Concrete admixtures, methods of making and use thereof

Abstract

This invention relates to the field of building material preparation technology, and discloses a concrete admixture, its preparation method, and its application. The method includes the following steps: (1) drying, crushing, and screening coal gasification slag to obtain pretreated coal gasification slag; (2) ball milling and screening the pretreated coal gasification slag to obtain coal gasification slag micro powder with a specific surface area of ​​280-320 m² / kg and a particle size of 3-50 μm; (3) mixing the coal gasification slag micro powder, fly ash, and mineral powder at a weight ratio of 100:(10-80):(5-80). This method, by crushing and screening the coal gasification slag, combined with activation technology, and synergistically optimizing the particle size distribution, and then compounding it with other admixtures, obtains a compound coal gasification slag micro powder admixture for preparing high-performance concrete, which achieves precise control of concrete workability while meeting application and environmental requirements.

Description

Technical Field

[0001] This invention relates to the field of building material preparation technology, specifically to a concrete admixture, its preparation method, and its application. Background Technology

[0002] With the advancement of the "dual carbon" target and the implementation of the energy self-sufficiency strategy, the scale of my country's coal chemical industry continues to expand. Taking 2023 data as an example, the annual emissions of coal gasification slag nationwide exceeded 30 million tons, with Ningxia, as a core coal chemical production area, accounting for over 15% of the annual emissions. If such slag is stored for a long period, it not only occupies arable land but may also lead to the infiltration of heavy metal ions (such as Cr and Pb) due to rainwater leaching, thereby polluting the soil and groundwater, resulting in significant ecological pressure. At the same time, the demand for concrete admixtures in the construction industry is increasing year by year. The supply stability of traditional admixtures (fly ash, mineral powder) is insufficient due to resource distribution and industry cycles. For example, due to the transformation of the thermal power industry, the market price of high-quality Grade I fly ash in 2024 increased by over 100% compared to 2020, and some regions experienced a shortage of fly ash, necessitating the search for low-cost, highly adaptable alternative materials.

[0003] Applying coal gasification slag to the preparation of concrete admixtures is one of the core pathways to realize its resource utilization. Currently, the industry's core research focuses on two major technical routes: "aggregate substitution" and "admixture preparation," but both have significant technical bottlenecks. While the "aggregate substitution" model can directly absorb large amounts of coal gasification slag, the large fluctuations in the slag's activity (the coefficient of variation of the activity index can reach 15-20%) and uneven particle size distribution mean that directly replacing natural aggregates can easily lead to a 20-30% increase in concrete slump loss, an 8-12% decrease in compressive strength after 28 days of hardening, and a significant risk of alkali-aggregate reaction (expansion rate far exceeding the national standard limit of 0.1%), making it difficult to meet structural engineering requirements. On the other hand, preparing coal gasification slag as admixtures faces significant bottlenecks in existing technologies: either the potential activity of the slag is not fully utilized, or the cost is too high and environmental protection is insufficient, making it difficult to simultaneously meet the synergistic requirements of "high performance, low cost, and high environmental protection."

[0004] Therefore, it is of great importance to develop a new type of concrete mineral admixture. This admixture aims to achieve efficient utilization of solid waste while significantly improving the workability, mechanical properties and durability of concrete, and has important practical significance and application prospects. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of uneven activation, poor raw material compatibility, inadequate environmental performance, high cost, and large performance fluctuations in existing coal gasification slag concrete admixtures, and to provide a concrete admixture, its preparation method, and its application. The method described in this invention involves crushing and screening coal gasification slag, combined with activation technology, to synergistically optimize the particle size distribution before blending it with other admixtures. This yields a blended coal gasification slag micro-powder admixture for preparing high-performance concrete, achieving precise control of concrete workability while meeting application and environmental requirements.

[0006] To achieve the above objectives, the present invention provides a method for preparing concrete admixtures, the method comprising the following steps: (1) The coal gasification slag is dried, crushed and screened to obtain pretreated coal gasification slag, wherein the carbon content of the pretreated coal gasification slag is <3% by weight and the bulk density is >1.8 g / cm³. 3 Moisture content < 1.5% by weight, particle size < 4.75 mm; (2) The pretreated coal gasification slag is ball-milled and sieved to obtain coal gasification slag powder with a specific surface area of ​​280-320m² / kg and a particle size of 3-50μm; (3) The coal gasification furnace slag powder, fly ash and mineral powder are mixed in a weight ratio of 100:(10-80):(5-80).

[0007] Preferably, in step (2), the specific process of ball milling includes: mixing the pretreated coal gasification slag with ball milling media and then ball milling, wherein, based on the total weight of the ball milling media, the ball milling media contains 20-60% by weight of first agate ball particles, 10-45% by weight of second agate ball particles and 10-45% by weight of third agate ball particles.

