A twice foamed foam concrete and a method for producing the same

Abstract

The application belongs to the technical field of concrete, and particularly relates to secondary foaming foam concrete and a preparation method thereof. The secondary foaming foam concrete provided by the application is prepared from raw materials including main materials and additives; the main materials include aggregate and mineral admixtures, cement and water; and the additives include emulsifiers, hydrogen peroxide aqueous solution, biomass and microorganisms, wherein the biomass is animal liver containing catalase. The hydrogen peroxide aqueous solution and the animal liver containing catalase are matched in the secondary foaming foam concrete provided by the application, and the animal liver containing catalase and the microorganisms are matched and foamed when contacted, so that the foam concrete provided by the application can be foamed twice, and thus is not affected by cement hardening or self-weight collapse. The foam concrete provided by the application has the characteristics of low thermal conductivity, high porosity and low production cost, and can be widely used in actual production.

Description

Technical Field

[0001] This invention belongs to the field of concrete technology, specifically relating to a secondary foamed concrete and its preparation method. Background Technology

[0002] Currently, reducing environmental pollution and promoting energy-efficient buildings have become mainstream development trends in the construction industry. It is estimated that the construction industry accounts for approximately 38% of global carbon dioxide emissions through intensive mining and high embodied energy consumption. With rapid urbanization, energy consumption in the construction industry will continue to increase in the foreseeable future. Against this backdrop, energy-efficient and sustainable buildings have received widespread attention globally to mitigate global warming emissions. The density of a typical concrete structure is 2360 kg / m³. 3 Its thermal conductivity ranges from 0.9 to 4 W / (m·K), resulting in relatively low thermal resistance. Foamed cement, on the other hand, has a lower density, typically ranging from 200 to 1600 kg / m³. 3 On the one hand, it can save building materials; on the other hand, its low density can reduce building weight. It also has good thermal insulation properties, with a thermal conductivity of 0.06–0.28 W / (m·K). Furthermore, due to its high porosity, it has a sound absorption capacity of approximately 0.09–0.19%, providing excellent sound absorption. It also boasts superior fire resistance and other properties. These superior properties perfectly meet the requirements of building energy conservation, and it is gradually becoming a new type of energy-saving wall material that has attracted widespread attention.

[0003] However, foamed concrete currently suffers from a short hardening time, which affects foaming stability and makes it prone to collapse due to its own weight. Summary of the Invention

[0004] The purpose of this invention is to provide a secondary foamed concrete and its preparation method. The secondary foamed concrete provided by this invention is not affected by cement hardening or collapse due to its own weight, and has the characteristics of reduced thermal conductivity, high porosity, and low production cost, and can be widely used in actual production.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a secondary foamed concrete, the raw materials of which include main materials and additives;

[0007] The main ingredients include aggregates and mineral admixtures, cement and water; the mass ratio of the aggregates and mineral admixtures, cement and water is (10-20):(40-60):(20-35);

[0008] The additives include emulsifiers, hydrogen peroxide aqueous solution, biomass, and microorganisms, wherein the biomass is animal liver containing catalase; the hydrogen peroxide aqueous solution has a mass percentage of 25-30%.

[0009] The emulsifier accounts for 0.5% to 3.5% of the mass of the main ingredient;

[0010] The mass percentage of the hydrogen peroxide aqueous solution to the mass of the main material is 0.5% to 2%;

[0011] The biomass constitutes 0.4% to 0.7% of the main ingredient by mass.

[0012] The mass of the microorganisms accounts for 0.5% to 1% of the mass of the main ingredient.

[0013] Preferably, the microorganisms include one or more of lactobacilli, propionibacteria, Leuconostoc mesenteroides, and streptococci.

[0014] Preferably, the emulsifier includes one or more of coconut oil fatty acid monoethanolamide, Span 60, Span 80, Tween 60, Tween 80 and Seppic 305.

[0015] Preferably, the cement is ordinary Portland cement 42.5.

[0016] Preferably, the aggregate in the aggregate and mineral admixture is fine sand; the mineral admixture in the aggregate and mineral admixture includes one or more of fly ash, limestone powder, zeolite powder, blast furnace slag and steel slag powder.

