Sulfate-erosion-resistant preparation method of solid waste concrete

Abstract

The invention discloses an anti-sulfate-attack preparation method of solid waste concrete, and relates to the technical field of building materials and civil engineering, the anti-sulfate-attack solid waste concrete is prepared from the following materials in parts by weight: 100 parts of cement, 30-50 parts of composite solid waste cementing material, fly ash, steel slag micro powder and coal gangue according to a given mass ratio, 60-80 parts of modified recycled aggregate; 0.05-0.1 wt% of sodium molybdate as an erosion inhibitor. According to the invention, solid waste activation-interface reconstruction-ion competition-structure self-healing is taken as a core, synchronous spanning of solid waste concrete in the dimensions of sulfate erosion resistance, resource consumption, construction convenience and the like is realized through multi-process collaboration, and the gelation potential of solid wastes such as fly ash and steel slag is accurately excited through microwave targeted activation, so that the construction efficiency is improved. And a dense microstructure is reconstructed by combining a nano-SiO2 induced crystallization technology, so that excellent mechanical properties are still ensured when the solid waste mixing amount exceeds 70%.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of building materials and civil engineering, in particular to a preparation method of solid waste concrete resistant to sulfate attack. BACKGROUND

[0002] Sulfate attack is common in saline-alkali land, coastal engineering, underground pipeline, industrial wastewater contact parts and other scenes, SO4 2- Ions in water react with cement hydration products such as Ca(OH)2 and hydrated calcium aluminate in concrete to form ettringite (expansive crystals) or gypsum, resulting in concrete expansion, cracking, strength degradation and shortened service life.

[0003] According to statistics, the average service life of concrete structures subjected to sulfate attack is only 1 / 3-1 / 2 of that in normal environment, and in particular in the saline-alkali regions of northwest China and the coastal engineering in south China, related diseases have become the main threat to the durability of concrete. The storage of industrial solid waste is huge, and more than 3 billion tons of industrial solid waste such as fly ash, slag and steel slag are generated in China every year. The traditional stacking method not only occupies land but also has the risk of environmental pollution, and resource utilization is an inevitable trend.

[0004] The application potential of solid waste in concrete, some solid waste (such as fly ash and slag) has pozzolanic activity or micro-aggregate effect, which can improve the workability and reduce the cement content after being mixed into concrete, and at the same time, the sulfate resistance can be improved, such as slag can reduce the Ca(OH)2 content in the pore solution of concrete, and reduce the substrate of the erosion reaction.

[0005] In view of this, a preparation method of solid waste concrete resistant to sulfate attack is provided. SUMMARY

[0006] To solve the above technical problems, a preparation method of solid waste concrete resistant to sulfate attack is provided, and to achieve the above purposes, the technical scheme adopted by the application is as follows:

[0007] A preparation method of solid waste concrete resistant to sulfate attack, comprising:

[0008] The solid waste concrete resistant to sulfate attack is prepared from the following materials in parts: cement 100 parts, composite solid waste cementitious material 30-50 parts, modified recycled aggregate 60-80 parts, wherein the composite solid waste cementitious material is composed of fly ash, steel slag powder and coal gangue in a mass ratio of (3-5):(2-4):(1-2).

[0009] Preferably, the erosion inhibitor is prepared from the following materials in parts:

[0010] Erosion inhibitor: 0.05-0.1wt% sodium molybdate, based on the total mass of cementitious material; water 35-45 parts; water reducing agent 0.8-1.5 parts.

[0011] Preferably, the preparation method is:

[0012] S1, mix fly ash, steel slag powder, coal gangue according to the proportion, in the microwave field intensity 5-10 kW / m 3 irradiate for 3-5 minutes;

[0013] S2, add nano-silica dispersion liquid, particle size 10-30 nm, hydroxyl density ≥3 / nm 2 , stir at 60-80°C for 20-40 minutes;

[0014] S3, immerse the recycled aggregate in the KH-550 silane coupling agent solution, 1-2wt%, ultrasonic treatment for 30 minutes;

[0015] S4, dry mix cement, composite solid waste cementitious material and modified recycled aggregate for 90-120 seconds;

[0016] S5, add water solution containing water reducing agent and sodium molybdate twice: first 70% water amount, stir for 60 seconds, and the remaining 30% water amount, stir until the fluidity reaches 180-220mm;

[0017] S6, after molding, pre-culture for 24 hours in an environment of 20±2°C and humidity ≥95%;

[0018] S7, transfer to a composite erosion medium containing 5% Na2SO4+0.1mol / L NaOH+0.05-0.1wt% sodium molybdate, pH=12.5-13.0, and cure at 40°C for 72 hours; finally, constant temperature curing in a 50°C drying oven for 48 hours.

