Quick-hardening, high-strength and high-fluidity type cementing material and preparation method thereof

Abstract

The invention discloses a quick-hardening, high-strength and high-fluidity type cementing material and a preparation method thereof. The cementing material comprises an all-solid waste material, calcium hydroxide, a water reducing agent and water, the all-solid waste material is prepared from the following components in percentage by mass: 20 to 40 percent of red mud, 0 to 20 percent of gypsum and 40 to 80 percent of mineral powder; the mixing amount of the calcium hydroxide is 0-2% of the mass of all solid wastes; the mixing amounts of the water reducing agent and the water respectively account for 0.6% and 35% of the mass of the all-solid waste material. The preparation method of the cementing material is simple, the solid waste material only needs to be dried, ground and screened and then is uniformly mixed with the calcium hydroxide, the water reducing agent and the water, special equipment and special reaction conditions are not needed, and the prepared cementing material has excellent mechanical properties (compressive strength in the early stage, the middle stage and the later stage), fluidity and viscosity, is short in setting time, and can be used for preparing the cementing material. The method can better meet actual construction and is suitable for industrial large-scale production and application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of materials, in particular to a full solid waste and calcium hydroxide synergistic fast-hardening high-strength high-fluidity type cementitious material and a preparation method thereof. BACKGROUND

[0002] Traditional solid waste cementitious materials need to be mixed with solid waste, such as red mud. Red mud is an industrial waste generated by the reaction of bauxite and NaOH at high temperature during aluminum production. 1.5 tons of red mud are generated for every ton of aluminum oxide produced. Due to the action of NaOH, red mud has high alkalinity (PH>11), and large-scale accumulation can easily pollute the soil and groundwater. However, the high alkalinity and amorphous silicate of red mud make it possible to prepare geopolymer gel and as an auxiliary cementitious material. The high alkali metal content of red mud leads to poor volume stability, direct incorporation causes retardation and strength decay, and the high specific surface area and porous characteristics significantly increase the water demand during application, resulting in poor fluidity, long setting time, and low strength of the prepared slurry, which cannot meet the construction requirements. SUMMARY

[0003] The purpose of the present application is to solve the above problems existing in the prior art, and to provide a fast-hardening high-strength high-fluidity type cementitious material and a preparation method thereof. The cementitious material prepared by the present application has the characteristics of fast setting, high strength, and excellent fluidity.

[0004] The technical scheme adopted by the present application is as follows: A fast-hardening high-strength high-fluidity type cementitious material, comprising full solid waste material, calcium hydroxide, water reducing agent and water; the full solid waste material is composed of 20% to 40% red mud, 0% to 20% gypsum and 40% to 80% mineral powder; the calcium hydroxide content is 0.5% to 2.0% of the mass of the full solid waste; the water reducing agent and water content are 0.6% and 35% of the mass of the full solid waste material, respectively.

[0005] The synergistic effect of red mud-gypsum-mineral powder cementitious material in the present application makes the prepared material generate more ettringite, thereby providing strength. The incorporation of calcium hydroxide increases the content of silicates and aluminates in the mineral in the alkaline solution. In the reaction system of geopolymer, Al 3+ (or Si 4+ ) can be partially replaced by low-valent Ca 2+ in Al-O octahedron and Si-O tetrahedron, which will produce excessive negative charge. Subsequently, the strong electrostatic repulsion between particles has a significant impact on the microstructure of the fresh slurry, i.e. the dispersion of the flocculated structure. Since the free water covered by the flocculated structure is released, the dispersion effect of free water on particles is enhanced. Finally, the apparent viscosity of the fresh slurry is reduced, and the fluidity is significantly increased. In addition, the Ca2+ , the dissociated free water in the alkaline environment can promote the rapid generation of ettringite and gel structure, form a dense structure, thereby improving the early strength.

[0006] Preferably, the total solid waste material is composed of 40% red mud, 10% gypsum and 50% mineral powder by mass percentage; the calcium hydroxide content is 1% of the total solid waste mass.

