CN116477646A - Method for in-situ growth of nano alumina modified gypsum slag cement based on fly ash - Google Patents
Method for in-situ growth of nano alumina modified gypsum slag cement based on fly ash Download PDFInfo
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- 239000004568 cement Substances 0.000 title claims abstract description 127
- 239000010881 fly ash Substances 0.000 title claims abstract description 120
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 title claims abstract description 103
- 239000002893 slag Substances 0.000 title claims abstract description 101
- 229910052602 gypsum Inorganic materials 0.000 title claims abstract description 94
- 239000010440 gypsum Substances 0.000 title claims abstract description 94
- 238000011065 in-situ storage Methods 0.000 title claims abstract description 77
- 238000000034 method Methods 0.000 title claims abstract description 29
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 35
- 238000003756 stirring Methods 0.000 claims abstract description 30
- 238000001354 calcination Methods 0.000 claims abstract description 16
- 229910052918 calcium silicate Inorganic materials 0.000 claims abstract description 16
- 235000012241 calcium silicate Nutrition 0.000 claims abstract description 16
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims abstract description 15
- JHLNERQLKQQLRZ-UHFFFAOYSA-N calcium silicate Chemical compound [Ca+2].[Ca+2].[O-][Si]([O-])([O-])[O-] JHLNERQLKQQLRZ-UHFFFAOYSA-N 0.000 claims abstract description 15
- 239000011734 sodium Substances 0.000 claims abstract description 15
- 229910052708 sodium Inorganic materials 0.000 claims abstract description 15
- 238000006243 chemical reaction Methods 0.000 claims abstract description 12
- 238000001035 drying Methods 0.000 claims abstract description 9
- 238000002156 mixing Methods 0.000 claims abstract description 9
- 239000004094 surface-active agent Substances 0.000 claims abstract description 9
- 238000001816 cooling Methods 0.000 claims abstract description 8
- 238000005406 washing Methods 0.000 claims abstract description 8
- 239000003638 chemical reducing agent Substances 0.000 claims description 17
- 238000001723 curing Methods 0.000 claims description 9
- 238000000465 moulding Methods 0.000 claims description 9
- LZZYPRNAOMGNLH-UHFFFAOYSA-M Cetrimonium bromide Chemical group [Br-].CCCCCCCCCCCCCCCC[N+](C)(C)C LZZYPRNAOMGNLH-UHFFFAOYSA-M 0.000 claims description 8
- 239000007787 solid Substances 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 3
- 229920005646 polycarboxylate Polymers 0.000 claims description 3
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 2
- 239000011707 mineral Substances 0.000 claims description 2
- 239000000843 powder Substances 0.000 claims description 2
- 238000004321 preservation Methods 0.000 claims 1
- 238000003763 carbonization Methods 0.000 abstract description 11
- 238000005336 cracking Methods 0.000 abstract description 7
- 230000007547 defect Effects 0.000 abstract description 3
- 238000002360 preparation method Methods 0.000 abstract description 3
- 239000000047 product Substances 0.000 description 23
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 21
- 230000000052 comparative effect Effects 0.000 description 16
- 238000006703 hydration reaction Methods 0.000 description 16
- 230000036571 hydration Effects 0.000 description 13
- 230000000694 effects Effects 0.000 description 9
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 8
- 239000000463 material Substances 0.000 description 7
- 239000002086 nanomaterial Substances 0.000 description 6
- 239000002002 slurry Substances 0.000 description 5
- 239000002956 ash Substances 0.000 description 4
- 229910001653 ettringite Inorganic materials 0.000 description 4
- 230000006872 improvement Effects 0.000 description 4
- 230000006911 nucleation Effects 0.000 description 4
- 238000010899 nucleation Methods 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 3
- 239000004567 concrete Substances 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 239000003469 silicate cement Substances 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- PPQREHKVAOVYBT-UHFFFAOYSA-H dialuminum;tricarbonate Chemical compound [Al+3].[Al+3].[O-]C([O-])=O.[O-]C([O-])=O.[O-]C([O-])=O PPQREHKVAOVYBT-UHFFFAOYSA-H 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 238000010348 incorporation Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 239000011398 Portland cement Substances 0.000 description 1
- 241001147416 Ursus maritimus Species 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 229940118662 aluminum carbonate Drugs 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 239000000378 calcium silicate Substances 0.000 description 1
