Environmentally friendly coal gangue-based all-solid waste road base mixture and preparation method thereof

Abstract

The present invention discloses an environmentally friendly coal gangue-based all-solid waste road base mixture and a preparation method thereof, wherein the mixture comprises coal gangue coarse aggregate, low-temperature sintering binder, setting agent, fly ash, stone chips, and activator. The present invention selects high-strength particles in coal gangue as coarse aggregate by sorting and crushing, mixes weak particles with high carbon content and low strength with carbide slag, calcium silicate slag, and desulfurized gypsum to form a low-temperature fired binder for replacing cement, and adjusts the performance of the mixture by setting agent and activator to prepare a semi-rigid base mixture with good construction performance and road performance, and the mixture can directly replace cement-stabilized crushed stone for road engineering construction. The present invention not only realizes the large-scale resource utilization of coal-fired power solid waste such as coal gangue, but also replaces cement by low-temperature fired binders of solid waste such as coal gangue, thereby reducing energy consumption and carbon emissions, realizing low-carbon emission reduction in road base construction, and having significant economic and environmental benefits.

Description

Technical Field

[0001] The present invention belongs to the field of building materials, and more specifically, relates to an environmentally friendly coal gangue-based all-solid waste road base mixture and a preparation method thereof. Background Art

[0002] Gangue is a hard rock that coexists or coexists with coal during its formation, and is a by-product of coal mining. Most of the abandoned gangue around coal mines is piled up around the mine in a cone or valley dumping style, resulting in a mountain of gangue around the coal mine, occupying a large amount of farmland. In addition, during the rainy season, the fine materials of gangue are washed to the surface by rainwater, causing serious desertification of farmland and reducing grain production. The natural decomposition of gangue during the stacking process may also release a variety of toxic gases, causing serious pollution of the atmospheric environment and water resources, seriously damaging the ecological environment, and endangering people's health. At present, the solid waste resource utilization of gangue is mainly used for recycling coal and pyrite, power generation, and for building materials such as sintered ceramsite, brick making, sintered lightweight aggregate, etc. The industrial model is relatively single and small in scale. Due to the limitations of technology, a large amount of waste liquid and waste residue will be generated, and the environmental and economic benefits are low. In road engineering, coal gangue is mainly used for soft soil foundation treatment, roadbed filling or admixture of the pavement base of low-grade highways. The coal gangue with spontaneous combustion or high stability is used. The loss on ignition is an indicator of the carbon content of coal gangue. It is generally believed that the greater the loss on ignition, the greater the negative effect on the stability of coal gangue. However, the coal gangue loss on ignition of most coal mines is greater than 12%, which has an adverse effect on road performance. The coal gangue with high fixed carbon and volatile components in the residual coal is prone to spontaneous combustion. The soft rock will undergo mudification and some chemical decomposition after being soaked in water, which will change the structure and density of the coal gangue, causing the compression deformation to increase, and at the same time reduce the shear strength and bearing capacity of the pavement structure. In addition, because the formation reasons of different coal mines are different, the locations and methods of producing coal gangue are different, resulting in obvious differences in chemical composition and properties. Therefore, many factors cannot be controlled when it is used as a road base material. Under certain conditions, the base material may be damaged and cannot be stable and durable, thus affecting the performance of the pavement structure. Therefore, it is difficult to use the original coal gangue in large quantities on the road base. Summary of the invention

[0003] An object of embodiments of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages to be described below.

[0004] Another object of the present invention is to provide a method for preparing an environmentally friendly coal gangue-based all-solid waste road base mixture. The present invention selects high-strength particles in coal gangue as coarse aggregates for semi-rigid base mixtures by sorting and crushing, mixes weak particles with high carbon content and low strength with carbide slag, calcium silicate slag, desulfurized gypsum, etc., and fires low-temperature binders to replace cement, and adjusts the performance of the mixture with the assistance of a coagulant and an activator to prepare a semi-rigid base mixture with good construction performance and road performance. The mixture can directly replace cement-stabilized crushed stone for road engineering construction. The present invention not only realizes the large-scale resource utilization of coal-fired power solid waste such as coal gangue, but also replaces cement by low-temperature firing binders of solid waste such as coal gangue, thereby reducing energy consumption and carbon emissions, realizing low-carbon emission reduction in road base construction, and having significant economic and environmental benefits.

[0005] Another object of the present invention is to provide an environmentally friendly coal gangue-based all-solid waste road base mixture.

[0006] In order to achieve these purposes and advantages of the present invention, the following technical solutions are provided:

[0007] A method for preparing an environmentally friendly coal gangue-based all-solid waste pavement base mixture comprises the following steps:

[0008] Step 1: crush the original coal gangue, the crushing value of the coal gangue aggregate after crushing is not more than 30%, the calorific value is not more than 500 cal / g, and three kinds of coal gangue particle sizes of 20-30 mm, 10-20 mm and 5-10 mm are selected and compounded as the coal gangue coarse aggregate;

[0009] Step 2: taking the coal gangue with a particle size of 0 to 5 mm after crushing in step 1, mixing it with carbide slag, calcium silicate slag, desulfurized gypsum, fluorite, fluorite and water, and pressing it into a raw sheet, then firing the raw sheet to obtain clinker, and then grinding the clinker to prepare a sintering binder;

[0010] Step three: respectively take the gangue coarse aggregate and the sintered binder, mix them and press them into shape to obtain a gangue-based all-solid waste pavement base mixture.

[0011] Preferably, in the preparation method of the environmentally friendly coal gangue-based all-solid waste road base mixture, in step 3, by weight, take 50-70 parts of the coal gangue coarse aggregate, take 3-8 parts of the sintered binder, and also take 0.05-0.6 parts of the setting agent, 0-15 parts of fly ash, 20-35 parts of stone chips and 0.01-0.06 parts of the activator, mix them with the coal gangue coarse aggregate and the sintered binder, and then press and shape them to obtain the coal gangue-based all-solid waste road base mixture. More preferably, take 59.19-66.35 parts of the coal gangue coarse aggregate, take 5 parts of the sintered binder, and also take 0.2-0.4 parts of the setting agent, 10 parts of fly ash, 25.37-25.43 parts of stone chips and 0.02-0.04 parts of the activator.

