Low-carbon foam concrete composite foaming agent and preparation method thereof

Abstract

The invention belongs to the field of low-carbon environment-friendly materials, and particularly relates to a low-carbon foam concrete composite foaming agent and a preparation method thereof. The invention relates to a low-carbon foam concrete composite foaming agent, which comprises the following components in percentage by mass: 10% of hydrolyzed protein with gelatin powder as a base material; the alkaline protease is selected from papain, and the mass fraction is 2.1%; the surface active substance is fatty ether polyoxyethylene alcohol sodium sulfate, and the mass fraction is 1-2%; sodium caseinate with a mass fraction of 8-9%; deionized water is selected as water for dissolving and accounts for the rest mass fraction. Compared with the existing foaming agent for foam concrete, the low-carbon foam concrete composite foaming agent provided by the invention avoids the problems of high cost, toxicity to operators and the like of the existing foaming agent; other organic solvents with dangerous properties do not need to be doped, only physical change occurs in the whole preparation process, no harmful gas is emitted, and no danger is caused by the fact that a solid powdery foaming agent is inhaled into a human body; the method has the advantages of fewer operation steps, reasonable process optimization, easiness in large-scale industrial production, and realization of the targets of low carbon and environmental protection.

Description

Technical Field

[0001] The present invention belongs to the field of low-carbon environmentally friendly materials, and in particular, relates to a low-carbon foam concrete composite foaming agent and a preparation method thereof. Background Art

[0002] Foamed concrete is a special type of concrete that is formed by injecting a foam group prepared by a foaming agent into a cement mortar made of cement, aggregate, water and admixtures and mixing them evenly. The foaming ability and foam stabilizing ability of the foaming agent mainly affect the fluidity of the fresh foamed concrete paste and the final volume after pouring and molding, and then affect the density and strength of the paste after hardening. For high-strength foamed concrete with partial load-bearing requirements, the type of foaming agent is particularly important (Zhang Leilei et al., 2011). The quality of the foam group produced will have a direct impact on the strength of the foamed concrete. If the foam group produced by the foaming agent is dense and continuous, and there is less natural defoaming during the mixing process with the mortar, the various properties of the foamed concrete are more ideal. Compared with chemical foaming agents, physical foaming agents have the advantage of being easier to foam, so people tend to use physical foaming agents. So far, physical foaming agents have the advantages of better performance, low price, and meeting the environmental protection needs of low-carbon development. Chinese patents CN101054275A, CN102964083A, and CN111116094A all disclose methods for preparing different foaming agents for foamed concrete, wherein the foaming agents are prepared by physical foaming, and the mechanical properties and performance of the foamed concrete are improved by modifying the foaming agents by adding additional surfactants.

[0003] Most of the existing foaming agents have the advantages of either foaming ability or foam stabilizing ability, but the compressive strength and dry density of the foamed concrete obtained by their products do not have uniform and clear targeting. There is still a large gap in foaming agents for low-carbon, environmentally friendly, lightweight and high-strength foamed concrete. Summary of the invention

[0004] In order to overcome the technical and environmental defects of the existing foaming agents for foamed concrete, the present invention provides a low-carbon foamed concrete composite foaming agent and a preparation method thereof. Specifically, protein mainly composed of animal protein is used as mother liquor protein and as a modification target, and an ionic or non-ionic surfactant is added to modify the mother liquor protein to obtain a composite foaming agent suitable for lightweight and high-strength foamed concrete, thereby achieving the goal of low carbon and environmental protection.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] Foam concrete composite foaming agent, the formula components are as follows:

[0007] Gelatin powder was used as the base material for hydrolyzing protein, with a mass fraction of 10%;

[0008] The alkaline protease is papain, with a mass fraction of 2.1%;

[0009] The surfactant is fatty ether polyoxyethylene alcohol sodium sulfate (hereinafter referred to as AES), with a mass fraction of 1-2%;

[0010] Sodium caseinate (hereinafter referred to as SCA), mass fraction is 8-9%;

[0011] Deionized water is used as the dissolving water, accounting for the remaining mass fraction.

