Carbon dioxide curing phosphogypsum-based cementitious material and preparation method thereof

Abstract

The application discloses a kind of carbon dioxide curing phosphogypsum-based cementitious materials and preparation method thereof, the preparation method includes the following steps: S1: obtaining phosphogypsum-based cementitious materials, and the phosphogypsum-based cementitious materials are pretreated, and obtain recycled aggregate particles;S2: obtaining expired dairy products, and the expired dairy products are heated and treated at 60-80 DEG C for 1-2h;S3: the recycled aggregate particles are added to the expired dairy products, and are mixed and stirred at 100-140 DEG C for 20-40min, obtain mixture;S4: the mixture is cooled to room temperature, add yeast, and under negative pressure and ultrasonic conditions are drop and are kept, and then maintain negative pressure and ultrasonic conditions curing 2h, obtain the carbon dioxide curing phosphogypsum-based cementitious materials.The application can efficiently and energy-efficiently conserve solid waste cementitious material, and the obtained conservation cementitious material has good mechanical properties, can provide technical support for the recycling of solid waste material.

Description

Technical Field

[0001] This invention relates to the field of cementitious materials technology, and in particular to a carbon dioxide-cured phosphogypsum-based cementitious material and its preparation method. Background Technology

[0002] Solid waste refers to solid and semi-solid waste materials generated by humans in production, construction, daily life, and other activities that cannot be utilized at a certain time and place and are discarded, polluting the environment. Large accumulations of industrial solid waste severely damage the ecological environment, occupy land resources, and destroy soil. It not only pollutes surface, groundwater, and atmospheric resources but also causes serious safety accidents.

[0003] Currently, solid waste is mainly recycled and reused through precise sorting and clean processes to produce recycled aggregates. However, recycled aggregates still have problems such as many angular particles, rough surfaces, microcracks, and inferior mechanical properties such as compressive strength, flexural strength, splitting tensile strength, etc. compared to ordinary concrete. Summary of the Invention

[0004] To address the above problems, the present invention aims to provide a carbon dioxide-cured phosphogypsum-based cementitious material and its preparation method.

[0005] The technical solution of the present invention is as follows:

[0006] On the one hand, a method for preparing a carbon dioxide-cured phosphogypsum-based cementitious material is provided, comprising the following steps:

[0007] S1: Obtain phosphogypsum-based cementitious material and pretreat the phosphogypsum-based cementitious material to obtain recycled aggregate particles;

[0008] S2: Obtain expired dairy products and heat the expired dairy products at 60-80℃ for 1-2 hours;

[0009] S3: Add the recycled aggregate particles to the expired dairy products and mix and stir at 100-140℃ for 20-40 minutes to obtain a mixture;

[0010] S4: Cool the mixture to room temperature, add yeast, and drip under negative pressure and ultrasonic conditions. Then maintain negative pressure and ultrasonic conditions for 2 hours to obtain the carbon dioxide-cured phosphogypsum-based gelling material.

[0011] Preferably, in step S1, the pretreatment includes crushing and screening.

[0012] Preferably, in step S4, the pressure under negative pressure is 0.01-0.02 MPa.

[0013] Preferably, in step S4, the ultrasonic frequency of the ultrasonic condition is 21-30 kHz.

[0014] Preferably, step S4 is performed in a curing device, which includes a housing, a spiral conveying device and a dripping device disposed within the housing, and an ultrasonic generator and a pressure control device respectively connected to the housing.

[0015] The top of the shell is provided with a feed inlet, and the bottom of the shell is provided with a discharge outlet and a liquid outlet;

[0016] The spiral conveyor is located between the feed inlet and the discharge outlet, and the conveying platform of the spiral conveyor is a filter screen structure.

[0017] The pressure control device is used to control the formation of negative pressure inside the housing.

[0018] Preferably, the dripping device includes an inlet pipe and drip nozzles; the inlet pipe is vertically disposed at the center of the housing, and multiple drip nozzles are disposed and evenly distributed in the radial and axial directions of the inlet pipe.

[0019] Preferably, the drip nozzles are provided between two adjacent conveyor platforms.