[0017] This invention provides a method for preparing secondary foamed concrete as described above, comprising the following steps:

[0018] (1) Cement, aggregates and mineral admixtures, water, emulsifier, hydrogen peroxide solution and biomass are mixed and foamed for the first time to obtain foamed concrete.

[0019] (2) After mixing the primary foamed concrete with microorganisms, a second foaming is carried out in a mold to obtain the secondary foamed concrete.

[0020] Preferably, the temperature of the first foaming is room temperature, the time is 20s to 1min, and the first foaming is carried out under stirring conditions with a stirring speed of 120r / min.

[0021] Preferably, the second foaming is performed at room temperature for 6 to 24 hours.

[0022] Preferably, in step (1): the mixing includes the following steps:

[0023] Biomass, water, and emulsifier are first mixed to obtain a biomass emulsion.

[0024] The aggregate is mixed with mineral admixtures, cement and biomass emulsion to obtain a paste.

[0025] The paste and hydrogen peroxide aqueous solution are mixed for the first foaming.

[0026] Preferably, the second mixing temperature is room temperature, the time is 1 minute, and the second mixing is carried out under stirring conditions at a stirring speed of 80 r / min.

[0027] This invention provides a secondary foamed concrete, the raw materials of which include main materials and additives; the main materials include aggregates and mineral admixtures, cement and water; the mass ratio of aggregates and mineral admixtures, cement and water is (10-20):(40-60):(20-35); the additives include emulsifiers, hydrogen peroxide aqueous solution, biomass and microorganisms, wherein the biomass is animal liver containing catalase; the mass percentage of the hydrogen peroxide aqueous solution is 25-30%; the mass percentage of the emulsifier to the mass of the main materials is 0.5-3.5%; the mass percentage of the hydrogen peroxide aqueous solution to the mass of the main materials is 0.5-2%; the mass percentage of the biomass to the mass of the main materials is 0.4-0.7%; and the mass percentage of the microorganisms to the mass of the main materials is 0.5-1%. The hydrogen peroxide aqueous solution in the secondary foamed concrete provided by this invention is combined with animal liver containing catalase, and animal liver containing catalase is combined with microorganisms. Upon contact, foaming occurs separately, allowing the foamed concrete to undergo two foaming processes. Furthermore, by adding an emulsifier and simultaneously controlling the mass content of the above-mentioned raw materials, the resulting concrete system is closer to an oil-based system. Compared to water-based systems, which typically have better fluidity, greater slump, shorter initial setting time, and are less conducive to porosity, the oil-based system of this invention hardens slowly, possesses plasticity, and is less prone to collapse due to its own weight. The foaming process is more thorough, thus the secondary foamed concrete provided by this invention is not affected by cement hardening or collapse due to its own weight. It features reduced thermal conductivity, high porosity, and lower production costs, making it suitable for widespread use in actual production.

[0028] This invention provides a method for preparing secondary foamed concrete as described in the above technical solution, comprising the following steps: (1) mixing cement, aggregates and mineral admixtures, water, emulsifier, hydrogen peroxide aqueous solution and biomass for a first foaming to obtain primary foamed concrete; (2) mixing the primary foamed concrete with microorganisms and then performing a second foaming in a mold to obtain secondary foamed concrete. The preparation method provided by this invention, by performing two foaming processes in steps, ensures that the two foaming processes are more thorough, thus preventing the secondary foamed concrete provided by this invention from being affected by cement hardening or collapse due to its own weight. It features reduced thermal conductivity, high porosity, and low production cost, and can be widely used in actual production.

[0029] The results of the embodiments show that the thermal conductivity of the secondary foamed concrete product provided by the present invention is 0.032–0.037 W / mK, the porosity is 72–76%, the compressive strength is 0.17–0.20 MPa, and the dry density is 133–142 kg / m³. 3 . Attached Figure Description

[0030] Figure 1 The test results of the initial setting time of the secondary foamed concrete provided by the present invention under different temperature and humidity conditions.

