阅读说明：本技术 一种可用于湿喷工艺的超快凝早强型无碱粉体速凝剂及其制备方法和应用 (Ultra-fast-setting early-strength alkali-free powder accelerator for wet spraying process and preparation method and application thereof ) 是由 马伟斌 马荣田 顾忠良 郭小雄 马超锋 欧志强 于 2020-12-28 设计创作，主要内容包括：本发明提供了一种可用于湿喷工艺的超快凝早强型无碱粉体速凝剂及其制备方法和应用,原料：活性铝酸钙20.0-30.0份、硫酸铝10.0-15.0份、石膏7.0-10.0份、高铝水泥30.0-40.0份、氢氧化铝1.0-5.0份、氧化钙1.0-5.0份、纳米二氧化硅1.0-5.0份、助剂0-5.0份。与现有技术相比,本发明提速凝剂不仅可以单独应用,也可与液体速凝剂配合使用,改善了湿喷工艺不能用于软岩和涌渗水地段的缺点,大大扩宽了湿喷工艺的应用范围；其通过各组分与水泥之间的相互作用,使混凝土急凝早强,初凝时间小于30s,终凝时间小于1min,混凝土5min内强度即可达1.0MPa以上。(The invention provides an ultra-fast-setting early-strength alkali-free powder accelerator for a wet spraying process and a preparation method and application thereof, wherein the accelerator comprises the following raw materials: 20.0-30.0 parts of activated calcium aluminate, 10.0-15.0 parts of aluminum sulfate, 7.0-10.0 parts of gypsum, 30.0-40.0 parts of high-alumina cement, 1.0-5.0 parts of aluminum hydroxide, 1.0-5.0 parts of calcium oxide, 1.0-5.0 parts of nano silicon dioxide and 0-5.0 parts of auxiliary agent. Compared with the prior art, the accelerating agent can be used alone or in combination with a liquid accelerating agent, so that the defect that a wet spraying process cannot be used for soft rock and water-inrush areas is overcome, and the application range of the wet spraying process is greatly widened; through the interaction between each component and the cement, the concrete is quickly set and early strengthened, the initial setting time is less than 30s, the final setting time is less than 1min, and the strength of the concrete within 5min can reach more than 1.0 MPa.)

1. The ultra-fast-setting early-strength alkali-free powder accelerator for the wet spraying process is characterized by comprising the following raw materials in parts by weight:

2. the ultra-fast setting early strength alkali-free powder accelerator for wet spraying process as claimed in claim 1, wherein the activated calcium aluminate is ultra-fine nano activated calcium aluminate with specific surface area greater than 4000cm²/g。

3. The ultra-fast setting early strength alkali-free powder accelerator for wet spraying process as claimed in claim 1, wherein the activated calcium aluminate is prepared by melt quenching at 1800-2000 ℃.

4. The ultra-fast setting early strength alkali-free powder accelerator for wet spraying process according to claim 1, wherein the assistant comprises one or more of tackifier, early strength assistant or accelerating assistant.

5. The ultra-fast setting early strength alkali-free powder accelerator for wet spraying process of claim 3, wherein the tackifier is one of cellulose ether, latex powder or polyacrylamide.

6. The ultra-fast-setting early-strength alkali-free powder accelerator for the wet spraying process according to claim 3, wherein the early-strength assistant is one of triethanolamine, diethanolamine, triisopropanolamine, diethylene glycol, ethylene glycol, urea, sodium sulfate or magnesium sulfate.

7. The ultra-fast setting early strength alkali-free powder accelerator for wet spraying process as claimed in claim 3, wherein the set accelerator comprises one of sodium silicate, sodium aluminate, sodium carbonate, ferric sulfate or copper sulfate.

8. The preparation method of the ultra-fast-setting early-strength alkali-free powder accelerator for the wet spraying process as claimed in any one of claims 1 to 7 is characterized by comprising the following steps: and uniformly mixing the raw materials according to the formula ratio by using a high-speed stirrer to obtain the composition.

