CN110746153A - Alkaline electrolyzed water fly ash concrete and preparation method thereof - Google Patents

Abstract

The invention provides alkaline electrolyzed water fly ash concrete and a preparation method thereof, belonging to the field of concrete preparation. The invention provides alkaline electrolyzed water fly ash concrete which is prepared from the following raw materials: cement, fly ash, broken stone, sand, a polycarboxylic acid water reducing agent and alkaline electrolyzed water. The invention improves the strength and durability of the fly ash concrete by adding the alkaline electrolyzed water as the mixing water into the fly ash concrete, and has good economic and environmental benefits. The results of the examples show that the alkaline electrolyzed water used as the mixing water for preparing the fly ash concrete can play a role of an alkali activator to excite the activity effect of the fly ash and effectively improve the working performance, the mechanical property, the chloride ion penetration resistance and the carbonization resistance of the fly ash concrete.

Description

Alkaline electrolyzed water fly ash concrete and preparation method thereof

Technical Field

The invention belongs to the field of concrete preparation, and particularly relates to alkaline electrolyzed water fly ash concrete and a preparation method thereof.

Background

SiO in fly ash component₂And Al₂O₃The content accounts for more than 60 wt% of the total content, and the volcanic ash admixture is a volcanic ash admixture with potential activity, and contributes to the improvement of concrete strength and performance mainly due to the activity effect. The activity effect of the fly ash is mainly determined by the active aluminosilicate glass body, and the more the aluminosilicate glass body content is, the stronger the pozzolanic activity effect is. Because the aluminosilicate glass body is a metastable structure which keeps the arrangement mode of a high-temperature liquid structure, the aluminosilicate glass body has high chemical stability under normal temperature and normal pressure, can not be spontaneously hydrated and hardened to form strength, and needs to be excited, otherwise, the fly ash has low activity in the early stage, and the activity effect in concrete is exerted very slowly and can be shown in the later stage. Therefore, the early hydration reaction of the fly ash concrete is slow, the strength is low, and the defect seriously restricts the engineering application of the large-dosage fly ash concrete.

The current methods for the activation of fly ash are roughly divided into physical activation and chemical activation. Firstly, the physical excitation methods such as temperature elevation or grinding processing and the like are carried out on the fly ash, so that the defects on the surface of a glass body of the fly ash are increased, a network structure is more easily damaged, and the reaction capability of the fly ash is improved, but the defects of long grinding time, high energy consumption, high cost, complex working procedures, adaptability problem of a grinding aid and materials and the like exist, the activity is difficult to greatly improve, and the construction is not facilitated; secondly, chemical excitation methods such as alkali excitant, sulfate excitant or chloride excitant are adopted to improve the early strength of the large-doped fly ash concrete, but the technical defects of the following aspects exist: (1) the introduced alkali activator only has a stage absorption reaction on the activity of the fly ash, although the early strength can be improved, the adaptability of the polycarboxylate superplasticizer can be greatly influenced, and the later strength and durability of concrete are reduced; (2) the concentration of the introduced alkali activator is too low to reach the pH value required by the dissolution of the aluminum-silicon glass body, so that the excitation effect is not ideal, and the early strength of the large-doped fly ash concrete cannot be improved; the concentration is too high, so that the caustic soda undoubtedly brings serious negative effects on human health and environment, and phenomena such as alkali precipitation, saltpetering and the like are very easy to occur in the using process, so that the caustic soda is not beneficial to actual construction and popularization and application, such as alkali activators such as sodium carbonate, water glass and the like.

Disclosure of Invention

In view of the above, the invention aims to provide an alkaline electrolyzed water fly ash concrete and a preparation method thereof.

In order to achieve the above purpose, the invention provides the following technical scheme:

the invention provides alkaline electrolyzed water fly ash concrete which is prepared from the following raw materials:

cement, fly ash, broken stone, sand, a polycarboxylic acid water reducing agent and alkaline electrolyzed water;

the water-cement ratio of the alkaline electrolyzed water fly ash concrete is 35-40%; the mass ratio of the cement to the fly ash is 1.5-9: 1; the mass ratio of the polycarboxylate superplasticizer to the cement is 0.012-0.020: 1; the mass ratio of the broken stone to the cement is 2.6-4.3: 1, the sand rate is 36-43%; the mass ratio of the alkaline electrolyzed water to the cement is 35-60%.

Preferably, the alkaline electrolyzed water is produced by a method comprising the steps of:

and electrolyzing the strong base salt electrolyte solution to produce alkaline electrolyzed water at the cathode.

