阅读说明：本技术 一种改性水滑石及其制备方法和应用 (Modified hydrotalcite and preparation method and application thereof ) 是由 王肇嘉 李扬 黄天勇 房桂明 陈旭峰 张增寿 于 2021-01-06 设计创作，主要内容包括：本发明提供一种改性水滑石及其制备方法和应用。所述改性水滑石原料包括铝镁钡水滑石和表面改性剂,所述铝镁钡水滑石由以下质量份的原料制备：铝质材料35～70份,钡质材料15～50份,镁质材料15～50份。本发明提供的改性水滑石用于海工混凝土中,发挥“外阻内吸”作用,混凝土抗硫酸盐侵蚀和抗氯离子渗透性能显著提升,改善了混凝土的耐久性。(The invention provides a modified hydrotalcite and a preparation method and application thereof. The modified hydrotalcite raw material comprises aluminum magnesium barium hydrotalcite and a surface modifier, wherein the aluminum magnesium barium hydrotalcite is prepared from the following raw materials in parts by mass: 35-70 parts of aluminum material, 15-50 parts of barium material and 15-50 parts of magnesium material. The modified hydrotalcite provided by the invention is used in marine concrete, plays a role of external resistance and internal absorption, remarkably improves the sulfate erosion resistance and chloride ion permeation resistance of the concrete, and improves the durability of the concrete.)

1. The modified hydrotalcite is characterized in that raw materials comprise aluminum magnesium barium hydrotalcite and a surface modifier, wherein the aluminum magnesium barium hydrotalcite is prepared from the following raw materials in parts by mass:

35-70 parts of aluminum material

15-50 parts of barium material

15-50 parts of magnesium material.

2. The modified hydrotalcite according to claim 1, wherein the mass ratio of the surface modifier to the aluminum magnesium barium hydrotalcite is 1 to 10: 90-99 parts.

3. The modified hydrotalcite of claim 2, wherein the aluminum material is aluminum nitrate, aluminum carbonate or aluminum hydroxide, the magnesium material is magnesium nitrate, magnesium carbonate or magnesium hydroxide, and the barium material is barium nitrate, barium carbonate or barium hydroxide.

4. The modified hydrotalcite of claim 2, wherein the surface modifier is selected from one or more of cetyltrimethylammonium bromide, 3-aminopropyltriethoxysilane, gamma-glycidoxypropyltrimethoxysilane and gamma-mercaptopropyltriethoxysilane.

5. The modified hydrotalcite of claim 3 or 4, wherein the aluminum, magnesium and barium materials are respectively aluminum nitrate, magnesium carbonate and barium carbonate, or aluminum carbonate, magnesium carbonate and barium carbonate, or aluminum nitrate, magnesium carbonate and barium hydroxide; the surface modifier is 3-aminopropyl triethoxysilane, gamma-glycidoxypropyl trimethoxysilane or gamma-mercaptopropyl triethoxysilane.

6. A process for producing the modified hydrotalcite according to any one of claims 1 to 5, which comprises:

1) dissolving the aluminum material, the barium material and the magnesium material in water, adjusting the pH value to 8-10, reacting, and then roasting at high temperature to obtain aluminum-magnesium-barium hydrotalcite;

2) and mixing the aluminum-magnesium-barium hydrotalcite and the surface modifier, reacting, and then roasting at high temperature to obtain the modified hydrotalcite.

7. The process for producing modified hydrotalcite according to claim 6, wherein in step 1), the pH is adjusted by sodium carbonate or sodium hydroxide; and/or the reaction temperature is 60-80 ℃, and the reaction time is 3-4 h; and/or the high-temperature roasting temperature is 100-300 ℃, and the roasting time is 1-3 h.

8. The method for preparing modified hydrotalcite according to claim 6 or 7, wherein in step 2), the reaction time is 1-2 h; and/or the high-temperature roasting temperature is 120-180 ℃, and the roasting time is 2-3 h.

