A low-carbon low-heat high-anti-crack mass concrete based on a full-solid waste cementitious material

Abstract

The application provides a full-solid-waste cementitious material-based low-carbon low-heat high-anti-crack mass concrete, and components of the cementitious material include: phase-change lithium slag powder, phosphorous slag, carbide slag, phosphorous gypsum and modified zeolite powder; the phase-change lithium slag powder is in a core-shell structure, porous lithium slag is used as a carrier, a first phase-change material is filled in a pore of the carrier, and a silicate shell layer is formed by wrapping the surface of the carrier with silicate; the modified zeolite powder is zeolite powder loaded with an organic shrinkage-reducing agent; the composite fiber is in a core-shell structure, a core material is composed of porous metal fiber loaded with organic or inorganic phase-change material; and a sheath layer is wrapped outside the core material by adopting heat-shrinkable fiber which is heat-treated to generate heat shrinkage. Through the synergistic effect of the full-solid-waste cementitious material and the sheath layer temperature shrinkage-core material phase-change composite fiber, optimal regulation and control of the whole process of heat-force-deformation of the mass concrete are realized, and finally, a high-performance mass concrete which is excellent in low-carbon environmental protection, low heat, high anti-crack and the like is obtained.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a low-carbon, low-heat, and high-crack-resistant large-volume concrete based on all-solid-waste cementitious materials. In particular, it relates to a combination of a low-carbon cementitious material prepared entirely from industrial solid waste and a sheath-core phase change composite fiber with dual functions of active temperature control and passive preloading, for the preparation of low-carbon, low-heat, and high-crack-resistant large-volume concrete. Background Technology

[0002] Large-volume concrete structures are prone to temperature cracks due to the internal and external temperature differences and shrinkage caused by the heat release during cement hydration, which seriously affects the durability and safety of the structure. Current technologies mainly face the following bottlenecks:

[0003] Material-level dependence on high-carbon cement: Using medium- and low-heat cement and adding fly ash / mineral powder can partially reduce the heat of hydration, but it still cannot get rid of the dependence on high-carbon-emission cement clinker, and the reduction in heat of hydration is limited.

[0004] Single fiber function: The addition of polypropylene fiber, steel fiber, etc. mainly inhibits crack propagation through physical bridging, which is a "passive resistance" and cannot reduce the temperature stress driving force that leads to cracking from the source.

[0005] Incomplete utilization of solid waste: In existing technologies, solid waste is mostly used as a substitute for cement, with limited dosage. Furthermore, there is insufficient research on the synergistic cementing mechanism of various solid wastes such as lithium slag, carbide slag, and red mud in a completely cement-free system, resulting in problems such as low early strength, high brittleness, and uncertain shrinkage performance in the material system.

[0006] Poor technical synergy: Existing crack control technologies are mostly "working alone" and lack a complete chain of time-series coordinated solutions from "stress source control" to "stress field regulation".

[0007] Therefore, this invention aims to provide a disruptive comprehensive solution that fundamentally solves the cracking problem of large-volume concrete through material innovation and functional synergy. Summary of the Invention

[0008] In view of this, the mass concrete of this invention utilizes the latent heat of phase change of cementitious materials and composite fibers to actively regulate the temperature field. The cementitious materials used construct a synergistic system integrating "low carbon," "alkaline-sulfate composite activation," "self-generated micro-expansion," and "intelligent shrinkage reduction." Beneficial pre-compression stress is introduced into the concrete through the thermal shrinkage effect of the fiber sheath, thereby synergistically improving the crack resistance of the concrete from multiple dimensions: "stress source control," "temperature field homogenization to reduce the temperature difference between the inner and outer surfaces of the concrete," and "matrix reinforcement," while ensuring that its mechanical properties are not significantly reduced due to the introduction of the phase change material PCM. Through the synergistic effect of the all-solid waste cementitious materials and the thermal shrinkage of the sheath-core phase change composite fiber, optimal control of the entire thermal-mechanical-deformation process of mass concrete is achieved, ultimately obtaining a high-performance mass concrete that exhibits excellent performance in terms of low carbon emissions, environmental friendliness, low heat, and high crack resistance.

[0009] The technical solution of the present invention is implemented as follows: In the first aspect, the present invention provides a solid waste cementitious material, which, calculated by mass percentage as 100%, comprises 20%~35% phase change lithium slag powder, 25%~40% phosphorus slag, 8%~20% carbide slag, 10%~20% phosphogypsum and 5%~15% modified zeolite powder;

[0010] The phase change lithium slag powder has a core-shell structure, with porous lithium slag as a carrier. The pores of the carrier are filled with a first phase change material, and the surface of the carrier is wrapped with an active aluminosilicate shell layer.

[0011] The modified zeolite powder is zeolite powder loaded with organic shrinkage reducing agents.

[0012] Specifically, the functions and synergistic mechanisms of the various components of the cementitious material are as follows:

[0013] 1. Phase change lithium slag powder:

[0014] 1) Carrier function: After calcination, the porous lithium slag has unobstructed pores and increased specific surface area, providing a basis for loading the first phase change material PCM and subsequent hydration reaction.

[0015] 2) Temperature control function: The PCM (preferably octadecane, phase change temperature ~28℃) under load actively and efficiently absorbs heat through the latent heat of phase change during the hydration exothermic peak, thereby reducing the temperature rise of the system to the extreme from a physical level.

[0016] 3) Self-healing function: The active aluminosilicate shell generated on the surface through in-situ reaction can not only prevent PCM leakage, but also generate CSH and other products in the later stage of hydration to repair the micropores that may be caused by changes in the occupancy of PCM phase transition, ensuring that the final strength is not damaged.

[0017] 4) Retarding and activation: Lithium slag itself has a certain retarding effect, which helps to reduce the early hydration rate and works synergistically with the physical cooling effect of PCM; its activated glass provides long-term strength.

