Hey presto... and the powerfloat disappears

A no-nonsense projects manager who leaves his suit at home, Kevin Hill is no new product groupie. But when it comes to Agilia Horizontal, a concrete that makes laying a floor a one-day operation, the 45-year-old Hallam Construction man is a convert. "It's the only thing that's floated my boat in a long time," he says.

Hill is building an eight-storey block of 282 bedsits with en suites for students at Newarke Street in the middle of Leicester. With no leeway at all on this year's September handover because students will be arriving then for the new academic year, excuses from subbies are just not on: any delay will incur swingeing penalties.

"In design and build, you're not aware of everything when you first walk onto site," says Hill. Just so. Getting out of the ground at Newarke Street was a nightmare. The basements of the building that previously stood there were filled with all sorts of bore-defying rubbish: collapsed walls and floors, and old machine bases. In order to drive in the 300-odd, 10m-deep piles for the residential block, Hill first had to dig out some 1,500 tonnes of rubble.

When Hill finally managed to start work on the floors, he built the first four levels the traditional way, pouring concrete onto metal decking, compacting it with a vibrator and finishing the surface off by powerfloating. But each floor was taking the concreting gang three or four visits to complete, and the project was now a month behind the programme.

Working wonders
Things then went from bad to worse. To get a hard, flat surface finish on concrete, you need to powerfloat it - a time-consuming operation that left Hill's powerfloaters working well into the night, sometimes till 3am, to finish each pour of concrete. But the site borders on student housing and the combined racket from the helicopter-like powerfloat blades striking the concrete and the powerfloating gangs pushing them drove the neighbours to distraction... and complaints to the council. If environmental health officials slapped a ban on after hours working, Hill could have been in real trouble: "A stop order would have knackered the contract."

In came Agilia, a concrete that doesn't need vibrating or powerfloating, and life on site changed utterly. "We were packing up and going home at five rather than powerfloating till three in the morning," says Hill.

It had taken months to concrete the 2700m2 of the first four floors, but the top four were finished in a fortnight with Agilia, which has now been specified for the second phase of the project (another eight floors with a total surface area of 3800m2).

Levelling, vibrating and, in particular, powerfloating are such time-consuming and time-sensitive operations that it simply wasn't a sensible strategy to pour each of the first four floors at Newarke Street in one go. So while Hill covered the 690m2 of each of the first four floors with three (or, as winter approached, four) pours, each of which took a day, each Agilia floor was poured in one go and completed on the very same day.

Agilia is self-compacting and self-levelling. After pumping it onto your floor all you need is one man with a laser level and another in wellies to rake it about a bit. With vibrating and powerfloating surplus to requirements, the site workforce becomes more flexible. "Powerfloating's an expert skill, but anyone can pump concrete," says Frank Noon, the concreters' foreman at Newarke Street.

agilia absolutely murders the flooring phase

Kevin Hill

Once the Agilia is down, you just spray a sealant on to prevent it drying out too quickly and tamp it down. And that's it. Follow-on trades can start working on it the next day. Within seven days it sets to a strength of 35 Newtons.

"It's idiot-proof," says Hill. "There's no shrinkage and no cracking." At least, there shouldn't be. Noon points out some cracking at Newarke Street, although that may be because the steel mesh in the concrete is too high.

Because Agilia uses smaller aggregate and is more watery than standard concrete – it has the consistency of pea soup – the deeper you pour it, the better the flow. Where laser levelling has to be spot-on with traditional concrete, it's a much reduced operation with Agilia because the product finds its own level more easily.

However, Agilia's liquidity does make site preparation a more rigorous job because the concrete can find its way out of any tiny hole. "It's like a fountain, this place, when we're pouring concrete on the floor above," says Noon. And Darren Williams, product manager for Lafarge, which supplies Agilia, recalls one job where the construction team was left scratching its head over where a missing two cubic metres had gone.

Spreading the load
But once you've done it a few times, blocking up all the outlets should become a standard methodology. There were plenty of spillages at Newarke Street, although clearing them off is easy enough – Noon reckons foot traffic from subsequent trades will disperse most of them.

Like calcium sulphate-based screeds, Agilia won't shrink, thanks to its admixtures, so you can cast huge floor areas in one go because movement joints aren't needed. But unlike calcium sulphate screeds, which go soggy if they get saturated and will revert to their plasterboard state, the cement-based Agilia is a direct replacement for traditional concrete.

Agilia costs around half as much again as traditional concrete, but the simplicity and speed of laying it makes for an equivalent installed cost. Using Agilia will add £10,000 to Hill's materials bill, but he reckons he's cut his pump costs alone by £3,000 while the cost of labour has fallen to around £2.50 per square metre installed compared with £4 for the lower four floors, which should cut installation costs by around £7,500 altogether.