Composite excitant, titanium extraction tailing-based cementing material applying composite excitant and preparation method of cementing material

Abstract

The invention discloses a composite activator, a titanium extraction tailing-based cementing material using the composite activator and a preparation method of the cementing material, and belongs to the technical field of constructional engineering materials. The composite exciting agent comprises the following components in percentage by mass: 19%-27% of calcium sulphoaluminate cement, 17%-38% of aluminum sulfate, 2%-16% of calcium formate, 0%-17% of sodium silicate and 16%-42% of copperas. The preparation method comprises the following steps: doping a composite activator into a standard gelling system consisting of titanium extraction tailings, titanium gypsum, cement and lime according to a proportion of 1-5%, and enabling the median particle diameter D50 of mixed powder to be less than 15 microns through a co-grinding process. In order to solve the problems of slow development of early strength and generally low performance of the titanium extraction tailing-based cementing material, the synergistic excitation effect among the components in the composite exciting agent is utilized to promote rapid formation of ettringite and acceleration of hydration reaction, so that efficient utilization of solid waste in the titanium extraction industry is realized, and the utilization rate of the titanium extraction tailing-based cementing material is improved. The technical bottleneck of low early strength of the existing titanium extraction tailing-based cementing material is effectively solved, and the titanium extraction tailing-based cementing material is suitable for occasions with higher requirements on early strength, such as mine filling, roadbed engineering and the like.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a composite activator, a titanium-based cementitious material using the composite activator, and a preparation method thereof. Background Technology

[0002] The Panxi region of my country is rich in vanadium-titanium magnetite resources, which produce unique high-titanium blast furnace slag during its smelting process. To recover the titanium resources from this slag, a "high-temperature carbonization-low-temperature chlorination" titanium extraction process has been developed. However, this process generates a large amount of titanium extraction tailings as a byproduct. Approximately 85% of the blast furnace slag after titanium extraction will be converted into this type of tailings. These tailings have a complex composition, generally containing 2.5-4 wt% chloride ions, with fine particle size and low activity. Although these tailings can be stockpiled as Class II general industrial solid waste, simple stockpiling not only occupies a large amount of land, but more seriously, under the leaching effect of rainwater, the chloride ions will slowly release and migrate, posing a persistent environmental pollution risk to the surrounding soil and water environment. Their disposal has become a key environmental problem restricting the sustainable development of the blast furnace slag titanium extraction industry. On the other hand, the traditional building materials sector currently heavily relies on cementitious materials, such as ordinary silicate cement. Cement production requires the large-scale extraction of non-renewable resources such as natural limestone and clay. The clinker calcination process is a key stage characterized by high energy consumption and significant carbon dioxide emissions, contradicting the current national "dual-carbon" strategy and the concept of green and low-carbon development. With increasingly tight resource constraints and stringent environmental requirements, the search for alternative cementitious materials with low environmental impact and high performance has become an urgent need for the building materials industry.

[0003] To address the aforementioned issues, existing technologies have explored the resource utilization of titanium extraction tailings as auxiliary cementitious materials or primary raw materials. For example, Chinese patent CN118388200A discloses a titanium extraction tailings-based whole tailings backfill cementitious material and its preparation method. This backfill cementitious material comprises titanium extraction tailings, titanium gypsum, cement, and lime. By compounding and adjusting the formula ratio, it aims to synergistically treat multiple solid wastes and improve the performance of the backfill cementitious material, providing a preliminary approach to the resource utilization of titanium extraction tailings. However, existing technologies, including the patent scheme disclosed in CN118388200A, share a significant common defect: the prepared titanium extraction tailings-based cementitious materials exhibit slow early strength development and generally low performance. Due to the limited cementitious activity of titanium extraction tailings, even after physical grinding or compounding with a small amount of alkaline activators such as lime, the hydration reaction rate remains slow. This results in the material's early compressive strength within 3 or 7 days failing to meet the urgent requirements of many practical engineering projects, especially in short-term projects such as rapid construction, early-load-bearing backfilling, and emergency repairs. This insufficient early strength severely restricts the application scope and market acceptance of such materials, becoming a major technical bottleneck for their large-scale commercialization. Summary of the Invention

