Spraying geopolymer capable of maintaining fluidity for long time and construction application method thereof

Abstract

The invention discloses a sprayed geopolymer capable of maintaining fluidity for a long time and a construction application method thereof, and belongs to the technical field of concrete. The invention relates to a jet geopolymer capable of maintaining fluidity for a long time. The jet geopolymer comprises a mixture and an exciting agent, the mixture is prepared from the following raw materials in parts by weight: 760 to 880 parts of slag powder, 40 to 80 parts of silica fume, 80 to 160 parts of cement, 200 to 220 parts of water, 5 to 15 parts of a water reducing agent and 500 to 1000 parts of sand; the exciting agent comprises the following raw materials: 213-284 parts of water glass and 20-28 parts of sodium hydroxide. According to the invention, peaceability loss and even coagulation hardening in pumping and transmission processes are avoided, and the jet geopolymer material still has the characteristic of rapid coagulation after jet, so that further application of the jet geopolymer material is promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and in particular to a sprayed geopolymer capable of maintaining fluidity for a long time and its construction application method. Background Art

[0002] Geopolymers have mechanical properties comparable to those of cement, better resistance to chemical erosion and fire resistance, and at the same time, the greenhouse gas emissions contained therein are greatly reduced. Therefore, geopolymers have become a powerful alternative to cement materials in the future construction industry.

[0003] The setting time of slag-based geopolymers is relatively short, and the initial setting can generally occur within 30 minutes, which may affect normal construction operations. In this regard, the Chinese invention patent with the publication number CN111439948A provides a retarder to reduce the setting speed of the geopolymer. Based on the total weight of the retarder, it contains 40 wt.% - 100 wt.% of alkali metal salts and 0 - 60 wt.% of alkaline earth metal salts.

[0004] However, for the sprayed concrete construction technology, in order to obtain sufficient strength to support the surrounding rock exposed by excavation as soon as possible, it is an important requirement for the cementitious material to set quickly. Currently, the cement system often uses a setting accelerator to achieve this purpose, but it will cause the problem of reduced later strength. Therefore, slag-based geopolymers that do not require the use of a setting accelerator have broad application prospects in the field of sprayed concrete.

[0005] For example, the Chinese invention patent with the publication number CN109503103A discloses an ultra-high toughness sprayed geopolymer concrete, which uses slag powder, lithium slag powder, and stone powder waste as precursor materials, and uses sodium hydroxide solution and sodium silicate solution as activators, which can effectively reduce the cement consumption of sprayed concrete and improve durability. The Chinese invention patent with the publication number CN112341053A provides a high-ductility geopolymer and its preparation method. The raw material composition is as follows by weight: 32 - 38 parts of fly ash, 7 - 9 parts of portland cement, 4 - 5 parts of calcined metakaolin, 1 - 3 parts of silica fume, 28 - 32 parts of quartz sand, 2 - 3 parts of sodium hydroxide, 4 - 8 parts of sodium silicate, 4 - 5 parts of water, and 0.5 - 0.7 parts of polypropylene fiber. The high-ductility geopolymer of this invention has a high ductility, which is 300% of the ductility of ordinary ductility geopolymers. It directly mixes solid sodium hydroxide and sodium silicate powder with the precursor, and the material can set within 35 minutes after being mixed with water. However, ductility is different from fluidity. Ductility reflects the plastic deformation ability of the material, while fluidity describes the flow characteristics of the material in the liquid or semi-solid state. Although rapid setting helps the sprayed concrete to form support in a short time and improve the engineering safety, this characteristic is also likely to cause the problem of hardening material clogging the pumping machine or the feeding pipeline during spraying construction, thus bringing heavy cleaning work and even scrapping the pipeline or equipment.

[0006] Therefore, how to effectively avoid the setting of slag-based geopolymers during pumping and transportation, so as to maintain good fluidity for a long time and enable the material to still set quickly after spraying, is of great significance for promoting the further popularization and application of this material in the field of shotcrete. Summary of the Invention

[0007] In view of the above-mentioned defects of the prior art, in the first aspect of the present invention, a shotcrete geopolymer that can maintain fluidity for a long time is provided, including a mixture and an activator; by weight, the mixture includes the following raw materials: 760-880 parts of slag powder, 40-80 parts of silica fume, 80-160 parts of cement, 200-220 parts of water, 5-15 parts of water reducer, and 500-1000 parts of sand; the activator includes the following raw materials: 213-284 parts of sodium silicate and 20-28 parts of sodium hydroxide.

