Long-term durability of foamed concrete filler in highway engineering

In highway engineering, foamed concrete used for subgrade filler is typically influenced by external environmental factors such as freeze-thaw cycles and vehicle loads. This study conducts freeze-thaw cycle tests, load cycle tests, and coupling (freeze-thaw-load) cycle tests under the designed wet density to simulate the field environment of highway engineering and examine the strength variation of foamed concrete under different conditions. Additionally, the pore structure and freezing damage mechanism of foamed concrete were analyzed using SEM. The results indicate that the strength loss of foamed concrete exceeds 20% after 100 freeze-thaw cycles. During the load cycle tests, the compressive strength of foamed concrete can be divided into three stages, corresponding to the development of micro-cracks in the material. In the coupled environment to simulate field conditions, the compressive strength of foamed concrete decreases rapidly to 0.96 MPa (20.66% loss) after the first 10 years, which followed by a slower decline (0.83 MPa in the 20th years and 0.78 MPa in the 40th years). SEM analysis shows that the internal damage caused by freeze–thaw cycles can be categorized into cavity failure and crack failure.