[0012] Preferably, in the method for preparing the environmentally friendly coal gangue-based all-solid waste pavement base mixture, in step 2, 40 to 60 parts of 0 to 5 mm coal gangue, 15 to 30 parts of carbide slag, 15 to 25 parts of calcium silicate slag, 5 to 15 parts of desulfurized gypsum, 5 to 15 parts of fluorite and 2 to 8 parts of fluorite are taken by weight to press into the raw material sheet;

[0013] The raw material sheet is fired at 850-950° C. for 60-90 minutes, then taken out and rapidly cooled in air to obtain clinker, and then the clinker is ground to 0.08 mm to obtain the sintering binder.

[0014] Preferably, in the method for preparing the environmentally friendly coal gangue-based all-solid waste pavement base mixture, in step 2, the sum of the masses of A12O3 and SiO2 in the coal gangue of 0 to 5 mm is not less than 80% of the total mass of the coal gangue of 0 to 5 mm, the sum of the masses of CaO and SiO2 in the calcium-silicate slag is not less than 65% of the total mass of the calcium-silicate slag, the CaO in the carbide slag is ≥85wt%, the CaSO4·2H2O in the desulfurized gypsum is ≥90wt%, the CaSO4·2H2O in the fluorinated gypsum is ≥90wt%, and the CaF2 in the fluorite is ≥40wt%.

[0015] Preferably, in the method for preparing the environmentally friendly coal gangue-based all-solid waste pavement base mixture, the setting regulator comprises the following components: fired desulfurized gypsum, borax and fulvic acid, wherein the weight ratio of fired desulfurized gypsum, borax and fulvic acid is (50-200):(1-10):(1-10);

[0016] The fired desulfurized gypsum is obtained by drying the solid waste desulfurized gypsum from a thermal power plant at 150-170° C. for 40 minutes. The SO3 content in the fired desulfurized gypsum is not less than 50wt%.

[0017] Preferably, in the method for preparing the environmentally friendly coal gangue-based all-solid waste pavement base mixture, the sum of the masses of A1203, SiO2 and Fe2O3 in the fly ash is not less than 70wt% of the fly ash, the loss on ignition is not more than 20wt%, and the stone chips are solid waste with a particle size less than 5mm generated in the process of producing crushed stone in a gravel field, and the content of particles below 0.075mm is not less than 10%.

[0018] Preferably, in the method for preparing the environmentally friendly coal gangue-based all-solid waste pavement base mixture, the activator comprises the following components: sodium lignin sulfonate, sodium dinaphthylmethane disulfonate, sodium dodecyl sulfonate and ferrous sulfate, wherein the weight ratio of sodium lignin sulfonate, sodium dinaphthylmethane disulfonate, sodium dodecyl sulfonate and ferrous sulfate is (10-30):(10-30):(1-5):(20-40).

[0019] An environmentally friendly coal gangue-based all-solid waste road base mixture is prepared by any of the above methods.

[0020] Preferably, the environmentally friendly coal gangue-based all-solid waste pavement base mixture comprises the following components by weight: 50-70 parts of coal gangue coarse aggregate; 3-8 parts of low-temperature sintering binder; 0.05-0.6 parts of setting agent; 0-15 parts of fly ash; 20-35% of stone chips; 0.01-0.06% of activator;

[0021] The gangue coarse aggregate is a compound of three particle sizes of 20-30mm, 10-20mm and 5-10mm of gangue crushed by a selective crushing method. The original gangue can be rock gangue, washed gangue or spontaneous combustion gangue. After crushing, the crushing value of the gangue aggregate is not more than 30%, and the calorific value is not more than 500cal / g.

[0022] The low-temperature sintering binder contains, by mass percentage, 8% to 15% of fluoroaluminate minerals, 5% to 15% of sulphoaluminate minerals, 25% to 35% of silicate minerals, and 1% to 3% of free calcium oxide.

[0023] Preferably, in the environmentally friendly coal gangue-based all-solid waste pavement base mixture, 59.19-66.35 parts of the coal gangue coarse aggregate, 5 parts of the sintered binder, 0.2-0.4 parts of the setting agent, 10 parts of fly ash, 25.37-25.43 parts of stone chips and 0.02-0.04 parts of the activator are taken;

[0024] The activator comprises the following components: sodium lignin sulfonate, sodium dinaphthylmethane disulfonate, sodium dodecyl sulfonate, and ferrous sulfate, wherein the weight ratio of sodium lignin sulfonate, sodium dinaphthylmethane disulfonate, sodium dodecyl sulfonate, and ferrous sulfate is (10-30):(10-30):(1-5):(20-40);

[0025] The stone chips are solid waste with a particle size of less than 5 mm generated during the production of stone in a stone crushing site, and the content of particles below 0.075 mm is not less than 10%;

[0026] The sum of the masses of Al2O3, SiO2 and Fe2O3 in the fly ash is not less than 70wt% of the fly ash, and the loss on ignition is not more than 20wt%;

[0027] The setting agent comprises the following components: fired desulfurized gypsum, borax and fulvic acid, wherein the weight ratio of fired desulfurized gypsum, borax and fulvic acid is (50-200):(1-10):(1-10); the fired desulfurized gypsum is obtained by drying the solid waste desulfurized gypsum from a thermal power plant at 160±10°C for 40 minutes, and the SO3 content in the fired desulfurized gypsum is not less than 50wt%.

[0028] The present invention has at least the following beneficial effects:

[0029] The present invention selects high-strength particles in coal gangue as coarse aggregate by sorting and crushing, mixes weak particles with high carbon content and low strength with carbide slag, calcium silicate slag, desulfurized gypsum, etc., and fires them at low temperature to replace cement, and adjusts the performance of the mixture with the assistance of a coagulant and an activator to prepare a semi-rigid base mixture with good construction performance and road performance. The mixture can directly replace cement-stabilized crushed stone for road engineering construction. The present invention not only realizes the large-scale resource utilization of coal-fired power solid waste such as coal gangue, but also replaces cement by firing cementing materials with solid waste such as coal gangue at low temperature, thereby reducing energy consumption and carbon emissions, realizing low-carbon emission reduction in road base construction, and having significant economic and environmental benefits.

[0030] The present invention provides an effective way to solve the large-scale resource utilization of solid waste such as coal gangue. The technology can be widely used in areas rich in coal gangue and other coal-fired power solid waste. The semi-rigid base mixture of coal gangue full solid waste not only realizes the large-scale utilization of solid waste such as coal gangue, but also can save a lot of natural crushed stone mining, which has significant social and economic benefits.

