Influence of coarse fly ash on the performance of foam concrete and its application in high-speed railway roadbeds

In this paper, the potential of using foam concrete as a lightweight filling material for high-speed railway roadbeds was studied. The influence of coarse fly ash on the workability, mechanical, shrinkage performances and durability of foam concrete were analyzed. X-ray Computed Tomography (XCT) was used to characterize the microstructure and quantitatively in situ monitor the water transfer behavior of foam concrete. The results show that coarse fly ash enhances many properties of foam concrete, including workability and mechanical and freeze-thaw resistance properties, while the reverse phenomenon is observed for water absorption and drying shrinkage properties. A good linear relationship was provided between the fine content and the absorption coefficients. Finally, continuous field testing of settlement, lateral displacement and soil pressure in the Hangzhou east railway station project shows good loading and differential settlement reduction properties when foam concrete was used as a filling material.