[0018] 2. Phosphorus slag and lithium slag work synergistically. Phosphorus slag provides the main source of silica and alumina, and its glassy structure dissolves and participates in the reaction under alkaline conditions. The retarding properties of phosphorus slag, combined with those of lithium slag, further smooth the hydration exothermic curve.

[0019] 3. Calcium carbide slag is used as an alkaline activator in the system, after being dried and ground (specific surface area ≥ 400 m²). 2 After ( / kg), it provides continuous Ca(OH)2 and OH. - It can stimulate the pozzolanic activity of lithium slag, phosphorus slag and zeolite powder.

[0020] 4. After calcination, phosphogypsum is converted into hemihydrate gypsum, which acts as a sulfate activator. It reacts with Al2O3 and Ca(OH)2 in the system to stably generate ettringite, which not only provides early strength, but more importantly, endows the material with continuous micro-expansion properties to compensate for later shrinkage.

[0021] 5. Modified zeolite powder: The shrinkage reducing agent adsorbed by the porous zeolite powder is intelligently released when the humidity inside the cement stone decreases, effectively reducing the surface tension of the capillary solution, thereby significantly inhibiting the drying shrinkage of concrete and preventing concrete cracking.

[0022] Based on the above technical solutions, preferably, the first phase change material is one or more of paraffin, fatty acids, and hydrated salts; the fatty acid is one or more of decanoic acid, lauric acid, myristic acid, and palmitic acid; the hydrated salt is one or more of disodium hydrogen phosphate dodecahydrate, barium hydroxide octahydrate, sodium sulfate decahydrate, and magnesium nitrate hexahydrate; and the organic shrinkage reducing agent is one or more of glycerol, 1,5-pentanediol, NH2-PEG-CH3, dipropylene glycol monobutyl ether, and dipropyl ethylene glycol.

[0023] Based on the above technical solutions, the preferred method for preparing the phase change lithium slag powder is as follows:

[0024] S11 involves calcining and grinding lithium slag to obtain a specific surface area of ​​450-750 m². 2 / kg of lithium slag powder;

[0025] S12, under vacuum and pressure conditions, lithium slag powder is impregnated in molten first phase change material; then the impregnated product is taken out, cooled and placed in sodium silicate solution for reaction; finally, the reacted product is filtered out, washed with water until the pH of the filtrate is neutral, and dried to obtain phase change lithium slag powder.

[0026] Based on the above technical solutions, preferably, in step S11, the calcination temperature of the lithium slag is 700-800℃ and the time is 2-3h; in step S12, the vacuum degree is -0.09~-0.1MPa and the pressure is 0.5-1.0MPa; the mass ratio of the first phase change material to the mixed powder is 1:3~5, the mass concentration of the sodium silicate solution is 8%-12%, and the pH value is 11-12.

[0027] Based on the above technical solutions, preferably, the preparation method of the modified zeolite powder is as follows: grinding the zeolite powder to a specific surface area ≥ 600 m². 2 / kg, then mix the zeolite powder with the organic shrinkage agent solution and stir at 200-300 rpm for 30-60 min; after that, dry the mixed slurry at 60-70℃ in an inert atmosphere.

[0028] Specifically, the zeolite powder after ultrafine grinding (specific surface area ≥ 600 m² / kg) exhibits high pozzolanic activity, contributing to early strength. Its porous structure pre-adsorbed shrinkage-reducing agent is intelligently released when the internal humidity of the cement stone decreases, effectively reducing the surface tension of the capillary solution and thus significantly inhibiting drying shrinkage.

[0029] Based on the above technical solutions, preferably, the mass ratio of zeolite powder to organic shrinkage agent solution is 1:5~15, and the mass concentration of organic shrinkage agent solution is 5%~10%.

[0030] Secondly, the present invention provides a method for preparing a solid waste cementitious material, comprising the following steps:

[0031] S21, Pretreatment: Dry the carbide slag and grind it to a specific surface area ≥ 400 m². 2 / kg, to obtain calcium carbide slag powder; grind phosphorus slag powder to obtain a specific surface area of ​​400-650m². 2 / kg of phosphorus slag powder; calcining phosphogypsum at 160-200℃ for 1.5-2h yields hemihydrate gypsum;

[0032] S22, mix phase change lithium slag powder, modified zeolite powder, carbide slag powder pretreated in step S21, phosphorus slag powder and hemihydrate gypsum in proportion.

[0033] Thirdly, the present invention provides a low-carbon, low-heat, high-crack-resistant large-volume concrete based on all-solid waste cementitious materials. According to the weight percentage, the raw materials of the concrete include 350-500 parts of the above-mentioned all-solid waste cementitious materials, 900-1250 parts of coarse aggregate, 650-850 parts of fine aggregate, 4-10.5 parts of polycarboxylate superplasticizer, 140-200 parts of water, and 4-20 parts of composite fiber.

[0034] The composite fiber has a core-shell structure, with the core material consisting of porous metal fibers loaded with a second phase change material; the sheath material includes one or more of polybutylene terephthalate, polypropylene, and high-density polyethylene; the sheath is heat-shrinkable and covers the outside of the core material after heat treatment.

[0035] This invention achieves superior results beyond those of using either solid waste cementitious material or composite fiber in terms of both time series and function. The specific synergistic benefits are as follows:

[0036] 1. The "double inhibition" effect of heat of hydration:

[0037] 1) First level (material origin): The hydration reaction rate and total heat release of the all-solid waste cementitious material system are much lower than those of silicate cement.

[0038] 2) Second stage (physical heat absorption): During the peak period of hydration heat release, the core material of the composite fiber undergoes a phase change and absorbs a large amount of latent heat (≥150 kJ / kg), just like implanting countless "micro radiators" inside the concrete.

