Preparation method of steel slag reinforced composite alkali-activated geopolymer

Abstract

The invention provides a preparation method of a steel slag reinforced composite alkali-activated geopolymer, belongs to the field of preparation of pavement base materials, and solves the problems of overlong coagulation time, lower geopolymer strength, poorer volume stability, higher cost of an alkali activator, difficulty in meeting engineering application and the like in the current geopolymer preparation process. Firstly, potassium hydroxide, sodium carbonate and water glass are used for preparing a composite alkali activator 24 hours in advance, and then the composite alkali activator is mixed with steel slag powder, slag powder and fly ash to prepare a geopolymer precursor. And then uniformly mixing and stirring the alkali activator and the geopolymer precursor to prepare a geopolymer neat paste, standing in a mold for 24 hours, demolding, curing for 3 days, 7 days and 28 days, and evaluating the performance of the geopolymer neat paste according to the compressive strength, the breaking strength and the dry shrinkage coefficient. According to the prepared steel slag reinforced composite alkali-activated geopolymer, sodium carbonate is used for preparing an exciting agent, the setting time is prolonged, the cost is reduced, the strength of the geopolymer is enhanced, and the steel slag reinforced composite alkali-activated geopolymer has very obvious environmental benefits, economic benefits and social benefits.

Description

Technical Field

[0001] The present application discloses a method for preparing a steel slag reinforced composite alkali-activated geopolymer, and belongs to the field of pavement base materials. Background Art

[0002] With the acceleration of the global industrialization process, the production of traditional building materials such as ordinary Portland cement faces huge resource and environmental challenges. Cement production is a process with high energy consumption and high carbon dioxide emissions. According to statistics, about 0.8 to 0.9 tons of carbon dioxide are released for every ton of cement produced. In addition, cement production requires a large amount of natural resources such as limestone as raw materials, while the main raw materials of geopolymers can be industrial waste residues, such as fly ash and slag. Fly ash is a waste generated by thermal power plants. The annual global emission of fly ash is huge, and China alone produces hundreds of millions of tons of fly ash each year. Slag is a by-product of the steel smelting process, and its annual output is also considerable. The accumulation of these industrial waste residues not only occupies a large amount of land, but also causes environmental pollution. For example, heavy metals in fly ash may seep into soil and water.

[0003] In many engineering fields such as construction and transportation, the requirements for material performance are getting higher and higher. Traditional materials have insufficient performance in certain special environments. For example, in some industrial plants and marine engineering environments with strong chemical corrosion, the durability of ordinary cement concrete is poor. Geopolymer materials have excellent chemical corrosion resistance, high early strength and good high temperature resistance. Taking its chemical corrosion resistance as an example, in an environment with acidic or alkaline liquid corrosion, the chemical stability of geopolymer enables it to better maintain the integrity and durability of the structure.

[0004] However, there are still some problems in the current research on geopolymers. First, the setting time of geopolymer is too short, and alkali-activated geopolymer reacts quickly. The initial setting time of geopolymer prepared with sodium hydroxide as the alkali activator is only 60 minutes, which cannot meet the requirements of practical engineering applications. Therefore, it is particularly important to find a suitable method to increase the setting time of alkali-activated geopolymer. This application starts with the alkali activator, reduces the alkalinity of the alkali activator by sodium carbonate, and achieves a slow setting effect by carbonate ions. Secondly, the volume stability of geopolymer is poor. The shrinkage deformation is serious, and cracks and other diseases are likely to occur when used in actual engineering. In addition, fly ash-based polymers have too low early strength, which limits their application in some projects that require rapid load-bearing.

[0005] Therefore, this application utilizes the expansion characteristics of steel slag during the reaction process, and uses steel slag as a gelling material to increase toughness while increasing the strength of geopolymer. Finally, although geopolymer has certain cost advantages by using industrial waste slag as raw materials, the production process needs to be further optimized in large-scale production applications. Some alkali activators are expensive, and in-depth research can be conducted to replace different alkalis to reduce costs.

