CN116375404A - Geopolymer recycled concrete and preparation method thereof - Google Patents
Geopolymer recycled concrete and preparation method thereof Download PDFInfo
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- CN116375404A CN116375404A CN202310366139.7A CN202310366139A CN116375404A CN 116375404 A CN116375404 A CN 116375404A CN 202310366139 A CN202310366139 A CN 202310366139A CN 116375404 A CN116375404 A CN 116375404A
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- 229920000876 geopolymer Polymers 0.000 title claims abstract description 54
- 239000004567 concrete Substances 0.000 title claims abstract description 50
- 238000002360 preparation method Methods 0.000 title abstract description 8
- 239000011259 mixed solution Substances 0.000 claims abstract description 20
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 19
- 238000000034 method Methods 0.000 claims abstract description 17
- 239000004576 sand Substances 0.000 claims abstract description 16
- 229910004298 SiO 2 Inorganic materials 0.000 claims abstract description 15
- 239000010881 fly ash Substances 0.000 claims abstract description 15
- 229920003041 geopolymer cement Polymers 0.000 claims abstract description 11
- 239000006087 Silane Coupling Agent Substances 0.000 claims abstract description 9
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 48
- 239000000203 mixture Substances 0.000 claims description 23
- 238000003756 stirring Methods 0.000 claims description 20
- 239000007788 liquid Substances 0.000 claims description 16
- 238000002156 mixing Methods 0.000 claims description 15
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims description 14
- 239000006185 dispersion Substances 0.000 claims description 10
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 claims description 9
- 239000003513 alkali Substances 0.000 claims description 7
- 238000007580 dry-mixing Methods 0.000 claims description 7
- 238000001179 sorption measurement Methods 0.000 claims description 7
- 239000002699 waste material Substances 0.000 claims description 6
- 235000019353 potassium silicate Nutrition 0.000 claims description 5
- 238000010521 absorption reaction Methods 0.000 claims description 3
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims description 2
- 230000008878 coupling Effects 0.000 claims description 2
- 238000010168 coupling process Methods 0.000 claims description 2
- 238000005859 coupling reaction Methods 0.000 claims description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims description 2
- 239000002245 particle Substances 0.000 claims description 2
- 238000002203 pretreatment Methods 0.000 claims description 2
- 229910000077 silane Inorganic materials 0.000 claims description 2
- 238000010276 construction Methods 0.000 claims 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 abstract description 33
- 239000000395 magnesium oxide Substances 0.000 abstract description 21
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 abstract description 21
- 230000000694 effects Effects 0.000 abstract description 12
- 238000006116 polymerization reaction Methods 0.000 abstract description 11
- 239000005543 nano-size silicon particle Substances 0.000 abstract description 10
- 235000012239 silicon dioxide Nutrition 0.000 abstract description 10
- 229920000642 polymer Polymers 0.000 abstract description 8
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 abstract description 7
- 238000006243 chemical reaction Methods 0.000 abstract description 5
- 239000013078 crystal Substances 0.000 abstract description 3
- 238000011049 filling Methods 0.000 abstract description 2
- 230000006911 nucleation Effects 0.000 abstract description 2
- 238000010899 nucleation Methods 0.000 abstract description 2
- 230000002195 synergetic effect Effects 0.000 abstract description 2
- 150000002148 esters Chemical class 0.000 abstract 1
- 230000003628 erosive effect Effects 0.000 description 18
- 239000004115 Sodium Silicate Substances 0.000 description 9
- 229910052911 sodium silicate Inorganic materials 0.000 description 9
- 239000000463 material Substances 0.000 description 8
- 230000008929 regeneration Effects 0.000 description 8
- 238000011069 regeneration method Methods 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- 230000006378 damage Effects 0.000 description 5
- 239000002994 raw material Substances 0.000 description 4
- UJOHNXQDVUADCG-UHFFFAOYSA-L aluminum;magnesium;carbonate Chemical compound [Mg+2].[Al+3].[O-]C([O-])=O UJOHNXQDVUADCG-UHFFFAOYSA-L 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 239000004566 building material Substances 0.000 description 3
- 239000004568 cement Substances 0.000 description 3
- GDVKFRBCXAPAQJ-UHFFFAOYSA-A dialuminum;hexamagnesium;carbonate;hexadecahydroxide Chemical compound [OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Al+3].[Al+3].[O-]C([O-])=O GDVKFRBCXAPAQJ-UHFFFAOYSA-A 0.000 description 3
- 238000009472 formulation Methods 0.000 description 3
- 229910001701 hydrotalcite Inorganic materials 0.000 description 3
- 229960001545 hydrotalcite Drugs 0.000 description 3
- 238000011056 performance test Methods 0.000 description 3
