A magnesium rebound inhibitor for shotcrete and its preparation method and application

Abstract

The present invention discloses a magnesium rebound inhibitor for shotcrete, a preparation method, and an application thereof, and belongs to the technical field of concrete admixtures. The magnesium rebound inhibitor for shotcrete of the present invention is prepared by a physical coating process using a ternary magnesium calcined mineral and an inorganic accelerating magnesium salt as core samples and an alkanolamine ester compound as a shell; the magnesium rebound inhibitor can be used for shotcrete alone or together with mineral admixtures and / or rheology-modifying components for shotcrete. The shotcrete rebound material can be fully recycled and reused, significantly reducing the rebound loss of shotcrete during the shotcrete spraying process, reducing the mid-to-late volume shrinkage of the shotcrete material, and restraining the long-term deformation of weak surrounding rocks. The preparation process is green and low-carbon, and the performance adaptability is wide.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete admixtures, and particularly relates to a magnesium rebound inhibitor for shotcrete, a preparation method and an application thereof. Background Art

[0002] Shotcrete is a special type of concrete developed from mining, tunnel support, and slope reinforcement. Without the need for formwork and under specific wind pressure conditions, it can adhere well to surrounding rock surfaces with poor self-stability and large loose deformation, achieving an initial support effect by controlling the loosening and deformation of the surrounding rock. However, due to internal and external construction factors such as fluctuations in aggregate quality, high-volume cementitious material composition, rapid-setting hydration and hardening characteristics, and specialized shotcrete processes, shotcrete often exhibits high rebound material loss. The measured average rebound material fluctuates between 20-40%, with rebound material concentrated on both sides of the arch base and in the arch crown. This high rebound material loss significantly increases the construction costs of tunnel lining structures, including manpower, equipment, machinery, and construction schedule. Furthermore, the resulting shotcrete material significantly decreases its cementitious activity due to accelerated early hydration, making it unusable without treatment, which in turn increases the costs of soil removal and landfill.

[0003] In recent years, how to effectively reduce the rebound rate of shotcrete has become an important branch of research on the low-carbonization of concrete materials. After realizing that conventional improvement methods such as optimizing the shotcrete process and increasing material costs (such as increasing cement dosage and using higher dosages of alkali-free accelerators) are difficult to meet the technical requirements for reducing the rebound loss of shotcrete under adverse geological conditions such as over-excavation, water seepage, and soft rock, many engineering practitioners and product developers have developed products with specific functional properties to reduce rebound losses. However, the development of this technology is still immature and there are many problems that need to be solved urgently. The following are some of the problems that need to be solved urgently:

[0004] The first problem is that it has a great impact on setting and hardening: some shotcrete rebound-reducing materials accelerate the early hydration rate and strength development of shotcrete by adding a certain amount of high-aluminum or sulfur-aluminum fast-hardening cement, or introduce organic macromolecular thickeners, clay minerals, copolymer emulsions or latex powders to improve the cohesion of the shotcrete slurry, thereby enhancing the cohesion of the interface between the shotcrete and the surrounding rock. However, when the above-mentioned rebound-reducing materials are added during the plastic stage of shotcrete, on the one hand, the fast-hardening gelling system or the introduction of organic macromolecular thickeners will cause the fluidity loss of the shotcrete mixture to increase, resulting in problems such as excessive injection pump pressure, pump blockage or difficulty in material discharge in the shotcrete. On the other hand, the copolymer emulsion or latex powder and clay minerals have a strong retarding effect on the early hydration of the cement mineral phase, affecting the effectiveness of the quick-setting agent, which is not conducive to shotcrete construction. Chinese patent CN114920491A discloses a rebound-reducing shotcrete admixture and its preparation method, in which 30-50% fast-hardening cement is added and a cellulose thickener is introduced, both of which will affect the workability of the shotcrete mixture. Chinese patent CN115626792A discloses a rebound inhibitor for shotcrete, which includes an epoxy resin emulsion as an interface bonding component and a cellulose ether and redispersible latex powder as a rheology control component, both of which affect the early setting and hardening of shotcrete. Korean patent KR101252962B1 discloses a shotcrete composition containing rapid-setting high-alumina cement, which also utilizes Portland cement, high-alumina cement, and rapid-setting cement in the cementitious system.

[0005] The second problem is the great influence on mechanical strength: some rebound-reducing materials are mixed with more low-hydration-activity mineral admixtures to achieve dispersion and loading of organic components, or alkali metal inorganic salts are introduced to improve early hydration and hardening strength. However, too many low-activity mineral admixtures can easily lead to slow development of the early mechanical strength of shotcrete with low early strength, thereby affecting its early restraint effect on weak surrounding rock. While alkali metal inorganic salts improve the early hydration and hardening strength, they have a greater impact on the later strength of shotcrete and will increase the risk of alkali-aggregate reaction. Chinese patent CN115490480A discloses a low-rebound shotcrete containing bioadhesive and its preparation and application methods. The components contain 18-27% of low-activity mineral admixtures such as mineral powder and fly ash, and lack compounds or components that stimulate early activity, which will cause the early strength of the shotcrete to decrease and affect the support effect; Chinese patent CN115536300A discloses a functional admixture for shotcrete and its preparation method and application, including three components with a mass ratio of 3~5:8~10:5. Among them, 50-80% of the second component magnesium sulfate and sodium silicate is used as a chemical activator to improve the early strength of concrete, but the introduction of too much alkali metal salt will affect its later strength and service durability.

