A lime-sand polymer building material capable of inhibiting efflorescence and a preparation method thereof

Abstract

The invention provides an ash-sand polymer building material capable of inhibiting efflorescence and a preparation method thereof, which belongs to the technical field of novel building materials. The material comprises a composite matrix material, a composite alkali activator, a slow-release organic acid microcapsule, a modified layered double metal hydroxide and an efflorescence inhibition adjuvant; the composite matrix material is a compound of fly ash and slag; the composite alkali activator is a compound of water glass and a NaOH aqueous solution; the slow-release organic acid microcapsule is a composite acid mixed with citric acid and tartaric acid, and is prepared by coating hydroxypropyl-β-cyclodextrin and sodium alginate; the modified layered double metal hydroxide is prepared by calcining MgAl-LDH, then surface-modifying the surface with a silane coupling agent, and then loading nano-SiO2; the efflorescence inhibition adjuvant is a compound of phytic acid-modified lignin microcapsules and a thermally responsive carbonate; the phytic acid-modified lignin microcapsules are prepared by modifying sodium lignin sulfonate with phytic acid and then coating it with ethyl cellulose and polyvinyl alcohol; and the thermally responsive carbonate is prepared by coating calcium carbonate with stearic acid.

Description

Technical Field

[0001] The invention belongs to the technical field of new building materials, and particularly relates to a lime-sand polymer building material capable of inhibiting efflorescence and a preparation method thereof. Background Art

[0002] Geopolymers are three-dimensional mesh gel materials generated by the reaction of active silica-alumina materials (such as fly ash and slag) with alkaline activators. Their production energy consumption is only one-third of that of traditional cement, and CO2 emissions are reduced by more than 60%, making them a green building material (Reference: Davidovits J. Geopolymer chemistry and applications. 5th ed. France: Geopolymer Institute; 2020). However, geopolymers will continuously release Na during the hardening process. + , K + Alkali metal ions such as Na2CO3 and K2CO3 migrate to the surface and react with CO2 in the air to form crystalline salts such as Na2CO3 and K2CO3 (i.e., efflorescence). Studies have shown that Na + When the concentration is >0.5 mol / L, the risk of efflorescence at 28 days is as high as 83% (data source: Zhang et al., Cement and Concrete Research, 2021, 139: 106284). Efflorescence not only causes surface color differences, chalking, and other cosmetic defects, but also leads to the following serious problems:

[0003] (1) Structural degradation: The crystallization process generates expansion stress, which causes microcracks inside the material;

[0004] (2) Decreased durability: After carbonate crystals block the surface pores, they hinder the evaporation of internal water and accelerate the corrosion of steel bars;

[0005] (3) Functional failure: When applying a protective coating, the alkali-based products will cause the bonding strength between the coating and the substrate to decrease, and the coating will easily peel off.

[0006] The main technical means and limitations of the current industry in dealing with efflorescence are as follows:

[0007] (1) Surface sealing method: Use silicone coating or fluorocarbon resin for surface sealing. However, actual engineering testing found that the coating is prone to peeling under temperature changes, the anti-permeability retention rate after one year is less than 30%, and it cannot inhibit deep alkali efflorescence caused by internal ion migration.

[0008] (2) Mineral admixture method: Add 10%-20% silica fume or metakaolin to consume free alkali. However, when the admixture exceeds 15%, the initial fluidity of the slurry decreases significantly, restricting the construction performance.

[0009] (3) Chemical solidification method: by introducing sulfates such as CaSO4 to generate calcium sulfate to fix Na + But the introduction of SO4 2- It will cause delayed ettringite expansion and accelerate the Mg 2+ Erosion and mass loss rate increase significantly.

[0010] None of the aforementioned methods can fundamentally address the migration and accumulation of alkali metal ions, and the common contradiction of "inhibiting efflorescence while deteriorating performance" exists. Therefore, it is necessary to develop an endogenous ion regulation system that can achieve long-term inhibition of efflorescence without affecting the mechanical properties of the material. Summary of the Invention

[0011] To inhibit efflorescence while maintaining good strength, impermeability, corrosion resistance, and expansion resistance, the present invention provides an efflorescence-inhibiting lime-sand polymer building material and its preparation method. This material utilizes a rationally proportioned composite matrix material and a composite alkali activator, along with slow-release organic acid microcapsules, modified layered double metal hydroxides, and an efflorescence-inhibiting auxiliary agent. This material significantly improves the efflorescence inhibition rate while also achieving good strength, impermeability, corrosion resistance, and expansion resistance. The specific technical solution is as follows:

[0012] A ash-sand polymer building material for inhibiting efflorescence is characterized by comprising the following raw materials in parts by mass: 60 to 75 parts of a composite matrix material, 20 to 30 parts of a composite alkali activator, 0.5 to 1.5 parts of a slow-release organic acid microcapsule, 3 to 5 parts of a modified layered double metal hydroxide, and 1 to 2 parts of an efflorescence inhibition auxiliary agent; wherein the composite matrix material is fly ash and slag compounded in a mass ratio of 1: (1 to 1.4); the composite alkali activator is composed of water glass with a modulus of 1.2 to 1.8 and a solid concentration of 35 wt% to 38 wt% and 6 mol / L to 10 mol / L NaOH aqueous solution is compounded in a volume ratio of 1:(1~1.2); the sustained-release organic acid microcapsules are a composite acid mixed with citric acid and tartaric acid, which is coated with hydroxypropyl-β-cyclodextrin and sodium alginate; the modified layered double hydroxide is prepared by calcining MgAl-LDH, surface-modifying it with a silane coupling agent, and then loading it with nano-SiO2; the alkali-inhibiting adjuvant is a compound of phytic acid-modified lignin microcapsules and thermally responsive carbonates in a mass ratio of 1:(0.8~1.2); the phytic acid-modified lignin microcapsules are sodium lignin sulfonate modified with phytic acid, and then coated with ethyl cellulose and polyvinyl alcohol; the thermally responsive carbonate is calcium carbonate coated with stearic acid.

[0013] Among the above raw materials, the preparation method of sustained-release organic acid microcapsules includes: preparing a composite acid solution containing 10wt% to 15wt% of citric acid and 10wt% to 15wt% of tartaric acid; preparing a sodium alginate aqueous solution with a concentration of 6wt% to 8wt%; preparing a saturated hydroxypropyl-β-cyclodextrin aqueous solution at 50°C to 60°C, adding the composite acid solution with a concentration of 30% to 35% by weight of hydroxypropyl-β-cyclodextrin under stirring, stirring for 1h to 2h, adding a sodium alginate aqueous solution with a concentration of 8% to 10% by weight of hydroxypropyl-β-cyclodextrin, stirring for 1h to 2h, adding a 0.5wt% to 0.6wt% CaCl2 aqueous solution with a concentration of 3% to 5% by weight of hydroxypropyl-β-cyclodextrin, stirring for 30min to 50min, and spray drying to obtain sustained-release organic acid microcapsules.

[0014] In the above-mentioned method for preparing sustained-release organic acid microcapsules, the temperature of the composite acid solution is 50°C to 60°C; the temperature of the sodium alginate aqueous solution is 50°C to 60°C; the stirring speed is 300rpm to 400rpm; and the spray drying temperature is below 40°C.

[0015] Among the above raw materials, the preparation method of the modified layered double hydroxide includes: heating MgAl-LDH to 350°C to 400°C under nitrogen protection and calcining for 1.5 hours to 2 hours to obtain the layered double hydroxide; after cooling to room temperature, immersing it in anhydrous ethanol containing 1wt% to 2wt% of a silane coupling agent at a mass of 8 times to 10 times the mass of the layered double hydroxide, ultrasonically dispersing it, centrifuging it, taking the solid and redispersing it in anhydrous ethanol at a mass of 8 times to 10 times the mass of the solid, adding SiO2 ethanol solution based on nano-SiO2 accounting for 3% to 5% of the solid mass, stirring and adsorbing it, loading the nano-SiO2, centrifuging it, and taking the solid and drying it to obtain the modified layered double hydroxide.

