CN110255996B - Fly ash geopolymer concrete and preparation method thereof - Google Patents
Fly ash geopolymer concrete and preparation method thereof Download PDFInfo
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- CN110255996B CN110255996B CN201910659478.8A CN201910659478A CN110255996B CN 110255996 B CN110255996 B CN 110255996B CN 201910659478 A CN201910659478 A CN 201910659478A CN 110255996 B CN110255996 B CN 110255996B
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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
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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
- 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
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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
- 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
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- 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
Abstract
The invention discloses a fly ash geopolymer concrete which is prepared by taking fly ash and metakaolin as base materials, taking one or the combination of more than two of sodium hydroxide, potassium hydroxide, sodium silicate and potassium silicate and water glass as an alkali activator and adding modified ceramic microsphere particles, polymer fibers, coarse aggregates, fine aggregates and water. The fly ash geopolymer concrete has good mechanical property, durability and corrosion resistance.
Description
Technical Field
The invention belongs to the technical field of concrete materials, and particularly relates to fly ash geopolymer concrete and a preparation method thereof.
Background
Ancient concrete and mortar buildings, such as Egypt pyramids, Roman arenas and the like, all have excellent durability, and can be maintained for thousands of years, even tens of thousands of years, without being damaged in a severe environment. In contrast, modern concrete prepared with portland cement has an average lifetime of only 40-50 years, not more than 100 years at the longest, and suffers serious damage in just a few years under the same ambient conditions. The reason for this is that the durable concrete contains an amorphous substance not contained in portland cement, which has a structure similar to the three-dimensional structure of an organic high-molecular polymer but mainly contains inorganic SiO4And AlO4Tetrahedrally, known as geopolymers by french materialist j. Davidovits (geopolymer).
The geopolymer is cement-free clinker cementing material with different strength grades, which is obtained by mixing a proper amount of metakaolin and a small amount of alkaline activator solution with a large amount of natural or artificial silica-alumina material and curing at the temperature lower than 150 ℃ or even at normal temperature. Compared with the prior inorganic Si-Al cementing material, the geopolymer has the following characteristics: 1, excellent durability; 2, a 'two-grinding one-burning' calcining process which consumes a large amount of resources and energy sources like the production of portland cement is not used in the preparation process, and CO is not basically discharged2The adopted raw materials are natural or artificial low-calcium Si-Al materials with abundant resources and low price; 3, rapid hardening, early strength and high later strength, the final strength of the geopolymer can be 70 percent in 1 day generally, and the later compressive strength can reach 20-100 MPa; 4, the shrinkage of the low shrinkage geopolymer in 7 days and 28 days is only 0.02% and 0.05%, respectively, while the shrinkage of the portland cement hardened paste in 7 days and 28 days is as high as 0.10% and 0.33%; low permeability, if augmented with chloride ionsThe diffusion coefficient represents the impermeability of the concrete, so that the chloride ion diffusion coefficient is similar to that of granite, and the impermeability is good; 6, high temperature resistance, good heat insulation effect, capability of resisting the high temperature of 1000-1200 ℃ without damage, and heat conductivity coefficient comparable with that of the light refractory clay brick. The characteristics lead the geopolymer and the concrete thereof to have very wide application prospect in the fields of municipal administration, bridges, roads, water conservancy, underground, ocean, military affairs and the like, and are expected to become the substitute products of the Portland cement.
Fly ash is a byproduct produced by a thermal power plant, the annual emission amount of the fly ash in China is nearly 3 hundred million tons at present, but less than half of the fly ash is utilized, and a large amount of stacked fly ash not only occupies land, but also causes serious environmental pollution and huge waste of energy and resources. However, the utilization rate of the fly ash in China is not 30% so far, and the fly ash is a low-calcium Si-Al material and has potential activity, so that the utilization rate of the fly ash can be obviously improved by using the fly ash to replace part of metakaolin to prepare the geopolymer, the environmental pollution is reduced, and the method has important social, economic and technical benefits.