[0006] The third problem is that the components are complex and difficult to produce or measure: some rebound-reducing materials introduce expensive raw materials, incorporate complex organic or inorganic components, or have a complicated preparation method to achieve comprehensive performance improvement, which causes many inconveniences to the market application, industrial production, and use and measurement of the materials. Chinese patent CN115849764A discloses a shotcrete admixture and its preparation method and application, including 8 to 15 parts of redispersible copolymer powder, 10 to 20 parts of early strength enhancer, 40 to 60 parts of composite mineral micropowder, 0.5 to 3 parts of modified composite fiber, 0.1 to 1.5 parts of water reducer, and 0.05 to 0.5 parts of polyamide wax powder. However, the raw materials such as silicon carbide nanopowder as composite mineral micropowder, CaAl-layered double hydroxide as early strength enhancer, composite fiber modified by 2-morpholineethanesulfonic acid / acetic acid solution, and polyamide wax powder are relatively expensive in the market, have limited sources, and are difficult to prepare; Chinese patent CN116161 893A discloses a method for preparing a cross-linking monomer for preparing high-early-strength, low-rebound concrete. The technical idea is to add 0.1-0.3 parts of a reducing agent and 5-15 parts of a cross-linking monomer to 0.5-2 parts of a water-reducing agent to prepare a water-reducing mixture, and add 0.3-2 parts of an initiator to 6-12 parts of an accelerator to prepare a quick-setting mixture. The monomers containing multiple saturated double bonds are cross-linked under the action of the initiator to achieve the rebound reduction effect. The cross-linking monomer and the initiator are fed separately, which is difficult to accurately measure during on-site construction. The initiator is one or more of sodium persulfate, potassium persulfate, ammonium persulfate and potassium hydrogen persulfate, which will affect the performance of the accelerator and cause adverse precipitation.

[0007] The fourth problem is the neglect of the durability of shotcrete: shotcrete is usually designed with a higher cement content and a larger water-cement ratio material component. Therefore, the material usually exhibits a higher tendency to shrink in the later stage of drying, which leads to a greater risk of cracking of shotcrete in the later stage, inducing durability problems such as a decrease in the bearing capacity of the primary support structure and an increase in water seepage and dissolution. However, simply introducing polymer rheology-modified materials into some rebound-reducing materials cannot improve the above-mentioned durability problems, and the adaptability of existing chemical shrinkage reducers or inorganic expansion and shrinkage components in shotcrete is still unknown. Chinese patent CN108147705 A discloses a magnesium-based high-efficiency anti-cracking agent for cement concrete, comprising a magnesium expansion component and a layer of cement hydration heat regulating component for filling its internal pores or covering its surface. However, the agent is mainly used for concrete structures with strength grades of C30 and above for side walls, bottom plates, and top plates that require shrinkage compensation, crack resistance, impermeability, and temperature control. It does not include sprayed concrete materials with a special spraying process. Furthermore, the cement hydration heat regulating component is dextrin, which has a strong effect of delaying early hydration, hindering the rapid setting and hardening effect of the accelerator, resulting in an increased spraying rebound rate.

[0008] Therefore, how to provide a rebound suppression material for shotcrete that has a wide preparation source, strong rebound reduction effect, good adaptability to concrete, can be used as a secondary solid waste for shotcrete rebound materials, and has better later crack resistance is an engineering and technical problem that needs to be solved urgently for those skilled in the art. Summary of the Invention

[0009] In response to the problems in the existing technology such as the large negative impact of rebound reducing materials on coagulation and hardening, the decline in mechanical strength in the early and late stages, the complex components and the difficulty in production and measurement, as well as the high cost and difficulty of disposing of the solid waste of the sprayed rebound materials, and the low improvement in the later crack resistance, the present invention provides a low-carbon and high-durability technology demand, as well as a magnesium rebound inhibitor for shotcrete, a preparation method and application thereof.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] A magnesium rebound inhibitor for shotcrete, comprising a shell A and a core sample B, wherein the shell A is coated on the surface of the core sample B, and the mass ratio of the shell A to the core sample B is 1:10-20;

[0012] The shell A is an alkanolamine ester compound, the relative molecular mass of the alkanolamine ester compound is less than 1000, and the hydrolysis temperature is 20-80°C;

[0013] The core sample B is composed of a ternary magnesia calcined mineral and an inorganic coagulant magnesium salt, and the mass ratio of the ternary magnesia calcined mineral to the inorganic coagulant magnesium salt is (95-75): (5-25); the ternary magnesia calcined mineral is prepared by a light-burning process of dolomite, clay mineral and spray rebound material, and the mass ratio of the dolomite, clay mineral and spray rebound material is (30-50): (20-40): (10-50), and the temperature of the light-burning process is 800-1000°C.

[0014] Furthermore, the alkanolamine ester compound is an ester compound of diethanolamine or an ester compound of triethanolamine.

[0015] Furthermore, the alkanolamine ester compound is selected from triethanolamine acrylate, triethanolamine stearate, triethanolamine propionate, triethanolamine methylpropionate, triethanolamine acetate, triethanolamine oleate or diethanolamine acetate or diethanolamine oleate.

[0016] Furthermore, the light firing process is selected from a vertical kiln process, a suspension kiln process or a rotary kiln process, preferably a suspension kiln process.

[0017] Furthermore, the magnesium carbonate content in the magnesite is greater than 90%.

[0018] Furthermore, the clay mineral is selected from kaolin, bentonite, montmorillonite, illite or chlorite, preferably kaolin.

[0019] Furthermore, the sprayed rebound material is a concrete material obtained by spraying, rebounding, and falling and then collecting dry-process sprayed concrete, damp-process sprayed concrete, or wet-process sprayed concrete.

[0020] Furthermore, the inorganic coagulant-accelerating magnesium salt is selected from magnesium phosphate, magnesium hydroxide, magnesium formate, magnesium nitrate or magnesium sulfate.

