A method for preparing concrete for filling goaf with high content of coal chemical solid waste

Abstract

The present invention discloses a method for preparing concrete for filling goafs with high content of coal chemical solid waste, comprising the preparation of a cement coating adhesion promoter, the formation of a coating and plugging coating on the surface of the coarse slag of the coal chemical solid waste, and the preparation of goaf-filling concrete with high content of coal chemical solid waste, wherein the adhesion promoter is a kind of agent that can be cross-linked under alkaline conditions in cement slurry to form a network structure, thereby promoting the cement slurry to adhere a layer of coating and plugging coating on the surface of the coarse slag of the coal chemical solid waste. The present invention prepares an adhesion promoter with self-cross-linking effect and a coating that forms a coating, plugging and isolating coating on the surface of the coarse slag of the coal chemical solid waste, thereby overcoming the defects of large water consumption, poor fluidity and low strength in the preparation of concrete with conventional coal chemical solid waste.

Description

Technical Field

[0001] The invention belongs to the field of cement-based composite material preparation, and particularly relates to a method for preparing concrete for filling goaf areas with high content of coal chemical solid waste. Background Art

[0002] Coal chemical solid waste refers to various solid wastes generated in the process of converting coal into gas and chemical products such as methanol, ethylene glycol, and fuel oil. In terms of form, coal chemical solid waste can be divided into fine powder ash and granular coarse slag. Fine powder solid waste is mainly fine powder ash recovered from the high-temperature combustion of coal at 1400℃~1600℃ using fluidized bed gasification technology, also known as fly ash; coarse slag mainly refers to the solid residue after coal is burned in a high-temperature gasifier. Ash and coarse slag account for about 90% of the total coal chemical solid waste (Shang Xiaofu, Ma Jianli, Zhang Jian, et al. Research status of coal gasification slag and prospect of utilization technology [J]. Journal of Environmental Engineering Technology, 2017, 7 (6): 712-716). This study focuses on the treatment of the largest amount of solid waste ash and coarse slag generated by coal chemical industry.

[0003] Currently, the resource utilization of coal chemical solid waste has become a major issue that my country's coal chemical enterprises urgently need to address. This is because the output of coal chemical solid waste is huge and is increasing year by year. This is related to my country's energy structure, which is characterized by being rich in coal, poor in oil, and less in gas. In recent years, my country has been vigorously developing coal chemical industry to improve the utilization rate of coal. The coal chemical process consumes a large amount of coal and also produces a large amount of coal chemical solid waste. A million-ton coal chemical enterprise produces 600,000 tons of solid waste annually, and the comprehensive utilization rate of solid waste is less than 30%. The annual increase and the cumulative accumulation have resulted in a huge stock of coal chemical solid waste. Therefore, finding a large-scale, low-cost, and harmless way to utilize solid waste as a resource is currently an urgent need.

[0004] From the analysis of the composition and properties of coal chemical solid waste, we know that its chemical composition is similar to that of cement and sand and gravel. Therefore, coal chemical solid waste can be used in the preparation of concrete. Ash slag can be directly used to replace part of the cement as an auxiliary cementitious material, and coarse slag can be used to fill the roadbed and replace sand and gravel to prepare concrete. However, when coal chemical solid waste is used as a raw material for conventional building concrete, the addition amount is generally less than 10%, otherwise it will affect the working performance and mechanical properties of the concrete. Therefore, the use of coal chemical solid waste in conventional concrete is limited (Xu Huichao, Yuan Benwang, Feng Junhong. Current status and development trend of comprehensive utilization of coal chemical gasification furnace slag [J]. Chemical Management, 2016, (6): 34-36).

[0005] Coal chemical companies are generally located in coal-producing areas, which often contain large goafs. Goafs are the main cause of future geological disasters such as ground subsidence and cracks. Goafs are large in size, and backfilling requires a large amount of filling materials. Coal chemical solid waste is huge, and using coal chemical solid waste to prepare goaf filling materials has many advantages. The cost is low. The resource utilization of coal chemical solid waste is of great significance to China's coal-producing and coal chemical companies and regions (Xiao Jiansheng, Wen Xianghao, Diao Yunyu, et al. Overview of solid waste resource utilization technology in coal preparation and coking [J]. Coal and Chemical Industry, 2019, 50 (2): 50-52).

