CN111732365A - A kind of concrete composite admixture and preparation method thereof - Google Patents

Abstract

The invention discloses a concrete composite admixture, comprising the following raw materials in parts by mass: 50-60 parts of silicon micropowder, 15-30 parts of fly ash, 15-30 parts of limestone powder, 10-20 parts of steel slag powder, and tuff powder 8-20 parts, 5-15 parts of the activator; the technical scheme of the present invention is to prepare the activator first, and then add it to the mixer together with other pulverized raw materials for stirring, so that the concrete can be fully stirred and evenly mixed. , the composite admixture of the present invention has higher activity and the compressive strength of concrete is further improved after 28 days, which greatly improves the properties of concrete and fully stimulates the performance of the mineral admixture.

Description

A kind of concrete composite admixture and preparation method thereof

technical field

The invention relates to the technical field of concrete, in particular to a concrete composite admixture and a preparation method thereof.

Background technique

Concrete refers to a mixture made of cement (organic, inorganic or organic-inorganic composite), granular aggregates, water, and chemical admixtures and mineral admixtures to be added in appropriate proportions. After hardening, a composite material with a stacked structure is formed (usually, cementitious material, water, fine aggregate, coarse aggregate, admixtures and mineral admixtures are added when necessary, and are mixed in appropriate proportions.

Concrete has the characteristics of abundant raw materials, low price and simple production process, so its consumption is increasing. At the same time, concrete also has the characteristics of high compressive strength, good durability, and a wide range of strength grades. These characteristics make it widely used, not only in various civil engineering, but also in shipbuilding, machinery industry, marine development, geothermal engineering, etc. Concrete is also an important material.

Concrete is a living building material. With the continuous development of concrete composition materials, people's understanding of material composite technology has been continuously improved. The performance requirements of concrete are not limited to compressive strength, but on the basis of strength, more attention is paid to the balance and coordination of comprehensive indicators such as durability and deformation performance of concrete. The requirements for various performance indicators of concrete are more clear, detailed and specific than before. At the same time, the improvement of construction equipment level and the continuous emergence and promotion of new construction techniques have made concrete technology adapt to different design, construction and use requirements and developed rapidly.

Concrete is not a single material that exists in isolation. It is inseparable from the development of concrete raw materials and the development and changes of concrete engineering application objects. Concrete should be taken seriously from the perspective of the discipline of civil engineering. The same is true for concrete mix design. First, we must analyze the structure, component characteristics, and design requirements of the project, estimate possible unfavorable situations and risks, and base ourselves on local raw materials. Then use scientific, reasonable, and feasible technical routes and technical means. Formulate high-quality concrete that meets design requirements, construction process requirements and usage requirements.

With the development of modern concrete application technology, mineral admixtures have become one of the essential and important components of concrete. However, with the rapid advancement of infrastructure construction in my country, high-quality mineral admixtures such as mineral powder and fly ash are facing the problem of shortage of resources and uneven distribution in regions, resulting in a gradual increase in the production cost of concrete manufacturers. Concrete admixtures are used to improve concrete properties, save water, adjust concrete strength levels, and incorporate natural or artificial substances that can improve concrete properties during concrete mixing. With the continuous expansion of the concrete industry and the country's restrictions on resource development, mineral admixtures are becoming more and more scarce, and the prices are getting higher and higher, resulting in higher and higher production costs of concrete. Therefore, many batching plants have begun to hope to find a better way to replace mineral admixtures, hoping to reduce the energy consumption of minerals through the use of compound admixtures.

Conventional composite admixtures use a large number of inactive admixtures such as limestone, and the late activity of the composite admixture itself is low, resulting in the use of the same amount of admixture to produce concrete of the same label compared with conventional active mineral admixtures. The performance drops a lot, especially after 28 days. The 28-day activity index of limestone powder is often only 60-70%, which is difficult to meet the needs of concrete for the activity of composite admixtures.

SUMMARY OF THE INVENTION

The purpose of the invention is to provide a concrete composite admixture and a preparation method thereof, which solves the problem that the conventional composite admixture uses a large number of inactive admixtures such as limestone, and the composite admixture itself has low activity in the later stage, resulting in mixing with conventional active minerals. Compared with the mixture, using the same amount of admixture to produce the same grade of concrete, the performance of the concrete will be greatly reduced, especially after 28 days, the performance will be greatly reduced.

