Preparation method of concrete pavement pyrite tailing early-strength repair mortar material

Abstract

The invention discloses a preparation method of a concrete pavement pyrite tailing early-strength repair mortar material. The preparation method comprises the following steps: (1) putting pyrite tailing fine aggregate into acid liquor, and heating for leaching treatment; and adding the calcined coal gangue admixture, uniformly mixing, and standing. And then adding alkali liquor to adjust the system to be alkaline. And (2) adding excessive calcium nitrate solution into the alkaline reaction system, then carrying out hydrothermal reaction, and after the hydrothermal reaction is completed, heating until water is evaporated to dryness to obtain the composite fine aggregate-admixture. And (3) uniformly mixing Portland cement, magnesium phosphate cement, the composite fine aggregate-admixture, emery, glass fibers and a water reducing agent, then adding water, and uniformly stirring to obtain the early-strength repair mortar material. According to the method, the adverse effect of the pyrite tailings on the repairing effect of the cement-based repairing mortar is effectively reduced, and dissolution of heavy metal ions is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of road surface repair material preparation, and in particular to a method for preparing a pyrite tailings early-strength repair mortar material for a concrete road surface. Background Art

[0002] Concrete pavement often has various diseases during use, such as cracking, breakage, surface shedding, pits, etc., which lead to damage to the concrete pavement. If not repaired in time, these diseases will further expand, which will not only affect the aesthetics of the pavement, but also affect driving safety. Cement-based repair mortar is one of the commonly used materials for repairing diseased parts. It has the characteristics of high strength, low cost, and simple construction, which can effectively improve the service life and aesthetics. Pyrite tailings are solid wastes generated during the mining and processing of pyrite. Not only does it contain ferrous disulfide (FeS2), an unstable factor, but it also contains heavy metal ions. However, pyrite tailings are difficult to be directly used in the preparation of cement-based repair mortar like other tailings. On the one hand, since pyrite tailings usually contain more heavy metal ions, they can easily cause pollution when they seep into the water body from the prepared cement-based materials or concrete materials. On the other hand, the sulfate ions formed by ferrous disulfide after acidification in water react with calcium ions produced by cement hydration to form calcium sulfate, and then further react with tricalcium silicate in cement clinker to form calcium sulfonate. This expansive product can easily cause problems such as cracking of the repair mortar and falling off from the pavement, affecting the repair effect, limiting the application of pyrite tailings, and resulting in a low utilization rate of this solid waste. Summary of the invention

[0003] In view of the above problems, the present invention provides a method for preparing a pyrite tailings early-strength repair mortar for concrete pavement, which effectively reduces the adverse effects of pyrite tailings on the repair effect of cement-based repair mortar and reduces the dissolution of heavy metal ions. Specifically, the technical solution of the present invention is as follows.

[0004] A method for preparing a concrete pavement pyrite tailings early-strength repair mortar comprises the following steps: (1) Pyrite tailings fine aggregate is placed in an acid solution and heated for leaching. Then, the calcined coal gangue admixture is added, mixed and allowed to stand. After completion, an alkali solution is added to adjust the system to alkalinity to obtain an alkaline reaction system.

[0005] (2) Adding an excess amount of calcium nitrate solution to the alkaline reaction system, and then carrying out a hydrothermal reaction. After completion, heating is performed to evaporate the water to obtain a composite fine aggregate-admixture.

[0006] (3) Mix the portland cement, magnesium phosphate cement, the composite fine aggregate - admixture, corundum sand, glass fiber, and water - reducing agent evenly, and then add water and stir evenly to obtain the early - strength repair mortar material.

[0007] Further, in step (1), the ratio of the pyrite tailings fine aggregate to the acid solution is 1 g: 10 - 30 ml. Optionally, the particle size of the pyrite tailings fine aggregate is 0.2 - 1.0 mm.

[0008] Further, in step (1), the acid solution includes at least one of nitric acid and sulfuric acid. Optionally, the concentration of the acid solution is 2 - 5 mol / L.

[0009] Further, in step (1), the heating temperature is 50 - 60 °C, and the leaching treatment time is 3 - 4 hours.