Preferably, the pH value of the alkaline electrolyzed water is 12-13, and the oxidation-reduction potential value is 167-210 mv.

Preferably, an ion exchange diaphragm is arranged between the cathode region and the anode region of the electrolytic cell.

Preferably, the permeability of the ion exchange membrane is 0.15-0.30 cc/cm²·min。

Preferably, the voltage of the electrolysis is 380V, the frequency is 50Hz, the current is 19A, and the time is 15-30 min.

Preferably, the fineness modulus of the fly ash is 13.11-20.

Preferably, the water reducing rate of the polycarboxylate superplasticizer is 25-35%.

The invention also provides a preparation method of the alkaline electrolyzed water fly ash concrete, which comprises the following steps:

and mixing cement, fly ash, broken stone, sand, a polycarboxylic acid water reducing agent and alkaline electrolyzed water, and curing to obtain the alkaline electrolyzed water fly ash concrete.

The invention provides alkaline electrolyzed water fly ash concrete which is prepared from the following raw materials: cement, fly ash, broken stone, sand, a polycarboxylic acid water reducing agent and alkaline electrolyzed water; the water-cement ratio of the alkaline electrolyzed water fly ash concrete is 35-40%; the mass ratio of the cement to the fly ash is 1.5-9: 1; the mass ratio of the polycarboxylate superplasticizer to the cement is 0.012-0.020: 1; the mass ratio of the broken stone to the cement is 2.6-4.3: 1, and the sand rate is 36-43%; the mass ratio of the alkaline electrolyzed water to the cement is 35-60%. The H-O ionic bond in the alkaline electrolyzed water added in the invention has the characteristics of long bond length and large bond angle, the attraction between the H-O ionic bond and water molecules is reduced, and the alkaline electrolyzed water has higher reaction activity. On one hand, the alkaline electrolyzed water is a small molecular group, has strong penetrability, can quickly permeate into the alumina-silica-glass network structure of the fly ash, accelerates the fracture of Si-O bonds and Al-O bonds on the surface of fly ash particles, promotes the depolymerization of the Si-O-Al network structure, forms more free unsaturated active bonds, and the generated unsaturated active bonds are easy to react with hydration products Ca (OH) of concrete₂The secondary reaction is carried out to generate gelling products of hydrated calcium silicate and hydrated aluminum silicate, which not only improves the interface structure between cement and coarse aggregate, but also plays a role in filling the cement pore structure, thereby improving the strength and durability of the fly ash concrete. On the other hand, the solution of alkaline electrolyzed water has a large number of free small molecular functional groups (OH)^-、SiO₃ ^2-、CO₃ ^2-And HCO₃ ^-) OH of negative potential^-Ions and positively charged metal ions, in which the small molecule functional group and the negatively charged OH group^-Ions can be wrapped on the surfaces of cement and fly ash particles to form a double-electron-layer structure, and electrostatic repulsion enables the cement and fly ash particles to be uniformly dispersed, more free water is released, and the reaction capacity is improvedPromoting the hydration reaction of concrete to generate more C-S-H gelling products and Ca (OH)₂The porosity is reduced, the compactness is improved, the activity effect of the fly ash is excited, and the strength and the durability of the fly ash concrete are improved. The alkaline electrolyzed water added in the invention is alkaline solution, is different from caustic alkali, can not cause human skin damage and environmental pollution, is green and pollution-free clean water, and can be used as drinking water. The results of the examples show that the alkaline electrolyzed water serving as the blending water is added into the fly ash concrete to play a role of an alkaline activator to activate the activity effect of the fly ash, so that the working performance, the mechanical property, the chloride ion penetration resistance and the carbonization resistance of the fly ash concrete are effectively improved, and the 28d compressive strength of the fly ash concrete is increased by 1.5-21.2 percent compared with that of common tap water concrete.

Drawings

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

FIG. 1 is a graph represented by K₂CO₃The electrolyte solution is taken as an example, and the invention is a schematic diagram of the principle of preparing alkaline electrolyzed water;

FIG. 2 is a comparison graph of water consumption of fly ash concrete with different mixing water;

FIG. 3 is a graph showing the results of testing the compressive strengths of fly ash concretes of different mixing water, wherein (a) is the compressive strength of 3d, (b) is the compressive strength of 14d, and (c) is the compressive strength of 28 d;

FIG. 4 is a graph comparing the permeability coefficient of 28d chloride ion for different mixed water fly ash concrete samples;

FIG. 5 is a graph showing the comparison of the carbonization depths of different water-mixed fly ash concrete samples;

