CN111848053A - A kind of fly ash-based nano-micron crystal nucleus admixture suitable for concrete prefabricated components and its preparation method and application - Google Patents

Abstract

The invention provides a fly ash-based nano-micron crystal nucleus admixture suitable for a concrete prefabricated part and a preparation method and application thereof, wherein the fly ash-based nano-micron crystal nucleus admixture is mainly prepared from the following components in parts by weight through a liquid phase grinding process: fly ash: 20-40 parts of water: 130-170 parts of ion dissolving agent: 1.8-2.4 parts of a surface modifier: 1.2 to 1.8 portions. The preparation method of the fly ash-based nano-micron crystal nucleus additive comprises the following steps: and mixing the fly ash, the ion dissolving agent, the surface modifier and water, and grinding to obtain the nano-micro fly ash crystal nucleus additive. When the fly ash-based nano-micron crystal nucleus admixture prepared by the method is applied to a concrete prefabricated part, energy can be saved, the early strength of the concrete can be improved, the later strength of the concrete can be kept stable, and the overall strength of the concrete can be improved.

Description

A fly ash-based nano-micron nuclei admixture suitable for prefabricated concrete components and Preparation method and application thereof

technical field

The invention belongs to the technical field of construction engineering materials, and in particular relates to a fly ash-based nano-micron crystal nucleus admixture suitable for concrete prefabricated components and a preparation method and application thereof.

Background technique

The vigorous development of building industrialization has higher and higher requirements for prefabricated components. There are two main methods for prefabricated components at this stage. One is to use steam curing, but there are disadvantages such as large energy consumption, maintenance equipment and cost. It also seriously restricts the application of steam curing in prefabricated components, so steam-free curing early-strength concrete has become a major research trend.

The second is by adding early-strength agents. At present, early-strength agents can be divided into three categories: inorganic, organic and composite based on their chemical components. Traditional early-strength agents are mostly inorganic types, such as chloride salts, which use industrial raw materials, and the production cost is high, and their use will be limited, for example, it will aggravate the corrosion of steel bars; organic early-strength agents such as alcohol amines also have many shortcomings. It is very sensitive to the amount of mixing, resulting in the inability to accurately control the setting time and affecting the early workability of concrete; the composite early-strength agent is compounded with a variety of early-strength agents, which requires high operation. There may be interactions and effects between the additives, which may not achieve the expected effect or even make the admixture ineffective.

In recent years, many industry researchers have found that adding nanoparticles to cement concrete can promote cement hydration, significantly increase the rate of cement hydration, and thus improve the early strength of concrete, such as nano-silica, etc. The crystal nucleus type early strength agent has complicated preparation process and high cost.

For example, CN109534755A discloses a special low-temperature steam curing concrete for prefabricated components and a preparation method thereof, belonging to the technical field of building materials. The strength of concrete under the condition of steam curing at 25℃ for 24h can reach the demoulding strength (15MPa). The invention needs to use the steam curing process, consumes a lot of energy, aggravates the expansion effect, affects the later strength, and adds a variety of admixtures and composite early strength agents to increase the cost.

For example, CN108249846A discloses a steam curing-free concrete prefabricated member and its forming method, which belong to the technical field of building materials. The invention adopts inorganic-organic composite early strength agent and crystal nucleus type early strength agent to be added to the raw materials of concrete precast members in a certain proportion. In order to improve its early strength, the inorganic salt early strength components in the inorganic-organic early strength agent are compounded by at least two of sodium sulfate, sodium carbonate, calcium nitrate, and calcium nitrite, and the organic early strength components are compounded. It is composed of at least 2 of calcium formate, calcium acetate, methanol and triethanolamine, and the nucleated early strength agent is composed of sodium silicate and calcium nitrate. The early strength agent and the early strength agent of the invention need A variety of materials are compounded, which greatly increases the cost of concrete.