[0021] The preparation method of the above-mentioned magnesium rebound inhibitor adopts a physical coating process and includes the following steps:

[0022] The ternary magnesia calcined mineral and inorganic coagulant magnesium salt are added to a suspension container, and the air flow or dispersion medium is turned on to fully disperse the materials to form a stable dispersed fluidized bed bottom layer or air flow layer; the alkanolamine ester compound is introduced into the liquid phase pipeline, and the preparation is completed under specific process temperature and operation time.

[0023] Furthermore, the physical coating process is a fluidized bed process or a spray drying process; preferably a fluidized bed process, the process temperature is 85-105° C., and the process time is 1.5-3 hours.

[0024] When using the above-mentioned magnesium rebound inhibitor, according to the spraying construction method, the magnesium rebound inhibitor is added during the mixing process of cement paste, mortar or concrete, and the addition amount accounts for 5-20% of the total mass of the cementitious material.

[0025] A liquid magnesium rebound inhibitor for shotcrete, comprising the aforementioned magnesium rebound inhibitor and water, wherein the water content is 40-60% of the total mass of the liquid magnesium rebound inhibitor, and the magnesium rebound inhibitor content is no less than 40% of the total mass of the liquid magnesium rebound inhibitor. The magnesium rebound inhibitor is used to prepare the liquid magnesium rebound inhibitor, effectively reducing the difficulty of pumping and metering the magnesium rebound inhibitor and improving its dispersion effect.

[0026] A rebound suppression composition for shotcrete, comprising the above-mentioned liquid magnesium rebound suppressant and an auxiliary rebound-reducing component, wherein the mass ratio of the liquid magnesium rebound suppressant to the auxiliary rebound-reducing component is (85-95): (5-15);

[0027] The auxiliary rebound reducing component is a mineral admixture and / or a rheology modifying component;

[0028] The mineral admixture is selected from fly ash, slag powder, silica fume, steel slag powder or metakaolin, and its function is to provide auxiliary gelation and improve the rheological properties of concrete paste;

[0029] The rheology-modifying component is an organic tackifier and / or a redispersible latex powder, wherein the organic tackifier is selected from amide organic matter, methyl cellulose ether, hydroxyethyl cellulose ether, hydroxypropyl cellulose ether, maltodextrin, xanthan gum or gellan gum, and the amide organic matter is selected from polyacrylamide, N-hydroxymethyl acrylamide, dimethylformamide or cyclopropamide; the redispersible latex powder is selected from vinyl propionate polymer latex powder, pure acrylic acid copolymer latex powder, styrene-acrylate copolymer latex powder, vinyl acetate-versatate copolymer latex powder, vinyl acetate-ethylene copolymer latex powder or vinyl acetate-vinyl chloride-acrylate copolymer latex powder, and its function is to improve the rheological viscosity of the concrete slurry and its bonding and adhesion to the rock mass or the sprayed surface.

[0030] The method for preparing the rebound suppression composition for shotcrete comprises the following steps:

[0031] Step 1, preparing the above-mentioned magnesium rebound inhibitor for shotcrete;

[0032] Step 2: Add water according to the material ratio, turn on the heating and wait until the temperature reaches 45-60°C, then add the auxiliary rebound reducing component while stirring for 30-60 minutes, the stirring rate is 500-1000 r / min, and the total stirring time is 1-1.5 hours;

[0033] Step 3: start cooling, add the magnesium rebound inhibitor after the temperature drops to 30° C., and keep stirring for 1.5 to 3.0 hours to obtain the rebound suppressing composition for shotcrete. The stirring rate is 300-500 r / min.

[0034] When using the above-mentioned rebound suppression composition for shotcrete, according to the wet shotcrete construction method, the rebound suppression composition is added to the shotcrete mixture and fully dispersed, and the addition amount accounts for 10-30% of the total mass of the cementitious material.

[0035] The present invention innovatively uses ternary magnesia calcined minerals and inorganic accelerating magnesium salts as core samples, and alkanolamine ester compounds as shells through a physical coating process to prepare a magnesium rebound inhibitor, and further compound it with other auxiliary rebound-reducing components to prepare a rebound suppression composition for shotcrete.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) It has no negative impact on coagulation and hardening, and significantly improves the quality of spraying. The magnesium rebound inhibitor of the present invention uses an alkanolamine ester compound as its shell. After being initially added to the concrete mixture, it is gradually hydrolyzed by the cement alkali solution to produce alkanolamine and corresponding organic acid salts, which have no adverse effects on the workability and coagulation and hardening properties of cement-based materials. As the mixing, transportation, and spraying processes proceed, the core components mainly composed of ternary magnesium calcined minerals and inorganic coagulation-promoting magnesium salts are gradually released and participate in the hydration of cement silicate-aluminum phase minerals, accelerating the dissolution and hydration of cement mineral phases, enriching early hydration products such as early calcium sulfonate and hydrated calcium silicate, and at the same time The calcined magnesia mineral phase provided by the ternary magnesia calcined mineral and the inorganic accelerating magnesium salt provide magnesium-containing hydration products such as hydrated magnesium silicate, which accelerate the setting and hardening of concrete, reduce the rebound loss during the spraying process, and improve the early strength. When used in combination with the auxiliary rebound-reducing component to prepare a sprayed concrete rebound inhibition composition, it can simultaneously improve the rheological properties of the slurry, increase the slurry viscosity and interfacial bonding properties, and promote the setting and hardening of cement, thereby jointly achieving the improvement of the bonding effect between the sprayed concrete and the weak rock mass under working conditions such as over-excavation and water seepage, and increasing the thickness of the single spraying. The use of the magnesium rebound inhibitor described in the present invention to prepare sprayed concrete can achieve 3h without slump workability loss, a spraying rebound rate of less than 10%, a single spraying thickness of more than 100mm, a bonding strength with the surrounding rock greater than 1.0MPa, a 7d compressive strength ratio greater than 135%, and a 28d compressive strength ratio greater than 120%, greatly reducing the time consumption of the initial support construction process and the loss of material costs;

