Sulfo-alumino-ferrous cement and method for its production

Abstract

The application relates to the technical field of building materials, and particularly discloses a sulphur-aluminum-iron cement and a preparation method thereof. The sulphur-aluminum-iron cement comprises the following raw materials: 55-65 parts of sulphur-aluminum-iron cement clinker, 10-15 parts of gypsum, 5-10 parts of silane modified metakaolin, 10-15 parts of superfine slag powder, 3-5 parts of filling material and 1 part of surface modified graphene dispersion liquid. The sulphur-aluminum-iron cement clinker comprises the following mineral components: 32-38% of anhydrous calcium sulphoaluminate, 26-32% of tetracalcium aluminoferrite, 20-26% of dicalcium silicate, 6-10% of tricalcium silicate and less than or equal to 1.5% of free calcium oxide. The application limits the mineral components and the proportion of the sulphur-aluminum-iron cement clinker, so that the mechanical properties of the cement system are improved; the active admixture and the filling material are used to fill the internal capillary holes of the cement system, the invasion channels of the erosion medium are reduced, the compactness is enhanced, and the structure of the hydration product is optimized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, and in particular to a sulfur-aluminum-iron cement and a preparation method thereof. BACKGROUND

[0002] As an important building material, cement plays an irreplaceable role in global infrastructure construction, real estate development and other fields. Compared with traditional Portland cement, sulfur-aluminum-iron cement has significant advantages in performance, environmental protection and application scenarios. In terms of performance, sulfur-aluminum-iron cement has the characteristics of early strength and high strength, which can greatly shorten the construction period, especially suitable for projects with tight schedules. At the same time, it has excellent anti-permeability, anti-frost and corrosion resistance, which can effectively deal with special scenarios such as seawater erosion of marine engineering and humid environment of underground engineering. In terms of environmental protection and energy saving, the production energy consumption of sulfur-aluminum-iron cement is 15%-20% lower than that of traditional Portland cement, the carbon dioxide emission is significantly reduced, and industrial waste residues such as steel slag and fly ash can be mixed, which not only reduces the dependence on raw materials, but also realizes the recycling of waste, with the characteristics of low carbon, environmental protection and resource saving. In terms of application field, sulfur-aluminum-iron cement has been preliminarily landed in marine engineering, winter construction, underground engineering and cement product field, for example, it can avoid the delay of construction period caused by insufficient early strength in winter construction, and can improve the durability in cement product production, effectively filling the application gap of traditional cement in special environment.

[0003] Although sulfur-aluminum-iron cement has obvious advantages, there are still two key problems in the prior art. In terms of production process, the current process has high heat consumption, which limits the production capacity, and the product quality stability is poor during the production process, the performance of the same batch of products fluctuates greatly, resulting in high production cost, which weakens its competitiveness in the market and makes it difficult to realize large-scale promotion. There are bottlenecks in application technology, the microstructure of sulfur-aluminum-iron cement is unstable, and the long-term stability of its corrosion resistance needs to be further improved to better meet the increasing use demand. Therefore, it is urgent to develop a new type of sulfur-aluminum-iron cement to improve the comprehensive performance of sulfur-aluminum-iron cement, meet the high demand for corrosion resistance and stability in application, and reduce production cost. SUMMARY

[0004] In view of the above problems, the present application provides a sulfur-aluminum-iron cement and a preparation method thereof, which further improves the mechanical properties of the existing sulfur-aluminum-iron cement, especially the corrosion resistance, by designing the mineral composition of the sulfur-aluminum-iron cement clinker and the raw materials of the sulfur-aluminum-iron cement.

[0005] To solve the above technical problems, the technical scheme provided by the present application is:

[0006] In a first aspect, the present application provides a sulpho-alumino-ferri cement, comprising the following raw materials in mass fraction: sulpho-alumino-ferri cement clinker 55-65 parts, gypsum 10-15 parts, silane-modified metakaolin 5-10 parts, superfine slag powder 10-15 parts, filler 3-5 parts, and surface-modified graphene dispersion 1 part.

[0007] The sulpho-alumino-ferri cement clinker comprises the following mineral components in mass percentage: calcium sulphoaluminate 32-38%, tetracalcium aluminoferrite 26-32%, dicalcium silicate 20-26%, tricalcium silicate 6-10%, and free calcium oxide ≤1.5%.

[0008] Compared with the prior art, the sulpho-alumino-ferri cement provided by the present application has sulpho-alumino-ferri cement clinker taking calcium sulphoaluminate (C3A) and tetracalcium aluminoferrite (C4AF) as main cementitious minerals, after hydration, generates ettringite (AFt) and aluminum hydroxide to provide early strength; the hydration product (calcium aluminate hydrate) of C4AF is structurally stable, has strong resistance to sulphate and chloride, and reduces hydration heat. The sulpho-alumino-ferri cement clinker takes dicalcium silicate (C2S) and tricalcium silicate (C3S) as secondary cementitious minerals, C2S has a slow hydration rate and supplements late strength, and its hydration product C-S-H gel has high compactness to assist in improving the impermeability of the cement system; C3S hydrates quickly to assist in improving early strength, but excessive C3S can easily lead to shrinkage and cracking of the cement system. Excessive free calcium oxide (f-CaO) can cause late expansion and cracking of the cement system, and its content needs to be strictly controlled. By limiting the mineral components and ratio of the sulpho-alumino-ferri cement clinker, the present application can further improve the comprehensive performance of the sulpho-alumino-ferri cement, such as corrosion resistance, and has high market application value.

