In shielded mechanized tunnelling, the annular void created during the advancement of a Tunnel Boring Machine (TBM) must be continuously filled to minimize surface settlements and ensure optimal contact between the segment lining and the surrounding soil. Two component grout is widely used in the backfilling process due to its ability to meet both operational and performance requirements. This grout system comprises component A (a mixture of water, bentonite, cement, retarding fluidifying agent and additives) and component B (an accelerator, typically sodium silicate). This study investigates the influence of bentonite dosage in a mix design on the properties of two-component grout, focusing on both freshly prepared component A and component A aged for 72 hours. Laboratory tests were conducted to analyse key parameters, including density, bleeding, gel time, viscosity, surface compressive strength (SCS), and uniaxial compressive strength (UCS) also in the case when the component A is not “fresh”. These tests provide insights into the role of bentonite dosage in optimizing the performance of two-component grout mixtures across different stages of preparation.

In shielded mechanized tunnelling, the annular void created during the advancement of a Tunnel Boring Machine (TBM) must be continuously filled to minimize surface settlements and ensure optimal contact between the segment lining and the surrounding soil. Two component grout is widely used in the backfilling process due to its ability to meet both operational and performance requirements. This grout system comprises component A (a mixture of water, bentonite, cement, retarding fluidifying agent and additives) and component B (an accelerator, typically sodium silicate). This study investigates the influence of bentonite dosage in a mix design on the properties of two-component grout, focusing on both freshly prepared component A and component A aged for 72 hours. Laboratory tests were conducted to analyse key parameters, including density, bleeding, gel time, viscosity, surface compressive strength (SCS), and uniaxial compressive strength (UCS) also in the case when the component A is not “fresh”. These tests provide insights into the role of bentonite dosage in optimizing the performance of two-component grout mixtures across different stages of preparation.