[0012] A method for preparing a composite foaming agent for low-carbon foamed concrete, comprising the preparation of mother liquor protein and the addition of surfactant:

[0013] S1. Take 20 parts of animal protein and 4.2 parts of alkaline protease and fully dissolve them in 175.8 parts of water, adjust the pH to the appropriate pH of alkaline protease with alkali, hydrolyze at a temperature of 40-60°C for at least 30 minutes, add acid to adjust the pH to near neutral after the hydrolysis is completed, cool the solution and filter it twice to obtain;

[0014] Preferably, the animal protein is gelatin powder;

[0015] Preferably, the hydrolysis temperature is 45°C;

[0016] Preferably, the base is an inorganic base solution with a concentration of 0.3 mol / L, such as sodium hydroxide, calcium hydroxide, etc., preferably sodium hydroxide;

[0017] Preferably, the acid is a 5% by mass dilute hydrochloric acid solution;

[0018] Preferably, the alkaline protease is papain, and the suitable pH range is 10-11;

[0019] Preferably, the protein stock solution is prepared by the following method:

[0020] Take 20 parts of animal protein gelatin powder and 4.2 parts of papain and fully dissolve them in 175.8 parts of water, adjust the pH to the suitable pH value of papain 10.86 with a 0.3 mol / L sodium hydroxide solution, keep it in a constant temperature water bath at 45°C for 30 minutes, add dilute hydrochloric acid solution after hydrolysis is completed to adjust the pH to about 7, and cool the solution for secondary filtration.

[0021] S2. Add SCA to the mother liquor protein in batches, with a single addition amount not exceeding 2.5% by mass. Stir continuously. Continue adding after no obvious precipitation until all SCA is incorporated. Then stir continuously for 5 minutes every 10 minutes until the solution presents a milky white milk texture and there is no precipitate. The emulsification reaction is considered to be complete. Too fast dilution of AES will form precipitate that is insoluble in water. In order to ensure accurate control of the single addition amount, add 1g AES to the mother liquor protein at a time as a gradient and slowly add. The single stirring time is not less than 5 minutes. When there is no obvious precipitation of the mother liquor protein, the preparation of the foaming agent is considered to be complete.

[0022] Compared with the existing foaming agent for foam concrete, the low-carbon foam concrete composite foaming agent of the present invention has the following beneficial effects:

[0023] 1. Protein, anionic surfactants, cationic surfactants and emulsifiers are low-cost and harmless to humans, avoiding the problems of high cost and toxicity to operators of previous foaming agents;

[0024] 2. The composite foaming agent is liquid and does not need to be mixed with other hazardous organic solvents. The entire preparation process involves physical changes, no harmful gases are released, and there is no danger of solid powder foaming agents being inhaled by the human body;

[0025] 3. The composite foaming agent has fewer operating steps, reasonable process optimization, and is easy to use in large-scale industrial production;

[0026] 4. The composite foaming agent and foam concrete slurry are mixed evenly, with good foam stability and low defoaming rate. The compressive strength of the new foam concrete products is 1.5-2 times that of the same dry density grade under the industry standard.

[0027] 5. The microscopic pore size of the foamed concrete produced by the composite foaming agent is evenly distributed, all within the range of 50-350μm, which is smaller than the pore size of ordinary foamed concrete.

[0028] 6. The density of the prepared liquid composite foaming agent is slightly greater than that of water, and its relative bulk density is low, which makes it easy to transport and store.

[0029] 7. The prepared foamed concrete is a low-carbon and environmentally friendly material, which can be widely used in road and bridge construction, filling engineering, underground geotechnical engineering, building energy-saving components, energy infrastructure construction, port water conservancy engineering, marine engineering, military engineering, oil field and mine engineering and other major infrastructure construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The dry density-compressive strength relationship curve of foamed concrete made by modified foaming agent mixed with fatty ether polyoxyethylene alcohol sodium sulfate and sodium caseinate;

[0031] Figure 2a This is a scanning electron microscope image of the foamed concrete prepared in Example 3 at a magnification of 100 times;

[0032] Figure 2b This is the electron microscope scanning image of the foam concrete of the control group at 100 times magnification;

[0033] Figure 3a This is a scanning electron microscope image of the foamed concrete prepared in Example 3 at a magnification of 10,000 times;

[0034] Figure 3b This is the electron microscope scanning image of the foam concrete of the control group at 10,000 times magnification;

[0035] Figure 4 It is the solidification settlement rate of the foam concrete slurry of Example 1, Example 2, Example 3 and the control group. DETAILED DESCRIPTION

[0036] The main raw materials and instruments required for the present invention are as follows:

[0037] The raw materials of the foaming agent formula are: the base material hydrolyzed protein is gelatin powder, with a mass fraction of 10%; the alkaline protease is papain, with a mass fraction of 2.1%; the surfactant is fatty ether polyoxyethylene alcohol sodium sulfate (hereinafter referred to as AES, with a mass fraction of 1-2%) and sodium caseinate (hereinafter referred to as SCA, with a mass fraction of 8-9%); the pH adjustment reagent is 0.3 mol / L sodium hydroxide solution, with a mass fraction of 1.9%; the dissolving water is deionized water, accounting for the remaining mass fraction.