[0031] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with the examples so that those skilled in the art can implement it according to the description. It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial sources unless otherwise specified.

[0033] The present invention aims at the problems existing in the application of coal gangue in road base. The present invention first adopts a sorting and crushing method to sort out coal gangue with a high carbon content, and then co-fires it with solid wastes such as calcium carbide slag and calcium silicate slag at low temperature to prepare a binder for the base, and then prepares a semi-rigid base material together with the sorted low-crushing value coal gangue aggregate, fly ash and other solid wastes, thereby realizing the large-scale utilization of solid wastes such as coal gangue.

[0034] Coal gangue, fly ash, desulfurization ash, calcium silicate slag and other coal-fired power solid waste and their derivatives have large storage capacity and are difficult to use on a large scale. This application makes full use of industrial solid waste such as coal gangue to prepare semi-rigid base mixture for roads, which can not only absorb such industrial solid waste, but also reduce the amount of cement in the semi-rigid base, which is in line with the country's sustainable development policy. It can also give full play to the potential active characteristics of industrial solid waste, improve the long-term performance of the road base, and achieve multiple goals at one stroke.

[0035] The invention provides a method for preparing an environmentally friendly coal gangue-based all-solid waste road base mixture, which comprises: 50% to 70% of coal gangue coarse aggregate; 3% to 8% of low-temperature sintered binder; 0.05% to 0.6% of setting agent; 0% to 15% of fly ash; 20% to 35% of stone chips; 0.01% to 0.06% of activator; the sum of the contents of the components is 100%, based on the total mass of the road base mixture;

[0036] Among them, the gangue coarse aggregate is the original gangue crushed by an impact crusher, and is screened by a vibrating screen into three grades of coarse aggregate of 20-30mm, 10-20mm and 5-10mm. When crushing the gangue, various types of gangue such as rock gangue, washed gangue or spontaneous combustion gangue can be used. After crushing, the crushing value of the gangue aggregate is not more than 30%, and the calorific value is not more than 500cal / g.

[0037] At present, most of the gangue base materials used for highway paving are undismaged gangue or gangue raw materials crushed by traditional crushers. They have high carbon content and too large crushing value. During the road construction process, with the increase of rolling times, the gangue will be significantly crushed, resulting in changes in its own structure, which seriously affects the original gradation, thereby affecting the mechanical properties of the gangue aggregate base material, and seriously affecting the promotion and application of gangue. However, under normal circumstances, when the material is crushed, the mineral with higher hardness is not easy to crush, while the mineral with lower hardness is easy to crush. The present invention utilizes the difference in mechanical strength between gangue minerals, and selects a suitable method to selectively crush it, so as to obtain gangue with different particle sizes and mineral compositions. After crushing, the particle size of weak particles and particles with high carbon content is small, and the particles with higher mineral strength such as sandstone are larger. The present invention uses graded crushing to select particles with higher strength and smaller crushing value as coarse aggregates of the road base mixture, and uses particles with higher carbon content and lower strength as low-temperature sintering binder to replace cement for semi-rigid base.

[0038] Among them, the main minerals in the low-temperature sintering binder are calculated by mass percentage: 8-15% fluoroaluminate mineral content, 5-15% sulphoaluminate mineral content, 25-35% silicate mineral content, and 1-3% free calcium oxide content.

[0039] In the above scheme, preferably, the method for preparing the low temperature sintering binder comprises:

[0040] 0-5mm coal gangue, carbide slag, calcium silicate slag, desulfurized gypsum, fluorite and fluorite are used as raw materials. After weighing each raw material according to the proportion, mix and grind to less than 200 mesh. The mass percentage of each raw material is: 0-5mm coal gangue 40-60%, carbide slag 15-30%, calcium silicate slag 15-25%, desulfurized gypsum 5-15%, fluorite 5-15%, fluorite 2-8%;

[0041] S2, adding 1% to 3% water by weight of the mixed material to the mixed and ground material obtained in step S1, mixing evenly, and then pressing into raw material sheets;

[0042] S3, firing the raw material slices at 900±50℃ for 60-90min, then taking them out and rapidly cooling them in air to obtain clinker, and then grinding the clinker to a residue of 0.08mm standard square hole sieve ≤10.0%, thus obtaining low-temperature sintering binder;

[0043] Among them, 0-5mm coal gangue refers to the original coal gangue that is crushed by an impact crusher and then crushed by a selective crushing method to particles with a particle size of less than 5mm, wherein A12O3+SiO2≥80wt%; CaO in carbide slag≥85wt%; CaO+SiO2 in silica-calcium slag≥65wt%; CaSO4·2H2O in desulfurized gypsum≥90wt%; CaSO4·2H2O in fluorite≥90wt%; CaF2 in fluorite≥40wt%.

[0044] In the above scheme, preferably, the setting agent comprises the following components: fired desulfurized gypsum, borax, and fulvic acid, wherein the weight ratio of fired desulfurized gypsum, borax, and fulvic acid is (50-200):(1-10):(1-10).

[0045] In the above scheme, preferably, the fired desulfurized gypsum is obtained by drying the solid waste desulfurized gypsum from a thermal power plant at 160±10°C for 40 minutes, and the SO3 content in the fired desulfurized gypsum is not less than 50wt%.

[0046] In the above scheme, preferably, the weight ratio of fired desulfurized gypsum, borax and fulvic acid is 25:1:1.

[0047] In one of the technical solutions of the present invention, preferably, the content of A12O3+SiO2+Fe2O3 in the fly ash is ≥70wt%, and the loss on ignition is not more than 20wt%.

[0048] In the above scheme, preferably, 59.19-66.35 parts of the gangue coarse aggregate, 5 parts of the sintering binder, 0.2-0.4 parts of the setting agent, 10 parts of fly ash, 25.37-25.43 parts of stone chips and 0.02-0.04 parts of the activator are taken.

[0049] In one of the technical solutions of the present invention, preferably, the stone chips are solid waste with a particle size less than 5 mm generated in the process of producing stone in a stone crushing site, and the content of particles below 0.075 mm is not less than 10%.

