阅读说明：本技术 喷射混凝土用复合掺和料及其制备方法与应用 (Composite admixture for sprayed concrete and preparation method and application thereof ) 是由 程书凯 李顺凯 屠柳青 汪华文 骆晚玥 于 2020-11-26 设计创作，主要内容包括：本发明公开了一种喷射混凝土用复合掺和料及其制备方法与应用,属于建筑用材料技术领域。该复合掺和料包括如下质量百分比的各原料组分：粉煤灰：50～70％,超细硅灰：15～25％,偏高岭土：5～15％,熟石膏：0～5％；α-Al_2O_3：0～5％；表面活性剂；0～10％；其中,粉煤灰为II级低钙粉煤灰,超细硅灰的平均粒径小于10μm,SiO_2含量≥95.0％；偏高岭土的平均粒径小于5μm,α-Al_2O_3纳米粉的平均粒径小于50nm。将该复合掺和料作为胶凝材料之一制备喷射混凝土,所制备的喷射混凝土回弹率≤7％、凝结时间≤4min、抗硫酸侵蚀等级＞KS150。相较于现有技术中混凝土较高的回弹率,本发明设计的混凝土回弹率大幅下降。(The invention discloses a composite admixture for sprayed concrete and a preparation method and application thereof, belonging to the technical field of building materials. The composite admixture comprises the following raw material components in percentage by mass: fly ash: 50-70%, superfine silica fume: 15-25%, metakaolin: 5-15%, plaster of paris: 0 to 5 percent; alpha-Al 2 O 3 : 0 to 5 percent; a surfactant; 0 to 10 percent; wherein the fly ash is II-grade low-calcium fly ash, the average particle size of the superfine silicon ash is less than 10 mu m, and SiO is 2 The content is more than or equal to 95.0 percent; the average particle diameter of the metakaolin is less than 5 mu m, alpha-Al 2 O 3 The average grain diameter of the nano powder is less than 50 nm. The compound admixture is used as one of cementing materials to prepare the shotcrete, the rebound rate of the prepared shotcrete is less than or equal to 7 percent, the setting time is less than or equal to 4min, and the shotcrete is resistant to sulfuric acid corrosionRating > KS 150. Compared with the higher rebound rate of the concrete in the prior art, the designed concrete has greatly reduced rebound rate.)

1. The composite admixture for the sprayed concrete is characterized by comprising the following raw material components in percentage by mass: fly ash: 40-70%, superfine silica fume: 15-25%, metakaolin: 5-15%, industrial by-product gypsum: 0 to 5% of alpha-Al₂O₃0-5% of nano powder and a surfactant; 0 to 10 percent;

wherein the fly ash is II-grade fly ash, the average grain diameter of the superfine silicon ash is less than 10 mu m, and SiO is₂The content is more than or equal to 95.0 percent; the average grain diameter of the metakaolin is less than 5 mu m, and the alpha-Al₂O₃The average grain diameter of the nano powder is less than 50 nm.

2. The composite admixture for shotcrete according to claim 1, wherein the class II fly ash is a low calcium fly ash having a density of 1 to 5g/cm³The loss on ignition is 2-6%, and the average particle size is 10-15 μm; the average grain diameter of the superfine silica fume is less than 10 mu m, the average grain diameter of the metakaolin is less than 5 mu m, and the alpha-Al₂O₃The average particle diameter of the nano powder is smallEqual to or less than 30 nm.

3. The composite admixture for shotcrete according to claim 1 or 2, wherein the industrial by-product gypsum has a density of 2 to 7g/cm³The average particle size is 120 to 200 μm.

4. The composite admixture for shotcrete according to claim 3, wherein the composite admixture comprises the following raw material components in percentage by mass: 55-70% of fly ash, and superfine silica fume: 18-22%, metakaolin: 7-12%, plaster of paris: 0.5-3%; alpha-Al₂O₃1.5-5% of nano powder and a surfactant; 1.0 to 8 percent.

5. The composite admixture for shotcrete according to claim 1, 2 or 4, wherein the surfactant is any one of polycarboxylic acids, naphthalene series, aliphatic series and sulfamate series.

6. A preparation method of the composite admixture for the shotcrete is characterized by comprising the step of uniformly mixing and grinding raw material components in corresponding proportions to prepare the composite admixture, wherein the particle size of the composite admixture is in a nanometer level.