[0019] Preferably, the raw materials in S1 step are pretreated:

[0020] Fly ash: pass through a 45μm square hole sieve, with a residue amount ≤12%, and a loss on ignition ≤5%;

[0021] Steel slag powder: specific surface area ≥450m 2 / kg, f-CaO content <1.5%, treated by heat sweating method;

[0022] Coal gangue: dehydroxylation activation at calcination temperature 750±50°C, and grinding to D50=10-15μm;

[0023] The mixing process includes using a double-shaft forced mixer with a rotation speed of 30±2rpm; the mixing sequence is to first dry mix fly ash and coal gangue for 60 seconds, and then add steel slag powder and mix for 90 seconds; the uniformity standard is to take 3 samples, and the XRF detection CaO content deviation is ≤0.5%;

[0024] Microwave irradiation operation includes the use of industrial microwave cavity, frequency 2.45GHz, with temperature control probe and inert gas protection; paving thickness ≤5cm, quartz container; temperature control measures for the import of N2anti-oxidation, flow rate of 5L / min; real-time monitoring of temperature, more than 200℃ trigger the cooling system; post-irradiation treatment for immediate water cooling to 80℃ or less.

[0025] Preferably, the S2 step dispersion liquid pre-activation treatment:

[0026] Solvent compounding, deionized water: ethanol volume ratio 6:4, ethanol reduces the surface tension to 28mN / m; 0.1% sodium hexametaphosphate is added as dispersant, adsorbing nanoparticles to form double electric layer; ultrasonic pretreatment, 40kHz ultrasonic for 10 minutes, breaking the initial agglomerates;

[0027] Gradient temperature stirring process: the temperature of initial miscibility is 60℃ constant, the stirring speed is 100rpm, and the time is 0-10min; the temperature of bonding reaction is 70℃-80℃ gradient, the stirring speed is 200rpm, and the time is 10-30min; the temperature of stabilization is 80℃ constant, the stirring speed is 150rpm, and the time is 30-40min;

[0028] End-point intelligent judgment: conductivity method, the slurry conductivity is stable at 1.5-2.0mS / cm, which corresponds to the maximum hydroxyl exposure; viscosity monitoring, Brookfield viscometer linked with PLC, maintaining 80-120mPa·s.

[0029] Preferably, the S3 raw material pretreatment:

[0030] Clean the recycled aggregate by soaking in 5% oxalic acid solution for 30 minutes to dissolve the surface cement residue; rinse with running water until neutral, and dry at 105℃ to constant weight; prepare KH-550 solution with a concentration of 1-2wt%: take 10-20g of KH-550 stock solution, add 1L of deionized water / ethanol mixed solvent with a volume ratio of 1:1; adjust the pH by adding acetic acid to 4.5-5.5;

[0031] Ultrasonic immersion modification: ultrasonic frequency is 40±2kHz, power density is 0.5W / cm 3 , treatment time is 30 minutes, the first 20 minutes complete surface coverage, the last 10 minutes realize the deep penetration of fissure; dynamic lifting, speed 2cm / s;

[0032] Post-processing and solidification: drain the liquid, suspend the aggregate to drain the liquid for 10 minutes, and recover the residual solution; gradient drying, 80℃ hot air drying for 2 hours, and room temperature standing for 24 hours.

[0033] Preferably, the S4 dry mixing process:

[0034] Layered feeding, first into the modified recycled aggregate and 30% solid waste glue, stirring 30 seconds; add the remaining solid waste glue and cement, continue to stir 60-90 seconds;

[0035] Stage speed regulation: initial 20 seconds low speed, 25 rpm, middle 70 seconds high speed, 40 rpm, final 20 seconds speed down, 30 rpm.