[0050] In one of the technical solutions of the present invention, preferably, the activator comprises the following components: sodium lignin sulfonate, sodium dinaphthylmethane disulfonate, sodium dodecyl sulfonate, and ferrous sulfate, wherein the weight ratio of sodium lignin sulfonate, sodium dinaphthylmethane disulfonate, sodium dodecyl sulfonate, and ferrous sulfate is (10-30):(10-30):(1-5):(20-40).

[0051] In the above scheme, preferably, the weight ratio of sodium lignin sulfonate, sodium dinaphthylmethane disulfonate, sodium dodecyl sulfonate and ferrous sulfate is 8:5:1:10.

[0052] In one of the technical solutions of the present invention, preferably, after coal gangue coarse aggregate, new inorganic gelling material, setting agent, fly ash, stone chips and activator are weighed according to the proportion, water is added to mix evenly, and the mixture is pressed into shape according to the specified compaction degree.

[0053] In the present invention, the low-temperature sintering binder is made of 0-5 mm coal gangue, carbide slag, and silicate-calcium slag as main raw materials, supplemented with desulfurized gypsum, fluorite, and fluorite as regulating mineral components, ground and mixed evenly, pressed into tablets, and fired at about 850-950° C. The fired binder has a fluoroaluminate mineral content of 8-15%, a sulphoaluminate mineral content of 5-15%, a silicate mineral content of 25-35%, and a free calcium oxide content of 1-3%. The firing of the binder mainly utilizes active oxides carried in industrial solid wastes such as CaO, SiO2, and Al2O3 in coal gangue, CaO in carbide slag, and CaO and SiO2 in silicate-calcium slag, and utilizes SO3 and CaF2 in auxiliary minerals such as desulfurized gypsum, fluorite, and fluorite to adjust the mineral composition of the binder and reduce the firing temperature of the binder.

[0054] Adding calcium fluoride and other minerals can promote the decomposition of carbonates more efficiently and fully, promote the breaking of Si-O bonds of crystalline silicon oxide, and promote solid-phase reactions. During calcination, adding CaF2 can reduce the temperature of the liquid phase. Reducing the viscosity of the liquid phase during clinker formation and increasing the amount of liquid phase are beneficial to the diffusion rate of particles in the liquid phase and accelerate the formation of silicate minerals. Solid wastes such as coal gangue, carbide slag, and calcium-silicon slag are calcined in the range of 850 to 950°C under the regulation of desulfurized gypsum, fluorite, etc., to form a certain amount of silicate minerals, fluoroaluminate minerals, sulfoaluminate minerals, and some ferrite minerals. In addition, some coal gangue can be activated at high temperature to form amorphous amorphous substances with potential activity in the presence of CaO.

[0055] The sintering temperature of low-temperature sintered binder is between 850 and 950°C, while the sintering temperature of Portland cement clinker is around 1450°C. The sintering temperature is greatly reduced, and the energy consumption of low-temperature sintered binder is much lower than that of Portland cement clinker. After selective crushing of coal gangue, the coal gangue less than 5mm contains a higher carbon content. When sintering the binder, the carbon in the coal gangue provides part of the calorific value, further reducing the energy consumption of the binder. Therefore, compared with ordinary cement, coal gangue-based binder can significantly reduce the energy consumption in the production process.

[0056] In the present invention, the setting agent is composed of fired desulfurized gypsum, borax, fulvic acid, etc., and the setting agent is used to adjust the setting time of the low-temperature sintering binder. The low-temperature sintering binder contains more early strength components, and SO3 in the fired desulfurized gypsum and the early strength minerals in the low-temperature sintering binder are used to form calcium sulfonate to adjust the setting time of the low-temperature sintering binder. At the same time, adding borax and fulvic acid can further extend the setting time of the low-temperature sintering binder, and can effectively adjust the delayed rolling time of the semi-rigid base material to avoid the strength loss caused by delayed rolling.

[0057] The fired desulfurized gypsum is obtained by drying the solid waste desulfurized gypsum from the thermal power plant at 160±10℃ for 40 minutes. The main component of the fired desulfurized gypsum is hemihydrated gypsum or anhydrous gypsum. The purpose of its addition is to form AFt crystals with the early strength component in the low-temperature sintered binder, which can not only adjust the setting time of the low-temperature sintered binder, but also produce an expansion effect in the semi-rigid base mixture, compensate for the shrinkage produced during the hydration process of the semi-rigid base mixture, and reduce the probability of cracking of the semi-rigid base. The fired desulfurized gypsum, borax, and fulvic acid synergistically adjust the setting time of the low-temperature fired binder, forming a synergistic effect with each other, which can adjust the setting time to avoid the strength loss caused by delayed rolling, and can also compensate for the shrinkage of the semi-rigid base by forming an expansion source, improve the overall performance of the semi-rigid base, and extend the service life of the semi-rigid base.

[0058] The borax and fulvic acid in the coagulant are both industrial grade.

[0059] The fly ash in the present invention is dry-discharged or wet-discharged fly ash from a coal-fired thermal power plant, wherein Al2O3+SiO2+Fe2O3≥70wt%, and the ignition loss is not more than 20wt%. The fly ash from the thermal power plant contains a large amount of active SiO2 and Al2O3, which can react with the hydration product Ca(OH)2 of the minerals in the low-temperature sintering binder to undergo a secondary hydration reaction similar to a volcanic ash reaction, thereby generating hydrated calcium silicate and hydrated calcium aluminate, which improves the late strength of the mixture. At the same time, the low-temperature sintering binder contains a large amount of alkaline substances such as CaO, and also contains a large amount of sulfate minerals (a part of the sulfate minerals can also be supplemented in the setting agent), so that Ca(OH)2 and sulfate composite excitation can be formed, the activity of the fly ash can be fully stimulated, the reaction of the active substances in the fly ash can be better promoted, and CSH and ettringite crystals can be generated by hydration, and the crystals are continuously grown and improved, so that the strength of the hydration products of the mixture system is continuously increased.

[0060] The fly ash in the semi-rigid base mixture has a certain fineness and can effectively fill the micro-voids of the material, especially between the interface of the aggregate and the binder, thereby improving the microstructure of the material, making it more dense and improving its performance. In addition, the semi-rigid base materials such as cement-stabilized crushed stone usually have less powder materials and a smaller contact area between aggregate particles. When they are damaged, stress concentration is easily generated, making the material more easily damaged. This is also an important reason why cement-stabilized materials are prone to cracking. After adding an appropriate amount of fly ash, the original point contact structure is transformed into a surface contact structure, which greatly increases the contact area between aggregates, effectively avoids stress concentration, and improves strength and crack resistance. On the other hand, more fine materials are introduced into the material system, which reduces the elastic modulus of the material and improves the material's adaptability to aggregate grading.

