A geopolymer concrete material, method of manufacture and use thereof

Abstract

The application relates to the technical field of geopolymer concrete preparation, in particular to a geopolymer concrete material, a preparation method and application thereof. The geopolymer concrete material comprises modified metakaolin, slag, modified glass microbeads, an activator solution and a mixed modifier. The preparation method of the modified glass microbeads comprises the following steps: soaking glass microbeads in a composite acid solution, then washing with water until neutral, drying, then immersing in an ethanol solution of 3-aminopropyl triethoxysilane with a concentration of 5 wt%, to obtain pretreated microbeads; dispersing the pretreated microbeads in a 1 wt% dopamine hydrochloride solution, oscillating for 1.5-2 h, cleaning with ethanol after centrifugation, vacuum drying to obtain dry microbeads; mixing molybdenum disulfide with the dry microbeads, adding anhydrous ethanol, ultrasonic dispersion, collecting the precipitate, drying the precipitate, and obtaining modified glass microbeads.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geopolymer concrete preparation, and particularly relates to a geopolymer concrete material, a preparation method and application thereof. BACKGROUND

[0002] Geopolymer, short for geopolymer, is a new type of high-performance inorganic polymer. Compared with ordinary Portland cement, there is no calcium silicate hydration reaction in the reaction process, and the final product is mainly composed of ionic bond and covalent bond, supplemented by van der Waals bond. It not only can reduce the emission of harmful gas, but also has excellent performance in all aspects.

[0003] Although the geopolymer has good high temperature resistance and environmental protection, and the raw material sources are widely available and the production energy consumption is low, the compressive strength of the geopolymer is low in a short time under the condition of room temperature curing, and high temperature curing can accelerate the reaction, but it is easy to cause surface cracking, which affects the rapid construction and cannot guarantee the mechanical strength.

[0004] The conventional alkali activator is often used to activate the silicate and aluminate raw materials in the preparation method of the geopolymer concrete. In terms of mechanical strength, the raw materials such as fly ash and slag have a complex pore structure, and micrometer-sized macropores and nanometer-sized mesopores coexist. The reaction product is difficult to uniformly fill the pores, which weakens the matrix density. In addition, the gel network generated by the geopolymer reaction has defects, poor impermeability, and harmful ions easily invade, which accelerates the material degradation, reduces the mechanical properties, and affects the long-term service performance.

[0005] The durability of concrete not only determines whether it can be applied in harsh environments, but also determines the service life of the structure. Taking municipal engineering as an example (such as soundproof wall columns, electric poles, etc.), on the one hand, it needs to withstand the influence of rain, strong wind and other harsh environments while meeting the basic bearing requirements, on the other hand, in the production of ordinary concrete, the process of producing cement will emit a large amount of carbon dioxide, and a standard electric pole needs to consume hundreds of kilograms of cement, so the large-scale use of ordinary concrete electric poles aggravates the carbon emission pressure. SUMMARY

[0006] The present application provides a geopolymer concrete material, a preparation method thereof and application thereof, so as to solve the problems of complex pore structure and insufficient matrix strength of the geopolymer concrete material in the related art.

[0007] In a first aspect, a geopolymer concrete material is provided, which comprises, in terms of mass fraction:

[0008] 40-50 parts of modified metakaolin, 20-30 parts of slag, 2-10 parts of modified glass beads, 30-40 parts of activator solution, and a mixed modifier, the mass fraction of the mixed modifier being 0.3-1% of the total mass of the modified metakaolin and the slag;

[0009] The preparation method of the modified glass microbeads comprises the following steps:

[0010] The glass microbeads are soaked in a composite acid solution for 1.5-2 hours, washed with water until neutral, dried, then immersed in an ethanol solution of 3-aminopropyl triethoxysilane with a concentration of 5wt%, stirred in a water bath at 50-60℃ for 1.5-2 hours, filtered and dried to obtain pretreated microbeads;

[0011] The pretreated microbeads are dispersed in a 1wt% dopamine hydrochloride solution, oscillated for 1.5-2 hours, washed with ethanol after centrifugation, and dried at 50-60℃ under vacuum to obtain dry microbeads;

[0012] The dry microbeads are mixed with molybdenum disulfide, then added to anhydrous ethanol, ultrasonically dispersed for 25-30 minutes, and the precipitate is collected and dried in a drying oven at 55-60℃ for 2.5-3 hours to obtain modified glass microbeads, the addition amount of molybdenum disulfide is 0.5-1% of the mass of the dry microbeads, and the mass-volume ratio of the dry microbeads to anhydrous ethanol is 1g:5mL.