[0031] Figure 2 This is a photograph of the secondary foamed concrete prepared in Example 1 of the present invention. Detailed Implementation

[0032] This invention provides a secondary foamed concrete, the raw materials of which include main materials and additives;

[0033] The main ingredients include aggregates and mineral admixtures, cement and water; the mass ratio of the aggregates and mineral admixtures, cement and water is (10-20):(40-60):(20-35);

[0034] The additives include emulsifiers, hydrogen peroxide aqueous solution, biomass, and microorganisms, wherein the biomass is animal liver containing catalase; the hydrogen peroxide aqueous solution has a mass percentage of 25-30%.

[0035] The emulsifier accounts for 0.5% to 3.5% of the mass of the main ingredient;

[0036] The mass percentage of the hydrogen peroxide aqueous solution to the mass of the main material is 0.5% to 2%;

[0037] The biomass constitutes 0.4% to 0.7% of the main ingredient by mass.

[0038] The mass of the microorganisms accounts for 0.5% to 1% of the mass of the main ingredient.

[0039] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0040] The raw materials for preparing secondary foamed concrete provided by this invention include main materials.

[0041] In this invention, the main materials include aggregates and mineral admixtures, cement, and water. The cement is preferably ordinary Portland cement 42.5. The aggregates and mineral admixtures are preferably fine sand. The mineral admixtures preferably include one or more of fly ash, limestone powder, zeolite powder, blast furnace slag, and steel slag powder. The aggregates and mineral admixtures are adjusted according to actual usage. In a specific embodiment of this invention, the mass ratio of aggregates to mineral admixtures is preferably 1:1.

[0042] In this invention, the mass ratio of aggregate to mineral admixture, cement and water is (10-20):(40-60):(20-35), preferably (12-18):(45-55):(25-30), and more preferably 20:50:30.

[0043] The raw materials for preparing secondary foamed concrete provided by this invention include additives.

[0044] In this invention, the additives include an emulsifier, an aqueous hydrogen peroxide solution, biomass, and microorganisms, wherein the biomass is animal liver containing catalase. In a specific embodiment of this invention, the biomass is preferably fresh pig liver containing catalase. The catalase in the animal liver containing catalase can decompose the hydrogen peroxide in the aqueous hydrogen peroxide solution, thereby causing foaming. The mass percentage of the aqueous hydrogen peroxide solution is 25-30%. The emulsifier preferably includes one or more of coconut oil fatty acid monoethanolamide, Span 60, Span 80, Tween 60, Tween 80, and Seppic 305, more preferably one or more of Span 60, Span 80, Tween 60, Tween 80, and Seppic 305. In a specific embodiment of this invention, the emulsifier is Tween 80 and / or Span 80. In a specific embodiment of this invention, when the emulsifier is preferably Tween 80 and Span 80, the mass ratio of Tween 80 to Span 80 is preferably 5:1.

[0045] In this invention, the microorganisms preferably include one or more of Lactobacillus, Propionibacterium, Leuconostoc, and Streptococcus. The microorganisms described in this invention are capable of decomposing the biomass for foaming.

[0046] In this invention, the mass percentage of the emulsifier to the mass of the main material is 0.5-3.5%, preferably 1-3%, and more preferably 1.5-2.5%. In this invention, the emulsifier is preferably Tween 80. Furthermore, by adjusting the amount of emulsifier added, this invention can maintain the foaming system provided by this invention in a state closer to an oily system. The oily system of this invention hardens slowly, has plasticity, and is not easily collapsed due to its own weight, resulting in a more complete foaming process. Therefore, the secondary foamed concrete provided by this invention is not affected by cement hardening or collapse due to its own weight, and has the characteristics of reduced thermal conductivity, high porosity, and low production cost.

[0047] In this invention, the mass percentage of the hydrogen peroxide aqueous solution to the mass of the main material is 0.5-2%, preferably 1-1.5%.

[0048] In this invention, the percentage of the biomass mass to the main material mass is 0.4-0.7%, preferably 0.5-0.6%.

[0049] In this invention, the mass of the microorganisms accounts for 0.5-1% of the mass of the main ingredient, preferably 0.6-0.8%.

[0050] This invention provides a method for preparing secondary foamed concrete as described above, comprising the following steps:

[0051] (1) Cement, aggregates and mineral admixtures, water, emulsifier, hydrogen peroxide solution and biomass are mixed and foamed for the first time to obtain foamed concrete.