FIG. 6 is an XRD spectrum of a 3d sample of ordinary tap water fly ash concrete, wherein a is PT-0%, b is PT-10%, c is PT-20%, d is PT-30%, and e is PT-40%;

FIG. 7 is an XRD spectrum of alkaline electrolyzed water fly ash concrete 3d sample, wherein a is DJ-0%, b is DJ-10%, c is DJ-20%, d is DJ-30%, and e is DJ-40%;

FIG. 8 shows Ca (OH) values of various water-mixed fly ash concrete samples₂A content comparison graph;

FIG. 9 is a schematic view of the adsorption of cement particles on the surface of fly ash concrete;

FIG. 10 is a schematic diagram illustrating the principle of alkaline electrolyzed water exciting the activity of fly ash.

Detailed Description

The invention provides alkaline electrolyzed water fly ash concrete which is prepared from the following raw materials:

cement, fly ash, broken stone, sand, a polycarboxylic acid water reducing agent and alkaline electrolyzed water.

In the invention, the water-cement ratio of the alkaline electrolyzed water fly ash concrete is 35-40%, more preferably 37-39%, the water in the water-cement ratio is the dosage of the alkaline electrolyzed water, and the ash in the water-cement ratio is the sum of the dosages of the cement and the fly ash; the mass ratio of the cement to the fly ash is 1.5-9: 1, and preferably 4-9: 1; the mass ratio of the polycarboxylate superplasticizer to the cement is 0.012-0.020: 1, more preferably 0.012-0.015: 1; the mass ratio of the broken stone to the cement is 2.6-4.3: 1, more preferably 2.6-3.3: 1, the sand rate is 36-43%, and more preferably 40-42%; the mass ratio of the alkaline electrolyzed water to the cement is 35-60%, and preferably 36-46%.

In the invention, the cement is preferably ordinary portland cement, and is further preferably P.O 42.5 in the embodiment of the invention, the fineness modulus of the cement is preferably 80 μm, and the fineness screen residue is preferably 1.2-1.5%.

In the invention, the fly ash is preferably grade II fly ash, and the fineness modulus of the fly ash is preferably 13.11-20.0. The invention adopts the cement and the fly ash with specific fineness modulus, has large specific surface area, is easy to carry out hydration reaction with alkaline electrolyzed water in the alkaline electrolyzed water fly ash concrete, and improves the strength of the fly ash concrete.

In the invention, the crushed stone is preferably continuous graded natural granite crushed stone, and the particle size of the crushed stone is preferably 5-31.5 mm. In the present invention, the continuous gradation is preferably synthesized by calculation based on the aggregate cumulative screen residue ratio, and the continuous gradation is preferably 2.36mm (100%), 4.75mm (99.52%), 9.5mm (70.93%), 19.0mm (33.26%), 31.5mm (0.2%) and 37.5mm (0%) in this order.

In the invention, the sand is preferably natural second-grade river sand, and the fineness modulus of the sand is preferably 2.4-3.0.

In the invention, the polycarboxylate superplasticizer is preferably a PC high-performance polycarboxylate superplasticizer, and the water reducing rate of the polycarboxylate superplasticizer is preferably 30-35%. The concrete sources of the cement, the fly ash, the broken stone, the sand and the polycarboxylic acid water reducing agent are not particularly limited, and the conventional commercial products in the field can be adopted. The invention adopts the polycarboxylate superplasticizer with specific water reducing rate, can reduce the consumption of alkaline electrolyzed water and cement, and can improve the fluidity of the fly ash concrete, thereby improving the strength and durability of the alkaline electrolyzed water fly ash concrete.

In the examples of the present invention and the comparative examples, the physical mechanical property indexes of the cement used are shown in table 1; the chemical composition of the cement is shown in table 2; the chemical composition of the fly ash is seen in table 3; the physical property indexes of the crushed stones are shown in a table 4; the physical properties of the sand are shown in table 5.

TABLE 1 index of physical and mechanical properties of cement

TABLE 2 chemical composition of cement

TABLE 3 chemical composition of fly ash

TABLE 4 physical Properties of crushed stones

TABLE 5 physical Properties of Sand

In the invention, the pH value of the alkaline electrolyzed water is preferably 12-13, more preferably 12.45, and the oxidation-reduction potential value is preferably 167-210 mv. The alkaline electrolyzed water with the pH value of 12-13 is used for preparing the alkaline electrolyzed water fly ash concrete, so that the early activity of the fly ash can be effectively excited.

In the present invention, the alkaline electrolyzed water is preferably produced by a method comprising the steps of:

and electrolyzing the strong base salt electrolyte solution to produce alkaline electrolyzed water at the cathode.