[0038] (2) Green and low-carbon preparation, wide adaptability in use and performance. The magnesium rebound inhibitor of the present invention utilizes magnesia, clay minerals and spray rebound material to prepare ternary magnesium calcined minerals. During the light burning process, magnesia and clay minerals are decomposed at high temperature to achieve secondary activation of the spray rebound material with low gelling properties, forming a ternary magnesium active cementitious material of calcined magnesium oxide-calcined clay-activated spray rebound material. The discarded spray rebound material can be fully recycled to achieve green and low-carbon preparation. The calcined product formed under the stable calcination process has stable performance. By introducing a new type of magnesium-containing hydration product, the cement hydration product system is enriched, providing good cement adaptability. In addition, the magnesium rebound inhibitor can be fed in powder or liquid form according to the transportation and feeding scenarios, which is easy to use and convenient to measure.

[0039] (3) Low risk of shrinkage cracking in the middle and late stages and good durability. The magnesium rebound inhibitor of the present invention makes full use of the mutual hydration between the ternary magnesium calcined mineral and the cement mineral phase, the accelerator and other components, and through the composite synergistic effect of the auxiliary rebound-reducing component, can form a good filling of the pores inside the shotcrete and its interface with the rock mass. In the late hydration stage, the magnesium mineral phase in the ternary magnesium calcined mineral gradually forms magnesium-containing hydration products with micro-expansion such as hydrated magnesium silicate and magnesium hydroxide, which refines the late hardening pores of the concrete and improves the slurry strength, promotes the improvement of the late strength of the shotcrete and reduces the late volume shrinkage of the concrete, and improves its crack resistance and service durability. It can achieve an electrical flux of less than 1000C for 56d shotcrete, a limited expansion rate in air of less than 0.012% for 21d, and a drying shrinkage deformation of the shotcrete of less than 450με for 28d, which has a good effect on improving the late deformation and cracking of the primary support structure. DETAILED DESCRIPTION

[0040] The preferred embodiments of the present invention will be described in detail below with reference to the examples. It should be understood that the following examples are provided for illustrative purposes only and are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications and substitutions to the present invention without departing from the purpose and spirit of the present invention.

[0041] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0042] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0043] Example I-1 / 3: A magnesium rebound inhibitor adopts a shell-core structure, different ratios and materials of ternary magnesium minerals, and inorganic coagulant-promoting magnesium salts.

[0044] Example I-1

[0045] A magnesium rebound inhibitor is prepared by the following steps:

[0046] (1) Shell A selection: an alkanolamine ester compound is selected as shell A, preferably an ester compound of diethanolamine, more preferably diethanolamine acetate; the relative molecular mass of the diethanolamine acetate is 245.4, and the hydrolysis temperature is 25°C;

[0047] (2) Preparation of core sample B: According to the set material ratio, calcination method and calcination temperature, magnesite, clay mineral and spray rebound material are subjected to a light burning process of raw material grinding, high temperature calcination, cooling and clinker grinding to prepare ternary magnesia calcined mineral, and the ternary magnesia calcined mineral and inorganic accelerating magnesium salt are mixed evenly according to the set proportion to obtain core sample B. Among them, the mass ratio of magnesite, clay mineral and spray rebound material is 30:20:50; the light burning process is selected as the rotary kiln process, and the calcination temperature is 1000℃; the magnesite has a magnesium carbonate content of 92%, the clay mineral is kaolin, and the spray rebound material is the concrete material obtained by spraying, rebounding and collecting dry shotcrete; the mass ratio of the ternary magnesia calcined mineral and the inorganic accelerating magnesium salt is 75:25; the inorganic accelerating magnesium salt is magnesium sulfate;

[0048] (3) Preparation by physical coating process: Core sample B is added to a suspension container, and air flow or dispersion medium is opened to fully disperse the material to form a stable dispersed fluidized bed bottom layer or air flow layer; shell A is introduced into the liquid phase pipeline, and the magnesium rebound inhibitor is prepared under a specific process temperature and operation time; the physical coating process is a fluidized bed process, the process temperature is 85°C, and the operation time is 1.5 hours. The mass ratio of shell A to core sample B is 1:10.

[0049] Example I-2

[0050] A magnesium rebound inhibitor is prepared by the following steps:

[0051] (1) Shell A selection: an alkanolamine ester compound is selected as shell A, preferably an ester compound of triethanolamine, more preferably triethanolamine acrylate; the relative molecular mass of the triethanolamine acrylate is 221.3, and the hydrolysis temperature is 80°C;

[0052] (2) Preparation of core sample B: According to the set material ratio, calcination method and calcination temperature, magnesite, clay mineral and spray rebound material are subjected to a light burning process of raw material grinding, high temperature calcination, cooling and clinker grinding to prepare ternary magnesia calcined mineral, and the ternary magnesia calcined mineral and inorganic accelerating magnesium salt are mixed evenly according to the set proportion to obtain core sample B. Among them, the mass ratio of magnesite, clay mineral and spray rebound material is 50:40:10; the light burning process is selected as the suspension kiln process, and the calcination temperature is 800℃; the magnesite has a magnesium carbonate content of 93%, the clay mineral is montmorillonite, and the spray rebound material is the concrete material obtained by spraying, rebounding and collecting the tidal method shotcrete; the mass ratio of the ternary magnesia calcined mineral and the inorganic accelerating magnesium salt is 75:25; the inorganic accelerating magnesium salt is magnesium sulfate;

[0053] (3) Preparation by physical coating process: Core sample B is added to a suspension container, and air flow or dispersion medium is activated to fully disperse the material to form a stable dispersed fluidized bed bottom layer or air flow layer; shell A is introduced into the liquid phase pipeline, and the magnesium rebound inhibitor is prepared under a specific process temperature and operation time; the physical coating process is a spray drying process, the process temperature is 105°C, and the operation time is 3 hours. The mass ratio of shell A to core sample B is 1:20.