The present invention is achieved in this way, a concrete composite admixture comprising the following raw materials by mass:

50-60 parts of microsilica, 15-30 parts of fly ash, 15-30 parts of limestone powder, 10-20 parts of steel slag powder, 8-20 parts of tuff powder, 5-15 parts of activator;

The activator includes the following raw materials by mass: 2-10 parts of slaked lime, 1-5 parts of sodium sulfate, 4-10 parts of sodium silicate, 10-30 parts of calcium sulfate, 0.5-2 parts of amide mixture, cellulose ether 0.2-0.8 parts, acrylic acid 0.5-1.5 parts, epoxy resin 1-3 parts, dispersant 0.2-1.5 parts and water 15-30 parts.

A further technical scheme of the present invention is: the concrete composite admixture includes the following raw materials by mass:

58 parts of microsilica, 20 parts of fly ash, 20 parts of limestone powder, 15 parts of steel slag powder, 12 parts of tuff powder, and 8 parts of activator.

The further technical scheme of the present invention is that: the silicon micropowder is made from quartzite by crushing, grinding and other processes, and the content of SiO ₂ is greater than 90%.

A further technical solution of the present invention is that: the amide mixture is composed of polyacrylamide, N-N dimethylacetamide and polyformamide, and the ratio of parts by mass is 1-3:1:1-2.

A further technical solution of the present invention is: the cellulose ether is hydroxypropyl methyl cellulose ether.

A further technical scheme of the present invention is: the dispersing agent is one of methanol, ethanol, isopropanol, ethylene glycol and propylene glycol.

A preparation method of a concrete composite admixture, the preparation method comprising the following steps:

Step 1, first dry silicon micropowder, fly ash, limestone powder, steel slag powder and tuff powder for use;

Step 2, adding the amide mixture, cellulose ether, acrylic acid, epoxy resin and dispersant in proportion to the reaction kettle, stirring, and reacting for 1.5 hours at a pressure of 4MPa and a temperature of 60°C;

Step 3, the mixture after the above reaction is placed in the ultrasonic generator, and the mixture is treated with the ultrasonic wave of 200-500W for 30-60min;

Step 4, adding slaked lime, sodium sulfate, sodium silicate and calcium sulfate to the water in proportion, and mixing and stirring with the mixture obtained in the second step for 30min to obtain an activator precursor;

Step 5, placing the prepared activator precursor under strong ultraviolet light with a power of 80W-100W and a wavelength of 100-200nm for 30min;

Step 6. Add the materials in step 1 to the ball mill for grinding according to the proportion, and the grinding fineness is not less than 400m ² /kg, or the balance of the 0.08mm square hole sieve is not more than 2%, or 0.045 The sieve allowance of mm square hole sieve is not more than 20%;

Step 7: Put the mixture obtained in Step 3 and the activator in Step 5 into a mixer, the rotating speed is 45-50r/min, and the mixture is stirred for 5-10min to obtain a concrete composite admixture.

Beneficial effects of the present invention:

1. The technical scheme of the present invention is to prepare the activator first, and then add it to the mixer together with other pulverized raw materials for mixing, so that the concrete can be fully stirred evenly. High activity and the compressive strength of concrete is further improved after 28 days, which greatly improves the properties of concrete and fully stimulates the performance of mineral admixtures;

2. In terms of the activator, the present invention introduces the ultrasonic treatment method to treat the activator prepared by the reaction. Ultrasonic treatment has two major effects of heating up the molecules and vibrating at high frequencies. By raising the temperature, the small molecules that are not fully reacted in the second step, such as acrylic acid and epoxy resin, can be fully reacted. Through the high frequency vibration of the molecules, the macromolecules (cellulose ethers) can be fully cross-linked, and the small molecules can be encapsulated, so that the activator can be fully dispersed, and the encapsulation of the small molecules can delay the release of the small molecules. The delayed release of small molecules overcomes the drawbacks of the traditional activator that the rapid hydration and high heat of hydration in the early stage will affect the strength of concrete, so that the compressive strength of concrete can be fully improved in the later stage. Then through ultraviolet light treatment, the remaining small amount of unsaturated bonds in the activator is broken, and free radicals are generated, so that it can strengthen the bonding with the concrete components during the process of cement hydration, and increase the tightness of the activator and cement. Can greatly improve the activity index of the admixture;

