Canadian Geotechnical Journal, Ahead of Print.
Thermally active structures such as crude oil pipelines and high-power voltage cables are usually embedded within local soils for their substructural stability. Based on site requirements, soils are amended with synthetic cementitious materials to improve their strength. However, synthetic binders such as cementation, geo-polymerization, and bio-cementation undermine thermal insulation while improving strength. Moreover, commonly used synthetic binders such as cement and lime are extremely harmful to the geoenvironment due to their hyper-alkalinity and high carbon footprint. Therefore, this study proposes a novel backfill composite consisting of clay loam, biochar, and biopolymer for superior thermal insulation and strength characteristics. Local soil containing high clay content was chosen due to its low thermal conductivity and potential to form stable hydrogen bonding with the biopolymer. The clay loam is amended with 2.5% to 7.5% (w/w) biochar and 0.5% to 1.5% (w/w) of biopolymer and their various combinations. Out of nine soil–biochar–biopolymer composites devised in the current study, six composites exhibited superior strength and lowered thermal conductivity than the plain soil in both conditions, i.e., optimum moisture state and upon drying. The findings of this study establish the synergistic attributes of biopolymer and biochar amendment for developing a high-strength thermal-insulating soil composite.

中文翻译：

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受粘壤土协同生物炭-生物聚合物改良剂启发，研究天然回填复合材料的热和强度特性

加拿大岩土工程杂志，印刷前。
原油管道和高压电缆等热活性结构通常嵌入当地土壤中，以保证其地下结构的稳定性。根据现场要求，用合成胶凝材料对土壤进行改良，以提高其强度。然而，水泥、地质聚合和生物水泥等合成粘合剂在提高强度的同时却破坏了隔热性。此外，常用的合成粘合剂（例如水泥和石灰）由于其高碱度和高碳足迹，对地质环境极其有害。因此，本研究提出了一种由粘土、生物炭和生物聚合物组成的新型回填复合材料，具有优异的隔热和强度特性。选择粘土含量高的当地土壤是因为其导热率低并且有可能与生物聚合物形成稳定的氢键。粘壤土用 2.5% 至 7.5% (w/w) 生物炭和 0.5% 至 1.5% (w/w) 生物聚合物及其各种组合进行修正。在当前研究中设计的九种土壤-生物炭-生物聚合物复合材料中，有六种复合材料在两种条件下（即最佳湿度状态和干燥时）都表现出比普通土壤更高的强度和更低的导热率。本研究的结果确立了生物聚合物和生物炭改良剂的协同属性，可用于开发高强度隔热土壤复合材料。