[0016] In the preparation method of the above-mentioned modified layered double metal hydroxide, the heating rate is 2°C / min to 3°C / min; the silane coupling agent KH-550; the ultrasonic dispersion is ultrasonic dispersion at 300W to 350W, 40kHz to 50kHz for 30min to 50min; the stirring adsorption is vacuum stirring adsorption at 55°C to 60°C, 300rpm to 500rpm for 2h to 2.5h; the centrifugation is centrifugation at 8000rpm to 10000rpm for 10min to 15min; the drying is drying at 60°C to 65°C for 12h to 14h; the particle size range of nano-SiO2 in the SiO2 ethanol solution is 5nm to 10nm; the SiO2 ethanol solution contains 6wt% to 8wt% nano-SiO2.

[0017] Among the above raw materials, the preparation method of phytic acid modified lignin microcapsules includes: dissolving sodium lignin sulfonate in deionized water, adjusting the pH to 4-5 with a hydrochloric acid aqueous solution; adding a 50wt%-70wt% phytic acid aqueous solution according to a mass ratio of sodium lignin sulfonate: phytic acid = 1: (0.2-0.3) under stirring, and then adding a P-TSA acid catalyst of 1%-1.5% by mass of sodium lignin sulfonate, stirring and reacting at 65°C-75°C, adjusting the reaction system with a NaOH aqueous solution to maintain the pH below 4 during the reaction, cooling to room temperature, and rinsing with NaOH. The pH value of the OH aqueous solution was adjusted to 7-8, concentrated under reduced pressure, dried to constant weight, and ground to obtain phytic acid-modified lignin; the phytic acid-modified lignin and ethyl cellulose were added to ethyl acetate containing 5wt%-10wt% ethanol in a mass ratio of 2: (1-1.5) to obtain a mixed solution; the mixed solution was added to an aqueous solution containing 0.4wt%-0.6wt% polyvinyl alcohol, emulsified, and microspheres were collected by centrifugation; an aqueous solution containing 0.5wt%-0.6wt% CaCl2 in an amount 5 times to 6 times the mass of the microspheres was added, stirred, and spray-dried to obtain phytic acid-modified lignin microcapsules.

[0018] In the preparation method of the above-mentioned phytic acid-modified lignin microcapsules, the preparation method of the phytic acid-modified lignin microcapsules comprises: dissolving sodium lignin sulfonate in 18 to 20 times the mass of 50°C to 60°C deionized water, adjusting the pH to 4 to 5 with a 1M to 1.2M hydrochloric acid aqueous solution; adding a 50wt% to 70wt% phytic acid aqueous solution at a mass ratio of sodium lignin sulfonate to phytic acid = 1: (0.2 to 0.3) under stirring at 200rpm to 400rpm, and then adding a P-TSA acid catalyst of 1% to 1.5% by mass of the sodium lignin sulfonate, stirring and reacting at 65°C to 75°C and 300rpm to 500rpm for 4h to 6h, adjusting the reaction system with a NaOH aqueous solution to keep the pH below 4 during the reaction, cooling to room temperature, and adjusting the pH to 7 to 8 with a NaOH aqueous solution. , concentrated under reduced pressure below 60°C, dried to constant weight below 60°C, ground, and passed through a 325-mesh sieve to obtain phytic acid-modified lignin; phytic acid-modified lignin and ethyl cellulose were added to ethyl acetate containing 5wt% to 10wt% ethanol in a mass ratio of 2: (1 to 1.5), and the material-liquid mass ratio was 1: (12 to 15) to obtain a mixed solution; the mixed solution was added to an aqueous solution containing 0.4wt% to 0.6wt% polyvinyl alcohol in an amount of 2 to 3 times the volume of the mixed solution, emulsified at 15°C to 20°C and 8000rpm to 9000rpm for 3min to 5min, microspheres were collected by centrifugation, and an aqueous solution containing 0.5wt% to 0.6wt% CaCl2 in an amount of 5 times to 6 times the mass of the microspheres was added, stirred for 30min to 60min, and spray-dried at 50°C to 60°C to obtain phytic acid-modified lignin microcapsules.

[0019] Among the above raw materials, the preparation method of thermally responsive carbonate includes: melting stearic acid at 80°C to 85°C, adding calcium carbonate powder in a mass ratio of stearic acid to calcium carbonate of 1: (3.5-4), dispersing at 3000rpm to 5000rpm for 10min to 15min, spray cooling and molding at below 60°C to obtain stearic acid-coated calcium carbonate, i.e., thermally responsive carbonate.

[0020] The above-mentioned method for preparing geopolymer from lime sand polymer building material with efflorescence inhibition comprises the following steps:

[0021] S1: calcining fly ash at 600°C to 650°C for 2h to 2.5h to remove unburned carbon, cooling, and grinding; grinding slag; and then mixing the fly ash and slag to obtain a composite matrix material;

[0022] S2: After uniformly mixing the composite matrix material, modified layered double metal hydroxide, slow-release organic acid microcapsules and efflorescence inhibitor, the composite alkali activator is added three times under continuous stirring at 60 rpm to 80 rpm. After the addition, the mixture is stirred at 300 rpm to 400 rpm for 5 min to 8 min, and water is added to control the slurry fluidity to 180 mm to 220 mm to obtain a mixture;

[0023] S3: The mixture is injected into the mold, heated to 38℃~42℃ for pre-curing for 4h~6h, and then transferred to a steam curing box at 58℃~62℃ and RH≥95% for treatment for 24h~28h; finally, cured at 20℃~25℃ and RH55%~65% for 28 days with daily spraying of curing agent to obtain the geopolymer.

[0024] In S1 of the above preparation method, the heating rate of the calcination is 8°C / min to 12°C / min, the fly ash is ground to a D90 of 8μm to 15μm, and the slag is ground to a D50 of 5μm to 10μm.

[0025] In S2 of the above preparation method, the composite alkali activator is added at intervals of 2 to 3 minutes each time, and the addition amounts are 40%, 30% and 30% of the mass of the composite alkali activator, respectively.

[0026] In S3 of the above preparation method, the curing agent is sprayed at 150 mL / m every 12 hours. 2 ~200mL / m 2 The curing agent is compounded by the following ingredients: 0.1wt% to 0.3wt% of sustained-release organic acid microcapsules, 0.1wt% to 0.3wt% of hydroxypropyl methylcellulose, 0.05wt% to 0.08wt% of sodium benzoate, and the balance is water.

[0027] The geopolymer prepared by the above method is used in prefabricated components of assembled buildings, marine concrete protective layers and floor engineering.

[0028] The present invention provides a lime-sand polymer building material capable of inhibiting efflorescence and a preparation method thereof, and has the following beneficial effects:

[0029] 1. Fly ash calcination removes unburned carbon, effectively reduces the adsorption of alkali activators, ensures the effective concentration of alkali activators, promotes the polymerization reaction of silicon-aluminum materials, and reduces alkali efflorescence; prevents the formation of weak structures inside the material, improves the density of the material, reduces the porosity, and thus improves the compressive strength and corrosion resistance of the material.