[0039] 3) Synergistic Results: The two work together to achieve dual suppression of hydration temperature rise from both chemical origin and physical process. Experiments have shown that the peak temperature rise of adiabatic concrete can be reduced by 12-16℃ compared to traditional cement concrete, significantly weakening the driving force of temperature cracks at the root.

[0040] 2. The sequential coordination mechanism of "compensation before preloading" for shrinkage stress:

[0041] 1) Early-stage compensation: The ettringite generated by phosphogypsum in the all-solid-waste cementitious materials produces micro-expansion in the early stages, compensating for chemical shrinkage and some autogenous shrinkage. The shrinkage-reducing agent loaded with zeolite powder can simultaneously exert a chemical shrinkage-reducing effect to reduce concrete shrinkage.

[0042] 2) Post-contraction: During the cooling stage, the all-solid waste cementitious material will shrink like ordinary concrete. At this time, the sheath of the composite fiber (because its thermal expansion coefficient is much greater than that of concrete) begins to shrink significantly. Due to its strong bond with the matrix and the prestressed design, this shrinkage is restrained, thereby applying a continuous three-dimensional prestress (0.5-15MPa) to the concrete matrix.

[0043] 3) Synergistic results: The micro-expansion of the material and the pre-compression stress of the fiber are connected in time, forming a multi-stage compensation system for the whole process of concrete shrinkage, so that the concrete is always under pressure or low stress during the most dangerous stage of shrinkage.

[0044] 3. The synergistic effect of "toughening and reinforcing" in mechanical properties:

[0045] 1) Shortcomings of solid waste cementitious materials: Although micro-expansion has been achieved through formula optimization, its inherent defects of high brittleness and low early tensile strength still exist.

[0046] 2) Compensation from composite fibers:

[0047] Bridging and toughening: High-modulus porous metal fiber core materials can effectively bridge cracks after concrete cracking, prevent crack propagation, and significantly improve the material's toughness (post-cracking behavior) and fracture energy.

[0048] Reinforcement and crack prevention: The random distribution of fibers inside concrete can block the generation and development of microcracks, thereby improving the early tensile strength of concrete, which is exactly what all-solid waste cementitious materials need.

[0049] 3) Synergistic results: The bridging and crack-resistant effects of the fibers directly compensate for the brittleness of the solid waste cementitious materials, while the pre-compression stress they provide further enhances the effective tensile strength of the materials, forming a strengthening mode that combines "strengthening the body" and "applying external assistance".

[0050] Based on the above technical solutions, preferably, the preparation method of the composite fiber is as follows: porous metal fibers are impregnated in a silane coupling agent solution to obtain surface-modified metal fibers. Then, under vacuum conditions of -0.09 to -0.1 MPa and pressure of 0.5 to 1.0 MPa, the modified metal fibers are impregnated in molten second phase change material. After completion, the two ends of the fiber are sealed with epoxy resin micro-adhesive to obtain a core material. Then, the core material is heated and coated with molten sheath polymer, followed by heat treatment at 100-110℃ for 10-20 minutes, and the sheath shrinks to obtain a sheath thermal shrinkage-core phase change composite fiber.

[0051] Based on the above technical solutions, preferably, the coarse aggregate is continuously graded crushed stone with a particle size of 5-25mm, and the fine aggregate is medium sand with a fineness modulus of 2.6-2.9; the second phase change material is paraffin (C18-C28), decanoic acid, lauric acid and sodium sulfate decahydrate.

[0052] Fourthly, this invention provides a method for preparing low-carbon, low-heat, and high-crack-resistant large-volume concrete based on all-solid waste cementitious materials, comprising the following steps:

[0053] S31, Feeding and Mixing: A forced mixer is used. First, coarse and fine aggregates are added and dry-mixed for 30 seconds; then, all-solid waste cementitious material is added and dry-mixed for 60 seconds until uniform; mixing water containing polycarboxylate superplasticizer is added and mixed for 120 seconds; finally, composite fibers are evenly sprinkled in and mixed for another 60 seconds before being discharged from the machine.

[0054] S32, Casting and Curing: Control the temperature upon pouring into the mold to ≤30℃. Cast in layers and vibrate thoroughly. Immediately after casting, cover with insulation and moisture-retaining material, and cure for no less than 14 days.

[0055] The low-carbon, low-heat, and high-crack-resistant large-volume concrete based on all-solid waste cementitious materials of the present invention has the following advantages over the prior art:

[0056] (1) The solid waste cementitious material of the present invention constructs a synergistic system that integrates "active heat absorption and cooling", "alkaline-sulfate composite activation", "self-generated micro-expansion" and "intelligent shrinkage", and simultaneously solves the problem of temperature control and crack prevention of large-volume concrete.

[0057] (2) This invention achieves optimal control of the entire process of thermal-mechanical-deformation of large-volume concrete through the synergistic effect of solid waste cementitious materials and sheath thermal shrinkage-core phase change composite fibers, and finally obtains a high-performance large-volume concrete that is excellent in terms of low carbon and environmental protection, low heat and high crack resistance. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0059] Figure 1 This is a schematic diagram of the phase change lithium slag powder of the present invention; in the figure, 11-the first phase change material internally loaded, 12-the internal pores of the lithium slag powder, 13-the active aluminosilicate shell.

[0060] Figure 2 This is a schematic diagram of the composite fiber of the present invention; in the figure, 21-the second phase change material loaded in the core layer, 22-the porous metal fiber in the core layer, and 23-the thermo-shrinkable fiber in the sheath layer.

[0061] Figure 3 This is a schematic diagram of zeolite powder loaded with shrinkage-reducing agent according to the present invention; in the figure, 31-the organic shrinkage-reducing agent loaded internally, 32-the internal pores of zeolite powder, and 33-the surface pores of zeolite powder. Detailed Implementation

[0062] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0063] The NH2-PEG-CH3 used in this invention is a polyethylene glycol with an amino (-NH2) end and a methyl (-CH3) end, and a molecular weight of 1000-5000 Da. Dipropylethylene glycol is dipropylene glycol.

