Effect of triethanolamine on the synthetic process of porous magnesia lightweight aggregates

Magnesia lightweight aggregates were synthesized by direct foaming method with light burned magnesia powder as raw material, sodium dodecyl benzene sulfonate (SDBS) as foaming agent and triethanolamine (TEA) as dispersant. Aqueous foams and magnesia foam slurry with foaming agent content of 3 wt% were prepared. The effects of different contents TEA (0.6 wt%, 1.0 wt%, 1.4 wt%, 1.8 wt%, and 2.2 wt%) on Zeta potential, viscosity, expansion ratio, contact angle, and surface tension of magnesia foam slurry were studied. The microstructure of aqueous foams and magnesia foam slurry were observed by optical microscope. After sintering at 1600 °C, the number and distribution of pores in the magnesia lightweight aggregates were analyzed by SEM. In aqueous foams, with the increase of TEA contents, the bubble liquid film became thicker and the shape became circle. In the magnesia foam slurry, when the TEA content was 1.4 wt%, the Zeta potential was 28.19 mV, the contact angle was 62.3°, and the surface tension was 45.2 mN∙m^− 1. The adsorption free energy of magnesia particles was about 7.3 × 10^− 9 J. The bubble size distribution was 31.48 μm to 114.30 μm. In magnesia lightweight aggregates, the average pore size was 30.98 μm to 95.43 μm.