A composite admixture for self-flowing filling slurry of ultra-high concentration coarse aggregate

Abstract

The application provides a composite admixture for self-flow filling of super-high-concentration coarse aggregate slurry, which is compounded by water-reducing agent mother liquor, slump retaining agent mother liquor, sodium gluconate, industrial white sugar and air entraining agent; the mass fraction of each raw material is as follows: the water-reducing agent mother liquor is 35-45 parts, the slump retaining agent mother liquor is 115-125 parts, the sodium gluconate is 3-5 parts, the industrial white sugar is 5-7 parts, the air entraining agent is 0.41-0.45 parts, and the dilution water is 400-410 parts. The composite admixture is used for self-flow filling of super-high-concentration coarse aggregate, can realize the conversion of the super-high-concentration filling slurry which cannot self-flow into the self-flow conveying mode, significantly improves the filling body strength, reduces the amount of cementing material, can improve the economic benefit and environmental protection benefit of filling mining, promotes the application of filling mining technology, and explores a path for the reduction, harmless and resource utilization of waste rock.

Description

Technical Field

[0001] This invention relates to the field of mine backfilling technology, and to a composite admixture for ultra-high concentration coarse aggregate self-flowing backfill slurry. Background Technology

[0002] With my country's rapid economic development and continuous exploitation of mineral resources, high-grade mineral resources with favorable mining conditions are becoming increasingly depleted, leaving more resources facing deep burial, high stress, water abundance, and unfavorable geological conditions. Backfilling mining is the primary choice for safe, environmentally friendly, and green mining. Backfilling involves preparing solid waste such as waste rock and slag into a flowable slurry, which is then transported to the underground goaf. This not only effectively treats solid waste but also improves ore recovery rates and provides safe ground pressure management, making it a green and sustainable mining method. The backfilling slurry is delivered to the underground stope via gravity flow or pumping, typically requiring... A certain degree of slump and diffusion is required for it to flow and fill the mining area; The slurry concentration needs to reach a certain level to ensure uniform distribution of internal materials, avoid or reduce segregation, stratification and bleeding, and improve the filling and top-contact ratio. The strength of the solidified filling body meets the requirements of the mining process.

[0003] These goals are somewhat contradictory. The requirement for the filling slurry to not stratify or segregate exceeds the critical concentration, and increasing the concentration is beneficial for enhancing the strength of the filling body and improving the roof contact rate. However, the higher the concentration, the worse the fluidity of the filling slurry, and the more difficult it is to achieve "self-leveling." In the environment of deep well mining, fully utilizing gravitational potential energy to achieve energy-saving self-flowing filling of the slurry is the mainstream trend in deep well filling and has positive significance for mine filling production. (1) Mines can obtain the superior properties of filling slurry, such as good integrity, high strength, no segregation, no stratification, no bleeding, reducing drainage and sludge removal costs and improving the level of civilized production on site; (2) It meets the requirements for building a green mine and can also reduce aggregate costs; (3) The filling system does not require a filling pump, which not only reduces equipment costs, operating parts costs and electricity costs, but also simplifies the filling system, reduces system failures and improves filling efficiency; (4) Improve the fluidity of the filling slurry itself, realize gravity flow transportation, take into account the advantages of both high concentration and gravity filling, avoid their respective disadvantages, and play an essential role in improving the filling quality and reducing the filling cost of mines.

[0004] The above analysis shows that ultra-high concentration self-flowing backfilling is of great significance in the field of mine backfilling. Research indicates that the preparation of special admixtures (composite water-reducing agents) for ultra-high concentration mine backfill slurries is an important way to achieve ultra-high concentration self-flowing backfilling. Admixtures refer to trace substances added to the backfill slurry, which can significantly improve various properties of the backfill slurry, such as workability, pumpability, strength, impermeability, frost resistance, carbonation resistance, and thermal and sound insulation. Among them, polycarboxylate-based high-performance water-reducing agents commonly used in concrete are a new type of green and environmentally friendly high-performance water-reducing agent. Compared with traditional water-reducing agents, they have significant comprehensive technical advantages such as strong dispersibility, high water reduction rate, small slump loss over time, adjustable molecular structure, and environmental friendliness. The water-reducing and dispersing properties of polycarboxylate water-reducing agents in slurry are mainly due to the steric hindrance effect generated by the interaction of long side chains of polycarboxylate polymers, the electrostatic repulsion effect generated by the anionic groups of polycarboxylate molecules, and the synergistic effect of multiple effects.

