Effect of hydroxypropyl methyl cellulose (HPMC) as foam stabilizer on the workability and pore structure of iron tailings sand autoclaved aerated concrete

The stock of iron tailings sand (ITS) is massive and increases annually, posing a severe threat to the environment and necessitating proper disposal. This study aims to solve the problems of mesoscopic pore coalescence and disproportionation caused by excessive ITS in the production of autoclaved aerated concrete (AAC). The effects of the water-to-solid ratio (W/S) and foam stabilizer content on the performance of ITS autoclaved aerated concrete (ITS-AAC) were assessed. Furthermore, the mesoscopic and microscopic pore structures of ITS-AAC were investigated using optical methods and mercury intrusion porosimetry, respectively. The hydration and microstructure of the selected ITS-AAC samples were also analyzed using X-ray diffraction and scanning electron microscopy. The results show that under the same fluidity, the incorporation of 0.3%-0.6% hydroxypropyl methyl cellulose (HPMC) can significantly increase the gas-retaining performance of the slurry. A finer and more homogeneous pore structure was achieved by incorporating 0.6% HPMC, resulting in a smaller bulk density (23.1% decrease) and thermal conductivity (34.3% decrease) at the expense of a slight loss of compressive strength (13.8% decrease). This study provides a basis for adjusting the physical-mechanical properties of AAC by using foam stabilizers.