Fly ash lightweight concrete material and preparation method thereof

Abstract

The invention discloses a fly ash lightweight concrete material and a preparation method thereof, and belongs to the technical field of lightweight concrete materials. The concrete is prepared from the following raw materials in parts by weight: 75 to 90 parts of activated fly ash system, 15 to 20 parts of gel material, 13 to 20 parts of lightweight aggregate, 0.85 to 2.4 parts of foaming system and 0.75 to 1.6 parts of functional additive. The fly ash is effectively activated, so that the overall performance of the foam concrete is integrally improved, more importantly, the fly ash is used as industrial waste in the light foam concrete, resource recycling is achieved, dependence on natural resources is reduced, the cost of raw materials is reduced, and the utilization rate of the fly ash in the light foam concrete is increased. Carbon dioxide emission in the cement production process can be reduced, so that energy conservation and emission reduction are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of lightweight concrete materials, and particularly relates to a fly ash lightweight concrete material and a preparation method thereof. Background Art

[0002] Cement is one of the most widely used materials in the modern construction industry, but its production process produces extremely high carbon emissions. Researching how to reduce cement usage and improve the environmental friendliness and economic benefits of building materials has become an important task in the contemporary building materials field.

[0003] Fly ash, due to its excellent physical properties and chemical activity, is considered a key admixture for reducing cement usage and improving concrete performance. Fly ash-based lightweight foamed concrete boasts key characteristics: lightweight, thermal insulation, sound insulation, fire resistance, durability, seismic resistance, and environmental friendliness. Due to its unique porous structure, fly ash-based lightweight foamed concrete exhibits excellent sound insulation. Consequently, fly ash-based lightweight foamed concrete is often used as a building material for sound insulation panels on floors and highways, and for sound insulation layers on the top floors of underground structures. Furthermore, because fly ash-based lightweight foamed concrete is an inorganic material, it is non-flammable and exhibits excellent fire resistance.

[0004] However, the strength of fly ash lightweight foam concrete will decrease with the increase of foam introduced. Specifically, as the amount of foam introduced increases, the porosity of the concrete after hardening will increase, and the bulk density will decrease. Correspondingly, its lightweight, thermal insulation, and sound insulation properties will become more obvious; but at the same time, its strength will decrease significantly, so the characteristics of fly ash lightweight foam concrete come at the cost of reduced strength.

[0005] Because fly ash lightweight foam concrete introduces a large amount of foam during production and typically uses raw materials primarily composed of pulverized material and fine aggregate, it exhibits high water absorption. Furthermore, as the amount of foam introduced increases, its water absorption and shrinkage also increase. This can lead to cracking on the surface of the hardened fly ash lightweight foam concrete. This has seriously impacted the effectiveness of fly ash lightweight foam concrete in engineering applications and restricted its scope of application.

[0006] Therefore, how to optimize the application effect of fly ash in foam soil is a technical problem that needs to be solved urgently. Summary of the Invention

[0007] The present invention aims to solve the problems existing in the prior art and provides a lightweight concrete material with fly ash as the main raw material. By effectively activating the fly ash, the overall performance of the foamed concrete is improved and the use of cement is reduced.

[0008] In order to achieve the above technical objectives, the technical solution adopted by the present invention is: A fly ash lightweight concrete material comprises the following raw materials in parts by weight: 75-90 parts of an activated fly ash system, 15-20 parts of a gel material, 13-20 parts of a lightweight aggregate, 0.85-2.4 parts of a foaming system, and 0.75-1.6 parts of a functional additive.

[0009] Furthermore, the activated fly ash system includes activated fly ash, slag powder and nano-silicon dioxide, and the weight proportions of the three are: 63-70 parts of activated fly ash, 10-15 parts of slag powder and 2-5 parts of nano-silicon dioxide.

[0010] Furthermore, the preparation method of the activated fly ash system is: (1) Acid activation: The raw fly ash is immersed in a dilute hydrochloric acid solution with a concentration of 1-3 mol / L, at a solid-liquid ratio of 1 kg: (2-4) L, and ultrasonically assisted for 30-60 min; (2) Rinse the treated fly ash with water three times to remove the upper suspension, and dry the cleaned fly ash; (3) Soak the dried fly ash in the composite modifier solution at a solid-liquid ratio of 5g:100mL, stir continuously at 30-60℃ for 1-2h, let it stand for 30min, and centrifuge to obtain the modified fly ash: (4) Mechanical activation: The fly ash obtained in step (3) is added with slag powder and nano-silica, and activated in a planetary ball mill at a speed of 200 r / min for 1-2 h, and finally dried to obtain an activated fly ash system.

