Self-excited geopolymer concrete and preparation method thereof

Abstract

A self-excited geopolymer concrete and a preparation method thereof belong to the technical field of inorganic gelling materials. The self-excited geopolymer concrete consists of two parts: a powder and a liquid material; the powder consists of silicate cement, fly ash, blast furnace slag, graded aggregate, modified calcium carbonate whisker, sepiolite-loaded aluminum hydroxide, calcium tetraborate powder, and polycarboxylate water-reducing agent powder; and the liquid material consists of sodium hydroxide, tetrabutylphosphonium hydroxide aqueous solution, sodium water glass solution, and water; the self-excited geopolymer concrete prepared by the invention has a 28-day compressive strength of 83.4-86.6 MPa, a 28-day flexural strength of 11.5-13.2 MPa, a 28-day shrinkage rate of 0.02-0.05%, a 28-day tensile bonding strength of 5.1-6.2 MPa, and in terms of freeze-thaw resistance, the 100-cycle compressive strength loss rate is 0.4-0.8%, and the 100-cycle tensile bonding strength loss rate is 0.3-0.6%.

Description

Technical Field

[0001] The invention relates to a self-excited geopolymer concrete and a preparation method thereof, belonging to the technical field of inorganic gelling materials. Background Art

[0002] Geopolymer is a cementitious material with a three-dimensional network structure formed by self-excitation, also known as alkali excitation, of inorganic materials rich in silicon-aluminum phases, such as fly ash, slag and kaolin. In recent years, the global awareness of carbon reduction and environmental protection in buildings has been continuously improved. Self-excited geopolymer concrete has low carbon emissions and has the advantages of excellent mechanical properties, high temperature resistance, freeze-thaw resistance, and strong anti-penetration ability. It is widely used in civil engineering. However, in the process of using geopolymer concrete, people continue to find that geopolymer concrete has the problem of large shrinkage. It is precisely because of the large shrinkage that the scope of application of geopolymer concrete in engineering is limited. Due to the defect of large shrinkage, it will cause related problems such as low compressive strength, poor flexural strength, poor freeze-thaw resistance and insufficient durability of geopolymer concrete.

[0003] Chinese patent CN117510143A discloses a self-excited geopolymer concrete and its preparation method, which is to mineralize steel slag with a mineralizer and add a grinding aid for fine grinding, and use it together with ultrafine mineral powder as a cementitious material to form a self-excited system, stimulate the potential volcanic ash activity of steel slag and slag, add aggregate, pre-excited agent, water reducer and water to prepare self-excited geopolymer concrete, and realize the recycling of steel smelting waste. The patent promotes the curing strength of geopolymer concrete by pre-excitation of sodium hydroxide and fine grinding activation of reaction raw materials, but the compressive strength of the geopolymer concrete obtained by the patent is only up to 42.6MPa, which is not very ideal, and other relevant data such as flexural strength and freeze-thaw resistance are not disclosed.

[0004] Chinese patent CN104496333BA discloses a fly ash-based polymer concrete material and its preparation method and application. The components and mass percentages of the fly ash-based polymer concrete material are: fly ash 25-45%, metakaolin 0-15%, cement 10-15%, gangue and slag 0-5%, alkali activator 25-35%, retarder 0.5-1%, deionized water 1-5%. The fly ash-based polymer concrete obtained in this patent has a very low compressive strength of only 25MPa, which is difficult to meet most engineering applications.

[0005] From the above, it can be seen that the current self-excited geopolymer concrete still has problems such as large curing shrinkage and the resulting low compressive strength, low flexural strength, poor freeze-thaw resistance, and insufficient durability. Therefore, the development of self-excited geopolymer concrete with low curing shrinkage and good mechanical properties is of great significance to broadening the engineering application scope of geopolymer concrete. Summary of the invention

[0006] In view of the deficiencies in the above-mentioned prior art, the present invention provides a self-excited geopolymer concrete and a preparation method thereof, so as to achieve the following invention objectives: to prepare a self-excited geopolymer concrete with low curing shrinkage, high compressive strength, high flexural strength and good freeze-thaw resistance.

[0007] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0008] A self-excited geopolymer concrete and a preparation method thereof, wherein the self-excited geopolymer concrete is composed of a powder material and a liquid material, and the powder material and the liquid material are mixed uniformly in a mass ratio of 16 to 24:19 before use;

[0009] The specific formula of the powder is, by weight:

[0010] 140~230 parts of Portland cement,

[0011] 80~200 parts of fly ash,

[0012] 70~180 parts of blast furnace slag,

[0013] 260~400 parts of graded aggregate,

[0014] Modified calcium carbonate whisker 50~100 parts,

[0015] Sepiolite loaded with 30-70 parts of aluminum hydroxide,

[0016] 5-13 parts of calcium tetraborate powder,

[0017] 4-10 parts of polycarboxylate water-reducing agent powder;

[0018] The fly ash is Class F primary low-calcium fly ash with a particle size of 0.3-350 μm;

[0019] The blast furnace slag is primary ground and granulated blast furnace slag with a particle size of 0.5-300 μm;

