High water-resistant magnesium oxychloride cement, sound-absorbing temperature-controlled magnesium oxychloride cement concrete and preparation method thereof

Abstract

This invention belongs to the field of road materials technology, specifically relating to a high water-resistant magnesium oxychloride cement, a sound-absorbing and temperature-controlled magnesium oxychloride cement concrete, and their preparation methods. The high water-resistant magnesium oxychloride cement of this invention comprises the following components in parts by weight: 550-600 parts magnesium oxide, 450-500 parts magnesium chloride hexahydrate, 300-350 parts water, and 55-180 parts water-resistant agent; the water-resistant agent is tannic acid and electroplating sludge water-quenched slag. In the high water-resistant magnesium oxychloride cement of this invention, after the addition of the water-resistant agent, the tannic acid and electroplating sludge water-quenched slag, through their synergistic effects of retarding and pozzolanic acid effects, inhibit the phase transformation process of the strength phase, improve the water stability of the five phases, and effectively enhance the water resistance and mechanical properties of the magnesium oxychloride cement.

Description

Technical Field

[0001] This invention belongs to the field of road materials technology, specifically relating to a high water-resistant magnesium oxychloride cement, a sound-absorbing and temperature-controlled magnesium oxychloride cement concrete, and their preparation methods. Background Technology

[0002] Traffic noise pollution is a key issue in the environmental management of cities and highways in my country. However, ordinary concrete roads have limited effectiveness in mitigating traffic noise due to their inherent acoustic defects. Magnesium oxychloride cement has attracted widespread attention due to its excellent performance, but its poor water resistance severely limits its application. Meanwhile, using recycled aggregates to prepare magnesium oxychloride cement concrete for road construction is of great significance for building a green, low-carbon, and circular development system. Therefore, how to improve the water resistance of magnesium oxychloride cement and enhance the noise reduction performance of roads has become an urgent technical problem to be solved.

[0003] Phase change materials (PCMs) possess significant potential for building temperature control due to their latent heat storage properties and their compatibility with magnesium oxychloride cement concrete. However, traditional microencapsulation methods for PCMs, with their high production costs, limit their widespread application in sound absorption and temperature control. In contrast, shape-encapsulation methods are low-cost and simple, achieving PCM loading by impregnating porous materials. However, the sound absorption performance of porous materials depends on their interconnected pores; if the PCM blocks these pores, its sound absorption capacity is severely compromised. Therefore, developing sound-absorbing and temperature-controlling PCMs is crucial for improving the noise reduction performance of cement concrete.

[0004] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0005] The purpose of this invention is to provide a high water-resistant magnesium oxychloride cement, a sound-absorbing and temperature-controlled magnesium oxychloride cement concrete, and a method for preparing the same, so as to help solve or improve the problems of poor water resistance or noise reduction effect of concrete roads in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a high water-resistant magnesium oxychloride cement, wherein the high water-resistant magnesium oxychloride cement comprises the following components in parts by weight: 550-600 parts of magnesium oxide, 450-500 parts of magnesium chloride hexahydrate, 300-350 parts of water and 55-180 parts of water-resistant agent; wherein the water-resistant agent comprises tannic acid and electroplating sludge water-quenched slag.

[0007] Preferably, the mass of the tannic acid is 0.2%-1.0% of the mass of the magnesium oxide.

[0008] Preferably, the electroplating sludge quenching residue is the tailings residue after extracting valuable metals from the electroplating sludge; the particle size of the electroplating sludge quenching residue is such that it can pass through a 200-mesh sieve.

[0009] The present invention also provides a sound-absorbing and temperature-controlled magnesium oxychloride cement concrete, which adopts the following technical solution: a sound-absorbing and temperature-controlled magnesium oxychloride cement concrete, wherein the components of the sound-absorbing and temperature-controlled magnesium oxychloride cement concrete include, as described above, high water-resistant magnesium oxychloride cement, standard sand and modified recycled aggregate; by mass parts, it includes: 900-950 parts of standard sand and 300-400 parts of modified recycled aggregate; the components of the modified recycled aggregate include recycled aggregate, lignocellulose temperature-controlled phase change material and an epoxy resin encapsulation layer covering the surface of the recycled aggregate.

[0010] Preferably, the lignocellulose temperature-controlled phase change material is prepared by a method comprising the following steps: A1, mechanically mixing biomass ash with a particle size of less than 60 mesh with a cellulose solution to obtain a mixture; A2, shaping the mixture to form biomass fiber foam; A3, immersing the biomass fiber foam in a molten inorganic phosphorus-based phase change material modification solution, vacuum impregnating for 2.5-4 hours, and then performing low-temperature crystallization at 13-17°C to obtain the lignocellulose temperature-controlled phase change material.

[0011] Preferably, the modified recycled aggregate is prepared by a method comprising the following steps: (I) placing the recycled aggregate into a vacuum impregnation tank and pouring in lignocellulose temperature-controlled phase change material at 60-70°C; (II) sealing and then vacuum impregnating; the vacuum impregnation temperature is 60-70°C and the vacuum impregnation time is 1-3 hours; the vacuum impregnation pressure is -0.08 to -0.10 MPa; (III) after vacuum impregnation, drying, and encapsulating the recycled aggregate treated in step (II) with epoxy resin to form an epoxy resin encapsulation layer, thereby obtaining the modified recycled aggregate.

[0012] Preferably, in step (II), the amount of epoxy resin used is 3%-5% of the mass of the recycled aggregate; the particle size of the modified recycled aggregate is 5-20 mm.

