A lithium slag non-autoclaved aerated concrete and its preparation method

Abstract

This invention provides a lithium slag-free autoclaved aerated concrete and its preparation method. The lithium slag-free autoclaved aerated concrete is made from the following raw materials in parts by weight: 75-90 parts lithium slag, 10-25 parts cement, 20-35 parts water glass solution, 0.5-0.9 parts physical foaming agent, 0.1-0.4 parts water-reducing agent, 0.02-0.2 parts polyacrylamide, and an appropriate amount of water. The physical foaming agent, water glass solution, and polyacrylamide are mixed to prepare foam, which is then added to a slurry solution obtained by mixing the other raw materials. The mixture is stirred evenly to obtain a finished slurry. The finished slurry is then cast, molded, and cured to obtain the lithium slag-free autoclaved aerated concrete. The water-to-solid ratio of the finished slurry is 0.3-0.35. This method can achieve efficient utilization of lithium slag and exhibits good mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a lithium slag non-autoclaved aerated concrete and its preparation method. Background Technology

[0002] Lithium slag is an industrial solid waste generated during the lithium extraction process from lithium ore. It possesses certain pozzolanic characteristics and can partially replace cement, reducing CO2 emissions and heat of hydration. However, the Al2O3 and SiO2 present in lithium slag have relatively low activity, significantly reducing the early mechanical properties of lithium slag-cement composites and limiting its large-scale utilization in building materials. Its overall resource utilization rate is less than 20%. Comprehensive utilization of lithium slag is of great significance to the economy, resources, and environment. Sodium silicate solution, also known as water glass, can improve the strength of pozzolanic cementitious materials such as lithium slag and fly ash, accelerating the hydration reaction and improving early strength. Therefore, lithium slag activated by water glass can serve as a cement substitute with better cementitious properties.

[0003] Autoclaved aerated concrete (AAC) possesses excellent properties such as lightweight, thermal insulation, earthquake resistance, and fire resistance, and is widely used as a new type of energy-saving building wall material. Current research has explored using lithium slag to replace part of the cement in non-autoclaved aerated concrete (AAC). However, issues such as the low activity of lithium slag and its high water requirement lead to problems like low lithium slag content, poor concrete performance (e.g., low strength), or long curing times resulting in low industrial production turnover efficiency. Currently, to address the low activity of lithium slag, most methods involve activating it with water glass, but these methods are limited in scope and effectiveness. Furthermore, the high water requirement of lithium slag remains a pressing issue. Summary of the Invention

[0004] To address the problems existing in the background technology, the present invention provides lithium slag non-autoclaved aerated concrete and its preparation method. The lithium slag non-autoclaved aerated concrete contains a large amount of lithium slag, which can realize the efficient utilization of lithium slag, and exhibits good mechanical properties, drying shrinkage properties and thermal insulation properties. Moreover, its preparation method is simple, efficient and low-cost, and has significant economic and environmental benefits.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] In a first aspect, the present invention provides a lithium slag non-autoclaved aerated concrete, which is made from raw materials comprising the following parts by weight: 75-90 parts lithium slag, 10-25 parts cement, 20-35 parts water glass solution, 0.5-0.9 parts physical foaming agent, 0.1-0.4 parts water-reducing agent, 0.02-0.2 parts polyacrylamide, and an appropriate amount of water.

[0007] The physical foaming agent, water glass solution and polyacrylamide are mixed to prepare foam, which is then added to the slurry solution obtained by mixing other raw materials. The mixture is stirred evenly to obtain the finished slurry. The finished slurry is then cast, molded and cured to obtain the lithium slag non-autoclaved aerated concrete. The water-to-solid ratio of the finished slurry is 0.3~0.35.

[0008] According to the above scheme, the specific surface area of ​​the lithium slag is 300~400 m². 2 / kg, with a total content of SiO2 and Al2O3 ≥55%.

[0009] According to the above scheme, the modulus of the water glass solution is 1.0~1.8, its alkali content is 4%~6%, and its solid content is 35%.

[0010] According to the above scheme, the water-reducing agent is a carboxylic acid water-reducing agent with a water-reducing efficiency of 30%~50%.

[0011] According to the above scheme, the physical foaming agent is a protein-based foaming agent with a foaming ratio of 25 to 50 times.

