Preparation method of nano-color paste for colored concrete

Abstract

The present invention discloses a preparation method of a nano-color paste for colored concrete, belonging to the technical field of dye preparation. The preparation method comprises the following steps: a nano-inorganic pigment fine emulsion and an acrylic acid solution are mixed in a weight ratio of 1:1-2 and treated with an ultrasonic power of 200-300 W for 5-10 min to obtain a mixed emulsion. The mixed emulsion is mixed with a redox initiator in a weight ratio of 1:0.002-0.005 and polymerized in a temperature environment of 40°C-50°C for 3-5 h to obtain the nano-color paste for colored concrete. The present invention first obtains a nano-inorganic pigment fine emulsion by high-pressure homogenization treatment of nano-inorganic pigments, and then forms a nano-color paste by emulsion polymerization to wrap the nano-inorganic pigments.

Description

Technical Field

[0001] The present invention belongs to the technical field of dye preparation, and particularly relates to a method for preparing a nano-color paste for colored concrete. Background Art

[0002] With the continuous, stable and rapid development of China's economy, a large number of infrastructure constructions are underway. Due to its non-toxic, odorless, high-strength, durable, easy-to-form and other advantages, concrete has become one of the most widely used building materials, and its applications have spread to many fields such as civil engineering, urban construction, and transportation. However, since concrete mostly appears in people's vision with a single color and a cold gray color, with the progress of modern society and the increasing improvement of people's living tastes, people's requirements for the material environment are not only to meet its practicality, but more importantly, to pursue its artistic visual effects. In the fields of urban construction and transportation, this is reflected in higher requirements for the decoration of buildings and the beautification and guiding effects of highway infrastructure. Large buildings and structures are basically composed of concrete, and their appearance colors are cold and single. In order to make them have a certain aesthetic effect and be naturally coordinated with the surrounding environment, the most commonly used method at present is to carry out secondary decoration, such as painting on their outer surfaces. Painting requires building a workbench outside the already built building, which is inconvenient for construction, and many exterior decoration materials have certain pollution. After long-term exposure to sunlight and rain, problems such as color fading and peeling are likely to occur, and the cost of maintenance and repair is expensive and the process is cumbersome. Against this background, a new type of decorative concrete - colored concrete has emerged. The use of colored concrete can effectively solve these problems: on the one hand, the use of the self-decoration of colored concrete can greatly enrich the colors of buildings, conveniently obtain a natural and elegant building finish, and relatively easily achieve the aesthetic effect expected by people; on the other hand, the decorative effect can be obtained through one-time construction of colored concrete, which exempts the secondary decoration of buildings. It can not only save a large amount of resources, reduce environmental pollution, but also has the advantages of fast construction and good durability. With the country's strong advocacy of resource conservation and building energy conservation, the application of colored concrete in the construction field has received more and more attention.

[0003] The color adjustment of colored concrete is mainly achieved by adding pigments. The types and quality of pigments directly affect the color effect and performance of concrete. According to the properties of pigments, they can be mainly divided into the following categories: (1) Inorganic pigments: Inorganic pigments refer to pigments made from inorganic compounds and are commonly used in colored concrete. Their main advantages include good light stability, not fading after long-term exposure to sunlight; not easily undergoing chemical reactions under various environmental conditions, being able to maintain long-term color stability, with high chemical stability; environmental friendliness: Most inorganic pigments are non-toxic and not easily volatile, meeting environmental protection requirements; (2) Organic pigments: Organic pigments are pigments made from organic compounds and usually have bright colors. Their main advantages include being able to provide more diverse and vivid colors and being widely used in occasions where specific color effects are required. However, organic pigments have relatively poor light resistance and durability, lower stability than inorganic pigments, and a higher impact on the environment than inorganic pigments.

