Complex-phase gypsum-based self-leveling mortar and preparation method thereof

Abstract

The invention relates to the field of solid waste co-processing and utilization, and particularly discloses complex-phase gypsum-based self-leveling mortar and a preparation method thereof. The mortar comprises the following raw materials in parts by mass: 75-95 parts of complex-phase gypsum, 3-25 parts of an auxiliary cementing material and 0.5-2.5 parts of an auxiliary mixture, the complex-phase gypsum comprises semi-hydrated gypsum, dihydrate gypsum and anhydrous gypsum; the auxiliary gelling material is a mixed compound material of ordinary Portland cement, aluminate cement, a calcium sulphoaluminate cementing material and sulphoaluminate cement; the additive mixture comprises one or more of a retarder, a water-retaining agent, a suspension / stabilizer, a water reducing agent, a flow promoter, a defoaming agent, a water repellent and an exciting agent. The gypsum-based self-leveling mortar prepared by the invention integrates the advantages of single semi-hydrated gypsum and single anhydrous gypsum, realizes the characteristics of high early strength and high later strength, and has the advantages of high strength, good wear resistance and low cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of solid waste synergistic treatment and utilization, in particular to a complex-phase gypsum-based self-leveling mortar and a preparation method thereof. BACKGROUND

[0002] Industrial by-product gypsum refers to a by-product or waste residue generated in industrial production due to chemical reactions, which is also called chemical gypsum. According to chemical products, it can be divided into desulfurization gypsum, phosphogypsum, citric acid gypsum, salt gypsum, monosodium glutamate gypsum, copper gypsum, fluorine gypsum, titanium gypsum, nickel gypsum, chromium gypsum, boron gypsum, mirabilite gypsum, tartaric acid gypsum, lactic acid gypsum, etc. Among them, the production amount of desulfurization gypsum and phosphogypsum accounts for about 85% of the total amount of by-product gypsum. Phosphogypsum has a large emission amount, complex composition, many impurities, and great difficulty in comprehensive utilization. Moreover, due to the characteristics of containing soluble harmful substances (P, F, S, etc.) and fine particles (5-300 μm), it will cause great pollution to water resources and atmospheric environment, and is an industrial by-product gypsum that needs to be effectively treated.

[0003] The content of dihydrate calcium sulfate in phosphogypsum is as high as more than 90%, which is an important renewable resource. However, the secondary effective utilization of phosphogypsum is hindered due to many impurities in phosphogypsum. Large-scale stacking of phosphogypsum not only occupies a large amount of land, but also pollutes the environment.

[0004] The comprehensive utilization of phosphogypsum has important practical significance for environmental protection, resource conservation and sustainable development of the phosphorus chemical industry. Through the unremitting efforts of a large number of scientific researchers, phosphogypsum utilization technology has made great progress and has been applied in the fields of industry, agriculture, building materials and fillers.

[0005] Gypsum-based self-leveling mortar has good fluidity and can precisely level the ground in a short time on a large area, which is beneficial to the improvement of construction speed and the application of engineering materials. Compared with cement-based self-leveling mortar, gypsum-based self-leveling mortar has the advantages of energy saving and environmental protection, high bonding strength, low cracking risk, fast hardening and curing, and simple natural curing.

[0006] However, the current gypsum-based self-leveling mortar products have the problems of low strength, poor wear resistance and high cost, and many products cannot meet the requirement of 20Mpa compressive strength of the industry standard, which is an obstacle to the resource utilization of by-product gypsum. SUMMARY

[0007] The application aims to solve the problems of low absolute dry strength of hemihydrate gypsum used in self-leveling mortar, poor early strength and poor wear resistance of anhydrite used in self-leveling mortar, and aims to provide a composite gypsum-based self-leveling mortar and a preparation method thereof, which combines the respective advantages of hemihydrate gypsum self-leveling mortar and anhydrite self-leveling mortar, so that the composite gypsum-based self-leveling mortar has the characteristics of fast setting, early strength and high later strength, and the wear resistance of the self-leveling mortar is significantly improved.

[0008] The application is implemented by adopting the following technical solutions: In a first aspect, the application provides a composite gypsum-based self-leveling mortar, which comprises the following raw materials in mass fractions: 75-95 parts of composite gypsum, 3-25 parts of auxiliary cementitious material, and 0.5-2.5 parts of additive mixture; the composite gypsum comprises a mixed composite phase gypsum of hemihydrate gypsum, dihydrate gypsum and anhydrite; the auxiliary cementitious material is a mixed composite material of ordinary Portland cement, aluminate cement, calcium sulfoaluminate cementitious material and sulfoaluminate cement; the additive mixture comprises multiple types of retarder, water retaining agent, suspending / stabilizing agent, water reducing agent, flow aid, defoaming agent, hydrophobic agent and activator.

[0009] The application uses a large proportion of composite gypsum as the main body, adopts a composite special cement auxiliary cementitious material, uses a composite activator to activate the composite gypsum powder, uses a water reducing agent and other additives to reduce the water consumption of the mortar and eliminate bubbles in the mortar, and improves the density of the mortar, so that the composite gypsum-based self-leveling mortar has high strength and good wear resistance, and is more likely to meet the requirements of the JC / T1023-2021 standard. At the same time, the composite gypsum-based self-leveling mortar also reduces the product cost, and solves the technical problem of high cost of existing high-strength gypsum-based self-leveling mortar.