[0013] The present invention also provides a method for preparing sound-absorbing and temperature-controlled magnesium oxychloride cement concrete, which adopts the following technical solution: The method for preparing sound-absorbing and temperature-controlled magnesium oxychloride cement concrete as described above includes the following steps: (a) weighing the magnesium oxide, magnesium chloride hexahydrate, water, standard sand, water-resistant agent and modified recycled aggregate; (b) mixing and stirring the magnesium oxide, magnesium chloride hexahydrate, water-resistant agent and water to form modified magnesium oxychloride cement slurry; (c) adding the standard sand to the magnesium oxychloride cement slurry obtained in step (b) and stirring to mix evenly; (d) adding the modified recycled aggregate to the mixture obtained in step (c) and stirring to mix evenly to obtain the sound-absorbing and temperature-controlled magnesium oxychloride cement concrete.

[0014] Preferably, step (d) further includes a step of compacting the sound-absorbing temperature-controlled magnesium oxychloride cement concrete by vibration and curing it at 25±1℃ and 60%-80% relative humidity.

[0015] Beneficial effects:

[0016] In the high water-resistant magnesium oxychloride cement of the present invention, after the addition of water-resistant agent, the tannic acid and electroplating sludge water-quenched slag work together through the retarding effect and pozzolanic effect to inhibit the phase transformation process of the strength phase and improve the water stability of the five phases, which can effectively improve the water resistance and mechanical properties of magnesium oxychloride cement.

[0017] The recycled aggregate in the sound-absorbing and temperature-controlled magnesium oxychloride cement concrete of this invention, after modification, has a lignocellulose temperature-controlled phase change material covering the surface and internal cracks, which can effectively fill the pores and micro-cracks inside the recycled aggregate. This phase change material possesses high strength, excellent sound absorption and temperature control, fire resistance, and biodegradability, enabling closed-loop recycling of biomass ash for fertilizer utilization. Furthermore, the porous structure and inter-particle gaps of the modified recycled aggregate extend the sound wave propagation path. When sound waves are incident on the surface, part is reflected at the porous material surface, while part penetrates into the porous material and propagates forward. During propagation, air movement occurs within the pores, rubbing against the solid ribs forming the pore walls. Due to viscosity and thermal conductivity, sound energy is converted into heat energy and dissipated. Combined with the density of the magnesium oxychloride cement paste, this improves the sound absorption coefficient and enhances the building's acoustic environment.

[0018] In the sound-absorbing and temperature-controlled magnesium oxychloride cement concrete of the present invention, an epoxy resin encapsulation layer is used to enhance the bonding force between the phase change material and the recycled aggregate. Combined with the skeleton effect of sand, the compressive strength and flexural strength of the concrete meet the requirements of building structure, thus solving the problem of insufficient mechanical properties of traditional recycled aggregate concrete. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0020] Figure 1 The graph shows the test results of compressive strength and softening coefficient of the samples from Examples 1-5 and Comparative Examples 1-10. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0022] The present invention will now be described in detail with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0023] This invention addresses the problems of poor water resistance or poor noise reduction effect of existing road concrete by providing a high water-resistant magnesium oxychloride cement.

[0024] The high water-resistant magnesium oxychloride cement of this invention comprises the following components in parts by weight: 550-600 parts of magnesium oxide (e.g., 550, 560, 570, 580, 590 or 600 parts), 450-500 parts of magnesium chloride hexahydrate (e.g., 450, 460, 470, 480, 490 or 500 parts), 300-350 parts of water (e.g., 300, 310, 320, 330, 340 or 350 parts), and 55-180 parts of water-resistant agent (e.g., 55, 90, 120, 150 or 180 parts); the water-resistant agent comprises tannic acid and electroplating sludge water-quenched slag.

[0025] This invention uses tannic acid and electroplating sludge quenching slag as water-resistant agents. Tannic acid is a type of water-soluble plant polyphenol, rich in hydrophobic aromatic rings and hydrophilic phenolic hydroxyl groups, thus possessing unique structural characteristics. It can interact with various molecules or groups, including hydrogen bond network construction, electrostatic interactions, hydrophobic binding, and π-π stacking, thereby firmly adhering to the target surface. Tannic acid, with its excellent ecological compatibility, shows great potential in improving the water resistance of magnesium oxychloride cement. Tannic acid and Mg... 2+ Metal ions form a three-dimensional network coordination structure, generating chelation that slows cement hydration and promotes the transformation of the strength phase in magnesium oxychloride cement from needle-like to gel-like, thus improving the water stability of magnesium oxychloride cement. Furthermore, the incorporation of electroplating sludge quenching slag can exert a micro-aggregate and pozzolanic effect, forming a dense, interlocking network structure that hinders water transport, thereby reducing the rate of water erosion. Tannic acid stabilizes the gel-like phase 5 and, synergistically with the electroplating sludge quenching slag, inhibits the phase transformation process of the strength phase, making the microstructure of magnesium oxychloride cement more stable and dense, and enhancing its resistance to water erosion. Simultaneously, Mg(OH)₂ can undergo a secondary hydration reaction with the active SiO₂ in the electroplating sludge quenching slag to generate hydrated magnesium silicate (MSH) gel, effectively filling the larger pores in the internal structure, making the microstructure more dense, and preparing magnesium oxychloride cement with high water resistance.

