Preparation method of composite waste lye activated synthetic freeze-thaw resistant pozzolan-based polymer

Abstract

The present application relates to the field of geopolymer materials, and particularly relates to a preparation method of a freeze-thaw resistant volcanic ash-based geopolymer synthesized by composite waste alkali activation. The geopolymer is a freeze-thaw resistant geopolymer based on volcanic ash and blast furnace slag synthesized by a triple composite alkali activator of carbide slag-mirabilite-sodium silicate, and has the characteristics of high compressive strength and good freeze-thaw durability. The present application uses an environmentally friendly material preparation method, fully utilizes the value of solid waste, and can reduce the production cost of the geopolymer. The triple composite alkali activator of carbide slag-mirabilite-sodium silicate improves the matrix density of the geopolymer, thereby improving the freeze-thaw durability. The triple composite waste alkali system has good alkali activation performance, can accelerate the geopolymerization process, and thus obtain a dense gel matrix. The geopolymer can replace ordinary Portland cement, can improve the service life of buildings in cold environments, and has good application prospects.

Description

Technical Field

[0001] This invention relates to the field of geopolymer materials, specifically to a method for preparing freeze-thaw resistant volcanic ash geopolymer synthesized by composite waste alkali activation. Background Technology

[0002] Geopolymers are a novel type of three-dimensional amorphous cementitious material, synthesized through a geopolymerization process from a mixture of aluminosilicate precursors (such as fly ash or blast furnace slag), alkali activators, and water. The silicate-aluminate raw materials dissolve in acidic or alkaline solutions to form silicate and aluminate monomers, which then recombine to form molecular chains. The polymerization between these chains and monomers results in geopolymers with a three-dimensional network structure. With rapid modernization, the demand for ordinary silicate cement (OPC) in infrastructure projects is increasing. However, OPC production consumes fossil fuels and emits significant amounts of carbon dioxide. To reduce energy consumption and mitigate the greenhouse effect, many researchers have developed geopolymer cementitious materials to replace OPC as building materials. Compared to OPC, geopolymers not only reduce carbon dioxide emissions and energy consumption but also exhibit superior mechanical properties. Researchers have also confirmed other properties of geopolymers, such as high flexural strength, fire resistance, corrosion resistance, carbonation resistance, and sulfate resistance. Researchers believe that geopolymers can serve as a potential alternative to OPC. However, considering the real-world application environments, replacing OPC requires high compressive strength and frost resistance. Concrete can be subject to various forms of erosion caused by extreme weather and temperatures. Larger temperature variations in remote areas place certain demands on the frost resistance of geopolymers. Compressive strength and frost resistance influence the use of geopolymers as building materials, which is a focus of attention for many researchers.

[0003] To improve the compressive strength and freeze-thaw resistance of geopolymers, researchers have proposed numerous strategies. The durability of geopolymers under freeze-thaw conditions is crucial for extending their service life and developing high-performance geopolymers. Some researchers have improved compressive strength by adjusting the proportions of raw materials. Simultaneously, studies have shown that the dissolution rate, degree of polymerization, and condensation reaction of the source aluminosilicate materials during geopolymerization are affected by alkali activators, which influence the gel structure, strength development, and chemical resistance of geopolymers. Alkali activators are typically expensive commercial chemicals, limiting the economically viable large-scale application of geopolymers as building materials. Therefore, research is being conducted on industrial byproducts characterized by abundant amorphous silica or alkali metal oxides to replace common alkali activators such as silica fume, waste glass shavings, and carbide slag. Carbide slag (CCR), a byproduct of acetylene production from the hydrolysis of calcium carbide, is mainly composed of calcium hydroxide and can be used in geopolymerization. However, few studies have simultaneously focused on compressive strength and freeze-thaw resistance. For geopolymers, the convincing gel evolution process during freeze-thaw cycles remains undiscovered. Studies have shown that the freeze-thaw resistance of alkali-activated pozzolanic geopolymers is significantly improved after incorporation with blast furnace slag. This is mainly due to the enrichment of C-(A)-SA gel and the refinement of its pore structure by the blast furnace slag. Therefore, it is necessary to study methods to simultaneously improve the compressive strength and freeze-thaw resistance of geopolymers.

