Precast Concrete Construction and India’s Way Forward
Precast Concrete Construction (PCCon) is an efficient construction paradigm, which enables parallel processing, employs industrialised production systems, and emphasises the hallmark of quality of work. It is one of the variants of the concept of Industrialised Building Systems (IBS), which involves the repetitive construction of standardised units, utilising standardised components, using automation and mass production concepts, with minimal wastage, maximum efficiency, and best quality possible. IBS systems necessarily involve thorough prior planning, employing appropriate designs, prefabricating various standardised components under factory conditions, transporting them to the site where required, and assembling them at the site using minimal, but efficient, interventions.
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- construction paradigm
- Industrialised Building Systems
- Ocean Engineering Department of IIT Madras
- L&T Construction
- precast building construction
- Hollow Core Slabs
- Indian National Academy of Engineering
- Precast Concrete for buildings
- Ministry of Housing
- Industrialised Building Systems
- Indian Institute of Technology Madras
- Prof. N.Raghavan
Precast Concrete Construction (PCCon) is an efficient construction paradigm, which enables parallel processing, employs industrialised production systems, and emphasises the hallmark of quality of work. It is one of the variants of the concept of Industrialised Building Systems (IBS), which involves the repetitive construction of standardised units, utilising standardised components, using automation and mass production concepts, with minimal wastage, maximum efficiency, and best quality possible. IBS systems necessarily involve thorough prior planning, employing appropriate designs, prefabricating various standardised components under factory conditions, transporting them to the site where required, and assembling them at the site using minimal, but efficient, interventions. The systems for the joints and connections between the various components become especially important to ensure proper functional and structural quality. The system also implies an aspiration for the least cost possible by leveraging mass production principles, automation, and standardisation. In this article let us examine the present status of PCCon in India, some examples from overseas, the various impediments holding up the success of PCCon, and what can be done by whom in our country to ameliorate the situation. PCCon is not new to India. It had been practiced for several decades, mainly for Industrial structures. The roofs used to be with precast concrete trusses folded plates and shells. Many innovative works have been carried out, for instance, the precast concrete folded plate roof in the Ocean Engineering Department of IIT Madras. Dr A. Ramakrishna, who was the Head of L&T Construction, was a pioneer and a great promoter of such works. Precast concrete girders have been a common feature in many bridge projects. Of late, precast concrete segmental construction has become a ubiquitous feature of metro viaducts all over India. However, what is of topical relevance here is the use of PCCon for buildings. Various systems for precast building construction and common features PCCon for buildings is generally practiced in the following broad forms: 3-D volumetric systems, slab, and wall panel system, framing elements system with columns and beams, and flooring systems mainly with Hollow Core Slabs. Apart from these, superior quality aesthetic architectural elements, particularly for facades, with intricate geometry, pleasing patterns, and exquisite finish which are possible only with PCCon are also prevalent. The first two are more commonly used for housing and the last two mainly for commercial and industrial applications. PCCon can be implemented both in urban and rural contexts. However, for rural settings locally suitable appropriate technologies can be adopted with non-load bearing applications such as internal partition walls, toilet pods, etc. Best results can be obtained with effective architectural interventions to take care of functionalities, sustainability practices, aesthetics, space utilisation, standardisation, etc. This method would be the best suited for mass housing when large volumes of construction are involved with a high degree of standardisation, with well-designed and executed precasting and erection systems, using good skilled labour, and with the availability of good lifting systems for erection, automated systems for precasting, etc. Good quality, high speed, overall cost economy, better construction-time safety, etc are usually the benefits of such practices. Advantages of the technology Nearly all components of building work are pre-manufactured in plant/casting yard and the jointing of components is done In-situ leading to a considerable reduction in construction time and many sustainable practices. The controlled factory environment brings resource optimisation, and improved quality, precision, and finish. The concrete can use industrial by-products such as fly ash, ground granulated blast furnace slag (GGBFS), micro silica, etc. resulting in improved workability and durability, while also conserving natural resources. With the inherent good finish of factory-made elements, plastering is not required. It helps in keeping the construction sites neat and clean and with a dust-free environment. Optimum use of water through recycling is possible. The use of shuttering and scaffolding materials is minimal. Construction in all weather conditions and better site organisation is possible, apart from better safety during construction. Essential requirements for making this technology successful Space for casting yard is required in addition to the site for actual construction. The project is not viable if the factory is located far away, requiring long transportation leads for the precast elements. Good quality access roads are also important. Setting up a casting yard requires time covering a few weeks depending on the project size and delivery schedule. The site should have adequate space for proper