CN115745548A - Phosphogypsum-based self-leveling material for ground heating backfill and preparation method thereof - Google Patents
Phosphogypsum-based self-leveling material for ground heating backfill and preparation method thereof Download PDFInfo
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Abstract
The invention provides a phosphogypsum-based self-leveling material for ground heating backfill and a preparation method thereof, belonging to the technical field of building materials. According to the self-leveling material provided by the invention, the high-thermal-conductivity phase-change energy storage component is added, the performance parameters of the phosphorus building gypsum are controlled, and other components are matched, so that the water requirement of the material is reduced and the heat transfer performance of the material is improved on the premise of ensuring the fluidity and the mechanical strength of the material. The self-leveling material obtained by the invention has the water demand of only 55-60% of the weight of the solid powder, the highest heat conductivity coefficient of 0.98W/(m.K), good uniformity and no delamination and bleeding; as can be seen from the SEM image, the fibrous dihydrate gypsum crystal network generated by hydration is wrapped around the granular waste rock powder, a large amount of dihydrate gypsum crystals are distributed around the flaky expanded graphite micro powder, and the microstructure is very compact, so that the mechanical strength and the heat transfer performance of the phosphogypsum-based self-leveling ground material for ground heating backfill are effectively ensured.
Description
Technical Field
The invention relates to the technical field of building materials, in particular to a phosphogypsum-based self-leveling material for ground heating backfill and a preparation method thereof.
Background
In recent years, with the popularization and development of building energy-saving technology in China, gypsum-based self-leveling materials are favored by the building industry by virtue of the advantages of high self-setting speed, stable volume, no cracking, no hollowing, energy conservation, environmental protection and the like, and especially pay attention to the fields of ground heating backfill and floor surface automatic leveling. However, the gypsum-based self-leveling materials on the market at present mostly adopt a cementing material system compounded by alpha-type high-strength gypsum, anhydrite and sulphoaluminate cement, high-quality quartz sand is used as a filler, and chemical additives such as latex powder, a water reducing agent, a retarder, a water-retaining agent, a defoaming agent and the like are added, so that the overall cost is high, and the popularization, the application and the development of the gypsum-based self-leveling materials are not facilitated. In addition, the gypsum-based material has the characteristics of natural porosity and heat preservation, has low heat conductivity coefficient, is not beneficial to heat transfer when used for ground heating backfill, and is easy to cause energy waste.
The phosphogypsum is an industrial byproduct generated in the process of industrially leaching phosphorite by a sulfuric acid wet method to prepare phosphoric acid, the yield of the phosphogypsum in China is about thousands of tons every year, but the utilization rate is less than 40 percent, and the utilization way is single. As the phosphorus building gypsum contains impurities such as soluble phosphorus, eutectic phosphorus and the like, which easily cause the problems of unstable setting time, generally low 24h strength and the like, most enterprises achieve the specific surface area of the phosphogypsum to be 500m 2 The setting time is controlled within 3-6 min, the phosphorus building gypsum can better meet the production requirements of gypsum boards and gypsum blocks, but for self-leveling gypsum and plastering gypsum, the setting time is too fast, which is not favorable for maintaining fluidity and construction.
Disclosure of Invention
In view of the above, the invention aims to provide a phosphogypsum-based self-leveling material for geothermal backfilling and a preparation method thereof.
In order to achieve the purpose, the invention provides the following technical scheme:
the phosphogypsum-based self-leveling material for the ground heating backfill comprises the following components in parts by weight: 750-800 parts of phosphorus building gypsum, 50-100 parts of high-strength gypsum, 100-200 parts of waste stone powder, 10-100 parts of high-heat-conductivity phase-change energy storage component, 1-10 parts of redispersible latex powder, 1-3 parts of water reducing agent, 0.1-0.5 part of water-retaining agent, 0.1-0.5 part of retarder and 0.1-0.5 part of defoaming agent;
wherein, the weight percentage content of the dihydrate gypsum in the phosphorus building gypsum is 10-15%, the weight percentage content of the hemihydrate gypsum is 80-85%, the weight percentage content of the anhydrous gypsum is 1-5%, and the specific surface area is 350m 2 /kg～500m 2 /kg；
The high-heat-conductivity phase-change energy storage component is prepared by compounding expandable graphite and phase-change paraffin.
Preferably, the preparation method of the phosphorous building gypsum comprises the following steps:
drying the original phosphogypsum for 40-55 h at 35-45 ℃ to obtain a dried product;
uniformly mixing the dried product and quartz sand according to a certain proportion, and mixing and grinding the mixture in a standard test mill for 30-45 min to obtain a mixture I;
calcining the mixture I at 160-190 ℃ for 1-3 h to obtain a calcined product;
and placing the calcined product in a closed plastic bucket for aging for 24-72 hours to obtain the phosphorus building gypsum.
Preferably, the weight ratio of the dried product to the quartz sand is (88-92): (8 to 12).
