CN116283102A - Method for regulating and controlling geopolymer coagulation time by using magnesium ions - Google Patents
Method for regulating and controlling geopolymer coagulation time by using magnesium ions Download PDFInfo
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- CN116283102A CN116283102A CN202310301234.9A CN202310301234A CN116283102A CN 116283102 A CN116283102 A CN 116283102A CN 202310301234 A CN202310301234 A CN 202310301234A CN 116283102 A CN116283102 A CN 116283102A
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- 229920000876 geopolymer Polymers 0.000 title claims abstract description 73
- 229910001425 magnesium ion Inorganic materials 0.000 title claims abstract description 65
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 title claims abstract description 63
- 238000000034 method Methods 0.000 title claims abstract description 29
- 230000001276 controlling effect Effects 0.000 title claims abstract description 25
- 230000015271 coagulation Effects 0.000 title claims abstract description 24
- 238000005345 coagulation Methods 0.000 title claims abstract description 24
- 230000001105 regulatory effect Effects 0.000 title claims abstract description 23
- 239000003513 alkali Substances 0.000 claims abstract description 37
- 230000005284 excitation Effects 0.000 claims abstract description 28
- 239000004115 Sodium Silicate Substances 0.000 claims abstract description 25
- 229910052911 sodium silicate Inorganic materials 0.000 claims abstract description 25
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims abstract description 25
- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical compound O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 claims abstract description 13
- 239000002002 slurry Substances 0.000 claims abstract description 12
- 238000006482 condensation reaction Methods 0.000 claims abstract description 10
- 239000004111 Potassium silicate Substances 0.000 claims abstract description 9
- 238000004090 dissolution Methods 0.000 claims abstract description 9
- 229910052913 potassium silicate Inorganic materials 0.000 claims abstract description 9
- NNHHDJVEYQHLHG-UHFFFAOYSA-N potassium silicate Chemical compound [K+].[K+].[O-][Si]([O-])=O NNHHDJVEYQHLHG-UHFFFAOYSA-N 0.000 claims abstract description 9
- 235000019353 potassium silicate Nutrition 0.000 claims abstract description 9
- 238000002156 mixing Methods 0.000 claims abstract description 7
- 239000000463 material Substances 0.000 claims abstract description 5
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 21
- 239000002243 precursor Substances 0.000 claims description 20
- 238000006243 chemical reaction Methods 0.000 claims description 13
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 12
- 229920000642 polymer Polymers 0.000 claims description 9
- 239000011777 magnesium Substances 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 239000011734 sodium Substances 0.000 claims description 7
- 239000000126 substance Substances 0.000 claims description 7
- 239000010881 fly ash Substances 0.000 claims description 5
- 159000000003 magnesium salts Chemical class 0.000 claims description 5
- 230000002035 prolonged effect Effects 0.000 claims description 3
- 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 description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 2
- 239000011591 potassium Substances 0.000 claims description 2
- 229910052700 potassium Inorganic materials 0.000 claims description 2
- 229910052708 sodium Inorganic materials 0.000 claims description 2
- 206010053567 Coagulopathies Diseases 0.000 claims 2
- 230000035602 clotting Effects 0.000 claims 2
- 238000006116 polymerization reaction Methods 0.000 abstract description 8
- 230000008569 process Effects 0.000 abstract description 7
- 230000000979 retarding effect Effects 0.000 abstract description 6
- 230000008859 change Effects 0.000 abstract description 5
- 239000011575 calcium Substances 0.000 abstract description 3
- 229910052791 calcium Inorganic materials 0.000 abstract description 3
- 229910052710 silicon Inorganic materials 0.000 abstract 1
- 239000010703 silicon Substances 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 49
- 230000000694 effects Effects 0.000 description 12