[0009] The present application takes silane-modified metakaolin and superfine slag powder as active admixtures, and takes surface-modified graphene dispersion as a functional additive. Metakaolin can consume Ca(OH)2 generated by cement hydration through the pozzolanic effect to generate C-S-H gel with low calcium-silicon ratio, thereby improving the structural compactness of the cement system; superfine slag powder not only reduces the hydration heat of the cement to avoid temperature cracks, but also reduces the easily-eroded Ca(OH)2 through the pozzolanic effect, and simultaneously refines the pores to reduce the penetration rate of Cl - into the cement system. The sheet structure of graphene forms a physical barrier layer inside the cement system to inhibit the migration of Cl - , SO4 2- ions, and a small amount of graphene can improve the impermeability of the cement system. The present application uses active admixtures and fillers to fill the internal capillary pores of the cement system, reduce the porosity, reduce or block the invasion channels of the erosion medium, enhance the compactness, and optimize the structure of the hydration product.

[0010] ​The particle size of the active admixture, filler and graphene is generally small, and the dispersion problem exists in the cement system. A large number of hydroxyl groups exist on the surface of metakaolin, which is easy to agglomerate due to hydrogen bond. The hydrophobicity and dispersibility of metakaolin can be effectively improved by the silane coupling agent. The graphene has strong van der Waals force between the layers, which is easy to stack and agglomerate. The compatibility of the graphene with the cement matrix can be effectively enhanced by modifying the graphene with a surface modifier.

[0011] Preferably, the sulpho-alumino-ferrous cement clinker further comprises a hybrid mineral component of 1.5% to 5%.

[0012] Illustratively, the hybrid mineral component comprises C2AS, MgO, C3A and the like.

[0013] Preferably, the sulpho-alumino-ferrous cement clinker comprises the following raw materials by mass fraction: limestone 35 to 40 parts, bauxite 10 to 15 parts and iron ore powder 8 to 12 parts.

[0014] Further preferably, the CaCO3 content in the limestone is ≥95%. The impurity oxide (SiO2, Al2O3) content in the limestone is ≤3%.

[0015] Further preferably, the Al2O3 content in the bauxite is 65% to 70%, and the Fe2O3 content is ≤5%.

[0016] Further preferably, the Fe2O3 content in the iron ore powder is ≥60%.

[0017] By adjusting the raw material ratio of the sulpho-alumino-ferrous cement clinker (reducing the bauxite content and increasing the iron ore powder content), the present application optimizes the ratio of the erodible mineral (C4AF) and the stable mineral (C4AF), which is more suitable for the erosion resistance requirement of the cement system.

[0018] Preferably, the preparation method of the sulpho-alumino-ferrous cement clinker comprises the following steps:

[0019] The limestone, bauxite and iron ore powder are weighed according to the designed ratio, mixed and ground to obtain raw material;

[0020] The raw material is calcined at 1320°C to 1380°C, and then cooled to obtain the sulpho-alumino-ferrous cement clinker.

[0021] Further preferably, the particle size of the raw material is ≤8% of the 0.08mm square hole sieve.

[0022] Further preferably, the excess air coefficient of the calcination is 1.1 to 1.2, and the calcination time is 20min to 30min.

[0023] ​For example, the calcination is carried out in a rotary kiln, and whether the reaction is complete can be judged by analyzing the kiln tail gas (monitoring the CO2 and O2 concentrations) to avoid under-burning (too many unreacted minerals) or over-burning (mineral decomposition).

[0024] The present application can ensure that C4AF is fully generated while avoiding excessive C3S, and can prevent Fe 3+ from being reduced to Fe 2+ to ensure normal generation of C4AF.

[0025] Further preferably, the cooling rate is ≥ 15℃ / min (more preferably ≥ 30℃ / min).

[0026] The present application can reduce the calcined clinker to below 200℃ within 30min by air cooling to maintain mineral stability and avoid decomposition into C3S and CaSO4, while avoiding the conversion of C2S into inert and non-cementitious γ-C2S.

[0027] For example, the cooling process further includes crushing after the cooling is completed.

[0028] Preferably, the specific surface area of the sulfur-aluminum-iron cement clinker is 400m 2 / kg ~ 460m 2 / kg.

[0029] Preferably, the gypsum includes anhydrite and dihydrate gypsum in a mass ratio of (7~9):(1~3).

[0030] Preferably, the SO3 content in the gypsum is ≥ 40%.

[0031] The preferred gypsum of the present application can reduce the SO4 2- concentration in the early hydration of cement to avoid the secondary generation of ettringite leading to volume expansion and cracking.

[0032] Preferably, the silane coupling agent in the silane-modified metakaolin includes at least one of amino silane or epoxy silane.

[0033] Further preferably, the silane coupling agent includes at least one of KH550 or KH560.