[0020] Preferably, the bottom of the housing is sloping, and an inclined filter screen is provided between the bottom of the housing and the spiral conveying device, with the inclined direction of the inclined filter screen being opposite to the inclined direction of the bottom of the housing; the lower end of the inclined filter screen is connected to the discharge port, and the lower end of the bottom of the housing is connected to the liquid outlet.

[0021] Preferably, in each step, by weight, the amount of the phosphogypsum-based gelling material is 50-70 parts, the amount of the expired dairy product is 200-240 parts, the amount of the yeast is 60-90 parts, and the amount of water used for dripping is 40-60 parts.

[0022] On the other hand, a carbon dioxide-cured phosphogypsum-based cementitious material prepared by any one of the above preparation methods is also provided.

[0023] The beneficial effects of this invention are:

[0024] This invention can efficiently and energy-savingly cure solid waste cementitious materials, and the resulting cured cementitious materials have good mechanical properties, providing technical support for the recycling and reuse of solid waste materials. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the curing device used in the preparation method of carbon dioxide curing phosphogypsum-based cementitious material of the present invention.

[0027] The numbers in the diagram are: 1-shell, 2-spiral conveyor, 3-drip device, 4-ultrasonic generator, 5-feed inlet, 6-discharge outlet, 7-liquid outlet, 8-tilted filter screen. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and technical features described in this application can be combined with each other. It should also be pointed out that, unless otherwise indicated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms "comprising" or "including" and similar words used in this invention refer to elements or objects preceding the word that encompass the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0029] On one hand, the present invention provides a method for preparing a carbon dioxide-cured phosphogypsum-based cementitious material, comprising the following steps:

[0030] S1: Obtain phosphogypsum-based cementitious material and pretreat the phosphogypsum-based cementitious material to obtain recycled aggregate particles.

[0031] In one specific embodiment, the pretreatment includes crushing and screening.

[0032] S2: Obtain expired dairy products and heat them at 60-80°C for 1-2 hours.

[0033] S3: Add the recycled aggregate particles to the expired dairy products and mix and stir at 100-140℃ for 20-40 minutes to obtain a mixture.

[0034] S4: Cool the mixture to room temperature, add yeast, and drip under negative pressure and ultrasonic conditions. Then maintain negative pressure and ultrasonic conditions for 2 hours to obtain the carbon dioxide-cured phosphogypsum-based gelling material.

[0035] In this invention, the use of phosphogypsum-based cementitious materials enables the utilization of phosphogypsum as a solid waste resource, preventing local environmental pollution caused by phosphogypsum accumulation. Expired dairy products produce carbon dioxide through yeast fermentation. The carbon dioxide reacts with water to produce carbonic acid, which then reacts with carbonatable substances produced during hydration to form a calcium carbonate film and calcium carbonate filler on the surface and pores of the recycled aggregate particles, thereby achieving a curing effect.

[0036] In the above embodiments, step S2, heating the expired dairy products denatures the proteins, facilitating subsequent decomposition by yeast. Step S3, setting the temperature above 100°C, evaporates the moisture in the expired dairy products, forming powder that coats the recycled aggregate particles under stirring. In subsequent step S4, the expired dairy products produce carbon dioxide through yeast fermentation, which is then used to condition the recycled aggregate particles. Setting a negative pressure condition in step S4 prevents air interference with carbon dioxide conditioning, resulting in a uniform carbonation reaction and increasing the rate of carbon dioxide conditioning. Setting an ultrasonic condition in step S4 utilizes the cavitation effect of ultrasound in liquids, allowing the carbon dioxide produced by fermentation to penetrate the aggregate particles through the collapse of cavitation bubbles, thus ensuring more thorough carbon dioxide conditioning of the recycled aggregate particles. Adding water via dripping ensures more complete contact between the water and the recycled aggregate particles, guaranteeing the conditioning effect.

[0037] In one specific embodiment, the pressure under negative pressure conditions is 0.01-0.02 MPa, and the ultrasonic frequency under ultrasonic conditions is 21-30 kHz.

[0038] In one specific embodiment, step S4 is performed in the curing device, such as... Figure 1 As shown, the maintenance device includes a housing 1, a spiral conveying device 2 and a dripping device 3 disposed in the housing 1, and an ultrasonic generator 4 and a pressure control device (not shown in the figure) respectively connected to the housing 1.

