Chief – Content Development,
CE – Infrastructure – Environment
The ultimate win-win scenario!
Just imagine a world, where not only complex buildings are constructed quickly, efficiently, and cost effectively but they are done so in a manner that aesthetics and construction integration converge seamlessly to deliver greater site productivity.
Going a step further, this is no hallucination, because the individual inputs for this were innovated since a century and the evolution had been on track sifting back and forth driven by the demands of particular times. Monolithic construction is one such adaptation. Here a structure in which all the components like walls, slabs, staircases, sunshades etc are cast monolithically at one time using one ho-mogenous material that is concrete. Therefore the basic essential input for monolithic concrete construction is
– Highly workable concrete mix
– Pre-engineered formwork system
Monolithic Construction technology is a means to quality and productivity for turning out unprecedented volumes in terms of built form.
Nevertheless such scenarios of delivering complex functional and aesthetic built forms to be made possible, the need is of an integrated and technologically advanced construction industry, augmented by ‘as required skill’ workforce. And the need has to be imperative to all stakeholders, that is consultants, builders and owners that they have to be diligent in adopting best practices and innovative ideas to increase construction productivity.
This narrative deals with the evolution of this technology in terms of conception & need, followed by vagaries of demand flip-flop followed by creation of demand by urbanization and ultimately ending up today, as an essentiality on the grounds of “Health, Safety & Environment (HSE).
Let’s get started with how at all it struck our nation. Much as the trend has been in recent times- yes- it started with the courts!!
As dust particles continue to contribute to rising pollution levels, a Parliamentary committee decided to examine the issue of implementation of dust-free technology in the construction sector.
The Parliamentary Standing Committee on Urban Development decided to include Implementation of dust free construction with innovative technologies in India as an additional subject for examination, as per a Lok Sabha bulletin.
The decision taken to study the subject of dust pollution caused by construction activities came based on a recent report by IIT-Kanpur titled Source Apportionment Study of PM2.5 and PM10 which identified trucks and road dust as the largest contributors behind Delhi’s air pollution. The study having recommended a switch to Euro VI fuel norms became a matter of great concern for hapless public breathing this air and headache for all who will be bearing the brunt if such change in regulation.
The Supreme Court favoured imposing a fine of Rs. 50,000 on a daily basis on construction sites for generating high levels of dust in Delhi and the national capital region. While hearing a PIL seeking directives to curb rising pollution in Delhi and the NCR, a bench headed by Chief Justice of India T S Thakur had said
“You (governments) should impose recurring cost of Rs. 50,000 on daily basis…,” In December last, the Delhi government had served notices to eight major construction projects, including one of the Airport Authority of India, for flouting dust pollution norms.
The proponents of the projects have been asked to deposit environment compensation penalty of Rs. 50,000 each and take rectification measures. Earlier, 38 other projects were slapped with similar penalties.
The projects included upcoming shopping malls, extension of NIFT campus in Hauz Khas and construction of district courts.
MoUD – Takes the Call
Amid rising concerns over dust pollution, state-run construction major Central Public Works Department will shift to a new dust-free construction technology for all its major projects worth Rs. 100 crore and above.
Monolithic construction technology is being followed in countries like the US, the UK, Russia, Germany, China, Singapore and Malaysia among others. “CPWD will henceforth, adopt modern Monolithic construction technology for all major projects of Rs. 100 crore and above each, abandoning traditional methods of construction which are marked by several disadvantages,” said a statement by Urban Development Ministry, under which CPWD comes.
It is recognised for its “quick, quality, dust free construction” for large projects, the statement said.
The Urban development ministry under M Venkaiah Naidu (Fig 1) has approved the technology shift in the context of rising concerns over dust pollution and recommendation of the Standing Committee on Urban Development, it added.
The minister also took note of the observations of National Green Tribunal (NGT) and Supreme Court over the alarming levels of air and noise pollution in Delhi and other major cities of the country.
CPWD has executed large scale construction projects worth Rs. 2,301 crore in 2015-16, while its total works were to the tune of Rs. 4,988 crore in last fiscal.
The Surprise Element – Edison’s brainchild!
Aficionados of modern poured-concrete design would have been surprised when they heard Matt Burgermaster’s presentation at the 64th annual meeting of the Society of Architectural Historians (in 2011). Burgermaster described how Thomas Edison invented and patented in 1917 an innovative construction system to mass produce prefabricated and seamless concrete houses. Typically this style of architectural design and type of building technology gets clubbed by most to the European avantgarde of the early 20th century.
