A method for preparing geopolymers by compositely activating solid wastes using carbide slag and white mud

Abstract

The present invention discloses a method for preparing geopolymers by compositely activating solid wastes using carbide slag and white mud. The method comprises the following steps: first, dissolving carbide slag and white mud in water, placing the mixture in a 5°C constant temperature box and letting it stand for 30 minutes to prepare an alkaline activator; then, uniformly mixing the polymer raw materials in a low-temperature stirring pot; then, pouring the alkaline activator into the low-temperature stirring pot and stirring at a temperature of 5°C; finally, pouring the uniformly mixed polymer gel material into a mold, placing the mold on a vibrating table to expel bubbles, and then placing the mold in a 5°C constant temperature curing box for curing. The alkaline activator in the present invention is derived from industrial solid waste, replacing commonly used, more expensive activators such as NaOH and water glass, thereby reducing costs. Furthermore, since all the polymer raw materials are solid waste, high-value utilization of industrial solid waste is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials and solid waste utilization, and in particular to a method for preparing geopolymer from solid waste by composite excitation of carbide slag and white mud. Background Art

[0002] The production of Portland cement consumes significant amounts of energy and produces significant amounts of carbon dioxide. Alkali-activated geopolymers involve mixing aluminosilicates, often rich in SiO₂ and Al₂O₃, as supplementary binders with an alkaline solution to produce amorphous to semi-crystalline polymer products. In recent years, the production of bulk industrial solid waste has been increasing with social development and construction. Whether dumped in the open air or in landfills, these wastes occupy significant amounts of land and pollute air and water. However, many industrial solid wastes contain the SiO₂ and Al₂O₃ required for geopolymer production. For example, coal gangue, coal gasification slag, high-alumina fly ash, and waste ceramic powder are rich in silica and aluminum. Silica fume, steel slag, blast furnace slag, and waste glass powder are also rich in silica. Using these industrial solid wastes to produce geopolymers can help achieve high-value utilization of these wastes.

[0003] Alkaline materials are the most effective activators for the preparation of geopolymers. Commercially available reagents are commonly used to prepare sodium silicate, sodium hydroxide, and mixtures of the two. Sodium silicate, when dissolved in water, is called water glass. However, its high cost and strong corrosiveness have severely hindered the widespread application of geopolymers. Therefore, using inexpensive activators derived entirely from industrial solid waste can mitigate the environmental impact to a certain extent. Carbide slag and white mud, whose main components are CaO, CaCO3, and residual alkali (NaOH), are highly alkaline when dissolved in water. A combination of these two can replace sodium silicate and sodium hydroxide as activators.

[0004] The present invention uses carbide slag and white mud as alkali activators, and uses coal gangue, silica fume, coal gasification slag, high-alumina fly ash, steel slag, blast furnace slag, waste glass powder, waste ceramic powder and other solid wastes as raw materials to prepare geopolymers. All materials are taken from industrial solid wastes to prepare low-energy consumption, low-carbon emission, environmentally friendly green cementitious materials, realizing the high-value utilization of industrial solid wastes. Summary of the Invention

[0005] The present invention aims to address the current shortcomings of high-cost and highly corrosive activators used to produce geopolymers using alkali-activated activators. By providing a method for producing geopolymers using a composite of carbide slag and white mud as an alkali activator, the method offers low cost, excellent activation effects, and high-performance geopolymer cementitious materials.

[0006] The technical solution adopted by the present invention is a method for preparing geopolymer from carbide slag and white mud composite activated solid waste, comprising the following steps:

[0007] (1) Preparation of composite alkali activator of carbide slag and white mud

[0008] The raw materials for preparing the composite alkali activator include calcium carbide slag, white mud, and water. Count by mass: 6 parts calcium carbide slag, 14 parts white mud, and 35 parts water. Pour the calcium carbide slag and white mud into water and stir to dissolve. Then place them in a thermostat, set the temperature to 5°C, and let them stand for 30 minutes. The purpose of this step is that the solubility of calcium hydroxide increases with decreasing temperature. Placing it in an environment below room temperature helps to increase the OH content in the solution. — ion concentration, thereby increasing the alkalinity of the solution.

