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It is a priority for Murphy to find the latest technology to minimise our impact on the environment.
As part of its involvement on the Austrey – Barston Gas Pipeline Diversion Murphy Ground Engineering (MGE) saw an opportunity to test, in agreement with the project client, the potential of cement-free concrete on a large scale project.
Cemfree has been used in the UK since 2010. However, so far it has only been used on small scale projects. It is an ultra-low carbon alternative to standard concrete whereby OPC is replaced with novel alkali activated cementitious material (AACM). As it does not contain any OPC, it can save up to 88% of CO2 emissions on a project.
The works for the pipeline diversion included:
In addition to the emissions savings, the trial of Cemfree would allow Murphy Ground Engineering to better understand and develop its characteristics for future use in piled structures.
The main works were completed successfully with the selected binder mix achieving a consistent strength gain profile and between 17N to 20N at 28 day strength.
Through trialling Cemfree on the HP11 gas main diversion project MGE has seen a number of benefits and have generated interest across both the Murphy family and HS2, including:
Additionally MGE was able to use Cemfree without having to develop different procedures or use alternative equipment. As a result, there were no added extra costs.
With the strength gain performance during the trials of the higher binder content has proving positive and MGE aim to progress the use of Cemfree for a full secant piled shaft in the very near future.
Further more, by demonstrating the sustainable and economic benefits of Cemfree MGE hope to encourage other ground engineering companies to consider using more sustainable materials and practises.
MGE's aim was to trial Cemfree to assess its installation characteristics (slump, flow, and placement), its strength gain profile and its ultimate strength gain performance, in the process measuring how much CO2 MGE could save over using a traditional concrete mix.
The main and initial process was to trial the various binder content mix designs to assess which binder content would be most suited to replace a typical C8/10 primary/soft pile concrete and also observe its in-situ behaviour prior to use in the main shaft piling.
In addition MGE also trialled higher strength binder contents to gather data to consider whether higher strength concretes could feasibly be replaced with Cemfree in the future.
With the temporary works design status of the TBM shafts there are less onerous design life criteria making this setting ideal for the trial as currently AACM’s in general are not appropriately covered by existing concrete standards making their use in permanent structures more complicated.
The scheme engineers COWI were positive in the adoption and use of Cemfree for the primary/soft piles based on the strength gains achieved during the trial process.
The Ground Engineering team at Murphy offers in-house pile design, value engineering and bespoke technical solutions throughout the UK and Ireland. We have a proven track record of successfully delivering both minor and major works across a range of sectors.