- OYACROKNLOSFPA-UHFFFAOYSA-N calcium;dioxido(oxo)silane Chemical compound [Ca+2].[O-][Si]([O-])=O OYACROKNLOSFPA-UHFFFAOYSA-N 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 230000015271 coagulation Effects 0.000 description 1
- 238000005345 coagulation Methods 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- 238000011534 incubation Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000011858 nanopowder Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000008030 superplasticizer Substances 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
- C01F7/14—Aluminium oxide or hydroxide from alkali metal aluminates
- C01F7/141—Aluminium oxide or hydroxide from alkali metal aluminates from aqueous aluminate solutions by neutralisation with an acidic agent
- C01F7/142—Aluminium oxide or hydroxide from alkali metal aluminates from aqueous aluminate solutions by neutralisation with an acidic agent with carbon dioxide
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/44—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water
- C01F7/441—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water by calcination
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B7/00—Hydraulic cements
- C04B7/24—Cements from oil shales, residues or waste other than slag
- C04B7/26—Cements from oil shales, residues or waste other than slag from raw materials containing flue dust, i.e. fly ash
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B7/00—Hydraulic cements
- C04B7/32—Aluminous cements
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/10—Production of cement, e.g. improving or optimising the production methods; Cement grinding
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
Abstract
The invention discloses a method for in-situ growth of nano alumina modified gypsum slag cement based on fly ash, which comprises the following steps: (1) preparation of nano alumina grown in situ by fly ash: adding fly ash into sodium metaaluminate solution, adding surfactant, and continuously introducing CO into the solution 2 The method comprises the steps of carrying out a first treatment on the surface of the Stopping the reaction when the pH value of the solution reaches 7-8, centrifuging, washing and drying to obtain an initial product, calcining the initial product at high temperature, and cooling to obtain the fly ash in-situ grown nano alumina; (2) Mixing gypsum, slag, P O52.5R cement, high belite sulphoaluminate cement and fly ash in-situ grown nano alumina, fully stirring, and adding water and reducing waterAnd stirring uniformly to obtain the modified gypsum slag cement. The modified gypsum slag cement obtained by the method has the advantages of high early strength, good fluidity, good carbonization performance and difficult cracking in the later stage, and can overcome the defects of the existing gypsum slag cement and integrally improve the performance of the existing gypsum slag cement.
Description
Technical Field
The invention relates to a method for in-situ growth of nano alumina modified gypsum slag cement based on fly ash, belonging to the application field of nano materials in cement-based materials.
Background
The super sulfate cement, also called gypsum slag cement, is a hydraulic cementing material prepared by grinding 75% -85% of slag, 10% -20% of gypsum and 1% -5% of alkaline components together or respectively and then mixing. The cement is different from the traditional silicate cement hydration, and strength is generated by exciting the activity of slag by depending on sulfate and alkaline components, so that the cement does not need to be subjected to a two-grinding one-firing process of the traditional cement in the production process, and only a plurality of materials required by the cement are ground to the required fineness and are uniformly mixed, and the emission of greenhouse gases is reduced.
The gypsum slag cement concrete has 49% less carbon dioxide discharge than ordinary silicate cement concrete, and is 26% cheaper, and the compressive strength of the gypsum slag cement concrete in 180d is equivalent to that of ordinary cement. Compared with common silicate cement, the super-sulfate cement has the characteristics of excellent alkali aggregate reactivity resistance, sulfate erosion resistance, high later strength, low hydration heat and the like. The cement is produced and used worldwide in the last 40-60 th century, and the early strength of the cement is lower than that of the general Portland cement due to the lower alumina content in slag, so that the cement gradually exits from the market. The existing gypsum slag cement has the problems of low early strength, poor carbonization performance and easy later cracking, because when the cementing material is hydrated to a certain extent, the local volume expansion can be caused to cause the later cracking due to the delay of the generation of ettringite.