[0004] Patent CN103275561B discloses an environmentally friendly water-based nano-color paste and its preparation method. In this invention, after adding a dispersant, a sterilizer, a barrier agent, and a water-based pigment and mixing them, a physical grinding method is used to make it reach the nano-level. Patent CN107603347B discloses a water-based nano-color paste dispersant and its preparation method. This invention uses cyclodextrin and oleic acid with good biocompatibility as raw materials, and then combines with a suitable surfactant to prepare a super-dispersible water-based nano-color paste dispersant through thermal-initiated polymerization, and then mixes it with the ground pigment to obtain a water-based nano-color paste. Patent CN114163875B discloses a red nano-color paste and its preparation method and application. In this invention, the red pigment is first subjected to pickling treatment to obtain an acid-treated pigment, and then the acid-treated pigment is mixed with sodium chloride and an organic solvent for salt grinding treatment to obtain a salt-ground pigment. Then, the salt-ground pigment is mixed with acrylate monomers, a dispersant, a stabilizer, and a co-dispersant for ball milling treatment to obtain a red nano-color paste. When preparing the above nano-color pastes, a dispersant needs to be added to prevent the aggregation of nano-sized pigments. However, due to the special alkaline environment of concrete, the dispersant is likely to react with the components in the concrete, thereby causing the dispersant to lose its protection of the nano-pigments. If the amount of the dispersant used is further increased, it may cause adverse effects such as excessive bubbles, increasing the porosity of the concrete and having a greater impact on the compactness of the concrete.

[0005] Therefore, designing a nano-color paste that can improve the dispersibility of nano-pigments is of great significance for the preparation of colored concrete. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention first obtains a nano-inorganic pigment fine emulsion by high-pressure homogenization of nano-inorganic pigments, and then forms a nano-color paste by emulsion polymerization to wrap the nano-inorganic pigments, thereby solving the technical problems raised in the background art. Specifically, the technical solution of the present invention includes the following content:

[0007] A preparation method of a nano-color paste for colored concrete, the preparation method comprising the following steps:

[0008] The nano-inorganic pigment fine emulsion and the acrylic acid solution are mixed in a weight ratio of 1:1-2 and treated with an ultrasonic power of 200-300 W for 5-10 min to obtain a mixed emulsion. The mixed emulsion is mixed with a redox initiator in a weight ratio of 1:0.002-0.005 and polymerized at a temperature of 40°C-50°C for 3-5 h to obtain the nano-color paste for colored concrete.

[0009] Further, the preparation method of the nano-inorganic pigment fine emulsion includes the following steps:

[0010] The nano-inorganic pigment is dispersed in absolute ethanol to form a dispersion phase, and an anionic surfactant is dissolved in deionized water to form an aqueous phase. The dispersion phase and the aqueous phase are mixed in a weight ratio of 1:3-5 and then subjected to high-pressure homogenization treatment to obtain the nano-inorganic pigment fine emulsion.

[0011] Further, the nano-inorganic pigment includes nano-titanium dioxide or nano-ferroferric oxide, and the particle size of the nano-inorganic pigment is 10-20 nm.

[0012] Further, the weight ratio of the nano-inorganic pigment to absolute ethanol is 1:10-15.

[0013] Further, the anionic surfactant includes sodium stearate or sodium oleate.

[0014] Further, the weight ratio of the anionic surfactant to deionized water is 1:30-40.

[0015] Further, the conditions of the high-pressure homogenization include a pressure of 70-80 MPa and a treatment time of 12-15 min.

[0016] Further, the mass concentration of the acrylic acid solution is 40-60%.

[0017] Further, the redox initiator is composed of ammonium persulfate and sodium bisulfite in a molar ratio of 1-2:1.

[0018] A nano-color paste for colored concrete prepared by the preparation method of the nano-color paste for colored concrete.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] The present invention uses nano-inorganic pigments with a specific particle size as one of the core raw materials of the nano-color paste. It is pretreated into a fine emulsion of nano-inorganic pigments by high-pressure homogenization. After mixing the fine emulsion of nano-inorganic pigments and acrylic acid solution, ultrasonic treatment is carried out. Using the low-temperature redox initiation mechanism, the nano-inorganic pigments can be polymerized and encapsulated by acrylic acid monomers in the emulsion system, and then a nano-color paste with nano-size is synthesized. The fine emulsion treatment of nano-inorganic pigments can form smaller droplets compared to conventional emulsions, preventing the nano-inorganic pigments in the emulsion from attracting each other and further forming larger-size particles, which is beneficial to the dispersion of nano-inorganic pigments. At this time, ammonium persulfate and sodium bisulfite are used together to construct a low-temperature redox initiation for polymerization reaction. The fine emulsion obtained by pretreatment combined with the low-temperature redox initiation process can solve the dispersion problem of nano-inorganic pigments while enabling the particles in the polymerized nano-color paste to maintain a good nano-size. At the same time, the polyacrylic acid structure formed by the polymerization of acrylic acid monomers has good hydrophilicity, which can increase the compatibility between the nano-color paste and concrete. Specific Embodiments

[0021] The technical solutions of the present invention will be clearly and completely described below through the embodiments of the present invention. Obviously, the described embodiments are only a part 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 skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0022] Unless otherwise specified, the raw materials and reagents used in the present invention below are all commercially available products or can be prepared by known methods.