3. The selected activator component of the present invention has strong pertinence. Among them, calcium sulfate supplements the sulfate radicals in the composite admixture, and adjusts the setting time and workability of the composite admixture to ensure the concrete construction performance. Hydrated lime keeps the composite admixture as a whole in an alkaline environment for easy preservation and compatibility with the alkaline environment of concrete. Sodium silicate is used as a grinding aid to improve the grinding efficiency of the whole process. The amide compound is a rust inhibitor, which can delay the corrosion of steel bars when applied to reinforced concrete. Epoxy resin is a cohesive agent and thickener to maintain the cohesiveness of concrete;

4. The present invention uses more silicon micropowder to replace lower active materials such as limestone powder. Silica micropowder has a large number of nano-scale particles with a particle size of 50-500nm, and its specific surface area is more than 30 times that of limestone powder. After the macromolecules in the activator release the small molecules, these silicon micropowder particles can be encapsulated to achieve better dispersion and cross-linking effects. At the same time, the extremely small particle size of the silica fume can fill the small gaps in the concrete and increase the compactness of the concrete, thereby improving the strength.

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

Example 1:

A concrete composite admixture, the concrete composite admixture comprises the following raw materials by mass:

50 parts of microsilica, 15 parts of fly ash, 15 parts of limestone powder, 10 parts of steel slag powder, 8 parts of tuff powder, and 5 parts of activator.

The silicon micropowder is made from quartzite by crushing, grinding and other processes, and the content of SiO ₂ is greater than 90%.

The activator includes the following raw materials by mass: 2 parts of slaked lime, 1 part of sodium sulfate, 4 parts of sodium silicate, 10 parts of calcium sulfate, 0.5 part of amide mixture, 0.2 part of cellulose ether, 0.5 part of acrylic acid, epoxy resin 1 part, 0.2 part of dispersant and 15 parts of water.

The amide mixture is composed of polyacrylamide, N-N dimethylacetamide and polyformamide, and the ratio of parts by mass is 1-3:1:1-2.

The cellulose ether is hydroxypropyl methylcellulose ether.

The dispersant is methanol.

A preparation method of a concrete composite admixture, the preparation method comprising the following steps:

Step 1, first dry silicon micropowder, fly ash, limestone powder, steel slag powder and tuff powder for use;

Step 2, adding the amide mixture, cellulose ether, acrylic acid, epoxy resin and dispersant in proportion to the reaction kettle, stirring, and reacting for 1.5 hours at a pressure of 4MPa and a temperature of 60°C;

Step 3, the mixture after the above-mentioned reaction is placed in an ultrasonic generator, and the mixture is treated with the ultrasonic wave of 200W for 30min;

Step 4, adding slaked lime, sodium sulfate, sodium silicate and calcium sulfate to the water in proportion, and mixing and stirring with the mixture obtained in the second step for 30min to obtain an activator precursor;

Step 5, placing the prepared activator precursor under strong ultraviolet light with a power of 80W and a wavelength of 100nm for 30min;

Step 6. Add the materials in step 1 to the ball mill for grinding according to the proportion, and the grinding fineness is not less than 400m ² /kg, or the balance of the 0.08mm square hole sieve is not more than 2%, or 0.045 The sieve allowance of mm square hole sieve is not more than 20%;

Step 7: Put the mixture obtained in step 3 and the activator in step 5 into a mixer, the rotating speed is 48r/min, and the mixture is stirred for 8min to obtain a concrete composite admixture.

Concrete composite admixture properties: slump: 215mm, compressive strength 1d: 20.3MPa; 3d: 22.7 MPa; 7d: 28.6 MPa; 14d: 35.7 MPa; 28d: 48.1 MPa.

Example 2:

A concrete composite admixture, the concrete composite admixture comprises the following raw materials by mass:

58 parts of microsilica, 20 parts of fly ash, 20 parts of limestone powder, 15 parts of steel slag powder, 12 parts of tuff powder, and 8 parts of activator.

The silicon micropowder is made from quartzite by crushing, grinding and other processes, and the content of SiO ₂ is greater than 90%.

The activator includes the following raw materials by mass: 8 parts of slaked lime, 3 parts of sodium sulfate, 8 parts of sodium silicate, 22 parts of calcium sulfate, 1 part of amide mixture, 0.5 parts of cellulose ether, 1.2 parts of acrylic acid, epoxy resin 2 parts, 1.0 part of dispersant and 26 parts of water.