[0039] The top of the housing 1 is provided with a feed inlet 5, and the bottom of the housing 1 is provided with a discharge outlet 6 and a liquid outlet 7; the spiral conveying device 2 is located between the feed inlet 5 and the discharge outlet 6, and the conveying platform of the spiral conveying device 2 is a filter screen structure; the pressure control device is used to control the formation of negative pressure inside the housing 1.

[0040] In the above embodiment, by setting the spiral conveyor 2, the recycled aggregate particles can be kept in motion within the shell 1 by controlling the conveying speed, thus making the curing more thorough.

[0041] In one embodiment using the curing device described above, in step S4, the yeast is first evenly sprinkled onto the conveying platform of the spiral conveyor, with the spiral conveyor's operating speed set at 0.5-0.8 rad / s. Then, the mixture cooled to room temperature (20-30°C) is conveyed from the feed inlet into the shell, with the spiral conveyor's operating speed set at 0.3-0.6 rad / s. Next, the ultrasonic generator and pressure control device are turned on, and the dripping device is started, controlling the flow rate of the dripping device to 1.1-1.4 L / min. After curing for 2 hours, the carbon dioxide-cured phosphogypsum-based gelling material is obtained.

[0042] In one specific embodiment, the dripping device 3 includes an inlet pipe and drip nozzles; the inlet pipe is vertically disposed at the center of the housing 1, and multiple drip nozzles are disposed and evenly distributed radially and axially along the inlet pipe. Optionally, drip nozzles are disposed between adjacent conveyor platforms. In this embodiment, the arrangement of the dripping device 3 enables more uniform dripping and ensures full utilization of water.

[0043] In one specific embodiment, the bottom of the housing 1 is sloped, and an inclined filter 8 is provided between the bottom of the housing 1 and the spiral conveying device 2, and the inclined direction of the inclined filter 8 is opposite to the inclined direction of the bottom of the housing 1; the lower end of the inclined filter 8 is connected to the discharge port 6, and the lower end of the bottom of the housing 1 is connected to the liquid outlet 7.

[0044] In the above embodiments, it is possible to better distinguish between well-cured recycled aggregate and curing liquid containing impurities, and to collect them separately. Recycling the curing liquid makes this invention more environmentally friendly.

[0045] In one specific embodiment, by weight, in each step, the amount of the phosphogypsum-based gelling material is 50-70 parts, the amount of the expired dairy product is 200-240 parts, the amount of the yeast is 60-90 parts, and the amount of dripping water is 40-60 parts.

[0046] In the above embodiments, the carbon dioxide concentration generated by using this amount of component is between 3% and 5%. Carbon dioxide curing of recycled aggregate particles can be achieved with a relatively small carbon dioxide concentration, thereby improving the mechanical properties of recycled aggregate particles.

[0047] On the other hand, a carbon dioxide-cured phosphogypsum-based cementitious material prepared by any one of the above preparation methods is also provided.

[0048] Example 1

[0049] A carbon dioxide-cured phosphogypsum-based cementitious material is prepared through the following steps:

[0050] (1) Obtain 60 parts of phosphogypsum-based cementitious material, and crush and screen it to obtain recycled aggregate particles.

[0051] (2) Obtain 220 portions of expired dairy products and place them in a heating chamber, adjust the temperature to 70°C, and heat for 1.5 hours.

[0052] (3) Add the recycled aggregate particles to the expired dairy products, then adjust the temperature to 120°C, mix and stir for 30 minutes, and cool to room temperature to obtain a mixture.

[0053] (4) Sprinkle 70 parts of yeast evenly on Figure 1 The maintenance device shown is mounted on a spiral conveyor platform, and the operating speed of the spiral conveyor is set to 0.6 rad / s.

[0054] (5) Add the mixture into the curing device, turn on the ultrasonic generator and pressure control device, control the ultrasonic frequency to 25kHz and the pressure to 0.015MPa, turn on the drip device to drip 50 parts of water, and cure for 2 hours to obtain the carbon dioxide cured phosphogypsum-based cementitious material.

[0055] Example 2

[0056] Unlike Example 1, the temperature in step (2) of this example is 60°C and the time is 2 hours.