It is unknown to most that many Edison houses still stand in towns surrounding West Orange, New Jersey. It was here that Edison’s factory was located , which now is a National Historic Park and right on the park grounds stands a prototype of Edison’s concrete house.
“Edison’s one-of-a-kind system was patented for the purpose of building a single, repeatable structure without any parts, with a single act of construction,” said Burgermaster, “And, remarkably, 100 years later many of these houses remain standing.”
Burgermaster’s paper analyzed Edison’s invention of the single-pour system for concrete construction as a novel application of this material’s dynamic behavior and speculated on its role in the development of a type of integrated building anatomy that, perhaps inadvertently, also invented the idea of a seamless architecture!
The objective of providing a cost-effective prototype for the working-class home was the driver for this early experiment in mass-production becoming one of Modern man’s first attempts to construct a building with a single material.
Edison’s 1917 patent proposed a building-sized mold that leveraged the intrinsically dynamic capacity of concrete to form itself into a variety of shapes and sizes, limited only by the design of its framework. The invention’s potential efficiencies resided in the distribution of this material as a continuous flow through an entire building instead of being confined to the prefabrication of its constituent parts.
By physically integrating all interior and exterior building components and their associated functions of structure, enclosure, and infrastructure within a single, monolithic concrete cast, all aspects of assembly were eliminated. It was a whole without any parts – a building without joints.
This radical proposition — a seamless architecture — was built by Edison before it was conceptualized by the European avantgarde (such as Le Corbusier and the Bauhaus) with whom it later became associated. While they imagined concrete as a material without a history or author — one well-suited to industrialized modes of production — and aestheticized such au-tonomy and anonymity as a material truth, Edison’s single-pour system matter-of-factly proposed an alternative causal relationship between material and form says the researcher.
Its physical seamlessness was not a representation of architecture as an idealized, machine-made object, but was an effect of actual material behavior. As such, this technological invention not only delivered an innovative construction method, but also an alternative way of thinking about the material itself.
After Thomas Edison constructed the first monolithic concrete house in 1908, many varieties of the original plan were seen in houses, apartments, and finally churches.
In 1912 the American Sheet and Tin-plate Company completed 14 buildings of monolithic concrete t e, costing something over $130,000, and houses for 74 families of workmen in its mills. Each house cost only $2,750. The structures were provided with all the conveniences of the period and it added attraction to living for the tinplate company’s employees in Gary, Indiana. The detached houses, 2 stories in height, contained shower baths, water pipes, drains, and guttersall of concrete.
Another attempt at monolithic concrete construction was initiated in 1911 when an entire church was built by casting concrete walls on the ground. Although each wall was 200 feet long and 3 stories in height, the entire casting was accomplished in a single day. After 48 hours each wall was raised from the in-side to its permanent vertical position by means of a gasoline engine. No forms were used in this project, except for the wooden jack platform, which was re used (see Fig. 2)
“I don’t think this research on Edison’s invention offers grounds for anyone to call those European architects copycats. As anyone in a creative field knows, sometimes these things are just in the air and like minds can be said to think alike,”
“Edison’s approach to invention remains as radical today as it was a century ago.
It’s been very interesting finding this body of work and making it visible. My hope is that this ‘lost’ chapter in the early history of concrete construction will demonstrate that Edison not only left a mark on the field of architecture right here in our back-yard, but that his unique ap-proach to design thinking offers a model for how today’s architects and designers can add value to the process of technological problem-solving.”
Evolution & Spread
Besides Edison there was parallel ongoing activity in the field of concrete making it difficult to pinpoint who was ahead or behind.
The late nineteenth century saw the parallel development of reinforced concrete frame construction by G. A. Wayss in Germany/ Austria, by Ernest L. Ransome in the United States, and by Francois Hennebique in France.
In the 1870s Ernest L. Ransome’s stone company was producing concrete blocks as artificial stone in San Francisco. Ransome’s major work was the Leland Stanford, Jr. Museum at Stanford University, the first building to use exposed aggregate. He put up several industrial buildings in New Jersey and Pennsylvania. The construction of the Kelly and Jones Machine Shop in Greensburg, Pennsylvania during 1903-1904 is attributed to him.
