Toughening method of geopolymer-stabilized waste water-stabilized macadam base regenerated mixture

Abstract

The invention provides a toughening method of a geopolymer-stabilized waste water-stable macadam base regeneration mixture, belongs to the technical field of pavement base regeneration, and solves the problems that the existing waste water-stable macadam base is low in reutilization rate, the waste water-stable macadam base regeneration mixture is insufficient in crack resistance and relatively poor in toughness, the service life of a pavement is seriously shortened and the like. Firstly, a geopolymer is used for replacing cement to stabilize a waste water-stable macadam base material, and the strength of a regenerated mixture is improved; secondly, pretreating rubber powder, and adding the pretreated rubber powder into the waste water-stabilized macadam regenerated mixture to increase toughness; and finally, evaluating the toughening effect of the rubber powder on the waste water-stable macadam regenerated mixture through a four-point bending test and a nanoindentation test in combination with an image processing technology. The geopolymer is used for replacing cement to stabilize the waste water-stable macadam base material, carbon dioxide emission is reduced, the early strength of the mixture is improved, the rubber powder is used for improving the toughness of the waste water-stable macadam base regenerated mixture, pavement cracks are reduced, and the service life of the mixture is prolonged.

Description

Technical Field

[0001] The present application discloses a method for toughening a geopolymer-stabilized waste water-stabilized crushed stone base regeneration mixture, and belongs to the technical field of pavement base regeneration. Background Art

[0002] The scale of transportation infrastructure construction in my country continues to expand, and the mileage of highways open to traffic continues to increase. According to highway data released by the Ministry of Transport, by the end of 2023, the total mileage of highways in my country has reached 5.4368 million kilometers, accounting for 99.9% of the total mileage of highways. At present, my country's highway development has entered a stage of large-scale maintenance and reconstruction. In the process of road maintenance and maintenance, a large amount of waste base materials will be generated, such as waste water-stabilized crushed stone base materials, waste fly ash stabilized soil base materials, etc. If these waste materials are left alone, land resources will be wasted, the environment will be polluted, and a lot of funds will be wasted on road maintenance. Therefore, recycling waste base materials can form good economic benefits, save land resources, and protect the environment. It is in line with the national goal of green development and high-quality development. At present, there are two methods of pavement regeneration: regeneration and thermal regeneration. Among them, thermal regeneration has high energy consumption, serious pollution, and low recovery rate, which cannot form good economic and environmental benefits. Regeneration is worthy of in-depth study due to its low energy consumption and low pollution of the recycled mixture.

[0003] Water-stabilized crushed stone is a commonly used semi-rigid material, which is widely used in the base of highways of all levels in my country. With the increase of service time of roads in my country, the phenomenon of overload and overlimit exists. Many highways often need to deal with diseases within a few years after opening to traffic, or even overhaul the pavement structure layer, which greatly compresses the time interval of maintenance and repair, resulting in an increasingly heavy task of road maintenance.

[0004] This application uses waste water-stabilized crushed stone base materials instead of new aggregates, saving a large amount of aggregates, which can greatly reduce the material costs in maintenance projects, thereby reducing maintenance costs, and reducing environmental damage caused by mining and excavation sites, thereby protecting the environment. In addition, the reduction in the amount of raw materials transported also greatly reduces energy consumption and damage to roads caused by transportation. At the same time, the construction time of the recycling technology is relatively short, and traffic can be opened quickly, minimizing the impact on road traffic. Compared with hot regeneration technology, cold regeneration technology consumes less energy, has little impact on the surrounding environment, and can effectively protect the ecological environment.

[0005] In the implementation of base layer regeneration technology, scientific design and reasonable construction technology are crucial. First, it is necessary to conduct a comprehensive assessment of the condition of the old base layer to determine the feasibility of its recycling. Then, according to the use requirements and design standards of the road, a reasonable regeneration plan is formulated, including crushing, screening, adding regeneration agents, etc. During the construction process, various parameters need to be strictly controlled to ensure that the recycled base material has good physical and mechanical properties and can meet the use requirements of the road.

