The Reckli Finish Exposed Retaining Wall at Sabarmati Riverfront in Ahmedabad, using a 9m high Exposed Retaining Wall with a textured finish, and outer face using Formliner Formwork (known as Reckli), has grabbed the eyes of the world. Besides its aesthetic value, it also protects the city’s low-lying areas from floods during the monsoons.
Manoj Didwania, (BE, MBA, CIPM, IGBC-AP, CIPP), Adani Green Energy
The 9 m wall at both sides of the riverfront at a stretch of 10.4 m, stands as a barrier against the high-water level and also creates a marvelous walkthrough (Lower Promenade) for the public. It has given a new dimension to the commercialization of public amenities, making the project sustainable in every aspect. Today, huge concrete walls are not only acting as barrier, but their Reckli exposed finish texture presents a new form of concrete which can be used in diverse ways.
The structure that stands on the 10.4km stretch of the Sabarmati Riverfront is designed for the public, with some parts reserved for residential and commercial use, creating a thriving public centre and giving the city of Ahmedabad a fresh new identity.
Its uniqueness lies in using concrete aesthetically. Riverfront upgrades 18 precincts located adjacent to the riverfront land, revitalizing the heart of Ahmedabad and leading the city’s future growth. The riverfront brings intrinsic value to the residents of Ahmedabad by making the banks of the Sabarmati free and accessible to them. In fact, the riverbanks will evolve continually, adapting to the diverse interests of a rapidly transforming city.
Low-lying areas of the city such as Khanpur, Paldi, etc. prone to flooding in the monsoon, are now protected by the retaining walls that run along the length of the river.
The Sabarmati Riverfront Development project brings global best practices to revive the river as a public sanctuary and establishes a new paradigm for central neighborhoods. It links river-facing precincts with enhanced public and water transport facilities, recreation and park spaces, and economic opportunities.
As one of the most durable, economic and cost-effective building materials, concrete offers all the advantages for creating a safe, aesthetic and variable construction. When in its liquid form it allows unlimited possibilities of forming and moulding to its final hardened shape.
RECKLI Formliners are made from an elastic material for the patterning and texturing of all finished and ‘as struck’ concrete surfaces. The RECKLI formliner system has a proven track record of over 40 years application throughout the world. Architectural design is only restricted by the type of formwork or mould employed. With RECKLI formliners, these boundaries can be crossed easily and in an aesthetic manner with limitless possibilities.
The elastic formliners not only aid the planner and operator in achieving the architectonic objective, a texture also runs through the varied interaction of light and shadow, leading to an effective revival of facades and concrete surfaces. The RECKLI elastic formliner system offers ideal possibilities to meet the highest quality requirements for finished and ‘as struck’ concrete surfaces.
The formliners are made from rubber-like polyurethane elastomers. Their high flexibility, elasticity and durability allow multiple damage free stripping and release to the concrete, and give an exact reproduction of any patterned or textured surface.
RECKLI Formliners are used in in-situ and pre-cast concrete construction. In both applications the formliners require suitable and sound foundation to be placed upon. Plywood should be of minimum quality with ‘smooth fir fair faced one side’. In pre-cast applications, the formliners can be placed loose into horizontal moulds, formwork or tilting tables or glued together. For vertical applications (in-situ concrete, battery-shutters) it is strongly advised that they be glued to the shutter.
For gluing use, RECKLI Formliner Adhesive with suitable RECKLI primers, if and when advised by RECKLI. The type and quality of concrete do not limit in any way the use and application of RECKLI Formliners (Shown in Photo-2). It is immaterial whether the concrete is standard concrete or one using heavy or lightweight aggregates, white cement, and coloured concrete or concrete with pigments. RECKLI Formliners can also be used with self-compacting concrete, fibre reinforced concretes such as glass fibres, polypropylene, textiles, steel etc. It has been used successfully for many years in the GRC Industry.
For this project, we have used 9mt high and 15mt wide shuttering panels, and on the face of the shuttering sheet the Reckli formliner were placed with adhesive. Proper care was taken while placing the Formwork so that the Formliner is aligned, and we could achieve the desired pattern. The most difficult part was the precaution and supervision during the concreting.