[0004] Volcanic ash is deposited in large quantities in nature and can be mined at low cost. Due to its amorphous phase and high reactivity, volcanic ash and its volcanic ash-based materials can form geopolymers with a three-dimensional network structure through dissolution, condensation, and solidification in an alkaline environment. Therefore, the room temperature compressive strength and freeze-thaw resistance of volcanic ash-based geopolymers can be improved by adding an appropriate proportion of blast furnace slag. This invention uses a composite calcium carbide slag-sodium sulfate-sodium silicate reaction in an alkaline-activated reaction, with volcanic ash and blast furnace slag as raw materials, to prepare a geopolymer with high compressive strength and good freeze-thaw resistance, and describes its preparation method in detail. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing a freeze-thaw resistant volcanic ash geopolymer synthesized by composite waste alkali activation. This geopolymer is synthesized from volcanic ash and blast furnace slag using a triple alkali activator composed of carbide slag, mirabilite, and sodium silicate. It exhibits high compressive strength and good freeze-thaw cycle durability. This invention utilizes an environmentally friendly material preparation method, fully leveraging the utilization value of solid waste and reducing the production cost of the geopolymer. Using carbide slag, mirabilite, and sodium silicate as a composite alkali activator increases the matrix density of the geopolymer, thereby improving its freeze-thaw durability. The triple composite waste alkali system has good alkali activation performance, accelerating the geopolymer reaction process to obtain a dense gel matrix. Using this geopolymer as a substitute for ordinary silicate cement can extend the lifespan of buildings in cold environments and has promising application prospects.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A freeze-thaw resistant volcanic ash-based polymer synthesized by composite waste alkali activation comprises the following raw materials: a mixture of volcanic ash and blast furnace slag, and a composite alkali activator.

[0008] Furthermore, a mixture of volcanic ash and blast furnace slag; wherein the mass fraction of volcanic ash in the mixture is 30%-60%, the mass fraction of blast furnace slag is 40%-70%, and the sum of the mass fractions is 100%;

[0009] Furthermore, the composite alkali activator is calcium carbide slag-miracle salt-sodium silicate-water; wherein the molar ratio of calcium carbide slag, mirabilite, sodium silicate and water is 0.44-0.64:0.15-0.25:0.2-0.3:6-6.67; wherein the mass ratio of the mixture of calcium carbide slag, volcanic ash and blast furnace slag is 32.9-47.3:120-150; the mass ratio of the mixture of mirabilite, volcanic ash and blast furnace slag is 21.3-35.5:120-150; the mass ratio of the mixture of sodium silicate, volcanic ash and blast furnace slag is 24.4-36.6:120-150; and the mass ratio of the mixture of water, volcanic ash and blast furnace slag is 108-120:120-150.

[0010] Furthermore, the calcium carbide slag is obtained from the waste residue after obtaining acetylene gas by calcium carbide hydrolysis, and it is ground and sieved to make its particle size less than 100μm, wherein the CaO content is 90-70wt%.

[0011] Furthermore, the Glauber's salt is sodium sulfate, which is an analytical grade reagent.

[0012] Furthermore, the sodium silicate is solid or liquid sodium silicate.

[0013] Furthermore, the volcanic ash is a powder with volcanic ash activity, with a particle size of less than 100 μm, wherein the Al2O3 content is 10-30 wt% and the SiO2 content is 90-70 wt%.

[0014] Furthermore, the blast furnace slag is ground and sieved to a particle size of less than 100 μm, and the CaO content is 20-50 wt%.

