Environment-friendly light-weight foam concrete and preparation method and application thereof

Abstract

The application discloses an environment-friendly light-weight foam concrete as well as a preparation method and application thereof, and belongs to the technical field of light-weight concrete materials. The concrete comprises the following raw materials in percentage by weight: 30-50% of gel materials, 40-60% of waste aggregates, 0.5-1.5% of reinforcing fibers, 0.8-1.2% of a composite microbial foaming agent, 1-2.5% of functional additives, and the balance of water, with the total amount being 100%. In the application, waste concrete is used to replace a part of raw cement, the carbon emission of CO2 is reduced by carbonization process, the waste resources are effectively utilized, the gas generated by the microbial foaming agent metabolism forms a uniform pore structure, and the sound wave transmission path caused by the connected pores is reduced. Compared with traditional concrete, the mass is reduced, and the heat preservation and sound insulation performance are significantly improved. In the production process of the concrete, no additional equipment is needed, the cost is lower, and the production efficiency is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lightweight concrete materials, and particularly relates to an environmentally friendly lightweight foam concrete as well as a preparation method and application thereof. BACKGROUND

[0002] Lightweight foam concrete, as a kind of porous lightweight building material, has been widely used in building walls, road filling, roof insulation and other fields due to its low density, heat preservation, fire resistance and earthquake resistance. Traditional lightweight foam concrete usually takes Portland cement as the matrix, introduces pore structure through physical or chemical foaming process, and uses industrial solid wastes such as fly ash and slag as admixtures to reduce the density of the material and improve the environmental benefits. However, with the increasing demand for comprehensive performance of modern buildings, especially the high standard demand for sound insulation performance, mechanical strength and environmental friendliness, the defects of lightweight foam concrete in the prior art have gradually been exposed, and breakthroughs are urgently needed through material design and process innovation.

[0003] Sound insulation performance is a key indicator of building envelope structure, and the acoustic characteristics of lightweight foam concrete are closely related to its pore structure. Existing patent technologies (such as CN109734397A and CN112194416A) generally use chemical foaming agents (such as hydrogen peroxide and aluminum powder) or surfactant foaming agents (such as sodium dodecyl sulfate) to form closed or semi-closed pore structures, which can reflect sound waves through pores to achieve a certain sound insulation effect, but there are the following bottlenecks:

[0004] Low-frequency sound insulation capacity is insufficient: The pore size formed by the existing foaming process is mostly concentrated in the range of 0.5-2 mm, and the uniformity of distribution is poor, resulting in low efficiency of the material in blocking low-frequency sound waves (<500 Hz). For example, the sound insulation amount of the foam concrete disclosed in CN113636827A at a frequency of 100 Hz is only 25 dB, which is difficult to meet the demand for low-frequency noise insulation of high-rise buildings or along the traffic line.

[0005] Sound bridge effect caused by pore connectivity: Some patents (such as CN111995258A) reduce the density by increasing the amount of foaming agent, but excessive foaming easily forms connected pores, and sound waves pass through the pore wall to form a "sound bridge", which actually weakens the overall sound insulation performance. Tests show that when the density is less than 300 kg / m³, the weighted sound reduction index (Rw) of the material decreases by more than 15%.

[0006] Stability defects of organic foaming agents: Patents using protein or synthetic foaming agents (such as CN112125577A) can improve the uniformity of pore size, but such foaming agents are easily decomposed in alkaline cement paste, causing the foam to collapse, which eventually leads to cracks and pore collapse in the hardened body, further reducing the sound insulation effect.

[0007] In addition, these traditional foam concretes mostly use cement, natural aggregate and other raw materials, which have problems of large resource consumption, high cost, high carbon emission and the like.

[0008] In summary, the existing lightweight foam concrete has significant technical bottlenecks in sound insulation performance, mechanical strength and environmental protection, and a new type of environmentally friendly material needs to be developed to optimize the foaming system, cementitious material composition and preparation process, to realize the organic unification of low density, high sound insulation and low carbon emission. SUMMARY

[0009] The present application aims at the problems in the prior art, and uses construction waste as raw material and a microbial foaming agent to prepare an environmentally friendly lightweight foam concrete with excellent sound insulation performance. The material can effectively insulate low-frequency sound waves, reduce the sound bridge effect caused by pore connectivity, and improve the comprehensive performance of sound insulation and heat insulation of the material.

[0010] To achieve the above technical purposes, the technical scheme adopted by the present application is as follows:

[0011] An environmentally friendly lightweight foam concrete comprises the following raw materials in percentage by weight: 30-50% of gel material, 40-60% of waste aggregate, 0.5-1.5% of reinforcing fiber, 0.8-1.2% of composite microbial foaming agent, 1-2.5% of functional additives, and the balance of water, with the total amount being 100%.

[0012] Further, the gel material is portland cement, carbonized waste concrete fine powder, fly ash and blast furnace slag micro powder; the proportions of the substances are as follows: 10-15 parts of portland cement, 15-25 parts of carbonized waste concrete fine powder, 3-7 parts of fly ash, and 2-5 parts of blast furnace slag micro powder.

[0013] Still further, the preparation method of the carbonized waste concrete fine powder is as follows:

[0014] (1) Take waste cement concrete, crush it to a particle size of less than 5 mm, and then grind to prepare regenerated micro powder, with a particle size of less than 0.3 mm;

[0015] (2) Mechanical activation: add 1% of the mass of the micro powder as an activator, mix uniformly, and then dry grind for 2-4 hours with a planetary ball mill to increase the specific surface area;

[0016] (3) High-efficiency carbonization: place the micro powder obtained in step (2) in a carbonization furnace, evacuate the kettle to -60 kPa to exclude air, and then inject CO2 gas with a concentration of more than 99.5% until the pressure reaches 10 kPa; carbonize for 15-20 hours at an ambient temperature of 20±1℃ and a relative humidity of not less than 70%; and after carbonization, vacuum dry at 50-60℃ for 24 hours to obtain carbonized waste concrete fine powder.