[0010] As a preferred embodiment, the composite gypsum comprises the following raw materials in mass fractions: 40-60 parts of hemihydrate gypsum, 25-40 parts of anhydrite, 0.5-2 parts of dihydrate gypsum, and 8-18 parts of silicon oxide compound.

[0011] The anhydrite in the composite gypsum has a slow activation effect under the action of external activators, which can lead to very low 1-day strength of the gypsum-based self-leveling mortar, and thus cannot meet the 1-day strength standard requirements of the self-leveling mortar.

[0012] The hemihydrate gypsum and the anhydrite have a hydration reaction under the rapid activation of the aluminate cement, the calcium sulfoaluminate cementitious material and the sulfoaluminate cement, and thus the 1-day strength of the composite gypsum-based self-leveling mortar can be improved to meet the requirements of the gypsum-based self-leveling mortar.

[0013] As a kind of preferred, auxiliary cementitious material includes the following mass parts of raw materials: Portland cement 20~70 parts, aluminate cement 0~50 parts, calcium sulphoaluminate cementitious material 0~60 parts, sulphoaluminate cement 0~50 parts.

[0014] Auxiliary cementitious material is Portland cement, aluminate cement, calcium sulphoaluminate cementitious material and sulphoaluminate cement are mixed and used according to different proportions, and the auxiliary cementitious material in the above-mentioned proportion plays the role of water reducing, retarding and early strength in self-leveling mortar, and cement also plays the role of activation of anhydrous gypsum.

[0015] As a kind of preferred, auxiliary cementitious material includes the following mass parts of raw materials: Retarder 0~0.5 parts, water retaining agent 0~0.5 parts, suspending / stabilizing agent 0~0.5 parts, water reducing agent 0~1 part, flow aid 0~0.2 parts, defoaming agent 0~0.1 parts, hydrophobic agent 0~0.15 parts, mixed activator 0~2 parts.

[0016] Retarder is convenient to control the initial setting and final setting time of self-leveling mortar, and can also well ensure the 30-minute flowability of self-leveling mortar product, and can also better improve the 1-day flexural and compressive strength of mortar.

[0017] Water retaining agent and suspending / stabilizing agent control the stability and flowability of self-leveling mortar slurry, and prevent the mortar from settling and stratifying.

[0018] Water reducing agent has high water reducing efficiency. Flow aid also has part of retarding effect.

[0019] Defoaming agent can quickly defoam and maintain long-acting defoaming effect.

[0020] Hydrophobic agent can repel water contact.

[0021] Activator can quickly activate the hydration reaction of hemihydrate gypsum and anhydrous gypsum, and then can improve the 1-day strength of complex-phase gypsum-based self-leveling mortar.

[0022] As a kind of preferred, mixed activator is the mixture of sulphate, silicate and early strength agent, and the mixing ratio is mass ratio 1-5:1-5:1-5, and the mixed use effect is better.

[0023] In the second aspect, the application also provides a preparation method of the above-mentioned complex-phase gypsum-based self-leveling mortar, and the complex-phase gypsum, auxiliary cementitious material and auxiliary agent mixture are mixed uniformly according to mass parts, and then are put into stirring equipment for stirring according to water-material ratio 1:0.25~0.5, and are stirred at low speed first and then at high speed, so that the complex-phase gypsum-based self-leveling mortar is prepared.

[0024] The preparation method of the present application fully utilizes the characteristics of fast initial setting of hemihydrate gypsum and high later strength of anhydrite, has good construction fluidity, and avoids the defects of ordinary mortar such as sanding and blackening.

[0025] As a preferred, the preparation method of the composite gypsum is as follows: In the calcining device, the crushed phosphogypsum raw material is directly contacted with hot flue gas at 300-500 DEG C to remove the attached water and the contained crystal water of the raw material, to obtain hemihydrate gypsum by removing 1.5 crystal water, to obtain type II anhydrite by removing 2 crystal water, and to obtain hemihydrate gypsum by converting the generated type III anhydrite into hemihydrate gypsum by contacting with water vapor in the later cooling and aging process.

[0026] The present application fully utilizes the phosphogypsum raw material, eliminates the influence of impurities on performance and environment through calcination modification, and prepares the composite gypsum-based self-leveling mortar product, which has the characteristics of fast setting and early strength of hemihydrate gypsum-based self-leveling mortar and high later strength of anhydrite-based self-leveling mortar, and has good dimensional stability.

[0027] As a preferred, the preparation method of the composite gypsum further comprises: The hemihydrate gypsum and type II anhydrite obtained by calcination at different temperatures are prepared into composite gypsum powder in a proportion of 40-60 parts of hemihydrate gypsum, 25-40 parts of anhydrite, 0.5-2 parts of dihydrate gypsum, and 8-18 parts of silicon oxide compound. The composite gypsum is a mixed phase gypsum, which contains hemihydrate gypsum, anhydrite and a small amount of dihydrate gypsum. The composite gypsum can be a one-time calcination product, or can be obtained by mixing the hemihydrate gypsum and the anhydrite after being calcined separately. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application. If the specific technology or condition is not specified in the examples, it is prepared according to the technology or condition described in the literature or according to the product manual. If the reagent or instrument is not specified by the manufacturer, it is a conventional product that can be obtained by purchase.

[0029] Unless otherwise specified, the percentage sign represents the mass fraction. The ratio is the mass ratio, and the concentration is the mass concentration.

[0030] At present, the gypsum-based self-leveling mortar product has low strength and poor wear resistance, and many products cannot meet the requirement of 20Mpa compressive strength of the industry standard.