[0026] In a preferred embodiment of the high water-resistant magnesium oxychloride cement of the present invention, the mass of tannic acid is 0.2%-1.0% of the mass of magnesium oxide (e.g., 0.2%, 0.4%, 0.6%, 0.8%, or 1.0%). If the amount of tannic acid is too small, its chelating effect with the magnesium oxychloride cement is not significant, thus failing to promote the transformation of the needle-like five-phase into a gel-like five-phase, resulting in limited improvement in the water resistance of the magnesium oxychloride cement. If the amount of tannic acid is too large, excessive internal crystallization stress will induce microcracks, leading to a decrease in the compressive strength of the magnesium oxychloride cement.

[0027] Preferably, the mass of tannic acid is 0.2%-0.8% of the mass of magnesium oxide (e.g., 0.2%, 0.25%, 0.3%, 0.35%, 0.45%, 0.5%, 0.55%, 0.7% or 0.8%).

[0028] In a preferred embodiment of the high water-resistant magnesium oxychloride cement of the present invention, the electroplating sludge water-quenched slag is the tailings after extracting valuable metals from the electroplating sludge; the particle size of the electroplating sludge water-quenched slag is such that it can pass through a 200-mesh sieve. The chemical composition of the electroplating sludge water-quenched slag is mainly CaO and Al2O3, and the amorphous glass structure formed during the water quenching process endows the electroplating sludge water-quenched slag with potential pozzolanic activity, possessing the potential to be used as an auxiliary cementing material in magnesium oxychloride cement to improve its water resistance and mechanical properties.

[0029] Preferably, the amount of electroplating sludge water quenching slag used is 15%-25% of the mass of magnesium oxide (e.g., 15%, 18%, 20%, 22% or 25%).

[0030] Preferably, the amount of electroplating sludge water-quenched slag used is 20% of the mass of magnesium oxide.

[0031] The present invention also proposes a sound-absorbing and temperature-controlled magnesium oxychloride cement concrete. The components of the sound-absorbing and temperature-controlled magnesium oxychloride cement concrete of the present invention include the high water-resistant magnesium oxychloride cement, standard sand and modified recycled aggregate as described above; by mass parts, it includes: 900-950 parts of standard sand (e.g., 900 parts, 910 parts, 920 parts, 930 parts, 940 parts or 950 parts), and 300-400 parts of modified recycled aggregate (e.g., 300 parts, 320 parts, 340 parts, 360 parts, 380 parts or 400 parts); the components of the modified recycled aggregate include recycled aggregate, lignocellulose temperature-controlled phase change material and an epoxy resin encapsulation layer coated on the surface of the recycled aggregate. This invention modifies recycled aggregate using a lignocellulose temperature-controlled phase change material. The surface and cracks of the recycled aggregate are covered with this lignocellulose temperature-controlled phase change material, which effectively fills the pores and micro-cracks within the aggregate. This phase change material possesses high strength, excellent sound absorption and temperature control, fire resistance, and biodegradability, thus optimizing the performance of the recycled aggregate. Simultaneously, lignocellulose is a porous material. When sound waves propagate within a porous material, the energy dissipation due to various mechanisms contributes to its noise reduction properties. The phase change material can dynamically regulate indoor temperature through a phase change process, significantly reducing building energy consumption. Therefore, the combination of these two technologies has significant application value in sound absorption and temperature control. The recycled aggregate modified with the lignocellulose temperature-controlled phase change material has a porous structure and gaps between particles that extend the sound wave propagation path. When sound waves are incident on the surface, part is reflected at the porous surface, while the other part penetrates into the porous material and propagates forward. During propagation, air movement occurs within the pores, rubbing against the solid ribs forming the pore walls. Due to viscosity and thermal conductivity, sound energy is converted into heat energy and dissipated. Combined with the density of magnesium oxychloride cement paste, this helps improve the sound absorption coefficient of concrete, enhancing the acoustic properties of cement concrete and improving noise reduction.

[0032] In a preferred embodiment of the sound-absorbing and temperature-controlled magnesium oxychloride cement concrete of the present invention, the lignocellulose temperature-controlled phase change material is prepared by a method comprising the following steps: A1. Biomass with a particle size of less than 60 mesh is mixed with a cellulose solution with a concentration of 2.0wt%-7.0wt% (e.g., 2.0wt%, 3.0wt%, 4.0wt%, 5.0wt%, 6.0wt%, or 7.0wt%) at a concentration of 0.40-0.55 g / mL (e.g., 0.40 g / mL, 0.45 g / mL, 0.50 g / mL, or 0.55 g / mL; the ratio of the mass of biomass to the volume of the cellulose solution is (0.4-0.55)). A1. The cellulose solution is mechanically mixed in a ratio of 1 mL g / mL (2.0 wt% - 7.0 wt%) to obtain a mixture. A2. The mixture is shaped to form biomass fiber foam. A3. The lignocellulose foam is placed in a molten inorganic phosphorus-based phase change material modification solution and vacuum impregnated at 55-65°C (e.g., 55°C, 57°C, 60°C, 62°C, or 65°C) for 2.5-4 hours (e.g., 2.5 hours, 3 hours, 3.5 hours, or 4 hours). After impregnation, it is subjected to low-temperature crystallization at 13-17°C (e.g., 13°C, 14°C, 15°C, 16°C, or 17°C) to obtain the lignocellulose temperature-controlled phase change material. In step A1, if the proportion of biomass used is too large, the cellulose solution will not be able to coat all the biomass particles, resulting in insufficient bonding of the porous structure and poor structural integrity. If the proportion of biomass used is too small, it will cause the interaction between cellulose molecules to be enhanced, the viscosity of the solution to increase sharply, resulting in increased stirring resistance, making it difficult for cellulose to be evenly dispersed and completely dissolved. Cellulose may agglomerate, failing to form a uniform and transparent solution, which will affect the subsequent bonding effect on biomass particles.