9. The application of the ultra-fast-setting early-strength alkali-free powder accelerator for the wet spraying process as claimed in any one of claims 1 to 7, which is characterized in that the accelerator is used for wet spraying concrete alone or is compounded with a liquid accelerator for the wet spraying concrete.

10. The use according to claim 8, characterized in that, when used alone in wet-sprayed concrete, the amount added is 8-12% of the mass of the cement, the initial setting time of the concrete is less than 28s, and the final setting time is less than 1 min;

or when the ultra-fast setting early strength type alkali-free powder accelerator and the liquid accelerator which can be used for the wet spraying process are compounded and used for wet spraying concrete, the mass ratio is 1: 1; the addition amount of the compound accelerator is 7-11% of the mass of the cement; the initial setting time of the concrete is less than 35s, and the final setting time is less than 1min30 s.

Technical Field

The invention belongs to the technical field of constructional engineering, and particularly relates to an ultra-fast-setting early-strength alkali-free powder accelerator for a wet spraying process, a preparation method and application thereof, which can be widely applied to sprayed concrete in various projects such as tunnels, mines and the like.

Background

In recent years, infrastructure construction in China is rapidly developed, and sprayed concrete is used as a special concrete material and widely applied to construction of traffic tunnels, hydraulic tunnels and mine roadways and various repair, reinforcement, protection and emergency projects. The sprayed concrete is an important component of a new-Australian tunnel construction method and is also the most common construction method applied to large tunnel construction engineering in China. The quick-setting admixture is required to be added into the sprayed concrete, so that the concrete is quickly set and hardened and is firmly combined with the sprayed rock surface, and the supporting and reinforcing effects are achieved.

The spraying method of sprayed concrete mainly comprises dry spraying and wet spraying. The wet spraying process, especially after the alkali-free liquid accelerator gradually matures, has become a development trend of domestic and foreign concrete spraying technology due to better homogeneity and durability, effective reduction of rebound quantity and dust concentration, and environmental protection. However, the traditional wet spraying process can only be matched with a liquid accelerator, can only be suitable for a hard rock waterless section, has great limitation, cannot be quickly formed for a soft rock and a water seepage section with a thicker sprayed layer, and has great resilience and poor effect.

The powder accelerator applied to the traditional dry spraying process has high alkali content, serious later strength retrogradation of concrete and low strength, generally only can reach C25 concrete, has low cohesiveness and large concrete resilience, generates a large amount of dust in the construction process, and has the dust concentration reaching 10mg/m after 5min of construction³Seriously harming the health of constructors and polluting the environmentAnd (4) environmental conditions. But because of the wide application range, the material can be applied to soft rock and permeable tunnels, and still occupies a certain share in the sprayed concrete.

Therefore, the development of an alkali-free accelerator product is urgently needed, and the advantages of a wet spraying process and a dry spraying process are integrated.

Disclosure of Invention

The invention aims to provide an ultra-fast-setting early-strength alkali-free powder accelerator for a wet spraying process, which can be widely applied to sprayed concrete in tunnels, mines and the like, improves various problems existing in the current sprayed concrete construction process, and is a green, environment-friendly and pollution-free accelerator product for the sprayed concrete with wide application range, good construction performance, small dust, low resilience.

The invention also aims to provide a preparation method of the ultra-fast-setting early-strength alkali-free powder accelerator for the wet spraying process.

The last purpose of the invention is to provide the application of the ultra-fast setting early strength type alkali-free powder accelerator which can be used for the wet spraying process, and the ultra-fast setting early strength type alkali-free powder accelerator is independently used for wet spraying concrete or is compounded with a liquid accelerator for the wet spraying concrete.

The specific technical scheme of the invention is as follows:

an ultra-fast-setting early-strength alkali-free powder accelerator for a wet spraying process comprises the following raw materials in parts by weight:

the activated calcium aluminate is superfine nano activated calcium aluminate with specific surface area more than 4000cm²/g。

The active calcium aluminate is prepared by melt quenching at 1800 and 2000 ℃.

