Preparation method of coal gangue-based high-ductility concrete

Abstract

The invention discloses a preparation method of gangue-based high-ductility concrete, and belongs to the technical field of solid waste treatment and resource utilization, and the preparation method comprises the following steps: crushing gangue to obtain a first material, and calcining the first material to obtain a first calcined material; in an anhydrous environment, a first compound and KH570 are subjected to an addition reaction to generate a second compound, the modifier is obtained, the first compound is fluorine-containing silane, the organic end of the first compound is hydrophobic, and the silicon end of the first compound contains siloxy. The siloxy group is used for hydrolysis, so that the siloxy group is condensed and bonded with hydroxyl on the surface of an inorganic phase base material, and molecules of the siloxy group are grafted on the surface of an inorganic phase; the coal gangue-based high-ductility concrete is prepared, concrete raw materials comprise a first calcined material and mixing water, and a modifier is added into the mixing water. Compared with the prior art, the method has the advantages that the treated coal gangue can be used for preparing the high-ductility concrete, resource utilization and high-valued utilization of the coal gangue solid waste are achieved, and value maximization of the solid waste is achieved.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment and resource utilization technology, and more specifically, to a method for preparing coal gangue-based high-ductility concrete. Background Technology

[0002] Coal gangue is a major solid waste generated during coal mining and washing. Its composition is complex, typically containing certain amounts of carbon, silicon, aluminum, iron, and other elements, as well as small amounts of other minerals. Given that coal is the primary energy source, coal gangue emissions have remained consistently high, with accumulated stockpiles exceeding several billion tons.

[0003] For a long time, coal gangue has been primarily disposed of through stockpiling, resulting in massive gangue mountains. This method is not only a huge waste of potential resources but also occupies a large amount of land, creating environmental pressure. Furthermore, the irregular structure of coal gangue mountains makes them susceptible to explosions, natural rainfall, mountain floods, or earthquakes, causing serious geological disasters such as mudslides and landslides. Coal gangue contains residual coal and other flammable substances; direct open-air stockpiling can easily lead to oxidation reactions with air, releasing heat. The accumulation of heat can easily ignite fires, and the irregular and unstable structure of the rock mountains increases the difficulty of controlling fires. Therefore, directly stockpiling gangue in the open not only occupies a large amount of valuable land resources, resulting in wasted space and environmental pressure, but also brings a series of safety hazards.

[0004] Therefore, how to promote the large-scale and resource-based utilization of coal gangue and realize its transformation from waste to resource, especially exploring higher value-added technological paths, has become an urgent issue in the field of solid waste treatment and circular economy. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing coal gangue-based high-ductility concrete to solve the aforementioned technical problems.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing coal gangue-based high-ductility concrete includes the following steps: Crushing coal gangue to obtain coal gangue material with a particle size ≤5mm is used as the first material; The first material is calcined to obtain the first calcined material; In an anhydrous environment, the first compound and KH570 are mixed, and the C=C bonds of the first compound and KH570 undergo an addition reaction to generate the second compound, thus obtaining a modifier. The first compound is a fluorinated silane. The organic end of the fluorinated silane is hydrophobic, and the silicon end contains silalkoxy groups. The silalkoxy groups are used for hydrolysis, thereby condensing and bonding with the hydroxyl groups on the surface of the inorganic phase substrate, and grafting the molecule containing it onto the surface of the inorganic phase. Prepare concrete raw materials, which include a first calcined material and mixing water, wherein a modifier is added to the mixing water, and use the concrete raw materials to prepare coal gangue-based high ductility concrete.

[0007] Optionally, coal gangue with a crushing value ≤30% is selected, and the coal gangue is crushed to obtain 30-100 mesh coal gangue aggregate; The raw materials for preparing coal gangue-based high-ductility concrete materials include the coal gangue aggregate.

[0008] Optionally, a calcining aid is added to the first material, mixed evenly, and then calcined to obtain the first calcined material. The calcining aid includes sodium carbonate and quicklime. The calcination temperature is 600-900℃ and the calcination time is 2-8 hours.

[0009] Optionally, after calcining the first material, the material is rapidly cooled and then removed and ground to ensure that the particle size of the first calcined material is ≤45μm.

[0010] Optionally, after obtaining the first calcined material through calcination, silica fume, quicklime, and the first calcined material are mixed to obtain composite activated coal gangue material, wherein the composite activated coal gangue material comprises 4%-6% silica fume, 2-4% quicklime, and the first calcined material by weight percentage. The concrete raw materials include the composite activated coal gangue.

[0011] Optionally, the organic end of the first compound contains a perfluoroalkane chain.

[0012] Optionally, the first compound contains Si-H bonds, and in an anhydrous environment, the first compound and the C=C bond of KH570 undergo an addition reaction to generate the second compound.