Fly Ash Geopolymer concrete (FAG) is known as a "green" material and studies have shown that carbon dioxide emissions during its production are reduced by about 80% compared to ordinary portland cement. The fly ash geopolymer concrete not only causes less pollution to the environment, but also has obvious advantages compared with the common fly ash concrete. In the non-patent document "the influence of curing conditions on the early shrinkage performance of the fly ash geopolymer concrete", researchers find that the compression strength of the fly ash geopolymer concrete in the early age is lower under the wrapping and curing conditions, the strength is increased faster within 7-28 days, and the strength is greater than that of the fly ash concrete after 28 days; the shrinkage rate of the fly ash geopolymer concrete is smaller than that of the fly ash concrete.
Patent document cn201410856420.x prepares a fly ash-based polymer concrete material by using an alkali-activated fly ash-based polymer as a main cementing material, wherein the fly ash-based polymer concrete material comprises the following components in percentage by mass: 25-45% of fly ash, 0-15% of metakaolin, 10-15% of cement, 0-5% of coal gangue and slag, 25-35% of alkali activator, 0.5-1% of retarder and 1-5% of deionized water.
In the prior art, other more novel features have been achieved by improvement based on the common composition of fly ash geopolymer concrete. For example, patent document CN201611127977.5 discloses a chitosan-modified polymer gel material. Adding chitosan into an alkaline activator, and fully stirring and dissolving to obtain a mixed solution; gradually adding the mixed solution into the silicon-aluminum solid material, and uniformly stirring; and injecting the mixture into a mold for reaction, and curing after demolding to obtain the chitosan modified geopolymer cementing material. The addition of chitosan can obviously reduce the compression ratio of the material and improve the bending toughness of the material, but the chitosan is a biological material and can cause the cost to be increased when being used for preparing concrete.
Patent document CN201410601488.3 discloses a fly ash based geopolymer foamed concrete composition containing fly ash, a foaming agent, water glass, aluminum powder and water. The prepared foam concrete has the advantages of light weight, heat insulation, sound insulation, fire resistance, good earthquake resistance and the like.
Patent document CN201510974523.0 discloses a fly ash based polymer cement and a porous concrete material, wherein the fly ash based polymer cement is composed of fly ash, granulated blast furnace slag, nano zeolite powder, gypsum powder and a composite alkali activator prepared from potassium sodium water glass and caustic alkali, and is used with special-grade coarse aggregates such as basalt or granite to prepare the porous concrete, and the porous concrete is applied to paving a road surface layer.
In general, prior art researchers have focused on modifying geopolymer concrete mostly on compressive and shrinkage resistance, but have focused less on corrosion resistance. The research shows that patent document CN201810595723.9 discloses a corrosion-resistant polymer concrete cast-in-place pile material, which comprises 100 parts of metakaolin, 10-40 parts of fly ash, 250 parts of modified water glass with the modulus of 1.2-1.8, 600 parts of fine sand, 1500 parts of stone 800-1500 parts, 5-20 parts of polyvinyl alcohol fiber and 5-10 parts of boric acid.
In order to make up for the defects of the prior art, the invention provides the fly ash geopolymer concrete which has better corrosion resistance and is suitable for the construction of saline-alkali soil engineering, ocean engineering and corrosive product production plants, such as chemical product production plants, medicine or fertilizer production plants and the like.
Disclosure of Invention
The invention aims to provide fly ash geopolymer concrete and a preparation method and application thereof.
In a first aspect, the invention provides a fly ash geopolymer concrete, which is prepared by adding modified ceramic microsphere particles, polymer fibers, coarse aggregates, fine aggregates and water into a base material of fly ash and metakaolin, wherein the base material of the concrete is one or more of sodium hydroxide, potassium hydroxide, sodium silicate and potassium silicate, and the base material of the concrete is water glass, and the raw materials for preparing the modified ceramic microsphere particles comprise: ceramic microspheres, silica sol, an anticorrosive rust inhibitor, and an acrylate emulsion and/or a styrene-acrylic emulsion.