[0064] Example 1

[0065] This embodiment provides a solid waste cementitious material, which includes 25 kg of phase change lithium slag powder, 35 kg of phosphorus slag, 15 kg of carbide slag, 20 kg of phosphogypsum, and 5 kg of modified zeolite powder, totaling 100 kg.

[0066] The preparation method of phase change lithium slag powder is as follows:

[0067] S11, 25 kg of lithium slag was calcined at 750℃ for 2.5 h and then ground to obtain a specific surface area of ​​500 m². 2 / kg of lithium slag powder.

[0068] S12, under vacuum of -0.095 MPa and pressure of 0.8 MPa, lithium slag powder was impregnated in octadecane, the first phase change material, at a mass of 4 times (100 kg) for 3 h; then the impregnated product was taken out, cooled, and placed in a sodium silicate solution with a mass concentration of 10% and a pH of 11 for 1.5 h; finally, the reacted lithium slag powder was filtered out, washed with water until the pH of the filtrate was neutral, and dried at 65 °C to constant weight to obtain phase change lithium slag powder.

[0069] The preparation method of modified zeolite powder is as follows: grind 15 kg of zeolite powder to a specific surface area ≥ 600 m². 2 / kg, then the zeolite powder was mixed with an organic shrinkage reducing agent (1000 Da NH2-PEG-CH3 and dipropylene glycol monobutyl ether, mixed at a mass ratio of 1:1) solution (mass concentration of 8%) at a mass ratio of 1:10, and then stirred at 250 rpm for 40 min; after the mixture was dried at 65℃ under an inert atmosphere to constant weight to obtain modified zeolite powder.

[0070] The preparation method of the above-mentioned solid waste cementitious material includes the following steps:

[0071] S21, Pretreatment: Dry the carbide slag and grind it to a specific surface area ≥ 400 m². 2 / kg of calcium carbide slag powder was obtained, and phosphorus slag powder was ground to obtain a specific surface area of ​​500m². 2 / kg of phosphorus slag powder, calcined at 180℃ for 2h to obtain hemihydrate gypsum;

[0072] S22, mix phase change lithium slag powder, modified zeolite powder, and carbide slag powder, phosphorus slag powder and hemihydrate gypsum pretreated in step S21 in proportion.

[0073] This embodiment also provides a low-carbon, low-heat, high-crack-resistant large-volume concrete based on all-solid waste cementitious materials. The raw materials of the concrete include 420 kg / m³ of all-solid waste cementitious materials. 3 Coarse aggregate (continuously graded granite with a particle size of 5-25mm) 1100kg / m³ 3 Fine aggregate (medium sand with a fineness modulus of 2.6-2.9) 700kg / m³ 3 Polycarboxylate superplasticizer 5.5kg / m 3 160kg / m³ of water 3 and composite fiber 12.6kg / m 3 .

[0074] The composite fiber was prepared as follows: Porous stainless steel fibers with a diameter of 0.3 mm, a length of 18 mm, and a porosity of 50% were impregnated (2 cm submerged) in a 1 wt% silane coupling agent ethanol solution for 10 min. After 10 min, the fibers were removed and dried at 80°C to obtain surface-modified metal fibers. Under a vacuum of -0.098 MPa and a pressure of 0.7 MPa, the modified metal fibers were impregnated (2 cm submerged) in molten paraffin wax (C25, phase change point 28.5°C, latent heat 180 kJ / g) as a second phase change material. After cooling, the fiber ends were sealed with epoxy numerical micro-adhesive to obtain the core material. The core material was preheated to 80°C and coated with molten high-density polyethylene (molecular weight 200,000) in a crosshead mold at 200°C. It was then cooled and shaped in a water-cooling bath to form a sheath layer with a thickness of 0.25 mm. This was followed by further cooling and shaping to obtain the composite fiber. The coated composite fiber was heat-treated at 105℃ for 15 minutes, causing the sheath to shrink, resulting in a sheath-core phase change composite fiber.

[0075] The above-mentioned method for preparing large-volume concrete includes the following steps:

[0076] S31, Feeding and Mixing: A forced mixer is used. First, coarse and fine aggregates are added and dry-mixed for 30 seconds; then, all-solid waste cementitious material is added and dry-mixed for 60 seconds until uniform; mixing water containing polycarboxylate superplasticizer is added and mixed for 120 seconds; finally, composite fibers are evenly sprinkled in and mixed for another 60 seconds before being discharged from the machine.

[0077] S32, Casting and Curing: Control the temperature upon pouring into the mold to ≤30℃. Cast in layers and vibrate thoroughly. Immediately after casting, cover with insulation and moisture-retaining material, and cure for no less than 14 days.

[0078] Example 2

[0079] This embodiment provides a solid waste cementitious material, which includes 20 kg of phase change lithium slag powder, 40 kg of phosphorus slag, 20 kg of calcium carbide slag, 10 kg of phosphogypsum, and 10 kg of modified zeolite powder.

[0080] The preparation method of phase change lithium slag powder is as follows:

[0081] S11, 20 kg of lithium slag was calcined at 700℃ for 3 hours and then ground to obtain a specific surface area of ​​450 m². 2 / kg of lithium slag powder;

[0082] S12, under vacuum of -0.09 MPa and pressure of 0.5 MPa, lithium slag powder was immersed in 3 times its mass (60 kg) of molten first phase change material (decanoic acid and lauric acid, mixed in a mass ratio of 1:1) for 2 h; then the immersed product was taken out, cooled and placed in a sodium silicate solution with a mass concentration of 8% and a pH of 11 for 2 h; finally, the reacted product was filtered out, washed with water until the pH of the filtrate was neutral, and dried at 65 °C to constant weight to obtain phase change lithium slag powder.