Height of the RECKLI - retaining wall formwork is almost 9.0 Rmt from the top of the raft. Thickness of the retaining wall is 300 mm at the top, tapering to 450 mm at the bottom, supported by counter fort (of 600 mm thickness) 3.0 Rmt c/c at the back side. Retaining wall using Reckli form liners is caste at a gap of every 15 Rmt panel. 103 MT of specially fabricated 390 sq. mt. of MS steel shuttering/formwork is used for this 15 Rmt panel, to produce 90 m3 of concrete and gives 135 sq. mt. of surface finish having Reckli Finish. A jointless concrete and single stretch pouring of concrete upto height of 9m was a most challenging job as we had to give the concrete a Reckli finish.
As the concrete is to be poured at a time (in a single pour) for height of 9 Rmt. special care was taken regarding mix design and placing of concrete. Slump value of 110-130 is advisable at point of pouring.
Procedure of Concrete work
- Concreting done with Boom Placer with 6 Rmt. length of hose.
- Concreting starting from 1st window of Counter fort wall (Window Opening shown in Photo 2). Concreting done by layer wise.
- 1st and 2nd layer concreting done by 1st window. (1st layer+2nd layer = 2.4 mtr. height) and than the First Window is Closed
- 3rd & 4th layer concreting done from 2nd window of counter fort. Concreting done by layer wise. Further 2.4 Rmt height’s concrete achieved from that.
- Balance height’s concreting done from top (third pouring). Insert hose pipe from top to wall portion up to 4 Rmt down and concreting done layer-wise
- Vibrating done by three types of Vibrators:
- Electrical Vibrator with 12 mtr. Length of needle, vibrating done from top.
- Surface Vibrator – 2 Nos of surface vibrator applied on Reckli shuttering (Front Side)
- Electrical Vibrator – Electrical vibrator 6 mtr. to 7 mtr. Length of needle which is applied from counter fort window and back side window of the retaining wall.
It is also advisable to do concrete in layer of 1Rmt. Concrete is pumped into Reckli retaining wall through its window and from top of the wall using very high pressure concrete pumping system i.e. Boom Placer, which generates a pressure of 65-90 Bar (Minimum Pressure utilized from Boom Placer by us) throwing concrete from ground up to 9.0 mt height. Maximum Pressure of Boom Placer is 300 Bar to be obtained if required. If we supply continuous concrete to Boom Placer and placed the concrete continuous at workplace then the output of Boom Placer is 75 – 90 cum/hr.
The concrete should be specially mix designed for Reckli retaining wall using higher extent of finer material, admixture and also cementious material like fly ash. Utmost care to be taken while vibrating the concrete in the wall to avoid honeycombing and undesired surface finishes.
|Table 1 : Plant and Machinery used|
|Sr. No.||Name of Equipment||Capacity|
|1||Concrete Batching & Mixing plant||30 m3 / hr|
|2||Transit Mixer||4 m3 / 6 m3|
|3||Reinforcement cutting and bending machine||4 Nos|
|4||Excavator||Bucket Capacity 0.3- 0.9 m3|
|5||Tippers/ Dumpers||10 MT|
|6||Hydraulic motor grader||170 HP|
|7||Vibratory Roller 10T capacity||2T|
|8||Placer Boom||96 m3/HR|
|9||Concrete Pump||46 / hr|
|10||Hydra||10 MT (Pick & Carry Cranes – Hydra)|
|11||Movable DG set||25 to 725 KVA|
|12||Movable lighting masts||-|
|13||Formwork to cast wall of 10m height in a single pour, with reckli liner||4 sets|
|14||Wheel mounted Hydraulic Crane||800Kg at 25mtr.|
Mix Design for the structure was to be given all the consideration such as workability, durability and proper slump. Use of flyash was done to reduce the initial heat of hydration, which can cause superficial cracks during bleeding. A proper blend and mix was designed so that the structure remained exposed and concrete could be placed in a single stretch for 9m height.
Use of admixture was finalized after several trials; mix and test was carried out, and finally the polymer based admixture was selected for a long Stretch Concreting and Durable Concrete.
Physical Properties of Admixture
Fly Ash: As per IS 3812 (Part -1) : 2003 & ASTM 618 Class F
Mineral Admixtures: 20 to 25 % FLY ASH - added to concrete to enhance workability of fresh concrete, to improve resistance of concrete to thermal cracking, alkali – aggregate expansion, sulfate attack, and to enable a reduction in cement content.