Preferably, the fly ash geopolymer concrete comprises the following preparation materials in parts by mass: 1-400 parts of fly ash, 1-400 parts of metakaolin, 20-30 parts of one or more of sodium hydroxide, potassium hydroxide, sodium silicate and potassium silicate in total, 200 parts of water glass 150-: 100-500 parts of ceramic microspheres, 20-60 parts of silica sol, 20-40 parts of anticorrosive rust inhibitor and 30-50 parts of acrylate emulsion and/or styrene-acrylic emulsion in total.
More preferably, the fly ash geopolymer concrete further comprises 5-15 parts of a water reducing agent, and the water reducing agent is selected from polycarboxylic acid water reducing agents.
Preferably, the polymer fiber of the present invention is selected from one or a combination of two or more of polypropylene fiber, polyacrylonitrile fiber, and polyvinyl alcohol fiber. In a preferred embodiment of the invention, the polymer fibers are selected from polyacrylonitrile fibers.
Preferably, the alkali-activator is selected from a combination of a potassium silicate solution having a modulus of 2.5 to 3.0 and water glass having a modulus of 1.2 to 2.0.
The coarse aggregate is selected from limestone broken stone or stone with 5-15 mm continuous gradation; the fine aggregate is selected from yellow sand with fineness modulus of 1.2-1.5, mud content is 0.7%, and particles below 5mm are sieved when in use.
The metakaolin used in the invention is powder with the particle size of more than 200 meshes obtained by calcining natural kaolin at the temperature of 600-900 ℃.
The fly ash is ash black powdery particles obtained after anthracite or bituminous coal is combusted in a boiler, and the density is 1900-2800 kg/m3In the meantime. Preferably, the fly ash can be primary or secondary fly ash, and the chemical components of the fly ash comprise silicon oxide and aluminum oxide with the content of more than 70%. The fly ash used in the invention is thermal power plant industrial class F first class fly ash, the particle size is 1-100 μm, and the main components comprise silicon dioxide, aluminum oxide, ferric oxide, calcium oxide, titanium oxide, phosphorus oxide and the like. The F-type fly ash is adopted because the F-type fly ash has lower calcium content than other types of fly ash and belongs to low-calcium fly ash, and the low calcium content can enhance the sulfate corrosion resistance of geopolymer concrete materials, and has low hydration heat degree, better mechanical property and durability.
The modified ceramic microsphere particles are formed by coating a functional coating containing an anti-corrosion and anti-rust agent on the surface of a common ceramic microsphere, and have good filling effect in a three-dimensional frame structure formed by geopolymers due to small particle size of the ceramic microsphere, so that a concrete structure is tighter, and the mechanical property of concrete is improved. The surface of the ceramic microsphere is coated with the corrosion and rust preventing coating, so that the corrosion and rust preventing agent is more uniform and stable along with the dispersion of the ceramic microsphere, and the acrylic ester emulsion and/or the styrene-acrylic emulsion and the silica sol have the functions of increasing the contact force between the corrosion and rust preventing agent and the surface of the ceramic microsphere and preventing the corrosion and rust preventing agent from falling off in the stirring process, so that the durability and the corrosion resistance of the concrete are improved.
Preferably, the ceramic microsphere particles may be selected from solid ceramic microspheres or hollow ceramic microspheres, and more preferably, the ceramic microspheres are solid ceramic microspheres. The ceramic microsphere is high-strength, inert and hard spherical superfine ceramic powder, and the grain size of the ceramic microsphere is 10-30 mu m.
In a preferred embodiment of the invention, the fly ash geopolymer concrete comprises the following preparation materials in parts by mass: 400 parts of fly ash 200-containing material, 400 parts of metakaolin 100-containing material, 23-25 parts of potassium silicate, 200 parts of water glass 180-containing material, 7-10 parts of polycarboxylic acid water reducing agent, 60-90 parts of modified ceramic microsphere particles, 20-30 parts of polymer fibers, 1200 parts of coarse aggregate 1000-containing material, 500 parts of fine aggregate 400-containing material and 15-20 parts of water, wherein the modified ceramic microsphere particles are prepared from the following raw materials: 500 portions of ceramic microspheres, 30 to 50 portions of acrylic ester emulsion and/or styrene-acrylic emulsion, 20 to 60 portions of silica sol and 20 to 40 portions of anticorrosive rust inhibitor.
