Chemical preparation process for replacing cement mortar fine aggregate with modified waste glass

Abstract

The invention discloses a chemical preparation process for modifying waste glass to replace cement mortar fine aggregate, and solves the problems that when the existing waste glass fine aggregate is used for lining mortar, the interfacial compatibility is poor, the high salt-sewage synergistic corrosion resistance is weak, and the lining mortar is easily damaged by dry-wet alternation and sewage scouring. The method comprises the following steps: a pretreatment stage: crushing waste glass, dispersing with an EDTA-2NaCa aqueous solution, drying to obtain surface activated glass fine aggregate, and synchronously preparing premixed slurry containing a maleic anhydride cross-linked modified soybean protein-pectin compound and alkaline leaching modified lithium iron phosphate residues; in the modification preparation stage, cement hydration is started firstly, then the premixed slurry and the modified bismuth system-MnO2 composite photocatalytic waste optical fiber preform glass powder are added, and finally the surface activated glass fine aggregate is mixed to be stirred and formed. According to the process, the interface bonding strength, corrosion resistance, scouring resistance and ASR resistance can be improved, waste glass solid waste recycling is facilitated, and the prepared fine aggregate adapts to the working condition of a coastal underground blow-off pipeline and can be used for preparing high-performance lining mortar.

Description

Technical Field

[0001] This invention belongs to the technical field of lining materials for underground sewage pipes, specifically a chemical preparation process for modifying waste glass to replace fine aggregate in cement mortar. Background Technology

[0002] The laying of underground sewage pipelines along the coast is a critical infrastructure project for ensuring the collection and treatment of urban sewage in coastal areas and protecting the nearshore marine ecological environment. These pipelines are mostly laid along coastal mudflats and around river estuaries, carrying out the function of transporting domestic sewage and industrial wastewater, and are crucial to the effectiveness of water environment management in the process of coastal urbanization. Due to the constraints of coastal geological and hydrological conditions, high-salinity groundwater environments are generally present around the pipelines, and the sewage transported has a complex composition. The pipeline lining mortar is in a corrosive environment for a long time, and its performance stability is crucial to the service life and operational safety of the pipeline.

[0003] Currently, the recycling rate of waste glass is low, and most of it is disposed of through landfill, which not only occupies land resources but also easily causes environmental pollution. Processing waste glass into fine aggregate to replace natural sand in the preparation of pipeline lining mortar can not only realize the resource utilization of solid waste but also alleviate the shortage of natural river sand and the high cost of sea sand desalination in coastal areas, showing promising engineering application prospects. However, the special working conditions of coastal underground sewage pipelines and the inherent limitations of waste glass itself interact, and existing technologies still face many technical challenges in practical applications, as follows: Firstly, there is the synergistic corrosion caused by high-salinity environment and mixed wastewater: Coastal groundwater levels fluctuate frequently due to tides, and high-salinity groundwater continuously seeps into the area around the pipeline, leaving the lining mortar in a high-salinity soaking environment for extended periods. Simultaneously, the mixed domestic and industrial wastewater transported by the pipeline contains high concentrations of chloride ions, sulfates, and small amounts of organic acids. These media, combined with the high-salinity environment, cause comprehensive penetration and erosion of the mortar. Lining mortar needs excellent impermeability and corrosion resistance to block the penetration of corrosive media. However, in practical applications, the smooth surface of waste glass aggregate creates gaps at the interface with the cement paste, leading to increased internal porosity and significantly reduced impermeability. Furthermore, the active silicon components in the glass readily react with alkali ions produced during cement hydration to undergo an alkali-silicon reaction (ASR), generating expansive products that trigger microcracks, further exacerbating the penetration of corrosive media and creating a "cracking-corrosion" cycle, ultimately resulting in a loose mortar structure and decreased strength.

[0004] Secondly, there is the combined damage from alternating wet and dry conditions and sewage erosion: Tidal-driven groundwater level fluctuations cause the pipe lining mortar to repeatedly experience a cycle of "soaking in high-salt groundwater – air-drying the empty pipe"; simultaneously, the scouring force generated by the flow of sewage within the pipe continuously erodes the lining surface, and suspended particles carried in the sewage further exacerbate surface wear. The mortar needs to possess good interfacial bonding strength, erosion resistance, and volume stability to resist this type of damage. However, in existing technologies, the interfacial bonding strength between waste glass sand and cement slurry is already insufficient. Under the volume shrinkage and expansion effects of alternating wet and dry conditions, the interface is prone to peeling cracks; sewage erosion further enlarges these cracks, destroying the integrity of the mortar surface and carrying away loose surface materials, ultimately leading to lining surface detachment and failure of protective function.