In the present invention, the alkali salt electrolyte is preferably Na₂SiO₃、NaHCO₃Or K₂CO₃Further preferred in the present embodiment is K₂CO₃. In the invention, the electrolysis is preferably carried out in a full-automatic diaphragm type water ionizer, an ion exchange diaphragm is preferably arranged between a cathode area and an anode area of the full-automatic diaphragm type water ionizer, and the permeability of the ion exchange diaphragm is preferably 0.15-0.30 cc/cm²And min, the materials of the anode and cathode electronic plates in the cathode region and the anode region are preferably platinum titanium. The ion exchange membrane adopted by the invention has extremely low permeability to water molecules, and can only enable free ions and functional groups (K)⁺、H⁺、OH^-、CO₃ ^2-And HCO₃ ^-) And (4) passing. In the invention, the power supply for electrolysis is preferably pulse direct current, the voltage for electrolysis is preferably 380V, the frequency is preferably 50Hz, the current is preferably 19A, the water inlet temperature is preferably 10-40 ℃, the water inlet flow is preferably 25-30L/h, and the time is preferably 15-30 min. The inventionThe obtained alkaline electrolyzed water is preferably stored in a sealed container. The H-O ionic bond in the alkaline electrolyzed water prepared by adopting the specific electrolysis condition has the characteristics of long bond length and large bond angle, the attraction between the H-O ionic bond and water molecules is reduced, and the alkaline electrolyzed water has higher reaction activity and is beneficial to exciting the activity of the fly ash.

With K₂CO₃The electrolyte solution is taken as an example to illustrate the principle of preparing alkaline electrolyzed water, as shown in FIG. 1, and as can be seen from FIG. 1, K₂CO₃After the electrolyte solution is electrolyzed, the reaction formula generated on the anode side is 1-2, water molecules are decomposed into oxygen and hydrogen ions to generate carbonic acid, and the anode solution is acidic; the reaction formula generated on the cathode side is 3-4, water molecules are decomposed into hydrogen and free hydroxyl ions to generate KOH, and the cathode solution is alkaline.

2H₂O→O₂+4H⁺+4e^- Formula 1

CO₃ ^2-+2H⁺→H₂CO₃Formula 2

2H₂O+2e^-→2OH^-+H₂Formula 3

K⁺+OH^-→ KOH formula 4

The invention also provides a preparation method of the alkaline electrolyzed water fly ash concrete, which comprises the following steps:

and mixing cement, fly ash, broken stone, sand, a polycarboxylic acid water reducing agent and alkaline electrolyzed water, and curing to obtain the alkaline electrolyzed water fly ash concrete.

In the present invention, the mixing is preferably carried out in a forced concrete mixer, the mixing preferably being at a rate of 45 to 50 rpm for a period of 120 to 150 seconds. The present invention is not limited to the specific operation of the mixing, and the mixing method known to those skilled in the art can be adopted. The specific operation mode of the curing is not particularly limited in the invention, and the curing mode known to those skilled in the art can be adopted.

The alkaline electrolyzed water fly ash concrete provided by the present invention will be described in detail with reference to the following examples, but they should not be construed as limiting the scope of the present invention.

In the examples of the present invention and the comparative examples, the physical mechanical property indexes of the cement used are shown in table 1; the chemical composition of the cement is shown in table 2; the chemical composition of the fly ash is seen in table 3; the physical property indexes of the crushed stones are shown in a table 4; the physical properties of the sand are shown in table 5.

Examples

Will K₂CO₃The electrolyte solution is electrolyzed in a full-automatic diaphragm type water ionizer, and the permeability of an ion exchange diaphragm in the full-automatic diaphragm type water ionizer is 0.2cc/cm²Min, the power supply for electrolysis is pulse direct current, the voltage is 380V, the frequency is 50Hz, the current is 19A, the water inlet temperature is 20 ℃, the water inlet flow is 25L/h, and the electrolysis time is 15 min.

The properties of the produced alkaline electrolyzed water were characterized by pH value and ORP value, the pH value of the alkaline electrolyzed water was 12.45, ORP value (oxidation-reduction potential value) was 167mV, electrolytic concentration was 320ppm, and conductivity was 3300. mu.s/m.

In the embodiment of the invention, the water-cement ratio of the alkaline electrolyzed water fly ash concrete is 37 percent; the total dosage of the cement and the fly ash is 430kg/m³(ii) a The dosage of the polycarboxylic acid water reducing agent is 1.2 percent of the dosage of the cement, and the water reducing rate is 30 percent; the sand rate is uniformly determined to be 40 percent; determining the actual water consumption by controlling the slump of the concrete mixture within the range of 180-220 mm; the proportion of the fly ash to replace the cement is 0 percent, 10 percent, 20 percent, 30 percent and 40 percent respectively.