[0006] Domestic research on the regeneration of waste water-stabilized crushed stone bases mainly revolves around its engineering application effects, material properties, cost control and other aspects. In the research on the regeneration of waste water-stabilized crushed stone bases, scholars not only focus on its basic physical and mechanical properties, such as 7-day unconfined compressive strength and crack resistance, but also deeply explore its durability and stability under different environmental conditions. Foreign researchers also explored the effects of different dosages, different mix ratios and different molding conditions on the performance of waste water-stabilized crushed stone bases. The researchers evaluated roller-compacted concrete with different cement contents and three different natural aggregates and recycled aggregates. The results showed that there was no significant difference between the use of recycled concrete aggregates and natural aggregates, which illustrates the feasibility of replacing natural aggregates with recycled aggregates.

[0007] However, most current studies use cement as a binder for recycled mixtures of waste water-stabilized crushed stone base. In conventional cement production systems, a large amount of carbon dioxide is emitted during clinker preparation and other processes due to key processes such as high-temperature calcination. Innovative technical solutions are urgently needed to solve the carbon emission problem. In addition, the recycled mixture of waste water-stabilized crushed stone base has insufficient toughness and poor crack resistance, and is prone to cracks, which seriously shortens the service life of the road surface and has a certain negative impact on road maintenance projects.

[0008] In view of this, this application reduces carbon dioxide emissions by using geopolymer instead of cement, while increasing the strength of the recycled mixture of waste water-stabilized crushed stone, and uses rubber powder to toughen the recycled mixture of waste water-stabilized crushed stone to reduce cracks, and pre-treats the rubber powder to improve the interfacial bonding strength of the rubber powder so as to increase the toughness of the recycled base layer of waste water-stabilized crushed stone. Finally, the toughening effect of rubber powder on the geopolymer-stabilized recycled mixture of waste water-stabilized crushed stone base layer is evaluated through four-point bending test, nanoindentation test and digital image processing technology. Summary of the invention

[0009] (1) Technical issues

[0010] The present application provides a method for toughening a geopolymer-stabilized recycled mixture of waste water-stabilized crushed stone base, which solves the current problems of low reuse rate of waste water-stabilized crushed stone base, insufficient crack resistance and poor toughness of the recycled mixture of waste water-stabilized crushed stone base, severely shortened pavement service life, and high carbon dioxide emissions, thereby improving the toughness of the recycled mixture of waste water-stabilized crushed stone base and reducing pavement cracks.

[0011] (2) Technical solution

[0012] In view of the low recycling rate of waste water-stabilized macadam base, the insufficient crack resistance and poor toughness of the recycled mixture of waste water-stabilized macadam base, the serious shortening of the service life of the road surface, and the high carbon dioxide emissions, this application provides a method for toughening the recycled mixture of waste water-stabilized macadam base stabilized by geopolymer, and its technical scheme is as follows: First, the waste water-stabilized macadam base material is tested, mainly to evaluate its gradation, mechanical properties, etc. For geopolymer, the surface response method is used to determine the optimal ratio of mineral powder, fly ash, and alkali activator in the geopolymer to prepare a geopolymer with sufficient strength, and the surface response method is used to determine the optimal dosage of geopolymer, rubber powder, waste water-stabilized macadam base material, and new aggregate. Finally, the unconfined compressive strength, splitting strength, and shrinkage coefficient are evaluated through experiments to ensure that its performance meets the relevant technical requirements. Finally, the four-point bending test and nanoindentation test are combined with digital image technology to evaluate the geopolymer reinforcement and rubber powder toughening effect.

[0013] (3) Beneficial effects

[0014] With the continuous increase in the scale of highways in my country, about 100,000 kilometers of roads need to be repaired and maintained every year, generating a large amount of old road base materials, which provides a broad prospect for the promotion and application of recycled waste water-stabilized crushed stone base. By using the geopolymer-stabilized waste water-stabilized crushed stone base recycled mixture provided by this application, a waste water-stabilized crushed stone recycled base with good performance can be obtained.