[0015] A method for preparing a freeze-thaw resistant volcanic ash-based polymer synthesized using composite waste alkali includes the following steps:

[0016] Step S1: Crush and grind the carbide slag in a grinding mill, then sieve it, and mix it with sodium sulfate and sodium silicate dissolved in water to obtain alkali activator A;

[0017] Step S2: Weigh out the volcanic ash and blast furnace slag separately, pour each of the above raw materials into a beaker and mix them evenly to obtain mixture B;

[0018] Step S3: Mix the prepared mixture B with the alkali activator A evenly and stir. After stirring, pour the mixture into a steel mold and vibrate it on a vibrating table to remove air bubbles from the slurry. Then seal the mold and cure it in an oven. After that, remove it from the oven, solidify it in a cement curing box, and demold it to obtain the composite waste alkali activated and synthesized freeze-thaw volcanic ash base polymer.

[0019] Furthermore, in step S1, the carbide slag is crushed and ground in a grinding mill for 30-50 minutes, and then sieved through a 100-300 mesh sieve.

[0020] Furthermore, the stirring time in step S3 is 10-30 min; the vibration time on the vibrating table is 5-10 min.

[0021] Furthermore, in step S3, the curing temperature is 60-90℃, the curing time is 6-24h, and the curing time is 28-40d.

[0022] The main innovation of this invention lies in the use of a composite waste alkali activator of carbide slag-sodium sulfate-sodium silicate. This triple composite waste alkali activator not only increases the compressive strength of the geopolymer but also its freeze-thaw durability. In the reaction system of this invention, the three-dimensional structure generated after the reaction of carbide slag-sodium sulfate-sodium silicate with volcanic ash and blast furnace slag can significantly increase its compressive strength and freeze-thaw durability. The compressive strength and freeze-thaw durability of the geopolymer samples prepared using the triple composite alkali activator of carbide slag, sodium sulfate, and sodium silicate are superior to those of geopolymers prepared with dual or single composite activators.

[0023] The beneficial effects of this invention are as follows:

[0024] 1) The high compressive strength and freeze-thaw resistance of the polymer of the present invention utilizes inexpensive industrial wastes such as carbide slag and blast furnace slag, which can reduce engineering costs and effectively improve the utilization rate of industrial waste;

[0025] 2) The volcanic ash used is composed of gravel and mineral particles produced by volcanic eruptions. It is widely available and non-toxic and harmless. No harmful substances are generated during the entire preparation process of the geopolymer, which has certain environmental benefits.

[0026] 3) The geopolymer prepared by this invention has higher compressive strength and better freeze-thaw resistance compared with ordinary concrete and geopolymer, and its compressive strength is more stable in the later stage.

[0027] 4) The geopolymer obtained by this invention is relatively stable in continuous freeze-thaw environments. Attached Figure Description

[0028] Figure 1 SEM image of the geopolymer sample prepared in Comparative Example 4 of this invention without undergoing freeze-thaw cycles.

[0029] Figure 2 This is a SEM image of the geopolymer sample prepared in Example 3 of the present invention that has not undergone freeze-thaw cycles;

[0030] Figure 3 The image shown is a SEM image of the geopolymer sample prepared in Comparative Example 4 of this invention after freeze-thaw cycles.

[0031] Figure 4 This is a SEM image of the geopolymer sample prepared in Example 3 of the present invention after freeze-thaw cycles. Detailed Implementation

[0032] The optimized embodiments of the present invention will now be described in more detail. While optimized embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art. The scope of protection of the present invention includes, but is not limited to, the following:

[0033] Example 1:

[0034] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 36g of volcanic ash and 84g of blast furnace slag are weighed and mixed evenly in a beaker to obtain mixture B. 30.5g of sodium silicate (0.25mol), 40g of calcium carbide slag (0.54mol) and 28.4g of sodium sulfate (0.2mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, it is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles in the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is taken out of the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0035] Example 2:

[0036] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 48g of volcanic ash and 72g of blast furnace slag are weighed and mixed evenly in a beaker to obtain mixture B. 30.5g of sodium silicate (0.25mol), 40g of calcium carbide slag (0.54mol) and 28.4g of sodium sulfate (0.2mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, it is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles in the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is taken out of the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0037] Example 3:

