Magnesium phosphate cement-based concrete as well as preparation method and application thereof

Abstract

The invention relates to the technical field of engineering structure reinforcement, and particularly discloses magnesium phosphate cement-based concrete as well as a preparation method and application thereof. The magnesium phosphate cement-based concrete provided by the invention is prepared from phosphate cement, a thickening time control agent, fine aggregate, calcined rice hull powder, modified hydrotalcite, a water reducing agent and water, wherein the modified hydrotalcite is hydrotalcite modified by a silane coupling agent and sodium stearate. After the magnesium phosphate cement-based concrete provided by the invention is treated for 2 hours under a high-temperature condition of 600 DEG C, the compressive strength and the breaking strength can reach 77.1 MPa and 16.7 MPa respectively; the compressive strength and the breaking strength can reach 90.7 MPa and 24.5 MPa respectively after the material is soaked in water for 28 days; and the compressive strength and the breaking strength at room temperature can respectively reach 99.62 MPa and 26.6 MPa.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of engineering structure reinforcement, and in particular to a magnesium phosphate cement-based concrete, a preparation method and application thereof. BACKGROUND

[0002] In the field of building materials, magnesium phosphate cement-based concrete has been widely used in road repair, engineering reinforcement and other scenes due to its fast hardening, early strength and excellent bonding performance.

[0003] However, the existing magnesium phosphate cement-based concrete has obvious performance short board: ① poor high temperature resistance: in a high temperature environment, the hydration products of the internal structure of the concrete are prone to thermal decomposition, thereby reducing the strength of the concrete, which greatly limits its application in tunnel fire repair and other scenes; ② insufficient water resistance: in a long-term humid environment, the hydration products of the concrete are prone to dissolution and decomposition, thereby causing the deterioration of the concrete structure, which is difficult to meet the requirements of durability in underground engineering, hydraulic structure and the like. Therefore, it is urgent to provide a magnesium phosphate cement-based concrete with high temperature resistance and water resistance and a preparation method thereof, which has important significance for expanding the application field, enhancing the long-term safety of engineering structures and promoting the green and efficient development of the building material industry. SUMMARY

[0004] In view of this, the present application provides a magnesium phosphate cement-based concrete, a preparation method and application thereof. The magnesium phosphate cement-based concrete provided by the present application is compounded by selecting phosphate cement, setting regulator, fine aggregate, calcined rice husk powder, modified hydrotalcite and water reducing agent, which greatly improves the water resistance, high temperature resistance and strength of the magnesium phosphate cement-based concrete.

[0005] To solve the above technical problems, the technical scheme provided by the present application is:

[0006] The present application provides a magnesium phosphate cement-based concrete, which comprises the following components in mass fraction: 100-110 parts of phosphate cement, 8-9 parts of setting regulator, 70-80 parts of fine aggregate, 30-40 parts of calcined rice husk powder, 15-20 parts of modified hydrotalcite, 4-5 parts of water reducing agent and 13-14 parts of water.

[0007] The modified hydrotalcite is hydrotalcite modified by silane coupling agent and sodium stearate.

[0008] The calcined rice husk powder comprises the following preparation steps: calcining rice husk powder at 650-700 DEG C to obtain the calcined rice husk powder.

[0009] Compared with the prior art, in the magnesium phosphate cement-based concrete provided by the application, the organic components in the rice husk powder are carbonized into rigid carbon skeletons with more stable structures after being calcined at a specific temperature, which, as coarse aggregate, cooperates with fine aggregate to form the support structure of the concrete, thereby improving the strength of the concrete; the inorganic silicon in the rice husk powder is converted into high-activity amorphous silicon dioxide after being calcined at a specific temperature, which can react with calcium hydroxide, the hydration product of cement, to generate dense C-S-H gel structure, thereby further improving the strength and water resistance of the concrete; the surface of the rice husk powder calcined at a specific temperature contains rich microporous structures, which can adsorb magnesium ions and phosphate ions generated in the hydration of cement, thereby improving the compactness of the concrete by reducing capillary porosity, and further improving the strength and water resistance of the concrete.

