CN110304894B - Preparation method of foaming hydrophobic magnesium oxychloride cement - Google Patents

Preparation method of foaming hydrophobic magnesium oxychloride cement Download PDF

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CN110304894B
CN110304894B CN201910607933.XA CN201910607933A CN110304894B CN 110304894 B CN110304894 B CN 110304894B CN 201910607933 A CN201910607933 A CN 201910607933A CN 110304894 B CN110304894 B CN 110304894B
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magnesium
oxychloride cement
magnesium oxychloride
hydrophobic
molar ratio
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CN110304894A (en
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陈若愚
黄家鑫
王红宁
刘小华
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Changzhou University
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/30—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing magnesium cements or similar cements
    • C04B28/32—Magnesium oxychloride cements, e.g. Sorel cement
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
    • C04B38/02—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by adding chemical blowing agents
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20—Resistance against chemical, physical or biological attack
    • C04B2111/27—Water resistance, i.e. waterproof or water-repellent materials
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/40—Porous or lightweight materials

Abstract

The invention belongs to the technical field of modification of magnesium oxychloride cement, and particularly relates to a preparation method of foaming hydrophobic magnesium oxychloride cement, which comprises the following steps: firstly, uniformly mixing magnesium chloride and water according to a molar ratio, adding a certain amount of hydrogen peroxide, tetraethyl orthosilicate (TEOS), triethoxy-1H, 1H,2H, 2H-tridecafluoro n-octylsilane (FAS), stirring and reacting to obtain a treated magnesium chloride solution, then uniformly mixing and stirring active magnesium oxide and the treated magnesium chloride solution according to the molar ratio to prepare magnesium oxychloride cement slurry, injecting the magnesium oxychloride cement slurry into a mold, and placing the magnesium oxychloride cement slurry in air for maintenance. The invention obtains the foaming hydrophobic magnesium oxychloride cement by pretreating the magnesium chloride solution and mixing with the active magnesium oxide, wherein the hydrophobic angle of the foaming hydrophobic magnesium oxychloride cement can reach 150 degrees, and the integral hydrophobicity of the magnesium oxychloride cement is greatly improved instead of being only limited to surface hydrophobicity, thereby solving the great defect of poor water resistance of the magnesium oxychloride cement.

Description

Preparation method of foaming hydrophobic magnesium oxychloride cement
Technical Field
The invention belongs to the technical field of modification of magnesium oxychloride cement, and particularly relates to a preparation method of foaming hydrophobic magnesium oxychloride cement.
Background
The foam concrete is a concrete material with light weight, good heat preservation and insulation effect and excellent sound insulation performance, meets the requirement of a new policy of building energy conservation in China, and is widely applied to building engineering in China. The foaming concrete is characterized in that oxygen, carbon dioxide and other gases are introduced into slurry through a physical or chemical foaming method to enable the slurry to foam naturally, and a concrete material with a pore structure is formed after curing for a period of time.
Magnesium oxychloride cement as a novel air-hardening gel material is undoubtedly a better choice of a foam concrete raw material, compared with the traditional portland cement, the magnesium oxychloride cement has the advantages of high setting speed, high strength, fire resistance and other excellent performances, and the magnesium oxychloride cement product does not need higher curing conditions, so that the energy consumption in the building production process can be greatly reduced. Compared with Portland cement, the magnesium oxychloride cement used for the foamed concrete can further reduce the apparent density of the product and improve the early strength, and the respective excellent performances of the foamed concrete and the magnesium oxychloride cement are combined to the greatest extent, so that the magnesium oxychloride cement has a great application prospect in the field of buildings. But both have the great disadvantage of poor water resistance.
In order to solve the defects, scholars at home and abroad make great efforts, and the current effective way for solving the problem of poor water resistance is to add phosphoric acid or soluble phosphate, but the problems of low condensation speed of the magnesium oxychloride cement, influence on later strength due to reduction of early strength and the like are also brought, so that the engineering value of the magnesium oxychloride cement is greatly reduced. The method has certain effect, but because the environment of the building material is changeable, even severe weather with extreme cold and extreme heat occurs, the film on the surface of the concrete is easy to fall off, and the purpose of long-term hydrophobic is not achieved.