In a second aspect, the invention provides a preparation method of fly ash geopolymer concrete, which specifically comprises the following steps:
(1) preparing modified ceramic microsphere particles: fully and uniformly stirring and mixing the acrylate emulsion and/or the styrene-acrylic emulsion and the silica sol, adding the corrosion and rust inhibitor, dispersing and stirring uniformly to obtain a spraying liquid, uniformly spraying the spraying liquid on the surface of the ceramic microsphere by using a spraying device, and drying at the temperature of 60-90 ℃ to obtain modified ceramic microsphere particles;
(2) preparing an alkaline activator mixture in advance: fully mixing one or more of sodium hydroxide, potassium hydroxide and potassium silicate with an alkaline activator consisting of water glass, stirring to dissolve, and standing at room temperature for later use;
(3) preparation of geopolymer gel material: firstly, mixing fly ash and metakaolin, then adding an alkaline activator mixture prepared in advance, fully stirring, adding polymer fiber, mixing and stirring;
(4) preparation of geopolymer concrete: adding coarse aggregate and fine aggregate into a stirring device, adding geopolymer cementing material, stirring, adding modified ceramic microsphere particles, and fully stirring to prepare the fly ash geopolymer concrete.
Preferably, in the step (1), in order to prevent the ceramic microspheres from agglomerating during the spraying process and accelerate the drying of the spraying liquid on the surfaces of the microspheres, the spraying process is carried out at a temperature of 50-60 ℃.
More preferably, the modified ceramic microspheres obtained in step (1) are sieved by a 300-400 mesh sieve, and the ceramic microspheres which do not form agglomerates are filtered.
Preferably, the step (3) further comprises adding a water reducing agent after adding the alkali activator.
In a third aspect, the invention provides application of the fly ash geopolymer concrete in the construction of saline-alkali soil engineering, ocean engineering, chemical plant, and pharmaceutical or chemical fertilizer production workshops.
The method has the beneficial effects that the fly ash and the metakaolin are used as base materials, and the ceramic microspheres, the polymer fibers and other components with the surfaces coated with the corrosion and corrosion inhibitors are added in the process of preparing the geopolymer concrete, so that the prepared concrete has good mechanical property, good durability and strong corrosion resistance.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
EXAMPLE 1 preparation of fly ash Geopolymer concrete
The metakaolin used in the invention is prepared by calcining kaolin at 700 ℃ for 12 hours, and the chemical components of the metakaolin are shown in the following table:
TABLE 1 chemical composition of metakaolin
The fly ash used in the invention is certain thermal power plant industrial grade F class first grade dry discharge ash, and the chemical components of the fly ash are shown in the following table:
TABLE 2 fly ash chemical composition
The preparation method of the fly ash geopolymer concrete comprises the following steps:
s1: fully and uniformly stirring 20 parts of acrylate emulsion, 10 parts of styrene-acrylic emulsion and 20 parts of silica sol, adding 30 parts of anticorrosion and rust-resistant agent while stirring, and stirring until no particulate matter exists in the solution to obtain a spraying solution; loading the spraying liquid into a spraying device, uniformly spraying the spraying liquid on the surface of the ceramic microspheres in a drying oven at 50 ℃, raising the temperature to 90 ℃ after the spraying is finished, quickly drying the microspheres, and sieving with a 400-mesh sieve to obtain modified ceramic microsphere particles;
s2: fully mixing 23 parts of potassium silicate, 8 parts of water and 184 parts of water glass with the modulus of 1.2-2.0, uniformly stirring to obtain an alkaline activator, and placing at room temperature for later use;
s3: firstly, 200 parts of fly ash and 200 parts of metakaolin are mixed in a stirrer, the alkaline activator prepared in the step S2 is added, the mixture is fully stirred, 20 parts of polyacrylonitrile fiber is added, and the mixture is mixed and stirred to obtain a geopolymer gel material;
s4: adding 1200 parts of limestone broken stone and 480 parts of yellow sand into a large-scale stirrer, adding the geopolymer cementing material prepared in the step S3, stirring, then adding 70 parts of modified ceramic microsphere particles prepared in the step S1, adding a proper amount of water, and fully stirring to prepare the fly ash geopolymer concrete.