[0023] Nano-ferroferric oxide with an average particle size of 10-20 nm was purchased from Hangzhou Hengna New Materials Co., Ltd.;

[0024] Nano-titanium dioxide with an average particle size of 10-20 nm was purchased from Shanghai Liangjiang Titanium White Chemical Co., Ltd.;

[0025] PCA ® -I polycarboxylate superplasticizer was purchased from Jiangsu Sobute New Materials Co., Ltd.;

[0026] Portland cement with a strength grade of P.O 42.5 was purchased from Tangshan Hongye Special Cement Co., Ltd.

[0027] Preparation Example 1:

[0028] The preparation method of the fine emulsion of nano-inorganic pigments includes the following steps:

[0029] Weigh 1 part by weight of nano-titanium dioxide powder with an average particle size of 10 nm and add it to 10 parts by weight of absolute ethanol. Then, disperse it for 20 min with an ultrasonic power of 100 W to obtain a dispersion phase. Dissolve 1 part by weight of an anionic surfactant, sodium stearate, in 30 parts by weight of deionized water to form an aqueous phase (dissolution can be promoted by heating). Take 1 part by weight of the dispersion phase and 3 parts by weight of the aqueous phase and mix them. Then, put them into a high-pressure homogenizer, control the pressure at 70 MPa, and homogenize for 12 min to obtain a fine emulsion of nano-inorganic pigment.

[0030] Preparation Example 2:

[0031] The preparation method of the fine emulsion of nano-inorganic pigment includes the following steps:

[0032] Weigh 1 part by weight of nano-titanium dioxide powder with an average particle size of 10 nm and add it to 11 parts by weight of absolute ethanol. Then, disperse it for 20 min with an ultrasonic power of 100 W to obtain a dispersion phase. Dissolve 1 part by weight of an anionic surfactant, sodium stearate, in 32 parts by weight of deionized water to form an aqueous phase (dissolution can be promoted by heating). Take 1 part by weight of the dispersion phase and 3 parts by weight of the aqueous phase and mix them. Then, put them into a high-pressure homogenizer, control the pressure at 70 MPa, and homogenize for 13 min to obtain a fine emulsion of nano-inorganic pigment.

[0033] Preparation Example 3:

[0034] The preparation method of the fine emulsion of nano-inorganic pigment includes the following steps:

[0035] Weigh 1 part by weight of nano-titanium dioxide powder with an average particle size of 10 nm and add it to 12 parts by weight of absolute ethanol. Then, disperse it for 20 min with an ultrasonic power of 100 W to obtain a dispersion phase. Dissolve 1 part by weight of an anionic surfactant, sodium stearate, in 34 parts by weight of deionized water to form an aqueous phase (dissolution can be promoted by heating). Take 1 part by weight of the dispersion phase and 4 parts by weight of the aqueous phase and mix them. Then, put them into a high-pressure homogenizer, control the pressure at 75 MPa, and homogenize for 13 min to obtain a fine emulsion of nano-inorganic pigment.

[0036] Preparation Example 4:

[0037] The preparation method of the fine emulsion of nano-inorganic pigment includes the following steps:

[0038] Weigh 1 part by weight of nano-ferroferric oxide powder with an average particle size of 20 nm and add it to 13 parts by weight of absolute ethanol. Then, disperse it for 20 min with an ultrasonic power of 100 W to obtain a dispersion phase. Dissolve 1 part by weight of the anionic surfactant sodium oleate in 36 parts by weight of deionized water to form an aqueous phase (dissolution can be promoted by heating). Take 1 part by weight of the dispersion phase and 4 parts by weight of the aqueous phase and mix them. Then, put them into a high-pressure homogenizer, control the pressure at 75 MPa, and homogenize for 14 min to obtain a fine emulsion of nano-inorganic pigment.