[0052] (2) After mixing the primary foamed concrete with microorganisms, a second foaming is carried out in a mold to obtain the secondary foamed concrete.

[0053] This invention involves mixing cement, aggregates and mineral admixtures, water, emulsifier, hydrogen peroxide aqueous solution, and biomass for a first foaming process to obtain one-time foamed concrete. In this invention, the biomass is preferably crushed before mixing. The mixing process preferably includes the following steps: first mixing biomass, water, and emulsifier to obtain a biomass emulsion; second mixing the aggregates and mineral admixtures, cement, and biomass emulsion to obtain a paste; and mixing the paste with hydrogen peroxide aqueous solution for a first foaming process. The temperature of the first mixing is preferably room temperature, and this invention does not have special requirements for the specific implementation process of the first mixing. The temperature of the second mixing is preferably room temperature, and the time is preferably 1 minute. The second mixing is carried out in a mixing device. The second mixing is carried out under stirring conditions, and the stirring speed is preferably 80 r / min. The paste is preferably a viscous, cream-like paste. The temperature of the first foaming is preferably room temperature, and the time is preferably 20 seconds to 1 minute. The first foaming is carried out in a mixing device. The first foaming is carried out under stirring conditions, and the stirring speed is preferably 120 r / min. The primary foamed concrete is a soft, relatively viscous, paste-like foamed concrete.

[0054] After obtaining primary foamed concrete, the present invention mixes the primary foamed concrete with microorganisms and then performs a second foaming in a mold to obtain secondary foamed concrete. In this invention, the mixing of the primary foamed concrete and microorganisms is preferably carried out under stirring conditions, the stirring speed is preferably 80 r / min, and the stirring time is preferably 2 min.

[0055] In this invention, the material obtained by mixing primary foamed concrete and microorganisms is injected into a mold. The temperature of the second foaming is preferably 15–40°C, specifically 15°C, 20°C, 25°C, 30°C, 35°C, or 40°C; the relative humidity of the environment during foaming is 50–90%, specifically 50%, 70%, or 90%. The time for the second foaming is preferably 6–24 hours, specifically 6 hours or 8 hours. The volume of the secondary foamed concrete obtained after the second foaming is 20–25% larger than that of the primary foamed concrete.

[0056] In this invention, after the secondary foaming is completed, the product of the second foaming is preferably cured, and the curing can be carried out in the same way as normal concrete.

[0057] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0058] Example 1

[0059] This embodiment provides a secondary foamed concrete, the raw materials of which include main materials and additives; the main materials include fine sand, mineral admixtures, cement and water; by mass percentage, the main materials contain: 10% fine sand, 10% mineral admixtures, 50% cement and 30% water; the additives include emulsifier, hydrogen peroxide aqueous solution, biomass and microorganisms; the mass percentage of the emulsifier to the main materials is 2.5%; the mass percentage of the hydrogen peroxide aqueous solution to the main materials is 1%; the mass percentage of the biomass to the main materials is 0.5%; the mass percentage of the microorganisms to the main materials is 0.7%. Wherein: the cement is ordinary Portland cement 42.5, the aggregate in the aggregate and mineral admixture is fine sand, the mineral admixture is fly ash, the emulsifier is Tween 80, the mass percentage of the hydrogen peroxide aqueous solution is 30%, the biomass is fresh pig liver containing catalase, and the microorganisms are lactobacilli.

[0060] The method for preparing secondary foamed concrete provided in this embodiment includes the following steps:

[0061] S1. Crush animal liver containing catalase, add water and Tween 80, and mix to obtain biomass emulsion.

[0062] S2. Add ordinary silicate cement, fine sand aggregate, mineral admixture and biomass emulsion to the mixing equipment in sequence, start the mixing equipment, the speed of the mixing equipment is 80 revolutions per minute, the mixing time is 1 minute, and a relatively thick paste similar to cream is obtained.

[0063] S3. Then add 30% hydrogen peroxide by mass, increase the rotation speed to 120 revolutions per minute, and stir for 1 minute at room temperature. After the hydrogen peroxide is completely decomposed, a soft and relatively viscous paste-like foamed concrete is obtained, which is the one-time foamed concrete.