[0013] Preferably, in the composite acid solution, the concentration of hydrochloric acid is 3wt%, and the concentration of oxalic acid is 0.1wt%.

[0014] Preferably, the preparation method of the mixed modifier comprises the following steps:

[0015] The azodicarbonamide, zinc borate, benzenesulfonyl amide, and N-phenylmaleimide are mixed in a mass ratio of 10:2:1:(1-2), stirred at 48-50℃ for 0.8-1 hours until uniform to obtain a mixed modifier.

[0016] Preferably, the mixed modifier further comprises ethylene-vinyl acetate, and the addition amount of ethylene-vinyl acetate is 50% of the mass of azodicarbonamide.

[0017] Preferably, the preparation method of the modified metakaolin comprises the following steps:

[0018] The metakaolin and the amino-terminated benzimidazole siloxane are mixed in a mass ratio of 1:0.05, then ball milled for 0.8-1 hours, and then diamino diphenyl methane is added and ball milled for 0.8-1 hours to obtain modified metakaolin, and the addition amount of diamino diphenyl methane is 2% of the mass of the metakaolin.

[0019] Preferably, the preparation method of the activator solution is:

[0020] Sodium hydroxide is dissolved in water and stirred at 60-80℃ until dissolved, then cooled to room temperature, and sodium silicate is added and stirred until uniform to obtain an activator solution;

[0021] The mass ratio of sodium hydroxide to water is 1:5, and the mass ratio of sodium silicate to sodium hydroxide is 1:(3-5).

[0022] In a second aspect, a preparation method is provided for preparing the geopolymer concrete material according to any one of the above aspects, comprising the following steps:

[0023] After mixing the modified metakaolin and the slag, the activator solution is added and stirred for 3-5 minutes, then the modified glass beads and the modifier are added and stirred for another 3-5 minutes to obtain a mixture;

[0024] The mixture is poured into a mold and vibrated to form and expel air;

[0025] After the forming, the test piece is demolded after being cured at 25±2℃ and humidity ≥95% for 22-24 hours, and then placed in a constant temperature curing box at 58-60℃ for curing for 3-5 days, and finally naturally cured at room temperature to the test age, to obtain the geopolymer concrete material.

[0026] In a third aspect, the geopolymer concrete material according to any one of the above aspects is provided for use as a building material in a power pole.

[0027] The technical solutions provided in the present application have the following beneficial effects:

[0028] The present application provides a geopolymer concrete material, a preparation method and an application thereof. After modification, the glass beads are uniformly dispersed in the geopolymer matrix, filling the internal pores and limiting the expansion direction to reduce the generation of cracks. The layered structure of molybdenum disulfide can further embed into the small pores to reduce the medium penetration path. The silane coupling agent enhances the interfacial adhesion between the microbeads and the matrix, forms a stable structure, reduces the porosity, and thus improves the compressive and flexural strength and durability. The modified metakaolin and slag fully react with the activator to generate a large amount of dense aluminosilicate gel, which is interwoven with the modified glass beads filling the pores, further densifying the matrix structure, and the obtained geopolymer concrete has the characteristics of high strength and good durability. The geopolymer concrete using industrial solid waste as raw material can effectively reduce carbon emissions while meeting the requirements of high strength and good durability, and also has significant environmental benefits. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0030] Figure 1A flow chart of the method for preparing the geopolymer concrete material provided in the present application;

[0031] Figure 2 A graph showing the change in the leaching concentration of Si 4+ , Al 3+ and Ca 2+ in NaOH solution over time for the modified glass beads provided in the present application;

[0032] Figure 3 A schematic diagram showing the change in the leaching rate of Si, Al and Ca ions in NaOH solution for the modified glass beads provided in the present application;

[0033] Figure 4 SEM images of the geopolymer concrete material after 28 d curing for GB-0 (0% of modified glass beads) and GB-2% (2% of modified glass beads), Figure 4 (a) is the image of GB-0, Figure 4 (b) is the image of GB-2%;

[0034] Figure 5 A schematic diagram showing the compressive strength of the geopolymer concrete material after 1, 3, 7 and 28 d curing at different GB (modified glass beads) contents;

[0035] Figure 6 A schematic diagram showing the percentage of harmless pores, relatively harmful pores and harmful pores in the geopolymer concrete material at different GB contents;

[0036] Figure 7 FTIR (Fourier Transform Infrared Spectroscopy) spectrum of the geopolymer concrete material after 28 d curing at different GB contents. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0038] Referring to Figures 1-7 , the present application provides a geopolymer concrete material, a preparation method and an application thereof.

