A composite modified admixture based on low-quality silica fume and lithium slag, and its preparation method and application

Abstract

The present invention discloses a composite modified admixture based on low-quality silica fume and lithium slag, the composition of which comprises, by weight, 20-30 parts of low-quality silica fume, 20-30 parts of lithium slag, 0.5-1 part of a composite dispersant, 0.1-0.3 parts of a grinding aid, and 40-60 parts of water; the composite dispersant comprises an electrostatic potential dispersion component, a suspension stabilization component, and water. The present invention uses low-quality silica fume and lithium slag as the main raw materials, combines the composite dispersant and the grinding aid, and adopts a wet grinding process to prepare a slurry-like composite admixture. This can effectively solve the problems of poor material flowability and large quality fluctuations caused by the high moisture content, low fineness, and high moisture content of powdered lithium slag. At the same time, it solves the technical difficulties existing in the application of silica fume as an ultrafine powder, such as low tank storage utilization rate, easy blockage in pipeline transportation, and poor stirring dispersibility. It can provide an effective way for the resource utilization of low-quality silica fume and lithium slag.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and in particular relates to a composite modified admixture based on low-quality silica fume and lithium slag, and a preparation method and application thereof. Background Art

[0002] With the reduction of energy consumption and production in the coal and steel industries, as well as restrictions on cement production capacity, high-quality, highly reactive industrial solid wastes such as fly ash, slag, and silica fume have gradually become a valuable resource as raw materials for cementitious materials. Unlike highly reactive solid waste resources, low-quality solid waste resources have low activity and poor stability. Their utilization is technically difficult, with poor economic benefits and low resource utilization. They can only be dumped on the surface in large quantities, which not only pollutes the environment but also wastes resources. It is imperative to achieve resource utilization of low-quality solid waste to reduce costs.

[0003] Silica fume is a smelting waste generated during the smelting of industrial silicon or ferrosilicon alloys. Most silica fume is highly active and suitable for large-scale application, but its price is relatively high. A small portion is low-quality silica fume with a low SiO2 content (<85%), low activity, and high water requirement, and is not effectively utilized. However, its low price and potential activity make it highly valuable. As an ultrafine powder, its application in the concrete industry faces technical challenges such as high transportation costs, low tank storage utilization, easy pipeline blockage, and poor mixing and dispersibility.

[0004] As an industrial waste, lithium slag has high SiO2 and Al2O3 content in its chemical composition, exhibiting potential pozzolanic activity and suitable for use as a concrete admixture. However, lithium slag suffers from issues such as high moisture content, high water demand, and low post-processing activity. Furthermore, the powdered lithium slag has poor fluidity in the silo, which can easily cause blockages in the feed stream.

[0005] Therefore, further development of admixtures based on industrial wastes such as low-quality silica fume and lithium slag has important research and application significance. Summary of the Invention

[0006] The main purpose of the present invention is to provide a composite modified admixture of low-quality silica fume and lithium slag, which can effectively improve the quality of silica fume and enhance the activity of lithium slag, and provide an effective way for the resource utilization of low-quality silica fume and lithium slag.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A composite modified admixture based on low-quality silica fume and lithium slag comprises, by weight, 20-30 parts of low-quality silica fume, 20-30 parts of lithium slag, 0.5-1 part of a composite dispersant, 0.1-0.3 part of a grinding aid, and 40-60 parts of water; the composite dispersant comprises an electrostatic potential dispersing component, a suspension stabilizing component, and water.

[0009] According to the above solution, the low-quality silica fume is in the form of gray powder, dense type, with SiO2 content less than 85wt%, activity index less than 105%, and water requirement ratio greater than 120%.

[0010] According to the above scheme, the lithium slag is in powder form, has a moisture content of 15-25%, and a specific surface area greater than 400m 2 / kg, the sum of its SiO2 and Al2O3 mass contents is greater than 80%.

