Rheological performance and strength on two component backfilling grout in shield TBM

Area of Science:

• Civil Engineering
• Materials Science
• Geotechnical Engineering

Background:

• Mechanized tunneling necessitates stable annular gap filling to prevent ground settlement and segmental displacement.
• Two-component grouts are essential for controlling gelation and compressive strength in tunnel backfilling.
• While ground granulated blast-furnace slag (GGBFS) shows promise, the combined impact of cement type and silicate hardener dosage requires further investigation.

Purpose of the Study:

• To investigate the influence of cement type (Ordinary Portland Cement vs. plasticized cement) and hardener-to-water (H/W) ratio on the properties of two-component backfill grouts.
• To evaluate the rheological, mechanical, and microstructural characteristics of these grouts.
• To understand the combined effects of cement type and silicate hardener dosage on grout performance.

Main Methods:

• Preparation of Component A using OPC or PLC with bentonite and stabilizer, and Component B as a sodium silicate hardener.
• Evaluation of rheological properties including bleeding, flow time, gelation time, plasticity retention time, and flow rate.
• Assessment of uniaxial compressive strength (UCS) and microstructural analysis using XRD, SEM, and MIP.

Main Results:

• Plasticized cement (PLC) resulted in lower bleeding, shorter flow time, longer gelation time, shorter plasticity retention time, and higher long-term UCS compared to Ordinary Portland Cement (OPC).
• Increasing the H/W ratio extended gelation time, shortened plasticity retention time, reduced flow rate, and enhanced UCS.
• Microstructural analyses confirmed reduced crystallinity and increased C-S-H gel formation with higher H/W ratios, correlating with improved pore structure and compressive strength.

Conclusions:

• Plasticized cement (PLC) offers superior rheological and mechanical properties for two-component backfill grouts compared to OPC.
• Optimizing the hardener-to-water (H/W) ratio is critical for balancing gelation, workability, and strength development.
• The study provides valuable insights into tailoring grout formulations for effective mechanized tunneling applications.