[0006] The use of ash and coarse slag from coal chemical solid waste as a substitute for gel materials and aggregates has been widely studied. However, the preparation of concrete using high amounts of solid waste has problems with fluidity and mechanical properties: poor fluidity, inability to pump, low strength, poor volume stability, and poor sealing. Therefore, the technology of the present invention aims to increase the amount of coal chemical solid waste added, as well as its fluidity and strength, when used to prepare concrete for goaf filling. The core problem that needs to be solved is that the coarse slag from coal chemical solid waste contains a large number of holes and pores and is irregular in shape. When preparing concrete, the coarse slag will absorb a large amount of mixing water, and has poor fluidity and low post-curing strength. Summary of the Invention

[0007] The present invention aims to provide a method for preparing high-content coal chemical solid waste goaf filling concrete based on the structure and performance characteristics of coarse slag from coal chemical solid waste in Yulin area. The coal chemical solid waste content is as high as 77%, and the concrete has excellent working performance with good flow and pumping performance, a strength of more than 30MPa, low cost and good economic benefits, and good prospects for promotion and application.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for preparing concrete for filling goaf with high content of coal chemical solid waste comprises the following steps, wherein the following parts are all parts by mass:

[0010] Step 1: Preparation of surface coating, sealing and dispersion coating for coal chemical solid waste coarse slag:

[0011] Add 100-150 parts of coal chemical solid waste coarse slag and 15-20 parts of PO 32.5R cement into a rotary mixer and stir for 10-20 minutes to mix evenly; slowly add 8-15 parts of a mixture of water and an adhesion promoter within 5 minutes under stirring conditions, and continue stirring for 20-25 minutes to promote the cement to evenly adhere to the surface of the coarse slag and quickly form a strong coating and plugging coating that can withstand the mechanical stirring during the subsequent preparation of concrete without being damaged; slowly add 15-20 parts of dry coal chemical solid waste ash within 5 minutes, continue stirring for 10-15 minutes, and then discharge and stack for 7 days before use;

[0012] Step 2: Preparation of concrete for filling the goaf with high content of coal chemical solid waste:

[0013] 150-180 parts of the coal chemical solid waste coarse slag containing the coating sealing coating and the isolation coating prepared in step 1, 25-30 parts of coal chemical solid waste ash, and 25-30 parts of cement are added into a concrete mixer and stirred evenly. Then, a mixed solution of 21-27 parts of mixing water and 5-6.5 parts of an excitation flow enhancer is added into the mixer and stirred evenly to prepare a high-content coal chemical solid waste goaf filling concrete;

[0014] The main components of the coal chemical solid waste coarse slag are: SiO2 content 39.31~41.58%, Al2O3 content 26.27~29.34%, Fe3O4 content 11.25~13.59%, CaO content 10.93~12.39%, MaO content 3.65~4.73%. The particles are crushed, granulated and screened, with a moisture content of less than 5%. The porosity of the coarse slag is 25.36~35.68%, and the density is 2.3~2.5g / cm 3 , its particle size is controlled in a continuous gradation of 3~35mm;

[0015] The coal chemical solid waste ash has the following main components: SiO2 content of 38.25~39.84%, Al2O3 content of 25.63~28.57%, Fe3O4 content of 10.62~12.86%, CaO content of 8.63~10.73%, MaO content of 2.36~3.81%, fineness of which the residue on a 0.045mm square hole sieve is no more than 20%, water requirement is no more than 105%, loss on ignition is no more than 5%, water content is no more than 5%, and sulfur trioxide content is no more than 3%.

[0016] The excitation flow enhancer is obtained by in-situ intercalation and compounding of a polycarboxylate water-reducing agent and a graphene oxide dispersion, wherein the solid content of the polycarboxylate water-reducing agent is 5%, the solid content of the graphene oxide nanosheet is 0.075%, the water reduction rate of the polycarboxylate water-reducing agent is 31%, the oxidation degree of the graphene oxide is 32% expressed by the oxygen content, the thickness of the nanosheet is 0.8-1.6 nm, and the plane size of the two-dimensional sheet is 180-450 nm.

[0017] The adhesion promoter is a viscous aqueous liquid with a solid content of 35%, soluble in water in any proportion, with a pH value of 6.5-7.0, a number average and weight average relative molecular mass of 63,100-86,500 and 92,700-117,600 respectively, a molecular weight dispersion coefficient of 1.35-1.86, and a pH value of 6.5-7.0. The adhesion promoter forms a cross-linked network structure and produces a curing effect in 15-30 minutes under alkaline conditions of pH 9-10 in cement slurry;

[0018] The specific preparation method of the adhesion promoter is as follows:

[0019] Step 1: Add 22-28 parts of allylmalonic acid, 6-8 parts of 2-vinyl-4,6-diamino-1,3,5-triazine, 11-16 parts of 2,5-divinyl-1,4-phthalaldehyde, 5-8 parts of allylamine, 0.4-0.7 parts of persulfate and 60-90 parts of water into a reactor, stir and heat to 40-50° C. to form a mixed monomer solution;