[0006] In view of this, the present application prepares geopolymer by mixing potassium hydroxide, sodium carbonate and water glass solution to prepare a composite alkali activator, using fly ash and slag powder as raw materials, and adding a large amount of slag powder to increase the strength of the geopolymer, so as to solve the problem that the current alkali-activated geopolymer has a too fast setting time and cannot meet the actual needs of the project. At the same time, the cost of sodium carbonate is relatively low, which can effectively reduce the cost of alkali activators. In the process of preparing geopolymer, steel slag powder is added as a binder material. Since steel slag powder has high strength and expands during the reaction, the strength of the geopolymer is increased, and the problem of excessive shrinkage deformation of the geopolymer is solved. Summary of the invention

[0007] (1) Technical issues

[0008] The present application provides a method for preparing a steel slag reinforced composite alkali-activated geopolymer, which solves the problems of long coagulation time in the current geopolymer preparation process, low early strength of fly ash-based geopolymer, poor volume stability, high cost of alkali activator, and difficulty in meeting engineering applications, thereby preparing higher quality alkali-activated geopolymer.

[0009] (2) Technical solution

[0010] In view of the problems in the current preparation process of geopolymers, such as long setting time, low early strength of fly ash-based polymers, poor volume stability, high cost of alkali activators, and difficulty in meeting engineering applications, the present application utilizes carbonate particles provided by sodium carbonate to coat geopolymer precursor powder, effectively reducing the setting time of geopolymers while reducing the cost and alkalinity of alkali activators; and adding steel slag powder to the geopolymer precursor powder, utilizing the characteristics of steel slag powder volume expansion to stabilize the volume of the geopolymer while increasing the strength of the geopolymer. The technical scheme of the present application is as follows: First, weigh a certain amount of water glass, potassium hydroxide, sodium carbonate, and water, and stir the sodium carbonate powder and water evenly. Then, mix the potassium hydroxide and water glass solution and stir evenly, and then stir the sodium carbonate aqueous solution and the sodium hydroxide water glass solution evenly to prepare a composite alkali activator. During the preparation of geopolymer precursor powder, steel slag powder, fly ash and mineral powder were first fully stirred in a stirring pot for two minutes, and then an alkali activator was added to prepare geopolymer slurry. The slurry was allowed to stand for 24 hours before demolding. After curing for 3 days, 7 days and 28 days, the mechanical and shrinkage properties of the steel slag reinforced composite alkali-activated geopolymer were tested through compressive strength test, flexural strength test and shrinkage test.

[0011] (3) Beneficial effects

[0012] As the global industrialization process accelerates, the production of traditional building materials such as ordinary Portland cement faces huge resource and environmental challenges. Every ton of cement produced releases about 0.8 to 0.9 tons of carbon dioxide. In addition, cement production requires a large amount of natural resources such as limestone as raw materials, while the main raw materials of geopolymers can be industrial waste residues, such as fly ash and slag. Fly ash is a waste generated by thermal power plants. The annual output of fly ash in the world is huge, and China alone produces hundreds of millions of tons of fly ash each year. Slag is a by-product of the steel smelting process, and the amount is also considerable. The accumulation of these industrial waste residues not only occupies a large amount of land, but also causes environmental pollution. For example, heavy metals in fly ash may seep into the soil and water.

[0013] By adopting the technology provided by this application, it is possible to prepare geopolymer materials with low cost, setting time that meets engineering needs, good volume stability, sufficient mechanical strength, and low carbon dioxide emissions. Geopolymer materials can be used as base materials or crack repairs for newly built roads, which can not only meet the "dual carbon development goals", but also make full use of industrial waste residues to avoid environmental damage to rivers and mountains caused by industrial waste residues. It has very obvious environmental, economic and social benefits, meets the country's requirements for sustainable development, and realizes resource conservation, energy cleaning, waste resource utilization, and environmental harmlessness. DETAILED DESCRIPTION

[0014] The present application provides a method for preparing a steel slag reinforced composite alkali-activated geopolymer, and the specific implementation steps are as follows:

[0015] (1) Weighing a certain amount of pure water and sodium carbonate powder, mixing the water and the sodium carbonate powder and stirring them evenly to fully dissolve the sodium carbonate powder in the solution, thereby preparing a sodium carbonate aqueous solution;

[0016] (2) Weighing a certain mass of water glass solution and flake potassium hydroxide respectively, slowly pouring potassium hydroxide into the water glass solution, and fully stirring to fully dissolve the potassium hydroxide in the solution, and adjusting the water glass modulus to 1.2 to obtain a potassium hydroxide water glass solution;

