A binder, its preparation method and application

Abstract

This invention provides a binder, its preparation method, and its application, belonging to the field of materials preparation technology. By adjusting the content of Al2O3, CaO, and SiO2 in the raw materials, this invention enables the prepared binder to possess both the characteristics of silicate cement and aluminate cement, allowing direct application under low, medium, and high temperature conditions. This invention can use only low- to medium-grade bauxite as raw material, replacing high-grade bauxite in conventional techniques, which is of great significance for the rational utilization of low- to medium-grade bauxite mines and the protection of natural resources of high-grade bauxite mines. The binder obtained by this invention has higher early strength and possesses composite silicate and aluminate cement characteristics. When used as a building material in the chemical building materials field, it can effectively improve construction efficiency and save working time. Furthermore, when used as a binder for refractory materials, it can directly replace aluminate CA50 cement, which has significant economic benefits.

Description

Technical Field

[0001] This invention relates to the field of materials preparation technology, and in particular to a binder, its preparation method, and its application. Background Technology

[0002] Cement is an important building material, which can be divided into silicate cement and special cement according to its different uses in industrial construction.

[0003] Silicate cement is widely used in general industrial and civil buildings. It is a hydraulic cementitious material with calcium silicate clinker as the main component, and is internationally known as Portland cement. It is characterized by rapid setting and hardening, high early strength, and high later strength. However, silicate cement has poor heat resistance and is not suitable for concrete projects with heat resistance requirements. It is generally only used in working conditions with temperatures below 400℃.

[0004] Specialty cements are building materials specifically formulated for special applications, such as dam cement, oil well cement, road cement, and refractory cement. Refractory cement generally refers to aluminate cement, an indispensable hydraulic binder in the refractory industry, widely used in refractory materials for high-temperature kilns in metallurgy, chemical, power, and building materials industries. Refractory materials formulated with aluminate cement generally have a refractoriness greater than 1580℃ and possess advantages such as high-temperature volume stability, thermal shock resistance, and good erosion resistance. Ordinary aluminate cement is a hydraulic binder made from bauxite and limestone through calcination, resulting in clinker with calcium aluminate as the main component and an alumina content of approximately 50%, which is then ground. Pure aluminate cement, on the other hand, requires high-purity alumina and calcium carbonate as main raw materials, leading to higher raw material costs and more precise production control, resulting in a very high product price. Aluminate cement is generally chosen as a binder for refractory applications requiring temperatures above 1100℃.

[0005] In practical applications, most chemical building material binders are composed of ordinary silicate cement, aluminate cement and gypsum, and their formulation is complex. If the mixing is uneven, it will cause local failure and affect the performance of building materials.

[0006] Current technology lacks low-cost cement binders that can be directly applied under operating conditions ranging from 400°C to 1100°C.

[0007] In addition, high-grade bauxite is required in the production of aluminates. Every year, a large amount of high-grade bauxite is consumed in the production of aluminate cement. Since bauxite is a non-renewable resource, the deposits of high-grade bauxite are on the verge of depletion due to over-exploitation, while low-grade bauxite cannot be used rationally. How to solve the development problem of cement binders from the perspective of raw materials has become the focus of relevant research.

[0008] Chinese patent CN113461348A discloses a method for preparing sulfoaluminate cement clinker using aluminum profile waste liquid. This method utilizes aluminum profile waste liquid to replace high-grade bauxite as the sole aluminum raw material for producing sulfoaluminate cement, thereby realizing the resource utilization of aluminum profile waste liquid. This reduces the filtration and drying process of treating aluminum profile waste liquid into waste residue, solves the pollution problem caused by its stockpiling, reduces the exploitation of natural resources, and lowers the production cost of sulfoaluminate cement. Summary of the Invention

[0009] The purpose of this invention is to provide a binder, its preparation method, and its application, which has the characteristics of both silicate cement and aluminate cement, and can be compounded with gypsum for use in the field of chemical building materials; at the same time, it can be directly applied under working conditions of 400℃ to 1100℃.

[0010] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0011] This invention provides a binder, wherein the raw materials of the binder contain the following components in percentage of the total mass of the raw materials:

[0012] Al2O3 30%~40%;

[0013] CaO 45%~50%;

[0014] SiO2 10%~15%.

[0015] Preferably, the binder contains the following components in percentage of the total mass of the raw materials:

[0016] MgO 0.4%~0.6%;

[0017] Fe2O3 1.5%~2.0%;

[0018] SO3 0.1%~0.3%;

[0019] K2O 0.3%~0.5%;

[0020] Na2O 0.05%~0.10%;

[0021] TiO2 1.5%~2.0%.