[0017] Further, the activator in step (2) is triethanolamine and sodium hydroxide, and the mass ratio of the two is 1:1.

[0018] The present application uses waste waste concrete as raw material to replace a part of cement raw material, which can greatly reduce the production cost. First, by mechanical crushing and ball milling, the original dense structure of waste concrete is destroyed, and the internal free Ca(OH)2, unhydrated cement particles (C2S, C3S) and C-S-H gel and other active components are exposed. Subsequently, equal mass of triethanolamine and sodium hydroxide is used as activator, and the strong alkaline environment provided by sodium hydroxide dissolves the silicate phase in the regenerated micro powder (such as C-S-H gel, unhydrated (C2S / C3S), releases Ca²⁺ and active SiO2, which can accelerate the reaction with CO2 to generate CaCO3 and silica gel (SiO2·nH2O). The added triethanolamine forms a soluble complex to promote ion migration; at the same time, as a surfactant, it improves the fluidity of the slurry, and has good activation effect on low-activity micro powder (such as high-age waste concrete). The two work together to achieve efficient activation of waste concrete powder. Subsequently, efficient carbonation is carried out, and the generated carbonate network is bonded with the residual gel and fills the pores, thereby improving the mechanical properties of the material as a whole. This carbonation process not only enhances the stability of the material, but also endows it with good durability. It can effectively replace commercial cement raw materials as gel materials, greatly reducing production costs and reducing dependence on natural resources. 2+ The present application uses waste waste concrete as raw material to replace a part of cement raw material, which can greatly reduce the production cost. First, by mechanical crushing and ball milling, the original dense structure of waste concrete is destroyed, and the internal free Ca(OH)2, unhydrated cement particles (C2S, C3S) and C-S-H gel and other active components are exposed. Subsequently, equal mass of triethanolamine and sodium hydroxide is used as activator, and the strong alkaline environment provided by sodium hydroxide dissolves the silicate phase in the regenerated micro powder (such as C-S-H gel, unhydrated (C2S / C3S), releases Ca²⁺ and active SiO2, which can accelerate the reaction with CO2 to generate CaCO3 and silica gel (SiO2·nH2O). The added triethanolamine forms a soluble complex to promote ion migration; at the same time, as a surfactant, it improves the fluidity of the slurry, and has good activation effect on low-activity micro powder (such as high-age waste concrete). The two work together to achieve efficient activation of waste concrete powder. Subsequently, efficient carbonation is carried out, and the generated carbonate network is bonded with the residual gel and fills the pores, thereby improving the mechanical properties of the material as a whole. This carbonation process not only enhances the stability of the material, but also endows it with good durability. It can effectively replace commercial cement raw materials as gel materials, greatly reducing production costs and reducing dependence on natural resources.

[0019] Further, the waste aggregate is obtained by mixing treated waste glass beads and waste EPS particles, and the specific preparation method is as follows: the waste glass beads are crushed and sieved to obtain particles with a particle size of 0.5-2mm, and the metal and plastic are removed, then the waste glass beads are soaked in a 5% NaOH solution for 30 minutes, and then dried to a water content of <1% to obtain treated waste glass beads; the waste EPS particles are mechanically crushed into 3-5mm fragments, washed with dilute sulfuric acid with pH=3 to remove surface oil stains, sprayed with a silane coupling agent solution with a mass concentration of 0.5%, the spraying amount is 3%, and then dried and solidified at 60°C to reduce the water absorption rate; then the particles are treated with hot air at 160°C for 5 seconds to expand the internal micropores of the particles, and treated waste EPS particles are obtained; finally, the waste glass beads and the waste EPS particles are mixed in a mass ratio of (5-10):(8-12) to obtain the waste aggregate.

[0020] The present application uses waste glass beads and waste EPS particles as aggregate, and alkali etching forms a rough surface to improve the mechanical interlocking force between glass beads and cement; the silane coating reduces the difference in hydrophobicity of EPS particles, and alleviates the risk of interfacial peeling. EPS and microporous matrix cooperatively absorb wideband noise to improve sound insulation effect.

[0021] Furthermore, the reinforcing fiber is polypropylene fiber with a length of 10-20 mm.

[0022] Furthermore, the specific preparation method of the composite microbial foaming agent is: Bacillus subtilis ( Bacillus subtilis ), Pediococcus acidilactici ( Pediococcus acidilactici ) and Saccharomyces cerevisiae ( Saccharomyces cerevisiae ) After activation, the cells were inoculated into liquid culture medium and cultured on a shaking platform at 25-42°C for 24 hours until the bacterial concentration reached 1×10 8 CFU / mL; the three bacterial solutions were mixed in a volume ratio of 5:3:2: Bacillus subtilis: Pediococcus acidilactici: Saccharomyces cerevisiae, and 1% of the mass of the mixed bacterial solution was added with cocamidopropyl betaine. The mixture was centrifuged and concentrated to a bacterial concentration of 5×10 9 CFU / mL, made into liquid bacterial agent, which is a composite microbial foaming agent.

[0023] Furthermore, the liquid culture medium is composed of glucose, yeast extract, peptone and phosphate buffer solution in a ratio of 10:5:5:2. After mixing, the mixture is sterilized at 121° C. for 15 minutes.

[0024] Furthermore, the strain number of the Bacillus subtilis is CGMCC No. 1.12939, and the original deposit date is May 30, 2014; the strain number of the Pediococcus acidilactici is CGMCC No. 1.12332, and the original deposit date is September 10, 2012; and the strain number of the Saccharomyces cerevisiae is CGMCC No. 2.3875, and the original deposit date is June 5, 2008. All three strains were purchased from the China General Microorganism Collection Center and can be purchased through public channels without the need for repeated biological deposits.

