CN115504726B - Preparation method of slow-release hydrophobic microcapsule and hydrophobic concrete - Google Patents

Abstract

The invention discloses a method for preparing slow-release hydrophobic microcapsules and hydrophobic concrete, which belongs to the field of building materials. The preparation steps of the slow-release hydrophobic microcapsules include: compounding an acidic solution and a soluble fluoride to form a corrosive solution. The fly ash beads are etched, and under mechanical agitation, the sinking beads are taken out and dried to obtain perforated beads; the perforated beads are then kept in a negative pressure state under a vacuum of ‑70kPa to ‑80kPa, and then The bleaching beads are loaded with a hydrophobic agent while maintaining the vacuum degree, and finally soaked under normal pressure so that the interior of the bleaching beads is filled with the hydrophobic agent, thereby producing a sustained-release hydrophobic microcapsule; the prepared slow-release hydrophobic microcapsules are Hydrophobic-releasing microcapsules are used in the preparation process of concrete to obtain hydrophobic concrete; the present invention enhances the protection of hydrophobic concrete by utilizing the slow-release characteristics of perforated floating beads and the coordinated regulation of nano-silica produced during the hydrolysis and condensation polymerization process of the hydrophobic agent. Performance and mechanical properties, significantly improving the side effects of water-repellent agents on concrete properties.

Description

Preparation method of sustained-release hydrophobic microcapsules and hydrophobic concrete

Technical field

The invention belongs to the field of building materials, and specifically relates to a preparation method of sustained-release hydrophobic microcapsules and hydrophobic concrete.

Background technique

Concrete has porous characteristics and is exposed to various environmental factors for a long time. It is easily corroded by harmful ions (Cl ^- , SO ₄ ^2-, etc.) using water or other liquids as carriers, leading to corrosion of steel bars, damage to building structures, and Performance degradation; in particular, concrete capillaries absorb chlorine-containing aqueous solutions, such as deicing salts or seawater, which can lead to rapid corrosion of steel bars. Research at home and abroad has shown that the corrosion of steel bars in concrete structures is mainly caused by moisture and other harmful substances (such as chloride ions) that invade the interior of the concrete along with the diffusion of moisture. Therefore, reducing the capillary water absorption performance and water permeability of concrete and delaying the erosion of various harmful substances using water as a medium are effective measures to improve the durability of concrete structures and reduce the risk of corrosion of internal steel bars.

There are many ways to enhance the durability of concrete, including improving the compactness of the concrete, adding rust inhibitors internally, or applying a protective layer on the outside. Although surface coatings can block gases or media from entering the interior of the concrete and thus play a protective role, they generally sacrifice the original appearance of the concrete substrate and gradually lose their protective properties after use for a period of time. Another effective way to control moisture ingress is to use hydrophobic agents to waterproof concrete. Silane hydrophobic agents, as a permeable waterproof material, have good waterproofing effects. Silane hydrophobic agent is different from other waterproof coatings. It reduces the permeability of concrete without blocking the capillary pores on the concrete surface, so that the waterproof-treated concrete still has good air permeability and original appearance without affecting Ca(OH) ₂ is carbonized into CaCO ₃ to improve the compaction of concrete and at the same time effectively prevent corrosion of steel bars. It reacts with inorganic silicate molecules on the surface of the concrete to form stable chemical bonds and produce a good hydrophobic effect. It is these excellent properties It prevents bulging, cracking, etc. after application, and can be used in wear-resistant and anti-corrosion situations such as pavement.

However, since the hydrophobic agent is an oily substance with strong hydrophobicity, being directly incorporated into concrete will affect the hydration reaction of cement, reduce the degree of hydration, and significantly reduce the mechanical properties. Therefore, in order to reduce the side effects of hydrophobic agents on concrete properties, it is necessary to develop new admixture delivery and release technologies to alleviate the "side effects" caused by the incompatibility between the two.

Contents of the invention

In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a method for preparing sustained-release hydrophobic microcapsules and hydrophobic concrete, which reduces the side effects of the hydrophobic agent on the performance of the concrete.

The object of the present invention can be achieved through the following technical solutions:

A preparation method of sustained-release hydrophobic microcapsules, including the following steps:

Step 1: Use an acidic solution and soluble fluoride to form a corrosive solution, etch the fly ash beads, and under mechanical stirring, take out the bottom beads and dry them to prepare perforated beads;

Step 2: First, keep the perforated floating beads in a negative pressure state under a vacuum degree of -70kPa to -80kPa, then inhale the hydrophobic agent under negative pressure while maintaining the vacuum degree, so that the floating beads are loaded with hydrophobic agent, and finally Soak under normal pressure so that the inside of the floating beads is filled with hydrophobic agent, thereby producing sustained-release hydrophobic microcapsules.