[0034] Preferably, the mass ratio of the silane coupling agent to the metakaolin in the silane-modified metakaolin is (1~3):100.

[0035] Preferably, the preparation method of the silane-modified metakaolin includes the following steps:

[0036] The silane coupling agent is added to ethanol to obtain a silane solution;

[0037] The silane solution is added to the metakaolin, mixed uniformly, dried, and the silane modified metakaolin is obtained.

[0038] Further preferably, the volume ratio of the silane coupling agent and ethanol is 1:(4~7).

[0039] Further preferably, the specific surface area of the metakaolin is ≥600m 2 / kg.

[0040] For example, when the silane solution is added to the metakaolin, high-speed stirring (800r / min~1000r / min) is required, and the mixing time is 30min~40min.

[0041] For example, after drying, it further includes passing through a 200-mesh sieve.

[0042] The present application finds, through a large number of tests, that after the metakaolin is modified, the number of surface hydroxyl groups is reduced by 30%~40%, the uniformity of dispersion in the cement paste is improved by more than 50%, and the interfacial bonding force with C-S-H gel is enhanced.

[0043] Preferably, the specific surface area of the superfine slag powder is ≥450m 2 / kg.

[0044] Preferably, the 28d activity index of the superfine slag powder is ≥95%.

[0045] Preferably, the filler includes modified quartz, and the modified quartz is prepared by coating the superfine quartz powder with a coating agent.

[0046] The superfine quartz powder has small particle size and large specific surface area, and is prone to agglomeration. After coating, an isolation layer is formed, so that the superfine quartz powder is effectively dispersed in the cement system.

[0047] Further preferably, the particle size of the superfine quartz powder is ≤5μm.

[0048] Further preferably, the coating agent includes at least one of nano calcium carbonate or nano titanium dioxide.

[0049] Further preferably, the mass ratio of the coating agent to the superfine quartz powder is (2~5):100.

[0050] Further preferably, the preparation method of the modified quartz includes the following steps:

[0051] The superfine quartz powder and a dispersing agent are added to water to obtain a suspension;

[0052] The coating agent is added to the suspension at 60℃~70℃, the pH of the system is adjusted to 8~9, and the system is stirred and reacted to obtain the modified quartz.

[0053] More preferably, the dispersant comprises sodium hexametaphosphate.

[0054] More preferably, the mass ratio of the superfine quartz powder and the dispersant is 100:(0.1~0.3).

[0055] More preferably, the mass concentration of the superfine quartz powder in the suspension is 30%~40%.

[0056] Illustratively, to improve dispersibility, the coating agent can be added dropwise into the suspension in the form of a solution.

[0057] More preferably, the stirring reaction time is 50min~70min.

[0058] Illustratively, after the stirring reaction, the method further comprises centrifugation, water washing, drying, and grinding to obtain the modified quartz.

[0059] The present application has found, through a large number of experiments, that after the superfine quartz powder is coated, the agglomerate particle size is reduced from 5μm~10μm to 1μm~2μm, and the superfine quartz powder can uniformly fill capillary pores in a cement matrix, and the porosity is further reduced by 8%~10%.

[0060] Preferably, the surface modifier in the surface-modified graphene dispersion liquid comprises at least one of sodium dodecyl benzene sulfonate (SDBS) or polycarboxylate superplasticizer (PCE).

[0061] Preferably, the mass ratio of the surface modifier and the graphene in the surface-modified graphene dispersion liquid is (5~10):100.

[0062] Preferably, the mass concentration of the graphene in the surface-modified graphene dispersion liquid is 0.01%~0.03%.

[0063] Preferably, the preparation method of the surface-modified graphene dispersion liquid comprises the following steps:

[0064] adding graphene into water, adding a surface modifier, and obtaining the surface-modified graphene dispersion liquid.

[0065] Further preferably, the preparation method of the surface-modified graphene dispersion liquid specifically comprises the following steps:

[0066] adding graphene into water, ultrasonic dispersing for 30min at 300W~500W, adding a surface modifier, continuing ultrasonic dispersing for 15min, and then stirring at 1500r / min~2000r / min for 10min to obtain the surface-modified graphene dispersion liquid.

[0067] The present application can form a uniformly dispersed graphene suspension by ultrasonic dispersion, and after adding a surface modifier, the surface modifier is adsorbed on the surface of graphene under ultrasonic dispersion conditions to form an electrostatic repulsion layer, and then high-speed stirring can form a surface modified graphene dispersion.

[0068] Through a large number of tests, it is found that after the surface modification of graphene, the single-layer dispersion ratio in the cement paste is increased to more than 70%, the sheet-shaped barrier effect of graphene is fully played, and the chloride ion permeability coefficient of the cement system can be reduced by 15%~20%.

[0069] In a second aspect, the present application provides a preparation method of the sulfur-aluminum-iron cement, comprising the following steps:

[0070] According to the designed ratio, each raw material is weighed and mixed, the sulfur-aluminum-iron cement clinker, silane modified metakaolin, superfine slag powder and filler are mixed to obtain a base material;

[0071] The gypsum is calcined at 300℃~350℃, then added into the base material, and then the surface modified graphene dispersion is added to obtain the sulfur-aluminum-iron cement.