EXAMPLE 2 preparation of fly ash Geopolymer concrete
S1: the preparation method of the modified ceramic microsphere particles is the same as that of example 1;
s2: the preparation method of the alkali-activator is the same as that of example 1;
s3: firstly, 200 parts of fly ash and 200 parts of metakaolin are mixed in a stirrer, the alkaline activator and 7.5 parts of polycarboxylic acid water reducer prepared in the step S2 are added, the mixture is fully stirred, 20 parts of polyacrylonitrile fiber is added, and the mixture is mixed and stirred;
s4: geopolymer concrete was prepared as in example 1.
Comparative example 1 preparation of fly ash geopolymer concrete without modified ceramic microspheres
S1: the preparation method of the alkali-activator is the same as that of example 1;
s2: geopolymer gel material preparation same as example 1;
s3: adding 1200 parts of limestone broken stone and 480 parts of yellow sand into a large-scale stirrer, adding the geopolymer cementing material prepared in the step S2, stirring, adding a proper amount of water, and fully stirring to prepare the fly ash geopolymer concrete.
Comparative example 2 preparation of fly ash geopolymer concrete without Polymer fibers
S1: the preparation method of the modified ceramic microsphere particles is the same as that of example 1;
s2: the preparation method of the alkali-activator is the same as that of example 1;
s3: firstly, 200 parts of fly ash and 200 parts of metakaolin are mixed in a stirrer, and the alkaline activator prepared in the step S2 is added and fully stirred;
s4: geopolymer concrete was prepared as in example 1.
Comparative example 3 preparation of Portland Cement concrete
Adding 1200 parts of limestone broken stone and stone, 680 parts of yellow sand, 300 parts of ordinary portland cement (portland cement), 50 parts of fly ash and 20 parts of an additive into a large-scale mixer, adding a proper amount of water, and fully stirring to prepare the ordinary portland cement concrete.
Effect example 1 comparison of basic Properties of fly ash Geopolymer concrete
The concrete pouring test pieces prepared in the examples 1-2 and the comparative examples 1-3 are used for comprehensively evaluating the basic performance of the fly ash geopolymer concrete prepared by the invention by detecting the compressive strength, the flexural strength, the contractibility and the impermeability of the concrete test pieces, and the specific method is as follows:
1, testing the compressive strength and the flexural strength: according to GB/T50081-2002 Standard of mechanical Properties test methods of ordinary concrete, test specimens are prepared, the size is 100mm multiplied by 100mm, and the reduction coefficient is 0.95.
2, shrinkage test: according to the contact method in GB/T50082-2009 Standard test method for testing long-term performance and durability of common concrete, the size of a prepared test piece is 100mm multiplied by 515 mm. The shrinkage test conditions were as follows: and after 24 hours of mold removal after pouring, placing the test piece in a standard curing box for curing for 48 hours, then moving the test piece into a constant-temperature and constant-humidity environment with the temperature of 20 +/-2 ℃ and the relative humidity of 60 +/-5%, determining the initial length of the test piece, determining the length of the test piece for 28 days under the standard curing condition, and calculating the shrinkage rate.
3, impermeability test: and (3) measuring the resistance and the relative chloride ion diffusion coefficient of the concrete according to JTJ 270-98 'fast test on the penetration of chloride ions to the concrete'.
The results of the various tests are summarized in the following table:
TABLE 3 comparison of basic Properties of fly ash geopolymer concrete
As can be seen from the comparison of the data in Table 3, the compression strength, the breaking strength, the shrinkage and the impermeability of the fly ash geopolymer concrete prepared by the method provided by the invention are better than those of the comparative examples. After the water reducing agent is added in the embodiment 2, the mechanical property and the impermeability are slightly improved; in comparative example 1, the concrete without the modified ceramic microsphere particles is shown to have significantly reduced mechanical properties, increased shrinkage rate and reduced impermeability, because the ceramic microspheres are effectively filled in a three-dimensional frame structure formed by geopolymers, the compressive strength and shrinkage deformation of the concrete are obviously reduced; comparative example 2 is a concrete without polymer fiber, and although the compression resistance and the impermeability are weakened, the weakening degree is not significant as compared with the effect brought by the ceramic microspheres; comparative example 3 is a conventional portland cement concrete, which is the worst in all of compressive strength, flexural strength, shrinkage and impermeability, and shows that the fly ash geopolymer concrete prepared according to the present invention is actually significantly improved in various basic properties as compared to conventional concrete.