- 239000002861 polymer material Substances 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 239000002910 solid waste Substances 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 2
- 239000001095 magnesium carbonate Substances 0.000 description 2
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000002893 slag Substances 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 241000282414 Homo sapiens Species 0.000 description 1
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 1
- 239000011398 Portland cement Substances 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 230000003487 anti-permeability effect Effects 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 229920000592 inorganic polymer Polymers 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000004083 survival effect Effects 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
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
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/02—Selection of the hardening environment
- C04B40/024—Steam hardening, e.g. in an autoclave
-
- 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
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00241—Physical properties of the materials not provided for elsewhere in C04B2111/00
- C04B2111/00293—Materials impermeable to liquids
-
- 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
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/20—Resistance against chemical, physical or biological attack
- C04B2111/27—Water resistance, i.e. waterproof or water-repellent materials
-
- 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
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
-
- 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)
- Ceramic Engineering (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Geology (AREA)
- Geochemistry & Mineralogy (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
Abstract
The application relates to a geopolymer recycled concrete and a preparation method thereof, wherein the geopolymer recycled concrete comprises the following components in parts by mass: 20-30 parts of fly ash, 30-40 parts of recycled coarse aggregate, 10-15 parts of natural river sand, 20-30 parts of alkali-exciting agent and nano SiO 2 1-2 parts of MgO, 0.5-1.5 parts of MgO and 5-8 parts of water. According to the method, nano silicon dioxide and magnesium oxide are added into the geopolymer recycled concrete, the filling seed crystal nucleation effect of the nano silicon dioxide is utilized, the generation of microcracks is reduced, the expansion effect after the magnesium oxide reaction is utilized, the shrinkage of the geopolymer concrete is restrained, and the synergistic effect of the nano silicon dioxide and the magnesium oxide can obviously improve the durability and the impermeability of the geopolymer recycled concrete. Aiming at the problem that the adhesion degree of the recycled coarse aggregate in the polymerization procedure is insufficient, the recycled coarse aggregate is pretreated so as to adsorb the orthosilicic acidThe mixed solution composed of the ester and the silane coupling agent can greatly improve the bonding effect, effectively improve the strength of the polymer regenerated concrete and optimize the micropore structure.
Description
Technical Field
The application relates to the technical field of building materials, in particular to geopolymer recycled concrete and a preparation method thereof.
Background
Concrete is used as the most widely used building material in the world today, brings great convenience to people, and simultaneously brings very serious problems of resources, energy and environment. In general, each ton of cement produced is accompanied by the emission of 0.83 ton of carbon dioxide, which aggravates the greenhouse effect, and in addition, the production of cement also causes a large amount of harmful dust emission, seriously pollutes the environment, destroys the ecological balance and brings serious harm to the sustainable development of society and economy and the survival of human beings.
The geopolymer is an amorphous silicon-aluminum network structure inorganic polymer obtained by adopting a chemical excitant and solid wastes such as natural minerals or fly ash, slag, red mud, steel slag, aggregates and the like through polymerization reaction. The carbon emission and energy consumption of the geopolymer production are respectively 1/15-1/10 and 1/6-1/4 of that of the traditional cement, so that the geopolymer can consume solid wastes in a large scale, and the advantages of environmental protection and energy conservation are outstanding. The geopolymers of different raw materials have differences in reaction mechanism, microstructure and macroscopic properties, but generally have very good durability, in particular sulfate and acid attack resistance, far superior to portland cement-based materials. Therefore, the geopolymer material has great application prospect in the aspects of building materials, high-strength materials, nuclear solid waste materials, high-temperature resistant materials and the like, and has environmental, social and economic benefits.
