Ultra-stable foam enabled by nano silica engineering for foam concrete improvement

Foam concrete is increasingly applied in construction due to its lightweight, good thermal insulation and fire resistance, and environmental sustainability, while its low strength limits its further popularization and applications. To enhance the stability and performance of foam concrete, amphiphilic nano silica (ANS) was employed in this study to modify the sodium dodecyl sulphate (SDS) based foaming agent. Then, the designed foam was utilized to fabricate foam concrete, of which the micro/macro performance was analysed in detail. The results showed that ANS-modified foam exhibited superior stability with a thicker foam wall thickness, contributing to the enhancement of foam stability within the cement matrix. The foam concrete with ANS exhibited higher strength compared to the control groups. The analysis of pore structures revealed that the ANS modification led to a more rounded and homogeneous pore configuration, characterized by an increased proportion of small and medium-sized pores and a decreased average pore size. The increase in pore roundness was accompanied by a reduction in the number of sharp edges of the pores and therefore a reduction in the stress concentration factor, while the moderately sized pore also was more conducive to increasing strength due to its lower stress concentration. As a result, the strength of the concrete is significantly increased. These findings demonstrate the potential of ANS as an effective foam stabilizer for foam concrete production, leading to enhanced foam stability and improved mechanical properties of concrete.