[0005] Thirdly, there is the challenge of erosion resistance: coastal underground sewage pipes need to withstand the pressure of the surrounding soil, tidal lateral forces, and sewage impact loads, which places high demands on the mechanical properties of the lining mortar. However, in existing technologies, when the replacement rate of waste glass sand exceeds 20%, the compressive strength and splitting tensile strength of the mortar will decrease significantly, making it difficult to meet the mechanical load-bearing requirements.

[0006] Therefore, it is of great significance to develop a chemical preparation process for waste glass to replace fine aggregate in cement mortar that can adapt to complex working conditions such as high-salt synergistic corrosion, alternating wet and dry conditions and combined damage from sewage flushing in coastal underground sewage pipes. Summary of the Invention

[0007] The purpose of this invention is to provide a chemical preparation process for modifying waste glass to replace fine aggregate in cement mortar. This process can effectively improve the problems faced by traditional waste glass fine aggregate cement-based materials under the combined conditions of high salt immersion, alternating wet and dry conditions, and sewage scouring in coastal underground sewage pipes, such as weak interfacial bonding and insufficient resistance to corrosion and scouring.

[0008] The objective of this invention is achieved through the following technical solution: A chemical preparation process for modifying waste glass to replace fine aggregate in cement mortar includes the following steps: S1. Pretreatment stage: After crushing waste glass, it is added to an aqueous solution of calcium disodium ethylenediaminetetraacetate (EDTA-2NaCa), ultrasonically dispersed and dried to obtain surface-activated glass fine aggregate; separately, maleic anhydride crosslinked modified soybean protein-pectin complex, alkali-impregnated modified waste lithium-ion battery cathode lithium iron phosphate residue, composite activator, and nano-calcium carbonate precursor are mixed, deionized water is added and stirred evenly to obtain a premixed slurry; S2. Preparation of modified waste glass fine aggregate: First, mix cement and deionized water, then add premixed slurry and modified bismuth-MnO2 composite photocatalytic waste optical fiber preform glass powder. After stirring thoroughly, add surface-activated glass fine aggregate and stir thoroughly to obtain modified waste glass fine aggregate. In step S1, the composite activator is composed of potassium fluoroaluminate and sodium metabisulfite. The nano-calcium carbonate precursor is composed of calcium nitrate and ammonium bicarbonate. In step S2, the modified bismuth-MnO2 composite photocatalyst waste optical fiber preform glass powder is made from waste optical fiber preform scraps through crushing, etching and hole making, bismuth-MnO2 composite photocatalyst modification, KH550 coating and secondary low-temperature plasma etching treatment. The bismuth-MnO2 composite photocatalyst is obtained by in-situ deposition and calcination on the surface of waste optical fiber preform glass powder after adjusting the pH of the bismuth nitrate-sodium tungstate-potassium permanganate precursor mixed solution with ammonia water.

[0009] As some possible implementation methods of this application, based on 100 parts of waste glass fine aggregate, the following components are used: 2.0-5.0 parts of maleic anhydride crosslinked modified soybean protein-pectin composite, 5-9 parts of modified bismuth-MnO2 composite photocatalytic waste optical fiber preform glass powder, 10-20 parts of alkali-leached modified waste lithium iron phosphate battery cathode residue, 1.5-3.5 parts of composite activator, and 0.3-1.2 parts of nano-calcium carbonate precursor.

[0010] As some possible implementations of this application, in step S1, the particle size of the waste glass fragments is 0.1~5.5mm; in the composite activator, the mass ratio of potassium fluoroaluminate to sodium metabisulfite is 1:(2.5~3.5); and in the nano calcium carbonate precursor, the molar ratio of calcium nitrate to ammonium bicarbonate is 1:(1.0~1.5).

[0011] As one possible implementation of this application, in step S2, the particle size of the modified bismuth-MnO2 composite photocatalytic waste optical fiber preform glass powder is 0.2~6.5μm.

[0012] As some possible implementations of this application, in step S2, in the preparation of the bismuth-MnO2 composite photocatalyst, the concentration of the bismuth nitrate-sodium tungstate mixed solution is 0.4~0.9mol / L; the pH is adjusted to 6.0~7.5 with ammonia water; the calcination temperature is 400~500℃ and the calcination time is 2~4h.

[0013] As one possible implementation of this application, in step S1, 0.2 to 0.6 parts of sodium citrate are added during the preparation of the premixed slurry. Sodium citrate can form a weak complexation system with the iron ions released from the alkali-modified lithium iron phosphate residue of waste lithium-ion battery cathodes, which helps to reduce the complexation competition between iron ions and EDTA-2NaCa, ensuring that EDTA-2NaCa can more fully chelate calcium ions on the glass surface and in the environment, and maintain its inhibitory effect on alkali-silicon reaction (ASR).

[0014] As one possible implementation of this application, in step S1, when preparing the premixed slurry, the alkaline-modified waste lithium-ion battery cathode lithium iron phosphate residue is first mixed and stirred with 0.1-0.5 parts of potassium dihydrogen phosphate, and then the remaining components are added.