In the embodiment of the invention, common tap water fly ash concrete is used as a blank control group, and water adopted in the blank control group is common tap water; the alkali activator fly ash concrete is used as a control group, the alkali activator adopted in the control group is KOH solution, and the mixing amount of the alkali activator KOH is 1.5 percent and 6.45kg/m of the total using amount of the cement and the fly ash by mass³(ii) a The alkaline electrolyzed water fly ash concrete is used as an experimental group, water adopted in the experimental group is alkaline electrolyzed water prepared by the method, and the specific dosage condition of each group of experimental raw materials is shown in table 6.

Preparing different fly ash concretes in a forced concrete mixer at the room temperature of 20 +/-2 ℃, preparing 45L of concrete in each group of experiments, and removing a mould for standard curing after 24 hours, wherein the standard of curing is GB/T50081-2002 standard of test method for mechanical properties of common concrete. When the sample reaches the specified age, the working performance, the mechanical property, the chloride ion penetration resistance and the carbonization resistance of the fly ash concrete under different series of conditions are respectively measured.

TABLE 6 design of mixing ratio of different mixing water fly ash concrete tests

Workability of concrete

FIG. 2 is a comparison graph of water consumption of different mixed water fly ash concrete, and it can be seen from the graph that, under the condition of slump of 180-220 mm, the water consumption of different mixed water fly ash concrete is obviously different, and the difference is from large to small: the common tap water fly ash concrete is more than the alkaline activator fly ash concrete is more than the alkaline electrolyzed water fly ash concrete. For the alkaline electrolyzed water fly ash concrete, the water consumption of the alkaline electrolyzed water fly ash concrete is reduced along with the increase of the substitution rate of the fly ash. The high activity and ionic property of the alkaline electrolyzed water accelerate the hydration of cement to wrap aggregate in the process of mixing with the cement, reduce the adsorption effect of the mud content on the water reducing agent and further reduce the water consumption; meanwhile, the surface of the fly ash is of a glass body structure and approaches to a spherical shape, and the ball effect improves the workability of concrete, so that the water consumption of the concrete reaching the same slump is further reduced, and the effect of reducing water is achieved, so that the workability of the fly ash concrete can be obviously improved by the alkaline electrolyzed water.

Mechanical properties of concrete

The mechanical property test method refers to the standard of ordinary concrete mechanical property test method (GB/T50081-2002). The sample sizes are uniformly 100mm multiplied by 100mm, the compressive strength of 3d, 14d and 28d are respectively tested after the standard curing chamber is cured to the specified age, and the test results are shown in figure 3.

Fig. 3 is a graph of the test results of the compressive strengths of different mixing water fly ash concretes, wherein (a) is 3d compressive strength, (b) is 14d compressive strength, and (c) is 28d compressive strength, and it can be seen from the graph that no matter the early strength (3d) or the later strength (28d), when the substitution rate of fly ash is constant, the strength grades of different fly ash concretes are sequentially from large to small: alkaline electrolysis water fly ash concrete (DJ) > alkaline excitant fly ash concrete (JF) > common tap water fly ash concrete (PT). Meanwhile, when the substitution rate of the fly ash is 20%, the strength of the alkaline electrolyzed water fly ash concrete at each age period reaches the highest value; when the substitution rate exceeds 20%, the strength of the alkaline electrolyzed water fly ash concrete tends to be reduced along with the increase of the substitution rate of the fly ash. However, even if the substitution rate of the fly ash reaches 40%, the strength of the alkaline electrolyzed water fly ash concrete is still higher than that of the common tap water cement concrete (0% of the substitution rate of the fly ash). This shows that the strength of the alkaline electrolyzed water concrete mixed with 40% fly ash is still higher than that of the common tap water cement concrete, but the cost is obviously reduced.

Taking the 28d strength as an example, when the substitution rate of the fly ash is 0%, 10%, 20%, 30% and 40%, the 28d compressive strength of the alkaline electrolyzed water fly ash concrete is increased by 7.2%, 15.9%, 21.2%, 10.1% and 1.5% respectively compared with that of the ordinary tap water portland cement concrete. Therefore, the alkaline electrolyzed water has a remarkable effect of exciting the activity of the fly ash. In addition, under the condition of the same substitution rate of the fly ash, the 3d strength of the alkali-activated fly ash concrete is lower than that of the alkaline electrolyzed water concrete; the 28d compressive strength of the alkaline activator fly ash concrete is slightly lower than the 28d strength of alkaline electrolyzed water fly ash concrete series, and the difference is not great. Meanwhile, the law of the activity excitation effect on the fly ash is similar, and the excitation effect is most obvious when the substitution rate of the fly ash is 20%, and the strength of the fly ash concrete reaches the highest.