[0009] The functions of each material are as follows: calcium oxide in carbide slag reacts with water to generate calcium hydroxide, forming an alkaline environment. The residual alkali (NaOH) content in white mud is relatively high, up to 3% to 5%. After dissolving in water, the solution is strongly alkaline, causing more serious corrosion damage to the surface of carbide slag and white mud particles. 2+ The dissolution amount increases, and the two compounds promote each other — The precipitation of ions increases the OH — Ion concentration. OH in carbide slag and white mud composite alkali activator — The continuous precipitation of ions promotes the increase of alkalinity, accelerates the decomposition of SiO2 and Al2O3 in the polymer raw materials, and provides sufficient calcium, creating conditions for the next hydration polymerization reaction to generate CSH and CASH gel phases.

[0010] Preferably, the CaO content in the carbide slag is more than 85% and the loss on ignition is less than 20%; the CaCO3 content in the white mud is more than 80%, the NaOH content is more than 3%, and the loss on ignition is less than 30%.

[0011] Preferably, the carbide slag and white mud are passed through a 200-mesh sieve with a sieve residue of less than 5%.

[0012] (2) Preparation and proportion of solid waste base polymer raw materials

[0013] The raw materials used to prepare the solid waste-based polymer include coal gangue, silica fume, coal gasification slag, high-alumina fly ash, steel slag, blast furnace slag, waste glass powder, and waste ceramic powder. By mass, the raw materials are: 21 parts coal gangue, 3 parts silica fume, 18 parts coal gasification slag, 17 parts high-alumina fly ash, 2 parts steel slag, 12 parts blast furnace slag, 7 parts waste glass powder, and 3 parts waste ceramic powder.

[0014] The functions of each material are as follows: Coal gangue and high-alumina fly ash, as aluminosilicate materials, contain high proportions of highly active SiO2 and Al2O3, and are the main sources of aluminum and calcium for polymer cementitious materials. Silica fume and waste glass powder are relatively fine, and their main component is highly active SiO2, which can serve as a supplementary source of silica for polymer cementitious materials. In addition to providing SiO2, coal gasification slag and steel slag also provide a certain amount of iron phase, which is conducive to the formation of calcium aluminoferrite, accelerating the setting rate and improving early strength. Blast furnace slag and waste ceramic powder contain Al2O3 and can serve as a supplementary source of aluminum. The material has a high hardness, and the appropriate addition can improve the density and structural strength of the cementitious material. The synergistic effect of coal gangue powder and blast furnace slag easily dissolves aluminum and silica in the highly alkaline activator, and diffuses and reorganizes in the solution to form a flocculated structure. The synergistic effects of blast furnace slag, coal gasification slag, and silica fume can adjust the fluidity and density of polymer cementitious materials. All three materials have high fineness and activity, which contribute to improving the structural strength of the cementitious materials. The synergistic effects of coal gasification slag, high-alumina fly ash, and waste ceramic powder can regulate the hydration rate. These materials are rich in aluminum and calcium, which react in a composite alkali-activated solution to form hydrated calcium aluminosilicate gel, contributing to the strength of the polymer cementitious materials. The synergistic effects of blast furnace slag, silica fume, and waste ceramic powder can improve the microstructure of the cementitious material slurry. Firstly, their small particle size and high activity create a pozzolanic effect. In ordinary Portland cement, they react with the hydration product, Ca(OH)2, to form hydrated calcium silicate. In polymer cementitious materials, they react directly with the Ca(OH)2 in the composite alkali activator, enhancing the strength of the cementitious materials. Secondly, their small particle size allows them to fill the micropores formed after hydration, thereby enhancing the density of the polymer cementitious materials. High-alumina fly ash, coal gangue, and steel slag work synergistically with carbide slag and white mud to produce calcium aluminoferrite gel with early strength and rapid hardening properties. By varying the ratio of these three ingredients, the setting time of polymer cementitious materials can be adjusted. The synergistic effect of high-alumina fly ash, waste glass powder, and silica fume reduces shrinkage and slows setting, maintaining the early strength of the cementitious material while increasing its later strength growth rate.