[0004] The main objective of this invention is to provide a composite activator, a titanium extraction tailings-based cementitious material using the composite activator, and a preparation method thereof. Based on the original formula that addresses the resource utilization issues of titanium extraction tailings and titanium gypsum solid waste, this invention prepares a composite activator for titanium extraction tailings-based cementitious materials with high early strength and a simple and easy-to-process manufacturing process. The composite activator can significantly improve the early mechanical properties of cementitious materials using titanium extraction tailings as the main raw material, solving a key bottleneck in their engineering applications, thereby promoting the high-value-added and large-scale utilization of such bulk industrial solid waste.

[0005] The first aspect of this invention provides a composite activator, comprising the following components by mass percentage:

[0006] Calcium sulfoaluminate cement 19wt%-27wt%, aluminum sulfate 17wt%-38wt%, calcium formate 2wt%-16wt%, sodium silicate 0wt%-17wt%, ferrous sulfate 16wt%-42wt%.

[0007] The second aspect of the present invention provides a titanium extraction tailings-based cementitious material, which applies the above-mentioned composite activator and comprises the following components by mass percentage: 50%~65% titanium extraction tailings, 18%~25% titanium gypsum, 5%~20% cement, 3%~10% lime, and 1%-5% composite activator.

[0008] Furthermore, the titanium gypsum is titanium gypsum with surface free water removed and calcium sulfate dihydrate crystal structure maintained.

[0009] Furthermore, the cement is P·I 42.5 silicate cement.

[0010] A third aspect of this invention provides a method for preparing a titanium tailings-based cementitious material, comprising the following steps:

[0011] The cement, lime, titanium extraction tailings, titanium gypsum, and composite activator are placed together in a ball mill for co-milling according to the measured amount; the co-milled mixed powder is then homogenized by a powder homogenizer to obtain the titanium extraction tailings-based cementitious material.

[0012] Furthermore, the median particle size D of the co-milled mixed powder 50 Less than 15μm.

[0013] Furthermore, the titanium extraction tailings are measured by dry weight.

[0014] Furthermore, titanium tailings-based cementitious materials are applied in mine backfill materials, roadbed engineering materials, or building cementitious materials.

[0015] This invention provides a composite activator, a titanium extraction tailings-based cementitious material using the composite activator, and a preparation method thereof. The core principle is that the composite activator and the integrated co-grinding process work synergistically to specifically solve the key technical bottlenecks of existing titanium extraction tailings-based materials, such as low early strength, easy migration of chloride ions, and poor pumpability.

[0016] The composite activator comprises sulfoaluminate cement, aluminum sulfate, calcium formate, sodium silicate, and ferrous sulfate helium. Its mechanism of action is a multi-pathway synergistic activation process. When the composite activator is incorporated into a baseline system consisting of titanium extraction tailings, titanium gypsum, lime, and cement, the components collectively construct a highly efficient sulfate-alkali composite activation environment. The sulfate ions provided by the composite activator and titanium gypsum, synergistically with the alkaline environment generated by the hydration of lime and cement, can rapidly activate the active silica-alumina substances in the titanium extraction tailings, promoting the early generation of large quantities of ettringite, which serves as the strength framework, in the early stages of the hydration reaction. Simultaneously, the sulfoaluminate cement and calcium formate in the composite activator play a precise role in promoting setting and early strength, while ferrous sulfate helium can generate ferric hydroxide colloids to fill micropores, thereby jointly driving a significant increase in the early strength of the material. A process that ball-mills all raw materials to a median particle size of less than 15 micrometers further activates the surface of the solid waste particles through mechanical force, making the aforementioned chemical reactions more rapid and complete.