[0011] According to the above scheme, the components and their weight proportions in the composite dispersant include: 20 to 35 parts of electrostatic potential dispersion component, 5 to 15 parts of suspension stabilization component, and 50 to 70 parts of water.

[0012] Furthermore, the electrostatic potential dispersion component has a structural formula as shown in formula (I),

[0013]

[0014] In formula (I), a is an integer of 1 to 5, b is an integer of 10 to 20, c is an integer of 5 to 10, and d is an integer of 10 to 20; the relative molecular weight of the electrostatically dispersed component is 4000 to 6000.

[0015] Furthermore, the suspension stabilizing component comprises bentonite, polyaspartic acid amide and hydroxypropyl methylcellulose ether.

[0016] Furthermore, in the suspension stabilizing component, each component and its weight percentage include: 50-60 parts of bentonite, 20-30 parts of polyaspartic acid amide, and 10-20 parts of hydroxypropyl methylcellulose ether.

[0017] According to the above scheme, the grinding aid comprises diethanol monoisopropanolamine, sodium tripolyphosphate, polyether polyol and water.

[0018] Furthermore, in the grinding aid, the components and their weight proportions include: 20-30 parts of diethanol monoisopropanolamine, 10-20 parts of sodium tripolyphosphate, 5-10 parts of polyether polyol, and 40-65 parts of water.

[0019] The method for preparing the composite modified admixture based on low-quality silica fume and lithium slag comprises the following steps:

[0020] (1) mixing weighed low-quality silica fume, lithium slag, composite dispersant, grinding aid and water to obtain a mixture;

[0021] (2) The obtained mixture is mixed uniformly and ground into fine powder by a wet grinding process to obtain the low-quality silica fume and lithium slag composite modified admixture.

[0022] Furthermore, the wet grinding process has a rotation speed of 2500 to 3000 r / min and a wet grinding time of 10 to 20 min.

[0023] Furthermore, the composite modified admixture is a composite slurry that is uniformly dispersed and stably suspended, has a solid content of 40 to 60%, and a viscosity of 2000 to 5000 mPa·s.

[0024] The present invention also provides an application of the low-quality silica fume modified composite admixture in cement concrete. In this application, the addition amount of the low-quality silica fume modified composite admixture is 10 to 30 wt% of the amount of cementitious material in the cement concrete.

[0025] The principle of the present invention is:

[0026] 1. The present invention uses low-quality silica fume, lithium slag and water as main raw materials, and prepares a highly active slurry composite admixture through a wet grinding process under the action of a composite dispersant and a grinding aid. The wet grinding process introduces a composite dispersant during the grinding process, wherein the polymer molecules of the electrostatically dispersed component carry a large number of plasma functional groups such as carboxyl (-COOH), sulfonic acid (-SO3H), and acetamide (-CONH2). During the wet grinding process, the ionic groups ionize quickly and tightly adsorb onto the surface of the silica fume and lithium slag particles, forming a stable double layer to generate electrostatic repulsion, which inhibits the agglomeration and flocculation of the slurry during the wet grinding process and can effectively improve the dispersibility of the particles; in addition, the polymer of the electrostatically dispersed component has a larger molecular weight and a longer chain, which can promote the silica fume and lithium slag particles to be more firmly adsorbed on their components or interfaces, forming a stable composite structure, and effectively improving the stability of the slurry system.

[0027] 2. The suspension stabilizing component of the present invention adopts an inorganic-organic composite method, utilizing the water absorption expansion and thixotropic viscosity-increasing effect of the inorganic bentonite to play a role in assisting suspension. At the same time, the introduced organic polymers polyaspartic acid amide and hydroxypropyl methylcellulose ether have a large molecular weight, a complex molecular structure and rich functional groups, which can form a protective layer around the silica fume and lithium slag particles, increase the steric hindrance between the particles, and further improve the suspension stability.

