Multifunctional shrinkage-reducing self-expanding rheological agent for sprayed ultra-high performance concrete

Abstract

The application discloses a multifunctional shrink-reducing self-expanding rheological agent for spraying ultra-high performance concrete, which comprises a composite rheological component, an expanding component and a corrosion-resisting shrink-reducing component; wherein the composite rheological component is 65-87 parts, the expanding component is 10-30 parts, and the corrosion-resisting shrink-reducing component is 3-5 parts. The multifunctional shrink-reducing self-expanding rheological agent can be prepared by using the composite rheological component, the expanding component and the corrosion-resisting shrink-reducing component, and is used for improving the thixotropy, shrinkage performance and durability of UHPC.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of injection super high performance concrete (UHPC) multifunctional shrinkage self-expanding rheological agent, especially to a kind of injection super high performance concrete multifunctional shrinkage self-expanding rheological agent for large self-shrinkage of inadequate thixotropy. BACKGROUND

[0002] With the continuous development of economy and the progress of science and technology, mankind is constantly exploring high altitude, underground and ocean fields. Modern civil engineering pays more attention to the development trend of high-rise, light and large-span. Ultra high performance concrete (UHPC) is a new type of building material, which has excellent mechanical properties and high impermeability, which makes UHPC become the building material that meets the above strategic requirements. In order to increase the application range of UHPC in practical engineering, UHPC is applied to injection construction as a damaged building renovation, repair and reinforcement material. The need for injection UHPC increases the yield stress to reduce the rebound of slurry and increase the thickness of the sprayed concrete layer, and the slurry should maintain a low plastic viscosity to improve the pumpability. High yield stress and low plastic viscosity of concrete can be represented by thixotropy, UHPC is a typical non-Newtonian fluid with certain thixotropy, but the thixotropy of newly mixed UHPC is not enough to support high thickness of spraying construction. At the same time, UHPC has high cementitious material content, which leads to its self-shrinkage much larger than that of ordinary concrete, which may cause cracks on the surface or inside of the concrete, reduce its strength and durability, and in marine engineering or humid environment, steel fiber reinforced UHPC often rusts due to chloride ion erosion, which affects its performance and appearance. SUMMARY

[0003] The purpose of the present application is to provide a kind of injection super high performance concrete (UHPC) multifunctional shrinkage self-expanding rheological agent, which can be prepared by using composite rheological component, expansion component and anticorrosive shrinkage component to improve the thixotropy, shrinkage performance and durability of UHPC.

[0004] The technical scheme adopted by the present application to solve the technical problem is: a kind of multifunctional shrinkage self-expanding rheological agent for injection super high performance concrete, including composite rheological component, expansion component and anticorrosive shrinkage component.

[0005] Among them, the composite rheological component is 65-87 parts, the expansion component is 10-30 parts, and the anticorrosive shrinkage component is 3-5 parts.

[0006] As a further scheme of the present application: it is composed of composite rheological component, expansion component and anticorrosive shrinkage component.

[0007] As a further scheme of the present application: the composite rheological component includes manganese slag and cellulose ether.

[0008] The content of the composite rheological component is 5-10% of the cementitious material, which is generally cement or cement plus mineral admixtures such as cement, fly ash, silica fume, slag, etc. The ratio of manganese slag to cellulose ether is 98:2, and the specific surface area of manganese slag is 600-800 m 2 / kg. The cellulose ether is hydroxyethyl methyl cellulose ether with a molecular weight of 30000-50000. A too low molecular weight reduces the mutual entanglement between molecular chains, resulting in poor thickening effect. A too high molecular weight causes excessive entanglement and wrapping of macromolecules around cement particles, hindering the dissolution of cement particles and thus inhibiting cement hydration and reducing the strength of concrete. The composite rheological component improves the rheological properties and matrix density of concrete mixture, and enhances the sprayability and mechanical properties of sprayed UHPC.

[0009] As a further scheme of the present application, the expansion component is a modified calcium oxide-calcium sulphoaluminate expansion agent prepared by mixing calcium oxide and calcium sulphoaluminate at a ratio of 7:3. Calcium sulphoaluminate participates in hydration or reacts with cement hydration products to form tri-sulphate type hydrated calcium sulphoaluminate (ettringite), and the generation of ettringite greatly increases the solid volume. Calcium oxide crystals hydrate with water to form calcium hydroxide crystals, which increase in volume and thus cause apparent volume expansion to reduce the shrinkage of UHPC caused by cement hydration or water evaporation.

