Additional-alkali-free multi-source solid waste-based wood aggregate ecological concrete and preparation method thereof

Abstract

The invention belongs to the technical field of ecological concrete and preparation, and provides multi-source solid-waste-based wood aggregate ecological concrete without additional alkali and a preparation method of the multi-source solid-waste-based wood aggregate ecological concrete. The method comprises the steps that waste wood is crushed and screened, and then wood aggregate is soaked in a Ca (OH) 2 solution to be in a saturated and wet state; the soaked wood aggregate is subjected to microwave radiation treatment, and chemical strengthening is achieved; the red mud is dried, ground and screened, distilled water is added, and the red mud is compounded with desulfurized petroleum coke residues to achieve the effect of replacing an alkali activator; mixing mineral powder, fly ash, red mud, desulfurized petroleum coke residues and regenerated sand powder, adding the modified wood fiber and the modified wood aggregate, then adding a water reducing agent and water, and mixing and stirring to prepare the ecological concrete. The red mud and the desulfurized petroleum coke residues are used as excitants, so that the cost is reduced, and shrinkage is reduced; strengthening is achieved through wood material pretreatment; and the shrinkage reducing and toughening effects are realized by utilizing good water-retaining property and high specific strength of a wood material.

Description

Technical Field

[0001] The present invention belongs to the technical field of ecological concrete and its preparation, and in particular relates to an alkali-free multi-source solid waste-based wood aggregate ecological concrete and a preparation method thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Portland cement (PC), the most commonly used cementitious material in concrete production, generates significant CO2 emissions during its production. The production of one ton of cement emits approximately 0.8-1 ton of CO2. Therefore, there is an urgent need to develop new cementitious materials to replace PC in order to reduce global energy consumption and improve the environment. Furthermore, the large-scale extraction of natural coarse aggregate, the second-largest source of CO2 emissions in concrete, not only consumes significant amounts of non-renewable resources but also places significant pressure on the environment.

[0004] At present, mineral powder, fly ash, red mud and other solid waste materials have been widely used in concrete preparation, but their solid waste proportion and performance still need to be improved.

[0005] Meanwhile, researchers have explored the resourceful utilization of waste wood in the building materials sector. They have developed products such as cement-wood concrete and wood-aggregate high-strength thermal insulation mortar. However, these technologies still use cement and natural river sand as binders and fine aggregates, resulting in relatively high CO2 emissions, poor shrinkage and crack resistance, and low solid waste utilization. Summary of the Invention

[0006] To address these issues, the present invention provides an alkali-free, multi-source solid waste-based wood aggregate eco-concrete and its preparation method. This method efficiently combines industrial, construction, and agricultural and forestry solid wastes, while utilizing red mud and desulfurized petroleum coke residue to achieve zero addition of industrial alkali activators. This method not only effectively reduces drying shrinkage and improves crack resistance, but also enhances solid waste resource utilization and reduces environmental pollution, contributing to the low-carbon and sustainable development of this concrete in the construction industry.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: The first aspect of the present invention provides an alkali-free multi-source solid waste-based wood aggregate ecological concrete, which is composed of the following raw materials in parts by weight: 1 part of mineral powder, 0.25-1.25 parts of fly ash, 0.25-1.25 parts of red mud, 0.5-1 part of desulfurized petroleum coke slag, 3.75-5 parts of regenerated sand powder, 0.25-0.5 part of modified wood aggregate, 0.025-0.125 part of modified wood fiber, 0.25-0.5 part of water reducer, and 0.6-0.8 part of water.

[0008] The second aspect of the present invention provides a method for preparing alkali-free multi-source solid waste-based wood aggregate ecological concrete, comprising: Weighing cementitious materials, aggregates, and modified wood fibers respectively; the cementitious materials are mineral powder, fly ash, red mud, and desulfurized petroleum coke slag; and the aggregates are regenerated sand powder and modified wood aggregates; Mixing the cementitious material and the regenerated sand powder evenly, adding the modified wood fiber and mixing evenly, then adding the modified wood aggregate and mixing evenly, adding the water reducing agent and water and mixing evenly to obtain a concrete mixture; The concrete mixture is placed into a mold, vibrated to form, cured, and demolded to obtain the product.

[0009] The third aspect of the present invention provides the application of the above-mentioned alkali-free multi-source solid waste-based wood aggregate ecological concrete in the field of construction.