[0064] S4. Add the microbial strain to the primary foamed concrete, mix thoroughly at a speed of 80 revolutions per minute for 2 minutes.

[0065] S5. Inject the mixture obtained in step S4 into the mold and wait in a constant temperature chamber at 35°C and 50% relative humidity for 6 hours for biological secondary foaming. When the volume increases by 25% and the mold is completely filled, the foaming is completed, and secondary foamed concrete is obtained.

[0066] The secondary foamed concrete product obtained in this embodiment has a thermal conductivity of 0.032 W / mK, a porosity of 76%, a compressive strength of 0.19 MPa, and a dry density of 135 kg / m³. 3 The compressive strength was determined according to JG T2662011.

[0067] A photograph of the secondary foamed concrete product prepared in this embodiment is shown below. Figure 2 As shown.

[0068] Example 2

[0069] This embodiment provides a secondary foamed concrete, the raw materials of which include main materials and additives; the main materials include fine sand, mineral admixtures, cement and water; by mass percentage, the main materials contain: 10% fine sand, 10% mineral admixtures, 50% cement and 30% water; the additives include emulsifier, hydrogen peroxide aqueous solution, biomass and microorganisms; the mass percentage of the emulsifier to the main materials is 2.5%; the mass percentage of the hydrogen peroxide aqueous solution to the main materials is 1%; the mass percentage of the biomass to the main materials is 0.5%; the mass percentage of the microorganisms to the main materials is 0.7%. Wherein: the cement is ordinary Portland cement 42.5, the aggregate in the aggregate and mineral admixture is fine sand, the mineral admixture is fly ash, the emulsifier is Span 80, the mass percentage of the hydrogen peroxide aqueous solution is 30%, the biomass is fresh pig liver containing catalase, and the microorganisms are lactobacilli.

[0070] The method for preparing secondary foamed concrete provided in this embodiment includes the following steps:

[0071] S1. Crush the animal liver containing catalase and add room temperature water, which should account for 70% of the total water volume.

[0072] S2. Use hot water (approximately 80°C) to mix the remaining 30% of water at a high temperature. Mix at high speed to obtain a viscous colloid containing flocculent matter.

[0073] S3. Add ordinary silicate cement, fine sand aggregate, mineral admixture and biomass and water mixture to the mixing equipment in sequence. Add 80 rpm mixture to the mixing equipment and start the mixing equipment. The mixing equipment speed is 80 rpm and the mixing time is 1 minute to obtain a relatively thick paste similar to butter.

[0074] S4. Then add 30% hydrogen peroxide by mass, increase the rotation speed to 120 revolutions per minute, and stir for 1 minute at room temperature. After the hydrogen peroxide is completely decomposed, a soft and relatively viscous paste-like foamed concrete is obtained, which is the one-time foamed concrete.

[0075] S5. Add the microbial strain to the primary foamed concrete and mix thoroughly at a speed of 80 revolutions per minute for 2 minutes.

[0076] S6. Inject the mixture obtained in step S5 into the mold and wait in a constant temperature chamber at 35°C and 50% relative humidity for 8 hours for biological secondary foaming. When the volume increases by 20% and the mold is completely filled, the foaming is completed, and secondary foamed concrete is obtained.

[0077] The secondary foamed concrete product obtained in this embodiment has a thermal conductivity of 0.037 W / mK, a porosity of 72%, a compressive strength of 0.19 MPa, and a dry density of 142 kg / m³. 3 The compressive strength was determined according to JG T2662011.

[0078] Example 3

[0079] This embodiment provides a secondary foamed concrete, the raw materials of which include main materials and additives; the main materials include fine sand, mineral admixtures, cement and water; by mass percentage, the main materials contain: 5% fine sand, 15% mineral admixtures, 50% cement and 30% water; the additives include emulsifier, hydrogen peroxide aqueous solution, biomass and microorganisms; the mass percentage of the emulsifier to the main materials is 3%; the mass percentage of the hydrogen peroxide aqueous solution to the main materials is 1%; the mass percentage of the biomass to the main materials is 0.5%; the mass percentage of the microorganisms to the main materials is 0.7%. Wherein: the cement is ordinary Portland cement 42.5, the aggregate in the aggregate and mineral admixture is fine sand, the mineral admixture is fly ash, the emulsifier is a mixture of Tween 80 and Span 80, the mass ratio of Tween 80 and Span 80 is 5:1, the mass percentage of the hydrogen peroxide aqueous solution is 30%, the biomass is fresh pig liver containing catalase, and the microorganisms are lactobacilli.

