Experimental investigation of mechanical behavior and microstructural properties in roadbed foam concrete at different densities and correlation analysis

Foamed concrete, due to its lightweight and high-strength characteristics, offers significant advantages as a roadbed material. However, its mechanical properties are notably influenced by its density and microstructure. Comprehensive research addressing the correlation between the density, mechanical properties, and microstructure of roadbed foamed concrete, especially within real construction scenarios, remains limited. To address this research gap, we undertook compressive strength tests and a set of microstructural analyses on four sets foamed concrete samples of varying densities prepared on-site. The objective was to deeply understand the mechanical and microstructural characterization of roadbed foamed concrete at different densities and correlation Analysis. The findings indicate an exponential correlation between density and compressive strength, most prominently within the density range of 800–1000 kg/m3, accompanied by commendable thermal stability. X-ray Computed Tomography (X-CT) analyses further demonstrate that density increase is pivotal in enhancing the pore structure, thereby achieving lower porosity, fewer detrimental pores, more homogeneous pore distribution, and superior pore sphericity. Scanning Electron Microscopy (SEM) evaluations suggest that enhancing the density of the sample can mitigate the damage to individual pores, reduce internal cavities, and curb initial defects. Furthermore, the pore intersections exhibit a more intact and dense crystalline structure. Upon assessment, we discerned a significant correlation between porosity, compressive strength, and density. The Pearson correlation coefficient (r) between any two of these parameters is notably close to 1 (−1). These research results show that it is feasible to optimize the density of foam concrete to enhance its microstructure and thereby enhance its compressive performance. This provides strong data support for the wider application of foam concrete in roadbed engineering.