阅读说明：本技术 一种高强度和高软化系数的疏水氯氧镁水泥的制备方法 (Preparation method of hydrophobic magnesium oxychloride cement with high strength and high softening coefficient ) 是由 陈若愚 黄家鑫 王红宁 刘小华 于 2021-01-14 设计创作，主要内容包括：本发明属于氯氧镁水泥改性技术领域,具体涉及一种高强度和高软化系数的疏水氯氧镁水泥的制备方法：首先将氯化镁、水按摩尔比混合均匀后加入一定量的磷酸,十六烷基三甲氧基硅烷,非离子表面活性剂聚环氧乙烷-聚环氧丙烷-聚环氧乙烷三嵌段共聚物(P123)后搅拌反应得到氯化镁混合溶液,然后将活性氧化镁、氯化镁溶液按摩尔比混合搅拌均匀制成氯氧镁水泥浆体,注入模具,放置于空气中养护。本发明通过加入低表面能的硅烷得到整体疏水氯氧镁水泥,疏水角可以达到135°,氯氧镁水泥的整体疏水性使得质量吸水率降低,软化系数提高的同时也保证了抗压强度,具有潜在的工程应用价值。(The invention belongs to the technical field of modification of magnesium oxychloride cement, and particularly relates to a preparation method of hydrophobic magnesium oxychloride cement with high strength and high softening coefficient, which comprises the following steps: firstly, uniformly mixing magnesium chloride and water according to a molar ratio, adding a certain amount of phosphoric acid, hexadecyl trimethoxy silane and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), stirring and reacting to obtain a magnesium chloride mixed solution, then uniformly mixing and stirring the active magnesium oxide and the 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 curing. According to the invention, the low surface energy silane is added to obtain the overall hydrophobic magnesium oxychloride cement, the hydrophobic angle can reach 135 degrees, the overall hydrophobicity of the magnesium oxychloride cement enables the mass water absorption to be reduced, the softening coefficient to be improved, and the compressive strength to be ensured, so that the magnesium oxychloride cement has potential engineering application value.)

1. A preparation method of hydrophobic magnesium oxychloride cement with high strength and high softening coefficient is characterized by comprising the following steps: the preparation method comprises the following steps of,

(1) uniformly mixing magnesium chloride and water according to a molar ratio, adding phosphoric acid, hexadecyl trimethoxy silane and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) to obtain a magnesium chloride mixed solution;

(2) and (2) uniformly mixing and stirring the magnesium chloride mixed solution obtained in the step (1) with active magnesium oxide and water according to a molar ratio to prepare magnesium oxychloride cement paste, and placing the magnesium oxychloride cement paste in air for curing.

2. The method of claim 1 for preparing a hydrophobic magnesium oxychloride cement of high strength and high softening coefficient, wherein: the dosage of the phosphoric acid is 0.5 to 2.5 percent of the mass of the active magnesium oxide.

3. The method of claim 1 for preparing a hydrophobic magnesium oxychloride cement of high strength and high softening coefficient, wherein: the dosage of the hexadecyl trimethoxy silane is 1 to 10 percent of the mass of the active magnesium oxide.

4. The method of claim 1 for preparing a hydrophobic magnesium oxychloride cement of high strength and high softening coefficient, wherein: the dosage of the nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) is 1 per mill-3% of the mass of the active magnesium oxide.

5. The method of claim 1 for preparing a hydrophobic magnesium oxychloride cement of high strength and high softening coefficient, wherein: mixing the magnesium chloride mixed solution with active magnesium oxide according to the molar ratio of MgO to magnesium chloride to water of 5-8: 1: 13-20; in the active magnesium oxide powder, the mass content of active magnesium oxide is more than or equal to 50 percent.

6. A hydrophobic magnesium oxychloride cement of high strength and high softening coefficient prepared by the process as claimed in any one of claims 1 to 5.

Technical Field

The invention belongs to the technical field of modification of magnesium oxychloride cement, and particularly relates to a preparation method of hydrophobic magnesium oxychloride cement with high strength and high softening coefficient.

