A magnesium-based fly ash porous sound-absorbing material with a surface hydrophobically modified, and a preparation method thereof are provided. In the preparation method, a basic magnesium sulfate cement is adopted as a cementing agent and a fly ash is adopted as a mineral admixture to prepare a slurry; foaming is conducted through a physical foaming process in a foaming machine to obtain a foam; and the foam is mixed with the slurry, and a resulting mixture is poured and cured, and then subjected to a surface hydrophobic modification through vapor deposition to obtain the sound-absorbing material. The sound-absorbing material has a density of 251 kg/m.sup.3 to 306 kg/m.sup.3, a noise reduction coefficient (NRC) of 0.65 to 0.7, a compressive strength of 1.8 MPa to 2.2 MPa, and a water contact angle of 129 to 151.

A method for producing a printed concrete element, in particular a printed concrete block, a printed concrete slab or a printed concrete step, is described, comprising at least the following steps: filling concrete into a mold to form a concrete element; printing at least one surface area of the concrete element with a printing composition comprising a binder A and a dye B, the binder A containing at least one siloxane and at least one silane; and curing the concrete element after printing.

A method for producing a printed concrete element, in particular a printed concrete block, a printed concrete slab or a printed concrete step, is described, comprising at least the following steps: filling concrete into a mold to form a concrete element; printing at least one surface area of the concrete element with a printing composition comprising a binder A and a dye B, the binder A containing at least one siloxane and at least one silane; and curing the concrete element after printing.