CN105712740A - Nano core-shell structure organic-inorganic compound concrete protective agent and preparation method and application thereof - Google Patents

Abstract

The invention discloses a nano core-shell structure organic-inorganic composite concrete protective agent and its preparation method and application, belonging to the technical field of building materials. In the present invention, the core-shell structure material formed by wrapping silane molecules on the surface of nanometer SiO ₂ effectively combines the organic protective agent and the inorganic protective agent to protect the hardened concrete on the surface. It not only avoids the characteristics of easy aging of organic materials, but also separates the preparation and application of materials, saves the time for hydrolysis of precursors, and plays a double role in protecting the concrete structure. It combines the advantages of organic and inorganic materials. On the one hand, silane in concrete The surface is flattened to form a protective film to play a hydrophobic role. On the other hand, nano-SiO ₂ has high pozzolanic activity, and it reacts with cement hydration product Ca(OH) ₂ to form a hydration gel to form a dense pore structure. role. The invention has the characteristics of good protective effect, simple preparation, easy construction and the like, and can be widely used in the field of concrete engineering.

Description

A nano-core-shell organic-inorganic composite concrete protective agent and its preparation Methods and Applications

technical field

The invention belongs to the technical field of building materials, and relates to a nano core-shell structure organic-inorganic composite protective agent for concrete, a preparation method and application thereof.

Background technique

Reinforced concrete is currently the most widely used man-made building material in the world, and is widely used in various engineering fields such as construction, municipal administration, and bridge construction. The quality and life of concrete are directly related to the quality and life of buildings. Therefore, the durability of concrete structures has an important impact on my country's economy, society, resources, and energy. The performance degradation of cement concrete under the action of stress and environmental factors during service is the most important factor reducing the service life of materials. The economic losses caused by the deterioration of concrete performance in the world are in the trillions every year, and my country is in the period of large-scale economic construction. Therefore, enhancing the ability of concrete to resist external erosion and improving the life of concrete have a prominent role in economic development. At the same time, it responded to the call for sustainable development of the country. The deterioration of concrete caused by the service environment is a process from the surface to the inside. The quality of the surface concrete directly affects the anti-deterioration ability of the overall structure. Improving the performance of the overall structure by improving the quality of the surface concrete is a long-term research direction that people have paid attention to. It is a common technical measure to improve the quality of surface concrete by using an external protective layer.

Generally speaking, the concrete protective layer is mainly divided into organic protective layer and inorganic protective layer. The organic protective layer mainly forms a continuous film on the surface of the concrete with the help of organic film-forming agents to prevent the medium, mainly water and air, from carrying harmful ions into the interior of the concrete. According to the surface protection mechanism, the organic protective layer is divided into silane protective agent and film-forming emulsion protective agent. The former mainly forms a film in the surface concrete pores to change the hydrophilicity of the pores, making it difficult for water to penetrate into the pores without affecting the gas exchange inside and outside the concrete. , the latter blocks all material exchange between concrete and the environment by forming a continuous film on the concrete surface. The main problem of this type of protective agent is the poor weather resistance of the organic components; the inorganic protective layer is mainly to use inorganic materials to form a sealing layer on the concrete surface, such as a crystalline protective layer, and its main functional component is alkali metal silicate, although It can effectively compact the concrete structure, but the alkali metal ions generated by the reaction are obviously unfavorable to the problems of concrete alkali-aggregate reaction and metal salt crystallization.

Existing concrete surface protection materials: such as the patent of "an in-situ reaction type concrete protection agent" with the application number CN201310221449.6, which is a method of protecting the surface hardened concrete by using sol-state nano-SiO ₂ or its precursor , emphasizing that nano- _SiO2 and its precursors react with cement matrix to generate CSH gel, which improves the pore structure of concrete materials and reduces porosity. Another example is "An Organosilicon Concrete Protective Agent and Its Manufacturing Method" with the application number CN201310019374.3, which discloses an organosilicon concrete protective agent and its manufacturing method. The invention is mainly that the paste material made of silane as the main raw material is coated on the concrete surface, and a layer of hydrophobic film is formed along the inner wall of the concrete pores, which hinders the intrusion of water and harmful ions.