[0012] Secondly, the present invention provides a method for preparing the above-mentioned lithium slag non-autoclaved aerated concrete, comprising the following steps:

[0013] S1. Preparation of slurry solution: Prepare the slurry solution by mixing lithium slag, cement, water and water-reducing agent evenly according to the formula;

[0014] S2. Foam preparation: After mixing the weighed physical foaming agent, water glass solution and polyacrylamide according to the formula, foam them into foam through a foaming machine;

[0015] S3. Preparation of finished slurry: Add the foam prepared in S2 to the slurry solution prepared in S1 and stir evenly to obtain the finished slurry;

[0016] S4. Casting and Curing: The finished slurry is poured into the mold to form the shape, and the mold is placed in the curing chamber for curing.

[0017] S5. Microwave curing: After the green body is demolded and cut, it is placed in a microwave curing mold for curing to obtain the lithium slag non-autoclaved aerated concrete.

[0018] According to the above scheme, the stirring time in step S1 is 3~5 min and the stirring rate is 300~600 r / min, and the stirring time in step S3 is 1~2 min and the stirring rate is 450~750 r / min.

[0019] According to the above scheme, the foaming time of the foaming agent in step S2 is 5~7 minutes, and the stirring speed is 600~800 r / min.

[0020] According to the above plan, the temperature for static curing in step S4 is 30~50℃, and the time is 2~3h.

[0021] According to the above scheme, the temperature for microwave curing in step S5 is 30~50℃, the microwave power is 200~450W, the relative humidity is 50~70%, and the time is 8~12h.

[0022] Microwave curing can promote the decomposition of mineral phases in lithium slag through physical modification, accelerate the transformation of silicon-aluminum phases to amorphous forms, and improve the hydration reaction activity of lithium slag. It can also depolymerize polysilicate particles formed by water glass condensation, eliminating the aging phenomenon of water glass. At the same time, microwave curing has high heating efficiency, uniform heating, easy control, energy saving and environmental protection, and can significantly shorten the curing time.

[0023] The beneficial effects of this invention are:

[0024] In this invention, lithium slag is chemically modified by alkali activation using water glass, and then applied to the preparation of aerated concrete. Water glass acts as both an activator and a reactant. The Na₂O in the water glass can activate the hydration activity of the lithium slag itself, causing the Si-O and Al-O bonds in the slag to break, promoting the dissolution of elements such as Si and Al. It readily reacts with Ca(OH)₂ to form CSH gel. The hydrolysis products of water glass can also react with calcium and aluminum ions produced during cement hydration to form hydrated calcium silicate or calcium aluminate, thus accelerating the hydration and setting of cement. The Al dissolved from the lithium slag... 3+ and Si 4+ Deeply penetrating near the water glass core, it undergoes a polymerization reaction with the SiO2 in the core. The polymerization products of adjacent cores overlap to form a whole, establishing a network structure to improve the structural strength of the green body. This solves the problems of long setting time of the adhesive, slow hardening of the aerated concrete green body, and low early strength caused by the large-scale use of lithium slag. It can be used on a large scale to prepare autoclaved aerated concrete without autoclaving, improving the resource utilization rate of lithium slag and greatly reducing the environmental harm of lithium slag.

[0025] Specifically, this invention involves adding a water glass solution to a physical foaming agent and polyacrylamide for foaming and stirring. This allows the water glass solution to be uniformly dispersed in the aerated concrete block. The polyacrylamide acts as a foam stabilizer, making the formed foam more stable, and also slows down the aging of the water glass, enhancing its alkali-activated activity against lithium slag. When the foam formed by the physical foaming agent, water glass solution, and polyacrylamide is added to a slurry containing lithium slag, the water glass can better contact the lithium slag, modifying the lithium slag through alkali-activated chemical modification. Simultaneously, Ca... 2+Cationic polyacrylamide improves the hydrophobicity of lithium slag surface by compressing the double electric layer of particles to reduce electrostatic repulsion between particles. It effectively reduces the water absorption of lithium slag while activating it, solving the problems of low activity of lithium slag and high water demand caused by large-scale use of lithium slag. It improves the activity of lithium slag while reducing the water-to-solid ratio, thereby improving the mechanical properties, drying shrinkage properties and thermal insulation properties of lithium slag-free autoclaved aerated concrete obtained by large-scale use of lithium slag. It also accelerates the hardening of the green body, shortens the static curing time, and improves the industrial turnover efficiency, which has significant environmental and economic benefits. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the production process of lithium slag autoclaved aerated concrete according to the present invention. Detailed Implementation

[0027] The principles and features of the present invention are described below with reference to the accompanying drawings and specific embodiments. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0028] This invention provides a lithium slag non-autoclaved aerated concrete, which is made from the following raw materials in parts by weight: 75-90 parts lithium slag, 10-25 parts cement, 20-35 parts water glass solution, 0.5-0.9 parts physical foaming agent, 0.1-0.4 parts water-reducing agent, 0.02-0.2 parts polyacrylamide, and appropriate amount of water. The physical foaming agent, water glass solution and polyacrylamide are mixed to prepare foam, which is then added to the slurry solution obtained by mixing the other raw materials. The mixture is stirred evenly to obtain the finished slurry. The finished slurry is then cast, molded and cured to obtain the lithium slag non-autoclaved aerated concrete. The water-to-solid ratio of the finished slurry is 0.3-0.35.