[0020] The graded aggregate is sea sand that meets the grading standard, and the grading standard is: the percentage passing through the 13.2mm sieve hole is 100wt%, the percentage passing through the 9.5mm sieve hole is 90-95wt%, the percentage passing through the 4.75mm sieve hole is 80-90wt%, the percentage passing through the 2.36mm sieve hole is 75-95wt%, the percentage passing through the 1.18mm sieve hole is 40-80wt%, and the percentage passing through the 0.6mm sieve hole is 10-30wt%;

[0021] The particle size of the calcium tetraborate powder is 1 to 20 μm;

[0022] The specific formula of the liquid material is, by weight:

[0023] 10-30 parts of sodium hydroxide,

[0024] 5-15 parts of tetrabutylphosphonium hydroxide aqueous solution,

[0025] 65~170 parts of sodium water glass solution,

[0026] 160~300 parts of water;

[0027] The mass concentration of tetrabutylphosphonium hydroxide in the tetrabutylphosphonium hydroxide aqueous solution is 15-25wt%;

[0028] In the sodium water glass solution, the modulus of the sodium water glass is 1.5-3.5, and the mass concentration of sodium metasilicate is 20-30wt%;

[0029] The following are further improvements to the above technical solution:

[0030] Step 1: Preparation of modified calcium carbonate whiskers

[0031] The calcium carbonate whisker is dried at 80-95° C. for 6-11 hours, cooled to room temperature in a dry environment, and then added to a high-speed dispersion reactor, followed by adding anhydrous ethanol, controlling the dispersion rate at 6000-9500 rpm, and strongly dispersing for 5-9 hours, then reducing the dispersion rate to 1500-2500 rpm, then adding ethyl silicate, stirring for 15-35 minutes, and then dropping deionized water into the reactor at a rate of 3-35 g / min, and after the dropwise addition is completed, continuing the dispersion reaction for 4-8 hours, and then dropping sodium methyl silicate at a rate of 1-25 g / min, and after the dropwise addition is completed, continuing the dispersion reaction for 5-8 hours, and then centrifuging, and the separated solid is naturally dried to obtain modified calcium carbonate whiskers;

[0032] The length of the calcium carbonate whisker is 30-200 μm and the diameter is 0.5-3 μm;

[0033] The mass ratio of the calcium carbonate whiskers, anhydrous ethanol, ethyl silicate, deionized water and sodium methyl silicate is 40-110:140-550:6-35:4-15:10-40.

[0034] Step 2: Preparation of sepiolite-loaded aluminum hydroxide

[0035] The sepiolite is placed in an oven at 80-100°C and dried for 6-12 hours. After cooling to room temperature, it is added into a dry high-speed dispersion kettle, and then toluene is added. The dispersion rate is controlled at 8000-10000 rpm. After strong dispersion for 7-13 hours, the dispersion rate is reduced to 2000-4000 rpm. Then, aluminum isopropoxide is added, and the dispersion is continued for 4-7 hours. Then, the dispersion is stopped and the mixture is allowed to stand for 10-20 hours. Then, the upper clear liquid is poured into a dry waste liquid collection container, and the lower turbid liquid is centrifuged and separated. The separated solid is placed in an oven at 30-50°C and dried for 9-17 hours. After cooling to room temperature, the solid is naturally allowed to stand in an environment with a relative air humidity of 35-60% for 18-26 hours to obtain the sepiolite-loaded aluminum hydroxide.

[0036] The particle size of the sepiolite is 600-1000 mesh;

[0037] The mass ratio of the sepiolite, toluene and aluminum isopropoxide is 50-150:200-450:10-60.

[0038] Step 3: Preparation of powder

[0039] According to the specific formula of self-activated geopolymer concrete powder in parts by weight, silicate cement, fly ash, blast furnace slag, graded aggregate, modified calcium carbonate whisker, sepiolite loaded aluminum hydroxide, calcium tetraborate powder, and polycarboxylate water reducer powder are put into a high-speed mixer, and the stirring rate is controlled at 110-160 rpm. After stirring and mixing for 60-100 minutes, the material is discharged to obtain self-activated geopolymer concrete powder.

[0040] Step 4: Preparation of liquid material

[0041] According to the specific formula of the self-excited geopolymer concrete liquid material in parts by weight, water, sodium hydroxide, tetrabutylphosphonium hydroxide aqueous solution and sodium water glass solution are put into a mixing kettle, stirred at a stirring rate of 600-1200 rpm for 25-50 minutes and then discharged to obtain the self-excited geopolymer concrete liquid material.

[0042] Compared with the prior art, the present invention achieves the following beneficial effects:

[0043] 1. The present invention utilizes low-cost calcium carbonate whiskers to strengthen and toughen geopolymer concrete. Calcium carbonate whiskers are difficult to withstand the strong alkaline reaction environment during the curing process of geopolymer concrete, which easily causes damage to the mechanical properties of the calcium carbonate whiskers themselves. Therefore, the present invention first utilizes the hydrolysis reaction of ethyl silicate to coat a layer of active silicic acid and active silicon dioxide with silanol groups on the surface of the calcium carbonate whiskers, and then uses sodium methyl silicate to react with these silanol groups, so that the surface of the calcium carbonate whiskers is coated with a layer of methyl silicic acid. The methyl silicic acid makes the calcium carbonate whiskers have a certain degree of hydrophobicity, which prevents the calcium carbonate whiskers from excessively agglomerating during the mixing process of geopolymer concrete powder and liquid material, thereby affecting the uniformity of the dispersion of the calcium carbonate whiskers in the geopolymer concrete. More importantly, the outermost layer of the surface of the calcium carbonate whiskers is coated with Methylsilicic acid and the active inorganic silicon wrapped in the second outer layer of the surface react chemically with the surface of the calcium carbonate whisker. In addition, these two layers of wrapping will participate in the alkali-excited reaction of the geopolymer during the curing process of the geopolymer concrete, providing active silicon for the alkali-excited curing reaction of the geopolymer raw materials. In this way, the two layers of wrapping protect the surface of the calcium carbonate whisker and avoid excessive etching of the surface of the calcium carbonate whisker by the strong alkaline environment. At the same time, the two layers of wrapping react with the geopolymer raw materials to form chemical bonds, so that the calcium carbonate whiskers also enter the geopolymer cross-linked curing network in a chemically bonded manner. The calcium carbonate whiskers can not only play a physical strengthening and toughening effect, but also have a strengthening and toughening effect brought about by chemical strong bonding, which will maximize the strengthening and toughening effect of the calcium carbonate whiskers on the geopolymer concrete.

[0044] 2. The present invention adds sepiolite to the powder, and also utilizes the adsorption performance of sepiolite. After being impregnated and adsorbed with aluminum isopropoxide, the internal pores of the sepiolite are adsorbed with a large amount of aluminum hydroxide by further utilizing the property of aluminum isopropoxide hydrolyzing to form aluminum hydroxide. First, sepiolite is a hydrous magnesium-rich silicate clay mineral. The SiO 2 The content is generally between 54 and 60%, and the MgO content is mostly in the range of 21 to 25%. During the alkali-induced reaction of geopolymer concrete, sepiolite can dissolve in a strong alkaline environment and provide active silica for the reaction system. The dissolved MgO is an expansion agent for cement concrete. Because its hydration expansion is delayed and irreversible, it is often used to compensate for the temperature drop shrinkage of large-volume concrete. Mg(OH) generated by hydration of MgO 2The crystals have stable chemical properties. After the cement paste is completely hardened, they fill the internal holes, capillaries and cracks of the concrete and improve the internal pore structure of the concrete. Secondly, the aluminum hydroxide loaded by the sepiolite is rapidly dissolved during the dissolution reaction of the sepiolite, providing active aluminum ions for the geopolymer concrete reaction system. These active aluminum ions combine with the active silicon dioxide dissolved from the sepiolite and the active silicon dissolved from the surrounding geopolymer raw materials to form polyaluminum-silicon-oxygen condensation macromolecular chains. The polyaluminum-silicon-oxygen condensation macromolecular chains are cross-linked themselves or interpenetrate and cross-link with the cross-linked network structure of cement silicate, which greatly increases the density of the solidified cross-linking of the geopolymer concrete, thereby greatly improving the various mechanical properties of the geopolymer concrete.

[0045] 3. The calcium tetraborate powder added to the geopolymer concrete powder of the present invention, during the alkali excitation reaction of the geopolymer concrete, will release calcium ions and borate ions after the calcium tetraborate dissolves in a strong alkaline environment, wherein the calcium ions will quickly combine with silicates to form a cement-cured calcium silicate consolidation body, and the more active borate will replace the silicates and embed into the silicon-aluminum network of the geopolymer, thereby promoting the cross-linking rate of the silicon-aluminum network and increasing the cross-linking density of the silicon-aluminum network, thereby greatly improving the mechanical properties of the geopolymer concrete;

[0046] 4. The alkalinity of the tetrabutyl phosphonium hydroxide added to the liquid material of the present invention is higher than that of potassium hydroxide and sodium hydroxide. The appropriate addition of tetrabutyl phosphonium hydroxide can greatly increase the alkalinity of the alkali excitation reaction of the geopolymer raw material, increase the reaction rate, and enhance the production of the geopolymer inorganic gel, thereby further increasing the total amount of the consolidated body formed by the geopolymer, so that the solidified geopolymer concrete has a denser degree of solidification and cross-linking, and finally obtains a geopolymer concrete consolidated body with better mechanical properties;

[0047] 5. The self-excited geopolymer concrete prepared by the present invention has a 28-day compressive strength of 83.4-86.6 MPa, a 28-day flexural strength of 11.5-13.2 MPa, a 28-day shrinkage rate of 0.02-0.05%, a 28-day tensile bond strength of 5.1-6.2 MPa, and in terms of freeze-thaw resistance, the loss rate of compressive strength after 100 cycles is 0.4-0.8%, and the loss rate of tensile bond strength after 100 cycles is 0.3-0.6%. DETAILED DESCRIPTION

[0048] The preferred embodiments of the present invention are described below. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0049] Example 1: A method for preparing self-excited geopolymer concrete

[0050] Step 1: Preparation of modified calcium carbonate whiskers

[0051] The calcium carbonate whisker was dried at 90° C. for 9 hours, cooled to room temperature in a dry environment, and then added to a high-speed dispersion reaction kettle, followed by adding anhydrous ethanol, and the dispersion rate was controlled to be 7500 rpm. After intensive dispersion for 8 hours, the dispersion rate was reduced to 2000 rpm, and then ethyl silicate was added. After stirring for 30 minutes, deionized water was added dropwise to the kettle at a rate of 15 g / min. After the addition was completed, the dispersion reaction was continued for 7 hours, and then sodium methyl silicate was added dropwise at a rate of 10 g / min. After the addition was completed, the dispersion reaction was continued for 7 hours, and then centrifuged. After the separated solid was naturally dried, the modified calcium carbonate whisker was obtained;

[0052] The length of the calcium carbonate whisker is 100 μm and the diameter is 1 μm;

[0053] The mass ratio of the calcium carbonate whiskers, anhydrous ethanol, ethyl silicate, deionized water and sodium methyl silicate is 90:300:18:11:15.

