Multi-solid-waste early strength type super sulfate cement as well as preparation method and application thereof

Abstract

The invention provides multi-solid-waste early strength type super sulfate cement as well as a preparation method and application thereof, and relates to the technical field of building materials, the super sulfate cement comprises the following components in parts by mass: 50-80 parts of mineral powder, 5-15 parts of alpha type semi-hydrated gypsum, 5-15 parts of industrial waste gypsum, 5-15 parts of concrete recycled micro powder and 5-10 parts of fly ash. According to the super sulfate cement disclosed by the invention, the alpha-type semi-hydrated gypsum and various industrial solid wastes such as the industrial waste gypsum, the concrete recycled micro powder and the fly ash are subjected to reaction synergy, and the alpha-type semi-hydrated gypsum has the characteristics of high hydration activity and high hydration speed, so that the early strength of the super sulfate cement is improved; the industrial solid waste replaces part of the cement clinker and the chemical activator, so that the cost is reduced, the reaction rate of the mineral powder can be increased, the generation amount of hydration products is increased, hardened body pores are filled, the compactness is enhanced, an interface transition region is eliminated, and the strength and durability of the super sulfate cement are improved.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a multi-solid waste early-strength supersulfate cement, its preparation method and application. Background Technology

[0002] Supersulfate cement is a low-carbon cementitious material made primarily of slag. It has excellent performance characteristics, a simple production process, and low cost. It is an energy-saving and environmentally friendly cement, which aligns with the national sustainable development strategy.

[0003] However, existing supersulfate cement has the drawback of low early strength (usually 3-day compressive strength of 10-15 MPa) in practical applications, which limits its application in scenarios such as rapid construction and precast components.

[0004] Currently, improving the early strength of supersulfate cement mainly relies on adding high-cost chemical activators (such as NaOH, Na2SiO3, KOH, etc.), nanomaterials, and cement clinker. For example, patent application CN200810197940.9 provides a nickel-chromium-ferroalloy slag supersulfate cement, whose composition (wt%) is: nickel-chromium-ferroalloy slag 20-60%, slag and / or fly ash 20-60%, sulfate activator 5-25%, cement clinker or calcium hydroxide 1-10%, and alkaline activator 0.05-3%. Although this scheme can improve early strength to a certain extent, its maximum early strength at 7 days and 28 days can only reach 26.6 MPa and 43.8 MPa, respectively. Moreover, the introduction of cement clinker and alkaline activator not only increases costs, leading to poor economic efficiency and secondary pollution to the environment, making it difficult to achieve large-scale promotion and application, but also results in a small amount of solid waste being mixed in, leading to the accumulation of large amounts of solid waste, low utilization rate, and a large occupation of land resources, which also has a detrimental impact on the environment.

[0005] Therefore, there is an urgent need to provide a supersulfate cement that can improve early strength, does not rely on high-cost activators, and can improve the utilization rate of industrial solid waste. Summary of the Invention

[0006] This invention provides a multi-solid-waste early-strength supersulfate cement, its preparation method, and its application. It utilizes α-type hemihydrate gypsum to react synergistically with various industrial solid wastes such as industrial waste gypsum, recycled concrete powder, fly ash, and mineral powder. This not only improves the early strength of supersulfate cement and the utilization rate of industrial solid waste, but also reduces the use of cement clinker and chemical alkaline activators, thereby lowering costs.

[0007] This invention provides a multi-solid waste early-strength supersulfate cement, comprising the following components in parts by weight: 50-80 parts mineral powder, 5-15 parts α-type hemihydrate gypsum, 5-15 parts industrial waste gypsum, 5-15 parts recycled concrete powder, and 5-10 parts fly ash.