[0005] The development trend of polycarboxylate superplasticizers can be roughly divided into three aspects: (1) In terms of production process, the simplification of production process, the normalization of polymerization temperature, the high efficiency of production rate, the pollution-free production process, and health and sustainability have become the development trend of polycarboxylate superplasticizer industry; (2) In terms of polyether macromonomers in the upstream industry of polycarboxylate superplasticizers, we should independently develop ether macromonomers with strong adaptability, high double bond activity, easy copolymerization of unsaturated carboxylic acids and environmental friendliness; (3) In terms of functionalization of polycarboxylate superplasticizers, researchers should develop functional monomers with strong functionality, high adaptability, easy preparation and no pollution.

[0006] To address problems encountered in actual production and improve the performance of ordinary polycarboxylate superplasticizers, modification of these superplasticizers is necessary. Based on their structure, polycarboxylate superplasticizer modification methods can be divided into two categories: traditional modification methods and hyperbranching modification. Polycarboxylate superplasticizers modified using traditional methods generally have a comb-like structure; hyperbranched polycarboxylate superplasticizers exhibit dendritic, star-shaped, or three-dimensional spherical structures. Furthermore, to improve the various properties of filling slurries, practical applications require the compounding of different superplasticizers to ensure good adaptability to mine filling cement, filling aggregates, and specific slurry proportions. It is necessary to find the composite admixture ratio that best optimizes the fluidity of ultra-high concentration self-flowing filling slurries and to investigate the relationship between fluidity indicators, strength, and the components of the admixture.

[0007] Using the keywords "filling" and "water-reducing agent," a search was conducted on publicly available composite admixtures for mine filling. Chinese invention patent CN112456859B discloses "a water-reducing agent composition for coal mine paste filling and its preparation method and application," CN114380532B discloses "a cement admixture for full tailings filling, its preparation method and filling slurry," and CN103979820B discloses "an early-strength water-reducing agent for mine filling materials and its preparation method." These invention patents all propose the application of water-reducing agents in the filling field, but none of them use a compounding method of multiple water-reducing agents, nor do they involve ultra-high concentration coarse aggregate filling slurry.

[0008] Therefore, it is necessary to study a composite admixture for ultra-high concentration coarse aggregate self-fluidized filling slurry to address the shortcomings of existing technologies and solve or mitigate one or more of the above-mentioned problems. Summary of the Invention

[0009] This invention provides a composite admixture for ultra-high concentration coarse aggregate self-flowing filling slurry, which can significantly improve the fluidity of coarse aggregate filling slurry, prepare ultra-high concentration filling materials that meet the requirements of self-flowing filling, and thus significantly improve the mechanical strength properties of the prepared filling body, providing support for ultra-high concentration coarse aggregate self-flowing filling.

[0010] A composite admixture for ultra-high concentration coarse aggregate self-flowing filling slurry is composed of water-reducing agent mother liquor, slump-retaining agent mother liquor, sodium gluconate, industrial white sugar, air-entraining agent, and dilution water. The raw materials are formulated in the following mass ratios: 35-45 parts water-reducing agent mother liquor, 115-125 parts slump-retaining agent mother liquor, 3-5 parts sodium gluconate, 5-7 parts industrial white sugar, 0.41-0.45 parts air-entraining agent, and 400-410 parts dilution water.

[0011] The ratio of composite admixtures needs to be determined through orthogonal test analysis of filling body strength and fluidity to meet the requirements of self-flowing and strength of filling slurry. The fluidity test index of self-flowing filling slurry is: slump ≥ 24cm, diffusion ≥ 80cm (i.e., fluidity index ≥ 200cm). The strength test index of filling body is: 3d uniaxial compressive strength ≥ 1.5MPa, 7d strength ≥ 2.5MPa, 28d strength ≥ 5.0MPa.