Disclosure of Invention
Aiming at the problem of poor water resistance of the foaming magnesium oxychloride cement in the prior art, the invention provides a preparation method of the hydrophobic foaming magnesium oxychloride cement, which comprises the following steps: hydrogen peroxide is used as a foaming agent, tetraethyl orthosilicate (TEOS), triethoxy-1H, 1H,2H, 2H-tridecafluoro n-octyl silane (FAS) are added into a magnesium oxychloride foaming cement system, and the tetraethyl orthosilicate, the triethoxy-1H, 1H,2H, 2H-tridecafluoro n-octyl silane (FAS) and the TEOS are co-hydrolyzed in the foaming cement system, so that the surface energy is reduced, and the magnesium oxychloride foaming cement which is hydrophobic as a whole but not only hydrophobic in.
The preparation method mainly comprises the following steps:
(1) magnesium chloride and water are uniformly mixed according to a certain molar ratio, then a certain amount of hydrogen peroxide, tetraethyl orthosilicate (TEOS), triethoxy-1H, 1H,2H, 2H-tridecafluoro n-octylsilane (FAS) are added, and then the mixture is stirred and reacts to obtain a treated magnesium chloride solution.
(2) And (2) uniformly mixing and stirring the treated magnesium chloride solution obtained in the step (1) and active magnesium oxide according to a molar ratio to prepare magnesium oxychloride cement paste, and placing the magnesium oxychloride cement paste in air for curing.
Wherein the dosage of the hydrogen peroxide is 2 to 10 percent of the mass of the active magnesium oxide;
the dosage of triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) is 1-3% of the mass of the active magnesium oxide.
Tetraethyl orthosilicate (TEOS) is added according to the molar ratio of triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) to tetraethyl orthosilicate (TEOS) of 1: 6-12.
And mixing the magnesium chloride solution with the active magnesium oxide according to the molar ratio of MgO to magnesium chloride to water of 5-8: 1: 13-20.
The invention has the beneficial effects that: the invention reduces the surface energy of magnesium oxychloride foam cement by cohydrolysis of tetraethyl orthosilicate (TEOS), triethoxy-1H, 1H,2H, 2H-tridecafluoro n-octylsilane (FAS) in magnesium chloride solution and then stirring and reacting with magnesium oxide, and meanwhile, the pore structure also provides certain surface roughness, so that the finished product achieves the effect of integral hydrophobicity.
Drawings
FIG. 1 is a picture of the hydrophobic effect of the finished magnesium oxychloride foamed cement obtained in example 1;
fig. 2 is a picture of the hydrophobic angle of the magnesium oxychloride foamed cement obtained in example 1.
Detailed Description
The present invention will be described in detail with reference to specific examples.
Example 1
(1) Magnesium chloride and water are mixed according to a molar ratio of 1:13, adding hydrogen peroxide, triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) and tetraethyl orthosilicate (TEOS), wherein the amount of the added hydrogen peroxide is 10 percent of the mass of the active magnesium oxide powder, the amount of the added triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) is 1 percent of the mass of the active magnesium oxide powder, and the tetraethyl orthosilicate (TEOS) is added according to the molar ratio of the triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) to the tetraethyl orthosilicate (TEOS) of 1:8, and stirring and reacting at 60 ℃ and 600r/min for 8 hours to obtain the treated magnesium chloride solution.
(2) Mixing and stirring active magnesium oxide, magnesium chloride and water uniformly according to the mol ratio of 6.5:1:13 to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a mold with the size of 20mm multiplied by 1 day, demolding and curing after 1 day, curing in the air for 3 days, and measuring to obtain a hydrophobic angle of about 150 degrees.
And (3) polishing the surface of the cement sample by using sand paper, and measuring that the hydrophobic angle is unchanged after polishing.