[0008] Preferably, the slag powder is S95 slag powder, and the specific surface area is 400-500 m 2 / kg.

[0009] Preferably, the amorphous content of the silica fume > 85%.

[0010] Preferably, the cement is ordinary Portland cement, and the strength grade > 42.5.

[0011] Preferably, the water reducer is a liquid polycarboxylate water reducer, and the solid content is 40%.

[0012] Preferably, the sand is machine-made quartz sand, and the particle size is 40-70 mesh.

[0013] Preferably, the composition of the sodium silicate is 27.3 wt.% SiO2, 8.54 wt.% Na2O and 64.16 wt.% H2O.

[0014] Preferably, the purity of the sodium hydroxide > 98%.

[0015] In the second aspect of the present invention, a construction application method of the shotcrete geopolymer that can maintain fluidity for a long time according to the first aspect of the present invention is provided, including the following steps: Prepare the activator from sodium hydroxide and sodium silicate; stir the remaining raw materials to prepare a fluid mixture; the mixture is transported to the nozzle through a pumping device, and the activator enters the nozzle through another pipeline, and the mixture and the activator are uniformly mixed at the nozzle under the action of high-pressure air and impact the sprayed surface at high speed.

[0016] Preferably, the construction application method of the shotcrete geopolymer that can maintain fluidity for a long time specifically includes the following steps: Preparation of the mixture: According to the amount of each component, add slag powder, silica fume and cement into the mixing device and mix them evenly; According to the amount of each component, mix the water reducer and water and stir evenly, then pour it into the stirring device and stir until the slurry becomes fluid; Add sand to the mixing device according to the amount of each component and stir thoroughly to obtain a mixture with good fluidity; Preparation of stimulant: According to the amount of each component, sodium hydroxide is added to water glass and stirred thoroughly, and then allowed to stand to obtain an activator; Construction of sprayed geopolymer: The mixture is transported to the nozzle through the main pipeline by a concrete pumping device, and the activator is also transported to the nozzle through another pipeline by a metering pump. Under the action of high-pressure air, the mixture and the activator are evenly mixed and shot to the sprayed surface at high speed, and the material then solidifies rapidly.

[0017] Based on the above technical solutions, the design concept and principle of the present invention are as follows: The sprayed geopolymer provided by the present invention uses a slag-based polymer as a cementitious material. It inherently sets rapidly, eliminating the need for an accelerator. This eliminates the late-stage strength shrinkage often associated with the addition of accelerators to ordinary cement shotcrete. The activators, including water glass and sodium hydroxide, are separated from the raw materials, and the remaining components are stirred to form a fluid mixture. This mixture, which has a long setting time, is pumped to a nozzle via a pumping line. After being thoroughly mixed with the activator by high-pressure air, it is sprayed onto the sprayed surface, where it rapidly sets.

[0018] The construction method of this invention separates the activator from the remaining components, preventing rapid solidification during pumping and transportation, ensuring long-term fluidity. By uniformly mixing the mixture with the activator at the nozzle and immediately spraying it, a rapid hydration reaction is initiated, resulting in rapid setting. This sprayed geopolymer not only fully utilizes the rapid setting properties of the geopolymer material, but also maintains excellent fluidity for extended periods during pumping and transportation, significantly reducing the risk of pump and pipe blockages. This effectively addresses the material performance deficiencies of current shotcrete technology.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects: The present invention provides a sprayed geopolymer that can maintain fluidity for a long time, avoids loss of workability or even coagulation and hardening during pumping and transportation, and still has the characteristic of rapid coagulation after spraying, thereby promoting further application of sprayed geopolymer materials.