[0022] Preferably, the raw materials for the binder include bauxite and limestone.

[0023] Preferably, the bauxite is of medium to low grade.

[0024] The present invention also provides a method for preparing the above-mentioned binder, comprising the following steps:

[0025] All raw materials are mixed and co-ground to obtain intermediate material;

[0026] The binder is obtained by calcining and cooling the intermediate material.

[0027] Preferably, the particle size of the intermediate material is 5~8µm.

[0028] Preferably, the calcination temperature is 1280~1320℃.

[0029] The present invention also provides the application of the above-described binder or the binder obtained by the above preparation method in building materials.

[0030] The beneficial effects of this invention are:

[0031] This invention, by setting the content of Al2O3, CaO and SiO2 in the raw material composition, enables the prepared binder to have both the characteristics of silicate cement and aluminate cement, and can be compounded with gypsum for use in the field of chemical building materials; at the same time, it can be directly applied under medium temperature (400℃ to 1100℃) working conditions.

[0032] This invention can use only low- to medium-grade bauxite as raw material, replacing the high-grade bauxite used in conventional technologies. This is of great significance for the rational utilization of low- to medium-grade bauxite deposits and the protection of natural resources from high-grade bauxite deposits.

[0033] The binder preparation method provided by this invention can retain more effective minerals (CA (CaO·Al2O3) and C2S (2CaO·SiO2)) in the product, while avoiding pulverization, thus improving product quality.

[0034] The binder obtained by this invention has higher early strength and composite silicate and aluminate cement characteristics. When used as a building material in the field of chemical building materials, it can effectively improve construction efficiency and save working time. At the same time, when used as a binder for refractory materials, it can directly replace aluminate CA50 cement, which has great economic significance. Attached Figure Description

[0035] Figure 1 This is a statistical chart of the effective phase content;

[0036] Figure 2 Photo of the cooked material;

[0037] Figure 3 Statistical chart of flow value detection results for different experimental groups;

[0038] Figure 4 The exothermic curves for different experimental groups;

[0039] Figure 5Statistical graph of the room temperature flexural strength results for different experimental groups;

[0040] Figure 6 This is a statistical chart showing the room temperature compressive strength results for different experimental groups. Detailed Implementation

[0041] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0042] Example

[0043] Experiments were conducted using three raw materials: bauxite-1, bauxite-2, and limestone. By controlling the ratio of the three raw materials, experimental groups with different component contents were obtained.

[0044] The composition of the three raw materials is shown in Table 1 below:

[0045] Table 1. Raw material composition content (%)

[0046]

[0047] The experimental groups with different component contents are shown in Tables 2 and 3 below:

[0048] Table 2. Component content of different experimental groups (N1~N4, %)

[0049]

[0050] Table 3. Component content of different experimental groups (N5~N9, %)

[0051]

[0052] After mixing the raw materials according to the proportions in the table above, grind them with a grinding mill until the particle size D50 = 5~8µm. The resulting pellets are green pellets, which are then sintered at 1275℃, 1300℃ and 1325℃ for 1 hour to obtain clinker.

[0053] The mineral composition of the clinker obtained from the N0-N9 experimental groups under sintering conditions of 1300℃ is shown in Table 4 below:

[0054] Table 4. Mineral composition (%) of clinker sintered at 1300℃ for each experimental group

[0055]

[0056] Based on the results in Table 4, the effective phase content was statistically analyzed, and the results are as follows: Figure 1 As shown, N0, N2, N3, N5, and N8 are better, with N3 being the best.

[0057] The mineral composition of the clinker obtained from experimental groups N0, N2, N3, N5, and N8 under different sintering temperatures is shown in Table 5 below:

[0058] Table 5. Mineral composition (%) of clinker obtained from the experimental group under different sintering temperatures

[0059]

[0060] The clinker state photographs obtained from experimental groups N0, N2, N3, N5, and N8 under a sintering temperature of 1325℃ are shown below. Figure 2 As shown.

[0061] As can be seen from the above component determination results, the sintered clinker obtained by the experimental group provided by the present invention has undergone mineral phase recombination in the preparation process, which transforms the non-hydrated phase C2AS into the hydrated phases C2S and CA. The final product has both the characteristics of silicate cement and aluminate cement, which improves the medium-temperature strength of the binder, enabling it to be directly applied under medium temperature conditions of 400℃ to 1100℃.

[0062] Meanwhile, the formulation provided by this invention can control the content of the active ingredient (C3A) in the product to a low level, thus avoiding affecting hydration.