The amide mixture is composed of polyacrylamide, N-N dimethylacetamide and polyformamide, and the ratio of parts by mass is 1-3:1:1-2.

The cellulose ether is hydroxypropyl methylcellulose ether.

The dispersant is ethanol.

A preparation method of a concrete composite admixture, the preparation method comprising the following steps:

Step 1, first dry silicon micropowder, fly ash, limestone powder, steel slag powder and tuff powder for use;

Step 2, adding the amide mixture, cellulose ether, acrylic acid, epoxy resin and dispersant in proportion to the reaction kettle, stirring, and reacting for 1.5 hours at a pressure of 4MPa and a temperature of 60°C;

Step 3, the mixture after the above-mentioned reaction is placed in an ultrasonic generator, and the mixture is treated with the ultrasonic wave of 300W for 40min;

Step 4, adding slaked lime, sodium sulfate, sodium silicate and calcium sulfate to the water in proportion, and mixing and stirring with the mixture obtained in the second step for 30min to obtain an activator precursor;

Step 5, placing the obtained activator precursor under strong ultraviolet light with a power of 90W and a wavelength of 150nm for 30min;

Step 6. Add the materials in step 1 to the ball mill for grinding according to the proportion, and the grinding fineness is not less than 400m ² /kg, or the balance of the 0.08mm square hole sieve is not more than 2%, or 0.045 The sieve allowance of mm square hole sieve is not more than 20%;

Step 7: Put the mixture obtained in step 3 and the activator in step 5 into a mixer, the rotating speed is 48r/min, and the mixture is stirred for 8min to obtain a concrete composite admixture.

Concrete composite admixture properties: slump: 220mm, compressive strength 1d: 21.8MPa; 3d: 24.2 MPa; 7d: 30.7 MPa; 14d: 38.3 MPa; 28d: 49.7 MPa.

Example 3:

A concrete composite admixture, the concrete composite admixture comprises the following raw materials by mass:

60 parts of microsilica, 30 parts of fly ash, 30 parts of limestone powder, 20 parts of steel slag powder, 20 parts of tuff powder, and 15 parts of activator.

The silicon micropowder is made from quartzite by crushing, grinding and other processes, and the content of SiO ₂ is greater than 90%.

The activator includes the following raw materials by mass: 10 parts of slaked lime, 5 parts of sodium sulfate, 10 parts of sodium silicate, 28 parts of calcium sulfate, 2 parts of amide mixture, 0.8 parts of cellulose ether, 1.4 parts of acrylic acid, epoxy resin 3 parts, 1.5 parts of dispersant and 28 parts of water.

The amide mixture is composed of polyacrylamide, N-N dimethylacetamide and polyformamide, and the ratio of parts by mass is 1-3:1:1-2.

The cellulose ether is hydroxypropyl methylcellulose ether.

The dispersant is isopropanol.

A preparation method of a concrete composite admixture, the preparation method comprising the following steps:

Step 1, first dry silicon micropowder, fly ash, limestone powder, steel slag powder and tuff powder for use;

Step 2, adding the amide mixture, cellulose ether, acrylic acid, epoxy resin and dispersant in proportion to the reaction kettle, stirring, and reacting for 1.5 hours at a pressure of 4MPa and a temperature of 60°C;

Step 3, the mixture after the above-mentioned reaction is placed in an ultrasonic generator, and the mixture is treated with the ultrasonic wave of 400W for 50min;

Step 4, adding slaked lime, sodium sulfate, sodium silicate and calcium sulfate to the water in proportion, and mixing and stirring with the mixture obtained in the second step for 30min to obtain an activator precursor;

Step 5, placing the prepared activator precursor under strong ultraviolet light with a power of 100W and a wavelength of 100-200nm for 30min;

Step 6. Add the materials in step 1 to the ball mill for grinding according to the proportion, and the grinding fineness is not less than 400m ² /kg, or the balance of the 0.08mm square hole sieve is not more than 2%, or 0.045 The sieve allowance of mm square hole sieve is not more than 20%;

Step 7: Put the mixture obtained in step 3 and the activator in step 5 into a mixer, the rotating speed is 50r/min, and the mixture is stirred for 10min to obtain a concrete composite admixture.

Concrete composite admixture properties: slump: 216mm, compressive strength 1d: 20.8MPa; 3d: 23.9MPa; 7d: 29.4 MPa; 14d: 36.5 MPa; 28d: 49.7MPa.

