阅读说明：本技术 一种硅铝酸钾纳米凝胶前驱体外加剂及其在低钙体系地聚合物中的应用 (Potassium aluminosilicate nanogel precursor additive and application thereof in low-calcium system geopolymer ) 是由 方媛 郑淑怡 邢锋 于 2021-08-23 设计创作，主要内容包括：本发明提供了一种硅铝酸钾纳米凝胶前驱体外加剂及其在低钙体系地聚合物中的应用,属于地聚合物外加剂技术领域。本发明提供的硅铝酸钾纳米凝胶前驱体外加剂,其结构为高活性硅铝酸钾短链结构,是低钙体系地聚合物的前驱体,化学组成包括K-(2)O、SiO-(2)和Al-(2)O-(3),K/Si摩尔比为1.0～4.0,Al/Si摩尔比为0.25～1.5。本发明提供的硅铝酸钾纳米凝胶前驱体外加剂添加到低钙体系地聚合物基体材料中,能有效优化低钙体系地聚合物如偏高岭土的水化进程,均衡内部反应,改善孔隙结构,从而提高力学性能。有效解决低钙体系地聚合物养护条件苛刻,水化反应不均匀,力学性能不达标的问题,为低钙体系地聚合物的应用提供可行方案。(The invention provides a potassium aluminosilicate nanogel precursor additive and application thereof in a low-calcium system geopolymer, belonging to the technical field of geopolymer additives. The potassium aluminosilicate nanogel precursor additive provided by the invention has a structure of a high-activity potassium aluminosilicate short-chain structure, is a precursor of a low-calcium system polymer, and comprises K 2 O、SiO 2 And Al 2 O 3 The molar ratio of K/Si is 1.0-4.0, and the molar ratio of Al/Si is 0.25-1.5. The potassium aluminosilicate nanogel precursor additive provided by the invention is added into a low-calcium system polymer matrix material, so that the hydration process of a low-calcium system polymer such as metakaolin can be effectively optimized, internal reaction is balanced, and a pore structure is improved, thereby improving the mechanical property. Effectively solve the problem ofThe polymer of the low-calcium system has the problems of harsh curing conditions, uneven hydration reaction and substandard mechanical property, and provides a feasible scheme for the application of the polymer of the low-calcium system.)

1. The potassium aluminosilicate nanogel precursor additive comprises the chemical composition K₂O、SiO₂And Al₂O₃The molar ratio of K/Si in the potassium aluminosilicate nanogel precursor additive is 1.0-4.0, and the molar ratio of Al/Si is 0.25-1.5.

2. The potassium aluminosilicate nanogel precursor admixture according to claim 1, wherein the particle size of the potassium aluminosilicate nanogel precursor admixture is 100-300 nm.

3. The potassium aluminosilicate nanogel precursor admixture according to claim 1 or 2, wherein the particle size of the nano silicon oxide and the nano aluminum oxide is 10-100 nm independently.

4. Use of the potassium aluminosilicate nanogel precursor admixture according to any one of claims 1 to 3 in a geopolymer with a low calcium system.

Technical Field

The invention relates to the technical field of geopolymer additives, in particular to a potassium aluminosilicate nanogel precursor additive and application thereof in a low-calcium geopolymer.

Background

The geopolymer is a novel gel material, has the advantages of environmental protection and energy conservation in the production process, simple process and excellent durability, and therefore has extremely high research value since the last century.

However, the instability of geopolymer properties has hindered the spread in the construction field. The following problems are associated with polymers of the low calcium system, particularly exemplified by metakaolin: the mechanical property is unstable, the hydration process is not uniform, the workability and the pore distribution in the component are influenced, the shrinkage is overlarge, and the cracking is easy to occur.

China is the main kaolin producing country in the world, and the yield accounts for 78 percent of the total world yield; the metakaolin has more than 700 sites, and has great potential in the application field of the polymer of a low-calcium system. Therefore, it is very necessary to research the improvement of polymer properties of low calcium systems.

Disclosure of Invention

The invention aims to provide a potassium aluminosilicate nanogel precursor additive and application thereof in a low-calcium system polymer.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a potassium aluminosilicate nanogel precursor additive which comprises K₂O、 SiO₂And Al₂O₃The molar ratio of K/Si in the potassium aluminosilicate nanogel precursor additive is 1.0-4.0, and the molar ratio of Al/Si is 0.25-1.5.

Preferably, the particle size of the potassium aluminosilicate nanogel precursor additive is 100-300 nm.

Preferably, the particle diameters of the nano silicon oxide and the nano aluminum oxide are independently 10-100 nm.