[0015] Preferably, the SiO2 content in coal gangue is 46.5%, the Al2O3 content is 48.3%, and the loss on ignition is 11.67%; the SiO2 content in silica ash is more than 94.5%; the SiO2 content in coal gasification slag is 52%, the Al2O3 content is 18.3%, the Fe2O3 content is 11.7%, and the loss on ignition is 22.1%; the Al2O3 content in high-alumina fly ash is more than 48%; the SiO2 content in blast furnace slag is 28.6%, the CaO content is 40.4%, and the Al2O3 content is 13.1%; the SiO2 content in steel slag is 60.4%, and the Fe2O3 content is 13.2%; the SiO2 content in waste glass powder is 82.6%; the SiO2 content in waste ceramic powder is 68.3%, and the Al2O3 content is 17.2%.

[0016] Preferably, the coal gangue, steel slag, waste glass powder and waste ceramic powder all pass 200 mesh, and the sieve residue is less than 3%.

[0017] Preferably, coal gasification slag, blast furnace slag, high-aluminum fly ash, and silica fume are sieved through a 325-mesh sieve with a sieve residue of less than 3%.

[0018] (3) Preparation process of solid waste base polymer

[0019] (1) Connect the low-temperature cooling circulation tank and the low-temperature stirring pot through a hose, turn on the power switch of the low-temperature cooling circulation tank, and start the instrument.

[0020] (2) Pour the coolant (ethylene glycol) into the low-temperature cooling circulation tank from the coolant inlet, turn on the circulation switch, and keep the coolant flowing between the low-temperature stirring pot and the low-temperature cooling circulation tank.

[0021] (3) Set the temperature of the low-temperature cooling circulation tank to 5°C in the temperature control panel, start the refrigeration switch, and cool down for 30 minutes so that the temperature of the low-temperature stirring pot drops to 5°C and remains stable.

[0022] (4) Weigh the polymer raw materials according to the proportion, pour them into a low-temperature stirring pot, and stir them at a low speed for 2 minutes to mix the raw materials evenly. The stirring speed is 150r / min.

[0023] (5) Take out the prepared carbide slag and white mud composite activator from the constant temperature box, stir it quickly until it becomes a suspended liquid, so that the carbide slag and white mud are evenly dispersed in the solution, and then quickly pour it into a low-temperature stirring pot. First, turn on the low-speed stirring switch and stir at low speed for 1 minute, the stirring speed is 150r / min; then turn on the high-speed stirring switch and stir at high speed for 1 minute, the stirring speed is 300r / min.

[0024] (6) Turn off the refrigeration switch, circulation switch and power switch of the low-temperature cooling circulation tank in sequence, then quickly pour the stirred polymer gel material into the mold, vibrate it on a vibration table for 30 seconds to expel bubbles, smooth the surface of the specimen, and then place it in a constant temperature phase, set the curing temperature to 5±0.5℃, and the humidity to 98%±1%. After curing to the specified age, take it out for testing.

[0025] Beneficial effects: The method of preparing geopolymers by compositely activating solid waste with carbide slag and white mud can realize the use of solid waste to prepare activators to replace the existing high-cost and highly corrosive commercially available alkali activators. At the same time, all the geopolymer raw materials are taken from solid waste, which reduces the cost of preparing geopolymer materials, reduces carbon emissions, and is economical and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the low-temperature mixing device of the present invention.

[0027] In the figure: 1- low-temperature stirring pot; 2- hose; 3- power switch; 4- coolant inlet; 5- circulation switch; 6- temperature control panel; 7- cooling switch; 8- low-speed stirring switch; 9- high-speed stirring switch. DETAILED DESCRIPTION

[0028] The invention will be further described below with reference to specific embodiments and accompanying drawings.