[0039] Embodiment 1

[0040] The preparation method of the geopolymer concrete material provided in the present embodiment is as follows:

[0041] After 450 g of modified metakaolin and 250 g of slag are mixed, 350 g of activator solution is added and stirred for 3 min, then 60 g of modified glass beads and 5.25 g of mixed modifier are added, and stirring is continued for 5 min to obtain a mixture;

[0042] The mixture is poured into a mold and vibrated to form and expel air;

[0043] After the formed test piece is demolded after curing at 25±2℃ and humidity ≥95% for 24 h, it is placed in a constant temperature curing oven at 60℃ for 3 days, and finally naturally cured at room temperature to the test age, to obtain a geopolymer concrete material.

[0044] The preparation method of the modified metakaolin is as follows:

[0045] 500 g of metakaolin is mixed with 25 g of amino-terminated benzimidazole siloxane and ball milled for 1 h, and then 10 g of diamino diphenyl methane is added and ball milled for 1 h to obtain the modified metakaolin.

[0046] The preparation method of the modified glass beads comprises the following steps:

[0047] 110 g of glass beads are soaked in a composite acid solution for 2 h (in the composite acid solution, the concentration of hydrochloric acid is 3 wt%, and the concentration of oxalic acid is 0.1 wt%; the composite acid solution can cover the glass beads), washed with water to neutral, and dried, then immersed in an ethanol solution of 3-aminopropyl triethoxysilane with a concentration of 5 wt% (submerged), stirred in a water bath at 60℃ for 2 h, filtered and dried to obtain pretreated microbeads;

[0048] The pretreated microbeads are dispersed in a 1 wt% dopamine hydrochloride solution, oscillated for 2 h, centrifuged, washed with ethanol, and dried at 50℃ under vacuum to obtain dry microbeads;

[0049] 0.8 g of molybdenum disulfide is mixed with 100 g of dry microbeads, added to 500 mL of anhydrous ethanol, ultrasonically dispersed for 30 min, and the precipitate is collected and dried in a 60℃ drying oven for 3 h to obtain modified glass beads.

[0050] The preparation method of the mixed modifier is as follows:

[0051] 10 g of azodicarbonamide, 2 g of zinc borate, 1 g of benzenesulfonamide, 1.5 g of N-phenylmaleimide, and 5 g of ethylene-vinyl acetate are mixed and stirred at 50℃ for 1 h until uniform to obtain the mixed modifier.

[0052] The preparation method of the activator solution is as follows:

[0053] 60 g of sodium hydroxide is dissolved in 300 g of water, stirred and dissolved at 60℃, cooled to room temperature, and then 15 g of sodium silicate is added, stirred until uniform to obtain the activator solution.

[0054] Example 2

[0055] The difference between this example and Example 1 is that no ethylene vinyl acetate is added to the mixed modifier in this example.

[0056] Example 3

[0057] The difference between this example and Example 1 is that the method for preparing the geopolymer concrete material provided in this example is:

[0058] After mixing 400 g of modified metakaolin and 200 g of slag, 300 g of activator solution is added and stirred for 5 min, then 20 g of modified glass beads and 1.8 g of mixed modifier are added, and stirring is continued for 5 min to obtain a mixture;

[0059] The mixture is poured into a mold and vibrated to form and expel air;

[0060] After the formed test piece is demolded after curing for 22 h in an environment of 25±2℃ and humidity ≥95%, it is placed in a constant temperature curing box at 58℃ for curing for 5 days, and finally naturally cured at room temperature to the test age, to obtain the geopolymer concrete material.