[0031] Further, in a first aspect, the embodiments of the present application provide a composite gypsum-based self-leveling mortar, which comprises the following raw materials in mass fraction: The complex gypsum 75-95 parts, the auxiliary cementing material 3-25 parts and the additive mixture 0.5-2.5 parts; the complex gypsum includes the mixed complex phase gypsum of the hemihydrate gypsum, the dihydrate gypsum and the anhydrous gypsum; the auxiliary cementing material is the ordinary Portland cement, the aluminate cement, the calcium sulphoaluminate cementing material and the mixed compound material of the sulphoaluminate cement; the additive mixture includes multiple kinds of the retarder, the water retaining agent, the suspending / stabilizing agent, the water reducing agent, the flow aid, the defoaming agent, the hydrophobic agent and the activator.

[0032] The present application uses a large proportion of complex gypsum, mainly uses complex gypsum, uses compound special cement auxiliary cementing material, uses composite activator to activate complex gypsum powder, uses water reducing agent and other additives to reduce the water consumption of mortar and eliminate mortar bubbles, etc., improves the density of mortar, and the prepared complex gypsum-based self-leveling mortar has high strength and good wear resistance, and can more easily meet the requirements of JC / T1023-2021 standard. At the same time, the complex gypsum-based self-leveling mortar also reduces the product cost, and solves the technical problem that the cost of the existing high-strength gypsum-based self-leveling mortar is also relatively high.

[0033] During the research and development of the present application, the complex gypsum contains hemihydrate gypsum and anhydrous gypsum, the proportion of anhydrous gypsum is relatively high, and the activation effect of anhydrous gypsum is poor, which leads to a long initial setting time of the complex gypsum-based self-leveling mortar. At the same time, due to the difference in hydration mechanism between hemihydrate gypsum and anhydrous gypsum, the 1d strength of the self-leveling mortar is poor. In order to make the best use of the characteristics of fast initial setting of hemihydrate gypsum and good late strength of anhydrous gypsum, we first add a retarder and add auxiliary cementing material to adjust the setting time of hemihydrate gypsum and the activation effect of anhydrous gypsum, so that the complex gypsum-based self-leveling mortar is better coordinated in terms of setting time and 1d strength. Second, adjust the composition and usage of auxiliary cementing material and composite activator, so that the activation effect of anhydrous gypsum can be reflected in the early strength of 1d strength as soon as possible, so that the complex gypsum-based self-leveling mortar can meet the requirements of JC / T1023-2021 standard.

[0034] As one of the embodiments, the complex gypsum includes the following raw materials by mass: Hemihydrate gypsum 40-60 parts, anhydrous gypsum 25-40 parts, dihydrate gypsum 0.5-2 parts, silicon oxide compound 8-18 parts.

[0035] The complex gypsum contains anhydrous gypsum, and the slow activation of anhydrous gypsum under the action of external activator will lead to very low 1d strength of the gypsum-based self-leveling mortar, and thus cannot meet the standard requirements of the 1d strength of the self-leveling mortar.

[0036] Hemihydrate gypsum and anhydrous gypsum undergo hydration reaction under the rapid activation of aluminate cement, calcium sulphoaluminate cementing material and sulphoaluminate cement, and thus the 1d strength of the complex gypsum-based self-leveling mortar can be improved to meet the requirements of the gypsum-based self-leveling mortar.

[0037] As one of the embodiments, the auxiliary cementitious material includes the following raw materials in parts by mass: Portland cement 20-70 parts, aluminate cement 0-50 parts, calcium sulfoaluminate cementitious material 0-60 parts, and sulfoaluminate cement 0-50 parts, i.e. a mixture of ordinary cement and special cement.

[0038] The auxiliary cementitious material is a mixture of Portland cement, aluminate cement, calcium sulfoaluminate cementitious material and sulfoaluminate cement in different proportions. The auxiliary cementitious material in the above proportions plays a role of water reducing, retarding and early strength in the self-leveling mortar, and the cement also plays a role of activation of anhydrous gypsum.

[0039] As one of the embodiments, the auxiliary agent mixture includes the following raw materials in parts by mass: retarder 0-0.5 parts, water retaining agent 0-0.5 parts, suspending / stabilizing agent 0-0.5 parts, water reducing agent 0-1 part, flow aid 0-0.2 parts, defoaming agent 0-0.1 part, hydrophobic agent 0-0.15 part, and mixed activator 0-2 parts.

[0040] Each auxiliary agent can also be a single variety or a mixture of multiple varieties, such as a mixture of a first water reducing agent and a second water reducing agent as a water reducing agent added to the mortar, and other auxiliary agents are also a single variety or a mixture of multiple varieties.

[0041] The retarder is a mixture of an alkaline protein type retarder and a sodium salt type retarder, which is convenient for controlling the initial setting and final setting time of the self-leveling mortar, can well ensure the 30-minute flowability of the self-leveling mortar product, and can better improve the 1-day flexural and compressive strength of the mortar.

[0042] The water retaining agent and the suspending / stabilizing agent are one or more mixed, which controls the stability and flowability of the self-leveling mortar slurry, prevents the mortar from settling and stratifying, and one of the stabilizing agents in the present application is an octahedral natural clay mineral.

[0043] The water reducing agent is one or more carboxylate salts, which has high water reducing efficiency.

[0044] The flow aid is a sodium salt, which also has a part of retarding effect.

[0045] The defoaming agent is a polyether modified type, which can quickly defoam and maintain long-acting defoaming effect.

[0046] The hydrophobic agent is an organosilicon type siloxane, which can repel water contact.