7. A sprayed concrete is characterized in that the sprayed concrete is prepared by using the composite admixture of any one of the claims 1-5 as one of cementing materials, and other reaction raw materials further comprise river sand, stones, cement, a water reducing agent, an accelerator and water; wherein the fineness modulus of the river sand is 2.3-3.3; the stones are continuous graded broken stones with the granularity of 5-15 mm.

8. The shotcrete of claim 7, wherein the mass of the composite admixture is 10-20% of the mass of the cement.

9. A method for preparing the shotcrete as claimed in claim 7, which comprises mixing river sand, gravel, composite admixture and a certain amount of water, stirring for a period of time, adding cement, water-reducing agent and the rest water, stirring, and spraying with accelerator in a spraying machine.

10. The application of the sprayed concrete in tunnel lining is characterized in that the resilience rate of the concrete is less than or equal to 7%, the setting time is less than or equal to 4min, and the sulfuric acid corrosion resistance grade is more than KS 150.

Background

The sprayed concrete is a concrete which is sprayed to a sprayed surface by a spraying machine through air conveying or pumping by using coarse and fine aggregates, cement, admixtures, an accelerating agent and the like in a certain mixing ratio, does not need manual vibration, can be quickly solidified and hardened, and is widely applied to primary support of excavation of surrounding rocks of caverns in tunnel engineering, mine engineering, subway engineering and the like. The sprayed concrete is classified into a wet spraying method and a dry spraying method according to a construction process. Relatively speaking, the dry spraying method has the advantages of low concrete strength, large resilience and large dust, but flexible operation and low cost; the wet spraying method has the advantages of small concrete rebound amount, small dust, easy control of strength, complex operation process, easy pipe blockage, inconvenient cleaning and high cost. Although the working environment of the wet spraying method is greatly improved and the strength rebound rate is lower, the on-site wet spraying concrete strength rebound rate is still higher than 15 percent, and the sprayed concrete is seriously corroded by sulfate.

In order to solve the problems of high rebound rate and insufficient sulfate corrosion resistance of sprayed concrete, domestic and foreign scholars improve the concrete performance in many ways, strive to reduce the rebound rate of the sprayed concrete and improve the sulfate corrosion resistance of the sprayed concrete. The Chinese patent application (application publication No. CN102826774A, application publication date) discloses a nano mineral admixture which can reduce the resilience rate of sprayed concrete to below 8%, but the admixture prepared by the application has high cost, the cost generated when the admixture is used for preparing the sprayed concrete is far higher than the cost consumed by dropping the concrete, and the operability is not strong.

Disclosure of Invention

In order to solve the technical problems, the invention discloses a composite admixture for sprayed concrete and a preparation method and application thereof. The composite admixture can effectively reduce the rebound rate of sprayed concrete and simultaneously improve the sulfate erosion resistance of the concrete.

In order to achieve the technical purpose, the invention discloses a composite admixture for sprayed concrete, which comprises the following raw material components in percentage by mass: fly ash: 40-70%, superfine silica fume: 15-25%, metakaolin: 5-15%, industrialAnd (3) byproduct gypsum: 0 to 5% of alpha-Al₂O₃0-5% of nano powder and a surfactant; 0 to 10 percent;

wherein the fly ash is II-grade fly ash, the average grain diameter of the superfine silicon ash is less than 10 mu m, and SiO is₂The content is more than or equal to 95.0 percent; the average grain diameter of the metakaolin is less than 5 mu m, and the alpha-Al₂O₃The average grain diameter of the nano powder is less than 50 nm.

Further, the II-grade fly ash is low-calcium fly ash with the density of 1-5 g/cm³The loss on ignition is 2-6%, and the average particle size is 10-15 μm; the average grain diameter of the superfine silica fume is less than 6.7 mu m, the average grain diameter of the metakaolin is less than or equal to 3.4 mu m, and the alpha-Al₂O₃The average grain diameter of the nano powder is less than or equal to 30 nm.

Further, the density of the industrial by-product gypsum is 2-7 g/cm³The average particle size is 120 to 200 μm.

Further, the composite admixture comprises the following raw material components in percentage by mass: 55-70% of fly ash, and superfine silica fume: 18-22%, metakaolin: 7-12%, plaster of paris: 0.5-3%; a-Al₂O₃1.5-5% of nano powder and a surfactant; 1.0 to 8 percent.