[0083] The preparation method of modified zeolite powder is as follows: grind 15 kg of zeolite powder to a specific surface area ≥ 600 m². 2 / kg, then the zeolite powder was mixed with an organic shrinkage reducing agent (glycerol and 1,5-pentanediol, mixed at a mass ratio of 1:1) solution (mass concentration of 5%) at a mass ratio of 1:15, and then stirred at 200 rpm for 60 min; after the mixture was finished, the slurry was dried at 60℃ under an inert atmosphere to constant weight to obtain modified zeolite powder.

[0084] The preparation method of the above-mentioned solid waste cementitious material includes the following steps:

[0085] S21, Pretreatment: Dry the carbide slag and grind it to a specific surface area ≥ 400 m². 2 / kg of calcium carbide slag powder was obtained, and phosphorus slag powder was ground to obtain a specific surface area of ​​450m². 2 / kg of phosphorus slag powder, phosphogypsum calcined at 160℃ for 2h to obtain hemihydrate gypsum;

[0086] S22, mix phase change lithium slag powder, modified zeolite powder, carbide slag powder pretreated in step S21, phosphorus slag powder and hemihydrate gypsum in proportion.

[0087] This embodiment also provides a low-carbon, low-heat, high-crack-resistant large-volume concrete based on all-solid waste cementitious materials. The raw materials of the concrete include 350 kg / m³ of all-solid waste cementitious materials. 3 Coarse aggregate (continuously graded granite with a particle size of 5-25mm) 1250kg / m³ 3 Fine aggregate (medium sand with a fineness modulus of 2.6-2.9) 650kg / m³ 3Polycarboxylate superplasticizer 4kg / m 3 140 kg / m³ of water 3 and composite fiber 4kg / m 3 .

[0088] The composite fiber is prepared as follows: Porous stainless steel fibers with a diameter of 0.3 mm, a length of 18 mm, and a porosity of 50% are impregnated (2 cm of fiber submerged) in a 1 wt% silane coupling agent ethanol solution for 10 min. After the impregnation, the fibers are removed and dried at 80°C to obtain surface-modified metal fibers. Under a vacuum of -0.09 MPa and a pressure of 0.5 MPa, the modified metal fibers are impregnated (2 cm of fiber submerged) in molten second phase change materials decanoic acid and lauric acid (mass ratio 1:1). After acceptance and cooling, the fiber ends are sealed with epoxy numerical micro-adhesive to obtain the core material. The core material is preheated to 80°C and coated with molten polypropylene (molecular weight 10000) in a crosshead mold at 200°C. It is then cooled and shaped in a water-cooling bath to form a sheath layer with a thickness of 0.25 mm. Finally, it is cooled and shaped again to obtain the composite fiber. The coated composite fiber was heat-treated at 100℃ for 20 minutes, causing the sheath to shrink, resulting in a sheath-core phase change composite fiber.

[0089] The above-mentioned method for preparing large-volume concrete includes the following steps:

[0090] S31, Feeding and Mixing: A forced mixer is used. First, coarse and fine aggregates are added and dry-mixed for 30 seconds; then, all-solid waste cementitious material is added and dry-mixed for 60 seconds until uniform; mixing water containing polycarboxylate superplasticizer is added and mixed for 120 seconds; finally, composite fibers are evenly sprinkled in and mixed for another 60 seconds before being discharged from the machine.

[0091] S32, Casting and Curing: Control the temperature upon pouring into the mold to ≤30℃. Cast in layers and vibrate thoroughly. Immediately after casting, cover with insulation and moisture-retaining material, and cure for no less than 14 days.

[0092] Example 3

[0093] This embodiment provides a solid waste cementitious material, which includes 35 kg of phase change lithium slag powder, 25 kg of phosphorus slag, 8 kg of calcium carbide slag, 17 kg of phosphogypsum, and 15 kg of modified zeolite powder.

[0094] The preparation method of phase change lithium slag powder is as follows:

[0095] S11, 35 kg of lithium slag was calcined at 800℃ for 2 hours and then ground to obtain a specific surface area of ​​750 m². 2 / kg of lithium slag powder;

[0096] S12, under vacuum of -0.1 MPa and pressure of 1.0 MPa, lithium slag powder was immersed in 5 times its mass (175 kg) of molten first phase change material (sodium hydrogen phosphate dodecahydrate and barium hydroxide octahydrate, mixed at a mass ratio of 1:1) for 4 h; then the immersed product was taken out, cooled and placed in a sodium silicate solution with a mass concentration of 12% and a pH of 12 for 2 h; finally, the reacted product was filtered out, washed with water until the pH of the filtrate was neutral, and dried at 65 °C to constant weight to obtain phase change lithium slag powder.

[0097] The preparation method of modified zeolite powder is as follows: grind 15 kg of zeolite powder to a specific surface area ≥ 600 m². 2 / kg, then the zeolite powder was mixed with an organic shrinkage reducing agent (5000 Da NH2-PEG-CH3 and dipropyl ethylene glycol, mixed at a mass ratio of 1:1) solution (mass concentration of 10%) at a mass ratio of 1:5, and then stirred at 300 rpm for 30 min; after the mixture was dried at 70℃ under an inert atmosphere to constant weight to obtain modified zeolite powder.

[0098] The preparation method of the above-mentioned solid waste cementitious material includes the following steps:

[0099] S21, Pretreatment: Dry the carbide slag and grind it to a specific surface area ≥ 400 m². 2 / kg of calcium carbide slag powder was obtained, and phosphorus slag powder was ground to obtain a specific surface area of ​​650m². 2 / kg of phosphorus slag powder, calcined at 200℃ for 1.5h to obtain hemihydrate gypsum;

[0100] S22, mix phase change lithium slag powder, modified zeolite powder, carbide slag powder pretreated in step S21, phosphorus slag powder and hemihydrate gypsum in proportion.

