30/04/2021
We’ve all had to be flexible over the last 12 months, adapting to circumstances and finding new ways of working.
Covid-19 has seen conventions torn up, and we’ve been forced to take a fresh approach to everyday tasks. If we’re honest, that’s no bad thing for some practices that have happened simply because they’ve always been done that way. So what better time to take a step back and innovate?
The government is rightly championing the use of off-site construction to improve productivity and reduce the number of hours required working in close proximity on a busy building site. Embracing new technologies and modern methods of construction (MMC) will only become more critical as the industry promises to ‘build back better’, become more resilient and kick start a green economic recovery.
With the sector rethinking how it should be constructing new homes and infrastructure, often overlooked is the importance of material selection. In responding to the government champion Mark Farmer’s ambitions for MMC, no material is better placed to deliver structures more sustainably, safely, aesthetically and affordably than concrete.
When it comes to building in concrete, wholly precast systems are available and have their definite place. But perhaps less well-known are the innovative structural systems that combine both precast and in-situ concrete, with each playing to the best of their strengths – hybrid concrete construction, or HCC.
HCC does this in large part by driving key critical decisions earlier in the design phase, making construction on site much simpler and more logical. HCC can also deliver very significant cost savings with economic structures, increased prefabrication, faster construction, and consistent performance. It additionally offers all of off-site construction’s other advantages, improving both speed of construction and safety.
Frame costs are reduced by using precast concrete for the repetitive elements, or to act as permanent formwork. These can be manufactured, stored at the factory, and delivered just-in-time to site before being lifted to their final position in a single crane movement – eliminating the need for site laydown and storage areas, and with minimum time spent on the hook.
By taking a proportion of work into the factory, off-site precasting reduces time spent on critical on-site operations that could affect the programme. It all takes place in a controlled environment, unaffected by weather and with no need for working at height. Rigorous inspection before installation removes causes of delay on site, while better buildability helps provide safer working conditions – reducing the potential for accidents by providing successive work platforms and a tidier site.
Some HCC techniques can also reduce or eliminate following trades – for example, installing ceilings and finishes. If precast concrete is used for more visible areas, the workmanship required takes place under factory-controlled conditions. This unlocks even faster programme times, although does require greater coordination and care in detailing and protection on site.
Furthermore, unlike combustible materials including cross laminated timber, concrete is able to help to keep people safe by minimising fire risk as a result of its inherent material properties – not requiring any additional fire protection because of its own built-in resistance to fire.
Hybrid concrete construction projects can therefore maximise cost efficiencies, and make for a smoother, smarter, decarbonised MMC build. As importantly, they also create attractive, practical buildings to be proud of.
Just as we all use the right tool for the job, clever combinations of precast and in situ concrete can be applied intelligently to offer the best of both worlds.
By Jenny Burridge, head of structural engineering, The Concrete Centre