工业副产品木质素改良路基粉土的微观机制研究

Research on stabilization microcosmic mechanism of lignin based industrial by-product treated subgrade silt

为揭示工业副产品木质素与土体间的相互作用机制,将木质素应用于路基粉土改良,通过对木质素及其改良土进行无侧限抗压强度、pH值、微观结构、化学元素、矿物成分和官能团等试验分析,研究不同掺量下木质素改良土的力学性能和pH值变化,对比分析改良前后粉土的微观结构变化,并基于化学分析结果探讨木质素的分子结构及与土体间的相互作用,提出木质素改良土体的机制。试验结果表明,改良土强度随木质素掺量增加而增加,掺量超过一定范围时,土体强度降低,木质素改良粉土的最优掺量为12%,且龄期对土体强度有着重要影响;强度与pH值基本呈线性相关关系;改良土微观结构更为致密、稳定,胶结物质将土颗粒相互联结,且未生成新的矿物;木质素通过水解、离子交换、质子化和静电引力等作用,导致双电层厚度减小,带正电荷的木质素高分子聚合物联结土颗粒并填充孔隙,改良土工程性质得以改善。提出的木质素改良土体机制可为工业副产品木质素的工程应用提供理论参考。

To reveal the stabilization mechanism of lignin based industrial by-product treated soil, the lignin is utilized to improve the silt of subgrade. The unconfined compressive strength, pH value, microstructure, chemical elements, mineral composition and functional groups of lignin and lignin treated silt are tested to evaluate the mechanical properties and p H values of silt after treatment. The difference of microstructure between silt and lignin treated silt is compared. The interactions between lignin and soil are also discussed based on the results of chemical analysis. A possible stabilization mechanism of lignin treated silt is proposed. The experimental results show that the unconfined compressive strength of lignin treated silt increases with the increase of lignin content, while the lignin content exceeds a certain range, the strength of soil exhibits a decreasing trend. The optimum percentage of lignin for silt is approximately 12% and curing time has an important influence on the strength of treated silt. The relationship between unconfined compressive strength and pH value of treated silt is approximately linear. Compared with natural silt, the microstructure of treated silt is more compact and stabler. Soil particles are bonded with cementing materials and no new clay minerals are formed after treatment. The engineering properties of silt are improved by the addition of lignin through hydrolysis, cation exchange, protonation and electrostatic reaction, which leads to the reduction of thickness for double-layer and filling the pore. The proposed model of microcosmic mechanism can provide a theoretical reference for engineering application of lignin based by-products.