Although the above two methods can protect the concrete structure to a certain extent, they also have shortcomings. The disadvantages of organic concrete protective agents are that they have little bonding force with the cement matrix, poor wear resistance and durability, and need to be painted regularly, and organic materials are easy to Ageing. Although the above-mentioned in-situ reaction type inorganic protective agent can effectively improve the pore structure of concrete, because it needs to use the water in the concrete pore structure to react with the nano- _SiO2 precursor, the process of hydrolysis to generate nano- _SiO2 is slow and takes a long time.

In "Construction and Building Materials" (Construction and Building Materials, volume 54, pages 99-105) in 2014, Giovana Collodetti et al. studied two new materials formed by grafting two different silanes on the surface of nano-SiO ₂ particles, and explored the inner structure of the material. The effect of mixing on the hydration of cement paste shows that it is not conducive to the development of cement performance, and then negates the mixing method of internal mixing.

Contents of the invention

The present invention aims at the above-mentioned shortcomings existing in the prior art, and provides a nano core-shell structure organic-inorganic composite concrete protective agent and a preparation method thereof, wherein ethyl orthosilicate, silane and deionized water are dissolved in polar Mix well in the organic solvent to make it fully react, so that the hydrophobic group of silane is grafted on the surface of nano-SiO ₂ , and the organic protective agent and the inorganic protective agent are effectively combined to form a core-shell structure material, which is used for surface hardening of concrete. Protection, make nano-SiO ₂ react with cement part, generate CSH gel, achieve the effect of plugging pores, avoid the characteristics of easy aging of organic materials, separate the preparation and application of materials, save the time of precursor hydrolysis, and The concrete structure acts as a double protection.

Technical scheme of the present invention is as follows:

An organic-inorganic composite concrete protective agent with a nano core-shell structure, the mass percentage of its raw materials is composed of:

Silane with hydrophobic groups 0.5~1.4%;

Ethyl orthosilicate 4.1～8%;

Polar organic solvent 89～94.8%;

Alkali 0.1%;

Water 0.5~1.5%.

Further, the above-mentioned organic-inorganic composite concrete protective agent with nano-core-shell structure has an optimal composition of raw material mass percentage:

Silane with hydrophobic groups 0.5%;

Orthosilicate 6%;

Polar organic solvent 92.9%;

Alkali 0.1%;

Water 0.5%.

The silane with hydrophobic groups is preferably polymethylhydrogensiloxane, vinyltriethoxysilane or isobutyltriethoxysilane;

The polar organic solvent is preferably tetrahydrofuran, ethanol or methanol;

The alkali is preferably ammonia water or ethylenediamine, and the mass concentration of the ammonia water is preferably 0.88g/ml.

The water is preferably deionized water.

The preparation method of the above-mentioned nano core-shell structure organic-inorganic composite concrete protective agent is: take a polar organic solvent according to the proportion, add alkali to adjust the pH to 8-12, then add silane with hydrophobic groups, stir for 30 minutes, and then add positive Ethyl silicate, continue to stir for 10-12 hours, and finally add deionized water and stir for 2-3.5 hours until the solution turns from transparent to turbid, then centrifuge at 10,000 rpm for 5 minutes to collect the solid at the bottom to obtain a nano-core-shell structure organic-inorganic composite concrete protection agent.

The application of the above-mentioned nano core-shell structure organic-inorganic composite concrete protective agent: it can be used as a protective material for surface hardened concrete; The mass concentration of % is super-dispersed in organic solvent to obtain a mixed solution, and then sprayed ^on the concrete surface, and the spraying is repeated 3 times, with an interval of 20 minutes each time. That's it.

The organic solvent is preferably tetrahydrofuran, ethanol or methanol.

The purpose of the present invention is based on the important effect of improving the quality of the cement concrete surface layer to the overall structure, and utilizes silane grafting to connect nano-SiO _The new material formed on the surface handles the hardened concrete surface layer, so that the organic protective layer and the inorganic protective layer are effectively combined. On the one hand Use the organic part to form a film in the pores of the surface concrete, change the hydrophilicity of the pores, make it difficult for water to penetrate into the pores without affecting the gas exchange inside and outside the concrete _; Generate hydration gel to compact the surface concrete structure, effectively seal micro-cracks in concrete, and improve the overall quality of concrete. In this way, the organic protective layer and the inorganic protective layer are organically combined, which not only enhances the binding ability of silane and cement-based materials, but also improves the compactness of the concrete pore structure, providing double protection for concrete. The invention has the advantages of both organic protective agent and inorganic protective agent, and at the same time overcomes the disadvantages of poor adhesion, easy aging of organic protective agent and long reaction time of inorganic protective agent, convenient preparation, low synthesis temperature and obvious waterproof effect.