[0061] Example 4

[0062] The difference between this example and Example 1 is that the method for preparing the geopolymer concrete material provided in this example is:

[0063] After mixing 500 g of modified metakaolin and 300 g of slag, 400 g of activator solution is added and stirred for 3 min, then 30 g of modified glass beads and 8 g of mixed modifier are added, and stirring is continued for 3 min to obtain a mixture;

[0064] The mixture is poured into a mold and vibrated to form and expel air;

[0065] After the formed test piece is demolded after curing for 23 h in an environment of 25±2℃ and humidity ≥95%, it is placed in a constant temperature curing box at 60℃ for curing for 4 days, and finally naturally cured at room temperature to the test age, to obtain the geopolymer concrete material.

[0066] Example 5

[0067] The difference between this example and Example 1 is that in this example, the method for preparing the modified glass beads is:

[0068] Put 110 g glass microbeads into a composite acid solution for 1.5 h (in the composite acid solution, the concentration of hydrochloric acid is 3 wt%, and the concentration of oxalic acid is 0.1 wt%; the composite acid solution can cover the glass microbeads), wash with water until neutral, and then dry; then immerse in an ethanol solution of 3-aminopropyltriethoxysilane with a concentration of 5 wt% (submerge), stir in a water bath at 50°C for 1.5 h, filter and dry to obtain pretreated microbeads;

[0069] Disperse the pretreated microbeads in a 1 wt% dopamine hydrochloride solution, oscillate for 1.5 h, wash with ethanol after centrifugation, and vacuum dry at 60°C to obtain dry microbeads;

[0070] Mix 0.5 g of molybdenum disulfide with 100 g of dry microbeads, add 500 mL of anhydrous ethanol, ultrasonic dispersion for 30 min, collect the precipitate, and dry the precipitate in a 55°C drying oven for 2.5 h to obtain modified glass microbeads.

[0071] In addition, the preparation method of the mixed modifier is:

[0072] Mix 10 g of azodicarbonamide, 2 g of zinc borate, 1 g of benzenesulfonamide, and 1 g of N-phenylmaleimide, stir at 48°C for 1 h until uniform to obtain a mixed modifier.

[0073] The preparation method of the activator solution is:

[0074] Dissolve 60 g of sodium hydroxide in 300 g of water, stir to dissolve at 70°C, cool to room temperature, add 20 g of sodium silicate, stir until uniform to obtain an activator solution.

[0075] Example 6

[0076] The difference between this example and Example 1 is that the preparation method of the geopolymer concrete material provided by this example is:

[0077] Mix 400 g of modified metakaolin and 200 g of slag, add 300 g of activator solution and stir for 4 min, then add 100 g of modified glass microbeads and 1.8 g of mixed modifier, continue to stir for 5 min to obtain a mixture;

[0078] Pour the mixture into a mold, vibrate to shape, and expel air;

[0079] After shaping, the test piece is demolded after curing at 25±2°C and humidity ≥95% for 24 h, then placed in a 60°C constant temperature curing box for 3 days, and finally naturally cured at room temperature to the test age to obtain a geopolymer concrete material.

[0080] In addition, the preparation method of the modified glass microbeads is:

[0081] Preparation of the pretreated glass microbeads: 110 g of glass microbeads were immersed in a composite acid solution (3 wt% of hydrochloric acid and 0.1 wt% of oxalic acid) for 1.8 h, washed with water until neutral, and then dried. The pretreated glass microbeads were immersed in an ethanol solution of 3-aminopropyltriethoxysilane (5 wt%) at 55°C for 1.8 h, filtered, and dried to obtain the pretreated glass microbeads.

[0082] The pretreated glass microbeads were dispersed in a 1 wt% dopamine hydrochloride solution, shaken for 1.8 h, centrifuged, washed with ethanol, and dried at 55°C under vacuum to obtain the dried glass microbeads.

[0083] 1 g of molybdenum disulfide was mixed with 100 g of dried glass microbeads, added to 500 mL of anhydrous ethanol, ultrasonically dispersed for 30 min, and the precipitate was collected and dried in a 58°C drying oven for 3 h to obtain the modified glass microbeads.

[0084] The preparation method of the mixed modifier is as follows:

[0085] 10 g of azodicarbonamide, 2 g of zinc borate, 1 g of benzenesulfonamide, 2 g of N-phenylmaleimide, and 5 g of ethylene-vinyl acetate were mixed and stirred at 50°C for 0.8 h until uniform to obtain the mixed modifier.

[0086] The preparation method of the activator solution is as follows:

[0087] 60 g of sodium hydroxide was dissolved in 300 g of water and stirred at 70°C until dissolved. After cooling to room temperature, 12 g of sodium silicate was added and stirred until uniform to obtain the activator solution.