Further, the surfactant is any one of polycarboxylic acids, naphthalene series, aliphatic series and sulfamate series.

In order to better realize the technical purpose of the invention, the invention also discloses a preparation method of the composite admixture for the sprayed concrete, which comprises the step of uniformly mixing the raw material components in corresponding proportion to prepare the composite admixture, wherein the granularity of the composite admixture is in a nanometer level.

In addition, the invention also discloses sprayed concrete, which comprises the steps of preparing the sprayed concrete by using the composite admixture as one of reaction raw materials, wherein the other reaction raw materials further comprise river sand, stones, cement, a water reducing agent, an accelerator and water; wherein the fineness modulus of the river sand is 2.3-3.3; the stones are continuous graded broken stones with the granularity of 5-15 mm.

Further, the mass of the composite admixture is 10-20% of that of the cement.

The invention also discloses a preparation method of the sprayed concrete, which is characterized by comprising the steps of uniformly mixing and stirring river sand, stones, the composite admixture and a certain amount of water for a period of time, adding cement, a water reducing agent and the rest water, continuously stirring, and spraying the mixture with an accelerating agent in a spraying machine. .

The invention also discloses application of the sprayed concrete in tunnel lining, which is characterized in that the resilience rate of the concrete is less than or equal to 7%, the setting time is less than or equal to 4min, and the sulfuric acid corrosion resistance grade is more than KS 150.

The invention has the following beneficial effects: the invention fully utilizes the excellent characteristics of various admixtures, integrally improves the compactness and durability of the sprayed concrete, and effectively ensures the long-term service life and the safety of the sprayed concrete. The preparation method has the characteristics of low production cost, simple process, low energy consumption and the like, and has very high economic benefit and social benefit.

Detailed Description

The invention discloses a composite admixture for sprayed concrete, which comprises the following raw material components in percentage by mass: fly ash: 40-70%, superfine silica fume: 15-25%, metakaolin: 5-15%, industrial by-product gypsum: 0 to 5% of alpha-Al₂O₃0-5% of nano powder and a surfactant; 0 to 10 percent; and the content of each raw material component is not zero.

Wherein the fly ash is II-grade fly ash, the average grain diameter of the superfine silicon ash is less than 10 mu m, and SiO is₂The content is more than or equal to 95.0 percent; the average grain diameter of the metakaolin is less than 5 mu m, and the alpha-Al₂O₃The average grain diameter of the nano powder is less than 50 nm.

Further, the II-grade fly ash is low-calcium fly ash with the density of 1-5 g/cm³The loss on ignition is 2-6%, and the average particle size is 10-15 μm; the average grain diameter of the superfine silica fume is less than 6.7 mu m, the average grain diameter of the metakaolin is less than or equal to 3.4 mu m, and the alpha-Al₂O₃The average grain diameter of the nano powder is less than or equal to 30 nm.

Preferably, the II-grade fly ash is low-calcium fly ash with the density of 2-4 g/cm³The loss on ignition is 3 to 5%, and the average particle diameter is 12 to 14 μm.

Preferably, the II-grade fly ash is low-calcium fly ash with the density of 2.2g/cm³The loss on ignition was 3.2%, and the average particle diameter was 12.8. mu.m.

Preferably, the average particle size of the superfine silica fume is 0-5 μm, and the superfine silica fume does not contain zero.

Preferably, the metakaolin has an average particle size of 0 to 3.5 μm and does not contain zero.

Preferably, the metakaolin has an average particle size of 3.4 μm.

Preferably, the alpha-Al₂O₃The average particle size of the nano powder is 5-30 nm.

Preferably, the alpha-Al₂O₃The average particle diameter of the nano powder is 30 nm.

Further, the density of the industrial by-product gypsum is 2-7 g/cm³The average particle size is 120 to 200 μm.

Preferably, the industrial by-product gypsum has a density of 2.98g/cm³The particle size was 150. mu.m.