[0008] Preferably, the diameter of the first agate ball is 1-6 mm, the diameter of the second agate ball is 6-10 mm, and the diameter of the third agate ball is 10-15 mm.

[0009] Preferably, in step (2), the weight ratio of the pretreated coal gasification slag to the ball milling media is 1:5-15, more preferably 1:7-12.

[0010] Preferably, in step (2), the conditions for ball milling include: a rotation speed of 150-300 rpm and a time of 50-150 min.

[0011] Preferably, in step (3), the weight ratio of the coal gasification furnace slag powder, the fly ash and the mineral powder is 100:(20-70):(10-70).

[0012] Preferably, in step (3), the fly ash has a particle size of 2-30 μm and a specific surface area of ​​300-600 m². 2 / kg.

[0013] Preferably, the mineral powder has a particle size of 3-45 μm and a specific surface area of ​​300-380 m². 2 / kg.

[0014] A second aspect of the present invention provides a concrete admixture prepared by the above method.

[0015] The third aspect of the present invention provides the application of the above-mentioned concrete admixture in the concrete preparation process.

[0016] A fourth aspect of the present invention provides a method for preparing concrete, the method comprising: mixing cement, the above-mentioned concrete admixture, medium sand, crushed stone, water-reducing agent and water; The weight ratio of the cement to the concrete admixture is 1-5:1.

[0017] A fifth aspect of the present invention provides concrete prepared by the above method.

[0018] The sixth aspect of the present invention provides the application of the above-mentioned concrete in the production process of building materials and products.

[0019] The method described in this invention first involves drying, crushing, and screening the coal gasification slag to obtain pretreated coal gasification slag with low carbon content and a dense structure. This eliminates the negative impact of high carbon content and porous coal gasification slag on the water requirement ratio and activity of the admixtures, ensuring the stability of the raw material's basic properties. Secondly, using "ball milling to increase specific surface area" as the core physical activation method, combined with particle size optimization, the specific surface area of ​​the coal gasification slag powder is precisely controlled between 280-320 μm². 2 / kg, with a particle size distribution range extended to 3-50μm, forming a complementary gradation with cement particles (3-30μm), achieving a 5-8% increase in concrete bulk density and solving the problems of uneven activation and large performance fluctuations in existing technologies; furthermore, the compounding ratio of coal gasification slag powder, fly ash, and mineral powder is optimized, utilizing the morphological effect of fly ash and the early strength compensation effect of mineral powder to compensate for the inhibition of early strength of concrete by coal gasification slag powder alone, achieving precise control over the workability, mechanical properties, and durability of concrete, promoting the utilization rate of coal-based solid waste resources to over 90%, and meeting the technical requirements of building engineering for admixtures and the needs of green and low-carbon development. Detailed Implementation

[0020] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] The method for preparing concrete admixtures according to the present invention includes the following steps: (1) The coal gasification slag is dried, crushed and screened to obtain pretreated coal gasification slag, wherein the carbon content of the pretreated coal gasification slag is <3% by weight and the bulk density is >1.8 g / cm³. 3 Moisture content < 1.5% by weight, particle size < 4.75 mm; (2) The pretreated coal gasification slag is ball-milled and sieved to obtain coal gasification slag powder with a specific surface area of ​​280-320m² / kg and a particle size of 3-50μm; (3) The coal gasification furnace slag powder, fly ash and mineral powder are mixed in a weight ratio of 100:(10-80):(5-80).

[0023] In this invention, there is no particular limitation on the source of the coal gasification slag; any gasification slag conventionally available in the art can be used. In some preferred embodiments, the gasification slag can be low-carbon, dense-structured coarse slag from Ningxia region, with the following phase composition and content: approximately 55-70% amorphous glass phase, mainly composed of silicon dioxide (SiO2) and aluminum oxide (Al2O3); approximately 30-45% crystalline phase, specifically including 15-22% quartz, 8-15% mullite, and 2-5% hematite. The high glass content of this type of coal gasification slag endows it with excellent potential activity. Its chemical composition includes 45-55% SiO2 and 20-30% Al2O3, with a total content ≥65%, fully meeting the key requirements of pozzolanic reaction for core active components. In some specific embodiments, the composition of the coal gasification slag is 45-55% SiO2, 20-30% Al2O3, 2-8% CaO, 1-5% Fe2O3, and 15-19% other impurities, wherein the other impurities will not have a negative impact on the implementation effect of the present invention.

[0024] In some embodiments, step (1) further includes: before drying the coal gasification slag, conducting carbon content testing and bulk density testing on it, and screening out slags with carbon content <3wt% and bulk density >1.8g / cm³. 3The raw material for coal gasification furnace slag; at the same time, high-carbon slag with a carbon content >5wt% and slag with a bulk density <1.6g / cm³ are excluded. 3 The slag is porous and loose, thus ensuring good stability of the active reference material. The carbon content can be detected using the ignition method, specifically as follows: the coal gasification slag sample to be tested is placed in an environment of 550℃ and ignited for 3 hours; a mass loss rate of <3% after ignition is used as the pass / fail criterion. The bulk density test can be performed using the graduated cylinder method, following relevant testing specifications.