[0072] The present application calcines the gypsum at a specific temperature to remove part of the crystal water to form hemihydrate gypsum, which can improve the reactivity with the sulfur-aluminum-iron cement clinker.

[0073] Preferably, the specific surface area of the base material is 400m 2 / kg~450m 2 / kg (0.08mm square hole sieve residue ≤3%).

[0074] By limiting the specific surface area of the base material, the hydration activity of the cement can be ensured, and at the same time, the excessive fineness which leads to high water demand and increased shrinkage can be avoided.

[0075] For example, when the surface modified graphene dispersion is added, the stirring rate is 1200r / min~1500r / min to ensure uniform dispersion of graphene without local enrichment.

[0076] Preferably, in the use method of the sulfur-aluminum-iron cement, the water-cement ratio is 0.40~0.45. DETAILED DESCRIPTION

[0077] 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 with examples. 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.

[0078] In the embodiment, in the raw materials of the sulpho-alumino-ferri cement clinker, the CaCO3 content in limestone is 96.3%, the impurity oxide (SiO2, Al2O3) content is <3%; the Al2O3 content in bauxite is 68.2%, the Fe2O3 content is 4.5%; the Fe2O3 content in iron ore powder is 67.4%. The specific surface area of metakaolin is 610 m 2 / kg. The specific surface area of superfine slag powder is 462 m 2 / kg, the 28d activity index is 95.8%. The average particle size of superfine quartz powder is 3.6 μm. Other manufacturers not specified are products that can be obtained by market purchase.

[0079] Embodiment 1

[0080] The embodiment provides a sulpho-alumino-ferri cement, which comprises the following raw materials in mass fraction: sulpho-alumino-ferri cement clinker 50 parts, gypsum 12 parts, silane modified metakaolin 8 parts, superfine slag powder 12 parts, modified quartz 4 parts and surface modified graphene dispersion liquid 1 part.

[0081] The sulpho-alumino-ferri cement clinker comprises the following raw materials in mass fraction: limestone 38 parts, bauxite 12 parts and iron ore powder 10 parts.

[0082] The gypsum is composed of anhydrous gypsum and dihydrate gypsum in a mass ratio of 7:3, and the total SO3 content is 44.8%.

[0083] The preparation method of the above high sulpho-alumino-ferri cement comprises the following steps:

[0084] S100, preparing sulpho-alumino-ferri cement clinker:

[0085] S101, limestone, bauxite and iron ore powder are weighed according to the designed ratio, mixed and ground, and the sieve residue is 6.8% after passing through a 0.08 mm square hole sieve, to obtain raw materials.

[0086] S102, the raw materials are placed in a rotary kiln with a temperature of 1350℃ and a surplus air coefficient of 1.15, calcined for 30 min, then air-cooled to 200℃ at a rate of 40℃ / min, and ground to obtain sulpho-alumino-ferri cement clinker with a specific surface area of 443 m 2 / kg.

[0087] The sulpho-alumino-ferri cement clinker is composed of the following mineral components in mass percentage: calcium sulphoaluminate 34.5%, tetracalcium aluminoferrite 28.7%, dicalcium silicate 23.4%, tricalcium silicate 7.8%, free calcium oxide 1.3% and miscellaneous mineral components 4.3%.

[0088] S200, preparing silane modified metakaolin:

[0089] S201, add silane coupling agent (KH550) into anhydrous ethanol, the volume ratio of silane coupling agent and anhydrous ethanol is 1:5, and a silane solution is obtained.

[0090] S202, add the silane solution into metakaolin under high-speed stirring (900 r / min) (the mass ratio of silane coupling agent and metakaolin is 2:100), mix uniformly, dry, and pass through a 200-mesh screen, and a silane modified metakaolin is obtained.

[0091] S300, prepare modified quartz:

[0092] S301, add superfine quartz powder and sodium hexametaphosphate into water, the mass ratio of superfine quartz powder and sodium hexametaphosphate is 100:0.2, and a 36wt% suspension is obtained;

[0093] S302, add coating agent (nano calcium carbonate) into the suspension at 65℃ (the mass ratio of coating agent and superfine quartz powder is 3:100), adjust the pH of the system to 8.4, stir for 60 min, centrifuge, wash with water, dry, and grind, and a modified quartz is obtained.

[0094] S400, prepare surface modified graphene dispersion:

[0095] Add graphene into water, ultrasonically disperse for 30 min at 400 W, then add surface modifier (SDBS4), the mass ratio of surface modifier and graphene is 8:100, continue to ultrasonically disperse for 15 min, and then stir at 1800 r / min for 10 min, and a surface modified graphene dispersion with a mass concentration of 0.02% of graphene is obtained.

[0096] S500, prepare hemihydrate gypsum:

[0097] Roast the gypsum at 320℃, and hemihydrate gypsum is obtained.

[0098] It should be noted that the order between S100-S500 is not limited in this embodiment.

[0099] S600, prepare base material:

[0100] According to the designed ratio, weigh each raw material, mix the sulfur-aluminum-iron cement clinker, silane modified metakaolin, superfine slag powder and modified quartz, and pass through a 0.08mm square hole screen with a sieve residue of 2.4%, and a base material is obtained.