[0029] A method for preparing geopolymers by compositely activating solid wastes of carbide slag and white mud comprises the following steps:

[0030] (1) Use a crusher to crush coal gangue, coal gasification slag, waste glass, waste ceramics, and white mud into small pieces with a diameter of less than 20 mm. Then, grind them in a closed grinder for 80 minutes. After taking them out, sieve them. Calcium carbide slag, white mud, coal gangue, steel slag, waste glass powder, waste ceramic powder, etc. should be sieved through a 200-mesh sieve. Coal gasification slag, blast furnace slag, high-alumina fly ash, silica fume, etc. should be sieved through a 325-mesh sieve.

[0031] (2) Calculate by mass fraction: 6 parts of carbide slag, 14 parts of white mud, and 35 parts of water. Pour the carbide slag and white mud into water and stir to dissolve for 3 minutes. Then place them in a constant temperature box, set the temperature to 5°C, and let them stand for 30 minutes to prepare a composite alkali activator. Then, calculate by mass fraction: 21 parts of coal gangue, 3 parts of silica fume, 18 parts of coal gasification slag, 17 parts of high-alumina fly ash, 2 parts of steel slag, 12 parts of blast furnace slag, 7 parts of waste glass powder, and 3 parts of waste ceramic powder to be used as raw materials for polymer cementitious materials.

[0032] (3) Figure 1As shown, connect the low-temperature cooling circulation tank to the low-temperature stirring pot 1 via a hose 2, turn on the low-temperature cooling circulation tank power switch 3, and start the instrument. Turn on the low-temperature cooling circulation tank power switch 3, pour coolant (ethylene glycol) into the low-temperature cooling circulation tank from the coolant inlet 4, turn on the circulation switch 5, then set the low-temperature cooling circulation tank temperature to 5°C on the temperature control panel 6, turn on the refrigeration switch 7, and cool the low-temperature stirring pot 1 for 30 minutes until the temperature drops to 5°C and remains stable.

[0033] (4) The polymer raw materials are weighed in proportion and poured into a low-temperature stirring pot 1. The low-speed stirring switch 8 is turned on and stirred at a low speed for 2 minutes to mix the raw materials evenly. The stirring speed is 150r / min. Then, the prepared calcium carbide slag and white mud composite activator is taken out from the constant temperature box, and quickly stirred until it becomes a suspended liquid. The calcium carbide slag and white mud are evenly dispersed in the solution. Then, it is quickly poured into a low-temperature stirring pot 1. The low-speed stirring switch 8 is first turned on and stirred at a low speed for 1 minute. The stirring speed is 150r / min; then the high-speed stirring switch 9 is turned on and stirred at a high speed for 1 minute. The stirring speed is 300r / min.

[0034] (5) Turn off the refrigeration switch 7, circulation switch 5 and power switch 3 of the low-temperature cooling circulation tank in sequence, then quickly pour the stirred polymer gel material into the mold, vibrate it on the vibration table for 30 seconds to expel bubbles, smooth the surface of the specimen, and then put it into the constant temperature phase and set the curing temperature to 5±0.5

[0035] The samples were cured at 98% ± 1% humidity and then taken out for testing after the prescribed age. The measured strengths are shown in Table 1.

[0036] Table 1 Compressive strength of geopolymer prepared from composite activated solid waste of carbide slag and white mud