[0025] In some specific embodiments, the drying process of the coal gasification slag in step (1) includes: placing the screened coal gasification slag in a drying yard, controlling the ambient temperature at 25-35℃ and the relative humidity at 40-60%, and drying it for 24-48 hours until the moisture content is <1.5%, to avoid excessive moisture content affecting the ball milling efficiency and the flowability of the admixture. The moisture content test can be performed using a drying method, specifically as follows: drying the sample to be tested at 105℃ to constant weight, with a mass loss <1.5% as the pass / fail criterion.

[0026] In some specific embodiments, the specific process of crushing and screening the coal gasification slag in step (1) may include: firstly, using a jaw crusher to coarsely crush the dried coal gasification slag and control the particle size to below 50 mm; then using an impact crusher to finely crush the slag and further control the particle size to below 10 mm; then using a vibrating screen (with a 4.75 mm square hole) for screening, with a screening time of 15-20 minutes, to ensure that the particle size of the bottom sample is all <4.75 mm, and the sample on the screen is returned to fine crushing.

[0027] In some embodiments, the specific process of ball milling in step (2) includes: mixing the pretreated coal gasification slag with ball milling media and then ball milling. In a preferred embodiment, agate balls with multiple particle size distribution are used to ball mill the pretreated coal gasification slag. This can effectively avoid the risk of material contamination caused by the introduction of metal impurities, and can also achieve fine and targeted grinding of slag particles of different particle sizes.

[0028] In some embodiments, in step (2), based on the total weight of the milling media, the milling media contains 20-60% by weight of first agate ball particles, 10-45% by weight of second agate ball particles, and 10-45% by weight of third agate ball particles. The diameter of the first agate ball particles is 1-6 mm, preferably 4-6 mm; the diameter of the second agate ball particles is 6-10 mm, preferably 7-9 mm; and the diameter of the third agate ball particles is 10-15 mm, preferably 10-12 mm.

[0029] In some preferred embodiments, in step (2), the grinding media contains 25-55% by weight of the first agate ball particles, 15-40% by weight of the second agate ball particles, and 15-40% by weight of the third agate ball particles, based on the total weight of the grinding media. In a further preferred embodiment, the grinding media contains 30-50% by weight of the first agate ball particles, 20-35% by weight of the second agate ball particles, and 20-35% by weight of the third agate ball particles, based on the total weight of the grinding media.

[0030] In some embodiments, in step (2), the weight ratio of the pretreated coal gasification slag to the ball milling media is 1:5-15, preferably 1:7-12, and more preferably 1:8-10. As a specific example, the weight ratio of the pretreated coal gasification slag to the ball milling media can be 1:8, 1:8.5, 1:9, 1:9.5, or 1:10.

[0031] In some embodiments, in step (2), the ball milling conditions include: a rotational speed of 150-300 rpm, preferably 200-250 rpm; and a time of 50-150 min, preferably 80-120 min. As a specific example, the rotational speed of the ball mill can be 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, or 250 rpm; and the ball milling time can be 80 min, 90 min, 100 min, 110 min, or 120 min.

[0032] In some specific implementations, in step (2), during the ball milling process, the machine is stopped for 1-5 minutes every 10-30 minutes to prevent the ball milled material from agglomerating.

[0033] It should be noted that in step (2), the ball milling time can be adjusted according to the specific surface area of ​​the material being ball-milled. Specifically, if the specific surface area of ​​the material after ball milling is <280m², the ball milling time can be adjusted accordingly. 2 / kg, can extend ball milling by 10-15 minutes; if specific surface area > 320m² 2 / kg can shorten the ball milling time by 5-10 minutes, ensuring that the material activity and flowability are balanced.

[0034] In some preferred embodiments, in step (2), the specific surface area of ​​the coal gasification slag powder is 300-320 m² / kg, and the particle size is 5-45 μm.

[0035] In some specific embodiments, in step (2), the specific process layer of the screening process includes: screening the ball-milled material through a 0.08mm square hole sieve and using a negative pressure sieve method to detect the residue rate and control it to be ≤3%.

[0036] In some preferred embodiments, in step (3), the weight ratio of the coal gasification slag powder, the fly ash, and the mineral powder is 100:(20-70):(10-70). In a further preferred embodiment, the weight ratio of the coal gasification slag powder, the fly ash, and the mineral powder is 100:(25-60):(12-40).