leveraging and functioning of cranes. It requires skilled labour and strict supervision. Plumbing and electrical services need to be pre-planned. Precast concrete construction is generally suitable up to Seismic Zone IV in the Indian context and for high rise structures special detailing provisions may need to be incorporated. Current status in India Potential for PCCon: The housing problem of India is a rather complicated issue considering the huge variations in socio-economic characteristics of the heterogeneous population, the variations in climatic conditions across the country, the large variations in the prevalence of locally available materials and locally appropriate technologies, the rural versus urban dichotomies, local preferences, and predilections for particular types of housing, etc. Given this, it is rather difficult to identify technologies for adoption across the board and prescribe the same for adoption and implementation on the large scales required. However, looking at the huge scale of the demand, the urgency associated with the need to address this demand rapidly, and the prior proven experiences in the country, PCCon can be identified as a prime candidate with the largest common denominator to serve the needs of housing judiciously. However, the unfortunate ground reality is that many architects and designers are not aware of the true potential of PCCon and how it can be leveraged to produce good functional and efficient products. The precasting factories: PCCon has been happening in India basically in two modes: One method being using precast elements manufactured in central factories, transported to the sites, and erected there; and the other method is setting up a dedicated precasting factory at the project site and erecting the elements immediately. One reason which could have contributed to this phenomenon was the dual excise duty regime earlier, which made ED applicable to factory-made components but not to site-fabricated components! In any case, some 40 to 50 precasting factories had sprung up all over India. Many conferences happened featuring PCCon. But lately, the market had a slump due to several factors and a few factories had to shut down, unfortunately. The industry associations: The precasting industry never really came together to form an effective Industry Body, until recently, a fledgling body called PSI (Pre-Engineered Structures Society of India)- earlier called PESSI- has come up. A flagship event called PEPSCON (Pre-Engineered and Precast Concrete Structures) conference is also being organised periodically. However, the industry has not made any significant progress jointly to be able to leverage common benefits from the other societal stakeholders. Governmental support: The Central Ministry of Housing & Urban Affairs (MOUHA) is coordinating many activities in allied areas, mainly through its arm BMTPC- Building Materials & Technology Promotion Council. The Government of India had come up with several housing-related schemes in the recent past, including the famous Housing For ALL, and BMPTPC plays a significant role in these activities. Various initiatives such as global housing technology challenge, light house projects, etc. are mainly targeting housing but PCCon is not a singular element in these activities and not many significant changes have taken place so far on PCCon. The Indian National Academy of Engineering (INAE) has also set up an Infrastructure Forum (in which the Author is also a member), which is in the process of compiling a Report on Housing and cataloguing in the process many issues related to PCCon. Available standards: PCCon, being a multi-nodal system with many diverse stakeholders need a system of common standards, specifications, and SOPs. The Bureau of Indian Standards has many specifications and codes of practice for related topics. Indian Concrete Institute had brought out the ICI Handbook on Precast Concrete for buildings– Indian Concrete Institute publication: ICI Bulletin 2016. However, this document has only limited coverage of Precast concrete construction and was the first step towards a proper handbook. For a full-fledged precast construction industry to flourish, apart from a comprehensive set of standards and specifications, a detailed handbook is required that sets up standardisation preferences for manufactured products, lays down detailed tolerances for various products for proper assembly at the site, indicates standard design procedures which would enable the construction industry to efficiently plan prefabricated structures systematically and choose available products for the best solution for a given problem, and has testing and acceptance standards for the manufactured components. The PCI design handbook of the Precast/ Prestressed Concrete Institute of USA is an excellent example of such a document and sorely needed in India. PCCon elsewhere in the world Many developed countries around the world have been using PCCon extensively for the last several decades. In the USA 8 per cent of total concrete construction is done using precasting. The major use of precasting is in parking structures contributing to 13 per cent of the market. Structural precasting contributes to 90 per cent of total precasting. 30 per cent of all housing in the US is using prefabrication technology. In the UK, 26 per cent of the total concrete production uses precasting. 45 per cent of precast concrete is used in housing projects. Stable economic conditions in the former Soviet Union helped in the rise of the pre-casting industry, with the market share of precasting being about 30 per cent. Many European countries, particularly from eastern Europe, have been using precasting systems as a preferred solution for housing. Precast concrete contributes to 10 per cent of housing in Germany and the Netherlands. 24 per cent of housing was constructed using precast concrete in former East Germany. 70 per cent of the total concrete construction uses precast construction in Finland. 