The invention effectively combines the organic protective agent with the inorganic protective agent. One end of the silane is a hydrophobic group to form a protective film on the surface of the concrete, which effectively blocks the infiltration of water and prevents harmful ions from invading the concrete pore structure through the water medium. The other end is bonded with nano-SiO ₂ , and nano-SiO ₂ reacts with the cement matrix, so it plays a role of plugging holes while firmly fixing the silane on the concrete surface. It greatly improves the durability of the silane material on the concrete surface and at the same time improves the pore structure of the concrete material. The double function hinders the infiltration of water and plays a role in blocking harmful ions.

Principle of the present invention:

The silane used is a silane with a hydrophobic group, such as polymethylhydrogensiloxane, vinyltriethoxysilane, isobutyltriethoxysilane; the preparation of nano-SiO ₂ materials usually uses ethyl orthosilicate (TEOS) as a precursor. Ethyl orthosilicate is used as a silicon source for the preparation of nano-SiO ₂ . Under certain conditions, it generates nanoparticles through chemical reactions such as hydrolysis, and the organic alcohol produced after hydrolysis is easy to volatilize. The mechanism of the dense concrete structure of tetraethyl orthosilicate is to enter the pore structure, and the moisture provided inside the pores hydrolyzes tetraethyl orthosilicate to produce silica that can participate in pozzolanic reactions and ethanol that is not harmful to cement-based materials.

Formula 1)

At this time, the silane with hydrophobic groups will react with nano-SiO ₂ with many hydroxyl groups on the surface (the mechanism is shown in Figure 1).

Even if the silane hydrophobic group is wrapped on the surface of nano- _SiO2 particles, its pozzolanic activity is also very high, and it will quickly absorb the Ca(OH) ₂ generated by the cement hydration reaction in concrete to form a hydration gel, which is an important factor for its use in cement concrete. The reaction mechanism is shown in formula (2):

Formula (2)

Dissolve the precursor orthosilicate of nano- _SiO2 in a certain proportion with silane and deionized water in a polar organic solvent and mix evenly to make it fully react, so that the hydrophobic group of silane is grafted on the surface of nano- _SiO2 . The synthesized material is used to treat the surface of concrete products, so that nano-SiO ₂ reacts with the cement part to form CSH gel to achieve the effect of plugging pores. At the same time, it exerts the hydrophobic effect of silane to prevent the harmful ions carried by the water medium from invading the interior of the concrete. damage to concrete structures.

After the present invention adopts the above-mentioned technical scheme, it mainly possesses the following characteristics:

1) The combination of organic and inorganic can not only have obvious hydrophobic effect on the surface, but also can penetrate deep into the concrete structure and react with the cement matrix to play the role of plugging holes, and have a double protection effect on the concrete matrix material, and the protection effect is better than that used alone The effect is better when silane or nano-SiO ₂ materials are used;

2) The organic and inorganic components are connected together through the core-shell structure, which effectively improves the shortcoming of easy aging of organic materials and increases the service life of materials;

3) The protective agent itself has strong volcanic ash reactivity, so that the protective agent reacts with the calcium hydroxide in the surface layer coagulation, and the generated volcanic ash reaction product can effectively compact the surface concrete structure.

Description of drawings

Fig. ₁ is nanometer SiO of the present invention Particle and silane binding mechanism schematic diagram;

Fig. 2 is the effect figure of water absorption of cement mortar test block under the different treatment modes of embodiment 4;

Fig. 3 is the contact angle of the cement paste surface under the situation of embodiment 5 water coating different protective materials:

(a) is the contact angle treated with nano core-shell structure organic-inorganic composite concrete protective agent (b) is the contact angle of the untreated surface;

Fig. 4 is the pore size distribution of the cement of Example 6.

detailed description

The present invention will be further described below in combination with specific embodiments.