[0020] The present invention provides a construction application method for a sprayed geopolymer that can maintain fluidity for a long time, which has the advantages of convenient process and wide applicability. Specific embodiments

[0021] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples. For the experimental methods without specific conditions in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0022] In the following examples of the present invention: The slag powder is S95 slag powder produced by Gongyi Bolrun Refractory Materials Co., Ltd.; the silica fume is high-activity silica fume (amorphous content > 85%) produced by Gongyi Bolrun Refractory Materials Co., Ltd.; the cement is ordinary Portland cement with a strength grade of 42.5; the water is tap water; the water reducer is liquid polycarboxylate water reducer (solid content is 40%); the sand is machine-made quartz sand (particle size is 40 - 70 mesh); the composition of the water glass is 27.3 wt.% SiO2, 8.54 wt.% Na2O and 64.16 wt.% H2O; the purity of sodium hydroxide > 98%.

[0023] Example 1 This example provides a sprayed geopolymer that can maintain fluidity for a long time, and its components are a mixture and an activator; by weight, the mixture is 880 parts of slag powder, 40 parts of silica fume, 80 parts of cement, 200 parts of water, 15 parts of water reducer, and 1000 parts of sand; the activator is 213 parts of water glass and 28 parts of sodium hydroxide.

[0024] Example 2 This example provides a sprayed geopolymer that can maintain fluidity for a long time, and its components are a mixture and an activator; by weight, the mixture is 800 parts of slag powder, 80 parts of silica fume, 120 parts of cement, 200 parts of water, 10 parts of water reducer, and 750 parts of sand; the activator is 213 parts of water glass and 28 parts of sodium hydroxide.

[0025] Example 3 This example provides a sprayed geopolymer that can maintain fluidity for a long time, and its components are a mixture and an activator; by weight, the mixture is 760 parts of slag powder, 80 parts of silica fume, 160 parts of cement, 220 parts of water, 5 parts of water reducer, and 500 parts of sand; the activator is 213 parts of water glass and 28 parts of sodium hydroxide.

[0026] Example 4 This embodiment provides a sprayable geopolymer that can maintain fluidity for a long time, and its components include a mixture and an activator. In parts by weight, the mixture is 800 parts of slag powder, 80 parts of silica fume, 120 parts of cement, 200 parts of water, 10 parts of water reducer, and 750 parts of sand; the activator is 248 parts of water glass and 24 parts of sodium hydroxide.

[0027] Example 5 This embodiment provides a sprayable geopolymer that can maintain fluidity for a long time, and its components include a mixture and an activator. In parts by weight, the mixture is 800 parts of slag powder, 80 parts of silica fume, 120 parts of cement, 200 parts of water, 10 parts of water reducer, and 750 parts of sand; the activator is 284 parts of water glass and 20 parts of sodium hydroxide.

[0028] Example 6 This embodiment uses the sprayed geopolymers of Examples 1 to 5 that can maintain fluidity for a long time to construct the structure. The steps are as follows: Preparation of the mixture: According to the amount of each component, add slag powder, silica fume and cement into the mixing device and mix them evenly; According to the amount of each component, mix the water reducer and water and stir evenly, then pour it into the mixer and stir until the slurry becomes fluid; Add sand to the mixer according to the amount of each component and stir thoroughly to obtain a mixture with good fluidity; Preparation of stimulant: According to the amount of each component, sodium hydroxide was added to water glass and stirred thoroughly, and then stored for 24 hours to obtain the activator; Construction of sprayed geopolymer: The mixture is transported to the nozzle through the main pipeline by concrete pumping equipment, and the activator is also transported to the nozzle through another pipeline by a metering pump. Under the action of high-pressure air, the mixture and the activator are evenly mixed and shot to the sprayed surface at high speed, and the material then solidifies rapidly.

[0029] This example tested the performance of Examples 1-5. The viscosity and yield stress of the mixture were measured using an RSX SST rotational rheometer manufactured by Brookfield Instruments, Inc. The mixture was sheared at angular velocities of 5, 10, 20, 30, 40, 50, 40, 30, 20, 10, and 5 rad / s to obtain the rotor shear stress response. The modified Bingham rheological model was used to fit the data during the decreasing angular velocity period to obtain viscosity and yield stress results. The initial setting time of the mixture was measured according to the national standard GB / T 1346-2011. The fluidity of the geopolymer after mixing the mixture with an activator was measured according to the national standard GB / T 2419-2005. The test results are shown in Table 1.