74 per cent of this contributes to structural precast concrete. Efforts by the Housing Development Board of Singapore have enabled the growth of precast construction and precast systems have been used in Singapore for high-rise housing for the past 30 years. Fast-growing requirements for housing in Malaysia prompted the Ministry of Housing to adopt Industrialised Building Systems. To promote IBS, the official system there gives an IBS score for a construction project depending on the extent of prefabrication used, and the levy on construction is reduced depending on how high a score is achieved. In 2019 about 39 per cent of private sector development was with IBS and by 2020 about 50 per cent was targeted. In China, the average prefabrication level is about 10 per cent of all construction processes. Compared to all the above, in India, the share of concrete in construction, let alone PCCon, is still a very small percentage of the total volume. Incidentally, incredible stories emanate from China regarding the prodigious feats of broad construction to complete a ten-story prefabricated building in 28 hours, and other similar examples, though the construction is mainly of steel. Some time back Katerra had completed a completely furnished 124 sqM, 4-bedroom house in Saudi Arabia in just 48 hours! Main impediments for growth Lack of awareness of the features and advantages of PCCon among some of the key players in the industry such as clients/owners, architects and designers is a key issue. Mistaken beliefs such as PCCon is an elitist practice, that it requires extensive plant and machinery and skilled labour, that it is repetitive and monotonous, more expensive than conventional construction, the joints result in leakage of water during rains, the joints cause weaknesses in the structures, etc militate against ready acceptance of PCCon. The need for heavy initial investments, lack of availability of many manufacturers, poor condition of the access roads posing limitations on the transportation of large and heavy precast components, the earlier regime of higher taxation, lack of availability of extensive Standards, etc are also negative factors. Poor contracting practices bracket PCCon along with in-situ construction and do not make allowances for its special features such as heavy initial investments, the need for extensive initial planning to design and fabricate the elements much before site work starts, do not take cognisance of its multi-theatre operations (planning, designing, manufacturing, transporting, erecting, etc). Possible boosters The government: The government can promote large PCCon projects and make available plots for the same, ensure policy changes to allow PCCon for low-cost mass housing bids, and provide incentives for its use; encourage EPC models, etc. The nodal agency-BMTPC- can promote PCCon and identify agencies and processes for testing and certification of elements and connections like practices in Singapore, etc; set up skills training institutes; develop a rating system for buildings based on design, construction methodology, innovations, and quality; conducting awareness programmes among owners, architects, and designers. The Bureau of Indian Standards can develop a comprehensive handbook in association with the industry stakeholders. Owners/clients/architects/designers: They can support precast construction; use appropriate contractual formats for PCCon. Architects can develop good solutions for PCCon using modular planning systems, aesthetic designs; use BIM with good suitability for construction and facilities management. Academia/R&D: They can develop standards and codes for fully precast construction, develop systems and procedures for testing and certification, develop new technologies for lightweight concrete, develop new effective connection systems, particularly for high seismic zones and new joint sealing materials with good durability; teaching comprehensive precast construction and conducting training programmes. The precasting industry: Manufacturers and Erectors- can develop fully integrated systems from initial functional planning to commissioning; improve productivity and develop modern technologies. They should form an effective Industry Body that can take up their key issues at the right Forums, including liaising with the Government. The way forward There are many bright developments of late for PCCon. With the inexorable urbanising of the population, the need for affordable housing in urban areas is increasing quite rapidly. It is estimated that by 2022 the shortage in the urban areas will be around 45-50 million units. To close this gap the Central Government has come up with Pradhan Mantri Awas Yojana (PMAY-U) and several State Governments have also come up with their schemes for housing. Many members of the PCCon industry are well equipped to meet the challenges with sophisticated automated production plants, international technology, global technical tie-ups, and advanced delivery systems backed up by integrated supply chains, BIM platforms, and VR/AR systems, etc. Considering the huge potential for PCCon to meet the posed challenges, the entire construction industry should strive forth to develop PCCon and strongly lobby with the powers that be to encourage the same. All the country’s needs for affordable housing and modern infrastructure for housing and commercial structures can be met efficiently and economically on a rapid scale by PCCon. 3D Printing using Concrete is still in its infancy and yet to pose any significant challenge to PCCon. Let us look forward to PCCon gaining its due primary position in the future. For this to happen, all the stakeholders should come forth to expeditiously deliver on the expectations placed on them by the developing situations as catalogued above. That will be the dawning of a period of the golden era for Precast Concrete Construction in India. Amen! About the author: Prof. N.Raghavan is the Professor of Practice, Department of Civil Engineering, Indian Institute of Technology Madras. He is a member of the Board-Institute for Lean Construction Excellence (ILCE); ICI Task Force on Handbook for Precast Concrete Construction; and INAE Forum on Civil Infrastructure (Traffic & Transportation, Housing). He was earlier the head of hydro and nuclear power sector and underground works at L&T ECC and chief executive at L&T-Ramboll Consulting Engineers.