[0011] Furthermore, the raw fly ash in step (1) is Class I or Class II fly ash, wherein the CaO content is greater than 10%.

[0012] Furthermore, the composite modifier solution is a mixed aqueous solution of lanthanum chloride and rubidium chloride, and the molar concentration of both is 0.5-2 mol / L.

[0013] Furthermore, the gel material is sulphoaluminate cement.

[0014] Furthermore, the lightweight aggregate comprises 10-15 parts by mass of glass microspheres and 3-5 parts of glass fibers.

[0015] Furthermore, the foaming agent system is composed of 0.5-1.5 parts of hydrogen peroxide, 0.05-0.1 parts of manganese dioxide, and 0.3-0.8 parts of protein foaming agent in parts by mass.

[0016] The protein foaming agent is an animal protein foaming agent, specifically FP-180 animal cement foaming agent, purchased from Yancheng Shilong Decoration Materials Co., Ltd.

[0017] Furthermore, the functional additives are composed of 0.5-1 parts of polycarboxylate water-reducing agent, 0.2-0.5 parts of sodium silicate, and 0.05-0.1 parts of hydroxypropyl methylcellulose ether in parts by mass.

[0018] A method for preparing fly ash lightweight concrete material, comprising the following steps: (1) preparing an activated fly ash system; (2) Dry material premixing: put the activated fly ash system, gel material, and vitrified microbeads in the lightweight aggregate into a mixer and dry mix for 3-5 minutes until uniform; (3) Add water and stir to mix: according to the water-binder ratio of 0.45-0.55, the total water amount is about 45%-55% of the total mass of the dry material, add mixing water, add functional additives at the same time, and stir for 8-10 minutes; then add glass fiber at three intervals, continue stirring for 30-50 minutes, and obtain slurry; (4) Stepwise foaming treatment: premix the hydrogen peroxide and manganese dioxide in the foaming agent system and add them to the slurry, stirring to trigger the foaming reaction; when the slurry temperature rises to 35°C, inject the pre-made microfoam of the protein foaming agent, and stir at a low speed of 30-50 rpm for 3-5 minutes to avoid bubble breaking to obtain a foamed slurry; (5) Forming and curing: Pour the slurry into the mold and vibrate it slightly at a frequency of 50 Hz for 10-15 seconds to eliminate large bubbles; the ambient temperature is ≥20°C and the relative humidity is ≥70%, and it is left to stand for 2-3 hours until initial setting; after demolding, cover it with plastic for curing, and maintain the ambient temperature at 40±2°C and humidity ≥95% for the first 3 days; naturally cure it for 4-7 days, spray the alkaline activator solution every day, and then naturally cure it for 15-20 days.

[0019] Furthermore, the alkaline activator solution is prepared by dissolving 10-20 parts by weight of solid sodium hydroxide in 10-22 parts by weight of water at 1-3° C. to obtain a sodium hydroxide solution, and mixing the sodium hydroxide solution with 220-240 parts by weight of water glass to obtain the alkaline activator solution.

[0020] The method for pre-making microfoam with protein foaming agent is as follows: mix the protein foaming agent with water in a ratio of 1:50 (mass ratio) and add it to the foaming equipment for foaming. The mixing water is tap water.

[0021] Beneficial effects: (1) First, the calcium-rich fly ash raw material is treated with acid solution to dissolve CaO to form soluble calcium salts and destroy the glass network structure. Subsequently, a mixed aqueous solution of lanthanum chloride and rubidium chloride with a molar concentration of no more than 2 mol / L is used for activation modification (excessive chloride may change the physical properties of fly ash, such as pore structure and specific surface area, affecting the mechanical properties of the final concrete). The rare earth element lanthanum acts as a Lewis acid, which can destroy the inert structure of aluminosilicate in fly ash and release active SiO44- and AlO4 5- , promoting its reaction with cement hydration products (such as Ca(OH)2) to generate more calcium silicate hydrate (CSH) gel and enhance the gelling properties; rubidium ions provide alkaline conditions, accelerate the dissolution of fly ash, and maintain a high pH environment, optimize the hydration reaction kinetics, and promote secondary pozzolanic reactions. 3+ Destroy the inert layer on the fly ash surface, Rb + Maintaining the alkaline environment required for the reaction, the two work synergistically to improve activation efficiency. Activated fly ash can replace more cement, reducing concrete density while also compensating for strength loss by enhancing the cementitious product, achieving lightweight yet high-strength results.