The existing gypsum slag cement improvement method mainly comprises the following steps: the improved method mainly accelerates the hydration reaction of cement by promoting the dissolution of slag.
There is no study on nano material modified gypsum slag cement, but there is a study on modification of other slag-containing cement-based materials (such as slag cement, alkali slag cement, etc.) by nano materials. The effect of the nano material on the cement-based material is different from that of the gypsum slag cement improvement method, and the interface transition area is improved mainly through the synergistic effect of the volcanic ash activity and the crystal nucleus of the nano material, so that the pore structure is refined, and the hydration degree of early cement is greatly improved.
The improvement effect of the common nano alumina on the performances of the gypsum slag cement such as strength, carbonization resistance and the like is not obvious, and the fluidity is greatly reduced; the in-situ growth of nano alumina can greatly improve early strength, improve carbonization resistance and reduce flowability loss. Commercial nano alumina is easy to agglomerate in the slurry to wrap a part of water, the nano alumina grown on the surface of the fly ash in situ has better dispersibility in the slurry and less loss of fluidity; the in-situ growth of nano alumina changes nucleation points of the nano alumina in volcanic ash reaction products, so that the nucleation points are concentrated on the surface of the fly ash and nearby the surface of the fly ash, the interface structure between the fly ash particles and hydration products is improved, and the degree of participation of active components in the fly ash subjected to surface treatment in volcanic ash reaction is promoted; the addition of in situ grown nano alumina fills the detrimental pores, resulting in a decrease in porosity.
Disclosure of Invention
The invention aims to: the invention aims to provide a method for in-situ growth of nano alumina modified gypsum slag cement based on fly ash, and the modified gypsum slag cement obtained by the method has the advantages of high early strength, good fluidity, good carbonization performance and difficult cracking in the later stage.
The technical scheme is as follows: the method for in-situ growth of nano alumina modified gypsum slag cement based on fly ash, disclosed by the invention, comprises the following steps of:
(1) Preparing nano alumina by in-situ growth of fly ash: adding the pretreated fly ash into a sodium metaaluminate solution, adding a surfactant into the solution, and continuously introducing CO into the solution 2 (CO introduced) 2 Can react with sodium metaaluminate solution to generate aluminum hydroxide), and stop the reaction when the pH value of the solution reaches 7-8 (if CO is continuously introduced) 2 Excess CO 2 Will be in contact with Al (OH) 3 Generating reaction to generate aluminum carbonate), centrifuging, washing and drying to obtain an initial product, calcining the initial product at high temperature, and cooling to obtain the fly ash in-situ grown nano-alumina;
(2) Mixing gypsum, slag, P. O52.5R cement, high belite sulphoaluminate cement and fly ash in-situ grown nano alumina, fully stirring, adding water and a water reducing agent into the mixture, and stirring to obtain the modified gypsum slag cement.
In the step (1), the pretreatment process of the fly ash comprises the following steps: and placing the fly ash into a sodium hydroxide solution, fully stirring, standing, centrifuging and drying. After the fly ash is pretreated, the surface becomes rougher, and the dislocation on the surface is more, so that nano alumina is easier to grow along the surface.
Wherein the fly ash is I, II-grade ash, and the mass ratio of the fly ash to the sodium hydroxide is 1:3-1:6.
Wherein in the step (1), the concentration of the sodium metaaluminate solution is 0.2-0.5 mol/L, and the mass ratio of the fly ash to the sodium metaaluminate is 1:15-1:20.
Wherein in the step (1), the surfactant is cetyl trimethyl ammonium bromide, and the addition amount of the surfactant is 15-30% of the mass of sodium metaaluminate. The cetyl trimethyl ammonium bromide serving as a surfactant is beneficial to the dispersion of the nano alumina particles on the fly ash.
Wherein in step (1), CO 2 The flow rate of the mixture is 20-40L/min, and the reaction temperature is 20-25 ℃.
Wherein in the step (1), the calcination temperature is 600-800 ℃, and the calcination time is not less than 2 hours. The aluminum hydroxide can be calcined into gamma-type nano aluminum oxide at the calcining temperature, the crystal structure (crystal form) of the nano aluminum oxide can influence the strength of the gypsum slag cement, and under the condition that the mixing amount is the same, the gamma-type nano aluminum oxide has larger improvement range of the compressive strength and the flexural strength of the gypsum slag cement than the alpha-type nano aluminum oxide.