[0030] Second, slow-release organic acid microcapsules are prepared, which can slowly release citric acid and tartaric acid, reduce the concentration of alkali metal ions in the pore fluid, and inhibit the migration of alkali metal ions to the surface to react with CO2 in the air, thereby reducing the phenomenon of efflorescence. They are also added to the curing agent to continuously play the role of inhibiting efflorescence. Compared with citric acid and tartaric acid, the advantage of slow-release organic acid microcapsules is that they can slowly release organic acids. Ordinary citric acid and tartaric acid will react rapidly after addition, consuming a large amount of alkali metal ions in a short period of time, but they cannot provide long-term continuous inhibition. Slow-release organic acid microcapsules can continuously and stably release citric acid and tartaric acid for a long time, so that the material can maintain a low alkali metal ion concentration at different stages, thereby achieving long-term inhibition of efflorescence and avoiding the adverse effects of the rapid reaction of organic acid and alkali on material properties.

[0031] 3. Modified layered double hydroxides can adsorb alkali metal ions and fix Na + etc., reducing ion migration. At the same time, its special structure and modified properties help to improve the density of the material, thereby enhancing the material's impermeability and corrosion resistance. Compared with MgAl-LDH, the modified layered double hydroxide has better adsorption performance and ion exchange capacity after calcination, silane coupling agent treatment and loading of nano-SiO2, and can more effectively fix alkali metal ions. At the same time, the modified layered double hydroxide has better compatibility with the matrix material, forming a more stable structure inside the material, improving the material's density and impermeability, thereby enhancing the material's corrosion resistance and durability, overcoming the shortcomings of MgAl-LDH in these aspects when used alone.

[0032] Fourth, calcining the MgAl-LDH at 350°C to 400°C under nitrogen protection converts it into a Mg(Al)O mixed metal oxide with a high specific surface area, high surface activity, and the crucial "memory effect." When this calcined product is subsequently immersed in a solution containing a silane coupling agent and a SiO2 sol, its active surface and ability to reconstruct the LDH structure (memory effect) provide a crucial reaction platform and binding sites for effective chemical bonding of the silane coupling agent and successful loading of the nano-SiO2 particles. This specific temperature range strikes an optimal balance between ensuring thorough activation while avoiding deactivation and crystallization (spinelization).

[0033] Fifth, the efflorescence inhibition adjuvant is a mixture of phytic acid-modified lignin microcapsules and thermoresponsive carbonates in a specific ratio. The phytic acid-modified lignin microcapsules absorb some alkali metal ions through their own structure, while the thermoresponsive carbonates change at a certain temperature, helping to regulate the microenvironment within the material. The two work synergistically to further inhibit efflorescence without adversely affecting the material's performance.

[0034] Phytic acid-modified lignin microcapsules have better adsorption performance and stability than direct use of sodium lignin sulfonate. After sodium lignin sulfonate is modified with phytic acid and made into microcapsules, its surface properties and internal structure change, increasing the adsorption selectivity and adsorption capacity of alkali metal ions. Moreover, the microcapsule structure protects the internal phytic acid-modified lignin, making it less susceptible to external environmental influences within the material, allowing it to more sustainably adsorb alkali metal ions and thus more effectively suppress efflorescence. In contrast, when sodium lignin sulfonate is used alone, its adsorption effect and stability are inferior to those of phytic acid-modified lignin microcapsules.

[0035] Compared to calcium carbonate micropowder, thermally responsive carbonate is obtained by coating calcium carbonate micropowder with stearic acid. The stearic acid coating makes calcium carbonate thermally responsive. Under different temperature conditions, the state of stearic acid will change, thereby affecting the properties and mode of action of calcium carbonate. Inside the material, the thermally responsive carbonate adjusts the internal microenvironment of the material to a certain extent according to the changes in ambient temperature, causing the activity of the calcium carbonate micropowder to change, helping to inhibit the migration and crystallization of alkali metal ions and reduce efflorescence. Ordinary calcium carbonate micropowder does not have this thermal response characteristic, its function is relatively simple, and it cannot self-regulate according to the ambient temperature to better adapt to the complex conditions inside the material.

[0036] 6. The present invention designs a curing plan based on the characteristics of each component, which can better promote the curing progress and strength and improve various performances. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to specific implementation cases, but the present invention is not limited to these embodiments.

[0038] Example 1

[0039] A ash-sand polymer building material for inhibiting efflorescence is characterized in that it comprises the following raw materials in parts by mass: 60 parts of a composite matrix material, 20 parts of a composite alkali activator, 0.5 parts of slow-release organic acid microcapsules, 3 parts of a modified layered double metal hydroxide, and 1 part of an efflorescence inhibition adjuvant; wherein the composite matrix material is fly ash and slag compounded in a mass ratio of 1:1; the composite alkali activator is water glass with a modulus of 1.2 and a solid concentration of 35 wt% and a 6 mol / L NaOH aqueous solution compounded in a volume ratio of 1:1; and the efflorescence inhibition adjuvant is phytic acid-modified lignin microcapsules and a thermally responsive carbonate compounded in a mass ratio of 1:0.8.

[0040] Among them, the preparation method of sustained-release organic acid microcapsules includes: preparing a composite acid solution containing 10wt% citric acid and 10wt% tartaric acid at a temperature of 50°C; preparing a sodium alginate aqueous solution with a concentration of 6wt% and a temperature of 50°C; preparing a saturated hydroxypropyl-β-cyclodextrin aqueous solution at 50°C, adding a composite acid solution with a mass percentage of 30% of hydroxypropyl-β-cyclodextrin under stirring at 300rpm, stirring at 300rpm for 1h, adding a sodium alginate aqueous solution with a mass percentage of 8% of hydroxypropyl-β-cyclodextrin, stirring at 300rpm for 1h, adding a 0.5wt% CaCl2 aqueous solution with a mass percentage of 3% of hydroxypropyl-β-cyclodextrin, stirring for 30min, and spray drying below 40°C to obtain sustained-release organic acid microcapsules.

[0041] The preparation method of the modified layered double hydroxide includes: heating MgAl-LDH to 350°C at a rate of 2°C / min under nitrogen protection and calcining for 1.5 hours to obtain the layered double hydroxide; after cooling to room temperature, immersing the MgAl-LDH in anhydrous ethanol containing 1wt% of silane coupling agent KH-550, which is 8 times the mass of the layered double hydroxide, ultrasonically dispersing the MgAl-LDH at 300W and 40kHz for 30 minutes, centrifuging the MgAl-LDH at 8000rpm for 10 minutes, and re-dispersing the solid in anhydrous ethanol, which is 8 times the mass of the solid, adding SiO2 ethanol solution containing 6wt% of nano-SiO2 (prepared and used) based on the mass of nano-SiO2 being 3% of the solid, and the particle size of the nano-SiO2 being in the range of 5nm to 10nm; adsorbing the nano-SiO2 at 55°C and 300rpm under vacuum stirring for 2 hours, loading the nano-SiO2, centrifuging the MgAl-LDH at 8000rpm for 10 minutes, and drying the solid at 60°C for 12 hours to obtain the modified layered double hydroxide.

[0042] Among them, the preparation method of phytic acid modified lignin microcapsules includes: dissolving sodium lignin sulfonate in 18 times the mass of 50°C deionized water, adjusting the pH to 4 with a 1M hydrochloric acid aqueous solution; adding a 50wt% phytic acid aqueous solution at a mass ratio of sodium lignin sulfonate: phytic acid = 1:0.2 under stirring at 200rpm, and then adding a P-TSA acid catalyst of 1% by mass of sodium lignin sulfonate, stirring at 65°C and 300rpm for 4h, adjusting the reaction system with a NaOH aqueous solution to maintain the pH below 4 during the reaction, cooling to room temperature, adjusting the pH to 7 with a NaOH aqueous solution, and stirring at 60°C and above for 4h. The mixture was concentrated under reduced pressure, dried below 60°C to constant weight, ground, and passed through a 325-mesh sieve to obtain phytic acid-modified lignin; the phytic acid-modified lignin and ethyl cellulose were added to ethyl acetate containing 5wt% ethanol in a mass ratio of 2:1, and the material-liquid mass ratio was 1:12 to obtain a mixed solution; the mixed solution was added to an aqueous solution containing 0.4wt% polyvinyl alcohol in a volume twice that of the mixed solution, emulsified at 15°C and 8000rpm for 3min, microspheres were collected by centrifugation, and an aqueous solution containing 0.5wt% CaCl2 in a volume 5 times that of the microspheres was added, stirred for 30min, and spray-dried at 50°C to obtain phytic acid-modified lignin microcapsules.