[0015] Potassium dihydrogen phosphate can form a stable potassium-phosphorus complex with the phosphorus ions released from the residue, thereby locking in the free phosphorus ions and effectively preventing the phosphorus ions from reacting with the calcium ions ionized from the nano-calcium carbonate precursor to form insoluble calcium phosphate precipitate. This ensures that the nano-calcium carbonate precursor can be successfully deposited in situ in subsequent processes.

[0016] As one of the possible implementation methods of this application, modified waste glass fine aggregate is used to prepare lining mortar for coastal underground sewage pipes.

[0017] Compared with the prior art, the beneficial effects of the present invention are: The chemical preparation process for modifying waste glass to replace fine aggregate in cement mortar provided by this invention can effectively improve the problems faced by traditional waste glass fine aggregate cement-based materials under the combined conditions of high salt immersion, alternating wet and dry conditions, and sewage scouring in coastal underground sewage pipes, such as weak interfacial bonding, insufficient corrosion and scouring resistance, and easy occurrence of alkali-silica reaction (ASR). The specific effects are as follows: After waste glass is ultrasonically dispersed in an EDTA-2NaCa aqueous solution, EDTA-2NaCa can chelate calcium ions on the glass surface and in the environment in advance. At the same time, through surface activation, it reduces the contact opportunity between active silicon in waste glass and alkali ions generated by cement hydration, thereby reducing the risk of alkali-silicon reaction (ASR) from the source.

[0018] The components in the premixed slurry exhibit good synergistic effects: the three-dimensional elastic network structure formed by the maleic anhydride crosslinked modified soybean protein-pectin complex can construct a flexible buffer layer on the surface of glass fine aggregate, alleviating the volume shrinkage and expansion stress of the mortar caused by alternating wet and dry cycles, and reducing glass-cement interface cracks; however, this bio-based coating layer is prone to "salting out-swelling" cycle damage and microcracks under the synergistic effects of coastal high-salt sewage and alternating wet and dry cycles. The introduced nano-calcium carbonate precursor can be deposited in situ inside and on the surface of the bio-based coating layer [in the alkaline environment generated by cement hydration, the nano-calcium carbonate precursor...]. [The reaction of calcium nitrate and ammonium bicarbonate in a metathesis reaction produces nano-calcium carbonate, which is deposited in situ inside and on the surface of the bio-based coating, forming a composite structure of "bio-based elastic network - nano-mineral rigid framework". This can alleviate and improve the salting-out and swelling problems of the bio-based coating, enhance its resistance to salting-out and swelling, and also enhance the load-bearing strength of the glass-cement interface.] In the alkaline leaching modification of waste lithium-ion battery cathode lithium iron phosphate residue, under the action of a composite activator (potassium fluoroaluminate and sodium metabisulfite), potassium fluoroaluminate can reduce the lattice energy of the residue surface and destroy the crystal structure. Fe in the lithium iron phosphate residue mainly exists in the +2 valence state and is easily oxidized by air during alkaline leaching to generate a small amount of Fe. 3+ Sodium metabisulfite provides a reducing environment, which can inhibit Fe... 2+ Oxidation reduces the hydrolysis and precipitation of iron ions; potassium fluoroaluminate and sodium metabisulfite work synergistically to lower the lattice energy of the residue surface, disrupt the crystal structure, and promote Fe... 2+ The active components such as phosphorus dissolve out, and the hydrated calcium phosphate (CPH) and hydrated calcium silicate (CSH) gels formed by the reaction of these components with cement hydration products can synergistically fill the gaps at the glass-cement interface and the pores inside the mortar, thereby improving the density of the mortar system.

[0019] Waste optical fiber preform glass powder, after etching and pore-forming and bismuth-MnO2 composite photocatalytic modification, can form a three-dimensional support structure inside the mortar, improving the material's resistance to sewage erosion and impact abrasion. The bismuth-MnO2 composite photocatalysis is suitable for weak visible light scenarios (light intensity ≥50 lx) such as pipeline maintenance lighting and emergency lighting. MnO2, as an electron capture agent, can accelerate the separation efficiency of electron-hole pairs on the surface of the bismuth catalyst, enhance the interfacial oxidation reaction with dissolved oxygen in sewage, and generate active species (hydroxyl radicals, superoxide anions) that preferentially degrade adsorbed oils, humic substances, and other organic matter that easily cause adhesion failure at the interface, reducing the damage to the glass-cement interface caused by the long-term adhesion of these substances, while also reducing the risk of corrosion from acidic substances produced by their decomposition. Combined with KH550 coating and secondary etching treatment, long-term effectiveness can be further guaranteed: KH550 silane coupling agent can form a dense organic-inorganic composite coating film on the surface of the composite catalyst, enhancing the adhesion between the composite catalyst and the cement. The interfacial bonding between glass powder and cement slurry can also reduce the dissolution channels of bismuth and Mn ions, thereby reducing the risk of dissolved ions interfering with the cement hydration process or polluting water bodies. Secondary low-temperature plasma etching forms micro-nano-level textures on the surface of the KH550 coating layer, which can enhance the mechanical interlocking force between the coating layer and the cement slurry and improve the interfacial bonding stability. At the same time, the micro-nano texture can disrupt the continuous adsorption layer of suspended particulate matter (such as silt and biofilm debris), reducing the obstruction of catalytic active sites by accumulated dirt. Combined with the low surface energy characteristics of the KH550 coating layer, the adsorption and adhesion of particulate matter are further reduced, making it easier for wastewater to carry away accumulated dirt and ensuring long-term catalytic effectiveness.