[0033] Preferably, the cellulose solution in step A1 is obtained by immersing α-cellulose successively in methanol and N,N-dimethylacetamide (to activate α-cellulose; preferably, the immersion time is 1 h), filtering, and then adding it to a mixed solution of LiCl and N,N-dimethylacetamide, and mechanically stirring (preferably, the stirring temperature is 60 °C) until uniformly dispersed; wherein, the mixed solution of LiCl and N,N-dimethylacetamide is obtained by adding 8.0 g of LiCl to 100.0 mL of N,N-dimethylacetamide and mixing them uniformly.

[0034] Preferably, step A2 includes: first, using a mold to preliminarily shape the mixture (e.g., pouring the mixture into a silicone rubber mold and manually flattening and smoothing it) to obtain a green body; letting the green body stand for 1-3 hours (preliminary regeneration; e.g., 1 hour, 2 hours, or 3 hours), then letting it stand in water for 3-4 hours (enhanced regeneration, by placing the green body in water for solvent replacement and enhanced cellulose regeneration; e.g., standing in water for 3 hours, 3.5 hours, or 4 hours); removing it from the water and pre-freezing it at a temperature of -20 to -80°C (e.g., -20°C, -40°C, -60°C, or -80°C) for 4-12 hours (e.g., 4 hours, 6 hours, 8 hours, 10 hours, or 12 hours), and then drying it (preferably at a drying temperature of -20 to -80°C for a drying time of 24-48 hours) to obtain biomass fiber foam. Under the conditions of pre-freezing and drying, the porous structure can be locked, completing the shaping process to form lignin fiber foam.

[0035] Preferably, in step A3, the mass ratio of lignocellulose foam to the inorganic phosphorus-based phase change material modification solution is 1:(1.25-7.1) (e.g., 1:1.25, 1:1.5, 1:2, 1:3, 1:4, 1:5, 1:6, or 1:7.1). If the proportion of lignocellulose foam is too high, the heat storage capacity of the prepared lignin temperature-controlled phase change material will be reduced; if the proportion of lignocellulose foam is too low, the prepared lignin temperature-controlled phase change material will have a leakage risk.

[0036] Preferably, the inorganic phosphorus-based phase change material modification solution is prepared by a method comprising the following steps: anhydrous sodium carbonate decahydrate (SCD) and disodium hydrogen phosphate dodecahydrate (DHPD) are mixed at a weight ratio of 2:(7-9) (e.g., 2:7, 2:8 or 2:9), without the need for additional water addition or purification, and directly melted at 60-70°C (e.g., 60°C, 63°C, 66°C, 68°C or 70°C) to form an inorganic phosphorus-based phase change material modification solution with low viscosity and fluidity similar to natural water.

[0037] In a preferred embodiment of the sound-absorbing temperature-controlled magnesium oxychloride cement concrete of the present invention, the modified recycled aggregate is prepared by a method comprising the following steps: (I) placing the recycled aggregate into a vacuum impregnation tank and pouring in lignocellulose temperature-controlled phase change material at 60-70°C (e.g., 60°C, 63°C, 66°C, 68°C or 70°C); (II) sealing and evacuating to -0.08~-0.10MPa (e.g., -0.08MPa, -0.09MPa or -0.10MPa), maintaining the temperature at 60-70°C (e.g., 60°C, 63°C, 66°C, 68°C or 70°C) for 1-3 hours (stirring once every 30 minutes during this period; e.g., impregnation for 1 hour, 2 hours or 3 hours); (III) after draining, spraying with epoxy resin and curing at room temperature for 30 minutes. By encapsulating recycled aggregates with epoxy resin, the interfacial bonding between recycled aggregates and cementitious matrix is ​​enhanced. Combined with the skeletal effect of sand, this helps to ensure that the compressive and flexural strengths of concrete meet the requirements of building structures, thus helping to solve the problem of insufficient mechanical properties of traditional recycled aggregate concrete.

[0038] Preferably, the mass ratio of recycled aggregate to lignocellulose temperature-controlled phase change material is (2-2.5):1 (e.g., 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1 or 2.5:1).

[0039] In a preferred embodiment of the sound-absorbing and temperature-controlled magnesium oxychloride cement concrete of the present invention, in step (II), the amount of epoxy resin is 3%-5% of the mass of recycled aggregate (e.g., 3%, 3.5%, 4%, 4.5% or 5%); the particle size of the modified recycled aggregate is 5-20 mm.

[0040] The present invention also proposes a method for preparing sound-absorbing and temperature-controlled magnesium oxychloride cement concrete as described above. The method for preparing sound-absorbing and temperature-controlled magnesium oxychloride cement concrete according to an embodiment of the present invention includes the following steps: (a) weighing the above-mentioned parts by weight of magnesium oxide, magnesium chloride hexahydrate, water, standard sand, water-resistant agent and modified recycled aggregate; (b) mixing and stirring magnesium oxide, magnesium chloride hexahydrate, water-resistant agent and water to form modified magnesium oxychloride cement paste; (c) adding standard sand to the magnesium oxychloride cement paste obtained in step (b) and stirring to mix evenly; (d) adding modified recycled aggregate to the mixture obtained in step (c) and stirring to mix evenly to obtain sound-absorbing and temperature-controlled magnesium oxychloride cement concrete.

[0041] Preferably, the molar ratio of magnesium oxide, magnesium chloride and water is (4.2-6):1:13 (e.g., 4.2:1:13, 4.8:1:13, 5.4:1:13 or 6.0:1:13), and the amount of water-resistant agent added is 10%-30% of the mass fraction of magnesium oxide (e.g., 10%, 15%, 20%, 25% or 30%).