[0022] (2) Slag powder and nano-silica are then used for further activation. The active SiO2 and Al2O3 in the slag powder can react with Ca(OH)2 generated by cement hydration to produce products such as calcium silicate hydrate (CSH). Nano-silica, due to its extremely fine particles (nanoscale) and large specific surface area, can react more quickly with cement hydration products, accelerating the formation of CSH gel, thereby improving early strength. This synergistic effect compensates for the low early reactivity of fly ash and improves the early and late strength of concrete. At the same time, fly ash itself can reduce thermal conductivity, while the addition of slag powder and nano-materials optimizes the pore distribution, allowing lightweight foam concrete to maintain a low density while improving thermal insulation performance. In short, the combined use of slag powder and nano-silica significantly improves the mechanical properties (such as compressive strength), durability (such as carbonization resistance) and functionality (such as thermal insulation) of lightweight foam concrete through volcanic ash activity, micro-aggregate filling effect and synergistic hydration reaction.

[0023] (3) The use of glass fiber and glass beads as lightweight aggregates can form a "rigid and flexible" reinforcement-lightweight synergistic system. Glass beads replace traditional aggregates, reducing the dry density of concrete and improving thermal insulation performance; glass fiber forms a three-dimensional network structure, improving mechanical strength, and has good adhesion with gel materials, inhibiting the expansion of microcracks and reducing drying shrinkage.

[0024] (4) Construct a composite foaming system that combines hydrogen peroxide decomposition to provide oxygen and protein to stabilize foam. Although hydrogen peroxide decomposes slowly, the addition of manganese dioxide can effectively control the foaming speed, matching it with the setting and hardening speed of the cement slurry, thereby avoiding problems such as mold collapse or excessive porosity. At the same time, the protein foam stabilizer can further stabilize the foam structure, reduce open porosity, and improve the overall performance of the foamed concrete.

[0025] (5) In summary, the present invention achieves an overall improvement in the comprehensive performance of foam concrete by effectively activating fly ash. More importantly, the use of fly ash, as an industrial waste, in lightweight foam concrete realizes the recycling of resources and reduces dependence on natural resources. It not only reduces the cost of raw materials, but also reduces carbon dioxide emissions in the cement production process, thereby achieving energy conservation and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Create a sample map for each experimental group; Figure 2 This is the SEM image of the fly ash cementitious specimen in Example 3. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be further described below with reference to specific embodiments, but is not limited thereto.

[0028] Example 1 A fly ash lightweight concrete material comprises the following raw materials in parts by weight: 75 parts of an activated fly ash system, 15 parts of a gel material, 13 parts of a lightweight aggregate, 0.85 parts of a foaming system, and 1.6 parts of a functional additive.

[0029] The activated fly ash system comprises activated fly ash, slag powder and nano-silicon dioxide, wherein the weight proportions of the three are as follows: 63 parts of activated fly ash, 10 parts of slag powder and 2 parts of nano-silicon dioxide.

[0030] The preparation method of the activated fly ash system is: (1) Acid activation: The raw fly ash was immersed in a 3 mol / L dilute hydrochloric acid solution at a solid-liquid ratio of 1 kg:2 L, and then ultrasonically assisted for 60 min. (2) Rinse the treated fly ash with water three times to remove the upper suspension, and dry the cleaned fly ash; (3) The dried fly ash was immersed in the composite modifier solution at a solid-liquid ratio of 5g:100mL, stirred continuously at 60℃ for 2h, then allowed to stand for 30min and centrifuged to obtain the modified fly ash: (4) Mechanical activation: The fly ash obtained in step (3) was added with slag powder and nano-silica, and activated in a planetary ball mill at a speed of 200 r / min for 2 h. Finally, the activated fly ash system was obtained after drying.

[0031] The raw fly ash of step (1) is of grade I, wherein the CaO content is greater than 10%.

[0032] The composite modifier solution is a mixed aqueous solution of lanthanum chloride and rubidium chloride, and the molar concentration of both is 2 mol / L.

[0033] The gel material is sulphoaluminate cement.

[0034] The lightweight aggregate comprises 10 parts by mass of vitrified microspheres and 3 parts by mass of glass fibers.

[0035] The foaming agent system is composed of 0.5 parts of hydrogen peroxide, 0.05 parts of manganese dioxide, and 0.3 parts of protein foaming agent in parts by mass.

[0036] The protein foaming agent is an animal protein foaming agent, specifically FP-180 animal cement foaming agent, purchased from Yancheng Shilong Decoration Materials Co., Ltd.

