Green lightweight foamed concrete and method for preparing the same

Abstract

The application is green light-weight foam concrete and a preparation method thereof. The light-weight foam concrete is prepared from the following components in parts by weight: cement 500-1000 parts, mineral admixture 50-100 parts, water 250-500 parts, fine aggregate 1500-2500 parts, modified straw fiber 50-150 parts, foaming agent 4-6 parts, foam stabilizer 2-4 parts, compensating agent 25-50 parts, water reducing agent 5-10 parts, and coupling agent 1-2 parts. The light-weight foam concrete prepared by the application not only has good heat preservation, heat insulation and sound insulation performance, but also realizes resource utilization of solid waste, and has certain environmental protection advantages.

Description

Technical Field

[0001] This invention relates to the field of building material preparation technology, and in particular to a green lightweight foamed concrete and its preparation method. Background Technology

[0002] Foamed concrete contains numerous closed pores, making it a porous building material with a density typically ranging from 300 to 1800 kg / m³. 3 Lightweight foamed concrete is a type of concrete characterized by its light weight, low density, high fluidity, and low modulus of elasticity. It possesses excellent thermal performance, fire resistance, thermal insulation, sound insulation, energy dissipation, and vibration damping properties. Since the 21st century, against the backdrop of energy conservation, low carbon emissions, and wall reform, green lightweight foamed concrete has been widely used due to its characteristics. However, as the scale and technical difficulty of projects gradually increase, higher requirements are being placed on the development of green lightweight foamed concrete, such as requirements for crack resistance and durability.

[0003] As a major agricultural residue, straw's effective utilization can not only create economic value but also address some current environmental problems. Its chemical composition mainly consists of cellulose, hemicellulose, and lignin, with fiber content accounting for 80%-90% of the total straw mass. Cellulose, being polar, exhibits a close molecular arrangement due to hydrogen bonds and van der Waals forces, resulting in high tensile strength and elastic modulus of straw fibers. Compared to steel fibers and synthetic fibers, straw fibers offer advantages such as low cost, easy availability, and biodegradability, making them an environmentally friendly material. Furthermore, its fiber structure is dense and fibrous, and its weight is relatively light; for example, the density of rice straw and wheat straw is approximately 0.23 g / cm³. 3 0.12g / cm 3 Meanwhile, crop straw has a high thermal resistance; for example, the thermal resistance of straw fiber walls is about 28 times that of ordinary masonry walls, thus significantly improving the building's insulation performance. When concrete cracks, the randomly distributed fibers improve the force field distribution within the concrete, preventing cracks from widening and mitigating vibration effects. Therefore, adding straw fiber as a plant fiber to foamed concrete can be considered to leverage its excellent thermal insulation and sound insulation properties.

[0004] However, studies have shown that the cement hydration reaction is inhibited after the addition of straw fiber. The inhibition mechanism is as follows: (1) Small pentosans in cellulose and hemicellulose are easily hydrolyzed into sugars such as glucose and galactose. In an alkaline environment, they will be further converted into sugar acid, which combines with free calcium ions in concrete to form calcium gluconate, which coats the surface of cement particles, hindering further cement hydration, resulting in reduced concrete strength and even affecting the molding.

[0005] (2) A layer of dense waxy ester composed of higher fatty alcohols and higher fatty acids forms on the surface of straw, which affects the adhesion between straw and matrix. Furthermore, the straw is easily pulled out or removed under external force, which leads to a reduction in concrete strength.

[0006] Therefore, providing a green lightweight foamed concrete with good crack resistance and durability based on reasonable straw fiber modification is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The present invention aims to address the shortcomings of the prior art by providing a green lightweight foamed concrete and its preparation method.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a green lightweight foamed concrete, which is composed of the following components by weight percentage: 500-1000 parts cement, 50-100 parts mineral admixtures, 250-500 parts water, 1500-2500 parts fine aggregate, 50-150 parts modified straw fiber, 4-6 parts foaming agent, 2-4 parts foam stabilizer, 25-50 parts compensating agent, 5-10 parts water-reducing agent, and 1-2 parts coupling agent.