[0015] According to the technical solution provided in this application, through the combination of production, learning and research, and active cooperation with relevant enterprises, it is possible to prepare a recycled waste water-stabilized macadam base with independent intellectual property rights, and use the old road base materials as the base materials for new highways, which can not only solve the problem of the treatment of waste base materials, but also reduce the mining of natural stones, thereby avoiding environmental damage, with obvious environmental benefits, economic benefits and social benefits, and meet the national requirements for sustainable development of resource conservation, energy cleaning, waste resource utilization, and environmental harmlessness. In addition, waste rubber tires are black pollution, and processing waste tires into rubber powder can effectively increase the toughness of the base and reduce the problem of base cracking. Compared with cement, geopolymer has the advantage of less carbon dioxide emissions, and is used to stabilize the recycled mixture of waste water-stabilized macadam base, and belongs to green building materials. DETAILED DESCRIPTION

[0016] The present application provides a method for toughening a geopolymer-stabilized recycled mixture of waste water-stabilized crushed stone base, and the specific implementation steps are as follows:

[0017] (1) Conduct raw material tests on fly ash, slag powder, steel slag powder, potassium hydroxide, sodium carbonate, water glass, waste water-stabilized crushed stone base material, rubber powder and water to ensure that all technical indicators meet the requirements of relevant specifications;

[0018] (2) Weighing a certain mass of water and sodium carbonate powder, mixing the sodium carbonate powder and water to obtain a sodium carbonate aqueous solution, then weighing a certain mass of water glass solution and potassium hydroxide, slowly adding potassium hydroxide to the water glass solution, stirring well, and adjusting the water glass modulus to 1.2 to obtain a potassium hydroxide water glass solution;

[0019] (3) slowly pouring the sodium carbonate aqueous solution prepared in step (2) into the prepared potassium hydroxide water glass solution, stirring thoroughly until it becomes a white turbid state, and then standing for 24 hours to make the mixed solution a light yellow transparent liquid and cool to room temperature to obtain a composite alkali activator;

[0020] (4) Screening and grading the waste cement-stabilized crushed stone base material to obtain coarse aggregate, fine aggregate and their passing rate of different particle sizes, and designing the mix ratio according to the Technical Specifications for Highway Pavement Base Construction (JTG / T F20-2015). New aggregate is used to fill the missing gradation of the waste cement-stabilized crushed stone base material to obtain the design gradation of new and old mixed aggregates;

[0021] (5) Weighing slag powder and fly ash in a mass ratio of 4:1, pouring them into a stirring pot, and stirring at a speed of 100 rpm for 2 minutes to evenly stir the slag powder and fly ash to obtain a geopolymer precursor powder;

[0022] (6) adding the geopolymer precursor powder to the new and old mixed aggregates of the designed gradation obtained in step (4), wherein the mass of the geopolymer precursor powder is 15% of the mass of the new and old mixed aggregates, and fully stirring and mixing the geopolymer precursor powder using a stirrer to allow the geopolymer precursor powder to penetrate into the pores of the aggregates, and then adding a certain amount of the composite alkali activator prepared in step (3), stirring evenly, and obtaining a geopolymer-stabilized waste water-stabilized crushed stone base regeneration mixture;

[0023] (7) Weighing a certain volume ratio of 200 mesh rubber powder to the polymer precursor powder, soaking the mixture in a 3 mol / L sodium hydroxide solution, and leaving the mixture to stand for 48 hours to obtain a pretreated rubber powder;

[0024] (8) pouring the pretreated rubber powder obtained in step (7) into the geopolymer-stabilized waste water-stabilized crushed stone base recycled mixture prepared in step (6), and fully mixing them to obtain a rubber powder-toughened geopolymer-stabilized waste water-stabilized crushed stone base recycled mixture;

[0025] (9) According to the Test Code for Inorganic Binder Stabilized Materials for Highway Engineering (JTG 3441-2024), the Test Code for Rock for Highway Engineering (JTG 3431-2024), and the Test Code for Cement and Cement Concrete for Highway Engineering (JTG 3420-2020), the unconfined compressive strength test specimens, splitting strength test specimens, and shrinkage test specimens of the geopolymer-stabilized waste water-stabilized crushed stone base recycled mixture toughened with rubber powder were prepared. After curing for 3 days, 7 days, and 28 days, the unconfined compressive strength, indirect tensile strength, and shrinkage coefficient were tested to ensure that they met the technical requirements of the relevant specifications;

[0026] (10) Four-point bending test and nanoindentation test were carried out, with crack propagation rate, crack area and rebound modulus as technical indicators respectively. Image technology was used to evaluate the toughening effect of rubber powder on the geopolymer-stabilized waste water-stabilized crushed stone base recycled mixture, and the toughening method of the geopolymer-stabilized waste water-stabilized crushed stone base recycled mixture was determined.