[0010] Further, in step (1), the calcination treatment includes: heating the coal gangue admixture to 420 - 570 °C, and then keeping it warm for 8 - 15 min. After completion, cool it to room temperature.

[0011] Further, in step (1), the coal gangue admixture is 13 - 25% of the mass of the pyrite tailings fine aggregate. Optionally, the fineness of the coal gangue admixture is 10 - 30 mesh.

[0012] Further, in step (1), the standing time is 30 - 60 min.

[0013] Further, in step (1), adjust the system to pH = 9 - 12. Optionally, the alkali solution includes at least one of sodium hydroxide solution, potassium hydroxide solution, etc.

[0014] Further, in step (2), the molar ratio of the hydroxide ions (OH - ) in the alkaline reaction system to calcium nitrate (Ca(NO3)2) is 1: 1.5 - 2.

[0015] Further, in step (2), the temperature of the hydrothermal reaction is 190 - 240 °C, and the time is 6 - 8 hours.

[0016] Further, in step (2), the evaporation - drying temperature is 70 - 100 °C, and heat it at this temperature until the mass of the solid product is constant to obtain the composite fine aggregate - admixture.

[0017] Further, in step (3), the proportions of the components are as follows: 30-40 parts by weight of portland cement, 6-8.5 parts by weight of magnesium phosphate cement, 65-100 parts by weight of composite fine aggregate-admixture, 5-11 parts by weight of corundum sand, 2-3.3 parts by weight of glass fiber, 0.5-0.8 parts by weight of water reducer, and 10-17 parts by weight of water.

[0018] Further, in step (3), the magnesium phosphate cement includes dead-burned magnesia powder and phosphate, and the mass ratio of the two is 3-5:1. Optionally, the phosphate includes at least one of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, etc. The magnesium phosphate cement helps to improve the early mechanical strength of the repair mortar of the present invention and facilitates rapid repair.

[0019] Further, in step (3), the particle size of the corundum sand is 0.1-0.25 mm. The corundum sand can effectively improve the wear resistance of the repair mortar of the present invention, thereby increasing the service life of the repaired part.

[0020] Further, in step (3), the water reducer includes any one of polycarboxylate water reducers, naphthalene-based water reducers, melamine-based water reducers, lignosulfonate water reducers, etc.

[0021] Further, in step (3), the length of the glass fiber is 1-5 mm. The glass fiber can effectively improve the crack resistance of the repair mortar of the present invention.

[0022] Compared with the prior art, the present invention has at least the following beneficial technical effects: The present invention uses pyrite tailings as the fine aggregate of the repair mortar to replace fine aggregates such as natural river sand, which helps to promote the resource utilization of pyrite tailings. For this purpose, the pyrite tailings fine aggregate is first treated with acid solution. On the one hand, the heavy metal ions therein can be fully dissolved, and on the other hand, the ferrous disulfide therein can be converted into ferrous ions and sulfate ions. Then, the calcined coal gangue admixture is added. Since the organic matter in the coal gangue admixture is removed after calcination treatment, a large number of micropores are formed. This porous property can not only be used to adsorb the dissolved heavy metal ions, but also eliminate the problem that the volume instability of the coal gangue admixture caused by these organic matters is likely to lead to the deterioration of the mechanical properties of the repair mortar of the present invention. Then, after the present invention adds an alkali solution to adjust the system to alkaline, on the one hand, the free heavy metal ions are converted into hydroxides for solidification to prevent the migration of heavy metal ions. On the other hand, the alkali solution can also activate the pyrite tailings fine aggregate and the coal gangue admixture, breaking the silicon-oxygen bonds and aluminum-oxygen bonds on their surfaces, thereby converting the inert silicon-oxygen tetrahedrons and aluminum-oxygen tetrahedrons on the surface into active ionic monomers. When calcium nitrate is further added for hydrothermal reaction, the active ionic monomers react with calcium ions to form nano-calcium silicate hydrate and calcium aluminate, which are loaded on the surfaces of the pyrite tailings fine aggregate and the coal gangue admixture. On the one hand, the addition of calcium nitrate also helps to convert arsenic elements existing in the form of arsenite and arsenate into calcium arsenite and calcium arsenate precipitates that are insoluble in water, thereby realizing the solidification of arsenic elements. On the other hand, these nano-calcium silicate hydrate and calcium aluminate can compact and fill the pores in the coal gangue admixture, which helps to further seal the heavy metal ion hydroxide precipitates therein, improve the solidification effect, and is also beneficial to the improvement of the strength of coal gangue particles. On the other hand, the nano-calcium silicate hydrate and calcium aluminate can induce the acceleration of the hydration of Portland cement in the repair mortar as crystal nuclei, improving its hydration rate and early strength. In addition, the calcium nitrate remaining in the composite fine aggregate - admixture acts as an early strength agent and also promotes the hydration rate of Portland cement, enabling the repair mortar of the present invention to not only help achieve rapid repair in emergency repair projects, but also form better early strength. Description of the Drawings