Resistance of concrete to penetration of chloride ions

The chlorine ion permeability resistance of the concrete is measured by a rapid chlorine ion migration coefficient method (RCM method), the penetration and erosion of chlorine ions in the concrete are accelerated by current, the penetration depth of the chlorine ions in a period of time is recorded, and the diffusion coefficient of the chlorine ions is calculated by combining a formula.

FIG. 4 is a comparison graph of the 28d chloride ion permeability coefficients of different water-mixed fly ash concrete samples, and it can be seen from the graph that the chloride ion permeability coefficients of different concretes are as follows from large to small: the common tap water fly ash concrete is more than the alkali-activated fly ash concrete is more than the alkaline electrolyzed water fly ash concrete. Therefore, the common tap water fly ash concrete has the worst chloride ion permeation resistance, and the alkaline electrolyzed water fly ash concrete has the best chloride ion permeation resistance at the substitution rate of 20 percent. Meanwhile, along with the increase of the substitution rate of the fly ash, the chloride ion permeability coefficient of the alkaline electrolyzed water fly ash concrete is increased, and the impermeability is reduced. When the substitution rate of the fly ash is improved to 40 percent, the chloride ion permeability coefficient of the alkaline electrolyzed water fly ash concrete is still lower than that of the alkaline electrolyzed water fly ash concrete. The change rule of the chlorine ion permeability resistance of the alkali-activated fly ash concrete is basically consistent with that of the alkaline electrolyzed water concrete, and the optimum chlorine ion permeability resistance change rule and the change rule of the alkaline electrolyzed water concrete are both reached when the substitution rate is 20 percent; however, the chloride ion permeability coefficient of the alkali-activated fly ash concrete is higher than that of the alkaline electrolyzed water fly ash concrete, and the chloride ion permeability resistance is obviously inferior to that of the alkaline electrolyzed water fly ash concrete.

Anti-carbonization performance of concrete

The concrete carbonation performance test is carried out according to GB/T50082-2009, the size of a prism sample is 100mm multiplied by 400mm, 3 blocks are in one group, and CO is contained in a carbonation test box₂The concentration of the phenolphthalein is controlled to be 18-22%, the humidity is controlled to be 65-75%, the temperature is controlled to be 15-25 ℃, after the sample reaches the specified age, the sample is dried and then split at the middle part, phenolphthalein alcohol solution with the concentration of 1% (the alcohol solution contains 20% of distilled water) is used for spraying treatment, phenolphthalein changes into red and purple when being subjected to alkali, and the phenolphthalein does not change color when being acidic and neutral. Determining the carbonization depth of each point according to the width of the edge white color to judge the concrete sampleThe carbonization performance of (2).

Fig. 5 is a comparison graph of the carbonization depths of different mixed water fly ash concrete samples, and it can be seen from the graph that the carbonization depths of different concretes are as follows from large to small: the common tap water fly ash concrete is more than the alkali-activated fly ash concrete is more than the alkaline electrolyzed water fly ash concrete. When the substitution rate of the fly ash is 20%, the carbonization depth of the alkaline electrolyzed water fly ash concrete is the minimum. Therefore, the carbonization resistance of common tap water concrete is the worst, and the carbonization resistance of alkaline electrolyzed water fly ash concrete is the best. Meanwhile, the carbonization resistance of the alkali-activated fly ash concrete is obviously inferior to that of the alkaline electrolyzed water fly ash concrete.

X-ray diffraction Pattern (XRD) analysis

The concrete sample was cut into thin pieces having a diameter of 50 mm and a height of 5mm along the central portion thereof by a cutter, avoiding the use of thin pieces with coarse aggregate for crushing. Cutting the thin sheet into 2.5-5.0 mm granular samples by using sharp-nose pliers, placing the granular samples in a drying box at 60 ℃ for drying for 12h, taking out the granular samples after drying, placing the granular samples in a vibration mill for grinding, and performing XRD analysis on micro powder collected and passing through a 40-micron sieve as a final test sample.