For example, CN109369088A discloses a method for configuring steam-free concrete containing an early-strength agent, which belongs to the technical field of cement and cement concrete admixtures. The early-strength agent of the invention is mixed with cement powder, and then sand, stone and water are added for mixing. After that, the early strength is significantly improved, but the early strength agent is composed of nano-silicon dioxide with a purity of more than 95%, lithium sulfate with a purity of more than 95% and a polycarboxylate water reducer. The production cost of nano-silicon dioxide is high, and the production conditions are more severe, which seriously affects the large-scale application of the early strength agent.

With the development of the power industry, the emission of fly ash is increasing year by year. Improper handling of the huge amount of fly ash can have a negative impact on the environment. The fly ash contains a large amount of alumina and silica, which are secondary resources with development and utilization value. Using the potential activity of fly ash to develop a low-cost and excellent cement early strength agent, it can not only improve the early strength of cement concrete, but also use industrial waste as raw materials to save costs.

SUMMARY OF THE INVENTION

In order to overcome the deficiencies and defects existing in the prior art, the present invention intends to provide a fly ash-based nano-micron crystal nucleus admixture suitable for concrete prefabricated components, which can save energy, improve the early strength of concrete, and maintain the stability of the later strength of concrete. Improve the overall strength of concrete.

The technical scheme adopted by the present invention for solving the problems existing in the prior art is as follows:

A fly ash-based nano-micron crystal nucleus admixture suitable for concrete prefabricated components, characterized in that: by weight, the fly ash-based nano-micron crystal nucleus admixture is mainly composed of the following components through a liquid phase grinding process Preparation: fly ash: 20-40 parts, water: 130-170 parts, ion dissolution agent: 1.8-2.4 parts, surface modifier: 1.2-1.8 parts.

The ion-dissolving agent comprises a mixture of calcium hydroxide, slaked lime and carbide slag; the mass ratio of the calcium hydroxide, slaked lime and carbide slag is (1-1.2):1:(1-1.1).

The median particle size of the fly ash-based nano-micron crystal nucleus admixture is 50-150 nm.

The surface modifier includes a mixture of a polycarboxylate water reducer and an aliphatic water reducer; the volume ratio of the polycarboxylate water reducer to the aliphatic water reducer is (1.2-1.8): 1, wherein the polymer The solid content of the carboxylate superplasticizer is 30-50%, and the solid content of the aliphatic superplasticizer is 30-50%.

The fly ash is obtained by burning anthracite and asphaltene coal in thermal power plants, and is rich in SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ , the mass fraction of the three accounts for more than 70%, and the content of CaO is relatively small , and the loss on ignition is less than 6%.

The preparation method of the fly ash-based nano-micron crystal nucleus admixture comprises the following steps: mixing the fly ash, ion-dissolving agent, surface modifier and water, and grinding to obtain the nano-micron fly ash crystal nucleus The admixture is characterized in that, specifically comprises the steps:

Step 1. Take 20-40 parts by mass of fly ash, 1.8-2.4 parts of ion dissolving agent, 2.4-3.0 parts of surface modifier, 130-170 parts of water and 300-400 parts of zirconia grinding body and pour them into the planet at the same time In the ball mill, the planetary ball mill is sealed and fixed in the planetary ball mill and ground at a speed of 350-450 until the median particle size is below 150nm, and the fly ash nano-micron admixture A is obtained after sieving the zirconia;

Step 2. Add the admixture A in step 1 into water to prepare a fly ash-based nano-micron admixture slurry B, and the amount of the water is the amount of water required for the precast concrete component minus the amount of the fly ash admixture A in the fly ash admixture A. water content;

Step 3. At the same time, the slurry B in step 2 is added to the raw material of the precast concrete component, and the water-to-binder ratio is 0.5, wherein each cubic meter of the raw material of the prefabricated concrete component is formed by the following components: cement: 300Kg; slurry B: 155-160Kg; Machine-made sand: 780Kg; Crushed stone: 1080Kg;

Step 4. The cement, machine-made sand and crushed stone weighed according to the weight components described in the formula in step 3 are poured into the concrete mixer for dry mixing for 30s, so that the cementitious material is evenly distributed, and then slurry B is added and stirred for 5-15min to obtain mixture C;

Step 5, distributing the mixture C, and then curing until the strength meets the requirements, to obtain a concrete prefabricated member.

