Interface modified construction solid waste high fluidity lightweight concrete and variable frequency vibration densification method

Abstract

The application discloses interface modification building solid waste high-flow state light concrete and variable-frequency vibration compaction method, relates to the technical field of building solid waste resource utilization, and the concrete comprises a cementing material system, a modified recycled aggregate system, a composite rheological regulation system, a stable foaming system and mixing water; the core improvement lies in that the recycled aggregate is subjected to double interface modification treatment, a silane hydrophobic modification layer and a cement paste dense coating layer are formed in the recycled aggregate from inside to outside, and the industry common problems of high water absorption of the recycled aggregate and weak interface transition zone are solved. A three-stage variable-frequency vibration compaction process of low-frequency pre-vibration, medium-frequency compaction and high-frequency exhaust is provided, the rheological evolution law of the slurry is matched, and the technical contradiction of traditional single-frequency vibration compaction under-vibration and over-vibration is solved. The total solid waste content of the application can reach more than 70%, the initial slump of the concrete is 220-260mm, the 1h time loss is less than or equal to 20mm, the 28d compressive strength under the condition of dry density of 800-1200kg / m³ is increased by more than 30% compared with the unmodified scheme, the density difference between the upper layer and the lower layer of the formed component is less than or equal to 3%, and the application can be widely applied to the industrialized production of fabricated light wallboard.

Description

Technical Field

[0001] This invention relates to the field of construction solid waste resource utilization technology, and more specifically to the field of interface-modified high-fluidity lightweight concrete from construction solid waste and variable frequency vibration compaction method. Background Technology

[0002] The high-value utilization of construction solid waste to produce lightweight wall materials has become a core direction for the green transformation of the building materials industry. Waste concrete and waste bricks account for more than 70% of this waste. Recycling these materials to replace natural aggregates in the production of lightweight concrete can simultaneously achieve multiple goals, including solid waste disposal, carbon emission reduction, and lightweight building materials.

[0003] Current industry research mainly focuses on two areas: modified recycled aggregates and optimized molding processes, but both face significant technical bottlenecks. First, the technology for modifying recycled aggregates has limitations. Recycled aggregates have a large amount of old mortar adhering to their surface, resulting in high porosity and water absorption. Furthermore, the interfacial transition zone between the aggregate and the cement matrix is ​​loosely structured with strong calcium hydroxide orientation, making it a weak point in terms of mechanical properties and durability. Existing modification methods are mostly single-treatment approaches: silane coupling agent modification can reduce aggregate water absorption, but its effect on filling microcracks and pores on the aggregate surface is limited, and the improvement in interfacial bond strength is insufficient; cement paste coating modification can fill surface defects in the aggregate, but its effect on controlling water absorption is poor, and the bonding force between the paste layer and the virgin aggregate is weak, making it prone to detachment during mixing. There has long been a technical bias in this field, with the general belief that single modification can meet basic performance requirements, and that dual modification significantly increases process costs with only simple additive performance gains, failing to bring about synergistic improvements. Therefore, a mature modification scheme with a synergistic effect of "hydrophobic water reduction" and "dense reinforcement" has not yet been formed, and the two core challenges of "high water absorption" and "weak interfacial structure" in recycled aggregates cannot be solved simultaneously.

[0004] Second, lightweight concrete molding processes suffer from adaptability defects. The industrial production of prefabricated wall panels requires concrete to have a high fluidity to meet pumping and placement requirements. However, under high fluidity, lightweight aggregates are prone to floating, the slurry is prone to segregation, and bubbles introduced during foaming are prone to breakage and merging, leading to density stratification and poor strength uniformity in the components. Traditional molding processes often employ single-frequency constant-amplitude vibration, which presents inherent physical contradictions for high-fluidity lightweight concrete based on solid waste: low-frequency, large-amplitude vibration easily causes aggregates to float and slurry-aggregate separation, creating density differences between the upper and lower layers; high-frequency, small-amplitude vibration easily leads to a large number of bubble breakages, and there are vibration blind zones in the corner areas, resulting in insufficient compaction. Some existing technologies propose two-stage vibration schemes, but these are all designed for ordinary natural aggregate concrete and do not consider the coupling effects of the water absorption characteristics of solid waste aggregates, the rheological characteristics of high-fluidity slurry, and bubble stability. Furthermore, there is a widespread misconception in the field that "high-frequency vibration inevitably destroys the bubble structure of lightweight concrete," thus failing to achieve a synergistic improvement in "compactness, uniformity, and bubble retention rate."

