Properties of foam concrete with hydrophobic starch nanoparticles as foam stabilizer

This study proposes the use of hydrophobic starch nanoparticles (H-SNPs) as a foam stabilizer. Simultaneously, the properties of foamed concrete prepared by adding a foaming agent to H-SNPs are investigated. The experimental results indicate that the foam prepared using a combination of H-SNPs and synthetic surfactants (SS) has increased stability and improved density and viscosity. When H-SNPs and synthetic surfactants (HS-SS) were used as a foaming agent, foam drainage decreased by 8% after 5 min. After 28 days of curing, the compressive strength of foamed concrete containing H-SNPs increased from 2.35 MPa to 2.77 MPa. And the percentage of pores in the range of 100–500 μm increased to 63.2% implying that the addition of H-SNPs makes the pore size distribution narrower, the pore size smaller. Meanwhile, foam concrete's shrinkage and uniformity are improved. There are two possible explanations. One is that due to the chemical reaction between the carboxyl group of citric acid and the hydroxyl group of starch, the starch changed from hydrophilicity to hydrophobicity. As a result, the H-SNPs can be evenly adsorbed onto the foam's surface. Another advantage is that H-SNPs can be used to fill the pores between the foam and the cement body, thereby increasing the strength of foam concrete. • A novel method for preparing an ultra-stable foam have been proposed. • The foaming agent prepared by hydrophobic modification of starch will affect the performance of foam concrete. • Modified starch granules will influence performance of the foam and foam concrete.