Most of the conventional geopolymer materials adopt coarse aggregates, so that the aggregates are not tightly connected with slurry; moreover, the geopolymer is accompanied by a large volume shrinkage during hardening, so that microcracks are liable to occur, and the presence of microcracks affects the impermeability and durability to a long extent.
Disclosure of Invention
In order to improve the comprehensive performance of geopolymer concrete, the application provides geopolymer recycled concrete and a preparation method thereof.
In the first aspect, the geopolymer recycled concrete adopts the following technical scheme:
the geopolymer recycled concrete comprises the following components in parts by weight:
20-30 parts of fly ash, 30-40 parts of recycled coarse aggregate, 10-15 parts of natural river sand, 20-30 parts of alkali-exciting agent and nano SiO 2 1 to 2 parts of MgO, 0.5 to 1.5 parts of MgO and 5 to 8 parts of water.
By adopting the technical scheme, nano SiO is added into the geopolymer recycled concrete 2 Nano SiO 2 Not only canTakes part in the polymerization reaction while part of the unreacted SiO 2 The particles can fill pores, improve the pore structure of the geopolymer, thereby reducing the exchange among substances and the damage of erosion medium to the geopolymer structure, reducing the occurrence of microcracks and improving the impermeability and durability of the material. MgO is also added in the application, and the active MgO is doped into the polymer to react with water to generate vermicular Mg (OH) 2 In high alkalinity liquid phase environment, mg (OH) is generated 2 The crystals are tiny and dispersed in the geopolymer slurry to generate uniform volume expansion, so that the volume shrinkage in the geopolymer hardening process is effectively compensated, and the generation of microcracks can be greatly reduced; and Mg (OH) formed 2 Can be combined with CO 2 Directly carbonized to generate magnesium carbonate and hydrated magnesium carbonate, and improves the carbonization resistance of the geopolymer material. By adding nano SiO in the application 2 And the polymer material and MgO cooperate to reduce microcracks of the polymer material and improve the impermeability and durability of the polymer material.
Preferably, the geopolymer recycled concrete comprises the following components in parts by weight: 24 parts of fly ash, 35 parts of recycled coarse aggregate, 12 parts of natural river sand, 25 parts of alkali-exciting agent and nano SiO 2 1.5 parts of MgO, 1 part of water and 6 parts of water.
By adopting the technical scheme, the comprehensive performance of the geopolymer can be optimized by controlling the proportion of the components.
Preferably, the alkali-activated agent is a mixed solution composed of sodium hydroxide and sodium silicate, wherein the mass ratio of the sodium hydroxide to the sodium silicate is (5-7) (11-13), and the concentration of the sodium hydroxide is 7-9 mol/L; the water glass has a modulus of 2-2.5.
Through adopting above-mentioned technical scheme, adopt sodium hydroxide and sodium silicate as alkali-activated agent in this application can improve its excitation effect, promotes the bonding strength of regeneration coarse aggregate and thick liquids, guarantees the intensity and the durability of geopolymer.
Preferably, the recycled coarse aggregate is waste concrete recycled coarse aggregate of building demolition waste, the grain diameter is 0.5-1.0 cm, and the apparent density is 2050-2070 kg/m 3 The water absorption is 9.6～9.7％。
By adopting the technical scheme, the physical properties of the recycled aggregate are controlled, so that the bonding strength of the geopolymer can be ensured, and the comprehensive properties of the geopolymer are improved.
Preferably, the recycled coarse aggregate is pretreated recycled coarse aggregate, and the pretreatment method comprises the following steps: and adding the recycled aggregate into a mixed solution containing tetraethoxysilane and silane coupling, and adsorbing the recycled aggregate with the mixed solution under the stirring condition, and obtaining the pretreated recycled aggregate after uniform mixing and adsorption.