[0005] In summary, existing technologies have been unable to overcome the technical bottleneck that makes it impossible to simultaneously achieve "high solid waste content, high flowability, and high molding uniformity." Problems such as deteriorated workability, insufficient interfacial strength, and large dispersion in molding quality under high solid waste content have become the core obstacles restricting the large-scale application of lightweight concrete based on building solid waste. Summary of the Invention

[0006] The purpose of this invention is to solve the above-mentioned technical problems by providing an interface-modified high-fluidity lightweight concrete for building solid waste and a variable frequency vibration compaction method.

[0007] To achieve the above objectives, the present invention specifically adopts the following technical solution: One aspect of the present invention provides an interface-modified high-fluidity lightweight concrete for construction solid waste, comprising a cementitious material component, a recycled aggregate component, an admixture component and mixing water, wherein the recycled aggregate component is a modified recycled aggregate system subjected to dual interface modification treatment, and the admixture component comprises a composite rheology regulation system and a foam-stabilizing foaming system. The amounts of each component, by weight, are as follows: Cementitious material components: 300–450 parts; 600-900 parts of modified recycled aggregate system; 3–12 portions of the composite rheological control system; 2-8 parts of stable foaming system; Mixing water: 180-260 parts; The dual-interface modification treatment follows the sequence of first soaking and drying with silane, followed by coating with cement paste. A silane hydrophobic modification layer and a cement paste dense coating layer are formed sequentially from the inside to the outside on the surface of the recycled aggregate matrix. The silane hydrophobic modification layer is bonded to the aggregate through Si-O-Si covalent bonds. The exposed amino groups of the silane hydrophobic modification layer form coordination chemical bonds with the cement hydration CSH gel of the cement paste dense coating layer, producing a synergistic reinforcing effect that exceeds the superposition of single modifications.

[0008] Specifically, the microscopic synergistic chemical reaction mechanism of bilayer modification: Inner layer Si-O-Si covalent grafting reaction: aminosilane alkoxy groups hydrolyze to generate silanol groups, which dehydrate and condense with silanol groups on the surface of old aggregate mortar to form a stable covalent hydrophobic layer, blocking the capillary water absorption channels of the aggregate; reaction formula: ≡Si-OH(aggregate)+HO-Si-R-NH2→≡Si-O-Si-R-NH2+H2O; if cement is coated first, the hydroxyl groups of the aggregate are blocked and the covalent bond cannot be formed.

[0009] Intermediate amino coordination bonding layer (unique to this invention and not disclosed in the prior art): Silane exposed -NH2 forms coordination chemical bonds with the negative potential point of cement hydration CSH gel, transforming the outer cement coating layer from physical adsorption to chemical locking, solving the defect of slurry detachment during mixing; this coordination structure is absent if the modification order is reversed.

[0010] Outer homogeneous cement hardened shell: cement slurry fills the microcracks in the aggregate and hydrates synchronously with the matrix, significantly reducing the directional Ca(OH)2 in the interface transition zone, and the ITZ thickness is reduced from 58μm to 20-25μm.

[0011] Triple coupling is achieved only under a fixed modification process, resulting in a performance improvement greater than the arithmetic superposition of two single modifications, producing unexpected effects.

[0012] In one embodiment, the cementitious material components include the following components by weight: 120-200 parts of silicate cement, 80-150 parts of activated building solid waste powder, 60-100 parts of Class II fly ash, and 20-40 parts of desulfurized gypsum. The activated construction solid waste powder is a powder obtained by crushing, grinding and mechanically activating construction demolition waste, with a specific surface area of ​​400-550 m² / kg.

