Experimental investigation of thermal and mechanical properties of lignin treated silt

This paper presents details of a study that deals with measurement of thermal resistivity, determination of mechanical properties, and microstructural characteristics of a lignin treated silt. Changes in thermal and mechanical properties of the lignin treated silt were studied over a curing period of 60days. Investigations were carried out with respect to the effect of the lignin content, moisture content, and curing time on the soil properties including compaction characteristics, thermal resistivity, unconfined compressive strength, and resilient modulus. In addition, the pore-size distribution and the microstructures of lignin treated silt with different packing moisture contents were analyzed. Relationships between the thermal resistivity and properties that capture compaction and mechanical characteristics of lignin treated silt were established. The study reveals that curing time and the amount of lignin content have a considerable influence on the thermal resistivity, mechanical properties, and microstructure of lignin treated silt. The initial thermal resistivity of lignin treated soil increases with an increase in lignin content and the difference in thermal resistivity disappears after 60days of curing. The increase in lignin content leads to the increase in the unconfined compressive strength and resilient modulus of lignin treated soil. The optimum content of lignin for silt in Jiangsu Province is approximately 12%. With an increase in the lignin content, both the unit pore volume and mean diameter of an intra-aggregate pore, and that of an inter-aggregate pore decrease, whereas the magnitude of the volume inter-aggregate pore increases considerably. The fundamental behavior of treated silt changes when the lignin content exceeds 8%. The impurities contained in lignin would affect the fundamental behavior of treated silt. Linear relationship is established between the initial thermal resistivity and unit weight.