[0020] Step 2: dissolving 0.2-0.4 parts of tyrosine and 0.1-0.3 parts of a molecular weight regulator in 40-50 parts of water to form a mixed solution of an initiator and a regulator, and then adding the mixture to the mixed monomer solution in a dropwise manner for 40-50 minutes. After the addition is complete, stirring is continued and the temperature is kept at 40-50°C for 2-3 hours, then cooled to 30-40°C, and the pH value of the product is adjusted to 6.5-7.0 with a 30% mass fraction of sodium hydroxide solution. The resulting product is an adhesion promoter with a solid content of 35%;

[0021] The allylmalonic acid, 2-vinyl-4,6-diamino-1,3,5-triazine, 2,5-divinyl-1,4-benzenedicarboxaldehyde and allylamine are all industrial grade, with a content of more than 96%;

[0022] The water is tap water, the persulfate is ammonium persulfate, sodium persulfate or potassium persulfate, and the tyrosine is of a purity greater than 99%;

[0023] The molecular weight regulator is thioglycolic acid, mercaptoethanol, and dodecyl mercaptan, and the content thereof is greater than 98%.

[0024] The molecular formula of the adhesion promoter is specifically

[0025] .

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The technology of the present invention includes three preparation methods: the preparation technology of the surface coating and plugging coating of coal chemical solid waste coarse slag, the preparation technology of the adhesion promoter, and the preparation technology of the concrete for filling goaf with high content of coal chemical solid waste. The novelty, creativity and practicality of these three preparation processes are particularly distinct and unique. The adhesion promoter is the premise and basis for the formation of the adhesion and plugging coating due to its unique monomer selection and the rapid formation of the self-crosslinking network structure under alkaline conditions. The formation of the coating and plugging coating on the surface of the coarse slag lays the foundation for the preparation of goaf concrete with high content of coal chemical solid waste. The creativity and applicability of these three technologies are very significant.

[0028] (2) The method of the present invention addresses the problems of large porosity, many voids and pores, and strong water absorption of coal chemical solid waste coarse slag, which leads to high water consumption, poor fluidity and low strength when used to prepare concrete. First, the coal chemical coarse slag is treated with cement coating to seal the surface pores. Cement slurry is used to form a coating and sealing coating on the surface of the coal chemical coarse slag, and an adhesion promoter is added to the cement slurry to form a cross-linked network structure, which promotes the rapid solidification of the cement coating and improves the strength of the coating, so that it can withstand the mechanical stirring during the subsequent concrete preparation without being damaged. At the same time, while forming the cement coating to seal the voids, the coal chemical solid waste ash is adsorbed on the surface of the cement coating to form an isolation and dispersion coating, which prevents the coarse slag coated with the cement sealing coating from adhering to anything and affecting the coating and sealing effect and subsequent use.

[0029] (2) An adhesion promoter capable of self-crosslinking under alkaline conditions of cement paste was creatively prepared. There are significant improvements in the selection of monomers and the preparation of macromolecular structures. Monomers such as allylmalonic acid, 2-vinyl-4,6-diamino-1,3,5-triazine, 2,5-divinyl-1,4-benzenedial, and allylamine were selected, which are distinctive. The prepared adhesion promoter macromolecules contain carboxyl groups with longer side chains, multiple amino groups on the cyclic structure, and their aldehyde groups, which are novel and creative. Under the alkaline conditions of cement paste, amidation, acetalization and other reactions will occur between these functional groups to form a cross-linked network structure, and as the viscosity increases, solidification and other phenomena will occur. Under the alkaline conditions of pH 9-10 in cement paste, the time for the adhesion promoter to form a cross-linking and solidification effect is about 15-30 minutes, which can promote the rapid solidification of the cement coating and produce a strong adhesion effect and form a firm coating sealing coating and isolation dispersion coating.

[0030] (3) Compared with other technologies, the technology of the present invention has achieved significant substantial progress and application effects. The content of coal chemical solid waste in the filling concrete prepared by the method of the present invention accounts for 66% to 80% of the total weight, which is a high-content coal chemical solid waste concrete; the initial value of the slump after 3 hours is greater than 280mm, the slump value after 3 hours is greater than 260mm; the slump loss after 3 hours is less than 35mm; the diameter of the concrete expansion after 3 hours is 400 to 450mm; after 28 days of curing, the compressive strength is ≥30MPa, the flexural strength is ≥5MPa, and the water penetration resistance height is <10mm; according to the current cost calculation, the cost price per cubic meter is 150 to 180 yuan, and the economic benefit is very good. At present, the strength requirements for high-content coal chemical solid waste filling concrete in goafs are 28-day compressive strength greater than 10MPa, flexural strength greater than 3MPa, and pumpable working performance. The preparation of filling concrete by the method of the present invention meets the technical requirements.