The aluminum sulfate is one of industrial aluminum sulfate or polymeric aluminum sulfate with the fineness of more than 30 meshes.

The gypsum is preferably hemihydrate gypsum.

The high alumina cement is one of CA70 or CA 80.

The aluminum hydroxide is nano aluminum hydroxide.

Preferably, the mass part of the auxiliary agent is 1-5.0 parts

The auxiliary agent comprises one or more of a tackifier, an early strength auxiliary agent or a coagulation accelerator.

The tackifier is one of cellulose ether, latex powder or polyacrylamide;

the early strength auxiliary agent is one of triethanolamine, diethanolamine, triisopropanolamine, diethylene glycol, ethylene glycol, urea, sodium sulfate or magnesium sulfate;

the coagulation accelerator is selected from alkaline component coagulation accelerators, preferably one of sodium silicate, sodium aluminate or sodium carbonate;

or the coagulation promoting assistant is selected from one of ferric sulfate or copper sulfate.

When the accelerating agent is selected from alkaline components, the addition amount of the accelerating agent is less than 2 wt%.

The invention provides an ultra-fast-setting early-strength alkali-free powder accelerator for a wet spraying process, which is prepared by the following steps:

and uniformly mixing the raw materials according to the formula ratio by using a high-speed stirrer to obtain the composition.

The ultra-fast-setting early-strength alkali-free powder accelerator for the wet spraying process is applied to wet spraying concrete independently or is compounded with a liquid accelerator to be used for the wet spraying concrete.

When the mortar is independently used for wet-spraying concrete, the addition amount is 8-12% of the mass of cement, the initial setting time is less than 28s, and the final setting time is less than 1 min; when the method is applied to the soft rock water seepage tunnel, the rebound rate is less than 10 percent, the strength reaches 1.0MPa in 10min, and the deformation and damage of surrounding rocks are avoided.

When the ultra-fast-setting early-strength alkali-free powder accelerator and the liquid accelerator which can be used for the wet spraying process are compounded and used for wet spraying concrete, the concrete spraying agent can be randomly adjusted according to the actual spraying effect, and the preferable mass ratio is 1: 1; the total adding amount of the compound accelerator is 7-11% of the mass of the cement, the initial setting time is less than 35s, and the final setting time is less than 1min30 s; when the method is applied to the soft rock water seepage tunnel, the rebound rate is less than 10 percent, the strength reaches 1.0MPa in 10min, and the deformation and damage of surrounding rocks are avoided.

The raw materials used in the present invention are commercially available without specific description.

The ultra-fast-setting early-strength alkali-free powder accelerator for the wet spraying process can be widely applied to sprayed concrete in various projects such as tunnels, mines and the like. The active calcium aluminate in the formula is prepared by melt quenching at 1800-2000 ℃, has higher activity and extremely high hydration speed compared with the common calcium aluminate, and can quickly set and harden the ordinary silicon cement by adding 5 percent of the active calcium aluminate to generate early strength; but simultaneously, the setting is too fast, so that the structure of the cement stone is loose, most of hydration products are ettringite with lower strength, the hydration of tricalcium silicate is hindered, the strength of the cement stone 1d is lower, the detection is carried out by taking the national standard GB/T35159-2017 accelerator for sprayed concrete as the basis, the compressive strength of the mortar 1d is lower than 3.0MPa, and the mortar directly applied to the sprayed concrete can cause the sprayed concrete to lose the supporting function, thereby generating engineering accidents; the invention adds proper amount of aluminum sulfate, gypsum (calcium sulfate) and early strength components, can adjust the crystal form of the cement stone, promotes the further reaction of the ettringite, improves the 1d strength while ensuring the early strength, introduces more soluble aluminum ions and calcium ions, accelerates the reaction speed of the active calcium aluminate and the cement, enhances the action effect of the calcium aluminate and reduces the mixing amount. The nanometer aluminum hydroxide and the nanometer silicon dioxide can ensure that the hardened cement is more compact, can promote the hydration of tricalcium silicate, and can interact with other components to ensure that the 1d strength and the later strength of the cement are not lost. The addition of the tackifier and the coagulation accelerator can further reduce the rebound rate of the sprayed concrete, and the effect is better.