[0042] In a preferred embodiment of the method for preparing sound-absorbing temperature-controlled magnesium oxychloride cement concrete of the present invention, step (d) is followed by a step of compacting the sound-absorbing temperature-controlled magnesium oxychloride cement concrete by vibration and curing it at 25±1℃ and relative humidity of 60%-80% (e.g., 60%, 65%, 70%, 75% or 80%).

[0043] Preferably, the curing period is 7 days.

[0044] The following detailed description of the high water-resistant magnesium oxychloride cement, sound-absorbing and temperature-controlled magnesium oxychloride cement concrete, and their preparation methods of the present invention will be provided through specific embodiments.

[0045] The main raw materials used in the following examples are sourced as follows: the active MgO content of the magnesium oxide powder is 66.00%; the purity of industrial magnesium chloride is 98%; tannic acid is produced by Shanghai Maclean Biochemical Co., Ltd.; the electroplating sludge water-quenched slag is taken from Ningbo Dadi Chemical Environmental Protection Co., Ltd., and this tailings is the smelting slag produced after extracting valuable metals from electroplating sludge in an oxygen-enriched side-blown furnace, which is then water-quenched to obtain amorphous tailings; the standard sand has good gradation and a fineness modulus of 2.4; the recycled aggregate is obtained from the mechanical crushing of waste concrete after the demolition of old bridges, with a crushing value of 14.5; the epoxy resin is an A / B two-component organic polymer emulsion with water-emulsion epoxy as the base material. The mass ratio of components A and B is 3:1; n-tetradecane / graphite uses n-tetradecane (C14) as the phase change material and expanded graphite (EG) as the carrier; the mass ratio of n-tetradecane to graphite is 1:4, and the n-tetradecane is produced by Jiangyin Wuyang Hydrogen Materials Technology Co., Ltd., and the graphite is produced by Suqian Zhongke New Materials Technology Co., Ltd.

[0046] Example 1

[0047] The high water-resistant magnesium oxychloride cement of this embodiment comprises the following components in parts by weight: 600 parts magnesium oxide, 450 parts magnesium chloride hexahydrate, 300 parts water, and a water-resistant agent; wherein the water-resistant agent comprises: tannic acid and electroplating sludge water-quenched slag (which can pass through a 200-mesh sieve); wherein the amount of tannic acid is 0.4% (i.e., 2.4 parts) of the mass of magnesium oxide, and the amount of electroplating sludge water-quenched slag is 20% (i.e., 120 parts) of the mass of magnesium oxide.

[0048] The preparation method of the high water-resistant magnesium oxychloride cement in this embodiment includes the following steps:

[0049] (1) Grind the electroplating sludge water quenching residue for 15 minutes and then sieve it through a 200-mesh sieve for later use;

[0050] (2) Dissolve tannic acid in deionized water and stir for 5-15 minutes to obtain a homogeneous tannic acid solution;

[0051] (3) Add magnesium chloride hexahydrate to the tannic acid solution, stir at 300 r / min for 15 min at room temperature using a magnetic stirrer, and let stand for 24 h to obtain a mixed solution;

[0052] (4) Add magnesium oxide and electroplating sludge water quenching slag to the mixed solution, stir evenly to obtain the high water resistant magnesium oxychloride cement of this embodiment, and test its performance after curing for 7 days at a temperature of 25±1℃ and a humidity of 60%-80%.

[0053] Example 2

[0054] The high water-resistant magnesium oxychloride cement of this embodiment comprises the following components in parts by weight: 600 parts magnesium oxide, 450 parts magnesium chloride hexahydrate, 300 parts water, and a water-resistant agent; wherein the water-resistant agent comprises: tannic acid and electroplating sludge water-quenched slag (which can pass through a 200-mesh sieve); wherein the amount of tannic acid is 0.4% (i.e., 2.4 parts) of the mass of magnesium oxide, and the amount of electroplating sludge water-quenched slag is 20% (i.e., 120 parts) of the mass of magnesium oxide.

[0055] The preparation method of the high water-resistant magnesium oxychloride cement in this embodiment includes the following steps:

[0056] (1) Grind the electroplating sludge water quenching residue for 30 minutes and then sieve it through a 200-mesh sieve for later use;

[0057] (2) Dissolve tannic acid in deionized water and stir for 5-15 minutes to obtain a homogeneous tannic acid solution;

[0058] (3) Add magnesium chloride hexahydrate to the tannic acid solution, stir at 300 r / min for 15 min at room temperature using a magnetic stirrer, and let stand for 24 h to obtain a mixed solution;

[0059] (4) Add magnesium oxide and electroplating sludge water quenching slag to the mixed solution, stir evenly to obtain the high water resistant magnesium oxychloride cement of this embodiment, and test its performance after curing for 7 days at a temperature of 25±1℃ and a humidity of 60%~80%.

[0060] Example 3

[0061] The high water-resistant magnesium oxychloride cement of this embodiment comprises the following components in parts by weight: 600 parts magnesium oxide, 450 parts magnesium chloride hexahydrate, 300 parts water, and a water-resistant agent; wherein the water-resistant agent comprises: tannic acid and electroplating sludge water-quenched slag (which can pass through a 200-mesh sieve); wherein the amount of tannic acid is 0.4% (i.e., 2.4 parts) of the mass of magnesium oxide, and the amount of electroplating sludge water-quenched slag is 20% (i.e., 120 parts) of the mass of magnesium oxide.

