Volume, strength, and stiffness characteristics of expandable foam grout

An expandable foam grout (EFG) is developed to fill underground cavities. The objective of this study is to evaluate the volume, strength, and stiffness of the EFG during curing using various testing methods. Flow, expansion, and unconfined compressive tests are conducted to investigate the fundamental material properties of the EFG. X-ray computed tomography is performed to verify the pore distribution of the EFG. Elastic waves and electrical resistivity are monitored to estimate the stiffness and strength characteristics of the EFG. The results show that EFG has high flowability, expanding within four hours depending on the temperature. The X-ray computed tomography images indicate a heterogeneous pore distribution in the EFG. A series of relationships between static and dynamic properties based on the elastic wave velocities and electrical resistivity are established. Furthermore, elastic wave measurement and electrical resistivity monitoring may be useful for estimating the volume, strength, and stiffness characteristics during curing.