[0031] (4) The present invention uses ultra-low-content graphene oxide to strengthen and toughen high-content coal chemical solid waste to prepare concrete for filling in mining voids. The graphene oxide content is 0.003%, which is ten times lower than the current conventional content of 0.03%, resulting in significant benefits. According to the current conventional content of 0.03%, 1 cubic meter of concrete requires approximately 0.03% × 400kg = 0.12kg of graphene oxide, and the price is 0.12kg × 1000 yuan / kg = 120 yuan; according to the 0.003% content of graphene oxide in the present invention, the price of adding graphene oxide is 12 yuan. Compared with the existing technology, the present invention has obvious creativity in terms of surface treatment technology for coal chemical solid waste, preparation and function of adhesion promoters, and ultra-low content of graphene oxide. Compared with the existing technology, the invention has outstanding substantive features and significant progress in terms of the technology and application effects produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the reaction and structure of the adhesion promoter of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be described in further detail below with reference to specific embodiments, but this is not intended to limit the present invention.

[0034] The present invention provides a method for preparing concrete for filling goafs with high content of coal chemical solid waste, which includes three preparation methods, the preparation technology of a coating for coating the surface of coal chemical solid waste coarse slag, the preparation technology of an adhesion promoter, and the preparation technology of concrete for filling goafs with high content of coal chemical solid waste. The novelty, creativity and practicality of these three preparation processes are particularly distinct and distinctive. The adhesion promoter is the premise and basis for the formation of the adhesion sealing coating due to its unique monomer selection and the rapid formation of a self-crosslinking network structure under alkaline conditions. The formation of the coating sealing coating on the surface of the coarse slag lays the foundation for the preparation of goaf concrete with high content of coal chemical solid waste. The creativity of these three technologies is remarkable.

[0035] The present invention discloses a method for preparing concrete for filling goaf with high content of coal chemical solid waste, comprising the following steps:

[0036] Step 1, preparation of surface coating, sealing and dispersion coating of coal chemical solid waste coarse slag: add 100-150 parts of coal chemical solid waste coarse slag and 15-20 parts of PO 32.5R cement into a rotary mixer according to mass parts and stir for 10-20 minutes to mix evenly; under stirring conditions, slowly add 8-15 parts of a mixture of water and an adhesion promoter within 5 minutes, and continue stirring for 20-25 minutes to promote the cement to evenly adhere to the surface of the coarse slag and quickly form a strong coating and sealing coating, which can withstand the mechanical stirring during the subsequent preparation of concrete without being damaged; slowly add 15-20 parts of dry coal chemical solid waste ash within 5 minutes, and continue stirring for 10-15 minutes to make the ash evenly adhere to the outer layer of the coating layer and quickly form a strong isolation and dispersion coating, and then discharge and stack it for 7 days before use. A cement coating for coating and sealing the voids on the surface and an isolation and anti-bonding ash coating are formed on the surface of the coal chemical solid waste coarse slag.

[0037] Step 2. Preparation method of high-content coal chemical solid waste goaf concrete: put 150-180 parts of coal chemical solid waste coarse slag containing coated sealing coating and isolation coating prepared in step 1, 25-30 parts of coal chemical solid waste ash, and 25-30 parts of cement into a concrete mixer and mix evenly, then add a mixed solution of 21-27 parts of mixing water and 5-6.5 parts of stimulating flow enhancer into the mixer and mix evenly to prepare goaf filling concrete with good workability, fluidity and pumpability, which can be used for concrete tank trucks and pipeline transportation for filling goafs in coal mines and other places.

[0038] The coal chemical solid waste coarse slag mainly adopts the coal chemical solid waste coarse slag from Shaanxi Yanchang Petroleum Group Yulin Coal Chemical Company and Shaanxi Coal Industry and Chemical Industry Group Co., Ltd. Its main components are: SiO2 content 39.31~41.58%, Al2O3 content 26.27~29.34%, Fe3O4 content 11.25~13.59%, CaO content 10.93~12.39%, MaO content 3.65~4.73%. Its particles are crushed, granulated and screened, with a moisture content of less than 5%. The porosity of the coarse slag is 25.36~35.68%, and the density is 2.3~2.5g / cm 3 , and its particle size is controlled in a continuous gradation of 3~35mm.

[0039] The coal chemical solid waste ash mainly uses the coal chemical solid waste ash produced by the following enterprises: Shaanxi Yanchang Petroleum Group Yulin Coal Chemical Company and Shaanxi Coal Industry and Chemical Industry Group Co., Ltd., and its main components are: SiO2 content 38.25~39.84%, Al2O3 content 25.63~28.57%, Fe3O4 content 10.62~12.86%, CaO content 8.63~10.73%, MaO content 2.36~3.81%, fineness on the 0.045mm square hole sieve is not more than 20%, water requirement is not more than 105%, loss on ignition is not more than 5%, water content is not more than 5%, and sulfur trioxide content is not more than 3%.