[0007] The present application provides a preparation method of the above-mentioned fast-hardening high-strength high-fluidity cementitious material, comprising the following steps: S1, drying, grinding and sieving the gypsum and red mud to obtain red mud and gypsum raw materials, respectively; S2, mixing the red mud and gypsum raw materials obtained in S1, mineral powder and calcium hydroxide to obtain a powdery mixture; S3, adding water reducing agent and water to the powdery mixture obtained in S2, stirring at low speed first and then at high speed, and mixing uniformly to obtain a cementitious material.

[0008] Preferably, the preparation method further comprises S4, curing the cementitious material obtained in S3 in an environment with a temperature of 20±2℃ and a humidity of >95%.

[0009] In the preparation method, calcium hydroxide needs to be pre-mixed with the powdery cementitious material, and then mixed with water reducing agent and water. 2+ quickly replaces Al 3+ (or Si 4+ ) in Al-O octahedron and Si-O tetrahedron, increases the fluidity of the slurry, and makes the stirring of the slurry more uniform.

[0010] Preferably, the drying temperature in S1 is 80℃; the grinding time is 60min; and the sieve hole sizes for sieving the red mud and gypsum are 150μm and 75μm, respectively.

[0011] Further preferably, the low-speed stirring time in S3 is 30s, and the high-speed stirring time is 3min.

[0012] The present application has the following beneficial effects: (1) The present application mixes red mud, gypsum, mineral powder and calcium hydroxide, and Ca 2+ quickly replaces Al 3+ (or Si 4+), increase the pulp fluidity, so that the pulp stirring is more fully uniform, and then adding water reducing agent and water to prepare the cementitious material. The cementitious material is immediately covered with polypropylene film after stirring and pouring at room temperature and put into the curing box for curing. A part of the sample is demolded after 1d to test the uniaxial compressive strength. Another part of the sample is demolded after 3d of standard curing to continue curing until 7d and 28d of age to test the compressive strength of the sample. The detection shows that the 1d, 7d and 28d compressive strengths of the sample are 11.57~16.52MPa, 32.27~35.59MPa and 43.76~52.97MPa respectively; the fluidity is 280~295mm; the viscosity is 989~1454mpa·s; the initial setting time and final setting time are 57~174min and 310~355min respectively. The above data fully show that the cementitious material prepared by the application has excellent mechanical properties (early, medium and late compressive strength), fluidity and viscosity, and short setting time, and can better meet the actual construction requirements.

[0013] (2) The raw materials of the application are mainly solid waste materials (red mud, gypsum and mineral powder), and the raw material cost is low; and the preparation process is simple, only needs to dry, grind and sieve the solid waste materials, and then mix with calcium hydroxide, water reducing agent and water to be uniform, without special equipment and special reaction conditions, easy to operate, suitable for industrialized large-scale production and application. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The compressive strength diagram of the sample prepared for Examples 1-4 and Comparative Example 1.

[0015] Figure 2 The fluidity and viscosity diagram of the sample prepared for Examples 1-4 and Comparative Example 1.

[0016] Figure 3 The setting time diagram of the sample prepared for Examples 1-4 and Comparative Example 1.

[0017] Figure 4 The XRD pattern of the 1d sample prepared for Examples 1-4 and Comparative Example 1.

[0018] Figure 5 The XRD pattern of the 28d sample prepared for Examples 1-4 and Comparative Example 1.

[0019] Figure 6 The SEM diagram of the 1d and 28d samples prepared for Example 2.

[0020] Figure 7 The fluidity and viscosity diagram of the sample prepared for Comparative Examples 2-16; wherein (a) fluidity; (b) compressive strength.

[0021] Figure 8The compressive strength diagrams of sample 7d and 28d are prepared for Comparative Example 2-16; wherein (a) 7d; (b) 28d. DETAILED DESCRIPTION

[0022] The application will be further described below in conjunction with the drawings and specific examples.

[0023] The fluidity is tested according to GB / T 8077-2012 "Concrete Admixture Homogeneity Test Method". The viscosity is tested according to GB / T 43876-2024 "Cement Paste Viscosity Determination Method", using an NDJ-5S digital rotary viscometer (the instrument has four rotors numbered 1-4, with rotation speeds of 6 r / min, 12 r / min, 30 r / min, and 60 r / min. The actual test viscosity range is 0-6,000,000 mpa·s). The setting time is tested according to GB / T 1346-2011 "Cement Standard Consistency Water Content, Setting Time, and Soundness Test Method". The compressive strength of the cementing body is tested according to GB / T 17671-2021 "Cement Mortar Strength Test Method (ISO Method)".