[0061] The stone chips in the present invention are solid waste with a particle size of less than 5 mm produced in the process of producing stone in a stone crushing field, and the content of particles below 0.075 mm is not less than 10%. Adding stone chips to semi-rigid base materials can optimize the gradation of the mixture and improve the construction performance and road performance of the mixture.

[0062] In one of the technical solutions of the present invention, preferably, the activator comprises the following components: sodium lignin sulfonate, sodium dinaphthylmethane disulfonate, sodium dodecyl sulfonate, and ferrous sulfate, wherein the weight ratio of sodium lignin sulfonate, sodium dinaphthylmethane disulfonate, sodium dodecyl sulfonate, and ferrous sulfate is (10-30):(10-30):(1-5):(20-40).

[0063] In the above scheme, preferably, the weight ratio of sodium lignin sulfonate, sodium dinaphthylmethane disulfonate, sodium dodecyl sulfonate and ferrous sulfate is 8:5:1:10.

[0064] The activator in the present invention includes sodium lignin sulfonate, sodium dinaphthylmethane disulfonate, sodium dodecylsulfonate, and ferrous sulfate. The activator is mainly a surfactant, which can improve the charged state of the surface of coal gangue and low-temperature sintering binder particles, help improve the compression performance of coal gangue mixture, and improve mechanical properties and water stability. The activator is compounded with a variety of surfactants. When macromolecules form a monolayer adsorption on the surface of particles such as coal gangue or binder, using its polymer effect, the strong ions in the solution can destroy its double electric layer structure, weaken the chemical force between the interface, fundamentally change the surface properties of particles in the mixture, make it tend to be hydrophobic, improve the water stability of the mixture, reduce its expansion and compressibility, and improve shear resistance. And ferrous sulfate in the activator can form calcium sulfonate in the early stage of the binder to provide a certain amount of sulfate ion supplement, and the formation of ferrous double salt helps to improve the splitting strength of the semi-rigid base mixture and improve the crack resistance of the mixture.

[0065] The present invention also provides the above-mentioned environmentally friendly coal gangue-based all-solid waste pavement base mixture and its preparation method, which includes: weighing coal gangue coarse aggregate, low-temperature sintering binder, setting agent, fly ash, stone chips, and activator according to the proportion, adding water to mix evenly, and pressing and molding according to the specified compaction degree.

[0066] In order to enable those skilled in the art to better understand the technical solution of the present invention, the following embodiments are provided for further explanation:

[0067] In the following environmentally friendly coal gangue-based all-solid waste pavement base mixture embodiment:

[0068] Coarse gangue aggregates are various types of gangue such as rock gangue, washed gangue or spontaneous combustion gangue, which are crushed by impact crushers and selected by vibration screening to obtain coarse gangue aggregates with particle sizes of 20-30mm, 10-20mm and 5-10mm. After selection, the crushing value of the selected gangue aggregates is not more than 30%, and the calorific value is not more than 500cal / g.

[0069] The main minerals in the low-temperature sintering binder are calculated by mass percentage: 8-15% fluoroaluminate mineral content, 5-15% sulphoaluminate mineral content, 25-35% silicate mineral content, and 1-3% free calcium oxide content. The preparation method of the anti-cracking masterbatch includes:

[0070] S1. Take 0-5 mm coal gangue, carbide slag, calcium silicate slag, desulfurized gypsum, fluorite and fluorite as raw materials, weigh each raw material according to the proportion, mix and grind to less than 200 mesh, the mass percentage of each raw material is: 0-5 mm coal gangue 40-60%, carbide slag 15-30%, calcium silicate slag 15-25%, desulfurized gypsum 5-15%, fluorite 5-15%, fluorite 2-8%;

[0071] S2, adding 1% to 3% water by weight of the mixed material to the mixed and ground material obtained in step S1, mixing evenly, and then pressing into raw material sheets;

[0072] S3, firing the raw material slices at 900±50℃ for 60-90min, then taking them out and rapidly cooling them in air to obtain clinker, and then grinding the clinker to a residue of 0.08mm standard square hole sieve ≤10.0%, thus obtaining low-temperature sintering binder;

[0073] Among them, 0-5mm coal gangue refers to particles with a particle size of less than 5mm after being crushed by selective crushing method, wherein A12O3+SiO2≥80wt%; CaO in carbide slag≥85wt%; CaO+SiO2 in silica-calcium slag≥65wt%; CaSO4·2H2O in desulfurized gypsum≥90wt%; CaSO4·2H2O in fluorgypsum≥90wt%; CaF2 in fluorite≥40wt%.

[0074] The setting agent mainly includes fired desulfurized gypsum, borax and fulvic acid, wherein the weight ratio of fired desulfurized gypsum, borax and fulvic acid is (50-200):(1-10):(1-10), and the optimal mixing ratio is 25:1:1. The fired desulfurized gypsum is obtained by drying the solid waste desulfurized gypsum from a thermal power plant at 160±10°C for 40 minutes, and the SO3 content in the fired desulfurized gypsum is not less than 50wt%.

[0075] Fly ash can be dry ash or wet ash, with A1203+SiO2+Fe2O3≥70wt% and loss on ignition not more than 20wt%. Stone dust is solid waste with a particle size less than 5mm produced in the process of producing stone in a stone crushing plant, and the content of particles below 0.075mm is not less than 10%.

[0076] The activator mainly includes sodium lignin sulfonate, sodium dinaphthylmethane disulfonate, sodium dodecyl sulfonate and ferrous sulfate, wherein the weight ratio of sodium lignin sulfonate, sodium dinaphthylmethane disulfonate, sodium dodecyl sulfonate and ferrous sulfate is (10-30):(10-30):(1-5):(20-40), and the optimal ratio is 8:5:1:10.