[0025] Traditional foamed concrete relies on chemical foaming agents (such as aluminum powder and hydrogen peroxide) or physical mechanical foaming, which poses challenges such as high cost, environmental pollution, and uneven pore size. Existing microbial foaming agents often use a single bacterial species, resulting in low gas production efficiency and insufficient foam stability. This invention utilizes a composite bacterial consortium for synergistic fermentation, achieving a balance between efficient gas production and foam stability. Bacillus subtilis, Pediococcus acidilactici, and Saccharomyces cerevisiae are combined in specific proportions to produce gas (CO2), acid to regulate pH, and secrete biosurfactants, creating a synergistic effect. Bacillus subtilis aerobically ferments to produce CO2 and metabolizes into lipopeptide biosurfactants. Pediococcus acidilactici metabolizes lactic acid, lowering the local pH to 4, inhibiting bacteria and activating yeast activity. Saccharomyces cerevisiae metabolizes sugars to produce CO2 and ethanol, which synergistically enhances foam stability. The three bacterial strains work synergistically, with the liquid fermentation agent added directly during the concrete mixing stage. The heat released by cement hydration (40-50°C) activates microbial metabolism, enabling simultaneous gas production and foaming with cement setting, eliminating the need for additional temperature control equipment. Moreover, the bubbles produced are uniform and stable, which can achieve lightweighting of concrete and improve thermal insulation and sound insulation performance.

[0026] Furthermore, the functional additive is a polycarboxylate water reducer.

[0027] A method for preparing environmentally friendly lightweight foam concrete comprises the following steps:

[0028] (1) Preparing carbonized waste concrete fine powder;

[0029] (2) Mixing silicate cement, carbonized waste concrete fine powder, fly ash, and blast furnace slag fine powder, adding water and waste aggregate, and stirring until a uniform slurry is formed;

[0030] (3) preparing a composite microbial foaming agent and adding it to the slurry, then adding functional additives and reinforcing fibers, and continuing stirring for 10-15 minutes;

[0031] (4) Place at 25-40°C for 2-4 hours to allow microbial metabolism and gas production to form a uniform closed-cell structure.

[0032] (5) The obtained concrete slurry is poured into a mold, and the solidified foam concrete is demoulded and placed in a room with a humidity of 90-95% and a temperature of 20-25°C for curing to the specified age.

[0033] Beneficial effects:

[0034] (1) The present application replaces a part of raw material cement with waste concrete, and the activity of carbonized waste concrete fine powder is significantly improved after mechanical activation and CO2 strengthening carbonization, and the matrix strength is synergistically enhanced with Portland cement; the proportion of waste aggregate in the foam concrete of the present application is high, the utilization rate of construction waste is effectively improved, the carbon emission of CO2 fixed by the carbonization process is lower than that of traditional concrete, and the waste resources are effectively utilized;

[0035] (2) The gas produced by the microbial foaming agent forms a uniform pore structure, reduces the sound transmission path caused by connected pores through sound wave scattering and damping effect, and effectively blocks low-frequency sound waves (100-500 Hz). Tests show that the 100 Hz sound insulation amount of Example 1 is 38 dB, which is significantly improved compared with Comparative Example 1 (traditional chemical foaming);

[0036] (3) In addition, the lightweight foam concrete prepared by the method has also improved in mechanical properties, meeting the strength requirements of general construction engineering. Compared with traditional concrete, the mass is reduced, and the thermal insulation and sound insulation performance is significantly improved. In the production process of concrete, no additional equipment is needed, the cost is lower, and the production efficiency is greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The microstructure of the foam in the initial state of Example 1 and Comparative Examples 3-5 of the present application;

[0038] Figure 2 The slice diagram of the foam concrete test piece of Example 1 of the present application;

[0039] Figure 3 The slice diagram of the foam concrete test piece of Comparative Examples 1-6. DETAILED DESCRIPTION

[0040] The technical solutions of the present application will be further described below in conjunction with specific embodiments, but are not limited thereto.

[0041] Example 1

[0042] An environment-friendly lightweight foam concrete comprises the following raw materials by weight percentage: gel material 50%, waste aggregate 40%, reinforcing fiber 0.5%, composite microbial foaming agent 1.2%, functional additive 1%, and the balance is water, with a total amount of 100%.

[0043] The gel material is Portland cement, carbonized waste concrete fine powder, fly ash and blast furnace slag micro powder; the proportions of the substances are as follows: Portland cement 10 parts, carbonized waste concrete fine powder 25 parts, fly ash 3 parts, and blast furnace slag micro powder 2 parts.

[0044] The preparation method of the carbonized waste concrete fine powder is as follows:

[0045] (1) taking waste cement concrete, crushing it to a particle size of less than 5 mm, and then grinding it to prepare recycled micropowder, the particle size of the recycled micropowder being less than 0.3 mm;

[0046] (2) Mechanical activation: Add 1% of the powder mass of the activator, mix well, and then use a planetary ball mill for 2 hours to increase the specific surface area;

[0047] (3) High-efficiency carbonization: The fine powder obtained in step (2) is placed in a carbonization furnace, the interior of the reactor is evacuated to -60 kPa to exclude air, and then CO2 gas with a concentration exceeding 99.5% is injected until the pressure reaches 10 kPa; carbonization is performed for 15 h at an ambient temperature of 20 ± 1 °C and a relative humidity of not less than 70%; after the carbonization is completed, vacuum drying is performed at 50-60 °C for 24 h to obtain carbonized waste concrete fine powder.

[0048] In step (2), the stimulators are triethanolamine and sodium hydroxide, and the mass ratio of the two is 1:1.

