Dry-type sprayed concrete and production and construction process thereof

Abstract

The invention discloses dry shotcrete. The dry shotcrete is prepared from the following components: a cementing material, coarse aggregate, fine aggregate, water, a water reducing agent and an accelerator, wherein the cementing material is cement; the ratio of glue to bone in the components of the dry-type sprayed concrete is 1: 4-1: 5; the water-binder ratio in the components of the dry shotcrete is 0.35 to 0.40; the use amount of the binding material added in the components of the dry-type sprayed concrete is not less than 400kg / m < 3 >. The invention belongs to the technical field of concrete, and aims to solve the problems of poor use effect, insufficient later strength, poor durability, heavy dust and high rebound rate in the prior art. The technical effects are as follows: by reasonably designing the mix proportion, the compressive strength and durability of the sprayed concrete are improved, and the pumpable performance and the sprayable performance of the sprayed concrete are both considered; a good effect is also achieved after verification of the dust amount and the rebound amount in the production and construction process; the use index of the sprayed concrete is optimized, the construction process is improved, and the use performance is improved.

Description

Technical Field

[0001] The invention relates to the technical field of concrete, and in particular to dry shotcrete and a production and construction process thereof. Background Art

[0002] With the continuous development of China's science and technology and construction technology, the scope of use of shotcrete is becoming wider and wider. Shotcrete is a process in which the mixed material is quickly sprayed to the construction site by pressurizing it during construction, and it can be compressed instantly. In engineering projects, the use of shotcrete construction technology can speed up construction, shorten project duration, and effectively reduce construction costs. The construction process of shotcrete is also relatively simple, and it has been rapidly popularized in the construction field.

[0003] At present, the spraying concrete technology mainly includes wet mixing method and dry mixing method. The wet mixing method of spraying concrete is to send the mixed concrete to the nozzle through a grouting pump, and then use compressed air for spraying. During construction, it is advisable to use the method of mixing and spraying to reduce the change of consistency. The spraying speed of this method is low, and due to the increase of water-cement ratio, the initial strength of concrete is also low. The pre-mixed cement, sand, gravel, water and a certain amount of admixtures are loaded into the sprayer, and they are sent to the nozzle and mixed with the accelerator by high-pressure air, and then sprayed at the surface of rock or concrete at a very high speed. Dry spraying concrete is formed by mixing cement, coarse and fine aggregates and accelerators manually or mechanically, and then transported from the conveying pipe to the spray nozzle by a dry spraying concrete sprayer with compressed air. At the spray nozzle, pressurized water is added according to the specified water-cement ratio, and mixed with dry materials quickly, and then sprayed onto the wall surface by the spray nozzle. Mix cement, sand, gravel and powdered accelerator in a certain proportion, stir them evenly by hand or machine, and use dry concrete spraying machine to transport them to the nozzle through the conveying pipe with compressed air as the power, and spray them onto the sprayed surface after mixing with a certain amount of pressurized water. This process is simple, easy to operate, and has a long conveying distance (up to 150-200m on average), but its fatal weaknesses are low technical strength, large dust, high rebound rate and poor durability.

[0004] At present, the strength grade of dry shotcrete is mainly C25. There is no corresponding mix design specification for the mix ratio of dry shotcrete, which leads to poor shotcrete effect in many cases in actual projects. The existing shotcrete strength grade is low and it is difficult to adapt to complex engineering environments. At the same time, the later strength shrinkage problem of shotcrete will directly lead to the deterioration of the later mechanical properties of the structure, thereby greatly reducing the durability of the structure. Shotcrete generates a lot of dust during the construction process, and will rebound and pollute the environment. Therefore, dry shotcrete has problems such as poor use effect, insufficient later strength, poor durability, large dust, and high rebound rate during the construction process. Summary of the invention

[0005] To this end, the present invention provides a dry shotcrete and a production and construction process thereof to solve the above-mentioned problems in the prior art.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] According to a first aspect of the present invention, a dry shotcrete comprises components of: a cementitious material, a coarse aggregate, a fine aggregate, water, a water reducing agent and an accelerating setting agent;

[0008] Wherein, the gelling material is cement;

[0009] The ratio of cement to concrete in the dry shotcrete composition is 1:4 to 1:5;

[0010] The water-binder ratio of the dry shotcrete composition is 0.35 to 0.40;

[0011] The amount of cementitious material added to the dry shotcrete components is not less than 400kg / m3.

[0012] Furthermore, the components of the dry shotcrete include, by weight, 100 parts of cement, 200 parts of coarse aggregate, 200 parts of fine aggregate, 35 parts of water, 2 parts of water reducing agent and 4 parts of accelerating setting agent.