[0077] The following are the steps for implementing a semi-rigid base mix:

[0078] The construction method of semi-rigid base mixture complies with the requirements of "Technical Specifications for Highway Pavement Base Construction" (JTG / TF 20-2015). The specific construction steps are as follows:

[0079] Step 1, weigh the raw materials according to the proportion and mix them evenly;

[0080] Step 2: Determine the maximum dry density and optimum moisture content by compaction test according to JTG E51-2009 "Testing Procedures for Stabilized Materials of Inorganic Binders for Highway Engineering", and calculate the amount of water added to each material and the mass of the inorganic binder according to a compaction degree of 98%;

[0081] Step 3: Put the weighed aggregate in a rectangular dish, add water to the aggregate to mix and simmer, the inorganic binder can be mixed with the aggregate, spray the pre-calculated amount of water evenly on the aggregate, and then put it into a sealed plastic bag to soak for later use;

[0082] Step 4: Form the test piece, demould it after 2 to 6 hours and seal it, and cure it to the specified age under standard curing conditions (20℃±2℃, humidity ≥95%).

[0083] Experimental Group 1:

[0084] Example 1 of coal gangue-based all-solid waste road base mixture

[0085] An environmentally friendly coal gangue-based all-solid waste road base mixture, wherein the contents of various components are as follows: 66.35% coal gangue coarse aggregate; 5% low-temperature sintering binder; 0.2% setting agent; 28.43% stone chips; and 0.02% activator.

[0086] The method for preparing the above-mentioned environmentally friendly coal gangue-based all-solid waste pavement base mixture comprises:

[0087] The gangue coarse aggregate is a mixture of three particle sizes of 20-30mm, 10-20mm and 5-10mm gangue crushed by selective crushing method and used as coarse aggregate;

[0088] After weighing the gangue coarse aggregate, low-temperature sintering binder, setting agent, stone chips and activator according to the proportion, add water and mix evenly according to the requirements of JTG E51-2009 "Test Procedure for Stabilized Materials of Inorganic Binders for Highway Engineering", and press into shape.

[0089] Cement stabilized macadam road base material comparison example 1

[0090] A cement-stabilized crushed stone pavement base material, wherein the contents of various components are as follows: 4.5% of PO42.5 cement, 66.85% of crushed stone coarse aggregate, and 28.65% of stone chips.

[0091] The coarse aggregate is limestone crushed stone with particle sizes of 20-30mm, 10-20mm, and 5-10mm, and the mass ratio of each particle size is 25:28:17. The crushing value and mixture gradation of the crushed stone meet the "Technical Specifications for Highway Pavement Base Construction" (JTG / TF 20-2015).

[0092] Cement stabilized gangue road base material comparison example 1

[0093] A cement-stabilized gangue pavement base material, wherein the contents of various components are as follows: 4.5% of PO42.5 cement, 66.85% of gangue coarse aggregate, and 28.65% of stone chips.

[0094] The gangue coarse aggregate is produced by selective crushing with an impact crusher with particle sizes of 20-30mm, 10-20mm, and 5-10mm, and the mass ratio of each particle size is 25:28:17.

[0095] The test compares the splitting strength, rebound modulus, shrinkage strain and other properties of the pavement base constructed by coal gangue-based all-solid waste pavement base mixture Example 1, the pavement base constructed by cement-stabilized crushed stone pavement base material Comparative Example 1, and the pavement base constructed by cement-stabilized coal gangue pavement base material Comparative Example 1. The experimental results are shown in Table 1.

[0096] Table 1 Physical and mechanical properties of pavement base mixture

[0097]

[0098] Experimental Group 2:

[0099] Example 2 of coal gangue-based all-solid waste road base mixture

[0100] An environmentally friendly coal gangue-based all-solid waste road base mixture, wherein the contents of various components are as follows: 59.35% coal gangue coarse aggregate; 5% low-temperature sintering binder; 0.2% setting agent; 25.43% stone chips; 10% fly ash; and 0.02% activator.

[0101] The preparation method of the above-mentioned environmentally friendly coal gangue-based all-solid waste pavement base mixture includes: weighing coal gangue coarse aggregate, low-temperature sintering binder, setting agent, stone chips, and activator according to the proportion, adding water and mixing evenly according to the requirements of JTG E51-2009 "Test Procedure for Stabilized Materials of Inorganic Binders for Highway Engineering", and pressing into shape.

[0102] Cement stabilized macadam road base material comparison example 2

[0103] A cement-stabilized crushed stone road base material, wherein the contents of various components are as follows: 4.5% of PO42.5 cement, 10% of fly ash; 59.28% of crushed stone coarse aggregate, and 25.4% of stone chips.

[0104] The coarse aggregate is limestone crushed stone with particle sizes of 20-30mm, 10-20mm, and 5-10mm, and the mass ratio of each particle size is 25:28:17. The crushing value and mixture gradation of the crushed stone meet the "Technical Specifications for Highway Pavement Base Construction" (JTG / TF 20-2015).

[0105] Cement stabilized gangue road base material comparison example 2

[0106] A cement-stabilized gangue road base material, wherein the contents of various components are as follows: 4.5% of PO42.5 cement, 10% of fly ash, 59.28% of gangue coarse aggregate, and 25.4% of stone chips.

[0107] The gangue coarse aggregate is produced by selective crushing with an impact crusher with particle sizes of 20-30mm, 10-20mm, and 5-10mm, and the mass ratio of each particle size is 25:28:17.

[0108] The test compares the splitting strength, rebound modulus, shrinkage strain and other properties of the pavement base constructed by coal gangue-based all-solid waste pavement base mixture Example 2, the pavement base constructed by cement-stabilized crushed stone pavement base material Comparative Example 2, and the pavement base constructed by cement-stabilized coal gangue pavement base material Comparative Example 2. The experimental results are shown in Table 2.

[0109] Table 2 Physical and mechanical properties of pavement base mixture

[0110]

[0111] Experimental Group 3:

[0112] Example 3 of coal gangue-based all-solid waste road base mixture

[0113] An environmentally friendly coal gangue-based all-solid waste road base mixture, wherein the contents of various components are as follows: 59.21% coal gangue coarse aggregate; 5% low-temperature sintering binder; 0.4% setting agent; 25.37% stone chips; 10% fly ash; and 0.02% activator.

[0114] The preparation method of the above-mentioned environmentally friendly coal gangue-based all-solid waste pavement base mixture includes: weighing coal gangue coarse aggregate, low-temperature sintering binder, setting agent, stone chips, and activator according to the proportion, adding water and mixing evenly according to the requirements of JTG E51-2009 "Test Procedure for Stabilized Materials of Inorganic Binders for Highway Engineering", and pressing into shape.