[0040] The excitation flow enhancer is obtained by in-situ intercalation and compounding of a polycarboxylate water-reducing agent and a graphene oxide dispersion, wherein the solid content of the polycarboxylate water-reducing agent is 5%, the solid content of the graphene oxide nanosheet is 0.075%, the water reduction rate of the polycarboxylate water-reducing agent is 31%, the oxidation degree of the graphene oxide is 32% expressed by the oxygen content, the thickness of the nanosheet is 0.8-1.6 nm, and the plane size of the two-dimensional sheet is 180-450 nm.

[0041] The preparation method of the adhesion promoter is as follows:

[0042] Step 1: Add 22-28 parts of allylmalonic acid, 6-8 parts of 2-vinyl-4,6-diamino-1,3,5-triazine, 11-16 parts of 2,5-divinyl-1,4-phthalaldehyde, 5-8 parts of allylamine, 0.4-0.7 parts of persulfate and 60-90 parts of water into a reactor, stir and heat to 40-50° C. to form a mixed monomer solution;

[0043] Step 2: Dissolve 0.2-0.4 parts of tyrosine and 0.1-0.3 parts of a molecular weight regulator in 40-50 parts of water to form a mixed solution of an initiator and a regulator, and then add the mixture to the mixed monomer solution dropwise for 40-50 minutes. After the addition is complete, continue stirring and keep warm at 40-50°C for 2-3 hours, then cool to 30-40°C, and use a 30% mass fraction of sodium hydroxide solution to adjust the pH value of the product to 6.5-7.0. The resulting product is an adhesion promoter with a solid content of about 35%.

[0044] In the above-mentioned method for preparing the adhesion promoter:

[0045] The allylmalonic acid, 2-vinyl-4,6-diamino-1,3,5-triazine, 2,5-divinyl-1,4-benzenedicarboxaldehyde and allylamine are all industrial grade, with a content of more than 96%;

[0046] The water is tap water, the persulfate is ammonium persulfate, sodium persulfate or potassium persulfate, and the tyrosine is of a purity greater than 99%;

[0047] The molecular weight regulator is thioglycolic acid, mercaptoethanol, and dodecyl mercaptan, and the content thereof is greater than 98%.

[0048] The reaction and structure of the adhesion promoter are as follows Figure 1 As shown, the adhesion promoter is polymerized from monomers with carboxyl, amino and aldehyde groups. It is a stable linear molecule under weakly acidic and neutral conditions. Under the strong alkaline conditions of the cement slurry, the carboxyl, amino and aldehyde groups in the adhesion promoter molecules can react chemically with the groups within or between molecules to form a cross-linked network structure, which plays a role in quickly bonding and solidifying the cement slurry to form a firm coating and isolation dispersion layer on the surface of the coal chemical solid waste coarse slag.

[0049] The adhesion promoter is a viscous aqueous liquid with a solid content of 35%, soluble in water in any proportion, with a pH value of 6.5-7.0, a number average and weight average relative molecular mass of 63,100-86,500 and 92,700-117,600 respectively, a molecular weight dispersion coefficient of 1.35-1.86, and a pH value of 6.5-7.0. The adhesion promoter forms a cross-linked network structure and produces a curing effect in cement slurry under alkaline conditions of pH 9-10 in about 15-30 minutes. The role of the adhesion promoter in the cement slurry is to form a cross-linked network structure by itself, so as to prompt the cement to quickly form a firm coating and sealing coating and ash isolation and separation layer.

[0050] The technical indicators of the high-content coal chemical solid waste goaf filling concrete prepared by the present invention are:

[0051] The prepared filling concrete contains 66% to 80% coal chemical solid waste by weight, making it a high-content coal chemical solid waste concrete. The initial 3-hour slump is >280mm, the 3-hour slump is >260mm, the 3-hour slump loss is <35mm, the 3-hour concrete expansion diameter is 400-450mm, and after 28 days of curing, the compressive strength is ≥30MPa, the flexural strength is ≥5MPa, and the water penetration resistance height is <10mm. Current strength requirements for high-content coal chemical solid waste-filled concrete in goafs are a 28-day compressive strength greater than 10MPa, a flexural strength greater than 3MPa, and pumpability. The present method for preparing filling concrete meets technical requirements and can also be used in other construction engineering fields. According to current cost calculations, the cost per cubic meter is approximately 150 to 180 yuan, while the price of ordinary C30 concrete is currently 450 to 500 yuan. Therefore, the present invention is highly innovative, practical, and economically beneficial.