[0010] Beneficial effects of the present invention (1) The raw materials used in this invention come from a wide range of sources, including industrial solid waste, construction solid waste, and agricultural and forestry solid waste. No cement is used. The cementitious materials are all derived from industrial solid waste, the fine aggregate is obtained from demolished construction waste, and the coarse aggregate is derived from waste wood collected from wood processing plants and furniture factories. The use of these materials has made significant contributions to saving natural resources, improving the utilization rate of solid waste, reducing production costs, and achieving sustainable development.

[0011] (2) The mineral powder, fly ash, red mud, and desulfurized petroleum coke residue used in the present invention are rich in components such as CaO, SiO2, Na2O, Fe2O3, and SO3. The cementitious material formed from these components is similar in composition to Portland cement and possesses potential cementitious properties. Furthermore, the soluble alkali contained in the red mud and the calcium-based activation potential of the desulfurized petroleum coke residue eliminate the need for alkaline activators in the alkali-activated material. This significantly reduces the environmental hazards caused by alkali leaching and reduces production costs.

[0012] (3) The processing method of the wood material used in the present invention is relatively simple, without the need for a large amount of modifiers and multiple drying, pulping and other process treatments. After multiple crushing and screening, the needle-like particles can be screened out, making its performance close to that of natural aggregate. The Ca(OH)2 solution is used to enhance the electrical conductivity of the wood material, so that the wood material absorbs radiation energy during the microwave pre-drying process, thereby generating carbon fibers and CaCO3 crystals on the surface. The above two methods not only enhance the hardness of the wood material, but also improve its poor bonding with cement-based materials, achieving dual physical and chemical reinforcement, thereby significantly improving the performance of ecological concrete.

[0013] (4) The present invention proposes a method for preparing alkali-free multi-source solid waste-based wood aggregate ecological concrete, which firstly mixes multi-source solid waste cementitious materials, recycled sand powder and wood fiber, and then adds modified wood aggregate to improve the toughness and shrinkage properties of the ecological concrete.

[0014] (5) The performance test results of the alkali-free multi-source solid waste-based wood aggregate ecological concrete prepared by the present invention show that its mixture has good fluidity; the 28d compressive strength is 35.6-43.1 MPa, and the flexural strength is 4.7-6.3 MPa, which is the same as or even better than the control group; the number of initial cracks is 28-43 times, the number of failures is 36-54 times, and the 150d drying shrinkage is (189.9-284.1×10 -6 ), easy to demould and smooth surface after molding, no cracking and alkali efflorescence occurred during the curing process; compared with the control group 1 and control group 2, the CO2 emissions of the multi-source solid waste-based wood aggregate ecological concrete without added alkali were reduced by 35-43% and 8.9-30.7%, and the cost was reduced by 33-43.6% and 25.4-37.2%, which greatly improved the environmental and economic benefits.

[0015] Obviously, the present invention combines industrial solid waste, construction solid waste and agricultural and forestry solid waste to develop a multi-level and diversified alkali-free multi-source solid waste-based wood aggregate ecological concrete, breaking through the technical bottlenecks of alkali-activated recycled concrete such as large shrinkage and easy cracking, achieving "zero addition" of alkali activators, and promoting the sustainable development of ecological concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0017] Figure 1This is a typical preparation flow chart of the alkali-free multi-source solid waste-based wood aggregate eco-concrete specimen of Example 1; wherein, 1-waste wood; 2-primary crushing product; 3-wood fiber and wood aggregate after secondary crushing; 4-wood material mixture after soaking; 5-wood material mixture after microwave burning; 6-mixing product of multi-source solid waste-based wood aggregate eco-concrete; 7-Ca(OH)2 solution; 8-mixture of water reducer and water; 9-mixture of mineral powder, fly ash, red mud, desulfurized petroleum coke slag and regenerated sand powder; 10-primary crushing; 11-secondary crushing and screening; 12-soaking; 13-microwave burning; 14-stirring; A-agricultural crusher; B-shaking screen; C-wood tearing machine; D-industrial microwave oven.

[0018] Figure 2 Figure 1 shows the failure morphology of the specimens from Example 1 after the compressive strength test. a is the modified wood aggregate, b is the modified wood fiber, and c is the hydration product of the multi-source solid waste-based wood aggregate eco-concrete. DETAILED DESCRIPTION

[0019] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0020] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in accordance with conventional methods in the art or according to product specifications. Similarly, unless otherwise specified, the test methods of the present invention are also tested in accordance with conventional methods in the art or the common methods or standards in the industry. In addition, any methods and materials similar to or equivalent to the described contents can be applied to the inventive method. The preferred embodiments and materials described herein are for demonstration purposes only.