[0023] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. Hereinafter, the embodiments of the present invention will be described in detail in conjunction with the drawings, wherein: Figure 1 The sample of the composite fine aggregate - admixture prepared for Example 1 below.

[0024] Figure 2 The compressive strength test chart for Example 1 below.

[0025] Figure 3 Samples of the composite fine aggregate - admixture prepared for Example 2 below.

[0026] Figure 4 The compressive strength test chart for Example 2 below. Detailed implementation manners

[0027] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The experimental methods without specific conditions noted in the following embodiments are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0028] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be obtained through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in the conventional manner in the art or according to the product instructions. The preparation method of the early - strength repair mortar material of pyrite tailings for concrete pavement of the present invention will be further described below in conjunction with the accompanying drawings of the specification and the detailed implementation manners.

[0029] Example 1 A preparation method of an early - strength repair mortar material of pyrite tailings for concrete pavement includes the following steps: (1) Heat the coal gangue admixture with a fineness of 10 mesh to 460 °C at a heating rate of 10 °C / min and keep it warm for 10 min. Then cool it to room temperature to obtain the calcined coal gangue admixture, which is reserved for use.

[0030] (2) Screen the pyrite tailings (from a certain mine in Tongling City, Anhui Province) to obtain the particulate matter with a particle size distribution between 0.5 and 1 mm as the fine aggregate for reserve. Then mix the fine aggregate with sulfuric acid with a concentration of 3 mol / L in a ratio of 1 g:20 ml, heat it to 50 °C and keep it warm for 4 hours for leaching treatment, and continuously stir during the heat - preservation process. After completion, add the calcined coal gangue admixture and stir evenly, and its mass is 18% of the pyrite tailings fine aggregate. After standing for 45 min, gradually add sodium hydroxide solution to adjust the system to pH = 10 to obtain an alkaline reaction system.

[0031] (3) Add a 5 wt.% calcium nitrate solution according to the molar ratio of hydroxide ions in the alkaline reaction system to calcium nitrate of 1:1.5, stir evenly, and heat it to 220 °C for hydrothermal reaction for 7 hours. After completion, heat and dry it in an oven at 90 °C until the mass of the solid product is constant to obtain the composite fine aggregate - admixture (as Figure 1 shown), which is reserved for use.

[0032] (4)Take raw materials in the following proportions: 32 parts by weight of Portland cement (P·O 42.5), 7.5 parts by weight of magnesium phosphate cement (prepared by mixing dead-burned magnesia powder with a mesh size of 200 and potassium dihydrogen phosphate powder in a mass ratio of 4:1), 80 parts by weight of the composite fine aggregate - admixture, 11 parts by weight of corundum sand with a particle size distribution between 0.1 and 0.25 mm, 2.5 parts by weight of glass fiber with a length of 3 mm, and 0.65 parts by weight of polycarboxylate water reducer. Mix the above raw materials evenly, and then add 13 parts by weight of water and stir evenly to obtain the repair mortar material.

