Girish
–    Mrs. U. A. Usha

For further details:
Tech Dry (India) Pvt. Ltd.
877, 1st Cross, Krishna Temple Road, 1st Stage
Indiranagar, Bangalore – 560038
Ph: + 91-80-25255294, 25255406, 25272616
E-mail: contact@techdryindia.com
Web: www.techdryindia.com

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