[0017] Regarding engineering adaptability, this invention makes key process considerations. Unlike the common approach of simply pursuing early setting by calcining titanium gypsum into hemihydrate gypsum, this invention specifically treats titanium gypsum only to a dihydrate gypsum state after removing surface free water. This treatment ensures that the cementitious material has suitable workability and setting time in long-distance pumping scenarios such as downhole filling, fundamentally avoiding pipeline blockage accidents caused by rapid setting, and making the high-performance material truly feasible for engineering applications. Attached Figure Description

[0018] Figure 1 The images show electron microscope comparisons of the products obtained in Example 1 and Comparative Example 1, with the left image showing the product obtained in Comparative Example 1 and the right image showing the product obtained in Example 1.

[0019] Figure 2 This is a comparison chart of thermogravimetric analysis of the products obtained in Example 1 and Comparative Example 1. Detailed Implementation

[0020] The following specific embodiments further illustrate the technical solution and effects of the present invention. These embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Simple modifications made to the present invention based on the concept of the present invention are all within the scope of protection claimed by the present invention.

[0021] The equipment used in the preparation method of this invention can all be equipment known in the art. Unless otherwise specified, all raw materials used in this invention are commercially available.

[0022] The first aspect of this invention provides a composite activator, comprising the following components by mass percentage:

[0023] The cement composition consists of 19wt%-27wt% calcium sulfoaluminate cement, 17wt%-38wt% aluminum sulfate, 2wt%-16wt% calcium formate, 0wt%-17wt% sodium silicate, and 16wt%-42wt% ferrous sulfate. The composite activator optimizes the cementitious system's performance through the synergistic effect of its multiple components. First, ferrous sulfate, aluminum sulfate, sodium silicate, and sulfoaluminate cement together form a rapid-setting, early-strength core, quickly forming hydration products such as ettringite, significantly improving early strength. Second, calcium formate acts as a setting accelerator, further accelerating cement mineral hydration. The combination of these components produces a synergistic effect of multiple activations and microstructure optimization.

[0024] The second aspect of this invention provides a titanium extraction tailings-based cementitious material, employing the aforementioned composite activator, comprising the following components by mass percentage: 50%–65% titanium extraction tailings, 18%–25% titanium gypsum, 5%–20% cement, 3%–10% lime, and 1%–5% composite activator. Lime, upon hydration, generates calcium hydroxide, which partially carbonizes during curing to form calcium carbonate precipitate. Its hydration products not only provide the necessary alkaline environment to promote the dissociation of silicon (aluminum) oxygen tetrahedra but also further activate the hydration activity of the titanium extraction tailings. The cement hydration reaction provides support for the early strength of the backfill, and the generated calcium hydroxide replenishes calcium ions in the liquid phase, reacting with active silica and alumina to form hydrated calcium silicate (aluminate) gel. Chloride ions present in the titanium extraction tailings dissociate and recombine with sulfate-derived compounds such as aluminum sulfate and ferrous sulfate in the titanium gypsum and composite activator within the system, forming corresponding insoluble products, thereby solidifying chloride ions within the backfill structure. This process significantly reduces the risk of chloride ion leaching, providing an effective solution for the resource utilization of chlorine-containing solid waste.

[0025] Furthermore, the titanium gypsum is a titanium gypsum with surface free water removed while maintaining the calcium sulfate dihydrate crystal structure. The calcium sulfate dihydrate contained in the titanium gypsum has a sulfate-activating effect on the siliceous calcium titanium extraction tailings, which can promote the dissolution of more ions and groups in the tailings that can form gels, thereby generating ettringite and strengthening the strength of the filling body. In the alkaline environment provided by the system, the gypsum dihydrate crystals in the titanium gypsum can contribute early strength to the quaternary cementing system; at the same time, the ferric ions in the titanium gypsum can combine with hydroxide ions to form ferric hydroxide, and further react to generate iron phase hydration products (such as CaO·Fe2O3·3H2O), which helps to improve the overall strength of the filling body.

