Composite foaming preparation method of light sound insulation hollow brick

Abstract

The invention relates to the technical field of building material preparation, and discloses a composite foaming preparation method of a light sound-insulation hollow brick, which comprises the following steps: firstly, preparing a negative coordination precursor solution, forming a complex by using sodium gluconate and borax, and dissolving sodium alginate; performing dry premixing on the lithium salt coagulant, the cement and the mineral admixture; mixing the precursor solution, the dry powder and the prefabricated foam to prepare slurry; after pouring, calcium ions excited by lithium salt are used for replacing borate radicals in the precursor solution, and the slurry is induced to generate rheological mutation in a standing stage, so that bubbles and a hollow structure are locked; and finally, curing and demolding to obtain a finished product. By constructing a negative coordination shielding and ion replacement triggering mechanism, the problems that high-porosity slurry is prone to mold collapse and poor in foam stability are solved, an organic gel network is formed in a matrix, and the acoustic damping performance and mechanical stability of the hollow brick are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of building material preparation technology, specifically to a composite foaming preparation method for lightweight sound-insulating hollow bricks. Background Technology

[0002] Lightweight hollow bricks are widely used in prefabricated buildings and non-load-bearing wall construction due to their low density and excellent thermal insulation properties. Currently, these materials are mostly prepared using foamed concrete or aerated concrete processes, which reduce density by introducing a large number of pores into the cement matrix. However, existing preparation processes have significant limitations in the pursuit of high porosity and integrated hollow structure molding.

[0003] In terms of rheological control, there is an inherent contradiction between the fluidity of the slurry and the stability of the bubbles. To ensure that the slurry can smoothly fill complex hollow molds and achieve self-leveling, the slurry needs to maintain a low initial viscosity. However, in a low-viscosity environment, physical foams are prone to floating, layering, or even merging and bursting due to buoyancy, leading to mold collapse, uneven density, or defects in the pore wall structure of the finished product. Although existing technologies often improve the stability of the slurry by adding thickeners or early-strength agents, this often increases the stirring resistance, causing mechanical damage to the foam during mixing, and makes it difficult to accurately control the time point at which the slurry loses its fluidity, thus failing to meet the special requirements of the construction window period for continuous casting of hollow bricks.

[0004] In terms of acoustic performance, according to the acoustic mass law, the sound insulation of a material is generally proportional to its surface density. Lightweight hollow bricks, due to their significantly reduced density, often experience a decline in sound insulation performance, especially in the low-frequency range. Furthermore, traditional cement-based porous materials are rigid porous bodies, lacking effective viscoelastic damping components. This results in low energy dissipation efficiency of sound waves propagating through the pore walls, making it difficult to achieve efficient sound insulation without increasing density.

[0005] Therefore, developing a composite foaming preparation method that can ensure good initial fluidity of the slurry, achieve rapid rheological locking after casting, and take into account both structural stability and acoustic damping performance is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a composite foaming preparation method for lightweight sound-insulating hollow bricks. The aim is to solve the problems in existing technologies where foamed cement slurry, in pursuit of high porosity and hollow molding, struggles to balance fluidity and foam stability, leading to easy mold collapse and uneven pore distribution. It also addresses the issues of insufficient low-frequency sound insulation performance of traditional lightweight cement-based materials due to their high rigidity and lack of damping components.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing lightweight sound-insulating hollow bricks through composite foaming, comprising the following steps: S1. Preparation of negative coordination precursor solution: Under heating conditions, sodium gluconate and borax are dissolved in process water, the pH value is adjusted to the alkaline range, and then sodium alginate is added and stirred to dissolve, thus obtaining the negative coordination precursor solution. S2, Solid-phase dry powder premix: Lithium salt accelerator is dry-mixed with cement and mineral admixtures to obtain homogenized dry powder; S3. Slurry compounding: The negative coordination precursor liquid is mixed with the homogenized dry powder, and then pre-made foam is added and mixed to obtain a composite foaming slurry. S4. Casting and rheological change: The composite foaming slurry is cast into a mold and left to stand to allow the slurry to solidify and maintain the bubble structure; S5. Curing and demolding: After the slurry has hardened, demold and cure it.

