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.
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.
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.
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!
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.
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.