[0039] Preparation Example 5:

[0040] The preparation method of the fine emulsion of nano-inorganic pigment includes the following steps:

[0041] Weigh 1 part by weight of nano-ferroferric oxide powder with an average particle size of 20 nm and add it to 14 parts by weight of absolute ethanol. Then, disperse it for 20 min with an ultrasonic power of 100 W to obtain a dispersion phase. Dissolve 1 part by weight of the anionic surfactant sodium oleate in 38 parts by weight of deionized water to form an aqueous phase (dissolution can be promoted by heating). Take 1 part by weight of the dispersion phase and 5 parts by weight of the aqueous phase and mix them. Then, put them into a high-pressure homogenizer, control the pressure at 80 MPa, and homogenize for 14 min to obtain a fine emulsion of nano-inorganic pigment.

[0042] Preparation Example 6:

[0043] The preparation method of the fine emulsion of nano-inorganic pigment includes the following steps:

[0044] Weigh 1 part by weight of nano-ferroferric oxide powder with an average particle size of 20 nm and add it to 15 parts by weight of absolute ethanol. Then, disperse it for 20 min with an ultrasonic power of 100 W to obtain a dispersion phase. Dissolve 1 part by weight of the anionic surfactant sodium oleate in 40 parts by weight of deionized water to form an aqueous phase (dissolution can be promoted by heating). Take 1 part by weight of the dispersion phase and 5 parts by weight of the aqueous phase and mix them. Then, put them into a high-pressure homogenizer, control the pressure at 80 MPa, and homogenize for 15 min to obtain a fine emulsion of nano-inorganic pigment.

[0045] Preparation Example 7:

[0046] The preparation method of the fine emulsion of nano-inorganic pigment includes the following steps:

[0047] Weigh 1 part by weight of nano-ferroferric oxide powder with an average particle size of 50 nm and add it to 15 parts by weight of absolute ethanol. Then, disperse it for 20 min with an ultrasonic power of 100 W to obtain a dispersion phase. Dissolve 1 part by weight of an anionic surfactant, sodium oleate, in 40 parts by weight of deionized water to form an aqueous phase (dissolution can be promoted by heating). Take 1 part by weight of the dispersion phase and 5 parts by weight of the aqueous phase and mix them. Then, put them into a high-pressure homogenizer, control the pressure at 80 MPa, and homogenize for 15 min to obtain a fine emulsion of nano-inorganic pigment.

[0048] Preparation Example 8:

[0049] The preparation method of the fine emulsion of nano-inorganic pigment comprises the following steps:

[0050] Weigh 1 part by weight of nano-ferroferric oxide powder with an average particle size of 20 nm and add it to 15 parts by weight of absolute ethanol. Then, disperse it for 20 min with an ultrasonic power of 100 W to obtain a dispersion phase. Dissolve 1 part by weight of a cationic surfactant, cetyltrimethylammonium chloride, in 40 parts by weight of deionized water to form an aqueous phase (dissolution can be promoted by heating). Take 1 part by weight of the dispersion phase and 5 parts by weight of the aqueous phase and mix them. Then, put them into a high-pressure homogenizer, control the pressure at 80 MPa, and homogenize for 15 min to obtain a fine emulsion of nano-inorganic pigment.

[0051] Preparation Example 9:

[0052] The preparation method of the fine emulsion of nano-inorganic pigment comprises the following steps:

[0053] Weigh 1 part by weight of nano-ferroferric oxide powder with an average particle size of 20 nm and add it to 15 parts by weight of absolute ethanol. Then, disperse it for 20 min with an ultrasonic power of 100 W to obtain a dispersion phase. Dissolve 1 part by weight of an anionic surfactant, sodium oleate, in 40 parts by weight of deionized water to form an aqueous phase (dissolution can be promoted by heating). Take 1 part by weight of the dispersion phase and 5 parts by weight of the aqueous phase and mix them. Then, put them into a high-pressure homogenizer, control the pressure at 90 MPa, and homogenize for 20 min to obtain a fine emulsion of nano-inorganic pigment. Example 1

[0054] A preparation method of a nano-color paste for colored concrete specifically comprises the following process:

[0055] Weigh 1 part by weight of the nano-inorganic pigment fine emulsion obtained in Preparation Example 1 and 1 part by weight of an acrylic acid solution (the mass concentration of the acrylic acid solution is 40%), mix and stir them, then adjust the ultrasonic power to 200 W, start ultrasonic treatment for 5 min to obtain a mixed emulsion, add a redox initiator composed of ammonium persulfate and sodium bisulfite (the molar ratio of ammonium persulfate to sodium bisulfite is 1:1) according to 0.004 times the weight of the mixed emulsion, use nitrogen as the protective gas, and then heat up to 40 °C for polymerization treatment for 3 h. After the polymerization reaction is completed, it is naturally cooled to room temperature to obtain the nano-color paste for colored concrete. Example 2