[0037] The functional additives are composed of 1 part of polycarboxylate water reducer, 0.5 part of sodium silicate, and 0.1 part of hydroxypropyl methylcellulose ether in parts by mass.

[0038] A method for preparing fly ash lightweight concrete material, comprising the following steps: (1) preparing an activated fly ash system; (2) Dry material premixing: put the activated fly ash system, gel material, and vitrified microbeads in the lightweight aggregate into a mixer and dry mix for 3-5 minutes until uniform; (3) Add water and stir to mix: according to the water-binder ratio of 0.45, the total water amount is about 45% of the total mass of the dry material, add mixing water, add functional additives at the same time, and stir for 8-10 minutes; then add glass fiber at three intervals and continue stirring for 30 minutes to obtain slurry; (4) Stepwise foaming treatment: premix the hydrogen peroxide and manganese dioxide in the foaming agent system and add them to the slurry, stirring to trigger the foaming reaction; when the slurry temperature rises to 35°C, inject the pre-made microfoam of the protein foaming agent, and stir at a low speed of 30-50 rpm for 3-5 minutes to avoid bubble breaking to obtain a foamed slurry; (5) Forming and curing: Pour the slurry into the mold and vibrate it slightly at a frequency of 50 Hz for 10-15 seconds to eliminate large bubbles; the ambient temperature is ≥20℃, the relative humidity is ≥70%, and it is left to stand for 3 hours until initial setting; after demolding, cover it with plastic for curing, and maintain the ambient temperature at 40±2℃ and humidity ≥95% for the first 3 days; natural curing for 7 days, spraying the alkaline activator solution every day, and then natural curing for 20 days.

[0039] The alkaline activator solution is prepared by dissolving 10 parts by weight of solid sodium hydroxide in 10 parts by weight of water at 1-3° C. to obtain a sodium hydroxide solution, and then mixing the sodium hydroxide solution with 220 parts by weight of water glass to obtain the alkaline activator solution.

[0040] The method for pre-making micro-foam with a protein foaming agent is as follows: the protein foaming agent is mixed with water in a ratio of 1:50 (mass ratio) and then added into a foaming equipment for foaming.

[0041] Example 2 A fly ash lightweight concrete material comprises the following raw materials in parts by weight: 90 parts of an activated fly ash system, 20 parts of a gel material, 15 parts of a lightweight aggregate, 1.8 parts of a foaming system, and 1 part of a functional additive.

[0042] The activated fly ash system comprises activated fly ash, slag powder and nano-silicon dioxide, wherein the weight proportions of the three are as follows: 70 parts of activated fly ash, 15 parts of slag powder and 5 parts of nano-silicon dioxide.

[0043] The preparation method of the activated fly ash system is: (1) Acid activation: The raw fly ash was immersed in a 2 mol / L dilute hydrochloric acid solution at a solid-liquid ratio of 1 kg:3 L, and then ultrasonically assisted for 50 min. (2) Rinse the treated fly ash with water three times to remove the upper suspension, and dry the cleaned fly ash; (3) The dried fly ash was immersed in the composite modifier solution at a solid-liquid ratio of 5g:100mL, stirred continuously at 40℃ for 1h, and then allowed to stand for 30min. The modified fly ash was obtained by centrifugation: (4) Mechanical activation: The fly ash obtained in step (3) was added with slag powder and nano-silica, and activated in a planetary ball mill at a speed of 200 r / min for 1 h. Finally, the activated fly ash system was obtained after drying.

[0044] The fly ash raw material in step (1) is Class II fly ash, wherein the CaO content is greater than 10%.

[0045] The composite modifier solution is a mixed aqueous solution of lanthanum chloride and rubidium chloride, and the molar concentration of both is 1.2 mol / L.

[0046] The gel material is sulphoaluminate cement.

[0047] The lightweight aggregate comprises 10 parts by mass of vitrified microspheres and 5 parts by mass of glass fibers.

[0048] The foaming agent system is composed of 0.9 parts of hydrogen peroxide, 0.1 parts of manganese dioxide, and 0.8 parts of protein foaming agent in parts by mass.

[0049] The protein foaming agent is an animal protein foaming agent, specifically FP-180 animal cement foaming agent, purchased from Yancheng Shilong Decoration Materials Co., Ltd.

[0050] The functional additives are composed of 0.5 parts of polycarboxylate water reducer, 0.4 parts of sodium silicate and 0.1 parts of hydroxypropyl methylcellulose ether in parts by mass.