[0038] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 60g of volcanic ash and 60g of blast furnace slag are weighed and mixed evenly in a beaker to obtain mixture B. 30.5g of sodium silicate (0.25mol), 40g of calcium carbide slag (0.54mol) and 28.4g of sodium sulfate (0.2mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, it is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles in the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is taken out of the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0039] Example 4:

[0040] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 72g of volcanic ash and 48g of blast furnace slag are weighed and mixed evenly in a beaker to obtain mixture B. 30.5g of sodium silicate (0.25mol), 40g of calcium carbide slag (0.54mol) and 28.4g of sodium sulfate (0.2mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, it is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles in the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is taken out of the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0041] Example 5:

[0042] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 60g of volcanic ash and 60g of blast furnace slag are weighed and mixed evenly in a beaker to obtain mixture B. 30.5g of sodium silicate (0.25mol), 47.3g of calcium carbide slag (0.64mol) and 21.1g of sodium sulfate (0.15mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, it is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles in the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is taken out of the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0043] Example 6:

[0044] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 60g of volcanic ash and 60g of blast furnace slag are weighed and mixed evenly in a beaker to obtain mixture B. 30.5g of sodium silicate (0.25mol), 32.9g of calcium carbide slag (0.44mol) and 35.5g of sodium sulfate (0.25mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, it is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles in the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is taken out of the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0045] Example 7:

[0046] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 60g of volcanic ash and 60g of blast furnace slag are weighed and mixed evenly in a beaker to obtain mixture B. 36.6g of sodium silicate (0.3mol), 40g of calcium carbide slag (0.54mol) and 22.3g of sodium sulfate (0.16mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, it is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles in the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is taken out of the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0047] Example 8:

[0048] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 60g of volcanic ash and 60g of blast furnace slag are weighed and mixed evenly in a beaker to obtain mixture B. 24.4g of sodium silicate (0.2mol), 40g of calcium carbide slag (0.54mol), and 34.5g of sodium sulfate (0.24mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, the mixture is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles from the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is removed from the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0049] Example 9:

[0050] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 60g of volcanic ash and 60g of blast furnace slag are weighed and mixed evenly in a beaker to obtain mixture B. 36.6g of sodium silicate (0.3mol), 33.9g of calcium carbide slag (0.46mol) and 28.4g of sodium sulfate (0.2mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, the mixture is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles in the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is removed from the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0051] Example 10:

[0052] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 60g of volcanic ash and 60g of blast furnace slag are weighed and mixed evenly in a beaker to obtain mixture B. 24.4g of sodium silicate (0.2mol), 46.1g of calcium carbide slag (0.62mol), and 28.4g of sodium sulfate (0.2mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, the mixture is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles from the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is removed from the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0053] The ultimate compressive strength of this invention was measured using the standard test method according to the "Standard Test Method for Mechanical Properties of Ordinary Concrete" GB / T50081-2019. The test results are shown in Table 1.

[0054] Table 1 Compressive strength of materials in Examples 1-10

[0055]

[0056] The present invention placed the above Examples 1-10 in a cement freeze-thaw cycle chamber for 30 days and then tested them using a compression and flexural strength tester. The test results are shown in Table 2.

[0057] Table 2 shows the compressive strength of Examples 1-10 after 30 days in a cement freeze-thaw cycle chamber.

[0058]

[0059]

[0060] Based on Example 3, the following comparative examples are set:

[0061] Comparative Example 1:

[0062] The carbide slag was crushed and ground to pass through a 100-mesh sieve. 120g of volcanic ash was weighed and mixed evenly in a beaker to obtain mixture B. 30.5g of sodium silicate (0.25mol), 40g of carbide slag (0.54mol), and 28.4g of sodium sulfate (0.2mol) were dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A was mixed evenly with raw material B and stirred for 10min. After stirring, the mixture was poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles from the slurry. The mold was then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it was removed from the oven and cured at room temperature for 7d before demolding. The slurry was then cured in a cement hydration box for 28d to obtain the geopolymer.