[0008] This invention utilizes the synergistic reaction of α-type hemihydrate gypsum and various industrial solid wastes (industrial waste gypsum, recycled concrete powder, fly ash, and mineral powder) to prepare supersulfate cement. α-type hemihydrate gypsum possesses high hydration activity and rapid hydration speed, which can enhance the early strength of supersulfate cement and cement mortar made from it. The substitution of various industrial solid wastes for some cement clinker and chemical activators not only reduces the use of cement clinker and chemical activators (such as alkaline activators) and lowers costs, but also increases the reaction rate of mineral powder, increases the amount of hydration products generated, fills the pores of the hardened body, enhances density, eliminates interfacial transition zones, and improves the strength and durability of supersulfate cement. The synergistic reaction of the above raw materials is as follows: The α-type hemihydrate gypsum used in this invention has hydration activity and a fast hydration rate, which can provide early strength for supersulfate cement. The reaction formula is: ; Furthermore, this invention incorporates industrial waste gypsum (phosphogypsum / desulfurized gypsum, dihydrate gypsum) into the system. The α-hemihydrate gypsum and dihydrate gypsum create a gradient reaction effect in the hypersulfate cement: in the early stages of the hypersulfate cement reaction, the α-hemihydrate gypsum can rapidly provide a large amount of SO4. 2- This promotes the early formation of ettringite (AFt), enhancing the early compressive strength of hypersulfate cement products. In the later stages of the hypersulfate cement reaction, phosphogypsum / desulfurized gypsum provides SO4 for the continued formation of ettringite. 2- This avoids the formation of monosulfide ettringite (AFm) and maintains the volume stability and strength of supersulfate cement. The reaction formula is: ; Simultaneously, using recycled concrete powder to replace alkaline activators promotes the dissolution and hydration of slag. The recycled concrete powder itself contains calcium hydroxide (Ca(OH)2) generated after cement hydration, and its unhydrated C3S and C2S will rehydrate to generate hydrated calcium silicate gel (CSH) and Ca(OH)2, further providing OH... - This promotes the dissolution and hydration of slag, while increasing hydration products and improving the strength of supersulfate cement. The reaction formula is: ; Furthermore, this invention introduces fly ash into the system. The active SiO2 and Al2O3 in the fly ash react with Ca(OH)2 produced during the hydration of supersulfate cement to generate additional CSH gel and a small amount of ettringite (AFt), which fills capillary pores and improves later-stage strength. At the same time, the small-diameter fly ash particles act as micro-aggregates, filling the gaps between cement hydration products, reducing porosity and pore size, and forming a dense cementitious system, indirectly improving compressive strength, flexural strength, and durability.

[0009] Furthermore, the supersulfate cement does not include an alkaline activator. The alkaline activator includes, but is not limited to, any one or more of NaOH, Na₂SiO₃, and KOH. This invention can achieve the effect of improving the compressive and flexural strength of supersulfate cement even without using an alkaline activator, greatly reducing the cost of using alkaline activators.

[0010] Furthermore, the aspect ratio of the α-type hemihydrate gypsum is 6~10:1. By controlling the aspect ratio of the α-type hemihydrate gypsum within this range, after hydration, the high aspect ratio α-type hemihydrate gypsum interweaves to form a three-dimensional network skeleton structure, creating a fiber-like effect in the product and improving the early flexural and compressive strength of the supersulfate cement.

[0011] Preferably, the α-type hemihydrate gypsum is in the shape of a long column.

[0012] Furthermore, the mass ratio of the α-type hemihydrate gypsum to the recycled concrete powder is 0.8~1.5:1. Controlling this mass ratio within this range ensures a sufficient and stable hydration reaction: α-type hemihydrate gypsum provides sulfate ions, promoting the formation of ettringite, a key hydration product for ensuring cement strength; recycled concrete powder has a micro-aggregate effect and potential activity, and can participate in secondary hydration reactions. When the ratio is appropriate, recycled concrete powder provides reaction sites for the hydration reaction initiated by α-type hemihydrate gypsum, and the sulfate ions from α-type hemihydrate gypsum can also activate the activity of recycled concrete powder, preventing insufficient hydration due to low activity. Too much α-type hemihydrate gypsum can easily lead to excessive expansion and cracking of ettringite, while too little will result in insufficient hydration and hindered strength development.