The ultra-fast setting early-strength alkali-free powder accelerator for the wet spraying process can be independently applied to wet sprayed concrete, or the alkali-free powder accelerator and a commercially available alkali-free liquid accelerator are mixed according to the mass ratio of 1:1, the composite application can reduce the mixing amount of the accelerator, lead the powder accelerator to be dispersed evenly, ensure the early strength of the concrete in quick setting and lead the wet spraying process to be applied to various severe conditions.

Compared with the prior art, the alkali-free powder accelerator provided by the invention can be used independently, and can also be used in combination with various liquid accelerators in the market, so that a synergistic effect is exerted, the defect that a wet spraying process cannot be used for soft rock and water-inrush areas is overcome, and the application range of the wet spraying process is greatly widened; through the interaction between each component and cement, the concrete is quick to set and early to strengthen, the initial setting time and the final setting time are short, the concrete can reach higher strength in a short time, the rebound rate is low, and meanwhile, the concrete does not contain chloride ions and fluoride ions, is alkali-free, non-toxic, non-corrosive and green and environment-friendly; the wet spraying process can be applied to various surrounding rock grades and tunnel geological conditions, and particularly can be used for quickly forming soft rocks and water-inrush sections with thicker sprayed layers, so that the effect is excellent.

Drawings

FIG. 1 is a schematic diagram of the wet spray process of the present invention;

FIG. 2 is a schematic view of the mixer configuration;

FIG. 3 is a sectional view of the junction of the communicating hole and the mixing protrusion.

The labels in the above figures are:

1. mixer, 2, concrete supply equipment, 3, accelerator supply equipment, 4 and nozzle.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Test materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

The specific techniques or conditions not specified in the examples can be performed according to the techniques or conditions described in the literature in the field or according to the product specification.

Example 1

A preparation method of an ultra-fast setting early strength type alkali-free powder accelerator for a wet spraying process comprises the following steps:

230g of activated calcium aluminate, 150g of aluminum sulfate, 100g of semi-hydrated gypsum, 400g of CA70 high-alumina cement, 40g of nano aluminum hydroxide, 40g of calcium oxide, 10g of nano silicon dioxide, 10g of latex powder, 10g of diethanolamine and 10g of ferric sulfate are accurately weighed and placed in a high-speed stirrer to be uniformly mixed, and the ultra-fast-setting early-strength alkali-free powder accelerator for the wet spraying process is obtained.

The active calcium aluminate is prepared by melting and quenching at 1900 ℃, is superfine nano active calcium aluminate and has a specific surface area of more than 4000cm²(ii)/g; the aluminum sulfate is industrial aluminum sulfate with the fineness of more than 30 meshes.

Example 2

A preparation method of an ultra-fast setting early strength type alkali-free powder accelerator for a wet spraying process comprises the following steps:

accurately weighing 300g of activated calcium aluminate, 100g of aluminum sulfate, 100g of semi-hydrated gypsum, 350g of CA80 high-alumina cement, 30g of nano aluminum hydroxide, 40g of calcium oxide, 20g of nano silicon dioxide, 10g of polyacrylamide, 10g of diethanolamine and 10g of sodium silicate, and uniformly mixing in a high-speed stirrer to obtain the ultra-fast-setting early-strength alkali-free powder accelerator.

The active calcium aluminate is prepared by melting and quenching at 1800 ℃, is superfine nano active calcium aluminate and has a specific surface area of more than 4000cm²(ii)/g; the aluminum sulfate is polymerized aluminum sulfate with the fineness of more than 30 meshes.