Further, the acidic solution is one or more of hydrochloric acid, nitric acid, and oxalic acid.

Further, the soluble fluoride in step 1 is ammonium fluoride or sodium fluoride.

Further, the mass ratio of the acidic solution to the soluble fluoride is 1:(1-1.5).

Further, the water repellent agent is one or a combination of several organic siloxanes, and is mixed with tetraethyl orthosilicate and a silane coupling agent, and is mixed evenly after stirring for compounding.

A hydrophobic concrete, including the following mass ratio ingredients: cement 10-25%, coarse aggregate 40-55%, fine aggregate 20-30%, water 6-10% and sustained-release hydrophobic microcapsules 0.1-30 %.

Further, a method for preparing hydrophobic concrete includes the following steps:

S1, add cement, coarse aggregate, and fine aggregate and stir thoroughly to make them disperse evenly;

S2, then add mixing water and stir to make a slurry;

S3: Finally, take the sustained-release hydrophobic microcapsules, saturate them and dry them, then disperse them into the above slurry and stir them to prepare hydrophobic concrete.

Beneficial effects of the present invention:

1. Compared with hydrophobic concrete prepared by directly incorporating a hydrophobic agent, it alleviates the problem of poor compatibility between the hydrophobic agent and the cement matrix. The slow-release effect of hydrophobic microcapsules can improve the mechanical properties of hydrophobic concrete, and It improves the hydrophobic effect of hydrophobic concrete, enhances the durability of concrete, and reduces the volatilization of hydrophobic agents during the mixing and hardening processes, thereby enhancing the protective effect of hydrophobic concrete;

2. During the development of concrete strength, the tetraethyl orthosilicate or silane coupling agent component in the compound hydrophobic agent will undergo hydrolysis-polycondensation reaction to generate silica particles in situ, promoting secondary hydration, and further Enhance the properties of concrete;

3. As a kind of hollow fly ash particles, floating beads belong to industrial solid waste. The perforated floating beads prepared by the chemical etching method of the present invention can promote the high value-added utilization of floating beads and the bulk consumption of solid waste; Preparation The perforated floating beads can be used as an excellent microcapsule carrier. Its shell material is composed of inorganic silica and aluminum oxide and has higher strength. Compared with existing hydrophobic microcapsules, it is a hard capsule. Carrier, in the actual application process, the survivability of microcapsules is significantly improved and it is not easy to break. When prepared into hydrophobic microcapsules and used in the construction field, they can still maintain their original shape and not be destroyed during the concrete mixing process. Moreover, the interface between floating beads and cement-based materials is small. Since the silica in the floating beads shell material has pozzolanic activity, it will react with cement-based materials during the curing process to further strengthen the interface and enhance the performance of concrete.

Description of the drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings needed to describe the embodiments or the prior art. Obviously, for those of ordinary skill in the art, Speaking of which, other drawings can be obtained based on these drawings without any creative effort.

Figure 1 is a diagram showing the compressive strength experimental results of Examples 1-3 and Comparative Examples 1-4 of the present invention;

Figure 2 is a diagram showing the capillary water absorption test results of Examples 1-3 and Comparative Examples 1-4 of the present invention;

Figure 3 is a diagram of the electric flux experimental results of Examples 1-3 and Comparative Examples 1-4 of the present invention;

Figure 4 is a diagram of the contact angle experimental results of Example 3 of the present invention;

Figure 5 is a diagram of the contact angle experimental results of Comparative Example 1 of the present invention;

Figure 6 is a diagram showing the contact angle experimental results of Comparative Example 4 of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

A preparation method of sustained-release hydrophobic microcapsules, including the following steps:

Step 1. Prepare perforated floating beads;

Use acidic solutions such as hydrochloric acid, nitric acid, oxalic acid and soluble fluoride (such as ammonium fluoride, sodium fluoride, etc.) to form a corrosive solution, and etch the floating beads (using industrial by-product fly ash floating beads) under mechanical stirring. , take the bottom floating beads and dry them to prepare perforated floating beads; wherein, the molar ratio of the acidic solution and the soluble fluoride is 1:(1-1.5), and the reaction time is 8min-2h.