The four admixtures of fly ash, silica fume, metakaolin and gypsum selected in the composite admixture are applied to a gelling system, and the fly ash is considered to be doped to improve the fluidity of slurry, prolong the setting time of the slurry and reduce the early strength of concrete. The addition of the silica fume and the metakaolin can obviously improve the cohesiveness of the fresh concrete, reduce bleeding and prevent the concrete from segregation. The fly ash, the silica fume and the metakaolin are active admixture, and can be mixed into the cement to perform secondary hydration reaction with a hydration product of the cement to generate C-S-H gel, the fly ash effect can be stable from a chemical angle, capillary pores can be refined from a physical angle, and the permeation of a sulfate medium is reduced. The three admixtures can play a role in performance complementation, the silica fume has extremely small particles and can be filled in pores among the fly ash particles, so that the microstructure of the concrete becomes more compact, the sulfate ions can be effectively prevented from entering, and the sulfate erosion resistance is finally improved. Plaster of parisThe hydration speed of the gypsum is very fast, after the gelling system is mixed with water, the calcined gypsum can quickly generate dihydrate gypsum and form ettringite, the early strength of hardened cement slurry can be improved, and the setting time can be shortened. Secondly, the reaction of the plaster of paris and the phase consumes Ca (OH)₂In addition, the Ca (OH) vulnerable to sulfate in a concrete system is reduced₂And a proper amount of plaster can generate stable gypsum crystals, so that the production of expansive gypsum crystals at the later stage of sulfate corrosion is inhibited, and meanwhile, the plaster can provide a certain amount of sulfate ions in concrete pores and can inhibit external sulfate from migrating to the interior of concrete.

Further, the composite admixture comprises the following raw material components in percentage by mass: 55-70% of fly ash, and superfine silica fume: 18-22%, metakaolin: 7-12%, plaster of paris: 0.5-3%; alpha-Al₂O₃1.5-5% of nano powder and a surfactant; 1.0 to 8 percent.

Further, the surfactant is any one of polycarboxylic acids, naphthalene series, aliphatic series and sulfamate series.

In order to better realize the technical purpose of the invention, the invention also discloses a preparation method of the composite admixture for the sprayed concrete, which comprises the steps of uniformly mixing and grinding the raw material components in the corresponding proportion to prepare the composite admixture, wherein the granularity of the composite admixture is in a nanometer level.

In addition, the invention also discloses sprayed concrete, which comprises the steps of preparing the sprayed concrete by using the composite admixture as one of reaction raw materials, wherein the other reaction raw materials further comprise river sand, stones, cement, a water reducing agent, an accelerator and water; wherein the fineness modulus of the river sand is 2.3-3.3; the stones are continuous graded broken stones with the granularity of 5-15 mm.

Further, the mass of the composite admixture is 10-20% of that of the cement.

The invention also discloses a preparation method of the sprayed concrete, which is characterized by comprising the steps of uniformly mixing and stirring river sand, stones, the composite admixture and a certain amount of water for a period of time, adding cement, a water reducing agent and the rest water, continuously stirring, and spraying the mixture with an accelerating agent in a spraying machine.

The invention also discloses application of the sprayed concrete in tunnel lining, which is characterized in that the resilience rate of the concrete is less than or equal to 7%, the setting time is less than or equal to 4min, and the sulfuric acid corrosion resistance grade is more than KS 150. In order to better explain the present invention, the following detailed description is given in conjunction with specific examples.

Example 1

The embodiment discloses a preparation method of a composite admixture for sprayed concrete, which comprises the following steps of uniformly mixing and grinding the following raw material components in percentage by mass, wherein the coal ash: 40 percent of the fly ash, wherein the fly ash is II-grade fly ash, and the II-grade fly ash is low-calcium fly ash with the density of 5g/cm³The loss on ignition is 2 percent, and the average grain diameter is 15 mu m;

ultra-fine silica fume: 25 percent; wherein the average grain diameter of the superfine silica fume is 6 μm;

metakaolin: 15%, wherein the metakaolin has an average particle size of 4 μm;

industrial by-product gypsum: 5 percent; wherein the density of the industrial byproduct gypsum is 6g/cm³The granularity is 200 mu m;

α-Al₂O₃5% of nano powder, wherein the alpha-Al₂O₃The average particle diameter of the nano powder is 50 nm. A surfactant; 10 percent; the particle size of the prepared composite admixture is 50-70 nm.

Example 2

The embodiment discloses a preparation method of a composite admixture for sprayed concrete, wherein the content of each raw material component is the same as that in the embodiment 1, and the difference is that the physicochemical characteristic parameters of each component are as follows: the fly ash is II-grade fly ash, and the II-grade fly ash is low-calcium fly ash with the density of 2.2g/cm³The loss on ignition is 3.2%, and the average particle size is 12.8 μm; the average grain diameter of the superfine silica fume is 4 mu m; the average particle size of the metakaolin is 3.4 mu m; the density of the industrial byproduct gypsum is 2.98g/cm³The particle size is 150 mu m; the alpha-Al₂O₃The average particle diameter of the nano powder is 30 nm. System for makingThe particle size of the composite admixture is 20-50 nm.