[0036] Preferably, the S5 aqueous solution formulation:

[0037] Water reducing agent selection polycarboxylic acid PC, water reducing rate ≥25%, dosage 0.15-0.25%, based on the quality ratio of glue; corrosion inhibitor added sodium molybdate Na2MoO4, dosage 0.5-1.0%, based on the quality ratio of cement;

[0038] Solvent ratio, total water content is 0.45 times the total amount of glue, water-binder ratio 0.45, first add 70% water, the remaining 30% after mixing;

[0039] First stirring, 70% water, 60 seconds stirring (40 rpm); secondary stirring, 30% water, stirring to the flow degree standard.

[0040] Preferably, the S6 process step:

[0041] Environmental precision control: temperature control system uses double-channel PID temperature control box, circulating water cooling and electric heating compensation, cement hydration heat release peak stable period, maintain 20±2℃; humidity guarantee ultrasonic atomizer, cooperate with humidity sensor, humidity ≥95%;

[0042] Covering and sealing technology, using double-layer film method, inner layer is polyethylene sealing film, thickness 0.1mm, directly wrapping the test piece; outer layer is wet cloth superposition; spray 0.5% silicone penetrant before film covering;

[0043] Hydration process regulation: slow-release water supply, pre-embedded high molecular water-retaining fiber, PVA fiber, dosage 0.1%, supply internal moisture according to Fick diffusion law; ion migration inhibition, pre-culture stage continuous release of sodium molybdate in S5 step, liquid phase ≥1500ppm.

[0044] Preferably, the S7 test piece pretreatment:

[0045] After pre-culture, the test piece surface is sprayed with deionized water to remove floating dust, and the water film contact angle is <10°; the erosion liquid is perfused, with a liquid level 30mm higher than the top surface of the test piece, based on a polytetrafluoroethylene tank and a liquid level sensor with a fluctuation of ±3mm automatic liquid supplement; constant temperature control, 40±0.5℃ circulating water bath, based on PID temperature control and external cooling tower, temperature >42℃ triggers liquid nitrogen emergency cooling; ion concentration maintenance, update 50% erosion liquid every 24 hours;

[0046] Drying and curing stage: the gradient temperature program includes a 40-50°C stage, the temperature rising rate is 1°C / h; the constant temperature is 50±1°C for 48 hours; the humidity control includes the relative humidity of the drying box of 30-40%.

[0047] Compared with the prior art, the present application has the beneficial effects that:

[0048] The present application proposes a microwave selective activation process. The Si-O-Si bond in the solid waste glass body is targeted to be broken by a high-frequency electromagnetic field, so that the inert silicate is converted into a highly active cementitious component, and the reactivity of the solid waste is improved by more than 40%. At the same time, in-situ crystal nucleus induction is combined with nano-SiO2, and Ca 2+ The low calcium-silicon ratio C-S-H gel is generated with the nano-particles, the excellent mechanical properties are maintained when the solid waste content is greater than 70%, and the technical bottleneck of the traditional solid waste concrete that "high content must sacrifice strength" is completely broken through.

[0049] Through ultrasonic treatment of KH-550 silane coupling agent, a dense hydrophobic film is constructed on the surface of the recycled aggregate, and the ion penetration channel caused by capillary pore water absorption is eliminated; the water is added in batches, so that sodium molybdate preferentially adsorbs the surface of the glue material in a high concentration environment, forms a nano-scale CaMoO4 passivation film, and occupies the SO4 2- binding sites; the erosion-drying synergistic curing drives the CaMoO4 crystal to grow directionally in the pores, and realizes in-situ sealing of the damaged part. The triple barrier reduces the sulfate erosion depth by more than 80%, and no additional anticorrosive coating is needed.

[0050] Through the three-stage intelligent curing chain of pre-curing-erosion-drying: in the pre-curing stage, a low-temperature and high-humidity environment of 20°C is used to inhibit plastic shrinkage and promote the ordered growth of C-A-S-H gel network; in the erosion stage, an alkaline environment is used to stabilize the ettringite structure and activate the corrosion inhibition effect of molybdate; in the drying stage, the CaMoO4 crystal is arranged directionally along the stress direction through stepwise heating, and a through anti-cracking sealing layer is formed. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 A flowchart of a preparation method of a solid waste concrete resistant to sulfate attack. DETAILED DESCRIPTION

[0052] The following description is used to disclose the present application so that those skilled in the art can implement the present application. The preferred embodiments in the following description are only as examples, and other obvious modifications can be thought of by those skilled in the art.