[0021] The first aspect of the present invention provides an alkali-free multi-source solid waste-based wood aggregate ecological concrete, which is composed of the following raw materials in parts by weight: 1 part of mineral powder, 0.25-1.25 parts of fly ash, 0.25-1.25 parts of red mud, 0.5-1 part of desulfurized petroleum coke slag, 3.75-5 parts of regenerated sand powder, 0.25-0.5 part of modified wood aggregate, 0.025-0.125 part of modified wood fiber, 0.25-0.5 part of water reducer, and 0.6-0.8 part of water.

[0022] In some embodiments, the quality of the mineral powder and fly ash is S95 grade mineral powder and grade II fly ash, respectively. Mineral powder and fly ash are typical solid wastes from metallurgy and coal-fired power plants, have high silicon-aluminum activity, and can react with alkali activators to form stable cementitious phases. Mineral powder and fly ash are representative materials of alkali-activated high-calcium materials and alkali-activated low-calcium materials, and their components are rich in CaO, SiO2 and Al2O3. Mineral powder is a high-activity powder obtained by drying, grinding and other processes of water-quenched blast furnace slag, and has good hydraulic cementitious properties. Ultrafine slag can not only reduce the cost of concrete, but also has obvious effects on inhibiting alkali-aggregate reaction, reducing hydration heat, and reducing early temperature cracks in concrete structures. Fly ash particles contain more than 70% spherical microspheres, which can exert a ball effect and effectively improve the workability of concrete slurry and the shrinkage of the hardened body.

[0023] In some embodiments, the red mud is dried, ground and sieved; The treated red mud was then placed in a volumetric flask, distilled water was added, and the mixture was shaken for 30 minutes. The clarified solution was filtered and dried to obtain a soluble alkali content of 3.87%. The soluble alkali content of different batches of red mud was determined according to the above method.

[0024] Alternatively, Bayer red mud, due to its high content of Na2O, SiO2, and Al2O3, also possesses potential for gelling properties. Red mud has a large specific surface area and contains a large amount of soluble NaOH. Proper use of red mud can not only reduce the use of industrial caustic soda and effectively address the ecological safety risks posed by leachate, but also improve the pore structure of hardened cement paste, enhancing its mechanical properties and durability.

[0025] In some embodiments, the red mud has a soluble alkali content of 3.87% or greater. Red mud, a waste residue from the alumina extraction process from bauxite, is rich in elements such as iron, aluminum, and silicon and has potential gelling activity. However, due to its strong alkalinity and complex composition, it can cause ecological imbalances around the storage area, posing a serious threat to the environment and ecological safety. However, through appropriate treatment, it can be enhanced with alkali activation and silica-alumina activity.

[0026] Desulfurized petroleum coke slag is the residual ash after petroleum coke and desulfurizer are calcined at high temperature in a circulating fluidized bed boiler. Its main components are CaO and SO3, which are the same as the components of lime and gypsum, and can provide the required calcium and sulfur elements for the hydration reaction. It has good calcium-based activator properties. At the same time, using desulfurized petroleum coke slag to replace cement in concrete production can not only reduce the emission of cement clinker and CO2, but also turn desulfurized petroleum coke slag from "waste" to "treasure", thereby improving its resource utilization. Therefore, in some embodiments, the main mineral components of the desulfurized petroleum coke slag are f-CaO and CaSO4, the fineness modulus is 1.8, and the effective CaO content is 42.78%. On the one hand, compared with sodium-based activators, it can better stimulate the activity of silicon and aluminum components in solid wastes such as mineral powder, fly ash, and red mud, ensuring the continuous growth of the strength of the cementitious system; on the other hand, although combining desulfurized petroleum coke slag with conventional cement systems can easily cause expansion, cracking and damage to the cementitious system, and conventional alkali-activated cementitious materials themselves shrink greatly, when it is introduced into alkali-activated cementitious materials as a calcium-based activator, its own expansion characteristics can be exerted, effectively reducing the shrinkage and cracking tendency of the corresponding alkali-activated cementitious system.