[0049] The waste aggregate is obtained by mixing waste glass microbeads and waste EPS particles after they are processed separately. The specific preparation method is as follows: the waste glass microbeads are crushed and sieved to obtain particles with a particle size of 0.5-2 mm, and metals and plastics are removed. The particles are then soaked in a 5% by mass NaOH solution for 30 minutes, and then dried to a moisture content of less than 1% to obtain treated waste glass microbeads; the waste EPS particles are mechanically crushed into 3-5 mm fragments, washed with dilute sulfuric acid with a pH value of 3 to remove surface oil stains, sprayed with a silane coupling agent solution with a mass concentration of 0.5% and a spraying amount of 3%, and dried at 60°C for curing to reduce water absorption; then hot air treatment is performed at 160°C for 5 seconds to expand the micropores inside the particles to obtain treated waste EPS particles; finally, the waste glass microbeads and waste EPS particles are mixed in a mass ratio of 5:12 to obtain waste aggregate.

[0050] The reinforcing fibers are polypropylene fibers with a length of 10-20 mm.

[0051] The specific preparation method of the composite microbial foaming agent is: Bacillus subtilis ( Bacillus subtilis ), Pediococcus acidilactici ( Pediococcus acidilactici ) and Saccharomyces cerevisiae ( Saccharomyces cerevisiae ) After activation, the cells were inoculated into liquid culture medium and cultured on a shaking platform at 25-42°C for 24 hours until the bacterial concentration reached 1×10 8 CFU / mL; the three bacterial solutions were mixed in a volume ratio of 5:3:2: Bacillus subtilis: Pediococcus acidilactici: Saccharomyces cerevisiae, and 1% of the mass of the mixed bacterial solution was added with cocamidopropyl betaine. The mixture was centrifuged and concentrated to a bacterial concentration of 5×10 9The CFU / mL is made into a liquid microbial inoculum, i.e., a composite microbial foaming agent.

[0052] The liquid culture medium is composed of glucose, yeast extract, peptone and phosphate buffer solution in a ratio of 10:5:5:2. After mixing, sterilization treatment is performed at a temperature of 121 DEG C for 15 minutes.

[0053] The strain number of the Bacillus subtilis is CGMCC No.1.12939, and the original preservation date is May 30, 2014; the strain number of the Pediococcus acidilactici is CGMCC No.1.12332, and the original preservation date is September 10, 2012; the strain number of the Saccharomyces cerevisiae is CGMCC No.2.3875, and the original preservation date is June 5, 2008; the three strains are purchased from the China General Microbiological Culture Collection Center and can be purchased through a public channel without repeated biological preservation.

[0054] The functional aid is a polycarboxylic acid water reducing agent.

[0055] An environment-friendly light-weight foam concrete preparation method comprises the following steps:

[0056] (1) preparing carbonized waste concrete fine powder;

[0057] (2) uniformly mixing silicate cement, carbonized waste concrete fine powder, fly ash, blast furnace slag micro powder, adding water and waste aggregate, and stirring to obtain a uniform slurry;

[0058] (3) preparing a composite microbial foaming agent, adding the microbial foaming agent to the slurry, and then adding a functional aid and reinforcing fibers, and continuing to stir for 10-15 minutes;

[0059] (4) placing the slurry in an environment at 25-40 DEG C for 2 hours, and forming a uniform closed pore structure through microbial metabolic gas production;

[0060] (5) pouring the obtained concrete slurry into a mold, demolding the solidified foam concrete, and placing the foam concrete in an indoor curing environment with a humidity of 90-95% and a temperature of 20-25 DEG C to a specified age.

[0061] Example 2

[0062] An environment-friendly light-weight foam concrete comprises the following raw materials in weight percentage: 30% of gel material, 60% of waste aggregate, 1.5% of reinforcing fiber, 0.8% of composite microbial foaming agent, 2% of functional aid, and the balance being water, with a total amount of 100%.

[0063] The gel material is silicate cement, carbonized waste concrete fine powder, fly ash and blast furnace slag micro powder; the proportion of each substance is 12 parts of silicate cement, 20 parts of carbonized waste concrete fine powder, 5 parts of fly ash and 4 parts of blast furnace slag micro powder.

[0064] The preparation method of the carbonized waste concrete fine powder is:

[0065] (1) Take waste cement concrete, crush it to a particle size of less than 5 mm, and then grind to prepare regenerated micro powder, the particle size of which is less than 0.3 mm;

[0066] (2) Mechanical activation: add 1% of the mass of the micro powder of an activator, mix uniformly, and then use a planetary ball mill for 3 hours of dry grinding to increase the specific surface area;

[0067] (3) High-efficiency carbonization: place the micro powder obtained in step (2) in a carbonization furnace, evacuate the kettle to -60 kPa to exclude air, and then inject CO2 gas with a concentration of more than 99.5%, until the pressure reaches 10 kPa; carbonize for 15 hours at an ambient temperature of 20±1℃ and a relative humidity of not less than 70%; after carbonization, vacuum dry at 50-60℃ for 24 hours to obtain carbonized waste concrete fine powder.

[0068] The activator in step (2) is triethanolamine and sodium hydroxide, and the mass ratio of the two is 1:1.

[0069] The waste aggregate is obtained by mixing treated waste glass beads and waste EPS particles, and the specific preparation method is as follows: crush the waste glass beads, sieve to obtain particles with a particle size of 0.5-2 mm, remove metal and plastic, then soak in a 5% NaOH solution for 30 minutes, and then dry to a water content of <1% to obtain treated waste glass beads; mechanically crush the waste EPS particles into 3-5 mm fragments, clean the surface with dilute sulfuric acid with pH=3, spray a 0.5% silane coupling agent solution with a spraying amount of 3%, and then dry and cure at 60℃ to reduce the water absorption rate; then treat at 160℃ for 5 seconds to expand the internal pores of the particles, and obtain treated waste EPS particles; finally, mix the waste glass beads and waste EPS particles according to a mass ratio of 7:10 to obtain the waste aggregate.