Effect example 2 comparison of Corrosion resistance of fly ash Geopolymer concrete
The concrete pouring test pieces prepared in the examples 1-2 and the comparative examples 1-3 are subjected to corrosion resistance detection by a conventional detection method of a person skilled in the art, and the specific method is as follows:
and (3) corrosion resistance test: pouring test pieces with the size of 100mm multiplied by 100mm, curing for 28 days under standard conditions, taking out, cleaning, drying for 16 hours in a drying oven at the temperature of 75 +/-5 ℃, and measuring the compressive strength. And then, placing the test piece into a medium solution (magnesium sulfate solution with the concentration of 1%) to be soaked for 6 months, taking out the test piece, washing, baking for 16 hours, measuring the compressive strength, and calculating the corrosion coefficient through a formula of 'compressive strength after corrosion/original compressive strength', wherein the smaller the numerical value, the higher the corrosion degree is, the worse the corrosion resistance of the concrete is. The results are shown in the following table:
TABLE 4 comparison of the Corrosion resistance of fly ash geopolymer concrete
Concrete poured test pieces are most vulnerable to sulfate attack in daily use, and the mechanism is that in an environment with sulfate, concrete absorbs sulfate liquid into a concrete body under the action of capillary tubes, and concrete exposed to the atmosphere evaporates transferred water due to the action of capillary tubes. Mineral substances dissolved in water are concentrated and precipitated, water is evaporated and remains on the surface and the inside of the concrete, white marks and white frost are presented, the concrete is subjected to expansion pressure of sulfate crystals, the concrete is promoted to be damaged from the surface layer, and the damage is firstly generated in a water level change area and a dry-wet alternate zone. In the moisture regain area, the ground is corroded, frost salt is crystallized in some areas, and bean curd dregs are formed in some areas, so that the strength of concrete of a building is reduced, and finally the concrete is completely damaged.
From the test data in table 4, it is found that the corrosion resistance of examples 1-2 is the best, and when the concrete does not contain the modified ceramic microsphere particles, the corrosion resistance is significantly reduced, because the corrosion inhibitor is coated on the surface of the modified ceramic microsphere first, which slows down the erosion rate to some extent, and in addition, even if the corrosion inhibitor is used up or falls off, the inert surface of the ceramic microsphere can resist chemical corrosion, and most importantly, the ceramic microspheres are tightly arranged among the concrete pores, so that the capillary action of the concrete as described above is reduced, thereby playing a good role in protecting the concrete. The results of comparative example 2 demonstrate that the polymer fibers also help to enhance the corrosion resistance of the concrete.
Example 3 optimization of fly ash content in fly ash geopolymer concrete
S1: the preparation method of the modified ceramic microsphere particles is the same as that of example 1;
s2: the preparation method of the alkali-activator is the same as that of example 1;
s3: the preparation method of the geopolymer gel material is the same as that of example 1, in order to screen the optimal addition amount of the fly ash, 400 parts of the fly ash and the metakaolin are respectively set as the proportion of the fly ash of 0, 10%, 30%, 50%, 70%, 90% and 100%, and 7 groups of tests are carried out;
s4: geopolymer concrete was prepared as in example 1.