[0054] Step 2: Preparation of sepiolite-loaded aluminum hydroxide

[0055] The sepiolite was placed in a 95°C oven and dried for 10 hours. After cooling to room temperature, it was added into a dry high-speed dispersion kettle, and then toluene was added. The dispersion rate was controlled at 9500 rpm. After intensive dispersion for 9 hours, the dispersion rate was reduced to 2500 rpm. Then, aluminum isopropoxide was added, and the dispersion was continued for 5 hours. Then, the dispersion was stopped and allowed to stand for 16 hours. Then, the upper clear liquid was poured into a dry waste liquid collection container. The lower turbid liquid was centrifuged and separated. The separated solid was placed in a 35°C oven and dried for 11 hours. After cooling to room temperature, it was naturally left to air in an environment with a relative air humidity of 45% for 22 hours to obtain the sepiolite-loaded aluminum hydroxide.

[0056] The particle size of the sepiolite is 800 mesh;

[0057] The mass ratio of the sepiolite, toluene and aluminum isopropoxide is 120:350:40.

[0058] Step 3: Preparation of powder

[0059] The specific formula of the powder is, by weight:

[0060] 200 parts of Portland cement,

[0061] 120 parts fly ash,

[0062] 110 parts of blast furnace slag,

[0063] 360 parts of graded aggregate,

[0064] 80 parts of modified calcium carbonate whisker,

[0065] Sepiolite loaded with aluminum hydroxide 60 parts,

[0066] Calcium tetraborate powder 9 parts,

[0067] 8 parts of polycarboxylate water reducing agent powder;

[0068] The fly ash is Class F primary low-calcium fly ash with a particle size of 100 μm;

[0069] The blast furnace slag is primary ground and granulated blast furnace slag with a particle size of 150 μm;

[0070] The graded aggregate is sea sand that meets the grading standard, and the grading standard is: the percentage passing through the 13.2mm sieve hole is 100wt%, the percentage passing through the 9.5mm sieve hole is 92wt%, the percentage passing through the 4.75mm sieve hole is 88wt%, the percentage passing through the 2.36mm sieve hole is 85wt%, the percentage passing through the 1.18mm sieve hole is 65wt%, and the percentage passing through the 0.6mm sieve hole is 19wt%;

[0071] According to the specific formula of self-activated geopolymer concrete powder in parts by weight, silicate cement, fly ash, blast furnace slag, graded aggregate, modified calcium carbonate whisker, sepiolite loaded aluminum hydroxide, calcium tetraborate powder, and polycarboxylate water reducer powder are put into a high-speed mixer, the stirring rate is controlled at 130 rpm, and the mixture is stirred and mixed for 90 minutes before discharging the mixture to obtain self-activated geopolymer concrete powder.

[0072] Step 4: Preparation of liquid material

[0073] The specific formula of the liquid material is, by weight:

[0074] 25 parts of sodium hydroxide,

[0075] 11 parts of tetrabutylphosphonium hydroxide aqueous solution,

[0076] 130 parts of sodium water glass solution,

[0077] 260 parts of water;

[0078] The mass concentration of tetrabutylphosphonium hydroxide in the tetrabutylphosphonium hydroxide aqueous solution is 22wt%;

[0079] In the sodium water glass solution, the modulus of the sodium water glass is 3, and the mass concentration of sodium metasilicate is 28wt%;

[0080] According to the specific formula of the self-excited geopolymer concrete liquid material in parts by weight, water, sodium hydroxide, tetrabutylphosphine hydroxide aqueous solution and sodium water glass solution are put into a mixing kettle, stirred at a stirring rate of 1000 rpm for 40 minutes and then discharged to obtain the self-excited geopolymer concrete liquid material.

[0081] Example 2: A method for preparing self-excited geopolymer concrete

[0082] Step 1: Preparation of modified calcium carbonate whiskers

[0083] The calcium carbonate whisker was dried at 80° C. for 6 hours, cooled to room temperature in a dry environment, and then added to a high-speed dispersion reaction kettle, followed by adding anhydrous ethanol, and the dispersion rate was controlled to be 6000 rpm. After intensive dispersion for 5 hours, the dispersion rate was reduced to 1500 rpm, and then ethyl silicate was added. After stirring for 15 minutes, deionized water was added dropwise to the kettle at a rate of 3 g / min. After the addition was completed, the dispersion reaction was continued for 4 hours, and then sodium methyl silicate was added dropwise at a rate of 1 g / min. After the addition was completed, the dispersion reaction was continued for 5 hours, and then centrifuged. After the separated solid was naturally dried, the modified calcium carbonate whisker was obtained;

[0084] The length of the calcium carbonate whisker is 30 μm and the diameter is 0.5 μm;

[0085] The mass ratio of the calcium carbonate whiskers, anhydrous ethanol, ethyl silicate, deionized water and sodium methyl silicate is 40:140:6:4:10.