[0027] Preferably, red mud and desulfurized petroleum coke residue are compounded so that the OH - Ion concentration and OH of conventional alkali activator (activator concentration is calculated as Na2O in the amount of cementitious material, concentration is 3%, modulus 1) - The ion concentration is the same. The specific calculation is as follows: Assume that the amount of cementitious materials in red mud, desulfurized petroleum coke residue and control group 2 are a, b and x respectively. According to formula (1), the required OH- ion concentration is 0.5219x. - The ion concentration is 0.016a. At the same time, according to formula (2), the OH contained in the desulfurized petroleum coke residue is - The ion concentration is 0.5599b. Based on the above, we can get formula (3).

[0028] 2NaOH=Na2O+H2O (1) CaO+H2O=Ca(OH)2(2) 0.5219x=0.016a+0.5599b(3) Furthermore, the reaction equations of red mud and desulfurized petroleum coke residue stimulating mineral powder and fly ash are as follows: ≡Si-O-Ca-O-Si≡+2NaOH→2(≡Si-O-Na )+Ca 2+ +2OH - (4) SiO2+m1Ca(OH)2+m2H2O→m1CaO·SiO2·(m1+ m2)H2O (5) Al2O3+M1Ca(OH)2+M2H2O→M1CaO·Al2O3·(M1+ M2) H2O (6) SiO2+n1NaOH+n2H2O→n1NaO·SiO2·(n1+ n2)H2O (7) Al2O3+N1NaOH+N2H2O→n1NaO·Al2O3·(N1+N2) H2O (8) Obviously, mineral powder, fly ash, red mud and desulfurized petroleum coke slag in industrial solid waste can be used to directly obtain multi-solid waste-based cementitious materials, while eliminating the addition of alkali activators, thereby balancing the workability, mechanical properties, volume stability, durability and economic and environmental benefits of the corresponding ecological concrete.

[0029] In some embodiments, the regenerated sand powder is Class II medium sand having a particle size of less than 4.75 mm and a fineness modulus of 2.7; In some embodiments, the regenerated sand powder is a regenerated sand powder formed by simple crushing and particle shaping of waste concrete, comprising regenerated micropowder with a particle size of less than 0.075 mm and regenerated sand with a particle size of 0.075-4.75 mm, wherein a large amount of old mortar and brick powder particles are contained. The components are mainly SiO2, Al2O3 and CaO in order of content, which are the same as the composition of silicate cement, and show a certain excitation activity.

[0030] In some embodiments, wood aggregate is collected from the wood processing industry and the furniture industry, and is subjected to simple crushing, secondary crushing, and screening by an agricultural crusher, a wood tearing machine, and a shaking screen, respectively, to obtain wood fiber, wood medium particles, and wood coarse particles with particle sizes ranging from 0-4.75 mm, 4.75-9.5 mm, and 9.5-19 mm, respectively; that is, a mixture of wood fiber and wood aggregate.

[0031] In some embodiments, the amount of wood fiber is 2% of the mass of the cementitious material, the mixing ratio of the medium wood particles and the coarse wood particles is 1:0.5, and the total amount of the two accounts for 20%-40% of the volume of the concrete; In some embodiments, the modified wood aggregate is prepared by pre-soaking the wood material in a Ca(OH)2 solution and then subjecting it to microwave radiation treatment; In some embodiments, the mass ratio of the wood material to Ca(OH)2 is 1.25-1.5:1, and the concentration of the Ca(OH)2 solution is 5%-8%; sufficient stirring is required during soaking to ensure that the wood material reaches a saturated state.

[0032] In some embodiments, the soaking time is ≥30 min; In some embodiments, the microwave radiation treatment is 800W microwave radiation for 3 minutes to generate a small amount of carbon fiber and CaCO3 crystals on the surface and improve the bonding between the wood material and the alkali-activated gelling material.

[0033] Compared to mineral aggregates and other biomass aggregates (corn cobs, coconut shells, and rice husks), wood aggregates offer high yield and specific strength. Their excellent water retention increases the humidity in the area surrounding the aggregates, effectively promoting the continuous hydration of the cementitious material and reducing drying shrinkage of the concrete. Furthermore, their high strength-to-weight ratio and ductility increase the deformability and toughness of concrete, potentially inhibiting shrinkage cracking. Ultimately, while maintaining mechanical properties and improving solid waste utilization, multi-source solid waste-based wood aggregate eco-concrete can achieve shrinkage reduction and toughening effects, reduce cracking, and improve volume stability.