According to GB/T50081 plus 2002 Standard of mechanical Properties test method of ordinary concrete, test pieces are prepared, the size is 100mm multiplied by 100mm, after 28 days of standard curing, the compression strength and the flexural strength of the geopolymer concrete test piece are tested, and the test results are shown in the following table:
TABLE 5 optimization of fly ash content in fly ash geopolymer concrete
From the data in the above table, it can be seen that the addition of fly ash improves the flexural strength of the concrete compared to geopolymer concrete without the addition of fly ash at all, probably because metakaolin is relatively inflexible, but when the addition of fly ash exceeds 50%, the flexural strength is reduced again; the same is true for the compressive strength of the fly ash to concrete, when the proportion of the fly ash is 30%, the compressive strength is strongest, the change is not obvious when the content is 50%, and when the addition amount exceeds 50%, the compressive strength also has a trend of remarkably decreasing, and the proportion of the addition amount of the fly ash is 30-50% by comprehensive consideration.
Example 4 Effect of modified ceramic microsphere particles on Corrosion resistance of concrete
In the invention, the modified ceramic microsphere particles are obtained by coating a layer of coating containing the corrosion and rust inhibitor on the surface of the common ceramic microsphere, and in order to enhance the adhesive force between the coating and the ceramic microsphere and ensure that the coating is not easy to fall off in the stirring process, the acrylate emulsion, the styrene-acrylic emulsion and the silica sol are matched to help the corrosion and rust inhibitor to be firmly fixed on the ceramic microsphere. Although the corrosion resistance of the traditional concrete is improved by adding the corrosion and rust inhibitor, the dispersion is uneven when a small amount of the corrosion and rust inhibitor is added into the concrete with larger volume, and the function of the corrosion and rust inhibitor is not good. In the invention, the corrosion and rust inhibitor is adhered to the surface of the ceramic microsphere, the microsphere is filled in the gap of the geopolymer three-dimensional frame structure due to the good fluidity of the ceramic microsphere, and the corrosion and rust inhibitor on the surface of the microsphere is dispersed in the ceramic microsphere, so that the corrosion and rust preventing effect is better exerted.
In order to verify the initial assumption of the inventor, four sets of tests are set for the test aiming at the modified ceramic microspheres, the preparation methods of the geopolymer gel material are the same as those of the example 1, and four kinds of concrete are prepared by the following four methods in the process of preparing the concrete by adding coarse and fine aggregates respectively: method 1, normally adding 70 parts of modified ceramic microsphere particles prepared by the invention; method 2, adding 70 parts of ceramic microspheres and 7 parts of corrosion and rust inhibitor separately; method 3, only 70 parts of ceramic microspheres are added; in the method 4, only 7 parts of the corrosion and rust inhibitor are added.
Pouring test pieces with the size of 100mm multiplied by 100mm, curing for 28 days under standard conditions, taking out, cleaning, drying for 16 hours in a drying oven at the temperature of 75 +/-5 ℃, and measuring the compressive strength. Then, the test piece is put into a medium solution (magnesium sulfate solution with the concentration of 1 percent) to be soaked for 6 months, the test piece is taken out and cleaned, the test piece is baked for 16 hours, the compressive strength is measured, the corrosion coefficient is calculated, and the detection results are shown in the following table:
TABLE 6 influence of modified ceramic microsphere particles on concrete Corrosion resistance
According to the comparison results in table 6, it can be seen that the original compressive strengths of the concrete prepared by the methods 1, 2 and 3 are not substantially different, because the time after 28 days of pouring is short and erosion is not caused, so even if the ceramic microspheres and the corrosion and corrosion inhibitor are added separately or only the ceramic microspheres are added, the compressive strengths are almost the same, and the data in the table show that the difference is more measurement errors, but when only the corrosion and corrosion inhibitor is added and no ceramic microspheres are added in the method 4, the original compressive strength is obviously reduced. After the concrete is soaked in a magnesium sulfate solution for 6 months, the concrete compressive strength weakening range of the modified ceramic microsphere particles added in the method 1 is minimum, and the corrosion coefficient is highest and is 0.96; the method 2 times shows that the separate and independent addition of the ceramic microspheres and the corrosion and rust inhibitor has poor effect; the concrete added with only the ceramic microspheres or only the corrosion and rust inhibitor has lower corrosion resistance effect. The test results prove that the corrosion and rust inhibitor is coated on the surface of the ceramic microsphere, and the ceramic microsphere is filled in the geopolymer frame structure with the corrosion and rust inhibitor, so that the corrosion and rust inhibitor can play a better role.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. The fly ash geopolymer concrete is prepared by taking fly ash and metakaolin as base materials, taking one or the combination of more than two of sodium hydroxide, potassium hydroxide and potassium silicate and water glass as an alkaline activator, and adding modified ceramic microsphere particles, polymer fibers, coarse aggregates, fine aggregates and water; the modified ceramic microsphere particles are prepared by coating a functional coating containing an anti-corrosion and anti-rust agent on the surface of a common ceramic microsphere, and the preparation raw materials comprise: 100-500 parts of ceramic microspheres, 20-60 parts of silica sol, 20-40 parts of anticorrosion rust inhibitor and 30-50 parts of acrylate emulsion and/or styrene-acrylic emulsion in total.