[0033] Performance test: (1) Pour the repair mortar material of this example into a mold, cure and demold it, and then cure it in a standard curing box for 24 hours. Then, according to the "Standard Test Method for Physical and Mechanical Properties of Concrete" (GBT 50081-2019), test the compressive strength of the specimen (as Figure 2 shown). (2) Pour the repair mortar material of this example into a mold, cure and demold it, and then cure it in a standard curing box for 7 days. Then, immerse the obtained specimen in distilled water, seal it, and let it stand for 3 days. Then, detect the total leaching amount of heavy metal elements (Pb, Cd, Cu, As) in the distilled water and calculate the curing rate. The results are: compressive strength = 17.24 MPa, curing rate = 92.16%.

[0034] Example 2 A preparation method of an early-strength repair mortar material for a concrete pavement with pyrite tailings includes the following steps: (1)Heat the coal gangue admixture with a fineness of 20 mesh to 420 °C at a heating rate of 10 °C / min and keep it warm for 15 min. Then cool it to room temperature to obtain the calcined coal gangue admixture for standby.

[0035] (2)Screen the pyrite tailings (from a certain mine in Tongling City, Anhui Province) to obtain particulate matter with a particle size distribution between 0.5 and 1.0 mm as the fine aggregate for standby. Then mix the fine aggregate with sulfuric acid with a concentration of 5 mol / L in a ratio of 1 g:10 ml, heat it to 50 °C, and keep it warm for 4.5 hours for leaching treatment, with continuous stirring during the warming process. After completion, add the calcined coal gangue admixture and stir evenly, and its mass is 13% of the pyrite tailings fine aggregate. Let it stand for 30 min, and then gradually add sodium hydroxide solution to adjust the system to pH = 9 to obtain an alkaline reaction system.

[0036] (3)Add a 5 wt.% calcium nitrate solution in a ratio such that the molar ratio of hydroxide ions to calcium nitrate in the alkaline reaction system is 1:1.7, stir evenly, and then heat it to 240 °C for hydrothermal reaction for 6 hours. After completion, heat and dry it in an oven at 100 °C until the mass of the solid product is constant to obtain the composite fine aggregate - admixture (as Figure 3As shown in the figure, reserve it.

[0037] (4) Take raw materials in the following proportions: 30 parts by weight of Portland cement (P·O 42.5), 6 parts by weight of magnesium phosphate cement (prepared by mixing dead-burned magnesia powder with a mesh size of 200 and potassium dihydrogen phosphate powder in a mass ratio of 5:1), 65 parts by weight of the composite fine aggregate - admixture, 8 parts by weight of corundum sand with a particle size distribution between 0.1 and 0.25 mm, 2 parts by weight of glass fiber with a length of 5 mm, and 0.5 parts by weight of polycarboxylate water reducer. Mix the above raw materials evenly, and then add 10 parts by weight of water and stir evenly to obtain the repair mortar material.

[0038] Performance test: Use the same method as in Example 1 above to test the 24-hour compressive strength of the repair mortar material of the example (as Figure 4 shown) and the solidification rate of heavy metal elements. The results are: compressive strength = 18.07 MPa, solidification rate = 89.68%.

[0039] Example 3 A preparation method of an early-strength repair mortar material for concrete pavement pyrite tailings, comprising the following steps: (1) Heat the coal gangue admixture with a fineness of 30 meshes to 570 °C at a heating rate of 10 °C / min and keep it warm for 8 min. Then cool it to room temperature to obtain the calcined coal gangue admixture, and reserve it.

[0040] (2) Screen the pyrite tailings (from a certain mine in Tongling City, Anhui Province) to obtain particulate matter with a particle size distribution between 0.2 and 0.5 mm as the fine aggregate and reserve it. Then mix the fine aggregate with nitric acid with a concentration of 2 mol / L in a ratio of 1 g:30 ml, heat it to 60 °C and keep it warm for 3 hours for leaching treatment, and continuously stir during the heat preservation process. After completion, add the calcined coal gangue admixture and stir evenly, and its mass is 25% of the pyrite tailings fine aggregate. After standing for 60 min, gradually add potassium hydroxide solution to adjust the system to pH = 12 to obtain an alkaline reaction system.