[0052] Example 1

[0053] Step 1: Preparation of adhesion promoter for cement slurry-coated plugging coating

[0054] 22 parts of allylmalonic acid, 6 parts of 2-vinyl-4,6-diamino-1,3,5-triazine, 11 parts of 2,5-divinyl-1,4-benzenedicarboxaldehyde, 5 parts of allylamine, 0.47 parts of persulfate and 60 parts of water were added into a reactor, stirred and heated at 40°C to form a mixed monomer solution; 0.2 parts of tyrosine and 0.1 parts of a molecular weight regulator were dissolved in 40 parts of water to form an initiator mixed solution, which was then added dropwise to the mixed monomer solution for 40 minutes. After the addition was complete, the temperature was kept at 40°C and stirred for 2 hours, then the temperature was lowered to 30°C, and the pH value was adjusted to 6.5 with 30% by mass of sodium hydroxide. The resulting product was an adhesion promoter with a solid content of 30.6%.

[0055] Step 2: Preparation of a coating on the surface of coal chemical solid waste coarse slag

[0056] Add 100 parts of crude coal chemical solid waste slag and 15 parts of PO 32.5R cement into a rotary mixer according to mass parts and stir for 10 minutes to mix them evenly. Slowly add 8 parts of a mixture of water and adhesion promoter within 5 minutes under stirring conditions, continue stirring for 20 minutes, and then slowly add 15 parts of dry coal chemical solid waste ash within 10 minutes. Stir for 10 minutes to allow the ash to evenly adhere to the outer layer of the coating to quickly form a firm isolation and dispersion coating. Then discharge the material and stack it for 7 days before use.

[0057] Step 3: Preparation method of high-content coal chemical solid waste goaf concrete

[0058] 150 parts of the prepared coal chemical solid waste coarse slag containing sealing coating and isolation coating, 25 parts of coal chemical solid waste ash, and 25 parts of cement are put into a concrete mixer and stirred evenly. Then 21 parts of mixing water and 5 parts of a mixed solution of stimulating flow enhancer are added into the mixer and stirred evenly. A concrete for filling goaf with good workability, fluidity and pumpability is obtained. The fluidity decreases to 8% of the initial fluidity within 3 hours. The concrete can be used for concrete tank truck transportation and pipeline transportation for filling goafs such as coal mines.

[0059] The technical indicators of the prepared high-content coal chemical solid waste goaf filling concrete are: the coal chemical solid waste content in the prepared filling concrete accounts for 69.8% of the total weight, which is a high-content coal chemical solid waste concrete; the initial slump value in 3 hours is 295mm, the slump value in 3 hours is 269mm; the slump loss in 3 hours is 23mm; the expansion diameter of concrete in 3 hours is 436mm; after 28 days of curing, the compressive strength is 39.8MPa, the flexural strength is 6.3MPa, and the water penetration resistance height is 9mm; according to current cost calculations, the cost price per cubic meter is about 168 yuan, which has good economic benefits.

[0060] Example 2

[0061] Step 1: Preparation of adhesion promoter for cement slurry-coated plugging coating

[0062] 25 parts of allylmalonic acid, 7 parts of 2-vinyl-4,6-diamino-1,3,5-triazine, 14 parts of 2,5-divinyl-1,4-benzenedicarboxaldehyde, 7 parts of allylamine, 0.5 parts of persulfate and 80 parts of water were added to a reactor, stirred and heated to 45°C to form a mixed monomer solution; 0.3 parts of tyrosine and 0.2 parts of a molecular weight regulator were dissolved in 45 parts of water to form an initiator mixed solution, which was then added dropwise to the mixed monomer solution for 50 minutes. After the addition was completed, the temperature was continued to be kept at 50°C and stirred for 2-3 hours, then the temperature was lowered to 40°C, and the pH value was adjusted to 7.0 with 30% by mass of sodium hydroxide. The resulting product was an adhesion promoter with a solid content of about 31.3%.

[0063] Step 2: Preparation of a coating on the surface of coal chemical solid waste coarse slag

[0064] Add 150 parts of crude coal chemical solid waste slag and 20 parts of PO 32.5R cement into a rotary mixer and stir for 20 minutes to mix them evenly. Slowly add 13 parts of a mixture of water and an adhesion promoter within 5 minutes under stirring conditions, continue stirring for 25 minutes, and then slowly add 20 parts of dry coal chemical solid waste ash within 10 minutes. Stir for 15 minutes to allow the ash to evenly adhere to the outer layer of the coating to quickly form a firm isolation and dispersion coating. Then, discharge the material and stack it for 7 days before use.