Comparative example 1

The preparation method of the powder accelerator comprises the following steps:

accurately weighing 300g of commercially available Tianhong No. 558 calcium aluminate, 100g of aluminum sulfate, 100g of semi-hydrated gypsum, 350g of high-alumina cement, 40g of calcium oxide, 20g of nano silicon dioxide, 10g of polyacrylamide, 10g of diethanolamine and 10g of sodium silicate, and uniformly mixing in a high-speed stirrer to obtain the powder accelerator.

Comparative example 2

The preparation method of the powder accelerator comprises the following steps:

1000g of activated calcium aluminate is put into a high-speed stirrer to be uniformly mixed, and the powder accelerator is obtained.

Comparative example 3

The preparation method of the alkali-free liquid accelerator comprises the following steps: 200g of deionized water and 60g of aluminum hydroxide micropowder are added into a three-neck flask provided with an electric stirrer and a thermometer, 120g of hydrofluoric acid with the concentration of 40 percent is added during stirring and stirred until the solution is completely dissolved, 180g of water, 410g of aluminum sulfate and 10g of triethanolamine are added at one time and stirred until the solution is completely dissolved, and the fluorine-containing alkali-free liquid accelerator is obtained.

Comparative example 4

The preparation method of the early strength type alkali-free liquid accelerator comprises the following steps: 350g of water, 50g of self-made activated aluminum, 550g of aluminum sulfate, 40g of triethanolamine, 2g of polyacrylamide, 3g of defoamer and 5g of ethylene glycol are sequentially added into a three-neck flask provided with an electric stirrer and a thermometer, heated to 50 ℃, and uniformly stirred to obtain the chlorine-free fluorine-free environment-friendly alkali-free liquid accelerator containing the nano early strength agent.

The products prepared by the above examples and comparative examples are separately used for detection, and then the product of example 1 and the product of comparative example 3, the product of example 2 and the product of comparative example 2 are respectively detected according to the compound application with the mass ratio of 1:1, and the reference cement and the sea snail cement are respectively adopted for detection according to the national standard GB/T35159-2017 accelerator for sprayed concrete, and the selected cements are all P.O.42.5 common portland cement. The results are shown in table 1 below:

TABLE 1 examination results of examples and comparative examples

TABLE 2 spray Resilience for each example and comparative example

From the above data it can be seen that: when the ultra-fast-setting early-strength alkali-free powder accelerator prepared by the invention is added, the concrete can be quickly set and early strengthened, and the 1d strength reaches more than 9 MPa; the calcium aluminate No. 558 sold in Tianhong brand in the market is adopted in the proportion 1, and because the activity is lower, the cement cannot generate the effect of quick setting and early strength and cannot be applied to sprayed concrete; comparative example 2 the concrete can be quickly solidified and early strengthened by simply adopting the active calcium aluminate as the accelerating agent, but the concrete is prevented from further hydration due to the production of a large amount of ettringite, so that the 1d compressive strength is extremely low, and the supporting requirement of the sprayed concrete can not be met; comparative example 3 and comparative example 4 are alkali-free liquid setting accelerators commonly used in the market at present, which can meet the support requirements of wet-type spraying of sprayed concrete in a hard rock water-free section, but due to low early strength, the concrete has large resilience and serious block falling when being applied to a water-permeable soft rock section, and is seriously or even difficult to spray on a base surface, so that the support effect cannot be exerted; when the ultra-fast-setting early-strength alkali-free powder accelerator is compounded with a commercially available liquid accelerator for use, the mixing amount can be reduced to 7 percent, the cost is saved, the initial setting time is less than 35s, and the final setting time is less than 1min30 s; when the method is applied to the soft rock water seepage tunnel, the rebound rate is less than 10 percent, the strength reaches 1.0MPa in30 min, and the deformation and damage of surrounding rocks are avoided. The sprayed concrete can be applied to various surrounding rock levels and tunnel geological conditions, and the application range of the wet spraying process is expanded.