[0024] Example 1

[0025] S1, the gypsum and red mud are respectively placed in an oven at 60°C for drying. The dried materials are respectively placed in a horizontal ball mill for dry grinding for 60 min. Then the ground red mud and gypsum are sieved, and the red mud and gypsum are respectively passed through 150 μm and 60 μm square hole sieves.

[0026] S2, the materials obtained in S1 are mixed with S105 grade mineral powder, and the dosages of red mud, gypsum, and mineral powder are 40%, 10%, and 50% respectively. Calcium hydroxide with a total solid waste mass ratio of 0.5% is mixed in advance during the mixing process. The dry powder raw material mixing time is 1 min.

[0027] S3, the mixed raw materials are added with water with a total solid waste mass ratio of 35% and 0.6% water reducing agent. First, slow stirring for 30 s, then high-speed stirring for 3 min, to obtain the cementing body (slurry).

[0028] The slurry obtained in this example is tested for fluidity, viscosity, and setting time, and the test results are shown in Table 1 and Figures 2-3

[0029] S4, then the remaining slurry is poured into a mold with a size of 40 mm x 40 mm x 40 mm and covered with a polyethylene film for standard curing (temperature 20±2℃, humidity >95%). A part of the sample is demolded after standard 1d, and then the uniaxial compressive strength is tested. Another part of the sample is demolded after standard curing for 3d, and continues to be cured to 7d and 28d age before testing the compressive strength of the sample, and the test results are shown in Table 1 and​Figure 1 XRD pattern is shown in FIG. 1. Figures 4-5 XRD pattern is shown in FIG. 1.

[0030] Table 1 Physical properties of cementitious body of Example 1

[0031] Example 2

[0032] The preparation method of the fast-hardening high-strength high-fluidity cementitious material of the full solid waste cooperated with calcium hydroxide in the present example comprises the following steps: S1, gypsum and red mud were placed in an oven at 60°C for drying. The dried materials were placed in a horizontal ball mill for dry grinding, with a grinding time of 60 min. Then the ground red mud and gypsum were sieved, and the red mud and gypsum were passed through 150 μm and 60 μm square hole sieves respectively.

[0033] S2, the materials obtained in S1 were mixed with S105 grade mineral powder, and the dosages of red mud, gypsum and mineral powder were 40%, 10% and 50% respectively. In addition, 1.0% of calcium hydroxide based on the total solid waste was mixed in the mixing process. The dry powder raw materials were mixed for 1 min.

[0034] S3, the mixed raw materials were added with 35% of water based on the total solid waste and 0.6% of water reducing agent. Slow stirring was first carried out for 30 s, followed by high speed stirring for 3 min, to obtain the cementitious body.

[0035] The fluidity, viscosity and setting time of the slurry obtained in the present example were tested, and the test results are shown in Table 2 and Figures 2-3 .

[0036] S4, then the remaining slurry was poured into a mold with a size of 40 mm x 40 mm x 40 mm and covered with a polyethylene film for standard curing (temperature 20±2°C, humidity >95%). A part of the sample was demolded after standard 1d, and then the uniaxial compressive strength was tested. Another part of the sample was demolded after standard curing for 3d, and the compressive strength of the sample was tested again at 7d and 28d ages, and the test results are shown in Table 1 and Figure 1 . XRD pattern and SEM are shown in FIG. 1 and Figures 4-6 .

[0037] Table 2 Physical properties of cementitious body of Example 2

[0038] Example 3

[0039] S1, the gypsum and red mud are respectively put into an oven at 60°C for drying. The dried materials are respectively put into a horizontal ball mill for dry grinding for 60 min. Then the ground red mud and gypsum are sieved, and the red mud and gypsum are respectively passed through a square hole sieve with a size of 150 μm and 60 μm.

[0040] S2, the materials obtained in S1 are mixed with S105 grade mineral powder, and the mixing amounts of the red mud, gypsum and mineral powder are respectively 40%, 10% and 50%. In the mixing process, 1.5% of calcium hydroxide based on the total solid waste is mixed in advance. The dry powder raw materials are mixed for 1 min.

