Objective Foam concrete is widely used in construction to reduce structural and foundation loads, thereby improving energy efficiency and lowering construction costs due to its favorable properties.

Method accurate determination of its unconfined compressive strength remains essential for promoting broader application. In this study, a fractal model of the pore structure of foam concrete with a water–cement ratio of 0.5 is proposed to calculate unconfined compressive strength.

Results Considering the size effect of the unconfined compressive strength of foam concrete, the fractal dimension of the pore structure of foam concrete is calculated, and the theoretical relationship between the unconfined compressive strength and the solid volume fraction is established to calculate the unconfined compressive strength of foam concrete. Compared with the empirical model of unconfined compressive strength, the theoretical relationship between unconfined compressive strength and solid volume fraction is only related to the fractal dimension of pore structure of foam concrete.

Conclusion The fractal model of pore structure of foam concrete provides a simple and effective theoretical tool for estimating the unconfined compressive strength of foam concrete, providing both accuracy and computational efficiency.