Step 2. Use the vacuum saturation method to load the hydrophobic agent;

First, under a vacuum degree of -70kPa to -80kPa, keep the perforated floating beads in a negative pressure state for 2 hours, and then suck in the hydrophobic agent under negative pressure while maintaining the vacuum degree, so that the floating beads are loaded with hydrophobic agent, and continue to maintain it for 15 minutes. Finally, soak under normal pressure for 12 hours so that the inside of the beads is filled with hydrophobic agent, thereby producing sustained-release hydrophobic microcapsules.

Among them, the hydrophobic agent in step 2 is selected from highly permeable organosilane or organosiloxane reagents (such as isobutyltriethoxysilane, tetraethoxysilane, etc.), and is mixed with tetrakis orthosilicate. Mix the ethyl ester and silane coupling agent evenly before compounding; mainly through the formation of Si-O bonds between silane hydrolysis and the cement matrix, so that the organic hydrophobic groups face the outside of the pores to achieve a hydrophobic effect, and use orthosilicic acid The hydrolysis-polycondensation reaction of tetraethyl ester or silane coupling agent inside the cement-based material forms silica particles in situ, promotes secondary hydration of concrete, densifies the microstructure of the cement matrix, and enhances the waterproof performance of the concrete. At the same time, the mechanical properties and durability of concrete are improved.

A kind of hydrophobic concrete includes: cement 10-25wt%, coarse aggregate 40-55wt%, fine aggregate 20-30wt%, water 6-10wt%, and hydrophobic microcapsules 0.1-10wt%.

Preparation steps of hydrophobic concrete:

Step 1: First add cement, coarse aggregate, and fine aggregate and stir thoroughly to make them disperse evenly;

Step 2, then add mixing water and stir;

Step 3: Finally, take an appropriate amount of hydrophobic microcapsules, saturate and dry them, then disperse them into the above slurry and mix them to prepare hydrophobic concrete.

Principle analysis:

Floating beads are a kind of hollow fly ash particles. The shell is mainly composed of silica and aluminum oxide, and the larger internal space has not been fully utilized. Therefore, the present invention is based on hydrofluoric acid and dioxic acid. The principle of the silicon oxide reaction is to etch penetrating holes on the surface of the beads, which provides a way to utilize the internal space of the beads, so that it can be used as an excellent additive carrier. The hydrophobic agent is loaded through the vacuum saturation method. The perforations on the surface of the floating beads are used to control the release of the internal hydrophobic agent to achieve the purpose of sustained release, thereby mitigating the negative impact of directly incorporating the hydrophobic agent on the mechanical properties of concrete.

Secondly, by controlling the proportion of the corrosive liquid, perforated floating beads with different perforated pore sizes can be designed to regulate the release rate of the hydrophobic agent inside the hydrophobic microcapsules, thereby reducing the incompatibility between the hydrophobic agent and the cement matrix.

In conventional organosilane or organosiloxane hydrophobic agents, compounding is carried out by adding tetraethyl orthosilicate or silane coupling agent, so that the organosilane or organosiloxane in the composite water repellent agent has a positive effect on the concrete. While achieving the protective effect, tetraethyl orthosilicate or silane coupling agent can undergo hydrolysis-polycondensation reaction in concrete to form silica particles in situ, further enhancing the performance of concrete.

The following sets up 3 examples and 4 comparative examples to prepare hydrophobic concrete and test its performance:

Example 1 (PC1):

A preparation method of sustained-release hydrophobic microcapsules, including the following steps:

Use hydrochloric acid and ammonium fluoride to form an acidic corrosive liquid at a molar ratio of 1:1.1. Add fly ash floating beads and stir. After surface corrosion, take the bottom part and dry it to make perforated floating beads; then - Under the vacuum degree of 70kPa to -80kPa, keep the perforated floating beads in a negative pressure state for 2 hours, and then suck in the hydrophobic agent under negative pressure while maintaining the vacuum degree, so that the floating beads are loaded with the hydrophobic agent, and continue to maintain it under negative pressure for 15 minutes. , and finally soaked under normal pressure for 12 hours, so that the inside of the floating beads is filled with hydrophobic agent, and the sustained-release hydrophobic microcapsules are obtained.

Preparation steps of hydrophobic concrete:

A kind of hydrophobic concrete includes: cement 14wt%, coarse aggregate 52wt%, fine aggregate 26wt%, water 7wt%, and hydrophobic microcapsules 1wt%.