[0013] Furthermore, the cement is selected from one of silicate cement, ordinary silicate cement or special cement.

[0014] Furthermore, the fineness modulus of the fine aggregate is greater than 2.5, the particles smaller than 0.075 mm in the fine aggregate are not greater than 20%, and the sand ratio of the dry shotcrete is preferably 45% to 60%.

[0015] Furthermore, the maximum particle size of the coarse aggregate is not greater than 16 mm, and the coarse aggregate adopts continuous particle sizes.

[0016] A production and construction process of dry shotcrete, the specific steps of the production and construction process are as follows:

[0017] Step 1, dry mixing: according to the weight parts of the components for preparing dry shotcrete, 100 parts of cement, 200 parts of coarse aggregate, 200 parts of fine aggregate and 35 parts of water are fed into a mixer and stirred evenly to obtain a dry concrete mixture;

[0018] Step 2: Transport by material truck: put the above dry concrete mixture into the transport material truck and transport it to the construction site;

[0019] Step 3: Use compressed air to deliver dry concrete mixture, accelerator and admixture to the nozzle of the shotcrete machine, mix with pressurized water and then spray to obtain shotcrete construction parts.

[0020] Furthermore, the moisture content of the dry concrete mixture is required to be: the dry concrete mixture can be held into a ball by hand, and it seems to be scattered when the hand is released, and there is no smoke when blown to prevent dust;

[0021] The mixing time of the dry concrete mixture is not less than 1.5 minutes;

[0022] The dry concrete mixture should be used immediately after mixing and the storage time should not exceed 30 minutes;

[0023] The concrete mixture must not be exposed to rain, soaked in water, or mixed with foreign objects during transportation and storage.

[0024] Furthermore, the precautions for the dry concrete mixture spraying are as follows:

[0025] 1) The concrete should be sprayed in sections and layers from bottom to top. The length of each section should not be greater than 6m. If there are large depressions on the rock surface, the depressions should be sprayed flat first. The concrete surface sprayed on the rock surface should not slip or fall. The thickness of one spray can be determined by on-site tests based on the spraying location.

[0026] 2) The nozzle should be perpendicular to the spraying surface, and the distance between them should be 0.6m to 1.8m. The nozzle should move horizontally and circularly continuously and slowly, and the spray layer thickness should be uniform;

[0027] 3) When spraying in layers, the rear layer of concrete should be sprayed after the front layer of concrete has finally set for 1 hour, and the surface of the sprayed layer should be cleaned with air and water before spraying;

[0028] 4) The rebound rate of concrete should be checked during the spraying process. The rebound rate of the side wall of the sprayed concrete should not be greater than 15%, and the rebound rate of the arch should not be greater than 25%;

[0029] 5) The ambient temperature of the spraying operation site shall not be lower than 5°C; the spraying concrete operation area shall have good ventilation and lighting conditions;

[0030] 6) After the spraying operation is completed, the thickness should be tested in time, and if it does not meet the requirements, it should be sprayed again in time.

[0031] Furthermore, during the spraying process, water and air are turned on, and the water volume is adjusted to maintain the wind pressure not less than 0.4MPa, and the water pressure should be 0.1MPa higher than the wind pressure. The amount of water added during the spraying process is controlled to ensure that there are no dry spots on the sprayed surface, no flow, strong adhesion, less rebound material, and the total amount of water added controls the water-cement ratio to 0.35;

[0032] The quick-setting agent is evenly added to the feed port of the shotcrete machine. The sprayer operates the nozzle to flush the rock surface from top to bottom. The sprayer sprays in sections in the order of first the wall and then the arch from bottom to top. When spraying, the nozzle should be as vertical as possible to the sprayed surface, and the angle should not be less than 70 degrees;

[0033] During spraying, the nozzle's trajectory should be spiral, with a diameter of 200-300mm, and it should move evenly and slowly in a circle-pressing semicircle method. The thickness of the sprayed concrete should be 50-70mm at a time, and it should be re-sprayed in time. The interval between re-spraying should not exceed 2 hours, otherwise the sprayed surface should be re-rinsed with high-pressure water.

[0034] Furthermore, the dry shotcrete can obtain a concrete strength of 28 to 34 MPa and good adhesion by applying the above parameters.

[0035] The present invention has the following advantages:

[0036] 1. The dry shotcrete and its production and construction process are very different from ordinary shotcrete in terms of mix ratio and construction process. The invention improves the compressive strength and durability of shotcrete by rationally designing the mix ratio, and while improving its performance, it also takes into account its pumpability and sprayability.