The concrete composite admixtures obtained in Example 1, Example 2 and Example 3 were compared in activity, and the following results were obtained as shown in Table 1:

Table 1 Activity comparison results

group Day 1 Active Day 3 Active Day 7 Active Day 14 Active Day 28 Active Example 1 97.2% 96.8% 96.5% 102.8% 115.2% Example 2 98% 97.8% 97.3% 105.6% 118.5% Example 3 97.5% 97.2% 96.6% 103.4% 116.4%

The excellent performance of the admixture of the present invention is mainly due to the strong pertinence of the activator component of the present invention. Among them, calcium sulfate supplements the sulfate radicals in the composite admixture, and adjusts the setting time and workability of the composite admixture to ensure the concrete construction performance. Hydrated lime keeps the composite admixture as a whole in an alkaline environment for easy preservation and compatibility with the alkaline environment of concrete. Sodium silicate is used as a grinding aid to improve the grinding efficiency of the whole process. The amide compound is a rust inhibitor, which can delay the corrosion of steel bars when applied to reinforced concrete. Epoxy resin is a cohesive agent and thickener to maintain the cohesiveness of concrete.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (7)

1. a concrete composite admixture, is characterized in that: this concrete composite admixture comprises the raw material of following mass parts: 50-60 parts of microsilica, 15-30 parts of fly ash, 15-30 parts of limestone powder, 10-20 parts of steel slag powder, 8-20 parts of tuff powder, 5-15 parts of activator; The activator includes the following raw materials by mass: 2-10 parts of slaked lime, 1-5 parts of sodium sulfate, 4-10 parts of sodium silicate, 10-30 parts of calcium sulfate, 0.5-2 parts of amide mixture, cellulose ether 0.2-0.8 parts, acrylic acid 0.5-1.5 parts, epoxy resin 1-3 parts, dispersant 0.2-1.5 parts and water 15-30 parts. 2. a kind of concrete composite admixture according to claim 1 is characterized in that: this concrete composite admixture comprises the raw material of following mass parts: 58 parts of microsilica, 20 parts of fly ash, 20 parts of limestone powder, 15 parts of steel slag powder, 12 parts of tuff powder, and 8 parts of activator. 3 . The composite admixture for concrete according to claim 1 , wherein the silicon micropowder is made from quartzite by crushing, grinding and other processes, and the content of SiO ₂ is greater than 90%. 4 . 4. a kind of concrete composite admixture according to claim 1, is characterized in that: described amide mixture is made up of polyacrylamide, N-N-dimethylacetamide and polyformamide, and its mass fraction ratio is: 1-3:1:1-2. 5 . The composite admixture for concrete according to claim 1 , wherein the cellulose ether is hydroxypropyl methyl cellulose ether. 6 . 6. A kind of concrete composite admixture according to claim 1, is characterized in that: described dispersant is a kind of in methanol, ethanol, isopropanol, ethylene glycol and propylene glycol. 7. the preparation method of a kind of concrete composite admixture according to any one of claim 1-6, is characterized in that: this preparation method comprises the following steps: Step 1, first dry silicon micropowder, fly ash, limestone powder, steel slag powder and tuff powder for use; Step 2, adding the amide mixture, cellulose ether, acrylic acid, epoxy resin and dispersant in proportion to the reaction kettle, stirring, and reacting for 1.5 hours at a pressure of 4MPa and a temperature of 60°C; Step 3, the mixture after the above reaction is placed in the ultrasonic generator, and the mixture is treated with the ultrasonic wave of 200-500W for 30-60min; Step 4, adding slaked lime, sodium sulfate, sodium silicate and calcium sulfate to the water in proportion, and mixing and stirring with the mixture obtained in the second step for 30min to obtain an activator precursor; Step 5, placing the prepared activator precursor under strong ultraviolet light with a power of 80W-100W and a wavelength of 100-200nm for 30min; Step 6. Add the materials in step 1 to the ball mill for grinding according to the proportion, and the grinding fineness is not less than 400m ² /kg, or the balance of the 0.08mm square hole sieve is not more than 2%, or 0.045 The sieve allowance of mm square hole sieve is not more than 20%; Step 7: Put the mixture obtained in Step 3 and the activator in Step 5 into a mixer, the rotating speed is 45-50r/min, and the mixture is stirred for 5-10min to obtain a concrete composite admixture.