Marble made from fly ash from garbage power plant and preparation method thereof

Abstract

The invention discloses marble made from fly ash from a garbage power plant and a preparation method thereof, belonging to the technical field of synthesis of inorganic non-metallic materials. The marble comprises the following raw materials in parts by weight: 15-20 parts of Portland cement, 45-55 parts of a composite filler, 35-45 parts of coal slag, 1-5 parts of an admixture, 5-10 parts of inorganic pigment powder, and a water-binder ratio of 0.3-0.4. The composite filler is added to the marble, and the composite filler is prepared from a fly ash chelate product, modified fly ash, allylbenzoxazine, and a capping monomer. The fly ash chelate product contains a disulfide bond and multiple alcoholic hydroxyl groups, and the modified fly ash contains amino groups and hydroxyl groups, which can form coordination bonds, electrostatic forces, and van der Waals forces with heavy metal ions in the fly ash. The modified fly ash also has a high silicon and aluminum content. The allylbenzoxazine has high mechanical strength. The capping monomer contains NCO and carbamate groups, which can not only chelate heavy metal ions but also enhance the mechanical properties of the marble.

Description

Technical Field

[0001] The invention relates to the technical field of synthesis of inorganic non-metallic materials, in particular to marble made from fly ash from a garbage power plant and a preparation method thereof. Background Art

[0002] Fly ash generated during the incineration process at waste-to-energy plants contains a variety of organic pollutants and heavy metals, making it a hazardous waste. Therefore, before being landfilled or recycled, the fly ash must be stabilized to remove toxic substances such as heavy metals and dioxins. After various treatment methods, fly ash can be used as a raw material to produce high-quality building materials.

[0003] Invention patent application CN114773017A discloses a hot-pressed, maintenance-free solid waste-based artificial stone and its preparation method. During the preparation process, the circulating fluidized bed fly ash and carbide slag undergo a pozzolanic reaction during the hot pressing process to obtain hydrated calcium silicate and hydrated calcium aluminate products. The main component of the desulfurized gypsum contains CaSO4·2H2O, and the SO4 contained in it is then used. 2- The characteristics of the circulating fluidized bed fly ash are subjected to a certain sulfate excitation, thereby improving the gelling activity of the circulating fluidized bed fly ash, and finally improving the strength of the prepared stone. However, in the preparation process of the present application, the fly ash used is the fly ash discharged after the sulfur-containing coal and the sulfur-fixing agent are mixed in a certain proportion in the prior art and burned at a temperature of 850-900°C in a fluidized bed boiler to fix the sulfur. In the preparation process of the stone, there is no targeted and effective solidification of the heavy metal ions in the fly ash, resulting in the problem of heavy metal ion precipitation during the use of the stone. At the same time, the preparation method only achieves the solidification effect through the hydration reaction between the base materials, and the strength of the stone finally prepared is limited.

[0004] Therefore, providing a high-strength marble made from fly ash from a waste power plant and a preparation method thereof is a technical problem that needs to be solved at present. Summary of the Invention

[0005] The object of the present invention is to provide a marble made from fly ash from a garbage power plant and a preparation method thereof, so as to solve the problems raised in the background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] Marble made from fly ash from a garbage power plant comprises the following raw materials in parts by weight:

[0008] 15-20 parts of Portland cement, 45-55 parts of composite filler, 35-45 parts of coal slag, 1-5 parts of admixture, 5-10 parts of inorganic pigment powder and water-binder ratio of 0.3-0.4;

[0009] The method for preparing marble made from fly ash from a garbage power plant comprises the following steps:

[0010] Step S1: Add cement, composite filler, coal slag, inorganic pigment powder, and admixtures by weight into a cement mortar mixer, dry-mix for 2 minutes, and continue mixing for 3 minutes while adding water to obtain a primary mixture;

[0011] Step S2: transferring the primary mixed material to a marble brick forming machine, pressing at 50 MPa for 10 seconds, and demolding to obtain an artificial marble brick embryo;

[0012] Step S3: placing the artificial marble bricks into a constant temperature and humidity curing box and hydrothermally curing at 70° C. for 28 days to obtain marble made from fly ash from the waste power plant.