[0020] The timing design of the preparation process has certain advantages: first, cement and deionized water are mixed and stirred to start hydration, and then the premixed slurry and modified bismuth-MnO2 composite photocatalytic waste optical fiber preform glass powder are added later. This timing can avoid the critical period of cement hydration (the stage of rapid calcium ion generation and initial formation of hydration products), reduce the risk of bismuth ions reacting directly with hydration products to form impurity phases, ensure the stability of the hydration process, and promote the uniform generation of hydration products (such as CSH gel). At the same time, it can allow the modified slurry to fill the pores of the cement slurry more smoothly, further improve the interfacial compatibility between the modified fine aggregate and the cement slurry, enhance the interfacial bonding strength, and reduce interfacial cracks during later service.

[0021] In summary, this process can effectively improve the interfacial transition zone performance between waste glass fine aggregate and cement slurry, optimize the internal pore structure of mortar, enhance the material's corrosion resistance, erosion resistance, and volume stability, and is suitable for the complex working conditions of coastal underground sewage pipelines. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to specific embodiments and comparative examples. Components for which preparation methods are not mentioned in the embodiments and comparative examples are all commercially available conventional products (such as P·O 42.5R grade ordinary silicate cement, calcium nitrate, ammonium bicarbonate, ammonia water, anhydrous ethanol, etc.). All "parts" refer to parts by mass. In industrial production, "kg" can be used as the unit of mass.

[0023] Example 1 1. Preparation of some non-commercially available components (1) Preparation of maleic anhydride crosslinked modified soybean protein-pectin complex: ① Take soybean meal, crush it and pass it through an 80-mesh sieve. Add 10 times the weight of deionized water and stir at 300 r / min for 1 h at 45℃. Centrifuge (5000 r / min, 10 min) and collect the supernatant. Concentrate under reduced pressure (60℃, 0.08 MPa) to a solid content of 20% to obtain soybean protein extract. Separately, take fresh citrus peel, remove impurities and crush it. Add 8 times the weight of deionized water and stir at 350 r / min for 1.5 h at 50℃. Filter and collect the filtrate. Concentrate under reduced pressure (65℃, 0.08 MPa) to a solid content of 20% to obtain pectin extract. ② Mix the above soybean protein extract and pectin extract at a mass ratio of 1:1, add 5% maleic anhydride of the total mass of the mixture, adjust the pH to 7.0 with 5% sodium hydroxide solution, and stir at 400 r / min at 60℃ for 3 h. After the reaction, add 10% hydrochloric acid solution to adjust the pH to 4.0, let it stand for 2 h to precipitate, centrifuge (6000 r / min, 15 min) to collect the precipitate, wash the precipitate with deionized water until neutral, dry it in an oven at 105℃ for 6 h, grind it through a 200 mesh sieve to obtain maleic anhydride crosslinked modified soybean protein-pectin complex.

[0024] (2) Preparation of alkaline-modified lithium iron phosphate residue from waste lithium-ion battery cathodes: ① Take the lithium iron phosphate residue after dismantling and recycling the positive electrode material of waste lithium-ion batteries, remove metal debris and plastic impurities, crush it with a jaw crusher, ball mill it, pass it through a 100-mesh sieve, and dry it in an oven at 105℃ for 4 hours to obtain the pretreated residue. ② Take 100 parts of the pretreatment residue, add 300 parts of 5% sodium hydroxide aqueous solution, stir at 350 r / min at 60℃ for 2 h, and ultrasonically disperse for 5 min every 30 min (power 300W, frequency 40kHz) during the reaction; after the reaction is completed, filter and collect the solid, wash with deionized water until the pH of the filtrate is 7.0, dry in an oven at 105℃ for 5 h, grind through a 200 mesh sieve to obtain alkaline-modified waste lithium iron phosphate battery cathode residue.