In the grinding step, the grinding body is a zirconia grinding body, wherein the zirconia grade specifications are: the diameter of the small ball is 0.5-1.0 mm, accounting for 50-100% of the total mass fraction; the diameter of the medium ball is 1.0-3.0 mm, accounting for the total mass fraction. 0-25% of the mass fraction; the diameter of the large ball is 3.0-5.0mm, accounting for 0%-25% of the total mass fraction.

The application of the fly ash-based nano-micron crystal nucleus admixture in cement-based materials: the content of the fly ash-based nano-micron crystal nucleus admixture is 1%-7% of the cement cementitious material.

The present invention has the following advantages:

1. The nano fly ash early-strength agent of the present invention takes fly ash as raw material, adopts wet grinding and physical grinding, then carries out chemical action on the basis of liquid phase grinding, and adds ion dissolution agent: Ca(OH) ₂ , slaked lime and calcium carbide slag, using Ca(OH) ₂ , slaked lime and calcium carbide slag form calcium ions, hydroxide ions in water, hydroxide ions can depolymerize silica and aluminum oxide in fly ash, calcium The ion energy and silicate ions form CSH gel, and the fly ash particles are ultra-fine to sub-micron level under the mechanical force of liquid-phase grinding. On the one hand, it provides crystal nuclei and attachment points for the growth of calcium silicate hydrate, which accelerates the growth of calcium silicate hydrate. The pore structure is more compact.

2. The present invention provides a new direction for the early strength agent of non-steam curing concrete. Through the early strength agent of nanocrystalline nucleation effect, the resource utilization rate of fly ash is greatly improved, and the additional value of fly ash products is improved. Moreover, the invention adopts liquid phase grinding to prepare the early strength agent, which can reduce the cost of the steam curing concrete early strength agent.

3. The present invention adopts the liquid phase grinding method to prepare the nano-fly ash admixture, the preparation process is simple, and the preparation process is easy to control. In the liquid phase grinding process, an ion leaching agent and a surface modifier are added to improve the liquid phase grinding efficiency and reduce the The energy consumption and the alkali excitation acting on the fly ash can further improve the efficiency of the nano fly ash early strength agent of the present invention.

4. The nano-micron fly ash crystal nuclei admixture of the present invention is externally mixed into C30 precast concrete according to 1%-7% of the cementitious material, and the compressive strength in 12h exceeds the demoulding strength (15MPa), and the strength continues to increase in 28 days. Therefore, the nano-micron fly ash-based admixture can effectively improve the early strength of precast concrete components without causing late strength shrinkage.

Detailed ways

Below by embodiment, the technical scheme of the present invention is described in further detail:

The fly ash adopted in the embodiment is discharged from a certain power plant in Wuhan; the water is tap water; the cement is ordinary Portland cement; the C30 concrete ratio configured in an experimental base in Wuhan is the benchmark.

Example 1

Step 1. Mix 35 parts by mass of fly ash, 150 parts of water and 300 parts of zirconia, wherein the ratio of small balls, medium balls and large balls is 4:1:1, and send them into a planetary ball mill at a speed of 400rps Grinding, adding 1.8 parts of ion dissolution agent and 2.4 parts of surface modifier, grinding to a median particle size of 150nm, and sieving zirconia to obtain fly ash-based nano-micron admixture A;

The ion dissolution agent is a mixture of calcium hydroxide, slaked lime and carbide slag, with a mass ratio of 1:1:1; the surface modifier includes a polycarboxylate water reducer and aliphatic water reducer, with a mass ratio of 1.2:1 , the solid content of polycarboxylate superplasticizer is 35%, and the solid content of aliphatic superplasticizer is 35%.

Step 2. Add the admixture A in step 1 into water to prepare a fly ash-based nano-micron admixture slurry B, and the amount of the water is the amount of water required for the precast concrete component minus the fly ash admixture A. of water content.