[0013] Furthermore, the inorganic pigment powder is selected from one or more of carbon black, red iron oxide and yellow iron oxide and mixed in any ratio.

[0014] Furthermore, the admixture is a polycarboxylate water reducer.

[0015] Furthermore, the preparation method of the composite filler comprises the following steps:

[0016] Step A1, adding KH-550 to deionized water and ultrasonicating for 25-35 minutes to obtain a pre-emulsion, wherein the amount ratio of KH-550 to deionized water is 0.50-0.56 mL: 20-30 mL;

[0017] Step A2, add fly ash to 90wt% ethanol solution, ultrasonicate for 45-55min to obtain fly ash solution, transfer the fly ash solution to a three-necked flask equipped with a condenser, adjust the pH to neutral with acetic acid, heat to 80-90°C, add the pre-emulsion and allyl glycidyl ether mixture a dropwise while stirring, control the dropwise addition rate to 2-4 drops / second, continue stirring and react for 3.5-4.5h, and after the reaction is completed, Aged for 2 hours, then washed with anhydrous ethanol and deionized water 2-4 times in sequence, filtered, and dried at 90°C for 10 hours to obtain modified fly ash, wherein the amount ratio of fly ash, 90wt% ethanol solution and mixed solution a is 5-8g:100mL:10.2-10.4mL, and the amount ratio of pre-emulsion and allyl glycidyl ether in mixed solution a is 10mL:0.2-0.4mL. In the above reaction process, with 90wt% ethanol solution as solvent, the amino group on KH-550 and the epoxy group on allyl glycidyl ether undergo a ring-opening reaction to obtain modified fly ash;

[0018] Step A3, adding the modified fly ash, fly ash chelate product and allylbenzoxazine to a 0.5M sodium hydroxide aqueous solution, stirring at 20-30°C and a speed of 500-1000 rpm for 10 hours, and then ultrasonically treating for 1-3 hours to obtain a precursor solution; ultrasonically dispersing the precursor solution and the initiator solution, continuing to heat to 65-75°C, stirring and reacting for 6-8 hours, cooling to room temperature after the reaction, filtering, washing 3-5 times, and drying at 70-90°C for 8 hours. -12h to obtain a prepolymer, wherein the amount ratio of modified fly ash, fly ash chelate product, allylbenzoxazine, and 0.5M sodium hydroxide aqueous solution is 3-5g:7-9g:6-8g:60-80mL, and the amount ratio of precursor solution to initiator solution is 45-55mL:20mL. Under the catalytic action of the initiator solution, the unsaturated double bonds on the modified fly ash and the unsaturated double bonds on the allylbenzoxazine undergo thermal polymerization to obtain a prepolymer;

[0019] The silicon and aluminum contents in fly ash are relatively low, while those in fly ash are relatively high. By blending the two materials, the utilization rate of fly ash is increased while the mechanical properties of the prepared marble are further improved.

[0020] Step A4: After mixing the prepolymer, the end-capping monomer and tetrabutylammonium bromide, the temperature is raised to 155-165° C. under nitrogen protection, and the reaction is stirred for 1.5-2.5 hours. The nitrogen is then removed, the reaction is carried out under reduced pressure for 2 hours, the temperature is lowered, and the material is discharged to obtain a composite filler. The amount ratio of the prepolymer, the end-capping monomer and the tetrabutylammonium bromide is 5-8 g: 3-4 g: 0.1-0.3 g. During the above reaction process, at high temperature, with tetrabutylammonium bromide as a catalyst, the hydroxyl groups on the prepolymer and the isocyanate groups on the end-capping monomer are chemically cross-linked to obtain a composite filler.

[0021] Furthermore, in step A3, the initiator solution is prepared by mixing sodium persulfate and deionized water in a ratio of 0.02-0.03 g: 20 mL.

[0022] Furthermore, in step A2, the fly ash is low calorific value coal fly ash taken from a 350MW supercritical circulating fluidized bed boiler of a power generation company in Shanxi Province, with a reddish brown color and a density of 2.48 g / cm 3 , moisture content 0.14%, particle size distribution concentrated below 100μm, the chemical composition of the fly ash is shown in Table 1 below.