Preferably, the standard consistency water demand of the phosphorus building gypsum is 62-68%, the initial setting time is 7-12 min, the final setting time is 15-20min, the compressive strength of 2h is 4.2-6.7MPa, and the flexural strength of 2h is 2.0-3.2 MPa.
Preferably, the high-strength gypsum is alpha-type high-strength gypsum powder, the water requirement of the standard consistency is 35-40%, the setting time is 12-15min, and the compressive strength of 2h is 15-20 MPa.
Preferably, the waste stone powder is waste solid powder produced in the production and processing process of machine-made sand, the granularity is less than 200 meshes, and the mud content is less than or equal to 5 percent; the redispersible latex powder is ethylene-vinyl acetate copolymer powder; the water reducing agent is a polycarboxylic acid water reducing agent and is in a powder shape, and the water reducing rate is more than or equal to 20%; the water retaining agent is hydroxypropyl methyl cellulose ether and is in a powder shape, and the viscosity is 40000mPa.s-80000mPa.s; the retarder is a protein retarder and is in a powder shape; the defoaming agent is polyether modified organic silicon and is powder.
Preferably, the preparation method of the high thermal conductivity phase change energy storage component comprises the following steps:
putting expandable graphite powder into a microwave oven, and heating for 10-15 s under 800W power to obtain expanded graphite;
cutting the phase-change paraffin into 0.1-5 mm particles, heating and melting in a water bath to obtain molten paraffin;
stirring and mixing the expanded graphite and the molten paraffin according to a certain proportion to obtain the high-thermal-conductivity phase-change energy storage component.
Preferably, the particle size of the expandable graphite powder is 300-400 meshes; the phase-change temperature range of the phase-change paraffin is 45-55 ℃; the temperature of the water bath for heating the water bath is 55-65 ℃; the weight ratio of the expanded graphite to the molten paraffin is 1: (12 to 19).
The invention also provides a preparation method of the phosphogypsum-based self-leveling material for ground heating backfill, which comprises the following steps:
weighing the raw materials according to the proportion, and stirring and mixing the raw materials uniformly in a cement mortar stirrer to obtain the cement mortar.
The invention also provides a using method of the phosphogypsum-based self-leveling material for ground heating backfill, which comprises the steps of adding water accounting for 55-60% of the weight of solid powder when in use, and adjusting the fluidity to 140-150 mm.
The beneficial technical effects are as follows: the invention provides a phosphogypsum-based self-leveling material for ground heating backfill, which reduces the water demand of the material and increases the heat-conducting property of the material on the premise of ensuring the fluidity and the mechanical property of the material by adding a high-heat-conducting phase-change energy storage component, controlling the performance parameters of phosphorus building gypsum and matching with other components. The water requirement of the phosphogypsum-based self-leveling material for ground heating backfill is only 55-60% of the weight of solid powder, the highest heat conductivity coefficient can reach 0.98W/(m.K), the fluidity loss is small, the uniformity is good, and the phenomena of layering and bleeding are avoided; as can be seen from the SEM image, the fibrous dihydrate gypsum crystal network generated by hydration wraps the granular waste rock powder, a large amount of dihydrate gypsum crystals are distributed around the flaky expanded graphite micro powder, the microstructure is very compact, and the mechanical strength and the heat transfer performance of the phosphogypsum-based self-leveling floor material for ground heating backfill can be well ensured.
Drawings
FIG. 1 is an XRD pattern of calcined phosphorus architectural gypsum from example 3;
FIG. 2 is an SEM image of calcined phosphogypsum of example 3;
fig. 3 is an SEM image of the phosphogypsum-based self-leveling material for ground heating backfill in example 3.
Detailed Description
The invention provides a phosphogypsum-based self-leveling material for ground heating backfill, which comprises the following components in parts by weight: 750-800 parts of phosphorus building gypsum, 50-100 parts of high-strength gypsum, 100-200 parts of waste stone powder, 10-100 parts of high-thermal-conductivity phase change energy storage component, 1-10 parts of redispersible latex powder, 1-3 parts of water reducing agent, 0.1-0.5 part of water retaining agent, 0.1-0.5 part of retarder and 0.1-0.5 part of defoaming agent;
in the invention, the high-strength gypsum is preferably alpha-type high-strength gypsum powder, the water requirement for the standard consistency is preferably 35-40%, the setting time is preferably 12-15min, and the compressive strength of 2h is preferably 15-20 MPa.
In the invention, the waste stone powder is preferably waste solid powder generated in the production and processing process of machine-made sand, the granularity is less than 200 meshes, and the mud content is less than or equal to 5 percent; by replacing quartz sand powder and part of organic water-retaining agent with waste stone powder, the industrial solid waste is reasonably utilized, the production cost of the material is reduced, the dispersing effect of the waste stone powder and the water retaining effect of clay-containing minerals are fully exerted, the dispersibility and the water retaining property of the self-leveling material are improved, the layering and bleeding risks in the material construction process are reduced, and the material has good economic benefits and technical effects.