[0012] The water-reducing agent mother liquor is obtained by copolymerizing methyl allyl polyoxyethylene ether (HPEG) macromonomer, acrylic acid (AA) small monomer, ammonium persulfate (APS), mercaptopropionic acid (MPA), hydrogen peroxide (H2O2) and L-ascorbic acid (Vc) in an aqueous solution at 40-42℃.

[0013] In this mixture, ammonium persulfate (APS) and hydrogen peroxide (H2O2) are used as oxidants, L-ascorbic acid (Vc) is used as a reducing agent, and mercaptopropionic acid (MPA) is used as a chain transfer agent. The acid-ether ratio (molar ratio of AA to HPEG) is 4.5:1; the amount of APS used is 0.06% of the mass of the methyl allyl polyoxyethylene ether (HPEG) macromonomer; the amount of H2O2 used is 0.63% of the mass of the methyl allyl polyoxyethylene ether (HPEG) macromonomer; the amount of Vc used is 0.13% of the mass of the methyl allyl polyoxyethylene ether (HPEG) macromonomer; and the amount of MPA used is 0.48% of the mass of the methyl allyl polyoxyethylene ether (HPEG) macromonomer.

[0014] The slump retainer mother liquor is obtained by copolymerizing isopentenyl polyoxyethylene ether (TPEG) macromonomer, acrylic acid (AA) small monomer, ammonium sulfate (APS), and hydrogen peroxide (H2O2) in an aqueous solution at 34-36℃.

[0015] Ammonium persulfate (APS) and hydrogen peroxide (H2O2) are used as oxidants. The acid-ether ratio (molar ratio of AA to TPEG) is 4.3:1; the amount of APS used is 0.06% of the mass of the isopentenyl polyoxyethylene ether (TPEG) macromonomer; the amount of H2O2 used is 0.63% of the mass of the isopentenyl polyoxyethylene ether (TPEG) macromonomer.

[0016] The ultra-high concentration coarse aggregate self-flowing filling slurry is composed of filling coarse aggregate, cement, and water. Its self-flowability is demonstrated by a comprehensive fluidity index consisting of slump and spread: Comprehensive fluidity index = slurry slump × 5 + slurry spread. The filling coarse aggregate consists of rod mill sand, river sand, and waste rock; the amount of composite admixture is 0.5% to 1.5% of the cement mass in the filling slurry.

[0017] In the coarse aggregate filling, the content of rod mill sand is 35-45%, the content of river sand is 10-20%, and the content of waste rock is 30-40%; in the mixed coarse aggregate filling, the content of particles with a maximum size ≤12mm and a stone content greater than 4.75mm is 35-45%, and the content of mud content less than 0.075mm is 8-13%.

[0018] The ultra-high concentration coarse aggregate self-fluidizing filler slurry has a solid mass concentration of 82-85% and a ash-sand ratio of 1:4-1:6.

[0019] The cement is 42.5R ordinary Portland cement, mining early-strength 42.5R Portland cement, or a mixture of 30% S95 slag powder and 70% 42.5R Portland cement.

[0020] In summary, this invention addresses the shortcomings of existing technologies by fully utilizing various coarse aggregates with different properties and characteristics, such as waste rock, river sand, and rod mill sand, to reduce the water-cement ratio and prepare ultra-high concentration backfill slurry materials. The use of a compounded special admixture further improves the slurry's fluidity and backfill strength, making it an important approach to developing deep well self-flowing backfilling and reducing backfill mining costs. This invention provides a special admixture for the self-flowing transport of ultra-high concentration coarse aggregate backfill slurry. The method utilizes water-reducing agent mother liquor, slump-preserving agent mother liquor, sodium gluconate, industrial white sugar, and air-entraining agent to formulate a composite admixture. By determining the appropriate dosage of the admixture, the fluidity of the ultra-high concentration coarse aggregate backfill slurry meets the requirements of self-flowing backfilling, while the strength of the backfill meets mining needs, providing a highly efficient admixture for ultra-high concentration deep well self-flowing backfilling.