[0009] Specifically, the mineral admixture is iron tailings.

[0010] Specifically, the fine aggregate is quartz sand with a particle size range of 130-250μm.

[0011] Specifically, the foaming agent is a rosin foaming agent with a mass percentage of 90%-95%.

[0012] Specifically, the foam stabilizer is an alkylolamide or an amine oxide.

[0013] Specifically, the compensator is CaO-Al2O3-CaSO3.

[0014] Specifically, the water-reducing agent is a polycarboxylate high-performance water-reducing agent.

[0015] Specifically, the coupling agent is KH-550.

[0016] Specifically, the modified straw fiber uses one of the following: wheat, rice, corn, cotton, or sorghum straw fiber. The modification method includes the following steps:

[0017] S1. Straw fiber pretreatment: The straw is crushed using a multi-functional crusher to obtain sheet-like straw with a length of 10-30mm. The straw is then placed in a 5% Ca(OH)2 solution and heated in a water bath at 60-80℃ for 30 minutes to obtain pretreated straw fiber.

[0018] S2. Prepare anaerobic biological culture medium:

[0019] S21. According to the composition of the culture medium, add the relevant solution, and boil the culture medium in a microwave oven for 2-4 minutes, then add the anaerobic indicator resazurin.

[0020] S22. Introduce carbon dioxide or nitrogen into the culture medium and place the culture medium on a magnetic stirrer to stir it, so that the components of the culture medium can be better dissolved and help remove oxygen from the liquid.

[0021] S23. Seal the bottle opening with tin foil and continuously purge nitrogen gas for 2-3 hours. After the culture medium color changes from blue to pink and finally to colorless or other light colors, add the oxygen scavenger cysteine ​​hydrochloride.

[0022] S24. After adjusting the pH to 8-9 with 5% Ca(OH)2 solution, quickly remove the vent tube, tighten the bottle cap, and store it in an anaerobic incubator.

[0023] S3. Anaerobic microbial culture: Microbial samples are added to anaerobic culture medium at an inoculation rate of 1% using a sterile syringe and cultured at the suitable growth temperature for 48 hours to obtain anaerobic microbial colonies; wherein, the anaerobic microorganisms are one or more of Clostridium, Bacteroides succinate-producing, Ruminococcus bovis, Ruminococcus albus, and Vibrio fibrinolyticus.

[0024] S4. Straw fiber modification: Pretreated straw fiber and anaerobic microbial colonies are placed in a fermenter and a certain amount of distilled water is added. The solution pH is maintained between 8 and 9 for fermentation. After fermentation for 72-144 hours, the straw is taken out and soaked in a water tank. After neutralizing to neutral with a 3% HCl solution, the bacterial cells, hemicellulose and lignin are centrifuged, and the cellulose is dried to obtain modified straw fiber.

[0025] A method for preparing green lightweight foamed concrete includes the following steps:

[0026] P1. Dilute the foaming agent with 35-42 times its mass of water, then add a foam stabilizer and mix to prepare foam;

[0027] P2. Mix cement, mineral admixtures, modified straw fiber, and fine aggregate evenly, then add the remaining water and mix evenly. Next, add compensating agent, water-reducing agent, and coupling agent and mix evenly to obtain cement slurry. Then, add the foam prepared in P1 to the cement slurry and mix thoroughly to obtain mixed slurry.

[0028] P3. After mixing, the resulting slurry is poured into a mold, sealed with a film, and placed at room temperature. After 24 hours, it is demolded and placed in a standard curing room for 28 days to obtain green lightweight foamed concrete.

[0029] The beneficial effects of this invention are:

[0030] 1. Adding modified straw fiber and mineral admixtures to lightweight foamed concrete can improve the utilization rate of solid waste, and significantly enhance the crack resistance and durability of foamed concrete while ensuring its strength. It also gives it good fire resistance, thermal insulation, sound insulation, energy dissipation and shock absorption properties.