[0088] Comparative Example 1

[0089] The difference between it and Example 1 is that the glass microbeads are not modified, i.e., the modified glass microbeads in Example 1 are replaced with an equal amount of glass microbeads.

[0090] Comparative Example 2

[0091] The difference between it and Example 1 is that the glass microbeads are not modified and no mixed modifier is added.

[0092] Comparative Example 3

[0093] The difference between it and Example 1 is that the metakaolin is not modified, i.e., the modified metakaolin in Example 1 is replaced with an equal amount of metakaolin.

[0094] It should be noted that in the preparation of modified glass beads of the examples and comparative examples, the 1wt% dopamine hydrochloride solution therein is Tris-HCl buffer solution, pH=8.5, that is, 1 gram of dopamine hydrochloride solute is contained in 100g of the solution. The Tris-HCl buffer solution is a buffer system prepared from tris(hydroxymethyl)aminomethane (Tris) and hydrochloric acid, and the pH of the solution is stabilized at 8.5 by adjusting the proportion of the two, and this pH condition is conducive to the self-polymerization reaction of dopamine hydrochloride; the entire solution system is a reaction medium formed by dissolving dopamine hydrochloride in Tris-HCl buffer solution (pH 8.5).

[0095] In the above examples and comparative examples, the chemical composition of the metakaolin used is shown in Table 1.

[0096] Table 1 Chemical composition of metakaolin

[0097]

[0098] The slag used is S105 grade slag in accordance with Chinese standard GB / T 18046-2017, provided by Longze Water Purification Material Co., Ltd. in Gongyi City. The average particle size is 7.264µm, and the chemical composition of the slag is shown in Table 2.

[0099] Table 2 Chemical composition of slag

[0100]

[0101] In addition, the azodicarbonamide used is VAE of model 5044N of German Wacker brand, which appears as white powder; the sodium silicate used is powdered instant sodium silicate provided by a company in Xi'an, Shaanxi, with a molar ratio of SiO2 to Na2O of 2.86, that is, the modulus of sodium silicate is 2.86.

[0102] In addition, the glass beads used are provided by Shenzhen Tongcheng New Material Technology Co., Ltd., with a bulk density of 0.75g / cm 3 , a crystal structure of amorphous state, and an activity coefficient of 115% at 28 days (calculated according to Chinese standard GB / T 1596-2017 fly ash activity). The average particle size is 0.919µm, and the main components are SiO2 and Al2O3, with mass fractions of 56.51% and 24.53% respectively.

[0103] The geopolymer concrete materials (hereinafter referred to as concrete) prepared in Examples 1-6 and Comparative Examples 1-3 were tested.

[0104] Expansion rate test:

[0105] According to GB / T 23439-2017 "Concrete Expanding Agent", the expansion rate is calculated according to the following formula:

[0106]

[0107] In the formula, ε is the limited expansion rate (%) of the measured age (28d), L1 is the length measurement value (mm) of the test body at the measured age, L is the initial length measurement value (mm) of the test body, and L0 is the reference length of the test body, which is 100 mm.

[0108] The test results are shown in Table 3.

[0109] Table 3: Expansion rates of geopolymer concrete materials prepared in Examples 1-6 and Comparative Examples 1-3

[0110]

[0111] Example 2 lacks ethylene-vinyl acetate (VAE) compared to Example 1, the interfacial adhesion decreases, the azodicarbonamide (AC) foaming is insufficiently constrained by the matrix, the expansion inhomogeneity increases, and the porosity slightly increases due to uncontrolled expansion. Example 3 reduces the amount of modified glass beads compared to Example 1, resulting in insufficient pore filling, and the proportion of mixed modifier is reduced, foaming is reduced, the internal pores of the concrete are not effectively filled, and the expansion driving force is insufficient, resulting in high porosity and low expansion rate.

[0112] In Example 4, compared to Example 1, the total amount of modified metakaolin and slag increases, more silicate gel is generated by reaction, the matrix is denser, the porosity is reduced, and the proportion of mixed modifier increases (close to 1%), the expansion driving force is enhanced, so the expansion rate is not much different from that of Example 1.