In the invention, the redispersible latex powder is preferably ethylene-vinyl acetate copolymer powder; the water reducing agent is preferably a polycarboxylic acid water reducing agent which is powdery, and the water reducing rate is more than or equal to 20%; the water retaining agent is preferably hydroxypropyl methyl cellulose ether, is powdery and has the viscosity of 40000mPa.s-80000mPa.s; the retarder is preferably a protein retarder and is in powder shape; the defoamer is preferably polyether modified silicone in powder form.
In the phosphorus building gypsum, the weight percentage content of dihydrate gypsum is 10-15%, the weight percentage content of hemihydrate gypsum is 80-85%, the weight percentage content of anhydrous gypsum is 1-5%, and the specific surface area is 350m 2 /kg～500m 2 (iv) kg; the phosphogypsum-based self-leveling material with the performance parameters has the advantages of low water demand and moderate setting time, and can effectively improve the fluidity retention capacity and mechanical strength of the phosphogypsum-based self-leveling material in the follow-up process.
In the present invention, the standard consistency water demand of the phosphogypsum is preferably 62-68%, more preferably 65%; the initial setting time is preferably 7min to 12min, and more preferably 10min; the final setting time is preferably 15min to 20min, and more preferably 18min; the 2h compressive strength is preferably 4.2MPa to 6.7MPa, and more preferably 6.0MPa; the breaking strength at 2h is preferably 2.0MPa to 3.2MPa, more preferably 2.9MPa.
In the invention, the preparation method of the phosphorous building gypsum comprises the following steps:
firstly, drying undisturbed phosphogypsum for 40-55 hours at 35-45 ℃ to obtain a dried product;
after obtaining a dried product, uniformly mixing the dried product and quartz sand according to a certain proportion, and mixing and grinding the mixture in a standard test mill for 30-45 min to obtain a mixture I; in the invention, the granularity of the quartz sand is preferably 80-120 meshes; the weight ratio of the dried product to the quartz sand is preferably (88-92): (8-12); the standard test mill is preferably a standard test mill with the diameter of 500mm multiplied by 500 mm; the rotating speed of a grinding barrel of the standard test mill is preferably 48r/min; the original phosphogypsum and the quartz sand are mixed and ground according to the proportion and the conditions, and the quartz sand with hard texture is used as a secondary grinding body to be dispersed among gypsum particles, so that the grinding process of the phosphogypsum is facilitated, the problems of ball sticking phenomenon, dispersion reduction and the like caused by crystal water removal of the phosphogypsum in the grinding process are solved, and the subsequent phosphogypsum is fully heated and uniformly calcined. In addition, the ground quartz sand powder can also be used as a filler of the phosphogypsum-based self-leveling material, and has positive contribution to improving the compactness and dimensional stability of the microstructure of the material.
After the mixture I is obtained, calcining the mixture I at 160-190 ℃ for 1-3 h to obtain a calcined product; in the present invention, the calcination is calcination in a resistance furnace.
After calcination, the calcined product is placed in a closed plastic bucket and aged for 24-72 h to obtain the phosphorus building gypsum. In the invention, the water demand and the hardening speed of the final phosphorus building gypsum can be effectively controlled by controlling the aging time.
The high-thermal-conductivity phase-change energy storage component is prepared by compounding expandable graphite and phase-change paraffin.
In the invention, the preparation method of the high-thermal-conductivity phase change energy storage component comprises the following steps:
the expandable graphite powder is put into a microwave oven and heated for 10 to 15 seconds under the power of 800W to obtain the expandable graphite; in the present invention, the particle size of the expandable graphite powder is preferably 300 to 400 mesh, and more preferably 350 mesh.
Cutting the phase-change paraffin into particles of 0.1-5 mm, and heating and melting in a water bath to obtain molten paraffin; the phase-change temperature range of the phase-change paraffin is preferably 45-55 ℃, and more preferably 48-50 ℃; the temperature of the water bath heated by the water bath is preferably 55-65 ℃, and more preferably 60 ℃.
Stirring and mixing the treated expanded graphite and the molten paraffin according to a certain proportion to obtain a high-thermal-conductivity phase-change energy-storage component; in the present invention, the weight ratio of the expanded graphite to the molten paraffin is preferably 1: (12 to 19), more preferably 1:15. the processed expanded graphite and the molten paraffin are stirred and mixed, so that the paraffin is fully absorbed and enters the interior of the expanded graphite to obtain the high-heat-conductivity phase-change energy storage component with the core-shell structure. The graphite shells are mutually overlapped to form a network structure, so that the heat conduction performance of the ground heating backfill material can be improved as a 'heat bridge', a 'micro heat pump' is formed in the ground heating backfill material through the phase change heat absorption/release effect of the paraffin of the inner core, the suction effect of heat from a hot end (a hot water pipe) to a cold end (the ground) is accelerated, the adverse effect of the temperature fluctuation of the hot end on heat transfer is reduced, and the heating power and the comprehensive energy consumption of a ground heating system are effectively reduced; the high-heat-conductivity phase-change energy storage component can also be dispersed among gypsum particles to play a role in lubrication, further improve the fluidity of slurry, and can also be used as a nucleation site of a supersaturated solution to promote crystallization nucleation and growth development of dihydrate gypsum crystals, so that the microstructure of the material is more compact.