[0034] In some embodiments, the water reducer is one of polycarboxylic acid, aliphatic, and melamine resin high-efficiency water reducers, and the water reduction rate exceeds 30%.

[0035] More specifically, they include: (1) Weigh the cementitious materials (mineral powder, fly ash, red mud, desulfurized petroleum coke slag), aggregates (recycled sand powder and modified wood aggregate), and modified wood fiber respectively; (2) The cementitious material and the regenerated sand powder were placed in a wet mixer and stirred for 30 seconds, and then the modified wood fiber was added and stirred for 30 seconds. The modified wood aggregate was added and stirred for 1 minute, and then the water reducer and water were added and stirred for 1 minute. (3) The concrete mixture obtained in (2) is placed into a mold and vibrated to form alkali-free multi-source solid waste-based wood aggregate ecological concrete. It should be noted that since wood materials are light in texture and have a large difference in specific gravity from cementitious materials, the vibration time should be strictly controlled within 8-10 seconds to avoid aggregate stratification and floating caused by excessive vibration time.

[0036] (4) After the vibration is completed and the film is covered and cured for 12 hours in a natural environment, the formwork is removed and then cured under standard conditions (20±2℃, relative humidity>90%) and dry conditions (20±2℃, relative humidity 60±5%) to the specified age for various performance tests such as strength, toughness and shrinkage.

[0037] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0038] The performance testing methods of the following examples and comparative examples are as follows: 1. According to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GB / T 50081-2019), the 100mm thick concrete of the multi-source solid waste-based wood aggregate prepared in this embodiment was tested. 3 28d compressive strength of the specimen, 100×100×400mm 3 Three-point flexural strength of the specimen.

[0039] 2. The number of initial cracks and the number of failures on the surface of the φ100×50 mm sample of the multi-source solid waste-based wood aggregate eco-concrete prepared in this embodiment were tested according to the drop hammer impact circular plate method recommended by the American Concrete Institute ACI-544.

[0040] 3. According to the "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete" (GB / T 50082-2009), the multi-source solid waste-based wood aggregate ecological concrete prepared in this example was tested. 3 Free shrinkage rate of the specimen at 150d.

[0041] 4. According to the "Building Carbon Emission Calculation Standard" (GB / T51366-2019), the CO2 emission of the multi-source solid waste-based wood aggregate eco-concrete prepared in this embodiment is 255.63 kg CO2 / m 3 .

[0042] 5. Based on Qingdao Construction Material Price and Cost Index and market research, as of March 2025.

[0043] In the following examples and comparative examples, collected waste wooden furniture was used as the wood material.

[0044] Example 1 This embodiment proposes an alkali-free, multi-source solid waste-based wood aggregate eco-concrete. The weight proportions of the raw materials are as follows: 1 part mineral powder, 0.25 part fly ash, 1.25 parts red mud, 0.5 parts desulfurized petroleum coke slag, 3.75 parts regenerated sand powder, 0.25 parts modified wood aggregate, 0.025 parts modified wood fiber, 0.25 parts water reducer, and 0.6 parts water. The preparation method of the alkali-free, multi-source solid waste-based wood aggregate eco-concrete is as follows: (1) Use an agricultural crusher, tearer, and shaker to crush and screen the wood material. Mix the wood medium particles with particle sizes ranging from 4.75 to 9.5 mm and 9.5 to 19 mm with the wood coarse particles at a ratio of 1:0.5 (mass ratio) to form the wood aggregate. At the same time, collect the wood fiber with a particle size range of 0 to 4.75 mm for later use.

[0045] (2) Pre-soak the wood aggregate and wood fiber obtained in (1) in a 5% Ca(OH)2 solution (0.2 parts by mass). Stir thoroughly to allow the wood to fully absorb the solution. Soak for 30 minutes, during which time the material must be sealed.

[0046] (3) After pre-soaking, the wood material was subjected to microwave irradiation treatment at a power of 800 W for 3 min to obtain modified wood aggregate and modified wood fiber, respectively.

[0047] (4) Use a jaw crusher, a particle shaper and a shaker to crush, shape and screen the waste concrete to obtain Class II recycled sand powder.

[0048] (5) According to the above-mentioned component proportions, mineral powder, fly ash, red mud, desulfurized petroleum coke slag, regenerated sand powder, modified wood aggregate, modified wood fiber and water are weighed and set aside.