[0053] A preparation method of a solid waste concrete resistant to sulfate attack, comprising:

[0054] The solid waste concrete sulfate attack resistance is prepared from the following parts of materials: cement 100 parts, composite solid waste cementitious material 30-50 parts, modified recycled aggregate 60-80 parts, wherein the composite solid waste cementitious material is composed of fly ash, steel slag powder and coal gangue in a mass ratio of (3-5):(2-4):(1-2).

[0055] The erosion inhibitor is specifically prepared from the following parts of materials:

[0056] The erosion inhibitor: 0.05-0.1wt% sodium molybdate, based on the total mass of cementitious material; water 35-45 parts; water reducing agent 0.8-1.5 parts.

[0057] Referring to Figure 1 The preparation method of the solid waste concrete sulfate attack resistance is as follows:

[0058] The industrial solid waste fly ash, steel slag powder and coal gangue are put into a mixing machine according to a preset mass ratio, and a typical ratio is 35%:40%:25%;

[0059] Microwave irradiation treatment: turn on the microwave generator, control the field strength in the range of 5-10kW / m 3 , and continuously irradiate for 3-5 minutes; the high-frequency electromagnetic wave penetrates the solid waste particles, and the internal temperature is instantaneously raised to above 800 DEG C through dielectric heating effect, which destroys the Si-O-Si bond in the glass body of fly ash, releases active SiO2 and Al2O3, and increases the cementitious activity by more than 40%;

[0060] Dispersion liquid addition: add a nano-silicon dioxide dispersion liquid with a particle size of 10-30nm and a hydroxyl density of ≥3 / nm 2 to the solid waste mixture after microwave activation (the dosage accounts for 1.5-2.5% of the total mass of cementitious material);

[0061] Heating and stirring: mechanically stir at 60-80 DEG C for 20-40 minutes. The high-temperature environment promotes the reaction between the Si-OH groups on the surface of nano-SiO2 and the dissolved Ca 2+ in the solid waste, generating C-S-H gel crystals with a low calcium-silicon ratio (Ca / Si≈1.2), filling micro-cracks and strengthening the interface transition zone (ITZ porosity is reduced to below 8%);

[0062] Coupling agent treatment: immerse the recycled aggregate in a KH-550 silane coupling agent solution with a concentration of 1-2wt%, and ensure that the aggregate is completely immersed;

[0063] Ultrasonic activation: start the ultrasonic processor for 30 minutes. The cavitation effect drives the coupling agent molecules to penetrate into the pores of the aggregate, and the amino groups (-NH2) of the coupling agent molecules condense with the hydroxyl groups on the surface of the aggregate to form a hydrophobic film. The contact angle increases from 70 DEG to more than 110 DEG, and the water absorption rate decreases from 7% to 3%;

[0064] Step 1: Pre-mixing of cement and 60% of the total amount of composite solid waste cementitious material obtained in S2 with modified recycled aggregates into a mixer for 30 seconds to form a "aggregate-cementitious material" pre-coating layer;

[0065] Final dry mixing: add the remaining 40% of the cementitious material and dry mix for 90-120 seconds at a speed of 40 rpm. The hydrophobicity of the aggregate surface promotes the preferential adsorption of solid waste fine powder, preventing cement aggregation.

[0066] First water addition and stirring: add 70% of the total water amount containing a water solution of water reducing agent (polycarboxylate, 0.2% of the mass of cementitious material) and sodium molybdate (0.8% of the mass of cement) and stir for 60 seconds. The high concentration environment (liquid phase [MoO4 2- ] ≈ 2000 ppm) allows the molybdate to quickly adsorb onto the surface of the cementitious material, forming a 50 nm thick CaMoO4 passivation film.

[0067] Second water addition and flow adjustment: slowly add the remaining 30% of the water while continuously stirring until the slump spread reaches 180-220 mm. The second water addition releases the dispersion potential of the water reducing agent, while avoiding excessive dilution of the passivation film (Zeta potential maintained at -45 mV).

[0068] Environmental control: immediately move the formed specimen into a curing chamber after molding, with strict temperature control at 20 ± 2°C and relative humidity ≥ 95%. Use an ultrasonic atomizer and humidity sensor for joint control.