- 239000000523 sample Substances 0.000 description 12
- 229910052749 magnesium Inorganic materials 0.000 description 6
- 230000035515 penetration Effects 0.000 description 6
- 239000004568 cement Substances 0.000 description 5
- 238000009833 condensation Methods 0.000 description 5
- 230000005494 condensation Effects 0.000 description 5
- 239000013074 reference sample Substances 0.000 description 5
- 238000003756 stirring Methods 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 238000011161 development Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- DGVMNQYBHPSIJS-UHFFFAOYSA-N dimagnesium;2,2,6,6-tetraoxido-1,3,5,7-tetraoxa-2,4,6-trisilaspiro[3.3]heptane;hydrate Chemical compound O.[Mg+2].[Mg+2].O1[Si]([O-])([O-])O[Si]21O[Si]([O-])([O-])O2 DGVMNQYBHPSIJS-UHFFFAOYSA-N 0.000 description 3
- 238000011049 filling Methods 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 2
- 239000011398 Portland cement Substances 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000001934 delay Effects 0.000 description 2
- 239000002440 industrial waste Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 239000002893 slag Substances 0.000 description 2
- 239000002253 acid Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 229910000323 aluminium silicate Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
- TXKMVPPZCYKFAC-UHFFFAOYSA-N disulfur monoxide Inorganic materials O=S=S TXKMVPPZCYKFAC-UHFFFAOYSA-N 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- HCWCAKKEBCNQJP-UHFFFAOYSA-N magnesium orthosilicate Chemical compound [Mg+2].[Mg+2].[O-][Si]([O-])([O-])[O-] HCWCAKKEBCNQJP-UHFFFAOYSA-N 0.000 description 1
- 239000000391 magnesium silicate Substances 0.000 description 1
- 229910052919 magnesium silicate Inorganic materials 0.000 description 1
- 235000019792 magnesium silicate Nutrition 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 239000003469 silicate cement Substances 0.000 description 1
- XTQHKBHJIVJGKJ-UHFFFAOYSA-N sulfur monoxide Chemical compound S=O XTQHKBHJIVJGKJ-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- 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
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/006—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing mineral polymers, e.g. geopolymers of the Davidovits type
-
- 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
- C04B12/00—Cements not provided for in groups C04B7/00 - C04B11/00
- C04B12/005—Geopolymer cements, e.g. reaction products of aluminosilicates with alkali metal hydroxides or silicates
-
- 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
-
- 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
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Organic Chemistry (AREA)
- Structural Engineering (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Inorganic Chemistry (AREA)
- Geology (AREA)
- Geochemistry & Mineralogy (AREA)
- Environmental & Geological Engineering (AREA)
- Silicates, Zeolites, And Molecular Sieves (AREA)
Abstract
The invention relates to a method for regulating and controlling the coagulation time of a geopolymer by utilizing magnesium ions, and belongs to the technical field of geopolymer materials. The magnesium ions are added into the sodium silicate or potassium silicate alkali excitation solution to change the pH value of the solution and the polymerization degree of silicon in the solution, so that the dissolution rate and early condensation reaction rate of metakaolin are reduced, and the setting time of geopolymer slurry is obviously increased. The method belongs to a mode of indirectly regulating and controlling the coagulation time, and can indirectly regulate and control the Si/Al ratio in the condensation reaction process of the geopolymer on the premise of not changing the mixing ratio, thereby playing a role in obviously retarding on the premise of ensuring that the later performance is not influenced and effectively solving the problem that the early coagulation of the low-calcium geopolymer is difficult to regulate and control.
Description
Technical Field
The invention relates to the technical field of geopolymer materials, in particular to a method for regulating and controlling the coagulation time of a geopolymer by utilizing magnesium ions.