Background

Magnesium oxychloride cement (MO)C) The air hardening gel material prepared by taking active magnesium oxide powder and magnesium chloride solution with certain concentration as raw materials has the advantages of high compressive strength, short condensation time, low alkalinity, fire prevention, heat resistance and the like compared with common silicate, is widely applied to the fields of building materials, heat insulation materials and biological materials, but has the defect of poor water resistance, wherein the main strength phase is P5 phase (5Mg (OH))₂·MgCl₂·8H₂O) is easy to change from a needle-like phase network structure into a loose-packed layer structure after being soaked in water, the softening coefficient is seriously reduced, and other properties are lost, so that how to improve the water resistance of the magnesium oxychloride cement is always the popular research direction in the field.

Magnesium oxychloride cement is undoubtedly the most effective way to start with the addition of modifiers due to its strong adulterability. The modifier mainly comprises an inorganic modifier and an organic modifier. The most used inorganic modifier is phosphoric acid (phosphate), fly ash containing certain active silicon dioxide, silica fume, incineration sludge ash, rice hull ash and the like, but the improvement of the inorganic additive on the water resistance is limited, and the fly ash silica fume belongs to a powder modifier, so that the excessive addition of the fly ash silica fume can influence the fluidity of a slurry body and further influence the demolding and the maintenance of a magnesium oxychloride cement sample. The organic modifier is mainly emulsion with hydrophobic property, such as styrene-acrylic emulsion, EVA emulsion and the like, the adding mode of the emulsion can be divided into surface coating and internal doping, the surface coating does not influence other properties of the magnesium oxychloride cement, but the thickness and the bonding force of the film cannot meet the changeable application environment of the building material, so that the film falls off, and water still enters the material to damage the structure. The internal doping can enable the magnesium oxychloride cement to achieve the overall hydrophobic effect, but the addition of the organic emulsion undoubtedly can affect the hydration of the magnesium oxychloride cement and even inhibit the hydration process of the magnesium oxychloride cement, so that the compressive strength and other engineering properties are seriously reduced, and the problems limit the development of the magnesium oxychloride cement in various fields.

Disclosure of Invention

The invention provides a preparation method of hydrophobic magnesium oxychloride cement with high strength and high softening coefficient, aiming at the problems of poor water resistance of magnesium oxychloride cement and negative influence on performances such as compressive strength after water-resistant modification in the prior art: phosphoric acid is taken as a water repellent agent, and hexadecyl trimethoxy silane is added to hydrolyze the phosphoric acid in the cement hydration process, so that the surface energy is reduced, and the integrally hydrophobic magnesium oxychloride cement is obtained. And the compressive strength of the magnesium oxychloride cement is increased by adding a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), so that the obtained sample has high compressive strength, low mass water absorption and high softening coefficient.

The preparation method mainly comprises the following steps:

(1) uniformly mixing magnesium chloride and water according to a certain molar ratio, adding a certain amount of phosphoric acid, hexadecyl trimethoxy silane and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) to obtain a magnesium chloride mixed solution;

(2) and (2) mixing and stirring the magnesium chloride mixed solution obtained in the step (1) with active magnesium oxide and water uniformly to prepare magnesium oxychloride cement paste, and placing the magnesium oxychloride cement paste in the air for curing.

Wherein, the dosage of the phosphoric acid is 0.5 to 2.5 percent of the mass of the active magnesium oxide, the dosage of the hexadecyl trimethoxy silane is 1 to 10 percent of the mass of the active magnesium oxide, and the dosage of the nonionic surfactant, namely the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) is 1 per thousand to 3 percent of the mass of the active magnesium oxide.

And mixing the magnesium chloride solution with active magnesium oxide and water 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 alkoxy film generated by hydrolysis of the hexadecyl trimethoxy silane endows the magnesium oxychloride cement with integral hydrophobicity, and the hexadecyl trimethoxy silane can be better combined with the magnesium oxychloride cement by adding the nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), so that the compressive strength of the magnesium oxychloride cement is increased while the hydrophobicity is ensured.