9. Marine concrete, characterized in that the raw material of the marine concrete comprises the modified hydrotalcite obtained by the method for preparing the modified hydrotalcite of claim 7 or 8; preferably, the feed comprises the following raw materials in parts by mass: 10-20 parts of modified hydrotalcite, 400-450 parts of cement, 700-800 parts of sand, 400-500 parts of small stones, 600-700 parts of large stones, 160-170 parts of water and 2-4 parts of water reducing agent.

10. The application of modified Al-Mg-Ba hydrotalcite in preparing marine concrete is characterized in that the modified hydrotalcite of any one of claims 1 to 6 is adopted.

Technical Field

The invention relates to the technical field of building materials and chemical building materials, in particular to modified hydrotalcite and a preparation method and application thereof.

Background

Water is an indispensable material for preparing concrete, and various aggregates of the concrete are bonded into artificial stone by coagulation of calcium silicate hydrate generated by hydration reaction of cement. However, harmful ions such as chloride ions and sulfate ions in the external environment also enter the concrete along with the moisture, and the durability of the concrete is affected.

At present, concrete engineering construction gradually expands to the ocean, but chloride ions and sulfate ions in seawater can erode concrete and influence the durability of the concrete. The chloride ions can destroy the passive film of the concrete reinforcing steel bar and accelerate the corrosion of the reinforcing steel bar. Reacting low-concentration chloride ions with cement hydration product polysulfide hydrated calcium sulphoaluminate (AFm) to generate a Kuzel salt; the high concentration chloride ion reacts with the AFm to generate Fridel salt, which reduces the yield of hydration products such as ettringite. The sulfate ions react with the hydration product AFm to generate secondary ettringite, the volume of which is doubled, so that expansion damage is caused. Sulfate ions can also react with hydration product calcium hydroxide to generate secondary gypsum, and the volume expansion damage is generated. The seawater contains chloride ions and sulfate radicals for combined action, and the corrosion to concrete is more serious than that under independent conditions.

At present, the method commonly adopted in marine concrete is to use a large amount of auxiliary cementing materials (fly ash, slag powder and the like) to reduce calcium hydroxide generated by cement hydration reaction through a volcanic ash effect so as to reduce the generation of secondary gypsum, and the hydration of the auxiliary cementing materials can increase the later strength of the concrete, but the method has limited effect. CN201410535703.4 added barium sulfide or barium sulfate to concrete, which reacted with sulfate to form barium sulfate to reduce the effect of sulfate, but this form of barium salt had a small specific surface area and limited ability to absorb solidified sulfate.

Disclosure of Invention

The embodiment of the invention provides modified hydrotalcite. The modified hydrotalcite provided by the invention is used in marine concrete, plays a role of external resistance and internal absorption, remarkably improves the sulfate erosion resistance and chloride ion permeation resistance of the concrete, and improves the durability of the concrete.

According to the present invention, the inventors have found that hydrotalcite having a layered structure has a strong adsorption capacity for corrosive ions such as chloride ions and sulfate ions, and is a good adsorbent. Therefore, the barium ions are introduced into the hydrotalcite structure to prepare the aluminum-magnesium-barium hydrotalcite, and the capability of adsorbing and combining sulfate radicals can be greatly improved. However, the ratio of the radius of barium ions to the radius of aluminum ions is too large, so that an optimized synthesis method is needed to synthesize the layered structure of the hydrotalcite with barium ion intercalation. Furthermore, the marine concrete can be coated with a hydrophobic anti-corrosion coating on the surface of the concrete to reduce the invasion of corrosive ions in seawater, but the coating on the surface increases the construction steps, and the strength and the durability of the coating are difficult to ensure. By internally doping the hydrophobic hydrotalcite material, a hydrophobic network can be formed in concrete, and corrosive ions are effectively prevented from invading. Meanwhile, the layered structure of the hydrotalcite can improve the surface roughness of the material, further enhance the hydrophobic capacity of the modified aluminum-magnesium-barium hydrotalcite, and limit the harmful ions entering the concrete along with the moisture.

The embodiment of the invention provides modified hydrotalcite, which comprises the following raw materials of aluminum magnesium barium hydrotalcite and a surface modifier, wherein the aluminum magnesium barium hydrotalcite is prepared from the following raw materials in parts by mass:

35-70 parts of aluminum material

15-50 parts of barium material

15-50 parts of magnesium material.