[0054] Example I-3

[0055] A magnesium rebound inhibitor is prepared by the following steps:

[0056] (1) Shell A selection: an alkanolamine ester compound is selected as shell A, preferably an ester compound of triethanolamine, more preferably triethanolamine acetate; the relative molecular mass of the triethanolamine acetate is 275.3, and the hydrolysis temperature is 50°C;

[0057] (2) Preparation of core sample B: According to the set material ratio, calcination method and calcination temperature, magnesite, clay mineral and spray rebound material are subjected to a light burning process of raw material grinding, high temperature calcination, cooling and clinker grinding to prepare ternary magnesia calcined mineral, and the ternary magnesia calcined mineral and inorganic accelerating magnesium salt are mixed evenly according to the set proportion to obtain core sample B. Among them, the mass ratio of magnesite, clay mineral and spray rebound material is 40:30:30; the light burning process is selected as the suspension kiln process, and the calcination temperature is 900℃; the magnesite has a magnesium carbonate content of 97%, the clay mineral is illite, and the spray rebound material is the concrete material obtained by spraying, rebounding and collecting the tidal method shotcrete; the mass ratio of the ternary magnesia calcined mineral and the inorganic accelerating magnesium salt is 75:25; the inorganic accelerating magnesium salt is magnesium sulfate;

[0058] (3) Preparation by physical coating process: Core sample B is added to a suspension container, and air flow or dispersion medium is activated to fully disperse the material to form a stable dispersed fluidized bed bottom layer or air flow layer; shell A is introduced into the liquid phase pipeline, and the magnesium rebound inhibitor is prepared under a specific process temperature and operation time; the physical coating process is a spray drying process, the process temperature is 90°C, and the operation time is 2 hours. The mass ratio of shell A to core sample B is 1:15.

[0059] Example I-4 / 5: A magnesium rebound inhibitor, with the type and proportion of inorganic coagulant magnesium salt replaced, and the rest is the same as above.

[0060] Example I-4

[0061] A magnesium rebound inhibitor

[0062] The materials and preparation steps of this embodiment are the same as those of Example I-1, except that the mass ratio of the ternary magnesian calcined mineral to the inorganic accelerating magnesium salt is 95:5, and the inorganic accelerating magnesium salt is magnesium nitrate.

[0063] Example I-5

[0064] A magnesium rebound inhibitor

[0065] The materials and preparation steps of this embodiment are the same as those of Example I-1, except that the mass ratio of the ternary magnesian calcined mineral to the inorganic accelerating magnesium salt is 80:20, and the inorganic accelerating magnesium salt is magnesium phosphate.

[0066] Comparative Example I-1

[0067] A magnesium-containing rebound inhibitor

[0068] The materials and proportions used in this embodiment are the same as those in Example I, but the components are simply compounded to protect the shell-core structure.

[0069] Specifically: the materials and preparation steps of shell A and core sample B are the same as those of Example I-3, but the physical coating process is not used, and they are only mixed evenly.

[0070] Comparative Example I-2

[0071] A magnesium rebound inhibitor

[0072] This embodiment adopts a shell-core structure, the shell is ethyl acetate, the core material and ratio remain unchanged, and what is protected is the alkanolamine ester compound and the difficulty of alkaline hydrolysis.

[0073] Specifically: the materials, preparation and physical coating process of core sample B are the same as those in Example I-3, but the shell A is selected to be ethyl acetate, the relative molecular mass of the ethyl acetate is 88.11, and the hydrolysis temperature is 65°C.

[0074] Comparative Example I-3

[0075] A magnesium rebound inhibitor

[0076] This embodiment adopts a shell-core sample structure, the core sample is pure calcined magnesia, and the other materials and proportions are the same as those in Example I. What is protected is the ternary magnesia calcined mineral component.

[0077] Specifically: the material, preparation and physical coating process of shell A are the same as those in Example I-3, but core sample B is composed of light-burned dolomite and inorganic coagulant magnesium salt, and the composition ratio and type of inorganic coagulant magnesium salt are the same as those in Example I-3.

[0078] Comparative Example I-4

[0079] A magnesium rebound inhibitor

[0080] This embodiment adopts a shell-core structure, the core sample is a calcined spray rebound material, and other materials and proportions are the same as those in Example I. The invention relates to a method for stimulating the gelling activity of the spray rebound material.

[0081] Specifically: the material, preparation and physical coating process of shell A are the same as those of Example I-3, but core sample B is composed of light-burned spray rebound material and inorganic coagulant magnesium salt, and the composition ratio and types of inorganic coagulant magnesium salt and spray rebound material are the same as those of Example I-3.

[0082] Comparative Example I-5

[0083] A magnesium rebound inhibitor

[0084] This embodiment does not contain inorganic coagulant magnesium salt, and other materials and proportions are the same as those in Example I, thereby protecting the synergistic coagulant effect of the inorganic coagulant magnesium salt.

[0085] Specifically: the material, preparation and physical coating process of shell A are the same as those in Example I-3, but core sample B is 100% ternary magnesia calcined mineral, and the material types and proportions are the same as those in Example I-3.

[0086] Example II-1 / 2: A liquid magnesium rebound inhibitor with water as the endpoint.

[0087] Example II-1

[0088] A liquid magnesium rebound inhibitor is prepared by the following steps:

[0089] (1) Preparation of magnesium rebound inhibitor: same as in Example I-1;

[0090] (2) The magnesium rebound inhibitor and water are thoroughly mixed in a set ratio, wherein the set ratio is 40:60 water:magnesium rebound inhibitor.