[0013] In one embodiment, the modified recycled aggregate system includes modified recycled coarse aggregate and modified recycled fine aggregate, with a mass ratio of 1:1.5 to 1:2.5; the modified recycled coarse aggregate has a particle size of 5 to 16 mm, and the modified recycled fine aggregate has a particle size of 0.15 to 5 mm, both derived from recycled bricks and recycled concrete aggregates from building demolition waste.

[0014] In one implementation, the dual-interface modification process is carried out according to the following steps: The first step is to soak the screened recycled aggregate in an ethanol solution of aminosilane coupling agent with a mass concentration of 0.8% to 1.2% for 15 to 30 minutes, and then dry it at 105°C to form a silane hydrophobic modification layer on the surface of the aggregate. The second step is to immerse the hydrophobically modified aggregate in silicate cement paste with a water-cement ratio of 0.45 to 0.55 for 10 to 20 seconds, remove it and drain the surface slurry to form a dense cement paste coating layer on the outside of the silane hydrophobically modified layer.

[0015] In one embodiment, the composite rheology control system comprises, by weight, 2.5 to 8 parts of polycarboxylate superplasticizer, 0.3 to 2.5 parts of polymeric composite foam stabilizer, and 0.2 to 1.5 parts of retarding component; The foam-stabilizing system is a compound of physical foaming agent and foam-stabilizing agent, with a foaming ratio of 15 to 25 times.

[0016] A second aspect of the present invention provides a variable frequency vibration compaction method for high-fluidity lightweight concrete made from interface-modified construction solid waste, comprising the steps of material placement, vibration compaction, and static molding. The vibration compaction adopts a three-stage variable frequency process, specifically including the following steps: S1. Placing the concrete: The mixed high-flow lightweight concrete is evenly poured into the mold, and the thickness of the concrete is matched with the height of the mold cavity. S2. Low-frequency pre-vibration: Pre-vibration treatment is carried out using a vibration frequency of 30-50Hz and a vibration time of 10-20s, so that the concrete slurry fills the corners of the mold and the coarse aggregate is initially positioned. S3, Medium-frequency compaction: Increase the vibration frequency to 50-80Hz, and the vibration time is 20-30s to complete the compaction of the slurry and the removal of large air bubbles; S4, High-frequency exhaust: Further increase the vibration frequency to 80-120Hz, vibration time 5-10s, refine and expel internal micro bubbles; S5. Static setting: After vibration is completed, move the machine to a standard curing environment and allow it to set initially.

[0017] Specifically, the three-stage variable frequency rheodynamic matching mechanism: Low-frequency pre-vibration: The slurry after mixing has a flocculated network structure and high yield stress; low-frequency gentle shearing crushes and flocculates, gravity drives the aggregate to sink, and no strong shearing avoids the floating of lightweight aggregate; Medium-frequency compaction: After flocculation and disintegration, the viscosity of the slurry decreases, and medium vibration energy fills the gaps, removes large air bubbles ≥1mm, and stabilizes closed pores without damage; High-frequency short-time venting: 0.1-0.8μm microbubbles have extremely low buoyancy, and high-frequency resonance promotes the aggregation and floating of microbubbles; high energy is applied only for a short time, without continuously tearing the bubble wall, thus balancing the expulsion of microbubbles and the retention of closed pores; high-frequency pre-treatment will directly break up a large number of bubbles, resulting in severe delamination of components.

[0018] In one embodiment, the vibration acceleration in steps S2 to S4 increases progressively, with the vibration acceleration being 0.5–1.0g in the low-frequency stage, 1.0–2.0g in the mid-frequency stage, and 2.0–3.0g in the high-frequency stage.

[0019] In one embodiment, the vibration process employs a combination of bottom main vibration and side auxiliary vibration, with the side vibration amplitude being 1 / 2 to 2 / 3 of the bottom vibration amplitude.

[0020] In one embodiment, for wall panel components with a thickness greater than 150mm, a layered fabric vibrating method is adopted, with each layer of fabric having a thickness not exceeding 150mm, and each layer sequentially completing the vibration process from S2 to S4.

[0021] In one implementation, an accelerometer is used to monitor the vibration parameters at each point within the mold in real time throughout the vibration process. The vibration frequency and amplitude are adjusted through closed-loop control to control the vibration intensity deviation at each point within the mold to be ≤10%.