[0013] Optionally, the first compound is γ-trifluoropropylhydrodiethoxysilane.

[0014] Optionally, in an anhydrous environment, the first compound undergoes an addition reaction with the C=C bond of KH570 to generate the second compound, yielding the second material. Ethylene glycol diethyl ether is then added to the second material to obtain a modifier.

[0015] Optionally, in the coal gangue-based high-ductility concrete material, the chopped fibers are surface-hydroxylated modified chopped fibers, and the interfacial bond strength between the surface-hydroxylated modified chopped fibers and the cement matrix is ​​≥2.5MPa.

[0016] Existing technologies treat coal gangue as solid waste and dump it in the open, occupying a large amount of land, wasting land resources, and causing a series of environmental pressures and safety hazards. This application addresses the crushing, calcining, and modification of coal gangue, using it as a raw material for high-ductility concrete, turning waste into treasure. This not only reduces the land occupation caused by ineffective waste but also enables the resource utilization and high-value utilization of coal gangue solid waste, maximizing the value of solid waste. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0018] Kaolinite, the main component of coal gangue, contains silica and aluminum components. It has the potential to react with cement-based systems through a pozzolanic reaction to form CSH gel, filling pores and creating a dense microstructure, significantly improving the later-stage strength and durability of concrete. High-ductility concrete (HDC) is a novel composite material formed by incorporating short fibers into a cement matrix. It possesses high toughness, high crack resistance, and excellent energy dissipation capacity, with mechanical properties far superior to ordinary concrete (elongation of 3%-10%). It is in urgent demand in fields such as earthquake resistance, seepage prevention, and repair in construction. Furthermore, HDC concrete requires a higher proportion of cement than ordinary concrete, and its raw material costs are 2-3 times higher. To save on HDC raw material costs and to achieve large-scale resource utilization of solid waste, reducing environmental pressure and the safety hazards of open-air gangue storage, the applicant intends to incorporate coal gangue into HDC raw materials. However, the following technical challenges have arisen during the development of coal gangue-based HDC materials and the application development of coal gangue in HDC preparation: The main component of coal gangue is kaolinite (Al2O3). 2SiO2 2H₂O), its crystal structure is a layered silicate structure: it is composed of tightly stacked Si-O tetrahedral sheets and Al-O octahedral sheets through interlayer hydrogen bonds (OH…O). The Si-O and Al-O bonds are enclosed inside and are in a saturated coordination state with no exposed active sites. Therefore, untreated coal gangue cannot effectively undergo pozzolanic reaction (i.e., the reaction between the silica-alumina component and calcium hydroxide) with the cement hydration system, and only exhibits an inert filling effect.

[0019] To solve this technical problem, this application provides a method for preparing coal gangue-based high-ductility concrete, comprising the following steps: Select coal gangue with a crushing value ≤30%, crush the coal gangue to obtain the first material and 30-100 mesh coal gangue aggregate. The first material is coal gangue powder with a particle size ≤45μm or coal gangue blocks with a particle size ≤5mm. Add calcination aids to the first material, mix well, and then calcine to obtain the first calcined material. The calcination aids include sodium carbonate and quicklime. The calcination temperature is 600-900℃ (preferably 700-800℃), and the calcination time is 2-8 hours. After calcination, the material is rapidly cooled, and then the first calcined material is taken out and ground to make the particle size of the first calcined material ≤45μm (if the first material is powder, it is ground to a finer size, preferably ≤30μm). By mixing silica fume, quicklime, and the first calcined material after grinding, a composite activated coal gangue material is obtained. By weight percentage, the composite activated coal gangue material includes 4%-6% silica fume, 2-4% quicklime, and the first calcined material. In an anhydrous environment, a first compound (preferably γ-trifluoropropylhydrodiethoxysilane) and KH570 are mixed. The C=C bonds of the first compound and KH570 undergo an addition reaction to generate a second compound, thus obtaining a modifier. The first compound is a fluorinated silane. The organic end of the fluorinated silane is hydrophobic, and the silicon end contains silalkoxy groups. These silalkoxy groups can undergo hydrolysis, thereby condensing and bonding with hydroxyl groups on the surface of the inorganic phase substrate, and grafting the molecule containing them onto the surface of the inorganic phase. Prepare concrete raw materials, including a first calcined aggregate and mixing water. A modifier is added to the mixing water, and a second compound of the modifier is uniformly dispersed in the mixing water, with silanoxy groups hydrolyzed. The dry-mixed materials (including the first calcined aggregate and lime) are mixed thoroughly, and the aforementioned mixing water (containing the modifier) ​​and chopped fibers are added. The mixture is stirred to obtain a slurry, which is then poured, vibrated, cured, demolded, and cured again to obtain coal gangue-based high-ductility concrete. The first calcined aggregate can be mixed with the modifier first, followed by the addition of water. Considering the ratio of the modifier to the dry-mixed materials and the ease of implementation, it is preferable to mix the modifier in the mixing water, while the coal gangue in the dry-mixed materials (the first calcined aggregate and the coal gangue aggregate described later) simultaneously contacts both the modifier and water. As is well known, silanoxy groups are used to modify inorganic materials; to ensure their effectiveness and allow them to exert their function, it is necessary to avoid the coal gangue coming into contact with water alone beforehand.