[0069] Curing duration: continue for 24 hours. High humidity environment inhibits plastic shrinkage cracking, and low temperature of 20°C allows stable hydration of C3S, generating a reinforced network of short fiber-like C-S-H and nano-sheet-like C-A-S-H.

[0070] Erosion solution immersion: immerse the specimen in a composite solution containing 5% Na2SO4 + 0.1 mol / L NaOH + 0.075 wt% sodium molybdate (compromise concentration) with pH adjusted to 12.5-13.0, and place it in a 40 ± 0.5°C circulating water bath for 72 hours. High temperature accelerates the diffusion of SO4 2- , and high pH stabilizes the ettringite structure, while molybdate continuously penetrates to form a deep CaMoO4 sealing layer.

[0071] Stepwise drying and curing: transfer to a 50°C drying oven:

[0072] Stepwise temperature increase: 40°C → 45°C (1 hour) → 50°C (1 hour) at a rate of ≤ 1°C / h.

[0073] Constant temperature dehydration: maintain a temperature of 50 ± 1°C and a humidity of 30-40% for 48 hours to promote the directional arrangement of CaMoO4 crystals along the stress direction (crystal size 50-80 nm), forming a penetrating corrosion-resistant barrier.

[0074] Note that solid waste activation, microwave disruption of Si-O bonds to release active silicon aluminum, nano-SiO2 restructuring low calcium C-S-H, and improved density;

[0075] Erosion path blocking, aggregate hydrophobization eliminates capillary water penetration, MoO4 2- Competitive inhibition of SO4 2- Adsorption, double barrier to block ion migration;

[0076] Microstructure self-repair, erosion-drying synergistic CaMoO4 nanocrystals in the pores of directional growth, realize the self-sealing of damage site.

[0077] S1 Step solid waste microwave activation:

[0078] Fly ash, steel slag powder, coal gangue in the microwave field intensity 5-10 kW / m 3 During the irradiation process, high-frequency electromagnetic waves generate local high temperature through dielectric loss, the instantaneous temperature can reach 800-1000℃, directly destroy the glass structure of solid waste particles, release active SiO2 and Al2O3. Non-thermal effects of microwaves, high-frequency vibration of polar molecules, further promote mineral phase rearrangement, make the solid waste cementitious activity improve more than 40%, provide high activity silicon aluminum source for subsequent hydration reaction.

[0079] S2 Step nano-silica interface enhancement:

[0080] The hydroxyl density of nano-SiO2 dispersion liquid is ≥3 / nm 2 , to ensure that its surface is rich in silanol groups (Si-OH), and react quickly with cement hydration product Ca(OH)2 at 60-80℃ under stirring to generate low calcium silicon ratio (Ca / Si≈1.2) C-S-H gel. This gel not only fills microcracks, but also repairs the aggregate-paste interfacial transition zone (ITZ) through chemical bonding, reducing ITZ porosity from 15% to below 8%, significantly blocking the sulfate penetration path.

[0081] S3 Step recycled aggregate hydrophobic modification:

[0082] The amino group (-NH2) of KH-550 silane coupling agent reacts with the hydroxyl group (-OH) on the surface of recycled aggregate through condensation reaction to form covalent bond, and a dense hydrophobic film layer is generated on the surface of the aggregate, the contact angle is increased from 70° to more than 110°. Ultrasonic treatment (frequency 40 kHz) forces the coupling agent to penetrate deep into the aggregate pores (depth > 50 μm) through cavitation effect, reducing the water absorption rate from 7% to 3% or less, completely eliminating the risk of internal sulfate migration caused by capillary water absorption.

[0083] S4 Step dry mixing process optimization:

[0084] The dry mixing stage adopts a two-stage feeding method: first, 40% of the solid waste glue material is premixed with the modified recycled aggregate for 30 seconds to form a "aggregate-solid waste" pre-wrapped structure; then the remaining glue material and cement are added, and the total mixing time is controlled within 90-120 seconds. This design takes advantage of the hydrophobic properties of the aggregate surface to preferentially adsorb fine solid waste powder, preventing cement particles from agglomerating due to static adsorption, reducing the dispersion coefficient from 12% to less than 5%, and improving the mixing uniformity by 60%.