[0086] Step 2: Preparation of sepiolite-loaded aluminum hydroxide

[0087] The sepiolite was placed in an oven at 80°C and dried for 6 hours. After cooling to room temperature, the mixture was added into a dry high-speed dispersion kettle. Toluene was then added. The dispersion rate was controlled at 8000 rpm. After intensive dispersion for 7 hours, the dispersion rate was reduced to 2000 rpm. Aluminum isopropoxide was then added. After dispersion was continued for 4 hours, the dispersion was stopped and the mixture was allowed to stand for 10 hours. The upper clear liquid was then poured into a dry waste liquid collection container. The lower turbid liquid was then centrifuged and separated. The separated solid was placed in an oven at 30°C and dried for 9 hours. After cooling to room temperature, the solid was naturally allowed to stand in an environment with a relative air humidity of 35% for 18 hours to obtain the sepiolite-loaded aluminum hydroxide.

[0088] The particle size of the sepiolite is 600 mesh;

[0089] The mass ratio of the sepiolite, toluene and aluminum isopropoxide is 50:200:10.

[0090] Step 3: Preparation of powder

[0091] The specific formula of the powder is, by weight:

[0092] 140 parts of Portland cement,

[0093] 80 parts of fly ash,

[0094] 70 parts of blast furnace slag,

[0095] 260 parts of graded aggregate,

[0096] 50 parts of modified calcium carbonate whisker,

[0097] Sepiolite loaded with aluminum hydroxide 30 parts,

[0098] 5 parts of calcium tetraborate powder,

[0099] 4 parts of polycarboxylate water reducing agent powder;

[0100] The fly ash is Class F first-grade low-calcium fly ash with a particle size of 0.3 μm;

[0101] The blast furnace slag is primary ground and granulated blast furnace slag with a particle size of 0.5 μm;

[0102] The graded aggregate is sea sand that meets the grading standard, and the grading standard is: the percentage passing through the 13.2mm sieve hole is 100wt%, the percentage passing through the 9.5mm sieve hole is 90wt%, the percentage passing through the 4.75mm sieve hole is 80wt%, the percentage passing through the 2.36mm sieve hole is 75wt%, the percentage passing through the 1.18mm sieve hole is 40wt%, and the percentage passing through the 0.6mm sieve hole is 10wt%;

[0103] According to the specific formula of self-activated geopolymer concrete powder in parts by weight, silicate cement, fly ash, blast furnace slag, graded aggregate, modified calcium carbonate whisker, sepiolite loaded aluminum hydroxide, calcium tetraborate powder, and polycarboxylate water reducer powder are put into a high-speed mixer, and the stirring rate is controlled to be 110 rpm. After stirring and mixing for 60 minutes, the material is discharged to obtain self-activated geopolymer concrete powder.

[0104] Step 4: Preparation of liquid material

[0105] The specific formula of the liquid material is, by weight:

[0106] 10 parts of sodium hydroxide,

[0107] 5 parts of tetrabutylphosphonium hydroxide aqueous solution,

[0108] 65 parts of sodium water glass solution,

[0109] 160 parts water;

[0110] The mass concentration of tetrabutylphosphonium hydroxide in the tetrabutylphosphonium hydroxide aqueous solution is 15wt%;

[0111] In the sodium water glass solution, the modulus of the sodium water glass is 1.5, and the mass concentration of sodium metasilicate is 20wt%;

[0112] According to the specific formula of the self-excited geopolymer concrete liquid material in parts by weight, water, sodium hydroxide, tetrabutylphosphine hydroxide aqueous solution and sodium water glass solution are put into a mixing kettle, stirred at a stirring rate of 600 rpm for 25 minutes and then discharged to obtain the self-excited geopolymer concrete liquid material.

[0113] Example 3: A method for preparing self-excited geopolymer concrete

[0114] Step 1: Preparation of modified calcium carbonate whiskers

[0115] The calcium carbonate whisker was dried at 95° C. for 11 hours, cooled to room temperature in a dry environment, and then added to a high-speed dispersion reaction kettle, followed by adding anhydrous ethanol, and the dispersion rate was controlled at 9500 rpm. After 9 hours of strong dispersion, the dispersion rate was reduced to 2500 rpm, and then ethyl silicate was added. After stirring for 35 minutes, deionized water was added dropwise to the kettle at a rate of 35 g / min. After the addition was completed, the dispersion reaction was continued for 8 hours, and then sodium methyl silicate was added dropwise at a rate of 25 g / min. After the addition was completed, the dispersion reaction was continued for 8 hours, and then centrifuged. After the separated solid was naturally dried, the modified calcium carbonate whisker was obtained;

[0116] The length of the calcium carbonate whisker is 200 μm and the diameter is 3 μm;

[0117] The mass ratio of the calcium carbonate whiskers, anhydrous ethanol, ethyl silicate, deionized water and sodium methyl silicate is 110:550:35:15:40.

