木质素改良粉土热学与力学特性相关性试验研究

为揭示木质素改良粉土热学与力学特性随养护龄期的演化规律,通过击实试验、热阻系数测试、无侧限抗压强度试验、回弹模量试验、压汞试验和扫描电镜分析试验,探讨改良土热阻系数、强度和刚度与木质素掺量、含水率和养护龄期的变化规律,同时定性/定量评价改良土微观结构变化,分析改良土热学特性与力学特性间的相互关系。结果表明:改良土最大干密度较素土增加,最优含水率减小,干密度对含水率变化的敏感性增加;热阻系数随掺量和养护龄期增加而增加,60 d养护龄期后热阻系数趋于相同,热阻系数与土体密实度和组成成分的热传导特性密切相关;改良土强度随掺量和龄期增长而增加,28 d龄期12%掺量改良土强度约为素土强度6倍;回弹模量的变化特征与无侧限抗压强度类似,对于改良粉土,木质素最优掺量约为12%;改良土孔隙总体积和平均孔径显著减小,木质素包裹、连结土颗粒并填充孔隙,形成更致密土体结构。

Experimental study on relationship between thermal and mechanical properties of treated silt by lignin

To illustrate the evaluation laws of thermal and mechanical properties of lignin-treated silt during curing period, a series of laboratory tests including standard proctor compaction test, thermal resistivity test, unconfined compressive strength test, modulus of resilience test, mercury intrusion porosimetry and scanning electron microscopy analysis are conducted to study the relationship among thermal resistivity, strength and stiffness and lignin content, moisture content and curing time of treated silt. Moreover, the changes of microstructure of lignin-treated silt are qualitatively or quantitatively evaluated to state the relationship between thermal and mechanical properties of treated silt. The test results show that the maximum dry density of treated silt is higher than that of natural silt, but the optimum moisture content is lower than that of natural silt. The sensitivity of the dry density to changes of moisture content increases. The thermal resistivity of treated silt increases nearly with the increase of lignin content and curing time, and after 60 days of curing all the treated soils, the thermal resistivity tends to be the same. It is closely related to the density of soils and the thermal properties of soil compositions. The strength of treated silt increases with the increase of lignin content and curing time and are 6.0 times higher than natural silt for 12% lignin treated after 28 days of curing. The variation of modulus of resilience for treated silt is similar to that of the unconfined compressive strength. The optimum content of lignin for treating silt is approximately 12%. The total pore volume and average pore diameter of silt are significantly reduced, and a more stable soil structure is formed by coating, connecting particles and filling pores after treatment of lignin.