[0085] S5 step: add water in batches and synergize with corrosion inhibitor:

[0086] When the first 70% of the water solution is added, sodium molybdate (Na2MoO4) quickly adsorbs onto the glue surface in a high concentration environment (liquid phase [MoO4 2- ] ≈ 2000 ppm), replaces the adsorption sites of SO4 2- by ion exchange, and forms a calcium molybdate (CaMoO4) passivation film with a thickness of about 50 nm. When the remaining 30% of the water is added, the carboxyl groups (-COOH) of the polycarboxylate superplasticizer chelate with the unreacted Ca 2+ on the glue surface, releasing the encapsulated free water, and allowing the fluidity to be precisely controlled to 200 ± 20 mm, ensuring workability while avoiding excessive dilution of the corrosion inhibitor.

[0087] S6 step: constant temperature and humidity pre-curing:

[0088] In an environment of 20 ± 2°C and humidity ≥ 95%, the early hydration of the cement-solid waste system is precisely controlled: C3S preferentially hydrates to form short fiber-like C-S-H gel, while the active SiO2 / Al2O3 in the solid waste reacts with Ca(OH)2 to form nano-sheet-like hydrated calcium silicate (C-A-S-H) through a secondary pozzolanic reaction. After 24 hours of pre-curing, a three-dimensional interpenetrating network structure is formed inside the paste, with a compressive strength of 12 MPa (1d strength), and no shrinkage cracks occur (crack density < 0.1 cracks / mm 2 ).

[0089] S7 step: combined erosion-drying:

[0090] In an erosion medium containing 5% Na2SO4, 0.1 mol / L NaOH, and sodium molybdate, 40°C high temperature accelerates the diffusion of sulfate ions (diffusion coefficient D = 4.2 × 10 -10 m 2 / s), but the high pH (12.5-13.0) environment inhibits the phase transition of ettringite (AFt) to gypsum (CaSO4·2H2O). At the same time, molybdate ions continuously penetrate into the deep layer of the paste and chelate with unreacted Ca 2+Nanoscale CaMoO4 crystals (particle size 50-80 nm) are generated, filling the pores and covering the C-S-H surface. The subsequent drying stage at 50°C causes a controllable dehydration shrinkage, which promotes the CaMoO4 crystal grains to align along the stress direction, forming a through anti-erosion barrier, reducing the sulfate expansion rate from 0.12% to below 0.03%.

[0091] In summary, the advantages of the present application are:

[0092] By microwave targeted activation, the cementitious potential of fly ash, steel slag and other solid wastes is precisely stimulated, and combined with the nano-SiO2 induced crystallization technology to reconstruct a dense microstructure, so that the solid waste content can exceed 70% while still ensuring excellent mechanical properties. The whole process absorbs industrial solid waste and construction waste, significantly reducing the consumption of natural resources and carbon emissions, and reshaping the green building materials industry paradigm.

[0093] Hydrophobicization of aggregates blocks the capillary water seepage path, and sodium molybdate is added in stages to form a nanoscale passivation film to occupy the sulfate erosion site, and the erosion-drying synergistic curing drives the directional growth of self-repairing crystals. This design blocks the ion migration channel from millimeter to nanometer scale, enabling concrete to achieve ultra-long service life in harsh environments such as saline soil and coastal areas, and completely breaking away from the passive protection mode of relying on external corrosion-resistant coatings.

[0094] Microwave activation and nano-enhanced low-temperature mixing are efficiently connected, and the flowability and corrosion inhibition film generation are precisely controlled by adding water in stages, with three-stage curing, constant humidity pre-curing, ion erosion, and stepwise drying, through dynamic matching of environmental parameters to the hydration process. The whole process is compatible with conventional mixing station equipment, and the construction convenience is no different from ordinary concrete, promoting the large-scale application of high-performance solid waste concrete in major infrastructure projects.

[0095] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above examples, and the above examples and descriptions in the specification are only the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection required by the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing sulfate-resistant solid waste concrete, characterized in that, Solid waste concrete resistant to sulfate attack is prepared from the following materials in parts: 100 parts cement, 30-50 parts composite solid waste cementitious material composed of fly ash, steel slag powder and coal gangue in a mass ratio of (3-5):(2-4):(1-2), 60-80 parts modified recycled aggregate, and 0.05-0.1 wt% sodium molybdate as an erosion inhibitor.