[0008] By adopting the above technical solution and utilizing the timing control of chemical reactions between components, the problems of easy collapse and insufficient strength of foamed cement slurry under high porosity were solved. Its specific mechanism of action is as follows: First, by adjusting the pH to an alkaline environment, a complex is formed between the polyhydroxyl structure of gluconate and borate ions. This complexation shields the borate ions, reducing their retarding effect on cement hydration, and also inhibits premature cross-linking of borax and sodium alginate. Therefore, during the slurry compounding stage, the slurry maintains a low viscosity, which is beneficial for powder dispersion and uniform mixing of physical foam, avoiding difficulties in mixing or bubble breakage caused by excessive viscosity.

[0009] Secondly, kinetic triggering and structural fixation are achieved in step S4. The lithium salt accelerator in the slurry accelerates the hydration of cement clinker, leading to an increase in calcium ion concentration in the liquid phase. This increase in calcium ions disrupts the coordination balance between boric acid and gluconic acid, displacing borate ions. The released borate ions complex with the sodium alginate molecular chains, while the generated calcium ions combine with guluronic acid blocks in sodium alginate to form a calcium-alginate gel.

[0010] Finally, the dual network formed by the above reactions causes rheological changes in the slurry during a specific settling period, increasing the yield stress. This process physically fixes air bubbles and hollow structures before the cement sets, preventing foam from rising or merging. Furthermore, the generated alginate-boronate interpenetrating network is distributed within the cement matrix, acting as a viscoelastic damping material and improving the low-frequency sound insulation performance of the hollow bricks.

[0011] Preferably, the composite foaming slurry is made from raw materials comprising the following parts by weight: the solid phase system comprises 70-90 parts cement, 10-30 parts mineral admixtures, and 0.05-0.4 parts lithium salt accelerator; the liquid phase system comprises 35-45 parts process water, 0.08-0.25 parts sodium gluconate, 0.22-0.8 parts borax, and 0.3-0.8 parts sodium alginate; and the foaming system comprises 1.0-3.0 parts foaming agent and 15-25 parts foaming water.

[0012] By adopting the above technical solution, the proportions of each component have been optimized, balancing the requirements for solid-phase framework strength and liquid-phase rheological control. The synergistic effect of the lithium salt, borax, and sodium alginate system ensures that the rheological abrupt change occurs within a suitable operating time, taking into account both the fluidity during casting and the structural stability after settling.

[0013] Preferably, in step S1, the heating condition is to control the solution temperature at 30-40°C; the adjustment of the pH value to alkaline specifically involves using a sodium hydroxide solution to adjust the pH value to 9.5-10.5.

[0014] By employing the above technical solution, the stability of the boric acid-gluconic acid complex is ensured through temperature and pH control. Deviations in pH or temperature from the set range may lead to premature dissociation of the complex or insufficient stability, thereby affecting the initial viscosity of the slurry or the subsequent reaction process.

[0015] Preferably, in step S1, the molar ratio of borax to sodium gluconate is (1.5-2.5):1; the dissolution process after adding sodium alginate is to stir at a speed of 800-1000 r / min for 20-30 minutes.

[0016] By employing the above technical solution, the molar ratio is controlled so that boron in the solution exists mainly in a complexed state, thereby controlling the reaction initiation threshold. The stirring process ensures that sodium alginate is fully dissolved and dispersed in a specific ionic environment, providing a basis for the formation of a uniform gel network.

[0017] Preferably, in step S2, the specific operation of the solid dry powder premix is ​​as follows: first, the lithium salt accelerator is mixed and dispersed with cement, and then the resulting mixture is mixed with the remaining cement and the mineral admixture, and the mixing time is not less than 3 minutes.

[0018] By adopting the above technical solution, the multi-stage dispersion process improves the uniformity of the distribution of trace lithium salt coagulant in the powder, reduces the fluctuation of slurry performance caused by local concentration differences, and ensures the consistency of overall rheological changes.

[0019] Preferably, in step S3, the mixing process for the slurry composite includes: a first stage: mixing the negative coordination precursor liquid with the homogenized dry powder and stirring the slurry at a speed of 1000-1500 r / min for 60-120 seconds; a second stage: adding the pre-made foam and stirring the slurry at a speed of 100-200 r / min for 30-60 seconds.

[0020] By adopting the above technical solution, the high-speed stirring in the first stage utilizes the low viscosity characteristics of the precursor liquid to achieve wetting and dispersion of the gelling material; the low-speed stirring in the second stage reduces the damage of mechanical force to the foam structure and maintains the integrity of the pores inside the hardened body.