[0041] (3) Add a 5 wt.% calcium nitrate solution in a ratio of 1:2 of the hydroxide ions in the alkaline reaction system to calcium nitrate, stir evenly, and then heat it to 190 °C for hydrothermal reaction for 8 hours. After completion, heat and dry it in an oven at 70 °C until the mass of the solid product is constant to obtain the composite fine aggregate - admixture, and reserve it.

[0042] (4) Take raw materials in the following proportions: 40 parts by weight of Portland cement (P·O 42.5), 8.5 parts by weight of magnesium phosphate cement (prepared by mixing dead-burned magnesia powder with a mesh size of 200 and ammonium dihydrogen phosphate powder in a mass ratio of 3:1), 100 parts by weight of the composite fine aggregate - admixture, 5 parts by weight of corundum sand with a particle size distribution between 0.1 and 0.25 mm, 3.3 parts by weight of glass fiber with a length of 1 mm, and 0.8 parts by weight of lignosulfonate water reducer. Mix the above raw materials evenly by stirring, and then add 17 parts by weight of water and stir evenly to obtain the repair mortar material.

[0043] Performance test: Use the same method as in Example 1 above to test the 24-hour compressive strength and the solidification rate of heavy metal elements of the repair mortar material in this example. The results are: compressive strength = 18.81 MPa, solidification rate = 93.27%.

[0044] Example 4 A preparation method of an early-strength repair mortar material for pyrite tailings in concrete pavements includes the following steps: (1) Heat the coal gangue admixture with a fineness of 10 meshes to 460 °C at a heating rate of 10 °C / min and keep it warm for 10 min. Then cool it to room temperature to obtain the calcined coal gangue admixture for standby.

[0045] (2) Screen the pyrite tailings (from a certain mine in Tongling City, Anhui Province) to obtain particulate matter with a particle size distribution between 0.5 and 1 mm as the fine aggregate for standby. Then take 18% of the mass of the calcined coal gangue admixture prepared in this example of the fine aggregate, mix the two evenly by stirring to obtain the composite fine aggregate - admixture for standby.

[0046] (3) Take raw materials in the following proportions: 32 parts by weight of Portland cement (P·O 42.5), 7.5 parts by weight of magnesium phosphate cement (prepared by mixing dead-burned magnesia powder with a mesh size of 200 and potassium dihydrogen phosphate powder in a mass ratio of 4:1), 80 parts by weight of the composite fine aggregate - admixture in this example, 11 parts by weight of corundum sand with a particle size distribution between 0.1 and 0.25 mm, 2.5 parts by weight of glass fiber with a length of 3 mm, and 0.65 parts by weight of polycarboxylate water reducer. Mix the above raw materials evenly by stirring, and then add 13 parts by weight of water and stir evenly to obtain the repair mortar material.

[0047] Performance test: Use the same method as in Example 1 above to test the 24-hour compressive strength and the solidification rate of heavy metal elements of the repair mortar material in this example. The results are: compressive strength = 13.75 MPa, solidification rate = 24.38%.

[0048] Example 5 A preparation method of an early-strength repair mortar material for concrete pavement with pyrite tailings is the same as that of Example 2 above, except that the composite fine aggregate - admixture in this example is prepared by the following method: (1) Heat the coal gangue admixture with a fineness of 20 mesh to 420 °C at a heating rate of 10 °C / min and keep it warm for 15 min. Then cool it to room temperature to obtain the calcined coal gangue admixture for standby.

[0049] (2) Screen the pyrite tailings (from a certain mine in Tongling City, Anhui Province) to obtain particulate matter with a particle size distribution between 0.5 and 1.0 mm as the fine aggregate for standby. Then mix the fine aggregate with sulfuric acid with a concentration of 5 mol / L in a ratio of 1 g:10 ml and heat it to 50 °C for leaching treatment for 4.5 hours, and continuously stir during the heat preservation process. After completion, add the calcined coal gangue admixture and stir evenly, and its mass is 13% of the pyrite tailings fine aggregate. After standing for 30 min, gradually add sodium hydroxide solution to adjust the system to pH = 9 to obtain an alkaline reaction system.