FIG. 6 is an XRD spectrum of a 3d sample of ordinary tap water fly ash concrete, wherein a is PT-0%, b is PT-10%, c is PT-20%, d is PT-30%, and e is PT-40%; FIG. 7 is an XRD spectrum of alkaline electrolyzed water fly ash concrete 3d sample, wherein a is DJ-0%, b is DJ-10%, c is DJ-20%, d is DJ-30% and e is DJ-40%. As can be seen from FIGS. 6 to 7, SiO in the diffraction pattern of ordinary tap water concrete₂、CaCO₃The peak of (a) is most obvious, which is mainly derived from fine aggregate in the sample, and some ettringite is generated besides the hydrated cementitious product; in contrast, when the substitution rate of fly ash is 0%, the diffraction pattern of the alkaline electrolyzed water concrete is except SiO₂In addition to the ettringite phase, a certain content of K₂Ca₅(SO₄)₆And potassium feldspar (K)₂O·Al₂O₃·SiO₂) And (4) generating. This is due to the early stage, alkaliCertain concentration of potassium hydroxide in the electrolyzed water and CaO-Al in the cement₂O₃·SiO₂Reaction takes place to produce a small amount of K₂Ca₅(SO₄)₆Potassium feldspar and calcium hydroxide, thereby improving the strength of the concrete. When the fly ash is added into the alkaline electrolytic water concrete, SiO is removed₂Ettringite phase and potash feldspar (K)₂O·Al₂O₃·SiO₂) In addition to the generation, there is also a significant amount of hydrated calcium sulfoaluminate (CaO. Al)₂O₃·2SiO₂·4H₂O) diffraction peaks, which are due to the fact that the alkaline environment in alkaline electrolyzed water can act as a catalyst during the hardening process of cement ("alkali excitation"), so that the silicon and aluminum compounds in cement and fly ash are easier to dissolve to form sodium silicate and sodium metaaluminate, and further Ca (OH)₂Calcium silicate and calcium aluminate minerals are formed by reaction, and the hardening product of the cement is calcium aluminosilicate, so that the compressive strength and the durability of the fly ash concrete are improved.

Next, as can be seen from FIGS. 6 to 7, Ca (OH) increases with the substitution rate of fly ash₂The diffraction peak is gradually weakened because the fly ash has the volcanic ash effect and the active SiO₂And Al₂O₃Will continuously consume Ca (OH) in the mortar₂Generates cementitious products such as calcium silicate hydrate, and thus CaO. SiO₂·nH₂Increased content of O, Ca (OH)₂The content gradually decreases.

Hydration products of concrete Ca (OH)₂Content analysis

The invention was carried out by means of differential thermal analysis equipment with a maximum temperature of 1500 ℃ according to Ca (OH)₂Performing dehydration reaction at about 450-500 ℃, and calculating to obtain a cement hydration product Ca (OH) in the sample₂The content of (a). Determination of Ca (OH) in ordinary tap water concrete and alkaline electrolyzed water concrete by adopting differential thermal analysis (TG/DTA)₂The content of (a). The test temperature range is room temperature-1000 ℃, and the heating speed is 20 ℃/min.

FIG. 8 shows Ca (OH) values of various water-mixed fly ash concrete samples₂The content is compared with the figure, and the figure shows that the content is compared with the common contentThe alkaline electrolytic water can promote the hydration reaction of cement in the concrete to generate more C-S-H gel and Ca (OH)₂The porosity of the concrete structure is reduced, and the compactness of the concrete is improved, so that the strength of the concrete is improved. Meanwhile, the Ca (OH) in the fly ash concrete is caused because the fly ash replaces a certain amount of cement₂The content is reduced; in addition, alkaline electrolyzed water can excite the activity of the fly ash and Ca (OH) generated by hydration₂Will further react with the fly ash for a second time, resulting in Ca (OH)₂The content is obviously reduced.

Alkaline electrolyzed water excited fly ash activity mechanism analysis

According to the experimental results, the mechanism of the activity effect of the fly ash in the alkaline electrolyzed water excited concrete can be analyzed.

FIG. 9 is a schematic diagram showing the adsorption of the surface of cement particles in fly ash concrete, and it can be seen that the cement particles have a large positive charge (C) on the surface thereof at the initial stage of hydration₃A，C₃S) adsorption sites, and a very strong negative charge (a large number of functional groups, OH) in highly active alkaline electrolysis water^-，CO₃ ^2-) Can be completely adsorbed on the surface of cement particles to form a diffused double electronic layer ionic structure, so that the cement particles are charged in the same way. Due to the electrostatic repulsion, the double-electronic-layer structure can uniformly disperse cement particles, the particle accumulation and flocculation rate is slowed down, bound free water in concrete is released, thereby promoting the cement hydration reaction and the connection between particles, and leading to more high-strength calcium silicate hydrate gel and Ca (OH)₂And sufficient calcium content is provided for the secondary hydration reaction of the fly ash. The fluidity and the workability of the concrete are improved, the total porosity of the concrete is reduced, the compactness of the concrete is increased, and the strength and various durability performances are obviously improved.