[0023] Furthermore, the coal slag is a low calorific value coal slag taken from a 350MW supercritical circulating fluidized bed boiler of a power generation company in Shanxi Province. It is dark gray and has a density of 3.50g / cm 3 , moisture content 0.10%, particle size distribution concentrated below 8μm, the chemical composition of the coal slag is shown in Table 1 below.

[0024] Furthermore, the method for preparing the fly ash chelate product comprises the following steps:

[0025] Step B1, under nitrogen protection, dithioglycolic acid was added to anhydrous DMF, stirred evenly, and then N, N-dicyclohexylcarbodiimide, 4-dimethylaminopyridine and diethanolamine were added, the temperature was raised to 65-75 ° C, and the reaction was stirred for 4-6 hours. After the reaction was completed, the filter was filtered, and the filter cake was washed with anhydrous ethanol and deionized water for 2-4 times, respectively, and freeze-dried to obtain dithiopolyol, wherein dithioglycolic acid, anhydrous DMF, N, N-dicyclohexylcarbodiimide, 4-dimethylaminopyridine and diethanolamine were added. The amount ratio of carbodiimide, 4-dimethylaminopyridine and diethanolamine is 3.5-4.5 g: 40-50 mL: 6-8 mL: 4-5 g: 2-3 mL. In the above reaction process, anhydrous DMF is used as solvent, 4-dimethylaminopyridine is used as catalyst, and N,N-dicyclohexylcarbodiimide is used as dehydrating agent. The carboxyl group on dithioglycolic acid and the amino group on diethanolamine undergo amidation reaction to obtain dithiopolyol, whose structural formula is as follows:

[0026]

[0027] Step B2: After the collected fly ash is dried and pre-treated by sieving, the fly ash is placed in a centrifuge tube, the dithiopolyol and deionized water prepared in step A1 are added, and the mixture is stirred at 2000-3000 rpm for 10-20 minutes. After the stirring is completed, the product is transferred to an aluminum plate and naturally cured for 24 hours, and then dried at 105° C. to obtain a fly ash chelate product, wherein the amount ratio of fly ash, dithiopolyol and deionized water is 8-10 g:4-5 g:90-110 mL. In the above process, the sulfur atoms on the carbon-sulfur bonds in the dithiopolyol can form stable coordination bonds with the heavy metal ions in the fly ash, thereby improving the chelating performance of the heavy metal cations in the fly ash.

[0028] Furthermore, the preparation method of allylbenzoxazine comprises the following steps:

[0029] 2,2'-diallylbisphenol A, m-toluidine and paraformaldehyde are added to a four-necked flask equipped with a stirrer, a thermometer and a condenser, stirred evenly, heated to 100°C, and stirred for 0.3-0.5h. After the reaction, the prepared product is dissolved in anhydrous ether, and then washed with 3M sodium hydroxide solution and deionized water 3-5 times in sequence. After the oil phase is separated, the anhydrous ether is removed by a rotary evaporator to obtain allylbenzoxazine, wherein the amount ratio of 2,2'-diallylbisphenol A, m-toluidine, polybenzaldehyde and anhydrous ether is 7-9mL:5-6mL:3-4g:30-50mL. During the above reaction process, 2,2'-diallylbisphenol A, m-toluidine and paraformaldehyde undergo a Mannich reaction to prepare allylbenzoxazine containing an unsaturated double bond.

[0030] The structural formula of the substance is shown below;

[0031]

[0032] Furthermore, the preparation method of the end-capping monomer comprises the following steps:

[0033] Isophorone diisocyanate, hydroquinone, dibutyltin dilaurate and acetone are added to a reaction kettle and stirred for 10-20 minutes. Hydroxyethyl methacrylate is added and stirred at 40°C for 4.5-5.5 hours. The acetone is removed by distillation under reduced pressure, and the distillate is washed with ether 3-5 times to obtain a capping monomer. The amount ratio of isophorone diisocyanate, hydroquinone, dibutyltin dilaurate, acetone and hydroxyethyl methacrylate is 45-50g:0.6-0.8g:0.38-0.42g:100-120mL:36-38g, so that the more active -NCO group in isophorone diisocyanate reacts with the -OH group of hydroxyethyl methacrylate at low temperature to obtain a capping monomer containing -NCO, carbamate group and unsaturated double bond. Compared with the prior art, the present invention has the following beneficial effects: (1) In the technical solution of the present invention, fly ash is added to an aqueous solution of dithiopolyol and subjected to hydrothermal treatment to obtain a fly ash chelating product, and then the prepared fly ash chelating product is thermally polymerized and chemically cross-linked with modified fly ash, allylbenzoxazine and end-capping monomer to obtain a composite filler. The dithiopolyol contains disulfide bonds and multiple alcohol hydroxyl groups, which can form coordination bonds, electrostatic forces and van der Waals forces with heavy metal ions in fly ash to effectively chelate heavy metal cations in fly ash; the modified fly ash forms electrostatic and van der Waals forces with heavy metal cations in fly ash through amino groups and hydroxyl groups on it, thereby further improving the chelating performance of heavy metal ions in fly ash. On the other hand, the modified fly ash has a higher silicon and aluminum content, and the modified fly ash and fly ash chelate The fly ash chelation product is blended to improve the utilization rate of fly ash and the mechanical properties of marble at the same time. Allylbenzoxazine itself has a fused polycyclic rigid structure with high rigidity and mechanical strength. Its introduction into the composite filler further improves the mechanical properties of marble. At the same time, the presence of unsaturated double bonds can chemically cross-link it with modified fly ash, strengthen the bonding force between molecules, and further improve the mechanical properties of marble. The end-capping monomer contains -NCO and carbamate groups. -NCO can chemically cross-link with the amino and hydroxyl groups on the fly ash chelation product and the modified fly ash. The carbamate group also has strong chelating and coordination ability with various heavy metal ions in fly ash. Through the synergistic effect between the above-mentioned base materials, not only can the heavy metal ions in the fly ash be stably chelated, but the strength of the marble can also be improved.

[0034] (2) In the present invention, fly ash produced by the incineration of a waste-to-energy plant and captured by heavy metal ions is added to silicate cement. Under a hydrothermal curing environment, the addition of the cement and fly ash chelate product causes deep hydration of the modified fly ash, generating a large amount of CSH and CAH gelling, which fully stimulates the activity of the modified fly ash. At the same time, a large amount of fibrous CSH gelling material fills the micropores and microcracks, well connecting the slag particles, enhancing the bonding strength of the aggregate interface, forming a dense microstructure, reducing the water absorption rate and porosity, and further improving the strength of the marble. DETAILED DESCRIPTION

[0035] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] The cement is PO·42.5 grade ordinary Portland cement produced by Henan Dadi Cement Group. The chemical composition is shown in Table 1. The polycarboxylate water reducer is the PCA-1 series polycarboxylate high-performance water reducer produced by Jiangsu Subote New Materials Co., Ltd., which is a light brown liquid with a solid content of 15% and a water reduction rate of 25-30%.

[0037] Table 1 Main chemical components of marble raw materials %

[0038]

[0039] Example 1

[0040] Preferably, this embodiment provides a method for preparing an end-capping monomer, comprising the following steps:

[0041] 47.5 g of isophorone diisocyanate, 0.7 g of hydroquinone, 0.40 g of dibutyltin dilaurate and 110 mL of acetone were added to a reactor and stirred for 15 min. 37 g of hydroxyethyl methacrylate was added and stirred at 40 ° C for 5 h. The acetone was removed by distillation under reduced pressure, and the distillation product was washed with ether 4 times to obtain a capped monomer.

[0042] Example 2

[0043] Preferably, this embodiment provides a method for preparing allylbenzoxazine, comprising the following steps:

[0044] In a four-necked flask equipped with a stirrer, a thermometer, and a condenser, 8 mL of 2,2'-diallylbisphenol A, 5.5 mL of m-toluidine, and 3.5 g of paraformaldehyde were added, stirred evenly, heated to 100°C, and stirred for 0.4 h. After the reaction, the prepared product was dissolved in 40 mL of anhydrous ether, and then washed four times with 3M sodium hydroxide solution and deionized water. After the oil phase was separated, the anhydrous ether was removed by rotary evaporator to obtain allylbenzoxazine.