Background
The geopolymer is an amorphous cementing material formed by exciting an aluminosilicate precursor (such as metakaolin, fly ash, slag and the like) by an alkaline solution, and has low energy consumption and CO in the production process 2 The discharge amount is only about 20 percent of the traditional Portland cement, and almost no nitrogen oxides are produced,The sulfur oxide and other harmful gases can effectively solve the environmental problems caused by cement production. Meanwhile, the cement has mechanical strength equivalent to that of the traditional silicate cement, and also has better performances of high temperature resistance, acid and alkali corrosion resistance and the like. In addition, the geopolymer has wide sources of raw materials, and the utilization of industrial wastes such as fly ash, slag and the like can not only reduce the manufacturing cost, but also solve the problem of environmental pollution caused by the industrial wastes. Thus, geopolymer is an economical, environmentally friendly cement and is considered to be the most potential cement substitute in the 21 world. However, as a novel cement, the admixture currently widely used for Portland cement cannot be well-adapted to the polymer due to its high alkalinity and different reaction mechanisms. Particularly, for low-calcium geopolymer represented by metakaolin or fly ash, the research and development of the additive has serious defects, the regulation and control of early setting time can only depend on the change of the mixing proportion, however, the change of the mixing proportion can influence the later performance, and the popularization and the application of the geopolymer are greatly restricted. There is therefore an urgent need to develop corresponding additives to control the setting time of low-calcium geopolymers to meet the requirements of the current geopolymer production and use.
Disclosure of Invention
Based on the defect that the early coagulation time of the geopolymer is difficult to flexibly regulate and control at present, the method for regulating and controlling the coagulation time of the geopolymer is provided. The invention utilizes the reaction of magnesium ions and alkali excitation solution to change the pH value of the alkali excitation solution and the polymerization degree of sodium silicate solution, thereby reducing the dissolution rate and condensation reaction rate of the precursor and playing a remarkable role in retarding.
According to an object of the present invention, there is provided a method for controlling coagulation time of a geopolymer by using magnesium ions, comprising the steps of:
(1) Adding magnesium salt into alkali excitation solution, wherein the alkali excitation solution is sodium silicate solution or potassium silicate solution;
(2) And (3) uniformly mixing the alkali excitation solution regulated and controlled by the magnesium ions in the step (1) with the geopolymer precursor, so that the dissolution rate and the condensation reaction rate of the precursor are reduced, and the coagulation time of the geopolymer slurry is prolonged.
Preferably, the magnesium salt is MgCl 2 、MgSO 4 Or Mg (NO) 3 ) 2 。
Preferably, the amount of the magnesium ion substance is 10% -20% of the amount of the sodium element in the sodium silicate solution or the potassium element in the potassium silicate solution.
Preferably, the reaction of step (1) takes more than 24 hours.
Preferably, the precursor is metakaolin or fly ash.
Preferably, in the step (2), the mass ratio of the alkali excitation solution and the precursor after the magnesium ion regulation is 1.3-1.6.
Preferably, the preparation method of the sodium silicate solution comprises the following steps: nano SiO 2 And NaOH are dissolved in water to prepare sodium silicate solution.
Preferably, the SiO 2 The ratio of the amount of the substance to NaOH is 1-2.
Preferably, the preparation method of the potassium silicate solution comprises the following steps: nano SiO 2 And KOH is dissolved in water to prepare the potassium silicate solution.
Preferably, the SiO 2 The ratio of the amount of the material to KOH is 1 to 2.
In general, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:
(1) The invention utilizes the reaction of magnesium ions and alkali excitation solution to change the pH value of the alkali excitation solution and the polymerization degree of sodium silicate solution, thereby reducing the dissolution rate and condensation reaction rate of the precursor and playing a remarkable role in retarding.
(2) The method utilizes the reaction of magnesium ions and alkali excitation solution, and can generate nano-hydrated magnesium silicate (M-S-H) gel to be adsorbed on the surface of precursor (metakaolin) particles, thereby further reducing the dissolution rate of the precursor.
(3) The method for regulating and controlling the condensation time of the geopolymer by utilizing magnesium ions changes the condensation time of the geopolymer by regulating and controlling the polymerization degree of an alkali-activated solution, belongs to a mode for indirectly regulating and controlling the condensation time, and can ensure that the later performance meets the requirements by indirectly regulating and controlling the Si/Al ratio in the condensation reaction process of the geopolymer on the premise of not changing the mixing ratio.
(4) The magnesium ion source for regulating and controlling the coagulation time of the geopolymer is wide, and the cost is low.