[0010] However, the inventors found in the research process that the use of calcined rice husk powder alone has limited effect on the improvement of the strength and water resistance of the magnesium phosphate cement-based concrete, and the application further adds modified hydrotalcite to the magnesium phosphate cement-based concrete, so that the modified hydrotalcite and the calcined rice husk powder greatly improve the strength and water resistance of the magnesium phosphate cement-based concrete through synergistic effect. The modified hydrotalcite provided by the application is hydrotalcite modified by silane coupling agent and sodium stearate. The siloxyl group at one end of the silane coupling agent can be combined with the hydroxyl group on the surface of the hydrotalcite, and the functional group at the other end of the silane coupling agent can also be combined with the groups on the surface of the cement matrix and the calcined rice husk powder. The silane coupling agent firmly combines the modified hydrotalcite and other components in the concrete, greatly improves the interfacial compatibility, improves the compactness of the concrete, and further improves the comprehensive performance of the concrete; under humid or water immersion conditions, the sodium stearate loaded in the interlayer structure of the modified hydrotalcite can slowly release its long-chain fatty groups to form a hydrophobic film in the concrete, thereby improving the water resistance of the concrete; the specific layered structure of the modified hydrotalcite can also be micro-filled between the particles of the concrete through a micro-filling effect, thereby reducing the porosity, improving the compactness of the concrete, and further improving the strength and water resistance of the concrete, solving the problem of limited improvement of water resistance when using calcined rice husk powder alone; in addition, under high temperature conditions, the modified hydrotalcite can absorb heat to remove interlayer water and hydroxyl groups, thereby delaying the temperature rise of the concrete matrix and improving the high-temperature resistance of the concrete; the carbon skeleton of the calcined rice husk powder and the high-temperature decomposition product of the modified hydrotalcite can form a composite heat insulation layer under high temperature conditions, thereby reducing heat conduction and further improving the high-temperature resistance of the concrete.

[0011] The magnesium phosphate cement-based concrete provided by the application can precisely control the hydration rate of the phosphate cement and the setting retarder, thereby ensuring the operability of the construction; the water reducing agent can improve the forming quality of the magnesium phosphate cement-based concrete; the phosphate cement, the setting retarder, the water reducing agent, the fine aggregate, the calcined rice husk powder and the modified hydrotalcite cooperate to significantly improve the strength of the magnesium phosphate cement-based concrete, and also make the magnesium phosphate cement-based concrete have excellent water resistance and high-temperature resistance.

[0012] Preferably, the particle size of the rice husk powder is 6mm-10mm.

[0013] Rice husk powder of a specific particle size can further improve the density of concrete, thereby improving its performance.

[0014] Preferably, the calcination time is 1h-1.5h.

[0015] Further preferably, the temperature is increased to 650℃-700℃ at a rate of 20℃ / min-30℃ / min.

[0016] By limiting the heating rate, a uniformly distributed microporous structure can be formed on the surface of rice husk powder, avoiding the problem of carbon skeleton collapse caused by excessively large pore size. The inventors have shown through a large number of experiments that both high and low heating rates will cause a significant reduction in the performance of magnesium phosphate cement-based concrete.

[0017] Preferably, the preparation method of the modified hydrotalcite includes the following steps:

[0018] S100. Sodium stearate, silane coupling agent and hydrotalcite are dispersed in an ethanol aqueous solution, the pH is adjusted to 8-9, and a hydrothermal reaction is carried out at 110℃-120℃. After washing, primary modified hydrotalcite is obtained.

[0019] S200. The primary modified hydrotalcite is calcined at 320℃-350℃ to obtain modified hydrotalcite.

[0020] The modified hydrotalcite preparation method provided by this invention involves a hydrothermal reaction at a specific temperature, which maximizes the insertion of sodium stearate into the interlayer of the modified hydrotalcite, and the silane coupling agent is coated on the surface of the modified hydrotalcite. Furthermore, calcination at a specific temperature significantly improves the bonding ability between the modified hydrotalcite and the silane coupling agent and sodium stearate, thereby enhancing the stability of the modified hydrotalcite structure and improving the overall performance of concrete.

[0021] For example, in S100, sodium hydroxide solution is used to adjust the pH of the solution to 8-9.

[0022] Preferably, in S100, the silane coupling agent is γ-aminopropyltriethoxysilane.

[0023] The present invention further defines the specific composition of the silane coupling agent. The preferred silane coupling agent can further improve the interfacial bonding force between the modified hydrotalcite and other components in concrete, thereby improving the overall performance of concrete.

[0024] Preferably, in S100, the hydrotalcite is magnesium aluminum hydrotalcite.

[0025] Preferably, in S100, the particle size of the hydrotalcite is 130nm-150nm.

[0026] Preferably, in S100, the volume concentration of the ethanol aqueous solution is 70%-75%.

[0027] Preferably, in S100, the hydrothermal reaction time is 12h-14h.