Example 2
(1) Magnesium chloride and water are mixed according to a molar ratio of 1:13, adding hydrogen peroxide, triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) and tetraethyl orthosilicate (TEOS), wherein the amount of the added hydrogen peroxide is 8 percent of the mass of the active magnesium oxide powder, the amount of the added triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) is 1 percent of the mass of the active magnesium oxide powder, and the tetraethyl orthosilicate (TEOS) is added according to the molar ratio of the triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) to the tetraethyl orthosilicate (TEOS) of 1:10, and stirring and reacting at 60 ℃ and 600r/min for 8 hours to obtain the treated solution.
(2) The cement product was prepared as in example 1(2) and the angle of hydrophobicity was measured to be about 100 deg., which is less effective than example 1.
And (3) polishing the surface of the cement sample by using sand paper, and measuring that the hydrophobic angle is unchanged after polishing.
Example 3
(1) Magnesium chloride and water are mixed according to a molar ratio of 1:13 adding hydrogen peroxide, triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) and tetraethyl orthosilicate (TEOS) after uniformly mixing, wherein the added hydrogen peroxide accounts for 6 percent of the mass of the active magnesium oxide powder, the added triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) accounts for 1 percent of the mass of the active magnesium oxide powder, the added materials are added according to the molar ratio of the triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) to the tetraethyl orthosilicate (TEOS) of 1:12, and stirring and reacting at 60 ℃ and 600r/min for 8 hours to obtain a treated solution.
(2) The cement product was prepared as in example 1(2) and the angle of hydrophobicity was measured to be about 120 deg., which is less hydrophobic than example 1.
And (3) polishing the surface of the cement sample by using sand paper, and measuring that the hydrophobic angle is unchanged after polishing.
Example 4
(1) Magnesium chloride and water are mixed according to a molar ratio of 1:13 adding hydrogen peroxide, triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) and tetraethyl orthosilicate (TEOS) after uniformly mixing, wherein the added hydrogen peroxide accounts for 4 percent of the mass of the active magnesium oxide powder, the added triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) accounts for 1 percent of the mass of the active magnesium oxide powder, the added materials are added according to the molar ratio of the triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) to the tetraethyl orthosilicate (TEOS) of 1:12, and stirring and reacting at 60 ℃ and 600r/min for 8 hours to obtain a treated solution.
(2) The cement product was prepared as in example 1(2) and the angle of hydrophobicity was measured to be about 120 deg., which is less hydrophobic than example 1.
And (3) polishing the surface of the cement sample by using sand paper, and measuring that the hydrophobic angle is unchanged after polishing.
Example 5
(1) Magnesium chloride and water are mixed according to a molar ratio of 1:18, adding hydrogen peroxide, triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) and tetraethyl orthosilicate (TEOS), wherein the amount of the added hydrogen peroxide is 4 percent of the mass of the active magnesium oxide powder, the amount of the added triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) is 1 percent of the mass of the active magnesium oxide powder, the adding is carried out according to the molar ratio of the triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) to the tetraethyl orthosilicate (TEOS) of 1:12, and stirring and reacting for 8 hours at the temperature of 60 ℃ and the speed of 600r/min to obtain a treated solution;
(2) mixing and stirring active magnesium oxide, magnesium chloride and water uniformly according to the mol ratio of 6.5:1:18 to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a mould with the thickness of 20mm multiplied by 20mm, demoulding and curing after 1 day, curing in air for 3 days, and measuring that the hydrophobic angle is about 100 degrees, compared with example 1, the hydrophobic effect is poor.
And (3) polishing the surface of the cement sample by using sand paper, and measuring that the hydrophobic angle is unchanged after polishing.
Example 6
(1) Magnesium chloride and water are mixed according to a molar ratio of 1:20, adding hydrogen peroxide, triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) and tetraethyl orthosilicate (TEOS) after uniformly mixing, wherein the added hydrogen peroxide accounts for 4 percent of the mass of the active magnesium oxide powder, the added triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) accounts for 1 percent of the mass of the active magnesium oxide powder, the added materials are added according to the molar ratio of the triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) to the tetraethyl orthosilicate (TEOS) of 1:12, and stirring and reacting for 8 hours at the temperature of 60 ℃ and the speed of 600r/min to obtain a treated solution;
(2) mixing and stirring active magnesium oxide, magnesium chloride and water uniformly according to the mol ratio of 6.5:1:20 to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a mould with the thickness of 20mm multiplied by 20mm, demoulding and curing after 1 day, curing in the air for 3 days, and measuring the hydrophobic angle to be about 80 degrees, compared with the example 1, the hydrophobic effect is poorer.