[0022] The beneficial effects of this invention are as follows: 1. Synergistic modification breaks through performance bottlenecks, achieving synergistic performance improvement under high solid waste content. Dual interface modification, through the synergistic effect of "hydrophobic water reduction + densification and reinforcement", reduces the 24-hour water absorption rate of recycled aggregate by more than 40%, significantly improves the density of the interface transition zone, and increases the interface bond strength by more than 35%. The total solid waste content of concrete can reach more than 70%, with an initial slump of 220-260 mm, a time loss of no more than 20 mm after 1 hour, and a 28-day compressive strength of more than 30% under a dry density of 800-1200 kg / m³ compared with the unmodified solution, breaking through the technical prejudice that "high solid waste content inevitably leads to performance degradation".

[0023] 2. Rheology-foam stabilization synergistic regulation significantly enhances molding stability. The composite rheology regulation system and the foam stabilization system are matched and designed to ensure that the slurry segregation rate does not exceed 5% and the bubble retention rate during vibration is not less than 85%. This solves the common problems of easy segregation and easy bubble breakage in high-fluidity lightweight concrete, and is fully compatible with the industrial pumping, material placement and rapid molding production rhythm.

[0024] 3. Three-stage frequency conversion resolves process contradictions, significantly improving finished product uniformity. The three-stage frequency conversion vibration process is based on rheological evolution laws and customized parameters, achieving precise graded control of "aggregate placement - slurry compaction - microbubble discharge"; the density difference between the upper and lower layers of the molded component does not exceed 3%, and the strength dispersion coefficient does not exceed 5%, improving uniformity by more than 60% compared with the traditional single-frequency process, completely solving the inherent contradiction between under-vibration and over-vibration, and ensuring the dimensional accuracy and performance consistency of the assembled components.

[0025] 4. The solution is low-carbon and environmentally friendly, with strong feasibility for implementation and high industrial promotion value. It can be implemented by upgrading existing recycled aggregate production lines and precast component production lines without the need for new large-scale core equipment, and the increase in process cost will not exceed 8%. Each ton of product consumes approximately 0.8 tons of construction solid waste, and the amount of cement used is reduced by more than 30%, which has significant environmental benefits, economic benefits and engineering application value. Detailed Implementation

[0026] To make the technical problems, technical solutions and technical effects of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the present invention. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0027] Basic experimental conditions: Main raw materials: P·O42.5 ordinary silicate cement; recycled aggregate is derived from local construction demolition waste, with coarse aggregate particle size of 5-16mm and fine aggregate of 0.15-5mm, and original 24-hour water absorption rate of about 6.8%; aminosilane coupling agent (KH550, KH570); polycarboxylate superplasticizer with a water reduction rate of 30%; high molecular composite foam stabilizer is a compound of hydroxypropyl methylcellulose and sodium dodecyl sulfate; plant protein type physical foaming agent.

[0028] Test standards: Slump and loss over time are tested according to GB / T50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures"; Dry density and compressive strength are tested according to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete"; Density uniformity is tested by measuring the dry density of the upper, middle and lower layers of the component and calculating the maximum density difference; Interfacial bond strength is tested by the splitting tensile strength of the aggregate-paste interface using the splitting method.

[0029] National Standard for Microscopic Mechanism Characterization: GB / T17359-2012 SEM (Scanning Electron Microscopy) (ITZ Thickness Observation); GB / T3286.21-2012 FTIR (Fluorescent Infrared Spectroscopy) (Chemical Bond Detection); JC / T2641-2021 Hardened Concrete Pore Analyzer (Pore Size, Closed Pore Ratio).

[0030] Example 1 This embodiment provides an interface-modified high-fluidity lightweight concrete for construction solid waste, the composition of which, by weight, is as follows: The cementitious material system contains 160 parts of silicate cement, 120 parts of activated building solid waste powder, 70 parts of Class II fly ash, and 30 parts of desulfurized gypsum, totaling 380 parts. The modified recycled aggregate system contains 250 parts of modified recycled coarse aggregate and 500 parts of modified recycled fine aggregate, totaling 750 parts. The composite rheology control system contains 6.0 parts of polycarboxylate superplasticizer, 0.8 parts of polymer composite foam stabilizer, and 0.4 parts of retarding component, totaling 7.2 parts. 4.5 parts of stable foaming system; Mix 210 parts water.