[0101] S700, prepare sulfur-aluminum-iron cement:

[0102] Add hemihydrate gypsum into the base material, and then add the surface modified graphene dispersion under stirring at 1400 r / min, and a sulfur-aluminum-iron cement is obtained.

[0103] Example 2

[0104] The embodiment provides a sulphur-aluminum-iron cement, which comprises the following raw materials in mass fractions: 55 parts of sulphur-aluminum-iron cement clinker, 13 parts of gypsum, 10 parts of silane modified metakaolin, 10 parts of superfine slag powder, 5 parts of modified quartz and 1 part of surface modified graphene dispersion.

[0105] The sulphur-aluminum-iron cement clinker comprises the following raw materials in mass fractions: 40 parts of limestone, 15 parts of bauxite and 10 parts of iron ore powder.

[0106] The gypsum is composed of anhydrite and dihydrate gypsum in a mass ratio of 8:2, and the total SO3 content is 45.4%.

[0107] The preparation method of the high-sulphur-aluminum-iron cement comprises the following steps:

[0108] S100, preparing a sulphur-aluminum-iron cement clinker:

[0109] S101, limestone, bauxite and iron ore powder are weighed according to the designed ratio, mixed and ground, and the sieve residue of 0.08 mm square hole screen is 7.2%, to obtain raw materials.

[0110] S102, the raw materials are placed in a rotary kiln with a temperature of 1340 DEG C and an excess air coefficient of 1.1, calcined for 25 min, air-cooled to 200 DEG C at a rate of 38 DEG C / min, and ground, to obtain 437 m 2 / kg of sulphur-aluminum-iron cement clinker.

[0111] The sulphur-aluminum-iron cement clinker is composed of the following mineral components in mass percentages: 37.8% of calcium sulphoaluminate, 31.7% of tetracalcium aluminoferrite, 20.3% of dicalcium silicate, 6.4% of tricalcium silicate, 0.9% of free calcium oxide and 2.9% of miscellaneous mineral components.

[0112] S200, preparing silane modified metakaolin:

[0113] S201, a silane coupling agent (KH560) is added into anhydrous ethanol, and the volume ratio of the silane coupling agent to the anhydrous ethanol is 1:6, to obtain a silane solution.

[0114] S202, the silane solution is added into metakaolin under high-speed stirring (900 r / min), and the mass ratio of the silane coupling agent to the metakaolin is 2:100, to obtain silane modified metakaolin after uniform mixing, drying and passing through a 200-mesh screen.

[0115] S300, preparing modified quartz:

[0116] S301, superfine quartz powder and sodium hexametaphosphate are added into water, and the mass ratio of the superfine quartz powder to the sodium hexametaphosphate is 100:0.2, to obtain a 40wt% suspension;

[0117] S302, add coating agent (nano-titanium dioxide) into the suspension at 70℃ (the mass ratio of coating agent to superfine quartz powder is 2:100), adjust the pH of the system to 8, stir for 50 min, centrifuge, wash with water, dry, and grind to obtain modified quartz.

[0118] S400, prepare surface-modified graphene dispersion liquid:

[0119] Add graphene into water, ultrasonically disperse for 30 min at 300W, then add surface modifier (PCE), the mass ratio of surface modifier to graphene is 10:100, continue to ultrasonically disperse for 15 min, and then stir at 2000 r / min for 10 min to obtain surface-modified graphene dispersion liquid with a mass concentration of 0.03% of graphene.

[0120] S500, prepare hemihydrate gypsum:

[0121] Roast the gypsum at 305℃ to obtain hemihydrate gypsum.

[0122] It should be noted that the order between S100-S500 is not limited in this embodiment.

[0123] S600, prepare base material:

[0124] According to the designed ratio, weigh each raw material, mix the sulfur-aluminum-iron cement clinker, silane-modified metakaolin, superfine slag powder, and modified quartz, and pass through a 0.08mm square hole screen with a 2.7% screen residue to obtain the base material.

[0125] S700, prepare sulfur-aluminum-iron cement:

[0126] Add hemihydrate gypsum into the base material, and then add surface-modified graphene dispersion liquid at 1500 r / min to obtain sulfur-aluminum-iron cement.

[0127] Example 3

[0128] The sulfur-aluminum-iron cement provided in this embodiment includes the following raw materials in mass parts: sulfur-aluminum-iron cement clinker 65 parts, gypsum 15 parts, silane-modified metakaolin 5 parts, superfine slag powder 15 parts, modified quartz 3 parts, and surface-modified graphene dispersion liquid 1 part.

[0129] The sulfur-aluminum-iron cement clinker includes the following raw materials in mass parts: limestone 35 parts, bauxite 13 parts, and iron ore powder 8 parts.

[0130] The gypsum is composed of anhydrous gypsum and dihydrate gypsum in a mass ratio of 9:1, and the total SO3 content is 45.9%.