[0065] Step 3: Preparation method of high-content coal chemical solid waste goaf concrete

[0066] 180 parts of the prepared coal chemical solid waste coarse slag containing sealing coating and isolation coating, 30 parts of coal chemical solid waste ash, and 25 parts of cement are put into a concrete mixer and stirred evenly. Then, a mixed solution of 27 parts of mixing water and 6.5 parts of stimulating flow enhancer is added into the mixer and stirred evenly. A goaf filling concrete with good workability, fluidity and pumpability is obtained. The fluidity reduction value within 4 hours is 12% of the initial fluidity. It can be used for concrete tank truck transportation and pipeline transportation for filling goafs such as coal mines.

[0067] The technical indicators of the prepared high-content coal chemical solid waste goaf filling concrete are: the coal chemical solid waste content in the prepared filling concrete accounts for 71.3% of the total weight, which is a high-content coal chemical solid waste concrete; the initial slump value in 3 hours is 291mm, the slump value in 3 hours is 265mm; the slump loss in 3 hours is 29m; the expansion diameter of concrete in 3 hours is 427mm; after 28 days of curing, the compressive strength is 36.7MPa, the flexural strength is 5.6MPa, and the water penetration resistance height is 8.3mm; according to current cost calculations, the cost price per cubic meter is about 154 yuan, which has good economic benefits.

[0068] Example 3

[0069] Step 1: Preparation of adhesion promoter for cement slurry-coated plugging coating

[0070] 28 parts of allylmalonic acid, 8 parts of 2-vinyl-4,6-diamino-1,3,5-triazine, 16 parts of 2,5-divinyl-1,4-benzenedicarboxaldehyde, 8 parts of allylamine, 0.7 parts of persulfate and 90 parts of water were added into a reactor, stirred and heated to 50°C to form a mixed monomer solution; 0.4 parts of tyrosine and 0.3 parts of a molecular weight regulator were dissolved in 50 parts of water to form an initiator mixed solution, which was then added dropwise to the mixed monomer solution for 50 minutes. After the addition was completed, the temperature was kept at 50°C and stirred for 3 hours, then the temperature was lowered to 40°C, and the pH value was adjusted to 7.0 with 30% by mass of sodium hydroxide. The resulting product was an adhesion promoter with a solid content of about 29.8%.

[0071] Step 2: Preparation of a coating on the surface of coal chemical solid waste coarse slag

[0072] Add 130 parts of crude coal chemical solid waste slag and 20 parts of PO 32.5R cement into a rotary mixer and stir for 20 minutes to mix them evenly. Slowly add 15 parts of a mixture of water and an adhesion promoter within 5 minutes under stirring conditions, continue stirring for 25 minutes, and then slowly add 20 parts of dry coal chemical solid waste ash within 10 minutes. Stir for 10 minutes to allow the ash to evenly adhere to the outer layer of the coating to quickly form a firm isolation and dispersion coating. Then, discharge the material and stack it for 7 days before use.

[0073] Step 3: Preparation method of high-content coal chemical solid waste goaf concrete

[0074] 170 parts of the prepared coal chemical solid waste coarse slag containing sealing coating and isolation coating, 28 parts of coal chemical solid waste ash, and 29 parts of cement are put into a concrete mixer and stirred evenly. Then, a mixed solution of 25 parts of mixing water and 6 parts of stimulating flow enhancer is added into the mixer and stirred evenly. A concrete for filling goaf with good workability, fluidity and pumpability is obtained. The fluidity decreases to 10% of the initial fluidity within 4 hours. The concrete can be used for concrete tank truck transportation and pipeline transportation for filling goafs such as coal mines.

[0075] The technical indicators of the prepared high-content coal chemical solid waste goaf filling concrete are: the coal chemical solid waste content in the prepared filling concrete accounts for 78.23% of the total weight, which is a high-content coal chemical solid waste concrete; the initial slump value in 3 hours is 287mm, the slump value in 3 hours is 268mm; the slump loss in 3 hours is 32mm; the expansion diameter of concrete in 3 hours is 418mm; after 28 days of curing, the compressive strength is 37MPa, the flexural strength is 5.8MPa, and the water penetration resistance height is 70mm; according to current cost calculations, the cost price per cubic meter is about 172 yuan, which has good economic benefits.