Example 1

An organic-inorganic composite concrete protective agent with a nano core-shell structure, the mass percentage of its raw materials is composed of:

Polymethylhydrogensiloxane 0.5%;

Orthosilicate 6%;

Tetrahydrofuran 92.9%;

Ethylenediamine 0.1%;

Deionized water 0.5%.

The preparation method is: weigh tetrahydrofuran according to the proportion, add ethylenediamine to adjust the pH to 8-12, then add polymethylhydrogensiloxane, stir with a magnetic stirrer for 30 minutes, then add ethyl orthosilicate, continue stirring for 11 hours, and finally add Stir with deionized water for 3 hours until the solution turns from transparent to turbid, and the reaction is complete. Use a high-speed centrifuge at a speed of 10,000 rpm for 5 minutes, filter the supernatant, and collect the solid at the bottom of the centrifuge tube, which is the nano-core-shell organic- Inorganic composite concrete protective agent.

Example 2

An organic-inorganic composite concrete protective agent with a nano core-shell structure, the mass percentage of its raw materials is composed of:

Vinyltriethoxysilane 1.4%;

Tetraethyl orthosilicate 8%;

Ethanol 89%;

Ethylenediamine 0.1%;

Deionized water 1.5%.

The preparation method is: weigh ethanol according to the proportion, add ethylenediamine to adjust the pH to 8-11, then add polymethyl hydrogen siloxane, stir with a magnetic stirrer for 30 minutes, then add ethyl orthosilicate, continue stirring for 10 hours, and finally add Stir with deionized water for 2 hours until the solution turns from transparent to turbid, and the reaction is complete. Use a high-speed centrifuge at a speed of 10,000 rpm for 5 minutes, filter the supernatant, and collect the solid at the bottom of the centrifuge tube, which is the nano-core-shell structure organic- Inorganic composite concrete protective agent.

Example 3

An organic-inorganic composite concrete protective agent with a nano core-shell structure, the mass percentage of its raw materials is composed of:

Isobutyltriethoxysilane 0.9%;

Ethyl orthosilicate 6%;

Methanol 92%;

Ammonia 0.1%;

Deionized water 1%.

The preparation method is: weigh methanol according to the proportion, add ammonia water to adjust the pH to 8-11, then add isobutyltriethoxysilane, stir with a magnetic stirrer for 30 minutes, then add ethyl orthosilicate, continue stirring for 12 hours, and finally add Stir the ionized water for 3.5 hours until the solution turns from transparent to turbid, and the reaction is complete. Use a high-speed centrifuge at a speed of 10,000 rpm for 5 minutes, filter the supernatant, and collect the solid at the bottom of the centrifuge tube, which is the nano-core-shell structure in this example. Organic-inorganic composite concrete protective agent.

Application test results

Example 4

The nano-core-shell structure organic-inorganic composite concrete protective agent prepared in Example 1 is used to treat cement mortar with a water-cement ratio of 0.6 and an age of one year. Dissolve in tetrahydrofuran to obtain a mixed solution, and then apply it to the surface of cement mortar by spraying. The spraying is repeated 3 times with an interval of 20 minutes between each spraying until the surface of the cement mortar is fully wetted. Measure the water absorption rate of cement mortar after 3 days of standard maintenance. At the same time, measure the water absorption rate of the cement mortar test block treated with silane material under the same conditions, the water absorption rate of the cement mortar test block treated with nano- _SiO2 precursor, and the cement mortar test block without any treatment Water absorption of mortar test block. The result is shown in Figure 2.

In Fig. 2, according to the trend of the curve, it can be seen that the use of the nano core-shell structure organic-inorganic composite concrete protective agent of the present invention significantly reduces the water absorption rate of the cement mortar test block, indicating that the protective agent material of the present invention has integrated both organic and inorganic protection. The advantages of the agent material, the silane material containing the hydrophobic group acts as a hydrophobic agent, which hinders the immersion of a part of the water, and the nano-SiO ₂ plays a role in plugging the pores, reducing the porosity of the concrete and reducing the migration of water in the surface concrete Quantity, the dual function hinders the intrusion of moisture, and also blocks the influence of harmful ions.

Example 5

The nano-core-shell structure organic-inorganic composite concrete protective agent prepared in Example 2 is used to process the cement slurry test block with a water-cement ratio of 0.38. The treatment method is the same as in Example 4, and the surface contact angle of the untreated blank control group is the same as that of the untreated blank control group. The result is shown in Figure 3.