[0056] A preparation method of a nano-color paste for colored concrete specifically includes the following process:

[0057] Weigh 1 part by weight of the nano-inorganic pigment fine emulsion obtained in Preparation Example 2 and 1.2 parts by weight of an acrylic acid solution (the mass concentration of the acrylic acid solution is 40%), mix and stir them, then adjust the ultrasonic power to 200 W, start ultrasonic treatment for 6 min to obtain a mixed emulsion, add a redox initiator composed of ammonium persulfate and sodium bisulfite (the molar ratio of ammonium persulfate to sodium bisulfite is 1:1) according to 0.006 times the weight of the mixed emulsion, use nitrogen as the protective gas, and then heat up to 40 °C for polymerization treatment for 3 h. After the polymerization reaction is completed, it is naturally cooled to room temperature to obtain the nano-color paste for colored concrete. Example 3

[0058] A preparation method of a nano-color paste for colored concrete specifically includes the following process:

[0059] Weigh 1 part by weight of the nano-inorganic pigment fine emulsion obtained in Preparation Example 3 and 1.4 parts by weight of an acrylic acid solution (the mass concentration of the acrylic acid solution is 50%), mix and stir them, then adjust the ultrasonic power to 250 W, start ultrasonic treatment for 7 min to obtain a mixed emulsion, add a redox initiator composed of ammonium persulfate and sodium bisulfite (the molar ratio of ammonium persulfate to sodium bisulfite is 1.5:1) according to 0.006 times the weight of the mixed emulsion, use nitrogen as the protective gas, and then heat up to 45 °C for polymerization treatment for 4 h. After the polymerization reaction is completed, it is naturally cooled to room temperature to obtain the nano-color paste for colored concrete. Example 4

[0060] A preparation method of a nano-color paste for colored concrete specifically includes the following process:

[0061] Weigh 1 part by weight of the nano-inorganic pigment fine emulsion obtained in Preparation Example 4 and 1.6 parts by weight of an acrylic acid solution (the mass concentration of the acrylic acid solution is 50%), mix and stir them, then adjust the ultrasonic power to 250 W, start ultrasonic treatment for 8 min to obtain a mixed emulsion, add a redox initiator composed of ammonium persulfate and sodium bisulfite (the molar ratio of ammonium persulfate to sodium bisulfite is 1.5:1) according to 0.008 times the weight of the mixed emulsion, use nitrogen as the protective gas, and then heat up to 45 °C for polymerization treatment for 4 h. After the polymerization reaction is completed, it is naturally cooled to room temperature to obtain a nano-color paste for colored concrete. Example 5

[0062] A preparation method of a nano-color paste for colored concrete specifically includes the following process:

[0063] Weigh 1 part by weight of the nano-inorganic pigment fine emulsion obtained in Preparation Example 5 and 1.8 parts by weight of an acrylic acid solution (the mass concentration of the acrylic acid solution is 60%), mix and stir them, then adjust the ultrasonic power to 300 W, start ultrasonic treatment for 9 min to obtain a mixed emulsion, add a redox initiator composed of ammonium persulfate and sodium bisulfite (the molar ratio of ammonium persulfate to sodium bisulfite is 2:1) according to 0.008 times the weight of the mixed emulsion, use nitrogen as the protective gas, and then heat up to 50 °C for polymerization treatment for 5 h. After the polymerization reaction is completed, it is naturally cooled to room temperature to obtain a nano-color paste for colored concrete. Example 6

[0064] A preparation method of a nano-color paste for colored concrete specifically includes the following process:

[0065] Weigh 1 part by weight of the nano-inorganic pigment fine emulsion obtained in Preparation Example 6 and 2 parts by weight of an acrylic acid solution (the mass concentration of the acrylic acid solution is 60%), mix and stir them, then adjust the ultrasonic power to 300 W, start ultrasonic treatment for 10 min to obtain a mixed emulsion, add a redox initiator composed of ammonium persulfate and sodium bisulfite (the molar ratio of ammonium persulfate to sodium bisulfite is 2:1) according to 0.01 times the weight of the mixed emulsion, use nitrogen as the protective gas, and then heat up to 50 °C for polymerization treatment for 5 h. After the polymerization reaction is completed, it is naturally cooled to room temperature to obtain a nano-color paste for colored concrete.