[0020] This application first crushes coal gangue to obtain the first material. Crushing increases the specific surface area of ​​coal gangue, and mechanical shearing can artificially create more dangling bonds on the surface of coal gangue, increasing the number of Si-O and Al-O bonds in a broken or uncoordinated unsaturated state, thereby enhancing its surface energy and reactivity; geometrically exposing more potential active sites originally located inside the coal gangue for subsequent thermal activation in the calcination process; and reducing the size of the coal gangue material to improve heat transfer efficiency and thermal activation effect.

[0021] Subsequently, a calcination aid is added to the first material, and the mixture is stirred to obtain the calcined raw material. This calcined raw material (the first material with the added calcination aid) is then calcined to obtain the first calcined material. Under high-temperature conditions of 600-900℃, kaolinite undergoes a dehydroxylation reaction as follows: Al2O3 2SiO2 2H2O→Al2O3 2SiO2 + 2H2O↑ This reaction disrupts the interlayer hydrogen bonds and some Si-O and Al-O bonds of kaolinite, transforming the ordered layered crystal structure into metastable amorphous metakaolinite (Al2O3). 2SiO2). At this time, the Si-O and Al-O bonds in metakaolin are in a state of coordination unsaturation (with dangling bonds and defect sites). The originally encapsulated active sites of silicon and aluminum are fully exposed, possessing the thermodynamic and kinetic conditions to react with the cement-based system. This transforms coal gangue from an inert filling mineral into an active silicon-aluminum source mineral that can undergo pozzolanic reaction and improve the performance of concrete.

[0022] Adding calcination aids has the following beneficial effects: 1. Mechanical crushing effect. At high temperatures, kaolinite loses its structural water, and when CaO reacts with water to form Ca(OH)2, the volume expands, which can form microcracks inside the coal gangue, destroying its dense aluminosilicate crystal structure and reducing the heat input required for crystal dissociation during subsequent calcination.

[0023] 2. Na2CO3 and CaO work together to react with coal gangue to produce low-melting-point salts such as Ca2SiO4 and NaAlSiO4. The products are blended with Na2CO3 to form low-melting-point complex salts, which lower the melting point of sodium carbonate, allowing it to melt and coat the surface of coal gangue particles and penetrate into microcracks to react, contacting more active sites and actively participating in the chemical reaction.

[0024] The diffusion rate of solid particles such as SiO2 and Al2O3 in the liquid phase is significantly higher than in the solid phase. The reaction changes from a slow "solid-solid reaction" to a rapid solid-liquid and liquid-liquid reaction, thus improving the mass transfer rate. Overcoming the lattice energy of minerals such as kaolinite and disrupting their stable structure to initiate a chemical reaction originally required very high local energy. However, the presence of the molten liquid phase medium provides a gentler pathway for structural reorganization through a dissolution-precipitation process, thereby significantly reducing the apparent activation energy required for the entire activation reaction. In other words, compared to a system without additives, this application can reduce the lattice energy of silicon and aluminum oxides (such as kaolinite and illite), improve activation efficiency, and thus reduce calcination energy consumption. Therefore, this application can promote the more complete conversion of silicon and aluminum oxides in coal gangue into active glass without the need to increase the temperature or extend the calcination holding time to ensure the activation effect, thereby further reducing the energy cost per unit product.

[0025] This application involves grinding the first calcined material to reduce the particle size, and adding quicklime and silica fume. The slow, long-term alkalization by quicklime continuously provides the hydroxyl groups consumed in the pozzolanic reaction, thus maintaining the necessary alkaline environment for the reaction. This allows the amorphous Si-O and Al-O bonds in the coal gangue to break after calcination, releasing active silicon and aluminum ions. The amorphous SiO2 in silica fume will react with Al released from coal gangue in a highly alkaline environment. 3+ The reaction with Ca(OH)2 generates hydrated calcium aluminosilicate (CASH gel) with stronger adhesion and better stability, forming a high-performance cementitious phase for concrete. This fills the tiny pores on the surface of coal gangue particles, further enhancing the bonding strength between solid waste and the cement matrix.