[0080] The method for preparing secondary foamed concrete provided in this embodiment includes the following steps:

[0081] S1. Crush animal liver containing catalase, add water and Tween 80 / Span 80 to obtain biomass emulsion.

[0082] S2. Add ordinary silicate cement, fine sand aggregate, mineral admixture and biomass emulsion to the mixing equipment in sequence, start the mixing equipment, the speed of the mixing equipment is 80 revolutions per minute, the mixing time is 1 minute, and a relatively thick paste similar to cream is obtained.

[0083] S3. Then add 30% hydrogen peroxide by mass, increase the rotation speed to 120 revolutions per minute, and stir for 1 minute at room temperature. After the hydrogen peroxide is completely decomposed, a soft and relatively viscous paste-like foamed concrete is obtained, which is the one-time foamed concrete.

[0084] S4. Add the microbial strain to the primary foamed concrete, mix thoroughly at a speed of 80 revolutions per minute for 2 minutes.

[0085] S5. Inject the mixture obtained in step S4 into the mold and wait in a constant temperature chamber at 35°C and 50% relative humidity for 6 hours for biological secondary foaming. When the volume increases by 25% and the mold is completely filled, the foaming is completed, and secondary foamed concrete is obtained.

[0086] The secondary foamed concrete product obtained in this embodiment has a thermal conductivity of 0.032 W / mK, a porosity of 77%, a compressive strength of 0.17 MPa, and a dry density of 133 kg / m³. 3 The compressive strength was determined according to JG T2662011.

[0087] Comparative Example 1

[0088] According to Example 1 of Chinese Patent CN112479651A, the following components were weighed: 80 parts silicate cement, 10 parts porous ceramic powder, 5 parts hydrogen peroxide foaming agent, 0.3 parts manganese oxide foaming catalyst, 5 parts sodium carbonate and triethanolamine mixed in a mass ratio of 10:1 as a coagulant accelerator, 2 parts calcium stearate foam stabilizer modified by nano-intercalation technology, 4 parts microbial foaming agent, and 37 parts water. The porous ceramic powder was made from existing waste porous ceramics processed into particles with a particle size of approximately 325 mesh. This mesh size is a common particle size for existing silicate cement; of course, it can also be larger, but not exceeding 180 mesh.

[0089] Weighed cement, porous ceramic powder, and foam stabilizer are added to a mixing tank and dry-mixed until homogeneous. The purpose of this dry-mixing is to ensure thorough mixing of the cement, porous ceramic powder, and foam stabilizer. Calcium stearate modified using nano-intercalation technology is selected as the foam stabilizer. During bubble growth, bubble stability is a key factor affecting the preparation process and performance of foamed cement. Microscopically, in porous materials, the liquid film (i.e., the liquid film generated by the cement slurry) separates bubbles; bubble destruction occurs when the liquid film surrounding the bubble ruptures. Bubble instability is also manifested in the fusion and growth of bubbles. Bubble stability is mainly affected by surface tension and the viscosity of the cement slurry. Changes in surface tension cause changes in bubble size, thus affecting bubble stability. In the early stages of cement slurry mixing, the friction between the internal fluid layers is quite complex, and the resulting slurry has a low plastic viscosity and a fast flow rate, making it easy for bubbles to fuse or break. Therefore, in this embodiment, cement, porous ceramic powder, and foam stabilizer are first added to the mixing tank and dry-mixed until homogeneous. The dry mixing time is 30 seconds and the rotation speed is 80 revolutions per minute.