[0041] S3, the mixed raw materials are added with 35% of water based on the total solid waste and 0.6% of water reducing agent. Slow stirring is performed for 30 s, and then high-speed stirring is performed for 3 min to obtain a cementing body.

[0042] The slurry obtained in the example is tested for flowability, viscosity and setting time, and the test results are shown in Table 3 and Figures 2-3 .

[0043] S4, then the remaining slurry is poured into a mold with a size of 40 mm x 40 mm x 40 mm and covered with a polyethylene film for standard curing (temperature 20±2°C, humidity >95%). A part of the sample is demolded after standard 1d, and then the uniaxial compressive strength is tested. Another part of the sample is demolded after standard curing for 3d, and continues to be cured to 7d and 28d age to test the compressive strength of the sample, and the test results are shown in Table 1 and Figure 1 . The XRD pattern is shown in Figures 4-5 .

[0044] Table 3 Physical properties of the cementing body of Example 3

[0045] Example 4

[0046] The preparation method of the fast-hardening high-strength high-flowability type cementing material in the example comprises the following steps: S1, the gypsum and red mud are respectively put into an oven at 60°C for drying. The dried materials are respectively put into a horizontal ball mill for dry grinding for 60 min. Then the ground red mud and gypsum are sieved, and the red mud and gypsum are respectively passed through a square hole sieve with a size of 150 μm and 60 μm.

[0047] S2, the materials obtained in S1 are mixed with S105 grade mineral powder, and the mixing amounts of the red mud, gypsum and mineral powder are respectively 40%, 10% and 50%. In the mixing process, 1.5% of calcium hydroxide based on the total solid waste is mixed in advance. The dry powder raw materials are mixed for 1 min.

[0048] S3, the mixed raw materials are added to water accounting for 35% of the total solid waste and 0.6% of water reducing agent. First, slow stirring for 30s, then high-speed stirring for 3min, to obtain the cementing body (slurry).

[0049] The slurry obtained in the embodiment is tested for fluidity, viscosity and setting time, and the test results are shown in Table 4 and Figures 2-3

[0050] S4, then the remaining slurry is poured into a mold with a size of 40mmx40mmx40mm and covered with a polyethylene film for standard curing (temperature 20±2℃, humidity >95%). A part of the sample is demolded after standard 1d, and then the uniaxial compressive strength is tested. Another part of the sample is demolded after standard curing for 3d, and continues to be cured to 7d and 28d age to test the compressive strength of the sample, and the test results are shown in Table 1 and Figure 1 Figures 4-5

[0051] Table 4 Physical properties of cementing body of Example 4

[0052] Comparative Example 1 S1, gypsum and red mud are respectively placed in an oven at 60℃ for drying. The dried materials are respectively placed in a horizontal ball mill for dry grinding for 60min. Then the red mud and gypsum after grinding are sieved, and the red mud and gypsum are respectively passed through 150μm and 60μm square hole sieves.

[0053] S2, the materials obtained in S1 are mixed with S105 grade mineral powder, and the dosages of red mud, gypsum and mineral powder are 40%, 10% and 50% respectively. The mixing time of dry powder raw materials is 1min.

[0054] S3, the mixed raw materials are added to water accounting for 35% of the total solid waste and 0.6% of water reducing agent. First, slow stirring for 30s, then high-speed stirring for 3min, to obtain the cementing body.

[0055] S4, then the remaining slurry is poured into a mold with a size of 40mmx40mmx40mm and covered with a polyethylene film for standard curing (temperature 20±2℃, humidity >95%). A part of the sample is demolded after standard 1d, and then the uniaxial compressive strength is tested. Another part of the sample is demolded after standard curing for 3d, and continues to be cured to 7d and 28d age to test the compressive strength of the sample.

[0056] The slurry obtained in the embodiment is tested for fluidity, viscosity and setting time, and the test results are shown in Table 4 and Figures 2-3 Figure 1 ​​​​The XRD pattern is shown in Figure 1. Figures 4-5 The XRD pattern is shown in Figure 1.

