Abstract: To optimize the mix proportion of fly ash foam concrete, the influences of different foaming agent combinations and dosages on the strength of fly ash mortar was first compared. This comparison determined the dosage of activator. Subsequently, through single-factor experiments, the optimal ranges of fly ash, CaSt, and H₂O₂ content in foam concrete were determined. Finally, based on the Box-Benhnken response surface methodology, the effects of fly ash, CaSt, and H₂O₂ content on the compressive strength, dry density, and thermal conductivity of foam concrete were studied. A response surface model was established to explore the degree of influence of each factor and their interaction effects, aiming to obtain optimal mix proportion. The results show that a dual-doping combination of 4.5% (mass fraction, the same as below) Na₂SO₄ and 4.5% Ca(OH)₂ significantly improves the performance of fly ash mortar. The interaction between fly ash and H₂O₂ content significantly influences compressive strength, CaSt and H₂O₂ content interaction significantly affects dry density, and the interaction between fly ash and CaSt content significantly influences thermal conductivity. When the water-to-binder ratio is 0.5, the fly ash content is 20.7%, the CaSt content is 1.9%, and the H₂O₂ content is 2.9%, an A07-grade foam concrete meeting the requirements is obtained.

Key words: fly ash, activator, foam concrete, response surface methodology, mix proportion