Preparation of biomass carbon dots for foam stabilizer of foamed concrete

This paper presents a novel method for preparing an ultra-stable foam based on carbon quantum dots. In this study, carbon quantum dots (RHBCDs) were synthesized using biological waste (rice husk) as carbon source. HRTEM analysis observed the formation of spherical carbon dots with a particle size of no more than 7 nm. The results of FTIR and XPS showed that RHBCDs had good water solubility. XRD analysis confirmed that RHBCDs had typical characteristic peaks of carbon dots. Meanwhile, the performance of foamed concrete prepared by adding RHBCDs to vegetable protein-based surfactant (PS) were studied. The experimental results show that the foams containing RHBCDs have higher density, viscosity and stability. When the addition of RHBCDs was 9.0 wt%, the foam (PS-RS) displacement decreased by 8 % in the first 5 min. PS-RS foam not only reduces the fluidity of foam concrete, but also reduces the hydration exothermic peak of cement. After standard curing, the mechanical properties of foamed concrete increased from 3.38 to 4.64 MPa due to the addition of RHBCDs. And the percentage of pores in the range of 100–500 μm increased to 70.47 %, which means that the addition of RHBCDs not only reduces the pore size distribution and pore size, but also reduces the thermal conductivity. In addition, the shrinkage resistance and homogeneity of foamed concrete have also been improved. In part, one reason is that RHBCDs can be evenly adsorbed on the surface of foam. Another reason is that RHBCDs can fill the pores.