[0045] Example 3

[0046] Preferably, this embodiment provides a method for preparing a fly ash chelate product, comprising the following steps:

[0047] Step B1: Under nitrogen protection, 4 g of dithioglycolic acid was added to 45 mL of anhydrous DMF and stirred evenly. Then, 7 mL of N,N-dicyclohexylcarbodiimide, 4.5 g of 4-dimethylaminopyridine and 2.5 mL of diethanolamine were added. The temperature was raised to 70°C and stirred for 5 h. After the reaction was completed, the filter cake was filtered and washed three times with anhydrous ethanol and deionized water, respectively, and freeze-dried to obtain dithiopolyol.

[0048] Step B2: After the collected fly ash is dried and sieved for pretreatment, 9 g of fly ash is placed in a centrifuge tube, 4.5 g of dithiopolyol prepared in step A1 and 100 mL of deionized water are added, and the mixture is stirred at 2500 rpm for 15 min. After the stirring is completed, the product is transferred to an aluminum plate and naturally cured for 24 h, and then dried at 105 ° C to obtain a fly ash chelate product.

[0049] Example 4

[0050] Preferably, this embodiment provides a method for preparing a composite filler, comprising the following steps:

[0051] Step A1: add 0.53 mL of KH-550 to deionized water and sonicate for 30 min to obtain a pre-emulsion;

[0052] Step A2, 6.5g of fly ash was added to 100mL of 90wt% ethanol solution, and ultrasonicated for 50min to obtain a fly ash solution. The fly ash solution was transferred to a three-necked flask equipped with a condenser, and the pH was adjusted to neutral with acetic acid. The temperature was raised to 85°C, and a mixture of 10mL of pre-emulsion and 0.3mL of allyl glycidyl ether was added dropwise with stirring at a dropping rate of 3 drops / second. After the dropping was completed, the stirring reaction was continued for 4.0h. After the reaction was completed, the mixture was allowed to stand for 2h, and then washed with anhydrous ethanol and deionized water three times in sequence, filtered, and dried at 90°C for 10h to obtain modified fly ash;

[0053] Step A3, 4 g of modified fly ash, 8 g of the fly ash chelate product prepared in Example 3, and 7 g of allylbenzoxazine were added to 70 mL of 0.5 M sodium hydroxide aqueous solution, stirred at 25 ° C and 750 rpm for 10 hours, and then ultrasonically treated for 2 hours to obtain a precursor solution; 50 mL of the precursor solution and 20 mL of the initiator solution were ultrasonically dispersed, and the temperature was continued to be raised to 70 ° C. and stirred for 7 hours. After the reaction was completed, it was cooled to room temperature, filtered, washed 4 times, and dried at 80 ° C for 10 hours to obtain a prepolymer, wherein the initiator solution was obtained by mixing 0.025 g of sodium persulfate and 20 mL of deionized water;

[0054] Step A4: Mix 6.5 g of the prepolymer, 3.5 g of the end-capping monomer prepared in Example 1, and 0.2 g of tetrabutylammonium bromide, and under nitrogen protection, heat to 160° C., stir and react for 2.0 h, then remove the nitrogen, react under reduced pressure for 2 h, cool, and discharge to obtain a composite filler.

[0055] Example 5

[0056] This embodiment provides a marble made from fly ash from a waste-to-energy plant, comprising the following raw materials in parts by weight:

[0057] 15 parts of Portland cement, 45 parts of the composite filler prepared in Example 4, 35 parts of coal furnace slag, 1 part of polycarboxylate water reducer, 5 parts of carbon black and a water-binder ratio of 0.3;

[0058] The method for preparing marble made from fly ash from a garbage power plant comprises the following steps:

[0059] Step S1: Add cement, the composite filler prepared in Example 4, coal furnace slag, carbon black, and polycarboxylate water reducer according to weight into a cement mortar mixer, dry-mix for 2 minutes, and continue mixing for 3 minutes while adding water to obtain a primary mixture;

[0060] Step S2: transferring the primary mixed material to a marble brick forming machine, pressing at 50 MPa for 10 seconds, and demolding to obtain an artificial marble brick embryo;

[0061] Step S3: placing the artificial marble bricks into a constant temperature and humidity curing box and hydrothermally curing at 70° C. for 28 days to obtain marble made from fly ash from the waste power plant.