[0063] Comparative Example 2:

[0064] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 120g of blast furnace slag is weighed and mixed evenly in a beaker to obtain mixture B. 30.5g of sodium silicate (0.25mol), 40g of calcium carbide slag (0.54mol), and 28.4g of sodium sulfate (0.2mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, it is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles in the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is removed from the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0065] Comparative Example 3:

[0066] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 60g of volcanic ash and 60g of blast furnace slag are weighed and mixed evenly in a beaker to obtain mixture B. 55.3g of calcium carbide slag (0.75mol) and 43.6g of sodium sulfate (0.31mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, it is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles in the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is taken out of the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0067] Comparative Example 4:

[0068] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 60g of volcanic ash and 60g of blast furnace slag are weighed and mixed evenly in a beaker to obtain mixture B. 50.5g of sodium silicate (0.41mol) and 48.4g of sodium sulfate (0.34mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, it is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles in the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is taken out of the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0069] Comparative Example 5:

[0070] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 60g of volcanic ash and 60g of blast furnace slag are weighed and mixed evenly in a beaker to obtain mixture B. 44.7g of sodium silicate (0.37mol) and 54.2g of calcium carbide slag (0.73mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, it is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles in the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is taken out of the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0071] Comparative Example 6:

[0072] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 60g of volcanic ash and 60g of blast furnace slag are weighed and mixed evenly in a beaker to obtain mixture B. 98.9g of sodium silicate (0.81mol) is dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, it is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles in the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is taken out of the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0073] Comparative Example 7:

[0074] Weigh 60g of volcanic ash and 60g of blast furnace slag, pour the raw materials into a beaker and mix them evenly to obtain mixture B; dissolve 98.9g of sodium sulfate (0.7mol) in 108g of water (6mol) to obtain alkali activator A; mix the prepared alkali activator A with raw material B evenly and stir for 10min, then pour the mixture into a steel mold and vibrate it on a vibrating table for 5min to remove air bubbles from the slurry. After that, seal the mold and cure it in an oven at 60℃ for 6h to form the slurry. Then remove it from the oven, cure it at room temperature for 7d, demold it, and cure it in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0075] Comparative Example 8:

[0076] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 60g of silica fume and 60g of blast furnace slag are weighed and mixed evenly in a beaker to obtain mixture B. 30.5g of sodium silicate (0.25mol), 40g of calcium carbide slag (0.54mol) and 28.4g of sodium sulfate (0.2mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, it is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles in the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is taken out of the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0077] Comparative Example 9:

[0078] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 60g of volcanic ash and 60g of fly ash are weighed and mixed evenly in a beaker to obtain mixture B. 30.5g of sodium silicate (0.25mol), 40g of calcium carbide slag (0.54mol), and 28.4g of sodium sulfate (0.2mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, the mixture is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles from the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is removed from the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0079] Comparative Example 10:

[0080] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 60g of volcanic ash and 60g of blast furnace slag are weighed and mixed evenly in a beaker to obtain mixture B. 30.5g of sodium hydroxide (0.76mol), 40g of calcium carbide slag (0.54mol) and 28.4g of sodium sulfate (0.2mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, it is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles in the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is taken out of the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0081] Comparative Example 11:

[0082] Calcium carbide slag is crushed and ground to pass through a 100-mesh sieve. 60g of volcanic ash and 60g of blast furnace slag are weighed and mixed evenly in a beaker to obtain mixture B. 30.5g of sodium hydroxide (0.76mol), 40g of calcium hydroxide (0.54mol), and 28.4g of sodium sulfate (0.2mol) are dissolved in 108g of water (6mol) to obtain alkali activator A. The prepared alkali activator A is mixed evenly with raw material B and stirred for 10min. After stirring, it is poured into a steel mold and vibrated on a vibrating table for 5min to remove air bubbles in the slurry. The mold is then sealed and cured in an oven at 60℃ for 6h to form the slurry. After that, it is taken out of the oven and cured at room temperature for 7d before demolding. It is then cured in a cement hydration box for 28d to obtain a geopolymer with high compressive strength and good freeze-thaw resistance.