[0057] Example 3

[0058] Unlike Example 1, the temperature in step (2) of this example is 80°C and the time is 1 hour.

[0059] Example 4

[0060] Unlike Example 1, the temperature in step (3) of this example is 100°C and the time is 40 min.

[0061] Example 5

[0062] Unlike Example 1, the temperature in step (3) of this example is 140°C and the time is 20 minutes.

[0063] Example 6

[0064] Unlike Example 1, the ultrasonic frequency in step (5) of this example is 21 kHz.

[0065] Example 7

[0066] Unlike Example 1, the ultrasonic frequency in step (5) of this example is 30 kHz.

[0067] Example 8

[0068] Unlike Example 1, the pressure in step (5) of this example is 0.01 MPa.

[0069] Example 9

[0070] Unlike Example 1, the pressure in step (5) of this example is 0.02 MPa.

[0071] Comparative Example 1

[0072] Unlike Example 1, the pressure in step (5) of this comparative example is 0.005 MPa.

[0073] Comparative Example 2

[0074] Unlike Example 1, the pressure in step (5) of this comparative example is 0.035 MPa.

[0075] Comparative Example 3

[0076] Unlike Example 1, the ultrasonic frequency in step (5) of this example is 35 kHz.

[0077] Comparative Example 4

[0078] Unlike Example 1, the ultrasonic frequency in step (5) of this example is 10 kHz.

[0079] Comparative Example 5

[0080] Unlike Example 1, the ultrasonic frequency in step (5) of this example is 10 kHz and the pressure is 0.005 MPa.

[0081] Comparative Example 6

[0082] Unlike Example 1, the ultrasonic frequency in step (5) of this example is 35 kHz and the pressure is 0.035 MPa.

[0083] Comparative Example 7

[0084] Unlike Example 1, the temperature in step (2) of this example is 90°C.

[0085] Comparative Example 8

[0086] Unlike Example 1, the temperature in step (2) of this example is 50°C.

[0087] Comparative Example 9

[0088] Unlike Example 1, in this example, the pressure control device is not turned on in step (5), that is, the maintenance is carried out under normal pressure conditions.

[0089] Comparative Example 10

[0090] Unlike Example 1, the ultrasonic generator is not turned on in step (5) of this example.

[0091] Comparative Example 11

[0092] Unlike Example 1, in this example, after obtaining the recycled aggregate particles in step (1), the process proceeds directly to step (5), and the carbon dioxide concentration in the curing device is maintained at 15-25%. In step (5), the pressure control device is not turned on, that is, curing is carried out under normal pressure conditions.

[0093] The performance of the carbon dioxide-cured phosphogypsum-based cementitious materials in each embodiment and comparative example was tested, and some of the compressive strength test results are shown in Table 1:

[0094] Table 1. Compressive strength test results of each embodiment and comparative example.

[0095] Case 3D compressive strength 28-day compressive strength Case 3D compressive strength 28-day compressive strength Example 1 40MPa 87MPa Comparative Example 2 28MPa 74MPa Example 2 37MPa 82MPa Comparative Example 3 25MPa 73MPa Example 3 34MPa 79MPa Comparative Example 4 29MPa 76MPa Example 4 36MPa 83MPa Comparative Example 5 21MPa 69MPa Example 5 34MPa 80MPa Comparative Example 6 24MPa 75MPa Example 6 37MPa 84MPa Comparative Example 7 33MPa 80MPa Example 7 36MPa 82MPa Comparative Example 8 26MPa 78MPa Example 8 35MPa 84MPa Comparative Example 9 27MPa 76MPa Example 9 38MPa 85MPa Comparative Example 10 25MPa 74MPa Comparative Example 1 30MPa 75MPa Comparative Example 11 38MPa 87MPa

[0096] As can be seen from Table 1:

[0097] (1) Using negative pressure is more effective than not using negative pressure for curing, but both too low and too high negative pressure levels will affect the effect of carbon dioxide curing.

[0098] (2) The frequency of ultrasonic waves can affect the efficiency of carbon dioxide curing. Since ultrasonic waves can induce cavitation, they can promote the reaction of carbon dioxide on the surface of aggregates. However, as the frequency of ultrasonic waves increases, carbon dioxide cannot come into good contact with recycled aggregates, making it difficult to achieve carbon dioxide curing.