[0043] Among them, the preparation method of thermally responsive carbonate includes: melting stearic acid at 80°C, adding calcium carbonate powder with a D50 of 10μm (the moisture content of the calcium carbonate powder is less than 0.2%) at a mass ratio of stearic acid to calcium carbonate of 1:3.5, dispersing at 3000rpm for 10 minutes, spray cooling and molding at below 60°C to obtain stearic acid-coated calcium carbonate, that is, thermally responsive carbonate.

[0044] The above-mentioned method for preparing geopolymer from lime sand polymer building material with efflorescence inhibition comprises the following steps:

[0045] S1: Fly ash was heated to 600°C at 8°C / min for 2 hours to remove unburned carbon (residual carbon content was less than 0.8 wt%), then cooled and ground to a D90 of 8 μm; slag was ground to a D50 of 5 μm; then the fly ash and slag were mixed to obtain a composite matrix material;

[0046] S2: After uniformly mixing the composite matrix material, modified layered double hydroxide, slow-release organic acid microcapsules and alkali-inhibiting adjuvant, the composite alkali activator was added three times with a 2-min interval between each addition at a rate of 40%, 30% and 30% of the mass of the composite alkali activator, respectively. After the addition, the mixture was stirred at 300 rpm for 5 minutes, and water was added to control the slurry fluidity at 180 mm to obtain a mixture.

[0047] S3: The mixture is injected into a mold, heated to 38°C for pre-curing for 4 hours, and then transferred to a steam curing box at 58°C and RH95% for 24 hours. Finally, the mixture is cured for 28 days at a temperature between 20°C and 25°C and a RH between 55% and 65%, sprayed with a curing agent daily, to obtain a geopolymer.

[0048] Among them, the curing agent is sprayed at 150mL / m every 12 hours. 2 The curing agent is compounded by the following ingredients: 0.1wt% slow-release organic acid microcapsules, 0.1wt% hydroxypropyl methylcellulose, 0.05wt% sodium benzoate, and the balance is water.

[0049] The geopolymer prepared by the above method is used in prefabricated components of assembled buildings, marine concrete protective layers and floor engineering.

[0050] Example 2

[0051] A ash-sand polymer building material for inhibiting efflorescence is characterized in that it comprises the following raw materials in parts by mass: 68 parts of a composite matrix material, 25 parts of a composite alkali activator, 1 part of a slow-release organic acid microcapsule, 4 parts of a modified layered double metal hydroxide, and 1.5 parts of an efflorescence inhibition adjuvant; wherein the composite matrix material is fly ash and slag compounded in a mass ratio of 1:1.2; the composite alkali activator is water glass with a modulus of 1.5 and a solid concentration of 36 wt% and an 8 mol / L NaOH aqueous solution compounded in a volume ratio of 1:1.1; and the efflorescence inhibition adjuvant is phytic acid-modified lignin microcapsules and a thermally responsive carbonate compounded in a mass ratio of 1:1.

[0052] Among them, the preparation method of sustained-release organic acid microcapsules includes: preparing a composite acid solution containing 12wt% citric acid and 13wt% tartaric acid at a temperature of 55°C; preparing a sodium alginate aqueous solution with a concentration of 7wt% and a temperature of 55°C; preparing a saturated hydroxypropyl-β-cyclodextrin aqueous solution at 55°C, adding a composite acid solution with a mass percentage of 32% of hydroxypropyl-β-cyclodextrin under stirring at 350rpm, stirring at 350rpm for 1.5h, adding a sodium alginate aqueous solution with a mass percentage of 9% of hydroxypropyl-β-cyclodextrin, stirring at 350rpm for 1.5h, adding a 0.5wt% CaCl2 aqueous solution with a mass percentage of 4% of hydroxypropyl-β-cyclodextrin, stirring for 40min, and spray drying below 40°C to obtain sustained-release organic acid microcapsules.

[0053] The preparation method of the modified layered double hydroxide includes: heating MgAl-LDH to 380°C at a rate of 3°C / min under nitrogen protection and calcining for 1.5 hours to obtain the layered double hydroxide; after cooling to room temperature, immersing it in anhydrous ethanol containing 1.5wt% of silane coupling agent KH-550, which is 9 times the mass of the layered double hydroxide, ultrasonically dispersing it at 320W and 45kHz for 40 minutes, centrifuging it at 9000rpm for 12 minutes, taking the solid and redispersing it in anhydrous ethanol with a mass of 9 times the mass of the solid, adding SiO2 ethanol solution containing 7wt% nano-SiO2 (freshly prepared and used) based on the mass of nano-SiO2 being 4% of the solid, and the particle size of the nano-SiO2 ranging from 5nm to 10nm; adsorbing it under vacuum stirring at 58°C and 400rpm for 2 hours, loading the nano-SiO2, centrifuging it at 9000rpm for 12 minutes, and drying the solid at 62°C for 13 hours to obtain the modified layered double hydroxide.

[0054] Among them, the preparation method of phytic acid modified lignin microcapsules includes: dissolving sodium lignin sulfonate in 19 times the mass of 55°C deionized water, adjusting the pH to 4.5 with a 1.1M hydrochloric acid aqueous solution; adding a 60wt% phytic acid aqueous solution at a mass ratio of sodium lignin sulfonate: phytic acid = 1:0.25 under stirring at 300rpm, and then adding a P-TSA acid catalyst with a mass ratio of 1.2% of the mass of sodium lignin sulfonate, stirring at 70°C and 400rpm for 5h, adjusting the reaction system with a NaOH aqueous solution to maintain the pH below 4 during the reaction, cooling to room temperature, adjusting the pH to 7.5 with a NaOH aqueous solution, and 60°C The mixture was concentrated under reduced pressure, dried below 60°C to constant weight, ground, and passed through a 325-mesh sieve to obtain phytic acid-modified lignin; the phytic acid-modified lignin and ethyl cellulose were added to ethyl acetate containing 8wt% ethanol in a mass ratio of 2:1.2, and the material-liquid mass ratio was 1:13 to obtain a mixed solution; the mixed solution was added to an aqueous solution containing 0.5wt% polyvinyl alcohol in a volume 2.5 times that of the mixed solution, emulsified at 18°C ​​and 8500rpm for 4min, microspheres were collected by centrifugation, and 0.55wt% CaCl2 aqueous solution in a volume 5.5 times that of the microspheres was added, stirred for 45min, and spray-dried at 55°C to obtain phytic acid-modified lignin microcapsules.

[0055] Among them, the preparation method of thermally responsive carbonate includes: melting stearic acid at 82°C, adding calcium carbonate powder with a D50 of 16μm (the moisture content of the calcium carbonate powder is less than 0.2%) at a mass ratio of stearic acid to calcium carbonate of 1:3.8, dispersing at 4000rpm for 12 minutes, spray cooling and molding at below 60°C to obtain stearic acid-coated calcium carbonate, that is, thermally responsive carbonate.