[0037] Age / d 1 3 7 14 28 Strength / MPa 11 24 32 35 48

[0038] It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, they can make appropriate adjustments to the raw material ratios to improve and optimize the performance of solid waste geopolymers. These improvements and optimizations without creative work should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing geopolymers by compositely activating solid wastes of carbide slag and white mud, characterized in that: The following steps are involved: (1) Preparation of composite alkali activator of carbide slag and white mud The raw materials for preparing the composite alkali activator include carbide slag, white mud, and water; by mass fraction, the carbide slag is 6 parts, the white mud is 14 parts, and the water is 35 parts; the carbide slag and the white mud are poured into water and stirred to dissolve, and then placed in a constant temperature box, set the temperature to 5°C, and allowed to stand for 30 minutes; (2) Preparation and proportion of raw materials of all-solid waste polymer gelling materials The raw materials for preparing the all-solid waste polymer cementitious material include coal gangue, silica fume, coal gasification slag, high-alumina fly ash, steel slag, blast furnace slag, waste glass powder, and waste ceramic powder. Counted by mass, the raw materials are 21 parts of coal gangue, 3 parts of silica fume, 18 parts of coal gasification slag, 17 parts of high-alumina fly ash, 2 parts of steel slag, 12 parts of blast furnace slag, 7 parts of waste glass powder, and 3 parts of waste ceramic powder. (3) Preparation process of solid waste base polymer (1) Connect the low-temperature cooling circulation tank and the low-temperature stirring pot through a hose, turn on the power switch of the low-temperature cooling circulation tank, and start the instrument; (2) Pour the coolant into the low-temperature cooling circulation tank from the coolant inlet, turn on the circulation switch, and keep the coolant flowing between the low-temperature stirring pot and the low-temperature cooling circulation tank; (3) Set the temperature of the low-temperature cooling circulation tank to 5°C in the temperature control panel, start the refrigeration switch, and cool down for 30 minutes until the temperature of the low-temperature stirring pot drops to 5°C and remains stable; (4) Weigh the polymer raw materials according to the proportion, pour them into a low-temperature stirring pot, and stir them at a low speed for 2 minutes to mix the raw materials evenly. The stirring speed is 150 r / min; (5) Take out the prepared calcium carbide slag and white mud composite activator from the constant temperature box, stir quickly until it is in a suspended liquid state, so that the calcium carbide slag and white mud are evenly dispersed in the solution, and then quickly pour it into a low-temperature stirring pot, first turn on the low-speed stirring switch and stir at a low speed for 1 minute, the stirring speed is 150r / min; then turn on the high-speed stirring switch and stir at a high speed for 1 minute, the stirring speed is 300r / min; (6) Turn off the refrigeration switch, circulation switch and power switch of the low-temperature cooling circulation tank in sequence, then quickly pour the stirred polymer gel material into the mold, vibrate it on a vibration table for 30 seconds to expel bubbles, smooth the surface of the specimen, and then place it in a constant temperature phase, set the curing temperature to 5±0.5℃, and the humidity to 98%±1%. After curing to the specified age, take it out for testing.

2. The method for preparing geopolymer from carbide slag and white mud composite activated solid waste according to claim 1, characterized in that: In the step (1), the CaO content in the carbide slag is more than 85%, and the loss on ignition is less than 20%; the CaCO3 content in the white mud is more than 80%, the NaOH content is more than 3%, and the loss on ignition is less than 30%.

3. The method for preparing geopolymer from carbide slag and white mud composite activated solid waste according to claim 1, characterized in that: In the step (1), the carbide slag and white mud are passed through a 200-mesh sieve, and the sieve residue is less than 5%.

4. The method for preparing geopolymer from carbide slag and white mud composite activated solid waste according to claim 1, characterized in that: In the step (2), the SiO2 content in the coal gangue is 46.5%, the Al2O3 content is 48.3%, and the loss on ignition is 11.67%; the SiO2 content in the silica ash is more than 94.5%; the SiO2 content in the coal gasification slag is 52%, the Al2O3 content is 18.3%, the Fe2O3 content is 11.7%, and the loss on ignition is 22.1%; the Al2O3 content in the high-alumina fly ash is more than 48%; the SiO2 content in the blast furnace slag is 28.6%, the CaO content is 40.4%, and the Al2O3 content is 13.1%; the SiO2 content in the steel slag is 60.4%, and the Fe2O3 content is 13.2%; the SiO2 content in the waste glass powder is 82.6%; and the SiO2 content in the waste ceramic powder is 68.3% and the Al2O3 content is 17.2%.

5. The method for preparing geopolymer from carbide slag and white mud composite activated solid waste according to claim 1, characterized in that: In the step (2), the coal gangue, steel slag, waste glass powder and waste ceramic powder are all sieved through 200 meshes, and the sieve residue is less than 3%.

6. The method for preparing geopolymer from carbide slag and white mud composite activated solid waste according to claim 1, characterized in that: In the step (ii), the coal gasification slag, blast furnace slag, high-aluminum fly ash and silica fume are sieved through a 325-mesh sieve, and the sieve residue is less than 3%.

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