Drawings

FIG. 1 is a picture of the hydrophobic effect and angle of hydrophobicity of the cement product obtained in example 8.

Detailed Description

The present invention is further described below with reference to examples, but is not limited thereto.

Example 1

(1) Uniformly mixing magnesium chloride and water according to a molar ratio of 1:13, adding phosphoric acid, hexadecyl trimethoxy silane and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) to obtain a magnesium chloride mixed solution. Wherein the dosage of the phosphoric acid is 0.5 percent of the mass of the active magnesium oxide, the dosage of the hexadecyl trimethoxy silane is 1 percent of the mass of the active magnesium oxide, and the dosage of the nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) is 1 per mill of the mass of the active magnesium oxide.

(2) Mixing and stirring the magnesium chloride mixed solution, active magnesium oxide and water uniformly according to the molar ratio of 6.5:1:13 of the active magnesium oxide to the active magnesium chloride to the water to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a 20mm multiplied by 20mm mould, demoulding and maintaining after 1 day, measuring to obtain a hydrophobic angle of about 140 degrees after maintaining in the air for 28 days, polishing the surface of a cement sample by using sand paper, and measuring to obtain the hydrophobic angle which is not changed after polishing. The compressive strength is 63MPa, the mass water absorption is 18.5 percent and the softening coefficient is 0.8 after 28 days of water soaking according to DB 32/T3696-2019.

Example 2

(1) Uniformly mixing magnesium chloride and water according to a molar ratio of 1:13, adding phosphoric acid, hexadecyl trimethoxy silane and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) to obtain a magnesium chloride mixed solution. Wherein the dosage of the phosphoric acid is 1 percent of the mass of the active magnesium oxide, the dosage of the hexadecyl trimethoxy silane is 1 percent of the mass of the active magnesium oxide, and the dosage of the nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) is 1 per mill of the mass of the active magnesium oxide.

(2) Mixing and stirring the magnesium chloride mixed solution, active magnesium oxide and water uniformly according to the molar ratio of 6.5:1:13 of the active magnesium oxide to the active magnesium chloride to the water to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a 20mm multiplied by 20mm mould, demoulding and maintaining after 1 day, measuring to obtain a hydrophobic angle of about 133 degrees after maintaining in the air for 28 days, polishing the surface of a cement sample by using sand paper, and measuring to obtain the hydrophobic angle which is not changed after polishing. The compressive strength is 51MPa, the mass water absorption is 13.8 percent and the softening coefficient is 0.85 measured after 28 days of water bubbles according to DB 32/T3696-2019.

Example 3

(1) Uniformly mixing magnesium chloride and water according to a molar ratio of 1:13, adding phosphoric acid, hexadecyl trimethoxy silane and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) to obtain a solution. Wherein the dosage of the phosphoric acid is 1.5 percent of the mass of the active magnesium oxide, the dosage of the hexadecyl trimethoxy silane is 1 percent of the mass of the active magnesium oxide, and the dosage of the nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) is 1 per thousand of the mass of the active magnesium oxide.

(2) Mixing and stirring the magnesium chloride mixed solution, active magnesium oxide and water uniformly according to the molar ratio of 6.5:1:13 of the active magnesium oxide to the active magnesium chloride to the water to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a 20mm multiplied by 20mm mould, demoulding and maintaining after 1 day, measuring to obtain a hydrophobic angle of about 120 degrees after maintaining in the air for 28 days, polishing the surface of a cement sample by using sand paper, and measuring to obtain the hydrophobic angle which is not changed after polishing. The compressive strength is 45MPa, the mass water absorption is 12.7 percent and the softening coefficient is 0.75 when measured after 28 days of DB 32/T3696-2019 water bubbles.

Example 4

(1) Uniformly mixing magnesium chloride and water according to a molar ratio of 1:13, adding phosphoric acid, hexadecyl trimethoxy silane and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) to obtain a magnesium chloride mixed solution. Wherein the dosage of the phosphoric acid is 2.5 percent of the mass of the active magnesium oxide, the dosage of the hexadecyl trimethoxy silane is 1 percent of the mass of the active magnesium oxide, and the dosage of the nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) is 1 per thousand of the mass of the active magnesium oxide.