2. The fly ash geopolymer concrete according to claim 1, which comprises the following preparation materials in parts by mass: 1-400 parts of fly ash, 1-400 parts of metakaolin, 150 parts of water glass, 200 parts of modified ceramic microsphere particles, 10-50 parts of polymer fibers, 800 parts of coarse aggregate, 500 parts of fine aggregate, 10-20 parts of water and 20-30 parts of one or more of sodium hydroxide, potassium hydroxide and potassium silicate.
3. The fly ash geopolymer concrete according to claim 1, further comprising 5-15 parts of a water reducing agent selected from polycarboxylic acid water reducing agents.
4. The fly ash geopolymer concrete according to claim 1, wherein the polymer fiber is selected from one or a combination of two or more of polypropylene fiber, polyacrylonitrile fiber and polyvinyl alcohol fiber; the alkali activator is selected from the combination of potassium silicate solution with modulus of 2.5-3.0 and water glass with modulus of 1.2-2.0.
5. The fly ash geopolymer concrete of claim 1, wherein the coarse aggregate is selected from the group consisting of 5-15 mm continuous graded stones; the fine aggregate is selected from yellow sand with fineness modulus of 1.2-1.5, mud content is 0.7%, and particle size is below 5 mm.
6. The fly ash geopolymer concrete as claimed in claim 1, wherein the metakaolin is powder of more than 200 meshes obtained by calcining natural kaolin at 600-900 ℃; the particle size of the fly ash is 1-100 mu m, and the content of silicon oxide and aluminum oxide is more than 70 percent.
7. The fly ash geopolymer concrete of claim 1, wherein the ceramic microsphere particles are selected from solid ceramic microspheres or hollow ceramic microspheres, and the ceramic microsphere particle size ranges from 10 to 30 μm.
8. The preparation method of the fly ash geopolymer concrete as claimed in claim 1, which comprises the following steps:
(1) preparing modified ceramic microsphere particles: fully and uniformly stirring and mixing the acrylate emulsion and/or the styrene-acrylic emulsion and the silica sol, adding the corrosion and rust inhibitor, dispersing and stirring uniformly to obtain a spraying liquid, uniformly spraying the spraying liquid on the surface of the ceramic microsphere by using a spraying device, and drying at the temperature of 60-90 ℃ to obtain modified ceramic microsphere particles;
(2) preparing an alkaline activator mixture in advance: fully mixing one or more of sodium hydroxide, potassium hydroxide and potassium silicate with an alkaline activator consisting of water glass, stirring to dissolve, and standing at room temperature for later use;
(3) preparation of geopolymer gel material: firstly, mixing fly ash and metakaolin, then adding an alkaline activator mixture prepared in advance, fully stirring, adding polymer fiber, mixing and stirring;
(4) preparation of geopolymer concrete: adding coarse aggregate and fine aggregate into a stirring device, adding geopolymer cementing material, stirring, adding modified ceramic microsphere particles, and fully stirring to prepare the fly ash geopolymer concrete.
9. The preparation method according to claim 8, wherein the spraying process in step (1) is performed at a temperature of 50-60 ℃, and the obtained modified ceramic microspheres are sieved with a 300-400 mesh sieve.
10. The use of the fly ash geopolymer concrete of claim 1 in the construction of saline-alkali soil engineering, ocean engineering, chemical plants, pharmaceutical or chemical fertilizer production plants.
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