[0026] It should be noted that there is no specific order requirement for the preparation of the first calcined material / composite coal gangue and the preparation of the modifier, as long as sufficient raw materials can be obtained when mixing and preparing coal gangue-based high-ductility concrete materials.

[0027] Coal gangue, as a coal-series solid waste, has a surface rich in hydrophilic groups (hydroxyl groups). The interfacial transition zone between coal gangue and cement is a natural weak point in concrete, and the hydrophilic properties of coal gangue directly exacerbate this problem: the hydrophilic surface of coal gangue adsorbs water to form a water film layer, creating a water-rich zone and an interfacial microenvironment with an extremely high water-cement ratio. Under a high water-cement ratio, the Ca produced during cement hydration... 2+ OH - SiO3 2- Plasma exhibits extremely high diffusion freedom in water films and will not rapidly polymerize due to insufficient water; among them, the solubility of Ca(OH)2 is much higher than that of CSH gel, and Ca... 2+ and OH - They will diffuse and aggregate fully in the water film. When the ion concentration reaches supersaturation, crystal nuclei will spontaneously form and grow continuously, eventually forming coarse hexagonal plate-shaped Ca(OH)2 crystals; while the formation of CSH gel requires SiO3. 2- With Ca 2+ The rapid cross-linking polymerization, under a high water-to-gel ratio, results in excessively fast ion diffusion, leading to extremely low nucleation density in the cross-linking polymerization (failing to form a large number of tiny gel nuclei). The small amount of CSH generated is also loose and flocculent rather than a dense network.

[0028] In summary, the hydrophilic properties of coal gangue lead to the formation of a water film at the interface between coal gangue and cement. During cement hydration, the hydration products (such as Ca(OH)2) at the water film crystallize in a coarse, directional manner, rather than forming a dense CSH gel. This results in a porous and loose interface with extremely low bonding strength. The poor interfacial bonding between cement and coal gangue makes the interface prone to microcracks under stress, ultimately leading to a decrease in the overall strength of the concrete.

[0029] This application utilizes a modifier to hydrophobically modify the surface of coal gangue. The coal gangue and a second compound are simultaneously exposed to water. The silanoxy groups of the second compound hydrolyze to silanol groups, which react with the hydroxyl groups on the coal gangue surface, thereby grafting a hydrophobic organic phase of silane onto the coal gangue surface.

[0030] This application involves mixing a first compound and KH570 in an anhydrous environment. The first compound is a fluorinated silane with a hydrophobic organic end. Under certain reaction conditions, the active groups at the silicon / organic ends of the first compound undergo an addition reaction with the C=C bond of KH570 to generate a second compound, yielding a second material. The second material can be used directly as a modifier or mixed with ethylene glycol diethyl ether and then used as a modifier.

[0031] It is known that both KH570 and the first compound contain silane groups, and when they undergo an addition reaction in an anhydrous environment, the silane groups of both do not participate in the addition reaction or undergo other chemical reactions, and still retain hydrolytic activity. That is, the organic / silicon end of the first compound is bonded to the original C=C bond of the organic end of KH570 through an addition reaction, and the resulting second compound has two active sites for hydrolysis, with at least one hydrophobic alkane chain from the organic end of KH570 separating the two active sites. When preparing coal gangue-based high-ductility concrete material by mixing various raw materials, after adding mixing water to the mixed dry material, the two active sites of the second compound hydrolyze, react with the hydroxyl groups on the surface of the coal gangue, and then graft onto the surface of the coal gangue. The second compound is anchored to the coal gangue surface with two claws, and the anchoring points are spaced apart and connected by a hydrophobic alkane chain of KH570. The hydrophobic alkane chain is folded outward, and the organic end hydrophobic structure of the original first compound is also arranged outward, forming a stable hydrophobic surface on the coal gangue. Compared with a linear hydrophobic structure with unidirectional anchoring, this application sets two bonding anchoring points in the second compound, and the two bonding anchoring points are connected by a hydrophobic alkane chain with a certain folding deformation capability. This can anchor both ends of the hydrophobic alkane chain to the coal gangue surface while ensuring the hydrophobic function. This can enhance the bonding stability, firmness, and mechanical strength of the hydrophobic chain on the coal gangue surface, effectively resisting external friction, scratching, and shear force of agitating fluids and the resulting internal stress in the structure. The hydrophobic layer covering the coal gangue surface is not easily damaged or detached, which can reduce the surface energy of the coal gangue, maintain hydrophobicity, inhibit the formation of water film on the coal gangue surface during mixing, and ensure the mechanical properties of the concrete structure.