[0049] (6) 1 part of mineral powder, 0.25 parts of fly ash and 1.25 parts of red mud were mixed evenly to obtain a multi-source solid waste cementitious material, and then mixed with 3.75 parts of recycled sand powder for 30 seconds, and then mixed with 0.05 parts of modified wood fiber for 30 seconds. Subsequently, modified wood aggregate was added and stirred for 1 minute. Finally, a water reducer and water were added and stirred for 1 minute to obtain a multi-source solid waste-based wood aggregate ecological concrete.

[0050] (7) The mixture is placed in a mold and vibrated on a vibration table for 8-10 seconds. After the vibration is completed, the mixture is covered and cured in a natural environment for 12 hours before being removed from the mold. The mixture is then cured to the specified age and tested for strength, toughness, carbon emission, and shrinkage properties.

[0051] Example 2 This embodiment proposes a multi-source solid waste-based wood aggregate ecological concrete without added alkali, which differs from Example 1 in that it contains 0.75 parts of mineral powder, 0.75 parts of fly ash, 0.75 parts of red mud, and 0.75 parts of desulfurized petroleum coke residue. The alkali-free multi-source solid waste-based wood aggregate ecological concrete and its preparation method in this embodiment are the same as those in Example 1 and will not be described in detail.

[0052] Example 3 This embodiment proposes a multi-source solid waste-based wood aggregate ecological concrete without added alkali, which differs from Example 1 in that it contains 0.5 parts of mineral powder, 1.25 parts of fly ash, 0.25 parts of red mud, and 1 part of desulfurized petroleum coke slag. The alkali-free multi-source solid waste-based wood aggregate ecological concrete and its preparation method in this embodiment are the same as those in Example 1 and will not be described in detail.

[0053] Example 4 This embodiment proposes a multi-source solid waste-based wood aggregate ecological concrete without added alkali. The weight proportions of the raw materials are as follows: 1 part of mineral powder, 0.25 parts of fly ash, 1.25 parts of red mud, 0.5 parts of desulfurized petroleum coke slag, 5 parts of regenerated sand powder, 0.375 parts of modified wood aggregate, 0.075 parts of modified wood fiber, and 0.7 parts of water.

[0054] The alkali-free multi-source solid waste-based wood aggregate ecological concrete and its preparation method in this embodiment are the same as those in Example 1 and will not be described in detail.

[0055] Example 5 This embodiment proposes an alkali-free multi-source solid waste-based wood aggregate ecological concrete, which differs from the fourth embodiment in that it contains 0.5 parts of modified wood aggregate, 0.125 parts of modified wood fiber, and 0.8 parts of water.

[0056] The alkali-free multi-source solid waste-based wood aggregate ecological concrete and its preparation method in this embodiment are the same as those in Example 1 and will not be described in detail.

[0057] Control group 1 C30 grade Portland cement concrete was prepared by conventional mechanical mixing method, and the corresponding material mass ratio was: cement: river sand: crushed stone: water reducer: water = 1:1.75:3:0.01:0.375.

[0058] Control group 2 Alkali-activated concrete was prepared by conventional mechanical mixing method. The concentration of alkali activator (the mass percentage of Na2O in cementitious material) was 3%, the modulus was 1, and the corresponding material mass ratio was: mineral powder: river sand: crushed stone: NaOH: water glass: water = 1:1.75:3:0.025:0.1:0.47.

[0059] Control group 3 The difference from Example 1 is that an equal amount of C30 grade Portland cement is used to replace the solid waste gel material (1 part of mineral powder, 0.25 parts of fly ash, 1.25 parts of red mud, and 0.5 parts of desulfurized petroleum coke residue).

[0060] Control group 4 The difference from Example 1 is that ordinary wood aggregate is used and no Ca(OH)2 solution pretreatment and microwave pre-drying are performed.

[0061] Table 1 shows the concrete mechanical properties, fracture toughness, shrinkage properties, carbon emissions and economic costs of Examples 1-5 of the present invention and Control Groups 1, 2, 3, 4, 5 and 6.

[0062]

[0063] From the comparison between Example 1 and Control Groups 1 and 2, it can be seen that compared with the cement slurry or alkali-activated concrete prepared by the traditional mixing method, the multi-source solid waste-based wood aggregate ecological concrete of the present invention has better strength performance, durability, lower carbon emissions and cost, and at the same time, the crack resistance is significantly improved.