(2) Mixing and stirring the magnesium chloride mixed solution, active magnesium oxide and water uniformly according to the molar ratio of 6.5:1:13 of the active magnesium oxide to the active magnesium chloride to the water to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a 20mm multiplied by 20mm mould, demoulding and maintaining after 1 day, measuring to obtain a hydrophobic angle of about 100 degrees after maintaining in the air for 28 days, polishing the surface of a cement sample by using sand paper, and measuring to obtain the hydrophobic angle unchanged after polishing. The compressive strength is 25MPa, the mass water absorption is 14.7 percent and the softening coefficient is 0.65 after 28 days of water soaking according to DB 32/T3696-2019.

Example 5

(1) Uniformly mixing magnesium chloride and water according to a molar ratio of 1:13, adding phosphoric acid, hexadecyl trimethoxy silane and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) to obtain a magnesium chloride mixed solution. Wherein the dosage of the phosphoric acid is 1 percent of the mass of the active magnesium oxide, the dosage of the hexadecyl trimethoxy silane is 2 percent of the mass of the active magnesium oxide, and the dosage of the nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) is 1 per mill of the mass of the active magnesium oxide.

(2) Mixing and stirring the magnesium chloride mixed solution, active magnesium oxide and water uniformly according to the molar ratio of 6.5:1:13 of the active magnesium oxide to the active magnesium chloride to the water to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a 20mm multiplied by 20mm mould, demoulding and maintaining after 1 day, measuring to obtain a hydrophobic angle of about 125 degrees after maintaining in the air for 28 days, polishing the surface of a cement sample by using sand paper, and measuring to obtain the hydrophobic angle which is not changed after polishing. The compressive strength is 46MPa, the mass water absorption is 11.1 percent and the softening coefficient is 0.81 after 28 days of water bubbles according to DB 32/T3696-2019.

Example 6

(1) Uniformly mixing magnesium chloride and water according to a molar ratio of 1:13, adding phosphoric acid, hexadecyl trimethoxy silane and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) to obtain a magnesium chloride mixed solution. Wherein the dosage of the phosphoric acid is 1 percent of the mass of the active magnesium oxide, the dosage of the hexadecyl trimethoxy silane is 5 percent of the mass of the active magnesium oxide, and the dosage of the nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) is 1 per mill of the mass of the active magnesium oxide.

(2) Mixing and stirring the magnesium chloride mixed solution, active magnesium oxide and water uniformly according to the molar ratio of 6.5:1:13 of the active magnesium oxide to the active magnesium chloride to the water to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a 20mm multiplied by 20mm mould, demoulding and maintaining after 1 day, measuring to obtain a hydrophobic angle of about 135 degrees after maintaining in the air for 28 days, polishing the surface of a cement sample by using sand paper, and measuring to obtain the hydrophobic angle unchanged after polishing. The compressive strength is 43MPa, the mass water absorption is 9.8 percent and the softening coefficient is 0.83 measured after 28 days of water bubbles according to DB 32/T3696-2019.

Example 7

(1) Uniformly mixing magnesium chloride and water according to a molar ratio of 1:13, adding phosphoric acid, hexadecyl trimethoxy silane and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) to obtain a magnesium chloride mixed solution. Wherein the dosage of the phosphoric acid is 1 percent of the mass of the active magnesium oxide, the dosage of the hexadecyl trimethoxy silane is 10 percent of the mass of the active magnesium oxide, and the dosage of the nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) is 1 per mill of the mass of the active magnesium oxide.

(2) Mixing and stirring the magnesium chloride mixed solution, active magnesium oxide and water uniformly according to the molar ratio of 6.5:1:13 of the active magnesium oxide to the active magnesium chloride to the water to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a 20mm multiplied by 20mm mould, demoulding and maintaining after 1 day, measuring to obtain a hydrophobic angle of about 147 degrees after maintaining in the air for 28 days, polishing the surface of a cement sample by using sand paper, and measuring to obtain the hydrophobic angle unchanged after polishing. The compressive strength is 38MPa, the mass water absorption is 7.1 percent and the softening coefficient is 0.86 measured after 28 days of water bubbles according to DB 32/T3696-2019.