The invention also provides a preparation method of the phosphogypsum-based self-leveling material for ground heating backfill, which comprises the following steps:
weighing the raw materials according to the proportion, and stirring and mixing the raw materials uniformly in a cement mortar stirrer to obtain the cement mortar.
In the present invention, in the case of the present invention,
the invention also provides a using method of the phosphogypsum-based self-leveling material for ground heating backfill, which comprises the steps of adding water accounting for 55-60% of the weight of solid powder when in use, and adjusting the fluidity to 140-150 mm.
In order to better understand the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples.
Example 1
The phosphogypsum-based self-leveling material for the geothermal backfilling comprises the following components in parts by mass: 750 parts of phosphorus building gypsum, 100 parts of high-strength gypsum, 100 parts of waste stone powder, 50 parts of high-thermal-conductivity phase-change energy storage component, 10 parts of redispersible latex powder, 1 part of water reducing agent, 0.5 part of water-retaining agent, 0.1 part of retarder and 0.1 part of defoaming agent.
Wherein the high-strength gypsum is alpha-type high-strength gypsum powder, the water requirement of the standard consistency is 35%, the setting time is 12min, and the compressive strength of 2h is 15MPa; the waste stone powder is waste solid powder produced in the production and processing process of machine-made sand, the granularity is 170 meshes, and the mud content is less than or equal to 5 percent; the re-dispersible latex powder is ethylene-vinyl acetate copolymer powder; the water reducing agent is a polycarboxylic acid water reducing agent which is powdery, and the water reducing rate is more than or equal to 20 percent; water-retaining agent hydroxypropyl methyl cellulose ether, powder, viscosity 40000mPa.s; the retarder is protein retarder and is in powder shape; the defoaming agent is polyether modified organic silicon and is powder;
the preparation method of the phosphorus building gypsum comprises the following steps: drying undisturbed phosphogypsum at 45 ℃ for 40h, uniformly mixing the undisturbed phosphogypsum with quartz sand according to the weight ratio of 92 to 8, grinding the mixture in a standard test mill with the diameter of 500 multiplied by 500mm for 45min, calcining the mixture at 190 ℃ for 1h, and placing the calcined product in a closed plastic bucket for aging for 72h to obtain the phosphorus building gypsum. Through detection, the weight percentage content of the dihydrate gypsum in the phosphorus building gypsum prepared by the preparation method is 14%, the weight percentage content of the hemihydrate gypsum is 85%, and the weight percentage content of the anhydrite is 1%; the specific surface area is 500m 2 The water demand of the standard consistency is 62 percent, the initial setting time is 7min, the final setting time is 15min, the compressive strength of 2h is 4.2MPa, and the flexural strength of 2h is 2.0MPa.
The preparation method of the high-thermal-conductivity phase-change energy storage component comprises the following steps: placing expandable graphite powder with the particle size of 300 meshes into a microwave oven, and heating for 10s under 800W power to obtain expanded graphite; cutting phase-change paraffin (the phase-change temperature range is 45-48 ℃) into particles with the diameter of about 0.1mm, and heating and melting the particles in a water bath at the temperature of 55 ℃ to obtain molten paraffin; stirring and mixing the expanded graphite and the molten paraffin according to the weight ratio of 1.
The preparation method of the phosphogypsum-based self-leveling material for ground heating backfill comprises the following steps: weighing the raw materials according to the proportion, and stirring and mixing the raw materials uniformly in a cement mortar stirrer to obtain the cement mortar.
The application method of the phosphogypsum-based self-leveling material for ground heating backfill comprises the steps of adding water accounting for 55% of the weight of solid powder when the phosphogypsum-based self-leveling material is used, adjusting the fluidity of slurry to be 140mm, and detecting that the initial setting time of the obtained slurry is 68min, the final setting time is 92min and the fluidity of 30min is 140mm. Pouring the slurry into a 40mm × 40mm × 160mm mould, solidifying and hardening for 2h, then removing the mould, placing the test block in an indoor environment, standing and maintaining for 24h, and measuring that the wet compressive strength of the test block in 24h is 8.6MPa and the wet flexural strength is 3.4MPa. And (3) placing the hardened test block into a drying oven for drying at 40 ℃, and measuring the absolute dry compressive strength of 25.6MPa, the absolute dry flexural strength of 8.8MPa and the tensile bonding strength of 2.3MPa, wherein the performances meet the requirements of standard JC/T1023-2021 gypsum-based self-leveling mortar.
The laser thermal conductivity meter tests the thermal conductivity of the phosphogypsum-based self-leveling material for ground heating backfill, and the result shows that the thermal conductivity is 0.72W/(m.K).