[0062] Example 6

[0063] This embodiment provides a marble made from fly ash from a waste-to-energy plant, comprising the following raw materials in parts by weight:

[0064] 17.5 parts of Portland cement, 50 parts of the composite filler prepared in Example 4, 40 parts of coal furnace slag, 3 parts of polycarboxylate water reducer, 7.5 parts of red iron oxide, and a water-binder ratio of 0.35;

[0065] The method for preparing marble made from fly ash from a garbage power plant comprises the following steps:

[0066] Step S1: Add cement, the composite filler prepared in Example 4, coal furnace slag, red iron oxide, and polycarboxylate water reducer according to weight into a cement mortar mixer, dry-mix for 2 minutes, and continue mixing for 3 minutes while adding water to obtain a primary mixture;

[0067] Step S2: transferring the primary mixed material to a marble brick forming machine, pressing at 50 MPa for 10 seconds, and demolding to obtain an artificial marble brick embryo;

[0068] Step S3: placing the artificial marble bricks into a constant temperature and humidity curing box and hydrothermally curing at 70° C. for 28 days to obtain marble made from fly ash from the waste power plant.

[0069] Example 7

[0070] This embodiment provides a marble made from fly ash from a waste-to-energy plant, comprising the following raw materials in parts by weight:

[0071] 20 parts of Portland cement, 55 parts of the composite filler prepared in Example 4, 45 parts of coal furnace slag, 5 parts of polycarboxylate water reducer, 10 parts of yellow iron oxide, and a water-binder ratio of 0.4;

[0072] The method for preparing marble made from fly ash from a garbage power plant comprises the following steps:

[0073] Step S1: Add cement, the composite filler prepared in Example 4, coal furnace slag, yellow iron oxide, and polycarboxylate water reducer according to weight into a cement mortar mixer, dry-mix for 2 minutes, and continue mixing for 3 minutes while adding water to obtain a primary mixture;

[0074] Step S2: transferring the primary mixed material to a marble brick forming machine, pressing at 50 MPa for 10 seconds, and demolding to obtain an artificial marble brick embryo;

[0075] Step S3: placing the artificial marble bricks into a constant temperature and humidity curing box and hydrothermally curing at 70° C. for 28 days to obtain marble made from fly ash from the waste power plant.

[0076] Comparative Example 1

[0077] The dithioglycolic acid in Example 3 was replaced by diglycolic acid, and the other raw materials and preparation process remained unchanged. The prepared substance was then replaced by the fly ash chelating product in Example 4, and the other raw materials and preparation process remained unchanged. The prepared substance was then replaced by the composite filler in Example 6, and the other raw materials and preparation process remained unchanged.

[0078] Comparative Example 2

[0079] The allylbenzoxazine in Example 4 was removed, and the other raw materials and preparation process remained unchanged. The prepared material was then replaced with the composite filler in Example 6, and the other raw materials and preparation process remained unchanged.

[0080] Comparative Example 3

[0081] The end-capping monomer in Example 4 was removed, and the other raw materials and preparation process remained unchanged. The prepared material was then replaced with the composite filler in Example 6, and the other raw materials and preparation process remained unchanged.

[0082] Comparative Example 4

[0083] The fly ash in Example 4 was removed, and the other raw materials and preparation process remained unchanged. The prepared material was then replaced with the composite filler in Example 6, and the other raw materials and preparation process remained unchanged.

[0084] Performance testing

[0085] (1) This test uses a heavy metal dynamic cycle leaching test and refers to the "Groundwater Quality Standard" (GB / T14848-2017) to evaluate the environmental impact of the marble prepared in Examples 5-7 and Comparative Examples 1-6. The content of heavy metal ions is analyzed and determined using an inductively coupled plasma emission spectrometer. Each group of experiments is performed twice in parallel and the average value is taken. The test results are shown in Table 1 below:

[0086] Table 1

[0087]

[0088] It can be seen from Table 1 that, compared with Comparative Examples 1-4, the marbles prepared in Examples 5-7 have excellent adsorption and chelation capabilities for heavy metal ions in fly ash.

