Modified ardealite-based self-leveling material and preparation method thereof

Abstract

The invention discloses a modified ardealite-based self-leveling material and a preparation method thereof, and the modified ardealite-based self-leveling material is prepared from the following components in parts by mass: 60 to 80 parts of carbide slag modified ardealite, 5 to 10 parts of sulphoaluminate cement, 15 to 30 parts of aggregate, 0.2 to 1 part of water reducing agent, 0.05 to 0.2 part of retarder, 0.02 to 0.15 part of water-retaining agent and 0.01 to 0.1 part of defoaming agent. The method comprises the following steps: uniformly mixing phosphogypsum, carbide slag and water according to a mass ratio of (85-98): (2-15): (45-50), and carrying out sealed reaction for set time; and after the reaction is completed, drying the mixture, and then treating at 150-180 DEG C for 0.5-1.5 h to obtain the carbide slag modified phosphogypsum. The ardealite-based self-leveling material based on calcium carbide slag pretreatment and solid waste-based sulphoaluminate cement reinforcement is excellent in mechanical property, the 24-hour compressive strength is higher than 10 MPa, the 28-day absolute dry compressive strength is higher than 23 MPa, and both the 24-hour compressive strength and the 28-day absolute dry compressive strength are higher than those of a traditional ardealite-based self-leveling material in the same period.

Description

Technical Field

[0001] The present invention belongs to the technical field of self-leveling materials, and particularly relates to a modified phosphogypsum-based self-leveling material and a preparation method thereof. Background Art

[0002] The statements herein only provide background art related to the present invention and do not necessarily constitute prior art.

[0003] Currently, to solve the problem of resource utilization of phosphogypsum, using industrial by-product gypsums such as phosphogypsum to replace natural gypsum to prepare gypsum-based self-leveling materials has become one of the research hotspots. However, since phosphogypsum usually contains impurities such as phosphorus and fluorine, the strength of traditional phosphogypsum-based self-leveling materials is relatively low and it is difficult to meet the minimum strength requirements of industry standards. The existing related modification technologies and methods mainly include adding cement-based materials, adding admixtures, and phosphogypsum pretreatment, etc. However, the cost of cement materials and admixtures is high and the energy consumption is high, and high proportion addition is not conducive to the popularization and application of phosphogypsum-based self-leveling materials. Neutralization pretreatment has become the most commonly used pretreatment method for phosphogypsum in engineering applications because it does not require expensive materials, complex processes or calcination treatment, and lime is the most commonly used alkaline additive.

[0004] The phosphogypsum-based self-leveling materials modified by cement-based materials and admixtures have many problems and defects: limited performance, high cost, high phosphorus leaching, etc., which affect product quality and environmental safety. The production raw materials of lime are mainly natural rocks such as limestone and dolomite, and its high-temperature calcination production process will generate a large amount of carbon dioxide, increasing the negative impact on the environment. Many factors lead to problems such as limited raw materials, high carbon emissions, complex processes, and high costs for self-leveling materials based on lime-pretreated phosphogypsum. In addition, due to the influence of impurities, the mechanical properties of phosphogypsum are poor, and the existing technology does not consider enhancing the mechanical properties of phosphogypsum through the hydration process. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a modified phosphogypsum-based self-leveling material and a preparation method thereof. This self-leveling material has the advantages of simple preparation process, cheap and easily available raw materials, excellent performance, environmental friendliness, etc.

[0006] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0007] In the first aspect, the present invention provides a modified phosphogypsum-based self-leveling material, which is composed of the following components in parts by mass: 60-80 parts of carbide slag-modified phosphogypsum, 5-10 parts of sulfoaluminate cement, 15-30 parts of aggregate, 0.2-1 part of water reducer, 0.05-0.2 part of retarder, 0.02-0.15 part of water retention agent, and 0.01-0.1 part of defoamer.

[0008] In some embodiments, the aggregate includes quartz sand with a particle size of 80 - 120 mesh and limestone powder with a particle size of 325 - 400 mesh, and the mass ratio of quartz sand to limestone powder is 1:0.5 - 1.5.