[0021] Preferably, in step S4, the mold is a steel mold with a hollow core mold inside, and release oil is applied to the inner wall of the mold and the surface of the core mold before casting; the casting method is a one-time continuous casting.

[0022] By employing the above technical solution and considering the rheological properties of the slurry, hollow structures can be formed. Continuous casting in a single operation reduces delamination interfaces, helping to ensure the overall mechanical properties of the product.

[0023] Preferably, in step S5, the specific process of curing is as follows: after standing at room temperature for 8-12 hours to reach the demolding strength, the material is demolded and then moved into an environment with a temperature of 20±2℃ and a relative humidity greater than 95% for curing.

[0024] By adopting the above technical solutions, the curing system promotes the formation of cement hydration products, and the wet curing conditions help maintain the calcium alginate gel structure and develop the strength of the cement matrix.

[0025] This invention provides a composite foaming preparation method for lightweight sound-insulating hollow bricks. It has the following beneficial effects: 1. This invention resolves the contradiction between the fluidity and foam stability of lightweight slurry by constructing a chemically induced rheological regulation mechanism. The use of a negative coordination precursor liquid reduces the initial viscosity of the slurry, which is beneficial for low-loss mixing and dispersion of physical foam. After casting, the calcium ions excited by lithium salt break the coordination equilibrium and induce sodium alginate crosslinking, causing a sudden increase in viscosity of the slurry during the standing stage. This specific rheological behavior effectively prevents the floating and merging of bubbles in the lightweight slurry, prevents collapse and deformation during the hollow structure forming process, and ensures the density and uniformity of the hollow brick hole walls.

[0026] 2. The hollow brick prepared by this invention exhibits excellent acoustic damping performance. During the preparation process, sodium alginate reacts with released borate and calcium ions to generate a uniformly distributed organic gel network in situ within the cement hydration products. This polymer network possesses viscoelastic characteristics and, as a damping component embedded in the inorganic matrix, can effectively dissipate vibrational energy during sound wave transmission. Combined with the hollow structure designed for the brick, it significantly improves the material's isolation efficiency against low-frequency noise, overcoming the shortcomings of traditional lightweight porous materials with poor sound insulation performance.

[0027] 3. This invention improves the mechanical property stability of the product through multi-stage dispersion and variable frequency stirring processes. The dry powder premixing process ensures the uniform distribution of trace lithium salt coagulants in the matrix, avoiding stress concentration caused by localized coagulation differences; the variable frequency stirring process reduces mechanical damage to the foam structure while ensuring thorough mixing of materials. In addition, the precisely controlled reaction latency allows the slurry to quickly gain early strength while meeting the requirements of continuous one-time casting, reducing demolding waiting time, improving production efficiency, and ensuring the dimensional accuracy of the finished product. Detailed Implementation

[0028] Examples 1-4: Example

[0029] This embodiment provides a composite foaming preparation method for lightweight sound-insulating hollow bricks, wherein the raw materials, by weight, specifically include the following steps: Raw material preparation: Solid phase system: 80 parts of ordinary silicate cement (PO 42.5), 20 parts of S95 grade slag powder, and 0.18 parts of industrial grade lithium carbonate (particle size passing 200 mesh).

[0030] Liquid phase system: 40 parts process water, 0.15 parts sodium gluconate, 0.45 parts borax (sodium tetraborate decahydrate), and 0.5 parts low-viscosity sodium alginate (viscosity 200 mPa·s).

[0031] Foaming system: 2.0 parts of compound plant protein foaming agent stock solution, 20 parts of foaming water. After foaming in a foaming machine, the resulting foam density is 50 kg / m³. 3 The water excretion rate is less than 8% within 1 hour.

[0032] Preparation process: S1. Preparation of the negative coordination precursor solution: Add 40 parts of process water to the reactor, heat to 35°C, and start stirring (400 r / min). Add 0.15 parts of sodium gluconate and 0.45 parts of borax sequentially, and stir for 10 minutes until completely dissolved. Adjust the pH to 10.0 using 1 mol / L NaOH solution. Then slowly sprinkle in 0.5 parts of sodium alginate, increase the stirring speed to 900 r / min, and continue stirring for 25 minutes until a homogeneous and transparent solution is formed. Let it stand to defoam and set aside for later use.