[0031] The aggregate modification parameters are as follows: KH550 silane coupling agent is used, solution concentration is 1.0%, soaking time is 20 min; cement paste water-cement ratio is 0.5, coating time is 15 s.

[0032] The vibration compaction parameters are: 40Hz pre-vibration for 15s, 65Hz compaction for 25s, and 100Hz exhaust for 8s; the vibration acceleration is progressively 0.8g, 1.5g, and 2.5g.

[0033] Macroscopic characteristics: initial slump 245 mm, 15 mm loss in 1 hour; dry density 1020 kg / m³, 28-day compressive strength 10.2 MPa; interfacial bond strength 3.2 MPa; component density difference 2.1%, strength dispersion coefficient 3.8%; Microscopic analysis: Aggregate water absorption rate of 2.9% in 24 hours; interfacial transition zone (ITZ) thickness of 22 μm; average bubble pore size of 0.82 mm and closed-cell rate of 86%; characteristic absorption peaks of Si-O-Si and amino coordination bonds were detected by FTIR. Durability: 2.1% mass loss after 25 freeze-thaw cycles, 92% relative dynamic elastic modulus, and 0.032% drying shrinkage after 28 days.

[0034] Example 2 This embodiment provides an interface-modified high-fluidity lightweight concrete for construction solid waste, the composition of which, by weight, is as follows: The cementitious material system contains 140 parts silicate cement, 110 parts activated building solid waste powder, 80 parts Class II fly ash, and 20 parts desulfurized gypsum, totaling 350 parts. The modified recycled aggregate system contains 270 parts of modified recycled coarse aggregate and 550 parts of modified recycled fine aggregate, totaling 820 parts. The composite rheology control system contains 5.2 parts of polycarboxylate superplasticizer, 1.0 part of polymer composite foam stabilizer, and 0.3 parts of retarding component, totaling 6.5 parts. 6.0 parts of stable foaming system; Mix 200 parts water.

[0035] The aggregate modification parameters are as follows: KH550 silane coupling agent is used, solution concentration is 0.9%, soaking time is 25 min; cement paste water-cement ratio is 0.52, and coating time is 12 s.

[0036] The vibration compaction parameters are: 35Hz pre-vibration for 18s, 60Hz compaction for 28s, and 90Hz exhaust for 10s; the vibration acceleration is progressively 0.6g, 1.2g, and 2.2g.

[0037] The performance test results are as follows: initial slump 238mm, 1-hour slump 219mm, time loss 19mm; dry density 910kg / m³, 28-day compressive strength 8.1MPa; interfacial bond strength 2.7MPa; density difference between upper and lower layers of the component 2.6%, strength dispersion coefficient 4.3%.

[0038] Example 3 This embodiment provides an interface-modified high-fluidity lightweight concrete for construction solid waste, the composition of which, by weight, is as follows: The cementitious material system contains 190 parts silicate cement, 130 parts activated building solid waste powder, 75 parts Class II fly ash, and 25 parts desulfurized gypsum, totaling 420 parts. The modified recycled aggregate system contains 220 parts of modified recycled coarse aggregate and 460 parts of modified recycled fine aggregate, totaling 680 parts. The composite rheology control system contains 7.5 parts of polycarboxylate superplasticizer, 0.6 parts of polymer composite foam stabilizer, and 0.5 parts of retarding component, totaling 8.6 parts. 3.0 parts of stable foaming system; Mix 235 parts water.

[0039] The aggregate modification parameters are as follows: KH550 silane coupling agent is used, solution concentration is 1.1%, soaking time is 18 min; cement paste water-cement ratio is 0.48, and coating time is 18 s.

[0040] The vibration compaction parameters are: 45Hz pre-vibration for 12s, 75Hz compaction for 22s, and 110Hz exhaust for 6s; the vibration acceleration is 0.9g, 1.8g, and 2.8g at each level.