2. The preparation method of sulfate-resistant solid waste concrete according to claim 1, characterized in that, The erosion inhibitor is specifically prepared from the following parts of materials: Erosion inhibitor: 0.05–0.1 wt% sodium molybdate, based on the total mass of cementitious materials, 35–45 parts water, and 0.8–1.5 parts water-reducing agent.

3. The method for preparing sulfate-resistant solid waste concrete according to claim 1, characterized in that, The preparation method is as follows: S1. Mix fly ash, steel slag powder, and coal gangue in a certain proportion, and then heat the mixture in a microwave field with a strength of 5-10 kW / m. 3 Irradiate for 3-5 minutes; S2. Add nano-silica dispersion with a particle size of 10-30 nm and a hydroxyl group density of ≥3 / nm. 2 Stir at 60-80℃ for 20-40 minutes; S3. Immerse the recycled aggregate in KH-550 silane coupling agent solution, 1-2wt%, and sonicate for 30 minutes. S4. Dry mix cement, composite solid waste cementitious material, and modified recycled aggregate for 90-120 seconds. S5. Add the aqueous solution containing water-reducing agent and sodium molybdate in two batches: first, add 70% water and stir for 60 seconds, then add the remaining 30% water and stir until the fluidity reaches 180-220 mm. S6. After molding, pre-cur in an environment of 20±2℃ and ≥95% humidity for 24 hours; S7. Transfer to a composite etching medium containing 5% Na2SO4 + 0.1mol / L NaOH + 0.05-0.1wt% sodium molybdate, pH=12.5-13.0, and cure at 40℃ for 72 hours; finally, cure at a constant temperature of 50℃ in a drying oven for 48 hours.

4. The preparation method of sulfate-resistant solid waste concrete according to claim 1, characterized in that: S1 Step Raw Material Pretreatment: Fly ash: Passing through a 45μm square-hole sieve, the residue on the sieve is ≤12%, and the loss on ignition is ≤5%; Steel slag powder: specific surface area ≥ 450 m² 2 / kg, f-CaO content <1.5%, treated by hot simmering method; Coal gangue: calcined at 750±50℃ to remove hydroxyl groups and activated, then ground to D50=10–15μm; The mixing process includes using a twin-shaft forced mixer at a speed of 30±2 rpm; the mixing sequence is to first add fly ash and coal gangue and dry mix for 60 seconds, then add steel slag powder and mix for 90 seconds; the uniformity standard is to take 3 samples and XRF test the CaO content deviation ≤0.5%; Microwave irradiation operation includes the use of an industrial microwave cavity with a frequency of 2.45 GHz, equipped with a temperature control probe and inert gas protection; a flat layer thickness of ≤5 cm, and quartz container; temperature control measures include introducing N2 to prevent oxidation at a flow rate of 5 L / min; real-time temperature monitoring, triggering the air cooling system when the temperature exceeds 200°C; and immediate water cooling to below 80°C after irradiation.

5. The method for preparing sulfate-resistant solid waste concrete according to claim 1, characterized in that, S2 Step Dispersion Pre-activation Treatment: Solvent compounding: deionized water: ethanol volume ratio 6:4, ethanol reduces surface tension to 28 mN / m; 0.1% sodium hexametaphosphate is added as a dispersant to adsorb nanoparticles and form an electric double layer; ultrasonic pretreatment: ultrasonication at 40 kHz for 10 minutes to break up initial agglomerates; Gradient temperature stirring process: The initial mixing temperature is constant at 60℃, the stirring speed is 100 rpm, and the duration is 0–10 min; the bonding reaction temperature is gradient from 70℃ to 80℃, the stirring speed is 200 rpm, and the duration is 10–30 min; the stabilization temperature is constant at 80℃, the stirring speed is 150 rpm, and the duration is 30–40 min. Intelligent endpoint determination: conductivity method, the endpoint is terminated when the slurry conductivity stabilizes at 1.5–2.0 mS / cm, corresponding to the maximum hydroxyl exposure; viscosity monitoring, Brookfield viscometer linked to PLC, maintains 80–120 mPa·s.