[0010] As a further scheme of the present application, the anti-corrosion and shrinkage-reducing component is a biotic membrane loaded with double metal hydroxide (LDHs), such as Figure 1 As shown in the figure, the LDHs loaded biotic membrane adsorbs harmful anions (such as Cl - , SO4 2- ) in the pore solution of concrete, reduces the corrosion of steel fiber and the erosion of the concrete matrix, improves the durability of concrete, improves the dispersibility of LDHs through the biotic membrane, and reduces the shrinkage stress and the shrinkage of concrete.

[0011] As a further scheme of the present application, the preparation method of the biotic membrane loaded with double metal hydroxide (LDHs) is as follows:

[0012] S1, the biotic membrane is formed by bacteria on various surfaces by synthesizing and secreting cell matrix with coagulation and protection.

[0013] S2, take the biotic membrane and heat it in water to 70-85℃, then add M 3+ solution and M 2+ solution, then add NaOH solution to adjust the pH to 11-12, fully stir, centrifuge, wash to neutral, and dry to obtain the biotic membrane loaded with double metal hydroxide (LDHs); wherein, the M3+ The solution includes FeCl3, AlCl3, and CoCl3, M 2+ The solution contains CaCl2, MgCl2, and ZnCl2.

[0014] In one preferred embodiment, the specific method for loading the LDHs onto the biofilm is as follows: A number of biofilms are placed in a beaker containing 2.0 L of distilled water and heated until the water temperature stabilizes at approximately 80°C; a 0.1 mol·L⁻¹ solution is prepared. -1 M 3+ Solutions (FeCl3, AlCl3, CoCl3) and 0.2 mol·L -1 M 2+ 200 ml of each of the solutions (CaCl2, MgCl2, ZnCl2) were simultaneously added to the beaker containing the original biofilm, and 10% NaOH solution was added to adjust the pH to approximately 11-12. The mixture was stirred vigorously for 4 hours. The stirred substrate was then removed and stirred at 1000-1500 rpm. -1 Centrifuge for 10 min under the specified conditions; wash the solid obtained after centrifugation, make its pH neutral, and dry it in an oven for 16 h to obtain LDHs-loaded biofilm.

[0015] As a further aspect of the present invention, the preparation of the biofilm in S1 specifically includes: inoculating frozen Bacillus subtilis into 15 ml of Luria / Miller LB-Medium liquid and incubating overnight at 37℃±2℃; then transferring the culture to a shaking incubator (250 rpm) for 12±1 hours of growth; then spreading the liquid culture onto an agar plate rich in LBPlus medium to allow the Bacillus subtilis liquid culture to produce a biofilm on the agar plate; after growing for at least 24 hours, the biofilm is obtained and scraped from the culture dish with a rubber spatula.

[0016] This invention provides at least the following beneficial effects: A multifunctional shrinkage-reducing self-expanding rheology modifier for sprayed ultra-high performance concrete (UHPC) effectively solves problems such as insufficient thixotropy, large shrinkage, and internal corrosion in UHPC. Specifically:

[0017] (1) The rough surface of manganese slag particles can increase the friction in the slurry and improve the yield stress of the slurry. When combined with cellulose ether, it can perform the first dispersion of cellulose ether, improve the dispersion effect of cellulose ether in the secondary dispersion in the cementitious material, and reduce the deterioration of the strength of UHPC by cellulose ether.

[0018] (2) The volume stability of UHPC is improved by compensating for the auto-shrinkage of UHPC with a special expansion component. Anhydrous calcium sulfoaluminate can quickly start the hydration reaction in the plastic stage to generate the expansion hydration product ettringite. Subsequently, in the solidification and hardening stage, the hydration reaction rate of calcium oxide gradually increases to generate the expansion hydration product calcium hydroxide, which, together with ettringite, compensates for the auto-shrinkage of UHPC.

[0019] (3) By reducing the shrinkage stress in the concrete capillaries through anti-corrosion and shrinkage-reducing components, the shrinkage of UHPC caused by cement hydration or water evaporation is reduced, while effectively adsorbing harmful anions (such as Cl-) in the concrete pore solution. - SO4 2- This reduces steel fiber corrosion and erosion of the concrete matrix, improving concrete durability.

[0020] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0021] Figure 1 This is a diagram of the LDHs-supported biofilm and the molecular structure of LDHs in this invention;

[0022] Figure 2 This is a schematic diagram of the capillary wall and pore water of the present invention. Detailed Implementation

[0023] The present invention will now be described in detail and completely with reference to the embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention with reference to the embodiments, it should be particularly noted that the technical solutions and features provided in various parts of the present invention, including the following description, can be combined with each other without conflict.