[0032] In one possible implementation, the chopped fibers in the coal gangue-based high-ductility concrete material are surface-hydroxylated modified chopped fibers. The chopped fibers include at least one of PE fibers and PVA fibers. Preferably, the interfacial bond strength between the surface-hydroxylated modified chopped fibers and the cement matrix is ​​≥2.5 MPa.

[0033] Optionally, the coal gangue-based high-ductility concrete material also includes a water-reducing agent, preferably a polycarboxylate water-reducing agent.

[0034] In one possible implementation, the active group of the first compound is located at the organic end. For example, the active group is a -SH bond, the perfluoroalkane chain is abbreviated as Rf, the acetyl group is abbreviated as AC, and the first compound is HS-X-Rf-Y-Si(OR)3. X and Y are connecting arms, and their specific structures are not limited. This application provides a specific preparation step as follows: Prepare thiourea SC(NH2)2, AcS, vinyltrialkoxysilane CH2=CH-Si(OR)3, and Rf-(CH2). n -Z, where Z is I / Br, preferably I-iodine; At 78°C, thiourea and Rf-(CH2) were reacted. n -I is refluxed with anhydrous ethanol, and affinity substitution is performed to form isothiourea salt: Rf-(CH2) n -I+SC(NH2)2→

Rf-(CH2) n -SC(NH2)2

[0035] Add the first reagent to anhydrous dichloromethane, followed by triethylamine and acetyl chloride (added slowly dropwise). Reflux at 40–50°C for 1 hour. Slowly pour in a saturated sodium bicarbonate aqueous solution cooled in an ice-water bath, stirring until no more bubbles are generated. Allow to separate into layers, discard the upper aqueous phase, and collect the lower organic phase. Dry the organic phase with anhydrous sodium sulfate, and remove the solvent by evaporation under reduced pressure to obtain the second reagent. Thioacetate is formed to protect the thiol groups; the second reagent obtained is mainly AcS. (CH2) n Rf.

[0036] The second reagent and KH560 were dissolved in 30 mL of anhydrous ethanol. Triethylamine was added as a catalyst, and the mixture was heated to 70°C and stirred for 6 hours under nitrogen protection. The solvent was removed by vacuum evaporation to obtain the third reagent, which was mainly AcS. (CH2) n Rf CH2 CH(OH) CH2 O (CH2)3 Si(OCH3)3.

[0037] The third reagent was dissolved in anhydrous methanol, and ammonia was bubbled through until the pH was >10. The mixture was stirred for 3 hours. Alkaline hydrolysis deprotected the thioester bonds to thiol groups.

[0038] The solvent was removed by vacuum evaporation, and the fourth reagent obtained was mainly the first compound. The chemical formula of the first compound is shown below: HS (CH2) n Rf CH2 CH(OH) CH2 O (CH2)3 Si(OCH3)3.

[0039] The photoinitiator, the fourth reagent, and KH570 were added to anhydrous ethanol to induce the aforementioned addition reaction between the first compound and KH570. The resulting second compound was... Si(OCH3)3-(CH2)3 C(O)O CH(CH3) CH2-S (CH2) n Rf CH2 CH(OH) CH2 O (CH2)3 Si(OCH3)3. Both ends are bonded to the surface of coal gangue, and the organic alkane chain in the middle is folded outwards and hydrophobic.

[0040] In one possible implementation, the steps for preparing concrete raw materials by using composite activated coal gangue as one of the concrete raw materials, and then using it to prepare coal gangue-based high-ductility concrete are as follows: Stir at 100-150 r / min for 3-10 minutes to mix all dry-mixed materials; set aside the remaining materials to prepare coal gangue-based high-ductility concrete. The dry-mixed materials include gelling materials and aggregates. The gelling materials include cement and composite activated coal gangue, which includes silica fume, quicklime, and the first calcined material. The dry-mixed materials and / or the remaining materials include chopped fibers, and the remaining materials include the aforementioned (mixed with modifier) ​​mixing water and water-reducing agent. Mix dry materials, mixing water and water-reducing agent, and wet mix at 100-150 r / min for 3-10 minutes to obtain a wet material with a slurry fluidity of 300-320 mm. Add short-cut fibers to the wet material in 3 batches, and stir at a speed of >300 r / min for 1-5 minutes after each addition to obtain wet concrete material. Use the wet concrete material to pour and cure to prepare coal gangue-based high ductility concrete.

[0041] Optionally, after being poured and vibrated into shape with wet concrete material, it is pre-cured at 20℃ for 24 hours, and then demolded for standard curing (20±2℃, humidity ≥95%) for 28 days to obtain coal gangue-based high ductility concrete.