[0033] S2. Solid-phase dry powder premixing: 0.18 parts of lithium carbonate and 2 parts of cement are premixed and dispersed, and then added to the dry powder mixer along with the remaining 78 parts of cement and 20 parts of slag powder. The mixture is mixed for 4 minutes to obtain homogenized dry powder containing kinetic compensator.

[0034] S3. Slurry Combining: The prepared negative coordination precursor liquid is added to a forced mixer. Homogenized dry powder is added at low speed (250 r / min), and after addition, high-speed mixing (1200 r / min) is started for 90 seconds. At this time, the slurry maintains a low viscosity due to the shielding effect of sodium gluconate. Then, physical foam (density 50 kg / m³) pre-formed by a foaming machine is added. 3 Adjust the speed to low (150r / min) and fold and stir for 45 seconds to obtain composite foamed slurry.

[0035] S4. Casting and Rheological Changes: Beforehand, apply release oil to the inner wall and core surface of the steel mold with a hollow core. Pour the slurry into the mold continuously in one go. The slurry maintains self-leveling properties for the first 5 minutes after entering the mold. During the 12-15 minute settling period, due to lithium carbonate promoting cement hydration and releasing a large amount of calcium ions, which displace borate ions and crosslink sodium alginate, the slurry viscosity changes abruptly, losing its fluidity and locking in air bubbles and a hollow structure.

[0036] S5. Curing: After curing at room temperature for 10 hours, the slurry will harden to the point of demolding strength. Remove the inner core mold and the outer mold. Transfer the product to a standard curing room (20℃, 95% humidity) for 28 days. Example

[0037] This embodiment provides a composite foaming preparation method for lightweight sound-insulating hollow bricks, wherein the raw materials, by weight, specifically include the following steps: Raw material preparation: Solid phase system: 90 parts of ordinary silicate cement (PO 52.5), 10 parts of grade I fly ash, and 0.08 parts of industrial grade lithium carbonate.

[0038] Liquid phase system: 35 parts process water, 0.08 parts sodium gluconate, 0.22 parts borax, and 0.3 parts low viscosity sodium alginate.

[0039] Foaming system: 1.0 part of sodium dodecyl sulfate compound foaming agent, 15 parts of foaming water.

[0040] Preparation process: S1. Preparation of negative coordination precursor solution: Heat 35 parts of process water to 30℃ and dissolve 0.08 parts of sodium gluconate and 0.22 parts of borax with stirring. Adjust the pH to 9.5. Add 0.3 parts of sodium alginate and stir at high speed for 20 minutes to dissolve.

[0041] S2, Solid-phase dry powder premix: Mix 0.08 parts of lithium carbonate with 90 parts of cement and 10 parts of fly ash in a dry powder mixer for 3 minutes.

[0042] S3. Slurry Combining: Mix the precursor liquid and dry powder, and stir at high speed (1000 r / min) for 60 seconds. Add the pre-made foam and stir at low speed for 30 seconds. Because all functional components are at their minimum limits, the initial viscosity of the slurry is extremely low, resulting in high mixing efficiency.

[0043] S4. Casting and Rheological Change: Casting grout. Due to the low lithium carbonate content but high cement ratio (90 parts), the hydration reaction starts relatively mildly. A rheological change occurs approximately 18-20 minutes after standing.

[0044] S5. Curing: After curing for 12 hours, demold and then perform standard curing. Example

[0045] This embodiment provides a composite foaming preparation method for lightweight sound-insulating hollow bricks, wherein the raw materials, by weight, specifically include the following steps: Raw material preparation: Solid phase system: 70 parts of ordinary silicate cement (PO 42.5), 30 parts of S95 grade slag powder, and 0.4 parts of industrial grade lithium carbonate.

[0046] Liquid phase system: 45 parts process water, 0.25 parts sodium gluconate, 0.8 parts borax, and 0.8 parts low viscosity sodium alginate.

[0047] Foaming system: 3.0 parts of high-stability foaming protein foaming agent and 25 parts of foaming water.

[0048] Preparation process: S1. Preparation of negative coordination precursor solution: Heat 45 parts of process water to 40℃ to dissolve 0.25 parts of sodium gluconate and 0.8 parts of borax. Adjust the pH to 10.5. Add 0.8 parts of sodium alginate. Due to the high concentration, high-speed stirring for 30 minutes is required to ensure complete dispersion and dissolution.