[0038] The cementitious materials used for mixing foam concrete are PO 42.5 cement and Class I fly ash; the cement mortar water reducer is a high-efficiency polycarboxylic acid water reducer; and the mixing water is purified water.

[0039] Instruments: constant temperature water bath, single-axis horizontal track forced concrete mixer, universal testing machine, foam quality tester, foam concrete foaming machine, beaker, test tube, pH test paper, concrete standard mold and concrete curing box.

[0040] The preparation method of low-carbon foam concrete composite foaming agent mainly includes the preparation of mother liquid protein and the addition of surfactant:

[0041] S1. Dissolve animal protein gelatin powder and papain in water, adjust the pH to 10-11 with 0.3 mol / L sodium hydroxide solution, heat in a constant temperature water bath at 45°C for 30 min, cool the solution and filter it twice.

[0042] S2 and SCA were added to the mother liquor protein in 4 batches and stirred continuously. When there was no obvious precipitation, the addition was continued until all SCA was incorporated. Then, stirring was continued for 5 minutes every 10 minutes until the solution showed a milky white milk texture and there was no precipitate, which was considered to be the completion of the emulsification reaction. AES would form precipitate that was insoluble in water if it was diluted too quickly. In order to ensure the precise control of the single addition amount, AES was added to the mother liquor protein in 2-4 batches with a single stirring time of not less than 5 minutes until there was no obvious precipitation of the mother liquor protein, which was considered to be the completion of the preparation of the foaming agent.

[0043] The specific embodiments are as follows:

[0044] Example 1

[0045] A low-carbon foam concrete composite foaming agent comprises mother liquor protein, sodium caseinate (SCA), fatty alcohol polyoxyethylene ether sodium sulfate solution (AES), sodium hydroxide solution and deionized water.

[0046] Wherein, based on the total mass of the foaming agent, the mass fraction of the protein is 10%, the mass fraction of sodium caseinate (SCA) is 8%, the mass fraction of fatty alcohol polyoxyethylene ether sodium sulfate solution (AES) is 1%, and the mass fraction of sodium hydroxide solution is 1.9%.

[0047] Example 2

[0048] A low-carbon foam concrete composite foaming agent comprises mother liquor protein, sodium caseinate (SCA), fatty alcohol polyoxyethylene ether sodium sulfate solution (AES) and deionized water.

[0049] Wherein, based on the total mass of the foaming agent, the mass fraction of the protein is 10%, the mass fraction of sodium caseinate (SCA) is 8%, the mass fraction of fatty alcohol polyoxyethylene ether sodium sulfate solution (AES) is 2%, and the mass fraction of sodium hydroxide solution is 1.9%.

[0050] Example 3

[0051] A low-carbon foam concrete composite foaming agent comprises mother liquor protein, sodium caseinate (SCA), fatty alcohol polyoxyethylene ether sodium sulfate solution (AES) and deionized water.

[0052] Wherein, based on the total mass of the foaming agent, the mass fraction of the protein is 10%, the mass fraction of sodium caseinate (SCA) is 9%, the mass fraction of fatty alcohol polyoxyethylene ether sodium sulfate solution (AES) is 1%, and the mass fraction of sodium hydroxide solution is 1.9%.

[0053] The experimental results are shown in Table 1

[0054] Table 1 Foam properties of composite foaming agents mixed with SCA and AES

[0055] Group SCA content / % AES dosage / % Average 1h water seepage / mm 1h water seepage rate / % Foaming multiple Example 1 8 1 172 46.03 16.0 Example 2 8 2 178 47.34 15.9 Example 3 9 1 170 44.36 15.6

[0056] The dilution multiple of the foaming agent in Example 1, Example 2 and Example 3 is 10. The above three examples all meet the requirement of the industry standard of foaming agent for foamed concrete that the water seepage rate in 1 hour is not more than 70%.