Example 2
The phosphogypsum-based self-leveling material for the geothermal backfilling comprises the following components in parts by mass: 750 parts of phosphorus building gypsum, 80 parts of high-strength gypsum, 200 parts of waste stone powder, 10 parts of high-thermal-conductivity phase-change energy storage component, 5 parts of redispersible latex powder, 3 parts of water reducing agent, 0.1 part of water-retaining agent, 0.5 part of retarder and 0.5 part of defoaming agent.
Wherein the high-strength gypsum is alpha-type high-strength gypsum powder, the water requirement of the standard consistency is 40%, the setting time is 15min, and the compressive strength of 2h is 20MPa; the waste stone powder is waste solid powder produced in the production and processing process of machine-made sand, the granularity is 150 meshes, and the mud content is less than or equal to 5 percent; the re-dispersible latex powder is ethylene-vinyl acetate copolymer powder; the water reducing agent is a polycarboxylic acid water reducing agent which is powdery, and the water reducing rate is more than or equal to 20 percent; water-retaining agent hydroxypropyl methyl cellulose ether, powder, viscosity 80000mPa.s; the retarder is protein retarder and is in powder shape; the defoaming agent is polyether modified organic silicon and is powder;
the preparation method of the phosphorus building gypsum comprises the following steps: drying undisturbed phosphogypsum at 35 ℃ for 55h, uniformly mixing the ardealite with quartz sand according to the weight ratio of 88 to 12, mixing and grinding the ardealite in a standard test mill with the diameter of 500 multiplied by 500mm for 30min, calcining the ardealite at 160 ℃ for 3h, and placing a calcined product in a closed plastic bucket for aging for 24h to obtain the phosphorus building gypsum. Through detection, the phosphorus building gypsum prepared by the preparation method contains 10 wt% of dihydrate gypsum, 85 wt% of hemihydrate gypsum, 5 wt% of anhydrous gypsum and specific surface areaProduct of 350m 2 The water requirement of standard consistency is 68 percent, the initial setting time is 12min, the final setting time is 20min, the compressive strength of 2h is 6.7MPa, and the flexural strength of 2h is 3.2MPa.
The preparation method of the high-thermal-conductivity phase-change energy storage component comprises the following steps: placing expandable graphite powder with the particle size of 400 meshes into a microwave oven, and heating for 15s under the power of 800W to obtain expanded graphite; cutting phase-change paraffin (the phase-change temperature range is 52-55 ℃) into particles with the size of about 5mm, and heating and melting the particles in a water bath at the temperature of 65 ℃ to obtain molten paraffin; stirring and mixing the expanded graphite and the molten paraffin according to the weight ratio of 1.
The preparation method of the phosphogypsum-based self-leveling material for ground heating backfill comprises the following steps: weighing the raw materials according to the proportion, and stirring and mixing the raw materials uniformly in a cement mortar stirrer to obtain the cement mortar.
The application method of the phosphogypsum-based self-leveling material for ground heating backfill comprises the steps of adding water accounting for 60% of the weight of solid powder when the phosphogypsum-based self-leveling material is used, adjusting the fluidity of slurry to be 150mm, and detecting that the initial setting time of the obtained slurry is 72min, the final setting time is 105min and the fluidity is 149mm. Pouring the slurry into a 40mm × 40mm × 160mm mould, solidifying and hardening for 2h, then removing the mould, placing the test block in an indoor environment, standing and curing for 24h, and measuring that the 24h wet compressive strength and the wet flexural strength of the test block are 6.4MPa and 2.8MPa. And (3) placing the hardened test block into a drying oven at 40 ℃ for drying, and measuring the oven-dry compressive strength of 20.6MPa, the oven-dry bending strength of 7.3MPa and the tensile bonding strength of 1.5MPa, wherein the performances all meet the standard requirements.
The laser thermal conductivity meter tests the thermal conductivity of the phosphogypsum-based self-leveling material for ground heating backfill, and the result shows that the thermal conductivity is 0.66W/(m.K).
Example 3
The phosphogypsum-based self-leveling material for the geothermal backfilling comprises the following components in parts by mass: 800 parts of phosphorus building gypsum, 50 parts of high-strength gypsum, 150 parts of waste stone powder, 100 parts of high-thermal-conductivity phase-change energy storage component, 1 part of redispersible latex powder, 2 parts of water reducing agent, 0.3 part of water-retaining agent, 0.5 part of retarder and 0.3 part of defoaming agent.
