Magnesium-based fly ash porous sound-absorbing material with surface hydrophobically modified and preparation method thereof

A preparation method of a magnesium-based fly ash porous sound-absorbing material with a surface hydrophobically modified, comprising the following steps:

• step 1:
• thoroughly mixing magnesium oxide, a fly ash, and a fiber to obtain a mixed dry material, wherein a mass of the fly ash is 10% to 30% of a total mass of the mixed dry material;
• step 2:
• dissolving magnesium sulfate heptahydrate and an admixture in water, and heating for dissolution to obtain an admixture-containing magnesium sulfate solution;
• step 3:
• adding the mixed dry material obtained in step 1 to the admixture-containing magnesium sulfate solution obtained in step 2, and stirring to obtain a cement slurry;
• step 4:
• diluting a foaming agent with water, using a foaming machine to prepare a foam, and adding the foam to the cement slurry obtained in step 3 under a low-speed stirring to obtain a foamed slurry, wherein the foaming agent is diluted 50 to 80 times with the water, and the foam has a density of 30 kg/m3 to 60 kg/m3;
• step 5:
• pouring the foamed slurry obtained in step 4 into a mold, covering with a layer of plastic wrap, curing in air at room temperature for 1 d, demolding, and further curing until a test age to obtain a magnesium-based fly ash porous material;
• step 6:
• adding a modifier dropwise around the magnesium-based fly ash porous material obtained in step 5, sealing, and conducting a surface deposition modification at a constant temperature to obtain a modified material, wherein the modifier is added dropwise at an amount of 1 mL to 10 mL per 1 m2 of the magnesium-based fly ash porous material;
• and
• step 7:
• fully cooling the modified material obtained in step 6 at room temperature, and taking the modified material out to obtain the magnesium-based fly ash porous sound-absorbing material with a surface hydrophobically modified.