[0091] Example II-2

[0092] A liquid magnesium rebound inhibitor is prepared by the following steps:

[0093] (1) Preparation of magnesium rebound inhibitor: same as in Example I-1;

[0094] (2) The magnesium rebound inhibitor and water are thoroughly mixed in a set ratio, wherein the set ratio is 60:40 water:magnesium rebound inhibitor.

[0095] Comparative Example II-1

[0096] The liquid magnesium rebound suppressant of this embodiment has a water ratio exceeding the range.

[0097] (1) Preparation of magnesium rebound inhibitor: same as in Example I-1;

[0098] (2) The magnesium rebound inhibitor and water are thoroughly mixed in a set ratio, wherein the set ratio is 80:20 water:magnesium rebound inhibitor.

[0099] Example III-1 / 2: A rebound suppressing composition with different endpoint values ​​of the auxiliary rebound reducing component ratio.

[0100] Example III-1

[0101] A rebound suppression composition for shotcrete is prepared by the following steps:

[0102] (1) Preparation of magnesium rebound inhibitor: same as in Example I-1;

[0103] (2) Add water first according to the material ratio setting, turn on the heating and wait until the temperature rises to 45°C, and add the auxiliary rebound-reducing component while stirring within 30-60 minutes, the stirring rate is 500r / min, and the total stirring time is 1 hour; the ratio of water to magnesium rebound inhibitor is the same as that in Example II-1; the mass ratio of the auxiliary rebound-reducing component to the liquid magnesium rebound inhibitor is 5:95; the auxiliary rebound-reducing component is selected from a mineral admixture and a rheology-modifying component, and the mineral admixture is selected from fly ash; the rheology-modifying component is selected from two types of organic tackifiers, amide organic matter and redispersible latex powder, preferably polyacrylamide and vinyl acetate-ethylene copolymer latex powder;

[0104] (3) Cooling is started, and after the temperature drops to 30°C, a magnesium rebound inhibitor is added, and stirring is continued for 1.5 hours to obtain the rebound suppressing composition for shotcrete. The stirring rate is 300 r / min.

[0105] Example III-2

[0106] A rebound suppression composition for shotcrete is prepared by the following steps:

[0107] (1) Preparation of magnesium rebound inhibitor: same as in Example I-1;

[0108] (2) Water is added first according to the material ratio setting, and after the heating is turned on and the temperature rises to 60°C, the auxiliary rebound-reducing component is added while stirring within 30-60 minutes, the stirring rate is 1000 r / min, and the total stirring time is 1.5 hours; the ratio of water to magnesium rebound inhibitor is the same as that in Example II-1; the mass ratio of the auxiliary rebound-reducing component to the liquid magnesium rebound inhibitor is 15:85; the auxiliary rebound-reducing component is selected from a mineral admixture and a rheology-modifying component, and the mineral admixture is selected from silica fume; the rheology-modifying component is selected from an organic tackifier and a redispersible latex powder, the organic tackifier is selected from methyl cellulose ether, and the redispersible latex powder is selected from vinyl propionate compound latex powder;

[0109] (3) Cooling is started, and after the temperature drops to 30° C., a magnesium rebound inhibitor is added, and stirring is continued for 1.5 hours to obtain the rebound inhibitor composition for shotcrete. The stirring rate is 500 r / min.

[0110] Example III-3

[0111] A rebound suppression composition for shotcrete

[0112] The rebound suppression composition of this embodiment does not contain a rheology modifying component in the auxiliary rebound reducing component.

[0113] Specifically: the material ratio, type and preparation sequence are the same as those in Example III-1, the auxiliary rebound-reducing component is selected from mineral admixtures, and the type of the mineral admixtures is the same as that in Example III-1.

[0114] Example III-4 / 5: A rebound suppressing composition, wherein the rheology modifying component is only an organic tackifier or a redispersible latex powder.

[0115] Example III-4

[0116] A rebound suppression composition for shotcrete

[0117] The material ratio, type and preparation sequence of this embodiment are the same as those of Example III-1. The rheology modifying component in the auxiliary rebound reducing component is selected from an organic tackifier, and the type of the organic tackifier is the same as that of Example III-1.

[0118] Example III-5

[0119] A rebound suppression composition for shotcrete

[0120] The material ratio, type and preparation sequence of this embodiment are the same as those of Example III-1. The rheology-modifying component in the auxiliary rebound-reducing component is selected from a redispersible latex powder, and the type of the redispersible latex powder is the same as that of Example III-1.

[0121] Comparative Example III-1

[0122] A rebound suppression composition for shotcrete

[0123] The rebound suppressing composition of this embodiment is prepared by simply compounding a magnesium rebound suppressing agent and an auxiliary rebound reducing component.

[0124] Specifically, the material ratio and types are the same as those in Example III-1, but the magnesium rebound inhibitor and the auxiliary rebound reducing component are simply mixed evenly by physical means.

[0125] Comparative Example III-2

[0126] A rebound suppression composition for shotcrete

[0127] In the rebound suppressing composition of this embodiment, the auxiliary rebound reducing component exceeds the proportion.

[0128] Specifically, the material types and preparation methods are the same as those in Example III-1, but the ratio of the auxiliary rebound reducing component to the magnesium rebound inhibitor is 20:80.