And (3) polishing the surface of the cement sample by using sand paper, and measuring that the hydrophobic angle is unchanged after polishing.
Example 7
(1) Magnesium chloride and water are mixed according to a molar ratio of 1:13 adding hydrogen peroxide, triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) and tetraethyl orthosilicate (TEOS) after uniformly mixing, wherein the added hydrogen peroxide accounts for 4% of the mass of the active magnesium oxide powder, the added triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) accounts for 1% of the mass of the active magnesium oxide powder, the added materials are added according to the molar ratio of the triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) and tetraethyl orthosilicate (TEOS) of 1:12, and stirring and reacting at 60 ℃ and 600r/min for 8 hours to obtain a treated solution;
(2) mixing and stirring active magnesium oxide, magnesium chloride and water uniformly according to the molar ratio of 5:1:20 to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a mould with the thickness of 20mm multiplied by 20mm, demoulding and curing after 1 day, curing in the air for 3 days, and measuring the hydrophobic angle to be about 80 degrees, compared with the example 1, the hydrophobic effect is poor.
And (3) polishing the surface of the cement sample by using sand paper, and measuring that the hydrophobic angle is unchanged after polishing.
Example 8
(1) Magnesium chloride and water are mixed according to a molar ratio of 1:13 adding hydrogen peroxide, triethoxy-1H, 1H,2H, 2H-tridecafluoro n-octylsilane (FAS) and tetraethyl orthosilicate (TEOS) after uniformly mixing, wherein the amount of the added hydrogen peroxide is 10 percent of the mass of the active magnesium oxide powder, the amount of the added triethoxy-1H, 1H,2H, 2H-tridecafluoro n-octylsilane (FAS) is 2 percent of the mass of the active magnesium oxide powder, and the tetraethyl orthosilicate (TEOS) is added according to the molar ratio of the triethoxy-1H, 1H,2H, 2H-tridecafluoro n-octylsilane (FAS) to the tetraethyl orthosilicate (TEOS) of 1:8, and stirring and reacting at 60 ℃ and 600r/min for 8 hours to obtain a treated magnesium chloride solution;
(2) the active magnesium oxide, the magnesium chloride and the water are mixed and stirred uniformly according to the mol ratio of 6.5:1:13 to prepare magnesium oxychloride cement paste, the magnesium oxychloride cement paste is injected into a mould with the thickness of 20mm multiplied by 20mm, demoulding and curing are carried out after 1 day, curing is carried out in the air for 3 days, and the measured hydrophobic angle is about 150 degrees, which has no obvious difference from the example 1.
And (3) polishing the surface of the cement sample by using sand paper, and measuring that the hydrophobic angle is unchanged after polishing.
Example 9
(1) Magnesium chloride and water are mixed according to a molar ratio of 1:13 adding hydrogen peroxide, triethoxy-1H, 1H,2H, 2H-tridecafluoro n-octylsilane (FAS) and tetraethyl orthosilicate (TEOS) after uniformly mixing, wherein the amount of the added hydrogen peroxide is 10 percent of the mass of the active magnesium oxide powder, the amount of the added triethoxy-1H, 1H,2H, 2H-tridecafluoro n-octylsilane (FAS) is 3 percent of the mass of the active magnesium oxide powder, and the tetraethyl orthosilicate (TEOS) is added according to the molar ratio of the triethoxy-1H, 1H,2H, 2H-tridecafluoro n-octylsilane (FAS) to the tetraethyl orthosilicate (TEOS) of 1:8, and stirring and reacting at 60 ℃ and 600r/min for 8 hours to obtain a treated magnesium chloride solution;
(2) the active magnesium oxide, the magnesium chloride and the water are mixed and stirred uniformly according to the mol ratio of 6.5:1:13 to prepare magnesium oxychloride cement paste, the magnesium oxychloride cement paste is injected into a mould with the thickness of 20mm multiplied by 20mm, demoulding and curing are carried out after 1 day, curing is carried out in the air for 3 days, and the measured hydrophobic angle is about 145 degrees, which has no obvious difference from the example 1.