[0049] S2, Solid-phase dry powder premix: Mix 0.4 parts of lithium carbonate with 70 parts of cement and 30 parts of slag powder for 5 minutes.

[0050] S3. Slurry Mixing: Mix the precursor liquid and dry powder, and stir at high speed (1500 r / min) for 120 seconds. Although the sodium alginate concentration is high, the slurry still maintains good pumpability due to the strong coordination and locking effect of the high dose of sodium gluconate / borax. Add foam and stir at low speed for 60 seconds.

[0051] S4. Casting and Rheological Change: Casting slurry. Due to the high lithium carbonate content (0.4 parts), despite the large amount of retarding components, the heat of hydration is released rapidly. A dramatic rheological change occurs approximately 8-10 minutes after standing, at which point the borate ester bond network and the calcium-alginate network simultaneously form with high strength, providing extremely strong anti-collapse support.

[0052] S5. Curing: After 8 hours of static curing, the product can be demolded and then cured according to standard procedures. Example

[0053] This embodiment provides a composite foaming preparation method for lightweight sound-insulating hollow bricks, wherein the raw materials, by weight, specifically include the following steps: Raw material preparation: Solid phase system: 75 parts of ordinary Portland cement (PO 42.5), 25 parts of Class F grade II fly ash, and 0.2 parts of lithium sulfate.

[0054] Liquid phase system: 42 parts process water, 0.12 parts sodium gluconate, 0.35 parts borax, and 0.45 parts low viscosity sodium alginate.

[0055] Foaming system: Same as in Example 1 (2.0 parts foaming agent + 20 parts water).

[0056] Preparation process: S1. Preparation of negative coordination precursor solution: Same as in Example 1, but at 35°C and pH adjusted to 10.0.

[0057] S2, Solid-phase dry powder premix: Mix 0.2 parts of lithium sulfate with cement and fly ash evenly. Lithium sulfate also has the function of providing early lithium ions to accelerate the aluminate reaction.

[0058] S3. Slurry compounding: Process parameters are the same as in Example 1. Note that the water requirement of fly ash is slightly lower than that of slag, and controlling the water-cement ratio at around 0.62 can ensure good slurry fluidity.

[0059] S4. Casting and Rheological Change: After casting, allow the mixture to stand. Because fly ash has lower activity than slag, lithium sulfate provides kinetic compensation, and the rheological change time is controlled at around 14 minutes, which is still within the suitable operating window.

[0060] S5. Curing: After curing at room temperature for 11 hours, demold and then perform standard curing.

[0061] Comparative Examples 1-5: Comparative Example 1: Compared with Example 1, the differences are as follows: sodium gluconate (0.15 parts), borax (0.45 parts), and sodium alginate (0.5 parts) are removed from the liquid phase system; lithium carbonate (0.18 parts) is removed from the solid phase system; 0.2 parts of high-viscosity hydroxypropyl methylcellulose (HPMC, viscosity 100,000 mPa·s) are added as a physical thickener during the S2 solid phase dry powder premixing; the amount of water used in the liquid phase process remains unchanged at 40 parts, and all other aspects are the same.

[0062] Comparative Example 2: Compared with Example 1, the difference is that borax (0.45 parts) in the liquid phase system is removed, and only sodium gluconate and sodium alginate are dissolved when preparing the negative coordination precursor in S1. Everything else is the same.

[0063] Comparative Example 3: The difference from Example 1 is that lithium carbonate (0.18 parts) was removed from the solid-phase system, while the rest were the same.

[0064] Comparative Example 4: Compared with Example 1, the difference is that sodium gluconate (0.15 parts) in the liquid phase system is removed, and borax and sodium alginate are directly dissolved when preparing the precursor solution in S1. All other aspects are the same.

[0065] Comparative Example 5: Compared with Example 1, the difference is that the preparation of the negative coordination precursor in S1 is omitted. During the operation, process water (40 parts) is directly added to the mixer, and sodium gluconate, borax, sodium alginate and the homogenized dry powder (containing lithium carbonate) prepared in S2 are added in sequence and mixed and stirred at one time. The rest are the same.

[0066] Test Example 1: Slurry Rheological Behavior and Process Adaptability Test Experimental steps: Slurries were prepared according to the formulations provided in Examples 1-4 and Comparative Examples 1-5, with the ambient temperature controlled at 25℃±2℃. The slurries were tested immediately after preparation.