[0021] Compared with the prior art, the present invention has the following advantages or beneficial effects: Using composite admixtures in self-flowing backfilling of ultra-high concentration coarse aggregates can transform non-self-flowing ultra-high concentration backfill slurry into a self-flowing conveying method, significantly improving the strength of the backfill and reducing the amount of cementitious materials used. This not only improves the economic and environmental benefits of backfilling mining and promotes the application of backfilling mining technology, but also explores a way for the reduction, harmlessness and resource utilization of waste rock. Attached Figure Description

[0022] Figure 1 This is the copolymerization reaction equation for the standard polycarboxylate superplasticizer provided in the embodiments of the present invention; Figure 2 This is the flow state of cement paste without admixtures provided in the embodiments of the present invention; Figure 3 These are the flow states of cement paste with two admixtures provided in the embodiments of the present invention; Figure 4 This is a particle size distribution curve of rod milling provided in an embodiment of the present invention; Figure 5 This is a particle size distribution curve of river sand provided in an embodiment of the present invention; Figure 6 This is a waste rock particle size distribution curve provided in an embodiment of the present invention; Figure 7 This is a comparison chart of the slump spread of the ultra-high concentration filling slurry before and after the addition of composite additives, provided in the embodiments of the present invention. Detailed Implementation

[0023] To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0024] This invention relates to the application of self-flowing filling in deep wells, proposing a composite admixture suitable for self-flowing filling slurries made from ultra-high concentration coarse aggregate. Through orthogonal compounding experiments, the proportion of the composite admixture was determined, achieving self-flowing filling of ultra-high concentration coarse aggregate filling slurry. An implementation case is provided below for illustration.

[0025] Example 1: Phosphogypsum-slag powder-carbide slag system A composite admixture suitable for ultra-high concentration coarse aggregate self-fluxing filler slurry is first prepared by synthesizing two mother liquors of the admixture. The water-reducing agent mother liquor is obtained by copolymerizing methyl allyl polyoxyethylene ether (HPEG) macromonomer, acrylic acid (AA) small monomer, ammonium persulfate (APS), mercaptopropionic acid (MPA), hydrogen peroxide (H2O2), and L-ascorbic acid (Vc) in an aqueous solution at 40-42℃. The acid-ether ratio (AA to HPEG molar ratio) is 4.5:1, the amounts of oxidant APS and H2O2 are 0.06% and 0.63% of the macromonomer mass, respectively, the amount of reducing agent Vc is 0.13% of the macromonomer mass, and the amount of chain transfer agent MPA is 0.48% of the macromonomer mass. At this point, the initial fluidity of the cement paste reaches 284 mm, and the fluidity reaches 234 mm after 2 hours. The copolymerization reaction equation of the standard polycarboxylate superplasticizer is... Figure 1 As shown.

[0026] The slump retainer mother liquor was obtained by copolymerizing isopentenyl polyoxyethylene ether (TPEG) macromonomer, acrylic acid (AA) small monomer, ammonium sulfate (APS), and hydrogen peroxide (H2O2) in an aqueous solution at 35°C. The acid-ether ratio (AA to TPEG molar ratio) was 4.3:1, and the amounts of oxidants APS and H2O2 were 0.06% and 0.63% of the macromonomer mass, respectively.

[0027] Through cement paste experiments, the adaptability of various admixtures to Jinchuan Jinni Group's 42.5R silicate cement was observed and analyzed. It was concluded that the larger the test cake diameter, the better the adaptability of the admixture. The results showed that without admixtures, the cement paste with a water-cement ratio of 0.29 maintained the original state of the truncated cone mold, with a measured paste column diameter of 60 mm (mold diameter), showing no slump or spread. Figure 2 As shown; the fluidity of the cement slurry due to the two admixture mother liquors is 330-350 mm, as... Figure 3 As shown.

[0028] An orthogonal mix design experiment was conducted on a composite mixture consisting of water-reducing agent mother liquor, slump-retaining agent mother liquor, sodium gluconate, industrial white sugar, and air-entraining agent. The optimal admixture ratio was determined by combining the strength and flowability requirements of the filling material: slump ≥ 24 cm, spread ≥ 80 cm, and the filling material's 3-day uniaxial compressive strength ≥ 1.5 MPa, 7-day strength ≥ 2.5 MPa, and 28-day strength ≥ 5.0 MPa. The mix proportions of ultra-high concentration coarse aggregate filling slurry are shown in Table 1. The particle size curves of rod mill sand, river sand, and waste rock are shown in the figures below. Figure 4-6 As shown.