[0057] Example 4: Low-carbon foamed concrete prepared by the foamed concrete composite foaming agent of the present invention, the specific foamed concrete preparation method is as follows:

[0058] ①. Use a mixer that meets the requirements of "Concrete Test Mixer" JG244-2009. The specific operation is to pour water into the mixing barrel, and slowly add cement and other cementitious materials into the mixing barrel within 5-10 seconds. After the mixing time reaches 90 seconds, stop for a few seconds, and scrape the cement slurry on the blades and the pot wall into the pot, and stir for another 90 seconds to finally obtain the clean slurry;

[0059] ②. Foam while preparing the pure slurry. Dilute the foaming agent according to the established dilution multiple, and after stirring evenly, use the air compression foaming machine specified in the standard to make foam. When sampling, the foaming outlet should be placed at the bottom of the container, and the impact pressure should be used to fill the container;

[0060] ③. Mix and stir the clean slurry and foam for 2 minutes, stop for a few seconds to clean the inner wall and blades, then stir for another 1 minute. When taking out the material, take it out all at once;

[0061] ④. After the mold is scraped flat, cure in a curing box at room temperature for 28 days.

[0062] This embodiment and subsequent embodiments all adopt the two foam concrete mix proportions shown in Table 2 below.

[0063] Table 2 1m 3 Foam concrete mix ratio

[0064] serial number Cement / kg Fly ash / kg Water / kg Water reducing agent / g Foam / L C0 642 275 321 550 439 C1 561 241 321 550 439

[0065] Use any one of the above three embodiments to foam to 439L to prepare 1m 3 Foamed concrete.

[0066] The experimental results are shown in Figure 1

[0067] like Figure 1, the control group is a foaming agent for foam concrete on the market. Obviously, the foamed concrete prepared by the various co-blended foaming agents of the present invention has a growth trend of dry density-compressive strength change that is greater than the growth trend of the dry density-compressive strength curve set according to the specification, and is also greater than the growth trend of the dry density-compressive strength curve of the control group. Among the composite foaming agents co-blended with SCA and AES, the ratio of compressive strength to dry density of Example 3 is the largest, and the specific strength advantage is obvious, making it the preferred component. In the foamed concrete of this embodiment, the foam group and the concrete slurry are mixed evenly, with less natural defoaming, better pore stability, more uniform distribution, and dry density grades of A10-A11, and the compressive strength is more than 1.5 times the compressive strength specified in the industry specification.

[0068] Example 5: Characterization of microscopic homogeneity of low-carbon foamed concrete prepared by the composite foaming agent of the present invention

[0069] Foamed concrete was prepared using the foaming agents described in Examples 1, 2 and 3 of the present invention, and the microscopic homogeneity of the foamed concrete test block of Example 3, which had better performance among the above examples, was characterized by SEM electron microscopy.

[0070] The distribution and pore size of microscopic pores were observed at a magnification of 100 times.

[0071] The experimental results are shown in Figure 2a , Figure 2b .

[0072] like Figure 2a and Figure 2b , the pore size distribution of the foaming agent is arranged in order of regularity as control group > embodiment. It can be seen from the figure that the foam group prepared by the foaming agent of the present invention has a relatively uniform distribution of foam. Although the regularity of the pore size distribution of the foam of the embodiment is weaker than that of the control group, the single pore size distribution is relatively ideal, and the pore sizes in the slurry are concentrated in a numerical range. The specific minimum pore size and maximum pore size measured are shown in Table 3.

[0073] Table 3 1m 3 Minimum and maximum pore sizes for foam concrete mix

[0074] Group Name Minimum pore size / μm Maximum pore size / μm Example 72.73 200.23 Control group 49.89 325.41

[0075] The distribution of microscopic hydration products and surfactant substances was observed at a magnification of 10,000 times.

[0076] The experimental results are shown in Figure 3a , Figure 3b

[0077] like Figure 3a , Figure 3bIt can be observed that the bubble connection form of the modified group of the embodiment has obvious "integrity" compared with the control group. In the control group at 10,000 times, the crystal clusters generated by the hydration product are densely distributed, and there is no obvious connection between the bubbles.

[0078] Example 6: Characterization of microscopic homogeneity of low-carbon foamed concrete prepared by the composite foaming agent of the present invention

[0079] Low-carbon foamed concrete was prepared using the foaming agents described in Examples 1, 2 and 3 of the present invention, and the solidification settlement rates of the foamed concrete slurries were measured.

[0080] The experimental results are shown in Figure 4

[0081] like Figure 4 Although the slurry solidification settlement rates of the foamed concrete prepared by the foaming agents described in Examples 1, 2 and 3 are greater than the slurry solidification settlement rate of the control group, they are generally less than 8% specified in the industry specifications, meeting the performance index requirements of low-carbon foamed concrete.