And (3) polishing the surface of the cement sample by using sand paper, and measuring that the hydrophobic angle is unchanged after polishing.
Comparative example 1
(1) Magnesium chloride and water are mixed according to a molar ratio of 1:13, adding hydrogen peroxide after uniformly mixing, wherein the amount of the added hydrogen peroxide is 10 percent of the mass of the active magnesium oxide powder, and stirring and reacting for 8 hours at 60 ℃ and 600r/min to obtain a treated magnesium chloride solution;
(2) mixing and stirring active magnesium oxide, magnesium chloride and water uniformly according to the mol ratio of 6.5:1:13 to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a mold with the size of 20mm multiplied by 20mm, demoulding and curing after 1 day, and curing in the air for 3 days without foaming and hydrophobic effect.
Comparative example 2
(1) Magnesium chloride and water are mixed according to a molar ratio of 1:13 adding hydrogen peroxide, triethoxy-1H, 1H,2H, 2H-tridecafluoro n-octyl silane (FAS) after uniformly mixing, wherein the amount of the added hydrogen peroxide is 10 percent of the mass of the active magnesium oxide powder, the amount of the added triethoxy-1H, 1H,2H, 2H-tridecafluoro n-octyl silane (FAS) is 1 percent of the mass of the active magnesium oxide powder, and stirring and reacting for 8 hours at 60 ℃ and 600r/min to obtain a treated magnesium chloride solution;
(2) mixing and stirring active magnesium oxide, magnesium chloride and water uniformly according to the mol ratio of 6.5:1:13 to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a mold with the size of 20mm multiplied by 20mm, demoulding and curing after 1 day, curing in air for 3 days, and measuring to obtain the water repellent angle of about 120 degrees, and compared with the example 1, the magnesium oxychloride cement paste has the advantages of water repellency, no foaming and slightly poor effect.
And (3) polishing the surface of the cement sample by using sand paper, and measuring that the hydrophobic angle is unchanged after polishing.
Comparative example 3
(1) Magnesium chloride and water are mixed according to a molar ratio of 1:13 adding hydrogen peroxide and tetraethyl orthosilicate (TEOS) after uniformly mixing, wherein the amount of the added hydrogen peroxide is 10 percent of the mass of the active magnesium oxide powder, the amount of the TEOS is added according to the amount of the embodiment 1, and stirring and reacting for 8 hours at the temperature of 60 ℃ and the speed of 600r/min to obtain a treated magnesium chloride solution;
(2) mixing and stirring active magnesium oxide, magnesium chloride and water uniformly according to the mol ratio of 6.5:1:13 to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a mold with the size of 20mm multiplied by 20mm, demoulding and curing after 1 day, and curing in the air for 3 days without foaming and hydrophobicity compared with example 1.
Comparative example 4
(1) Magnesium chloride and water are mixed according to a molar ratio of 1:13, adding hydrogen peroxide after uniformly mixing, wherein the amount of the added hydrogen peroxide is 10 percent of the mass of the active magnesium oxide powder, and obtaining the treated magnesium chloride solution. Mixing and stirring active magnesium oxide, magnesium chloride and water uniformly according to the molar ratio of 6.5:1:13 to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a mold with the size of 20mm multiplied by 20mm, demoulding and curing after 1 day, and curing in the air for 3 days to obtain a foamed cement material;
(2) mixing a precursor tetraethyl orthosilicate (TEOS), an in-situ modifier triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) and ethanol according to a molar ratio of 8:1:100, adding the mixture into a beaker, stirring and reacting for 6 hours, and adding a certain amount of ammonia water to adjust the pH value to be about 12 to obtain hydrophobic silica sol;
(3) and (3) pouring the hydrophobic silica sol prepared in the step (2) into a container, putting the foamed cement obtained in the step (1) into the container, and performing vacuum impregnation on the composite foamed cement by using a vacuum drying oven to obtain the hydrophobic foamed cement. The hydrophobic angle was measured to be 150 deg., and the same effect as in example 1 was obtained.