[0037] In this invention, there is no special limitation on the source of the fly ash; commonly used fly ash in this industry can be used. In some preferred embodiments, the fly ash is mostly spherical, with a SEM particle size of 2-30 μm, preferably 5-20 μm, and a specific surface area of ​​300-600 m². 2 / kg, preferably 400-550 m 2 / kg. The fly ash particles can be mixed with the irregularly shaped coal gasification slag powder to reduce inter-particle frictional resistance, thereby increasing the concrete slump by 10-15% and controlling the slump loss rate to within 10%. In some specific embodiments, the fly ash is Class II fly ash as defined in GB / T 1596-2017 "Fly Ash for Cement and Concrete," provided by Inner Mongolia Mengtai Group Co., Ltd., with the following composition: SiO2 45-50%, Al2O3 20-30%, Fe2O3 4-8%, CaO 2-6%, and other impurities 14-18%. These other impurities will not negatively affect the implementation effect of the present invention.

[0038] In this invention, there is no particular limitation on the source of the mineral powder, and commonly used mineral powders in this industry can be used. In some preferred embodiments, the particle size of the mineral powder is 3-45 μm, preferably 5-35 μm; and the specific surface area is 300-380 m². 2 / kg, preferably 320-360m 2 / kg. In some specific implementations, The mineral powder is S95 mineral powder as defined in GB / T 18046-2017 "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete", provided by Tangshan Iron and Steel Group Co., Ltd. Its composition is 35-40% SiO2, 15-20% Al2O3, 30-40% CaO, 4-8% MgO, and 1-5% other impurities. The other impurities will not have a negative impact on the implementation effect of the present invention.

[0039] The concrete admixture prepared by the method provided in this invention has multiple advantages: more stable performance and better control precision of workability; lower preparation cost and more outstanding economic applicability; higher resource utilization efficiency and stronger adaptability to different application scenarios; and significant environmental benefits, which are highly in line with the current low-carbon development trend.

[0040] This invention also provides a concrete admixture prepared by the above method. This concrete admixture achieves precise control over the workability of concrete and fully meets practical application scenarios and environmental protection requirements.

[0041] The present invention also provides the application of the above-mentioned concrete admixtures in the concrete preparation process.

[0042] The present invention also provides a method for preparing concrete, the method comprising: mixing cement, the above-mentioned concrete admixture, medium sand, crushed stone, water-reducing agent and water; The weight ratio of the cement to the concrete admixture is 1-5:1.

[0043] In some preferred embodiments, the weight ratio of cement to concrete admixture is 2-4:1. As specific examples, the weight ratio of cement to concrete admixture can be 2:1, 2.5:1, 3:1, 3.5:1, or 4:1.

[0044] In some embodiments, relative to 100 parts by weight of the concrete admixture, the amount of cement is 100-500 parts by weight, preferably 200-400 parts by weight; the amount of medium sand is 500-1000 parts by weight, preferably 700-800 parts by weight; the amount of crushed stone is 800-1200 parts by weight, preferably 900-1100 parts by weight; the amount of water-reducing agent is 1-10 parts by weight, preferably 3-5 parts by weight; and the amount of water is 100-200 parts by weight, preferably 150-170 parts by weight.

[0045] In this invention, the sources of the cement, medium sand, and crushed stone are not limited, and all can be cement, medium sand, and crushed stone conventionally used in the art. In some specific embodiments, the cement is P. O42.5 ordinary Portland cement (strength grade 42.5); the fineness modulus of the medium sand is 2-3; the crushed stone is continuously graded crushed stone with a particle size of 5-25mm.

[0046] In this invention, the type of water-reducing agent is not limited, and any water-reducing agent commonly used in the art can be used. Preferably, the water-reducing agent is selected from at least one of polycarboxylate water-reducing agents, naphthalene-based water-reducing agents, and aminosulfonate water-reducing agents. In a further preferred embodiment, the water-reducing agent is a polycarboxylate water-reducing agent.

[0047] The present invention also provides concrete prepared by the above method, wherein the concrete admixture can undergo pozzolanic reaction with other components to achieve precise control over the workability (slump loss rate <10%), mechanical properties (28-day compressive strength ≥36MPa), and durability (impermeability grade ≥P8) of the concrete, thereby promoting the utilization rate of coal-based solid waste resources to over 90% and meeting the technical requirements of construction engineering for admixtures with workability and the needs of green and low-carbon development.

[0048] In this invention, the mechanism of the pozzolanic reaction is as follows: Initial stage of cement hydration: After cement and water are mixed, tricalcium silicate (C3S) and dicalcium silicate (C2S) rapidly hydrate, generating calcium hydroxide (CH) and hydrated calcium silicate (CSH) gel. At this time, the concrete system is strongly alkaline (pH=12-13), providing an environment for the pozzolanic reaction; Secondary reaction: The active SiO2 and Al2O3 in the coal gasification slag powder are activated in the alkaline environment and react with CH. SiO2 + Ca(OH)2 + H2O → CSH (fibrous gel) Al2O3 + Ca(OH)2 + H2O → CAH (flocculated gel) The reaction begins 1-3 days after hydration, reaches its peak rate at 7 days, and continues until 28 days. The generated CSH and CAH gels can fill the 0.01-1μm capillary pores inside the concrete. Microstructure optimization: The synergistic effect of gel filling and particle gradation—the gasification slag micro powder (3-50μm) fills the gaps between cement particles (3-30μm), forming a dense "cement-micro powder-gel" structure, which reduces the porosity of concrete by 8-12%, significantly improves the density, and thus improves the durability properties such as impermeability and frost resistance.

