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<p>Fully grouted cable bolts are widely used in underground mining; however, the cementitious grouts governing their load-transfer performance remain predominantly Portland-cement based and are rarely optimised for sustainability. This study evaluates the mechanical and bonding performance of newly developed “green” grouts incorporating partial cement replacement with waste glass powder (WGP), tyre rubber waste (TRW), and construction and demolition waste (CDW), with the aim of promoting circular-economy principles in underground reinforcement systems. Following preliminary mechanical screening, selected grout formulations were used to encapsulate cable-bolt specimens. A total of 20 pull-out tests were conducted using 70-t, 12-wire Sumo cable bolts embedded in rifled steel confinements and tested in a custom single-embedment pull-out testing (SEPT) rig incorporating a rotation-mitigation system to isolate axial bond–slip behaviour. The mixtures included WGP with four particle-size bands (&lt; 75–425&#xa0;μm) at 2.5–20% replacement, TRW at 0.75–3% in two size ranges (&lt; 300 and 300–600&#xa0;μm), and CDW at 2.5% in two size bands (150–300 and 300–600&#xa0;μm). Results show that 10% WGP with particles finer than 75&#xa0;μm increased the ultimate pull-out load from 415 kN (reference) to 490 kN (18% gain) while maintaining comparable stiffness and residual capacity. Other well-graded WGP mixtures matched or exceeded the control performance, whereas 20% replacement with intermediate particle sizes led to premature failure and reduced capacity (as low as 212 kN). TRW-modified grouts exhibited substantially degraded bond performance, with ultimate loads as low as 119 kN due to weak, hydrophobic interfaces and early debonding. CDW-modified grouts achieved capacities close to the reference (372–413 kN), with failure behaviour governed by particle size. A dataset comprising grout composition, uniaxial compressive strength (UCS), and peak load was subsequently analysed using Random Forest (RF) and XGBoost models to predict axial bearing capacity. RF demonstrated superior predictive performance, and SHAP analysis identified UCS as the dominant controlling parameter, with grout composition exerting secondary influence. The findings demonstrate that fine WGP can serve as a technically robust and sustainable additive for high-performance cable-bolt grouts, CDW acts as a largely neutral filler at low dosages, and TRW is unsuitable for bond-critical applications. The study provides a practical framework for engineering low-carbon grout formulations without compromising axial load-transfer performance.</p>

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Performance evaluation of waste-modified cementitious grouts for cable bolting encapsulation

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月31日

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  • Alireza Entezam,
  • Hadi Nourizadeh,
  • Paulomi Polly Burey,
  • Behshad Jodeiri Shokri,
  • Shima Entezam,
  • Kevin McDougall,
  • Peter Craig,
  • Naj Aziz,
  • Ali Mirzaghorbanali

摘要

Fully grouted cable bolts are widely used in underground mining; however, the cementitious grouts governing their load-transfer performance remain predominantly Portland-cement based and are rarely optimised for sustainability. This study evaluates the mechanical and bonding performance of newly developed “green” grouts incorporating partial cement replacement with waste glass powder (WGP), tyre rubber waste (TRW), and construction and demolition waste (CDW), with the aim of promoting circular-economy principles in underground reinforcement systems. Following preliminary mechanical screening, selected grout formulations were used to encapsulate cable-bolt specimens. A total of 20 pull-out tests were conducted using 70-t, 12-wire Sumo cable bolts embedded in rifled steel confinements and tested in a custom single-embedment pull-out testing (SEPT) rig incorporating a rotation-mitigation system to isolate axial bond–slip behaviour. The mixtures included WGP with four particle-size bands (< 75–425 μm) at 2.5–20% replacement, TRW at 0.75–3% in two size ranges (< 300 and 300–600 μm), and CDW at 2.5% in two size bands (150–300 and 300–600 μm). Results show that 10% WGP with particles finer than 75 μm increased the ultimate pull-out load from 415 kN (reference) to 490 kN (18% gain) while maintaining comparable stiffness and residual capacity. Other well-graded WGP mixtures matched or exceeded the control performance, whereas 20% replacement with intermediate particle sizes led to premature failure and reduced capacity (as low as 212 kN). TRW-modified grouts exhibited substantially degraded bond performance, with ultimate loads as low as 119 kN due to weak, hydrophobic interfaces and early debonding. CDW-modified grouts achieved capacities close to the reference (372–413 kN), with failure behaviour governed by particle size. A dataset comprising grout composition, uniaxial compressive strength (UCS), and peak load was subsequently analysed using Random Forest (RF) and XGBoost models to predict axial bearing capacity. RF demonstrated superior predictive performance, and SHAP analysis identified UCS as the dominant controlling parameter, with grout composition exerting secondary influence. The findings demonstrate that fine WGP can serve as a technically robust and sustainable additive for high-performance cable-bolt grouts, CDW acts as a largely neutral filler at low dosages, and TRW is unsuitable for bond-critical applications. The study provides a practical framework for engineering low-carbon grout formulations without compromising axial load-transfer performance.