[0013] Preferably, the mass ratio of the α-type hemihydrate gypsum to the recycled concrete powder is 0.8~1.2:1.

[0014] More preferably, the mass ratio of the α-type hemihydrate gypsum to the recycled concrete powder is 1:1.

[0015] Furthermore, the industrial waste gypsum is selected from any one or more of phosphogypsum or desulfurized gypsum discharged from the factory, and its average particle size is 10~15 μm.

[0016] Preferably, the average particle size of the industrial waste gypsum is 13 μm.

[0017] Preferably, the desulfurized gypsum or phosphogypsum contains... The content is greater than 85 wt%.

[0018] Furthermore, the recycled concrete powder is made from construction waste concrete, with an average particle size of 5~10 μm.

[0019] Preferably, the average particle size of the recycled concrete powder is 15 μm.

[0020] Furthermore, the content of CaO is 40 wt%~55 wt%, the content of SiO2 is 25 wt%~35 wt%, and the content of Al2O3 is 4 wt%~8 wt%.

[0021] Furthermore, the particle size of the fly ash is 10~20 μm.

[0022] The present invention also provides a method for preparing the supersulfate cement as described above, comprising the following steps: mixing the mineral powder, α-type hemihydrate gypsum, industrial waste gypsum, recycled concrete powder and fly ash.

[0023] Preferably, the preparation method of the α-type hemihydrate gypsum includes the following steps: first, aluminum sulfate, industrial waste gypsum and water are mixed to form a slurry, and then the slurry is subjected to heat preservation and drying in sequence.

[0024] Preferably, the mass ratio of aluminum sulfate, industrial waste gypsum and water is 0.3~0.6:80~100:300~320.

[0025] More preferably, the mass ratio of aluminum sulfate, industrial waste gypsum and water is 0.4:100:300.

[0026] Furthermore, the temperature during the heat preservation is 140~160℃, and the heat preservation time is 1~3h.

[0027] Preferably, the temperature during heat preservation is 150°C, and the heat preservation time is 2 hours.

[0028] Furthermore, the drying temperature is 110~130℃, and the time is 2~5h.

[0029] Preferably, the drying temperature is 120°C and the drying time is 3 hours.

[0030] Preferably, when aluminum sulfate, industrial waste gypsum, and water are mixed, aluminum sulfate is first dissolved in water to obtain an aluminum sulfate solution; then the industrial waste gypsum is dissolved in the aluminum sulfate solution.

[0031] The present invention also provides the application of the multi-solid waste early-strength supersulfate cement as described above or the multi-solid waste early-strength supersulfate cement prepared by the preparation method as described above, wherein the supersulfate cement is used to prepare building materials. Preferably, the building materials include any one or more of the following: (1) Used to prepare cement mortar; (2) Used to prepare concrete.

[0032] Furthermore, the cement mortar includes the supersulfate cement, water, and sand, wherein the weight ratio of the supersulfate cement to water is 1.2 to 3:1, and the weight ratio of the supersulfate cement to sand is 1:1 to 5.

[0033] Preferably, the weight ratio of the supersulfate cement to water is 2:1, and the weight ratio of the supersulfate cement to sand is 1:3.

[0034] Furthermore, the cement mortar also includes triisopropanolamine, the content of which is 0-0.005% of the weight of the hypersulfate cement. This cement mortar is prepared using the hypersulfate cement of this invention. The triisopropanolamine added to its raw materials not only acts as a grinding aid but also has a synergistic effect with α-type hemihydrate gypsum in the hypersulfate cement, further enhancing the compressive and flexural strength of the cement mortar in the specific hypersulfate cement system of this invention.