(5) The invention does not need complex operation, has simple working procedure and is beneficial to practical application.
Drawings
FIG. 1 is a graph of the effect of magnesium ions on geopolymer set time (specifically, geopolymer set time was measured using a Vicat, and the geopolymer curing time versus penetration was plotted, 5% Mg sample).
FIG. 2 is a graph showing the effect of magnesium ions on the early reaction heat of geopolymer (5% Mg sample).
FIG. 3 is a graph of the effect of magnesium ions on the strength development of geopolymers (5% Mg sample).
FIG. 4 is a graph of the effect of magnesium ions on geopolymer set time (specifically, geopolymer set time was measured using a Vicat, plotted against geopolymer curing time and penetration, 10% Mg sample).
FIG. 5 is a graph showing the effect of magnesium ions on the early reaction heat of geopolymer (10% Mg sample).
FIG. 6 is a graph of the effect of magnesium ions on the strength development of geopolymers (10% Mg sample).
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
According to the invention, the pH value and the polymerization degree of the alkali excitation solution are regulated and controlled by adding magnesium ions into the alkali excitation solution, so that the dissolution and condensation reaction rate of the precursor are influenced, and finally, the purpose of regulating and controlling the coagulation time of the geopolymer is achieved. The geopolymer obtained by the method has obviously prolonged coagulation time on the premise of ensuring the later performance.
The invention aims at realizing the following technical steps:
step one: and preparing an alkali excitation solution, and preparing the sodium silicate alkali excitation solution with the required modulus according to actual requirements. Specifically, sodium silicate of formula Na 2 O·nSiO 2 N is the modulus of the sodium silicate solution, and NaOH can be added into the sodium silicate solution for regulating and controlling the modulus of the sodium silicate solution.
Step two: adding magnesium salt (such as MgCl) into sodium silicate alkali excitation solution 2 ) The method is characterized in that required magnesium ions are provided and react with an alkali excitation solution for more than 24 hours at normal temperature, the process is kept stirring, the rotating speed is 300 r/min, so that the magnesium ions can fully react, the step is used for regulating and controlling the pH value of the alkali excitation solution and the polymerization degree of the sodium silicate solution, and the process is key for achieving the regulation and control purpose.
Step three: the prepared alkali excitation solution and the precursor (such as metakaolin) are mixed and stirred for 3-5min, specifically, firstly, the mixture is stirred for 1 min at a slow speed and then stirred for three min at a fast speed, so that the mixture is uniformly mixed, the dissolution rate and the condensation reaction rate of the precursor can be remarkably reduced due to the reduction of the alkalinity of the alkali excitation solution and the increase of the polymerization degree, and the magnesium ions and the sodium silicate alkali excitation solution can react to generate nano magnesium silicate hydrate (M-S-H) to be adsorbed on the surface of the precursor, thereby further reducing the dissolution rate of the precursor and obtaining the geopolymer slurry with obvious retarding result.
Step four: the heat of reaction and the setting time of the geopolymer were tested.
Step five: and (3) filling the prepared geopolymer paste into a mould, vibrating to compact, putting the geopolymer paste into a curing box, curing for two days at 20 ℃, removing the mould, continuously curing to a specified age, and testing the compressive strength.
The invention changes the condensation time of geopolymer by regulating and controlling the polymerization degree of alkali-activated solution, belongs to a mode of indirectly regulating and controlling the condensation time, and can ensure that the later performance meets the requirement by indirectly regulating and controlling the Si/Al ratio in the condensation reaction process of geopolymer on the premise of not changing the mixing ratio.
The invention is further illustrated below in conjunction with specific examples.
Example 1
The invention prepares a geopolymer which takes sodium silicate solution as alkali excitant and metakaolin as precursor, and the chemical molar ratio is Na 2 O:Al 2 O 3 :SiO 2 :H 2 O=1:1:4:11, the ratio has excellent mechanical properties, and MgCl is selected 2 To provide the desired Mg ions. The specific implementation steps are as follows:
step one: preparation of alkali-activated solution 65g of nano SiO 2 (purity 99.8%) and 45.9g of NaOH (purity 98.7%) were dissolved in 102.8g of water to prepare a sodium silicate alkali-activated solution.