[0056] The above-mentioned method for preparing geopolymer from lime sand polymer building material with efflorescence inhibition comprises the following steps:

[0057] S1: Fly ash was heated to 620°C at a rate of 10°C / min and calcined for 2 hours to remove unburned carbon (residual carbon content was less than 0.8 wt%), then cooled and ground to a D90 of 12 μm; slag was ground to a D50 of 8 μm; and then the fly ash and slag were mixed uniformly to obtain a composite matrix material;

[0058] S2: After uniformly mixing the composite matrix material, modified layered double metal hydroxide, slow-release organic acid microcapsules and efflorescence inhibition adjuvant, the composite alkali activator was added three times under continuous stirring at 70 rpm, with an interval of 3 minutes between each addition. The addition amounts were 40%, 30% and 30% of the mass of the composite alkali activator, respectively. After the addition, the mixture was stirred at 350 rpm for 6 minutes, and water was added to control the slurry fluidity at 200 mm to obtain a mixture;

[0059] S3: The mixture is injected into a mold, heated to 40°C for pre-curing for 5 hours, and then transferred to a steam curing box at 60°C and RH98% for 26 hours. Finally, the mixture is cured for 28 days at a temperature between 20°C and 25°C and a RH between 55% and 65%, sprayed with a curing agent daily, to obtain a geopolymer.

[0060] Among them, the curing agent is sprayed at 180mL / m every 12h. 2 The curing agent is compounded by the following ingredients: 0.2wt% slow-release organic acid microcapsules, 0.2wt% hydroxypropyl methylcellulose, 0.06wt% sodium benzoate, and the balance is water.

[0061] The geopolymer prepared by the above method is used in prefabricated components of assembled buildings, marine concrete protective layers and floor engineering.

[0062] Example 3

[0063] A ash-sand polymer building material for inhibiting efflorescence is characterized in that it comprises the following raw materials in parts by mass: 75 parts of a composite matrix material, 30 parts of a composite alkali activator, 1.5 parts of slow-release organic acid microcapsules, 5 parts of a modified layered double metal hydroxide, and 2 parts of an efflorescence inhibition adjuvant; wherein the composite matrix material is fly ash and slag compounded in a mass ratio of 1:1.4; the composite alkali activator is water glass with a modulus of 1.8 and a solid concentration of 38 wt% and a 10 mol / L NaOH aqueous solution compounded in a volume ratio of 1:1.2; and the efflorescence inhibition adjuvant is phytic acid-modified lignin microcapsules and a thermally responsive carbonate compounded in a mass ratio of 1:1.2.

[0064] Among them, the preparation method of sustained-release organic acid microcapsules includes: preparing a composite acid solution containing 15wt% citric acid and 15wt% tartaric acid at a temperature of 60°C; preparing a sodium alginate aqueous solution with a concentration of 8wt% and a temperature of 60°C; preparing a saturated hydroxypropyl-β-cyclodextrin aqueous solution at 60°C, adding a composite acid solution with a mass percentage of 35% of hydroxypropyl-β-cyclodextrin under stirring at 400rpm, stirring at 400rpm for 2h, adding a sodium alginate aqueous solution with a mass percentage of 10% of hydroxypropyl-β-cyclodextrin, stirring at 400rpm for 2h, adding a 0.6wt% CaCl2 aqueous solution with a mass percentage of 5% of hydroxypropyl-β-cyclodextrin, stirring for 50min, and spray drying below 40°C to obtain sustained-release organic acid microcapsules.

[0065] The preparation method of the modified layered double hydroxide includes: heating MgAl-LDH to 400°C at a rate of 3°C / min under nitrogen protection and calcining for 2 hours to obtain the layered double hydroxide; after cooling to room temperature, immersing it in anhydrous ethanol containing 2wt% of silane coupling agent KH-550, which is 10 times the mass of the layered double hydroxide, ultrasonically dispersing it at 350W and 50kHz for 50 minutes, centrifuging it at 10,000rpm for 15 minutes, taking the solid and redispersing it in anhydrous ethanol with a mass of 10 times the mass of the solid, adding SiO2 ethanol solution containing 8wt% nano-SiO2 (freshly prepared and used) based on the mass of nano-SiO2 being 5% of the solid, and the particle size of the nano-SiO2 being in the range of 5nm to 10nm; vacuum stirring and adsorbing it at 60°C and 500rpm for 2.5 hours, loading the nano-SiO2, centrifuging it at 10,000rpm for 15 minutes, and taking the solid and drying it at 65°C for 14 hours to obtain the modified layered double hydroxide.

[0066] Among them, the preparation method of phytic acid modified lignin microcapsules includes: dissolving sodium lignin sulfonate in 20 times the mass of 60°C deionized water, adjusting the pH to 5 with 1.2M hydrochloric acid aqueous solution; adding a 70wt% concentration of phytic acid aqueous solution at a mass ratio of sodium lignin sulfonate: phytic acid = 1:0.3 under stirring at 400rpm, and then adding 1.5% P-TSA acid catalyst by mass of sodium lignin sulfonate, stirring and reacting at 75°C and 500rpm for 6h, adjusting the reaction system with NaOH aqueous solution to maintain pH below 4 during the reaction, cooling to room temperature, adjusting the pH to 8 with NaOH aqueous solution, and 60°C The mixture was concentrated under reduced pressure, dried below 60°C to constant weight, ground, and passed through a 325-mesh sieve to obtain phytic acid-modified lignin; the phytic acid-modified lignin and ethyl cellulose were added to ethyl acetate containing 10wt% ethanol in a mass ratio of 2:1.5, and the material-liquid mass ratio was 1:15 to obtain a mixed solution; the mixed solution was added to an aqueous solution containing 0.6wt% polyvinyl alcohol in a volume 3 times that of the mixed solution, emulsified at 20°C and 9000rpm for 5min, microspheres were collected by centrifugation, and 0.6wt% CaCl2 aqueous solution in a volume 6 times that of the microspheres was added, stirred for 60min, and spray-dried at 60°C to obtain phytic acid-modified lignin microcapsules.

[0067] Among them, the preparation method of thermally responsive carbonate includes: melting stearic acid at 85°C, adding calcium carbonate powder with a D50 of 20μm (the moisture content of the calcium carbonate powder is less than 0.2%) at a mass ratio of stearic acid to calcium carbonate of 1:4, dispersing at 5000rpm for 15 minutes, spray cooling and molding at below 60°C to obtain stearic acid-coated calcium carbonate, that is, thermally responsive carbonate.

[0068] The above-mentioned method for preparing geopolymer from lime sand polymer building material with efflorescence inhibition comprises the following steps:

[0069] S1: Fly ash was heated to 650°C at a rate of 12°C / min and calcined for 2.5 hours to remove unburned carbon (residual carbon content was less than 0.8 wt%), then cooled and ground to a D90 of 15 μm; slag was ground to a D50 of 10 μm; and then the fly ash and slag were mixed uniformly to obtain a composite matrix material;

[0070] S2: After uniformly mixing the composite matrix material, modified layered double metal hydroxide, slow-release organic acid microcapsules and alkali-inhibiting adjuvant, the composite alkali activator was added three times under continuous stirring at 80 rpm, with an interval of 3 minutes between each addition. The addition amounts were 40%, 30% and 30% of the mass of the composite alkali activator, respectively. After the addition, the mixture was stirred at 400 rpm for 8 minutes, and water was added to control the slurry fluidity at 220 mm to obtain a mixture;

[0071] S3: The mixture is injected into a mold, heated to 42°C for pre-curing for 6 hours, and then transferred to a steam curing box at 62°C and RH 96% for 28 hours. Finally, the mixture is cured for 28 days at a temperature between 20°C and 25°C and a RH between 55% and 65%, sprayed with a curing agent daily, to obtain a geopolymer.

[0072] Among them, the curing agent is sprayed at 200mL / m every 12h. 2 The curing agent is compounded by the following ingredients: 0.3wt% slow-release organic acid microcapsules, 0.3wt% hydroxypropyl methylcellulose, 0.08wt% sodium benzoate, and the balance is water.