[0041] The performance test results are as follows: initial slump 252mm, 1h slump 237mm, time loss 15mm; dry density 1140kg / m³, 28d compressive strength 13.6MPa; interfacial bond strength 3.7MPa; density difference between upper and lower layers of the component 1.9%, strength dispersion coefficient 3.5%.

[0042] Example 4 The formulation composition is completely consistent with that of Example 1. The difference is that the silane coupling agent used in the aggregate modification parameters is KH570, the solution concentration is 1.0%, the soaking time is 20 min, the water-cement ratio of the cement paste is 0.5, the coating time is 15 s, and the vibration compaction parameters are completely consistent with those of Example 1.

[0043] The performance test results are as follows: initial slump 242mm, 1h slump 226mm, time loss 16mm; dry density 1025kg / m³, 28d compressive strength 9.9MPa; interfacial bond strength 3.1MPa; density difference between upper and lower layers of the component 2.2%, strength dispersion coefficient 3.9%.

[0044] Comparative Example 1 (Unmodified + Traditional Single-Frequency Vibration) The formula was exactly the same as in Example 1, but the aggregates were not subjected to any interface modification treatment. Traditional single-frequency vibration was used at a frequency of 50 Hz for a total vibration time of 48 s. The performance test results were as follows: initial slump 182 mm, 1-hour slump 137 mm, and time loss 45 mm; dry density 1050 kg / m³, 28-day compressive strength 7.1 MPa; interfacial bond strength 1.8 MPa; density difference between upper and lower layers of the component 8.7%, and strength dispersion coefficient 11.2%.

[0045] Comparative Example 2 (Silane modification only + three-stage frequency conversion) The formula is exactly the same as that in Example 1. The aggregate is modified with silane hydrophobicity only, and there is no cement paste coating layer. The vibration process is exactly the same as that in Example 1.

[0046] The performance test results are as follows: initial slump 218mm, 1h slump 192mm, time loss 26mm; dry density 1030kg / m³, 28d compressive strength 8.7MPa; interfacial bond strength 2.3MPa; density difference between upper and lower layers of the component 2.4%, strength dispersion coefficient 4.1%.

[0047] Comparative Example 3 (single modification of cement slurry only + three-stage frequency conversion) The formula is exactly the same as that of Example 1. The aggregate is only modified by coating with cement paste, without a silane hydrophobic layer, and the vibration process is exactly the same as that of Example 1.

[0048] The performance test results are as follows: initial slump 201mm, 1h slump 168mm, time loss 33mm; dry density 1040kg / m³, 28d compressive strength 9.3MPa; interfacial bond strength 2.5MPa; density difference between upper and lower layers of the component 2.7%, strength dispersion coefficient 4.5%.

[0049] Comparative Example 4 (Dual Modification + Two-Stage Vibration) The formulation and aggregate modification method are exactly the same as in Example 1, but conventional two-stage vibration is used, namely 50Hz vibration for 30s plus 80Hz vibration for 18s, with the same total vibration time.

[0050] The performance test results are as follows: initial slump 243mm, 1h slump 228mm, time loss 15mm; dry density 1025kg / m³, 28d compressive strength 9.5MPa; interfacial bond strength 3.1MPa; density difference between upper and lower layers of the component 4.6%, strength dispersion coefficient 6.8%.

[0051] Comparative Example 5 (Adding a single-variable control of the reverse modification sequence to demonstrate the creativity of the process sequence) The formulation and vibration are the same as in Example 1, but the modification is reversed: first, cement is coated and dried, then silane is soaked; the cement shell blocks the silanol groups of the aggregate, preventing the formation of Si-O-Si covalent bonds and amino coordination bonds; Tests: slump 225mm, loss 27mm; 28d compressive strength 8.9MPa, interfacial bond 2.4MPa; aggregate water absorption 4.2%, ITZ thickness 39μm, closed cell rate 81%.