Claims

1. A method for toughening a geopolymer-stabilized recycled mixture of waste water-stabilized crushed stone base, characterized in that The specific steps of this method are as follows: (1) Conduct raw material tests on fly ash, slag powder, steel slag powder, potassium hydroxide, sodium carbonate, water glass, waste water-stabilized crushed stone base material, rubber powder and water to ensure that all technical indicators meet the requirements of relevant specifications; (2) Weighing a certain mass of water and sodium carbonate powder, mixing the sodium carbonate powder and water to obtain a sodium carbonate aqueous solution, then weighing a certain mass of water glass solution and potassium hydroxide, slowly adding potassium hydroxide to the water glass solution, stirring well, 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 (2) into the prepared potassium hydroxide water glass solution, stirring thoroughly until it becomes a white turbid state, and then standing for 24 hours to make the mixed solution a light yellow transparent liquid and cool to room temperature to obtain a composite alkali activator; (4) Screening and grading the waste cement-stabilized crushed stone base material to obtain coarse aggregate, fine aggregate and their passing rate of different particle sizes, and designing the mix ratio according to the Technical Specifications for Highway Pavement Base Construction (JTG / T F20-2015). New aggregate is used to fill the missing gradation of the waste cement-stabilized crushed stone base material to obtain the design gradation of new and old mixed aggregates; (5) Weighing slag powder and fly ash in a mass ratio of 4:1, pouring them into a stirring pot, and stirring at a speed of 100 rpm for 2 minutes to evenly stir the slag powder and fly ash to obtain a geopolymer precursor powder; (6) adding the geopolymer precursor powder to the new and old mixed aggregates of the designed gradation obtained in step (4), wherein the mass of the geopolymer precursor powder is 15% of the mass of the new and old mixed aggregates, and stirring and mixing them fully with a stirrer so that the geopolymer precursor powder can penetrate into the pores of the aggregates, and then adding a certain amount of the composite alkali activator prepared in step (3), stirring evenly, and obtaining a geopolymer-stabilized waste water-stabilized crushed stone base regeneration mixture; (7) Weighing a certain volume ratio of 200 mesh rubber powder to the polymer precursor powder, soaking the mixture in a 3 mol / L sodium hydroxide solution, and leaving the mixture to stand for 48 hours to obtain a pretreated rubber powder; (8) pouring the pretreated rubber powder obtained in step (7) into the geopolymer-stabilized waste water-stabilized crushed stone base recycled mixture prepared in step (6), and fully mixing them to obtain a rubber powder-toughened geopolymer-stabilized waste water-stabilized crushed stone base recycled mixture; (9) According to the Test Code for Inorganic Binder Stabilized Materials for Highway Engineering (JTG 3441-2024), the Test Code for Rock for Highway Engineering (JTG 3431-2024), and the Test Code for Cement and Cement Concrete for Highway Engineering (JTG 3420-2020), the unconfined compressive strength test specimens, splitting strength test specimens, and shrinkage test specimens of the geopolymer-stabilized waste water-stabilized crushed stone base recycled mixture toughened with rubber powder were prepared. After curing for 3 days, 7 days, and 28 days, the unconfined compressive strength, indirect tensile strength, and shrinkage coefficient were tested to ensure that they met the technical requirements of the relevant specifications; (10) Four-point bending test and nanoindentation test were carried out, with crack propagation rate, crack area and rebound modulus as technical indicators respectively. Image technology was used to evaluate the toughening effect of rubber powder on the geopolymer-stabilized waste water-stabilized crushed stone base recycled mixture, and the toughening method of the geopolymer-stabilized waste water-stabilized crushed stone base recycled mixture was determined.