[0035] The beneficial effects of the multi-solid waste early-strength supersulfate cement, its preparation method, and its application provided by this invention are as follows: This invention utilizes a gradient reaction formed by α-type hemihydrate gypsum and industrial waste gypsum. In the early stages, the high hydration activity of α-type hemihydrate gypsum and the SO4 it provides contribute to the high strength. 2- It can promote the formation of trisulfide-type ettringite (AFt), enhancing the early compressive and flexural strength of the product; in the later stage, SO4 is continuously replenished by industrial waste gypsum. 2- To avoid the formation of monosulfide ettringite (AFm), volume stability is ensured. The addition of fly ash for pozzolanic reaction, hydration supplementation of recycled concrete powder, and micro-aggregate effect further enhances the later strength, resulting in a significant increase in the early compressive and flexural strength of supersulfate cement. At the same time, various industrial solid wastes replace part of the cement clinker and chemical activators, achieving cost reduction and solid waste resource utilization. The synergistic reaction of solid wastes increases hydration products and refines pores, making the cementitious system denser and effectively improving the impermeability, erosion resistance, and durability of supersulfate cement products. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0037] Figure 1 This is a microscopic morphology diagram of α-type hemihydrate gypsum.

[0038] Figure 2 This is a microscopic morphology diagram of the hydration products of the hardened supersulfate cement mortar in Example 3 of the present invention.

[0039] Figure 3 This is a microscopic interface transition zone morphology diagram of the hardened body of supersulfate cement mortar in Example 3 of the present invention.

[0040] Figure 4 This is a microscopic morphology diagram of the hydration products of the hardened ordinary persulfate cement mortar in Comparative Example 4. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0042] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0043] The raw material information in the following examples and comparative examples is as follows: Preparation method of α-type hemihydrate gypsum: First, weigh the raw materials according to the mass ratio of aluminum sulfate: industrial waste gypsum: water = 0.4:100:300; then, add aluminum sulfate to water and stir until fully dissolved to obtain an aluminum sulfate solution; subsequently, add industrial waste gypsum to the aluminum sulfate solution and stir for 5 minutes to form a slurry; finally, place the slurry in a sealed reactor at 150℃ and keep it at that temperature for 2 hours; after the holding time, place it in an oven at 120℃ to dry the moisture. Its microstructure is as follows. Figure 1 As shown, α-type hemihydrate gypsum with an aspect ratio of 6 to 10:1 was prepared. Industrial waste gypsum: Grind industrial waste gypsum to an average particle size of 10~15 μm; Recycled concrete powder: The recycled concrete powder is ground to an average particle size of 5~10 μm; Mineral powder: S95 grade and above; Fly ash: emitted from factory thermal power generation, with an average particle size of 10~20μm; The composition information of mineral powder, industrial waste gypsum, recycled concrete powder, and fly ash is shown in the table below: Sand: (GB / T17671-2021) Standard Sand.

[0044] Example 1 A multi-solid waste early-strength supersulfate cement comprises the following components in parts by weight: 80 parts mineral powder, 5 parts α-type hemihydrate gypsum, 5 parts industrial waste gypsum, 5 parts recycled concrete powder, and 5 parts fly ash.

[0045] This embodiment also provides a method for preparing the supersulfate cement, including the following steps: mineral powder, α-type hemihydrate gypsum, industrial waste gypsum, recycled concrete powder and fly ash are put into a mixer according to the formula and premixed for 3 minutes to obtain supersulfate cement.

[0046] This embodiment also provides a cement mortar, the preparation method of which includes the following steps: the obtained supersulfate cement, 50 parts of water, 0.001 parts of triisopropanolamine, and 300 parts of sand are put into a cement mortar mixer in sequence and stirred. After stirring, cement mortar is obtained.

[0047] The composition information of the mineral powder, industrial waste gypsum, recycled concrete powder, and fly ash used in this embodiment is shown in the table below: Example 2 A multi-solid waste early-strength supersulfate cement comprises the following components in parts by weight: 80 parts mineral powder, 5 parts α-type hemihydrate gypsum, 2.5 parts industrial waste gypsum, 7.5 parts recycled concrete powder, and 5 parts fly ash.