[0070] The reinforcing fiber is polypropylene fiber with a length of 10-20 mm.

[0071] The specific preparation method of the composite microbial foaming agent is as follows: mix Bacillus subtilis ( Bacillus subtilis ), Pediococcus acidilactici ( Pediococcus acidilactici ) and Saccharomyces cerevisiae ( Saccharomyces cerevisiae) After activation, access to the liquid medium, 25-42℃, shaking table culture 24 hours, the concentration of bacteria liquid 1×10 8 CFU / mL; three bacteria liquid according to the volume ratio: Bacillus subtilis: Pediococcus acidilactici: Saccharomyces cerevisiae = 5:3:2 mixed, added mixed bacteria liquid mass 1% of cocamide propyl betaine, centrifugal concentration to bacteria concentration 5×10 9 CFU / mL, made into liquid microbial inoculum, which is a composite microbial foaming agent.

[0072] The composition of the liquid medium is: glucose, yeast extract, peptone and phosphate buffer solution, the ratio is 10:5:5:2. After mixing, sterilization treatment, temperature is 121℃, lasts for 15 minutes.

[0073] The strain number of the Bacillus subtilis is CGMCC No.1.12939, the original preservation date is May 30, 2014; the strain number of the Pediococcus acidilactici is CGMCC No.1.12332, the original preservation date is September 10, 2012; the strain number of the Saccharomyces cerevisiae is CGMCC No.2.3875, the original preservation date is June 5, 2008; the three strains are purchased from China General Microbiological Culture Collection Center, can be purchased through public channels, and do not need to be repeatedly preserved.

[0074] The functional aid is polycarboxylic acid water reducing agent.

[0075] A preparation method of an environment-friendly light-weight foam concrete, comprising the following steps:

[0076] (1) preparing carbonized waste concrete fine powder;

[0077] (2) mixing silicate cement, carbonized waste concrete fine powder, fly ash, blast furnace slag micro powder uniformly, adding water and waste aggregate, and stirring to uniform slurry;

[0078] (3) preparing a composite microbial foaming agent and adding it to the slurry, and then adding a functional aid and reinforcing fibers, and continuing to stir for 10-15 minutes;

[0079] (4) placing in an environment of 25-40℃ for 3 hours, and forming a uniform closed pore structure by microbial metabolism gas;

[0080] (5) pouring the obtained concrete slurry into a mold, demolding the solidified foam concrete and placing it in a room with humidity of 90-95% and temperature of 20-25℃ for curing to the specified age.

[0081] Example 3

[0082] The environment-friendly light-weight foam concrete comprises the following raw materials in percentage by weight: 45% of gel material, 43% of waste aggregate, 1% of reinforcing fiber, 1% of composite microbial foaming agent, 2.5% of functional additive, and the balance of water, with the total amount being 100%.

[0083] The gel material is silicate cement, carbonized waste concrete fine powder, fly ash and blast furnace slag micro powder; the proportion of each substance is 15 parts of silicate cement, 25 parts of carbonized waste concrete fine powder, 7 parts of fly ash and 5 parts of blast furnace slag micro powder.

[0084] The preparation method of the carbonized waste concrete fine powder is as follows:

[0085] (1) The waste cement concrete is crushed to a particle size of less than 5 mm, and then ground to prepare regenerated micro powder with a particle size of less than 0.3 mm;

[0086] (2) Mechanical activation: 1% of the mass of the micro powder is added to the activator, mixed uniformly, and then dry ground for 2-4 hours by a planetary ball mill to increase the specific surface area;

[0087] (3) High-efficiency carbonization: the micro powder obtained in step (2) is placed in a carbonization furnace, the kettle is vacuumized to-60kPa to exclude air, and then CO2 gas with a concentration of more than 99.5% is injected until the pressure reaches 10kPa; carbonization is carried out at an ambient temperature of 20±1℃ and a relative humidity of not less than 70% for 20h; after carbonization, vacuum drying is carried out at 50-60℃ for 24h to obtain the carbonized waste concrete fine powder.

[0088] The activator in step (2) is triethanolamine and sodium hydroxide, and the mass ratio of the two is 1:1.

[0089] The waste aggregate is obtained by mixing treated waste glass beads and waste EPS particles, and the specific preparation method is as follows: the waste glass beads are crushed and sieved to obtain particles with a particle size of 0.5-2mm, and the metal and plastic are removed; then the waste glass beads are soaked in a 5% NaOH solution for 30 minutes, and then dried to a water content of less than 1% to obtain treated waste glass beads; the waste EPS particles are mechanically crushed into 3-5mm fragments, cleaned with dilute sulfuric acid with pH=3 to remove surface oil stains, sprayed with a silane coupling agent solution with a mass concentration of 0.5%, and the spraying amount is 3%, and then dried and solidified at 60℃ to reduce the water absorption; then the particles are treated at 160℃ for 5 seconds to expand the internal micropores of the particles, and treated waste EPS particles are obtained; finally, the waste glass beads and the treated waste EPS particles are mixed according to a mass ratio of 10:12 to obtain the waste aggregate.

[0090] The reinforcing fiber is polypropylene fiber with a length of 10-20mm.

[0091] The specific preparation method of the composite microbial foaming agent is: Bacillus subtilis ( Bacillus subtilis ), Pediococcus acidilactici ( Pediococcus acidilactici ) and Saccharomyces cerevisiae ( Saccharomyces cerevisiae ) are activated and then inoculated into a liquid culture medium, and cultured at 25-42℃ for 24 hours on a shaking table, so that the concentration of the bacterial liquid reaches 1×10 8 CFU / mL; the three kinds of bacterial liquids are mixed in a volume ratio of Bacillus subtilis: Pediococcus acidilactici: Saccharomyces cerevisiae = 5:3:2, 1% cocamide propyl betaine is added to the mixed bacterial liquid, and the bacterial concentration is concentrated to 5×10 9 CFU / mL by centrifugation to prepare a liquid bacterial agent, that is, the composite microbial foaming agent.