And (3) polishing the surface of the cement sample by using sand paper, and measuring that the hydrophobic angle is less than 10 degrees after polishing, and the hydrophobic effect is not generated.
Comparative example 5
(1) Magnesium chloride and water are mixed according to a molar ratio of 1:13 adding hydrogen peroxide, Methyl Triethoxysilane (MTES) and tetraethyl orthosilicate (TEOS) after uniformly mixing, wherein the amount of the added hydrogen peroxide is 10% of the mass of the active magnesium oxide powder, the amount of the added Methyl Triethoxysilane (MTES) is 1% of the mass of the active magnesium oxide powder, the tetraethyl orthosilicate (TEOS) is added according to the molar ratio of the Methyl Triethoxysilane (MTES) to the tetraethyl orthosilicate (TEOS) of 1:8, and stirring and reacting for 8 hours at 60 ℃ and 600r/min to obtain the treated magnesium chloride solution.
(2) Mixing and stirring active magnesium oxide, magnesium chloride and water uniformly according to the mol ratio of 6.5:1:13 to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a mould with the thickness of 20mm multiplied by 20mm, demoulding and curing after 1 day, curing in the air for 3 days, wherein the measured hydrophobic angle is 60 degrees, and the hydrophobic effect has a great difference compared with triethoxy-1H, 1H,2H, 2H-tridecafluoro n-octyl silane (FAS).
And (3) polishing the surface of the cement sample by using sand paper, and measuring that the hydrophobic angle is unchanged after polishing.

Claims (6)

1. A preparation method of foaming hydrophobic magnesium oxychloride cement is characterized by comprising the following steps: the preparation method comprises the following steps:
(1) uniformly mixing magnesium chloride and water according to a molar ratio, adding hydrogen peroxide, then adding tetraethyl orthosilicate (TEOS), triethoxy-1H, 1H,2H, 2H-tridecafluoro n-octylsilane (FAS), heating, stirring and reacting to obtain a treated magnesium chloride solution;
(2) and (2) uniformly mixing and stirring the treated magnesium chloride solution obtained in the step (1) and active magnesium oxide according to a molar ratio to prepare magnesium oxychloride cement slurry, injecting the magnesium oxychloride cement slurry into a mold, and placing the mold in air for curing.
2. The method of preparing a foamed hydrophobic magnesium oxychloride cement of claim 1, wherein: the dosage of the hydrogen peroxide is 2-10% of the mass of the active magnesium oxide.
3. The method of preparing a foamed hydrophobic magnesium oxychloride cement of claim 1, wherein: the dosage of the triethoxy-1H, 1H,2H, 2H-tridecafluoro n-octyl silane (FAS) is 1-3% of the mass of the active magnesium oxide.
4. The method of preparing a foamed hydrophobic magnesium oxychloride cement of claim 1, wherein: the tetraethyl orthosilicate (TEOS) is added according to the molar ratio of triethoxy-1H, 1H,2H, 2H-tridecafluorooctylsilane (FAS) to tetraethyl orthosilicate (TEOS) of 1: 6-12.
5. The method of preparing a foamed hydrophobic magnesium oxychloride cement of claim 1, wherein: the heating and stirring reaction is specifically a stirring reaction at 60-80 ℃ for 8-10 hours, and the stirring speed is 600 r/min.
6. The method of preparing a foamed hydrophobic magnesium oxychloride cement of claim 1, wherein: and mixing the magnesium chloride solution and the active magnesium oxide according to the molar ratio of MgO to magnesium chloride to water of 5-8: 1: 13-20.
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CN113185259B (en) * 2021-03-09 2022-08-23 四川大学 Integrally hydrophobic fireproof magnesium oxychloride thermal insulation foam material and preparation method thereof
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