Wherein the high-strength gypsum is alpha-type high-strength gypsum powder, the water requirement of the standard consistency is 38%, the setting time is 13min, and the compressive strength of 2h is 18MPa; the waste stone powder is waste solid powder produced in the production and processing process of machine-made sand, the granularity is 180 meshes, and the mud content is less than or equal to 5 percent; the re-dispersible latex powder is ethylene-vinyl acetate copolymer powder; the water reducing agent is a polycarboxylic acid water reducing agent which is powdery, and the water reducing rate is more than or equal to 20 percent; water-retaining agent hydroxypropyl methyl cellulose ether, powder, viscosity 60000mPa.s; the retarder is protein retarder and is powder; the defoaming agent is polyether modified organic silicon and is powder;
the preparation method of the phosphorus building gypsum comprises the following steps: drying undisturbed phosphogypsum at 40 ℃ for 48h, uniformly mixing the ardealite with quartz sand according to the weight ratio of 90 to 10, mixing and grinding the ardealite in a standard test mill with the diameter of 500 multiplied by 500mm for 40min, calcining the ardealite at 170 ℃ for 2h, and putting a calcined product in a closed plastic bucket for aging for 48h to obtain the phosphorus building gypsum. Through detection, in the phosphorus building gypsum obtained by the preparation method, the content of the dihydrate gypsum is 15 percent by weight, the content of the hemihydrate gypsum is 80 percent by weight, the content of the anhydrite is 5 percent by weight, and the specific surface area is 400m 2 The water requirement of standard consistency is 65 percent, the initial setting time is 10min, the final setting time is 18min, the compressive strength of 2h is 6.0MPa, and the flexural strength of 2h is 2.9MPa.
The phosphorous building gypsum obtained in this example was subjected to XRD analysis and SEM test, wherein the XRD analysis is shown in FIG. 1, and the SEM test result is shown in FIG. 2. As can be seen from fig. 1, the calcined phosphorous building gypsum is composed mainly of hemihydrate (hemihydrate) and quartz (quartz), and also has diffraction peaks for a portion of dihydrate (dihydrate) and anhydrite (anhydrite). As can be seen from figure 2, the calcined phosphogypsum has clear particle appearance, loose and porous surface, particle size distribution within 50 μm and 20 μm particle distribution. In the prepared phosphorus building gypsum, quartz is mainly used as an inert filler to be dispersed among gypsum particles, so that the fluidity of slurry is improved, and the water requirement of standard consistency is reduced; the hemihydrate gypsum has high dissolution speed and hydration activity, provides early network strength, and the anhydrous gypsum has low dissolution speed and hydration activity in a gelling system, can fill network gaps in the middle and later hydration of the gelling system, improves the network strength, has the lowest solubility and hydration activity of the dihydrate gypsum, and can be used as an ion adsorption and crystallization site in the gelling system to promote the development of the network strength.
The preparation method of the high-thermal-conductivity phase-change energy storage component comprises the following steps: putting expandable graphite powder with the particle size of 350 meshes into a microwave oven, and heating for 13s under the power of 800W to obtain expanded graphite; cutting phase-change paraffin (with phase-change temperature ranging from 48 ℃ to 52 ℃) into particles with the diameter of about 3mm, and heating and melting the particles in a water bath at the temperature of 60 ℃ to obtain molten paraffin; stirring and mixing the expanded graphite and the molten paraffin according to the weight ratio of 1.
The preparation method of the phosphogypsum-based self-leveling material for ground heating backfill comprises the following steps: weighing the raw materials according to the proportion, and stirring and mixing the raw materials uniformly in a cement mortar stirrer to obtain the cement mortar.
A use method of the phosphogypsum-based self-leveling material for ground heating backfill is characterized in that water accounting for 58% of the weight of solid powder is added when the phosphogypsum-based self-leveling material is used, the fluidity of slurry is adjusted to 145mm, and through detection, the initial setting time of the obtained slurry is 62min, the final setting time is 88min and the fluidity of 30min is 143mm. Pouring the slurry into a 40mm × 40mm × 160mm mould, solidifying and hardening for 2h, then removing the mould, placing the test block in an indoor environment, standing and curing for 24h, and measuring that the 24h wet compressive strength of the test block is 7.2MPa and the wet flexural strength is 2.9MPa. And (3) placing the hardened test block into a drying oven at 40 ℃ for drying, and measuring the oven-dry compressive strength of 22.3MPa, the oven-dry bending strength of 7.8MPa and the tensile bonding strength of 1.8MPa, wherein the performances all meet the standard requirements.
The laser thermal conductivity meter tests the thermal conductivity of the phosphogypsum-based self-leveling material for ground heating backfill, and the result shows that the thermal conductivity is 0.98W/(m.K).
SEM analysis of the micro-morphology of the phosphogypsum-based self-leveling floor material for ground heating backfill obtained in this example was performed, and the result is shown in fig. 3. As can be seen from fig. 3, the fibrous dihydrate gypsum crystal network generated by hydration wraps around the granular waste rock powder (stone powder), and meanwhile, a large amount of dihydrate gypsum crystals are distributed around the scale-like expanded graphite micropowder (graphite) in the magnified SEM image, so that the microstructure is very dense. The result shows that the expanded graphite micropowder on the one hand disperses to the middle of the crystal network structure to play the thermal bridge effect and the 'micro heat pump' effect, thereby improving the overall thermal conductivity of the material, and on the other hand can be used as a crystal nucleus agent to promote the formation of the dihydrate gypsum crystal network structure, so that the material microstructure is more compact.