[0049] In the concrete described in this invention, the fly ash particles are mostly spherical, which, when mixed with the irregularly shaped coal gasification slag powder, can reduce the frictional resistance between particles, thereby increasing the concrete slump by 10-15% and controlling the slump loss rate to within 10%. This is because the specific surface area of ​​the coal gasification slag powder (280-320 m²) is... 2 / kg) and cement (300-330m 2 The particle size distribution is close to that of cement particles (3-50μm), and the particle size distribution is wider. It can fill the voids formed by the accumulation of cement particles, increase the bulk density by 5-8%, and reduce the weak areas inside the concrete. The active Al2O3 in the mineral powder can react quickly with CH to generate CAH gel, which makes up for the slow early reaction of the coal gasification slag powder, and increases the 7-day compressive strength of concrete by 5-8%, avoiding the problem of "low early strength" of traditional coal gasification slag admixtures.

[0050] This invention further provides the application of the aforementioned concrete in the production process of building materials. Because the concrete possesses excellent workability, mechanical properties, and durability, its application scenarios cover residential, municipal, and underground engineering projects, thus solving the problem of "narrow applicability" in existing technologies.

[0051] The concrete admixture, its preparation method, and its application according to the present invention are further illustrated below through examples. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0052] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0053] In the following examples and comparative examples, the coal gasification slag was provided by Ningxia Baofeng Energy Group Co., Ltd., and its composition was 50% SiO2, 25% Al2O3, 5% CaO, 3% Fe2O3, and 17% other components. The fly ash in question is Class II fly ash as defined in GB / T 1596-2017 "Fly Ash for Cement and Concrete", provided by Inner Mongolia Mengtai Group Co., Ltd., and its composition is 48% SiO2, 26% Al2O3, 6% Fe2O3, 4% CaO, and 16% other components. The mineral powder is classified as S95 mineral powder according to GB / T 18046-2017 "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete", and is provided by Tangshan Iron and Steel Group Co., Ltd. Its composition is 38% SiO2, 18% Al2O3, 35% CaO, 6% MgO, and 3% other components. The polycarboxylate superplasticizer was purchased from Jiangsu Subote New Material Co., Ltd.

[0054] Example 1 (1) Carbon content and density were tested on the coal gasification slag, and slag with carbon content <3% and bulk density >1.8 g / cm³ was selected. 3The coal gasification slag is then screened and placed in a drying yard. The ambient temperature is controlled at 30℃ and the relative humidity at 50%, and the slag is dried for 30 hours until the moisture content is <1.5%. A jaw crusher is then used for coarse crushing of the dried coal gasification slag to control the particle size to below 50mm. An impact crusher is then used for fine crushing to further control the particle size to below 10mm. Finally, a vibrating screen (4.75mm square mesh) is used for sieving for 15 minutes to ensure that all samples at the bottom of the screen have a particle size <4.75mm, resulting in pretreated coal gasification slag. Samples remaining on the screen are returned to the fine crushing process. (2) The pretreated coal gasification slag is mixed with ball milling media at a weight ratio of 1:9, and then ball milled for 90 minutes at a speed of 225 rpm. During the ball milling process, the machine is stopped for 5 minutes every 30 minutes to prevent the ball milled material from agglomerating. Then the ball milled material is screened through a 0.08 mm square hole sieve to obtain coal gasification concrete admixture slag powder. Based on the total weight of the ball milling media, the ball milling media contains 40% by weight of agate ball particles with a diameter of 5 mm, 30% by weight of agate ball particles with a diameter of 8 mm, and 30% by weight of agate ball particles with a diameter of 10 mm. (3) The coal gasification furnace slag powder, Class II fly ash and S95 mineral powder are mixed in a weight ratio of 100:60:40 to obtain concrete admixture S1; (4) Use P·O 42.5 cement 260 kg / m 3 Concrete admixture S1 100 kg / m³ 3 155 kg / m³ of water 3 Medium sand (fineness modulus 2.5) 750 kg / m³ 3 Crushed stone (5-25mm continuous gradation) 1080 kg / m³ 3 Polycarboxylate high-performance water-reducing agent 4.0 kg / m 3 After mixing and stirring evenly, the slump loss rate is measured. After molding, demolding, and standard curing, the 7-day compressive strength, 28-day compressive strength, and impermeability grade are tested.