Example 3

The embodiment discloses a preparation method of a composite admixture for sprayed concrete, which is different from the embodiment 2 in the content of each raw material component, and specifically comprises the following steps of uniformly mixing and grinding the raw material components in percentage by mass, wherein the fly ash: 70 percent, superfine silica fume: 15%, metakaolin: 5%, industrial by-product gypsum: 2%, alpha-Al₂O₃3% of nano powder and surfactant; 5 percent; the particle size of the prepared composite admixture is 20-70 nm.

Example 4

The embodiment discloses a preparation method of a composite admixture for sprayed concrete, which is different from the embodiment 2 in the content of each raw material component, and specifically comprises the following steps of uniformly mixing and grinding the raw material components in percentage by mass, wherein the fly ash: 50%, ultrafine silica fume: 15%, metakaolin: 15%, industrial by-product gypsum: 5%, alpha-Al₂O₃5% of nano powder and surfactant; 10 percent; the particle size of the prepared composite admixture is 20-70 nm.

Example 5

The embodiment discloses a preparation method of a composite admixture for sprayed concrete, which is different from the embodiment 2 in the content of each raw material component, and specifically comprises the following steps of uniformly mixing and grinding the raw material components in percentage by mass, wherein the fly ash: 60%, ultrafine silica fume: 20%, metakaolin: 10%, industrial by-product gypsum: 5%, alpha-Al₂O₃3% of nano powder and surfactant; 2 percent; the particle size of the prepared composite admixture is 20-70 nm.

In addition, the invention also discloses a concrete prepared by mixing the composite admixture prepared in the embodiment with other reaction raw materials, and the concrete is specifically prepared by the following embodiment.

Example 6

The embodiment discloses a preparation method of sprayed concrete, which comprises the steps of uniformly mixing river sand, broken stone, a composite admixture and half of water, stirring for a period of time, adding cement and the rest half of water of a water reducing agent, continuously stirring, and spraying with an accelerating agent in a spraying machine. Wherein the composite admixture is prepared by the method of the embodiment 1, and the mass of the composite admixture is 10% of that of cement.

Wherein the type of the adopted cement is Huaxin P.O 42.5; the river sand is natural river sand, and the fineness modulus is 2.8; the stones are continuous graded broken stones with the granularity of 5-15 mm; the water reducing agent is a CP-J type polycarboxylic acid high-efficiency water reducing agent, and the water reducing rate is 18 percent; the accelerator is a self-made SN01 alkali-free accelerator.

Example 7

This example differs from example 6 in that the compounded blend was made as described above for example 2.

Example 8

This example differs from example 6 in that the composite blend was made as described above in example 3.

Example 9

This example differs from example 6 in that the composite blend was made as described above for example 4.

Example 10

This example differs from example 6 in that the compounded blend was made as described above for example 2.

Example 11

The difference between the embodiment and the embodiment 6 is that the mass of the composite admixture is 15 percent of that of cement.

Example 12

The difference between the embodiment and the embodiment 6 is that the mass of the composite admixture is 20 percent of that of cement.

Comparative example 1

This example selects the raw material components of example 6 without adding the composite blend claimed in the present invention.

Comparative example 2

This example selected the product prepared in example 3 of application publication No. CN 107986671A.

And the performance lists of the shotcretes prepared in the embodiments 6 to 12 and the comparative examples 1 to 2 on the market are shown in the following table 1;

TABLE 1 product Property List

The rebound rate of the existing sprayed concrete is generally more than 20 percent, and after the special composite admixture for the sprayed concrete prepared by the invention is added, the rebound rate of the concrete is reduced to be less than 7 percent, so that the rebound rate of the sprayed concrete can be greatly reduced, and the cost is saved. Meanwhile, the compressive strength of the prepared sprayed concrete is greatly enhanced, the strength range is 42-45 MPa, and the durability indexes such as the corrosion resistance coefficient, the chloride ion diffusion coefficient, the sulfate erosion resistance grade and the like all meet the standard requirements. Therefore, the sprayed concrete designed by the invention can be better applied to tunnel lining.