[0073] The geopolymer prepared by the above method is used in prefabricated components of assembled buildings, marine concrete protective layers and floor engineering.

[0074] In the above embodiments, the preparation method of MgAl-LDH includes: preparing a 0.2 mol / L magnesium nitrate solution; preparing a 0.05 mol / L aluminum nitrate solution; preparing a 1.0 mol / L sodium hydroxide solution; mixing the magnesium nitrate solution and the aluminum nitrate solution in an equal volume ratio, and then adding the sodium hydroxide solution at a rate of 2 drops / second under stirring at 300 r / min, controlling the pH value between 9.5 and 10.5, and performing a precipitation reaction. After the precipitation reaction is completed, the temperature is raised to 70°C, and the mixture is allowed to stand for aging for 12 hours to allow the precipitated particles to fully grow and crystallize, and filtered to obtain a precipitate. The precipitate is repeatedly washed with deionized water 5 times, and dried at 70°C for 12 hours to obtain a magnesium-aluminum layered double hydroxide powder, i.e., MgAl-LDH.

[0075] The sources of some raw materials in the above embodiments are as follows: fly ash is sourced from Lingshou County Fuda Mineral Products Processing Plant, first-grade fly ash. Slag is sourced from Lingshou County Jinhong New Materials Co., Ltd., S95-grade granulated blast furnace slag powder. Sodium lignin sulfonate is sourced from Jinan Feiyue Chemical Co., Ltd. Phytic acid is sourced from Jingjiang Shengjin Technology Co., Ltd., phytic acid powder. Sodium alginate is sourced from Zhengzhou Juepai Chemical Products Co., Ltd., industrial grade. Hydroxypropyl-β-cyclodextrin is sourced from Xi'an Cuibang Biotechnology Co., Ltd. Ethyl cellulose is sourced from Xi'an Shouhe Biotechnology Co., Ltd., industrial grade. Polyvinyl alcohol is sourced from Langfang Feitai New Materials Technology Co., Ltd. Stearic acid is sourced from Tai'an Tonglida Chemical Co., Ltd. Hydroxypropyl methylcellulose is sourced from Shandong Dechun Chemical Co., Ltd. Silane coupling agent KH-550 is sourced from Henan Wanshan New Materials Technology Co., Ltd. The P-TSA acid catalyst is AMORSO-7801 closed-type P-TSA acid catalyst.

[0076] Comparative Example 1

[0077] In the material, the sustained-release organic acid microcapsules were directly replaced by citric acid and tartaric acid without preparing microcapsules; in the curing agent, the sustained-release organic acid microcapsules were directly replaced by citric acid and tartaric acid; other parameters and methods were the same as in Example 1.

[0078] Comparative Example 2

[0079] In the preparation method of sustained-release organic acid microcapsules, sodium alginate is not added; other parameters and methods are the same as in Example 1.

[0080] Comparative Example 3

[0081] In the material, 5 parts of sustained-release organic acid microcapsules were added (excess); other parameters and methods were the same as those in Example 1.

[0082] Comparative Example 4

[0083] The modified layered double hydroxide was replaced by MgAl-LDH; other parameters and methods were the same as in Example 1.

[0084] Comparative Example 5

[0085] In the preparation method of the modified layered double hydroxide, MgAl-LDH is not calcined; other parameters and methods are the same as in Example 1.

[0086] Comparative Example 6

[0087] In the preparation method of the modified layered double hydroxide, nano-SiO2 is not loaded; other parameters and methods are the same as in Example 1.

[0088] Comparative Example 7

[0089] Phytic acid modified lignin microcapsules were directly replaced by sodium lignin sulfonate; other parameters and methods were the same as in Example 1.

[0090] Comparative Example 8

[0091] Phytic acid modified lignin microcapsules were directly replaced by phytic acid modified lignin (without preparing microcapsules); other parameters and methods were the same as in Example 1.

[0092] Comparative Example 9

[0093] The thermally responsive carbonate was directly replaced by calcium carbonate powder; other parameters and methods were the same as in Example 1.

[0094] Comparative Example 10

[0095] In preparation method S1, the fly ash is not calcined; other parameters and methods are the same as in Example 1.

[0096] Comparative Example 11

[0097] In the material, 1 part of modified layered double hydroxide was added (too little), and 5 parts of efflorescence inhibition auxiliary agent was added (excessive); other parameters and methods were the same as in Example 1.

[0098] Control group: no slow-release organic acid microcapsules, modified layered double metal hydroxides and alkali-inhibiting adjuvant were added to the material; no slow-release organic acid microcapsules were added to the curing agent; other parameters and methods were the same as in Example 1.

[0099] 1. Sample preparation

[0100] Size specifications: Prepare cubic specimens with a side length of 100 mm for compressive strength, efflorescence inhibition rate, and porosity testing; prepare long cylindrical specimens with a size of 10 mm × 10 mm × 100 mm for 90-day sulfate erosion expansion rate testing.

[0101] Number of samples prepared: For each embodiment and comparative example, three parallel samples were prepared for each test item.

[0102] Sample preparation process: Prepare test specimens according to the schemes of each embodiment and comparative example.

[0103] 2. Specific detection methods

[0104] 1. Compressive strength: According to the Standard for Test Methods of Mechanical Properties of Ordinary Concrete (GB / T 50081), the specimen was uniformly loaded at a loading rate of 0.5 MPa / s until the specimen failed. The failure load was recorded and the compressive strength was calculated.

[0105] 2. Efflorescence inhibition rate: The image software analysis method was used to identify and calculate the efflorescence area on the specimen surface. Efflorescence inhibition rate = (efflorescence area of ​​the control group - efflorescence area of ​​the experimental group) / efflorescence area of ​​the control group × 100%.

[0106] 3. Porosity: Using the mercury intrusion method, grind the sample into 0.1mm-0.5mm powder, dry it to constant weight, and place it in a mercury intrusion instrument. The porosity of the material is calculated by measuring the volume of mercury entering the pores of the material under pressure.

[0107] 4. 90-day sulfate erosion expansion rate: Immerse the specimen in a 5wt% sodium sulfate solution. Calculate the expansion rate after 90 days: Expansion rate = (length after immersion - length before immersion) / length before immersion × 100%.

[0108] Table 1 Test results (interval values ​​of 3 parallel samples)

[0109]

[0110] In Examples 1 to 3, the sustained-release organic acid microcapsules continuously release organic acid to neutralize migrating alkali metal ions and inhibit efflorescence. The modified layered double hydroxide, with its layered structure and high specific surface area, adsorbs more alkali metal ions. The phytic acid-modified lignin microcapsules in the efflorescence inhibition adjuvant chelate ions, while the thermally responsive carbonates regulate the pore environment. These three factors work synergistically to significantly improve efflorescence inhibition and compressive strength, while reducing porosity and sulfate swelling. This offers significant advantages without compromising material flowability, maintaining excellent pumpability.

[0111] Comparative Example 1 directly replaces the sustained-release organic acid microcapsules with citric acid and tartaric acid. The acid is rapidly released early in the material, neutralizing a large amount of alkali metal ions in the short term. However, this acid is unable to maintain its effect over the long term after the material hardens. Excessive acid in the early stages also interferes with the hydration reaction of the geopolymer, resulting in insufficient hydration product formation, a loose internal structure, increased porosity, and reduced compressive strength. Structural defects facilitate the migration of alkali metal ions to the surface, causing efflorescence and weakening sulfate resistance.