[0113] In Example 5, the proportion of molybdenum disulfide in the modified glass beads is reduced, and the proportion of sodium silicate in the activator is increased, the reaction rate is accelerated, local heat release may cause uneven decomposition of AC, and the expansion dispersion increases relatively.

[0114] In Example 6, the amount of modified glass beads is increased compared to Example 1, but the proportion of mixed modifier is consistent with Example 1, which cannot match the matrix constraint brought by high microbead filling, resulting in some pores not being effectively regulated; at the same time, the alkalinity of the activator is increased, the structure of the reaction product is loose, and the porosity of the concrete is increased.

[0115] The unmodified glass beads in Comparative Example 1 have poor interfacial bonding with the matrix, so the interfacial porosity increases accordingly, the expansion rate is high and dispersed, and the porosity increases significantly; Comparative Example 2 does not add mixed modifier based on Comparative Example 1, and the expansion rate is greatly increased; Comparative Example 3 does not modify the metakaolin, resulting in a decrease in active sites and insufficient reaction with slag, and the porosity increases.

[0116] The relevant properties of the modified glass microspheres were tested.

[0117] Regarding the elemental dissolution and leaching of modified glass microspheres (hereinafter referred to as GB) in alkaline solution: 10g of GB powder was added to 40mL of 4.5mol / L NaOH solution, mixed thoroughly, and then left to stand at room temperature. After soaking for 12h, 24h, 48h, and 72h respectively, the solid and liquid were separated using a 0.1μm nylon microporous membrane. To meet the sample concentration requirements of Agilent 720ES inductively coupled plasma optical emission spectroscopy (ICP-OES), the solution was diluted to two different degrees (10-fold and 1-fold, respectively). The diluted solutions were used to determine Si. 4+ Al 3+ and Ca 2+ The concentration of elements dissolved and the concentration of elements leached (R) l With leaching change rate V r Calculate according to the following formulas respectively:

[0118]

[0119] In the formula, R l The leaching concentration is t (mg / g), t is the dilution factor, and C is the concentration of the leaching solution. x V represents the element leaching concentration (mg / L), V represents the volume of the diluent used (L), and M represents the mass of GB used (g).

[0120]

[0121] In the formula, V r R represents the leaching change rate (%). i (i=12h, 24h, 48h, 72h) represents the concentration (mg / g) of element leaching at hour i, R N This represents the elemental concentration (mg / g) in the NaOH solution.

[0122] See Figure 2 As shown, Figure 2 GB in NaOH solution Si 4+ Al 3+ and Ca 2+ The leaching concentration changes over time. It can be seen that within 72 hours, Si... 4+ And Al 3+The leaching concentration of GB increases linearly with time, meaning that GB can provide more Si and Al monomers—[SiO4] and [AlO4]—in the polymerization reaction of geopolymer concrete, and can also promote the formation of more Si-O-Al polymer bonds. These polymer bonds will eventually condense into a three-dimensional network of polyaluminosilicate gel, which will then gradually solidify and harden into geopolymer material.

[0123] Figure 3 The leaching rates of Si, Al, and Ca ions in GB in NaOH solution at different times represent the leaching changes.

[0124] Taking 72 hours as an example, Si 4+ V r The variation range was 43.1% to 307.17%, while Al 3+ V r The variation range was 21.56% to 94.93%, indicating that silicon was more easily leached than aluminum in a highly alkaline medium. Based on the above formula, the leaching concentrations of calcium ions at 12h, 24h, 48h, and 72h were 0.0064 mg / g, 0.0022 mg / g, 0.0036 mg / g, and 0.019 mg / g, respectively, which were relatively low.

[0125] The effect of the amount of modified glass microspheres added was tested.

[0126] The modified glass microspheres were named GB, and geopolymer concrete materials with different GB contents were prepared according to the preparation method of Example 1. According to the GB addition ratio, they were named GB-0, GB-2%, GB-4%, GB-6%, GB-8% and GB-10%, respectively.

[0127] The GB addition ratio is the proportion of modified glass microspheres to the total mass of modified metakaolin, slag, modified glass microspheres, activator solution and mixed modifier. For example, in Example 1, the GB addition ratio is 5.38%.

[0128] See Figure 4 As shown, it is a SEM image of GB-0 and GB-2% concrete after 28 days of curing.

