Ultra-high performance fibre-reinforced concrete is considered the core for building the future of any nation. This high performance material allows the construction of sustainable and economic buildings with an extraordinarily slim design. Its high strength and ductility makes it the ultimate building material, writes A Shivkamal.
In the 1980s, when China wanted to embark on a large-scale housing programme for its ever-expanding cities, its engineers turned to ultra-high performance fibre-reinforced concrete, which was developed through the latest innovation back then. China’s adoption of ultra-high performance fibre-reinforced concrete was so successful and quick that the technology found its way into other infrastructure projects, such as grade separators, sea bridges, and public amenities across that nation. The Chinese soon discovered a manifold uses in the technology. These days, the Chinese are building highways and roads with ultra-high performance fibre-reinforced concrete (pre-cast beams/piers, walls, road surface) at the core.
Experts attribute the success of China’s massive infrastructure building over the last two decades to the extensive adoption and the use of ultra-high performance fibre-reinforced concrete by the country’s administrators. The public sector as well as the private sector was successful in using ultra-high performance fibre-reinforced concrete for construction.
Fibre-reinforced concrete in India
“The evolution of ultra-high performance fibre-reinforced concrete has been a boon to the construction industry. Endurance, ability to withstand pressures, durability and stability are some of the basic characteristics of ultra-high performance fibre-reinforced concrete. Some of the most advanced countries have been using ultra-high performance fibre-reinforced concrete in all public infrastructure projects. Unfortunately, India was late in adopting ultra-high performance fibre-reinforced concrete in construction because the ecosystem was yet to evolve,” points out NG Somashekar, a retired chief structural engineer from Central Public Works Department (CPWD).
However, in the last 15-20 years, India has made rapid progress in terms of adopting ultra-high performance fibre-reinforced concrete. The CPWD, National Highways Authority of India (NHAI) and other infrastructure development agencies have mandated the use of ultra-high performance fibre-reinforced concrete in all projects from two perspectives – completion of project in time and durability. Even the state governments have mandated the optimum use of ultra-high performance fibre-reinforced concrete in all construction projects.
Ultra-high performance fibre-reinforced concrete is a type of reinforced concrete with exceptional performance. Its mix design makes use of superplasticisers, specific types of aggregate, ultrafine particles and fibres (metal or polymer).
The presence of fibres and the tensile performance make passive reinforcement unnecessary. Concrete of this type has exceptional performance: Very good workability, compressive strength of between 150 and 200 MPa (1.5 to 2 tonne per sq cm) (the strength of ordinary concrete is 35 MPa); very high durability (which means it can be used in very aggressive environments) and high ductility (it is deformed prior to failure).
A quantum leap in concrete technology
“The Ultra-High Performance Concrete (UHPC), with its high compressive strength of more than 200 MPa and an improved durability, marks a quantum leap in concrete technology. This high performance material offers a variety of interesting applications. It allows the construction of sustainable and economic buildings with an extraordinarily slim design. Its high strength and ductility makes it the ultimate building material, for eg, bridge decks, storage halls, thin-wall shell structures, and highly loaded columns. Due to its outstanding resistance against several kinds of corrosion, it is deemed suitable for new fields of application where concrete has not been considered viable before. To make use of its superior properties, special knowledge of production, construction, and design is required. Fortunately, we now have engineers with the right knowledge,” explains Mahesh Rangarajan, Managing Director, Uttara Constructions, a leading real estate developer from Bangalore.
The real estate companies have been successful in delivering homes in time to their customers with the introduction of ultra-high performance fibre-reinforced concrete in buildings. This has further helped the real estate companies improve their performance as well as enhance the customer satisfaction levels.
“A decade ago, it was not possible to adhere to the timelines of delivery period of homes. The construction was through several phases and there were unforeseen delays from the builders. While we had our own construction teams, most of the times, they were outsourced to contractors, who neither had the right technology nor any idea about ultra-high performance fibre-reinforced concrete. This led to unnecessary delays in handing over homes to the customers and cost overruns. This impacted the image of the company as well as project delivery schedule. Now, we do not suffer from such problems because we select partners and contractors, who are adept at using ultra-high performance fibre-reinforced concrete in construction,” Rangarajan adds.
Now, even leading government agencies have incorporated ultra-high performance fibre-reinforced concrete in infrastructure works. Since the end of the 18th century, when metallic bridges first began to be built, up to the second half of the 20th century, bridge design has always been in the process of constant and rapid development. There were times when the development was basically due to the types of structures that appeared in modern bridges, and then there were other times when it was due to new materials. In the present period, promising new materials have appeared, especially more durable and with a high property-to-weight ratio: ultra-high performance fibre-reinforced concrete and fibre reinforced polymers.
Ideal for bridge construction
According to structural design engineers, ultra-high performance fibre-reinforced concrete is the ideal option for building bridges. “Adapted designs should be developed which fruitfully apply these enhanced properties towards more efficient and durable bridge structures. Ultra high performance fibre reinforced concrete represents a technological breakthrough by offering a characteristic compressive strength comprised between 150 to 250 MPa along with a matrix tensile strength in excess of 7 MPa, and outstanding durability characteristics. Ultra-high performance fibre-reinforced concrete materials are characterised by a highly compact cementious matrix, the absence of capillary pores, and the mandatory use of fibre reinforcement in the constructive applications in order to ensure non-brittleness failure. This technology allows designers to build structural elements without passive reinforcements and to combine lightness and extreme durability in innovative solutions, as already evident from the first bridge built using ultra-high performance fibre-reinforced concrete. Light weight decks made of ultra-high performance fibre-reinforced concrete in composite bridges are an alternative to conventional steel orthotropic decks, which are known to suffer fatigue degradation, and can extend the range of applications of steel-concrete composite bridges which nowadays are effectively used for bridge span between 50 m and 100 m. Moreover, the benefits include reduced erection costs, reduced construction times and resource savings,” explained Andy Gandadhar, Chief Structural Engineer, Bridge Designs & Co.
Also, ultra-high performance fibre-reinforced concrete is considered the ideal choice for building earthquake resistant structures. The benefits of using strain-hardening, ultra high-performance fibre-reinforced concrete in critical regions of earthquake-resistant structures are increasingly recognised.
“We discovered through studies that building constructed using ultra-high performance fibre-reinforced concrete can withstand earthquakes as evidenced in Japan and some parts of the US. Unless we adopt this technology aggressively going forward in infrastructure projects, we cannot develop earthquake-resistant buildings in the Himalayan region where seismic activity is very high. We have advised the states of Uttarakhand, Uttar Pradesh, Himachal Pradesh, Sikkim, Maharashtra and Gujarat to extensively adopt ultra-high performance fibre-reinforced concrete in all buildings,” observed Prof T Hanumanthaiah, well-known geologist and member of the Geological Society of India.
“In some of the countries like the Scandinavian nations, the use of ultra-high performance fibre-reinforced concrete in public infrastructure projects is legislated making it mandatory for third-party inspections. However, such a scenario is still not prevalent in India. Going forward, we need such revolutionary approach,” Prof Hanumanthaiah concludes.