[0050] (3) Add clear water (the added volume is the same as the volume of the calcium nitrate solution in Example 2 above) to the alkaline reaction system, and then heat it to 240 °C for hydrothermal reaction for 6 hours. After completion, heat and dry it in an oven at 100 °C until the mass of the solid product is constant to obtain the composite fine aggregate - admixture.

[0051] Performance test: Use the same method as in Example 1 above to test the 24-hour compressive strength of the repair mortar material in this example and the solidification rate of heavy metal elements. The results are: compressive strength = 15.12 MPa, solidification rate 80.44%.

[0052] Example 6 A preparation method of an early-strength repair mortar material for concrete pavement with pyrite tailings is the same as that of Example 1 above, except that the composite fine aggregate - admixture in this example is prepared by the following method: (1) Heat the coal gangue admixture with a fineness of 10 mesh to 460 °C at a heating rate of 10 °C / min and keep it warm for 10 min. Then cool it to room temperature to obtain the calcined coal gangue admixture for standby.

[0053] (2) Screen the pyrite tailings (from a certain mine in Tongling City, Anhui Province) to obtain particulate matter with a particle size distribution between 0.5 and 1 mm as fine aggregate for standby. Then mix the fine aggregate with sulfuric acid at a concentration of 3 mol / L in a ratio of 1 g:20 ml, heat to 50 °C, keep warm for 4 hours for leaching treatment, and continuously stir during the heat preservation process. After completion, add the calcined coal gangue admixture and stir evenly, and its mass is 18% of the pyrite tailings fine aggregate. After standing for 45 min, add clear water (the added volume is the same as the added volume of the sodium hydroxide solution in Example 1 above) to obtain a reaction system.

[0054] (3) Add 5 wt.% calcium nitrate solution (the added volume is the same as that in Example 1 above) to the reaction system, stir evenly, and heat to 220 °C for hydrothermal reaction for 7 hours. After completion, heat and dry in an oven at 90 °C until the mass of the solid product is constant to obtain the composite fine aggregate - admixture for standby.

[0055] Performance test: Use the same method as in Example 1 above to test the 24-hour compressive strength and the solidification rate of heavy metal elements of the repair mortar in this example. The results are: compressive strength = 14.23 MPa, solidification rate = 33.52%.

[0056] Example 7 A preparation method of an early-strength repair mortar for concrete pavement with pyrite tailings is the same as that in Example 3 above, except that the composite fine aggregate - admixture in this example is prepared by the following method: (1) Screen the pyrite tailings (from a certain mine in Tongling City, Anhui Province) to obtain particulate matter with a particle size distribution between 0.2 and 0.5 mm as fine aggregate for standby. Then mix the fine aggregate with nitric acid at a concentration of 2 mol / L in a ratio of 1 g:30 ml, heat to 60 °C, keep warm for 3 hours for leaching treatment, and continuously stir during the heat preservation process. After completion, add a coal gangue admixture with a fineness of 30 meshes and stir evenly, and its mass is 25% of the pyrite tailings fine aggregate. After standing for 60 min, gradually add potassium hydroxide solution to adjust the system to pH = 12 to obtain an alkaline reaction system.

[0057] (2) Add 5 wt.% calcium nitrate solution according to the molar ratio of hydroxide ions to calcium nitrate in the alkaline reaction system of 1:2, stir evenly, and heat to 190 °C for hydrothermal reaction for 8 hours. After completion, heat and dry in an oven at 70 °C until the mass of the solid product is constant to obtain the composite fine aggregate - admixture.

[0058] Performance test: Use the same method as in Example 1 above to test the 24-hour compressive strength and the solidification rate of heavy metal elements of the repair mortar in this example. The results are: compressive strength = 17.09 MPa, solidification rate = 76.64%.