[0031] 2. By using a reasonable modification method to ferment straw fibers, the low-strength hemicellulose and lignin are gradually decomposed under the action of alkaline solution pretreatment and microbial fermentation, exposing the active cellulose groups. The modified straw fibers have abundant and highly active surface groups, which enhances the bonding performance between straw fibers and the matrix, and at the same time improves the hydrophobicity of foamed concrete.

[0032] 3. During the straw modification process, CaCl2 concrete-promoting aqueous solution is generated by neutralizing Ca(OH)2 alkaline solution with HCl acid solution. After the straw fibers are dried, CaCl2 can still exist in the form of crystals on the fiber surface. During the mixing and preparation process, it plays an adsorption role for water molecules, thereby reducing the water-cement ratio and free water in the concrete mixture, enhancing the bonding of the concrete around the fibers, and improving the hardness of the foamed concrete after setting and hardening.

[0033] 4. The straw fiber fermentation process employs strictly anaerobic bacteria. The bacteria selectively utilize lignin and hemicellulose as carbon sources for growth and reproduction by producing oxidizing and hydrolytic enzymes, thereby breaking down the stable structure of lignin and cellulose in the straw to facilitate centrifugal separation of cellulose. The decomposition process is relatively fast. In addition, while removing lignin, anaerobic microorganisms also obtain unstable carbon from carbohydrate polymers. This carbon can directly mineralize greenhouse gases, offering advantages such as being green and environmentally friendly, not producing inhibitory compounds, and being low in cost. Furthermore, the microorganisms are easy to separate by centrifugation and inactivate by drying, and will not have a deteriorating effect on concrete structures. Detailed Implementation

[0034] The present invention will be further described below with reference to embodiments:

[0035] A green lightweight foamed concrete, by weight percentage, is composed of the following components: 500-1000 parts cement, 50-100 parts mineral admixtures, 250-500 parts water, 1500-2500 parts fine aggregate, 50-150 parts modified straw fiber, 4-6 parts foaming agent, 2-4 parts foam stabilizer, 25-50 parts compensating agent, 5-10 parts water-reducing agent, and 1-2 parts coupling agent.

[0036] The mineral admixture is iron tailings, and its grinding regime is as follows: ball mill speed is 350 r / min; ball-to-material ratio is 4:1; average ball diameter is 8.70 mm; ball gradation is selected as follows. The grinding time is 3 hours.

[0037] The fine aggregate is quartz sand with a particle size range of 130-250 μm; the foaming agent is rosin foaming agent with a mass percentage of 90%-95%; the foam stabilizer is alkylolamide or amine oxide; the compensating agent is CaO-Al2O3-CaSO3; the water-reducing agent is polycarboxylate high-performance water-reducing agent; and the coupling agent is KH-550. The chemical composition of cement and iron tailings is shown in Table 1.

[0038] Table 1 Chemical composition of cement and iron tailings

[0039] chemical composition <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO <![CDATA[K2O]]> <![CDATA[TiO2]]> MgO <![CDATA[SO3]]> MnO LOI cement 19.36 4.37 3.12 68.09 0.72 0.23 1.36 2.41 0.04 2.40 Iron tailings 78.64 2.16 5.56 2.84 0.62 0.10 4.46 0.10 0.02 2.34

[0040] The modified straw fiber uses one of the following: wheat, rice, corn, cotton, or sorghum straw fiber. The modification method includes the following steps:

[0041] S1. Straw fiber pretreatment: The straw is crushed using a multi-functional crusher to obtain sheet-like straw with a length of 10-30mm. The straw is then placed in a 5% Ca(OH)2 solution and heated in a water bath at 60-80℃ for 30 minutes to obtain pretreated straw fiber.