[0067] Initial scalability (liquidity characterization): First, the initial spread was tested using a standard cement paste flowability test cone mold (upper diameter 36mm, lower diameter 60mm, height 60mm). The mixed paste was quickly poured into the cone mold, leveled, and then lifted vertically. The maximum diameter of the paste after spreading freely on a glass plate for 30 seconds was measured. This value reflects the paste's pumping and filling capacity into the mold.

[0068] Operable window period: Timing begins after the foaming slurry mixing is complete, and the container is tilted every minute to observe the slurry flow. The time is recorded when the slurry loses its self-leveling ability (i.e., when the container is tilted, the slurry no longer exhibits significant shear flow, or the yield stress increases significantly, preventing it from spreading naturally). This indicator reflects the point in time when the system experiences a sudden change in rheological properties.

[0069] Hollow structure collapse rate (stability characterization): The slurry was poured into a steel mold with a hollow inner core with a height of 300mm. The surface was smoothed and allowed to stand until final hardening. The actual height of the test block was measured, and the collapse rate was calculated based on the height difference. The calculation formula is as follows: (300 - actual height of the test block) / 300 × 100%. This index measures the physical support ability of the slurry for air bubbles and hollow structures before gelation.

[0070] Demolding time: The penetration resistance method was used to assist in the judgment of the static curing time when the surface of the test block showed no marks from finger pressure and had the strength to be handled.

[0071] Test results: Table 1. Test data on slurry rheological properties and molding stability Group Initial expansion (mm) Operable window period (min) Collapse rate (%) Demolding time (h) Remark Example 1 243 14 0.4 10.5 Smooth surface and uniform pore structure Example 2 258 21 1.2 13.5 Intensity development is slightly slower Example 3 215 8 0.2 7.5 The viscosity is high, requiring auxiliary vibration. Example 4 236 16 0.6 11.0 / Comparative Example 1 162 ＞60 12.8 12.0 The slurry was viscous and the bottom collapsed significantly. Comparative Example 2 246 13 9.5 10.5 Bubbles rise to the surface, resulting in severe stratification. Comparative Example 3 241 ＞120 2.1 ＞48 The paste is ointment-like and has not hardened. Comparative Example 4 N / A ＜1 N / A N / A Mixing results in clumping, making it impossible to pour. Comparative Example 5 188 5 4.3 11.5 The slurry contains insoluble gel particles Note: " / " in the table indicates that the experiment performed normally during the preparation and molding process, and no obvious macroscopic defects or abnormal phenomena requiring special recording were observed.

[0072] Results Analysis and Conclusions: The initial expansion of Examples 1-4 was all above 215 mm, and the collapse rate was controlled below 1.2%, indicating that the dual coordination system of this invention provides filling properties in the initial stage of casting and allows for structural support after settling. Comparative Example 1, using cellulose ether for physical thickening, had an initial expansion of only 162 mm and a collapse rate of 12.8%, demonstrating that single physical thickening is insufficient to balance flowability and anti-collapse performance at the same water-cement ratio, and the lack of a chemical crosslinking triggering mechanism leads to insufficient bubble and gravitational stability.

[0073] Regarding the role of borates, in Comparative Example 2, although the flowability (246 mm) was comparable to that of Example 1 after the removal of borax, the mold collapse rate increased to 9.5%. The data indicate that the chelation reaction between calcium ions and sodium alginate alone cannot provide sufficient yield stress in the early stages; the boronic acid ester bond network formed by borax provides thixotropic support, which is key to controlling mold collapse.

[0074] Regarding the kinetic compensation mechanism, in Comparative Example 3, after the removal of lithium carbonate, the operable window exceeded 120 minutes, and demolding still occurred after 48 hours. This indicates that sodium gluconate and borax have an inhibitory effect on cement hydration, while the introduction of lithium carbonate can promote hydration kinetics, counteract the retarding side effects, and restore the demolding time to the normal range.