In the step (1), the primary product (the aluminum hydroxide grown in situ by the fly ash) is washed 3 times by using organic solution such as ethanol, isopropanol and the like to remove the adhesion of the surfactant, and then the solid is separated by a centrifuge and dried for 12-24 hours at the temperature of 100 ℃.
In the step (1), the obtained fly ash grows nano alumina in situ, and the growth amount of the nano alumina on the fly ash is 11.2% of the mass of the fly ash.
In the step (2), the mixing mass ratio of gypsum, slag, P. O52.5R cement, high belite sulphoaluminate cement, fly ash in-situ grown nano alumina, water and water reducer is as follows: 140:750:40:40:9 to 45:362 to 370:1.
wherein in the step (2), the gypsum is desulfurized gypsum, the water content is 12%, and the specific surface area is 360m 2 Per kg, average particle size less than 1mm, requires calcination at 750℃and incubation for 2h.
In the step (2), the slag is S95 grade mineral powder.
In the step (2), the water reducer is a solid polycarboxylate water reducer, and the solid content is 50%.
In the step (2), gypsum, slag, P. O52.5R cement, high belite sulphoaluminate cement and fly ash in-situ grown nano alumina are mixed, and the stirring time is 2-3 min.
In the step (2), water and a water reducing agent are added and stirred for 5-7 min, and after full stirring, molding and curing are carried out, so that the modified gypsum slag cement is obtained.
The fly ash is added into the gypsum slag cement to grow nano alumina in situ, so that the in situ growth of nano alumina can enhance the dissolution degree of Si in slag and promote the generation of hydrated calcium silicate; meanwhile, the nano alumina promotes the formation of aluminum-containing hydration products, such as AFt, AFm and the like, so that the addition of the in-situ grown nano alumina can change the quantity of the reaction hydration products (the in-situ grown nano alumina promotes the formation of the hydration products (the hydration products are cemented together to form a network structure) by participating in the hydration reaction, and the hydration products are uniformly distributed to enable the microstructure of the cement paste to be more compact), thereby improving the early mechanical properties of the gypsum slag cement. According to the invention, nano alumina growing on the surface of the fly ash is added into the gypsum slag cement, so that on one hand, the mechanical property of the gypsum slag cement can be improved, and on the other hand, the influence on the fluidity of slurry is small, so that the nano alumina growing on the surface of the fly ash in situ is added into the gypsum slag cement, thereby not only playing a role in improving the early strength of the gypsum slag cement, but also avoiding the great reduction of the fluidity of the gypsum slag cement caused by the agglomeration of nano materials, and the surface of the gypsum slag cement is smooth and not easy to crack.
The beneficial effects are that: compared with the prior art, the invention has the following remarkable advantages: according to the invention, nano alumina growing on the surface of the fly ash in situ is added into the gypsum slag cement to modify the gypsum slag cement, so that on one hand, compared with direct doping, the nano alumina is more uniformly dispersed in cement slurry, the water demand of the gypsum slag cement is reduced due to the moisture of the nano alumina agglomeration package, and on the other hand, the slurry structure is more compact due to the introduction of the nano alumina, and more C-S-H, C-A-S-H (hydration product) is generated due to the participation of the nano alumina in hydration reaction, so that the early compressive strength of the gypsum slag cement is improved, the air holes are reduced, and the cracking condition is avoided. In addition, the incorporation of in-situ grown nano-alumina also increases the content of C-S-H, compared to Ca (OH) 2 And the carbonization is more difficult, so that the carbonization resistance of the gypsum slag cement is improved. The modified gypsum slag cement obtained by the method has the advantages of high early strength, good fluidity, good carbonization performance and difficult cracking in the later period, and can overcome the defects of the existing gypsum slag cement.
Drawings
FIG. 1 shows the expansion ratio of gypsum slag cement of example 4 and comparative examples 1 to 2. Figure 2 is an XRD pattern for preparing nano-alumina by carbonization. FIG. 3 is a scanning electron microscope image and energy spectrum of in situ grown nano-alumina.