[0131] The preparation method of the above high sulfur-aluminum-iron cement includes the following steps:

[0132] S100, preparing a sulphur-aluminum-iron cement clinker:

[0133] S101, limestone, bauxite and iron ore powder were weighed according to the designed ratio, mixed and ground, and the residue was screened through a 0.08 mm square hole screen with a residue of 7.3%, to obtain raw meal.

[0134] S102, the raw meal was placed in a rotary kiln at 1370°C with a surplus air coefficient of 1.2, calcined for 20 min, air-cooled to 200°C at a rate of 40°C / min, and ground, to obtain a sulphur-aluminum-iron cement clinker with a specific surface area of 423 m 2 / kg.

[0135] The sulphur-aluminum-iron cement clinker was composed of the following mineral components by mass percentage: calcium sulphoaluminate 32.3%, tetracalcium aluminoferrite 26.5%, dicalcium silicate 25.6%, tricalcium silicate 8.9%, free calcium oxide 1.1%, and miscellaneous mineral components 5.6%.

[0136] S200, preparing silane-modified metakaolin:

[0137] S201, a silane coupling agent (KH550) was added to anhydrous ethanol, and the volume ratio of the silane coupling agent to the anhydrous ethanol was 1:7, to obtain a silane solution.

[0138] S202, the silane solution was added to metakaolin under high-speed stirring (800 r / min) (the mass ratio of the silane coupling agent to the metakaolin was 1:100), mixed uniformly, dried, and screened through a 200 mesh screen, to obtain silane-modified metakaolin.

[0139] S300, preparing modified quartz:

[0140] S301, superfine quartz powder and sodium hexametaphosphate were added to water, and the mass ratio of the superfine quartz powder to the sodium hexametaphosphate was 100:0.3, to obtain a 30 wt% suspension;

[0141] S302, a coating agent (nano calcium carbonate) was added to the suspension at 60°C (the mass ratio of the coating agent to the superfine quartz powder was 5:100), the pH of the system was adjusted to 9, and stirring was performed for 70 min, followed by centrifugation, water washing, drying, and grinding, to obtain modified quartz.

[0142] S400, preparing a surface-modified graphene dispersion:

[0143] Graphene was added to water, ultrasonically dispersed at 500 W for 30 min, a surface modifier (PCE) was further added, the mass ratio of the surface modifier to the graphene was 5:100, ultrasonic dispersion was continued for 15 min, and then stirring was performed at 1500 r / min for 10 min, to obtain a surface-modified graphene dispersion with a mass concentration of the graphene of 0.01%.

[0144] S500, preparing hemihydrate gypsum:

[0145] The gypsum is calcined at 330℃ to obtain hemihydrate gypsum.

[0146] It is to be noted that the sequence between S100-S500 is not limited in the embodiment.

[0147] S600, preparing base material:

[0148] The raw materials are weighed according to the designed ratio, and the ferialumino-sulphate cement clinker, silane-modified metakaolin, superfine slag powder and modified quartz are mixed, and the sieve residue is 2.3% after passing through a 0.08mm square hole screen to obtain the base material.

[0149] S700, preparing ferialumino-sulphate cement:

[0150] The hemihydrate gypsum is added into the base material, and then the surface-modified graphene dispersion liquid is added at 1300r / min to obtain the ferialumino-sulphate cement.

[0151] Embodiment 4

[0152] The embodiment provides a ferialumino-sulphate cement, which comprises the following raw materials in mass fraction: ferialumino-sulphate cement clinker 60 parts, gypsum 10 parts, silane-modified metakaolin 7 parts, superfine slag powder 13 parts, modified quartz 4 parts and surface-modified graphene dispersion liquid 1 part.

[0153] The ferialumino-sulphate cement clinker comprises the following raw materials in mass fraction: limestone 37 parts, bauxite 10 parts and iron ore powder 12 parts.

[0154] The gypsum is composed of anhydrite and dihydrate gypsum in a mass ratio of 8:2, and the total SO3 content is 45.4%.

[0155] The preparation method of the above high ferialumino-sulphate cement comprises the following steps:

[0156] S100, preparing ferialumino-sulphate cement clinker:

[0157] S101, limestone, bauxite and iron ore powder are weighed according to the designed ratio, mixed and ground, and the sieve residue is 7.0% after passing through a 0.08mm square hole screen to obtain raw material.

[0158] S102, the raw material is placed in a rotary kiln at 1320℃ and the excess air coefficient is 1.1, calcined for 30min, then air-cooled to 200℃ at a rate of 34℃ / min, and ground to obtain ferialumino-sulphate cement clinker with a specific surface area of 436m 2 / kg.

[0159] The sulphoaluminate cement clinker is composed of the following mineral components with mass percentage: calcium sulphoaluminate 35.4%, tetracalcium aluminoferrite 26.2%, dicalcium silicate 23.9%, tricalcium silicate 9.8%, free calcium oxide 1.0% and miscellaneous mineral components 3.7%.

[0160] S200, preparing silane modified metakaolin:

[0161] S201, adding silane coupling agent (KH560) into anhydrous ethanol, the volume ratio of silane coupling agent and anhydrous ethanol is 1:4, to obtain a silane solution.