In 1904 The Ingalls Building, a landmark structure in Cincinnati, was built using a variation of the Ransome system. It was the first concrete skyscraper, rea-ching 16 stories (210 feet) and was de-signed by the firm of Elzner and Henderson
Meanwhile right across the Atlantic, Francois Hennebique, in Paris, started building reinforced concrete houses in the late 1870s. He took out patents in France and Belgium for the Hennebique system of construction and established several franchises in major cities promoting the material through conferences and developing standards within his company network. Most of his buildings (like Ransome’s) were industrial.
When at its’ peak, Hennebique quota was 1500+ contracts annually (Collins, 1959). He was major driver for acceleration of reinforced concrete construction in Europe.
The increasing importance of Monolithic construction
In the last 50 years, a tremendous amount of knowledge has been accumulated from research, design and construction of precast/prestressed concrete structures. Over the years these structures have performed very well and have shown excellent durability even when subjected to severe earthquakes.
With advancements in the quality of materials, workmanship and new technologies, precast concrete has become a very modern, high tech industry.
Hence, for the past half century, precast/prestressed concrete construction has been marketed on the basis of
– Savings in materials and labor,
– Improved quality of product and workmanship
– High speed in construction.
The high degree of success for this method of Monolithic construction was therefore dependent on economic criteria for contractors considering equivalent desired quality the precast technology offered. In fact it became a high quality low cost deliverable!
Today’s Concerns Go beyond Economics
Today, this technology has added another feather to its cap. The additional compelling reason for using precast construction comes from an erstwhile non critical and attention drawing being environmental & logistical. In recent years, precast concrete technology besides economic aspects is seen more the important perspective of its impact on social and environmental issues.
With heightened awareness of traffic congestion, environmental pollution, natural resource depletion and accompanying social problems, precast concrete has come to be seen as not only preferable but the best alternative to avoid in situ construction, especially when it comes to sites in large congested urban areas.
In today’s context, a great amount of rebuilding the urban infrastructure is in-volved and these are within dense urban areas. Renovation, rehabilitation or rebuilds can be techno commercially and environmentally feasible only by such technologies and techniques like ‘monolithic’.
It is these reasons that had turned policy makers to make technology shifts all over the world. The powers that be need to diligently implement adoption of precast concrete as a powerful weapon in mitigating these problems that can cause long term detrimental effects to HSE.
Contractors have long recognized that conventional in situ construction in large cities has resulted in excessive Labor costs due to time lost in transporting workers to and from the project site through congested vehicular traffic. This loss of time is further compounded by the accompanying need to transport materials, equipment, tools, and other items to the construction site, all of which add vehicular traffic to an already congested roadway situation.
Firstly high land values in urban centres, construction sites in large cities tend to be relatively small which means limited working space for the project’s resource accommodation and operation. This means extremely less land space for storage of materials and maneuvering of equipment, requiring larger number of trips to/fro the site to maintain deliveries of material and equipment. The same applies to the removal of construction debris, which needs to be done as per regulatory norms.
Currently, in case of sites involving in situ construction there is invariably ex-treme activity characteristic of conventional in situ works causing high degree of dust, noise, air pollution, traffic congestion, and a host of other disturbances hindering normal citizen activities. all of which present constant nuisances to the people living in nearby buildings, as well as aggravations to motorists driving through the area.
Moreover, statistics indicate that presently, 50 percent of the world’s population of six billion people lives in large cities. Also by the year 2050, an estimated that 67 percent will be living in big cities. These are indicative figures but the trend is definitely showing alarming numbers pouring into cities. The logical take away from this trend is sporadic construction activity in the midst of a combined effect of high rate of pollution and traffic congestion.
And, mind it, this construction is in a plotted land generally involving demolition of existing built structure to put in place a higher occupancy capacity one by vertically expanding. This will warrant the material, equipment and manpower to maneuver through limited space to reach as well as operate on site. Government officials are becoming conscious of disturbances to citizens in the area that often leads to growing complaints of traffic congestion and air quality.
A God Sent Savior
Monolithic construction in this context is nothing less than a god sent savior. In precast concrete construction, prefabrication of structural and architectural concrete products is performed at more accessible sites away from such congested urban centres, where the site for new building to be raised is situated.