[0083] The ultimate compressive strength of this invention was measured using the standard test method according to the "Standard Test Method for Mechanical Properties of Ordinary Concrete" GB / T50081-2019. The test results are shown in Table 3.

[0084] Table 3 Compressive strength of materials in Comparative Examples 1-11

[0085]

[0086] The present invention placed the above comparative examples 1-11 in a cement freeze-thaw cycle chamber for 30 days and then tested them using a compression and flexural strength tester. The test results are shown in Table 4.

[0087] Table 4 shows the compressive strength of Comparative Examples 1-11 after 30 days in a cement freeze-thaw cycle chamber.

[0088]

[0089]

[0090] from Figures 1-2 It can be seen that the sample prepared by the triple alkali activation of carbide slag-sodium sulfate-sodium silicate has a denser surface. The samples prepared by the triple alkali activator have no obvious cracks, and the sample surface is denser, smoother, and has higher strength.

[0091] from Figures 3-4 It can be seen that the matrix damage of the samples prepared by the triple compound alkali activator of calcium carbide slag-sodium sulfate-sodium silicate after freeze-thaw cycles is less than that of the samples prepared by the comparative example. The triple compound alkali activator can prevent freeze-thaw expansion from damaging the internal structure of the geopolymer. The addition of matrix density can increase the compressive strength of the geopolymer and reduce the strength loss of the geopolymer after freeze-thaw cycles. The effect of the triple compound alkali activator of calcium carbide slag-sodium sulfate-sodium silicate is better than that of the dual compound alkali activator and the single alkali activator. The compressive strength and freeze-thaw cycle durability of the geopolymer samples prepared by the triple compound alkali activator of calcium carbide slag-sodium sulfate-sodium silicate are better than those of the geopolymers prepared by other compound alkali activators. Moreover, the addition of an appropriate proportion of calcium carbide slag greatly improves the freeze-thaw resistance of the geopolymer after freeze-thaw cycles. Compared with Example 3, the geopolymer prepared by the triple composite alkali activator exhibits significantly higher freeze-thaw durability than the geopolymer prepared by the carbide slag-sodium sulfate dual composite alkali activator. This indicates that in the reaction system of the present invention, the combination of three alkali activators—carbide slag, sodium sulfate, and sodium silicate—along with the addition of blast furnace slag, can synergistically improve the freeze-thaw resistance and compressive strength of the geopolymer. The principle is that the triple composite alkali activator of carbide slag, sodium sulfate, and sodium silicate can significantly improve the compressive strength of the geopolymer. It can accelerate the dissolution of aluminosilicates in an alkaline environment, thereby promoting the occurrence of geopolymerization reaction, forming a three-dimensional network structure, and further improving the compressive strength of the geopolymer. The improved compressive strength makes it less likely to damage the internal structure of the geopolymer during freeze-thaw cycles, thus achieving the effect of freeze-thaw durability.

[0092] In summary, this invention discloses a method for preparing a freeze-thaw resistant volcanic ash-based geopolymer synthesized using a composite waste alkali-activated synthesis. This geopolymer is a freeze-thaw resistant geopolymer synthesized from a triple alkali activator composed of carbide slag, mirabilite, and sodium silicate, and from volcanic ash and blast furnace slag. It exhibits high compressive strength and good freeze-thaw cycle durability. This invention utilizes an environmentally friendly material preparation method, fully leveraging the utilization value of solid waste and reducing the production cost of the geopolymer. Using carbide slag, mirabilite, and sodium silicate as a composite alkali activator increases the matrix density of the geopolymer, thereby improving freeze-thaw durability. The triple composite waste alkali system has good alkali activation performance, accelerating the geopolymer reaction process to obtain a dense gel matrix. Using this geopolymer as a substitute for ordinary silicate cement can extend the lifespan of buildings in cold environments, demonstrating promising application prospects.