[0009] CaCO3 in the limestone powder participates in the hydration of calcium anhydrous sulfoaluminate in the sulfoaluminate cement to form products such as hydrated calcium carboaluminate, improving the early compressive strength of the self - leveling mortar and being beneficial to the long - term stability of the compressive strength. The limestone powder fills the pores and capillary pores of the gypsum - based self - leveling through fine particles, improving the density, reducing the shrinkage rate, and inhibiting early plastic cracking; the limestone powder reduces the friction between gypsum particles through the "ball - bearing effect" and enhances the fluidity of the gypsum - based self - leveling.

[0010] Preferably, the mass ratio of quartz sand to limestone powder is 1:0.8 - 1.2, and more preferably 1:1.

[0011] In some embodiments, the sulfoaluminate cement is a solid - waste - based sulfoaluminate cement.

[0012] In some embodiments, the water - reducing agent is a polycarboxylate water - reducing agent or a sulfonated melamine formaldehyde resin.

[0013] In some embodiments, the retarder is a plant - protein retarder or boric acid.

[0014] In some embodiments, the water - retaining agent is hydroxypropyl methyl cellulose ether, ethyl cellulose or redispersible latex powder.

[0015] In some embodiments, the defoaming agent is a polyether defoaming agent or a silicone defoaming agent.

[0016] Second, the present invention provides a preparation method of the modified phosphogypsum - based self - leveling material, including the following steps:

[0017] Mix phosphogypsum, carbide slag and water in a mass ratio of 85 - 98:2 - 15:45 - 50, and seal and react for a set time;

[0018] After the reaction is completed, dry the mixture, and then treat it at 150 - 180 °C for 0.5 - 1.5 h to obtain carbide - slag - modified phosphogypsum;

[0019] Mix the carbide - slag - modified phosphogypsum, sulfoaluminate cement, aggregate, water - reducing agent, retarder, water - retaining agent and defoaming agent in proportion to obtain the product.

[0020] Phosphogypsum and carbide slag react in a sealed container for a set time, and the sealed setting is to avoid water evaporation. During this reaction process, Ca(OH)2 in the carbide slag will combine with HPO4 in the phosphogypsum 2- 、PO4 3-Combined with soluble phosphorus impurities such as this, insoluble substances are formed, reducing the adverse effects of soluble phosphorus impurities on the strength of gypsum.

[0021] Through experiments, it was found that after the reaction of carbide slag and phosphogypsum, further heating the modified phosphogypsum at 150 - 180 °C for 0.5 - 1.5 h can effectively improve the compressive strength and long-term dry compressive strength of the modified phosphogypsum-based self-leveling material.

[0022] In some embodiments, in the carbide slag-modified phosphogypsum, the mass percentage of hemihydrate calcium sulfate is 75% - 90%.

[0023] In some embodiments, the temperature of the sealed reaction is 20 - 35 °C, and the time of the sealed reaction is 0.5 - 1.5 h.

[0024] In some embodiments, the temperature for drying the mixture is 40 ± 2 °C.

[0025] In some embodiments, when preparing the self-leveling material, the prepared self-leveling powder is mixed with water, and the mass percentage of water in the self-leveling powder is 30 - 50%, and after mixing evenly, it is obtained.

[0026] The beneficial effects obtained from one or more of the above embodiments of the present invention are as follows:

[0027] 1. Using carbide slag to treat phosphogypsum can not only save natural resources, reduce carbon emissions in the production process, but also reduce the production cost of phosphogypsum-based self-leveling materials. At the same time, it also helps to expand the resource utilization ways of carbide slag.

[0028] 2. The carbide slag pretreatment process can effectively solidify phosphorus elements. The leaching rate of phosphorus elements in the pretreated phosphogypsum powder is almost 0, and the solidification rate can reach 100%.

[0029] 3. The sulfoaluminate cement prepared from all solid wastes has low cost, early strength, high strength, and rapid hardening. Adding a small amount can significantly improve the early and late mechanical properties of phosphogypsum-based self-leveling materials.

[0030] 4. The phosphogypsum-based self-leveling material based on carbide slag pretreatment and solid waste-based sulfoaluminate cement strengthening has excellent mechanical properties. The 24-hour compressive strength is higher than 10 MPa, and the 28-day dry compressive strength is higher than 23 MPa, both higher than the same-period performance of traditional phosphogypsum-based self-leveling materials.