[0062] The preparation method of the high water-resistant magnesium oxychloride cement in this embodiment includes the following steps:

[0063] (1) Grind the electroplating sludge water quenching residue for 45 minutes and then sieve it through a 200-mesh sieve for later use;

[0064] (2) Dissolve tannic acid in deionized water and stir for 5-15 minutes to obtain a homogeneous tannic acid solution;

[0065] (3) Add magnesium chloride hexahydrate to the tannic acid solution, stir at 300 r / min for 15 min at room temperature using a magnetic stirrer, and let stand for 24 h to obtain a mixed solution;

[0066] (4) Add magnesium oxide and electroplating sludge water quenching slag to the mixed solution, stir evenly to obtain the high water resistant magnesium oxychloride cement of this embodiment, and test its performance after curing for 7 days at a temperature of 25±1℃ and a humidity of 60%~80%.

[0067] Example 4

[0068] The only difference between this embodiment and Embodiment 2 is that the amount of tannic acid used is 0.6% of the mass of magnesium oxide; all other aspects are the same as in Embodiment 2.

[0069] Example 5

[0070] The sound-absorbing and temperature-controlled magnesium oxychloride cement concrete of this embodiment comprises the following components in parts by weight: 600 parts magnesium oxide, 450 parts magnesium chloride hexahydrate, 300 parts water, water-resistant agent, 900 parts standard sand, and 300 parts modified aggregate; wherein, the water-resistant agent comprises: tannic acid and electroplating sludge water-quenched slag (which can pass through a 200-mesh sieve); wherein, the amount of tannic acid is 0.4% of the mass of magnesium oxide (i.e., 2.4 parts), and the ball milling time of the electroplating sludge water-quenched slag is 30 minutes, and the amount is 20% of the mass of magnesium oxide (i.e., 120 parts).

[0071] The method for preparing sound-absorbing and temperature-controlled magnesium oxychloride cement concrete in this embodiment includes the following steps:

[0072] (a) Weigh out magnesium oxide, magnesium chloride hexahydrate, water, standard sand, water-resistant agent and modified recycled aggregate;

[0073] (b) Mix and stir magnesium oxide, magnesium chloride hexahydrate, water-resistant agent and water to form modified magnesium oxychloride cement paste;

[0074] (c) Add standard sand to the magnesium oxychloride cement slurry obtained in step (b) and stir to mix evenly;

[0075] (d) Add modified recycled aggregate to the mixture obtained in step (c), stir and mix evenly to obtain the sound-absorbing and temperature-controlled magnesium oxychloride cement concrete of this embodiment.

[0076] The modified recycled aggregate is prepared by the following steps: (I) Take waste concrete from building demolition, crush and screen it, select particles with a particle size of 5mm-10mm, wash it with clean water until the pH value is stable at 7-8, and dry it until the moisture content is ≤2% to obtain recycled aggregate; (II) Put the recycled aggregate into a vacuum impregnation tank, pour in 60℃ lignocellulose temperature-controlled phase change material (at 60℃, the lignocellulose temperature-controlled phase change material is in a low viscosity liquid state; the mass ratio of recycled aggregate to lignocellulose temperature-controlled phase change material is 2:1); (III) After sealing, evacuate to -0.09MPa and maintain 60℃ for impregnation for 2h (stir once every 30min during the period); (IV) After draining, spray epoxy resin (the amount is 3% of the mass of recycled aggregate) and cure at room temperature for 30min.

[0077] The lignocellulose temperature-controlled phase change material used in step (II) was prepared by a method including the following steps: Rice straw with a particle size less than 60 mesh was mixed with a 6wt% cellulose solution (by soaking commercially available α-cellulose successively in methanol and N,N-dimethylacetamide for 1 h each, filtering, and then adding the α-cellulose to a mixed solution of LiCl and N,N-dimethylacetamide, mechanically stirring at 60°C until uniformly dispersed to obtain the cellulose solution; wherein, the mixed solution of LiCl and N,N-dimethylacetamide was prepared by adding 8.0 g of N,N-dimethylacetamide to 100.0 mL of N,N-dimethylacetamide). After uniformly mixing LiCl, the mixture was mechanically mixed at a ratio of 0.50 g / mL (the amount of straw is in g and the amount of cellulose solution is in mL) to obtain a mixture; A2, the mixture was poured into a silicone rubber mold and manually pressed flat to obtain a green body; the green body was left to stand for 2 hours (preliminary regeneration), and then the preliminarily regenerated green body was placed in water (the standing time in water was 3.5 hours) to carry out enhanced regeneration of the sample, so as to completely replace the DMAC / LiCl solvent (a mixed solution of LiCl and N,N-dimethylacetamide) with water, and at the same time reconstruct the cellulose hydrogen bond network. The regenerated blank was pre-frozen at -50℃ for 8 hours, and then freeze-dried at -50℃ for 24 hours to lock the porous structure and complete the shaping process to form lignin fiber foam; A3, the lignin fiber foam was placed in a molten inorganic phosphorus-based phase change material modification solution (the mass ratio of lignin cellulose foam to inorganic phosphorus-based phase change material modification solution was 1:5), and vacuum impregnated at 60℃ for 3 hours. After impregnation, low-temperature crystallization was carried out at 15℃ to obtain lignin cellulose temperature-controlled phase change material.

[0078] The inorganic phosphorus-based phase change material modification solution is prepared by the following steps: anhydrous sodium carbonate decahydrate (SCD) and disodium hydrogen phosphate dodecahydrate (DHPD) are mixed at a weight ratio of 2:8 without the need for additional water or purification, and directly melted at 60°C to form an inorganic phosphorus-based phase change material modification solution with low viscosity and fluidity similar to natural water.