6. The method for preparing sulfate-resistant solid waste concrete according to claim 1, characterized in that, The S3 raw material pretreatment: Clean the recycled aggregate by soaking it in a 5% oxalic acid solution for 30 minutes to dissolve surface cement residue; rinse it with running water until neutral, and dry it at 105℃ to constant weight; prepare the KH-550 solution with a concentration of 1–2 wt%: take 10–20 g of KH-550 stock solution and add 1 L of deionized water / ethanol mixed solvent at a volume ratio of 1:1; adjust the pH by adding acetic acid dropwise to adjust the pH to 4.5–5.5; Ultrasonic impregnation modification: ultrasonic frequency 40±2kHz, power density 0.5W / cm³ 3 The processing time is 30 minutes, with the first 20 minutes completing surface coverage and the last 10 minutes achieving deep penetration into the cracks; dynamic lifting and lowering at a speed of 2cm / s; Post-treatment and curing: drain and remove liquid, suspend aggregate to drain for 10 minutes, and recover residual solution; gradient drying, hot air drying at 80℃ for 2 hours, and stand at room temperature for 24 hours.

7. The method for preparing sulfate-resistant solid waste concrete according to claim 1, characterized in that, The S4 dry mixing process: Add materials in layers: first add modified recycled aggregate and 30% solid waste adhesive, and stir for 30 seconds; then add the remaining solid waste adhesive and cement, and continue stirring for 60–90 seconds. Adjust the speed in stages: initially 20 seconds at low speed (25 rpm), mid-term 70 seconds at high speed (40 rpm), and final 20 seconds at reduced speed (30 rpm).

8. The method for preparing sulfate-resistant solid waste concrete according to claim 1, characterized in that, The S5 aqueous solution formulation is as follows: The water-reducing agent is selected from polycarboxylate-based PCs with a water reduction rate ≥25% and a dosage of 0.15–0.25% based on the mass ratio of the adhesive material; the corrosion inhibitor is added with sodium molybdate (Na2MoO4) at a dosage of 0.5–1.0% based on the mass ratio of cement. Solvent ratio: Total water volume is 0.45 times the total amount of adhesive material, water-to-adhesive ratio is 0.45, 70% water is added initially, and the remaining 30% is added later; For the first stirring, add 70% water and stir for 60 seconds (40 rpm); for the second stirring, add 30% water and stir until the desired fluidity is achieved.

9. The method for preparing sulfate-resistant solid waste concrete according to claim 1, characterized in that, The S6 process step: Precise environmental control: The temperature control system adopts a dual-channel PID temperature control box with circulating water cooling and electric heating compensation to maintain 20±2℃ during the stable period of cement hydration heat release peak; the humidity protection system uses an ultrasonic atomizer, in conjunction with a humidity sensor, to maintain humidity ≥95%; The covering and sealing technology employs a double-layer coating method. The inner layer is a polyethylene sealing film with a thickness of 0.1 mm, which directly wraps the specimen. The outer layer is made of layered wet burlap. 0.5% organosilicon penetrant is sprayed before coating. Hydration process control: slow-release water supply, pre-embedded high-molecular water-retaining fibers, PVA fibers, with a dosage of 0.1%, replenish internal water according to Fick's diffusion law; ion migration inhibition, continuous release of sodium molybdate from step S5 during the pre-conditioning stage, with a liquid phase concentration ≥1500ppm.

10. The method for preparing sulfate-resistant solid waste concrete according to claim 1, characterized in that, The pretreatment of the S7 specimen: After pre-curing, the specimen surface is sprayed with deionized water to remove floating dust, with a water film contact angle of <10°; the etching solution is poured in, with the liquid level exceeding the top surface of the specimen by 30mm, based on a PTFE tank and a liquid level sensor, with automatic replenishment for fluctuations of ±3mm; constant temperature control is implemented, with a 40±0.5℃ circulating water bath, based on PID temperature control and an external cooling tower, triggering liquid nitrogen emergency cooling when the temperature exceeds 42℃; ion concentration maintenance is performed, with 50% of the etching solution being replaced every 24 hours; Drying and curing stage: The gradient temperature rise program includes a 40℃-50℃ stage with a temperature rise rate of 1℃ / h; the constant temperature is maintained at 50±1℃ for 48 hours; humidity control includes a relative humidity of 30–40% in the drying oven.

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