[0037] 2. The dry shotcrete and its production and construction process. The invention is based on experimental research on the mix of dry shotcrete and proposes a new dry shotcrete composition design method and production and construction process. The mix design process mainly includes raw material selection, theoretical mix calculation, pump performance and spray performance adjustment, strength, durability and volume stability verification, etc. It has also achieved good results in controlling dust and rebound during production and construction.

[0038] Therefore, in summary, the present invention optimizes the relevant performance of dry shotcrete, optimizes the use indicators of shotcrete, improves the construction process, and enhances its use performance. By improving the original shotcrete mix ratio and production process, the problems of poor use effect, insufficient later strength, poor durability, large dust, high rebound rate, etc. of dry shotcrete in the construction process are solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A production and construction process diagram of dry shotcrete and its production and construction process provided in some embodiments of the present invention. DETAILED DESCRIPTION

[0040] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Example 1

[0042] like Figure 1 As shown, a dry shotcrete in an embodiment of the first aspect of the present invention comprises the following components: a cementitious material, a coarse aggregate, a fine aggregate, water, a water reducing agent and an accelerating setting agent;

[0043] In the above embodiments, it should be noted that, the gelling material is cement;

[0044] The ratio of cement to concrete in the dry shotcrete composition is 1:4 to 1:5;

[0045] The water-binder ratio of the dry shotcrete composition is 0.35 to 0.40;

[0046] The amount of cementitious material added to the dry shotcrete components is not less than 400kg / m3.

[0047] The technical effect achieved by the above embodiment is: it is very different from ordinary shotcrete in terms of mix ratio and construction process. The invention improves the compressive strength and durability of shotcrete by reasonably designing the mix ratio, while improving its performance in use, taking into account its pumpability and sprayability.

[0048] Example 2

[0049] like Figure 1 As shown, a dry shotcrete includes all the contents of Example 1. In addition, the components of the dry shotcrete, by weight, include 100 parts of cement, 200 parts of coarse aggregate, 200 parts of fine aggregate, 35 parts of water, 2 parts of water reducer and 4 parts of accelerator.

[0050] The cement is selected from one of silicate cement, ordinary silicate cement or special cement.

[0051] The fineness modulus of the fine aggregate is greater than 2.5, the particles smaller than 0.075 mm in the fine aggregate are not greater than 20%, and the sand ratio of the dry shotcrete is preferably 45% to 60%.

[0052] The maximum particle size of the coarse aggregate is not greater than 16 mm, and the coarse aggregate adopts continuous particle sizes.

[0053] The technical effect achieved by the above embodiment is: in order to improve the pumpability and sprayability of shotcrete, a water reducer needs to be added when mixing the materials, and an accelerator should be a product of stable quality, which should have good compatibility with cement, and the performance indicators should comply with the provisions of relevant standards. The dosage of the accelerator should not be greater than 5% of the cement dosage; other admixtures can be added to the shotcrete as needed, and their dosage is determined by experiments.

[0054] Example 3

[0055] like Figure 1 As shown, a production and construction process of dry shotcrete includes all the contents of Example 2. In addition, a production and construction process of dry shotcrete, the specific steps of the production and construction process are as follows:

[0056] Step 1, dry mixing: according to the weight parts of the components for preparing dry shotcrete, 100 parts of cement, 200 parts of coarse aggregate, 200 parts of fine aggregate and 35 parts of water are fed into a mixer and stirred evenly to obtain a dry concrete mixture;

[0057] Step 2: Transport by material truck: put the above dry concrete mixture into the transport material truck and transport it to the construction site;

[0058] Step 3: Use compressed air to deliver dry concrete mixture, accelerator and admixture to the nozzle of the shotcrete machine, mix with pressurized water and then spray to obtain shotcrete construction parts.

[0059] The moisture content requirement of the dry concrete mixture is: the dry concrete mixture can be held into a ball by hand, and it seems to be scattered when the hand is released, and there is no smoke when blown to prevent dust;

[0060] The mixing time of the dry concrete mixture is not less than 1.5 minutes;

[0061] The dry concrete mixture should be used immediately after mixing and the storage time should not exceed 30 minutes;

[0062] The concrete mixture must not be exposed to rain, soaked in water, or mixed with foreign objects during transportation and storage.