[0042] S2. Prepare anaerobic biological culture medium:

[0043] S21. According to the composition of the culture medium, add the relevant solutions, and boil the culture medium in a microwave oven for 2-4 minutes, then add the anaerobic indicator resazurin (final concentration 0.1mg / 100ml);

[0044] S22. Introduce carbon dioxide or nitrogen into the culture medium and place the culture medium on a magnetic stirrer to stir it, so that the components of the culture medium can be better dissolved and help remove oxygen from the liquid.

[0045] S23. Seal the bottle opening with tin foil and continuously purge nitrogen gas for 2-3 hours. After the culture medium color changes from blue to pink and finally to colorless or other light colors, add the oxygen scavenger cysteine ​​hydrochloride.

[0046] S24. After adjusting the pH to 8-9 with 5% Ca(OH)2 solution, quickly remove the vent tube, tighten the bottle cap, and store it in an anaerobic incubator.

[0047] S3. Anaerobic microbial culture: Microbial samples are added to anaerobic culture medium at an inoculation rate of 1% using a sterile syringe and cultured at the suitable growth temperature for 48 hours to obtain anaerobic microbial colonies; wherein, the anaerobic microorganisms are one or more of Clostridium, Bacteroides succinate-producing, Ruminococcus bovis, Ruminococcus albus, and Vibrio fibrinolyticus.

[0048] S4. Straw fiber modification: Pretreated straw fiber and anaerobic microbial colonies are placed in a fermenter and a certain amount of distilled water is added. The solution pH is maintained between 8 and 9 for fermentation. After fermentation for 72-144 hours, the straw is taken out and soaked in a water tank. After neutralizing to neutral with a 3% HCl solution, the bacterial cells, hemicellulose and lignin are centrifuged, and the cellulose is dried to obtain modified straw fiber.

[0049] A method for preparing green lightweight foamed concrete includes the following steps:

[0050] P1. Dilute the foaming agent with 35-42 times its mass of water, then add a foam stabilizer and mix to prepare foam;

[0051] P2. Mix cement, mineral admixtures, modified straw fiber, and fine aggregate evenly, then add the remaining water and mix evenly. Next, add compensating agent, water-reducing agent, and coupling agent and mix evenly to obtain cement slurry. Then, add the foam prepared in P1 to the cement slurry and mix thoroughly to obtain mixed slurry.

[0052] P3. After mixing, the resulting slurry is poured into a mold, sealed with a film, and placed at room temperature (20±2℃). After 24 hours, it is demolded and placed in a standard curing room (20±2℃, relative humidity 95%) for 28 days to obtain green lightweight foamed concrete.

[0053] Example 1

[0054] A green lightweight foamed concrete, by weight percentage, is composed of the following components: 500 parts cement, 50 parts mineral admixtures, 250 parts water, 1500 parts fine aggregate, 50 parts modified straw fiber, 4 parts foaming agent, 2 parts foam stabilizer, 25 parts compensating agent, 5 parts water-reducing agent, and 1 part coupling agent.

[0055] The mineral admixture is high-silica iron tailings, and its grinding regime is as follows: ball mill speed is 350 r / min; ball-to-material ratio is 4:1; average ball diameter is 8.70 mm; ball gradation is selected as follows. The grinding time is 3 hours.

[0056] The fine aggregate is quartz sand with a particle size range of 130-250μm; the foaming agent is rosin foaming agent with a mass percentage of 90%-95%; the foam stabilizer is alkylolamide or amine oxide; the compensator is CaO-Al2O3-CaSO3; the water-reducing agent is polycarboxylate high-performance water-reducing agent; and the coupling agent is KH-550.

[0057] Modified straw fiber is obtained by modifying wheat straw fiber. The modification method includes the following steps:

[0058] S1. Straw fiber pretreatment: The straw is crushed using a multi-functional crusher to obtain sheet-like straw with a length of 10-30mm. The straw is then placed in a 5% Ca(OH)2 solution and heated in a water bath at 60-80℃ for 30 minutes to obtain pretreated straw fiber.