Comparative example 1
Compared with example 3, the phosphorus building gypsum of the comparative example has the content of dihydrate gypsum of 4 percent by weight, the content of hemihydrate gypsum of 88 percent by weight, the content of anhydrous gypsum of 8 percent by weight and the specific surface area of 500m 2 Perkg, the phosphorus building gypsum from example 3 was replaced by the same parts by weight of the above phosphorus building gypsum. Through detection, the water requirement of the finally obtained self-leveling gypsum slurry is 65%, the initial fluidity is 145mm, the initial setting time is 51min, the final setting time is 64min, and the fluidity of 30min is 134mm. Pouring the slurry into a 40mm × 40mm × 160mm mould, solidifying and hardening for 2h, then removing the mould, placing the test block in an indoor environment, standing and maintaining for 24h, and measuring that the 24h wet compressive strength and the wet flexural strength of the test block are 5.8MPa and 1.9MPa. And (3) placing the hardened test block into a drying oven at 40 ℃ for drying, and measuring the oven-dry compressive strength of 18.7MPa, the oven-dry flexural strength of 6.2MPa and the tensile bonding strength of 1.1MPa. The laser thermal conductivity meter tests the thermal conductivity of the phosphogypsum-based self-leveling material for ground heating backfill, and the result shows that the thermal conductivity is 0.79W/(m.K).
Comparative example 2
Compared with example 3, the phosphorus building gypsum of the comparative example has the content of dihydrate gypsum of 18 percent by weight, the content of hemihydrate gypsum of 76 percent by weight, the content of anhydrous gypsum of 6 percent by weight and the specific surface area of 550m 2 Perkg, the phosphorus building gypsum of example 3 was replaced by the same parts by weight of the above phosphorus building gypsum, and the other components and operations were the same as in example 3. Through detection, the water demand of the finally obtained self-leveling gypsum slurry is 69%, the initial fluidity is 145mm, the initial setting time is 48min, the final setting time is 57min, and the fluidity of 30min is 113mm. Pouring the slurry into a 40mm × 40mm × 160mm mould, solidifying and hardening for 2h, then removing the mould, placing the test block in an indoor environment, standing and curing for 24h, and measuring that the 24h wet compressive strength and the wet flexural strength of the test block are respectively 3.8MPa and 1.1MPa. Placing the hardened test block into a 40 ℃ oven for drying, and measuring the oven-dry compressive strength of 12.7MPaThe breaking strength is 4.1MPa, and the tensile bonding strength is 0.6MPa. The laser thermal conductivity meter tests the thermal conductivity of the phosphogypsum-based self-leveling material for ground heating backfill, and the result shows that the thermal conductivity is 0.61W/(m.K).
Comparative example 3
Compared with the embodiment 3, the high-thermal-conductivity phase change energy storage component is replaced by the same weight part of graphite powder in the comparative example, and the rest components and operation are the same as those in the embodiment 3. Through detection, the water requirement of the finally obtained self-leveling gypsum slurry is 64 percent, the initial fluidity is 145mm, the initial setting time is 39min, the final setting time is 52min, and the fluidity of 30min is 92mm. Pouring the slurry into a 40mm × 40mm × 160mm mould, solidifying and hardening for 2h, then removing the mould, placing the test block in an indoor environment, standing and curing for 24h, and measuring that the 24h wet compressive strength and the wet flexural strength of the test block are 6.1MPa and 2.4MPa. And (3) placing the hardened test block into a 40 ℃ oven for drying, and measuring the oven dry compressive strength of 19.7MPa, the oven dry bending strength of 7.1MPa and the tensile bonding strength of 1.6MPa. The laser thermal conductivity meter tests the thermal conductivity of the phosphogypsum-based self-leveling material for ground heating backfill, and the result shows that the thermal conductivity is 1.08W/(m.K). From the results, although the heat conduction effect is more obvious by adding the pure graphite powder, the water requirement of the self-leveling gypsum slurry is obviously increased, the mechanical strength is reduced to some extent, and meanwhile, the fluidity loss is increased, so that the self-leveling gypsum slurry is not beneficial to the automatic leveling construction of the self-leveling material.
Comparative example 4
Compared with the embodiment 3, the phase-change energy storage component with high thermal conductivity is replaced by the phase-change paraffin powder with the same weight part, and the rest components and operation are the same as the embodiment 3. Through detection, the water requirement of the finally obtained self-leveling gypsum slurry is 57%, the initial fluidity is 147mm, the initial setting time is 68min, the final setting time is 94min, and the fluidity of 30min is 145mm. Pouring the slurry into a 40mm × 40mm × 160mm mould, solidifying and hardening for 2h, then removing the mould, placing the test block in an indoor environment, standing and curing for 24h, and measuring that the 24h wet compressive strength and the wet flexural strength of the test block are 4.8MPa and 1.7MPa. And (3) placing the hardened test block into a 40 ℃ oven for drying, and measuring the oven-dry compressive strength of 14.1MPa, the oven-dry bending strength of 5.4MPa and the tensile bonding strength of 0.9MPa. The laser thermal conductivity meter tests the thermal conductivity of the phosphogypsum-based self-leveling material for ground heating backfill, and the result shows that the thermal conductivity is 0.35W/(m.K).