[0079] Comparative Example 1

[0080] The only difference between this comparative example and Example 1 is that no water-resistant agent is used; all other aspects are the same as in Example 1.

[0081] Comparative Example 2

[0082] The only difference between this comparative example and Example 1 is that tannic acid is not used; all other aspects are the same as in Example 1.

[0083] Comparative Example 3

[0084] The only difference between this comparative example and Example 2 is that tannic acid is not used; all other aspects are the same as in Example 2.

[0085] Comparative Example 4

[0086] The only difference between this comparative example and Example 3 is that tannic acid is not used; all other aspects are the same as in Example 3.

[0087] Comparative Example 5

[0088] The only difference between this comparative example and Example 2 is that tannic acid is not used, and the amount of electroplating sludge water quenching slag is 5% (30 parts) of the mass of magnesium oxide. All other aspects are the same as in Example 2.

[0089] Comparative Example 6

[0090] The only difference between this comparative example and Example 2 is that tannic acid is not used, and the amount of electroplating sludge quenching slag is 30% (180 parts) of the mass of magnesium oxide. All other aspects are the same as in Example 2.

[0091] Comparative Example 7

[0092] The only difference between this comparative example and Example 1 is that electroplating sludge water quenching residue is not used; otherwise, they are the same as in Example 1.

[0093] Comparative Example 8

[0094] The only difference between this comparative example and Example 2 is that tannic acid is not used, and fly ash is used instead of electroplating sludge water quenching slag; otherwise, they are the same as in Example 2.

[0095] Comparative Example 9

[0096] The only difference between this comparative example and Example 5 is that an equal amount of recycled aggregate is used to replace the modified recycled aggregate (i.e., the step of modifying the recycled aggregate is omitted), and all other aspects are consistent with Example 5.

[0097] Comparative Example 10

[0098] This comparative example is unmodified magnesium oxychloride cement concrete, comprising the following components by weight: 600 parts magnesium oxide, 450 parts magnesium chloride hexahydrate, 300 parts water, 900 parts standard sand, and 300 parts recycled aggregate.

[0099] The preparation method of the unmodified magnesium oxychloride cement concrete in this comparative example includes the following steps:

[0100] (a) Weigh the magnesium oxide, magnesium chloride hexahydrate, water, standard sand (same as in Example 5) and recycled aggregate (take waste concrete from building demolition, crush and screen it to select particles with a particle size of 5mm to 10mm, wash it with clean water until the pH value is stable at 7 to 8, and dry it until the moisture content is ≤2% to obtain recycled aggregate).

[0101] (b) The magnesium oxide, magnesium chloride hexahydrate and water are mixed and stirred to form magnesium oxychloride cement paste;

[0102] (c) Add standard sand to the magnesium oxychloride cement slurry obtained in step (b) and stir to mix evenly;

[0103] (d) Add recycled aggregate to the mixture obtained in step (c) and stir to mix evenly to obtain the magnesium oxychloride cement concrete of this embodiment.

[0104] Comparative Example 11

[0105] The only difference between this comparative example and Example 5 is that n-tetradecane / graphite is used instead of lignin temperature-controlled phase change material in the preparation of modified recycled aggregate; all other aspects are the same as in Example 5.

[0106] Experimental Example

[0107] 1. Mechanical property testing:

[0108] The mechanical properties of magnesium oxychloride cement were tested according to GB / T17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)". The mechanical properties of magnesium oxychloride cement concrete were tested according to "Standard for Strength Testing and Evaluation of Concrete" (GB / T50107-2010). The water resistance was tested according to GB / T 20473-2021 "Building Thermal Insulation Mortar". The test results are shown in […]. Figure 1 As shown in Table 1.

[0109] Table 1

[0110]

[0111] Note: Magnesium oxychloride cement is a rapid-hardening cement with early strength. Its 7-day compressive strength can generally reach 80%-90% of its 28-day compressive strength.

[0112] Depend on Figure 1It can be seen that the compressive strength of magnesium oxychloride cement increases with the increase of water-resistant agent. Among them, the high water-resistant magnesium oxychloride cement in Example 2, where the ball milling time of the electroplating sludge water-quenched slag is 30 min and the dosage of the electroplating sludge water-quenched slag is 20% of the magnesium oxide mass, has the highest compressive strength. The softening coefficient of magnesium oxychloride cement increases with the increase of water-resistant agent; Comparative Example 1, which did not use water-resistant agent, therefore has the lowest softening coefficient.

[0113] 2. The phase transition enthalpy was determined according to GB / T 19466.3-2004 Differential Scanning Calorimetry (DSC) Part 3 for Plastics; the water absorption rate and crushing value were determined according to GB / T 14685-2011 Gravel and Crushed Stone for Construction; and the interfacial bond strength was determined according to JTJ / T 270-1998 Test Procedure for Concrete in Water Transport Engineering. Unmodified recycled aggregate was used as a blank control. The test results are shown in Table 2.

[0114] Table 2 Results of test on the performance of recycled aggregate

[0115]

[0116] As shown in Table 2, the water absorption and crushing value of the modified concrete were significantly reduced, indicating that the performance of the modified recycled aggregate was improved, reaching the Class I standard for natural aggregates. The interfacial bond strength was increased to 3.4 MPa and 3.1 MPa, effectively improving the core defect of weak interface between recycled aggregate and cement matrix.

[0117] 3. The thermal conductivity was tested according to GB10294-2008 Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials, and the sound absorption coefficient was tested according to GBJ88-85 Measurement Specification for Sound Absorption Coefficient and Acoustic Impedance by Standing Wave Tube Method. The results are shown in Table 3.