[0162] S202, adding the silane solution into metakaolin under high speed stirring (1000r / min) (the mass ratio of silane coupling agent and metakaolin is 3:100), mixing uniformly, drying, and passing through a 200 mesh screen, to obtain silane modified metakaolin.

[0163] S300, preparing modified quartz:

[0164] S301, adding superfine quartz powder and sodium hexametaphosphate into water, the mass ratio of superfine quartz powder and sodium hexametaphosphate is 100:0.1, to obtain a 34wt% suspension;

[0165] S302, adding coating agent (nano titanium dioxide) into the suspension at 65℃ (the mass ratio of coating agent and superfine quartz powder is 4:100), adjusting the pH of the system to 8.6, stirring for 60min, centrifuging, washing with water, drying, and grinding, to obtain modified quartz.

[0166] S400, preparing surface modified graphene dispersion:

[0167] Adding graphene into water, ultrasonic dispersing for 30min at 400W, then adding surface modifier (SDBS), the mass ratio of surface modifier and graphene is 7:100, continuing ultrasonic dispersing for 15min, then stirring at 1700r / min for 10min, to obtain surface modified graphene dispersion with mass concentration of graphene of 0.02%.

[0168] S500, preparing hemihydrate gypsum:

[0169] Baking gypsum at 350℃, to obtain hemihydrate gypsum.

[0170] It should be noted that the sequence between S100~S500 is not limited in the embodiment.

[0171] S600, preparing base material:

[0172] According to the design ratio, each raw material is weighed, and the sulfur-aluminum-iron cement clinker, the silane modified metakaolin, the ultra-fine slag powder and the modified quartz are mixed, and the mixture is passed through a 0.08 mm square hole screen with a 2.5% screen residue to obtain a base material.

[0173] S700, preparing a sulfur-aluminum-iron cement:

[0174] The hemihydrate gypsum is added to the base material, and then the surface modified graphene dispersion liquid is added at 1500 r / min to obtain the sulfur-aluminum-iron cement.

[0175] Example 5

[0176] This example provides a sulfur-aluminum-iron cement, which is similar to Example 1, except that the modified quartz is replaced by an equal amount of ultra-fine slag powder. The remaining raw materials and the ratio are the same as those in Example 1, and will not be repeated here.

[0177] The preparation method of the above-mentioned sulfur-aluminum-iron cement is similar to that of Example 1, except that the preparation of the modified quartz is omitted, and the modified quartz in S600 is replaced by the ultra-fine slag powder. The remaining steps and parameter conditions are the same as those in Example 1, and will not be repeated here.

[0178] Comparative Example 1

[0179] This comparative example provides a sulfur-aluminum-iron cement, which is similar to Example 1, except that the silane modified metakaolin is replaced by an equal amount of metakaolin. The remaining raw materials and the ratio are the same as those in Example 1, and will not be repeated here.

[0180] The preparation method of the above-mentioned sulfur-aluminum-iron cement is similar to that of Example 1, except that the preparation of the silane modified metakaolin is omitted, and the silane modified metakaolin in S600 is replaced by the metakaolin. The remaining steps and parameter conditions are the same as those in Example 1, and will not be repeated here.

[0181] Comparative Example 2

[0182] This comparative example provides a sulfur-aluminum-iron cement, which is similar to Example 1, except that the surface modified graphene dispersion liquid is replaced by an equal amount of graphene aqueous solution. The remaining raw materials and the ratio are the same as those in Example 1, and will not be repeated here.

[0183] The preparation method of the above-mentioned sulfur-aluminum-iron cement is similar to that of Example 1, except that the preparation of the surface modified graphene dispersion liquid is omitted, and the surface modified graphene dispersion liquid in S600 is replaced by 0.02wt% of the graphene aqueous solution. The remaining steps and parameter conditions are the same as those in Example 1, and will not be repeated here.

[0184] Comparative Example 3

[0185] The comparative example provides a sulfur-aluminum-iron cement, which is similar to example 1, except that the preparation method of the sulfur-aluminum-iron cement clinker is different, specifically comprising the following steps:

[0186] S101, 42 parts of limestone, 22 parts of bauxite and 6 parts of iron ore powder are weighed according to the designed proportion, mixed and ground, and the sieve residue is 6.8% after passing through a 0.08mm square hole screen, to obtain raw materials.

[0187] S102, the raw materials are placed in a rotary kiln at 1300℃ and a excess air coefficient of 1.1, calcined for 30min, then air-cooled to 300℃ at a rate of 10℃ / min, and ground to obtain a sulfur-aluminum-iron cement clinker with a specific surface area of 440m 2 / kg.

[0188] The sulfur-aluminum-iron cement clinker is composed of the following mineral components with mass percentage: calcium sulphoaluminate 43.1%, tetracalcium aluminoferrite 18.2%, dicalcium silicate 14.7%, tricalcium silicate 14.8%, free calcium oxide 2.5% and miscellaneous mineral components 6.7%.

[0189] The remaining steps and parameter conditions are the same as those of example 1, and will not be repeated here.

[0190] Verification test

[0191] The sulfur-aluminum-iron cements provided in examples 1-5 and comparative examples 1-3 are mixed with water and cured, with a water-cement ratio of 0.45, and the performance of each sulfur-aluminum-iron cement is tested according to T / CCPA 42-2023 “Sulfur-aluminum-iron low-carbon cementitious material”, and the test results are shown in Tables 1-2.