[0055] Example 2 (1) Carbon content and density were tested on the coal gasification slag, and slag with carbon content <3% and bulk density >1.8 g / cm³ was selected. 3The coal gasification slag is then screened and placed in a drying yard. The ambient temperature is controlled at 25℃ and the relative humidity at 40%, and the slag is dried for 48 hours until the moisture content is <1.5%. A jaw crusher is then used for coarse crushing of the dried coal gasification slag to control the particle size to below 50mm. An impact crusher is then used for fine crushing to further control the particle size to below 10mm. Finally, a vibrating screen (4.75mm square mesh) is used for sieving for 15 minutes to ensure that all samples at the bottom of the screen have a particle size <4.75mm, resulting in pretreated coal gasification slag. Samples remaining on the screen are returned to the fine crushing process. (2) The pretreated coal gasification slag is mixed with ball milling media at a weight ratio of 1:8, and then ball milled for 120 minutes at a speed of 200 rpm. During the ball milling process, the machine is stopped for 5 minutes every 30 minutes to prevent the ball milled material from agglomerating. Then the ball milled material is screened through a 0.08 mm square hole sieve to obtain coal gasification concrete admixture slag powder. Based on the total weight of the ball milling media, the ball milling media contains 30% by weight of agate ball particles with a diameter of 5 mm, 35% by weight of agate ball particles with a diameter of 8 mm, and 35% by weight of agate ball particles with a diameter of 10 mm. (3) The coal gasification furnace slag powder, Class II fly ash and S95 mineral powder are mixed in a weight ratio of 100:46.7:25 to obtain concrete admixture S2; (4) Use P·O 42.5 cement 260 kg / m 3 Concrete admixture S2 100 kg / m³ 3 155 kg / m³ of water 3 Medium sand (fineness modulus 2.5) 750 kg / m³ 3 Crushed stone (5-25mm continuous gradation) 1080 kg / m³ 3 Polycarboxylate high-performance water-reducing agent 4.0 kg / m 3 After mixing and stirring evenly, the slump loss rate is measured. After molding, demolding, and standard curing, the 7-day compressive strength, 28-day compressive strength, and impermeability grade are tested.

[0056] Example 3 (1) Carbon content and density were tested on the coal gasification slag, and slag with carbon content <3% and bulk density >1.8 g / cm³ was selected. 3The coal gasification slag is then screened and placed in a drying yard. The ambient temperature is controlled at 35℃ and the relative humidity at 60%, and the slag is dried for 24 hours until the moisture content is <1.5%. A jaw crusher is then used for coarse crushing of the dried coal gasification slag to control the particle size to below 50mm. An impact crusher is then used for fine crushing to further control the particle size to below 10mm. Finally, a vibrating screen (4.75mm square mesh) is used for sieving for 15 minutes to ensure that all samples at the bottom of the screen have a particle size <4.75mm, resulting in pretreated coal gasification slag. Samples remaining on the screen are returned to the fine crusher. (2) The pretreated coal gasification slag is mixed with ball milling media at a weight ratio of 1:10, and then ball milled for 80 minutes at a speed of 250 rpm. During the ball milling process, the machine is stopped for 4 minutes every 20 minutes to prevent the ball milled material from agglomerating. Then the ball milled material is screened through a 0.08 mm square hole sieve to obtain coal gasification concrete admixture slag powder. Based on the total weight of the ball milling media, the ball milling media contains 50% by weight of agate ball particles with a diameter of 5 mm, 25% by weight of agate ball particles with a diameter of 8 mm, and 25% by weight of agate ball particles with a diameter of 10 mm. (3) The coal gasification furnace slag powder, Class II fly ash and S95 mineral powder are mixed in a weight ratio of 100:28.57:14.29 to obtain concrete admixture S3; (4) Use P·O 42.5 cement 260 kg / m 3 Concrete admixture S3 100 kg / m³ 3 155 kg / m³ of water 3 Medium sand (fineness modulus 2.5) 750 kg / m³ 3 Crushed stone (5-25mm continuous gradation) 1080 kg / m³ 3 Polycarboxylate high-performance water-reducing agent 4.0 kg / m 3 After mixing and stirring evenly, the slump loss rate is measured. After molding, demolding, and standard curing, the 7-day compressive strength, 28-day compressive strength, and impermeability grade are tested.

[0057] Example 4 The method described in Example 1 is implemented, except that in step (2), the pretreated coal gasification slag is mixed with ball milling media at a weight ratio of 1:20 to obtain concrete admixture S4. (4) Use P·O 42.5 cement 260 kg / m 3 Concrete admixture S4 100 kg / m³ 3 155 kg / m³ of water 3Medium sand (fineness modulus 2.5) 750 kg / m³ 3 Crushed stone (5-25mm continuous gradation) 1080 kg / m³ 3 Polycarboxylate high-performance water-reducing agent 4.0 kg / m 3 After mixing and stirring evenly, the slump loss rate is measured. After molding, demolding, and standard curing, the 7-day compressive strength, 28-day compressive strength, and impermeability grade are tested.