[0089] (2) The mechanical strength of the marble prepared in Examples 5-7 and Comparative Examples 1-4 was tested. The specific test items and test standards are as follows: the compressive strength test was carried out with reference to GB / T 9966.1-2020 "Test methods for natural stone - Part 1: Compression strength test after drying, water saturation and freeze-thaw cycles"; the flexural strength test was carried out with reference to GB / T 9966.2-2020 "Test methods for natural stone - Part 2: Flexural strength test after drying, water saturation and freeze-thaw cycles"; the density, water absorption and porosity were tested with reference to GB / T 3810.3-2016 "Test methods for ceramic tiles - Part 3: Determination of water absorption, apparent porosity, apparent relative density and bulk density". The test results are shown in Table 2 below:

[0090] Table 2

[0091]

[0092] It can be seen from Table 2 that, compared with Comparative Examples 1-4, the marbles prepared in Examples 5-7 have better compressive strength and bending strength, and at the same time, lower water absorption.

[0093] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A marble made from fly ash from a garbage power plant, characterized by: It includes the following raw materials in parts by weight: 15-20 parts of Portland cement, 45-55 parts of composite filler, 35-45 parts of coal slag, 1-5 parts of admixture, 5-10 parts of inorganic pigment powder and water-binder ratio of 0.3-0.4; The composite filler is prepared by firstly subjecting fly ash chelate product, modified fly ash and allylbenzoxazine to free radical polymerization to obtain a prepolymer, and then chemically cross-linking with a terminal monomer; The fly ash chelate product is prepared by first subjecting dithioglycolic acid and diethanolamine to an amidation reaction to obtain dithiopolyol, which is then further subjected to a heat curing treatment with fly ash and deionized water; The modified fly ash is first prepared by a ring-opening reaction between fly ash modified with KH-550 and allyl glycidyl ether; The allylbenzoxazine is prepared by Mannich reaction of 2,2'-diallylbisphenol A, m-toluidine and paraformaldehyde; The end-capping monomer is prepared by chemically cross-linking isophorone diisocyanate and hydroxyethyl methacrylate; The preparation method of the composite filler comprises the following steps: Step A1: Add KH-550 to deionized water and ultrasonicate for 25-35 minutes to obtain a pre-emulsion; Step A2, adding fly ash to a 90wt% ethanol solution, ultrasonicating for 45-55min to obtain a fly ash solution, transferring the fly ash solution to a three-necked flask equipped with a condenser, adjusting the pH to neutral with acetic acid, heating to 80-90°C, and adding dropwise a mixture of the pre-emulsion and allyl glycidyl ether while stirring at a rate of 2-4 drops / second. After the addition is complete, stirring and reacting for 3.5-4.5h. After the reaction is complete, standing and aging for 2h, then washing with anhydrous ethanol and deionized water 2-4 times, filtering, and drying at 90°C for 10h to obtain modified fly ash; Step A3, adding the modified fly ash, the fly ash chelate product and allylbenzoxazine to a 0.5M sodium hydroxide aqueous solution, stirring at 20-30° C. and 500-1000 rpm for 10 hours, and then ultrasonically treating for 1-3 hours to obtain a precursor solution; ultrasonically dispersing the precursor solution and the initiator solution, continuing to raise the temperature to 65-75° C., stirring and reacting for 6-8 hours, cooling to room temperature after the reaction, filtering, washing 3-5 times, and drying at 70-90° C. for 8-12 hours to obtain a prepolymer; Step A4: After mixing the prepolymer, the end-capping monomer and tetrabutylammonium bromide, the mixture was heated to 155-165° C. under nitrogen protection, stirred and reacted for 1.5-2.5 hours, then the nitrogen was removed, the mixture was reacted under reduced pressure for 2 hours, cooled, and discharged to obtain a composite filler; The method for preparing the fly ash chelate product comprises the following steps: Step B1: Under nitrogen protection, dithioglycolic acid is added to anhydrous DMF and stirred evenly. Then, N,N-dicyclohexylcarbodiimide, 4-dimethylaminopyridine, and diethanolamine are added. The temperature is raised to 65-75° C. and stirred for 4-6 hours. After the reaction is completed, the filter is filtered and the filter cake is washed 2-4 times with anhydrous ethanol and deionized water, respectively, and freeze-dried to obtain a dithiopolyol. Step B2: After the collected fly ash is dried and sieved for pretreatment, the fly ash is placed in a centrifuge tube, the dithiopolyol prepared in step A1 and deionized water are added, and the mixture is stirred at 2000-3000 rpm for 10-20 minutes. After the stirring is completed, the product is transferred to an aluminum plate and naturally cured for 24 hours, and then dried at 105° C. to obtain a fly ash chelate product.