[0059] S2. Prepare anaerobic biological culture medium:

[0060] S21. According to the composition of the culture medium, add the relevant solutions, and boil the culture medium in a microwave oven for 2-4 minutes, then add the anaerobic indicator resazurin (final concentration 0.1mg / 100ml);

[0061] S22. Introduce carbon dioxide or nitrogen into the culture medium and place the culture medium on a magnetic stirrer to stir it, so that the components of the culture medium can be better dissolved and help remove oxygen from the liquid.

[0062] S23. Seal the bottle opening with tin foil and continuously purge nitrogen gas for 2-3 hours. After the culture medium color changes from blue to pink and finally to colorless or other light colors, add the oxygen scavenger cysteine ​​hydrochloride.

[0063] S24. After adjusting the pH to 8-9 with 5% Ca(OH)2 solution, quickly remove the vent tube, tighten the bottle cap, and store it in an anaerobic incubator.

[0064] S3. Anaerobic microbial culture: Microbial samples were added to anaerobic culture medium at an inoculation rate of 1% using a sterile syringe and cultured at the suitable growth temperature for 48 hours to obtain anaerobic microbial colonies; among them, the anaerobic microorganisms were Clostridium difficile;

[0065] S4. Straw fiber modification: Pretreated straw fiber and anaerobic microbial colonies are placed in a fermenter and a certain amount of distilled water is added. The solution pH is maintained between 8 and 9 for fermentation. After fermentation for 72-144 hours, the straw is taken out and soaked in a water tank. After neutralizing to neutral with a 3% HCl solution, the bacterial cells, hemicellulose and lignin are centrifuged, and the cellulose is dried to obtain modified straw fiber.

[0066] A method for preparing green lightweight foamed concrete includes the following steps:

[0067] P1. Dilute the foaming agent with 35-42 times its mass of water, then add a foam stabilizer and mix to prepare foam;

[0068] P2. Mix cement, mineral admixtures, modified straw fiber, and fine aggregate evenly, then add the remaining water and mix evenly. Next, add compensating agent, water-reducing agent, and coupling agent and mix evenly to obtain cement slurry. Then, add the foam prepared in P1 to the cement slurry and mix thoroughly to obtain mixed slurry.

[0069] P3. After mixing, the resulting slurry is poured into a mold, sealed with a film, and placed at room temperature (20±2℃). After 24 hours, it is demolded and placed in a standard curing room (20±2℃, relative humidity 95%) for 28 days to obtain green lightweight foamed concrete.

[0070] Example 2

[0071] A green lightweight foamed concrete, by weight percentage, is composed of the following components: 625 parts cement, 63 parts mineral admixtures, 313 parts water, 1750 parts fine aggregate, 75 parts modified straw fiber, 4 parts foaming agent, 2 parts foam stabilizer, 36 parts compensating agent, 6 parts water-reducing agent, and 1 part coupling agent.

[0072] The mineral admixture is high-alumina iron tailings, and its grinding process is the same as in Example 1; the fine aggregate is quartz sand with a particle size range of 130-250 μm; the foaming agent is rosin foaming agent with a mass percentage of 90%-95%; the foam stabilizer is alkylolamide or amine oxide; the compensator is CaO-Al2O3-CaSO3; the water-reducing agent is polycarboxylate high-performance water-reducing agent; and the coupling agent is KH-550.

[0073] The modified straw fiber was obtained by modifying rice straw fiber, and the modification method was the same as in Example 1, wherein the anaerobic microorganism in S3 was Bacteroides succinate-producing.

[0074] The preparation method of green lightweight foamed concrete is the same as in Example 1.

[0075] Example 3

[0076] A green lightweight foamed concrete, by weight percentage, is composed of the following components: 750 parts cement, 75 parts mineral admixtures, 375 parts water, 2000 parts fine aggregate, 100 parts modified straw fiber, 5 parts foaming agent, 3 parts foam stabilizer, 38 parts compensating agent, 8 parts water-reducing agent, and 1 part coupling agent.