[0031] 5. The production cost of the phosphogypsum-based self-leveling material of the present invention is lower than that of the phosphogypsum-based self-leveling materials on the market. It has high market value and a large market, and can realize the large-scale, high-value and high-quality utilization of solid wastes such as phosphogypsum and carbide slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0033] Figure 1 is the process flow chart of the present invention. Detailed Description of the Invention

[0034] It should be noted that the following detailed descriptions are all illustrative and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0035] The present invention will be further described below in conjunction with embodiments.

[0036] Example 1

[0037] As Figure 1 shown, phosphogypsum, carbide slag and water are mixed evenly according to a mass ratio of 96:4:50. After reacting at room temperature and sealing for 1 day, it is dried to constant weight, and then placed in an oven at 170 °C and heated for 1 h to obtain pretreated phosphogypsum powder, which is sealed and reserved.

[0038] Take 10 grams each of untreated phosphogypsum and pretreated phosphogypsum and immerse them in 200 mL of deionized water. Place them on a magnetic stirrer and stir for 30 minutes. After the solution stands for 5 minutes, filter it with a 0.45 μm filter paper. Dilute 20 ml of each of the above two leachates with deionized water by 5 times. Use an inductively coupled plasma optical emission spectrometer (ICP-OES) to measure the soluble phosphorus concentration therein. Record the soluble phosphorus concentration in untreated phosphogypsum as c1, and the soluble phosphorus concentration in pretreated phosphogypsum as c2. Then the solidification rate of phosphorus element is (c1 - c2) / c2. The measured solidification rate of phosphorus element is 96.2%.

[0039] Then, 78 parts of pretreated phosphogypsum powder, 6 parts of solid waste-based sulphoaluminate cement, 8 parts of quartz sand, 8 parts of limestone powder, 0.5 part of polycarboxylate superplasticizer, 0.1 part of boric acid, 0.06 part of hydroxypropyl methylcellulose ether water retention agent and 0.05 part of silicone defoamer are mixed evenly to obtain the modified phosphogypsum-based self-leveling material.

[0040] During use, add water accounting for 33% of the total mass of the mixed powder to the modified phosphogypsum-based self-leveling material and mix evenly to obtain the self-leveling material.

[0041] Example 2

[0042] Mix phosphogypsum, carbide slag and water evenly according to a mass ratio of 94:6:50. After reacting at room temperature and sealing for 1 day, dry it to constant weight, then place it in an oven at 170 °C and heat for 1 h to obtain pretreated phosphogypsum powder, and seal it for standby. The phosphorus element solidification rate is 99.8%.

[0043] Then, mix 74 parts of the pretreated phosphogypsum powder, 10 parts of solid waste-based sulphoaluminate cement, 8 parts of quartz sand, 8 parts of limestone powder, 0.6 parts of polycarboxylate water reducer, 0.08 parts of boric acid, 0.1 part of hydroxypropyl methyl cellulose ether water retainer and 0.06 parts of polyether defoamer evenly to obtain the modified phosphogypsum-based self-leveling material.

[0044] When in use, add water accounting for 36% of the total mass of the mixed powder to the modified phosphogypsum-based self-leveling material and mix evenly.

[0045] Example 3

[0046] Mix phosphogypsum, carbide slag and water evenly according to a mass ratio of 92:8:50. After reacting at room temperature and sealing for 1 day, dry it to constant weight, then place it in an oven at 170 °C and heat for 1 h to obtain pretreated phosphogypsum powder and seal it for standby. The phosphorus element solidification rate is 100%.

[0047] Then, mix 70 parts of the pretreated phosphogypsum powder, 10 parts of solid waste-based sulphoaluminate cement, 10 parts of quartz sand, 10 parts of limestone powder, 0.8 parts of polycarboxylate water reducer, 0.07 parts of plant protein retarder, 0.08 parts of hydroxypropyl methyl cellulose ether water retainer and 0.06 parts of polyether defoamer evenly to obtain the modified phosphogypsum-based self-leveling material.

[0048] When in use, add water accounting for 35% of the total mass of the mixed powder to the modified phosphogypsum-based self-leveling material and mix evenly.

[0049] Comparative Example 1

[0050] The difference from Example 2 is that the step of modifying phosphogypsum with carbide slag is omitted, and self-leveling material is directly prepared using phosphogypsum.