[0099] (3) The heat treatment temperature of expired dairy products also affects the reaction efficiency of yeast, and thus the degree of carbon dioxide preservation. Too high or too low a heating temperature will affect protein denaturation, thereby affecting the yeast reaction and reducing the carbon dioxide preservation rate.

[0100] (4) Compared with conventional carbon dioxide curing, the aggregate strength after curing with low concentration carbon dioxide under negative pressure system is stronger than that of aggregate cured with conventional high concentration carbon dioxide. The negative pressure system has a significant effect on curing effect under low concentration carbon dioxide environment.

[0101] In summary, this invention enables the use of expired dairy products for carbon dioxide curing of solid waste gelling materials, allowing for resource recycling and reuse. Compared with existing technologies, this invention represents a significant advancement.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a carbon dioxide-cured phosphogypsum-based cementitious material, characterized in that, Includes the following steps: S1: Obtain phosphogypsum-based cementitious material and pretreat the phosphogypsum-based cementitious material to obtain recycled aggregate particles; the phosphogypsum-based cementitious material is a cementitious material containing phosphogypsum and capable of producing carbonizable substances during hydration. S2: Obtain expired dairy products and heat the expired dairy products at 60-80℃ for 1-2 hours; S3: Add the recycled aggregate particles to the expired dairy products and mix and stir at 100-140℃ for 20-40 minutes to obtain a mixture; S4: Cool the mixture to room temperature, add yeast, and drip under negative pressure and ultrasonic conditions. Then maintain negative pressure and ultrasonic conditions for curing for 2 hours to obtain the carbon dioxide-cured phosphogypsum-based gelling material. The pressure under negative pressure conditions is 0.01-0.02 MPa, and the ultrasonic frequency under ultrasonic conditions is 21-30 kHz.

2. The method for preparing carbon dioxide-cured phosphogypsum-based cementitious material according to claim 1, characterized in that, In step S1, the pretreatment includes crushing and screening.

3. The method for preparing carbon dioxide-cured phosphogypsum-based cementitious material according to claim 1, characterized in that, Step S4 is carried out in a curing device, which includes a housing, a spiral conveying device and a dripping device disposed within the housing, and an ultrasonic generator and a pressure control device respectively connected to the housing. The top of the shell is provided with a feed inlet, and the bottom of the shell is provided with a discharge outlet and a liquid outlet; The spiral conveyor is located between the feed inlet and the discharge outlet, and the conveying platform of the spiral conveyor is a filter screen structure. The pressure control device is used to control the formation of negative pressure inside the housing.

4. The preparation method of the carbon dioxide-cured phosphogypsum-based cementitious material according to claim 3, characterized in that, The dripping device includes an inlet pipe and drip nozzles; the inlet pipe is vertically arranged at the center of the housing, and multiple drip nozzles are provided and evenly distributed in the radial and axial directions of the inlet pipe.

5. The method for preparing carbon dioxide-cured phosphogypsum-based cementitious material according to claim 4, characterized in that, The drip nozzles are installed between adjacent conveyor platforms.

6. The method for preparing carbon dioxide-cured phosphogypsum-based cementitious material according to claim 3, characterized in that, The bottom of the housing is sloping, and an inclined filter screen is provided between the bottom of the housing and the spiral conveying device, with the inclined direction of the inclined filter screen being opposite to the inclined direction of the bottom of the housing; the lower end of the inclined filter screen is connected to the discharge port, and the lower end of the bottom of the housing is connected to the liquid outlet.

7. The method for preparing carbon dioxide-cured phosphogypsum-based cementitious material according to any one of claims 1-6, characterized in that, By weight, in each step, the amount of the phosphogypsum-based gelling material is 50-70 parts, the amount of the expired dairy product is 200-240 parts, the amount of the yeast is 60-90 parts, and the amount of water used for dripping is 40-60 parts.

8. A carbon dioxide-cured phosphogypsum-based cementitious material, characterized in that, It is prepared by the method for preparing carbon dioxide-cured phosphogypsum-based cementitious material according to any one of claims 1-7.

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