In the invention, aluminum-magnesium-barium hydrotalcite reacts with a surface modification component to obtain hydrophobic barium ion intercalated hydrotalcite; particularly, the barium ions can be more effectively inserted into the hydrotalcite layers by adjusting the dosage of the barium material.

According to the modified hydrotalcite provided by the embodiment of the invention, the mass ratio of the surface modifier to the aluminum-magnesium-barium hydrotalcite is 1-10: 90-99 parts.

According to the modified hydrotalcite provided by the embodiment of the invention, the aluminum material is aluminum nitrate, aluminum carbonate or aluminum hydroxide, the magnesium material is magnesium nitrate, magnesium carbonate or magnesium hydroxide, and the barium material is barium nitrate, barium carbonate or barium hydroxide.

According to the modified hydrotalcite provided by the embodiment of the invention, the surface modifier is selected from one or more of hexadecyl trimethyl ammonium bromide, 3-aminopropyl triethoxysilane, gamma-glycidoxypropyl trimethoxysilane and gamma-mercaptopropyl triethoxysilane.

In the invention, the aluminum-magnesium-barium hydrotalcite can better play a hydrophobic role by adopting the surface modifier, particularly gamma-glycidyl ether oxypropyl trimethoxysilane and gamma-mercaptopropyl triethoxysilane, in the surface modification process, thereby better preventing corrosive ions from invading.

According to the modified hydrotalcite provided by the embodiment of the invention, the aluminum material, the magnesium material and the barium material are respectively aluminum nitrate, magnesium carbonate and barium carbonate, or aluminum carbonate, magnesium carbonate and barium carbonate, or aluminum nitrate, magnesium carbonate and barium hydroxide; the surface modifier is 3-aminopropyl triethoxysilane, gamma-glycidoxypropyl trimethoxysilane or gamma-mercaptopropyl triethoxysilane.

In the invention, the aluminum material, the magnesium material and the barium material, especially aluminum nitrate, magnesium carbonate and barium carbonate, are adopted in the coprecipitation process, so that aluminum ions, magnesium ions and barium ions can better play roles of a layered framework and an intercalation, and a hydrotalcite layered structure of the barium ion intercalation is better formed.

The embodiment of the invention also provides a preparation method of the modified hydrotalcite, which comprises the following steps:

1) dissolving the aluminum material, the barium material and the magnesium material in water, adjusting the pH value to 8-10, reacting, and then roasting at high temperature to obtain aluminum-magnesium-barium hydrotalcite;

2) and mixing the aluminum-magnesium-barium hydrotalcite and the surface modifier, reacting, and then roasting at high temperature to obtain the modified hydrotalcite.

According to the preparation method of the modified hydrotalcite provided by the embodiment of the invention, in the step 1), the pH is adjusted by sodium carbonate or sodium hydroxide; and/or the reaction temperature is 60-80 ℃, and the reaction time is 3-4 h; and/or the high-temperature roasting temperature is 100-300 ℃, and the roasting time is 1-3 h.

According to the preparation method of the modified hydrotalcite provided by the embodiment of the invention, in the step 2), the reaction time is 1-2 h; and/or the high-temperature roasting temperature is 120-180 ℃, and the roasting time is 2-3 h. According to the invention, the combination of the surface modifier and the hydrotalcite can be better promoted by adopting the roasting temperature and roasting at 140-160 ℃, and the hydrophobic effect is fully exerted, so that harmful ions are better prevented from invading.

The embodiment of the invention also provides marine concrete, wherein the raw material of the marine concrete comprises the modified hydrotalcite obtained by the preparation method of the modified hydrotalcite of claim 7 or 8; preferably, the feed comprises the following raw materials in parts by mass: 12-26 parts of modified hydrotalcite, 400-430 parts of cement, 720-760 parts of sand, 420-460 parts of small stones, 640-700 parts of large stones, 160-170 parts of water and 2-4 parts of water reducing agent.