[0192] Table 1 Performance test results of the sulfur-aluminum-iron cements of examples and comparative examples

[0193]

[0194] Table 2 Performance test results 2 of the sulfur-aluminum-iron cements of examples and comparative examples

[0195]

[0196] The above only describes the preferred embodiments of the present application, and is not intended to limit the present application, and any modifications, equivalent replacements or improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A sulfur-aluminum-iron-based cement, characterized in that, The raw materials include the following parts by weight: 55-65 parts of sulfur-aluminum-iron cement clinker, 10-15 parts of gypsum, 5-10 parts of silane-modified metakaolin, 10-15 parts of ultrafine slag powder, 3-5 parts of filler and 1 part of surface-modified graphene dispersion. The sulfur-aluminum-iron cement clinker comprises the following mineral components by mass percentage: anhydrous calcium sulfoaluminate 32%~38%, tetracalcium aluminoferrite 26%~32%, dicalcium silicate 20%~26%, tricalcium silicate 6%~10%, and free calcium oxide ≤1.5%; The preparation method of the surface-modified graphene dispersion includes the following steps: adding graphene to water, then adding a surface modifier to obtain the surface-modified graphene dispersion; wherein the surface modifier in the surface-modified graphene dispersion includes at least one of sodium dodecylbenzenesulfonate or polycarboxylate superplasticizer.

2. The sulfur-aluminum-iron cement as described in claim 1, characterized in that, The sulfur-aluminum-iron cement clinker comprises the following raw materials in parts by weight: 35-40 parts limestone, 10-15 parts bauxite, and 8-12 parts iron ore powder.

3. The sulfur-aluminum-iron cement as described in claim 2, characterized in that, The limestone contains ≥95% CaCO3; the bauxite contains 65%~70% Al2O3 and ≤5% Fe2O3; and the iron ore powder contains ≥60% Fe2O3.

4. The sulfur-aluminum-iron cement as described in claim 1, characterized in that, The gypsum comprises anhydrite and dihydrate gypsum in a mass ratio of (7~9):(1~3), and the SO3 content in the gypsum is ≥40%. The 28-day activity index of the ultrafine slag powder is ≥95%; The filler includes modified quartz, which is obtained by coating ultrafine quartz powder with a coating agent.

5. The sulfur-aluminum-iron cement as described in claim 4, characterized in that, The preparation method of the sulfur-aluminum-iron cement clinker includes the following steps: Limestone, bauxite, and iron ore powder are weighed according to the design ratio, mixed and ground to obtain raw material; The raw material is calcined at 1320℃~1380℃ and cooled to obtain the sulfur-aluminum-iron cement clinker. and / or The preparation method of the silane-modified metakaolin includes the following steps: Add the silane coupling agent to ethanol to obtain a silane solution; The silane solution was added to metakaolin, mixed evenly, and dried to obtain the silane-modified metakaolin. and / or The method for preparing the modified quartz includes the following steps: Ultrafine quartz powder and a dispersant are added to water to obtain a suspension; The coating agent is added to the suspension at 60℃~70℃, the pH of the system is adjusted to 8~9, and the reaction is stirred to obtain the modified quartz.

6. The sulfur-aluminum-iron cement as described in claim 5, characterized in that, In the method for preparing sulfur-aluminum-iron cement clinker, the excess air coefficient during calcination is 1.1~1.2, the calcination time is 20min~30min, and the cooling rate is ≥15℃ / min.

7. The sulfur-aluminum-iron cement as described in claim 5, characterized in that, In the silane-modified metakaolin, the silane coupling agent includes at least one of aminosilane or epoxysilane, and the mass ratio of the silane coupling agent to metakaolin is (1~3):

100. In the preparation method of silane-modified metakaolin, the volume ratio of the silane coupling agent to ethanol is 1:(4~7).

8. The sulfur-aluminum-iron cement as described in claim 5, characterized in that, In the modified quartz, the coating agent includes at least one of nano-calcium carbonate or nano-titanium dioxide, and the mass ratio of the coating agent to the ultrafine quartz powder is (2~5):

100. In the preparation method of the modified quartz, the mass ratio of the ultrafine quartz powder to the dispersant is 100:(0.1~0.3), the mass concentration of the ultrafine quartz powder in the suspension is 30%~40%, and the stirring reaction time is 50min~70min.

9. The sulfur-aluminum-iron cement as described in claim 5, characterized in that, In the surface-modified graphene dispersion, the mass ratio of the surface modifier to graphene is (5~10):100, and the mass concentration of graphene is 0.01%~0.03%.

10. The method for preparing sulfur-aluminum-iron cement according to any one of claims 1 to 9, characterized in that, Includes the following steps: Weigh each raw material according to the design ratio, and mix sulfur-aluminum-iron cement clinker, silane-modified metakaolin, ultrafine slag powder and filler to obtain the base material; Gypsum is calcined at 300℃~350℃, then added to the base material, and then surface-modified graphene dispersion is added to obtain sulfur-aluminum-iron cement.

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