Thus the Wall panels, beams, columns, slabs, stairways, architectural façades, and other components are fabricated un-der controlled conditions in areas (workshops & fabrication yards) with adequate operational and storage space. The precast components are formed with high strength, durable steel and high quality concrete in steel or fiberglass molds, which provide for extensive repetitive and economic re-use commensurate with today’s standards.
When these structural and architectural components are completed, they are temporarily stored waiting onward transport directly to the project site for erection.
Based on sequential erection plan the needed workers, materials, equipment, and other items are easily transported to and from these prefabrication sites. Thus these finished components make only one trip to the construction site through the congested city traffic.
Furthermore, the precast components can be transported during offpeakhours, such as in the middle of the night, when vehicular traffic is at its lowest volume.
Exterior façade units can be pre-painted at the pre-casting plant to offset the need for exterior gondola or scaffolding and painting at the job site.
This by itself is a demonstration of how efficient monolithic construction is when compared to convention in situ one. Wherever the possibility exists any contractor will not opt for conventional in situ technique. The disadvantage obviously are that if these very components were fabricated at the project site, it will mean repeated trips to/from the site to transport workers, materials, and equipment as well as the removal of debris, to accomplish the same results. And all this during working hours!
The distinct advantage of controlled conditions at workshops in case of precast concrete construction technology provides both economic opportunities as well as physical advantages since it is possible to conveniently pretension the concrete structural members in the precast manufacturing process. By this method there is great reduction in the material as well as labor requirement for equivalent structural strength parameter as compared to any other conventional construction method. There are many a classic example of how this technology has proved itself. A few examples are illustrated here to show different advantages in tangible terms in form of material savings, high strength , superior seismic tolerance besides speed of construction.
The 33-story Ala Moana Building in Honolulu, Hawaii
Ala Moana Building(33-story) in Honolulu, Hawaii, which was built in 1966 at a time when the precast concrete industry was growing strong, has stood the test of time. The immaculate Ala Moana Building is an all-precast, pre-stressed concrete building (see Fig. 3).
The framing of this 33-story building consists of precast, prestressed concrete floor slabs 31/2 in. (89 mm) thick, with an in situ composite topping 21/2 in. (63 mm) thick, for a total slab thickness of 6 in. (152 mm). For the floor loads and spans required, a conventional floor slab would need to have a total thickness of 9 in. (229 mm).
Total savings in concrete for the floor slabs alone on this building would be equivalent to a block of concrete 8.34 ft (2.54 m) thick, covering the entire footprint of a typical floor.
Not only would this result in considerable savings in material and costs required for the column, beam, bearing wall and foundation support system but with the height restrictions in this area, one extra floor of saleable apartments can be realized within the cumulative void area due to reductions in floor slab thicknesses.
An Aircraft hangar structure
Considering a diverse case validating seismic tolerance and cost savings is that of an Aircraft Hanger where, the substitution of alternative precast designs for conventional in situ construction has resulted in savings of as much as 55 percent of the concrete quantities and 40 percent of the reinforcing steel requirements. (see Figs. 4 through 6).
An aircraft hangar designed for Seismic Zone 3 and a wind velocity of 155 miles per hour (250 km/hr) was done by pre cast concrete technology. The contractor awar-ded the bid for the project went for a value engineering design involving precast concrete construction. In the process he could save costs as also increase construction speed (see Fig. 4 – Typical cross section of aircraft hanger) .
In the value engineering process, an alternate design utilizing a precast segmental folded plate framing system resulted in substantial savings in materials. For instance, concrete quantities were reduced by 55 percent and reinforcing steel by 40 percent. Formwork costs were virtually eliminated by precasting at ground level with a short, fixed, folded-plate mold capable of casting various incremental sizes (see Fig.5).
This aircraft hangar was completed on schedule with major cost savings. Over the years, this structure has successfully withstood several severe hurricanes of wind velocities exceeding 155 miles per hour (250 km/hr) and seismic occurrences of magnitudes as high as 8.1 on the Richter Scale without damage (see Fig. 6a,b.c).
Materials savings using precast/pre-stressed concrete.
In the case of typical floor slabs, the combination of precast, pretensioned slab soffits and a composite in situ topping can result in savings over conventional in situ construction of about 28 percent in concrete quantities and about 45 percent in steel requirements (see Fig. 7a).
In the case of conventional in situ beams, savings of 60 percent in concrete quantities and 65 percent in steel requirements can be realized by the use of precast, prestressed concrete technology (see Fig.7b). The above savings vary ac-cording to span lengths and loading requirements.