Through adopting above-mentioned technical scheme, the regeneration aggregate is carried out the preliminary treatment in this application, mainly utilizes regeneration aggregate to have certain adsorptivity, adds it into the solution that contains tetraethoxysilane and silane coupling agent, makes it take place to adsorb, makes regeneration aggregate's inside and top layer contain mixed solution, therefore in the polymer reaction polymerization's in-process, regeneration aggregate surface and inside absorptive tetraethoxysilane and silane coupling agent can participate in the polymerization process to promote regeneration aggregate and the bonding strength of thick liquids by a wide margin.
Preferably, the mass volume ratio of the recycled aggregate to the mixed solution is 1kg (100-150 mL), the mass ratio of the tetraethoxysilane to the silane coupling agent is (0.6-0.9): 1, and the adsorption time is 3-5 h.
Through adopting above-mentioned technical scheme, through the proportion of control regeneration aggregate and mixed solution in this application, make regeneration aggregate can fully adsorb mixed solution, avoid introducing too much mixed solution simultaneously, too fast acceleration ground polymer's polymerization process influences ground polymer's comprehensive properties.
Preferably, the geopolymer recycled concrete further comprises 0.2-0.5 part of layered double hydroxide LDHs.
By adopting the technical scheme, LDHs and inter-ion interchangeability are added in the method, so that the method has high CO conversion efficiency 3 2－ 、Cl － And SO 4 2- The isoerosive ions have good layer adsorption effect, and can be replaced into the layered structure in the erosion process,reducing the damage degree of the polymer structure.
In a second aspect, the present application provides a method for preparing geopolymer recycled concrete, comprising the steps of:
s1: nano SiO 2 Stirring and dispersing the mixture with water according to a proportion to obtain a dispersion liquid;
s2: dry-mixing fly ash, recycled coarse aggregate, natural river sand and MgO, adding the dispersion liquid in the step S1, stirring and mixing uniformly, adding an alkali-exciting agent into the mixture, stirring and mixing uniformly to obtain a mixture, placing the mixture into a mould, tamping, curing, and obtaining the geopolymer recycled concrete after curing.
By adopting the technical scheme, the nano silicon dioxide is firstly dispersed in the geopolymer concrete, so that the dispersibility of the nano silicon dioxide in the geopolymer concrete can be ensured, and the effect of the nano silicon dioxide can be better achieved. After the fly ash, the recycled coarse aggregate, the natural river sand and the MgO are firstly and evenly mixed, the uniformity among the components can be ensured, and after the alkali excitant is added, the polymerization can be better carried out, so that the strength of the concrete is improved.
Preferably, when the components further comprise LDHs, they are added during the dry mixing in step S2.
Preferably, in the step S2, after tamping, the autoclave curing is performed at 100 to 180 ℃ for 15 to 20 hours, and then the curing is performed at normal temperature for 28 days.
Through adopting above-mentioned technical scheme, the high temperature autoclaved curing of curing in this application is advanced, can promote the polymerization, further improves the pore structure, reduces the formation of microcrack, promotes the intensity and the anti permeability performance of oligomer.
In summary, the present application includes at least one of the following beneficial technical effects:
1. according to the method, nano silicon dioxide and magnesium oxide are added into the geopolymer recycled concrete, the filling seed crystal nucleation effect of the nano silicon dioxide is utilized, the generation of microcracks is reduced, the expansion effect after the magnesium oxide reaction is utilized, the shrinkage of the geopolymer concrete is restrained, and the synergistic effect of the nano silicon dioxide and the magnesium oxide can obviously improve the durability and the impermeability of the geopolymer recycled concrete.
2. Aiming at the problem that the adhesion degree of the recycled coarse aggregate is insufficient in the polymerization procedure, the recycled coarse aggregate is pretreated in the method, so that the recycled coarse aggregate is adsorbed with the mixed solution consisting of the orthosilicate and the silane coupling agent, the adhesion effect can be greatly improved, the strength of the polymer recycled concrete is effectively improved, and the microporous structure is optimized.
3. LDHs is further added into the geopolymer recycled concrete, so that the LDHs has a strong adsorption effect on various corrosive anions, damage to the geopolymer recycled concrete structure is avoided, and the durability of the LDHs is improved.
Detailed Description
The modulus of the water glass adopted in the application is 2.5; the recycled concrete is waste concrete recycled coarse aggregate of building demolition waste, the grain diameter is 0.5-1.0 cm, and the apparent density is 2064kg/m 3 The water absorption was 9.7%.