[0092] The composition of the liquid culture medium is: glucose, yeast extract, peptone and phosphate buffer solution, and the ratio is 10:5:5:2. After mixing, sterilization treatment is carried out at a temperature of 121℃ for 15 minutes.

[0093] The strain number of the Bacillus subtilis is CGMCC No.1.12939, and the original preservation date is May 30, 2014; the strain number of the Pediococcus acidilactici is CGMCC No.1.12332, and the original preservation date is September 10, 2012; the strain number of the Saccharomyces cerevisiae is CGMCC No.2.3875, and the original preservation date is June 5, 2008; the three strains are purchased from the China General Microbiological Culture Collection Center, and can be purchased through the public channel, without the need for repeated biological preservation.

[0094] The functional aid is a polycarboxylic acid water reducing agent.

[0095] A preparation method of an environment-friendly light-weight foam concrete, comprising the following steps:

[0096] (1) preparing carbonized waste concrete fine powder;

[0097] (2) uniformly mixing silicate cement, carbonized waste concrete fine powder, fly ash, blast furnace slag micro powder, adding water and waste aggregate, and stirring until a uniform slurry is obtained;

[0098] (3) preparing a composite microbial foaming agent and adding it to the slurry, and then adding a functional aid and reinforcing fibers, and continuing to stir for 10-15 minutes;

[0099] (4) standing for 4 hours in an environment of 25-40℃, and forming a uniform closed pore structure by microbial metabolic gas production;

[0100] (5) The obtained concrete slurry is poured into a mold, and the solidified foam concrete is demoulded and placed in a room with a humidity of 90-95% and a temperature of 20-25°C for curing to the specified age.

[0101] Comparative Example 1

[0102] This comparative example is compared with Example 1, except that in the preparation of carbonized waste concrete fine powder, only triethanolamine is used as the activator, and the rest of the raw materials and preparation process are the same as Example 1. That is:

[0103] The preparation method of the carbonized waste concrete fine powder is:

[0104] (1) taking waste cement concrete, crushing it to a particle size of less than 5 mm, and then grinding it to prepare recycled micropowder, the particle size of the recycled micropowder being less than 0.3 mm;

[0105] (2) Mechanical activation: Add 1% of the powder mass of the activator, mix well, and then use a planetary ball mill for 2-4 hours to increase the specific surface area;

[0106] (3) High-efficiency carbonization: The fine powder obtained in step (2) is placed in a carbonization furnace, the interior of the reactor is evacuated to -60 kPa to exclude air, and then CO2 gas with a concentration exceeding 99.5% is injected until the pressure reaches 10 kPa; carbonization is performed for 20 h at an ambient temperature of 20 ± 1 °C and a relative humidity of not less than 70%; after the carbonization is completed, vacuum drying is performed at 50-60 °C for 24 h to obtain carbonized waste concrete fine powder.

[0107] In step (2), the stimulator is triethanolamine.

[0108] Comparative Example 2

[0109] This comparative example is compared with Example 1, except that in the preparation of carbonized waste concrete fine powder, only sodium hydroxide is used as the activator, and the rest of the raw materials and preparation process are the same as Example 1. That is:

[0110] The preparation method of the carbonized waste concrete fine powder is:

[0111] (1) taking waste cement concrete, crushing it to a particle size of less than 5 mm, and then grinding it to prepare recycled micropowder, the particle size of the recycled micropowder being less than 0.3 mm;

[0112] (2) Mechanical activation: Add 1% of the powder mass of the activator, mix well, and then use a planetary ball mill for 2 hours to increase the specific surface area;

[0113] (3) High-efficiency carbonization: the micro-powder obtained in step (2) is placed in a carbonization furnace, the kettle is vacuumed to -60 kPa to exclude air, and then CO2 gas with a concentration of more than 99.5% is injected until the pressure reaches 10 kPa; carbonization is carried out at an ambient temperature of 20±1℃ and a relative humidity of not less than 70% for 15 hours; after the carbonization is completed, vacuum drying is carried out at 50-60℃ for 24 hours to obtain carbonized waste concrete fine powder.

[0114] The activator in step (2) is sodium hydroxide.

[0115] Comparative Example 3

[0116] In this comparative example, compared with Example 1, only in the preparation of the composite microbial foaming agent, the microorganism does not use Bacillus subtilis, and the rest of the raw materials and preparation process are the same as those of Example 1. That is:

[0117] The specific preparation method of the composite microbial foaming agent is: after the Pediococcus acidilactici and Saccharomyces cerevisiae are activated, they are inoculated into a liquid culture medium, and then cultured at 25-42℃ on a shaking bed for 24 hours, and the concentration of the bacterial solution reaches 1×10 8 CFU / mL; the two kinds of bacterial solutions are mixed in a volume ratio of Pediococcus acidilactici: Saccharomyces cerevisiae = 3:2, 1% cocamide propyl betaine is added to the mixed bacterial solution, and the bacterial concentration is concentrated to 5×10 9 CFU / mL by centrifugation to prepare a liquid bacterial agent, which is the composite microbial foaming agent.

[0118] Comparative Example 4

[0119] In this comparative example, compared with Example 1, only in the preparation of the composite microbial foaming agent, the microorganism does not use Pediococcus acidilactici, and the rest of the raw materials and preparation process are the same as those of Example 1. That is:

[0120] The specific preparation method of the composite microbial foaming agent is: after the Bacillus subtilis and Saccharomyces cerevisiae are activated, they are inoculated into a liquid culture medium, and then cultured at 25-42℃ on a shaking bed for 24 hours, and the concentration of the bacterial solution reaches 1×10 8 CFU / mL; the two kinds of bacterial solutions are mixed in a volume ratio of Bacillus subtilis: Saccharomyces cerevisiae = 5:2, 1% cocamide propyl betaine is added to the mixed bacterial solution, and the bacterial concentration is concentrated to 5×10 9 CFU / mL by centrifugation to prepare a liquid bacterial agent, which is the composite microbial foaming agent.