[0028] Preferably, in S100, the mass ratio of the hydrotalcite, sodium stearate, silane coupling agent and ethanol aqueous solution is 1:(0.5-0.8):(0.1-0.3):(20-25).

[0029] Preferably, in S200, the calcination time is 3-5 hours.

[0030] Optimal calcination time can prevent structural collapse of modified hydrotalcite.

[0031] Preferably, the setting regulator is boric acid.

[0032] Preferably, the water-reducing agent is a polycarboxylate water-reducing agent.

[0033] Preferably, the fine aggregate is manufactured sand.

[0034] Preferably, the particle size of the fine aggregate is 20-80 mesh.

[0035] This invention provides a method for preparing the above-mentioned magnesium phosphate cement-based concrete, comprising the following steps:

[0036] The weighed phosphate cement, setting regulator, fine aggregate, calcined rice husk powder, modified hydrotalcite, water-reducing agent and water are mixed evenly to obtain magnesium phosphate cement-based concrete.

[0037] The method for preparing magnesium phosphate cement-based concrete provided by this invention uses readily available raw materials, is inexpensive, requires no complex equipment or special processes, reduces production energy consumption and equipment investment, and efficiently utilizes industrial and agricultural by-products, thereby reducing overall costs. This allows magnesium phosphate cement-based concrete to have good economic benefits and market competitiveness while ensuring high performance.

[0038] This invention provides the application of the above-mentioned magnesium phosphate cement-based concrete in tunnel lining reinforcement.

[0039] The present invention has the following beneficial effects:

[0040] The magnesium phosphate cement-based concrete provided by this invention utilizes modified and reused rice husks, an agricultural waste, reducing solid waste pollution and demonstrating outstanding environmental friendliness. Hydrotalcite raw materials are abundant, and modification with sodium stearate and silane coupling agents ensures readily available raw materials and a simple process, without the use of expensive additives. Adding calcined rice husk powder and modified hydrotalcite to magnesium phosphate cement-based concrete significantly improves its overall performance. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0042] To better illustrate the present invention, further examples are provided below.

[0043] Example 1

[0044] This embodiment provides a magnesium phosphate cement-based concrete, comprising the following components in parts by weight: 100 parts phosphate cement, 8 parts boric acid, 80 parts manufactured sand, 40 parts calcined rice husk powder, 15 parts modified hydrotalcite, 4 parts HK41274 water-reducing agent, and 14 parts water.

[0045] The preparation method of calcined rice husk powder includes the following steps: heating rice husk powder with a particle size of 6 mm to 650 °C at a rate of 20 °C / min and calcining for 1 h to obtain calcined rice husk powder.

[0046] The preparation method of modified hydrotalcite includes the following steps:

[0047] S100. Sodium stearate, γ-aminopropyltriethoxysilane, and magnesium aluminum hydrotalcite with a particle size of 130 nm are dispersed in a 70% (v / v) aqueous ethanol solution and hydrothermally reacted at pH 8 and 110 °C for 12 h. After washing, primary modified hydrotalcite is obtained. The mass ratio of magnesium aluminum hydrotalcite, sodium stearate, γ-aminopropyltriethoxysilane, and aqueous ethanol solution is 1:0.8:0.1:25.

[0048] S200. The primary modified hydrotalcite is calcined at 320°C for 3 hours to obtain modified hydrotalcite.

[0049] This embodiment also provides a method for preparing the above-mentioned magnesium phosphate cement-based concrete, including the following steps:

[0050] The weighed phosphate cement, boric acid, manufactured sand, calcined rice husk powder, modified hydrotalcite, HK41274 water-reducing agent and water are mixed evenly to obtain magnesium phosphate cement-based concrete.

[0051] Example 2

[0052] This embodiment provides a magnesium phosphate cement-based concrete, comprising the following components in parts by weight: 110 parts phosphate cement, 9 parts boric acid, 70 parts manufactured sand, 30 parts calcined rice husk powder, 20 parts modified hydrotalcite, 5 parts HK41274 water-reducing agent, and 13 parts water.

[0053] The preparation method of calcined rice husk powder includes the following steps: heating rice husk powder with a particle size of 10 mm to 700 °C at a rate of 30 °C / min and calcining for 1.5 h to obtain calcined rice husk powder;

[0054] The preparation method of modified hydrotalcite includes the following steps:

[0055] S100. Sodium stearate, γ-aminopropyltriethoxysilane, and magnesium aluminum hydrotalcite with a particle size of 150 nm are dispersed in a 75% (v / v) aqueous ethanol solution and hydrothermally reacted at pH 9 and 120 °C for 14 h. After washing, primary modified hydrotalcite is obtained. The mass ratio of magnesium aluminum hydrotalcite, sodium stearate, γ-aminopropyltriethoxysilane, and aqueous ethanol solution is 1:0.5:0.3:20.