[0101] This embodiment also provides a low-carbon, low-heat, high-crack-resistant large-volume concrete based on all-solid waste cementitious materials, wherein the raw materials of the concrete include 500 kg / m³ of all-solid waste cementitious materials. 3 900 kg / m³ of coarse aggregate (continuously graded granite with a particle size of 5-25 mm) 3 Fine aggregate (medium sand with a fineness modulus of 2.6-2.9) 850kg / m³ 3 Polycarboxylate superplasticizer 10.5 kg / m 3 200kg / m 3 and composite fiber 20kg / m 3 .

[0102] The composite fiber is prepared as follows: porous stainless steel fibers with a diameter of 0.3 mm, a length of 18 mm, and a porosity of 50% are impregnated (2 cm of fiber submerged) in a 1 wt% silane coupling agent ethanol solution for 10 min. After the impregnation, the fibers are removed and dried at 80°C to obtain surface-modified metal fibers. Under a vacuum of -0.1 MPa and a pressure of 1.0 MPa, the modified metal fibers are impregnated (2 cm of fiber submerged) in molten sodium sulfate decahydrate, a second phase change material. After cooling, the fiber ends are sealed with epoxy numerical micro-adhesive to obtain the core material. The core material is preheated to 80°C and coated with molten polybutylene terephthalate (molecular weight 30,000) in a crosshead mold at 200°C. It is then cooled and shaped in a water-cooling bath to form a sheath layer with a thickness of 0.25 mm. Finally, it is cooled and shaped again to obtain the composite fiber. The coated composite fiber was heat-treated at 110℃ for 10 minutes, causing the sheath to shrink, resulting in a sheath-core phase change composite fiber.

[0103] The above-mentioned method for preparing large-volume concrete includes the following steps:

[0104] S31, Feeding and Mixing: A forced mixer is used. First, coarse and fine aggregates are added and dry-mixed for 30 seconds; then, all-solid waste cementitious material is added and dry-mixed for 60 seconds until uniform; mixing water containing polycarboxylate superplasticizer is added and mixed for 120 seconds; finally, composite fibers are evenly sprinkled in and mixed for another 60 seconds before being discharged from the machine.

[0105] S32, Casting and Curing: Control the temperature upon pouring into the mold to ≤30℃. Cast in layers and vibrate thoroughly. Immediately after casting, cover with insulation and moisture-retaining material, and cure for no less than 14 days.

[0106] Example 4

[0107] Compared with Example 1, Example 4 has a reduced content of phase change lithium slag powder and an increased content of phosphorus slag, while the other components remain unchanged. Specifically, the cementing material includes 20 kg of phase change lithium slag powder, 40 kg of phosphorus slag, 15 kg of calcium carbide slag, 20 kg of phosphogypsum, and 5 kg of modified zeolite powder, totaling 100 kg. The rest of the contents are the same as in Example 1.

[0108] Example 5

[0109] Compared with Example 1, Example 5 increased the content of phase change lithium slag powder and decreased the content of phosphorus slag, while the other components remained unchanged. Specifically, the cementing material included 30 kg of phase change lithium slag powder, 30 kg of phosphorus slag, 15 kg of calcium carbide slag, 20 kg of phosphogypsum, and 5 kg of modified zeolite powder, totaling 100 kg. The rest of the contents were the same as in Example 1.

[0110] Example 6

[0111] Compared with Example 1, Example 6 has an increased content of phase change lithium slag powder and a decreased content of phosphorus slag, while the other components remain unchanged. Specifically, the cementing material includes 35 kg of phase change lithium slag powder, 25 kg of phosphorus slag, 15 kg of calcium carbide slag, 20 kg of phosphogypsum, and 5 kg of modified zeolite powder, totaling 100 kg. The rest of the contents are the same as in Example 1.

[0112] Example 7

[0113] Compared with Example 1, Example 7 shows an increase in the content of modified zeolite powder and a decrease in the content of phosphogypsum, while the other components remain unchanged. Specifically, the cementing material includes 25 kg of phase change lithium slag powder, 35 kg of phosphorus slag, 15 kg of carbide slag, 15 kg of phosphogypsum, and 10 kg of modified zeolite powder, totaling 100 kg. The rest of the contents are the same as in Example 1.

[0114] Example 8

[0115] Compared with Example 1, Example 8 has an increased content of modified zeolite powder and a decreased content of phosphogypsum, while the other components remain unchanged. Specifically, the cementing material includes 25 kg of phase change lithium slag powder, 35 kg of phosphorus slag, 15 kg of carbide slag, 10 kg of phosphogypsum, and 15 kg of modified zeolite powder, totaling 100 kg. The rest of the contents are the same as in Example 1.

[0116] Example 9

[0117] Compared with Example 1, Example 9 reduces the amount of composite fiber used in large-volume concrete, specifically to 5 kg / m³ of composite fiber. 3 The rest of the content is the same as in Example 1.

[0118] Example 10

[0119] Compared with Example 1, Example 10 increased the amount of composite fiber used in large-volume concrete, specifically 20 kg / m³ of composite fiber. 3 The rest of the content is the same as in Example 1.

[0120] Comparative Example 1

[0121] Compared with Example 1, Comparative Example 1 lacked phase change lithium slag powder in the all-solid waste cementitious material, which was replaced with lithium slag of equal mass. The rest of the contents were the same as in Example 1.

[0122] Comparative Example 2

[0123] Compared with Example 1, Comparative Example 2 lacked modified zeolite powder in its all-solid waste cementitious material, which was replaced with an equal mass of zeolite powder. The rest of the contents were the same as in Example 1.