[0066] Comparative Example 1:

[0067] A preparation method of a nano-color paste for colored concrete specifically includes the following process:

[0068] Replace the nano-inorganic pigment fine emulsion in Example 4 with the nano-inorganic pigment fine emulsion obtained in Preparation Example 7, and keep the other conditions the same as in Example 4.

[0069] Comparative Example 2:

[0070] A preparation method of nano-color paste for colored concrete specifically includes the following process:

[0071] Replace the nano-inorganic pigment fine emulsion in Example 4 with the nano-inorganic pigment fine emulsion obtained in Preparation Example 8, and keep the other conditions the same as those in Example 4.

[0072] Comparative Example 3:

[0073] A preparation method of nano-color paste for colored concrete specifically includes the following process:

[0074] Replace the nano-inorganic pigment fine emulsion in Example 4 with the nano-inorganic pigment fine emulsion obtained in Preparation Example 9, and keep the other conditions the same as those in Example 4.

[0075] Comparative Example 4:

[0076] A preparation method of nano-color paste for colored concrete specifically includes the following process:

[0077] Weigh 1 part by weight of the nano-inorganic pigment fine emulsion obtained in Preparation Example 4 and 1.6 parts by weight of acrylic acid solution (the mass concentration of the acrylic acid solution is 50%), mix and stir them, then adjust the ultrasonic power to 250 W, start ultrasonic treatment for 8 min to obtain a mixed emulsion, add ammonium persulfate according to 0.008 times the weight of the mixed emulsion, use nitrogen as the protective gas, and then heat up to 60 °C for polymerization treatment for 4 h. After the polymerization reaction ends, naturally cool to room temperature to obtain the nano-color paste for colored concrete.

[0078] Dilute the nano-color pastes for colored concrete prepared in Examples 1 - 6 and Comparative Examples 1 - 4 with deionized water to 1000 times respectively to obtain Samples 1 - 10, and then in a temperature environment of 25 °C, use a particle size analyzer to measure the particle size of Samples 1 - 10 respectively. The results are shown in Table 1 below.

[0079] Table 1 Particle Size Test

[0080]

[0081] Take 25 kg of ordinary Portland cement (strength grade P.O 42.5), 71 kg of river sand, 110 kg of crushed stone (particle size controlled at 5 - 20 mm), 13 kg of water, 1 kg of water reducing agent (PCA ®Mix 3.75 kg of nano-color paste for colored concrete with 1 kg of polycarboxylate superplasticizer to form concrete, and then prepare standard compressive specimens in the shape of a cube with dimensions of 150 mm × 150 mm × 150 mm. The specimens are molded and cured according to the "Manufacture and Curing of Specimens" in Chapter 2 of "GBJ81-85" until the age of 28 days, and then tested using a 1000 kN pressure testing machine. The loading speed during the test is controlled within the range of 0.4 - 0.5 MPa / s, and the compressive strength is obtained through the test. The results are shown in Table 2 below.

[0082] Table 2 Compressive Strength Values of Concrete on the 28th Day

[0083]

[0084] From the test results in Table 1 and Table 2 above, the following conclusions can be drawn:

[0085] (1) Through Examples 1 - 6, it can be found that in the present invention, nano-inorganic pigments with specific particle sizes are first obtained through high-pressure homogenization treatment to form nano-inorganic pigment fine emulsions, and then nano-color pastes for colored concrete are formed through emulsion polymerization encapsulation using a redox initiation polymerization system at low temperature. This method of emulsion polymerization encapsulation can improve the dispersion performance of nano-inorganic pigments, achieve good nano-sizes, and the prepared concrete has good compressive performance.

[0086] (2) Through Comparative Example 1, it can be found that by further increasing the particle size of nano-ferroferric oxide, the particle size of the nano-color paste obtained after polymerization is 136.6 nm, which does not meet the size of nano-materials. This may be because the reaction conditions in this system are not suitable for larger nano-inorganic pigments, resulting in a further increase in the particle size in the emulsion after the polymerization reaction. And due to the increase in particle size, the compactness of the concrete during preparation becomes poor, and the porosity is high, resulting in poor compressive performance of the concrete.

