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CN-121974647-A - Preparation method and application of phosphogypsum geopolymer with retarding and crack resistance enhancing properties

CN121974647ACN 121974647 ACN121974647 ACN 121974647ACN-121974647-A

Abstract

The invention discloses a preparation method and application of phosphogypsum geopolymer with retarding and crack resistance enhancing properties. The construction method comprises the steps of preprocessing phosphogypsum slag to obtain processed alpha semi-hydrated phosphogypsum, then compounding the preprocessed F-level low-calcium fly ash, adopting NaOH alkali to excite and adding 1-2% of biomass material, and finally curing. The biomass material is formed by compounding modified tapioca starch and raffinose according to a certain proportion. The phosphogypsum-based composite geopolymer prepared by the method can be used for road base materials, building wall materials, heat insulation materials and the like. Compared with the prior art, the polysaccharide biomass material added by the invention not only can shorten the final setting time and reduce the maintenance cost while prolonging the setting time of the polymer, but also can inhibit gel pores and microcracks caused by the continuous production of ettringite in the phosphogypsum with large doping amount, thereby improving the later strength of the phosphogypsum base polymer and optimizing the construction performance of the phosphogypsum base polymer. The environment-friendly biomass material tapioca starch and raffinose are used as the additive, so that the phosphogypsum slag is recycled, the method is low in carbon and environment-friendly, the preparation method is simple, the cost is low, and the application prospect is wide.

Inventors

  • WANG JIAQING
  • ZHU RUNZE
  • LI QIANG
  • WANG NING
  • QIN WENJING

Assignees

  • 南京林业大学

Dates

Publication Date
20260505
Application Date
20260121

Claims (6)

  1. 1. A preparation method and application of phosphogypsum geopolymer with retarding and crack resistance enhancing properties are characterized by comprising the following steps: S1, preprocessing raw materials, namely preprocessing phosphogypsum slag, washing and calcining to obtain semi-hydrated phosphogypsum, and sieving until particles completely pass through a 30 mu m screen; S2, compounding fly ash, namely compounding F-level low-calcium fly ash into semi-hydrated phosphogypsum obtained through washing and calcining, wherein wet grinding treatment is required to be carried out on the fly ash in advance. The semi-hydrated phosphogypsum accounts for about 60 percent by weight and the fly ash accounts for about 40 percent by weight; S3, alkali excitation and retarding, namely alkali excitation is carried out by adopting sodium hydroxide, a biomass material is added, the addition amount of the biomass material is 0.5% -1.5% of the mass of the composite geopolymer, so that the defect that the setting time of the phosphogypsum geopolymer is short and construction is not facilitated is overcome, meanwhile, the concentration of sulfuric acid in the composite phosphogypsum geopolymer is diluted, gel holes and microcracks caused by disordered production of ettringite in the composite phosphogypsum geopolymer in a large amount are inhibited, and the later strength of the phosphogypsum geopolymer is improved; S4, sectional curing, namely standing and curing for 4-5 hours in an environment with the temperature of 20-25 ℃ and the relative humidity of more than 90%, heating to 30-40 ℃ and performing high-temperature curing for 4-8 hours, and promoting the full progress of a retarding reaction through sectional curing to improve the later-stage self-repairing capability and the strength stability of the geopolymer.
  2. 2. The preparation method and application of phosphogypsum geopolymer with retarding and anti-cracking reinforcing performances, as claimed in claim 1, are characterized in that the biomass material with retarding effect is a mixture of tapioca sodium carboxymethyl starch CMS-Na and raffinose obtained by modifying tapioca starch.
  3. 3. The preparation method and application of phosphogypsum polymer with retarding and crack resistance enhancing properties according to claim 1, wherein the phosphogypsum is alpha semi-hydrated phosphogypsum, and the fly ash is F-grade low-calcium fly ash subjected to wet grinding.
  4. 4. The composite phosphogypsum geopolymer according to any one of claims 1 to 4, which is used for one or more of road base materials, building wall materials and heat insulation materials.
  5. 5. The retarding biomass material of claim 1 which is a mixture of sodium carboxymethyl starch and raffinose and is characterized by comprising the following steps: S1, raw material pretreatment, namely respectively selecting tapioca starch, sieving with a 100-mesh sieve to remove impurities, washing tapioca starch with deionized water for 2-3 times, removing surface free sugar, drying at 80 ℃ until the moisture content is less than or equal to 10%, preparing high-quality cotton seeds from the raw materials, firstly removing shells to obtain cotton seed kernels, degreasing by oil extraction at 60-80 ℃ and 15-20 MPa, crushing, and sieving with a 10-mesh sieve to obtain defatted cotton seed powder; S2, preparing cassava starch-based CMS-Na, namely dispersing cassava starch in an isopropanol-water mixed solution according to a solid-to-liquid ratio of 1:4, heating to 40-45 ℃ according to a volume ratio of 2:1, adding sodium hydroxide solid with the mass of 15-20% of starch, performing alkalization reaction for 50-70 minutes, adding sodium monochloroacetate and starch according to a mass ratio of 0.6:1-0.7:1, heating to 60-65 ℃ for 4-5 hours, neutralizing, filtering, washing with ethanol, and performing vacuum drying at 65 ℃ after the reaction is finished to obtain a finished product; S3, preparing raffinose, namely adding 70-80 ℃ deionized water into defatted cotton seed powder according to a solid-to-liquid ratio of 1:10-1:15, stirring and extracting for 2-3 hours, filtering, re-washing filter residues, and obtaining a crude extract, removing protein by diatomite and chitosan, decoloring by activated carbon, refining by anion-cation exchange resin, ensuring that the conductivity of the refined solution is less than or equal to 10 mu S/cm, concentrating under reduced pressure to a solid content of 40-50% by 50-60 ℃, spray drying, feeding air at 160-180 ℃ and discharging air at 80-90 ℃, and sieving with a 100 mu m sieve to obtain a raffinose finished product with the purity of more than or equal to 98% and the moisture content of less than or equal to 1.5%; S4, mixing and blending, namely weighing 60 g of cassava starch-based CMS-Na and 40 g of raffinose by taking 100g of total mass as an example, wherein the ratio of the two is about 3:2. Placing into a high-speed mixer, stirring at 800-1000r/min for 15-20 min, or respectively preparing into 20% aqueous solution, mixing at a certain proportion, concentrating under reduced pressure at 60deg.C to dry to obtain uniform mixture.
  6. 6. A preparation method and application of phosphogypsum geopolymer with retarding and crack resistance enhancing properties are characterized by comprising the following components, by mass, 60% of phosphogypsum, 39% -40% of F-level fly ash, 0.5% -1.5% of biomass materials and 100% of the sum of the components in the composite geopolymer treated by the method of any one of claims 1-4.