[0026] Furthermore, the pretreatment conditions for titanium gypsum are as follows: drying until only surface free water is removed, thus preserving its dihydrate gypsum crystal structure. This aims to utilize the stable hydration properties of dihydrate gypsum to continuously provide sulfate activation during the hardening stage of the filler, while avoiding premature hydration of hemihydrate gypsum that could affect the long-distance pumping performance of the slurry.

[0027] Furthermore, the cement is P·I 42.5 silicate cement.

[0028] A third aspect of this invention provides a method for preparing a titanium tailings-based cementitious material, comprising the following steps:

[0029] The cement, lime, titanium extraction tailings, titanium gypsum, and composite activator are co-milled in a ball mill according to metering. The co-milled mixture is then homogenized by a powder homogenizer to obtain the titanium extraction tailings-based cementitious material. This invention achieves mechanical activation and microscopic homogenization of each material through co-milling. Titanium extraction tailings have potential pozzolanic activity, which, after mechanical activation, allows them to participate more fully in the reaction, forming a geopolymer cementitious phase. The titanium gypsum, after pretreatment, only removes surface free water, maintaining its stable calcium sulfate dihydrate (CaSO4·2H2O) form, avoiding rapid setting caused by the formation of hemihydrate gypsum, ensuring the workability of the filling slurry during pipeline transportation, and preventing pipe blockage. Cement and lime not only provide early strength and an alkaline environment through their own hydration, but their fine particles also further stimulate the physical and chemical properties of other solid waste components during co-milling. Through the above synergistic effects, the components maximize the cementitious potential of the solid waste material.

[0030] Furthermore, the median particle size D of the co-milled mixed powder 50 The particle size is less than 15 μm. The raw titanium extraction tailings contain a large amount of amorphous active substances, primarily composed of active silica and active alumina. Ball milling of the tailings releases more amorphous active components under mechanical force. These components undergo hydration reactions in an alkaline environment, generating large amounts of hydrated calcium silicate (aluminate) and ettringite, thereby further enhancing the strength of the filling material. Furthermore, some of the dihydrate gypsum in the dried titanium gypsum can be converted into hemihydrate gypsum. Hemihydrate gypsum exhibits accelerating properties during hydration, speeding up the reaction rate of the cementitious system and contributing to improved early compressive strength of the filling material after hardening.

[0031] Furthermore, the titanium extraction tailings are measured by dry weight, i.e., after deducting the attached water and crystal water contained therein.

[0032] Furthermore, titanium tailings-based cementitious materials are applied in mine backfill materials, roadbed engineering materials, or building cementitious materials.

[0033] Example 1

[0034] This embodiment provides a method for preparing a titanium-extraction tailings-based whole tailings backfill cementitious material. The material comprises 55.3 wt% titanium-extraction tailings, 25 wt% titanium gypsum, 17 wt% cement, 3.7 wt% lime, and 5.0 wt% composite activator. The composite activator includes: 27 wt% calcium sulfoaluminate cement, 38 wt% aluminum sulfate, 2 wt% calcium formate, 17 wt% sodium silicate, and 16 wt% ferrous sulfate. The materials are co-milled in a ball mill. The median particle size D of the co-milled mixed powder is... 50 With a particle size of less than 15μm, the co-milled mixed powder is homogenized by a powder homogenizer to obtain a titanium-extraction tailings-based cementitious material.

[0035] Example 2

[0036] Unlike Example 1, the total amount of composite activator in this example is 4.8 wt%, including: 19 wt% calcium sulfoaluminate cement, 25 wt% aluminum sulfate, 13 wt% calcium formate, 12 wt% sodium silicate, and 31 wt% ferrous sulfate. The rest is the same as in Example 1 and will not be repeated here.

[0037] Example 3

[0038] Unlike Example 1, the total amount of composite activator in this example is 3.6 wt%, including: 25 wt% calcium sulfoaluminate cement, 17 wt% aluminum sulfate, 16 wt% calcium formate, and 42 wt% ferrous sulfate. The rest is the same as in Example 1 and will not be repeated here.