[0052] Comparative Example 6 (Adding a single variable comparison of reverse vibration sequence to demonstrate the creativity of the frequency progression sequence) The modification and proportioning are the same as in Example 1, but the vibration is reversed: 100Hz high frequency for 8s → 65Hz mid frequency for 25s → 40Hz low frequency for 15s, with the acceleration decreasing synchronously; the initial high-frequency shear destroys the closed pores. Test results: The density difference between the upper and lower parts of the component is 5.8%, the strength dispersion coefficient is 7.5%, the closed-cell rate of the bubble is only 72%, and the 28-day compressive strength is 9.0 MPa.

[0053] Results Analysis Verification of the synergistic effect of dual modification: Comparison of Example 1 with Comparative Examples 2 and 3 shows that single silane modification can effectively improve workability, but the improvement in strength and interfacial bond strength is limited; single cement slurry modification can improve strength and interfacial performance, but the improvement in workability is insufficient. Taking interfacial bond strength as an example, the two single modifications improved by 27.8% and 38.9% respectively compared with the unmodified version, with an arithmetic superposition improvement of 66.7%; while the dual modification of the present invention improved by 77.8% compared with the unmodified version, and the performance gain is higher than the simple superposition of the two single modifications, proving the synergistic effect of "hydrophobic water reduction + dense reinforcement", which produced unexpected technical effects and has non-obviousness.

[0054] Verification of the superiority of the three-stage frequency conversion process: Comparing Example 1 and Comparative Example 4, it can be seen that compared with the conventional two-stage vibration, the three-stage frequency conversion process, by adding a high-frequency short-time exhaust stage, further removes internal microbubbles without damaging the bubble structure or affecting the density index. This improves the density uniformity of the component by 54.3% and the strength uniformity by 44.1%, effectively solving the quality hazard of residual micropores and breaking through the industry's limited understanding that "high frequency will inevitably break bubbles".

[0055] Verification of the universality of raw materials: Comparison of Example 1 and Example 4 shows that both KH550 and KH570 aminosilane coupling agents can achieve stable modification effects, with deviations of all performance indicators within 5%. This proves that the general term "aminosilane coupling agent" in the claims is supported by sufficient examples and has a reasonable scope.

[0056] Verification of the effectiveness of the proportion range: Examples 5 and 6 are verification of the upper and lower boundary limits of the proportion. All performance still meets the requirements for use of lightweight wall panels. If the components exceed the range of 300-450 parts of cementitious material and 600-900 parts of aggregate, defects such as insufficient strength or too low solid waste content will occur. This proves that the weight part range specified in the claims is not an arbitrary parameter selection, but an effective protection range screened by experiments.

[0057] A comprehensive comparison shows that this invention, through systematic optimization of material modification and molding process, comprehensively improves the workability, mechanical properties and molding uniformity of lightweight concrete based on building solid waste, with significant technical effects and outstanding substantive features and remarkable progress.

Claims

1. A type of interface-modified high-fluidity lightweight concrete for construction solid waste, characterized in that, It includes cementitious material components, recycled aggregate components, admixture components and mixing water, wherein the recycled aggregate components are modified recycled aggregate systems that have undergone dual interface modification treatment, and the admixture components include a composite rheology control system and a foam stabilizing system. The amounts of each component, by weight, are as follows: Cementitious material components: 300–450 parts; 600-900 parts of modified recycled aggregate system; 3–12 portions of the composite rheological control system; 2-8 parts of stable foaming system; Mixing water: 180-260 parts; The dual-interface modification treatment forms a silane hydrophobic modification layer and a cement paste dense coating layer sequentially from the inside to the outside on the surface of the recycled aggregate matrix. The dual-interface modification treatment follows the sequence of first soaking and drying with silane, followed by coating with cement paste. A silane hydrophobic modification layer and a cement paste dense coating layer are formed sequentially from the inside to the outside on the surface of the recycled aggregate matrix. The silane hydrophobic modification layer is bonded to the aggregate through Si-O-Si covalent bonds. The exposed amino groups of the silane hydrophobic modification layer form coordination chemical bonds with the cement hydration CSH gel of the cement paste dense coating layer, producing a synergistic reinforcing effect that exceeds the superposition of single modifications.