[0112] In Comparative Example 2, sodium alginate was not added to the preparation of sustained-release organic acid microcapsules. Sodium alginate acts as a gelling agent and stabilizer, and its absence reduces the structural stability of the microcapsules. This leads to rupture and uneven release during storage and release of the organic acid within the material. This prevents the organic acid from achieving the desired sustained-release effect, weakening its neutralization of alkali metal ions and thus reducing the efflorescence inhibition rate. This unstable microcapsule performance also indirectly affects the uniformity of the material's hydration reaction, resulting in increased porosity and reduced compressive strength and other properties.

[0113] In Comparative Example 3, excessive addition of sustained-release organic acid microcapsules creates an overly acidic environment within the material, inhibiting the aluminosilicate polymerization reaction, a key step in the geopolymer hydration reaction. The large amount of organic acid takes up space, hindering the normal growth and accumulation of hydration products, resulting in a loose and porous structure that significantly reduces compressive strength and increases porosity. While increased organic acid can neutralize more alkali metal ions to a certain extent, the excessive addition degrades the material structure, impairing corrosion resistance.

[0114] The unmodified MgAl-LDH in Comparative Example 4 exhibited poor dispersibility within the material and poor compatibility with the matrix, failing to fully utilize the ion exchange and adsorption properties of its layered structure. Compared to modified layered double hydroxides, the unmodified MgAl-LDH struggled to uniformly and effectively adsorb and immobilize alkali metal ions, leading to increased migration of alkali metal ions within the material and exacerbated efflorescence, which impacted porosity. Furthermore, it failed to provide uniform and good structural support and optimization for the material, resulting in decreased mechanical properties, impermeability, and, consequently, sulfate corrosion resistance.

[0115] In Comparative Example 5, the MgAl-LDH was not calcined, resulting in a dense crystal structure, encapsulated active sites, a small specific surface area, and a failure to expel internal moisture adsorbed during storage, resulting in weak ion exchange capacity. The calcination process dehydrates and dehydroxylates the MgAl-LDH, forming a highly reactive layered structure that facilitates subsequent modification and ion adsorption. Uncalcined MgAl-LDH is less likely to react fully with alkali metal ions within the material, reducing its effectiveness in inhibiting efflorescence. Furthermore, it does not adequately improve the material's internal structure, resulting in increased porosity and reduced compressive strength and corrosion resistance.

[0116] Comparative Example 6: Nano-SiO2 loading significantly improves the dispersibility of the layered double hydroxide, strengthens its adhesion to the matrix, and enhances its ion adsorption efficiency. Without nano-SiO2 loading, the modified layered double hydroxide tends to agglomerate within the material, preventing uniform dispersion and functioning. This weakens its ability to fix alkali metal ions, resulting in a decrease in efflorescence inhibition and overall material performance. Agglomerates also form defects within the material, affecting its density and mechanical properties.

[0117] In Comparative Example 7, sodium lignin sulfonate itself exhibits far inferior alkali metal ion chelation and sustained-release properties to phytic acid-modified lignin microcapsules. Phytic acid modification introduces a large number of chelating groups, which form stable complexes with alkali metal ions. Microencapsulation enables slow release and sustained inhibition of efflorescence. Direct use of sodium lignin sulfonate fails to effectively inhibit alkali metal ion migration, resulting in a reduced efflorescence inhibition rate. Furthermore, its limited effect on optimizing the material structure reduces the material's compressive strength, impermeability, and corrosion resistance.

[0118] In Comparative Example 8, the phytic acid-modified lignin, if not microencapsulated, would be rapidly released from the material. This would result in excessive alkali metal ion consumption in the early stages, affecting the proper hydration reaction of the geopolymer. Later, due to premature depletion, alkali metal ions could not be continuously suppressed. Microencapsulation, however, controlled the release of the phytic acid-modified lignin at the appropriate stage, ensuring a balance between hydration and alkali inhibition. Failure to microencapsulate the material resulted in unstable material performance and reduced performance indicators.

[0119] Comparative Example 9: The thermoresponsive carbonate, coated with stearic acid, imparts unique temperature-responsive properties. This allows it to adjust the pore environment and synergistically inhibit efflorescence when the humidity and temperature within the material change. Conventional calcium carbonate micropowder, acting solely as an inert filler, lacks the ability to inhibit alkali metal ion migration or regulate the pore environment, and thus fails to synergize with other additives. This results in a material with lower efflorescence inhibition and overall performance than the examples.

[0120] In Comparative Example 10, the fly ash was not calcined. The unburned carbon in the fly ash adsorbed the alkali activator, reducing its effective concentration and slowing down and hindering the polymerization reaction of the silicon-alumina material. The unburned carbon also formed a weak structure within the material, affecting its density. This reduced its compressive strength, increased its porosity, facilitated the migration of alkali metal ions, led to severe efflorescence, and reduced its corrosion resistance.

[0121] In Comparative Example 11, too little modified layered double hydroxide is added, which cannot provide sufficient ion adsorption sites and has insufficient fixation capacity for alkali metal ions, resulting in a decrease in the efflorescence inhibition rate; excessive efflorescence inhibition adjuvant will form excess fillers inside the material, interfering with the normal hydration reaction and structure formation of the material, making the internal structure of the material uneven and reducing the compressive strength; excessive adjuvant also affects the uniformity of pore size and reduces the corrosion resistance.

Claims

1. A lime-sand polymer building material for inhibiting efflorescence, characterized in that: The method comprises the following raw materials in parts by weight: 60 to 75 parts of composite matrix material, 20 to 30 parts of composite alkali activator, 0.5 to 1.5 parts of slow-release organic acid microcapsules, 3 to 5 parts of modified layered double metal hydroxide and 1 to 2 parts of efflorescence inhibition auxiliary agent; The composite matrix material is fly ash and slag in a mass ratio of 1: (1-1.4); the composite alkali activator is composed of a modulus of 1.2-1.8, a solid concentration of 35wt%-38wt% water glass and 6mol / L-10mol / L The NaOH aqueous solution is compounded in a volume ratio of 1:(1-1.2); the sustained-release organic acid microcapsules are a composite acid mixed with citric acid and tartaric acid, which is coated with hydroxypropyl-β-cyclodextrin and sodium alginate; the modified layered double hydroxide is prepared by calcining MgAl-LDH, surface-modifying it with a silane coupling agent, and then loading nano-SiO2; the alkali-inhibiting adjuvant is a compound of phytic acid-modified lignin microcapsules and thermally responsive carbonates in a mass ratio of 1:(0.8-1.2); the phytic acid-modified lignin microcapsules are sodium lignin sulfonate modified with phytic acid, and then coated with ethyl cellulose and polyvinyl alcohol; the thermally responsive carbonate is calcium carbonate coated with stearic acid.

2. The lime-sand polymer building material for inhibiting efflorescence according to claim 1, characterized in that: The preparation method of the sustained-release organic acid microcapsules comprises: preparing a composite acid solution containing 10wt% to 15wt% of citric acid and 10wt% to 15wt% of tartaric acid; preparing a sodium alginate aqueous solution with a concentration of 6wt% to 8wt%; preparing a saturated hydroxypropyl-β-cyclodextrin aqueous solution at 50°C to 60°C, adding the composite acid solution with a concentration of 30% to 35% by weight of hydroxypropyl-β-cyclodextrin under stirring, stirring for 1h to 2h, adding a sodium alginate aqueous solution with a concentration of 8% to 10% by weight of hydroxypropyl-β-cyclodextrin, stirring for 1h to 2h, adding a CaCl2 aqueous solution with a concentration of 3% to 5% by weight of hydroxypropyl-β-cyclodextrin, stirring for 30min to 50min, and spray drying to obtain the sustained-release organic acid microcapsules.