[0029] In some specific embodiments, the specific surface area of ​​the lithium slag is 300~400m². 2 / kg, with a total content of SiO2 and Al2O3 ≥55%.

[0030] In some specific embodiments, the modulus of the water glass solution is 1.0 to 1.8, its alkali content is 4% to 6%, and its solid content is 30% to 40%.

[0031] In some specific embodiments, the water-reducing agent is a carboxylic acid-based water-reducing agent with a water-reducing efficiency of 30% to 50%.

[0032] In some specific embodiments, the physical foaming agent is a protein-based foaming agent with a foaming ratio of 30 to 60 times.

[0033] This invention also provides a method for preparing the above-mentioned lithium slag non-autoclaved concrete, the production process flow diagram of which is shown below. Figure 1 As shown, it includes the following steps:

[0034] S1. Preparation of slurry solution: Prepare the slurry solution by mixing lithium slag, cement, water and water-reducing agent evenly according to the formula;

[0035] S2. Foam preparation: Mix the weighed physical foaming agent, water glass and polyacrylamide according to the formula, and then foam them into foam through a foaming machine;

[0036] S3. Preparation of finished slurry: Add the foam prepared in S2 to the slurry solution prepared in S1 and stir evenly to obtain the finished slurry;

[0037] S4. Casting and Curing: Pour the finished slurry into the mold to form the shape, and place the mold in the curing chamber for curing.

[0038] S5. Microwave curing: After the green body is demolded and cut, it is placed in a microwave curing mold for curing to obtain the lithium slag non-autoclaved aerated concrete.

[0039] Specifically, in step S2, the physical foaming agent and water glass solution can be stirred evenly first, and then polyacrylamide can be added and stirred evenly, and then foamed by a foaming machine.

[0040] In some specific embodiments, the stirring time in step S1 is 3~5 min and the stirring rate is 300~600 r / min, and the stirring time in step S3 is 1~2 min and the stirring rate is 450~750 r / min.

[0041] In some specific embodiments, the foaming time of the foaming agent in step S2 is 5~7 minutes, and the stirring rate is 600~800 r / min.

[0042] In some specific implementations, the static curing temperature in step S4 is 30~50℃ and the time is 2~3h.

[0043] In some specific implementations, the temperature for microwave curing in step S5 is 30~50℃, the microwave power is 200~450W, the relative humidity is 50~70%, and the time is 8~12h.

[0044] In the following examples and comparative examples, the cement, lithium slag, and water-reducing agent used were provided by Huaxin Cement Co., Ltd., wherein the P.O42.5 silicate cement has a specific surface area of ​​350 m². 2 / kg; The main mineral composition and their mass percentage in lithium slag are: CaO 4.5%, SiO2 48.3%, Al2O3 16.4%, MgO 1.3%, Fe2O3 0.7%, SO3 3.8%, K2O 8.2%, Na2O 6.9%, and the specific surface area after ball milling is 330m². 2 / kg; the water glass solution used was prepared in the laboratory, with a modulus of 1.4, an alkali content of 5%, and a solid content of 35%; the water-reducing agent had a water-reducing efficiency of 30%; the physical foaming agent used was a protein-based concrete foaming agent, with a 1-hour settling distance of 6.5 mm, a 1-hour water bleeding volume of 78.5 ml, and a foaming ratio of 40 times; the polyacrylamide was provided by Shanghai Huiye Chemical Technology Co., Ltd., with a solid content ≥99%; the microwave reactor was modified from a Galanz P70F20CL microwave heater, with a rated power of 700W.

[0045] Example 1

[0046] This embodiment prepares a lithium slag non-autoclaved aerated concrete with the following raw materials: 90 parts lithium slag, 10 parts P.O42.5 cement, 0.3 parts water-reducing agent, 0.7 parts physical foaming agent, 0.1 parts polyacrylamide, 30 parts water glass solution, and a water-to-solid ratio of 0.32.