[0048] This embodiment also provides a method for preparing the supersulfate cement, including the following steps: mineral powder, α-type hemihydrate gypsum, industrial waste gypsum, recycled concrete powder and fly ash are put into a mixer according to the formula and premixed for 3 minutes to obtain supersulfate cement.

[0049] This embodiment also provides a cement mortar, the preparation method of which includes the following steps: the obtained supersulfate cement, 50 parts of water, 0.001 parts of triisopropanolamine, and 300 parts of sand are put into a cement mortar mixer in sequence and stirred. After stirring, cement mortar is obtained.

[0050] The mineral powder, industrial waste gypsum, recycled concrete powder, and fly ash used in this embodiment have the same content as in Example 1.

[0051] Example 3 A multi-solid waste early-strength supersulfate cement comprises the following components in parts by weight: 70 parts mineral powder, 10 parts α-type hemihydrate gypsum, 5 parts industrial waste gypsum, 10 parts recycled concrete powder, and 5 parts fly ash.

[0052] This embodiment also provides a method for preparing the supersulfate cement, including the following steps: mineral powder, α-type hemihydrate gypsum, industrial waste gypsum, recycled concrete powder and fly ash are put into a mixer according to the formula and premixed for 3 minutes to obtain supersulfate cement.

[0053] This embodiment also provides a cement mortar, the preparation method of which includes the following steps: the obtained supersulfate cement, 50 parts of water, 0.003 parts of triisopropanolamine, and 300 parts of sand are put into a cement mortar mixer in sequence and stirred. After stirring, cement mortar is obtained.

[0054] The mineral powder, industrial waste gypsum, recycled concrete powder, and fly ash used in this embodiment have the same content as in Example 1.

[0055] Example 4 A multi-solid waste early-strength supersulfate cement comprises the following components in parts by weight: 70 parts mineral powder, 10 parts α-type hemihydrate gypsum, 5 parts industrial waste gypsum, 7.5 parts recycled concrete powder, and 7.5 parts fly ash.

[0056] This embodiment also provides a method for preparing the supersulfate cement, including the following steps: mineral powder, α-type hemihydrate gypsum, industrial waste gypsum, recycled concrete powder and fly ash are put into a mixer according to the formula and premixed for 3 minutes to obtain supersulfate cement.

[0057] This embodiment also provides a cement mortar, the preparation method of which includes the following steps: the obtained supersulfate cement, 50 parts of water, 0.003 parts of triisopropanolamine, and 300 parts of sand are put into a cement mortar mixer in sequence and stirred. After stirring, cement mortar is obtained.

[0058] The mineral powder, industrial waste gypsum, recycled concrete powder, and fly ash used in this embodiment have the same content as in Example 1.

[0059] Example 5 A multi-solid waste early-strength supersulfate cement comprises the following components in parts by weight: 60 parts mineral powder, 15 parts α-type hemihydrate gypsum, 5 parts industrial waste gypsum, 10 parts recycled concrete powder, and 10 parts fly ash.

[0060] This embodiment also provides a method for preparing the supersulfate cement, including the following steps: mineral powder, α-type hemihydrate gypsum, industrial waste gypsum, recycled concrete powder and fly ash are put into a mixer according to the formula and premixed for 3 minutes to obtain supersulfate cement.

[0061] This embodiment also provides a cement mortar, the preparation method of which includes the following steps: the obtained supersulfate cement, 50 parts of water, 0.004 parts of triisopropanolamine, and 300 parts of sand are put into a cement mortar mixer in sequence and stirred. After stirring, cement mortar is obtained.

[0062] The mineral powder, industrial waste gypsum, recycled concrete powder, and fly ash used in this embodiment have the same content as in Example 1.

[0063] Example 6 A multi-solid waste early-strength supersulfate cement comprises the following components in parts by weight: 60 parts mineral powder, 10 parts α-type hemihydrate gypsum, 10 parts industrial waste gypsum, 10 parts recycled concrete powder, and 10 parts fly ash.