Example 8

(1) Uniformly mixing magnesium chloride and water according to a molar ratio of 1:13, adding phosphoric acid, hexadecyl trimethoxy silane and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) to obtain a magnesium chloride mixed solution. Wherein the dosage of the phosphoric acid is 1 percent of the mass of the active magnesium oxide, the dosage of the hexadecyl trimethoxy silane is 5 percent of the mass of the active magnesium oxide, and the dosage of the nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) is 5 per mill of the mass of the active magnesium oxide.

(2) Mixing and stirring the magnesium chloride mixed solution, active magnesium oxide and water uniformly according to the molar ratio of 6.5:1:13 of the active magnesium oxide to the active magnesium chloride to the water to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a 20mm multiplied by 20mm mould, demoulding and maintaining after 1 day, measuring to obtain a hydrophobic angle of about 135 degrees after maintaining in the air for 28 days, polishing the surface of a cement sample by using sand paper, and measuring to obtain the hydrophobic angle unchanged after polishing. The compressive strength is 45MPa, the mass water absorption is 7.2 percent and the softening coefficient is 0.85 when measured according to DB 32/T3696-2019 after 28 days of water soaking.

Example 9

(1) Uniformly mixing magnesium chloride and water according to a molar ratio of 1:13, adding phosphoric acid, hexadecyl trimethoxy silane and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) to obtain a magnesium chloride mixed solution. Wherein the dosage of the phosphoric acid is 1 percent of the mass of the active magnesium oxide, the dosage of the hexadecyl trimethoxy silane is 5 percent of the mass of the active magnesium oxide, and the dosage of the nonionic surfactant, namely the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) is 1 percent of the mass of the active magnesium oxide.

(2) Mixing and stirring the magnesium chloride mixed solution, active magnesium oxide and water uniformly according to the molar ratio of 6.5:1:13 of the active magnesium oxide to the active magnesium chloride to the water to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a 20mm multiplied by 20mm mould, demoulding and maintaining after 1 day, measuring to obtain a hydrophobic angle of about 137 degrees after maintaining in the air for 28 days, polishing the surface of a cement sample by using sand paper, and measuring to obtain the hydrophobic angle unchanged after polishing. The compressive strength is 56MPa, the mass water absorption is 7.3 percent and the softening coefficient is 0.89 after 28 days of water soaking according to DB 32/T3696-2019.

Example 10

(1) Uniformly mixing magnesium chloride and water according to a molar ratio of 1:13, adding phosphoric acid, hexadecyl trimethoxy silane and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) to obtain a magnesium chloride mixed solution. Wherein the dosage of the phosphoric acid is 1 percent of the mass of the active magnesium oxide, the dosage of the hexadecyl trimethoxy silane is 5 percent of the mass of the active magnesium oxide, and the dosage of the nonionic surfactant, namely the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) is 2 percent of the mass of the active magnesium oxide.

(2) Mixing and stirring the magnesium chloride mixed solution, active magnesium oxide and water uniformly according to the molar ratio of 6.5:1:13 of the active magnesium oxide to the active magnesium chloride to the water to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a 20mm multiplied by 20mm mould, demoulding and maintaining after 1 day, measuring to obtain a hydrophobic angle of about 134 degrees after maintaining in the air for 28 days, polishing the surface of a cement sample by using sand paper, and measuring to obtain the hydrophobic angle unchanged after polishing. The compressive strength is 57MPa, the mass water absorption is 7.2 percent and the softening coefficient is 0.88 after 28 days of water bubbles according to DB 32/T3696-2019.

Example 11

(1) Uniformly mixing magnesium chloride and water according to a molar ratio of 1:13, adding phosphoric acid, hexadecyl trimethoxy silane and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) to obtain a magnesium chloride mixed solution. Wherein the dosage of the phosphoric acid is 1 percent of the mass of the active magnesium oxide, the dosage of the hexadecyl trimethoxy silane is 5 percent of the mass of the active magnesium oxide, and the dosage of the nonionic surfactant, namely the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) is 3 percent of the mass of the active magnesium oxide.