Claims

1. A method for preparing concrete for filling goaf with high content of coal chemical solid waste, characterized in that: The method comprises the following steps, wherein the following parts are all parts by mass: Step 1: Preparation of surface coating, sealing and dispersion coating for coal chemical solid waste coarse slag: Add 100-150 parts of coal chemical solid waste coarse slag and 15-20 parts of PO 32.5R cement into a rotary mixer and stir for 10-20 minutes to mix evenly; slowly add 8-15 parts of a mixture of water and an adhesion promoter within 5 minutes under stirring conditions, and continue stirring for 20-25 minutes to promote the cement to evenly adhere to the surface of the coarse slag and quickly form a strong coating and plugging coating that can withstand the mechanical stirring during the subsequent preparation of concrete without being damaged; slowly add 15-20 parts of dry coal chemical solid waste ash within 5 minutes, continue stirring for 10-15 minutes, and then discharge and stack for 7 days before use; Step 2: Preparation of concrete for filling the goaf with high content of coal chemical solid waste: 150-180 parts of the coal chemical solid waste coarse slag containing the coated plugging and dispersed coating prepared in step 1, 25-30 parts of coal chemical solid waste ash, and 25-30 parts of cement are added into a concrete mixer and stirred evenly. Then, a mixed solution of 21-27 parts of mixing water and 5-6.5 parts of an excitation flow enhancer is added into the mixer and stirred evenly to prepare a high-content coal chemical solid waste goaf filling concrete; The main components of the coal chemical solid waste coarse slag are: SiO2 content 39.31~41.58%, Al2O3 content 26.27~29.34%, Fe3O4 content 11.25~13.59%, CaO content 10.93~12.39%, MaO content 3.65~4.73%. The particles are crushed, granulated and screened, with a moisture content of less than 5%. The porosity of the coarse slag is 25.36~35.68%, and the density is 2.3~2.5g / cm 3 , its particle size is controlled in a continuous gradation of 3~35mm; The coal chemical solid waste ash has the following main components: SiO2 content of 38.25-39.84%, Al2O3 content of 25.63-28.57%, Fe3O4 content of 10.62-12.86%, CaO content of 8.63-10.73%, MaO content of 2.36-3.81%, fineness of which the residue on a 0.045 mm square hole sieve is not more than 20%, water requirement is not more than 105%, loss on ignition is not more than 5%, water content is not more than 5%, and sulfur trioxide content is not more than 3%; The excitation flow enhancer is obtained by in-situ intercalation of a polycarboxylate water-reducing agent and a graphene oxide dispersion, wherein the solid content of the polycarboxylate water-reducing agent is 5%, the solid content of the graphene oxide nanosheet is 0.075%, the water reduction rate of the polycarboxylate water-reducing agent is 31%, the oxidation degree of the graphene oxide is 32% expressed by the oxygen content, the thickness of the nanosheet is 0.8-1.6 nm, and the plane size of the two-dimensional sheet is 180-450 nm; The specific preparation method of the adhesion promoter is as follows: Step 1: Add 22-28 parts of allylmalonic acid, 6-8 parts of 2-vinyl-4,6-diamino-1,3,5-triazine, 11-16 parts of 2,5-divinyl-1,4-phthalaldehyde, 5-8 parts of allylamine, 0.4-0.7 parts of persulfate and 60-90 parts of water into a reactor, stir and heat to 40-50° C. to form a mixed monomer solution; Step 2: dissolving 0.2-0.4 parts of tyrosine and 0.1-0.3 parts of a molecular weight regulator in 40-50 parts of water to form a mixed solution of an initiator and a regulator, and then adding the mixture to the mixed monomer solution in a dropwise manner for 40-50 minutes. After the addition is complete, stirring is continued and the temperature is kept at 40-50°C for 2-3 hours, then cooled to 30-40°C, and the pH value of the product is adjusted to 6.5-7.0 with a 30% mass fraction of sodium hydroxide solution. The resulting product is an adhesion promoter with a solid content of 35%; The allylmalonic acid, 2-vinyl-4,6-diamino-1,3,5-triazine, 2,5-divinyl-1,4-benzenedicarboxaldehyde and allylamine are all industrial grade, with a content of more than 96%; The water is tap water, the persulfate is ammonium persulfate, sodium persulfate or potassium persulfate, and the tyrosine is of a purity greater than 99%; The molecular weight regulator is thioglycolic acid, mercaptoethanol, and dodecyl mercaptan, and the content thereof is greater than 98%.

2. The method for preparing concrete for filling goaf with high content of coal chemical solid waste according to claim 1, characterized in that: The adhesion promoter is a viscous aqueous liquid with a solid content of 35%, soluble in water in any proportion, with a pH value of 6.5-7.0, a number average and weight average relative molecular mass of 63,100-86,500 and 92,700-117,600 respectively, a molecular weight dispersion coefficient of 1.35-1.86, and a pH value of 6.5-7.

0. The adhesion promoter forms a cross-linked network structure and produces a curing effect in 15-30 minutes under alkaline conditions of pH 9-10 in cement slurry.

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