[0118] Table 3 Results of sound absorption and temperature control test

[0119]

[0120] As shown in Table 3, the lignocellulose temperature-controlled phase change material has strong sound absorption and temperature control capabilities. It can be used to modify recycled aggregates, and the modified recycled aggregates can be added to magnesium oxychloride cement concrete to enhance the sound absorption capacity of the concrete and achieve the effect of sound absorption and temperature control.

[0121] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A sound-absorbing and temperature-controlled magnesium oxychloride cement concrete, characterized in that, The components of the sound-absorbing and temperature-controlled magnesium oxychloride cement concrete include high water-resistant magnesium oxychloride cement, standard sand, and modified recycled aggregate. The high water-resistant magnesium oxychloride cement comprises: magnesium oxide, magnesium chloride hexahydrate, water, and a water-resistant agent; the water-resistant agent comprises tannic acid and electroplating sludge water-quenched slag; by mass parts, it comprises: 900-950 parts of standard sand and 300-400 parts of modified recycled aggregate. The modified recycled aggregate comprises recycled aggregate, lignocellulose temperature-controlled phase change material, and an epoxy resin encapsulation layer coated on the surface of the recycled aggregate. The modified recycled aggregate is prepared by a method comprising the following steps: (I) placing the recycled aggregate into a vacuum impregnation tank and pouring in lignocellulose temperature-controlled phase change material at 60-70°C; (II) sealing and then vacuum impregnating; the vacuum impregnation temperature is 60-70°C and the vacuum impregnation time is 1-3 hours; the vacuum impregnation pressure is -0.08 to -0.10 MPa; (III) after vacuum impregnation, drying, and encapsulating the recycled aggregate treated in step (II) with epoxy resin to form an epoxy resin encapsulation layer, thereby obtaining the modified recycled aggregate; The lignocellulose temperature-controlled phase change material is prepared by a method comprising the following steps: A1. Mechanically mixing biomass ash with a particle size of less than 60 mesh with a cellulose solution to obtain a mixture; A2. Shaping the mixture to form biomass fiber foam; A3. Placing the biomass fiber foam into a molten inorganic phosphorus-based phase change material modification solution, vacuum impregnating for 2.5-4 hours, and then performing low-temperature crystallization at 13-17℃ to obtain the lignocellulose temperature-controlled phase change material. The cellulose solution in step A1 is obtained by soaking α-cellulose successively in methanol and N,N-dimethylacetamide, filtering, adding it to a mixed solution of LiCl and N,N-dimethylacetamide, and mechanically stirring until uniformly dispersed. Step A2 includes: first, using a mold to pre-shape the mixture to obtain a blank; then, letting the blank stand for 1-3 hours, then standing in water for 3-4 hours, taking it out of the water and pre-freezing it at a temperature of -20~-80℃ for 4-12 hours, and then drying it to obtain biomass fiber foam. In step A3, the mass ratio of lignocellulose foam to inorganic phosphorus-based phase change material modification solution is 1:(1.25-7.1); the inorganic phosphorus-based phase change material modification solution is prepared by a method including the following steps: anhydrous sodium carbonate decahydrate and disodium hydrogen phosphate dodecahydrate are mixed at a weight ratio of 2:(7-9) and directly melted at 60-70℃ to form inorganic phosphorus-based phase change material modification solution.

2. The sound-absorbing and temperature-controlled magnesium oxychloride cement concrete as described in claim 1, characterized in that, In step (III), the amount of epoxy resin used is 3%-5% of the mass of the recycled aggregate; The modified recycled aggregate has a particle size of 5-20 mm.

3. The sound-absorbing and temperature-controlled magnesium oxychloride cement concrete as described in claim 1 or 2, characterized in that, The high water-resistant magnesium oxychloride cement comprises the following components in parts by weight: Magnesium oxide 550-600 parts, magnesium chloride hexahydrate 450-500 parts, water 300-350 parts, and water-resistant agent 55-180 parts; The mass of the tannic acid is 0.2%-1.0% of the mass of the magnesium oxide, the electroplating sludge quenching residue is the tailings after extracting valuable metals from the electroplating sludge, and the amount of the electroplating sludge quenching residue is 15%-25% of the mass of the magnesium oxide cement.

4. The sound-absorbing and temperature-controlled magnesium oxychloride cement concrete as described in claim 3, characterized in that, The particle size of the electroplating sludge quenching slag is such that it can pass through a 200-mesh sieve.

5. The method for preparing sound-absorbing, temperature-controlled magnesium oxychloride cement concrete as described in any one of claims 1-4, characterized in that, Includes the following steps: (a) Weigh the magnesium oxide, magnesium chloride hexahydrate, water, standard sand, water-resistant agent and modified recycled aggregate; (b) The magnesium oxide, magnesium chloride hexahydrate, water-resistant agent and water are mixed and stirred to form a modified magnesium oxychloride cement paste; (c) Add the standard sand to the magnesium oxychloride cement slurry obtained in step (b) and stir to mix evenly; (d) Add the modified recycled aggregate to the mixture obtained in step (c), stir and mix evenly to obtain the sound-absorbing temperature-controlled magnesium oxychloride cement concrete.

6. The method for preparing sound-absorbing, temperature-controlled magnesium oxychloride cement concrete as described in claim 5, characterized in that, Step (d) is followed by a step of compacting the sound-absorbing temperature-controlled magnesium oxychloride cement concrete by vibration and curing it at 25±1℃ and 60%-80% relative humidity.

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