[0042] In one possible implementation, the coal gangue-based high-ductility concrete material, by mass fraction, comprises: Cementitious materials: 200-450 parts cement, 200-300 parts composite activated coal gangue, and 50-80 parts auxiliary admixtures; Aggregates: 750-850 parts river sand, 300-400 parts fine coal gangue aggregate; Other materials: 4-8 parts polycarboxylate superplasticizer, 160-180 parts mixing water, and 1-25 parts surface-hydroxylated PE or PVA fibers.

[0043] The first calcined material (the aforementioned block material) is calcined to obtain the first calcined material. After rapid cooling, the first calcined material is immediately taken out, ground, and crushed (to a particle size ≤ 45 μm), and then immediately mixed with silica fume and quicklime. The resulting composite activated coal gangue material includes 5% silica fume, 3% quicklime, and the remainder is the first calcined material. The 7-day activity index of the composite activated coal gangue material is ≥ 90%, and the 28-day activity index is ≥ 95%, as measured by standard methods.

[0044] After crushing coal gangue to obtain coal gangue aggregate (30-100 mesh), it is washed with water to remove impurities and then naturally dried until the moisture content of the coal gangue solids drops to 6%-7%. Subsequently, it is used as one of the raw materials for preparing coal gangue-based concrete materials.

[0045] PE or PVA fiber: short chopped fiber with a length of 6-18mm, a diameter of 20-40μm, a hydroxyl-modified surface, and an interfacial bond strength with the cement matrix ≥2.5MPa.

[0046] In one possible implementation, pretreatment involves crushing coal gangue, then screening and further grinding it until the coal gangue powder particle size is ≤45μm. The coal gangue powder with a particle size of ≤45μm obtained by screening is used as the first material.

[0047] Through screening and further grinding, coal gangue aggregate with a particle size of 30-100 mesh is obtained. After washing to remove impurities, it is naturally dried until the moisture content of the coal gangue solids drops to 6%-7% for later use.

[0048] After calcination, the first calcined material is rapidly cooled and removed, and then ground until the particle size of the first calcined material is ≤45μm.

[0049] In one possible implementation, the mass ratio of quicklime to sodium carbonate in the calcination aid is 1:(1-2). Rapid cooling refers to a cooling rate ≥50℃ / min (depending on the specific active cooling capacity of the calciner, preferably 80-200℃ / min, more preferably 100℃ / min), quickly cooling the hot coal gangue to room temperature. The gangue is then rapidly removed, ground into a finer powder, and mixed with quicklime and silica fume to obtain composite activated coal gangue material for easy storage and later use.

[0050] In one possible implementation, the specific steps for preparing the modifier include: Add γ-methacryloxypropyltrimethoxysilane (KH570) to anhydrous ethanol and stir to dissolve, preparing a silane coupling agent solution with a mass fraction of 20-30% as the first solution; Add γ-trifluoropropylhydrodiethoxysilane and chloroplatinic acid catalyst to the first solution. The molar ratio of γ-trifluoropropylhydrodiethoxysilane to KH570 is 1:(1.2-1.5). The amount of chloroplatinic acid is 0.1-0.3% of the mass of the first solution. Heat to 60-80℃ and stir at a constant temperature for 4-6 hours to carry out the hydrosilylation reaction and obtain the second solution. Anhydrous ethanol is removed by vacuum distillation to obtain a second material (liquid). The second material is mixed with ethylene glycol diethyl ether at a mass ratio of 7:(2-4) and stirred evenly to obtain the modifier.

[0051] To better illustrate this application, the following embodiments and comparative examples are also provided: Example 1: Pretreatment: Select coal gangue with a crushing value ≤30%. Crush the coal gangue, and then process it through screening and further grinding until the coal gangue powder particle size is ≤5mm. Screen the coal gangue blocks with a particle size ≤5mm as the first material.

[0052] Through screening and further grinding, coal gangue aggregate with a particle size of 30-100 mesh is obtained. After washing to remove impurities, it is naturally dried until the moisture content of the coal gangue solids drops to 6%-7% for later use.