[0025] (3) Preparation of modified bismuth-MnO2 composite photocatalytic waste optical fiber preform glass powder: ① Take scraps of waste optical fiber preforms from the optical communication industry, remove impurities, crush and ball mill them, pass them through a 300-mesh sieve, and dry them at 105℃ for 4 hours to obtain crude glass powder from the waste optical fiber preforms; immerse the crude glass powder in a 10% hydrofluoric acid aqueous solution (the amount is 5 times the mass of the crude glass powder), stir and etch at 300r / min at 25℃ for 30 minutes, filter, wash with deionized water 3 times, and dry at 105℃ for 3 hours to obtain etching and hole-forming glass powder; ② Prepare a mixed solution of bismuth nitrate-sodium tungstate-potassium permanganate precursor (bismuth nitrate concentration 0.6 mol / L, sodium tungstate concentration 0.3 mol / L, potassium permanganate concentration 0.08 mol / L, MnO2 is generated by calcination and decomposition of potassium permanganate), add etching and pore-forming glass powder (solid-liquid ratio 1:20, g:ml), and ultrasonically disperse for 30 min (power 300W, frequency 40kHz); adjust the pH to 6.8 with 10% ammonia water, and let it stand and age at 35℃ for 2 h; filter and collect the solid, dry at 105℃ for 4 h, place it in a muffle furnace and calcine at 450℃ for 3 h (heating rate 5℃ / min), and cool to room temperature to obtain bismuth-based MnO2 composite photocatalytic modified glass powder; ③ Take 100 parts of the above modified glass powder, add 200 parts of KH550 silane coupling agent ethanol aqueous solution (ethanol to water volume ratio 1:3, KH550 added amount is 0.4 parts of glass powder mass), ultrasonically disperse for 20 min (power 300W, frequency 40kHz), stir at 300r / min for 1 h at 25℃, dry at 120℃ for 1 h, and then place the obtained coated glass powder in a plasma etching instrument for secondary low temperature (75℃) argon plasma etching treatment, power 90W, etching time 6 min, to obtain modified bismuth-MnO2 composite photocatalytic waste optical fiber preform glass powder (particle size 0.2~6.5μm).

[0026] (4) Preparation of composite activator: Potassium fluoroaluminate and sodium metabisulfite were mixed at a mass ratio of 1:3, pulverized by air jet mill, and passed through a 200-mesh sieve to obtain composite activator.

[0027] (5) Preparation of nano-calcium carbonate precursor: Calcium nitrate and ammonium bicarbonate were mixed and ground through a 200-mesh sieve at a molar ratio of 1:1.2 to obtain nano-calcium carbonate precursor.

[0028] 2. Preparation process of modified waste glass as a substitute for fine aggregate in cement mortar (1) Preprocessing stage: ① Take waste glass, crush it to a particle size of 0.1~5.5mm, add 0.08wt% EDTA-2NaCa aqueous solution (solid-liquid ratio 1:15, g:ml), ultrasonically disperse for 25min (power 300W, frequency 40kHz), take it out and dry it at 105℃ to constant weight to obtain surface activated glass fine aggregate. ② Take 3.0 parts of maleic anhydride cross-linked modified soybean protein-pectin complex, 15 parts of alkali-leached modified waste lithium iron phosphate residue, 2.5 parts of composite activator, and 0.8 parts of nano calcium carbonate precursor, add 50 parts of deionized water, and stir at 400 r / min for 25 min to form a premixed slurry. (2) Preparation of modified waste glass fine aggregate: ① Take 30 parts of P·O 42.5R grade ordinary silicate cement, add 20 parts of deionized water, and stir at 350 r / min for 5 min to start hydration; add all the above premixed slurry and 7 parts of modified bismuth-MnO2 composite photocatalytic waste optical fiber preform glass powder, stir at 450 r / min for 10 min, then add 100 parts of surface-activated glass fine aggregate, stir at 250 r / min at low speed for 25 min, after stirring, place in an environment of 20℃ and 85% humidity for 1 h to obtain modified waste glass fine aggregate; (3) Preparation of lining mortar: Take modified waste glass fine aggregate, P·O 42.5R grade ordinary silicate cement, and river sand in a mass ratio of 1:1.2:2.5, add an appropriate amount of deionized water (to adjust the slurry fluidity to 180±5mm), and stir at 500r / min for 8min to obtain the lining mortar for coastal underground sewage pipes. (4) Curing: Pour the mortar into a 100mm×100mm×100mm mold, place it on a vibrating table (vibration frequency 50Hz, amplitude 0.5mm) and vibrate for 3 minutes to remove air bubbles, and scrape the surface smooth; immediately cover with a moisturizing film and cure for 24 hours at 20℃ and 85% humidity; then spray water twice a day to keep the surface moist and cure for 28 days to obtain the finished product.