Step 1: First add cement, coarse aggregate, and fine aggregate and stir thoroughly to make them disperse evenly;

Step 2, then add mixing water and stir;

Step 3: Finally, take an appropriate amount of hydrophobic microcapsules, saturate and dry them, then disperse them into the above slurry and mix them to prepare hydrophobic concrete.

Example 2 (PC3):

A preparation method of sustained-release hydrophobic microcapsules, including the following steps:

Use hydrochloric acid and ammonium fluoride to form an acidic corrosive liquid at a molar ratio of 1:1.1. Add fly ash floating beads and stir. After surface corrosion, take the bottom part and dry it to make perforated floating beads; then - Under the vacuum degree of 70kPa to -80kPa, keep the perforated floating beads in a negative pressure state for 2 hours, and then suck in the hydrophobic agent under negative pressure while maintaining the vacuum degree, so that the floating beads are loaded with the hydrophobic agent, and continue to maintain it under negative pressure for 15 minutes. , and finally soaked under normal pressure for 12 hours, so that the inside of the floating beads is filled with hydrophobic agent, and the sustained-release hydrophobic microcapsules are obtained.

Preparation steps of hydrophobic concrete:

A kind of hydrophobic concrete includes: cement 14wt%, coarse aggregate 52wt%, fine aggregate 24wt%, water 7wt%, and hydrophobic microcapsules 3wt%.

Step 1: First add cement, coarse aggregate, and fine aggregate and stir thoroughly to make them disperse evenly;

Step 2, then add mixing water and stir;

Step 3: Finally, take an appropriate amount of hydrophobic microcapsules, saturate and dry them, then disperse them into the above slurry and mix them to prepare hydrophobic concrete.

Example 3 (PC5):

A preparation method of sustained-release hydrophobic microcapsules, including the following steps:

Use hydrochloric acid and ammonium fluoride to form an acidic corrosive liquid at a molar ratio of 1:1.1. Add fly ash floating beads and stir. After surface corrosion, take the bottom part and dry it to make perforated floating beads; then - Under the vacuum degree of 70kPa to -80kPa, keep the perforated floating beads in a negative pressure state for 2 hours, and then suck in the hydrophobic agent under negative pressure while maintaining the vacuum degree, so that the floating beads are loaded with the hydrophobic agent, and continue to maintain it under negative pressure for 15 minutes. , and finally soaked under normal pressure for 12 hours, so that the inside of the floating beads is filled with hydrophobic agent, and the sustained-release hydrophobic microcapsules are obtained.

Preparation steps of hydrophobic concrete:

A kind of hydrophobic concrete includes: cement 14wt%, coarse aggregate 52wt%, fine aggregate 22wt%, water 7wt%, and hydrophobic microcapsules 5wt%.

Step 1: First add cement, coarse aggregate, and fine aggregate and stir thoroughly to make them disperse evenly;

Step 2, then add mixing water and stir;

Step 3: Finally, take an appropriate amount of hydrophobic microcapsules, saturate and dry them, then disperse them into the above slurry and mix them to prepare hydrophobic concrete.

Comparative Example 1(C):

A kind of hydrophobic concrete includes: cement 14wt%, coarse aggregate 53wt%, fine aggregate 26wt%, water 7wt%, and hydrophobic microcapsules 0wt%.

The preparation steps are:

Step 1: First add cement, coarse aggregate, and fine aggregate and stir thoroughly to make them disperse evenly;

Step 2, then add mixing water and stir;

Prepare hydrophobic concrete.

Comparative example 2 (S1):

A kind of hydrophobic concrete includes: cement 14wt%, coarse aggregate 52wt%, fine aggregate 26wt%, water 7wt%, hydrophobic microcapsules 0wt%, and hydrophobic agent 1wt%.

The preparation steps are:

Step 1: First add cement, coarse aggregate, and fine aggregate and stir thoroughly to make them disperse evenly;

Step 2, then add mixing water and stir;

Step 3: Finally, add an appropriate amount of hydrophobic agent directly into the above slurry and stir to prepare hydrophobic concrete.

Comparative Example 3 (S3):

A kind of hydrophobic concrete includes: cement 14wt%, coarse aggregate 52wt%, fine aggregate 24wt%, water 7wt%, hydrophobic microcapsules 0wt%, and hydrophobic agent 3wt%.

The preparation steps are:

Step 1: First add cement, coarse aggregate, and fine aggregate and stir thoroughly to make them disperse evenly;

Step 2, then add mixing water and stir;

Step 3: Finally, add an appropriate amount of hydrophobic agent directly to the above slurry and stir to prepare hydrophobic concrete Comparative Example 4 (S5):

A kind of hydrophobic concrete includes: cement 14wt%, coarse aggregate 52wt%, fine aggregate 22wt%, water 7wt%, hydrophobic microcapsules 0wt%, and hydrophobic agent 5wt%.