Step two: 5.18g of MgCl 2 (purity 99.5%, equivalent to Na) 2 5% of the number of moles of O) was added to the sodium silicate solution and reacted at ambient temperature for 24 hours while maintaining stirring (about 300 rpm) with care taken to seal against water loss.
Step three: 134.38g of metakaolin and an alkali excitation solution added with magnesium ions are mixed, and the stirring time is set to be 4 minutes, so that the metakaolin and the alkali excitation solution are completely and uniformly mixed to obtain geopolymer slurry. While the same process was used to prepare a geopolymer without magnesium ions for comparison.
Step four: and testing the coagulation time of the slurry by using a Vicat under the condition of the ambient temperature of 20 ℃, drawing a relation curve of the filling depth of a Vicat probe and the curing time at 30s, and comparing the coagulation time. An additional sample of approximately 16g of geopolymer was prepared and the effect of magnesium ions on the heat of reaction of the geopolymer was tested using an isothermal calorimeter.
Step five: the geopolymer paste prepared by the same steps is put into a mould, vibrated uniformly, cubic test blocks with the dimensions of 40mm multiplied by 40mm are prepared, cured at the temperature of 20 ℃ for 3 days, 5 days and 28 days, and the compressive strength is tested to characterize the influence of magnesium ions on the physical properties of the geopolymer.
FIG. 1 is a plot of geopolymer penetration depth versus curing time (Control is the reference sample in the figure, 5Mg is the sample to which 5% magnesium ions are added, each 3 times). It can be found that the addition of 5% magnesium ions delays the initial setting time by about 4 hours, and the overall penetration curve is obviously shifted to the right, which indicates that the addition of magnesium ions has a remarkable retarding effect.
FIG. 2 is a graph showing the effect of magnesium ions on the early reaction heat of geopolymer slurry. It was found that the addition of 5% magnesium ions significantly reduced the early heat release rate and total heat release, e.g., 24 hours of curing, and that the addition of magnesium ions reduced the total heat release by 28%, indicating that the addition of magnesium ions changed the heat release characteristics of the geopolymer slurry.
FIG. 3 is a graph showing the effect of magnesium ions on the strength development of geopolymers. The strength of the geopolymer added with magnesium ions is lower than that of a reference sample in three days, but the strength difference gradually reduces along with the increase of the age, the strength is basically equivalent at 28 days, and the later performance is not obviously influenced.
Example 2
The invention prepares a geopolymer which takes sodium silicate solution as alkali excitant and metakaolin as precursor, and the chemical molar ratio is Na 2 O:Al 2 O 3 :SiO 2 :H 2 O=1:1:4:11, the ratio has excellent mechanical properties, and MgCl is selected 2 To provide the desired Mg ions. The specific implementation steps are as follows:
step one: preparation of alkali-activated solution 65g of nano SiO 2 (purity 99.8%) and 45.9g of NaOH (purity 98.7%) were dissolved in 102.8g of water to prepare a sodium silicate alkali-activated solution.
Step two: 10.36g of MgCl 2 (purity 99.5%, equivalent to Na) 2 10% of the number of moles of O) was added to the sodium silicate solution and reacted at room temperature for 24 hours while maintaining stirring (about 300 rpm) with care taken to seal against water loss.
Step three: 134.38g of metakaolin and an alkali excitation solution added with magnesium ions are mixed, and the stirring time is set to be 4 minutes, so that the metakaolin and the alkali excitation solution are completely and uniformly mixed to obtain geopolymer slurry. While the same process was used to prepare a geopolymer without magnesium ions for comparison.
Step four: and testing the coagulation time of the slurry by using a Vicat under the condition of the ambient temperature of 20 ℃, drawing a relation curve of the filling depth of a Vicat probe and the curing time at 30s, and comparing the coagulation time. An additional sample of approximately 16g of geopolymer was prepared and the effect of magnesium ions on the heat of reaction of the geopolymer was tested using an isothermal calorimeter.