[0029] Example 2 Compared to Example 1, the following adjustments are made (all other aspects not mentioned are considered the same as in Example 1): 1. Adjustment of preparation parameters for some non-commercially available components: (1) In the preparation of maleic anhydride crosslinked modified soybean protein-pectin complex, the mass ratio of soybean protein extract to pectin extract was adjusted to 1.2:1, the amount of maleic anhydride added was adjusted to 4% of the total mass of the mixture, and the crosslinking reaction temperature was adjusted to 55℃; (2) In the preparation of alkaline leaching modified lithium iron phosphate residue, the mass fraction of sodium hydroxide aqueous solution was adjusted to 4%, the reaction temperature was adjusted to 55℃, and the stirring speed was adjusted to 320r / min; (3) In the preparation of modified bismuth-MnO2 composite photocatalytic glass powder, the concentration of bismuth nitrate in the mixed solution was adjusted to 0.5 mol / L, the concentration of sodium tungstate was 0.4 mol / L, the concentration of potassium permanganate was 0.07 mol / L, the pH was adjusted to 6.5 with ammonia water, and the calcination temperature was adjusted to 480℃; 2. Adjustment of preparation process parameters: (1) Pretreatment stage: The ultrasonic dispersion time of surface activated glass fine aggregate was adjusted to 40 min, and the amount of premixed slurry components was adjusted to 3.5 parts of maleic anhydride crosslinking modified composite, 13 parts of alkali leaching modified lithium iron phosphate residue, 2.2 parts of composite activator, and 0.6 parts of nano calcium carbonate precursor; (2) Preparation of modified fine aggregate: The amount of cement was adjusted to 28 parts, and the hydration mixing time was adjusted to 4 min; (3) Preparation of lining mortar: The fluidity of the mortar is adjusted to 182±3mm; (4) Curing: The initial curing temperature is adjusted to 22℃ and the humidity to 82%. After 22 hours of curing, the curing is switched to regular water spraying.

[0030] Example 3 Compared to Example 1, the preparation of the premixed slurry involves the following adjustments (unless otherwise mentioned, it is considered the same as in Example 1): Preparation of premixed slurry: Take 3.0 parts of maleic anhydride crosslinked modified soybean protein-pectin complex, 15 parts of alkali-leached modified waste lithium iron phosphate residue, 2.5 parts of composite activator, and 0.8 parts of nano calcium carbonate precursor. First, mix 15 parts of alkali-leached modified lithium iron phosphate residue with 0.3 parts of potassium dihydrogen phosphate, add 10 parts of deionized water, and stir at 350 r / min for 5 min. Then add the remaining components, 0.4 parts of sodium citrate, and 40 parts of deionized water, and stir at 400 r / min for 25 min to form a premixed slurry.

[0031] Testing showed that the modified fine aggregates prepared in Examples 1-3 had leaching concentrations of bismuth and Mn ions that were lower than the limits specified in the "Surface Water Environmental Quality Standard" under long-term soaking conditions, indicating no risk of secondary pollution.

[0032] Testing showed that after soaking in 3.5wt% NaCl solution for 90 days, the bismuth ion leaching concentration of the modified fine aggregates prepared in Examples 1-3 was less than 0.005 mg / L and the Mn ion leaching concentration was less than 0.05 mg / L, both of which were lower than the limits for bismuth and manganese in the "Surface Water Environmental Quality Standard", indicating no risk of secondary pollution.

[0033] Comparative Example 1 Compared to Example 1, the maleic anhydride crosslinked modified soybean protein-pectin complex in the raw materials was removed, while the remaining raw materials and dosages, the preparation process of non-commercially available components, and the preparation process steps of cement-based materials were all the same as in Example 1.

[0034] Comparative Example 2 Compared to Example 1, the alkaline-modified waste lithium-ion battery cathode lithium iron phosphate residue was replaced with an equal mass of unmodified waste lithium-ion battery cathode lithium iron phosphate residue, while all other conditions remained the same as in Example 1.

[0035] Comparative Example 3 Compared to Example 1, the modified bismuth-MnO2 composite photocatalytic waste optical fiber preform glass powder in the raw materials was removed and replaced with an equal mass of unmodified waste optical fiber preform glass powder (only crushed, ball-milled, and dried, without etching for hole formation, photocatalytic modification, KH550 coating, and secondary etching), while all other conditions were the same as in Example 1.

[0036] Comparative Example 4 Compared to Example 1, the nano-calcium carbonate precursor in the raw materials was removed, while all other conditions were the same as in Example 1.

[0037] Comparative Example 5 Compared to Example 1, the composite activator was replaced with an equal mass of the single activator potassium fluoroaluminate, and all other conditions were the same as in Example 1.