[0124] Comparative Example 3

[0125] Compared to Example 1, Comparative Example 3 shows that the amount of phase change lithium slag powder used in the all-solid waste cementitious material exceeds the limit by more than 35%, specifically 40 kg. The corresponding amount of phosphorus slag is reduced by 15 kg. Specifically, the cementitious material includes 40 kg of phase change lithium slag powder, 20 kg of phosphorus slag, 15 kg of calcium carbide slag, 20 kg of phosphogypsum, and 5 kg of modified zeolite powder, totaling 100 kg. The remaining contents are the same as in Example 1.

[0126] Comparative Example 4

[0127] Compared to Example 1, Comparative Example 4 shows that the amount of modified zeolite powder in the all-solid waste cementitious material exceeds the limit by more than 15%, specifically 20 kg. The corresponding amount of phase change lithium slag powder is reduced by 15 kg. Specifically, the cementitious material includes 10 kg of phase change lithium slag powder, 35 kg of phosphorus slag, 15 kg of calcium carbide slag, 20 kg of phosphogypsum, and 20 kg of modified zeolite powder, totaling 100 kg. The rest of the contents are the same as in Example 1.

[0128] Comparative Example 5

[0129] Compared with Example 1, Comparative Example 5 is a large-volume concrete without composite fibers, which is replaced with an equal amount of polypropylene fibers, and the rest is the same as Example 1.

[0130] Comparative Example 6

[0131] Compared with Example 1, Comparative Example 6 incorporated an excessive amount of composite fiber in its large-volume concrete, specifically 35 kg / m³ of composite fiber. 3 The rest of the content is the same as in Example 1.

[0132] Comparative Example 7

[0133] Compared with Example 1, in Comparative Example 7, the mass concrete used an equal amount of P·O42.5 cement to replace the all-solid waste cementitious material obtained in this invention, and the rest of the contents were the same as in Example 1.

[0134] The strength, heat of hydration, restricted expansion rate, and drying shrinkage rate of the mortars prepared in Examples 1-8, Comparative Examples 1-4, and 7 were tested according to the national standards "Test Method for Strength of Cement Mortar" (GB17671-1999), "Test Method for Drying Shrinkage and Cracking Performance of Cement Mortar and Concrete" (GBT29417-2012), "Test Method for Drying Shrinkage of Cement Mortar" (JC / T 603-2004), and "Test Method for Expansion Rate of Expansive Cement" (JC / T 313-2009). The results are shown in Table 1.

[0135] Table 1. Strength, heat of hydration, restricted expansion rate, and drying shrinkage of the mortars prepared in Examples 1-8, Comparative Examples 1-4, and 7.

[0136]

[0137] Table 1 shows that, within a suitable range, the all-solid waste expansion gelling material obtained by this invention exhibits high early and late strength (3d > 20MPa, 28d > 45MPa), low heat (7d heat of hydration < 180 kJ / kg), and slight expansion (90d expansion rate > 180 × 10⁻⁶). -6 The characteristics of this cementitious material can significantly improve its crack resistance in large-volume concrete.

[0138] Compared with Comparative Example 1, the all-solid waste cementitious material obtained in Example 1 of the present invention has lower heat of hydration and higher early and late compressive strength, which is beneficial to improving the crack resistance of this cementitious material for use in large-volume concrete.

[0139] Compared with Comparative Example 2, the solid waste cementitious material obtained in Example 1 of this invention has a larger expansion rate, better long-term volume stability, and higher early and late compressive strength, which is beneficial to improving the crack resistance of this cementitious material for use in large-volume concrete.

[0140] Compared with Comparative Examples 3 and 4, the solid waste cementitious material obtained in Example 1 of this invention has a larger expansion rate, better long-term volume stability, and higher early and late compressive strength, which is beneficial to improving the crack resistance of this cementitious material for use in large-volume concrete.

[0141] Compared with the P·O42.5 cement of Comparative Example 7, the all-solid waste cementitious material obtained in Example 1 of this invention has higher early and late strength, lower heat of hydration, greater expansion rate, and better long-term volume stability (comparative Example 7 shows shrinkage), which is beneficial to significantly improve the crack resistance of this cementitious material for use in large-volume concrete.

[0142] The concrete prepared in Examples 1-10 and Comparative Examples 1-7 were cured, and the compressive strength, early crack area, peak adiabatic temperature rise (°C), and 56-day chloride ion diffusion coefficient (×10-12 m³) of the mass concrete were tested according to the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T 50081-2019) and the "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete" (GB / T 50082-2024). 2 / s), and observe the fiber dispersion at the cross-section. Calculate the carbon footprint (kg CO) of concrete according to the "Technical Standard for Carbon Footprint Accounting and Evaluation of Ready-Mixed Concrete Products" (T / SCIA 003-2024). 2 / m 3 Meanwhile, concrete samples prepared in the examples and comparative examples were used to pour 1m×1m×1m concrete entities. Temperature rise of the concrete hydration heat was monitored by embedding temperature sensors. The comparison results are shown in Table 2.

[0143] Table 2 Performance of Mass Concrete

[0144]

[0145] The results show that, within a suitable range, mass concrete prepared using the all-solid-waste cementitious material and sheath thermal shrinkage-core phase change composite fiber of this invention exhibits high splitting tensile strength, low heat (adiabatic temperature rise < 40℃), and high crack resistance (total crack area on a single surface < 80mm). 2 / m 2 It has the characteristics of being able to disperse well in concrete within a suitable dosage range, which can significantly improve the crack resistance of this cementitious material in large-volume concrete.

[0146] Compared with Comparative Examples 1, 2 and 5, the large-volume concrete based on all-solid waste cementitious materials obtained in Example 1 of the present invention has a lower thermal temperature rise, higher splitting tensile strength, and better crack resistance and durability.

[0147] Compared with Comparative Examples 3 and 4, the large-volume concrete based on all-solid waste cementitious materials obtained in Example 1 of the present invention has higher splitting tensile strength, better crack resistance and durability.