(2) Mixing and stirring the magnesium chloride mixed solution, active magnesium oxide and water uniformly according to the molar ratio of 6.5:1:13 of the active magnesium oxide to the active magnesium chloride to the water to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a 20mm multiplied by 20mm mould, demoulding and maintaining after 1 day, measuring to obtain a hydrophobic angle of about 134 degrees after maintaining in the air for 28 days, polishing the surface of a cement sample by using sand paper, and measuring to obtain the hydrophobic angle unchanged after polishing. The compressive strength is 52MPa, the mass water absorption is 8.6 percent and the softening coefficient is 0.83 measured after 28 days of water bubbles according to DB 32/T3696-2019.

Example 12

(1) Uniformly mixing magnesium chloride and water according to a molar ratio of 1:13, adding phosphoric acid, hexadecyl trimethoxy silane and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) to obtain a magnesium chloride mixed solution. Wherein the dosage of the phosphoric acid is 1 percent of the mass of the active magnesium oxide, the dosage of the hexadecyl trimethoxy silane is 5 percent of the mass of the active magnesium oxide, and the dosage of the nonionic surfactant, namely the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) is 1 percent of the mass of the active magnesium oxide.

(2) Mixing and stirring the magnesium chloride mixed solution, active magnesium oxide and water uniformly according to the molar ratio of 5:1:13 of the active magnesium oxide to the active magnesium chloride to the water to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a 20mm multiplied by 20mm mould, demoulding and maintaining after 1 day, and measuring to obtain a hydrophobic angle of about 137 degrees after maintaining in the air for 28 days, polishing the surface of a cement sample by using sand paper, and measuring to obtain the hydrophobic angle unchanged after polishing. The compressive strength is 50MPa, the mass water absorption is 8.3 percent and the softening coefficient is 0.87 after 28 days of water soaking according to DB 32/T3696-2019.

Example 13

(1) Uniformly mixing magnesium chloride and water according to a molar ratio of 1:13, adding phosphoric acid, hexadecyl trimethoxy silane and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) to obtain a magnesium chloride mixed solution. Wherein the dosage of the phosphoric acid is 1 percent of the mass of the active magnesium oxide, the dosage of the hexadecyl trimethoxy silane is 5 percent of the mass of the active magnesium oxide, and the dosage of the nonionic surfactant, namely the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) is 1 percent of the mass of the active magnesium oxide.

(2) Mixing and stirring the magnesium chloride mixed solution, active magnesium oxide and water uniformly according to the molar ratio of 6.5:1:18 of the active magnesium oxide to the active magnesium chloride to the water to prepare magnesium oxychloride cement paste, injecting the magnesium oxychloride cement paste into a 20mm multiplied by 20mm mould, demoulding and maintaining after 1 day, measuring to obtain a hydrophobic angle of about 137 degrees after maintaining in the air for 28 days, polishing the surface of a cement sample by using sand paper, and measuring to obtain the hydrophobic angle unchanged after polishing. The compressive strength is 40MPa, the mass water absorption is 8.5 percent and the softening coefficient is 0.82 measured after 28 days of water bubbles according to DB 32/T3696-2019.

Comparative example 1

(1) And uniformly mixing magnesium chloride and water according to the molar ratio of 1:13 to obtain a 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, demolding and maintaining after 1 day, and measuring to obtain a hydrophobic angle of about 87 degrees after maintaining in air for 28 days, polishing the surface of a cement sample by using sand paper, and measuring to obtain the hydrophobic angle which is not changed after polishing. The compressive strength is 126MPa, the mass water absorption is 32 percent and the softening coefficient is 0.22 after 28 days of water bubbles according to DB 32/T3696-2019.

Comparative example 2

(1) Magnesium chloride and water are uniformly mixed according to the molar ratio of 1:13, and hexadecyl trimethoxy silane is added to obtain a solution. Wherein, the dosage of the hexadecyl trimethoxy silane is 5 percent of the mass of the active magnesium oxide.