Detailed Description
The raw materials used in the embodiment of the invention are as follows: calcining at 750 ℃ and preserving heat for 2 hours; s95-grade slag; p O52.5R cement produced by field; high belite sulphoaluminate cement produced by polar bear building materials, inc. of Tangshan; and the solid content of the polycarboxylate superplasticizer is 50%.
Example 1
The invention relates to a method for in-situ growth of nano alumina modified gypsum slag cement based on fly ash, which comprises the following steps:
(1) Pretreatment of fly ash: 200g of fly ash is placed in 1L of sodium hydroxide solution with the concentration of 1mol/L, fully stirred for twenty minutes, and dried for standby after standing for 24 hours;
(2) Preparing nano alumina by in-situ growth of fly ash: adding the dried fly ash into 1L of sodium metaaluminate solution with the concentration of 0.25mol/L, adding 15g of cetyl trimethyl ammonium bromide into the solution, stirring, and continuously introducing CO 2 Stopping the reaction when the pH value of the solution reaches 7-8, centrifuging, washing and drying to obtain the in-situ growth aluminum hydroxide of the fly ash as a primary product, calcining the primary product at 750 ℃, preserving heat for 2 hours, and cooling to obtain the in-situ growth nano-alumina of the fly ash; the growth amount of nano alumina on the fly ash is 11.2% of the mass of the fly ash;
(3) 140g of gypsum, 750g of slag, 40g of P O52.5R cement, 40g of high belite sulphoaluminate cement and 9g of fly ash in-situ grown nano alumina are stirred in a planetary stirrer for 3min, 362g of water and 1g of water reducer are added after uniform stirring, and molding and curing are carried out after full stirring for 6min, so that a modified gypsum slag cement sample is obtained and marked as A1.
Example 2
The invention relates to a method for in-situ growth of nano alumina modified gypsum slag cement based on fly ash, which comprises the following steps:
(1) Pretreatment of fly ash: 200g of fly ash is placed in 1L of sodium hydroxide solution with the concentration of 1mol/L, fully stirred for twenty minutes, and dried for standby after standing for 24 hours;
(2) Preparing nano alumina by in-situ growth of fly ash: adding the dried fly ash into 1L of sodium metaaluminate solution with the concentration of 0.25mol/L, adding 15g of cetyl trimethyl ammonium bromide into the solution, stirring, and continuously introducing CO 2 Stopping the reaction when the pH value of the solution reaches 7-8, centrifuging, washing and drying to obtain the in-situ growth aluminum hydroxide of the fly ash as a primary product, calcining the primary product at 750 ℃, preserving heat for 2 hours, and cooling to obtain the in-situ growth nano-alumina of the fly ash; the growth amount of nano alumina on the fly ash is 11.2% of the mass of the fly ash;
(3) 140g of gypsum, 750g of slag, 40g of P O52.5R cement, 40g of high belite sulphoaluminate cement and 18g of fly ash in-situ grown nano alumina are stirred in a planetary stirrer for 3min, 365g of water and 1g of water reducer are added after uniform stirring, and molding and curing are carried out after full stirring for 6min, so that a modified gypsum slag cement sample is obtained and marked as A2.
Example 3
(1) Pretreatment of fly ash: 200g of fly ash is placed in 1L of sodium hydroxide solution with the concentration of 1mol/L, fully stirred for twenty minutes, and dried for standby after standing for 24 hours;
(2) Preparing nano alumina by in-situ growth of fly ash: adding the dried fly ash into 1L of sodium metaaluminate solution with the concentration of 0.25mol/L, adding 15g of cetyl trimethyl ammonium bromide into the solution, stirring, and continuously introducing CO 2 Stopping the reaction when the pH value of the solution reaches 7-8, centrifuging, washing and drying to obtain the in-situ growth aluminum hydroxide of the fly ash as a primary product, calcining the primary product at 750 ℃, preserving heat for 2 hours, and cooling to obtain the in-situ growth nano-alumina of the fly ash; the growth amount of nano alumina on the fly ash is 11.2% of the mass of the fly ash;
(3) 140g of gypsum, 750g of slag, 40g of P O52.5R cement, 40g of high belite sulphoaluminate cement and 24g of fly ash in-situ grown nano alumina are stirred in a planetary stirrer for 3min, 368g of water and 1g of water reducer are added after uniform stirring, and molding and curing are carried out after full stirring for 6min, so that a modified gypsum slag cement sample is obtained and marked as A3.