Step 3. Add the slurry B in step 2 to the raw material of the precast concrete component, and the water-to-binder ratio is changed to 0.5, wherein each cubic meter of the raw material of the precast concrete component is formed by the following components: cement: 300Kg; slurry B: 155Kg; Machine-made sand: 780Kg; Crushed stone: 1080Kg;

The specific methods applied to precast concrete are as follows:

The cement, machine-made sand and crushed stone weighed according to the weight components described in the formula in step 3 are poured into the concrete mixer for dry mixing for 30s, so that the cementitious material is evenly distributed, and then the slurry B is added and stirred for 5-15min to obtain the mixture C , the mixture C is distributed, and then cured until the strength meets the requirements, and the concrete prefabricated member is obtained.

Example 2

Step 1. Mix 35 parts by mass of fly ash, 150 parts of water and 300 parts of zirconia, wherein the ratio of small balls, medium balls and large balls is 4:1:1, and send them into a planetary ball mill at a speed of 400rps Grind, and add 2.0 parts of ionic dissolving agent and 2.8 parts of surface modifier, grind to a median particle size of 121 nm, and obtain fly ash-based nano-micron admixture A after sieving zirconia;

The ion-dissolving agent is a mixture of calcium hydroxide, slaked lime and carbide slag, with a mass ratio of 1.1:1:1.1; the surface modifier includes polycarboxylate water-reducing agent and aliphatic water-reducing agent, with a mass ratio of 1.2:1 , the solid content of polycarboxylate superplasticizer is 35%, and the solid content of aliphatic superplasticizer is 35%.

Step 2. Add the admixture A in step 1 into water to prepare a fly ash-based nano-micron admixture slurry B, and the amount of the water is the amount of water required for the precast concrete component minus the fly ash admixture A. of water content.

Step 3. Add the slurry B in step 2 to the raw material of the precast concrete component, and the water-to-binder ratio is changed to 0.5, wherein each cubic meter of the raw material of the precast concrete component is formed by the following components: cement: 300Kg; slurry B: 156Kg; Machine-made sand: 780Kg; Crushed stone: 1080Kg;

The specific methods applied to precast concrete are as follows:

The cement, machine-made sand and crushed stone weighed according to the weight components described in the formula in step 3 are poured into the concrete mixer for dry mixing for 30s, so that the cementitious material is evenly distributed, and then the slurry B is added and stirred for 5-15min to obtain the mixture C , the mixture C is distributed, and then cured until the strength meets the requirements, and the concrete prefabricated member is obtained.

Example 3

Step 1. Mix 30 parts by mass of fly ash, 150 parts of water and 300 parts of zirconia, wherein the ratio of small balls, medium balls and large balls is 4:1:1, and send them into a planetary ball mill at a speed of 400rps Grind, add 2.4 parts of ion dissolution agent and 3.0 parts of surface modifier, grind to a median particle size of 50nm, and obtain fly ash-based nano-micron admixture A after sieving zirconia;

The ion-dissolving agent is a mixture of calcium hydroxide, slaked lime and carbide slag, with a mass ratio of 1:1:1; the surface modifier includes polycarboxylate water-reducing agent and aliphatic water-reducing agent, with a mass ratio of 1.5:1 , the solid content of polycarboxylate superplasticizer is 35%, and the solid content of aliphatic superplasticizer is 35%.

Step 2. Add the admixture A in step 1 into water to prepare a fly ash-based nano-micron admixture slurry B, and the amount of the water is the amount of water required for the precast concrete component minus the fly ash admixture A. of water content.

Step 3. Add the slurry B in step 2 to the raw material of the precast concrete component, and the water-to-binder ratio is changed to 0.5, wherein each cubic meter of the raw material of the precast concrete component is formed by the following components: cement: 300Kg; slurry B: 160Kg; Machine-made sand: 780Kg; Crushed stone: 1080Kg;

The specific methods applied to precast concrete are as follows:

The cement, machine-made sand and crushed stone weighed according to the weight components described in the formula in step 3 are poured into the concrete mixer for dry mixing for 30s, so that the cementitious material is evenly distributed, and then the slurry B is added and stirred for 5-15min to obtain the mixture C , the mixture C is distributed, and then cured until the strength meets the requirements, and the concrete prefabricated member is obtained.