[0063] The preparation method provided by this invention can retain more effective minerals (CA and C2S, C12A7) in the clinker product, resulting in higher product quality.

[0064] The formulation provided by this invention is also applicable to the preparation of binders by melt method, and the specific steps are as follows:

[0065] All raw materials are mixed, ground together according to the N3 ratio, then melted in an electric furnace, and cooled to obtain a binder.

[0066] Using refractory aluminate A600 cement, which is commonly used in the existing technology, as a control, XRD and XRF analyses were performed. The chemical composition of the compounds of the two is shown in Table 6 below.

[0067] Table 6 Comparison of chemical composition of compounds (%)

[0068]

[0069] The phase compositions of the two are shown in Table 7 below:

[0070] Table 7 Comparison of phase composition (%)

[0071]

[0072] The main phase contents of A600 cement are: CA (38.51%), CA2 (13.21%), and C2AS (37.78%).

[0073] The main phase contents of the sample (named CAC2S) provided by this invention are: CA (32.32%), C12A7 (10.65%), and C2S (26.20%).

[0074] The results show that the binder preparation process provided by the present invention successfully transforms the non-hydrated mineral C2AS (useless mineral) into hydrated minerals C2S, CA and C12A17.

[0075] Application testing was conducted on both:

[0076] Medium-strength cement refractory castables were prepared using different amounts of A600 and CAC2S, and the specific formulations are shown in Table 8 below:

[0077] Table 8 Formulations of Different Cement Castables

[0078]

[0079] First, prepare the dry materials according to the above formula. Then, pour the dry materials into a forced mixer and mix for 3 minutes. During the mixing process, add 6.4% deionized water and continue mixing for 4 minutes. After stopping mixing, measure the flow value of the mortar according to the national standard GB / T 2419-2005 "Determination of Flowability of Cement Mortar" and measure the heat of hydration release according to GB / T12959-2008 "Determination of Heat of Hydration of Cement". Next, pour the remaining mortar into 160*40*40mm specimens in a triple mold. Cure with the mold at 20℃ for 24 hours, then demold and cure naturally at 20℃ for 24 hours, followed by drying at 110℃ for 24 hours. Perform heat treatment at 800℃ for 3 hours and 1100℃ for 3 hours on some specimens to obtain the required test specimens. Finally, measure the room temperature flexural strength and compressive strength of the specimens according to GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)".

[0080] The flow values ​​of different experimental groups were measured, and the results are as follows: Figure 3 As shown.

[0081] The exothermic curves of different experimental groups were detected, and the results are as follows: Figure 4 As shown.

[0082] The room temperature flexural strength of different experimental groups was tested, and the results are as follows: Figure 5 As shown.

[0083] The room temperature compressive strength of different experimental groups was tested, and the results are as follows: Figure 6 As shown.

[0084] The results showed that, compared with A600, CAC2S exhibited a lower T0 and faster flow decay for the same water demand. Due to the high C12A7 content in CAC2S, citric acid was added to the CAC2S formulation as a retarder to achieve better workability (citric acid primarily acts as a retarder in cement. When added to cement, it reacts with aluminates to form a stable complex, hindering the early hydration reaction of aluminates in the cement, thereby slowing down the setting and hardening process).

[0085] CAC2S and A600 exhibit different exothermic intensities, but CAC2S containing citric acid and A600 without citric acid show similar exothermic trends.

[0086] The CAC2S provided by this invention has higher early strength, which can improve construction efficiency and save working time in practical applications.

[0087] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A binder, characterized in that, The binder contains the following components in percentage of its total mass: Al2O3 30%~40%; CaO 45%~50%; SiO2 10%~15%; MgO 0.4%~0.6%; Fe2O3 1.5%~2.0%; SO3 0.1%~0.3%; K2O 0.3%~0.5%; Na2O 0.05%~0.10%; TiO2 1.5%~2.0%; The binder is made from bauxite and limestone, wherein the bauxite is of medium to low grade.

2. The method for preparing the binder according to claim 1, characterized in that, Includes the following steps: All raw materials are mixed and co-ground to obtain intermediate material; The binder is obtained by calcining and cooling the intermediate material.

3. The method for preparing the binder according to claim 2, characterized in that, The particle size of the intermediate material is 5~8µm.

4. The method for preparing the binder according to claim 2, characterized in that, The calcination temperature is 1280~1320℃.

5. The use of the binder according to claim 1 or the binder obtained by any one of the preparation methods described in claims 2 to 4 in the preparation of chemical building materials or refractory materials.

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