Example 1
The raw material ratio of the geopolymer recycled concrete in the embodiment is as follows: 24kg of fly ash, 35kg of recycled coarse aggregate, 12kg of natural river sand, 25kg of alkali-exciting agent and nano SiO 2 1.5kg, mgO 1kg and water 6kg. Wherein: the alkali-activated agent consists of aqueous solution of sodium hydroxide and sodium silicate, wherein the concentration of the sodium hydroxide is 8mol/L, and the mass ratio of the sodium hydroxide to the sodium silicate is 6:12.
The preparation method comprises the following steps:
s1: nano SiO 2 Stirring and dispersing the mixture with water according to a proportion to obtain a dispersion liquid;
s2: dry-mixing fly ash, recycled coarse aggregate, natural river sand and MgO, adding the dispersion liquid in the step S1, stirring and mixing uniformly, adding an alkali-exciting agent into the mixture, stirring and mixing uniformly to obtain a mixture, placing the mixture in a mould, tamping, curing, wherein the first-day curing after tamping is autoclaved at 120 ℃ for 18 hours, and then curing is continued at room temperature for 28 days to obtain the geopolymer recycled concrete.
Example 2
Substantially the same as in example 1, except that the autoclaved curing was not performed, but the conventional curing was employed.
Comparative example 1
Substantially the same as in example 1, except that no nano SiO was added 2 The natural river sand with equal quality is adopted for substitution.
Comparative example 2
Substantially identical to example 1, except that MgO was not added and the same mass of natural river sand was used instead.
The geopolymer recycled concrete prepared in examples and comparative examples was tested, and the test method was performed with reference to GBT 50081-2019 "test method for physical mechanical properties of concrete".
Erosion resistance test: the erosion liquid is seawater, the geopolymer regenerated concrete in the cured examples and the comparative examples is respectively immersed into the erosion liquid and placed at normal temperature, after 120 days of placing, the compressive strength of the erosion liquid and the compressive strength of the concrete placed at normal temperature are respectively tested, and the ratio of the erosion liquid to the compressive strength placed at normal temperature is the corrosion resistance value.
The test results of example 1 and comparative examples 1 and 2 are shown in table 1.
TABLE 1
As can be seen from the data in Table 1, in example 1, compared with comparative example 1, mainly no autoclaved curing was performed, and from the viewpoint of performance, the polymerization strength was weak and thus the strength was slightly lowered, and the bonding strength was not sufficiently tight, and thus the erosion resistance was slightly lowered. Compared with comparative examples 1 and 2, the mechanical properties of the concrete are reduced to a certain extent without adding nano silicon dioxide and magnesium oxide, and the erosion resistance of the concrete is also reduced, which shows that the addition of the two components can improve the void structure of the geopolymer recycled concrete and improve the mechanical strength and the erosion resistance of the concrete.
Example 3
The raw material ratio of the geopolymer recycled concrete in the embodiment is as follows: 20kg of fly ash, 40kg of recycled coarse aggregate, 15kg of natural river sand, 30kg of alkali-exciting agent and nano SiO 2 2.0kg, mgO 0.5kg and water 8kg. Wherein: the alkali-activated agent consists of aqueous solution of sodium hydroxide and sodium silicate, wherein the concentration of the sodium hydroxide is 7mol/L, and the mass ratio of the sodium hydroxide to the sodium silicate is 5:13.
The preparation method comprises the following steps:
s1: nano SiO 2 Stirring and dispersing the mixture with water according to a proportion to obtain a dispersion liquid;
s2: dry-mixing fly ash, recycled coarse aggregate, natural river sand and MgO, adding the dispersion liquid in the step S1, stirring and mixing uniformly, adding an alkali-exciting agent into the mixture, stirring and mixing uniformly to obtain a mixture, placing the mixture in a mould, tamping, curing, wherein the first-day curing after tamping is autoclaved at 100 ℃ for 20 hours, and then curing is continued at room temperature for 28 days to obtain the geopolymer recycled concrete.