[0129] Test Example 1

[0130] Cement paste or mortar performance test

[0131] A fixed magnesium rebound inhibitor or rebound suppressing composition was used to replace 5% of cement, and a liquid alkali-free accelerator was selected to replace 7%. The setting time of the accelerator paste with or without the magnesium rebound inhibitor or rebound suppressing composition and the stability of the magnesium rebound inhibitor or rebound suppressing composition were tested with reference to GB35159-2017 "Accelerators for Shotcrete". The total alkali content of the magnesium rebound inhibitor or rebound suppressing composition was tested with reference to GB / T8077-2012 "Test Method for Homogeneity of Concrete Admixtures". The restricted expansion rate and specific surface area of ​​the magnesium rebound inhibitor or rebound suppressing composition were tested with reference to GB / T 23439-2017 "Concrete Expansion Agents". The corresponding results are shown in Table 1.

[0132] Table 1 Test results of cement paste or mortar performance of examples and comparative examples

[0133]

[0134] From the basic physical properties of the magnesium rebound inhibitor or rebound suppressing composition described in Table 1, it can be seen that the magnesium rebound inhibitor or rebound suppressing composition for shotcrete of the present invention has a specific surface area of ​​150-300 m 2 / kg range, the total alkali content is less than 1%, the liquid form meets the stability requirement of more than 28d, it is green and environmentally friendly, and has good homogeneity. Comparative Example I-3 Comparative Example I-1 adopts a simple physical mixing method to mix ternary magnesia calcined minerals, alkanolamine ester compounds and inorganic accelerator magnesium salts to obtain a product with a small specific surface area and coarse particles, indicating that the use of a physical coating method can obtain a magnesium rebound inhibitor product with relatively uniform and fine particles, which is conducive to its dispersion and dissolution; Comparative Example I-3 and Comparative Example I-4 respectively use pure dolomite or pure jet rebound material to lightly burn to obtain core sample B, and the obtained magnesium rebound inhibitor particles have a specific surface area of ​​less than 200 m 2 / kg, indicating that a single calcined mineral has a greater impact on the fineness of the magnesium rebound inhibitor. Comparing Example II-1 with Example II-2, the liquid magnesium rebound inhibitor prepared in Comparative Example II-1 uses more than 60% water, and the stratification problem occurs at room temperature for 4 days, indicating that the excessive water consumption of the liquid magnesium rebound inhibitor prepared with magnesium rebound inhibitor and water will lead to a decrease in its stability, which is not conducive to its actual use and extraction and metering. Comparative Example III-1, Comparative Example III-1 uses a simple compounding and mixing method to prepare a rebound suppressing composition by combining the liquid magnesium rebound inhibitor with the auxiliary rebound reducing component. After being placed for 2 days, precipitation occurs, and the precipitate is mainly the auxiliary rebound reducing component, indicating that the preparation method of the rebound suppressing composition of the present invention promotes the mutual dispersion and dissolution of the liquid magnesium rebound inhibitor and the auxiliary rebound reducing component, forming a better physically stable structure and improving its room temperature stability. Compared with Example III-1, the rebound suppressing composition obtained in Comparative Example III-2 using a 20% auxiliary rebound reducing component also exhibited the problem of precipitation at room temperature, and the precipitate was also mainly the rheology-modifying component in the auxiliary rebound reducing component, indicating that the proportion of the auxiliary rebound reducing component in the rebound suppressing composition should not exceed 20%, and the proportion range of 5-15% given in the present invention is more appropriate.

[0135] From the setting time results of the alkali-free quick-setting agent-added slurry in Table 1, it can be seen that the magnesium rebound inhibitor or rebound inhibition composition of the present invention significantly shortens the setting time of the quick-setting slurry, and the restricted expansion rate in the air for 21 days is less than -0.012%. This is because the ternary magnesium calcined mineral and the inorganic accelerating magnesium salt in the magnesium rebound inhibitor act together with the alkali-free quick-setting agent and cement during the release process, participate in the hydration of cement silicon-aluminum phase minerals, accelerate the dissolution and hydration of the cement mineral phase, enrich the early hydration products such as early ettringite and hydrated calcium silicate, thereby shortening the setting time. At the same time, in the late hydration stage, the magnesium mineral phase in the ternary magnesium calcined mineral gradually forms magnesium silicate hydrate and magnesium hydroxide, which are micro-expandable magnesium-containing hydration products with equal volume, reduce the tendency of drying shrinkage in the middle and late stages, and have a late compensatory shrinkage effect. Comparative Example I-3, Comparative Example I-1 uses a simple physical mixing method to mix ternary magnesia calcined minerals, alkanolamine ester compounds and inorganic accelerating magnesium salts to prepare a product. The alkanolamine ester compound is difficult to hydrolyze under the action of an acidic alkali-free accelerating setting agent. In the hydration liquid phase, it complexes calcium ions, affecting the early formation of hydration products such as ettringite and hydrated calcium silicate. Therefore, the effect of shortening the setting time of the system is significantly weakened. Comparative Example I-2 uses a non-alkanolamine ester compound and ethyl acetate as the shell. The ethanol or acetic acid monomer released by the alkaline hydrolysis of cement has a strong effect on cement hydration. The delayed effect also affects the effect of the magnesium rebound inhibitor in shortening the setting time. The products prepared in Comparative Examples I-3 and I-4, respectively, using pure magnesite and spray rebound material as core sample B, also show a decrease in the effect of shortening the setting time, indicating that the calcined calcium oxide core sample is difficult to play a strong role in shortening the setting time, and the calcined spray rebound material alone cannot activate its internal gelling properties. Comparative Example I-5 lacks inorganic magnesium salts to accelerate the setting. The ternary magnesium calcined product alone has a weak effect on the dissolution and hydration of the cement mineral phase in the early stage of hydration, thus affecting its effect of shortening the setting time. Compared with Example II-1, Comparative Example II-1 uses more than 60% water to prepare the liquid magnesium rebound inhibitor, which weakens the concentration of the effective magnesium rebound inhibitor and thus affects its effect of shortening the setting time. Comparative Example III-1, in which a rebound suppressing composition is prepared by a simple compounding and mixing method of a liquid magnesium rebound suppressant and an auxiliary rebound-reducing component, the rheology-modifying component plays a role in delaying hydration when participating in hydration, while Comparative Example III-2 uses a rebound suppressing composition obtained by using a 20% auxiliary rebound-reducing component, which also introduces excessive rheology-modifying components. Both extend the final setting time of the slurry added with an alkali-free accelerator.