[0047] As one of the embodiments, the mixed activator is a mixture of sulfate, silicate and early strength agent, and the mixing ratio is 1-5:1-5:1-5 by mass, and the mixed use effect is better. The activator is used alone or mixedly used, and the activator is sulfate, silicate, calcium salt, organic amine and strong alkali.

[0048] In the second aspect, the embodiment of the present application also provides a preparation method of the above-mentioned composite gypsum-based self-leveling mortar. The composite gypsum, auxiliary cementitious material and additive are mixed uniformly according to the mass fraction, and then are put into a stirring device for stirring according to a water-material ratio of 1:0.25-0.5. The stirring is first carried out at a low speed and then at a high speed, so that the composite gypsum-based self-leveling mortar is prepared. The stirring and subsequent testing are carried out according to the standard method specified in JC / T1023-2021.

[0049] The preparation method of the embodiment of the present application fully utilizes the characteristics of fast initial setting of hemihydrate gypsum and high later strength of anhydrite, has good construction fluidity, and avoids the defects of ordinary mortar, such as sanding and blackening.

[0050] As one of the embodiments, the preparation method of the composite gypsum is as follows: In the calcining device, the crushed phosphogypsum raw material is directly contacted with hot flue gas at 300-500 DEG C to remove the attached water and the contained crystal water of the raw material, so that 1.5 crystal waters are removed to obtain hemihydrate gypsum, and 2 crystal waters are removed to obtain II-type anhydrite. The III-type anhydrite generated in the calcining process is converted into hemihydrate gypsum by contacting with water vapor in the later cooling and aging process. The phosphogypsum raw material is fully utilized, the influence of impurities on performance and environment is eliminated through calcining modification, and the prepared composite gypsum-based self-leveling mortar product has the characteristics of fast setting and early strength of hemihydrate gypsum-based self-leveling mortar and high later strength of anhydrite-based self-leveling mortar. Meanwhile, the dimensional stability of the composite gypsum-based self-leveling mortar is good. The composite gypsum can be mechanically ground and sieved through a 250-mesh screen during the calcining process.

[0051] As one of the embodiments, the preparation method of the composite gypsum further includes: The hemihydrate gypsum and II-type anhydrite obtained by calcining at different temperatures are prepared into the composite gypsum powder according to the proportions of 40-60 parts of hemihydrate gypsum, 25-40 parts of anhydrite, 0.5-2 parts of dihydrate gypsum and 8-18 parts of silicon oxide compound. The composite gypsum is a mixed phase gypsum, which contains hemihydrate gypsum, anhydrite and a small amount of dihydrate gypsum. The composite gypsum can be a one-time calcined product, or can be obtained by mixing the hemihydrate gypsum and the anhydrite after being calcined respectively.

[0052] The composite gypsum can use a one-time sintered mixed-phase gypsum powder, and the composition of the composite gypsum powder is: hemihydrate gypsum, anhydrite, dihydrate gypsum, silicon oxide compound. The composite gypsum powder can also be prepared by mixing hemihydrate gypsum and anhydrite after being sintered respectively, and the composition is close to the composition ratio of the one-time sintered gypsum powder.

[0053] In order to further illustrate the present application, the composite gypsum-based self-leveling mortar and the preparation method thereof provided by the present application are described in detail below in combination with examples.

[0054] Example 1 The composite gypsum-based self-leveling mortar of the present example is prepared by the following method: In the sintering device, the crushed phosphogypsum raw material is directly contacted with hot flue gas at 400 DEG C to remove the attached water and the contained crystal water of the raw material, and 1.5 crystal waters are removed to obtain hemihydrate gypsum, and 2 crystal waters are removed to obtain type II anhydrite, and the type III anhydrite generated in the sintering process is converted into hemihydrate gypsum by contacting with water vapor in the later cooling and aging process.

[0055] After the composite gypsum powder is aged, the composition is detected as follows: hemihydrate gypsum 60%, anhydrite 30%, dihydrate gypsum 1%, and silicon oxide compound 9%. The gypsum powder is a gypsum powder prepared by sintering dihydrate phosphogypsum.

[0056] The mass fraction of the composite gypsum powder is 90 parts, the mass fraction of the auxiliary cementitious material is 10 parts, and the mass fraction of the additive mixture is 1.26 parts.

[0057] The auxiliary cementitious material is compounded according to ordinary Portland cement 30%, calcium sulphoaluminate cementitious material 40%, sulphoaluminate cement 20%, and aluminate cement 10%.

[0058] The additive mixture is mixed according to the mass ratio of retarder: water retention agent: stabilizer: water reducing agent: defoaming agent: flowability agent: activator = 1:2:1:1:2:1:6.

[0059] The above composite gypsum powder, auxiliary cementitious material and additive mixture are uniformly mixed, and then a composite gypsum-based self-leveling mortar is prepared by low-speed stirring and then high-speed stirring according to the water-material ratio of 0.37:1.

[0060] Example 2 The composite gypsum-based self-leveling mortar of the present example is prepared by the following method: In the sintering device, the crushed phosphogypsum raw material is directly contacted with hot flue gas at 500 DEG C, and the rest is the same as in Example 1.

[0061] The total mass fraction of the composite gypsum powder is 80 parts, of which: hemihydrate gypsum 50%, anhydrite 35%, dihydrate gypsum 2%, and silicon oxide compound 13%.

[0062] The auxiliary cementitious material has a mass fraction of 20 parts, and is compounded according to 50% of ordinary Portland cement, 20% of calcium sulfoaluminate cementitious material, 30% of sulfoaluminate cement, and 20% of aluminate cement.