[0024] Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific implementation process is as follows:

[0026] This paper presents a method for preparing a multifunctional shrinkage-reducing self-expanding rheology modifier (LDH) for sprayed ultra-high performance concrete (UHPC). First, the thixotropic properties of UHPC are improved through composite rheology components, enhancing its sprayability. Second, an expansion component is used to reduce the shrinkage of UHPC. Finally, an anti-corrosion and shrinkage-reducing component is used to lower the surface tension of the liquid phase in the concrete capillary, reducing the negative pressure in the capillary, decreasing shrinkage stress, and thus reducing concrete shrinkage. Simultaneously, it improves the dispersibility of LDHs, effectively adsorbing harmful anions (such as Cl-) in the concrete pore solution. - SO4 2- This reduces steel fiber corrosion and erosion of the concrete matrix, improving concrete durability. The multifunctional shrinkage-reducing self-expanding rheology modifier for sprayed UHPC prepared by the above method effectively solves problems such as insufficient thixotropy, large shrinkage, and internal corrosion in sprayed UHPC.

[0027] A method for preparing a multifunctional shrinkage-reducing self-expanding rheology modifier for shotcrete ultra-high performance concrete (UHPC) specifically includes:

[0028] (1) The multifunctional shrinkage-reducing self-expanding rheology modifier is composed of a composite rheology component, an expansion component and a corrosion-resistant shrinkage-reducing component, wherein the composite rheology component is 65-87 parts, the expansion component is 10-30 parts, and the corrosion-resistant shrinkage-reducing component is 3-5 parts.

[0029] (2) The composite rheological component is composed of manganese slag and cellulose ether, and its dosage is 5-10% of the cementitious material. The cementitious material is generally cement, or cement plus mineral admixtures, such as cement, fly ash, silica fume, slag, etc. The ratio of manganese slag to cellulose ether is 98:2, and the specific surface area of ​​manganese slag is 600-800 m². 2 / kg; the cellulose ether is hydroxyethyl methyl cellulose ether with a molecular weight of 30,000–50,000. Too low a molecular weight reduces the entanglement between molecular chains, resulting in poor thickening effect; too high a molecular weight causes excessive entanglement and coating of cement particles by large molecules, hindering the dissolution of cement particles, thereby inhibiting cement hydration and reducing the strength of concrete. By using composite rheological components to improve the rheological properties and matrix density of concrete mixtures, the sprayability and mechanical properties of sprayed UHPC are enhanced.

[0030] (3) The expansion component is a modified calcium oxide-calcium sulfoaluminate expansion agent, which is prepared by mixing calcium oxide and calcium sulfoaluminate in a 7:3 ratio. Calcium sulfoaluminate participates in hydration or reacts with cement hydration products to form trisulfide-type hydrated calcium sulfoaluminate (ettringite). The formation of ettringite greatly increases the solid phase volume. Calcium oxide crystals hydrate with water to form calcium hydroxide crystals, which increase in volume and thus cause apparent volume expansion, reducing the shrinkage of UHPC caused by cement hydration or water evaporation.

[0031] (4) The corrosion-preventing and shrinkage-reducing component is a bimetallic layer hydroxide (LDHs) supported on a biofilm, such as... Figure 1 As shown, LDHs-supported biofilms adsorb harmful anions (such as Cl-) from the concrete pore solution. - SO4 2- This reduces steel fiber corrosion and erosion of the concrete matrix, improving concrete durability. It also enhances the dispersibility of LDHs through a biofilm, while simultaneously reducing shrinkage stress and lowering concrete shrinkage. The preparation method is as follows:

[0032] S1; The biofilm is formed by bacteria synthesizing and secreting a cohesive and protective cellular matrix on various surfaces. The biofilm is prepared as follows: First, frozen Bacillus subtilis is inoculated into 15 ml of Luria / Miller LB-Medium liquid and incubated overnight at 37°C. Next, the culture is transferred to a shaking incubator (250 rpm) and grown for 12 hours. Then, the liquid culture is spread onto an agar plate rich in LBPlus medium, allowing the Bacillus subtilis liquid culture to form a biofilm on the agar plate. After 24 hours of growth, the biofilm is scraped from the culture dish using a rubber spatula.

[0033] S2; The specific method for loading biofilms with LDHs is as follows: Take a number of biofilms and place them in a beaker containing 2.0L of distilled water and heat until the water temperature stabilizes at around 80℃; prepare 0.1mol·L⁻¹ -1 M 3+ Solutions (FeCl3, AlCl3, CoCl3) and 0.2 mol·L -1 M 2+ 200 ml of each of the solutions (CaCl2, MgCl2, ZnCl2) were simultaneously added to the beaker containing the original biofilm, and 10% NaOH solution was added to adjust the pH to approximately 11-12. The mixture was stirred vigorously for 4 hours. The stirred substrate was then removed and stirred at 1000-1500 rpm. -1 Centrifuge for 10 min under the specified conditions; wash the solid obtained after centrifugation, make its pH neutral, and dry it in an oven for 16 h to obtain LDHs-loaded biofilm.