[0115] Cement stabilized macadam road base material comparison example 2

[0116] A cement-stabilized crushed stone road base material, wherein the contents of various components are as follows: 4.5% of PO42.5 cement, 10% of fly ash; 59.28% of crushed stone coarse aggregate, and 25.4% of stone chips.

[0117] The coarse aggregate is limestone crushed stone with particle sizes of 20-30mm, 10-20mm, and 5-10mm, and the mass ratio of each particle size is 25:28:17. The crushing value and mixture gradation of the crushed stone meet the "Technical Specifications for Highway Pavement Base Construction" (JTG / TF 20-2015).

[0118] Cement stabilized gangue road base material comparison example 2

[0119] A cement-stabilized gangue road base material, wherein the contents of various components are as follows: 4.5% of PO42.5 cement, 10% of fly ash, 59.28% of gangue coarse aggregate, and 25.4% of stone chips.

[0120] The gangue coarse aggregate is produced by selective crushing with an impact crusher with particle sizes of 20-30mm, 10-20mm, and 5-10mm, and the mass ratio of each particle size is 25:28:17.

[0121] The test compares the splitting strength, rebound modulus, shrinkage strain and other properties of the pavement base constructed by coal gangue-based all-solid waste pavement base mixture Example 3, the pavement base constructed by cement-stabilized crushed stone pavement base material Comparative Example 2, and the pavement base constructed by cement-stabilized coal gangue pavement base material Comparative Example 2. The experimental results are shown in Table 3.

[0122] Table 3 Physical and mechanical properties of pavement base mixture

[0123]

[0124] Experimental Group 4:

[0125] Example 4 of coal gangue-based all-solid waste road base mixture

[0126] An environmentally friendly coal gangue-based all-solid waste road base mixture, wherein the contents of various components are as follows: 59.19% coal gangue coarse aggregate; 5% low-temperature sintered binder; 0.4% setting agent; 25.37% stone chips; 10% fly ash; and 0.04% activator.

[0127] The preparation method of the above-mentioned environmentally friendly coal gangue-based all-solid waste pavement base mixture includes: weighing coal gangue coarse aggregate, low-temperature sintering binder, setting agent, stone chips, and activator according to the proportion, adding water and mixing evenly according to the requirements of JTG E51-2009 "Test Procedure for Stabilized Materials of Inorganic Binders for Highway Engineering", and pressing into shape.

[0128] Cement stabilized macadam road base material comparison example 2

[0129] A cement-stabilized crushed stone road base material, wherein the contents of various components are as follows: 4.5% of PO42.5 cement, 10% of fly ash; 59.28% of crushed stone coarse aggregate, and 25.4% of stone chips.

[0130] The coarse aggregate is limestone crushed stone with particle sizes of 20-30mm, 10-20mm, and 5-10mm, and the mass ratio of each particle size is 25:28:17. The crushing value and mixture gradation of the crushed stone meet the "Technical Specifications for Highway Pavement Base Construction" (JTG / TF 20-2015).

[0131] Cement stabilized gangue road base material comparison example 2

[0132] A cement-stabilized gangue road base material, wherein the contents of various components are as follows: 4.5% of PO42.5 cement, 10% of fly ash, 59.28% of gangue coarse aggregate, and 25.4% of stone chips.

[0133] The gangue coarse aggregate is produced by selective crushing with an impact crusher with particle sizes of 20-30mm, 10-20mm, and 5-10mm, and the mass ratio of each particle size is 25:28:17.

[0134] The test compares the splitting strength, rebound modulus, shrinkage strain and other properties of the pavement base constructed by coal gangue-based all-solid waste pavement base mixture Example 4, the pavement base constructed by cement-stabilized crushed stone pavement base material Comparative Example 2, and the pavement base constructed by cement-stabilized coal gangue pavement base material Comparative Example 2. The experimental results are shown in Table 4.

[0135] Table 4 Physical and mechanical properties of pavement base mixture

[0136]

[0137] Experimental Group 5:

[0138] Example 5 of coal gangue-based all-solid waste road base mixture

[0139] An environmentally friendly coal gangue-based all-solid waste road base mixture, wherein the contents of various components are as follows: 59.33% coal gangue coarse aggregate; 5% low-temperature sintering binder; 0.2% setting agent; 25.43% stone chips; 10% fly ash; and 0.04% activator.

[0140] The preparation method of the above-mentioned environmentally friendly coal gangue-based all-solid waste pavement base mixture includes: weighing coal gangue coarse aggregate, low-temperature sintering binder, setting agent, stone chips, and activator according to the proportion, adding water and mixing evenly according to the requirements of JTG E51-2009 "Test Procedure for Stabilized Materials of Inorganic Binders for Highway Engineering", and pressing into shape.

[0141] Cement stabilized macadam road base material comparison example 2

[0142] A cement-stabilized crushed stone road base material, wherein the contents of various components are as follows: 4.5% of PO42.5 cement, 10% of fly ash; 59.28% of crushed stone coarse aggregate, and 25.4% of stone chips.

[0143] The coarse aggregate is limestone crushed stone with particle sizes of 20-30mm, 10-20mm, and 5-10mm, and the mass ratio of each particle size is 25:28:17. The crushing value and mixture gradation of the crushed stone meet the "Technical Specifications for Highway Pavement Base Construction" (JTG / TF 20-2015).

[0144] Cement stabilized gangue road base material comparison example 2

[0145] A cement-stabilized gangue road base material, wherein the contents of various components are as follows: 4.5% of PO42.5 cement, 10% of fly ash, 59.28% of gangue coarse aggregate, and 25.4% of stone chips.

[0146] The gangue coarse aggregate is produced by selective crushing with an impact crusher with particle sizes of 20-30mm, 10-20mm, and 5-10mm, and the mass ratio of each particle size is 25:28:17.

[0147] The test compares the splitting strength, rebound modulus, shrinkage strain and other properties of the pavement base constructed by coal gangue-based all-solid waste pavement base mixture Example 5, the pavement base constructed by cement-stabilized crushed stone pavement base material Comparative Example 2, and the pavement base constructed by cement-stabilized coal gangue pavement base material Comparative Example 2. The experimental results are shown in Table 5.