[0064] This embodiment also provides a method for preparing the supersulfate cement, including the following steps: mineral powder, α-type hemihydrate gypsum, industrial waste gypsum, recycled concrete powder and fly ash are put into a mixer according to the formula and premixed for 3 minutes to obtain supersulfate cement.

[0065] This embodiment also provides a cement mortar, the preparation method of which includes the following steps: the obtained supersulfate cement, 50 parts of water, 0.003 parts of triisopropanolamine, and 300 parts of sand are put into a cement mortar mixer in sequence and stirred. After stirring, cement mortar is obtained.

[0066] The mineral powder, industrial waste gypsum, recycled concrete powder, and fly ash used in this embodiment have the same content as in Example 1.

[0067] Example 7 A multi-solid waste early-strength supersulfate cement comprises the following components in parts by weight: 50 parts mineral powder, 15 parts α-type hemihydrate gypsum, 10 parts industrial waste gypsum, 15 parts recycled concrete powder, and 10 parts fly ash.

[0068] This embodiment also provides a method for preparing the supersulfate cement, including the following steps: mineral powder, α-type hemihydrate gypsum, industrial waste gypsum, recycled concrete powder and fly ash are put into a mixer according to the formula and premixed for 3 minutes to obtain supersulfate cement.

[0069] This embodiment also provides a cement mortar, the preparation method of which includes the following steps: the obtained supersulfate cement, 50 parts of water, 0.005 parts of triisopropanolamine, and 300 parts of sand are put into a cement mortar mixer in sequence and stirred. After stirring, cement mortar is obtained.

[0070] The mineral powder, industrial waste gypsum, recycled concrete powder, and fly ash used in this embodiment have the same content as in Example 1.

[0071] Example 8 A multi-solid waste early-strength supersulfate cement comprises the following components in parts by weight: 50 parts mineral powder, 15 parts α-type hemihydrate gypsum, 15 parts industrial waste gypsum, 10 parts recycled concrete powder, and 10 parts fly ash.

[0072] This embodiment also provides a method for preparing the supersulfate cement, including the following steps: mineral powder, α-type hemihydrate gypsum, industrial waste gypsum, recycled concrete powder and fly ash are put into a mixer according to the formula and premixed for 3 minutes to obtain supersulfate cement.

[0073] This embodiment also provides a cement mortar, the preparation method of which includes the following steps: the obtained supersulfate cement, 50 parts of water, 0.005 parts of triisopropanolamine, and 300 parts of sand are put into a cement mortar mixer in sequence and stirred. After stirring, cement mortar is obtained.

[0074] The mineral powder, industrial waste gypsum, recycled concrete powder, and fly ash used in this embodiment have the same content as in Example 1.

[0075] Comparative Example 1 A supersulfate cement comprises the following components in parts by weight: 80 parts mineral powder, 10 parts industrial waste gypsum, 5 parts recycled concrete powder, and 5 parts fly ash. Its preparation method includes: pre-mixing the mineral powder, industrial waste gypsum, recycled concrete powder, and fly ash in a mixer according to the formula amount for 3 minutes to obtain the supersulfate cement.

[0076] A cement mortar is prepared by the following steps: the prepared supersulfate cement, 50 parts of water and 300 parts of sand are put into a cement mortar mixer in sequence and stirred. After stirring, the cement mortar is obtained.

[0077] The mineral powder, industrial waste gypsum, recycled concrete powder, and fly ash used in this comparative example have the same composition and content as in Example 1.

[0078] Comparative Example 2 A type of supersulfate cement comprises the following components in parts by weight: 80 parts mineral powder, 5 parts α-type hemihydrate gypsum, 5 parts industrial waste gypsum, 5 parts 42.5 silicate cement clinker produced by Jidong Cement, and 5 parts fly ash. The preparation method includes: pre-mixing the mineral powder, α-type hemihydrate gypsum, industrial waste gypsum, silicate cement clinker, and fly ash in a mixer according to the formula proportions for 3 minutes to obtain the supersulfate cement.