Example 4
The raw material ratio of the geopolymer recycled concrete in the embodiment is as follows: 30kg of fly ash, 30kg of recycled coarse aggregate, 10kg of natural river sand, 20kg of alkali-exciting agent and nano SiO 2 1.0kg, mgO 1.5kg and water 5kg. Wherein: the alkali-activated agent consists of aqueous solution of sodium hydroxide and sodium silicate, wherein the concentration of the sodium hydroxide is 9mol/L, and the mass ratio of the sodium hydroxide to the sodium silicate is 5:13.
The preparation method comprises the following steps:
s1: nano SiO 2 Stirring and dispersing the mixture with water according to a proportion to obtain a dispersion liquid;
s2: dry-mixing fly ash, recycled coarse aggregate, natural river sand and MgO, adding the dispersion liquid in the step S1, stirring and mixing uniformly, adding an alkali-exciting agent into the mixture, stirring and mixing uniformly to obtain a mixture, placing the mixture in a mould, tamping, curing, wherein the first-day curing after tamping is autoclaved at 100 ℃ for 20 hours, and then curing is continued at room temperature for 28 days to obtain the geopolymer recycled concrete.
The geopolymer concretes in example 3 and example 4 were subjected to performance test, and the results are shown in Table 2.
TABLE 2
From the data in examples 3 and 4, the components and proportions of examples 3 and 4 are changed, and the compressive strength is changed to a certain extent, but the change is not very large, the whole maintains good mechanical properties, and the erosion resistance value is maintained above 91%.
Example 5
Substantially the same as in example 1, the difference is that the recycled coarse aggregate is the recycled aggregate after pretreatment, and the specific treatment method is as follows: adding 35kg of recycled aggregate into a mixed solution containing 1.72L of tetraethoxysilane and 2.48L of silane coupling agent KH-550, and uniformly mixing and adsorbing the mixed solution by the recycled aggregate under the stirring condition for 4 hours to obtain the pretreated recycled aggregate. And adding all the pretreated regenerated coarse aggregate into the components.
Example 6
The proportion is basically the same as that of example 3, except that the recycled coarse aggregate is the pretreated recycled aggregate, and the specific treatment method is as follows: adding 30kg of recycled aggregate into a mixed solution containing 1.65L of ethyl orthosilicate and 2.75L of silane coupling agent KH-550, and uniformly mixing and adsorbing the mixed solution by the recycled aggregate under the stirring condition for 5 hours to obtain the pretreated recycled aggregate. And adding all the pretreated regenerated coarse aggregate into the components.
Example 7
The proportion is basically the same as that of example 4, except that the recycled coarse aggregate is the pretreated recycled aggregate, and the specific treatment method is as follows: adding 35kg of recycled aggregate into a mixed solution containing 1.73L of tetraethoxysilane and 2.17L of silane coupling agent KH-550, and allowing the recycled aggregate to adsorb the mixed solution under the stirring condition, and obtaining the pretreated recycled aggregate after uniform mixing and adsorption. And adding all the pretreated regenerated coarse aggregate into the components.
The geopolymer recycled concrete of examples 5 to 7 was subjected to performance test, and the results are shown in table 3.
TABLE 3 Table 3
| Compressive Strength (MPa) after 28 days of curing | Erosion resistance value (%) | |
| Example 5 | 29.7 | 95.8 |
| Example 6 | 27.3 | 96.7 |
| Example 7 | 25.9 | 93.7 |
As can be seen from the data in Table 3, the compressive strength and erosion resistance of the recycled coarse aggregate in examples 5 to 7 are obviously improved after the recycled coarse aggregate is pretreated, which means that the bonding strength of the treated recycled aggregate is further improved in the polymerization process of the geopolymer, so that the strength and erosion resistance of the recycled aggregate are obviously improved.
Example 8
Substantially the same as in example 1, except that 0.3kg of LDHs (magnesium aluminum carbonate hydrotalcite) was added to the formulation in example 1.
Example 9
Substantially the same as in example 5, except that 0.3kg of LDHs (magnesium aluminum carbonate hydrotalcite) was added to the formulation in example 6.