FIG. 10 is a schematic diagram of the basic electrolyzed water for activating the activity of fly ash, and it can be seen from the diagram that certain concentration of potassium hydroxide in the basic electrolyzed water will react with un-hydrated CaO. Al₂O₃·SiO₂The reaction takes place to produce a small amount of potassium of higher strengthFeldspar and calcium hydroxide are favorable for exciting the activity effect of the fly ash and further improving the performance of the concrete, the reaction equation is shown as formula 5,

CaO·Al₂O₃·SiO₂+6KOH＝3K₂O·Al₂O₃·SiO₂+3Ca(OH)₂formula 5;

in addition, since the alkaline electrolyzed water is a small molecular group and has strong penetrability, OH in the alkaline environment^-Under the action of ions, the active SiO can quickly permeate into the glass body structure of the fly ash₂And Al₂O₃The reaction is carried out to accelerate the excitation of the activity effect of the fly ash. Simultaneously, the OH content in a hydration reaction system is increased^-The ion concentration is also very necessary to promote the activity of the fly ash. High activity, strong alkalinity and Na in solution of alkaline electrolyzed water⁺、K⁺、OH^-Under the action of ions, Si-O and Al-O bonds on the surface of the fly ash glass body can be broken rapidly, so that the polymerization degree of Si-O-Si and Si-O-Al networks is reduced, a polymer structure is decomposed to form free unsaturated active bonds, so that silicon dioxide and aluminum oxide in fly ash particles are dissolved out greatly, the activity effect of the fly ash is excited, and the fly ash is further mixed with Ca (OH)₂The reaction forms higher-strength hydrated calcium silicate and calcium aluminate minerals, and the hardening product of the cement is calcium aluminosilicate (CaO. Al)₂O₃·2SiO₂·4H₂O) diffraction peak, thereby improving the strength of the fly ash concrete, reducing the porosity, and improving the durability of the fly ash concrete due to a more compact structure.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (9)

1. The alkaline electrolyzed water fly ash concrete is characterized by being prepared from the following raw materials:

cement, fly ash, broken stone, sand, a polycarboxylic acid water reducing agent and alkaline electrolyzed water;

the water-cement ratio of the alkaline electrolyzed water fly ash concrete is 35-40%; the mass ratio of the cement to the fly ash is 1.5-9: 1; the mass ratio of the polycarboxylate superplasticizer to the cement is 0.012-0.020: 1; the mass ratio of the broken stone to the cement is 2.6-4.3: 1, and the sand rate is 36% -43%; the mass ratio of the alkaline electrolyzed water to the cement is 35-60%.

2. The alkaline electrolyzed water fly ash concrete according to claim 1, wherein the alkaline electrolyzed water is prepared by a method comprising the steps of:

and electrolyzing the strong base salt electrolyte solution to produce alkaline electrolyzed water at the cathode.

3. The alkaline electrolyzed water fly ash concrete according to claim 1 or 2, wherein the pH value of the alkaline electrolyzed water is 12-13, and the oxidation-reduction potential value is 160-210 mV.

4. The alkaline electrolyzed water fly ash concrete according to claim 2, wherein an ion exchange membrane is arranged between the cathode region and the anode region of the electrolysis cell.

5. The alkaline electrolyzed water fly ash concrete according to claim 4, wherein the permeability of the ion exchange membrane is 0.15-0.30 cc/cm²·min。

6. The alkaline electrolyzed water fly ash concrete according to claim 2 or 4, wherein the electrolysis voltage is 380V, the frequency is 50Hz, the current is 19A, and the time is 15-30 min.

7. The alkaline electrolyzed water fly ash concrete according to claim 1, wherein the fineness modulus of the fly ash is 13.11-20.

8. The alkaline electrolyzed water fly ash concrete according to claim 1, wherein the water reduction rate of the polycarboxylic acid water reducing agent is 25-35%.

9. The preparation method of the alkaline electrolyzed water fly ash concrete as claimed in any one of claims 1 to 8, which is characterized by comprising the following steps:

and mixing cement, fly ash, broken stone, sand, a polycarboxylic acid water reducing agent and alkaline electrolyzed water, and curing to obtain the alkaline electrolyzed water fly ash concrete.

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