3. The lime-sand polymer building material for inhibiting efflorescence according to claim 2, characterized in that: The temperature of the composite acid solution is 50° C. to 60° C.; the temperature of the sodium alginate aqueous solution is 50° C. to 60° C.; the stirring speed is 300 rpm to 400 rpm; and the temperature of the spray drying is below 40° C.

4. The lime-sand polymer building material for inhibiting efflorescence according to claim 1, characterized in that: The preparation method of the modified layered double metal hydroxide comprises: heating MgAl-LDH to 350° C. to 400° C. and calcining for 1.5 to 2 hours under nitrogen protection to obtain the layered double metal hydroxide; after cooling to room temperature, immersing the MgAl-LDH in anhydrous ethanol containing 1wt% to 2wt% of a silane coupling agent at a mass of 8 to 10 times that of the layered double metal hydroxide, ultrasonically dispersing the MgAl-LDH, centrifuging the MgAl-LDH, taking the solid and redispersing it in anhydrous ethanol at a mass of 8 to 10 times that of the solid, adding SiO2 ethanol solution based on nano-SiO2 accounting for 3% to 5% of the solid mass, stirring and adsorbing the MgAl-LDH, loading the nano-SiO2, centrifuging the MgAl-LDH, and drying the solid to obtain the modified layered double metal hydroxide.

5. The lime-sand polymer building material for inhibiting efflorescence according to claim 4, characterized in that: The heating rate is 2°C / min to 3°C / min; the silane coupling agent KH-550; the ultrasonic dispersion is ultrasonic dispersion at 300W to 350W and 40kHz to 50kHz for 30min to 50min; the stirring adsorption is vacuum stirring adsorption at 55°C to 60°C and 300rpm to 500rpm for 2h to 2.5h; the centrifugation is centrifugation at 8000rpm to 10000rpm for 10min to 15min; the drying is drying at 60°C to 65°C for 12h to 14h; the particle size range of nano-SiO2 in the SiO2 ethanol solution is 5nm to 10nm; the SiO2 ethanol solution contains 6wt% to 8wt% nano-SiO2.

6. The lime-sand polymer building material for inhibiting efflorescence according to claim 1, characterized in that: The preparation method of the phytic acid modified lignin microcapsules comprises: dissolving sodium lignin sulfonate in deionized water, adjusting the pH to 4-5 with a hydrochloric acid aqueous solution; adding a phytic acid aqueous solution with a concentration of 50wt%-70wt% according to a mass ratio of sodium lignin sulfonate: phytic acid = 1: (0.2-0.3) under stirring, then adding a P-TSA acid catalyst with a mass ratio of 1%-1.5% of the mass of the sodium lignin sulfonate, stirring and reacting at 65°C-75°C, adjusting the reaction system with a NaOH aqueous solution to maintain the pH below 4 during the reaction, cooling to room temperature, and rinsing with NaOH. The aqueous solution is adjusted to pH 7-8, concentrated under reduced pressure, dried to constant weight, and ground to obtain phytic acid-modified lignin; the phytic acid-modified lignin and ethyl cellulose are added to ethyl acetate containing 5wt%-10wt% ethanol in a mass ratio of 2: (1-1.5) to obtain a mixed solution; the mixed solution is added to an aqueous solution containing 0.4wt%-0.6wt% polyvinyl alcohol, emulsified, and microspheres are collected by centrifugation; an aqueous solution containing 0.5wt%-0.6wt% CaCl2 in an amount 5 times to 6 times the mass of the microspheres is added, stirred, and spray-dried to obtain phytic acid-modified lignin microcapsules.

7. The lime-sand polymer building material for inhibiting efflorescence according to claim 6, characterized in that: The preparation method of the phytic acid modified lignin microcapsules comprises: dissolving sodium lignin sulfonate in 18 to 20 times the mass of 50 to 60° C. deionized water, adjusting the pH to 4 to 5 with a 1M to 1.2M hydrochloric acid aqueous solution; adding a phytic acid aqueous solution with a concentration of 50 wt% to 70 wt% at a mass ratio of sodium lignin sulfonate to phytic acid of 1: (0.2 to 0.3) under stirring at 200 to 400 rpm, then adding a P-TSA acid catalyst with a concentration of 1% to 1.5% by mass of the sodium lignin sulfonate, stirring at 65 to 75° C. and 300 to 500 rpm for 4 to 6 hours, adjusting the reaction system with a NaOH aqueous solution to maintain a pH below 4 during the reaction, cooling to room temperature, adjusting the pH to 7 to 8 with a NaOH aqueous solution, and concentrating under reduced pressure below 60° C. , dried below 60°C to constant weight, ground, and passed through a 325-mesh sieve to obtain phytic acid-modified lignin; the phytic acid-modified lignin and ethyl cellulose are added to ethyl acetate containing 5wt%~10wt% ethanol in a mass ratio of 2: (1~1.5), and the material-liquid mass ratio is 1: (12~15) to obtain a mixed solution; the mixed solution is added to an aqueous solution containing 0.4wt%~0.6wt% polyvinyl alcohol in an amount of 2 times to 3 times the volume of the mixed solution, emulsified at 15°C~20°C and 8000rpm~9000rpm for 3min~5min, microspheres are collected by centrifugation, and an aqueous solution containing 0.5wt%~0.6wt% CaCl2 in an amount of 5 times to 6 times the mass of the microspheres is added, stirred for 30min~60min, and spray-dried at 50°C~60°C to obtain phytic acid-modified lignin microcapsules.

8. The lime-sand polymer building material for inhibiting efflorescence according to claim 1, characterized in that: The preparation method of the thermally responsive carbonate comprises: melting stearic acid at 80°C to 85°C, adding calcium carbonate powder in a mass ratio of stearic acid to calcium carbonate of 1:(3.5-4), dispersing at 3000rpm to 5000rpm for 10min to 15min, and spray cooling and molding at below 60°C to obtain stearic acid-coated calcium carbonate, i.e., the thermally responsive carbonate.

9. A method for preparing a geopolymer, using the lime-sand polymer building material with efflorescence inhibition according to claim 1, characterized in that: The method comprises the following steps: S1: calcining fly ash at 600°C to 650°C for 2h to 2.5h to remove unburned carbon, cooling, and grinding; grinding slag; and then mixing the fly ash and slag to obtain a composite matrix material; S2: After uniformly mixing the composite matrix material, modified layered double metal hydroxide, slow-release organic acid microcapsules and efflorescence inhibitor, the composite alkali activator is added three times under continuous stirring at 60 rpm to 80 rpm. After the addition, the mixture is stirred at 300 rpm to 400 rpm for 5 min to 8 min, and water is added to control the slurry fluidity to 180 mm to 220 mm to obtain a mixture; S3: The mixture is injected into the mold, heated to 38℃~42℃ for pre-curing for 4h~6h, and then transferred to a steam curing box at 58℃~62℃ and RH≥95% for treatment for 24h~28h; finally, cured at 20℃~25℃ and RH55%~65% for 28 days with daily spraying of curing agent to obtain the geopolymer.

10. The method for preparing a geopolymer according to claim 9, characterized in that: In S1, the heating rate of the calcination is 8°C / min to 12°C / min, the fly ash is ground to a D90 of 8μm to 15μm, and the slag is ground to a D50 of 5μm to 10μm; in S2, the composite alkali activator is added at intervals of 2min to 3min each time, and the addition amount is 40%, 30% and 30% of the mass of the composite alkali activator respectively; in S3, the curing agent is sprayed at an interval of 12h at 150mL / m 2 ~200mL / m 2 The curing agent is compounded by the following ingredients: 0.1wt% to 0.3wt% of sustained-release organic acid microcapsules, 0.1wt% to 0.3wt% of hydroxypropyl methylcellulose, 0.05wt% to 0.08wt% of sodium benzoate, and the balance is water.

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