The invention also provides the application of the potassium aluminosilicate nanogel precursor additive in the technical scheme in a geopolymer of a low-calcium system.

The invention provides a potassium aluminosilicate nanogel precursor additive which comprises K₂O、 SiO₂And Al₂O₃The molar ratio of K/Si in the potassium aluminosilicate nanogel precursor additive is 1.0-4.0, and the molar ratio of Al/Si is 0.25-1.5. The microstructure of the potassium aluminosilicate nanogel precursor additive provided by the invention is an aluminosilicate short chain structure with high activity, and the aluminosilicate short chain structure is added into a base material containing metakaolin, so that the base material is guided to generate a polymerization reaction, the hydration process is optimized, the random disordered hydration reaction of the full range of geopolymer particles is avoided, and further, the hydration is insufficient in the initial pouring process, the internal structure of a component is not uniform, and the mechanical property is influenced. A small amount of microcrystal particles in the potassium aluminosilicate nanogel precursor additive provided by the invention can play a crystal nucleus effect, geopolymer particles are guided to be attached to the potassium aluminosilicate nanogel precursor additive nano precursor for hydration reaction, and the effect of enabling the internal pore structure of the geopolymer matrix material to be more uniform and compact is achieved.

Drawings

FIG. 1 is an SEM image of a silica-alumina-potassium nanogel precursor admixture prepared in example 1;

FIG. 2 is a conceptual view of the microstructure of the sial-k nanogel precursor admixture prepared in example 1;

FIG. 3 is a graph showing the 7-day compressive strength of test pieces obtained in application examples 1 to 2 and comparative examples 1 to 2;

FIG. 4 is a 7-day flexural strength chart of test blocks obtained by applying examples 1 to 2 and comparative examples 1 to 2;

FIG. 5 is a model diagram of the internal pore distribution XCT of test blocks obtained in application example 1 and comparative example 1, wherein a is comparative example 1 and b is application example 1.

Detailed Description

The invention provides a potassium aluminosilicate nanogel precursor additive which comprises K₂O、 SiO₂And Al₂O₃The molar ratio of K to Si in the potassium aluminosilicate nanogel precursor additive is 1.0-4.0, preferably 0.8-1.8, and more preferably 1-1.5; molar ratio of Al to SiThe ratio is 0.25 to 1.5, preferably 0.5 to 1.25, and more preferably 0.75 to 1.

In the invention, the particle size of the nano silicon oxide and the nano aluminum oxide is independently preferably 10-100 nm, more preferably 30-80 nm, and most preferably 50-60 nm. In the invention, the particle size of the potassium aluminosilicate nanogel precursor additive is preferably 100-300 nm, more preferably 150-250 nm, and most preferably 200-250 nm. The potassium aluminosilicate nanogel precursor additive provided by the invention is a nanoscale material, has small particle size, can be used as a microaggregate in a geopolymer, plays a role in filling, can reduce the porosity of the geopolymer, and improves the compactness of the geopolymer.

In the present invention, the preparation method of the potassium aluminosilicate nanogel precursor admixture preferably comprises the following steps:

mixing potassium hydroxide, nano silicon oxide, nano aluminum oxide and water, and carrying out hydrothermal synthesis reaction to obtain the potassium aluminosilicate nanogel precursor additive.

In the present invention, all the raw material components are commercially available products well known to those skilled in the art unless otherwise specified.

In the invention, the mass ratio of the potassium hydroxide, the nano silicon oxide, the nano aluminum oxide and the water is preferably (4-15): (1.5-4): (0.75-2): (30-100), more preferably (5-12): (2-3.5): (0.8-1.5): (40-80), most preferably (8-10): (2.5-3): (1-1.2): (50-80). In the present invention, the water is preferably deionized water.

In the invention, the mixing temperature is preferably 70-100 ℃, more preferably 75-95 ℃, and most preferably 80-90 ℃; the mixing mode is preferably stirring mixing, and the stirring mixing speed is preferably 180-250 r/min, more preferably 190-230 r/min, and most preferably 200-210 r/min. In the invention, the mixing preferably comprises dissolving potassium hydroxide in water, heating to 70-100 ℃, adding nano silicon oxide, mixing for 1-2 min, adding nano aluminum oxide, mixing for 1-2 min, and then mixing for 30-90 min, more preferably for 50-60 min under a closed condition. In the present invention, the mixing is preferably carried out in a polytetrafluoroethylene container.