[0030] Table 1: Main Performance Indicators of Examples 1 - 5

[0031] As can be seen from the data in the table, the mixtures of Examples 1 - 5 all have appropriate viscosities, which can ensure good fluidity. In addition, the initial setting times of the mixtures are all greater than 4 h, and the materials have sufficient workable time windows, facilitating the handling of various working conditions at the shotcreting construction site without the occurrence of pump and pipeline blockage accidents caused by the setting and hardening of the materials. After the mixture is mixed with the activator, the slag-based geopolymer will undergo rapid setting. Its fluidity is suitable for general shotcreting operations.

[0032] In summary, aiming at the problems of material hardening and blockage of pumping machines or conveying pipelines that are prone to occur when the current rapidly setting slag-based geopolymer is applied to shotcrete technology, as well as potential hazards such as heavy cleaning work and even pipeline or equipment scrapping caused thereby, the present invention provides a shotcrete geopolymer that can maintain fluidity for a long time and a construction method during its application. This shotcrete geopolymer can avoid the loss of workability and even setting and hardening during pumping and transmission, and still has the characteristic of rapid setting after spraying, which will promote the further application of shotcrete geopolymer materials.

[0033] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field based on the concept of the present invention through logical analysis, reasoning, or limited experiments on the basis of the prior art shall fall within the protection scope determined by the claims.

Claims

1. An injectable geopolymer capable of maintaining fluidity for a long time, characterized in that, It includes a mixture and an activator; the mixture includes the following raw materials in parts by weight: 760-880 parts of slag powder, 40-80 parts of silica fume, 80-160 parts of cement, 200-220 parts of water, 5-15 parts of water reducer, and 500-1000 parts of sand; the activator includes the following raw materials: 213-284 parts of water glass and 20-28 parts of sodium hydroxide.

2. The sprayable geopolymer capable of maintaining fluidity for a long time according to claim 1, characterized in that: The slag powder is S95 slag powder with a specific surface area of 400 - 500 m 2 / kg.

3. The sprayable geopolymer capable of maintaining fluidity for a long time according to claim 1, characterized in that: The amorphous content of the silica fume is greater than 85%.

4. The sprayable geopolymer capable of maintaining fluidity for a long time according to claim 1, characterized in that: The cement is ordinary Portland cement with a strength grade of >42.

5.

5. The sprayable geopolymer capable of maintaining fluidity for a long time according to claim 1, characterized in that: The water reducer is a liquid polycarboxylate water reducer with a solid content of 40%.

6. The sprayable geopolymer capable of maintaining fluidity for a long time according to claim 1, wherein: The sand is machine-made quartz sand with a particle size of 40 to 70 meshes.

7. The sprayable geopolymer capable of maintaining fluidity for a long time according to claim 1, characterized in that: The composition of the water glass is 27.3 wt.% SiO2, 8.54 wt.% Na2O and 64.16 wt.% H2O.

8. The sprayable geopolymer capable of maintaining fluidity for a long time according to claim 1, wherein: The purity of the sodium hydroxide is >98%.

9. A construction application method of a sprayable geopolymer capable of maintaining fluidity for a long time according to any one of claims 1 to 8, characterized in that, The steps include: Sodium hydroxide and water glass are prepared as stimulants; the remaining raw materials are stirred to prepare a fluid mixture; the mixture is transported to the nozzle through a pumping device, and the stimulant enters the nozzle through another pipeline. Under the action of high-pressure air, the mixture and the stimulant are evenly mixed at the nozzle and impacted onto the sprayed surface at high speed.

10. The construction application method of the sprayable geopolymer capable of maintaining fluidity for a long time according to claim 9, characterized in that, The steps include: Preparation of the mixture: According to the amount of each component, add slag powder, silica fume and cement into the mixing device and mix them evenly; According to the amount of each component, mix the water reducer and water and stir evenly, then pour it into the stirring device and stir until the slurry becomes fluid; Add sand to the mixing device according to the amount of each component and stir thoroughly to obtain a mixture with good fluidity; Preparation of stimulant: According to the amount of each component, sodium hydroxide is added to water glass and stirred thoroughly, and then allowed to stand to obtain an activator; Construction of sprayed geopolymer: The mixture is transported to the nozzle through the main pipeline by a concrete pumping device, and the activator is also transported to the nozzle through another pipeline by a metering pump. Under the action of high-pressure air, the mixture and the activator are evenly mixed and shot to the sprayed surface at high speed, and the material then solidifies rapidly.

Images