[0064] From the comparison between Example 1 and Control Group 3, it can be seen that compared with the commercially available C30 grade Portland cement, the multi-source solid waste-based wood aggregate eco-concrete of the present invention has significantly improved strength, crack resistance and durability, lower carbon emissions and lower cost.

[0065] From the comparison between Example 1 and Control Group 4, it can be seen that compared with ordinary wood aggregate, the concrete prepared using the modified wood material has better strength, crack resistance and durability, and the carbon emissions and costs are only slightly increased. The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. An alkali-free multi-source solid waste-based wood aggregate ecological concrete, characterized in that: The invention is composed of the following raw materials in parts by weight: 1 part of mineral powder, 0.25-1.25 parts of fly ash, 0.25-1.25 parts of red mud, 0.5-1 part of desulfurized petroleum coke slag, 3.75-5 parts of regenerated sand powder, 0.25-0.5 part of modified wood aggregate, 0.025-0.125 part of modified wood fiber, 0.25-0.5 part of water reducer and 0.6-0.8 part of water.

2. The alkali-free multi-source solid waste-based wood aggregate ecological concrete according to claim 1, characterized in that: The quality of the mineral powder and fly ash are S95 grade mineral powder and II grade fly ash respectively.

3. The alkali-free multi-source solid waste-based wood aggregate ecological concrete according to claim 1, characterized in that: The red mud is dried, ground and sieved; Alternatively, the red mud has a soluble alkali content of ≥3.87%.

4. The alkali-free multi-source solid waste-based wood aggregate ecological concrete according to claim 1, characterized in that: The main mineral components of the desulfurized petroleum coke slag are f -CaO and CaSO4, the fineness modulus is 1.8, and the effective CaO content is 42.78%.

5. The alkali-free multi-source solid waste-based wood aggregate ecological concrete according to claim 1, characterized in that: The regenerated sand powder is Class II medium sand with a particle size of less than 4.75 mm and a fineness modulus of 2.7; Alternatively, the regenerated sand powder is formed by simply crushing and particle shaping of waste concrete, and comprises regenerated micro powder with a particle size of less than 0.075 mm and regenerated sand with a particle size of 0.075-4.75 mm.

6. The alkali-free multi-source solid waste-based wood aggregate ecological concrete according to claim 1, characterized in that: Wood aggregates are collected from the wood processing and furniture industries and are subjected to simple crushing, secondary crushing, and screening using agricultural crushers, wood tearers, and shaker screens, respectively, to obtain wood fiber, wood medium particles, and wood coarse particles with particle sizes ranging from 0-4.75mm, 4.75-9.5mm, and 9.5-19mm, respectively. Alternatively, the amount of wood fiber is 2% of the mass of the cementitious material, the mixing ratio of medium wood particles and coarse wood particles is 1:0.5, and the total amount of the two accounts for 20%-40% of the concrete volume.

7. The alkali-free multi-source solid waste-based wood aggregate ecological concrete according to claim 1, characterized in that: The wood material was pre-soaked in Ca(OH)2 solution and then subjected to microwave irradiation treatment; Alternatively, the mass ratio of wood material to Ca(OH)2 is 1.25-1.5:1, and the concentration of Ca(OH)2 solution is 5%-8%; Or, soaking time ≥30min; Alternatively, the microwave radiation treatment is 800W microwave radiation for 3 minutes.

8. The alkali-free multi-source solid waste-based wood aggregate ecological concrete according to claim 1, characterized in that: The water reducer is one of the polycarboxylic acid, aliphatic and melamine resin high efficiency water reducers with a water reduction rate of more than 30%.

9. A method for preparing alkali-free multi-source solid waste-based wood aggregate ecological concrete, characterized in that: include: Weighing cementitious materials, aggregates, and modified wood fibers respectively; the cementitious materials are mineral powder, fly ash, red mud, and desulfurized petroleum coke residue; and the aggregates are regenerated sand powder and modified wood aggregates; Mixing the cementitious material and the regenerated sand powder evenly, adding the modified wood fiber and mixing evenly, then adding the modified wood aggregate and mixing evenly, adding the water reducing agent and water and mixing evenly to obtain a concrete mixture; The concrete mixture is placed into a mold, vibrated to form, cured, and demolded to obtain the product.

10. Application of the alkali-free multi-source solid waste-based wood aggregate ecological concrete according to any one of claims 1 to 8 in the field of construction.

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