The preparation steps are:

Step 1: First add cement, coarse aggregate, and fine aggregate and stir thoroughly to make them disperse evenly;

Step 2, then add mixing water and stir;

Step 3: Finally, add an appropriate amount of hydrophobic agent directly into the above slurry and stir to prepare hydrophobic concrete.

According to GB/T50081 "Standard for Testing Methods of Mechanical Properties of Ordinary Concrete", according to the ingredient ratio in the example, pour a 100×100×100mm cube specimen, and use a universal testing machine to test the compressive strength value of the concrete specimen; according to GB/T50082 " "Standard for Test Methods for Long-term Performance and Durability of Ordinary Concrete", pour a cylindrical specimen with d×h=50×100mm, and use an electric flux tester to test the total electric flux value of the concrete specimen within 6 hours; according to ASTMC1585, prepare d ×h=50×100mm cylindrical specimen, the capillary water absorption performance of the concrete specimen is evaluated by testing the change of water absorption mass of the specimen within 8 days.

Figure 1 shows the compressive strength data of hydrophobic concrete. The incorporation of hydrophobic agents significantly reduces the compressive strength value of concrete and has a negative impact on the mechanical properties of concrete. After the incorporation of sustained-release hydrophobic microcapsules, it is significantly different from the direct incorporation into Compared with the hydrophobic agent, it alleviates the loss of mechanical strength, increases the mechanical properties, and effectively improves the incompatibility between the hydrophobic agent and the cement matrix causing a significant reduction in mechanical properties; in addition, it can also be seen in Figure 2-6 The hydrophobic microcapsules significantly improve the chloride ion penetration resistance and capillary water absorption performance of concrete, increase the static contact angle of concrete, and improve the protective performance of concrete.

In the description of this specification, reference to the terms "one embodiment," "example," "specific example," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one aspect of the invention. in an embodiment or example. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the industry should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have other aspects. Various changes and modifications are possible, which fall within the scope of the claimed invention.

Claims (8)

1. A method for preparing sustained-release hydrophobic microcapsules, which is characterized by comprising the following steps: Step 1: Use an acidic solution and soluble fluoride to form a corrosive solution, etch the fly ash beads, and under mechanical stirring, take out the bottom beads and dry them to prepare perforated beads; Step 2: First, keep the perforated floating beads in a negative pressure state under a vacuum degree of -70kPa to -80kPa, then load the floating beads with a hydrophobic agent while maintaining the vacuum degree, and finally soak them under normal pressure to make them The inside of the floating beads is filled with hydrophobic agent to prepare sustained-release hydrophobic microcapsules; The hydrophobic agent is one or several combinations of organic silanes, and is mixed with tetraethyl orthosilicate and a silane coupling agent, and is mixed evenly by stirring for compounding. 2. A method for preparing sustained-release hydrophobic microcapsules according to claim 1, characterized in that in step 1, the acidic solution is one or more of hydrochloric acid, nitric acid, and oxalic acid. 3. A method for preparing sustained-release hydrophobic microcapsules according to claim 1, characterized in that the soluble fluoride in step 1 is one or more of ammonium fluoride and sodium fluoride. 4. A method for preparing sustained-release hydrophobic microcapsules according to claim 1, characterized in that the mass ratio of the acidic solution and soluble fluoride is 1: (1-1.5). 5. A sustained-release hydrophobic microcapsule prepared by the method described in any one of claims 1-4. 6. Application of the sustained-release hydrophobic microcapsules according to claim 5 in the preparation of hydrophobic concrete. 7. A hydrophobic concrete, the ingredients of which include the slow-release hydrophobic microcapsules according to claim 5, characterized in that the hydrophobic concrete includes the following mass ratio ingredients: cement 10-25%, coarse aggregate 40-55% %, fine aggregate 20-30%, water 6-10% and sustained-release hydrophobic microcapsules 0.1-30%. 8. A method for preparing the hydrophobic concrete according to claim 7, characterized in that it includes the following steps: S1, add cement, coarse aggregate, and fine aggregate and stir thoroughly to make them disperse evenly; S2, then add mixing water and stir to make a slurry; S3: Finally, take the sustained-release hydrophobic microcapsules, saturate them and dry them, then disperse them into the above slurry and stir them to prepare hydrophobic concrete.