[0063] The technical effects achieved by the above embodiments are as follows: based on experimental research on the formulation of dry shotcrete, a new dry shotcrete composition design method and production and construction process are proposed, and its mix ratio design process mainly includes raw material selection, theoretical mix ratio calculation, pump performance and spray performance adjustment, strength, durability and volume stability verification, etc., and good results have been achieved after verification for controlling dust and rebound during production and construction; the present invention optimizes the relevant properties of dry shotcrete, optimizes the use indicators of shotcrete, improves the construction process, and enhances its use performance. By improving the original shotcrete mix ratio and production process, the problems of poor use effect, insufficient late strength, poor durability, large dust, high rebound rate, etc. of dry shotcrete in the construction process are solved.

[0064] Example 4

[0065] like Figure 1 As shown, a production and construction process of dry shotcrete includes all the contents of Example 3. In addition, the precautions for the dry concrete mixture spraying are as follows:

[0066] 1) The concrete should be sprayed in sections and layers from bottom to top. The length of each section should not be greater than 6m. If there are large depressions on the rock surface, the depressions should be sprayed flat first. The concrete surface sprayed on the rock surface should not slip or fall. The thickness of one spray can be determined by on-site tests based on the spraying location.

[0067] 2) The nozzle should be perpendicular to the spraying surface, and the distance between them should be 0.6m to 1.8m. The nozzle should move horizontally and circularly continuously and slowly, and the spray layer thickness should be uniform;

[0068] 3) When spraying in layers, the rear layer of concrete should be sprayed after the front layer of concrete has finally set for 1 hour, and the surface of the sprayed layer should be cleaned with air and water before spraying;

[0069] 4) The rebound rate of concrete should be checked during the spraying process. The rebound rate of the side wall of the sprayed concrete should not be greater than 15%, and the rebound rate of the arch should not be greater than 25%;

[0070] 5) The ambient temperature of the spraying operation site shall not be lower than 5°C; the spraying concrete operation area shall have good ventilation and lighting conditions;

[0071] 6) After the spraying operation is completed, the thickness should be tested in time, and if it does not meet the requirements, it should be sprayed again in time.

[0072] The technical effect achieved by the above embodiment is: cement, wet sand, stone and admixture are mixed evenly in a mixing station, transported to the construction site, and then sent to the nozzle with compressed air and mixed with pressurized water for spraying. Before spraying concrete, the rock surface to be sprayed should be treated, machinery and equipment and wind, water, electricity and other lines should be checked, and trial operation should be carried out.

[0073] Example 5

[0074] like Figure 1 As shown, a production and construction process of dry shotcrete includes all the contents of Example 4. In addition, during the spraying process, water and air are turned on, the water volume is adjusted, and the wind pressure is maintained at not less than 0.4MPa, the water pressure should be 0.1MPa higher than the wind pressure, and the amount of water added during the spraying process is controlled to ensure that there are no dry spots on the sprayed surface, no flow, strong adhesion, less rebound material, and the total amount of water added controls the water-cement ratio to 0.35;

[0075] The quick-setting agent is evenly added to the feed port of the shotcrete machine. The sprayer operates the nozzle to flush the rock surface from top to bottom. The sprayer sprays in sections in the order of first the wall and then the arch from bottom to top. When spraying, the nozzle should be as vertical as possible to the sprayed surface, and the angle should not be less than 70 degrees;

[0076] During spraying, the nozzle's trajectory should be spiral, with a diameter of 200-300mm, and it should move evenly and slowly in a circle-pressing semicircle method. The thickness of the sprayed concrete should be 50-70mm at a time, and it should be re-sprayed in time. The interval between re-spraying should not exceed 2 hours, otherwise the sprayed surface should be re-rinsed with high-pressure water.

[0077] The technical effect achieved by the above embodiment is: by improving the original shotcrete mix ratio and production process, the problems of poor use effect, insufficient later strength, poor durability, large dust, high rebound rate, etc. of dry shotcrete in the construction process are solved.

[0078] Example 6

[0079] like Figure 1 As shown, a production and construction process of dry shotcrete includes all the contents of Example 5. In addition, the dry shotcrete can obtain a concrete strength of 28 to 34 MPa and good adhesion by applying the above parameters.

[0080] The technical effects achieved by the above embodiments are: good concrete strength and good adhesion.

Claims

1. A dry shotcrete, characterized in that: The components of the dry shotcrete include: cementitious material, coarse aggregate, fine aggregate, water, water reducing agent and accelerating setting agent; Wherein, the gelling material is cement; The ratio of cement to concrete in the dry shotcrete composition is 1:4 to 1:5; The water-binder ratio of the dry shotcrete composition is 0.35 to 0.40; The amount of cementitious material added to the dry shotcrete composition is not less than 400 kg / m 3 .