[0051] A method for preparing fly ash lightweight concrete material, comprising the following steps: (1) preparing an activated fly ash system; (2) Dry material premixing: put the activated fly ash system, gel material, and vitrified microbeads in the lightweight aggregate into a mixer and dry mix for 3-5 minutes until uniform; (3) Add water and stir to mix: according to the water-binder ratio of 0.45, the total water amount is about 45% of the total mass of the dry material, add mixing water, add functional additives at the same time, and stir for 8-10 minutes; then add glass fiber at three intervals and continue stirring for 50 minutes to obtain slurry; (4) Stepwise foaming treatment: premix the hydrogen peroxide and manganese dioxide in the foaming agent system and add them to the slurry, stirring to trigger the foaming reaction; when the slurry temperature rises to 35°C, inject the pre-made microfoam of the protein foaming agent, and stir at a low speed of 30-50 rpm for 3-5 minutes to avoid bubble breaking to obtain a foamed slurry; (5) Forming and curing: Pour the slurry into the mold and vibrate it slightly at a frequency of 50 Hz for 10-15 seconds to eliminate large bubbles; the ambient temperature is ≥20℃, the relative humidity is ≥70%, and it is left to stand for 2 hours until initial setting; after demolding, cover it with plastic for curing, and maintain the ambient temperature at 40±2℃ and humidity ≥95% for the first 3 days; natural curing for 4 days, spraying the alkaline activator solution every day, and then natural curing for 20 days.

[0052] The preparation method of the alkaline activator solution is as follows: 20 parts by weight of solid sodium hydroxide is dissolved in 22 parts by weight of water at 1-3° C. to obtain a sodium hydroxide solution, and the sodium hydroxide solution is mixed with 240 parts by weight of water glass to obtain the alkaline activator solution.

[0053] Example 3 A fly ash lightweight concrete material comprises the following raw materials in parts by weight: 80 parts of an activated fly ash system, 6 parts of a gel material, 20 parts of a lightweight aggregate, 2.4 parts of a foaming system, and 0.75 parts of a functional additive.

[0054] The activated fly ash system comprises activated fly ash, slag powder and nano-silicon dioxide, wherein the weight proportions of the three are as follows: 65 parts of activated fly ash, 10 parts of slag powder and 5 parts of nano-silicon dioxide.

[0055] The preparation method of the activated fly ash system is: (1) Acid activation: The raw fly ash was immersed in a 1 mol / L dilute hydrochloric acid solution at a solid-liquid ratio of 1 kg:4 L, and then ultrasonically assisted for 30 min. (2) Rinse the treated fly ash with water three times to remove the upper suspension, and dry the cleaned fly ash; (3) Soak the dried fly ash in the composite modifier solution at a solid-liquid ratio of 5g:100mL, stir continuously at 30℃ for 1h, let it stand for 30min, and centrifuge to obtain the modified fly ash: (4) Mechanical activation: The fly ash obtained in step (3) was added with slag powder and nano-silica, and activated in a planetary ball mill at a speed of 200 r / min for 1 h. Finally, the activated fly ash system was obtained after drying.

[0056] The fly ash raw material in step (1) is Class I, wherein the CaO content is greater than 10%.

[0057] The composite modifier solution is a mixed aqueous solution of lanthanum chloride and rubidium chloride, and the molar concentration of both is 0.5 mol / L.

[0058] The gel material is sulphoaluminate cement.

[0059] The lightweight aggregate comprises 15 parts of vitrified microspheres and 5 parts of glass fibers in terms of mass.

[0060] The foaming agent system is composed of 1.5 parts of hydrogen peroxide, 0.1 parts of manganese dioxide, and 0.8 parts of protein foaming agent in parts by mass.

[0061] The protein foaming agent is an animal protein foaming agent, specifically FP-180 animal cement foaming agent, purchased from Yancheng Shilong Decoration Materials Co., Ltd.

[0062] The functional additives are composed of 0.5 parts of polycarboxylate water reducer, 0.2 parts of sodium silicate and 0.05 parts of hydroxypropyl methylcellulose ether in parts by mass.