[0087] (3) Through Comparative Example 2, it can be found that due to the oxide functional groups present on the surface of nano-ferroferric oxide, when it is mixed with the aqueous phase, it interacts with water molecules, resulting in a negatively charged surface. And the surface active ions generated when the cationic surfactant dissociates upon contact with the aqueous phase are mainly positively charged. The electrostatic attraction between the positive charge and the negative charge on the surface of nano-ferroferric oxide may lead to particle aggregation, which is not conducive to dispersion. As a result, the particle size of the nano-color paste for colored concrete finally prepared is 203.1 nm, exceeding the nano-size. And due to the increase in particle size, the compactness of the concrete during preparation becomes poor, and the porosity is high, resulting in poor compressive performance of the concrete.

[0088] (4)It can be found from Comparative Example 3 that in this system, by further increasing the pressure and time during the high-pressure homogenization process, the particle size of the nano-color paste for colored concrete prepared is 187.3 nm. This may be because the excessively high high-pressure homogenization pressure and too long high-pressure homogenization treatment time may damage the active structure of the anionic surfactant, resulting in a weakened dispersion ability of the anionic surfactant for the nano-inorganic pigment, and further leading to the aggregation of the nano-inorganic pigment. This makes the particle size of the finally prepared nano-color paste for colored concrete larger, exceeding the nano size, and may due to the increase in particle size, resulting in poor compactness and high porosity during the preparation of concrete, making the compressive performance of the concrete poor.

[0089] (5)It can be found from Comparative Example 4 that in this system, when ammonium persulfate is used alone as an initiator, ammonium persulfate requires a relatively high temperature to initiate the polymerization reaction by thermal initiation. The initiation temperature of thermal initiation is relatively high, and the initiation activation energy is high, resulting in a relatively high conversion efficiency of monomers in the polymerization reaction, which may lead to rapid growth of polymer chains, and further leading to the aggregation of particles in the emulsion to form particles with larger particle sizes. And may due to the increase in particle size, resulting in poor compactness and high porosity during the preparation of concrete, making the compressive performance of the concrete poor. Therefore, in the system of the present invention, there are relatively strict requirements for the use of initiators.

[0090] The above-described embodiments have detailed the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A method for preparing nano-color paste for colored concrete, characterized in that: The preparation method comprises the following steps: The nano inorganic pigment fine emulsion and the acrylic acid solution are mixed in a weight ratio of 1:1-2 and subjected to an ultrasonic power treatment of 200-300W for 5-10 minutes to obtain a mixed emulsion, and the mixed emulsion is mixed with a redox initiator in a weight ratio of 1:0.002-0.005, and subjected to a polymerization treatment in a temperature environment of 40°C-50°C for 3-5 hours to obtain the nano color paste for colored concrete; The preparation method of the nano inorganic pigment miniemulsion comprises the following steps: The nano inorganic pigment is dispersed in anhydrous ethanol to form a dispersed phase, an anionic surfactant is dissolved in deionized water to form an aqueous phase, the dispersed phase and the aqueous phase are mixed in a weight ratio of 1:3-5 and then subjected to high pressure homogenization to obtain the nano inorganic pigment miniemulsion; The conditions of the high pressure homogenization include a pressure of 70-80 MPa and a processing time of 12-15 min; The nano inorganic pigment includes nano titanium dioxide or nano ferroferric oxide, and the average particle size of the nano inorganic pigment is 10-20 nm; The anionic surfactant is sodium stearate or sodium oleate.

2. The method for preparing a nano-color paste for colored concrete according to claim 1, characterized in that: The weight ratio of the nano inorganic pigment to anhydrous ethanol is 1:10-15.

3. The method for preparing a nano-color paste for colored concrete according to claim 1, characterized in that: The weight ratio of the anionic surfactant to deionized water is 1:30-40.

4. The method for preparing a nano-color paste for colored concrete according to claim 1, characterized in that: The mass concentration of the acrylic acid solution is 40-60%.

5. The method for preparing a nano-color paste for colored concrete according to claim 1, characterized in that: The redox initiator is composed of ammonium persulfate and sodium bisulfite in a molar ratio of 1-2:

1.

6. A nano-color paste for colored concrete prepared by the method for preparing a nano-color paste for colored concrete according to any one of claims 1 to 5.

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