In general, longer spans and higher live loads result in larger material savings when precast/prestressed components are employed.
In the last 40 years, precast concrete structures of both low- and high-rise buil-dings have proven their capacity to withstand major earthquake occurrences in Manila, Philippines; Kobe, Japan; Guam (United States); and other regions throughout the world with minimal or no damage.
In Tokyo, Japan, where the world’s severest seismic design criteria exist, many precast concrete high-rise buildings ranging from 35 to 43 stories constructed have functioned very well with respect to seismic tolerance. Major advances in the development of reliable mechanical connection devices including “fail safe” connections for precast members are a novelty as these provide monolithic and full continuity in structures. Extensive engineering research with laboratory testing have created precast concrete structures situated on the Pacific-Rim to successfully withstand most severe earthquakes. The knowledge bank in behavior and design of precast/pre stressed concrete structures in seismic areas is greatly reliable.
In Dalian City, China, a 43-story high-rise office building designed for seismic activity is shown in Figure 8. A 39-story precast, prestressed concrete building, designed for Seismic Zone 4, in San Francisco, California is shown in Figure 9. These are credible examples of material savings in actual high-rise buildings constructed by this technique.
Dalian Xiwang Building, Dalian City, China
This building is located in a high seismic zone and, therefore, savings in materials will result in lower building dead weight and subsequently lower shear forces due to seismic loads.
The Table ‘A’ shows substantial savings in concrete and steel quantities by using precast/prestressed concrete technology.
The Nett Gain of Precast/Prestressed Monolithic Technology
The direct inference of lower consumption translates into not just direct but also multitude of indirect benefits. So is the case with this technology. The use of lesser construction materials directly lowers building dead loads, reduces earthquake forces impacting the structures, thus saving structural framing and foundation support materials as well as costs.
Many take aways!
The advantage and actual overall benefits of a technology today is not measured in immediate upfront gain in terms of reduction in the consumption of materials such as cement, stone, sand, steel, timber, formwork etc. The overall gain is to be measured by accounting for energy saved due to reduction in energy employed in the mining, manufacturing and processing of these raw materials added to costs saved by reduction in the air pollution that will have accompanied the use of this energy. As a guideline one can take is that one ton of cement manufacture is responsible for approx. one ton of Carbon dioxide (a GHG) emission into the atmosphere.
Besides, savings in construction materials directly mean lesser depletion of all natural resources that get consumed to produce the construction material and during construction process. This includes minerals(limestone, gypsum etc), fossil fuels (coal, oil ,gas etc) and similar items which will be saved since all these get used in the mining, manufacture, transportation and installation of construction materials.
Similarly timber, largely consumed in the conventional in situ construction process for temporary bracing, shuttering, forming, dunnage etc too will be largely reduced leading forest conservation.
Material reductions result in lower traffic impact on the highways during the construction phase of the building project. This means reduction in highway maintenance costs and the associated materials and energy required for re-pairs. Less of Road repairs is great relief to commuters in terms of nuisance and fuel wastage by traffic congestion coupled with engine idling as well as air pollution.
Lowers Carbon Footprint
Construction sector is a major contributor of Greenhouse Gases (GHGs) and ethically has the responsibility to control by technology as well as best practices wherever possible and innovating means to curtail its carbon footprint.
Precast concrete construction, definitely results in less green house gases than in the case of conventional in situ construction. Fortunately since it does provide ample economic advantages the technology will be preferred option to all stakeholders. While it has this inbuilt economic incentive to be the builder’s choice, stricter environmental regulations on pollution are also making this technique to be a credible choice.
In a nutshell the need is to utilize al-ready available existing engineering know-ledge and construction technology as well as the experience to develop more economical means of safe construction practices that consume less natural resour-ces, energy and labor.
The skillful and efficient use of construction materials will result in lighter, stronger, more earthquake resistant structures. It is bad enough that catastrophic earthquakes cause building collapses, heavy loss of life and multiple injuries. However, it also puts an added burden on our ecosystem in terms of further depletion of natural resources as well as the addition of greenhouse gases generated in rescue operations, demolition, clean up of debris and the reconstruction that follows.
Today, an increasing demand for higher quality construction, trend towards the adoption of more labor-efficient designs and the growing use of prefabricated products and pre-assembled units in construction has set in to contain costs while maintaining quality.