[0090] The addition of porous ceramic powder particles is mainly due to the fact that most of the particles have a plate-like structure rather than a granular structure. Their presence can improve the smoothness of the air bubbles. This is mainly because porous ceramic powder particles do not react, and their granular filling is used to fill the gaps. At the same time, the addition of plate-like porous ceramic powder particles provides early strength for foamed cement and forms a good network-like framework structure.

[0091] After the mixture is evenly mixed, add water to the mixing vessel and continue mixing. According to current research, the optimal water-cement ratio is around 0.46. Since the microbial foaming agent itself contains a large amount of water, the overall mixing ratio of the microbial foaming agent and water should be 0.46. The wet mixing time is 2 minutes and the speed is 80 revolutions per minute.

[0092] Then, the manganese oxide foaming catalyst is rapidly added to the hydrogen peroxide, and after rapid stirring, it is quickly added to the mixing tank and stirred continuously at a speed of 1000 rpm. In this embodiment, the main purpose of adding the catalyst is to accelerate the reaction of the hydrogen peroxide. Similarly, the high stirring speed serves the same purpose, ensuring that the hydrogen peroxide completes the reaction within 10 to 20 seconds. This is mainly because hydrogen peroxide has strong oxidizing properties, i.e., it has a strong bactericidal effect. Only after it has reacted quickly and completely can the microbial catalyst be added. At the same time, the high stirring speed also helps to break up the bubbles formed by the hydrogen peroxide. This prevents bubbles from rising and causing the bottom of the mold to be bubble-free while the top has many bubbles, ensuring a uniform distribution of bubbles. Another reason is that the slurry will solidify and harden during the preparation of foamed cement. Therefore, accelerating its reaction speed and stirring speed allows the microbial foaming agent to be better implemented. In this case, manganese oxide and hydrogen peroxide are added, and the stirring time is 1 minute at a speed of 1000 rpm.

[0093] Using a pipette, four 4 mL portions of distilled water were mixed with 40 mg of glucose, trypsin, and 20 mg of yeast extract. The mixture was stirred thoroughly and then dispensed into Erlenmeyer flasks. The flasks were then sterilized in an autoclave. After sterilization, the mixture was removed and placed on a sterile work surface. After cooling, a 10% yeast stock solution (0.4 mL distilled water + 0.4 mg dry yeast) was inoculated to obtain a yeast solution. The yeast solution was then cultured in a constant temperature shaking incubator at 170 rpm and 30 °C for 48 h to obtain a microbial foaming agent. The microbial foaming agent and coagulant were then added to a stirred tank.

[0094] Stir for 1 minute at 80 rpm. After stirring, pour the slurry into the mold for curing. While curing, stir for another minute at 80 rpm. The total wet mixing time is 4 minutes.

[0095] After curing, the dry density of the test block was measured, and the density value was 310 kg / m³. 3It is much greater than 159.7 kg / m 3 The results of Example 1 in Chinese Patent CN112479651A could not be obtained.

[0096] Test case

[0097] Weigh the raw materials according to the content in Example 1, and repeat steps S1 to S5 of Example 1. After the first foaming, a second foaming experiment was conducted at ambient temperatures of 20℃, 25℃, 30℃, 35℃, and 40℃, and ambient humidity of 90%, 70%, and 50%, respectively. The results are as follows. Figure 1 .

[0098] Excluding groups with initial and final setting times exceeding 10 hours, the sample a was selected under the conditions of 35℃ and 50% relative humidity. The initial setting time was 6 hours and the final setting time was 8 hours. After final setting and curing, sample a was tested and found to have a compressive strength of 0.20 MPa, a thermal conductivity of 0.034 W / mK, and a dry density of 138 kg / m³. 3 Under conditions of 40℃ and 70% relative humidity, the initial setting time was 9 hours and the final setting time was 10 hours, denoted as sample b. After curing, sample b was tested and found to have a compressive strength of 0.19 MPa, a thermal conductivity of 0.032 W / mK, and a dry density of 135 kg / m³. 3 Under conditions of 40℃ and 50% relative humidity, the initial setting time was 5 hours and the final setting time was 6 hours, denoted as sample c. After curing, sample c was tested and found to have a compressive strength of 0.20 MPa, a thermal conductivity of 0.034 W / mK, and a dry density of 140 kg / m³. 3 This indicates that the secondary foamed concrete provided by the present invention also has a longer initial setting time under high temperature and relatively dry conditions.