[0077] The mineral admixture is high-calcium-magnesium iron tailings, and its grinding process is the same as in Example 1; the fine aggregate is quartz sand with a particle size range of 130-250 μm; the foaming agent is rosin foaming agent with a mass percentage of 90%-95%; the foam stabilizer is alkylolamide or amine oxide; the compensator is CaO-Al2O3-CaSO3; the water-reducing agent is polycarboxylate high-performance water-reducing agent; and the coupling agent is KH-550.

[0078] The modified straw fiber was obtained by modifying corn straw fiber, and the modification method was the same as in Example 1, wherein the anaerobic microorganism in S3 was Ruminococcus bovis.

[0079] The preparation method of green lightweight foamed concrete is the same as in Example 1.

[0080] Example 4

[0081] A green lightweight foamed concrete, by weight percentage, is composed of the following components: 875 parts cement, 88 parts mineral admixtures, 438 parts water, 2250 parts fine aggregate, 135 parts modified straw fiber, 5 parts foaming agent, 3 parts foam stabilizer, 44 parts compensating agent, 9 parts water-reducing agent, and 2 parts coupling agent.

[0082] The mineral admixture is Jiuquan Iron and Steel Group type iron tailings, and its grinding process is the same as in Example 1; the fine aggregate is quartz sand with a particle size range of 130-250μm; the foaming agent is rosin foaming agent with a mass percentage of 90%-95%; the foam stabilizer is alkylolamide or amine oxide; the compensator is CaO-Al2O3-CaSO3; the water-reducing agent is polycarboxylate high-performance water-reducing agent; and the coupling agent is KH-550.

[0083] The modified straw fiber was obtained by modifying cotton straw fiber, and the modification method was the same as in Example 1, wherein the anaerobic microorganism in S3 was Ruminococcus albus.

[0084] The preparation method of green lightweight foamed concrete is the same as in Example 1.

[0085] Example 5

[0086] A green lightweight foamed concrete, by weight percentage, is composed of the following components: 1000 parts cement, 100 parts mineral admixture, 500 parts water, 2500 parts fine aggregate, 150 parts modified straw fiber, 6 parts foaming agent, 4 parts foam stabilizer, 50 parts compensating agent, 10 parts water-reducing agent, and 2 parts coupling agent.

[0087] The mineral admixture is polymetallic iron tailings, and its grinding process is the same as in Example 1; the fine aggregate is quartz sand with a particle size range of 130-250 μm; the foaming agent is rosin foaming agent with a mass percentage of 90%-95%; the foam stabilizer is alkylolamide or amine oxide; the compensator is CaO-Al2O3-CaSO3; the water-reducing agent is polycarboxylate high-performance water-reducing agent; and the coupling agent is KH-550.

[0088] The modified straw fiber was obtained by modifying sorghum straw fiber, and the modification method was the same as in Example 1, wherein the anaerobic microorganism in S3 was Vibrio cellulose-dissolving bacteria.

[0089] The preparation method of green lightweight foamed concrete is the same as in Example 1.

[0090] Comparative Example 1

[0091] Compared to Example 1, the straw fiber was not modified.

[0092] A green lightweight foamed concrete, by weight percentage, is composed of the following components: 500 parts cement, 50 parts mineral admixtures, 250 parts water, 1500 parts fine aggregate, 50 parts straw fiber, 4 parts foaming agent, 2 parts foam stabilizer, 25 parts compensating agent, 5 parts water-reducing agent, and 1 part coupling agent.

[0093] The mineral admixture is high-silica iron tailings, and its grinding process is the same as in Example 1; the fine aggregate is quartz sand with a particle size range of 130-250 μm; the foaming agent is rosin foaming agent with a mass percentage of 90%-95%; the foam stabilizer is alkylolamide or amine oxide; the compensator is CaO-Al2O3-CaSO3; the water-reducing agent is polycarboxylate high-performance water-reducing agent; and the coupling agent is KH-550.