Description

Preparation method and application of phosphogypsum geopolymer with retarding and crack resistance enhancing properties Technical Field The invention relates to the field of civil engineering material additives, in particular to a preparation method and application of phosphogypsum geopolymer with retarding and anti-cracking reinforcing performances. Background Phosphogypsum is a byproduct in the production process of phosphate fertilizer, and the annual waste phosphogypsum used as an agricultural large country in China has huge discharge amount and lower recycling rate. And the phosphogypsum slag can cause the excessive content of heavy metals and radioactive elements on the periphery after being piled for a long time, and serious pollution is caused to the water quality, the atmosphere and the soil on the periphery. Therefore, a plurality of planning and guiding opinions are successively sent out in China so as to promote the large-scale utilization of large-scale industrial solid wastes such as phosphogypsum and the like in a plurality of fields. Phosphogypsum base polymers have a number of problems in practical applications. On the one hand, the setting and hardening speed is too high, in the scenes such as road base construction, the construction progress can be seriously influenced by shorter setting time, the construction cost is increased, and the existing phosphogypsum base polymer retarder is focused on organic acid and salts and proteins thereof, so that the retarder has higher cost and has negative influence on the physical properties of the ground polymer. On the other hand, the phosphogypsum base polymer has lower later strength, gel cracks caused by ettringite expansion in the later maintenance of the phosphogypsum base polymer with large doping amount can cause the reduction of mechanical properties such as compression resistance, and the excessively high sulfuric acid concentration in the phosphogypsum base polymer is a key factor influencing the disordered production of ettringite. The problems of too high setting speed and lower post curing strength of phosphogypsum base polymer are solved, and the preparation method and application of the phosphogypsum base polymer with retarding and crack resistance enhancing properties are adopted, so that the application scene of the phosphogypsum base polymer is widened. Disclosure of Invention Object of the Invention The invention aims to solve the problems of over-high setting speed, low later strength and the like of phosphogypsum base polymers in the prior art, and provides a preparation method and application of phosphogypsum base polymers with retarding and crack resistance enhancing properties. Through the innovative preparation process and raw material combination, the internal sulfuric acid concentration is diluted while the hydration reaction of phosphogypsum geopolymer is delayed, the setting time is delayed, the final setting time is reduced, gel holes and microcracks caused by the fact that a large amount of phosphogypsum is doped because ettringite in the phosphogypsum is continuously produced are inhibited, the later maintenance strength of the geopolymer is enhanced, and the efficient recycling of waste phosphogypsum slag is realized. Technical proposal The phosphogypsum geopolymer with retarding and crack resistance enhancing properties comprises, by mass, 50-70 parts of alpha semi-hydrated phosphogypsum pretreated by washing and calcining, 50-70 parts of low-calcium fly ash subjected to graded grinding, 10-20 parts of sodium hydroxide alkaline excitant and 10-20 parts of biomass material. The preparation method of the phosphogypsum-based composite geopolymer comprises the following steps: S1, phosphogypsum and fly ash are pretreated, namely phosphogypsum slag is taken, and is subjected to washing and calcination treatment, and then is sieved by a vibrating screen, so that all particles pass through a 30 mu m screen to obtain pretreated alpha semi-hydrated phosphogypsum with uniform particle size, F-level low-calcium fly ash is taken, wherein the phosphogypsum accounts for about 60 percent of the total mass, and the fly ash accounts for about 40 percent of the total mass; s2, mixing raw materials, namely sequentially adding pretreated phosphogypsum slag, low-calcium fly ash after classified grinding and biomass material tapioca starch-based CMS-Na compound raffinose into stirring equipment according to the mass part ratio, and fully stirring and uniformly mixing to obtain a mixed material; S3, alkali excitation and retarding reaction, namely adding an alkali excitant into the mixed material to enable the sodium hydroxide alkali excitant to react, and simultaneously enabling the biomass material to play a role in retarding, so as to delay the hydration reaction of the phosphogypsum-based composite polymer; S4, sectional curing, namely placing the reacted materials into a high-temperature curing environment, curing at a certain tempera