From the contact angle results in Figure 3, it can be seen that the organic-inorganic composite concrete protective agent with nano-core-shell structure significantly changes the hydrophilicity of the concrete surface and increases the contact angle, making it difficult for moisture carrying harmful ions to invade the internal structure of the concrete.

Example 6

The nano-core-shell structure organic-inorganic composite concrete protective agent prepared in Example 1 is used for surface treatment of cement slurry with a water-cement ratio of 0.4. The treatment method is the same as in Example 4. Compared with the blank sample, it is measured by mercury porosimetry. The pore structure and the obtained data are shown in Figure 4.

The total porosity of the blank control group was 17.74%, and the porosity of the cement treated with the nano-core-shell structure organic-inorganic composite concrete protective agent of the present invention was 18.20%, and the porosity was not much different, within the error range. However, it can be seen from Figure 4 that when the cement is treated with a nano-core-shell structure organic-inorganic composite concrete protective agent, the harmful pores (50-200nm) are significantly reduced, and the peak corresponding to the pore diameter in the range of less harmful pores (20-50nm) Obviously shifting to the harmless pores, it shows that after the cement is treated with the nano core-shell structure organic-inorganic composite concrete protective agent, the harmful pores in the cement are transformed into less harmful pores. significantly less than untreated. It shows that the protective agent of the present invention can play the role of plugging holes and improve the compactness of the concrete pore structure. The pore size distribution is shown in Table 1.

Table 1 Pore size distribution of cement after treatment

Claims (10)

1. A nano core-shell structure organic-inorganic composite protective agent for concrete is characterized in that its raw material mass percentage consists of: Silane with hydrophobic groups 0.5~1.4%; Ethyl orthosilicate 4.1～8%; Polar organic solvent 89～94.8%; Alkali 0.1%; Water 0.5~1.5%. 2. The nano core-shell structure organic-inorganic composite protective agent for concrete according to claim 1, characterized in that, its raw material mass percentage consists of: Silane with hydrophobic groups 0.5%; Orthosilicate 6%; Polar organic solvent 92.9%; Alkali 0.1%; Water 0.5%. 3. The nano core-shell structure organic-inorganic composite concrete protective agent according to claim 1, characterized in that: the silane with hydrophobic groups is polymethylhydrogensiloxane, vinyl triethoxy silane or isobutyltriethoxysilane. 4. The nano core-shell structure organic-inorganic composite protective agent for concrete according to claim 1, characterized in that: the polar organic solvent is tetrahydrofuran, ethanol or methanol. 5. The nano core-shell structure organic-inorganic composite protective agent for concrete according to claim 1, characterized in that: the alkali is ammonia water or ethylenediamine, and the mass concentration of the ammonia water is 0.88g/ml. 6. The organic-inorganic composite protective agent for concrete with nano-core-shell structure according to claim 1, characterized in that: said water is deionized water. 7. A method for preparing a nano-core-shell structure organic-inorganic composite concrete protective agent according to any one of claims 1 to 6, characterized in that: take a polar organic solvent according to the proportion, add alkali to adjust the pH to 8-12, Then add silane with hydrophobic groups, stir for 30 minutes, add tetraethyl orthosilicate, continue stirring for 10-12 hours, and finally add deionized water and stir for 2-3.5 hours until the solution turns from transparent to turbid, centrifuge at 10,000 rpm for 5 minutes, collect The bottom is solid, and the organic-inorganic composite concrete protective agent with nano-core-shell structure is obtained. 8. The application of the nano core-shell structure organic-inorganic composite concrete protective agent according to any one of claims 1 to 6 above, characterized in that it can be used as a protective material for surface-hardened concrete. 9. The application according to claim 8, characterized in that the method of use is: super-disperse the above-mentioned nano core-shell structure organic-inorganic composite concrete protective agent in an organic solvent according to a mass concentration of 5% Get the mixed solution, and then spray it on the concrete surface, repeat the spraying 3 times, with an interval of 20 minutes between each spraying, and spray the mixed solution in an amount of 2.5-3.5L/ ^m2 until the concrete surface is fully wetted. 10. The application according to claim 8, characterized in that: the organic solvent is tetrahydrofuran, ethanol or methanol.