[0063] A method for preparing fly ash lightweight concrete material, comprising the following steps: (1) preparing an activated fly ash system; (2) Dry material premixing: put the activated fly ash system, gel material, and vitrified microbeads in the lightweight aggregate into a mixer and dry mix for 3-5 minutes until uniform; (3) Add water and stir to mix: according to the water-binder ratio of 0.55, the total water amount is about 45%-55% of the total mass of the dry material, add mixing water, add functional additives at the same time, and stir for 8-10 minutes; then add glass fiber at three intervals, continue stirring for 30-50 minutes, and obtain slurry; (4) Stepwise foaming treatment: premix the hydrogen peroxide and manganese dioxide in the foaming agent system and add them to the slurry, stirring to trigger the foaming reaction; when the slurry temperature rises to 35°C, inject the pre-made microfoam of the protein foaming agent, and stir at a low speed of 30-50 rpm for 3-5 minutes to avoid bubble breaking to obtain a foamed slurry; (5) Forming and curing: Pour the slurry into the mold and vibrate it slightly at a frequency of 50 Hz for 10-15 seconds to eliminate large bubbles; the ambient temperature is ≥20℃, the relative humidity is ≥70%, and it is left to stand for 3 hours until initial setting; after demolding, cover it with plastic for curing, and maintain the ambient temperature at 40±2℃ and humidity ≥95% for the first 3 days; naturally cure it for 7 days, spray the alkaline activator solution every day, and then naturally cure it for 15 days.

[0064] The alkaline activator solution is prepared by dissolving 15 parts by weight of solid sodium hydroxide in 16 parts by weight of water at 1-3° C. to obtain a sodium hydroxide solution, and then mixing the sodium hydroxide solution with 230 parts by weight of water glass to obtain the alkaline activator solution.

[0065] Comparative Example 1 In this comparative example, except that only lanthanum chloride was used in the preparation of the activated fly ash system, the rest of the raw materials and preparation methods were the same as those in Example 3. That is: A fly ash lightweight concrete material comprises the following raw materials in parts by weight: 80 parts of an activated fly ash system, 6 parts of a gel material, 20 parts of a lightweight aggregate, 2.4 parts of a foaming system, and 0.75 parts of a functional additive.

[0066] The activated fly ash system comprises activated fly ash, slag powder and nano-silicon dioxide, wherein the weight proportions of the three are as follows: 65 parts of activated fly ash, 10 parts of slag powder and 5 parts of nano-silicon dioxide.

[0067] The preparation method of the activated fly ash system is: (1) Acid activation: The raw fly ash was immersed in a 1 mol / L dilute hydrochloric acid solution at a solid-liquid ratio of 1 kg:4 L, and then ultrasonically assisted for 30 min. (2) Rinse the treated fly ash with water three times to remove the upper suspension, and dry the cleaned fly ash; (3) Soak the dried fly ash in the composite modifier solution at a solid-liquid ratio of 5g:100mL, stir continuously at 30℃ for 1h, let it stand for 30min, and centrifuge to obtain the modified fly ash: (4) Mechanical activation: The fly ash obtained in step (3) was added with slag powder and nano-silica, and activated in a planetary ball mill at a speed of 200 r / min for 1 h. Finally, the activated fly ash system was obtained after drying.

[0068] The fly ash raw material in step (1) is Class I, wherein the CaO content is greater than 10%.

[0069] The composite modifier solution is an aqueous solution of lanthanum chloride with a molar concentration of 0.5 mol / L.

[0070] Comparative Example 2 In this comparative example, except that only rubidium chloride was used in the preparation of the activated fly ash system, the rest of the raw materials and preparation methods were the same as those in Example 3. That is: The composite modifier solution is an aqueous solution of rubidium chloride with a molar concentration of 0.5 mol / L.

[0071] Comparative Example 3 In this comparative example, except for reducing the molar concentrations of lanthanum chloride and rubidium chloride in the preparation of the activated fly ash system, the rest of the raw materials and preparation method are the same as those in Example 3. That is: The composite modifier solution is a mixed aqueous solution of lanthanum chloride and rubidium chloride, and the molar concentration of both is 0.1 mol / L.

[0072] Comparative Example 4 In this comparative example, except for increasing the molar concentrations of lanthanum chloride and rubidium chloride in the preparation of the activated fly ash system, the rest of the raw materials and preparation method are the same as those in Example 3. That is: The composite modifier solution is a mixed aqueous solution of lanthanum chloride and rubidium chloride, and the molar concentration of both is 3 mol / L.

[0073] Comparative Example 5 In this comparative example, except that slag powder is not used in the activated fly ash system, the rest of the raw materials and preparation methods are the same as those in Example 3. The activated fly ash system comprises activated fly ash and nano-silicon dioxide, wherein the weight proportion of the activated fly ash and the nano-silicon dioxide is 65 parts and 15 parts, respectively.