Example 3

An application of an ultra-fast setting early strength type alkali-free powder accelerator for a wet spraying process comprises the following specific steps:

the product of the example 1 and the product of the comparative example 3 are compounded according to the mass ratio of 1:1 and are used for spraying in a soft rock water seepage area, preferably, a wet spraying system for the soft rock water seepage area is adopted, and the wet spraying system comprises an accelerator supply device 3, a concrete supply device 2 and a spraying mechanism; the spraying mechanism comprises a nozzle 4; the nozzle 4 is connected with a mixer 1, and the mixer 1 is respectively connected with an accelerator supply device 3 and a concrete supply device 2; the accelerator supply device 3 comprises a powder accelerator supply device 31 and a liquid accelerator supply device 32; so that the mixer 1 can be added with two accelerating agents to realize the application; conventional supply equipment can be used for the concrete supply equipment 2, and can be set according to requirements, and similarly, the accelerator supply equipment 3 can also be used for conventional supply equipment, so that the change of the components of the conventional wet spraying system can be reduced, and the cost of changing the equipment of the wet spraying system is reduced.

Further, the mixer 1 comprises a mixer body, the mixer body comprises an outer sleeve 11 and an inner sleeve 12, and the inner sleeve 12 is located inside the outer sleeve 11; the inner sleeve body 12 is provided with a communication hole 13, and the outer sleeve body 11 is provided with a connecting opening 14; one end of the inner sleeve body 12 is connected with the concrete supply equipment 2, the other end of the inner sleeve body is connected with the nozzle 4, and the inner sleeve body 12 is mainly used for concrete flowing and subsequent mixing of concrete and an accelerating agent; the outer sleeve body 11 is connected with the accelerator supply device 3, the accelerator supply device 3 supplies the accelerator into the outer sleeve body 11, and the accelerator needs to enter the inner sleeve body 12 in order to ensure the mixing of the accelerator and the concrete, so the communication hole 13 is arranged on the inner sleeve body 12 in the invention, and the communication hole 13 can be used for the accelerator to enter the inner sleeve body 12, so that the accelerator is mixed with the concrete, and the subsequent use effect is ensured.

The inner wall of the outer sleeve body 11 and the outer wall of the inner sleeve body 12 are distributed at intervals to form a material mixing cavity, and the setting of the material mixing cavity facilitates the accelerator to enter the outer sleeve body 11; in addition, a separation plate 15 is arranged in the mixing cavity; the separation plate 15 divides the mixing cavity into a first cavity 151 and a second cavity 152; the first cavity 151 is used for the entry of the powder accelerator, and the second cavity 152 is used for the entry of the liquid accelerator, so that the mixing of the powder accelerator and the liquid accelerator can be avoided, and the difficulty of the accelerator entering the communication hole 13 is reduced.

Meanwhile, the inner sleeve body 12 and the outer sleeve body 11 can be coaxially distributed, and the coaxial distribution can facilitate the integral arrangement of the mixer 1, so that the dynamic balance of the whole device is more suitable.

The connecting opening 14 comprises a first feeding hole 141 and a second feeding hole 142, the first feeding hole 141 is communicated with the first cavity 151, and the second feeding hole 142 is communicated with the second cavity 152; by the arrangement, the accelerating agent supply equipment 3 can supply different accelerating agents for the inner sleeve 12 in different areas, and powder and liquid accelerating agents are prevented from being mixed.

The first cavity 151 is connected with the powder accelerator supply device 31, and the second cavity 152 is connected with the liquid accelerator supply device 32; this arrangement is also provided to facilitate the zonal feeding of the accelerator, and the first cavity 151 is arranged on the side of the mixer 1 close to the concrete feeding apparatus 2; the second cavity 152 is arranged on the mixer close to the side of the nozzle 4; due to the arrangement, the alkali-free powder accelerator is supplied before the alkali-free liquid accelerator is supplied after the alkali-free liquid accelerator is supplied, so that the powder accelerator can be mixed with concrete better and conveniently, and the powder accelerator which is difficult to disperse is uniformly mixed with the concrete; meanwhile, the mixing uniformity of the integral accelerator and the concrete is better ensured.