[0075] Regarding the precursor solution preparation process, in Comparative Example 4, without the addition of sodium gluconate, the slurry solidified immediately upon mixing and could not be molded, confirming that the shielding effect of sodium gluconate on calcium ions is a prerequisite for preventing early precipitation of sodium alginate. In Comparative Example 5, the precursor solution preparation step was omitted, and the components were directly mixed, resulting in an initial expansion of 188 mm and a collapse rate of 4.3%. This indicates that without establishing a precursor solution complexation equilibrium, sodium gluconate cannot preferentially complex borate ions, leading to disordered reactions in some components and the inability to form a uniform interpenetrating network structure.

[0076] Test Example 2: Physical and Mechanical Performance and Sound Insulation Test Experimental steps: The test blocks prepared in Examples 1-4, Comparative Examples 1-3, and Comparative Example 5 were cured under standard curing conditions for 28 days, and then subjected to various performance tests. Comparative Example 4 was not tested because the slurry could not be molded.

[0077] First, test the dry apparent density by drying the sample block in an oven at 105℃ until constant weight, measuring the mass and volume after cooling, and calculating the density value.

[0078] Next, the compressive strength is tested. According to the test standards for mechanical properties of building materials, a universal testing machine is used to apply pressure to the test block until it fails, the maximum failure load is recorded and the compressive strength is calculated.

[0079] Subsequently, the softening coefficient was tested, and the ratio of the compressive strength under saturated water absorption state to the compressive strength under oven-dry state was determined to characterize the water resistance of the material.

[0080] Finally, the sound insulation performance was tested by measuring the airborne sound insulation of the masonry wall constructed from the test blocks in a reverberation chamber. The weighted sound insulation was recorded, and the low-frequency sound insulation gain was calculated separately. The low-frequency sound insulation gain was defined as the improvement in average sound insulation of the test sample relative to ordinary fly ash hollow blocks of the same thickness and density in the 125Hz to 500Hz frequency band.

[0081] Test results: Table 2. Physical, mechanical, and acoustic performance test data Group <![CDATA[Dry apparent density (kg / m 3 )]]> 28-day compressive strength (MPa) Softening coefficient Weighted sound insulation (dB) Low-frequency sound insulation gain (dB) Example 1 605 5.4 0.86 48.5 5.3 Example 2 618 4.6 0.82 46.2 4.1 Example 3 582 4.9 0.88 50.4 6.8 Example 4 612 5.2 0.85 47.8 5.0 Comparative Example 1 845 3.8 0.65 41.5 0.2 Comparative Example 2 720 4.1 0.72 43.1 1.5 Comparative Example 3 590 0.8 / / / Comparative Example 5 635 4.3 0.76 44.6 2.1 Note: The " / " in the table indicates that the test sample is missing because the strength of the test block is too low or the structure is damaged, which fails to meet the test sample preparation requirements.

[0082] Results Analysis and Conclusions: The dry apparent density of Examples 1-4 remained at 582-618 kg / m³. 3Within the specified range, the 28-day compressive strength is greater than 4.5 MPa, and the softening coefficient is higher than 0.8, indicating that this method maintains matrix strength and water resistance while reducing density. Comparative Example 1 used cellulose ether for physical thickening, increasing the dry apparent density to 845 kg / m³. 3 The compressive strength decreased to 3.8 MPa. The increase in density was due to the collapse of the slurry, which led to a decrease in porosity, while the decrease in strength was attributed to internal structural defects and uneven component distribution caused by the mold collapse. This indicates that physical thickening alone is insufficient to maintain structural integrity under high porosity conditions.

[0083] In terms of acoustic performance, the weighted sound insulation of the example group was 46.2-50.4 dB, and the low-frequency sound insulation gain reached 4.1-6.8 dB. Compared with Comparative Example 1, which had a gain of only 0.2 dB, this indicates that the interpenetrating network structure generated by this scheme plays an acoustic damping role in the pore walls of the matrix, improving the low-frequency sound insulation performance. Example 3 had the highest sodium alginate content and the highest corresponding low-frequency gain, which corroborates the energy dissipation mechanism of the polymer gel network for sound waves.

[0084] Comparative Example 2: After removing borax, the density increased to 720 kg / m³ due to mold collapse. 3 The low-frequency sound insulation gain dropped to 1.5 dB. The lack of borate ester crosslinking prevented the formation of an effective interpenetrating network structure, reducing the acoustic damping effect. In Comparative Example 3, after removing lithium carbonate, the compressive strength was only 0.8 MPa, making further testing impossible. This confirms that the accelerated coagulation compensation of lithium carbonate is a condition for normal matrix hardening under a strongly retarded coagulation system. Comparative Example 5, which did not use a precursor liquid process, had lower compressive strength and sound insulation performance than Example 1, indicating that direct mixing of the components failed to form a uniform chemical locking and damping structure, affecting the overall performance of the product.