[0074] Comparative Example 6 In this comparative example, except that nano-silicon dioxide is not used in the activated fly ash system, the rest of the raw materials and preparation methods are the same as those in Example 3. The activated fly ash system includes activated fly ash and slag powder, and the weight proportion of the activated fly ash and the slag powder is 65 parts and 15 parts respectively.

[0075] Fly ash activation effect performance test The raw fly ash, the activated fly ash system prepared in Examples 1-3, and the activated fly ash system prepared in Comparative Examples 1-6 were tested. The test method is: Take a certain amount of the sample to be tested with a water-cement ratio of 0.3, mix according to the ratio and place in a cement slurry mixer, stir slowly for 120s, stop for 30s, and stir quickly for 120s. Place the mixed mixture in a triple mold with a size of 40×40×160mm, place it in a curing box with a temperature (20±2℃) and a humidity of more than 90% for 24 hours, then remove the mold. After demolding, place it in a standard curing room and cure it to the specified age before conducting a mechanical property test. According to the specification GB / T17671-2021 "Test method for strength of cement mortar (ISO method)", the compressive strength test of fly ash cementitious test blocks with an age of 3d, 7d, and 28d was carried out. Each experimental group formed the samples to be tested as follows Figure 1 The mechanical properties test results are shown in Table 1.

[0076] Table 1 Performance test results From the data in the table, we can see that compared to the untreated fly ash raw material experimental group, the early-stage and 28-day mechanical properties of the fly ash geopolymer test blocks obtained in Examples 1-3, which adopted the activation method of the present invention, were significantly improved. However, in Comparative Examples 1-6, which changed the composition of the composite modifier and lacked silica fume and nano-silicon dioxide, the synergistic effect between the raw materials weakened, and the activation effect on the fly ash was weakened, resulting in limited improvement in the mechanical properties of the test blocks. The SEM images of the gel test blocks also show that the test block structure is continuously denser, thereby improving the compressive strength performance of the fly ash gel test blocks. The fly ash is effectively activated.

[0077] Actual preparation of lightweight foam concrete performance test: Foamed concrete slurries were prepared according to the methods of the examples and comparative examples of the present invention and tested according to relevant standards. Basic parameters of the foamed concrete, such as thermal conductivity and compressive strength, were tested according to the standard "Foamed Concrete," JG / T 266-2011. Water absorption was also tested according to JG / T 266-2011.

[0078] Drying shrinkage, impermeability, and frost resistance: refer to CB / T50082-2009 "Standard for Test Methods for Long-term Performance and Durability of Ordinary Concrete".

[0079] Sound absorption performance test: The sound absorption performance of the specimens was measured using an AW6122 standing wave tube system from Hangzhou Aihua Instruments. The sound absorption coefficient and noise reduction coefficient were calculated according to the "Classification of Sound Absorption Performance of Building Sound-Absorbing Products" (GB / T 16731-2023). The test range was 125–20,000 Hz. The fly ash ceramsite concrete specimens were cylindrical specimens measuring 96 mm × 100 mm.

[0080] The principle of the standing wave tube method: Use a loudspeaker to simulate noise, emit a single-frequency sound wave into the standing wave tube, and vertically shoot into the material surface in the tube. The sound wave is repeatedly emitted and reflected, forming a standing wave sound field in the standing wave tube. Alternating distribution of maximum and minimum sound pressure values occurs along the tube axis, and the maximum and minimum sound pressure values can be measured by moving the probe microphone.

[0081] The sound absorption coefficient is measured at six frequencies: 125, 250, 500, 1000, 1500, and 2000 Hz. The average sound absorption coefficient is calculated. The noise reduction coefficient (NRC) is the arithmetic mean of the sound absorption coefficients at 250, 500, 1000, and 2000 Hz, which provides a rough estimate of the material's sound absorption performance.

[0082] Carbonation Resistance Test: Concrete carbonation testing was conducted in accordance with the "Standard for Test Methods for Long-Term Properties and Durability of Ordinary Concrete" (GB / T 20082-2009). The test instrument used was the Beijing Naild Company's fully automatic NELD-CA070 concrete carbonation test chamber. Concrete specimen dimensions were 100 mm x 100 mm x 100 mm.

[0083] There are 3 specimens in each group, and the average value of all results is taken.

[0084] The test results are shown in Table 2: Table 2 Performance test results The data in the table show that the foamed concrete in the examples of the present invention exhibits excellent thermal insulation and sound insulation properties, as well as good durability and carbonation resistance. However, in Comparative Examples 1-6, where process parameters were varied, these changes affected the overall performance of the concrete to a certain extent. This also demonstrates that the process steps of the present invention are an integral whole, working together and each one being indispensable.

