Effects of free iron oxide on thermal properties of undisturbed lateritic clay subjected to drying and wetting: Fid-Bau Portal

Effects of free iron oxide on thermal properties of undisturbed lateritic clay subjected to drying and wetting

Xu, Yunshan / Sun, De’an / Zeng, Zhaotian

Knowledge of soil thermal properties is necessary for the thermal evaluation and design in geotechnical engineering. In this study, the soil thermal properties of undisturbed lateritic clay with and without free iron oxides were measured during drying and wetting. Furthermore, mercury intrusion porosimetry and scanning electron microscopy tests were conducted on specimens to investigate how the free iron oxides affect the soil microstructure. Test results revealed that the thermal conductivity and diffusivity of the undisturbed lateritic clay with the free iron oxides removed (i.e., treated specimens) were higher than those with the free iron oxides (i.e., untreated specimens). The hysteresis effect on the soil thermal conductivity had reduced after removing the free iron oxides. Investigations showed that the microstructure of the treated specimens was denser, and the debris and granular units considerably increased compared with those of untreated specimens. The number and size of soil pores in the treated specimens was lower and smaller than those of untreated specimens. The difference in thermal conductivity and diffusivity between the treated and untreated specimens was mainly attributed to the different extent or quality of connections between neighbouring soil particles that affected the conductive heat transfer in specimens. After removing the free iron oxides, the connection and inclusion of the stable aggregates were destroyed; thus, the relatively large soil pores disappeared. The further dispersion of the soil particles forming the aggregates filled the relatively small pores in specimens, which increased the heat transfer path between neighbouring soil particles.