Claims

1. A method for preparing lightweight sound-insulating hollow bricks using composite foaming, characterized in that, Includes the following steps: S1. Preparation of negative coordination precursor solution: Under heating conditions, sodium gluconate and borax are dissolved in process water, the pH value is adjusted to the alkaline range, and then sodium alginate is added and stirred to dissolve, thus obtaining the negative coordination precursor solution. S2, Solid-phase dry powder premix: Lithium salt accelerator is dry-mixed with cement and mineral admixtures to obtain homogenized dry powder; S3. Slurry compounding: The negative coordination precursor liquid is mixed with the homogenized dry powder, and then pre-made foam is added and mixed to obtain a composite foaming slurry. S4. Casting and rheological change: The composite foaming slurry is cast into the mold and left to stand, so that the composite foaming slurry solidifies and maintains the bubble structure; S5. Curing and Demolding: After the composite foaming slurry has hardened, demold and cure it.

2. The method for preparing lightweight sound-insulating hollow bricks by composite foaming according to claim 1, characterized in that, The composite foaming slurry is made from raw materials comprising the following parts by weight: The solid phase system includes 70-90 parts cement, 10-30 parts mineral admixtures, and 0.05-0.4 parts lithium salt accelerator; The liquid phase system includes 35-45 parts process water, 0.08-0.25 parts sodium gluconate, 0.22-0.8 parts borax, and 0.3-0.8 parts sodium alginate; The foaming system comprises 1.0-3.0 parts of foaming agent and 15-25 parts of foaming water; The mineral admixture is selected from slag powder or fly ash; the lithium salt coagulant is selected from lithium carbonate or lithium sulfate.

3. The method for preparing lightweight sound-insulating hollow bricks using composite foaming according to claim 1, characterized in that, In step S1, the heating condition is to control the solution temperature at 30-40°C; The adjustment of the pH value to alkaline specifically involves using a sodium hydroxide solution to adjust the pH value to 9.5-10.

5.

4. The method for preparing lightweight sound-insulating hollow bricks by composite foaming according to claim 3, characterized in that, In step S1, the molar ratio of borax to sodium gluconate is (1.5-2.5):1; the dissolution process after adding sodium alginate is to stir at a speed of 800-1000 r / min for 20-30 minutes.

5. The method for preparing lightweight sound-insulating hollow bricks by composite foaming according to claim 1, characterized in that, In step S2, the specific operation of the solid-phase dry powder premixing is as follows: First, the lithium salt accelerator is mixed and dispersed with cement. Then, the resulting mixture is mixed with the remaining cement and the mineral admixture, and the mixing time is not less than 3 minutes.

6. The method for preparing lightweight sound-insulating hollow bricks by composite foaming according to claim 1, characterized in that, In step S3, the mixing process for slurry compounding includes: First stage: Mix the negative coordination precursor liquid with the homogenized dry powder, and stir the slurry at a speed of 1000-1500 r / min for 60-120 seconds; Second stage: After adding the pre-made foam, stir the slurry at a speed of 100-200 r / min for 30-60 seconds.

7. The method for preparing lightweight sound-insulating hollow bricks by composite foaming according to claim 1, characterized in that, In step S3, the density of the pre-fabricated foam is 40-60 kg / m³. 3 .

8. The method for preparing lightweight sound-insulating hollow bricks by composite foaming according to claim 1, characterized in that, In step S4, the settling time of the composite foaming slurry is controlled to be 8-20 minutes.

9. The method for preparing lightweight sound-insulating hollow bricks by composite foaming according to claim 1, characterized in that, In step S4, the mold is a steel mold with a hollow core mold inside. Before pouring, release oil is applied to the inner wall of the mold and the surface of the core mold. The pouring method is a one-time continuous pouring.

10. The method for preparing lightweight sound-insulating hollow bricks by composite foaming according to claim 1, characterized in that, In step S5, the specific curing process is as follows: after standing at room temperature for 8-12 hours to reach the demolding strength, the material is demolded and then moved into an environment with a temperature of 20±2℃ and a relative humidity greater than 95% for curing.