[0056] S200. The primary modified hydrotalcite is calcined at 350°C for 5 hours to obtain modified hydrotalcite.

[0057] This embodiment also provides a method for preparing the above-mentioned magnesium phosphate cement-based concrete, including the following steps:

[0058] The weighed phosphate cement, boric acid, manufactured sand, calcined rice husk powder, modified hydrotalcite, HK41274 water-reducing agent and water are mixed evenly to obtain magnesium phosphate cement-based concrete.

[0059] Example 3

[0060] This embodiment provides a magnesium phosphate cement-based concrete, comprising the following components in parts by weight: 105 parts phosphate cement, 9 parts boric acid, 75 parts manufactured sand, 35 parts calcined rice husk powder, 20 parts modified hydrotalcite, 5 parts HK41274 water-reducing agent, and 13 parts water.

[0061] The preparation method of calcined rice husk powder includes the following steps: heating rice husk powder with a particle size of 8 mm to 680 °C at a rate of 25 °C / min and calcining for 1.5 h to obtain calcined rice husk powder;

[0062] The preparation method of modified hydrotalcite includes the following steps:

[0063] S100. Sodium stearate, γ-aminopropyltriethoxysilane, and magnesium aluminum hydrotalcite with a particle size of 140 nm were dispersed in a 75% (v / v) aqueous ethanol solution and hydrothermally reacted at pH 9 and 120 °C for 13 h. After washing, primary modified hydrotalcite was obtained. The mass ratio of magnesium aluminum hydrotalcite, sodium stearate, γ-aminopropyltriethoxysilane, and aqueous ethanol solution was 1:0.6:0.2:22.

[0064] S200. The primary modified hydrotalcite is calcined at 340°C for 4 hours to obtain modified hydrotalcite.

[0065] This embodiment also provides a method for preparing the above-mentioned magnesium phosphate cement-based concrete, including the following steps:

[0066] The weighed phosphate cement, boric acid, manufactured sand, calcined rice husk powder, modified hydrotalcite, HK41274 water-reducing agent and water are mixed evenly to obtain magnesium phosphate cement-based concrete.

[0067] Comparative Example 1

[0068] This comparative example provides a magnesium phosphate cement-based concrete. Compared with Example 1, the difference is that the calcination temperature of the calcined rice husk powder is different. The preparation method of the calcined rice husk powder includes the following steps: heating rice husk powder with a particle size of 6 mm to 600 °C at a rate of 20 °C / min and calcining for 1 h to obtain calcined corn cob.

[0069] Other operations are the same as in Example 1.

[0070] Comparative Example 2

[0071] This comparative example provides a magnesium phosphate cement-based concrete. The difference between this example and Example 1 lies in the preparation method of the modified hydrotalcite, as detailed below:

[0072] S100. Sodium stearate and magnesium aluminum hydrotalcite with a particle size of 130 nm are dispersed in an ethanol aqueous solution with a volume concentration of 70% and hydrothermally reacted at pH 8 and 110℃ for 12 h. After washing, primary modified hydrotalcite is obtained. The mass ratio of magnesium aluminum hydrotalcite, sodium stearate and ethanol aqueous solution is 1:0.8:25.

[0073] S200. The primary modified hydrotalcite is calcined at 320°C for 3 hours to obtain modified hydrotalcite.

[0074] Other operations are the same as in Example 1.

[0075] Comparative Example 3

[0076] This comparative example provides a magnesium phosphate cement-based concrete. Compared with Example 1, the preparation method of the modified hydrotalcite is different from that of Example 1, as detailed below:

[0077] S100. γ-aminopropyltriethoxysilane and magnesium aluminum hydrotalcite with a particle size of 130 nm are dispersed in a 70% (v / v) aqueous ethanol solution and hydrothermally reacted at pH 8 and 110 °C for 12 h. After washing, primary modified hydrotalcite is obtained. The mass ratio of magnesium aluminum hydrotalcite, γ-aminopropyltriethoxysilane and aqueous ethanol solution is 1:0.1:25.

[0078] S200. The primary modified hydrotalcite is calcined at 320°C for 3 hours to obtain modified hydrotalcite.

[0079] Other operations are the same as in Example 1.