[0038] Experimental Example Using the 28-day standard-cured finished lining mortar (size: 100mm×100mm×100mm) prepared in Examples 1-3 and Comparative Examples 1-5 as test samples, performance tests were conducted to adapt to the composite working conditions of coastal underground sewage pipelines. Three parallel samples were set up in each group, and the average value was taken as the final test result. The test results are shown in Table 1. The specific test methods are as follows: 1. High-salt immersion-wet-dry alternating corrosion test: Simulating the coastal underground high-salt groundwater and tidal wet-dry alternating conditions, the test uses "immersion in a mixed salt solution of 3.5wt% NaCl + 0.5wt% Na2SO4 for 12 hours → air drying at 25℃ for 12 hours" as one cycle, and completes a total of 60 cycles; after the cycle, the following are tested: ① Mass loss rate: Mass loss rate = (initial mass - mass after cycle) / initial mass × 100%; ② Compressive strength retention rate: Retention rate = (compressive strength after cycle / initial compressive strength) × 100%; The compressive strength test is based on the "Standard for Test Methods of Physical and Mechanical Properties of Concrete".

[0039] 2. Wastewater flushing-suspended particle abrasion performance test: Simulating the flushing and abrasion conditions of sewage flow in the sewage pipe and suspended particles, under a constant temperature of 25℃, the sample was completely immersed in simulated composite sewage (containing 0.2wt% grease, 0.1wt% humus, and 0.3wt% silt particles with a particle size of 0.1-2mm). The water flow velocity was 2.0m / s for continuous flushing, and a turbulence disturbance device was set up (the water flow direction was switched every 3 hours) for continuous flushing for 96 hours. After flushing, the surface abrasion mass loss was tested: abrasion mass loss = (initial mass - mass after flushing) / initial mass × 100% (Note: Before the test, the sample surface was rinsed with deionized water to remove the grease and silt adsorbed on it, dried to constant weight, and then weighed to eliminate adsorption interference).

[0040] 3. Alkali-Silica Reaction (ASR) Inhibition Effect Test: This test is a necessary item for addressing the core problem of expansion cracking caused by reactive silica in waste glass. The test is conducted according to the "Test Method for Alkali-Aggregate Reaction in Concrete". The rapid mortar bar method is used, and the sample is placed in 80℃, 1mol / L NaOH solution for accelerated curing for 14 days. The test results are as follows: ① 14-day expansion rate: Expansion rate = (Length after accelerated curing - Length after 28-day standard curing) / Length after 28-day standard curing × 100%; ② Surface cracking level: Classified into 0-4 levels according to crack width and distribution density [Level 0: No obvious cracks; Level 1: A few micro-cracks (width < 0.05mm); Level 2: Medium cracks (0.05mm ≤ width ≤ 0.1mm); Level 3: Many cracks (0.1mm < width ≤ 0.2mm); Level 4: Dense cracks (width > 0.2mm)].

[0041] 4. Mechanical performance testing: To verify the mechanical bearing capacity of waste glass fine aggregate, the initial compressive strength and splitting tensile strength of the samples were tested in accordance with the "Standard for Test Methods of Physical and Mechanical Properties of Concrete".

[0042] Table 1: Note: "-" indicates that no relevant experiments were conducted for this performance test.

[0043] As can be seen from Table 1: In Examples 1-2, the mass loss rate after alternating high-salt wet and dry conditions was controlled between 1.2% and 1.4%, and the compressive strength retention rate remained above 89.1%, indicating that both materials possess good resistance to high-salt corrosion and damage from alternating wet and dry conditions. This helps reduce mass loss and strength degradation caused by the penetration of corrosive media in coastal tidal environments. The abrasion mass loss rate after sewage flushing did not exceed 0.55%, indicating good resistance to sewage flushing and suspended particle abrasion, and the ability to cope with surface wear caused by sewage flow in pipelines. The 14-day ASR expansion rate was less than 0.1%, and the surface cracking grade was 1, indicating that both materials had a good inhibitory effect on alkali-silica reaction, and the interface bonding between glass fine aggregate and cement paste was relatively stable, making it less prone to harmful microcracks. The 28-day compressive strength reached above 42.6 MPa, and the 28-day splitting tensile strength was not less than 3.8 MPa, which can meet the basic mechanical bearing requirements of lining mortar for coastal underground sewage pipelines. In summary, the performance indicators of Examples 1-2 are basically suitable for the complex service environment of coastal underground sewage pipelines.

[0044] Example 3, based on Example 1, adds sodium citrate and potassium dihydrogen phosphate, which improves corrosion resistance, erosion resistance and interface stability, making it suitable for coastal sewage pipeline sections with more severe high salt pollution.