Example 4

Step 1. Mix 30 parts by mass of fly ash, 150 parts of water and 300 parts of zirconia, wherein the ratio of small balls, medium balls and large balls is 4:1:1, and send them into a planetary ball mill at a speed of 400rps Grind, add 2.2 parts of ion dissolving agent and 3.0 parts of surface modifier, grind to a median particle size of 84nm, and obtain fly ash-based nano-micron admixture A after sieving zirconia;

The ion dissolution agent is a mixture of calcium hydroxide, slaked lime and calcium carbide slag, and the mass ratio is 1:1:1; the surface modifier includes polycarboxylate water-reducing agent and aliphatic water-reducing agent, and the mass ratio is 1.8:1 , the solid content of polycarboxylate superplasticizer is 35%, and the solid content of aliphatic superplasticizer is 35%.

Step 2. Add the admixture A in step 1 into water to prepare a fly ash-based nano-micron admixture slurry B, and the amount of the water is the amount of water required for the precast concrete component minus the fly ash admixture A. of water content.

Step 3. Add the slurry B in step 2 to the raw material of the precast concrete component, and the water-to-binder ratio is changed to 0.5, wherein each cubic meter of the raw material of the precast concrete component is formed by the following components: cement: 300Kg; slurry B: 159Kg; Machine-made sand: 780Kg; Crushed stone: 1080Kg;

The specific methods applied to precast concrete are as follows:

The cement, machine-made sand and crushed stone weighed according to the weight components described in the formula in step 3 are poured into the concrete mixer for dry mixing for 30s, so that the cementitious material is evenly distributed, and then the slurry B is added and stirred for 5-15min to obtain the mixture C , the mixture C is distributed, and then cured until the strength meets the requirements, and the concrete prefabricated member is obtained.

Comparative Example 1

Comparative example 1 is a blank group, without adding nano-micron fly ash-based admixture, and configuring C30 concrete raw materials is formed by the following components: cement: 300Kg; fly ash: 60Kg; machine-made sand: 780Kg; crushed stone: 1080Kg; water : 165Kg;

The specific methods applied to precast concrete are as follows:

The cement, fly ash, machine-made sand, and crushed stone weighed according to the weight components described in the formula are poured into the concrete mixer for dry mixing for 30s, so that the cementitious material is evenly distributed, and the mixture A is obtained, and the mixture A is distributed, and then curing to obtain prefabricated concrete components.

With reference to the standard GB8076-2008, the mechanical properties of Example 1-Example 4 and Comparative Example 1 were tested, and the prepared C30 non-steam curing concrete was prepared. The specific performance indicators are shown in Table 1.

Table 1 Compressive strength test results of concrete members (unit: MPa)

Numbering 12h 1d 3d 7d 28d Example 1 15.2 18.6 23.6 36.3 47.2 Example 2 16.1 20.4 26.8 37.6 49.3 Example 3 17.4 24.8 30.2 42.8 53.6 Example 4 16.9 23.2 29.7 40.1 52.4 Comparative Example 1 5.1 7.9 21.7 33.3 43.5

It can be seen from Table 1 that the concrete strength of Examples 1-4 is greatly improved after adding 1%, 3%, 5%, and 7% of nano-micron fly ash-based admixtures; 1 In comparison, the strength of concrete mixed with nano-micron fly ash-based admixture increased from 5.1 MPa to 15.2-17.4 MPa at 12h, and reached 17.4 MPa and 16.9 MPa when the dosage was 5% and 7%, respectively. Reached the national standard demoulding strength (15MPa). And after adding fly ash early strength agent, the strength of 28d is still improved, and will not affect the later strength. Therefore, fly ash is used as a raw material to prepare a fly ash-based nano-micron admixture, which has a significant effect when applied to concrete, improves production efficiency, saves energy consumption, and reduces costs, thereby promoting the sustainable development of the cement concrete industry.

The protection scope of the present invention is not limited to the above-mentioned embodiments. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the scope and spirit of the present invention. If these changes and modifications belong to the scope of the claims of the present invention and their equivalents, the present invention is intended to include these changes and modifications.