[0034] (5) The LDHs are typically stacked in a tight layer, such as Figure 1 As shown, LDHs tend to form dense particles or lumps, resulting in low hydraulic conductivity, limited exposed active sites, and significantly reduced adsorption performance in practical applications. Biofilms can effectively disperse LDHs and enhance their adsorption performance.

[0035] (6) The biofilm can reduce surface tension. The contact angle between the biofilm and water is 143°, while the contact angle between the capillary wall and water is usually 0°. Therefore, when the capillaries lose water, the biofilm can reduce the capillary pressure and reduce concrete shrinkage. A schematic diagram of pore water and pore walls is shown below. Figure 2 As shown, the formula for calculating capillary pressure is as shown in Formula 1.

[0036]

[0037] In formula (1): σ is the capillary pressure (MPa);

[0038] γ is the surface tension (N);

[0039] θ is the water contact angle of the capillary wall;

[0040] r is the radius of the hole.

[0041] Example 1 is concrete with a multifunctional shrinkage-reducing self-expanding rheology modifier. The concrete mix proportions of Example 1 are shown in Table 1.

[0042] Table 1 Concrete mix proportions for Example 1 (kg / m³) 3 )

[0043]

[0044]

[0045] The raw materials used in Example 1 were: PO 52.5 ordinary Portland cement; fly ash, silica fume, quartz powder, quartz sand, steel fiber, and water-reducing agent were all commercially available products meeting the requirements, with a water reduction rate of 18%. The ratio of the composite rheological component, expansion component, and corrosion-resistant shrinkage-reducing component in the multifunctional shrinkage-reducing self-expanding rheology modifier was 66:30:4. The composite rheological component was manganese slag and cellulose ether in a ratio of 98:2; the expansion component was calcium oxide-calcium sulfoaluminate; and the corrosion-resistant shrinkage-reducing component was LDHs-supported biofilm. The dosage of each component is shown in Table 1. Comparative Example 1 used the same raw materials as Example 1, but without the multifunctional shrinkage-reducing self-expanding rheology modifier. The rheological properties, 7-day shrinkage, and chloride ion penetration resistance of the UHPC are shown in Table 2.

[0046] Table 2. Results of plastic viscosity, yield stress, 7-day shrinkage, chloride ion permeability resistance coefficient, and thixotropic value of UHPC in Example 1 and Comparative Example 1.

[0047]

[0048] (Thixotropic value (yield stress value / plastic viscosity value))

[0049] As shown in Table 2, the addition of a multifunctional shrinkage-reducing self-expanding rheology modifier significantly improved the thixotropic properties, shrinkage properties, and chloride ion penetration resistance of UHPC. The plastic viscosity decreased by 62.7%, the yield stress increased by about 3 times, the 7-day shrinkage decreased by 32.8%, and the chloride ion penetration resistance increased by about 3 times.

[0050] The formulation of Comparative Example 2 was the same as that of Example 1, but the corrosion-preserving and shrinkage-reducing component LDHs was not loaded with biofilm. The biofilm and LDHs of the two materials in the corrosion-preserving and shrinkage-reducing component were added in the same amounts as in Example 1. The results of the rheological properties, 7-day shrinkage and chloride ion penetration resistance of UHPC are shown in Table 3.

[0051] Table 3. Results of plastic viscosity, yield stress, 7-day shrinkage, chloride ion permeability resistance coefficient, and thixotropic value of UHPC in Example 1 and Comparative Example 2.

[0052]

[0053] As shown in Table 3, the thixotropic and shrinkage properties of Comparative Example 2 are not much different from those of Example 1. It has a significant impact on the chloride ion penetration resistance of concrete, and the chloride ion penetration resistance coefficient is reduced by 37.5%, indicating that LDHs are not loaded, which has a significant impact on the dispersibility of LDHs and reduces the adsorption capacity for chloride ions.

[0054] Examples 2-3

[0055] The formulation ratios of Examples 2 and 3 were the same as those of Example 1, but the proportions of the composite rheological component, the expansion component, and the corrosion-resistant and shrinkage-reducing component in the multifunctional shrinkage-reducing self-expanding rheology modifier were different. In Example 2, the ratio of the composite rheological component, the expansion component, and the corrosion-resistant and shrinkage-reducing component was 67:30:3. In Example 3, the ratio was 65:30:5. The results of the UHPC rheological properties, 7-day shrinkage, and resistance to chloride ion penetration are shown in Table 4.