[0028] 3. The present invention performs wet grinding and refining treatment on silica fume and lithium slag to obtain silica fume with better dispersion effect and lithium slag particles with a particle size smaller than that of conventional grinding process, which is beneficial to the rapid hydrolysis of SiO2 in silica fume and the secondary reaction of active silica and aluminum in lithium slag with Ca(OH)2 provided in the cement hydration process, thereby generating more hydration products and effectively improving the strength.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1) To address the problems of low activity, high water demand and poor dispersibility of low-quality silica fume, the present invention adopts a wet grinding process and incorporates a composite dispersant and a grinding aid, which greatly improves the dispersion performance of the silica fume and enhances the activity of the low-quality silica fume. At the same time, the electrostatic potential dispersion-anti-sedimentation effect is utilized to inhibit the agglomeration and flocculation of the slurry during the wet grinding process, effectively improving the dispersibility and stability of the powder particles, and ensuring the performance of the low-quality silica fume wet grinding admixture.

[0031] 2. The present invention uses low-quality silica fume and lithium slag as main raw materials, combines composite dispersants and grinding aids, and adopts wet grinding process to prepare slurry composite admixture, which can effectively solve the problems of poor material fluidity and large quality fluctuation caused by high moisture content, low fineness and high moisture content of powdered lithium slag. At the same time, it also solves the technical difficulties of low tank storage utilization rate, easy blockage in pipeline transportation, poor stirring and dispersibility of silica fume when used as ultrafine powder.

[0032] 3. The wet-ground composite admixture of the present invention can replace 10 to 30% of cementitious materials, providing a new direction for the resource utilization of low-quality silica fume and lithium slag, greatly improving their resource utilization rate, and reducing the amount of cementitious materials used, which can effectively reduce the production cost of cement-based materials. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] Specific embodiments provide a composite modified admixture based on low-quality silica fume and lithium slag, the composition of which is as follows in parts by weight: 20-30 parts of low-quality silica fume, 20-30 parts of lithium slag, 0.5-1 part of composite dispersant, 0.1-0.3 part of grinding aid, and 40-60 parts of water.

[0035] Specifically, the SiO2 content in low-quality silica fume is less than 85%, its activity index is less than 105%, and its water requirement ratio is greater than 120%; the lithium slag is powdery, with a moisture content of 15-25% and a specific surface area greater than 400m 2 / kg, the sum of its SiO2 and Al2O3 mass contents is greater than 80%.

[0036] The composite dispersant is prepared by mixing 20 to 35 parts by mass of an electrostatically dispersible component, 5 to 15 parts by mass of a suspension stabilizing component, and 50 to 70 parts by mass of water; the electrostatically dispersible component has a structural formula as shown in formula (I), wherein a is an integer of 1 to 5, b is an integer of 10 to 20, c is an integer of 5 to 10, and d is an integer of 10 to 20;

[0037]

[0038] The preparation method of the electrostatic potential dispersing component used in the embodiment is as follows: under a nitrogen atmosphere, maleic anhydride is added to water, stirred and dissolved, and then the temperature is raised to 50-70°C, and then a mixed aqueous solution formed by methacrylic acid, acrylamide, and methacrylic acid and an aqueous solution of azobisisobutyronitrile (initiator) are added dropwise. After reacting for 2-3 hours, the temperature is cooled to room temperature. The molar ratio of the maleic anhydride, methacrylic acid, acrylamide, and methacrylic acid is 1:0.6:0.4:0.2, and the initiator is 0.05% of the molar amount of maleic anhydride. The molecular weight of the obtained electrostatic potential dispersing component is 4800.

[0039] The suspension stabilizing component is prepared by mixing 60 parts of bentonite, 30 parts of polyaspartic acid amide (relative molecular weight 5300) and 10 parts of hydroxypropyl methylcellulose ether (relative molecular weight 13300) by mass.