[0047] The preparation method is as follows:

[0048] 1) Preparation of slurry solution: 10 parts of P.O42.5 cement, 90 parts of lithium slag, 0.3 parts of water-reducing agent and water are placed in a forced mixer and stirred at 500 r / min for 240 s to obtain slurry solution;

[0049] 2) Foam preparation with foaming agent: 0.7 parts of physical foaming agent were foamed 50 times, and 0.1 parts of polyacrylamide and 30 parts of water glass solution were added during the foaming process. The mixture was stirred at 700 r / min for 360 s to prepare foam.

[0050] 3) Preparation of finished slurry: Weigh the foam according to the ratio and add it to the slurry solution. Stir at a speed of 650 r / min for 1 min until the mixture is uniform to obtain the finished slurry.

[0051] 4) Static curing: The finished slurry is poured into the mold frame and statically cured at 40℃ for 3 hours before demolding and cutting;

[0052] 5) Microwave curing: After demolding the blocks cured in step 4), place them in a microwave reactor, control the microwave power to be 280W, the curing temperature to be 40℃, the relative humidity to be 60%, and the time to be 10h.

[0053] After the above steps are completed, lithium slag non-autoclaved aerated concrete blocks can be obtained.

[0054] Example 2

[0055] The difference between this embodiment and Embodiment 1 is as follows: the raw materials are as follows: 80 parts lithium slag, 20 parts P.O42.5 cement, 0.2 parts water-reducing agent, 0.6 parts physical foaming agent, 0.1 parts polyacrylamide, 27 parts water glass solution, and water-to-solid ratio of 0.31; the static curing time is 2.5 hours, and all other aspects are the same as in Embodiment 1. The product number obtained is #2.

[0056] Example 3

[0057] The difference between this embodiment and Embodiment 1 is that the raw materials are as follows: 85 parts lithium slag, 15 parts P.O42.5 cement, 0.2 parts water-reducing agent, 0.6 parts physical foaming agent, 0.1 parts polyacrylamide, 32 parts water glass solution, and water-to-solid ratio of 0.32; all other aspects are the same as in Embodiment 1, and the product number obtained is #3.

[0058] Comparative Example 1

[0059] The difference between this comparative example and Example 1 is that the water glass solution was directly added to the slurry solution for mixing, and then foaming agent and polyacrylamide were added to make foam; everything else was the same as in Example 1, and the product number obtained was #4.

[0060] Comparative Example 2

[0061] The difference between this comparative example and Example 1 is that no polyacrylamide was added, and the water-to-solid ratio was 0.47; all other aspects were the same as in Example 1, the static curing time was 4.5 hours, and the product number obtained was #5.

[0062] Comparative Example 3

[0063] The difference between this comparative example and Example 1 is that: no polyacrylamide is added, the water-to-solid ratio is 0.47, the water glass solution is directly added to the slurry solution for mixing, and then foaming agent is added to make foam. The static curing time is 5 hours. Everything else is the same as in Example 1. The product number obtained is #6.

[0064] Comparative Example 4

[0065] The difference between this comparative example and Example 1 is that natural curing is used instead of microwave curing, and the curing time is increased from 10 hours to 28 days. All other aspects are the same as in Example 1, and the product number obtained is #7.

[0066] The performance of the aerated concrete prepared in the above examples and comparative examples was tested according to the standard GB / T11969-2008, and the results are shown in Table 1:

[0067] Table 1

[0068]

[0069] Compared with Comparative Examples 1-4, the mechanical properties, drying shrinkage properties, and thermal conductivity of the lithium slag non-autoclaved aerated concrete obtained in Examples 1-4 of this invention are significantly improved. This is because the water glass solution is mixed with a foaming agent and a foam stabilizer to form foam, which is then added to a slurry containing a large amount of lithium slag. Combined with a specific foam stabilizer, polyacrylamide, the large-scale industrial application of lithium slag in aerated concrete is realized, resulting in a non-autoclaved aerated concrete product with optimal performance.

[0070] The comparison of the results of Example 1 and Comparative Example 1 (water glass solution directly added to the slurry) shows that: when water glass is mixed with foaming agent and foam stabilizer and then added to the slurry, the water glass is more evenly dispersed in the slurry, and the foam stabilizer polyacrylamide modifies the water glass and delays its aging, resulting in a better modification effect on lithium slag. Therefore, it further improves the compressive strength, splitting tensile strength, thermal conductivity and drying shrinkage performance of lithium slag autoclaved aerated concrete.