[0053] In the calcination aid, the mass ratio of quicklime to sodium carbonate is 1:1.5. The first material and the calcination aid are mixed at a mass ratio of 9:1. The first material with the added calcination aid is fed into a calcination furnace and heated to 800℃ at a heating rate of 10℃ / min, held at that temperature for 2.5 hours, and then rapidly cooled to room temperature at a cooling rate of 90℃ / min. The first calcined material is then dried in an oven at 110℃ until the moisture content is ≤1.5%, and then ball-milled to a maximum particle size of 45μm. Silica fume and quicklime are then added and mixed evenly to obtain composite activated coal gangue. By mass fraction, the composite activated coal gangue comprises 3% quicklime, 5% silica fume, and 92% of the first calcined material. KH570 was added to anhydrous ethanol and stirred to dissolve, preparing a 25% (w / w) silane coupling agent solution as the first solution. γ-trifluoropropyl hydrogen diethoxysilane and chloroplatinic acid catalyst were added to the first solution, with a molar ratio of γ-trifluoropropyl hydrogen diethoxysilane to KH570 of 1:1.3 and an amount of chloroplatinic acid of 0.2% of the mass of the first solution. The temperature was raised to 70°C and the reaction was stirred at a constant temperature for 5 hours to carry out the hydrosilylation reaction, yielding the second solution. Anhydrous ethanol was removed by vacuum distillation at 0.06 MPa, 100 r / min, and room temperature to obtain the second material. The second material was mixed with ethylene glycol diethyl ether at a mass ratio of 7:3 and stirred until homogeneous to obtain the modifier. The modifier was added to water in proportion to obtain the aforementioned mixed water.

[0054] According to the specified proportions, ordinary Portland cement (P·O 42.5 grade), composite activated coal gangue, admixtures, river sand (20-70 mesh), and coal gangue aggregate are added to a forced mixer and dry-mixed at 100 r / min for 5 minutes. The admixtures, by mass percentage, include 70% S95 grade granulated blast furnace slag powder, 27% secondary fly ash, and 3% nano-silica. Then, with the speed unchanged, the mixing water and water-reducing agent were mixed and poured into the mixer for wet mixing for 3 minutes, and the fluidity of the slurry reached 310±10mm. The mixing speed was changed to 300 r / min, and surface-hydroxyl-treated PVA fibers were added to the mixer in three batches (each batch was mixed for 1.5 min, with a 1.5 min interval between batches) to obtain wet concrete material. By mass, the wet concrete material included: 400 parts of P·O 42.5 grade ordinary Portland cement; 250 parts of composite activated coal gangue; 350 parts of coal gangue aggregate; 60 parts of admixture; 700 parts of river sand; 20 parts of PVA fiber (30 μm in diameter, 8 mm in length); 4.5 parts of polycarboxylate superplasticizer; 180 parts of water; and 12 parts of modifier.

[0055] The concrete was poured using wet concrete material, vibrated to form the desired shape, and pre-cured at 20℃ for 24 hours before demolding. It was then subjected to standard curing (20±2℃, humidity ≥95%) until length was measured at 1 day, and again after 28 days. The drying shrinkage rate of the coal gangue-based high-ductility concrete after 28 days is shown in Table 1. The compressive strength, tensile strength, and elongation are also shown in Table 1. The prepared coal gangue-based high-ductility concrete was obtained after 28 days of curing.

[0056] Comparative Example 1: No calcination aids were added to the first material; the first material was directly placed into the calcination furnace for calcination. Everything else was completely consistent with Example 1.

[0057] Comparative Example 2: Replace the modifier in Example 1 with an equal amount of water. Everything else is exactly the same as in Example 1.

[0058] Comparative Example 3: KH570 was added to anhydrous ethanol and stirred to dissolve, preparing a 25% (w / w) silane coupling agent solution as the first solution. γ-trifluoropropyltriethoxysilane (PFTEOS) and chloroplatinic acid catalyst were added to the first solution, with a molar ratio of PFTEOS to KH570 of 1:1.3 and an amount of chloroplatinic acid of 0.2% of the mass of the first solution. The temperature was raised to 70°C, and the reaction was stirred at a constant temperature for 5 hours to carry out a hydrosilylation reaction, yielding the second solution. Anhydrous ethanol was removed by vacuum distillation at 0.06 MPa, 100 r / min, and room temperature to obtain the second material. The second material was mixed with ethylene glycol diethyl ether at a mass ratio of 7:3 and stirred until homogeneous to obtain the modifier. The modifier was added to water in proportion to obtain the aforementioned mixed water.

[0059] Everything else is exactly the same as in Example 1.

[0060] Comparative Example 4: Instead of using coal gangue, P·O 42.5 grade ordinary Portland cement was used to replace the first calcined material in Example 1, and 20-70 mesh river sand was used to replace the coal gangue aggregate in Example 1. The rest was completely consistent with Example 1.

[0061] Comparative Example 5: No calcination aids were added to the first material, and the first material was not calcined. The first material was used to replace the first calcined material in Example 1. After crushing coal gangue to obtain the first material, it was directly fed into a ball mill and ball-milled until the maximum particle size was 45 μm. Then, silica fume and quicklime were added in proportion and mixed evenly to obtain "composite activated coal gangue material". Everything else was completely the same as in Example 1.

[0062] The performance test results for Example 1 and Comparative Examples 1-5 are shown in Table 1.

[0063] Table 1: Test results of compressive strength, tensile strength, elongation and drying shrinkage of coal gangue-based high ductility concrete in Examples 1 and Comparative Examples 1-5.