[0058] Example 5 The method described in Example 1 is implemented, except that in step (3), the coal gasification slag powder, Class II fly ash and S95 mineral powder are mixed in a weight ratio of 100:60:80 to obtain concrete admixture S5. (4) Use P·O 42.5 cement 260 kg / m 3 Concrete admixture S5 100 kg / m³ 3 155 kg / m³ of water 3 Medium sand (fineness modulus 2.5) 750 kg / m³ 3 Crushed stone (5-25mm continuous gradation) 1080 kg / m³ 3 Polycarboxylate high-performance water-reducing agent 4.0 kg / m 3 After mixing and stirring evenly, the slump loss rate is measured. After molding, demolding, and standard curing, the 7-day compressive strength, 28-day compressive strength, and impermeability grade are tested.

[0059] Example 6 The method described in Example 1 is implemented, except that in step (3), the coal gasification slag powder, Class II fly ash and S95 mineral powder are mixed in a weight ratio of 100:80:40 to obtain concrete admixture S6. (4) Use P·O 42.5 cement 260 kg / m 3 Concrete admixture S6 100 kg / m³ 3 155 kg / m³ of water 3 Medium sand (fineness modulus 2.5) 750 kg / m³ 3 Crushed stone (5-25mm continuous gradation) 1080 kg / m³ 3 Polycarboxylate high-performance water-reducing agent 4.0 kg / m 3 After mixing and stirring evenly, the slump loss rate is measured. After molding, demolding, and standard curing, the 7-day compressive strength, 28-day compressive strength, and impermeability grade are tested.

[0060] Comparative Example 1 The method described in Example 1 is implemented, except that step (1) is omitted, and a carbon content > 3% by weight and a bulk density < 1.8 g / cm³ are used.3 The coal gasification slag is processed through steps (2) and (3) to obtain concrete admixture D1; (4) Use P·O 42.5 cement 260 kg / m 3 Concrete admixture D1 100 kg / m³ 3 155 kg / m³ of water 3 Medium sand (fineness modulus 2.5) 750 kg / m³ 3 Crushed stone (5-25mm continuous gradation) 1080 kg / m³ 3 Polycarboxylate high-performance water-reducing agent 4.0 kg / m 3 After mixing and stirring evenly, the slump loss rate is measured. After molding, demolding, and standard curing, the 7-day compressive strength, 28-day compressive strength, and impermeability grade are tested.

[0061] Comparative Example 2 The method described in Example 1 was implemented, except that the ball milling conditions in step (2) were changed so that the specific surface area of ​​the obtained coal gasification slag powder was >320m² / kg, and concrete admixture D2 was obtained. (4) Use P·O 42.5 cement 260 kg / m 3 Concrete admixture D2 100 kg / m³ 3 155 kg / m³ of water 3 Medium sand (fineness modulus 2.5) 750 kg / m³ 3 Crushed stone (5-25mm continuous gradation) 1080 kg / m³ 3 Polycarboxylate high-performance water-reducing agent 4.0 kg / m 3 After mixing and stirring evenly, the slump loss rate is measured. After molding, demolding, and standard curing, the 7-day compressive strength, 28-day compressive strength, and impermeability grade are tested.

[0062] Comparative Example 3 The method described in Example 1 is implemented, except that in step (3), the coal gasification slag powder, Class II fly ash and S95 mineral powder are mixed in a weight ratio of 100:100:40 to obtain concrete admixture D3. (4) Use P·O 42.5 cement 260 kg / m 3 Concrete admixture D3 100 kg / m³ 3 155 kg / m³ of water 3 Medium sand (fineness modulus 2.5) 750 kg / m³ 3 Crushed stone (5-25mm continuous gradation) 1080 kg / m³ 3 Polycarboxylate high-performance water-reducing agent 4.0 kg / m 3After mixing and stirring evenly, the slump loss rate is measured. After molding, demolding, and standard curing, the 7-day compressive strength, 28-day compressive strength, and impermeability grade are tested.

[0063] Comparative Example 4 The method described in Example 1 is implemented, except that in step (3), the coal gasification slag powder, Class II fly ash and S95 mineral powder are mixed in a weight ratio of 100:60:100 to obtain concrete admixture D4. (4) Use P·O 42.5 cement 260 kg / m 3 Concrete admixture D4 100 kg / m³ 3 155 kg / m³ of water 3 Medium sand (fineness modulus 2.5) 750 kg / m³ 3 Crushed stone (5-25mm continuous gradation) 1080 kg / m³ 3 Polycarboxylate high-performance water-reducing agent 4.0 kg / m 3 After mixing and stirring evenly, the slump loss rate is measured. After molding, demolding, and standard curing, the 7-day compressive strength, 28-day compressive strength, and impermeability grade are tested.