[0029] The orthogonal experimental results of the strength and fluidity of the filling body obtained when the composite admixture dosage was 1% of cement are shown in Table 2: The optimal mix proportion of the composite admixture suitable for the ultra-high concentration coarse aggregate filling slurry of this embodiment is shown in Table 3. The slump expansion of the ultra-high concentration filling slurry before and after adding the composite admixture is compared below. Figure 7 As shown.

[0030] The addition amount of the composite admixture ranges from 0.5% to 1.5% of the cement mass, all of which meet the fluidity requirements.

[0031] The foregoing has provided a detailed description of a composite admixture for ultra-high concentration coarse aggregate self-fluxing filler slurry, as provided in the embodiments of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this application; furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A self-flushing filler slurry with ultra-high concentration coarse aggregate, characterized in that: The ultra-high concentration coarse aggregate self-flowing filling slurry is composed of filling coarse aggregate, cement, composite admixture, and water. The filling coarse aggregate consists of rod mill sand, river sand, and waste rock. The composite admixture dosage is 0.5% to 1.5% of the cement mass in the filling slurry. The coarse aggregate used for backfilling comprises, by mass percentage, 35-45% rod mill sand, 10-20% river sand, and 30-40% waste rock; the mixed coarse aggregate used for backfilling comprises 35-45% particles with a maximum diameter ≤12mm, 35-45% particles with a maximum diameter greater than 4.75mm, and 8-13% particles with a maximum diameter less than 0.075mm. The solid mass concentration of the ultra-high concentration coarse aggregate self-flowing filling slurry is 82-85%, and the mass ratio of cement to filling coarse aggregate is 1:4-1:

6. The composite admixture is composed of water-reducing agent mother liquor, slump-retaining agent mother liquor, sodium gluconate, industrial white sugar, air-entraining agent, and dilution water; the raw materials are mixed in the following mass ratios: water-reducing agent mother liquor 35-45 parts, slump-retaining agent mother liquor 115-125 parts, sodium gluconate 3-5 parts, industrial white sugar 5-7 parts, air-entraining agent 0.41-0.45 parts, and dilution water 400-410 parts. The water-reducing agent mother liquor is obtained by copolymerizing methyl allyl polyoxyethylene ether macromonomer, acrylic acid small monomer, ammonium persulfate, mercaptopropionic acid, hydrogen peroxide and L-ascorbic acid in an aqueous solution at 40-42℃. The slump retainer mother liquor is obtained by copolymerizing isopentenyl polyoxyethylene ether macromonomer, acrylic acid small monomer, ammonium persulfate, and hydrogen peroxide in an aqueous solution at 34-36℃.

2. The ultra-high concentration coarse aggregate self-fluidizing filler slurry according to claim 1, characterized in that: In the water-reducing agent mother liquor, the molar ratio of acrylic acid to methyl allyl polyoxyethylene ether is 4.5:1; the amount of ammonium persulfate is 0.06% of the mass of the methyl allyl polyoxyethylene ether macromonomer; the amount of hydrogen peroxide is 0.63% of the mass of the methyl allyl polyoxyethylene ether macromonomer; the amount of L-ascorbic acid is 0.13% of the mass of the methyl allyl polyoxyethylene ether macromonomer; and the amount of mercaptopropionic acid is 0.48% of the mass of the methyl allyl polyoxyethylene ether macromonomer.

3. The ultra-high concentration coarse aggregate self-flushing filler slurry according to claim 1, characterized in that: In the slump retainer mother liquor, the molar ratio of acrylic acid to isopentenyl polyoxyethylene ether is 4.3:1; the amount of ammonium persulfate is 0.06% of the mass of the isopentenyl polyoxyethylene ether macromonomer; and the amount of hydrogen peroxide is 0.63% of the mass of the isopentenyl polyoxyethylene ether macromonomer.

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