As new building laws are progressively getting enacted that lay down minimum buildability scores based on “principles of standardization, simplicity and single integrated elements to achieve a buildable design.” Standardized factory cast concrete components erected on site with simply executed connection details in repetitive grid layouts are graded to significantly higher buildability scores. These are getting manifested everywhere as the demand is for standardization to increase efficiency in terms of productivity, less labor intensity, higher strength structures to face natural calamities and stress on HSE. These factors have made construction process to look out for innovation in materials and technology for production cum erection.
Where are we vis-a vis the World?
To gauge this, I restrict myself to just Singapore’s call for newer methods, Hongkong’s expert opinion and plan on innovative precast technologies to stress India’s need to gear up by real work not paper policies. Nevertheless to get the right feel, there is presented an Indian institution’s work on monolithic concrete constructions alongwith a construction company’s tryst with these projects. The sequence is:
– Singapore – Pressing for Game changing technologies
– Hongkong – Full steam on Precast / Prestressed Monolithic concrete
– BMTPC – lays down guidelines for Monolithic tech & pilots the cause
– Private Construction using monolithic concrete construction technology in group housing
Construction sector to adopt “game-changing technologies” in Singapore
In Singapore it was proposed that developers who successfully bid for projects on selected government land sales sites will have to adopt more productive construction methods by the end of 2014.
These techniques can yield manpower and time savings of between 35 per cent and 50 per cent over conventional methods, as per National Development Minister Khaw Boon Wan in (Fig.10)
“We need game-changing construction technologies to boost our construction productivity and reduce our reliance on construction workers,” he said.
One of the methods is to use “prefab” construction, in which complete flats or modules of multiple units, complete with internal fixtures, are manufactured in factories. They are later assembled on site like lego blocks.
This relies on building components made in a factory, “thus reducing the need for workers, and cutting down on noise and dust at the construction site”, said Mr. Khaw of the method called prefabricated pre-finished volumetric construction.
Another method involves the use of cross laminated timber, a multi-layered wood commonly used in Europe, which meets the same fire safety requirements as concrete and steel. Usually used for the construction of walls, lift shafts and floors, it can also support heavier loads than sawn timber, and is lighter than concrete.
Among the first to use the new prefab method here will be a 10-storey building extension of the Crowne Plaza Changi Airport hotel, while Nanyang Technological University’s upcoming sports hall will be built using cross laminated timber.
To facilitate the push for these “game -changing technologies”, the Building and Construction Authority will provide funding support to those who adopt them and provide training to build up expertise in the area.
“The desired outcome of these efforts is for our construction industry to be cleaner, quieter and faster, without compromising on safety and quality.” says Mr.Khaw.
PPVC – A Game Changer?
“Prefabricated Prefinished Volumetric Construction (PPVC)” is one of the game changing technologies that support the ‘Design for Manufacturing and Assembly (DfMA) concept’ to significantly speed up construction(See Fig. 10a & b).
“Prefabricated Prefinished Volumetric Construction (PPVC)” means a construction method whereby free-standing volumetric modules (complete with finishes for walls, floors and ceilings) are .
- Constructed and assembled; or
- Manufactured and assembled,
In an accredited fabrication facility, in accordance with any accredited fabrication method, and then installed in a building under building works.
Benefits of Using PPVC: To raise construction productivity and fundamentally change the design and construction processes, BCA encourage the industry to embrace the concept of Design for Manufacturing and Assembly (DfMA), where con-struction is designed such that as much work may be done off-site in a controlled manufacturing environment as possible.
PPVC is one of the game changing technologies that support the DfMA concept to significantly speed up construction. It can potentially achieve a productivity improvement of up to 50% in terms of manpower and time savings, depending on the complexity of the projects. Furthermore, dust and noise pollution can be minimised as more activities are done off-site. With the bulk of the installation activities and manpower moved off-site to a factory controlled environment, site safety will also improve.
Mandated Use of PPVC: The use of Prefabricated Prefinished Volumetric Construction (PPVC) is mandatory for selected non-landed residential Government Land Sale (GLS) sites from 1 Nov 2014 onwards. Further details on the mandatory requirement are stipulated in the Code of Practice on Buildability 2015.
PPVC Acceptance Framework: To ensure that the different PPVC systems being used at the mandated development sites are reliable and durable, BCA has set up an acceptance framework consisting of building regulatory agencies as well as industry experts to ensure that the design and materials used are robust and can meet the minimum standards set.