[0129] Figure 4 (a) Modified metakaolin (MK) particles can be seen in GB-0, which are embedded in the matrix in a multi-layered structure; Figure 4 (b) It can be seen that GB-2% has spherical traces of GB falling off due to cracks, and it is clear that the incorporation of GB makes the whole system more compact, which is beneficial to improving the strength of concrete, indicating that GB has a pore filling effect. Figure 4 In (b), SL stands for slag, and "Steading GB" means stable modified glass microspheres.

[0130] Figure 5 The compressive strength of geopolymer concrete materials after curing for 1, 3, 7 and 28 days is shown in the figure for different GB contents.

[0131] As can be seen, under the same curing age, the compressive strength of concrete shows a trend of first increasing and then decreasing with the increase of GB content, and this trend becomes more significant with increasing age; when the GB content is 4%, the compressive strength reaches its maximum value at all ages. Compared with GB content of 0, except for the similar strength at 1 day, the strength at 3, 7, and 28 days with GB-4% increased by 10.38%, 12.09%, and 24.16%, respectively, indicating that the addition of modified glass microspheres (GB) enhances the compressive strength of concrete; when the GB content exceeds 4%, the strength begins to show a decreasing trend. Although modified glass microspheres can enhance reactivity, excessive addition will lead to a decrease in the bulk density of concrete, thereby reducing strength.

[0132] See Figure 6 As shown, pores can be divided into three types: harmless pores with a diameter of less than 20 nm, relatively harmless pores with a diameter between 20 and 50 nm, and harmful pores with a diameter of more than 50 nm. Figure 6 The percentages of harmless pores, relatively harmful pores, and harmful pores in geopolymer concrete at different GB contents are shown. Compared to GB-0%, GB-2% significantly increases the proportion of harmless pores smaller than 20 nm and correspondingly reduces the proportion of harmful pores larger than 50 nm. This phenomenon gradually weakens with increasing GB content until the opposite trend is observed when the dosage exceeds 6%. This is mainly because the potential filling effect and gel enrichment effect of GB reduce the number of harmful pores larger than 50 nm, and a smaller number of harmful pores may be one of the main factors contributing to enhanced mechanical properties. Furthermore, GB has almost no effect on relatively harmless pores between 20 and 50 nm; the proportion of harmful pores larger than 50 nm shows a trend of first decreasing and then increasing with increasing GB content, indicating that the effect is better when the GB content of modified glass microspheres is 4-6%.

[0133] When the amorphous or low-crystallinity silica phase in the aggregate is coupled with water by OH- ions from alkali hydroxide in the matrix pores, an alkali-silica reaction (ASR) occurs:

[0134] The dissolution of reactive silica is shown in the following formula:

[0135] (1)

[0136] pH > 13 and the solution is rich in Na + or K + When ions are present, ASR gel is formed, and the reaction formula is shown below:

[0137] (2)

[0138] (3)

[0139] (4)

[0140] pH<13, the high reactivity of silica and Ca 2+ The dissolution rate of ions will significantly enhance the pozzolanic effect, thus promoting the formation of additional C-S-H or C-A-S-H gel in the system. When PH>13, the high alkaline environment will destroy the dissolution equilibrium between reactive silica and Ca 2+ , making the amorphous silica activity further enhanced (equation 2) and easily reacting to generate ions (equation 3), resulting in the system more easily generating harmful ASR gel. The accumulation of this gel will eventually produce internal stress, causing structural swelling and deformation, cracking, and reducing the durability of the system.

[0141] The characteristic band of C-A-S-H gel is usually in the range of 950-980 cm -1 From Figure 7 it can be seen that the most obvious bands appear at 970.89 cm -1 and 432.50 cm -1 , respectively, of which 970 cm -1 is a typical band of glassy aluminosilicate materials. Specifically, this band may be related to the vibration of Si-O-Si bonds. With the increase of GB content, the peak at 970 cm -1 shows a trend of first increasing and then decreasing, and when the GB content is 4%, the peak reaches a maximum, which is consistent with the mechanical performance test, indicating that the appropriate GB incorporation will promote the formation of Si-O-Si bonds. The bond energy of Si-O-Si is higher than that of Si-O-Al, and the formation speed is slower than that of Si-O-Al, which is also an important reason why the 28-day mechanical performance is significantly higher than that of other groups when the GB content is 4%.