[0094] The straw fiber is wheat straw fiber.

[0095] The preparation method of green lightweight foamed concrete is the same as in Example 1.

[0096] Comparative Example 2

[0097] Compared to Example 1, the modified straw fiber was removed.

[0098] A green lightweight foamed concrete, by weight percentage, is composed of the following components: 500 parts cement, 50 parts mineral admixtures, 250 parts water, 1500 parts fine aggregate, 4 parts foaming agent, 2 parts foam stabilizer, 25 parts compensating agent, 5 parts water-reducing agent, and 1 part coupling agent.

[0099] The mineral admixture is high-silica iron tailings, and its grinding process is the same as in Example 1; the fine aggregate is quartz sand with a particle size range of 130-250 μm; the foaming agent is rosin foaming agent with a mass percentage of 90%-95%; the foam stabilizer is alkylolamide or amine oxide; the compensator is CaO-Al2O3-CaSO3; the water-reducing agent is polycarboxylate high-performance water-reducing agent; and the coupling agent is KH-550.

[0100] The preparation method of green lightweight foamed concrete is the same as in Example 1.

[0101] The raw material proportions for Examples 1-5 and Comparative Examples 1-2 are shown in Table 2:

[0102] Table 2 Raw material ratios for Examples 1-5 and Comparative Examples 1-2

[0103]

[0104]

[0105] Note: The straw fiber in Comparative Example 1 is unmodified straw fiber.

[0106] The mixed slurry from Examples 1-5 and Comparative Examples 1-2 was poured into a mold to prepare test blocks. The test blocks for testing compressive strength were cubic blocks with dimensions of 100mm×100mm×100mm. After molding, the blocks were cured in a standard curing room for 28 days. The testing method was in accordance with JG / T 266-2011 "Foamed Concrete".

[0107] The test blocks for testing dry density were cubic blocks with dimensions of 100mm×100mm×100mm. After molding, they were cured in a standard curing room for 28 days. The test blocks were then dried in an oven at a temperature of (60±5)℃ until constant weight and then cooled to room temperature. The test method was in accordance with JG / T 266-2011 "Foamed Concrete".

[0108] The test blocks for testing thermal conductivity were cubic blocks with dimensions of 300mm × 300mm × 300mm. After molding, they were cured in a standard curing room for 28 days. The blocks were then dried in an oven at (60±5)℃ until constant weight, and then cooled to room temperature. The test method followed GB / T 10294-2008, "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Protective Hot Plate Method". The specific results of the performance tests are shown in Table 3.

[0109] Table 3 Performance test results of Examples 1-5 and Comparative Examples 1-2

[0110]

[0111]

[0112] As shown in Table 3, the green lightweight foamed concrete prepared in Examples 1-5 of this invention has excellent thermal insulation and mechanical properties, which can better meet the increasingly high requirements of the construction industry for the comprehensive performance of green lightweight foamed concrete and has great market prospects.

[0113] As can be seen from the comparison between Comparative Example 1 and Example 1, the modification treatment of straw in this invention can effectively improve the strength and thermal insulation performance of green lightweight foamed concrete, and significantly reduce the water absorption rate of foamed concrete.

[0114] A comparison of Comparative Example 2 and Example 1 shows that, although the compressive strength of the foamed concrete with modified straw fiber is lower than that of the baseline foamed concrete, its thermal insulation performance and self-weight are significantly improved, and its lower water absorption rate can improve the durability of the foamed concrete to a certain extent. When cracks appear in the concrete, the randomly distributed fibers also improve the force field distribution in the concrete, prevent the cracks from expanding, and weaken its vibration effect.