[0085] It should be noted that the above embodiments are only some of the preferred embodiments of the present invention, and not all of them. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present invention.

Claims

1. A fly ash lightweight concrete material, characterized in that: The invention comprises the following raw materials in parts by weight: 75-90 parts of activated fly ash system, 15-20 parts of gel material, 13-20 parts of lightweight aggregate, 0.85-2.4 parts of foaming system and 0.75-1.6 parts of functional additive.

2. The fly ash lightweight concrete material according to claim 1, characterized in that: The activated fly ash system comprises activated fly ash, slag powder and nano silicon dioxide, wherein the weight proportions of the three are as follows: 63-70 parts of activated fly ash, 10-15 parts of slag powder and 2-5 parts of nano silicon dioxide.

3. The fly ash lightweight concrete material according to claim 2, characterized in that: The preparation method of the activated fly ash system is: (1) Acid activation: The raw fly ash is immersed in a dilute hydrochloric acid solution with a concentration of 1-3 mol / L, at a solid-liquid ratio of 1 kg: (2-4) L, and ultrasonically assisted for 30-60 min; (2) Rinse the treated fly ash with water three times to remove the upper suspension, and dry the cleaned fly ash; (3) Soak the dried fly ash in the composite modifier solution at a solid-liquid ratio of 5g:100mL, stir continuously at 30-60℃ for 1-2h, let it stand for 30min, and centrifuge to obtain the modified fly ash: (4) Mechanical activation: The fly ash obtained in step (3) is added with slag powder and nano-silica, and activated in a planetary ball mill at a speed of 200 r / min for 1-2 h, and finally dried to obtain an activated fly ash system.

4. The fly ash lightweight concrete material according to claim 3, characterized in that: The raw fly ash in step (1) is Class I or Class II fly ash, wherein the CaO content is greater than 10%.

5. The fly ash lightweight concrete material according to claim 3, characterized in that: The composite modifier solution is a mixed aqueous solution of lanthanum chloride and rubidium chloride, and the molar concentration of both is 0.5-2 mol / L.

6. The fly ash lightweight concrete material according to claim 1, characterized in that: The gel material is sulphoaluminate cement.

7. The fly ash lightweight concrete material according to claim 1, characterized in that: The lightweight aggregate comprises 10-15 parts by mass of glass beads and 3-5 parts by mass of glass fibers.

8. The fly ash lightweight concrete material according to claim 1, characterized in that: The foaming agent system is composed of 0.5-1.5 parts of hydrogen peroxide, 0.05-0.1 parts of manganese dioxide, and 0.3-0.8 parts of protein foaming agent in parts by mass.

9. The fly ash lightweight concrete material according to claim 1, characterized in that: The functional additive comprises, in parts by mass, 0.5-1 part of polycarboxylate water reducer, 0.2-0.5 part of sodium silicate, and 0.05-0.1 part of hydroxypropyl methylcellulose ether.

10. A method for preparing the fly ash lightweight concrete material according to any one of claims 1 to 9, characterized in that: The following steps are involved: (1) preparing an activated fly ash system; (2) Dry material premixing: put the activated fly ash system, gel material, and vitrified microbeads in the lightweight aggregate into a mixer and dry mix for 3-5 minutes until uniform; (3) Add water and stir to mix: according to the water-binder ratio of 0.45-0.55, the total water amount is about 45%-55% of the total mass of the dry material, add mixing water, add functional additives at the same time, and stir for 8-10 minutes; then add glass fiber at three intervals, continue stirring for 30-50 minutes, and obtain slurry; (4) Stepwise foaming treatment: premix the hydrogen peroxide and manganese dioxide in the foaming agent system and add them to the slurry, stirring to trigger the foaming reaction; when the slurry temperature rises to 35°C, inject the pre-made microfoam of the protein foaming agent, and stir at a low speed of 30-50 rpm for 3-5 minutes to avoid bubble breaking to obtain a foamed slurry; (5) Forming and curing: Pour the slurry into the mold and vibrate it slightly at a frequency of 50 Hz for 10-15 seconds to eliminate large bubbles; the ambient temperature is ≥20℃, the relative humidity is ≥70%, and it is left to stand for 2-3 hours until initial setting; after demolding, cover it with plastic for curing, and maintain the ambient temperature at 40±2℃ and humidity ≥95% for the first 3 days; natural curing for 4-7 days, spraying the alkaline activator solution every day, and then natural curing for 15-20 days.

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