[0093] The various embodiments of the present invention have now been described. The above description is exemplary and not exhaustive, nor is it limited to the described embodiments. Many modifications and variations will be included within the scope and spirit of the described embodiments by those skilled in the art without departing from the scope and spirit of the invention.

Claims

1. A freeze-thaw resistant volcanic ash-based polymer synthesized using composite waste alkali, characterized in that, The raw materials include: a mixture of volcanic ash and blast furnace slag, and a composite alkali activator; wherein the mixture of volcanic ash and blast furnace slag comprises 30wt%-60wt% volcanic ash and 40wt%-70wt% blast furnace slag; the composite alkali activator is a mixture of carbide slag, mirabilite, sodium silicate, and water; the mass ratio of water to the mixture of volcanic ash and blast furnace slag is 108-120:120-150. The volcanic ash is a powder with volcanic ash activity, a particle size of less than 100 μm, and contains 10-30 wt% Al2O3 and 90-70 wt% SiO2. The blast furnace slag is ground and sieved to a particle size of less than 100 μm, and contains 20-50 wt% CaO.

2. The freeze-thaw resistant volcanic ash-based polymer synthesized by composite waste alkali activation as described in claim 1, characterized in that, The calcium carbide slag is obtained from the waste residue after acetylene gas is obtained by hydrolysis of calcium carbide. It is ground and sieved to make the particle size less than 100 μm, and the CaO content is 70-90 wt%. The molar ratio of calcium carbide slag, mirabilite, sodium silicate and water is 0.44-0.64:0.15-0.25:0.2-0.3:6-6.

67. The mass ratio of the mixture of calcium carbide slag, volcanic ash and blast furnace slag is 32.9-47.3:120-150.

3. The freeze-thaw resistant volcanic ash-based polymer synthesized by composite waste alkali activation as described in claim 1, characterized in that, The mirabilite is sodium sulfate; the mass ratio of the mixture of mirabilite, volcanic ash and blast furnace slag is 21.3-35.5:120-150.

4. The freeze-thaw resistant volcanic ash-based polymer synthesized by composite waste alkali activation as described in claim 1, characterized in that, The sodium silicate is solid or liquid; the mass ratio of the mixture of sodium silicate, volcanic ash and blast furnace slag is 24-36.6:120-150.

5. The preparation method of a freeze-thaw resistant volcanic ash-based polymer synthesized by composite waste alkali activation as described in claim 1, characterized in that, The preparation method specifically includes the following steps: Step S1: Crush and grind the carbide slag in a grinding mill, then sieve it, and mix it with sodium sulfate and sodium silicate dissolved in water to obtain alkali activator A; Step S2: Weigh out the volcanic ash and blast furnace slag separately, pour each of the above raw materials into a beaker and mix them evenly to obtain mixture B; Step S3: Mix the prepared mixture B with the alkali activator A evenly and stir. After stirring, pour the mixture into a steel mold and vibrate it on a vibrating table to remove air bubbles from the slurry. Then seal the mold and cure it in an oven. After that, remove it from the oven, solidify it in a cement curing box, and demold it to obtain the composite waste alkali activated and synthesized freeze-thaw volcanic ash base polymer.

6. The method for preparing a freeze-thaw resistant volcanic ash-based polymer synthesized by composite waste alkali activation as described in claim 5. Its features are, In step S1, the carbide slag is crushed and ground in a grinding mill for 30-50 minutes, and then sieved through a 100-300 mesh sieve.

7. The method for preparing a freeze-thaw resistant volcanic ash-based polymer synthesized by composite waste alkali activation as described in claim 5. Its features are, The stirring time in step S3 is 10-30 min; the vibration time on the vibrating table is 5-10 min.

8. The method for preparing a freeze-thaw resistant volcanic ash-based polymer synthesized by composite waste alkali activation as described in claim 5. Its features are, In step S3, the curing temperature is 60-90 ℃, the curing time is 6-24 h, and the curing time is 28-40 days.

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