[0099] Test Example 2

[0100] Repeating Example 1 of Chinese Patent CN112479651A: After adding the microbial foaming agent and accelerator to the mixing tank and mixing, the slurry showed no significant volume change during the continued stirring process, including after being poured into the mold; the volume of the slurry remained almost unchanged. Therefore, it can be determined that the method in Example 1 of Chinese Patent CN112479651A involves pre-preparing biological foam and then mixing it with foam generated by chemical foaming. Due to the addition of the accelerator, the initial setting time of the concrete prepared by Chinese Patent CN112479651A is approximately 40-60 minutes, which is relatively short. However, in Example 1 of Chinese Patent CN112479651A, without the addition of the accelerator, the slurry collapses within 5 minutes in the mold due to its own weight.

[0101] In step S5 of this invention, the slurry is injected into the mold, but it does not need to be filled completely. There is a relatively long foaming process before the concrete hardens and initially sets. Also, due to its inherent plasticity, it will not collapse even with the long initial setting time.

[0102] As can be seen from the above embodiments, compared with the prior art, the advantages of the present invention are as follows: Compared with traditional foamed concrete, the secondary foamed concrete of the present invention has a lower thermal conductivity, higher porosity, and lower production cost, and can be widely used in actual production, reducing engineering costs. Furthermore, compared with traditional biological and chemical methods, the biological foaming process is more complete and is not affected by cement hardening or collapse due to its own weight.

[0103] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A type of secondary foamed concrete, characterized in that, Including main ingredients and additives; The main ingredients include aggregates and mineral admixtures, cement and water; the mass ratio of the aggregates and mineral admixtures, cement and water is (10~20):(40~60):(20~35). The additives include emulsifiers, aqueous hydrogen peroxide solution, biomass, and microorganisms, wherein the biomass is animal liver containing catalase; the aqueous hydrogen peroxide solution has a mass percentage of 25-30%; the microorganisms include one or more of lactobacillus, propionibacterium, Leuconostoc mesenteroides, and streptococcus; the emulsifiers include one or more of coconut oil fatty acid monoethanolamide, Span 60, Span 80, Tween 60, Tween 80, and Seppic 305. The emulsifier accounts for 0.5% to 3.5% of the mass of the main ingredient. The mass percentage of the hydrogen peroxide aqueous solution to the mass of the main ingredient is 0.5-2%; The biomass accounts for 0.4% to 0.7% of the mass of the main ingredient. The mass of the microorganisms accounts for 0.5% to 1% of the mass of the main ingredient.

2. The secondary foamed concrete according to claim 1, characterized in that, The cement is ordinary Portland cement 42.

5.

3. The secondary foamed concrete according to claim 1, characterized in that, The aggregate in the aggregate and mineral admixture is fine sand; the mineral admixture in the aggregate and mineral admixture includes one or more of fly ash, limestone powder, zeolite powder, blast furnace slag and steel slag powder.

4. The method for preparing secondary foamed concrete according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Cement, aggregates and mineral admixtures, water, emulsifier, hydrogen peroxide solution and biomass are mixed and foamed for the first time to obtain foamed concrete; (2) After mixing the primary foamed concrete with microorganisms, a second foaming is carried out in a mold to obtain the secondary foamed concrete.

5. The preparation method according to claim 4, characterized in that, The first foaming is carried out at room temperature for 20 seconds to 1 minute, and is conducted under stirring conditions at a stirring speed of 120 r / min.

6. The preparation method according to claim 4, characterized in that, The second foaming process takes place at room temperature for 6 to 24 hours.

7. The preparation method according to claim 4 or 5, wherein step (1) includes the following steps: Biomass, water, and emulsifier are first mixed to obtain a biomass emulsion. The aggregate is mixed with mineral admixtures, cement and biomass emulsion to obtain a paste. The paste and hydrogen peroxide aqueous solution are mixed for the first foaming.

8. The preparation method according to claim 7, characterized in that, The second mixing was carried out at room temperature for 1 minute, and was conducted under stirring conditions at a stirring speed of 80 r / min.

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