[0063] The additive mixture has a mass fraction of 1.2 parts, and is mixed according to a ratio of 1:2:2:1:2:1:4 of retarder, water retaining agent, stabilizer, water reducing agent, defoaming agent, flowability agent, and activator.

[0064] The composite gypsum powder, the auxiliary cementitious material, and the additive mixture are uniformly mixed, and then a composite gypsum-based self-leveling mortar is prepared by stirring at a low speed and then at a high speed according to a water-material ratio of 0.35:1.

[0065] Example 3 The composite gypsum-based self-leveling mortar of the present example is prepared according to the following method: In the calcination device, the crushed phosphogypsum raw material is directly contacted with hot flue gas at 300°C, and the rest is the same as in Example 1.

[0066] The total mass fraction of the composite gypsum powder is 75 parts, of which: 70% of hemihydrate gypsum, 20% of anhydrite, 2% of dihydrate gypsum, and 8% of silicon oxide compound.

[0067] The auxiliary cementitious material has a mass fraction of 25 parts, and is compounded according to 30% of ordinary Portland cement, 40% of calcium sulfoaluminate cementitious material, 10% of sulfoaluminate cement, and 20% of aluminate cement.

[0068] The additive mixture has a mass fraction of 1.1 parts, and is mixed according to a ratio of 1:1:2:3:2:1:3 of retarder, water retaining agent, stabilizer, water reducing agent, defoaming agent, flowability agent, and activator.

[0069] The composite gypsum powder, the auxiliary cementitious material, and the additive mixture are uniformly mixed, and then a composite gypsum-based self-leveling mortar is prepared by stirring at a low speed and then at a high speed according to a water-material ratio of 0.35:1.

[0070] Example 4 The composite gypsum-based self-leveling mortar of the present example is prepared according to the following method: In the calcination device, the crushed phosphogypsum raw material is directly contacted with hot flue gas at 500°C, and the rest is the same as in Example 1.

[0071] The total mass fraction of the composite gypsum powder is 95 parts, of which: 70% of hemihydrate gypsum, 20% of anhydrite, 2% of dihydrate gypsum, and 8% of silicon oxide compound.

[0072] The auxiliary cementitious material has a mass fraction of 5 parts, and is compounded according to 30% of ordinary Portland cement, 40% of calcium sulfoaluminate cementitious material, 10% of sulfoaluminate cement, and 20% of aluminate cement.

[0073] The additive mixture has a mass fraction of 1.4 parts, and the retarder, water retaining agent, stabilizer, water reducing agent, defoaming agent, flowability agent and activator are mixed in a ratio of 1:1:2:3:2:1:3.

[0074] The composite gypsum powder, auxiliary cementitious material and additive mixture are uniformly mixed, and then a composite gypsum-based self-leveling mortar is prepared by stirring at a low speed and then at a high speed in a water-material ratio of 0.36:1.

[0075] Example 5 The composite gypsum-based self-leveling mortar of the present example is prepared by the following method: In the calcining device, the crushed phosphogypsum raw material is directly contacted with hot flue gas at 300°C to remove the attached water and the contained crystal water of the raw material, and the rest is the same as in Example 1.

[0076] The total mass fraction of the composite gypsum powder is 88 parts, of which: hemihydrate gypsum 70%, anhydrite 20%, dihydrate gypsum 2%, and silicon oxide compound 8%.

[0077] The auxiliary cementitious material has a mass fraction of 12 parts, and is compounded according to ordinary Portland cement 60%, calcium sulfoaluminate cementitious material 10%, sulfoaluminate cement 20% and aluminate cement 10%.

[0078] The additive mixture has a mass fraction of 1.28 parts, and the retarder, water retaining agent, stabilizer, water reducing agent, defoaming agent, flowability agent and activator are mixed in a ratio of 1:2:1:4:1:1:4. The activator is a mixed activator, which is a mixture of sulfate, silicate and early strength agent in a ratio of 1:2:3.

[0079] The composite gypsum powder, auxiliary cementitious material and additive mixture are uniformly mixed, and then a composite gypsum-based self-leveling mortar is prepared by stirring at a low speed and then at a high speed in a water-material ratio of 0.37:1.

[0080] Example 6 The composite gypsum-based self-leveling mortar of the present example is prepared by the following method: In the calcining device, the crushed phosphogypsum raw material is directly contacted with hot flue gas at 400°C, and the rest is the same as in Example 1.

[0081] The total mass fraction of the composite gypsum powder is 85 parts, of which: hemihydrate gypsum 60%, anhydrite 30%, dihydrate gypsum 2%, and silicon oxide compound 8%.

[0082] The auxiliary cementitious material has a mass fraction of 15 parts, and is compounded according to ordinary Portland cement 30%, calcium sulfoaluminate cementitious material 40%, sulfoaluminate cement 10% and aluminate cement 20%.

[0083] The additive mixture has a mass fraction of 1.28 parts, which is composed of retarder, water retaining agent, stabilizer, water reducing agent, defoaming agent, flowability agent and activator in a ratio of 2:1:2:3:2:1:3.

[0084] The composite gypsum powder, the auxiliary cementitious material and the additive mixture are mixed uniformly, and then a composite gypsum-based self-leveling mortar is prepared by stirring at a low speed and then at a high speed according to a water-material ratio of 0.37:1.