Example 4
(1) Pretreatment of fly ash: 200g of fly ash is placed in 1L of sodium hydroxide solution with the concentration of 1mol/L, fully stirred for twenty minutes, and dried for standby after standing for 24 hours;
(2) Preparing nano alumina by in-situ growth of fly ash: adding the dried fly ash into 1L of sodium metaaluminate solution with the concentration of 0.25mol/L, adding 15g of cetyl trimethyl ammonium bromide into the solution, stirring, and continuously introducing CO 2 Stopping the reaction when the pH value of the solution reaches 7-8, centrifuging, washing and drying to obtain the in-situ growth aluminum hydroxide of the fly ash as the initial product, calcining the initial product at 750 ℃, preserving heat for 2 hours, and cooling to obtain the in-situ growth nano-powder coal ashRice alumina; the growth amount of nano alumina on the fly ash is 11.2% of the mass of the fly ash;
(3) 140g of gypsum, 750g of slag, 40g of P O52.5R cement, 40g of high belite sulphoaluminate cement and 36g of fly ash in-situ grown nano alumina are stirred in a planetary stirrer for 3min, 370g of water and 1g of water reducer are added after uniform stirring, and molding and curing are carried out after full stirring for 6min, so that a modified gypsum slag cement sample is obtained and marked as A4.
Example 5
(1) Pretreatment of fly ash: 200g of fly ash is placed in 1L of sodium hydroxide solution with the concentration of 1mol/L, fully stirred for twenty minutes, and dried for standby after standing for 24 hours;
(2) Preparing nano alumina by in-situ growth of fly ash: adding the dried fly ash into 1L of sodium metaaluminate solution with the concentration of 0.25mol/L, adding 15g of cetyl trimethyl ammonium bromide into the solution, stirring, and continuously introducing CO 2 Stopping the reaction when the pH value of the solution reaches 7-8, centrifuging, washing and drying to obtain the in-situ growth aluminum hydroxide of the fly ash as a primary product, calcining the primary product at 750 ℃, preserving heat for 2 hours, and cooling to obtain the in-situ growth nano-alumina of the fly ash; the growth amount of nano alumina on the fly ash is 11.2% of the mass of the fly ash;
(3) 140g of gypsum, 750g of slag, 40g of P O52.5R cement, 40g of high belite sulphoaluminate cement and 45g of fly ash in-situ grown nano alumina are stirred in a planetary stirrer for 3min, 376g of water and 1g of water reducer are added after uniform stirring, and molding and curing are carried out after full stirring for 6min, so that a modified gypsum slag cement sample is obtained and marked as A5.
Comparative example 1
Comparative example 1 differs from example 4 in that 32g of fly ash (36 x 88.8% = 31.968 g) corresponding to 36g of fly ash in-situ grown nano alumina with a growth amount of 11.2% was added, and 4g of commercial gamma nano alumina (36 x 11.2% = 4.032 g), namely, preparation of gypsum slag cement: 140g of gypsum, 750g of slag, 40g P. O52.5R of cement, 40g of high belite sulphoaluminate cement, 32g of fly ash and 4g of commercial nano alumina are stirred in a planetary stirrer for 3min, 370g of water and 1g of water reducer are added after uniform stirring, and molding and curing are carried out after full stirring for 6min, so that gypsum slag cement is obtained and marked as B4.
Comparative example 2
Gypsum slag cement modified by in-situ grown nano alumina is not adopted:
140g of gypsum, 750g of slag, 40g of P O52.5R cement, 40g of high belite sulphoaluminate cement and 32g of fly ash are stirred in a planetary stirrer for 3min, 370g of water and 1g of water reducer are added after uniform stirring, and molding and curing are carried out after full stirring for 6min, so that a modified gypsum slag cement sample is obtained and marked as B5.