[0079] A cement mortar is prepared by the following steps: the prepared supersulfate cement, 50 parts of water and 300 parts of sand are put into a cement mortar mixer in sequence and stirred. After stirring, the cement mortar is obtained.

[0080] The mineral powder and industrial waste gypsum used in this comparative example have the same composition as in Example 1.

[0081] Comparative Example 3 A type of supersulfate cement comprises the following components in parts by weight: 80 parts mineral powder, 5 parts α-type hemihydrate gypsum, 5 parts industrial waste gypsum, 5 parts sodium hydroxide, and 5 parts fly ash. Its preparation method includes: pre-mixing the mineral powder, α-type hemihydrate gypsum, industrial waste gypsum, sodium hydroxide, and fly ash in a mixer according to the formula for 3 minutes to obtain the supersulfate cement.

[0082] A cement mortar is prepared by the following steps: the prepared supersulfate cement, 50 parts of water and 300 parts of sand are put into a cement mortar mixer in sequence and stirred. After stirring, the cement mortar is obtained.

[0083] The mineral powder, industrial waste gypsum, and fly ash used in this comparative example have the same composition and content as in Example 1.

[0084] Comparative Example 4 A supersulfate cement comprises the following components in parts by weight: 80 parts mineral powder, 10 parts industrial waste gypsum, and 10 parts 42.5 silicate cement clinker produced by Jidong Cement. Its preparation method includes: pre-mixing the mineral powder, industrial waste gypsum, and ordinary silicate cement clinker in a mixer for 3 minutes according to the formula to obtain the supersulfate cement.

[0085] A cement mortar is prepared by the following steps: the prepared supersulfate cement, 50 parts of water and 300 parts of sand are put into a cement mortar mixer in sequence and stirred. After stirring, the cement mortar is obtained.

[0086] The mineral powder and industrial waste gypsum used in this comparative example have the same composition as in Example 1.

[0087] Comparative Example 5 A type of supersulfate cement comprises the following components in parts by weight: 80 parts mineral powder, 10 parts industrial waste gypsum, and 10 parts sodium hydroxide. Its preparation method includes: pre-mixing the mineral powder, industrial waste gypsum, and sodium hydroxide in a mixer for 3 minutes according to the formula to obtain the supersulfate cement.

[0088] A cement mortar is prepared by the following steps: the prepared supersulfate cement, 50 parts of water and 300 parts of sand are put into a cement mortar mixer in sequence and stirred. After stirring, the cement mortar is obtained.

[0089] The mineral powder and industrial waste gypsum used in this comparative example have the same composition as in Example 1.

[0090] In this invention, the cement mortar prepared in the examples and comparative examples was poured into a 40×40×160mm cement mortar triple mold. The mold was then placed in a standard cement curing chamber for 24 hours. After curing, the mold was demolded to obtain test blocks. The compressive and flexural strengths of the test blocks were tested according to GB / T17671-2021, and the results are shown in the table below: The early compressive and flexural strengths of the cement mortar specimens prepared in Examples 1-8 were higher than those of the comparative example at 1 day, 3 days, and 7 days. Furthermore, the later-stage strengths of the examples at 28 days and 90 days, corresponding to compressive and flexural strengths, were also generally higher than those of the comparative example. This indicates that the raw material combination of the present invention can effectively improve the early flexural and compressive strengths of supersulfate cement, and also increase the utilization rate of industrial solid waste and reduce the cost of alkaline activators and cement clinker.

[0091] Microscopic images of the embodiments and comparative examples are as follows Figure 2-4 As shown, Figure 2 The microscopic morphological features of Example 3 in this invention are typical characteristics. Figure 2 As can be seen above, the fibrous crystals generated by α-type hemihydrate gypsum are interspersed in the hydration products, forming a skeletal structure, which lays the foundation for improving the early compressive and flexural strength of supersulfates. Figure 3 The figure shows the microstructure of the transition zone between the supersulfate cement and sand in Example 3. As can be seen from the figure, through the multi-solid waste synergistic reaction designed in this system, the cement and sand are tightly bonded and there should be no weak interface transition zone. Moreover, the hydration products are densely formed with few pores, which can reduce the erosion of harmful gases and ions. This shows that the supersulfate cement of the present invention has the characteristics of high strength and durability.

