Experimental research on employed expanded polystyrene (EPS) for lightened sulfate heave of subgrade by thermal insulation properties

摘要

In sulfate-rich soils with high sodium sulfate contents, sulfate heave can occur and then generate severe damages to engineering facilities such as pavement, airplane runway due to the hydration of thenardite or crystallization of mirabilite when the temperature is below 32.4 degrees C. Based on the significant effect of expanded polystyrene (EPS) geofoam in reducing the temperature variations, a comparative experimental investigation on the sulfate heave of subgrade generated by the artificial coarse-grained saline soil with and without EPS material is conducted. Parameters of swell displacement and temperature fluctuation obtained from this comparative experiment are further validated and analyzed. The X-Ray Diffraction (XRD) measurement result is used to demonstrate the performance of EPS in microstructure. Test results indicate that: (1) The presence of crystallized mirabilite is proved within subgrade with saline soil when the temperature drops below 32.4 degrees C; (2) sulfate heave of subgrade is dependent on temperature fluctuation, but more specifically, on the temperature drop that occurs below 32.4 degrees C; and (3) EPS thermal insulation can reduce sulfate heave in pavement subgrade by effectively reducing the temperature fluctuation within the subgrade.