The embodiment of the invention also provides an application of the modified aluminum-magnesium-barium hydrotalcite in preparing marine concrete, and the modified hydrotalcite is adopted. In the invention, the modified aluminum-magnesium-barium is doped into the concrete, so that the moisture exchange between the concrete and the external environment can be prevented, the corrosion of chloride ions, sulfate radicals and other ions in the external environment to the concrete is prevented, the corrosion resistant material can absorb harmful ions which are solidified and immersed into the concrete, and the corrosion resistance of the concrete is improved through external resistance and internal absorption. The durability of the marine concrete is excellently improved under the condition of not influencing the strength of the concrete.

The invention has the beneficial effects that:

1. when the modified magnesium-aluminum-barium hydrotalcite provided by the invention is used in marine concrete, the hydrophobicity of the concrete is increased, and the corrosion resistance coefficient of the concrete is improved by 18-25%;

2. the modified magnesium-aluminum-barium hydrotalcite provided by the invention aims at the severe environment of the service environment of concrete, such as ocean, salt lake and the like, under the condition that the workability and the strength of the concrete are not influenced, even if the surface of the concrete is damaged to a certain degree, the inner layer concrete still has the corrosion resistance effect, and the durability of the concrete is improved;

3. the modified magnesium-aluminum-barium hydrotalcite provided by the invention adopts organic hydrophobic modification to prevent the invasion of harmful ions, absorbs, solidifies and soaks the harmful ions in concrete, plays a role of external resistance and internal absorption, improves the frozen durability of the concrete, and provides powerful technical support for ocean engineering and western construction.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention are described clearly and completely below, and it is obvious that the described embodiments are some, not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The examples do not show the specific techniques or conditions, according to the technical or conditions described in the literature in the field, or according to the product specifications. The instruments and the like are conventional products which are purchased by normal distributors and are not indicated by manufacturers. The process is conventional unless otherwise specified, and the starting materials are commercially available from the open literature. The examples do not show the specific techniques or conditions, according to the technical or conditions described in the literature in the field, or according to the product specifications.

The embodiment of the invention provides a preparation method of modified hydrotalcite, which comprises the following steps:

1) mixing 35-70 parts by mass of an aluminum material, 15-50 parts by mass of a barium material and 15-50 parts by mass of a magnesium material, uniformly stirring, adding water for dissolving, stirring and heating, dropwise adding sodium carbonate or sodium hydroxide, adjusting the pH to 8-10, then reacting for 3-4 h at 60-80 ℃, performing suction filtration and drying, and roasting for 2h at 100-300 ℃ to obtain aluminum-magnesium-barium hydrotalcite;

2) mixing 90-99 parts by mass of aluminum-magnesium-barium hydrotalcite and 1-10 parts by mass of surface modifier, reacting for 1-2 hours, and roasting at 120-180 ℃ for 2-3 hours to obtain the modified hydrotalcite.

The following is a further description by way of specific examples.

Example 1

The embodiment provides a modified aluminum magnesium barium hydrotalcite NCC-58, and the preparation method of the modified aluminum magnesium barium hydrotalcite comprises the following steps:

putting 1000g of aluminum nitrate nonahydrate, 170g of magnesium carbonate and 250g of barium carbonate into a reaction kettle, uniformly stirring, adding 500g of water, mechanically stirring at 250r/min, dropwise adding sodium carbonate, adjusting the pH to 10, heating in a water bath to 70 ℃, reacting for 3h, carrying out suction filtration and drying, and roasting for 2h at 300 ℃ to obtain the aluminum-magnesium-barium hydrotalcite.

Adding 1000g of aluminum magnesium barium hydrotalcite and 100g of gamma-mercaptopropyltriethoxysilane into a reaction kettle, stirring for reaction for 2 hours, and roasting at 160 ℃ for 2 hours to obtain modified aluminum magnesium barium hydrotalcite NCC-58.