Table 1 shows the strength results of gypsum slag cements of examples 1 to 5 and comparative examples 1 to 2
As is evident from the comparison of examples 1 to 5, the 3d, 7d and 28d strengths of the modified gypsum slag cements prepared in examples 1 to 4 are all improved. However, in example 5, the mixing amount of nano alumina grown in situ of the fly ash is increased, the corresponding introducing amount of the fly ash is increased, and the pozzolanic activity is low due to the excessive introducing amount of the fly ash, so that the strength of the modified gypsum slag cement is reduced. As is clear from the comparison of example 4 and comparative example 1, the direct incorporation of nano alumina is liable to agglomerate in gypsum slag cement to form defects, and the density of the matrix is lowered, so that the structure is cracked, resulting in the decrease of the strength of the modified gypsum slag cement. As can be seen from a comparison of example 4 with comparative example 2, the 3d, 7d, 28d compressive strengths of example 4 are all higher than the corresponding compressive strengths of comparative example 2, because the nano-alumina grown on the fly ash surface provides more nucleation sites, improves the interfacial transition zone, and reduces the porosity.
TABLE 2 setting times and carbonization depths of gypsum slag cements of examples 1 to 5 and comparative examples 1 to 2
After the gypsum slag cement is doped with in-situ grown nano alumina, the carbonization resistance of the gypsum slag cement is gradually improved along with the increase of the doping amount. The nano alumina in situ grown by the fly ash uniformly forms a plurality of nucleation sites in the gypsum slag cement, so that more hydration products are generated, the hydration products are interwoven together, the structure is more compact, the mechanical property is increased, and the nano alumina is not easy to be subjected to CO 2 Intrusion. Both in-situ growth of nano-alumina and commercial nano-alumina can reduce the initial setting and final setting time of cement-based materials, and the larger the doping amount is, the more the setting time is shortened. Under the condition that the mixing amount of the nano alumina is the same, the in-situ growth of the nano alumina has more obvious effect on shortening the coagulation time.
Table 3 shows the activity index of the fly ash and the modified fly ash 28d
The reactive index of the fly ash is low, and after nano alumina grows in situ, the reactive activity of the fly ash can be greatly improved, so that the fly ash can react with other substances to generate more hydration products in the cement preparation process, and the mechanical property of gypsum slag cement is improved.
Table 4 shows the expansion degree of gypsum slag cements of examples 1 to 5 and comparative examples 1 to 2
As can be seen from Table 4, the in-situ growth of nano alumina incorporated into fly ash has little effect on the fluidity of gypsum slag cement, whereas in example 4, the former was added with fly ash in-situ growth of alumina, and the latter was added with corresponding fly ash and nano alumina, as compared with comparative example 1. The fluidity of comparative example 1 was found to be significantly reduced.
Table 5 shows the expansion ratios of gypsum slag cements of example 4 and comparative examples 1 to 2
As can be seen from table 5 and fig. 1, the expansion ratio of example 4 is significantly smaller than that of comparative example 1. The main reason is that the strength of A4 is higher, and the volume increase is limited, so that the stability of the volume is well maintained, the method can be better used for engineering service, and the problem of later cracking is better solved. The expansion ratio of example 4 is significantly smaller than that of comparative example 2 because after nano alumina is grown in situ on fly ash, the form of ettringite is affected, the ettringite is distributed more uniformly in the pores, and more ettringite is attached to the surface of slag particles in comparative example 2, more capillary pores are generated, and the strength of cement is reduced.
Claims (10)
1. The method for in-situ growth of the nano alumina modified gypsum slag cement based on the fly ash is characterized by comprising the following steps of:
(1) Preparing nano alumina by in-situ growth of fly ash: adding the pretreated fly ash into a sodium metaaluminate solution, adding a surfactant into the solution, and continuously introducing CO into the solution 2 The method comprises the steps of carrying out a first treatment on the surface of the Stopping the reaction when the pH value of the solution reaches 7-8, centrifuging, washing and drying to obtain an initial product, calcining the initial product at high temperature, and cooling to obtain the fly ash in-situ grown nano alumina;
(2) Mixing gypsum, slag, P. O52.5R cement, high belite sulphoaluminate cement and fly ash in-situ grown nano alumina, fully stirring, adding water and a water reducing agent into the mixture, and stirring to obtain the modified gypsum slag cement.