2. The marble made from fly ash from a waste power plant according to claim 1, characterized in that: The preparation method of the allylbenzoxazine comprises the following steps: Add 2,2'-diallylbisphenol A, m-toluidine and paraformaldehyde to a four-necked flask equipped with a stirrer, a thermometer and a condenser, stir evenly, heat to 100°C, and stir to react for 0.3-0.5h. After the reaction is completed, dissolve the prepared product in anhydrous ether, and then wash it with 3M sodium hydroxide solution and deionized water 3-5 times in sequence. After the oil phase is separated, remove the anhydrous ether with a rotary evaporator to obtain allylbenzoxazine.

3. The marble made from fly ash from a waste-to-energy plant according to claim 1, characterized in that: The method for preparing the end-capping monomer comprises the following steps: Isophorone diisocyanate, hydroquinone, dibutyltin dilaurate and acetone were added to a reaction kettle and stirred for 10-20 minutes. Hydroxyethyl methacrylate was added and stirred at 40°C for 4.5-5.5 hours. Acetone was removed by vacuum distillation. The distillation product was washed with ether for 3-5 times to obtain a capped monomer.

4. The marble made from fly ash from a waste-to-energy plant according to claim 1, characterized in that: In step A1, the amount ratio of KH-550 and deionized water is 0.50-0.56 mL:20-30 mL. In step A2, the amount ratio of fly ash, 90wt% ethanol solution and mixed solution a is 5-8 g:100 mL:10.2-10.4 mL. In mixed solution a, the amount ratio of pre-emulsion and allyl glycidyl ether is 10 mL:0.2-0.4 mL. In step A3, the amount ratio of modified fly ash, fly ash chelate product, allyl benzoxazine and 0.5M sodium hydroxide aqueous solution is 3-5 g:7-9 g:6-8 g:60-80 mL. The amount ratio of precursor solution and initiator solution is 45-55 mL:20 mL. In step A4, the amount ratio of prepolymer, end-capping monomer and tetrabutylammonium bromide is 5-8 g:3-4 g:0.1-0.3 g.

5. The marble made from fly ash from a waste-to-energy plant according to claim 1, characterized in that: In the step B1, the usage ratio of dithioglycolic acid, anhydrous DMF, N,N-dicyclohexylcarbodiimide, 4-dimethylaminopyridine and diethanolamine is 3.5-4.5 g: 40-50 mL: 6-8 mL: 4-5 g: 2-3 mL. In the step B2, the usage ratio of fly ash, dithiopolyol and deionized water is 8-10 g: 4-5 g: 90-110 mL.

6. The marble made from fly ash from a waste-to-energy plant according to claim 2, characterized in that: The usage ratio of 2,2'-diallylbisphenol A, m-toluidine, polybenzaldehyde and anhydrous ether is 7-9 mL: 5-6 mL: 3-4 g: 30-50 mL.

7. The marble made from fly ash from a waste-to-energy plant according to claim 3, characterized in that: The usage ratio of isophorone diisocyanate, hydroquinone, dibutyltin dilaurate, acetone and hydroxyethyl methacrylate is 45-50g:0.6-0.8g:0.38-0.42g:100-120mL:36-38g.

8. A method for preparing marble made from fly ash from a waste-to-energy plant according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step S1: Add cement, composite filler, coal slag, inorganic pigment powder, and admixtures by weight into a cement mortar mixer, dry-mix for 2 minutes, and continue mixing for 3 minutes while adding water to obtain a primary mixture; Step S2: transferring the primary mixed material to a marble brick forming machine, pressing at 50 MPa for 10 seconds, and demolding to obtain an artificial marble brick embryo; Step S3: placing the artificial marble bricks into a constant temperature and humidity curing box and hydrothermally curing at 70° C. for 28 days to obtain marble made from fly ash from the waste power plant.

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