ABSTRACT
For the past thirty years, the tunnelling industry has predominantly used two-component grouts (A+B) for backfilling the annular gap between the segment and the ground. This technology has become the norm and is straightforward to manage in terms of specifications, performance, and application. However, the industry’s emphasis on cost has shifted attention away from the technical purpose of backfill grouts, which is to prevent surface settlements and tunnel lining flotation. The use of low-quality, cheap materials has led to inferior grouts and a significantly higher carbon footprint contribution. A newly developed grout can help reduce the carbon emissions produced by the conventional grout by approximately 50%. The grout has been developed and evaluated in SIKA’s laboratories, those tests were followed by large scale tests on site with the help of PORR Qatar demonstrating the performance of the grout while taking into consideration the scale factor and extreme site conditions. This low carbon annular grout contributes to overall sustainability in mechanized tunnelling since it contains a lower cement content. It also enhances the durability due to the higher solids content in the grout.