[0085] Example 7 The composite gypsum-based self-leveling mortar of the present example is prepared by the following method: In the calcination device, the crushed phosphogypsum raw material is directly contacted with hot flue gas at 500°C, and the rest is the same as in Example 1.

[0086] The total mass fraction of the composite gypsum powder is 92 parts, of which: hemihydrate gypsum 50%, anhydrous gypsum 35%, dihydrate gypsum 2%, silicon oxide compound 13%.

[0087] The auxiliary cementitious material has a mass fraction of 8 parts, which is composed of ordinary portland cement 50%, calcium sulphoaluminate cementitious material 20%, sulphoaluminate cement 30%, and aluminate cement 20%.

[0088] The additive mixture has a mass fraction of 1.29 parts, which is composed of retarder, water retaining agent, stabilizer, water reducing agent, defoaming agent, flowability agent and activator in a ratio of 1:2:3:1:2:1:4.

[0089] The composite gypsum powder, the auxiliary cementitious material and the additive mixture are mixed uniformly, and then a composite gypsum-based self-leveling mortar is prepared by stirring at a low speed and then at a high speed according to a water-material ratio of 0.37:1.

[0090] Example 8 The composite gypsum-based self-leveling mortar of the present example is prepared by the following method: In the calcination device, the crushed phosphogypsum raw material is directly contacted with hot flue gas at about 300°C to remove the attached water and the contained crystal water of the raw material, and 1.5 crystal waters are removed to obtain hemihydrate gypsum. The phosphogypsum is directly contacted with hot flue gas at about 100°C for heat exchange to remove 2 crystal waters to obtain type II anhydrous gypsum. The type III anhydrous gypsum generated in the calcination process is converted into hemihydrate gypsum by contacting with water vapor during the later cooling and aging process. The hemihydrate gypsum and type II anhydrous gypsum obtained by calcination at different temperatures are prepared in a ratio of hemihydrate gypsum 60%, anhydrous gypsum 20%, dihydrate gypsum 2%, and silicon oxide compound 18% to obtain the composite gypsum powder.

[0091] The mass fraction of the composite gypsum powder is 90 parts.

[0092] The auxiliary cementitious material is 10 parts by mass, and is compounded according to 30% of ordinary Portland cement, 40% of calcium sulfoaluminate cementitious material, 10% of sulfoaluminate cement, and 20% of aluminate cement.

[0093] The additive mixture is 1.25 parts by mass, and is mixed according to a ratio of 1:1:2:3:2:1:3 of retarder, water retaining agent, stabilizer, water reducing agent, defoaming agent, flowability agent, and activator.

[0094] The composite gypsum powder, the auxiliary cementitious material, and the additive mixture are uniformly mixed, and then a composite gypsum-based self-leveling mortar is prepared by stirring at a low speed and then at a high speed according to a water-material ratio of 0.38:1.

[0095] Example 9 The composite gypsum-based self-leveling mortar of this example is prepared as follows: In the calcination device, the crushed phosphogypsum raw material is directly contacted with hot flue gas at about 300°C to remove the attached water and the contained crystal water of the raw material, and 1.5 crystal waters are removed to obtain hemihydrate gypsum. The phosphogypsum is directly contacted with hot flue gas at about 100°C for heat exchange, and 2 crystal waters are removed to obtain type II anhydrite. The type III anhydrite generated in the calcination process is converted into hemihydrate gypsum by contacting with water vapor in the later cooling and aging process.

[0096] The hemihydrate gypsum and the type II anhydrite obtained by calcination at different temperatures are compounded according to a ratio of 50% of hemihydrate gypsum, 33% of anhydrite, 2% of dihydrate gypsum, and 15% of silicon oxide compound to obtain the composite gypsum powder.

[0097] The composite gypsum powder is 85 parts by mass.

[0098] The auxiliary cementitious material is 15 parts by mass, and is compounded according to 40% of ordinary Portland cement, 40% of calcium sulfoaluminate cementitious material, 10% of sulfoaluminate cement, and 10% of calcium sulfoaluminate cementitious material.

[0099] The additive mixture is 1.28 parts by mass, and is mixed according to a ratio of 1:1:2:3:2:1:3 of retarder, water retaining agent, stabilizer, water reducing agent, defoaming agent, flowability agent, and activator.

[0100] The composite gypsum powder, the auxiliary cementitious material, and the additive mixture are uniformly mixed, and then a composite gypsum-based self-leveling mortar is prepared by stirring at a low speed and then at a high speed according to a water-material ratio of 0.38:1.

[0101] Comparative Example 1 A single gypsum powder is selected for comparison with Example 1, and all hemihydrate gypsum is used, and the rest is the same as Example 1, and is prepared as follows: The semi-hydrated gypsum powder is 90 parts by mass, the auxiliary cementing material is 10 parts by mass, and the additive mixture is 1.26 parts by mass.

[0102] The auxiliary cementing material is compounded according to 30% of ordinary Portland cement, 40% of calcium sulfoaluminate cementing material, 20% of sulfoaluminate cement, and 10% of aluminate cement.

[0103] The additive mixture is mixed according to a mass ratio of 1:2:1:1:2:1:6 of retarder, water-retaining agent, stabilizer, water-reducing agent, defoaming agent, flowability agent, and activator.

[0104] The semi-hydrated gypsum powder, the auxiliary cementing material, and the additive mixture are uniformly mixed, and then a semi-hydrated gypsum-based self-leveling mortar is prepared by low-speed stirring and then high-speed stirring according to a water-material ratio of 0.37:1.