Step five: the geopolymer paste prepared by the same steps is put into a mould, vibrated uniformly, cubic test blocks with the dimensions of 40mm multiplied by 40mm are prepared, cured at the temperature of 20 ℃ for 3 days, 5 days and 28 days, and the compressive strength is tested to characterize the influence of magnesium ions on the physical properties of the geopolymer.
FIG. 4 is a plot of geopolymer penetration depth versus curing time (Control is the reference sample, 10Mg is the sample to which 10% magnesium ions are added, each at least 2 times). It can be found that the addition of 10% magnesium ions delays the initial setting time by about 11 hours, and the overall penetration curve is obviously shifted to the right, which indicates that the addition of magnesium ions has a remarkable retarding effect.
FIG. 5 is a graph showing the effect of magnesium ions on the early reaction heat of geopolymer slurry. It was found that the addition of 10% magnesium ions significantly reduced the early heat release rate and total heat release, e.g., 24 hours of curing, and that the addition of magnesium ions reduced the total heat release by 46%, indicating that the addition of magnesium ions changed the heat release characteristics of the geopolymer slurry.
FIG. 6 is a graph showing the effect of magnesium ions on the strength development of geopolymer. The strength of the geopolymer added with magnesium ions is lower than that of a reference sample for three days, but the strength difference gradually reduces along with the increase of the age, the strength of the geopolymer is slightly stronger than that of the reference sample at 28 days, and the geopolymer has no obvious influence on the later performance.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (10)
1. A method for regulating the coagulation time of a geopolymer by using magnesium ions, which comprises the following steps:
(1) Adding magnesium salt into alkali excitation solution, wherein the alkali excitation solution is sodium silicate solution or potassium silicate solution;
(2) And (3) uniformly mixing the alkali excitation solution regulated and controlled by the magnesium ions in the step (1) with the geopolymer precursor, so that the dissolution rate and the condensation reaction rate of the precursor are reduced, and the coagulation time of the geopolymer slurry is prolonged.
2. The method for regulating the clotting time of a polymer by magnesium ions of claim 1, wherein said magnesium salt is MgCl 2 、MgSO 4 Or Mg (NO) 3 ) 2 。
3. The method for controlling the setting time of a polymer using magnesium ions according to claim 1 or 2, wherein the amount of the substance of magnesium ions is 10% to 20% of the amount of the substance of sodium element in the sodium silicate solution or potassium element in the potassium silicate solution.
4. The method for regulating the clotting time of a polymer by magnesium ions of claim 1, wherein the time of said reaction of step (1) is greater than 24 hours.
5. The method for controlling the setting time of a geopolymer by using magnesium ions according to claim 1, wherein the precursor is metakaolin or fly ash.
6. The method for controlling coagulation time of a polymer by using magnesium ions according to claim 1 or 5, wherein in the step (2), the mass ratio of the alkali excitation solution and the precursor after the magnesium ions are controlled is 1.3 to 1.6.
7. The method for controlling the coagulation time of a polymer by using magnesium ions according to claim 1, wherein the sodium silicate solution is prepared by the following steps: nano SiO 2 And NaOH are dissolved in water to prepare sodium silicate solution.
8. The method for controlling coagulation time of a polymer with magnesium ions as set forth in claim 7, wherein said SiO 2 The ratio of the amount of the substance to NaOH is 1-2.
9. The method for controlling the coagulation time of a polymer by using magnesium ions according to claim 1, wherein the potassium silicate solution is prepared by the following steps: nano SiO 2 And KOH is dissolved in water to prepare the potassium silicate solution.
10. The method for controlling coagulation time of a polymer with magnesium ions as set forth in claim 9, wherein said SiO 2 The ratio of the amount of the material to KOH is 1 to 2.
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|---|---|---|---|
| CN202310301234.9A CN116283102A (en) | 2023-03-24 | 2023-03-24 | Method for regulating and controlling geopolymer coagulation time by using magnesium ions |
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