[0064] The test results in the table above show that: The coal gangue-based high-ductility concrete prepared in Example 1 all have excellent mechanical properties, with a 28-day compressive strength ≥50.0 MPa, tensile strength ≥4.0 MPa, ultimate elongation ≥6.0%, and drying shrinkage of only 0.021%.

[0065] Example 1 shows improved compressive strength compared to Comparative Examples 1, 3, and 5; reduced drying shrinkage compared to Comparative Example 2; and essentially equivalent overall mechanical properties compared to Comparative Example 4. This demonstrates that the present invention can improve the properties of coal gangue, turning waste into treasure while ensuring the mechanical properties of concrete.

[0066] Compared with the prior art, the present invention has the following advantages: 1. High-value utilization of solid waste: The total replacement rate of coal gangue reaches 30%-50%; the total replacement rate of coal gangue (first calcined material + coal gangue aggregate) reaches 30%-50%, significantly improving the utilization rate of solid waste; 2. Significant cost advantages: Cement usage is reduced by 25%-30%, river sand usage is reduced by 25%-30%, raw material costs are reduced by 18%, and overall economic benefits are increased by more than 20%, balancing economic efficiency and environmental protection. 3. The process is easy to industrialize: It adopts conventional mixing equipment, requires no special modification, and is suitable for direct production in existing concrete mixing plants.

[0067] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing coal gangue-based high-ductility concrete, characterized in that, Includes the following steps: Crushing coal gangue to obtain coal gangue material with a particle size ≤5mm is used as the first material; The first material is calcined to obtain the first calcined material; In an anhydrous environment, the first compound and KH570 are mixed, and the C=C bonds of the first compound and KH570 undergo an addition reaction to generate the second compound, thus obtaining a modifier. The first compound is a fluorinated silane. The organic end of the fluorinated silane is hydrophobic, and the silicon end contains silalkoxy groups. The silalkoxy groups are used for hydrolysis, thereby condensing and bonding with the hydroxyl groups on the surface of the inorganic phase substrate, and grafting the molecule containing it onto the surface of the inorganic phase. Prepare concrete raw materials, which include a first calcined material and mixing water, wherein a modifier is added to the mixing water, and use the concrete raw materials to prepare coal gangue-based high ductility concrete.

2. The method for preparing coal gangue-based high-ductility concrete according to claim 1, characterized in that, Select coal gangue with a crushing value ≤30%, and crush the coal gangue to obtain 30-100 mesh coal gangue aggregate; The raw materials for preparing coal gangue-based high-ductility concrete materials include the coal gangue aggregate.

3. The method for preparing coal gangue-based high-ductility concrete according to claim 1, characterized in that, Add calcination aids to the first material, mix well, and then calcine to obtain the first calcined material. The calcination aids include sodium carbonate and quicklime. The calcination temperature is 600-900℃ and the calcination time is 2-8 hours.

4. The method for preparing coal gangue-based high-ductility concrete according to claim 1, characterized in that, After calcining the first material, it is rapidly cooled down and then taken out and ground to make the particle size of the first calcined material ≤45μm.

5. The method for preparing coal gangue-based high-ductility concrete according to claim 1, characterized in that, After obtaining the first calcined material through calcination, silica fume, quicklime, and the first calcined material are mixed to obtain composite activated coal gangue material. By weight percentage, the composite activated coal gangue material includes 4%-6% silica fume, 2-4% quicklime, and the first calcined material. The concrete raw materials include the composite activated coal gangue.

6. The method for preparing coal gangue-based high-ductility concrete according to claim 1, characterized in that, The organic end of the first compound contains a perfluoroalkane chain.

7. The method for preparing coal gangue-based high-ductility concrete according to claim 1, characterized in that, The first compound contains Si-H bonds. In an anhydrous environment, the first compound undergoes an addition reaction with the C=C bond of KH570 to generate the second compound.

8. The method for preparing coal gangue-based high-ductility concrete according to claim 7, characterized in that, The first compound is γ-trifluoropropylhydrodiethoxysilane.

9. The method for preparing coal gangue-based high-ductility concrete according to claim 1, characterized in that, In an anhydrous environment, the first compound undergoes an addition reaction with the C=C bond of KH570 to generate the second compound, yielding the second material. Ethylene glycol diethyl ether is then added to the second material to obtain a modifier.

10. The method for preparing coal gangue-based high-ductility concrete according to claim 1, characterized in that, In the coal gangue-based high ductility concrete material, the short-cut fibers are surface-hydroxylated modified short-cut fibers, and the interfacial bond strength between the surface-hydroxylated modified short-cut fibers and the cement matrix is ​​≥2.5MPa.

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