[0148] Table 5 Physical and mechanical properties of pavement base mixture

[0149]

[0150] Through the comparison of the above test results, it is not difficult to find that the performance of the environmentally friendly coal gangue-based all-solid waste pavement base mixture of the present invention meets the requirements of the "Technical Specifications for Highway Pavement Base Construction" (JTG / TF 20-2015), and can directly replace cement-stabilized crushed stone base materials for road engineering construction. The unconfined compressive strength, splitting strength and maximum shrinkage rate of the environmentally friendly coal gangue-based all-solid waste pavement base mixture of the present invention are better than the technical indicators of ordinary cement-stabilized crushed stone, and the performance of the coal gangue aggregate mixture can be significantly improved by the application of low-temperature sintering binder and auxiliary coagulant and activator, providing an effective way for large-scale utilization of solid waste such as coal gangue.

[0151] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the embodiments shown and described herein.

Claims

1. A method for preparing an environmentally friendly coal gangue-based all-solid waste pavement base mixture, characterized in that: The steps include: Step 1: crush the original coal gangue, the crushing value of the coal gangue aggregate after crushing is not more than 30%, the calorific value is not more than 500 cal / g, and three kinds of coal gangue particle sizes of 20-30 mm, 10-20 mm and 5-10 mm are selected and compounded as the coal gangue coarse aggregate; Step 2: Take 40-60 parts of coal gangue with a particle size of 0-5 mm after crushing in step 1, 15-30 parts of carbide slag, 15-25 parts of calcium silicate slag, 5-15 parts of desulfurized gypsum, 5-15 parts of fluorite and 2-8 parts of fluorite, and press them into raw material sheets; The raw material slices are fired at 850-950° C. for 60-90 min, then taken out and rapidly cooled in air to obtain clinker, and the clinker is ground to 0.08 mm to prepare a sintering binder, wherein the sum of the masses of Al2O3 and SiO2 in the 0-5 mm coal gangue is not less than 80% of the total mass of the 0-5 mm coal gangue, the sum of the masses of CaO and SiO2 in the calcium-silicon slag is not less than 65% of the total mass of the calcium-silicon slag, the CaO in the carbide slag is ≥85wt%, the CaSO4·2H2O in the desulfurized gypsum is ≥90wt%, the CaSO4·2H2O in the fluorite is ≥90wt%, and the CaF2 in the fluorite is ≥40wt%; Step 3: Take 50-70 parts of the gangue coarse aggregate and 3-8 parts of the sintered binder, and also take 0.05-0.6 parts of a setting agent, 0-15 parts of fly ash, 20-35 parts of stone chips and 0.01-0.06 parts of an activator, mix them with the gangue coarse aggregate and the sintered binder, and then press them into shape to obtain a gangue-based all-solid waste pavement base mixture; The setting agent is composed of the following components: fired desulfurized gypsum, borax and fulvic acid, wherein the fired desulfurized gypsum is obtained by drying the solid waste desulfurized gypsum from a thermal power plant at 150-170° C. for 40 min, the SO3 content in the fired desulfurized gypsum is not less than 50wt%, and the weight ratio of the fired desulfurized gypsum, borax and fulvic acid is (50-200):(1-10):(1-10); The sum of the masses of Al2O3, SiO2 and Fe2O3 in the fly ash is not less than 70wt% of the fly ash, and the loss on ignition is not more than 20wt%; The stone chips are solid waste with a particle size of less than 5 mm generated during the production of stone in a stone crushing site, and the content of particles below 0.075 mm is not less than 10%; The activator is composed of the following components: sodium lignin sulfonate, sodium dinaphthylmethane disulfonate, sodium dodecyl sulfonate and ferrous sulfate, wherein the weight ratio of sodium lignin sulfonate, sodium dinaphthylmethane disulfonate, sodium dodecyl sulfonate and ferrous sulfate is (10-30):(10-30):(1-5):(20-40).

2. An environmentally friendly coal gangue-based all-solid waste pavement base mixture, characterized in that: The environmentally friendly coal gangue-based all-solid waste pavement base mixture is prepared by the method according to claim 1.

3. The environmentally friendly coal gangue-based all-solid waste pavement base mixture according to claim 2, characterized in that: The environmentally friendly coal gangue-based all-solid waste pavement base mixture includes the following components by weight: 50-70 parts of coal gangue coarse aggregate; 3-8 parts of low-temperature sintering binder; 0.05-0.6 parts of setting agent; 0-15 parts of fly ash; 20-35 parts of stone chips; 0.01-0.06 parts of activator; The gangue coarse aggregate is a compound of three particle sizes of 20-30mm, 10-20mm and 5-10mm obtained by crushing the original gangue by a selective crushing method. The original gangue can be rock gangue, washed gangue or spontaneous combustion gangue. After crushing, the crushing value of the gangue aggregate is not more than 30%, and the calorific value is not more than 500cal / g. The low-temperature sintering binder contains, by mass percentage, 8% to 15% of fluoroaluminate minerals, 5% to 15% of sulphoaluminate minerals, 25% to 35% of silicate minerals, and 1% to 3% of free calcium oxide.

4. The environmentally friendly coal gangue-based all-solid waste pavement base mixture according to claim 3, characterized in that: Take 59.19-66.35 parts of the gangue coarse aggregate, 5 parts of the sintering binder, 0.2-0.4 parts of the setting agent, 10 parts of the fly ash, 25.37-25.43 parts of the stone chips and 0.02-0.04 parts of the activator; The activator is composed of the following components: sodium lignin sulfonate, sodium dinaphthylmethane disulfonate, sodium dodecyl sulfonate, and ferrous sulfate, wherein the weight ratio of sodium lignin sulfonate, sodium dinaphthylmethane disulfonate, sodium dodecyl sulfonate, and ferrous sulfate is (10-30):(10-30):(1-5):(20-40); The stone chips are solid waste with a particle size of less than 5 mm generated in the process of producing stone in the stone crushing site, and the content of particles below 0.075 mm is not less than 10%; The sum of the masses of Al2O3, SiO2 and Fe2O3 in the fly ash is not less than 70wt% of the fly ash, and the loss on ignition is not more than 20wt%; The setting agent is composed of the following components: fired desulfurized gypsum, borax and fulvic acid, wherein the weight ratio of fired desulfurized gypsum, borax and fulvic acid is (50~200):(1~10):(1~10); the fired desulfurized gypsum is obtained by drying the solid waste desulfurized gypsum from a thermal power plant at 160±10°C for 40 minutes, and the SO3 content in the fired desulfurized gypsum is not less than 50wt%.

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