CEMFREE RAPID | CEMFREE OPTIMA
In January 2020, Cemfree and its partners undertook a series of tests to gain information on different characteristics of Cemfree when used on live projects. The purpose of the trials was also to prove the use of Cemfree in underground piling applications as part of the Innovate UK project LOCOWAG (Low Carbon Concrete within Aggressive Ground).
The first demonstrator project took place in Austrey, Barston, where Murphy Ground Engineering, BRE Group and Centrum Pile, experimented with different mix designs provided by Cemfree. The purpose of the test, to find out the installation characteristics such as sump, flow, ease of placement, strength gain profile and ultimate strength gain. The trials were successful to the point that Murphy felt confident in using Cemfree to produce a basement area contiguous secant wall, using a series of ‘male’ and ‘female’ piles.
Following the successful trials in Austrey, Murphy Ground Engineering moved on to a second demonstration in Newman Street, Westminster. This time, they would be using Cemfree to create both 750mm and 850mm rotary piles, to be placed 34m deep, forming a 3 storey basement secant wall. It was a necessity that the concrete mix for these piles reached a strength class of C32/40. This strength would have to be achieved in 56 days. On top of this, in order for the trial to be deemed a success, the Cemfree concrete had to perform to all of the same characteristics as regular Portland cement (PC) based concrete.
95m3 of C32/40 strength concrete was specified and ordered for the site. Cemfree had to perform. The findings showed that the Cemfree did indeed reach the required strength, defining it as a 410 mix binder. Both sump and visual examination proved that the mix was consistent with PC based concrete. An excellent result considering it was the first time that a mix of this design had been implemented.
With research at Newman Street complete, demonstrations were moved to Newark, Nottinghamshire, where Aarsleff Ground Engineering carried out the world’s first trials of precast driven piles using a cement-free ultra-low carbon concrete. Testing here proved more difficult than expected due to ‘onerous installation conditions’. These tests took place over 18 months, with all teams working hard on the trial. Ultimately, all of the effort put into the trial allowed for the fine tuning of the specific precast cemfree mix design that could be used on site.
Alongside these live trials, BRE carried out their own trials to test the effects of different ground conditions on Cemfree concrete. This included sulphate and acid attack. Findings showed Cemfree to be more resistant to these conditions than PC based concrete.
These demonstration projects all took place over two years. They proved that Cemfree can be suitable for use by ground engineers and also in aggressive ground conditions. It also demonstrated that with fine tuning, Cemfree can adapt to suit the specific needs of individual sites. Thanks to all of these trials and testing, Cemfree can be used in new ways, allowing us to save on embodied carbon emissions in new areas such as concrete foundations, bringing us closer to a more sustainable future for the construction industry.