2. The method for in-situ growth of nano alumina modified gypsum slag cement based on fly ash according to claim 1, wherein: in the step (1), the concentration of the sodium metaaluminate solution is 0.2-0.5 mol/L, and the mass ratio of the fly ash to the sodium metaaluminate solution is 1:15-1:20.
3. The method for in-situ growth of nano alumina modified gypsum slag cement based on fly ash according to claim 1, wherein: in the step (1), the surfactant is cetyl trimethyl ammonium bromide, and the addition amount of the surfactant is 15-30% of the mass of sodium metaaluminate.
4. The method for in-situ growth of nano alumina modified gypsum slag cement based on fly ash according to claim 1, wherein: in the step (1), the calcination temperature is 600-800 ℃, and the calcination time is not less than 2 hours.
5. The method for in-situ growth of nano alumina modified gypsum slag cement based on fly ash according to claim 1, wherein: in the step (1), the obtained fly ash grows nano alumina in situ, and the growth amount of the nano alumina on the fly ash is 11.2% of the mass of the fly ash.
6. The method for in-situ growth of nano alumina modified gypsum slag cement based on fly ash according to claim 1, wherein: in the step (2), the mixing mass ratio of gypsum, slag, P. O52.5R cement, high belite sulphoaluminate cement, fly ash in-situ grown nano alumina, water and water reducer is as follows: 140:750:40:40:9 to 45:362 to 370:1.
7. the method for in-situ growth of nano alumina modified gypsum slag cement based on fly ash according to claim 1, wherein: in the step (2), the gypsum is desulfurized gypsum, the water content is not less than 12%, and the specific surface area is 360m 2 And/kg, wherein the average grain diameter is smaller than 1mm, and the calcination is required at 750-760 ℃ and the heat preservation is required for 2-3 h.
8. The method for in-situ growth of nano alumina modified gypsum slag cement based on fly ash according to claim 1, wherein: in the step (2), the slag is S95 grade mineral powder; the water reducer is a solid polycarboxylate water reducer, and the solid content is 50%.
9. The method for in-situ growth of nano alumina modified gypsum slag cement based on fly ash according to claim 1, wherein: in the step (2), gypsum, slag, P O52.5R cement, high belite sulphoaluminate cement and fly ash in-situ grown nano alumina are mixed, and the stirring time is 2-3 min.
10. The method for in-situ growth of nano alumina modified gypsum slag cement based on fly ash according to claim 1, wherein: in the step (2), water and a water reducing agent are added and stirred for 5-7 min, and molding and curing are carried out after full stirring, so as to obtain the modified gypsum slag cement.
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| CN107954623A (en) * | 2017-11-17 | 2018-04-24 | 东南大学 | A kind of preparation method of solid waste surface in situ growth nano particle |
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| CN114735955A (en) * | 2022-05-20 | 2022-07-12 | 宁夏交通建设股份有限公司 | Desulfurized gypsum based super-sulfate cement and preparation method thereof |
| CN115724640A (en) * | 2022-05-12 | 2023-03-03 | 东南大学 | Gypsum slag cement concrete and preparation method thereof |
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| CN107954623A (en) * | 2017-11-17 | 2018-04-24 | 东南大学 | A kind of preparation method of solid waste surface in situ growth nano particle |
| CN108947449A (en) * | 2018-09-05 | 2018-12-07 | 江苏夫科技股份有限公司 | A kind of ardealite ultra-sulphate cement and preparation method thereof |
| CN115724640A (en) * | 2022-05-12 | 2023-03-03 | 东南大学 | Gypsum slag cement concrete and preparation method thereof |
| CN114735955A (en) * | 2022-05-20 | 2022-07-12 | 宁夏交通建设股份有限公司 | Desulfurized gypsum based super-sulfate cement and preparation method thereof |
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