[0148] Compared with Comparative Example 6, the large-volume concrete based on all-solid waste cementitious material obtained in Example 1 of the present invention has better fiber dispersion, higher splitting tensile strength, and better crack resistance and durability.

[0149] Compared with Comparative Example 7, the large-volume concrete based on all-solid waste cementitious materials obtained in Example 1 of this invention has a lower thermal insulation temperature rise, higher splitting tensile strength, better crack resistance and durability, and a smaller carbon footprint, showing obvious advantages of low carbon and environmental protection.

[0150] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A solid waste cementitious material, characterized in that, Based on a mass percentage of 100%, the cementing material comprises 20%~35% phase change lithium slag powder, 25%~40% phosphorus slag, 8%~20% carbide slag, 10%~20% phosphogypsum, and 5%~15% modified zeolite powder; The phase change lithium slag powder has a core-shell structure, with porous lithium slag as a carrier. The pores of the carrier are filled with a first phase change material, and the surface of the carrier is wrapped with an active aluminosilicate shell layer. The first phase change material is one or more of paraffin, fatty acids, and hydrated salts; The modified zeolite powder is zeolite powder loaded with organic shrinkage reducing agents.

2. The all-solid waste cementitious material as described in claim 1, characterized in that, The fatty acid is one or more of decanoic acid, lauric acid, myristic acid, and palmitic acid; the hydrated salt is one or more of disodium hydrogen phosphate dodecahydrate, barium hydroxide octahydrate, sodium sulfate decahydrate, and magnesium nitrate hexahydrate; the organic shrinkage reducing agent is one or more of glycerol, 1,5-pentanediol, NH2-PEG-CH3, dipropylene glycol monobutyl ether, and dipropyl ethylene glycol.

3. The all-solid waste cementitious material as described in claim 1, characterized in that, The preparation method of the phase change lithium slag powder is as follows: S11 involves calcining and grinding lithium slag to obtain a specific surface area of ​​450-750 m². 2 / kg porous lithium slag powder; S12, under vacuum and pressure conditions, lithium slag powder is impregnated in molten first phase change material; then the impregnated product is taken out, cooled and placed in sodium silicate solution for reaction; finally, the reacted product is filtered out, washed with water until the pH of the filtrate is neutral, and dried to obtain phase change lithium slag powder.

4. The all-solid waste cementitious material as described in claim 3, characterized in that, In step S11, the lithium slag is calcined at a temperature of 700-800℃ for 2-3 hours; in step S12, the vacuum degree is -0.09~-0.1MPa, the pressure is 0.5-1.0MPa; the mass ratio of the first phase change material to the mixed powder is 1:3~5, the mass concentration of the sodium silicate solution is 8%-12%, and the pH value is 11-12.

5. The all-solid waste cementitious material as described in claim 1, characterized in that, The modified zeolite powder is prepared by grinding the zeolite powder to a specific surface area ≥ 600 m². 2 / kg, then mix the zeolite powder with the organic shrinkage agent solution and stir at 200-300 rpm for 30-60 min; after that, dry the mixed slurry at 60-70℃ in an inert atmosphere.

6. The all-solid waste cementitious material as described in claim 5, characterized in that, The mass ratio of zeolite powder to organic shrinkage agent solution is 1:5~15, and the mass concentration of organic shrinkage agent solution is 5%~10%.

7. A method for preparing a solid waste cementitious material as described in any one of claims 1-6, characterized in that, Includes the following steps: S21, Pretreatment: Dry the carbide slag and grind it to a specific surface area ≥ 400 m². 2 / kg, to obtain calcium carbide slag powder; grind phosphorus slag powder to obtain a specific surface area of ​​400-650m². 2 / kg of phosphorus slag powder; calcining phosphogypsum at 160-200℃ for 1.5-2h yields hemihydrate gypsum; S22, mix phase change lithium slag powder, modified zeolite powder, carbide slag powder pretreated in step S21, phosphorus slag powder and hemihydrate gypsum in proportion.

8. A type of low-carbon, low-heat, high-crack-resistant mass concrete based on all-solid waste cementitious materials, characterized in that, The raw materials of the concrete, by weight, include 350-500 parts of the all-solid waste cementitious material as described in any one of claims 1-6, 900-1250 parts of coarse aggregate, 650-850 parts of fine aggregate, 4-10.5 parts of polycarboxylate superplasticizer, 140-200 parts of water, and 4-20 parts of composite fiber. The composite fiber has a core-shell structure, with the core material consisting of porous metal fibers loaded with a second phase change material; the sheath material includes one or more of polybutylene terephthalate, polypropylene, and high-density polyethylene; the sheath is heat-shrinkable and covers the outside of the core material after heat treatment.

9. The low-carbon, low-heat, high-crack-resistant mass concrete based on all-solid waste cementitious materials as described in claim 8, characterized in that... The method for preparing the composite fiber is as follows: porous metal fibers are impregnated in a silane coupling agent solution to obtain surface-modified metal fibers. Then, under vacuum conditions of -0.09 to -0.1 MPa and pressure of 0.5 to 1.0 MPa, the modified metal fibers are impregnated in molten second phase change material. After the impregnation is completed, the two ends of the fiber are sealed with epoxy resin micro-adhesive to obtain a core material. Then, the core material is heated and coated with molten sheath polymer, followed by heat treatment at 100-110℃ for 10-20 min. The sheath shrinks to obtain a sheath thermal shrinkage-core phase change composite fiber.

10. The low-carbon, low-heat, high-crack-resistant mass concrete based on all-solid waste cementitious materials as described in claim 8, characterized in that, The coarse aggregate is continuously graded crushed stone with a particle size of 5-25mm, and the fine aggregate is medium sand with a fineness modulus of 2.6-2.9; the second phase change material is one or more of paraffin wax, decanoic acid, lauric acid and sodium sulfate decahydrate.

Images