The PPVC acceptance framework consists of two parts:
- Building Innovation Panel (BIP)
PPVC suppliers and manufacturers who intend to supply their PPVC systems to be used at development sites where PPVC is mandated must first ensure that their PPVC system and the in-built bathrooms (if any) to meet the PPVC performance requirements. Performance requirements are per Code of Practice on Buildability 2015.
PPVC suppliers and manufacturers are required to submit their applications and proposals to the BIP ac-cording to the PPVC checklist and in-built bathroom checklist with documents as
- Evidence of compliance with co-des of practice (Singapore or overseas);
- Documentary track record of im-plementation overseas;
- Material or product specifications;
- Quality certifications or test re-ports by accredited laboratories;
The proposed PPVC systems are subjected to the evaluation and acceptance of the BIP; thereof In-Principle Acceptance (IPA) are issued to the PPVC supplier / manufacturer.
- PPVC Manufacturer Accreditation Scheme (PPVC MAS)
In addition, the PPVC systems production facilities which have been accepted through the BIP will be required to be accredited under the PPVC MAS. This is managed by the Singapore Concrete Institute (SCI) and the Structural Steel Society of Singapore (SSSS) an effort to promote greater self-regulation by the industry. The accreditation criteria were join-tly developed by SCI, SSSS and BCA.
The HONGKONG story – From the horse’s mouth.
An Interview with this Productivity Expert goes somewhat like this,
When was precast concrete adopted in Hong Kong? How does the use of precast lead to higher productivity and quality in Hong Kong?
Before the 1980s, Hong Kong was using the conventional construction system, which posed many problems. These included water leakage issues, high maintenance cost and poor quality concrete finishes. It was also labour intensive with associated safety and environmental concerns as there was extensive use of timber materials for temporary works.
By the mid-1980s, post-installation of precast facades was introduced in public housing projects. Beginning the early 1990s, Hong Kong adopted the semi-precast construction system and combined it with the pre-installation of precast facade construction method.
There are many advantages to the semi-precast construction system, namely.
The use of precast elements reduces in-situ concreting activities and substantial wet trades on site. As it only involves assembly of precast elements and installation of panel formwork with small amount of concreting works, timely completion of the construction project is ensured. Furthermore, it is less affected by inclement weather. Upon completion of the structural frame of building blocks, other works such as external finishes and window frame installation can be done concurrently, which helps to mitigate critical path activities and programme delays.
Better Quality to End User
Quality is assured as precast elements are prefabricated at factories using the factory management system, which requires a tighter tolerance to ensure better workmanship. Water leakage is-sues are also eliminated through the monolithic casting of the facade with the floor slab, including the steel system formwork. Window frames are cast at the factory which also helps minimise the water leakage problem, thus reducing long-term maintenance costs. In summary, the precast production process can be closely monitored in a factory with a team of trained quality control personnel before the product is delivered.
Enhanced Health & Safety for Workers
The semi-precast construction system is much safer because it can reduce a large amount of work, such as reinforcement fixing, formwork erection and concrete pouring at height at construction sites. The steel wall form design provides a safe working platform for workers.
India’s Work – Monolithic Construction Portrayal
The intent here is to draw attention to fill gaps that exist in India’s approach and the world including equipment cum automation degree.
Government Sector – BMTPC’s Monolithic Concrete Construction System Using Plastic- Aluminium Formwork
This system, replaces traditional column and beam construction by an all walls, floors, slabs, columns, beams, stairs, together with door and window openings being cast in place in one operation at site using specially designed, easy to handle (with minimum labour and without use of any equipment) modular form work made of Aluminium Plastic composite. As per BMTPC literature using the formwork system, rapid construction of multiple units of repetitive type can be achieved. (See Profile)
Example of Private Sector Work
Portrayed here is a Monolithic concrete construction sequence presented by a private Indian construction Co. P. G Setty Construction Technology Pvt Ltd at Green Building Congress – 2014 Seminar. The structure has all the components like walls, slabs, staircases, sunshades etc cast monolithically using concrete.
The Essentials for Monolithic Concrete Construction are a Highly workable concrete mix, Pre-engineered formwork system and Reinforcement
Construction Sequence of Monolithic Construction
(See Figures 13 to 16).