Example 2

The embodiment provides a modified aluminum magnesium barium hydrotalcite CCC-55, and the preparation method of the modified aluminum magnesium barium hydrotalcite comprises the following steps:

350g of aluminum carbonate, 170g of magnesium carbonate and 400g of barium carbonate are put into a reaction kettle and stirred uniformly, 500g of water is added, mechanical stirring is carried out at 250r/min, sodium carbonate is dripped, the pH is adjusted to 9, the mixture is heated to 60 ℃ in a water bath, reaction is carried out for 3h, and the aluminum-magnesium-barium hydrotalcite is obtained after filtration, drying and roasting at 200 ℃ for 2 h.

Adding 1000g of aluminum-magnesium-barium hydrotalcite and 50g of 3-aminopropyltriethoxysilane into a reaction kettle, stirring for reaction for 2 hours, and roasting at 180 ℃ for 2 hours to obtain modified aluminum-magnesium-barium hydrotalcite CCC-55.

Example 3

The embodiment provides a modified aluminum magnesium barium hydrotalcite CCH-57, and the preparation method of the modified aluminum magnesium barium hydrotalcite comprises the following steps:

350g of aluminum carbonate, 170g of magnesium carbonate and 250g of barium hydroxide are put into a reaction kettle and stirred uniformly, 500g of water is added, mechanical stirring is carried out at 250r/min, sodium carbonate is dripped, the pH is adjusted to 9, the mixture is heated to 65 ℃ in a water bath, reaction is carried out for 3h, and the aluminum-magnesium-barium hydrotalcite is obtained after filtration, drying and roasting at 250 ℃ for 2 h.

Adding 1000g of aluminum magnesium barium hydrotalcite and 50g of gamma-glycidyl ether oxypropyl trimethoxy silane into a reaction kettle, stirring for reaction for 2 hours, and roasting at 180 ℃ for 2 hours to obtain modified aluminum magnesium barium hydrotalcite CCH-57.

Experimental example 1 (Marine concrete Performance test)

The raw materials of the marine concrete used for the test are as follows:

the raw materials comprise P.I 42.5 cement, river sand fineness modulus of 2.8, limestone aggregate (two-stage gradation of 5-10mm and 10-20mm, namely small pebble and large pebble), a polycarboxylic acid water reducing agent, and modified aluminum-magnesium-barium hydrotalcite NCC-58, CCC-55 and CCH-57.

The formula of the marine concrete is shown in the following table 1.

TABLE 1 Marine concrete mix proportion (kg/m)³)

Cement	Sand	Small stone	Big stone	Water (W)	Water reducing agent	Modified hydrotalcite
							420	745	447	670	168	2.8	15

Comparative example 1

Comparative example the same concrete raw materials as those used in the test examples were as follows:

the raw materials comprise P.I 42.5 cement, river sand fineness modulus of 2.8, limestone aggregate (two-stage gradation of 5-10mm and 10-20 mm) and polycarboxylic acid water reducing agent.

Adding auxiliary cementing materials: class II fly ash, S95 slag powder.

The formulation of the concrete of comparative example 1 is shown in table 2 below.

TABLE 2 Marine concrete mix proportion (kg/m)³)

Cement	Fly ash	Slag of mine	Sand	Small stone	Big stone	Water (W)	Water reducing agent
								200	120	100	745	447	670	168	2.8

The sulfate erosion resistance of marine concrete after 120 dry-wet cycles was tested according to GB50082-2016 and the results are shown in Table 3:

TABLE 3 application effect of different modified hydrotalcites in marine concrete

As can be seen from Table 3, the corrosion resistance coefficient of comparative example 1 is increased by 13%, which shows that the use of a large amount of supplementary cementitious material can increase the corrosion resistance coefficient of concrete to some extent, but the effect is limited and the 28d strength of concrete is slightly reduced.

The maritime work concrete doped with the modified aluminum-magnesium-barium hydrotalcite in the embodiment basically does not affect the fluidity and the strength of the maritime work concrete, and the corrosion resistance coefficient of the maritime work concrete can be improved by 18-25%. From the above, the modified (aluminum-magnesium-barium) hydrotalcite provided by the invention can obviously improve the corrosion resistance of the marine concrete and improve the comprehensive performance of the marine concrete.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.