Finding of visual examination and field investigation of the water body:
- No expansion joints and construction joints in the concrete floor were found.
- At number of places long cracks were visible.
- The brick walls were painted with enamel paint after the Cement Plaster.
- Cracks of size > 5mm present all over the bed floor longitudinally and transversely.
- More than 5mm wide gap (about 1 metre to 2.5m) long at the joint of wall and bed were found at several locations.
- Honey combing and damaged concrete floor were noticed.
- Compacted earth base in the bottom.
- 150 mm thick lean concrete over base.
- 25mm thick cement mortar for fixing 20mm thick Kota stone over PCC.
- 100 mm Cement Concrete (1:2:4) over Kota stone flooring.
Reconstruction of lake with water-proofed RCC wall & proper joint with bed was a costly option and NDMC authorities were not inclined to accept such proposal, since earlier piece meals efforts had not yielded satisfactory results.
Other option was to make the joint of wall and bed structurally strong enough and repairing of damaged portion of the concrete floor and injecting the cementious grounting polymer modified slurry to make concrete bed compact. The wide cracks has to be repaired and filled with flexible material. All micro and macro cracks should be strengthened by the polymer modified cementitious slurry with glass fiber mat, since water depth was not more than 4 ft.
It was a big challenge to repair and to provide an appropriate waterproofing system which should not only be cost effective but long lasting also, so that lake can be revamped as an water body and for other social uses/ occasion.
Reasons of cracks were debated. Once it became evident that cracks developed due to unusual expansion and contraction of the structure on account of thermal variation, the choice of Polyurethane as a filling and sealing material for cracks was considered inescapable.
Strengthening of Concrete Floor:
For the portion of honey combing, damaged concrete floor etc., it was necessary to provide additional strengthening of joints of walls and floor and Honey combing in floor by grouting and injecting cementitious polymer material. Ferrocement for joints and wall was selected for structurally strengthening the wall and floor.
Water-proofing of Water Body:
Provision of suitable waterproofing system on both wall and floor of the lake was considered critical and incorporation of following features in the chosen waterproofing system became inevitable:
- Environment friendly.
- Abrasion and impact resistant.
- Flexible to absorb expansion/contraction due to temperature variations
- Long life and cost effective, Defect free with a guarantee of at least 10 years
- Water resistant and non- reactive.
- Cracks wider than 5 mm be further widened and filled/sealed using flexible material.
- Macro/micro cracks to be covered by PMCC (Polymer modified cementitious Coating over sand witched glass mat.
- Weak concrete floor to be strengthened by injecting polymer grout at pressure.
- The joint of wall and floor to be provided with Ferro cement before water-proofing Treatment flexible.
- Poly urethane based flexible and impermeable water-proofing system over the walls and floor as per section below:-
- Repair to joints on floor by cutting V grooves using poly-crete R and cement mix in the ratio of 1:2.
- Two coats of PMCC using polycrete R or equivalent @ 0.25 kg per square metre and cement @ 0.50 kg per square meter per coat with embedment of glass mat.
- Two coats of polyurethane screed of polyeuro -1050 (I) by mixing part A, part B and part C (fine additive aggregate) in the ratio of 1:2:2 respectively.
- Top coat of neat polyurethane polyeuro 1050 1 admixed with colour pigment.
- Ferrocement strengthening screed comprising of layers of hot galvanized 22 gauge or woven wire mesh with 12 mm size mesh openings stretched and fixed to substrate with 100 mm over laps in both directions at a clear spacing of 4 mm and also maintaining a clear bottom cover of 4mm complete with plasticizer and polymeric sealant admixed in appropriate ratio.
The ferrocement layer was vibrated using a special type of vibrator (orbital type)
The above work was executed by M/s JBM Engineer Pvt. Ltd. successfully in the year 2006 under the team of Shri H.P. Singh, Superintending Engineer (Civil) the then Executive Engineer (Civil) and consultant Sh. P.C. Sharma, Retd Head M.S. SERC Ghaziabad. After water testing for evaluation of lake, the same was opened to public and still working satisfactorily even after 8 years.
Synopsis of the Work
|Client:-||New Delhi Municipal Council, New Delhi.|
|Agency:-||M/s JBM Engineers Pvt. Ltd. Janak Puri, N. Delhi|
|Date of Start:-||30.06.2006|
|Date of Completion:-||04.12.2006|
|Amount:-||Rs. 48.00 Lacs|
|Total area executed for water proofing:-||3837 M²|