[0039] Example 4

[0040] Unlike Example 1, the total amount of composite activator in this example is 1.0 wt%, including: 20 wt% calcium sulfoaluminate cement, 35 wt% aluminum sulfate, 15 wt% calcium formate, 10 wt% sodium silicate, and 20 wt% ferrous sulfate. The rest is the same as in Example 1 and will not be repeated here.

[0041] Comparative Example 1

[0042] Unlike Example 1, no composite activator was added in Comparative Example 1.

[0043] The cementitious materials prepared in Examples 1-3 and Comparative Example 1 were tested according to the Cement Mortar Strength Test Method (ISO Method) (GB / T 17671-2021).

[0044] The mass ratio of the mortar is one part cementitious material, three parts Chinese ISO standard sand, and half a part water (water-cement ratio w / c = 0.50). Each batch of material requires 450g ± 2g cementitious material, 1350g ± 5g sand, and 225mL ± 1mL or 225g ± 1g water. Three specimens are formed from one batch of mortar. After the filler slurry has initially set, the surface of the mold is smoothed and numbered, then sealed with plastic wrap and placed in a standard curing room for curing. After final setting, the specimens are demolded and divided into two groups and placed in a standard curing chamber for further curing. Unconfined compressive strength tests should be conducted at the measured ages (3d and 7d). Three parallel samples are tested for each specimen, and the average value is taken.

[0045] Figure 1 The images show electron microscope comparisons of the products obtained in Example 1 and Comparative Example 1, with the left image showing the product obtained in Comparative Example 1 and the right image showing the product obtained in Example 1. Figure 2 This is a comparison chart of thermogravimetric analysis of the products obtained in Example 1 and Comparative Example 1.

[0046] The bonding strength of the cementitious materials prepared in Examples 1-3 and Comparative Example 1 with the specimens prepared with standard sand was tested, and the results are shown in Table 1.

[0047] Table 1. Results of bonding strength tests on specimens prepared in Examples 1-3 and Comparative Example 1.

[0048]

[0049] As shown in Table 1, compared with Comparative Example 1, the uniaxial compressive strength of the cementitious materials prepared in Examples 1 to 3 and the standard sand after being prepared into specimens can reach 132% to 150% of the strength of the specimens prepared with the reference cementitious materials and standard sand at a curing age of 3 days.

[0050] The above embodiments are merely illustrative examples to clearly illustrate the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A composite activator, characterized in that: By mass percentage, it includes the following components: calcium sulfoaluminate cement 19%~27%, aluminum sulfate 17%~38%, calcium formate 2%~16%, sodium silicate 0%~17%, and ferrous sulfate 16%~42%.

2. A titanium-extraction tailings-based cementitious material, employing the composite activator described in claim 1, characterized in that: By mass percentage, it includes the following components: 50%~65% titanium extraction tailings, 18%~25% titanium gypsum, 5%~20% cement, 3%~10% lime, and 1%-5% composite activator.

3. The titanium extraction tailings-based cementitious material according to claim 2, characterized in that: The titanium plaster is titanium plaster with surface free water removed and calcium sulfate dihydrate crystal structure preserved.

4. The titanium extraction tailings-based cementitious material according to claim 2, characterized in that: The cement is P·I 42.5 silicate cement.

5. The method for preparing titanium-extraction tailings-based cementitious material according to any one of claims 2 to 4, characterized in that, Includes the following steps: The cement, lime, titanium extraction tailings, titanium gypsum, and composite activator are placed together in a ball mill for co-milling according to the measured amount; the co-milled mixed powder is then homogenized by a powder homogenizer to obtain the titanium extraction tailings-based cementitious material.

6. The method for preparing the titanium extraction tailings-based cementitious material according to claim 5, characterized in that: The median particle size D of the co-milled mixed powder 50 Less than 15μm.

7. The method for preparing the titanium extraction tailings-based cementitious material according to claim 5, characterized in that: The titanium extraction tailings are measured by dry weight.

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