[0056] Table 4 shows the results of plastic viscosity, yield stress, 7-day shrinkage, chloride ion permeability resistance coefficient, and thixotropic value of UHPC in Examples 1, 2, and 3.

[0057]

[0058] As shown in Table 4, the rheological properties and shrinkage properties of Examples 2 and 3 are not much different from those of Example 1, but the chloride ion permeation resistance coefficient is slightly reduced. This indicates that when the anti-corrosion and shrinkage reduction component is 4, the anti-corrosion performance of the multifunctional shrinkage reduction self-expanding rheology modifier is the best.

[0059] Comparative Examples 3-5

[0060] The formulations of Comparative Examples 3-5 were the same as those of Example 1, but Comparative Example 3 contained no composite rheology component in its multifunctional shrinkage-reducing self-expanding rheology modifier, Comparative Example 4 contained no expansion component, and Comparative Example 5 contained no corrosion-preventing and shrinkage-reducing component. The results of the rheological properties, 7-day shrinkage, and resistance to chloride ion penetration of UHPC are shown in Table 5.

[0061] Table 5 shows the results of plastic viscosity, yield stress, 7-day shrinkage, chloride ion permeation resistance coefficient, and thixotropic value of comparative examples 3–5 UHPC.

[0062]

[0063] As shown in Table 5, without the addition of composite rheological components, the thixotropic properties of UHPC decrease significantly. At the same time, the expansion component has a greater impact on the shrinkage performance of concrete than the anti-corrosion and shrinkage-reducing component. The shrinkage reduction capacity of the anti-corrosion and shrinkage-reducing component is about 50% of that of the expansion component. The anti-corrosion and shrinkage-reducing component is crucial for improving the durability of concrete.

[0064] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A multifunctional shrinkage-reducing self-expanding rheology modifier for sprayed ultra-high performance concrete, characterized in that, Including composite rheological components, expansion components, and corrosion-resistant and shrinkage-reducing components; The composite rheological component is 65-87 parts, the expansion component is 10-30 parts, and the corrosion-preventing and shrinkage-reducing component is 3-5 parts. The composite rheological component includes manganese slag and cellulose ether; The ratio of manganese slag to cellulose ether is 98:2, and the specific surface area of ​​the manganese slag is 600~800 m². 2 / kg; The cellulose ether is hydroxyethyl methyl cellulose ether with a molecular weight of 30,000~50,000; The corrosion-preventing and shrinkage-reducing component is a bimetallic layer hydroxide-supported biofilm.

2. The multifunctional shrinkage-reducing self-expanding rheology modifier for sprayed ultra-high performance concrete as described in claim 1, characterized in that, It is composed of composite rheological components, expansion components, and corrosion-resistant and shrinkage-reducing components.

3. The multifunctional shrinkage-reducing self-expanding rheology modifier for sprayed ultra-high performance concrete as described in claim 1 or 2, characterized in that, The expanding component is a modified calcium oxide-calcium sulfoaluminate expanding agent, which is prepared by mixing calcium oxide and calcium sulfoaluminate in a 7:3 ratio.

4. The multifunctional shrinkage-reducing self-expanding rheology modifier for sprayed ultra-high performance concrete as described in claim 1, characterized in that, The method for preparing the bimetallic hydroxide-supported biofilm is as follows: S1. Preparation of biomembranes; S2. Place the biofilm in water and heat to 70°C to 85°C, then add M. 3+ Solution and M 2+ The solution was then mixed with NaOH solution to adjust the pH to 11-12. After thorough stirring, the mixture was centrifuged, washed until neutral, and dried to obtain a bimetallic hydroxide-supported biofilm; wherein, M... 3+ The solution includes FeCl3, AlCl3, and CoCl3, M 2+ The solution contains CaCl2, MgCl2, and ZnCl2.

5. The multifunctional shrinkage-reducing self-expanding rheology modifier for sprayed ultra-high performance concrete as described in claim 4, characterized in that, The preparation of the biofilm in S1 specifically includes: inoculating frozen Bacillus subtilis into Luria / Miller LB-Medium liquid and incubating overnight at 37℃±2℃; then transferring the culture to a shaking incubator for growth for 12±1 hours, and then spreading the liquid culture onto an agar plate rich in LBPlus medium to allow the Bacillus subtilis liquid culture to produce a biofilm on the agar plate. After growth for at least 24 hours, the biofilm is obtained.

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