Govt.VHSS Poovar

Repairs and Structural Rehabilitation to the main building of Govt.VHSS Poovar in Thiruvananthapuram District :-

This article is presented to highlight one of the most innovative works undertaken by the LGSD engineering wing. During the middle of October 2012, the Executive Engineer, LSGD Division, Thiruvananthapuram District Panchayath got an SOS message from the PTA President of Poovar VHSS regarding the dangerous situation of the two storied main building of the Govt.VHSS Poovar in which classes are going on. The Executive Engineer immediately rushed to the spot and he was taken aback on seeing the existing condition of the L-shaped main building.

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Condition of the building during mid October, 2012

  • There are two RCC columns each of size 30cmx30cm inside the science lab. These columns were having vertical cracks. A piece of an edge of one of these columns has already given away exposing reinforcement at that portion. There were vertical cracks in both the RCC columns.
  • Each of the above columns supports two beams of 7.17m and 5.30m span in the same axis. Set aside the deteriorated condition of these columns, the existing size of the columns is also not suitable for a double storied school building.
  • Portions of the underside of the 7.15m long beams had also spalled, leaving portions of the bottom reinforcements exposed.
  • Almost all the beams in the ground floor of the building were having cracks in the longitudinal direction of the reinforcement steel and some portions of the underside of the beams had already spallen. Beams in the Verandah portions were the most damaged ones.
  • Spalling had occurred in some portions of the slabs also.

The building was constructed around 20 years back. The proximity of the sea might have accelerated the deterioration. No substantial cracks were seen in the first floor of the building. May be this is due to the major repairs carried out some time back.

How to repair became a big question before the engineers. After detailed discussions with various agencies, the members of the Indian Concrete Institute and the experts in the College of Engineering, Trivandrum and the IIT Chennai, the engineers of the LSGD became convinced that repair and structural rehabilitation is possible and they moved into that direction.

The demand of the PTA and the Division member of the District Panchayath was to dismantle this building and to construct a new one. The Executive Engineer was able to convince them that the building can be repaired using latest technologies, after putting forward the following points.

    • If the building is dismantled, the waste disposal will be a major problem.
    • Cement and steel are the major components in a building that consumes large amount of energy in their production. Hence the energy that was input in this building years back will be wasted. This is in addition to the labour input at that time.
    • Fresh cement and steel will have to be used for the new building. Thus new energy has to be input for producing these materials. This will certainly add to the global warming.
    • An amount of nearly rupees two crores will be required for constructing a new building of this size.
    • If we are going for repairs and structural rehabilitation of the building, we need only rupees ten lakhs. These works can be executed through specialized agencies and a guarantee period of 3 years can be included while calling tenders, instead of the existing 6 months period for repairs.

The Executive Engineer then took the Public Works Standing Committee Chairman and the Working Group Chairperson of the District Panchayath to the site and convinced them also of the existing situation and also the modus operandi for the repairs and structural rehabilitation works. Thus the project materialized and this was included in the revision of projects and Administrative Sanction for rupees ten lakhs was obtained.

Meanwhile a letter was sent to the Manager, Centre for Continuing Education, College of Engineering, Thiruvananthapuram, requesting them to inspect the building and suggest remedial measures. An amount of Rs.28,090/- was also remitted for the test, report and remedial measures. They performed ReboundHammer Test as per IS:13311(Part 2):1992 and Ultra Sonic Pulse Velocity Test as per IS:13311(Part 1):1992.

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Based on the test result they have found that the concrete is of grade M15 and that the concrete quality grading is ‘doubtful’. They have opined that the concrete in question is not sufficiently dense and is porous and because of that carbonation has occurred, penetrating the cover deep enough so as to reduce alkalinity of concrete which caused rusting of reinforcement. They have suggested the following method for the repairs and structural rehabilitation of the building.

  • Prop and support the structure in order to relieve the RCC elements of stresses due to load coming over it.
  • Remove plaster and finishes all around the distressed RCC elements, remove the cracked and spalled concrete to expose the rusted reinforcement. Remove concrete all around the reinforcement in order to get a 25mm air gap all round and clean the reinforcement and concrete. The concrete substrate shall be thoroughly soaked with clean water prior to priming.
  • Apply appropriate passivating primer (Nito Zinc Primer) and bond coat over the reinforcement and the prepared RCC surface.

If the reinforcement diameter has been reduced by more than 35%, put additional reinforcement there with necessary overlap or welding with the existing reinforcement. Fix shear keys of appropriate diameter at specified spacings.

  • Provide necessary shuttering. The prepared concrete surface should be covered with polymer modified cement sand mortar in layers including behind reinforcement over a bond coat with polymer modified cement slurry. (Adopt shotcreting technique).
  • Apply 6mm thick finishing coat with sand plaster 1:3, if felt necessary.
  • Wet curing shall be done over the finished surface for a minimum period of 7 days. Necessary white washing/ painting has to be carried out.
  • After getting the report and suggestions from the CET, the engineers searched the local market and enquired about the products available. After a thorough enquiry, they prepared an estimate amounting to Rs.10,00,000/-incorporating the suggestions put forth by the CET and put to tender. M/s Con-Chem Solutions, Thiruvananthapuram, quoted at estimate rate and the work commenced immediately after completing all formalities.
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The work was a specialized one and so it progressed slowly but steadily. The work was done as suggested by the CET. The following chemicals were used.

Anti corrosive coating on reinforcement CERA ZINC-ZR
Epoxy bonding coat on concrete CERABOND EP
Preparing polymer modified cement mortar CERABOND SBR REPAIR
Wrapping the finished surface Carbon Wrapping with Adhesive
Plastering CERA FIBRECRETE
Rust remover CERA RUST CONVERTER
For holding stirrups CERA-ANCHOR SET-S-HARDENER & CERA ANCHORSET BASE
Secondary Reinforcement CERAFIBER-MIX
Super Plasticizer CERA HYPER PLAST XR W 40
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The work was started on 4.04.2013 and was completed on 20.08.2013 at an amount of Rs.8,78,020/-. The entire school authorities and the PTA are fully satisfied with this specialized work and the PTA honoured the Executive Engineer with an award of ‘Engineering Excellence’.

Thus a building which was in a distressed state and which would have been dismantled and reconstructed for which an amount of rupees two crores would have been spend, was saved at a cost of less than rupees nine lakhs adopting latest engineering materials and techniques. The efforts and initiatives taken by Sri. Er. Sam Vaidyanath, Assistant Executive Engineer, LSGD Parassala Sub Division and Smt.Anithakumari.M, Assistant Engineer, LSGD Poovar Section preparing estimate and executing this work are exemplary and should be appreciated. The inspection of the building and suggestive remedial measures were given by Prof.Biju.V and Prof.Mitra.D.C, Assistant Professors and Dr.Bindhu.K.R, Associate Professor of the College of Engineering, Thiruvananthapuram.