[0118] Step 2: Preparation of sepiolite-loaded aluminum hydroxide

[0119] The sepiolite was placed in a 100°C oven and dried for 12 hours. After cooling to room temperature, it was added into a dry high-speed dispersion kettle, and then toluene was added. The dispersion rate was controlled at 10,000 rpm. After intensive dispersion for 13 hours, the dispersion rate was reduced to 4,000 rpm. Then, aluminum isopropoxide was added, and the dispersion was continued for 7 hours. Then, the dispersion was stopped and allowed to stand for 20 hours. Then, the upper clear liquid was poured into a dry waste liquid collection container. The lower turbid liquid was centrifuged and separated. The separated solid was placed in a 50°C oven and dried for 17 hours. After cooling to room temperature, it was naturally left to air in an environment with a relative air humidity of 60% for 26 hours to obtain the sepiolite-loaded aluminum hydroxide.

[0120] The particle size of the sepiolite is 1000 mesh;

[0121] The mass ratio of the sepiolite, toluene and aluminum isopropoxide is 150:450:60.

[0122] Step 3: Preparation of powder

[0123] The specific formula of the powder is, by weight:

[0124] 230 parts of Portland cement,

[0125] 200 parts of fly ash,

[0126] 180 parts of blast furnace slag,

[0127] 400 parts of graded aggregate,

[0128] 100 parts of modified calcium carbonate whisker,

[0129] Sepiolite loaded with aluminum hydroxide 70 parts,

[0130] 13 parts of calcium tetraborate powder,

[0131] 10 parts of polycarboxylate water reducing agent powder;

[0132] The fly ash is Class F first-grade low-calcium fly ash with a particle size of 350 μm;

[0133] The blast furnace slag is primary ground and granulated blast furnace slag with a particle size of 300 μm;

[0134] The graded aggregate is sea sand that meets the grading standard, and the grading standard is: the percentage passing through the 13.2mm sieve hole is 100wt%, the percentage passing through the 9.5mm sieve hole is 95wt%, the percentage passing through the 4.75mm sieve hole is 90wt%, the percentage passing through the 2.36mm sieve hole is 95wt%, the percentage passing through the 1.18mm sieve hole is 80wt%, and the percentage passing through the 0.6mm sieve hole is 30wt%;

[0135] According to the specific formula of self-activated geopolymer concrete powder in parts by weight, silicate cement, fly ash, blast furnace slag, graded aggregate, modified calcium carbonate whisker, sepiolite loaded aluminum hydroxide, calcium tetraborate powder, and polycarboxylate water reducer powder are put into a high-speed mixer, the stirring rate is controlled at 160 rpm, and the mixture is stirred and mixed for 100 minutes before discharging the mixture to obtain self-activated geopolymer concrete powder.

[0136] Step 4: Preparation of liquid material

[0137] The specific formula of the liquid material is, by weight:

[0138] 30 parts of sodium hydroxide,

[0139] 15 parts of tetrabutylphosphonium hydroxide aqueous solution,

[0140] 170 parts of sodium water glass solution,

[0141] 300 parts water;

[0142] The mass concentration of tetrabutylphosphonium hydroxide in the tetrabutylphosphonium hydroxide aqueous solution is 25wt%;

[0143] In the sodium water glass solution, the modulus of the sodium water glass is 3.5, and the mass concentration of sodium metasilicate is 30wt%;

[0144] According to the specific formula of the self-excited geopolymer concrete liquid material in parts by weight, water, sodium hydroxide, tetrabutylphosphine hydroxide aqueous solution and sodium water glass solution are put into a mixing kettle, stirred at a stirring rate of 1200 rpm for 50 minutes and then discharged to obtain the self-excited geopolymer concrete liquid material.

[0145] Comparative Example 1: Based on Example 1, step 1, preparation of modified calcium carbonate whiskers, is not performed. In step 3, preparation of powder, 80 parts of modified calcium carbonate whiskers are replaced by 80 parts of calcium carbonate whiskers in equal amounts. The specific operation is as follows:

[0146] The step 1, preparation of modified calcium carbonate whiskers is not performed;

[0147] The operation of step 2 is the same as that of embodiment 1;

[0148] Step 3: Preparation of powder

[0149] 80 parts of modified calcium carbonate whiskers were replaced by 80 parts of calcium carbonate whiskers, and the other operations were the same as in Example 1;

[0150] The length of the calcium carbonate whisker is 100 μm and the diameter is 1 μm;

[0151] The operation of step 4 is the same as that of embodiment 1.

[0152] Comparative Example 2: Based on Example 1, step 2, preparation of aluminum hydroxide loaded on sepiolite, is not performed. In step 3, preparation of powder, 60 parts of aluminum hydroxide loaded on sepiolite are replaced by 60 parts of sepiolite in equal amounts. The specific operation is as follows:

[0153] The operation of step 1 is the same as that of embodiment 1;

[0154] Step 2, preparation of sepiolite-loaded aluminum hydroxide, is not performed;

[0155] Step 3: Preparation of powder

[0156] The 60 parts of sepiolite loaded with aluminum hydroxide were replaced by 60 parts of sepiolite, and the other operations were the same as in Example 1;

[0157] The particle size of the sepiolite is 800 mesh;

[0158] The operation of step 4 is the same as that of embodiment 1.