Example 10
Substantially the same as in example 6, except that 0.3kg of LDHs (magnesium aluminum carbonate hydrotalcite) was added to the formulation in example 6.
The geopolymer recycled concrete prepared in examples 8 to 10 was subjected to performance test, and the results are shown in table 4.
TABLE 4 Table 4
| Compressive Strength (MPa) after 28 days of curing | Erosion resistance value (%) | |
| Example 8 | 26.0 | 96.8％ |
| Example 9 | 28.9 | 98.7％ |
| Example 10 | 26.7 | 99.0％ |
From the data in table 4, it can be seen that when LDHs is added to geopolymer concrete, the compressive strength is reduced to a small extent, but the erosion resistance is improved significantly, probably because LDHs has stronger adsorptivity to erosive ions, so that the damage to the polymer base structure is avoided, and the erosion resistance is improved significantly.
The foregoing are all preferred embodiments of the present application, and are not intended to limit the scope of the present application in any way, therefore: all equivalent changes in structure, shape and principle of this application should be covered in the protection scope of this application.
Claims (10)
1. The geopolymer recycled concrete is characterized by comprising the following components in parts by weight:
20-30 parts of fly ash, 30-40 parts of recycled coarse aggregate, 10-15 parts of natural river sand, 20-30 parts of alkali-exciting agent and nano SiO 2 1-2 parts of MgO, 0.5-1.5 parts of MgO and 5-8 parts of water.
2. The geopolymer recycled concrete according to claim 1, which comprises the following components in parts by weight: 24 parts of fly ash, 35 parts of recycled coarse aggregate, 12 parts of natural river sand, 25 parts of alkali-exciting agent and nano SiO 2 1.5 parts of MgO, 1 part of water and 6 parts of water.
3. The geopolymer recycled concrete according to claim 1, wherein the alkali-activated agent is a mixed solution composed of sodium hydroxide and water glass, the mass ratio of the sodium hydroxide to the water glass is (5-7): (11-13), and the concentration of the sodium hydroxide is 7-9 mol/L; the water glass has a modulus of 2-2.5.
4. The recycled geopolymer concrete according to claim 1, wherein the recycled coarse aggregate is waste concrete recycled coarse aggregate of construction demolition waste, the particle size is 0.5-1.0 cm, and the apparent density is 2050-2070 kg/m 3 The water absorption rate is 9.6 to 9.7 percent.
5. The recycled geopolymer concrete according to claim 1, wherein the recycled coarse aggregate is a pretreated recycled coarse aggregate, and the pretreatment method comprises the following steps: and adding the recycled aggregate into a mixed solution containing tetraethoxysilane and silane coupling, and adsorbing the recycled aggregate with the mixed solution under the stirring condition, and obtaining the pretreated recycled aggregate after uniform mixing and adsorption.
6. The geopolymer recycled concrete according to claim 5, wherein the mass-to-volume ratio of the recycled aggregate to the mixed solution is 1kg (100-150) mL, the mass ratio of the tetraethoxysilane to the silane coupling agent is (0.6-0.9): 1, and the adsorption time is 3-5 h.
7. The recycled geopolymer concrete of claim 1, further comprising 0.2-0.5 parts of layered double hydroxide LDHs.
8. A method for preparing the geopolymer recycled concrete according to any one of claims 1 to 7, comprising the steps of:
s1: nano SiO 2 Stirring and dispersing the mixture with water according to a proportion to obtain a dispersion liquid;
s2: dry-mixing fly ash, recycled coarse aggregate, natural river sand and MgO, adding the dispersion liquid in the step S1, stirring and mixing uniformly, adding an alkali-exciting agent into the mixture, stirring and mixing uniformly to obtain a mixture, placing the mixture into a mould, tamping, curing, and obtaining the geopolymer recycled concrete after curing.
9. The method for preparing geopolymer recycled concrete according to claim 8, wherein LDHs are added when dry mixing is performed in step S2 when the components further comprise LDHs.
10. The method for preparing recycled geopolymer concrete according to claim 8, wherein in the step S2, after tamping, autoclaved curing is performed for 15-20 hours at 100-180 ℃ and then cured for 28 days at normal temperature.
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