[0080] Comparative Example 4

[0081] This comparative example provides a magnesium phosphate cement-based concrete. The difference from Example 1 is that sodium stearate is replaced with an equal amount of sodium palmitate, while other operations are the same as in Example 1.

[0082] The concrete samples provided in Examples 1-3 and Comparative Examples 1-4, after 28 days of standard curing, were used as test specimens to test their water resistance, high temperature resistance, and strength, as detailed below:

[0083] Among them, the high-temperature treatment conditions during the high-temperature resistance test are as follows: the sample is heated to 200℃, 400℃ and 600℃ respectively at a rate of 1℃ / min, held at the temperature for 2h, cooled to room temperature and then tested for its flexural strength and compressive strength.

[0084] The testing standards for flexural strength and compressive strength are: GB / T 17671-2021;

[0085] The specific test results are shown in Table 1:

[0086] Table 1. Experimental Results

[0087]

[0088]

[0089] As shown in Table 1 of this invention, the concrete prepared using the components and preparation method provided in the embodiments of this invention has high strength as well as excellent water resistance and high temperature resistance. When the concrete treatment temperature provided in the embodiments reaches 600℃, its compressive strength and flexural strength can reach 77.1MPa and 16.7MPa, respectively; after soaking in water for 28 days, its compressive strength and flexural strength can reach 90.7MPa and 24.5MPa, respectively; and at room temperature, its compressive strength and flexural strength can reach 99.7MPa and 26.6MPa, respectively.

[0090] As can be seen from Comparative Examples 1-4, after replacing any component of the concrete provided in Example 1 of the present invention or changing the calcination temperature of the rice husk powder, the strength, water resistance and high temperature resistance of the concrete prepared in Comparative Examples 1-4 are significantly lower than those in Examples 1-3 of the present invention.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A magnesium phosphate cement-based concrete, characterized in that, The components include the following parts by weight: 100-110 parts of phosphate cement, 8-9 parts of setting regulator, 70-80 parts of fine aggregate, 30-40 parts of calcined rice husk powder, 15-20 parts of modified hydrotalcite, 4-5 parts of water-reducing agent and 13-14 parts of water. The modified hydrotalcite is a hydrotalcite modified with silane coupling agent and sodium stearate. The calcined rice husk powder includes the following preparation steps: calcining rice husk powder at 650℃-700℃ to obtain the calcined rice husk powder.

2. The magnesium phosphate cement-based concrete as described in claim 1, characterized in that, The rice husk powder has a particle size of 6mm-10mm.

3. The magnesium phosphate cement-based concrete as described in claim 1, characterized in that, The calcination time is 1-1.5 hours.

4. The magnesium phosphate cement-based concrete as described in claim 1, characterized in that, The temperature is increased to 600℃-700℃ at a rate of 20℃ / min-30℃ / min.

5. The magnesium phosphate cement-based concrete as described in claim 1, characterized in that, The preparation method of the modified hydrotalcite includes the following steps: S100. Sodium stearate, silane coupling agent and hydrotalcite are dispersed in an ethanol aqueous solution, the pH is adjusted to 8-9, and a hydrothermal reaction is carried out at 110℃-120℃. After washing, primary modified hydrotalcite is obtained. S200. The primary modified hydrotalcite is calcined at 320℃-350℃ to obtain modified hydrotalcite.

6. The magnesium phosphate cement-based concrete as described in claim 5, characterized in that, In S100, the silane coupling agent is γ-aminopropyltriethoxysilane; and / or In S100, the particle size of the hydrotalcite is 130nm-150nm.

7. The magnesium phosphate cement-based concrete as described in claim 5, characterized in that, In S100, the hydrothermal reaction time is 12-14 hours; and / or In S100, the mass ratio of the hydrotalcite, sodium stearate, silane coupling agent and ethanol aqueous solution is 1:(0.5-0.8):(0.1-0.3):(20-25).

8. The magnesium phosphate cement-based concrete as described in claim 5, characterized in that, In S200, the calcination time is 3h-5h.

9. A method for preparing magnesium phosphate cement-based concrete according to any one of claims 1-8, characterized in that, Includes the following steps: The weighed phosphate cement, setting regulator, fine aggregate, calcined rice husk powder, modified hydrotalcite, water-reducing agent and water are mixed evenly to obtain magnesium phosphate cement-based concrete.

10. The application of magnesium phosphate cement-based concrete according to any one of claims 1-8, or magnesium phosphate cement-based concrete prepared by the method for preparing magnesium phosphate cement-based concrete according to claim 9, in tunnel lining reinforcement.

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