[0092] Figure 4The figure shows the typical microstructure of ordinary persulfate cement in Comparative Example 4. As can be seen from the figure, its structure is loose and porous, with only a small amount of ettringite formed on the particle surface. The hydration products are few and the overlap between the hydration products is not tight, which makes ordinary persulfate cement have the defects of low early strength and poor durability.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-solid-waste early-strength supersulfate cement, characterized in that, The composition includes the following components in parts by weight: 50-80 parts mineral powder, 5-15 parts α-type hemihydrate gypsum, 5-15 parts industrial waste gypsum, 5-15 parts recycled concrete powder, and 5-10 parts fly ash.

2. The multi-solid waste early-strength supersulfate cement according to claim 1, characterized in that, The aspect ratio of the α-type hemihydrate gypsum is 6~10:

1.

3. The multi-solid-waste early-strength supersulfate cement according to claim 1 or 2, characterized in that, The mass ratio of the α-type hemihydrate gypsum to the recycled concrete powder is 0.8~1.5:

1.

4. The multi-solid waste early-strength supersulfate cement according to any one of claims 1-3, characterized in that, The industrial waste gypsum is selected from any one or more of phosphogypsum or desulfurized gypsum discharged from the factory, and its average particle size is 10~15 μm; Preferably, the desulfurized gypsum or phosphogypsum contains... The content is greater than 85 wt%.

5. The multi-solid-waste early-strength supersulfate cement according to any one of claims 1-3, characterized in that, The recycled concrete powder is made from construction solid waste concrete, with an average particle size of 5~10 μm. Preferably, the content of CaO in the recycled concrete powder is 40 wt%~55 wt%, the content of SiO2 is 25 wt%~35 wt%, and the content of Al2O3 is 4 wt%~8 wt%.

6. The multi-solid-waste early-strength supersulfate cement according to any one of claims 1-3, characterized in that, The particle size of the fly ash is 10~20 μm.

7. The method for preparing multi-solid waste early-strength supersulfate cement according to any one of claims 1-6, characterized in that, Includes the following steps: The mineral powder, α-type hemihydrate gypsum, industrial waste gypsum, recycled concrete powder and fly ash are mixed together; Preferably, the preparation method of the α-type hemihydrate gypsum includes the following steps: first, aluminum sulfate, industrial waste gypsum and water are mixed to form a slurry, and then the slurry is subjected to heat preservation and drying treatment in sequence; Preferably, the mass ratio of aluminum sulfate, industrial waste gypsum, and water is 0.3~0.6:80~100:300~320; Preferably, when aluminum sulfate, industrial waste gypsum, and water are mixed, aluminum sulfate is first dissolved in water to obtain an aluminum sulfate solution; then the industrial waste gypsum is dissolved in the aluminum sulfate solution.

8. The application of the multi-solid waste early-strength hypersulfate cement according to any one of claims 1-6 or the multi-solid waste early-strength hypersulfate cement prepared by the preparation method according to claim 7, characterized in that, The supersulfate cement is used to prepare building materials; Preferably, the building materials include any one or more of the following: (1) Used to prepare cement mortar; (2) Used to prepare concrete.

9. The application of the multi-solid waste early-strength supersulfate cement according to claim 8, characterized in that, The cement mortar comprises supersulfate cement, water, and sand, wherein the weight ratio of supersulfate cement to water is 1.2 to 3:1, and the weight ratio of supersulfate cement to sand is 1:1 to 5.

10. The application of the multi-solid waste early-strength supersulfate cement according to claim 8 or 9, characterized in that, The cement mortar also includes triisopropanolamine, the content of which is 0 to 0.005% of the weight of the supersulfate cement.

Images