[0059] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments or make equivalent replacements for some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a concrete pavement pyrite tailings early strength repair mortar, characterized in that: The steps include: (1) placing pyrite tailings fine aggregate in an acid solution and heating it for leaching treatment; then adding calcined coal gangue admixture, mixing evenly and letting it stand; after completion, adding alkali solution to adjust the system to alkalinity, thereby obtaining an alkaline reaction system; (2) adding an excess amount of calcium nitrate solution to the alkaline reaction system, and then carrying out a hydrothermal reaction. After completion, heating is performed to evaporate the water to obtain a composite fine aggregate-admixture; (3) Mix silicate cement, magnesium phosphate cement, the composite fine aggregate-admixture, corundum sand, glass fiber, and water reducer evenly, then add water and stir evenly to obtain the early strength repair mortar.

2. The method for preparing the early-strength repair mortar for concrete pavement pyrite tailings according to claim 1, characterized in that: In step (1), the ratio of the pyrite tailings fine aggregate to the acid solution is 1 g: 10-30 ml; optionally, the particle size of the pyrite tailings fine aggregate is 0.2-1.0 mm.

3. The method for preparing the early-strength repair mortar for pyrite tailings of concrete pavement according to claim 1, characterized in that: In step (1), the acid solution comprises: at least one of nitric acid and sulfuric acid; Optionally, in step (1), the concentration of the acid solution is 2-5 mol / L; Optionally, in step (1), the heating temperature is 50-60° C., and the leaching treatment time is 3-4 hours.

4. The method for preparing the early-strength repair mortar for pyrite tailings of concrete pavement according to claim 1, characterized in that: In step (1), the calcination treatment includes: heating the coal gangue admixture to 420-570°C, and then keeping the temperature for 8-15 minutes; after completion, cooling to room temperature.

5. The method for preparing the early-strength repair mortar for pyrite tailings of concrete pavement according to claim 1, characterized in that: In step (1), the coal gangue admixture is 13-25% of the mass of the pyrite tailings fine aggregate; Optionally, in step (1), the fineness of the coal gangue admixture is 10-30 mesh; Optionally, in step (1), the standing time is 30 to 60 minutes.

6. The method for preparing the early-strength repair mortar for pyrite tailings of concrete pavement according to claim 1, characterized in that: In step (1), the system is adjusted to pH = 9-12; Optionally, in step (1), the alkaline solution includes at least one of a sodium hydroxide solution and a potassium hydroxide solution.

7. The method for preparing the early-strength repair mortar for pyrite tailings of concrete pavement according to claim 1, characterized in that: In step (2), the molar ratio of hydroxide ions to calcium nitrate in the alkaline reaction system is 1:1.5-2; Optionally, in step (2), the temperature of the hydrothermal reaction is 190-240° C., and the time is 6-8 hours; Optionally, in step (2), the evaporation temperature is 70-100° C., and the solid product is heated at this temperature until the mass is constant, thereby obtaining the composite fine aggregate-admixture.

8. The method for preparing the early-strength repair mortar for pyrite tailings of concrete pavement according to claim 1, characterized in that: In step (3), the proportions of the components are: 30-40 parts by weight of silicate cement, 6-8.5 parts by weight of magnesium phosphate cement, 65-100 parts by weight of composite fine aggregate-admixture, 5-11 parts by weight of corundum sand, 2-3.3 parts by weight of glass fiber, 0.5-0.8 parts by weight of water reducer, and 10-17 parts by weight of water.

9. The method for preparing the early-strength repair mortar for pyrite tailings of concrete pavement according to any one of claims 1 to 8, characterized in that: In step (3), the magnesium phosphate cement comprises dead-burned magnesium oxide powder and phosphate, and the mass ratio of the two is 3-5:1; optionally, the phosphate comprises: at least one of potassium dihydrogen phosphate and ammonium dihydrogen phosphate.

10. The method for preparing the early-strength repair mortar for pyrite tailings of concrete pavement according to any one of claims 1 to 8, characterized in that: In step (3), the particle size of the corundum sand is 0.1-0.25 mm; Optionally, in step (3), the water reducer includes: any one of a polycarboxylate water reducer, a naphthalene-based water reducer, a melamine-based water reducer, and a lignin sulfonate water reducer; Optionally, in step (3), the length of the glass fiber is 1-5 mm.

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