(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, demolding and maintaining after 1 day, measuring to obtain a hydrophobic angle of about 137 degrees after maintaining in the air for 28 days, polishing the surface of a cement sample by using sand paper, and measuring to obtain the hydrophobic angle which is not changed after polishing. The compressive strength is 76MPa, the mass water absorption is 16.3 percent and the softening coefficient is 0.42 measured after 28 days of water bubbles according to DB 32/T3696-2019.

Comparative example 3

(1) Uniformly mixing magnesium chloride and water according to a molar ratio of 1:13, and adding phosphoric acid and hexadecyl trimethoxy silane to obtain a solution. Wherein the dosage of the phosphoric acid is 1 percent of the mass of the active magnesium oxide, and the dosage of the hexadecyl trimethoxy silane is 5 percent of the mass of the active magnesium oxide.

(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, demolding and maintaining after 1 day, and measuring to obtain a hydrophobic angle of about 127 degrees after maintaining in air for 28 days, and polishing the surface of a cement sample by using sand paper, wherein the hydrophobic angle is not changed after polishing. The compressive strength is 35MPa, the mass water absorption is 7.5 percent and the softening coefficient is 0.82 measured after 28 days of water bubbles according to DB 32/T3696-2019.

Comparative example 4

(1) Uniformly mixing magnesium chloride and water according to a molar ratio of 1:13, and adding phosphoric acid, Methyl Triethoxysilane (MTES) and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) to obtain a solution. Wherein the dosage of the phosphoric acid is 1 percent of the mass of the active magnesium oxide, the dosage of the Methyltriethoxysilane (MTES) is 5 percent of the mass of the active magnesium oxide, and the dosage of the nonionic surfactant, namely the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) is 1 percent of the mass of the active magnesium oxide.

(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, demolding and maintaining after 1 day, and measuring to obtain a hydrophobic angle of about 87 degrees after maintaining in air for 28 days, polishing the surface of a cement sample by using sand paper, and measuring to obtain the hydrophobic angle which is not changed after polishing. The compressive strength is 65MPa, the mass water absorption is 13.1 percent and the softening coefficient is 0.73 measured after 28 days of water bubbles according to DB 32/T3696-2019.

Comparative example 5

(1) Uniformly mixing magnesium chloride and water according to the molar ratio of 1:13, adding phosphoric acid and a nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) to obtain a solution. Wherein the dosage of the phosphoric acid is 1 percent of the mass of the active magnesium oxide, and the dosage of the nonionic surfactant polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) is 1 percent of the mass of the active magnesium oxide.

(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, demolding and maintaining after 1 day, and measuring to obtain a hydrophobic angle of about 76 degrees after maintaining in air for 28 days, and polishing the surface of a cement sample by using sand paper, wherein the hydrophobic angle is not changed after polishing. The compressive strength is 85MPa, the mass water absorption is 15 percent and the softening coefficient is 0.73 measured after 28 days of water bubbles according to DB 32/T3696-2019.

Comparative example 6

(1) Uniformly mixing magnesium chloride and water according to a molar ratio of 1:13, and adding phosphoric acid, hexadecyl trimethoxy silane and a cationic surfactant, namely hexadecyl trimethyl ammonium bromide (CTAB), to obtain a solution. Wherein the dosage of the phosphoric acid is 1 percent of the mass of the active magnesium oxide, the dosage of the hexadecyl trimethoxy silane is 5 percent of the mass of the active magnesium oxide, and the dosage of the cationic surfactant hexadecyl trimethyl ammonium bromide (CTAB) is 1 percent of the mass of the active magnesium oxide.

(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, demolding and maintaining after 1 day, and measuring to obtain a hydrophobic angle of about 122 degrees after maintaining in air for 28 days, and polishing the surface of a cement sample by using sand paper, wherein the hydrophobic angle is not changed after polishing. The compressive strength is 38MPa, the mass water absorption is 11.8 percent and the softening coefficient is 0.77 measured after 28 days of water bubbles according to DB 32/T3696-2019.