In the invention, the temperature of the hydrothermal synthesis reaction is preferably 70-100 ℃, more preferably 75-95 ℃, and most preferably 80-90 ℃; the time of the hydrothermal synthesis reaction is preferably 2-12 h, more preferably 3-10 h, and most preferably 5-8 h; the hydrothermal reaction is preferably carried out under the conditions of standing and sealing; the invention carries out hydrothermal synthesis reaction under a closed condition, can isolate water-vapor exchange with the outside, provides a high-pressure reaction environment, and is beneficial to accelerating the hydrothermal synthesis reaction speed and the combination of silicon-aluminum bonds. In the present invention, during the hydrothermal synthesis reaction, the microstructure undergoes the following four stages: depolymerization, short-range polymerization, structural rearrangement, and disordered polycondensation.

After the hydrothermal synthesis reaction, the invention preferably further comprises the steps of carrying out solid-liquid separation on the hydrothermal synthesis reaction system, removing the supernatant, and sequentially washing, drying and grinding the obtained solid product to obtain the potassium aluminosilicate nanogel precursor additive. In the invention, the solid-liquid separation mode is preferably centrifugal separation, and the rotating speed of the centrifugal separation is preferably 3000-8000 r/min, more preferably 4000-7000 r/min, and most preferably 5000-6000 r/min; the time of the centrifugal separation is preferably 3-10 min, more preferably 5-8 min, and most preferably 6-7 min. In the invention, the water washing is preferably to add deionized water into the solid product, stir and mix the mixture, then carry out centrifugal separation, and remove the supernatant; the conditions for the centrifugal separation are preferably the same as those for the centrifugal separation, and are not described herein again; the number of washing is preferably 2-5, more preferably 3-4, and the purpose of washing is to remove potassium hydroxide on the surface of the solid product. In the invention, the drying mode is preferably vacuum drying, and the drying temperature is preferably 40-80 ℃, and more preferably 55-65 ℃; the drying time is preferably 24-72 hours, and more preferably 36-48 hours. The grinding is not particularly limited, and the grinding is carried out until the particle size of the potassium aluminosilicate nanogel precursor additive is 100-300 nm.

The preparation method provided by the invention is simple to operate, the reaction raw materials are cheap and easy to obtain, and the energy consumption is low. The potassium aluminosilicate nanogel precursor additive can effectively improve the mechanical property of geopolymer and optimize the internal pore structure.

The invention also provides the application of the potassium aluminosilicate nanogel precursor additive in the technical scheme in a geopolymer of a low-calcium system. In the present invention, the method for applying the potassium aluminosilicate nanogel precursor admixture preferably comprises the following steps: mixing the potassium aluminosilicate nanogel precursor additive, the alkali activator and the raw materials. The mixing speed and time are not specially limited, and the raw materials can be uniformly mixed. In the invention, the addition amount of the potassium aluminosilicate nanogel precursor additive is 1-8% of the mass of the slag, more preferably 2-6%, and most preferably 3-5%. In the invention, the raw material preferably comprises one or more of slag, metakaolin and low-calcium fly ash; the slag, metakaolin and low-calcium fly ash used in the present invention are not particularly limited, and those known to those skilled in the art can be used.

The potassium aluminosilicate nanogel precursor additive provided by the invention is added into a geopolymer matrix material containing metakaolin, so that the hydration process of a geopolymer with a low calcium system can be effectively optimized, internal reaction is balanced, and the distribution of an internal pore structure is improved, thereby improving the mechanical property. The problems that the polymer curing conditions of a low-calcium system are harsh and the mechanical property does not reach the standard are effectively solved, and a feasible scheme is provided for the application of metakaolin.

The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

Adding 300 parts of deionized water and 30 parts of KOH by mass into a polytetrafluoroethylene reaction tank, and placing the polytetrafluoroethylene reaction tank at a stirring speed of 200r/min and a temperature of 95 DEG CAfter the temperature is raised to 95 ℃, 16 parts by mass of nano SiO with the particle size of 50-100 nm are added into the water bath kettle₂Stirring for 2min, adding 14 parts by mass of nano Al with the particle size of 50-100 nm₂O₃Then stirring for 2min, taking out the polytetrafluoroethylene tank, sealing the polytetrafluoroethylene tank by using a preservative film and an adhesive tape, then continuously stirring for 1h in a water bath kettle, turning off a stirring knob, carrying out thermostatic hydrothermal synthesis reaction for 4h under the condition of standing and 95 ℃, carrying out centrifugal separation for 4min at the speed of 4000r/min, pouring out liquid components, adding deionized water, stirring and mixing, continuously carrying out centrifugal separation for 4min at the speed of 4000r/min, and repeating centrifugal washing for 3 times to obtain the potassium aluminosilicate nanogel precursor additive;

the molar ratio of K/Si in the potassium aluminosilicate nanogel precursor additive is 2, and the molar ratio of Al/Si is 1.