[0115] The present invention has been described above by way of example. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any improvements made by adopting the inventive concept and technical solution of the present invention, or direct application to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A green, lightweight foamed concrete, characterized in that, The formula is composed of the following components by weight: 500-1000 parts cement, 50-100 parts mineral admixtures, 250-500 parts water, 1500-2500 parts fine aggregate, 50-150 parts modified straw fiber, 4-6 parts foaming agent, 2-4 parts foam stabilizer, 25-50 parts compensating agent, 5-10 parts water-reducing agent, and 1-2 parts coupling agent. The modified straw fiber uses one of the following: wheat, rice, corn, cotton, or sorghum straw fiber. The modification method includes the following steps: S1. Straw fiber pretreatment: The straw is crushed using a multi-functional crusher to obtain sheet-like straw with a length of 10-30mm. The sheet-like straw is then placed in a 5% Ca(OH)2 solution and heated in a water bath at 60-80℃ for 30 minutes to obtain pretreated straw fiber. S2. Prepare anaerobic biological culture medium: S21. According to the composition of the culture medium, add the relevant solution, and boil the culture medium in a microwave oven for 2-4 minutes, then add the anaerobic indicator resazurin. S22. Introduce carbon dioxide or nitrogen into the culture medium and place the culture medium on a magnetic stirrer to stir it, so that the components of the culture medium can be better dissolved and help remove oxygen from the liquid. S23. Seal the bottle opening with tin foil and continuously purge nitrogen gas for 2-3 hours. After the culture medium color changes from blue to pink and finally to colorless or other light colors, add the oxygen scavenger cysteine ​​hydrochloride. S24. After adjusting the pH to 8-9 with 5% Ca(OH)2 solution, quickly remove the vent tube and tightly cap the bottle, then store it in an anaerobic incubator. S3. Anaerobic microbial culture: Microbial samples are added to anaerobic culture medium at an inoculation rate of 1% using a sterile syringe and cultured at the suitable growth temperature for 48 hours to obtain anaerobic microbial colonies; wherein, the anaerobic microorganisms are one or more of Clostridium, Bacteroides succinate-producing, Ruminococcus bovis, Ruminococcus albus, and Vibrio fibrinolyticus. S4. Straw fiber modification: Pretreated straw fiber and anaerobic microbial colonies are placed in a fermenter and a certain amount of distilled water is added. The solution pH is maintained between 8 and 9 for fermentation. After fermentation for 72-144 hours, the straw is taken out and soaked in a water tank. After neutralizing to neutral with a 3% HCl solution, the bacterial cells, hemicellulose and lignin are centrifuged, and the cellulose is dried to obtain modified straw fiber.

2. The green lightweight foamed concrete according to claim 1, characterized in that, The mineral admixture is iron tailings.

3. The green lightweight foamed concrete according to claim 1, characterized in that, The fine aggregate is quartz sand with a particle size range of 130-250μm.

4. The green lightweight foamed concrete according to claim 1, characterized in that, The foaming agent is rosin foaming agent with a mass percentage of 90%-95%.

5. The green lightweight foamed concrete according to claim 1, characterized in that, The foam stabilizer is an alkylolamide or an amine oxide.

6. The green lightweight foamed concrete according to claim 1, characterized in that, The compensator used is CaO-Al2O3-CaSO3.

7. The green lightweight foamed concrete according to claim 1, characterized in that, The water-reducing agent is a high-performance polycarboxylate water-reducing agent.

8. The green lightweight foamed concrete according to claim 1, characterized in that, The coupling agent is KH-550.

9. A method for preparing green lightweight foamed concrete as described in any one of claims 1-8, characterized in that, Includes the following steps: P1. Dilute the foaming agent with 35-42 times its mass of water, then add a foam stabilizer and mix to prepare foam; P2. Mix cement, mineral admixtures, modified straw fiber, and fine aggregate evenly, then add the remaining water and mix evenly. Next, add compensating agent, water-reducing agent, and coupling agent and mix evenly to obtain cement slurry. Then, add the foam prepared in P1 to the cement slurry and mix thoroughly to obtain mixed slurry. P3. After mixing, the resulting slurry is poured into a mold, sealed with a film, and placed at room temperature. After 24 hours, it is demolded and placed in a standard curing room for 28 days to obtain lightweight foamed concrete.

Images