[0057] Table 5 Physical properties of the cementitious body of Comparative Example 1

[0058] As shown in Tables 1-4, Figures 2-3 it can be found that the flowability and setting time of the fresh paste gradually decrease and the viscosity gradually increases with the increase of the calcium hydroxide content (0.5% to 2.0%). However, the flowability of the examples with calcium hydroxide is higher than that of Comparative Example 1, and the setting time and viscosity are less than those of Comparative Example 1. Among them, the flowability of Examples 1-4 is 280-295 mm and the viscosity is 989-1454 mpa·s. The flowability of the cementitious body is increased by 107.41%-118.52% compared with that of the comparative example; the viscosity is reduced by 71.33%-80.51%. The initial setting time and final setting time are 57-174 min and 310-355 min, respectively, which are reduced by 92.69%-77.69% and 75.35%-78.47%, respectively. In addition, the 1d compressive strength of the cementitious material prepared by the full solid waste cooperated with calcium hydroxide gradually increases, and the 7d and 28d compressive strengths show a trend of first increasing and then decreasing. Among them, the cementitious body prepared by adding 1.0% of calcium hydroxide based on the mass of the full solid waste has the highest strength, reaching 52.97 MPa. This is due to the formation of ettringite in the cementitious body, which can be known in Figure 1 However, under the conditions of 1.5% and 2.0% of calcium hydroxide, the generation amount of ettringite is large, and the micro-expansion characteristics cause micro-cracks in the cementitious body, so the compressive strength is lower than that of the group with 1.0% of calcium hydroxide.

[0059] Figures 4-5 and Figures 1-5 The XRD patterns of the cementitious body prepared by the full solid waste cooperated with calcium hydroxide of the present application at 1d and 28d are given. As Figures 4-6 can be seen, the cementitious body with calcium hydroxide can obviously observe the decrease of the gypsum diffraction peak intensity and the increase of the ettringite diffraction peak. It shows that the Ca 2+ , alkaline environment, and dissociated free water can promote the rapid generation of ettringite and gel structure, form a dense structure, and thus improve the early strength. The gypsum diffraction peak intensity of the cementitious body without calcium hydroxide at 1d is high, and no obvious ettringite can be observed. It shows that the internal reaction is slow, and no hydration product is formed, so it cannot provide observable strength. However, with the increase of the age, the hydration reaction process in the cementitious body gradually increases, and at 28d Figure 4 , the generation of ettringite can be obviously observed, and the strength gradually develops.

[0060] Comparative Example 2-16 The preparation method (steps S1-S3) of the slurry in Comparative Example 2-16 is the same as Comparative Example 1, except that the proportions of the mineral powder, red mud and gypsum are shown in Table 6. The prepared slurry is tested for flowability, viscosity and setting time, and the remaining slurry is poured into a mold with a size of 40 mm x 40 mm x 40 mm for room temperature curing. The main purpose of Comparative Example 2-16 is to explore the influence of the proportions of gypsum and red mud on the physical and mechanical properties of the cementitious system, and to provide a theoretical basis for the selection of the proportions of the raw materials in Example 1-4. The uniaxial compressive strength is tested at the ages of 7d and 28d of room temperature curing. The test results are shown in Table 6, Figure 5 .

[0061] Table 6 Proportions of mineral powder, red mud and gypsum in Comparative Example 2-16 and performance test results

[0062] From Figure 4 (a) it can be seen that the flowability of the slurry is positively correlated with the proportion of gypsum and negatively correlated with the proportion of red mud. Even at different proportions of gypsum, the flowability is still negatively correlated with the proportion of red mud, indicating that the decrease in flowability caused by the addition of red mud is not affected by the proportion of gypsum. The flowability of the slurry with a red mud proportion of 40% is the lowest. Specifically, when the red mud proportion is 40% (Comparative Examples 12-16), the flowability of the slurry is 125-160 mm, and the flowability of the sample is poor. In summary, the addition of gypsum can increase the flowability of the slurry, while the high water demand of red mud significantly reduces the flowability of the slurry as the proportion increases.