[0071] The results of Example 1, Comparative Example 2 (no polyacrylamide added, water glass and physical foaming agent mixed for foaming) and Comparative Example 3 (no polyacrylamide added, water glass directly added to the slurry) show that: on the one hand, polyacrylamide can enhance the activity of water glass, thereby improving its effect on lithium slag modification; on the other hand, it can reduce the water-solid ratio of the concrete system, improve the performance of concrete and shorten the static curing time.

[0072] In summary, the method of incorporating water glass (whether it is mixed with foaming agent and foam stabilizer and then added to the slurry or added directly to the slurry) and the selection of a specific foam stabilizer, polyacrylamide, are two key technical aspects of lithium slag-free autoclaved aerated concrete (AAC). Adding water glass to the foaming agent creates foam that is more evenly dispersed in the slurry, resulting in better modification of the lithium slag. This can further improve the compressive strength, splitting tensile strength, thermal conductivity, and drying shrinkage performance of AAC. Incorporating polyacrylamide can effectively reduce the water absorption of lithium slag, lower the water-to-solid ratio, significantly shorten the static curing time, and improve the turnover efficiency of industrial production. It can also improve the compressive strength, splitting tensile strength, thermal conductivity, and drying shrinkage performance of AAC. Together, these two methods enhance the mechanical properties, shrinkage performance, and thermal insulation performance of the resulting AAC.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A lithium slag non-autoclaved aerated concrete, characterized in that, It is made from the following raw materials in parts by weight: 75-90 parts lithium slag, 10-25 parts cement, 20-35 parts water glass solution, 0.5-0.9 parts physical foaming agent, 0.1-0.4 parts water-reducing agent, 0.02-0.2 parts polyacrylamide, and appropriate amount of water; The physical foaming agent, water glass solution and polyacrylamide are mixed to prepare foam, which is then added to the slurry solution obtained by mixing other raw materials. The mixture is stirred evenly to obtain the finished slurry. The finished slurry is then cast, molded and cured to obtain the lithium slag non-autoclaved aerated concrete. The water-to-solid ratio of the finished slurry is 0.3~0.

35.

2. The lithium slag non-autoclaved aerated concrete according to claim 1, characterized in that, The specific surface area of ​​the lithium slag is 300~400 m². 2 / kg, with a total content of SiO2 and Al2O3 ≥55%.

3. The lithium slag non-autoclaved aerated concrete according to claim 1, characterized in that, The water glass solution has a modulus of 1.0 to 1.8, an alkali content of 4% to 6%, and a solid content of 30% to 40%.

4. The lithium slag non-autoclaved aerated concrete according to claim 1, characterized in that, The water-reducing agent is a carboxylic acid-based water-reducing agent with a water-reducing efficiency of 30% to 50%.

5. The lithium slag non-autoclaved aerated concrete according to claim 1, characterized in that, The physical foaming agent is a protein-based foaming agent with a foaming ratio of 30 to 60 times.

6. The method for preparing lithium slag non-autoclaved aerated concrete according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Preparation of slurry solution: Prepare the slurry solution by mixing lithium slag, cement, water and water-reducing agent evenly according to the formula; S2. Foam preparation: Mix the weighed physical foaming agent, water glass solution and polyacrylamide according to the formula, and then foam them to prepare foam. S3. Preparation of finished slurry: Add the foam prepared in S2 to the slurry solution prepared in S1 and stir evenly to obtain the finished slurry; S4. Casting and Curing: Pour the finished slurry into the mold to form the shape, and place the mold in the curing chamber for curing. S5. Microwave curing: After the green body is demolded and cut, it is placed in a microwave curing mold for curing to obtain the lithium slag non-autoclaved aerated concrete.

7. The method for preparing lithium slag non-autoclaved aerated concrete according to claim 6, characterized in that, In step S1, the stirring time is 3-5 minutes and the stirring rate is 300-600 r / min. In step S3, the stirring time is 1-2 minutes and the stirring rate is 450-750 r / min.

8. The method for preparing lithium slag non-autoclaved aerated concrete according to claim 6, characterized in that, In step S2, the foaming agent is stirred for 5-7 minutes at a stirring speed of 600-800 r / min.

9. The method for preparing lithium slag non-autoclaved aerated concrete according to claim 6, characterized in that, In step S4, the static curing temperature is 30~50℃ and the time is 2~3 hours.

10. The method for preparing lithium slag non-autoclaved aerated concrete according to claim 6, characterized in that, Step S5 involves microwave curing at a temperature of 30-50℃, a microwave power of 200-450W, a relative humidity of 50-70%, and a time of 8-12 hours.

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