Test Certificate reviewed & property testing of Fly Ash: Grade 1 / Class F
Specific Gravity, Setting Time (Initial & Final), Specific surface, Soundness, Compressive strength, Sieve analysis.
Silica (Sio2), Aluminium Oxide, Iron Oxide, Magnesium Oxide, Sodium Oxide, Moisture content etc.
Linear polymer containing sulfonic acid type of super plasticizers used in concrete to reduce water or cement content, for plasticization of fresh concrete mixtures, and control setting time. The sulfonic acid groups are responsible for neutralizing the surface charges on the cement particles and causing dispersion, thus releasing the water tied up in the cement particles and thereafter reducing the viscosity of the paste and concrete.
Advantages of Mix Design
Flowable concrete with the lowest water:cement ratio without segregation or bleeding.
It is an ideal admixture for the high quality concrete due to its excellent dispersion effect
It works with an extremely low water/cement ratio and allows high performance concrete increasing high early (18-24 hours) and final strength, flexural and tensile strength, low permeability, and high density.
- Increases adhesion to reinforcement
- Reduces micro porosity. Very high water reducing capability.
- Increases workability, density and strength without increase in cement.
- Increasing compressive strength of concrete mix with reducing water content of the mix.
- Allows reduction of curing cycles - time and temperature
- Less vibration and workmanship required
|M25 Grade||SSD||WA %||Water||Actual||For 0.5M3||For 1 Bag Cement|
|Cement + FA||330+82.5||412.5||206.25||50|
|Admixture (liters) Samplast (polymer base)||1.00||4.125||2.06||0.5|
The use of Reckli systems eliminates the need for conventional framing on retaining walls. The structure will always remain in contact with water and various adverse conditions like heavy wind and various sulfate attacks. The above physical and chemical properties of fly ash was useful in carrying out the 10m height concrete wall in a single stretch.
- Using the latest technology and Reckli Formliner has given the concrete new shape with texture finish on wall.
- With single concrete pour of 9m wall has eliminated joints in the concrete, making structure more sustainable and durable.
- The new form of concrete can be used anywhere for an aesthetic look and finish
- Interconnected, linear waterfront development with broad public access
- Encouraging use of riverfront greenway as a daily commuter path and recreational amenity.
- Demonstrating the connection between access, greenway development and market demand.
- Creating a coherent, visually pleasing order to the water’s edge.
- Creating a synergy between office, retail, residential and recreational use of key waterfront sites.
- Selecting the most imaginative development concepts and architectural designs.
- Establishing the riverfront as a front door to the city.
- Enhancing real value and competitive market advantages for private developers.
- Protecting and enhancing the natural riverfront environment.
- Documenting the ecological state of our riverfronts in order to preserve environmental biodiversity
- Preserving natural habitat.
- Preventing and, where possible, eliminating inappropriate uses and practices from rivers’ edge.
- Protecting existing natural areas from development.
- Reclaiming identity as river cities.
- Raising public expectations of what the city’s riverfront offers.
- Attracting people, investment, and the best aspects of urban living.
Concrete can be finished in this new form. The future belongs to such type of advanced construction techniques, which give concrete a new identity. It’s also important to understand that not only the designing of the concrete and structure is important but proper care and precautions must be taken during the execution with proper planning and use of resources. This type of construction has redefined Sustainable Construction where both the structure and the aesthetic aspect of concrete has been given equal importance.
This is just the beginning of such Sustainable Construction at the riverbanks of India, and after the success of this project, many such projects will be initiated in the country. Recently, the global advisory firm KPMG categorized Ahmedabad’s Sabarmati Riverfront Development Project under the 100 most innovative projects towards urban regeneration that make cities livable and sustainable. It is one of the six urban infrastructure projects in the country to be selected by KPMG.
- SFRDC www.sabarmatiriverfront.com
- HCP Design Consultant, Ahmedabad (main designer)
- RECKLI Formliner www.reckli.net
- JMC Projects (India) Ltd, Ahmedabad (one of the civil contractors)
- PRANAV Construction (Indian partner of Reckli for producing formliners in India).
- KPMG for statistical data
Manoj Didwania graduated from Dharamsinh Desai University, Nadiad, and has 10 years of experience and research on Advanced Construction, Concrete Technology, and Supplementary Cementious Materials. He has been part of Innovation Growth Program Organized by FICCI.