[0063] Figure 5 (b) is the viscosity test result of the fresh slurry. As can be seen from the figure, the proportion of gypsum is negatively correlated with the viscosity of the slurry, and the proportion of red mud is positively correlated with the viscosity of the slurry, which is contrary to the test result of the flowability. Among them, the viscosity in Comparative Example 6 is the smallest, which is 1047 mpa·s. Compared with Comparative Example 2, the viscosity is reduced by 8.77%. This is because the introduction of SO4²⁻ by gypsum destroys the Si-O-Al bond in the slag, releases more Ca²⁺ and Al³⁺, and promotes hydration. Without gypsum, the disorderly generation of active ions causes a sharp increase in viscosity. By comparing Comparative Example 2 and Comparative Example 12, it can be found that the increase in the proportion of red mud significantly increases the flowability of the slurry. The viscosity of Comparative Example 12 increases by 254.72% compared with Comparative Example 2. This is mainly because the porous structure of red mud increases the water demand, thereby increasing the viscosity of the slurry.

[0064] From Figures 7-8 Figure 7 Figure 7 Figure 8It can be seen that, in the 28d strength, under the condition of the same amount of red mud, with the increase of the amount of gypsum, the compressive strength of the cementing body first increases and then decreases. Among them, when the amount of gypsum is 10%, the cementing body shows the highest strength. Under the condition of the same amount of gypsum, the strength of the cementing body shows an increasing trend as the amount of red mud increases. However, when the amount of gypsum is 0%, it is just the opposite. This may be because the high viscosity and low fluidity of the slurry cause the bubbles in the cementing body to be unable to be discharged and stored inside, resulting in a decrease in the compressive strength. Therefore, by combining the fluidity and strength results, the comparative example 14 (red mud 40%, gypsum 10%, mineral powder 50%) is selected for modification, and then a fast-hardening high-strength high-fluidity type cementing material is prepared by using calcium hydroxide.

[0065] In summary, the present application provides a fast-hardening high-strength high-fluidity type cementing material and a preparation method thereof, which is prepared by using full solid waste (red mud-mineral powder-gypsum) and calcium hydroxide, and has fast setting, high strength and excellent fluidity.

[0066] The specification and drawings of the present application are considered to be illustrative rather than restrictive, and on the basis of the present application, those skilled in the art can make some substitutions and modifications to some technical features according to the disclosed technical content without creative labor, which are all within the protection scope of the present application.

Claims

1. A fast-setting, high-strength, and high-flowability cementitious material, characterized in that, The cementing material comprises a total solid waste material, calcium hydroxide, a water reducing agent and water; the total solid waste material is composed of 20-40% red mud, 0-20% gypsum and 40-80% mineral powder by mass percentage; the calcium hydroxide is mixed in an amount of 0.5-2.0% of the total solid waste by mass; and the water reducing agent and water are mixed in amounts of 0.6% and 35% of the total solid waste material by mass, respectively.

2. The fast-hardening high-strength high-fluidity mold cement according to claim 1, wherein The total solid waste material is composed of 40% red mud, 10% gypsum and 50% mineral powder by mass percentage; and the calcium hydroxide is mixed in an amount of 1% of the total solid waste by mass.

3. The fast-hardening high-strength high-fluidity type cementitious material according to claim 1, characterized by, The step size of the red mud is 10%, the step size of the gypsum is 5%, and the step size of the calcium hydroxide is 0.5%.

4. A method of producing a high early-strength high-strength high-fluidity cementitious material according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: S1, drying, grinding and screening the gypsum and the red mud to obtain red mud and gypsum raw materials; S2, mixing the red mud, the gypsum raw material, the mineral powder and the calcium hydroxide obtained in S1 to obtain a powdery mixture; S3, adding the water reducing agent and water to the powdery mixture obtained in S2, stirring at a low speed first and then at a high speed, and mixing uniformly to obtain a cementing material.

5. The preparation method according to claim 4, characterized in that, The preparation method further comprises S4, curing the cementing material obtained in S3 in an environment with a temperature of 20±2℃ and a humidity of >95%.

6. The preparation method according to claim 4, characterized in that, In S1, the drying temperature is 80℃, the grinding time is 60 min, and the screen hole sizes for the red mud and the gypsum are 150μm and 75μm, respectively.

7. The preparation method according to claim 4, characterized in that, In S3, the low-speed stirring time is 30 s, and the high-speed stirring time is 3 min.

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