[0159] Comparative Example 3: Based on Example 1, in step 3, in the preparation of the powder, no calcium tetraborate powder is added, and 9 parts of calcium tetraborate powder are replaced by 9 parts of Portland cement in equal amounts. The specific operation is as follows:

[0160] The operations of steps 1 and 2 are the same as those of Example 1;

[0161] Step 3: Preparation of powder

[0162] 9 parts of calcium tetraborate powder were replaced by 9 parts of Portland cement, and the other operations were the same as in Example 1;

[0163] The operation of step 4 is the same as that of embodiment 1.

[0164] Comparative Example 4: Based on Example 1, in step 4, in the preparation of the liquid material, 11 parts of tetrabutylphosphonium hydroxide aqueous solution were replaced by 11 parts of water in equal amounts, and the specific operation was as follows:

[0165] The operations of steps 1, 2, and 3 are the same as those of Example 1;

[0166] Step 4: Preparation of liquid material

[0167] The 11 parts of tetrabutylphosphonium hydroxide aqueous solution were replaced by 11 parts of water in equal amounts, and the other operations were the same as in Example 1.

[0168] Performance Test:

[0169] The self-excited geopolymer concrete powder and liquid material obtained in Examples 1, 2, 3 and Comparative Examples 1, 2, 3, 4 were uniformly mixed in a mass ratio of 20:19, and test samples were prepared according to the corresponding test standards and the following indicators were tested:

[0170] 1. 28-day compressive strength: According to the national standard GB / T17671-2021 cement mortar strength test

[0171] Preparation of test specimens and testing of compressive strength according to the method specified in the ISO Method;

[0172] 2. 28-day flexural strength: According to the national standard "GB / T17671-2021 cement mortar strength test

[0173] Preparation of test pieces and testing of flexural strength according to the method specified in the ISO Method;

[0174] 3. 28-day shrinkage rate: According to GB / T50082-2009 Long-term performance and durability of concrete

[0175] Prepare specimens and conduct tests according to the method specified in the "Standard for Durability Test Methods";

[0176] 4. Freeze-thaw resistance: According to GB / T50082-2009 Long-term performance and durability of concrete

[0177] Prepare specimens and conduct tests according to the method specified in the "Standard for Durability Test Methods";

[0178] 5. Tensile bond strength: According to GB / T50082-2009 Long-term tensile strength of concrete

[0179] Preparation and testing of test pieces according to the method specified in the "Standard for Test Methods of Energy and Durability Performance";

[0180] The test results of the above indicators are shown in Table 1:

[0181] Table 1

[0182]

[0183] It can be seen from the data in Table 1 that the 28-day compressive strength of Examples 1-3 is higher than 83MPa, the 28-day flexural strength is also greater than 11MPa, the 28-day shrinkage is less than 0.05%, the 28-day tensile bond strength is also greater than 5.1MPa, and the loss rates of compressive strength and tensile bond strength in terms of freeze-thaw resistance are all below 0.8%, which shows that the present invention obtains a self-excited geopolymer concrete with low solid shrinkage, high compressive strength, high flexural strength and good freeze-thaw resistance; the calcium carbonate whiskers in Comparative Example 1 are not surface modified, and the 28-day compressive strength and 28-day flexural strength of Comparative Example 1 are reduced to a very low state, the 28-day shrinkage also increases sharply to 0.86%, and the 28-day tensile strength is less than 5.1MPa. This indicates that the surface modified calcium carbonate whiskers can effectively improve the mechanical properties and freeze-thaw resistance of geopolymer concrete. This may be because if the calcium carbonate whiskers are not surface modified, they are easily damaged in the solidification process driven by the strong alkaline excitation reaction of the geopolymer concrete. Then, the calcium carbonate whiskers are difficult to effectively enhance and toughen the geopolymer concrete because their own mechanical properties are severely damaged. In Comparative Example 2, the sepiolite is not loaded with aluminum hydroxide, and the 28-day compressive strength, flexural strength and tensile bonding strength of Comparative Example 2 are significantly reduced, especially the 28-day shrinkage rate, which increases most significantly, and the freeze-thaw resistance is better. The performance also decreased quite sharply accordingly, which indicates that the aluminum hydroxide loaded by sepiolite can effectively improve the density of the geopolymer concrete after curing, reduce the 28-day shrinkage rate, and thus improve the various mechanical properties of the geopolymer concrete; no calcium tetraborate powder is added to the powder of Example 3, and the 28-day compressive strength, flexural strength and tensile bond strength of Example 3 are significantly decreased, the 28-day shrinkage rate is also significantly increased, and the freeze-thaw resistance is also reduced to a certain extent, which shows that calcium tetraborate powder has a very obvious effect on reducing the 28-day shrinkage rate of geopolymer concrete. This may be because calcium tetraborate can increase the curing cross-linking density of geopolymer concrete, thereby improving the density of geopolymer concrete after curing. degree, reduced the shrinkage rate, and finally promoted the improvement of the mechanical properties of the geopolymer concrete; the tetrabutyl phosphonium hydroxide aqueous solution was not added to the liquid material of Comparative Example 4, and the 28-day compressive strength, flexural strength and tensile bond strength of Comparative Example 4 were greatly reduced, especially the 28-day shrinkage rate, which increased to 1.10%, and the freeze-thaw resistance also decreased significantly, which shows that tetrabutyl phosphonium hydroxide plays a vital role in improving the mechanical properties of geopolymer concrete. It may be because tetrabutyl phosphonium hydroxide provides a more alkaline reaction environment, promotes the degree of gel reaction between the geopolymer raw materials, forms a denser and stronger gel solidified body, and can greatly improve the various mechanical properties of the geopolymer concrete.