[0040] The grinding aid is prepared by mixing 20-30 parts of diethanol monoisopropanolamine, 10-20 parts of sodium tripolyphosphate, 5-10 parts of polyether polyol and 40-65 parts of water in parts by mass.

[0041] In the following examples, the preparation method of the low-quality silica fume modified composite admixture includes the following steps:

[0042] (1) mixing weighed low-quality silica fume, lithium slag, composite dispersant, grinding aid and water to obtain a mixed material A;

[0043] (2) The mixed material A is ground and mixed uniformly by a wet grinding process (3000 r / min, 10 min), thereby obtaining a low-quality silica fume modified composite admixture, which is a composite slurry with uniform dispersion and stable suspension, a solid content of 40-60%, and a viscosity of 2000-5000 mPa·s.

[0044] A specific embodiment also provides an application of the above-mentioned low-quality silica fume modified composite admixture in cement concrete. In this application, the low-quality silica fume modified composite admixture replaces cement or fly ash, mineral powder and other admixtures to improve the working performance of concrete and enhance the strength of concrete.

[0045] Example 1

[0046] A low-quality silica fume and lithium slag composite modified admixture, the composition of which is as follows in parts by weight: 20 parts of low-quality silica fume, 20 parts of lithium slag, 0.5 parts of composite dispersant, 0.1 parts of grinding aid, and 60 parts of water;

[0047] The low-quality silica fume used is gray powder, dense type, SiO2 content 81%, activity index 102%, water requirement ratio 123%; the lithium slag is powder, moisture content 21%, specific surface area 410m2 / kg, the sum of the mass contents of SiO2 and Al2O3 is 84%;

[0048] The composite dispersant used is obtained by mixing 25 parts of electrostatic potential dispersing component, 10 parts of suspension stabilizing component and 65 parts of water by weight;

[0049] The grinding aid used is prepared by mixing 20 parts of diethanol monoisopropanolamine, 10 parts of sodium tripolyphosphate, 5 parts of polyether polyol (relative molecular weight 2300) and 65 parts of water in parts by mass.

[0050] Example 2

[0051] A low-quality silica fume and lithium slag composite modified admixture, the composition of which is as follows in parts by weight: 25 parts of low-quality silica fume, 25 parts of lithium slag, 0.5 parts of composite dispersant, 0.1 parts of grinding aid, and 50 parts of water;

[0052] The low-quality silica fume used is gray powder, dense type, SiO2 content 81%, activity index 102%, water requirement ratio 123%; the lithium slag is powder, moisture content 21%, specific surface area 410m 2 / kg, the sum of the mass contents of SiO2 and Al2O3 is 84%;

[0053] The composite dispersant used is obtained by mixing 30 parts of electrostatic potential dispersing component, 10 parts of suspension stabilizing component and 60 parts of water in parts by mass;

[0054] The grinding aid used is prepared by mixing 20 parts of diethanol monoisopropanolamine, 10 parts of sodium tripolyphosphate, 10 parts of polyether polyol (relative molecular weight 2300) and 60 parts of water in parts by mass.

[0055] Example 3

[0056] A low-quality silica fume and lithium slag composite modified admixture, the composition of which is as follows in parts by weight: 30 parts of low-quality silica fume, 20 parts of lithium slag, 1 part of composite dispersant, 0.2 parts of grinding aid, and 50 parts of water;

[0057] The low-quality silica fume used is gray powder, dense type, SiO2 content 81%, activity index 102%, water requirement ratio 123%; the lithium slag is powder, moisture content 21%, specific surface area 410m 2 / kg, the sum of the mass contents of SiO2 and Al2O3 is 84%;

[0058] The composite dispersant used is obtained by mixing 25 parts of electrostatic potential dispersing component, 15 parts of suspension stabilizing component and 60 parts of water in parts by mass;

[0059] The grinding aid used is prepared by mixing 30 parts of diethanol monoisopropanolamine, 10 parts of sodium tripolyphosphate, 5 parts of polyether polyol (relative molecular weight 2300) and 55 parts of water in parts by mass.