[0082] Example 7: Characterization of microscopic chemical composition and mechanism analysis of low-carbon foamed concrete prepared by the present invention

[0083] The foamed concrete was prepared by using the foaming agent of the present invention, and the microscopic chemical composition of the foamed concrete test block with better performance was characterized by XRD diffractometer, and the mechanism analysis was further performed.

[0084] The XRD spectrum of the foamed concrete prepared in Example 1 shows a very narrow polymerization peak at about 2θ=18°, 2θ=27°, 2θ=30° and 2θ=34°, which characterizes the incorporation of composite cement-based crystalline materials, and the response intensity of each peak is different; while the XRD spectrum of Example 3 also shows a very narrow polymerization peak at about 2θ=18°, 2θ=27° and 2θ=34°, and a peak appears at 2θ=30°, but its peak size is relatively smaller than the other three groups of peaks, indicating that the crystallinity of the compound at this position is significantly lower than that of Example 1. In general, the presence of CSH gel with more peaks in both groups of foamed concretes indicates that the crystals inside the concrete have multiple configurations, indicating that the foaming agent of the present invention plays a positive role in the development of the strength of foamed concrete and energy saving and carbon reduction.

Claims

1. Low-carbon foamed concrete composite foaming agent, characterized in that: The formula components are as follows: Base material hydrolyzed protein, mass fraction is 10%; Alkaline protease, mass fraction is 2.1%; Surfactant, mass fraction is 1-2%; Sodium caseinate, mass fraction is 8-9%; Deionized water is used as the dissolving water, accounting for the remaining mass fraction.

2. The low-carbon foamed concrete composite foaming agent according to claim 1, characterized in that The base material hydrolyzed protein is made of gelatin powder, the alkaline protease is papain, and the surfactant is fatty ether polyoxyethylene alcohol sodium sulfate.

3. The method for preparing the low-carbon foamed concrete composite foaming agent according to claim 2, comprising the steps of preparing mother liquor protein and adding a surfactant: S1. Take 20 parts of animal protein and 4.2 parts of alkaline protease and fully dissolve them in 175.8 parts of water, adjust the pH to the appropriate pH of alkaline protease with alkali, hydrolyze at a temperature of 40-60°C for at least 30 minutes, add acid to adjust the pH to near neutral after the hydrolysis is completed, cool the solution and filter it twice to obtain; Preferably, the animal protein is gelatin powder; Preferably, the hydrolysis temperature is 45°C; Preferably, the base is an inorganic base solution with a concentration of 0.3 mol / L, such as sodium hydroxide, calcium hydroxide, etc., preferably sodium hydroxide; Preferably, the acid is a 5% by mass dilute hydrochloric acid solution; Preferably, the alkaline protease is papain, and the suitable pH range is 10-11; Preferably, the protein stock solution is prepared by the following method: Take 20 parts of animal protein gelatin powder and 4.2 parts of papain and fully dissolve them in 175.8 parts of water, adjust the pH value to the suitable pH value of papain 10.86 with a 0.3 mol / L sodium hydroxide solution, keep it in a constant temperature water bath at 45°C for 30 minutes, add dilute hydrochloric acid solution after hydrolysis is completed to adjust the pH to about 7, and cool the solution for secondary filtration. S2. Add SCA to the mother liquor protein in batches, with a single addition amount not exceeding 2.5% by mass. Stir continuously. Continue adding after no obvious precipitation until all SCA is incorporated. Then stir continuously for 5 minutes every 10 minutes until the solution presents a milky white milk texture and there is no precipitate, which means the emulsification reaction is complete. Too fast dilution of AES will form precipitate that is insoluble in water. In order to ensure accurate control of the single addition amount, add 1g AES to the mother liquor protein at a time as a gradient and slowly add it. The single stirring time is not less than 5 minutes, until there is no obvious precipitation of the mother liquor protein, which means the preparation of the foaming agent is complete.

4. A low-carbon foamed concrete composite foaming agent, the foaming agent is prepared according to claim 3, characterized in that: The dry density of the foamed concrete obtained at a 10-fold expansion ratio is greater than 800 kg / cm 3 When the compressive strength is greater than 12MPa.

5. The low-carbon foamed concrete composite foaming agent according to claim 4, characterized in that: The pore size of the corresponding foamed concrete prepared at a foaming ratio of 10 times is 50-300 μm.

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