[0064] Test case Test Example 1 (1) The carbon content of the pretreated coal gasification slag obtained in the examples and comparative examples was tested by the burning method, the bulk density of the pretreated coal gasification slag obtained in the examples and comparative examples was tested by the graduated cylinder method, and the moisture content of the pretreated coal gasification slag obtained in the examples and comparative examples was tested by the drying method. The results are shown in Table 1.

[0065] (2) The present invention uses a laser particle size analyzer to test the particle size and specific surface area of ​​the coal gasification slag powder obtained in the examples and comparative examples. The results are shown in Table 1.

[0066] Table 1

[0067] Test Example 2 (1) The slump loss rate of the mixed soil was tested by GB / T 50080-2016 "Standard for Test Method of Performance of Ordinary Concrete Mixtures", and the results are shown in Table 2.

[0068] (2) The 7-day and 28-day compressive strength of the mixed soil were tested according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The results are shown in Table 2.

[0069] (3) The impermeability grade of the mixed soil was tested by GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete", and the results are shown in Table 2.

[0070] Table 2

[0071] The results in Tables 1 and 2 show that the pretreated coal gasification slag used in the concrete admixtures prepared in Examples 1-6 all meet the requirements of carbon content <3% by weight, bulk density >1.8 g / cm³, and moisture content <1.5% by weight. The specific surface area of ​​the coal gasification slag powder is controlled within the range of 280-320 m² / kg and particle size 3-50 μm. The concrete prepared in this way has a slump loss rate of <10%, a 28-day compressive strength ≥36 MPa, and a permeability grade ≥P8, demonstrating excellent overall performance. In summary, the performance of Examples 1-3 is superior to that of Examples 4-6. Comparative Example 1, due to the lack of pretreatment of the coal gasification slag, had a high carbon content and low bulk density, resulting in a significant increase in the slump loss rate of the concrete to 25.3%, a 28-day compressive strength of only 25.8 MPa, and a permeability grade of only P6, indicating a significant deterioration in performance. Comparative Example 2, due to the specific surface area of ​​the coal gasification slag powder exceeding the set range, had a slump loss rate of 18.7%, and its mechanical properties also declined. Comparative Examples 3 and 4, due to the compounding ratio exceeding the preferred range, both had slump loss rates exceeding 12%, and their overall performance was inferior to that of the product in the example. This demonstrates that the present invention, through precise control of raw material pretreatment, ball milling parameters, and compounding ratio, can effectively improve the overall performance of concrete admixtures and corresponding concrete, achieving the expected technical effect.

[0072] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a concrete admixture, characterized in that, The method includes the following steps: (1) The coal gasification slag is dried, crushed and screened to obtain pretreated coal gasification slag, wherein the carbon content of the pretreated coal gasification slag is <3% by weight and the bulk density is >1.8 g / cm³. 3 Moisture content < 1.5% by weight, particle size < 4.75 mm; (2) The pretreated coal gasification slag is ball-milled and sieved to obtain coal gasification slag powder with a specific surface area of ​​280-320m² / kg and a particle size of 3-50μm; (3) The coal gasification furnace slag powder, fly ash and mineral powder are mixed in a weight ratio of 100:(10-80):(5-80).

2. The method according to claim 1, characterized in that, In step (2), the specific process of ball milling includes: mixing the pretreated coal gasification slag with ball milling media and then ball milling, wherein, based on the total weight of the ball milling media, the ball milling media contains 20-60% by weight of first agate ball particles, 10-45% by weight of second agate ball particles and 10-45% by weight of third agate ball particles; Preferably, the diameter of the first agate ball is 1-6 mm, the diameter of the second agate ball is 6-10 mm, and the diameter of the third agate ball is 10-15 mm.

3. The method according to claim 2, characterized in that, In step (2), the weight ratio of the pretreated coal gasification slag to the ball milling media is 1:5-15, preferably 1:7-12.

4. The method according to any one of claims 1-3, characterized in that, In step (2), the conditions for ball milling include: a rotation speed of 150-300 rpm and a time of 50-150 min.

5. The method according to claim 1 or 4, characterized in that, In step (3), the weight ratio of the coal gasification furnace slag powder, the fly ash and the mineral powder is 100:(20-70):(10-70). Preferably, the fly ash has a particle size of 2-30 μm and a specific surface area of ​​300-600 m². 2 / kg; Preferably, the mineral powder has a particle size of 3-45 μm and a specific surface area of ​​300-380 m². 2 / kg.

6. A concrete admixture prepared by the method according to any one of claims 1-5.

7. The application of the concrete admixture as described in claim 6 in the concrete preparation process.

8. A method for preparing concrete, characterized in that, The method includes: mixing cement, the concrete admixture as described in claim 6, medium sand, crushed stone, water-reducing agent, and water; The weight ratio of the cement to the concrete admixture is 1-5:

1.

9. Concrete prepared by the method of claim 8.

10. The application of the concrete as described in claim 9 in the production process of building materials and products.

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