Claims (6)

1. The fly ash-based nano-micron crystal nucleus additive suitable for the concrete prefabricated part is characterized in that: the fly ash-based nano-micron crystal nucleus admixture is mainly prepared from the following components in parts by weight through a liquid phase grinding process: fly ash: 20-40 parts of water: 130-170 parts of ion dissolving agent: 1.8-2.4 parts of a surface modifier: 1.2-1.8 parts; the fly ash-based nano-micro powder crystal nucleus admixture is mainly prepared by grinding a mixture of an ion dissolving agent, hydrated lime and carbide slag through a liquid phase; the mass ratio of the calcium hydroxide, the hydrated lime and the carbide slag is (1-1.2) to 1 (1-1.1); the median particle size of the fly ash-based nano-micro powder crystal nucleus additive is 50-150 nm.

2. The fly ash-based nano-micron crystal nucleus admixture suitable for the concrete prefabricated part as claimed in claim 1, wherein: the surface modifier comprises a mixture of a polycarboxylic acid water reducing agent and an aliphatic water reducing agent; the volume ratio of the polycarboxylic acid water reducing agent to the aliphatic water reducing agent is (1.2-1.8): 1, wherein the solid content of the polycarboxylic acid water reducing agent is 30-50 percent, and the solid content of the aliphatic water reducing agent is 30-50 percent.

3. The fly ash-based nano-micron crystal nucleus admixture suitable for the concrete prefabricated part as claimed in claim 1, wherein: the fly ash is obtained by burning anthracite and bituminous coal in a thermal power plant, and is rich in SiO₂、Al₂O₃And Fe₂O₃The mass fraction of the three components is more than 70%, the CaO content is relatively less, and the loss on ignition is less than 6%.

4. The preparation method of the fly ash-based nano-micron crystal nucleus additive suitable for the concrete prefabricated part as claimed in any one of claims 1 to 3, which is characterized by comprising the following steps:

step 1, 20-40 parts by mass of fly ash, 1.8-2.4 parts of ion dissolving agent, 2.4-3.0 parts of surface modifier, 170 parts of water and 400 parts of zirconia grinding body of 300-ion addition agent are poured into a planetary ball milling tank at the same time, the planetary ball milling tank is sealed and fixed in a planetary ball milling machine to grind at the rotating speed of 350-ion addition agent 450 until the median particle size is below 150nm, and the fly ash-based nano-micron additive A is obtained after the zirconia is sieved;

step 2, adding the admixture A obtained in the step 1 into water to obtain a fly ash-based nano-micron admixture slurry B, wherein the water consumption is obtained by subtracting the water content in the fly ash admixture A from the water consumption required by the precast concrete component;

and 3, adding the slurry B in the step 2 into the precast concrete member raw material at the water-cement ratio of 0.5, wherein each cubic meter of the precast concrete member raw material is formed by the following components: cement: 300 Kg; slurry B: 155-160 Kg; and (3) machining sand: 780 Kg; crushing stone: 1080 Kg;

step 4, pouring the cement, the machine-made sand and the broken stone weighed according to the weight components in the formula in the step 3 into a concrete mixer for dry mixing for 30s to ensure that the cementing material is uniformly distributed, and then adding the slurry B and stirring for 5-15min to obtain a mixture C;

and 5, distributing the mixture C, and then curing until the strength meets the requirement to obtain the concrete prefabricated part.

5. The method for preparing the fly ash-based nano-micron crystal nucleus additive suitable for the concrete prefabricated part as claimed in claim 4, wherein the method comprises the following steps: the grinding body in the step 2 is a zirconia grinding body, wherein zirconia grade specifications are as follows: the diameter of the small ball is 0.5-1.0mm, and accounts for 50-100% of the total mass fraction; the diameter of the medium ball is 1.0-3.0mm, and accounts for 0-25% of the total mass fraction; the diameter of the large ball is 3.0-5.0mm, and accounts for 0-25% of the total mass fraction.

6. A fly ash-based nano-micro crystal nucleus admixture suitable for concrete prefabricated parts according to any one of claims 1 to 3, wherein: the concrete application of the fly ash-based nano-micron crystal nucleus admixture in the cement-based material is as follows: the mixing amount of the fly ash-based nano-micron crystal nucleus admixture is 1-7% of that of the cement cementing material.