[0105] Comparative Example 2 A single gypsum powder is selected for comparison with Example 1, and anhydrous gypsum is used instead of semi-hydrated gypsum, and the rest is the same as Example 1, and is prepared according to the following method: The anhydrous gypsum powder is 90 parts by mass, the auxiliary cementing material is 10 parts by mass, and the additive mixture is 1.26 parts by mass.

[0106] The auxiliary cementing material is compounded according to 30% of ordinary Portland cement, 40% of calcium sulfoaluminate cementing material, 20% of sulfoaluminate cement, and 10% of aluminate cement.

[0107] The additive mixture is mixed according to a mass ratio of 1:2:1:1:2:1:6 of retarder, water-retaining agent, stabilizer, water-reducing agent, defoaming agent, flowability agent, and activator.

[0108] The anhydrous gypsum powder, the auxiliary cementing material, and the additive mixture are uniformly mixed, and then an anhydrous gypsum-based self-leveling mortar is prepared by low-speed stirring and then high-speed stirring according to a water-material ratio of 0.37:1.

[0109] Comparative Example 3 Two kinds of gypsum powder are selected for comparison with Example 1, and semi-hydrated gypsum and anhydrous gypsum are mixed in equal proportions, and the rest is the same as Example 1, and is prepared according to the following method: The semi-hydrated gypsum powder is 45 parts by mass, the anhydrous gypsum powder is 45 parts by mass, the auxiliary cementing material is 10 parts by mass, and the additive mixture is 1.26 parts by mass.

[0110] The auxiliary cementing material is compounded according to 30% of ordinary Portland cement, 40% of calcium sulfoaluminate cementing material, 20% of sulfoaluminate cement, and 10% of aluminate cement.

[0111] Admixture mixture: retarder, water retaining agent, stabilizer, water reducing agent, defoaming agent, flowability agent and activator, mixed in a mass ratio of 1:2:1:1:2:1:6.

[0112] The semi-hydrated anhydrous gypsum powder, auxiliary cementitious material and admixture mixture are mixed uniformly, and then a semi-hydrated anhydrous gypsum-based self-leveling mortar is prepared by stirring at a low speed first and then at a high speed in a water-material ratio of 0.37:1.

[0113] Comparative Example 4 In this example, only ordinary Portland cement is used, and the rest is the same as in Example 1. The following method is used for preparation: The mass fraction of the composite gypsum powder is 90 parts, the mass fraction of the auxiliary cementitious material is 10 parts, and the mass fraction of the admixture mixture is 1.26 parts.

[0114] Auxiliary cementitious material: ordinary Portland cement 100%.

[0115] Admixture mixture: retarder, water retaining agent, stabilizer, water reducing agent, defoaming agent, flowability agent and activator, mixed in a mass ratio of 1:2:1:1:2:1:6.

[0116] The semi-hydrated anhydrous gypsum powder, auxiliary cementitious material and admixture mixture are mixed uniformly, and then a semi-hydrated anhydrous gypsum-based self-leveling mortar is prepared by stirring at a low speed first and then at a high speed in a water-material ratio of 0.37:1.

[0117] Comparative Example 5 The auxiliary cementitious material is a mixture of ordinary Portland cement and aluminate cement in equal proportions, and the rest is the same as in Example 1.

[0118] In this example, ordinary Portland cement and aluminate cement are mixed in equal proportions, and the rest is the same as in Example 1. The following method is used for preparation: The mass fraction of the composite gypsum powder is 90 parts, the mass fraction of the auxiliary cementitious material is 10 parts, and the mass fraction of the admixture mixture is 1.26 parts.

[0119] Auxiliary cementitious material: a mixture of ordinary Portland cement 50% and aluminate cement 50%.

[0120] Admixture mixture: retarder, water retaining agent, stabilizer, water reducing agent, defoaming agent, flowability agent and activator, mixed in a mass ratio of 1:2:1:1:2:1:6.

[0121] The semi-hydrated anhydrous gypsum powder, auxiliary cementitious material and admixture mixture are mixed uniformly, and then a semi-hydrated anhydrous gypsum-based self-leveling mortar is prepared by stirring at a low speed first and then at a high speed in a water-material ratio of 0.37:1.

[0122] Comparative Example 6 This example selects not to use retarder, and the amount of stabilizer is used to expand 1 times, compared with Example 1. Not to use retarder, the amount of stabilizer is expanded 1 times, and the rest is the same as Example 1. It is prepared according to the following method: The mass fraction of composite gypsum powder is 90 parts, the mass fraction of auxiliary cementing material is 10 parts, and the mass fraction of additive mixture is 1.26 parts.

[0123] The auxiliary cementing material is compounded according to 30% of ordinary Portland cement, 40% of calcium sulfoaluminate cementing material, 20% of sulfoaluminate cement, and 10% of aluminate cement.

[0124] The additive mixture is mixed according to the mass ratio of water retaining agent, stabilizer, water reducing agent, defoaming agent, flowability agent, and activator, which is 2:2:1:2:1:6.

[0125] The composite gypsum powder, auxiliary cementing material, and additive mixture are mixed uniformly, and then a composite gypsum-based self-leveling mortar is prepared by low-speed stirring and then high-speed stirring according to the water-material ratio of 0.37:1.

[0126] Comparative Example 7 The activator is not used, and the same amount of stabilizer is replaced. The rest is the same as Example 1.

[0127] This example selects not to use activator, and the amount of stabilizer is used to expand 1 times, compared with Example 1. Not to use activator, the amount of stabilizer is expanded 1 times, and the rest is the same as Example 1. It is prepared according to the following method: The mass fraction of composite gypsum powder is 90 parts, the mass fraction of auxiliary cementing material is 10 parts, and the mass fraction of additive mixture is 1.26 parts.