[0142] The application also provides the application of the above-mentioned geopolymer concrete material as a building material in electric poles. Taking a ring electric pole as an example, the above-mentioned mixture is uniformly injected into a mold in which a steel reinforcement framework is placed by using a pumping or manual pouring method, the mold filled with the mixture is placed on a centrifugal machine, the centrifugal machine is first operated at a low speed to preliminarily distribute the mixture, and then the speed is gradually increased to a suitable speed, the mixture is uniformly attached to the inner wall of the mold by centrifugal force, and the mixture is further compacted, vibrated and discharged of excess water and air to form a dense structure and preliminarily form the electric pole. The formed electric pole is demolded after being cured at 25±2℃ and humidity ≥95% for 24 hours, and then is placed in a constant temperature curing box at 60℃ for curing for 3 days, and finally is naturally cured at room temperature to a test age, and a formed electric pole is obtained.

[0143] The above description is merely a detailed description of implementation. It is obvious to those skilled in the art that various modifications can be made to the embodiments, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A geopolymer concrete material characterised in that, It comprises, in parts by mass: 40~50 parts of modified metakaolin, 20~30 parts of slag, 2~10 parts of modified glass beads, 30~40 parts of activator solution, and a mixed modifier, the mass fraction of the mixed modifier being 0.3~1% of the total mass of the modified metakaolin and slag; The preparation method of the modified metakaolin comprises the following steps: Mix the metakaolin and the amino-terminated benzimidazole siloxane at a mass ratio of 1:0.05, ball mill for 0.8~1h, then add diamino diphenyl methane, ball mill for 0.8~1h, to obtain the modified metakaolin, the addition amount of diamino diphenyl methane being 2% of the mass of the metakaolin; The preparation method of the modified glass beads comprises the following steps: Soak the glass beads in a composite acid solution for 1.5~2h, wash with water until neutral, then dry, immerse in an ethanol solution of 3-aminopropyl triethoxysilane with a concentration of 5wt%, stir in a water bath at 50~60℃ for 1.5~2h, filter and dry to obtain pretreated beads; Disperse the pretreated beads in a 1wt% dopamine hydrochloride solution, oscillate for 1.5~2h, centrifuge, then clean with ethanol, and vacuum dry at 50~60℃ to obtain dry beads; Mix the dry beads with molybdenum disulfide, add anhydrous ethanol, ultrasonic dispersion for 25~30min, collect the precipitate, dry the precipitate in a drying oven at 55~60℃ for 2.5~3h to obtain modified glass beads, the addition amount of molybdenum disulfide being 0.5~1% of the mass of the dry beads, and the mass-volume ratio of the dry beads to anhydrous ethanol being 1g:5mL; The preparation method of the mixed modifier comprises the following steps: Mix azodicarbonamide, zinc borate, benzenesulfonamide, and N-phenylmaleimide at a mass ratio of 10:2:1:(1~2), stir at 48~50℃ for 0.8~1h until uniform to obtain the mixed modifier.

2. The geopolymer concrete material of claim 1, wherein: In the composite acid solution, the concentration of hydrochloric acid is 3wt%, and the concentration of oxalic acid is 0.1wt%.

3. The geopolymer concrete material of claim 1, wherein: The mixed modifier further comprises ethylene-vinyl acetate, and the addition amount of ethylene-vinyl acetate is 50% of the mass of azodicarbonamide.

4. The geopolymer concrete material of claim 1, wherein, The preparation method of the activator solution is: Dissolve sodium hydroxide in water, stir and dissolve at 60~80℃, cool to room temperature, then add sodium silicate, stir until uniform to obtain the activator solution; The mass ratio of sodium hydroxide to water is 1:5, and the mass ratio of sodium silicate to sodium hydroxide is 1:(3~5).

5. A method of manufacture for producing a geopolymer concrete material as claimed in any one of claims 1 to 4, characterised in that, It comprises the following steps: Mix the modified metakaolin and slag, add the activator solution and stir for 3~5min, then add the modified glass beads and the mixed modifier, continue to stir for 3~5min to obtain a mixture; Pour the mixture into a mold, vibrate to form, and discharge air; After the molding of the test piece, the test piece is demolded after curing at 25±2℃, humidity≥95% for 22~24h, and then is placed into a constant temperature curing box for curing at 58~60℃ for 3~5 days, and finally is naturally cured at room temperature to a test age, to obtain a geopolymer concrete material.

6. Use of the geopolymer concrete material according to any one of claims 1~4 as a building material in a pole.

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