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. The phosphogypsum-based self-leveling material for the ground heating backfill is characterized by comprising the following components in parts by weight: 750-800 parts of phosphorus building gypsum, 50-100 parts of high-strength gypsum, 100-200 parts of waste stone powder, 10-100 parts of high-heat-conductivity phase-change energy storage component, 1-10 parts of redispersible latex powder, 1-3 parts of water reducing agent, 0.1-0.5 part of water-retaining agent, 0.1-0.5 part of retarder and 0.1-0.5 part of defoaming agent;
wherein, the weight percentage content of the dihydrate gypsum in the phosphorus building gypsum is 10-15%, the weight percentage content of the hemihydrate gypsum is 80-85%, the weight percentage content of the anhydrous gypsum is 1-5%, and the specific surface area is 350m 2 /kg～500m 2 /kg；
The high-heat-conductivity phase-change energy storage component is prepared by compounding expandable graphite and phase-change paraffin.
2. The phosphogypsum-based self-leveling material for ground heating backfill according to claim 1, wherein the preparation method of the phosphorous building gypsum comprises the following steps:
drying the undisturbed phosphogypsum for 40-55 h at 35-45 ℃ to obtain a dried product;
uniformly mixing the dried product and quartz sand according to a certain proportion, and mixing and grinding the mixture in a standard test mill for 30-45 min to obtain a mixture I;
calcining the mixture I at 160-190 ℃ for 1-3 h to obtain a calcined product;
and placing the calcined product in a closed plastic bucket for aging for 24-72 hours to obtain the phosphorus building gypsum.
3. The phosphogypsum-based self-leveling material for ground heating backfill according to claim 2, wherein the weight ratio of the drying product to the quartz sand is (88-92): (8 to 12).
4. The phosphogypsum-based self-leveling material for ground heating backfill according to claim 1, wherein the standard consistency water requirement of the phosphogypsum building gypsum is 62-68%, the initial setting time is 7-12 min, the final setting time is 15-20min, the compressive strength at 2h is 4.2-6.7MPa, and the flexural strength at 2h is 2.0-3.2 MPa.
5. The phosphogypsum-based self-leveling material for ground heating backfill according to claim 1, characterized in that the high-strength gypsum is alpha-type high-strength gypsum powder, the water requirement for standard consistency is 35-40%, the setting time is 12-15min, and the compressive strength of 2h is 15-20 MPa.
6. The phosphogypsum-based self-leveling material for ground heating backfill according to claim 1, wherein the waste rock powder is waste solid powder generated in the production and processing process of machine-made sand, the granularity is less than 200 meshes, and the mud content is less than or equal to 5%; the redispersible latex powder is ethylene-vinyl acetate copolymer powder; the water reducing agent is a polycarboxylic acid water reducing agent and is in a powder shape, and the water reducing rate is more than or equal to 20%; the water retaining agent is hydroxypropyl methyl cellulose ether, is powdery and has viscosity of 40000mPa.s-80000mPa.s; the retarder is a protein retarder and is in a powder shape; the defoaming agent is polyether modified organic silicon and is powder.
7. The phosphogypsum-based self-leveling material for ground heating backfill according to claim 1, wherein the preparation method of the high-thermal-conductivity phase-change energy storage component comprises the following steps:
placing expandable graphite powder into a microwave oven, and heating for 10-15 s under 800W power to obtain expanded graphite;
cutting the phase-change paraffin into fine particles of 0.1-5 mm, and heating and melting in a water bath to obtain molten paraffin;
stirring and mixing the expanded graphite and the molten paraffin according to a certain proportion to obtain the high-thermal-conductivity phase-change energy storage component.
8. The phosphogypsum-based self-leveling material for ground heating backfill according to claim 7, wherein the particle size of the expandable graphite powder is 300-400 meshes; the phase change temperature range of the phase change paraffin is 45-55 ℃; the temperature of the water bath for heating the water bath is 55-65 ℃; the weight ratio of the expanded graphite to the molten paraffin is 1: (12 to 19).
9. A preparation method of the phosphogypsum-based self-leveling material for floor heating backfill according to any one of claims 1 to 8 is characterized by comprising the following steps:
weighing the raw materials according to the proportion, and stirring and mixing the raw materials uniformly in a cement mortar stirrer to obtain the cement mortar.
10. A use method of the phosphogypsum-based self-leveling material for floor heating backfill according to any one of claims 1 to 8 is characterized in that water accounting for 55 to 60 percent of the weight of solid powder is added when the phosphogypsum-based self-leveling material is used, and the fluidity is adjusted to be 140 to 150 mm.
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| CN112851284A (en) * | 2021-01-29 | 2021-05-28 | 南京工业大学 | Gypsum self-leveling mortar for ground heating backfill and preparation method thereof |
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