The potassium aluminosilicate nanogel precursor additive prepared in the embodiment belongs to polymer gel of a low-calcium system, and is of a short-range disordered amorphous structure.

The SEM image of the potassium aluminosilicate nanogel precursor admixture prepared in this example is shown in fig. 1, the microstructure of molecular scale is shown as aluminosilicate short chain structure, the structural concept diagram is shown in fig. 2, and potassium ions are not used as structural framework components, and play a role in balancing charges when aluminum atoms and silicon atoms are combined into Si-O-Al bonds, wherein potassium ions are not shown in fig. 2.

Application example 1

20g of the potassium aluminosilicate nanogel precursor additive prepared in the example 1, 490g of slag, 490g of metakaolin, 285g of sodium silicate with the modulus of 2.2 and 273g of deionized water are uniformly mixed to obtain a potassium aluminosilicate nanogel precursor additive modified two-component geopolymer experimental group. The slurry was poured into a 40X 160mm crush-resistant form, 40X 40mm crush-resistant form, vibrated for one minute, and subjected to standard curing (temperature 25. + -. 1 ℃ C., humidity > 95%) for 7 days and 28 days, wherein the ratio of slag to metakaolin was 1:1 by mass.

Application example 2

20g of the potassium aluminosilicate nanogel precursor additive prepared in the example 1, 686g of slag, 294g of metakaolin, 285g of sodium silicate with the modulus of 2.2 and 273g of deionized water are uniformly mixed to obtain the potassium aluminosilicate nanogel precursor additive modified two-component geopolymer experimental group. The slurry was poured into a 40X 160mm crush-resistant form, 40X 40mm crush-resistant form, vibrated for one minute, and subjected to standard curing (temperature 25. + -. 1 ℃ C., humidity > 95%) for 7 days and 28 days, wherein the ratio of slag to metakaolin was 7:3 by mass.

Comparative example 1

0g of the potassium aluminosilicate nanogel precursor additive prepared in example 1, 500g of slag, 500g of metakaolin, 285g of sodium silicate with the modulus of 2.2 and 273g of deionized water are uniformly mixed to obtain a two-component geopolymer control group. The slurry was poured into a 40X 160mm crush-resistant form, 40X 40mm crush-resistant form, vibrated for one minute, and subjected to standard curing (temperature 25. + -. 1 ℃ C., humidity > 95%) for 7 days and 28 days, wherein the ratio of slag to metakaolin was 1:1 by mass.

Comparative example 2

0g of the potassium aluminosilicate nanogel precursor additive prepared in example 1, 700g of slag, 300g of metakaolin, 285g of sodium silicate with the modulus of 2.2 and 273g of deionized water are uniformly mixed to obtain a two-component geopolymer control group. The slurry was poured into a 40X 160mm crush-resistant form, 40X 40mm crush-resistant form, vibrated for one minute, and subjected to standard curing (temperature 25. + -. 1 ℃ C., humidity > 95%) for 7 days and 28 days, wherein the ratio of slag to metakaolin was 7:3 by mass.

The compressive strength of the test blocks obtained by the microcomputer controlled compression testing machine in the application examples 1-2 and the comparative examples 1-2 after 7 days is shown in figure 3, and the flexural strength of the test blocks after 7 days is shown in figure 4. As can be seen from FIGS. 3 to 4, when the briquette curing time was 7 days, the compressive and flexural strengths of the application examples were generally improved as compared with the comparative example, in which the compressive strengths of the matrix materials (slag + metakaolin) of the 1:1 components of the application example 1 and the comparative example 1 were increased by 16.6%, the flexural strengths were increased by 43.7%, the compressive strengths of the matrix materials of the 7:3 components of the application example 2 and the comparative example 2 were increased by 4.5%, and the flexural strengths were increased by 30.2%. The potassium aluminosilicate nanogel additive provided by the invention has the effect of improving the compressive strength and the flexural strength of geopolymer, and has a more obvious effect on a matrix material with higher metakaolin content.

The comparison example 1 and the application example 1 were tested by a three-dimensional reconstruction imaging X-ray microscope, and an XCT model graph of the internal pore distribution of the geopolymer with the age of 1 day before and after adding the potassium aluminosilicate nanogel precursor additive is shown in FIG. 5, wherein a is before adding (comparison example 1) and b is after adding (application example 1). As can be seen from FIG. 5, the geopolymer added with the potassium aluminosilicate nanogel precursor additive prepared by the invention has more uniform pore distribution, is beneficial to structural stress, reduces the total porosity, obviously reduces the ratio of macropore porosity, increases the ratio of micropore porosity and is beneficial to improving the self-shrinkage performance of the geopolymer.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.