The inner walls of the inner sleeve body 12 and the outer sleeve body 11 are both provided with material mixing bulges 17; the setting of compounding arch 17 plays a barrier effect, can restrict the concrete flow in the inner cover body 12 for certain regional flow of concrete obtains the restriction, thereby makes the concrete with including in the inner cover body 12 the flow direction mixed and disorderly, thereby plays better mixed action.

At least one mixing bulge 17 is arranged on the periphery of each communication hole 13, the mixing bulge 17 is arranged in front of the communication hole 13, the front is calibrated in the concrete flowing direction, in other words, a certain mixing bulge 17 and the communication hole 13 are used as reference points, and when concrete flows; concrete contacts the mixing bulge 17 firstly, the mixing bulge 17 is arranged, the mixing uniformity of the accelerating agent and the concrete is increased on the basis, the mixing bulge 17 also plays a role in blocking and shunting, and the difficulty of the concrete flowing into the mixing cavity through the communicating hole 13 is increased; during the specific use, the material mixing protrusion 17 is to the concrete that will flow through from the intercommunicating pore 13 to carry out the reposition of redundant personnel operation for the concrete can not get into the intercommunicating pore 13 basically, thereby has avoided the concrete to drop the problem of material mixing cavity from the intercommunicating pore 13, and in addition, the accelerating agent is through the pressurized entering of high-pressure gas when getting into interior cover 12, thereby the impact of high-pressure gas is also fine avoids the concrete to get into in the material mixing cavity through the intercommunicating pore 13.

The specific application method comprises the following steps:

the principle of the wet spraying system is shown in figure 1, concrete is mixed according to required performance by a mixing station and then is transported to a construction site to be placed into a concrete storage tank of a wet spraying unit, the concrete enters an inner cavity of a mixer 1 through supply equipment, meanwhile, an alkali-free powder accelerator prepared in example 1 and an alkali-free liquid accelerator prepared in comparative example 3 are respectively supplied into a mixing cavity through a powder accelerator supply equipment 32 and a liquid accelerator supply equipment 32, enter the concrete in the inner cavity of the mixer 1 through communication holes 13 distributed on an inner sleeve body 12 and are uniformly mixed, and the concrete mixed with the accelerators is sprayed to a soft rock permeable section through a nozzle 4; the pressurizing device is connected with the accelerator supply device 3, when the accelerator supply device 3 supplies the accelerator to the mixer 1, the alkali-free powder accelerator and the alkali-free liquid accelerator are pressurized by the pressurizing device to form pressurized powder and liquid, and finally enter the concrete in the inner sleeve 12 through the communicating hole 13. The pressurizing equipment sets up quantity and can sets up as required, and the pressurizing equipment still has a guard action except that being used for mixing with the accelerator, just requires, before mixer 1 supplies the concrete, and high-pressure gas is let in earlier to mixer 1, can avoid mixing earth to get into mixer 1 back like this, and mixer 1 gets into in the compounding cavity because of the intercommunicating pore 13 of mixer 1 lower extreme of gravity.

The concrete was formulated according to the following formulation in Table 3, with the addition of the accelerator being 7% by weight of the concrete, and the results are shown in Table 4.

Example 4

An application of an ultra-fast setting early strength type alkali-free powder accelerator for a wet spraying process comprises the following specific steps:

the product of the example 1 and the product of the comparative example 4 are compounded according to the mass ratio of 1:1 and are used for spraying in the soft rock permeable area, and the specific spraying method and the system are the same as those in the example 3.

TABLE 3 concrete mix proportions

The results of the injection are shown in table 4:

TABLE 4 results of injection

The ultra-fast-setting early-strength alkali-free powder accelerator for the wet spraying process can be applied to any severe geological conditions and achieve a good spraying effect as dry spraying, and also has good concrete spraying performance and construction performance as wet spraying, and has the characteristics of excellent durability, low resilience, low dust, good construction environment, no alkali, no fluorine, no chlorine, no toxicity, no corrosion, proper mixing amount, low strength loss, high cost performance and the like.