2. A dry shotcrete according to claim 1, characterized in that: The dry shotcrete comprises, by weight, 100 parts of cement, 200 parts of coarse aggregate, 200 parts of fine aggregate, 35 parts of water, 2 parts of water reducing agent and 4 parts of accelerating setting agent.

3. The dry shotcrete according to claim 1, characterized in that: The cement is selected from one of silicate cement, ordinary silicate cement or special cement.

4. The dry shotcrete according to claim 1, characterized in that: The fineness modulus of the fine aggregate is greater than 2.5, the particles smaller than 0.075 mm in the fine aggregate are not greater than 20%, and the sand ratio of the dry shotcrete is preferably 45% to 60%.

5. The dry shotcrete according to claim 1, characterized in that: The maximum particle size of the coarse aggregate is not greater than 16 mm, and the coarse aggregate adopts continuous particle sizes.

6. A production and construction process of dry shotcrete according to claim 1, characterized in that: The specific steps of the production and construction process are as follows: Step 1, dry mixing: according to the weight parts of the components for preparing dry shotcrete, 100 parts of cement, 200 parts of coarse aggregate, 200 parts of fine aggregate and 35 parts of water are fed into a mixer and stirred evenly to obtain a dry concrete mixture; Step 2: Transport by material truck: put the above dry concrete mixture into the transport material truck and transport it to the construction site; Step 3: Use compressed air to deliver dry concrete mixture, accelerator and admixture to the nozzle of the shotcrete machine, mix with pressurized water and then spray to obtain shotcrete construction parts.

7. A production and construction process for dry shotcrete according to claim 6, characterized in that: The moisture content requirement of the dry concrete mixture is: the dry concrete mixture can be held into a ball by hand, and it seems to be scattered when the hand is released, and there is no smoke when blown to prevent dust; The mixing time of the dry concrete mixture is not less than 1.5 minutes; The dry concrete mixture should be used immediately after mixing and the storage time should not exceed 30 minutes; The concrete mixture must not be exposed to rain, soaked in water, or mixed with foreign objects during transportation and storage.

8. The production and construction process of dry shotcrete according to claim 6, characterized in that: The precautions for dry concrete mixture spraying are as follows: 1) The concrete should be sprayed in sections and layers from bottom to top. The length of each section should not be greater than 6m. If there are large depressions on the rock surface, the depressions should be sprayed flat first. The concrete surface sprayed on the rock surface should not slip or fall. The thickness of one spray can be determined by on-site tests based on the spraying location. 2) The nozzle should be perpendicular to the spraying surface, and the distance between them should be 0.6m to 1.8m. The nozzle should move horizontally and circularly continuously and slowly, and the spray layer thickness should be uniform; 3) When spraying in layers, the rear layer of concrete should be sprayed after the front layer of concrete has finally set for 1 hour, and the surface of the sprayed layer should be cleaned with air and water before spraying; 4) The rebound rate of concrete should be checked during the spraying process. The rebound rate of the side wall of the sprayed concrete should not be greater than 15%, and the rebound rate of the arch should not be greater than 25%; 5) The ambient temperature of the spraying operation site shall not be lower than 5°C; The sprayed concrete operation area should have good ventilation and lighting conditions; 6) After the spraying operation is completed, the thickness should be tested in time, and if it does not meet the requirements, it should be sprayed again in time.

9. A production and construction process of dry shotcrete according to claim 6, characterized in that: During the spraying process, water and air are turned on, and the water volume is adjusted to maintain the air pressure not lower than 0.4MPa. The water pressure should be 0.1MPa higher than the air pressure. The amount of water added during the spraying process is controlled to ensure that there are no dry spots on the sprayed surface, no flow, strong adhesion, and less rebound material. The total amount of water added controls the water-cement ratio to 0.35; The quick-setting agent is evenly added to the feed port of the shotcrete machine. The sprayer operates the nozzle to flush the rock surface from top to bottom. The sprayer sprays in sections in the order of first the wall and then the arch from bottom to top. When spraying, the nozzle should be as vertical as possible to the sprayed surface, and the angle should not be less than 70 degrees; During spraying, the nozzle's trajectory should be spiral, with a diameter of 200-300mm, and it should move evenly and slowly in a circle-pressing semicircle method. The thickness of the sprayed concrete should be 50-70mm at a time, and it should be re-sprayed in time. The interval between re-spraying should not exceed 2 hours, otherwise the sprayed surface should be re-rinsed with high-pressure water.

10. A production and construction process of dry shotcrete according to claim 6, characterized in that: The dry shotcrete can obtain a concrete strength of 28-34 MPa and good adhesion by applying the above parameters.

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