[0121] Comparative Example 5

[0122] In this comparative example, compared with Example 1, only in the preparation of the composite microbial foaming agent, the microorganism does not use Saccharomyces cerevisiae, and the rest of the raw materials and preparation process are the same as those of Example 1. That is:

[0123] The specific preparation method of the composite microbial foaming agent is: after the Bacillus subtilis and Pediococcus acidilactici are activated, they are inoculated into a liquid culture medium, and cultured at 25-42 DEG C for 24 hours on a shaking table, and the concentration of the bacterial liquid reaches 1x10 8 CFU / mL; the two bacterial liquids are mixed in a volume ratio of Bacillus subtilis:Pediococcus acidilactici = 5:3, 1% of the mass of the mixed bacterial liquid is added to the cocamide propyl betaine, and the bacterial concentration is concentrated to 5x10 9 CFU / mL by centrifugation to prepare a liquid bacterial agent, which is the composite microbial foaming agent.

[0124] Comparative Example 6

[0125] Compared with the traditional chemical foaming agent (hydrogen peroxide), that is, compared with Example 1, only the composite microbial foaming agent is replaced by the hydrogen peroxide foaming agent, and the remaining raw materials and preparation process are the same as those of Example 1. That is:

[0126] An environment-friendly light foam concrete comprises the following raw materials in percentage by weight: gel material 50%, waste aggregate 40%, reinforcing fiber 0.5%, foaming agent 1.2%, functional additive 1%, and the balance is water, and the total amount is 100%.

[0127] A preparation method of an environment-friendly light foam concrete comprises the following steps:

[0128] (1) preparing carbonized waste concrete fine powder;

[0129] (2) diluting the foaming agent hydrogen peroxide with water at a dilution ratio of 1:30 to obtain a foaming agent solution;

[0130] (3) uniformly mixing silicate cement, carbonized waste concrete fine powder, fly ash, and blast furnace slag micro powder, adding the foaming agent solution, and then adding the remaining water and waste aggregate, and stirring until a uniform slurry is obtained; then adding the functional additive and the reinforcing fiber, and continuing to stir for 10-15 minutes;

[0131] (4) because the decomposition speed of hydrogen peroxide is fast, the slurry should be poured immediately after stirring, the obtained concrete slurry is poured into a mold, the solidified foam concrete is demolded and placed in a room with a humidity of 90-95% and a temperature of 20-25 DEG C for curing to a specified age.

[0132] Performance test

[0133] Foaming performance comparison of different foaming agents:

[0134] The preparation of the composite microbial foaming agent was carried out according to the method of Example 1, Comparative Examples 3-5, and the foaming ratio, 1h subsidence distance and 1h water bleeding rate of the microbial foaming agent were determined according to JC / T 2199-2013 "Foaming agent for foamed concrete". The microscopic image of the foam was obtained by using an ultra-depth microscope, and the image was processed by using Image-Pro plus software.

[0135] Table 1 Foaming performance test results of foaming agent

[0136]

[0137] As can be seen from Table 1, the foaming ratio, 1h subsidence distance and 1h water bleeding rate of Example 1 using the composite microbial foaming agent are all better than those of other comparative experiments. Especially the water bleeding rate and the subsidence distance, which are significantly higher than those of Comparative Examples 3, 4, 5 and hydrogen peroxide foaming agent. This result shows that the composite microbial foaming agent can meet the foaming performance requirements of foamed concrete, and its foaming performance is equivalent to or even better than that of the traditional chemical hydrogen peroxide foaming agent, which can replace the chemical foaming agent. At the same time, the foaming performance of Comparative Examples 4-5 with different microbial compositions is reduced due to the disappearance of the synergistic effect between the strains of different microbial species. The microstructure of the foam from the initial state (when the foam is just prepared) Figure 1 It can be seen that the foam boundary obtained by the foaming agent of Example 1 is clearer, the bubble independence is better, and the foam size and shape are uniform, while the foam liquid film of Comparative Examples 3-5 is mixed with small bubbles, the foam boundary is not clear, and the bubble independence is poor.

[0138] Foamed concrete performance test

[0139] According to the standard of "Foamed Concrete" (JG / T 266-2011), the compressive and flexural strength of the sample cured for 28d was tested. According to the method of "Foamed Concrete" (JG / T 266-2011), the dry density and water absorption rate of the sample cured for 28d were tested, and the size of the test block was 100 mm x 100 mm x 100 mm. Thermal conductivity test: tested according to GB / T 10294-2008. Sound insulation performance: according to GB / T 19889.3-2005, the sound insulation amount in the frequency band of 100-5000 Hz was tested by using the standing wave tube method. The weighted sound insulation amount (Rw) was calculated according to ISO 717-1. The sample was scanned by using nanoVoxel-2740E type X-ray high-precision industrial CT, and the experimental results were analyzed by using software Avizo to obtain the two-dimensional pore structure of the sample. The test results are shown in Table 2:

[0140] Table 2 Foamed concrete performance test results

[0141]

[0142] From the data in the table, we can see that the foam concrete of the present application is better than the traditional foam concrete prepared by hydrogen peroxide foaming agent in compressive strength and flexural strength, has lower dry density, smaller water absorption, and significantly improved sound insulation performance. This shows that the composite microbial foaming agent not only improves the mechanical properties of the foam concrete, but also significantly improves its thermal insulation and sound insulation effect, providing a new direction for the optimization of building materials. While changing the microbial species of the foaming agent in Comparative Examples 4-5, the mechanical properties and thermal insulation and sound insulation effect are all decreased, verifying the importance of the synergistic effect of the strains. At the same time, the experimental data also shows that the effective excitation of sodium hydroxide and triethanolamine effectively improves the gel performance of waste concrete, which can replace part of the cement, reduce the cost, and is more environmentally friendly. From the two-dimensional slice images of the foam concrete of Example 1 and Comparative Examples 1-6, it can be seen that the pore distribution in the foam concrete is uniform, and a small amount of large pores are occasionally seen. Comparative Examples 1-6 all show obvious large pore structure, the pore connectivity increases, and the pore size difference is obvious, which leads to the decrease of the strength performance and sound insulation performance.