[0017] (3) slowly pouring the sodium carbonate aqueous solution prepared in step (1) into the potassium hydroxide water glass solution prepared in step (2), stirring thoroughly until the solution becomes a white turbid state, and then standing for 24 hours to make the solution a light yellow transparent liquid and cooling to room temperature to obtain a composite alkali activator;

[0018] (4) Weigh fly ash and slag powder in a fly ash to slag powder mass ratio of 1:3, and then weigh steel slag powder accounting for 15% of the total mass of the fly ash and slag powder, pour them into a stirring pot and stir at 100 rpm for 2 minutes to mix the three powders evenly, and prepare a steel slag reinforced geopolymer precursor;

[0019] (5) slowly pouring a certain amount of the composite alkali activator prepared in step (3) into the stirring pot to fully stir the geopolymer precursor and the composite alkali activator to prevent slag powder and fly ash from overflowing. When the geopolymer precursor and the composite alkali activator in the stirring pot are evenly mixed, the speed is adjusted to 200 rpm and stirred for another 2 minutes to obtain a slag-reinforced geopolymer slurry;

[0020] (6) pouring the geopolymer slurry prepared in step (5) into a mold, vibrating the mold 60 times with a trampoline to remove bubbles in the geopolymer slurry, allowing the geopolymer slurry to fill the mold after the vibration, smoothing the surface with a scraper, and allowing the geopolymer slurry to stand for 24 hours to allow the geopolymer slurry to solidify and form strength, thereby obtaining a steel slag reinforced composite alkali-activated geopolymer specimen;

[0021] (7) The test specimens prepared in step (6) were placed in a standard curing box and cured for 3 days, 7 days and 28 days respectively. The compressive strength, flexural strength and shrinkage coefficient of the steel slag reinforced composite alkali-activated geopolymer specimens were tested according to the "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-1999) to determine the preparation method of the steel slag reinforced composite alkali-activated geopolymer.

Claims

1. A method for preparing a steel slag reinforced composite alkali-activated geopolymer, characterized in that The specific steps of this method are as follows: (1) Weighing a certain amount of pure water and sodium carbonate powder, mixing the water and the sodium carbonate powder and stirring them evenly to fully dissolve the sodium carbonate powder in the solution, thereby preparing a sodium carbonate aqueous solution; (2) Weighing a certain mass of water glass solution and flake potassium hydroxide respectively, slowly pouring potassium hydroxide into the water glass solution, and fully stirring to fully dissolve the potassium hydroxide in the solution, and adjusting the water glass modulus to 1.2 to obtain a potassium hydroxide water glass solution; (3) slowly pouring the sodium carbonate aqueous solution prepared in step (1) into the potassium hydroxide water glass solution prepared in step (2), stirring thoroughly until the solution becomes a white turbid state, and then standing for 24 hours to make the solution a light yellow transparent liquid and cooling to room temperature to obtain a composite alkali activator; (4) Weigh fly ash and slag powder in a fly ash to slag powder mass ratio of 1:3, and then weigh steel slag powder accounting for 15% of the total mass of the fly ash and slag powder, pour them into a stirring pot and stir at 100 rpm for 2 minutes to mix the three powders evenly, and prepare a steel slag reinforced geopolymer precursor; (5) slowly pouring a certain amount of the composite alkali activator prepared in step (3) into the stirring pot to fully stir the geopolymer precursor and the composite alkali activator to prevent slag powder and fly ash from overflowing. When the geopolymer precursor and the composite alkali activator in the stirring pot are evenly mixed, the speed is adjusted to 200 rpm and stirred for another 2 minutes to obtain a slag-reinforced geopolymer slurry; (6) pouring the geopolymer slurry prepared in step (5) into a mold, vibrating the mold 60 times with a trampoline to remove bubbles in the geopolymer slurry, allowing the geopolymer slurry to fill the mold after the vibration, smoothing the surface with a scraper, and allowing the geopolymer slurry to stand for 24 hours to allow the geopolymer slurry to solidify and form strength, thereby obtaining a steel slag reinforced composite alkali-activated geopolymer specimen; (7) The test specimens prepared in step (6) were placed in a standard curing box and cured for 3 days, 7 days and 28 days respectively. The compressive strength, flexural strength and shrinkage coefficient of the steel slag reinforced composite alkali-activated geopolymer specimens were tested according to the "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-1999) to determine the preparation method of the steel slag reinforced composite alkali-activated geopolymer.