PRECAST CONCRETE TECHNOLOGY - A BOON FOR INNOVATIVE ARCHITECTS

PRE-Cast and PRE-Fabricated are terms which have been in use in the construction industry since the beginning of human civilization. The earliest examples of use of pre-cast components in construction were the Adobe dwellings in the river valley civilizations of Mesopotamia. Pre-Cast Sun-Dried Bricks were mass manufactured by the Sumerians from clay as the principal material, sand as the aggregate, straws for reinforcement, water for mixing, and the natural heat of the Sun for baking into building blocks. Other components like half-round drains, roofing and flooring tiles and decorative embellishments soon followed. Similar mass produced pre-manufactured building components were also found to be used in the ancient dwellings of the Indus Valley civilizations of Mohinjo Daro and Harappa. Subsequently, too the construction industry was regularly using pre-cast concrete hume pipes, septic tanks, pre-cast ferrocrete water tanks, building blocks, paving blocks etc.. So, PRE-CAST construction is not really NEW.

Why then, is there a fresh excitement in our field of building construction about Pre-Cast and Pre-Fab technology ? The answer lies in the evolution and new technology developments in Concrete as a material for Pre-Casting and Steel as the material for Pre-Fabrication. These, combined with the increasing demand of the three fundamental requirements of the construction industry -  Speed, Quality and Economy – has resulted in Pre-Cast Concrete and Pre-Fab Steel components becoming a big boon for Architects.

While pre-fabricated pre-engineered Steel structures have become hugely popular in Industrial building construction for the same three reasons, the development of a wide variety of heavy load-lifting tower cranes and special transport vehicles with heavy load bearing capacities has resulted in Pre-cast Concrete technology coming in vogue.

Parallel advances in Industrial engineering, manufacturing equipment, smart management and globalisation has brought pre-casting to our doorstep as a viable option to conventional construction. For innovative Architects, factory manufactured, pre-cast, pre-stressed and pre-designed concrete building components of a highly superior quality have opened up interesting avenues for outstanding architectural designs that comply with the primary demands of Speed, Quality and Economy, with Durability and Environmental friendliness as a bonus. How does Pre-casting achieve these objectives ?

SPEED  -  Projects can be completed in a much SHORTER PERIOD OF TIME  in comparison with conventional construction technology. Manufacturing of Footings, Foundations, Columns, Beams and Slabs can be started in the Factory well BEFORE the long official approval process, and nearly 30 % to 50 % construction can be READY in the factory stock yard by the time excavation and site development commences on site.

QUALITY -  As a Factory manufactured product made horizontally at a human work-top level under expert supervision - in the best of computer controlled environments - the QUALITY of Pre-Cast Concrete is HIGHLY SUPERIOR to any in-situ Concrete work. Grades of Concrete are M-30 to M-60  and, there is virtually NO Honeycombing or casting defects. Surface Finishes are good enough to eliminate the requirement of Plastering

ECONOMY  - Economy in construction Cost is primarily due to FIVE important factors –

1)              Faster construction reduces the time period for Returns on Investments. The building can be USED much earlier.

2)              Economy in Cost due to virtually ZERO WASTAGE in Steel and Cement – 100 % wastage is Re-Used & Recycled in the Factory.

3)              Economy in Cost due to MINIMAL MANPOWER on site, and lesser supervision need.

4)              Economy in Cost due to ZERO REJECTION – No re-work, No testing. No delays … Only QC-tested products are used.

5)              Economy in Cost due to SAVING IN PLASTER, No ACP.  No Cladding … Only Painting is adequate as external finish.

Imagine your building construction project where there is NO need to check the quality of Raw Material… NO Erection of Scaffoldings… NO Carpentry or Form work… NO Mixing, Pouring, Vibrating, or Curing of Concrete on site … NO Wastage … NO Honeycombing … NO Re-work … NO Debris… NO Congestion… NO Pollution… ?

Besides these obvious attractions, if your project can be completed with HIGHLY SUPERIOR QUALITY of workmanship and finishes, in HALF THE TIME that a conventional construction process would need, and that too at a LOWER LIFE CYCLE COST than that of conventional construction, what more could you ask for? The advantages of pre-cast concrete buildings are multi-fold.

For Architects, the mere possibility of providing large span RCC slabs – say 12 to 15 Meters in length – WITHOUT any Columns or Beams in the interior, or Large Wall Panels with high precision openings for doors and windows, Arches, 3-dimensional surface moulds, Circular and angular apertures and a wide array of ready-to-use façade elements is exciting enough. Add to these benefits, a zero-defect high grade (M-40 or M-60) concrete  with razor sharp edges and corners and NO requirement of plaster work, the choice becomes a certainty.

The advantages of receiving such factory manufactured components on an uncluttered construction site and assembling them in almost half the conventional time span of construction cannot be over emphasized. The ONLY adjustment or change in the present pattern of working that an Architect may have to do, in return for these benefits is 

(a) Design with a modular structural discipline that is conducive to mass manufacturing and 

(b) Provide the complete building design with all details and dimensions well in advance to enable manufacturing during the time a project site is being prepared or during the time the project is being approved by the local Authority.

To cater to the present trends in contemporary façade design, the present speed of construction demanded by a highly competitive market, and the growing demand of highly superior quality from the clients, Pre-cast concrete becomes a viable option for Architects.

Research and prospective further developments in concrete construction technology are even more mind-boggling.

Here is a sample of some amazing new developments in Concrete on the horizon :

a)              Intelligent Concrete- Radio Frequency Identification Devices – RFIDs buried in benign concrete can feed back performance data from completed structures, they can even warn of overloading and stress. Readable tags can contain vast banks of data and drawings and auto-alerting mechanisms for 100 % safety of users.

b)              Photo-engraving – by using retarding techniques, precast components can carry detailed photographic images and displays, and intricate textures can be engraved.

c)              Carbon Fabric Reinforcement – the use of textile fabrics opens up the prospect of a new generation of ultra thin sections – Imagine a 50 mm thick concrete slab !

d)              UHPFRC - Ultra high performance fibre reinforced concrete admixtures like Ductal and Ceracem – for use in light weight, super strong, thin and flexible concrete.

e)              Translucent concrete– No Architect can resist the appeal of a translucent precast concrete wall panel – or a fine custom designed grille finer than the best in marble.

f)               Self-cleaning pre-cast surfaces – the addition of titanium dioxide means that concrete surfaces can remain free of dirt and microbial growth. White concrete will stay white for centuries. Moreover, self cleaning concrete will help to reduce nitrous oxide fumes in urban environments, and will be a 'green' product to use.

g)              Thermal control in concrete wall panels by embedded heating elements or cooling fluid conduits as in refrigeration panels and heated glazing.

In conclusion, Pre-Cast concrete construction technology is the solution to many demands of the industry today. For Architects, especially for the innovative ones experimenting with futuristic digital and fractal architectural façade designs, it is a boon.

by-Rajiv Raje                  

Ar. Rajiv Raje is a Senior Architect, Planner based in Pune. He has worked on numerous Institutional and Industrial Projects. He is actively involved in City Development issues. He has a first hand experience regarding Precast structures being associated with Precast India Pvt.Ltd, a company manufacturing precast products, in the capacity of Consulting Architect.