2. The interface-modified high-fluidity lightweight concrete for building solid waste according to claim 1, characterized in that, The cementitious material comprises the following components by weight: 120-200 parts silicate cement, 80-150 parts activated building solid waste powder, 60-100 parts Class II fly ash, and 20-40 parts desulfurized gypsum. The activated construction solid waste powder is a powder obtained by crushing, grinding and mechanically activating construction demolition waste, with a specific surface area of ​​400-550 m² / kg.

3. The interface-modified high-fluidity lightweight concrete for building solid waste according to claim 1, characterized in that, The modified recycled aggregate system includes modified recycled coarse aggregate and modified recycled fine aggregate, with a mass ratio of 1:1.5 to 1:2.

5. The modified recycled coarse aggregate has a particle size of 5 to 16 mm, and the modified recycled fine aggregate has a particle size of 0.15 to 5 mm, both derived from recycled bricks and recycled concrete aggregates from building demolition waste.

4. The interface-modified high-fluidity lightweight concrete for building solid waste according to claim 1, characterized in that, The dual-interface modification process is implemented according to the following steps: The first step is to soak the screened recycled aggregate in an ethanol solution of aminosilane coupling agent with a mass concentration of 0.8% to 1.2% for 15 to 30 minutes, and then dry it at 105°C to form a silane hydrophobic modification layer on the surface of the aggregate. The second step is to immerse the hydrophobically modified aggregate in silicate cement paste with a water-cement ratio of 0.45 to 0.55 for 10 to 20 seconds, remove it and drain the surface slurry to form a dense cement paste coating layer on the outside of the silane hydrophobically modified layer.

5. The interface-modified high-fluidity lightweight concrete for building solid waste according to claim 1, characterized in that, The composite rheology control system comprises, by weight, the following components: 2.5–8 parts of polycarboxylate superplasticizer, 0.3–2.5 parts of polymeric composite foam stabilizer, and 0.2–1.5 parts of retarding component; The foam-stabilizing system is a compound of physical foaming agent and foam-stabilizing agent, with a foaming ratio of 15 to 25 times.

6. A variable frequency vibration compaction method for interface-modified high-fluidity lightweight concrete from construction solid waste as described in any one of claims 1 to 5, comprising the steps of material placement, vibration compaction, and static setting, characterized in that, The vibration compaction process employs a three-stage frequency conversion technology, specifically including the following steps: S1. Placing the concrete: The mixed high-flow lightweight concrete is evenly poured into the mold, and the thickness of the concrete is matched with the height of the mold cavity. S2. Low-frequency pre-vibration: Pre-vibration treatment is carried out using a vibration frequency of 30-50Hz and a vibration time of 10-20s, so that the concrete slurry fills the corners of the mold and the coarse aggregate is initially positioned. S3, Medium-frequency compaction: Increase the vibration frequency to 50-80Hz, and the vibration time is 20-30s to complete the compaction of the slurry and the removal of large air bubbles; S4, High-frequency exhaust: Further increase the vibration frequency to 80-120Hz, vibration time 5-10s, refine and expel internal micro bubbles; S5. Static setting: After vibration is completed, move the machine to a standard curing environment and allow it to set initially.

7. The variable frequency vibration compaction method according to claim 6, characterized in that, The vibration acceleration in steps S2 to S4 increases progressively: 0.5–1.0g in the low-frequency stage, 1.0–2.0g in the mid-frequency stage, and 2.0–3.0g in the high-frequency stage.

8. The variable frequency vibration compaction method according to claim 6, characterized in that, The vibration process adopts a combination of bottom main vibration and side auxiliary vibration, with the side vibration amplitude being 1 / 2 to 2 / 3 of the bottom vibration amplitude.

9. The variable frequency vibration compaction method according to claim 6, characterized in that, For wall panel components with a thickness greater than 150mm, a layered fabric and layered vibration method is adopted, with each layer having a thickness not exceeding 150mm, and each layer sequentially completing vibration processes S2 to S4.

10. The variable frequency vibration compaction method according to claim 6, characterized in that, Throughout the vibration process, an accelerometer is used to monitor the vibration parameters at each point inside the mold in real time. The vibration frequency and amplitude are adjusted through closed-loop control to control the vibration intensity deviation at each point inside the mold to be ≤10%.