[0060] Example 4

[0061] A low-quality silica fume and lithium slag composite modified admixture, the composition of which is as follows in parts by weight: 30 parts of low-quality silica fume, 30 parts of lithium slag, 1 part of composite dispersant, 0.3 parts of grinding aid, and 40 parts of water;

[0062] The low-quality silica fume used is gray powder, dense type, SiO2 content 81%, activity index 102%, water requirement ratio 123%; the lithium slag is powder, moisture content 21%, specific surface area 410m 2 / kg, the sum of the mass contents of SiO2 and Al2O3 is 84%;

[0063] The composite dispersant used is obtained by mixing 30 parts of electrostatic potential dispersing component, 15 parts of suspension stabilizing component and 55 parts of water by weight;

[0064] The grinding aid used is prepared by mixing 25 parts of diethanol monoisopropanolamine, 15 parts of sodium tripolyphosphate, 10 parts of polyether polyol (relative molecular weight 2300) and 55 parts of water in parts by mass.

[0065] Comparative Example 1

[0066] A low-quality silica fume and lithium slag composite modified admixture, the preparation method of which is roughly the same as that of Example 1, except that its composition is as follows by weight: 20 parts of low-quality silica fume, 20 parts of lithium slag, 0.1 parts of grinding aid, 60 parts of water, and no composite dispersant is added.

[0067] Comparative Example 2

[0068] A low-quality silica fume and lithium slag composite modified admixture, the preparation method of which is roughly the same as that of Example 1, except that its composition is as follows by weight: 20 parts of low-quality silica fume, 20 parts of lithium slag, 0.5 parts of dispersant, 60 parts of water, and no grinding aid is added.

[0069] Comparative Example 3

[0070] A low-quality silica fume and lithium slag composite modified admixture, the preparation method of which is roughly the same as that of Example 1, except that its composition by weight is as follows: the low-quality silica fume is replaced by normal silica fume (SiO2 content 91%, activity index 125%, water requirement ratio 106%), and no dispersant and grinding aid are added.

[0071] Comparative Example 4

[0072] A low-quality silica fume and lithium slag composite modified admixture, the preparation method of which is roughly the same as that of Example 1, except that the dispersant used is obtained by mixing 15 parts of electrostatic potential dispersion component, 20 parts of suspension stabilization component and 65 parts of water by mass.

[0073] Comparative Example 5

[0074] A low-quality silica fume and lithium slag composite modified admixture, the preparation method of which is roughly the same as that of Example 1, except that no acrylamide is added during the preparation of the electrostatic potential dispersing component, and the obtained electrostatic potential dispersing component is then compounded with polyacrylamide (relative molecular weight 4800) in a mass ratio of 5:1 before use.

[0075] The slurry fluidity and mortar activity of the low-quality silica fume modified composite admixtures prepared in Examples 1 to 4 and Comparative Examples 1 to 5 when applied to cement are shown in Table 1.

[0076] Table 1 Performance test results of composite admixtures obtained from Examples 1 to 4 and Comparative Examples 1 to 5

[0077]

[0078]

[0079] As shown in Table 2, when 30% of cement is replaced by an equal mass of low-quality silica fume modified composite admixture, Example 2 has the best slurry fluidity performance, followed by Examples 1, 3, and 4, then Comparative Examples 5 and 4, and finally Comparative Examples 1 to 3; in terms of 28d activity, Example 4 is the best, followed by Examples 3, 2, and 1, then Comparative Examples 5 and 4, and finally Comparative Examples 1, 3, and 2 in descending order. By comparison, it can be seen that the low-quality silica fume modified composite admixture provided by the present invention can improve the working performance of the cement slurry by adjusting the ratio of low-quality silica fume, lithium slag, dispersant, and grinding aid, while also significantly improving the activity of the low-quality silica fume modified composite admixture.