[0051] Comparative Example 2

[0052] The difference from Example 2 is that carbide slag is replaced with lime, and the others are the same as in Example 2.

[0053] Comparative Example 3

[0054] The difference from Example 2 is that in the step of modifying phosphogypsum with carbide slag, the step of "then placing it in an oven at 170 °C and heating for 1 h" is omitted, and the others are the same as in Example 2.

[0055] The physical and mechanical properties of the phosphogypsum-based self-leveling materials prepared in Examples 1-3 and Comparative Examples 1-3 were tested with reference to the standard JC / T 1023-2021 "Gypsum-based Self-leveling Mortar", and the test results are shown in Table 1.

[0056] Table 1 Comparison Table of Performance Characterization

[0057]

[0058]

[0059] As can be seen from Table 1, the phosphogypsum-based self-leveling materials prepared by the present invention have good fluidity and mechanical properties.

[0060] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A modified phosphogypsum-based self-leveling material, characterized in that: The invention is composed of the following components by weight: 60-80 parts of calcium carbide slag modified phosphogypsum, 5-10 parts of sulphoaluminate cement, 15-30 parts of aggregate, 0.2-1 parts of water reducing agent, 0.05-0.2 parts of retarder, 0.02-0.15 parts of water retaining agent and 0.01-0.1 parts of defoaming agent; The preparation method of the carbide slag modified phosphogypsum is as follows: phosphogypsum, carbide slag and water are mixed at a mass ratio of 85-98:2-15:45-50, and the mixture is sealed for a set reaction time; after the reaction is completed, the mixture is dried, and then treated at 150-180° C. for 0.5-1.5 h to obtain the carbide slag modified phosphogypsum.

2. The modified phosphogypsum-based self-leveling material according to claim 1, characterized in that: The aggregate comprises quartz sand with a particle size of 80-120 meshes and limestone powder with a particle size of 325-400 meshes, and the mass ratio of quartz sand to limestone powder is 1:0.5-1.5; Preferably, the mass ratio of quartz sand to limestone powder is 1:0.8-1.2, more preferably 1:

1.

3. The modified phosphogypsum-based self-leveling material according to claim 1, characterized in that: The sulphoaluminate cement is solid waste-based sulphoaluminate cement.

4. The modified phosphogypsum-based self-leveling material according to claim 1, characterized in that: The water reducer is a polycarboxylate water reducer or a sulfonated melamine formaldehyde resin; Alternatively, the retarder is a vegetable protein retarder or boric acid.

5. The modified phosphogypsum-based self-leveling material according to claim 1, characterized in that: The water retaining agent is hydroxypropyl methyl cellulose ether, ethyl cellulose or redispersible latex powder; Alternatively, the defoamer is a polyether defoamer or a silicone defoamer.

6. The method for preparing the modified phosphogypsum-based self-leveling material according to any one of claims 1 to 5, characterized in that: The steps include: The phosphogypsum, carbide slag and water are mixed in a mass ratio of 85-98:2-15:45-50, and the mixture is sealed and reacted for a set time; after the reaction is completed, the mixture is dried, and then treated at 150-180°C for 0.5-1.5h to obtain carbide slag modified phosphogypsum; The phosphogypsum modified by carbide slag, sulphoaluminate cement, aggregate, water reducing agent, retarder, water retaining agent and defoaming agent are mixed in proportion to obtain the product.

7. The method for preparing the modified phosphogypsum-based self-leveling material according to claim 6, characterized in that: The mass percentage of calcium sulfate hemihydrate in the carbide slag modified phosphogypsum is 75%-90%.

8. The method for preparing the modified phosphogypsum-based self-leveling material according to claim 6, characterized in that: The temperature of the sealing reaction is 20-35°C, and the time of the sealing reaction is 0.5-1.5h.

9. The method for preparing the modified phosphogypsum-based self-leveling material according to claim 6, characterized in that: The temperature of drying the mixture is 40±2°C.

10. The method for preparing the modified phosphogypsum-based self-leveling material according to claim 6, characterized in that: When preparing the self-leveling material, the prepared self-leveling powder is mixed with water, the mass percentage of water to the self-leveling powder is 30-50%, and the mixture is stirred evenly to obtain the self-leveling material.

Images