[0184] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A self-excited geopolymer concrete, characterized in that: The self-excited geopolymer concrete consists of two parts: powder material and liquid material; The powder material is composed of silicate cement, fly ash, blast furnace slag, graded aggregate, modified calcium carbonate whisker, sepiolite-loaded aluminum hydroxide, calcium tetraborate powder, and polycarboxylate water-reducing agent powder; The powder composition comprises, by weight, 140 to 230 parts of Portland cement, 80 to 200 parts of fly ash, 70 to 180 parts of blast furnace slag, 260 to 400 parts of graded aggregate, 50 to 100 parts of modified calcium carbonate whiskers, 30 to 70 parts of sepiolite-loaded aluminum hydroxide, 5 to 13 parts of calcium tetraborate powder, and 4 to 10 parts of polycarboxylate water-reducing agent powder; The modified calcium carbonate whisker has a preparation method comprising: drying and cooling the calcium carbonate whisker to room temperature, adding the calcium carbonate whisker to a high-speed dispersion reaction kettle, then adding anhydrous ethanol, vigorously dispersing and uniformly dispersing, then adding ethyl silicate, stirring evenly, then dripping deionized water into the kettle at a rate of 3 to 35 g / min, continuing the dispersion reaction after the dripping is completed, then dripping sodium methyl silicate at a rate of 1 to 25 g / min, continuing the dispersion reaction after the dripping is completed, centrifuging, and naturally drying the separated solid to obtain the modified calcium carbonate whisker; The sepiolite-loaded aluminum hydroxide has a preparation method comprising: drying the sepiolite completely and cooling it to room temperature, then adding it into a dry high-speed dispersion kettle, adding toluene, vigorously dispersing it evenly, adding aluminum isopropoxide, continuing to disperse it until the reaction is complete, stopping the dispersion, standing it, then pouring the upper clear liquid into a dry waste liquid collection container, centrifuging the lower turbid liquid, and drying and naturally airing the separated solid to obtain the sepiolite-loaded aluminum hydroxide; The mass ratio of the sepiolite, toluene and aluminum isopropoxide is 50-150:200-450:10-60; The liquid material is composed of sodium hydroxide, tetrabutylphosphine hydroxide aqueous solution, sodium water glass solution and water; The liquid material comprises, by weight, 10 to 30 parts of sodium hydroxide, 5 to 15 parts of tetrabutylphosphonium hydroxide aqueous solution, 65 to 170 parts of sodium water glass solution, and 160 to 300 parts of water; The mass concentration of tetrabutylphosphonium hydroxide in the tetrabutylphosphonium hydroxide aqueous solution is 15-25wt%.

2. The self-excited geopolymer concrete according to claim 1, characterized in that: The fly ash is Class F primary low-calcium fly ash with a particle size of 0.3-350 μm; The blast furnace slag is primary ground and granulated blast furnace slag with a particle size of 0.5-300 μm; The graded aggregate is sea sand that meets the grading standard, and the grading standard is: the percentage passing through the 13.2mm sieve hole is 100wt%, the percentage passing through the 9.5mm sieve hole is 90-95wt%, the percentage passing through the 4.75mm sieve hole is 80-90wt%, the percentage passing through the 2.36mm sieve hole is 75-95wt%, the percentage passing through the 1.18mm sieve hole is 40-80wt%, and the percentage passing through the 0.6mm sieve hole is 10-30wt%; The particle size of the calcium tetraborate powder is 1-20 μm.

3. The self-excited geopolymer concrete according to claim 1, characterized in that: In the sodium water glass solution, the modulus of the sodium water glass is 1.5-3.5, and the mass concentration of sodium metasilicate is 20-30wt%.

4. The self-excited geopolymer concrete according to claim 1, characterized in that: The length of the calcium carbonate whisker is 30-200 μm, and the diameter is 0.5-3 μm.

5. The self-excited geopolymer concrete according to claim 1, characterized in that: The particle size of the sepiolite is 600-1000 meshes.

6. The method for preparing the self-excited geopolymer concrete according to claim 1, characterized in that: The preparation method of the self-excited geopolymer concrete, wherein the preparation method of the powder is: according to the specific formula of the self-excited geopolymer concrete powder in parts by weight, silicate cement, fly ash, blast furnace slag, graded aggregate, modified calcium carbonate whisker, sepiolite loaded aluminum hydroxide, calcium tetraborate powder, polycarboxylate water reducer powder are put into a high-speed mixer, the stirring speed is controlled at 110-160 rpm, the mixture is stirred and mixed for 60-100 minutes, and then the mixture is discharged to obtain the self-excited geopolymer concrete powder; The preparation method of the liquid material is as follows: according to the specific formula of the self-excited geopolymer concrete liquid material in parts by weight, water, sodium hydroxide, tetrabutylphosphonium hydroxide aqueous solution and sodium water glass solution are put into a mixing kettle, stirred at a stirring rate of 600 to 1200 rpm for 25 to 50 minutes, and then discharged to obtain the self-excited geopolymer concrete liquid material; When the self-excited geopolymer concrete is used for construction, the powder material and the liquid material are evenly mixed in a mass ratio of 16-24:19 and then used.

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