[0080] The low-quality silica fume-modified composite admixture prepared in Example 3 was used in trial concrete mixes according to the mix proportions in Table 2. These concretes are numbered Application Examples 1 to 3, depending on the proportion of the low-quality silica fume-modified composite admixture added. Because the low-quality silica fume-modified composite admixture in Example 3 had a moisture content of 50%, to maintain a constant water-binder ratio, the water used in the mix proportions was the actual amount used after deducting the water content of the low-quality silica fume-modified composite admixture. The workability and compressive strength of the trial concretes are shown in Table 3.

[0081] Table 2 Concrete formula

[0082]

[0083] Table 3 Concrete performance test results

[0084]

[0085]

[0086] As can be seen from Table 3, the low-quality silica fume modified composite admixture prepared by the present invention is used to partially replace cement or fly ash in concrete. In terms of concrete performance, the prepared concrete has good workability, and the initial slump expansion and 2h loss are significantly improved compared to the pure cement and fly ash baseline groups. The initial strength is significantly higher than that of the fly ash group, and the later strength development is stable. The 60d strength is higher than that of the pure cement baseline group 1. From the perspective of cost and environmental protection, at the same strength grade, due to the addition of low-quality silica fume modified composite admixture, the price is lower, and the cost per cubic meter of concrete is lower. At the same time, it provides a solution for the efficient resource utilization of low-quality silica fume and lithium slag, with better green environmental protection effects.

[0087] Those skilled in the art will readily be able to make improvements and modifications to the present invention without departing from the techniques of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. The present invention is not limited to the above-described embodiments, and any changes that do not depart from the scope of the claims of the present invention are encompassed by the scope of protection.

Claims

1. A composite modified admixture based on low-quality silica fume and lithium slag, characterized in that: The composition includes, by weight, 20-30 parts of low-quality silica fume, 20-30 parts of lithium slag, 0.5-1 part of a composite dispersant, 0.1-0.3 parts of a grinding aid, and 40-60 parts of water; the composite dispersant includes an electrostatic potential dispersing component, a suspension stabilizing component, and water; The low-quality silica fume has a SiO2 content of less than 85wt%, an activity index of less than 105%, and a water requirement ratio of greater than 120%; The composite dispersant comprises the following components and their weight proportions: 20 to 35 parts of an electrostatic dispersion component, 5 to 15 parts of a suspension stabilization component, and 50 to 70 parts of water; The electrostatic potential dispersion component has a structural formula as shown in formula (I), Ⅰ； In formula (I), a is an integer of 1 to 5, b is an integer of 10 to 20, c is an integer of 5 to 10, and d is an integer of 10 to 20; the relative molecular weight of the electrostatically dispersed component is 4000 to 6000; The suspension stabilizing component comprises bentonite, polyaspartic acid amide and hydroxypropyl methylcellulose ether.

2. The composite modified admixture according to claim 1, characterized in that: The lithium slag is in powder form, has a moisture content of 15-25%, and a specific surface area greater than 400m 2 / kg, the sum of its SiO2 and Al2O3 mass contents is greater than 80%.

3. The composite modified admixture according to claim 1, characterized in that: The grinding aid comprises diethanol monoisopropanolamine, sodium tripolyphosphate, polyether polyol and water.

4. The method for preparing the composite modified admixture based on low-quality silica fume and lithium slag according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Mixing weighed low-quality silica fume, lithium slag, composite dispersant, grinding aid and water to obtain a mixture; (2) The obtained mixture is mixed uniformly and ground into fine powder by a wet grinding process, thereby obtaining the low-quality silica fume and lithium slag composite modified admixture.

5. Application of low-quality silica fume modified composite admixture in cement concrete, characterized in that The addition amount of the low-quality silica fume modified composite admixture is 10-30wt% of the cementitious material amount of the cement concrete.

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