[0143] It should be noted that the above examples are only part of the preferred modes of implementing the present application, not all. Obviously, based on the above examples of the present application, all other examples obtained by a person of ordinary skill in the art without creative labor should belong to the scope of protection of the present application.

Claims

1. An environmentally friendly lightweight foam concrete, characterized in that: The raw materials include the following weight percentages: gel material 30-50%, waste aggregate 40-60%, reinforcing fiber 0.5-1.5%, composite microbial foaming agent 0.8-1.2%, functional additive 1-2.5%, and the balance is water, with the total amount being 100%; The waste aggregate is obtained by mixing waste glass microspheres and waste EPS particles after treatment. The specific preparation method is as follows: the waste glass microspheres are crushed and sieved to obtain particles with a particle size of 0.5-2 mm, and metal and plastic are removed. The particles are then soaked in a 5% by mass NaOH solution for 30 minutes, and then dried to a moisture content of less than 1% to obtain treated waste glass microspheres; the waste EPS particles are mechanically crushed into 3-5 mm particles, washed with dilute sulfuric acid with a pH of 3 to remove surface oil stains, sprayed with a 0.5% by mass concentration silane coupling agent solution in a spraying amount of 3%, and dried at 60° C. to reduce water absorption; and then subjected to hot air treatment at 160° C. for 5 seconds to obtain treated waste EPS particles; and finally, the waste glass microspheres and waste EPS particles are mixed in a mass ratio of (5-10):(8-12) to obtain waste aggregate. The specific preparation method of the composite microbial foaming agent is: Bacillus subtilis ( Bacillus subtilis ), Pediococcus acidilactici ( Pediococcus acidilactici ) and Saccharomyces cerevisiae ( Saccharomyces cerevisiae ) After activation, the cells were inoculated into liquid culture medium and cultured on a shaking platform at 25-42°C for 24 hours until the bacterial concentration reached 1×10 8 CFU / mL; the three bacterial solutions were mixed in a volume ratio of Bacillus subtilis: Pediococcus acidilactici: Saccharomyces cerevisiae = 5:3:2, and 1% of the mass of the mixed bacterial solution was added with cocamidopropyl betaine. The mixture was centrifuged and concentrated to a bacterial concentration of 5×10 9 CFU / mL, made into liquid bacterial agent, that is, composite microbial foaming agent; The strain number of the Bacillus subtilis is CGMCC No. 1.12939; the strain number of the Pediococcus acidilactici is CGMCC No. 1.12332; and the strain number of the Saccharomyces cerevisiae is CGMCC No. 2.3875. All three strains were purchased from the China General Microorganism Collection Center.

2. The environmentally friendly lightweight foam concrete according to claim 1, characterized in that: The gel material comprises silicate cement, carbonized waste concrete fine powder, fly ash and blast furnace slag powder; the proportions of the materials in parts by weight are: 10-15 parts silicate cement, 15-25 parts carbonized waste concrete fine powder, 3-7 parts fly ash and 2-5 parts blast furnace slag powder.

3. The environmentally friendly lightweight foam concrete according to claim 2, characterized in that: The preparation method of the carbonized waste concrete fine powder is: (1) taking waste cement concrete, crushing it to a particle size of less than 5 mm, and then grinding it to prepare recycled micropowder, the particle size of the recycled micropowder being less than 0.3 mm; (2) Mechanical activation: Add 1% of the powder mass of the activator, mix well, and then use a planetary ball mill for 2-4 hours to increase the specific surface area; (3) High-efficiency carbonization: The fine powder obtained in step (2) is placed in a carbonization furnace, the interior of the reactor is evacuated to -60 kPa to exclude air, and then CO2 gas with a concentration exceeding 99.5% is injected until the pressure reaches 10 kPa; carbonization is carried out for 15-20 hours at an ambient temperature of 20±1°C and a relative humidity of not less than 70%; after the carbonization is completed, vacuum drying is carried out at 50-60°C for 24 hours to obtain carbonized waste concrete fine powder.

4. The environmentally friendly lightweight foam concrete according to claim 3, characterized in that: In step (2), the stimulators are triethanolamine and sodium hydroxide, and the mass ratio of the two is 1:

1.

5. The environmentally friendly lightweight foam concrete according to claim 1, characterized in that: The reinforcing fibers are polypropylene fibers with a length of 10-20 mm.

6. The environmentally friendly lightweight foam concrete according to claim 1, characterized in that: The functional auxiliary agent is a polycarboxylate water reducer.

7. A method for preparing the environmentally friendly lightweight foamed concrete according to any one of claims 2 to 4, characterized in that: The following steps are involved: (1) preparing carbonized waste concrete fine powder; (2) Mixing silicate cement, carbonized waste concrete fine powder, fly ash, and blast furnace slag fine powder evenly, adding water and waste aggregate, and stirring until a uniform slurry is formed; (3) preparing a composite microbial foaming agent and adding it to the slurry, then adding functional additives and reinforcing fibers, and continuing stirring for 10-15 minutes; (4) Place at 25-40°C for 2-4 hours to allow microbial metabolism and gas production to form a uniform closed-cell structure. (5) The obtained concrete slurry is poured into a mold, and the solidified foam concrete is demoulded and placed in a room with a humidity of 90-95% and a temperature of 20-25°C for curing to the specified age.

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