[0045] Comparative Example 1, lacking the addition of maleic anhydride cross-linked modified soybean protein-pectin complex, showed significant deterioration in all core properties, indicating that this bio-based composite component plays a crucial role in improving the interfacial bonding strength of the mortar and blocking the penetration of corrosive media. Its absence makes it unsuitable for the combined conditions of high salinity and sewage scouring in coastal areas. Comparative Example 2, using unmodified waste glass fine aggregate, showed slightly improved performance compared to Comparative Example 1, but still significantly worse than the examples, demonstrating that the composite modification treatment of waste glass fine aggregate is crucial for improving system stability. Comparative Example 3, by using unmodified glass powder… The lack of etching and pore-forming, photocatalytic modification, and KH550 coating effects significantly reduced the resistance to sewage erosion and the interfacial stability. Comparative Example 4, due to the absence of nano-calcium carbonate precursor, showed a decline in salt corrosion resistance and interfacial integrity, indicating that the mineral framework formed by this component helps to strengthen the bio-based coating layer and improve the resistance to salting out and swelling. Comparative Example 5, due to the replacement of the composite activator with potassium fluoroaluminate, lacked the synergistic effect of sodium metabisulfite, resulting in insufficient release of activity from the alkaline leaching modified lithium iron phosphate residue, and weaker mortar density and corrosion resistance.

Claims

1. A chemical preparation process for modifying waste glass to replace fine aggregate in cement mortar, characterized in that, The process includes the following steps: S1. Pretreatment stage: After crushing waste glass, add it to an EDTA-2NaCa aqueous solution, disperse it ultrasonically, and dry it to obtain surface-activated glass fine aggregate; Separately, mix maleic anhydride crosslinked modified soybean protein-pectin complex, alkali-leached modified waste lithium-ion battery cathode lithium iron phosphate residue, composite activator, and nano calcium carbonate precursor, add deionized water and stir evenly to obtain a premixed slurry; S2. Preparation of modified waste glass fine aggregate: First, mix cement and deionized water, then add premixed slurry and modified bismuth-MnO2 composite photocatalytic waste optical fiber preform glass powder. After stirring thoroughly, add surface-activated glass fine aggregate and stir thoroughly to obtain modified waste glass fine aggregate. In step S1, the composite activator is composed of potassium fluoroaluminate and sodium metabisulfite; The nano-calcium carbonate precursor is composed of calcium nitrate and ammonium bicarbonate. In step S2, the modified bismuth-MnO2 composite photocatalyst waste optical fiber preform glass powder is made from waste optical fiber preform scraps through crushing, etching and hole making, bismuth-MnO2 composite photocatalyst modification, KH550 coating and secondary low-temperature plasma etching treatment. The bismuth-MnO2 composite photocatalyst is obtained by in-situ deposition and calcination on the surface of waste optical fiber preform glass powder after adjusting the pH of the bismuth nitrate-sodium tungstate-potassium permanganate precursor mixed solution with ammonia water.

2. The chemical preparation process according to claim 1, characterized in that, Based on 100 parts of waste glass fine aggregate, the following components were used: 2.0-5.0 parts of maleic anhydride crosslinked modified soybean protein-pectin composite, 5-9 parts of modified bismuth-MnO2 composite photocatalytic waste optical fiber preform glass powder, 10-20 parts of alkali-leached modified waste lithium iron phosphate battery cathode residue, 1.5-3.5 parts of composite activator, and 0.3-1.2 parts of nano-calcium carbonate precursor.

3. The chemical preparation process according to claim 1, characterized in that, In step S1, the particle size of the waste glass is 0.1~5.5mm; in the composite activator, the mass ratio of potassium fluoroaluminate to sodium metabisulfite is 1:(2.5~3.5); in the nano calcium carbonate precursor, the molar ratio of calcium nitrate to ammonium bicarbonate is 1:(1.0~1.5).

4. The chemical preparation process according to claim 1, characterized in that, In step S2, the particle size of the modified bismuth-MnO2 composite photocatalytic waste optical fiber preform glass powder is 0.2~6.5μm.

5. The chemical preparation process according to claim 1, characterized in that, In step S2, during the preparation of the bismuth-MnO2 composite photocatalyst, the concentration of the bismuth nitrate-sodium tungstate mixed solution is 0.4~0.9 mol / L; the pH is adjusted to 6.0~7.5 with ammonia; the calcination temperature is 400~500℃ and the calcination time is 2~4h.

6. The chemical preparation process according to claim 2, characterized in that, In step S1, when preparing the premixed slurry, 0.2 to 0.6 parts of sodium citrate also need to be added.

7. The chemical preparation process according to claim 2, characterized in that, In step S1, when preparing the premixed slurry, the alkaline-modified waste lithium-ion battery cathode lithium iron phosphate residue is first mixed and stirred with 0.1-0.5 parts of potassium dihydrogen phosphate, and then the remaining components are added.

8. The chemical preparation process according to claim 1, characterized in that, The modified waste glass fine aggregate is used to prepare lining mortar for coastal underground sewage pipes.

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