[0128] The auxiliary cementing material is compounded according to 30% of ordinary Portland cement, 40% of calcium sulfoaluminate cementing material, 20% of sulfoaluminate cement, and 10% of aluminate cement.

[0129] The additive mixture is mixed according to the mass ratio of water retaining agent, stabilizer, water reducing agent, defoaming agent, and flowability agent, which is 2:2:1:2:1:6.

[0130] The composite gypsum powder, auxiliary cementing material, and additive mixture are mixed uniformly, and then a composite gypsum-based self-leveling mortar is prepared by low-speed stirring and then high-speed stirring according to the water-material ratio of 0.37:1.

[0131] The composite gypsum-based self-leveling mortar prepared in Examples 1-9 and Comparative Examples 1-7 is tested for physical properties according to the standard of JC / T 1023-2021 “Gypsum-based self-leveling mortar”. The actual test results are shown in Table 1.

[0132] Table 1 Comparative examples of the composite gypsum-based self-leveling mortar product The compressive strength can reflect the abrasion resistance, and the abrasion resistance will increase with the increase of the compressive strength.

[0133] The size change rate can reflect the dimensional stability, and the smaller the value of the change rate, the better the dimensional stability.

[0134] The composite gypsum-based self-leveling mortar of examples 1-9 fully utilizes the characteristics of fast initial setting of hemihydrate gypsum and high later strength of anhydrite, has good construction fluidity, and avoids the defects of ordinary mortar such as sanding and blackening.

[0135] As can be seen from comparative examples 1-3, the strength performance will be affected by selecting single gypsum powder and two kinds of gypsum powder, which is not as good as examples 1-9.

[0136] Comparative examples 4 and 5 use single ordinary portland cement and mix ordinary portland cement and aluminate cement in equal proportions, which also affects the strength due to the limitation of the activation effect.

[0137] Comparative examples 6 and 7 do not use retarder and activator, which affects the fluidity and strength.

[0138] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as the above preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and any brief introduction, modification, equivalent change and modification of the above examples according to the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. A multi-phase gypsum-based self-leveling screed, characterized in that: The raw materials include the following mass fractions: The composite gypsum 75-95 parts, the auxiliary cementing material 3-25 parts, and the additive mixture 0.5-2.5 parts; The composite gypsum includes hemihydrate gypsum, dihydrate gypsum, and anhydrous gypsum; The auxiliary cementing material is ordinary Portland cement, aluminate cement, calcium sulfoaluminate cementing material, and mixed compound of sulfoaluminate cement; The additive mixture includes multiple kinds of retarder, water retaining agent, suspending / stabilizing agent, water reducing agent, flow aid, defoaming agent, hydrophobic agent, and activator.

2. The multi-phase gypsum-based self-leveling mortar according to claim 1, characterized in that: The composite gypsum includes the following mass fractions: The hemihydrate gypsum 40-60 parts, the anhydrous gypsum 25-40 parts, the dihydrate gypsum 0.5-2 parts, and the silicon oxide compound 8-18 parts.

3. The multi-phase gypsum-based self-leveling mortar according to claim 1, characterized in that: The auxiliary cementing material includes the following mass fractions: The ordinary Portland cement 20-70 parts, the aluminate cement 0-50 parts, the calcium sulfoaluminate cementing material 0-60 parts, and the sulfoaluminate cement 0-50 parts.

4. The multi-phase gypsum-based self-leveling mortar according to claim 1, characterized in that: The additive mixture includes the following mass fractions: The retarder 0-0.5 parts, the water retaining agent 0-0.5 parts, the suspending / stabilizing agent 0-0.5 parts, the water reducing agent 0-1 part, the flow aid 0-0.2 part, the defoaming agent 0-0.1 part, the hydrophobic agent 0-0.15 part, and the mixed activator 0-2 parts.

5. The multi-phase gypsum-based self-leveling mortar according to claim 4, characterized in that: The mixed activator is a mixture of sulfate, silicate, and early strength agent, and the mixing ratio is 1-5:1-5:1-5.

6. A preparation method of the composite gypsum-based self-leveling mortar according to any one of claims 1-5, characterized in that: The composite gypsum, the auxiliary cementing material, and the additive mixture are mixed uniformly according to the mass fractions, and then are put into a stirring device for stirring at a water-material ratio of 1:0.25-0.5, and are stirred at a low speed first and then at a high speed, to obtain the composite gypsum-based self-leveling mortar.

7. The method of claim 6, wherein: The preparation method of the composite gypsum is as follows: In a calcination device, the crushed phosphogypsum raw material is directly contacted with hot flue gas at 300-500 ℃ to remove the attached water and the contained crystal water of the raw material, to obtain hemihydrate gypsum by removing 1.5 crystal water, and to obtain type II anhydrous gypsum by removing 2 crystal water, and the generated type III anhydrous gypsum is converted into hemihydrate gypsum by contacting with water vapor in the later cooling and aging process.

8. The method of claim 7, wherein: The preparation method of the composite gypsum further includes: The hemihydrate gypsum and the type II anhydrous gypsum obtained by calcination at different temperatures are prepared according to the following proportions: hemihydrate gypsum 40-60 parts, anhydrous gypsum 25-40 parts, dihydrate gypsum 0.5-2 parts, and silicon oxide compound 8-18 parts, to obtain the composite gypsum powder.

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