[0136] Test Example 2

[0137] To test the performance of shotcrete, the benchmark shotcrete mix ratio was set as follows: 450kg cement + 890kg 5-10mm guami stone + 950kg medium river sand + 185kg water per cubic meter. The concrete preparation method was as follows: according to the wet shotcrete construction method, the magnesium rebound inhibitor or rebound inhibitor composition was added to the shotcrete mixture and fully dispersed, with the addition amount accounting for 5-20% of the total mass of the cementitious material; the concrete except the accelerator was fully mixed at the mixing station and then transported to the spraying site; the liquid alkali-free accelerator was pre-pumped into the accelerator drum storage tank in the wet shotcrete machine; the accelerator dosage was set to 7% according to the wet shotcrete machine instrument parameters; and the hourly concrete discharge volume was selected to be 15-30m 3 A robotic arm sprayer was used. After the spray material stabilized, it was sprayed into a 500mm × 450mm × 200mm test mold. The mold was placed in a corner at a 60°–75° angle to the ground. The spray distance was maintained at 1.2–1.5 m to prevent excessive friction and impact between the spray material and the mold, which could cause a loss of rebound. The spray gun was held perpendicular to the forming surface. After spraying, the concrete specimens were cured in the mold for 24 hours before being cut into the corresponding test specimens using a rock cutter.

[0138] The effects of magnesium rebound inhibitors or rebound-inhibiting compositions on the initial slump and 3-hour slump loss of shotcrete were tested according to GB / T 50080-2016, "Test Methods for Properties of Ordinary Concrete Mixtures." An Anton Paar concrete rotational viscometer was used to test the initial plastic viscosity of the concrete. The 1-day, 7-day, and 28-day compressive strength of the concrete were tested according to GB / T 50081-2019, "Test Methods for Physical and Mechanical Properties of Concrete." The drying shrinkage, electric flux, and late-stage crack resistance of the shotcrete were tested according to GB / T 50082-2009, "Test Methods for Long-term Properties and Durability of Ordinary Concrete." The shotcrete performance (average rebound rate, single shot thickness, and bond strength with the surrounding rock) of the corresponding shotcrete was tested in an inclined shaft with Class IV surrounding rock, an overexcavation depth of 30 cm, and a single shot volume of 60 cubic meters. The shotcrete performance results are summarized in Tables 2 / 3.

[0139] Table 2 Working and mechanical properties test results of shotcrete of embodiment and comparative example

[0140]

[0141] Note: Except for Example I-1, the dosage of the other examples and comparative examples is fixed at 10% of the cementitious material.

[0142] From the test results of the workability and mechanical properties of the shotcrete of the examples and comparative examples in Table 2, it can be seen that the results of Examples I-1 to I-5 show that the magnesium rebound inhibitor of the present invention has little effect on the workability of shotcrete, but significantly improves the early and late mechanical strength of shotcrete, with the 7d compressive strength ratio greater than 135% and the 28d compressive strength ratio greater than 120%, and the improvement effect is proportional to its dosage (5-20%). The results of Examples II-1 and II-2 show that the workability of shotcrete is greatly improved after being added in the form of a liquid magnesium rebound inhibitor with better dispersion effect, and its improvement effect on the early and late mechanical strength is not affected, and it is suitable for application scenarios using liquid product metering. The results of Examples III-1 to III-5 show that the rebound suppression composition prepared with a liquid magnesium rebound inhibitor and an auxiliary rebound-reducing component also has little effect on the workability and early and late strength of shotcrete, while improving the cohesion of the mixture (the viscosity value is increased), which indicates that the rheology modifying component and the magnesium rebound inhibitor have good functional complementarity.

[0143] Comparative Example I-3, Comparative Example I-1 uses a simple physical mixing method to mix ternary magnesia calcined minerals, alkanolamine ester compounds and inorganic accelerating magnesium salts to prepare a product. Since the ternary magnesia calcined minerals and inorganic accelerating magnesium salts gradually exert high hydration activity characteristics when added to the shotcrete mixture, the slump workability is greatly lost, which significantly increases the difficulty of transporting the mixture, and the viscosity of the mixture is significantly increased, which also affects its effect on improving the mechanical strength in the later stage; Comparative Example I-2 uses a non-alkanolamine ester compound and ethyl acetate as the shell. After being added to the shotcrete, the slump workability is lost 3h, and the ethanol released by ethyl acetate in the alkaline hydrolysis of cement Or acetic acid monomer has a strong retarding effect on the early hydration of cement, thus resulting in a decrease in the strength of the shotcrete at 1d, and the increase in the later strength is also lower than that of the comparative example I-1; the products prepared in comparative examples I-3 or I-4 using pure dolomite and shot rebound material as core sample B respectively, and the hydration activity of the calcined product magnesium oxide as the core sample is not as good as that of the ternary magnesia calcined product, and the simple calcination of the shot rebound material cannot activate the gelling properties of the hydrated part of its internal part, so the improvement in the early and late mechanical strength of the shotcrete is not high; comparative example I-5 lacks inorganic accelerating magnesium salt, resulting in its improvement in the strength of the shotcrete at 1d not as good as the combined effect of the ternary magnesia calcined mineral and the inorganic accelerating magnesium salt.

[0144] Comparative Example II-1, Comparative Example II-1 uses more than 60% water to prepare the liquid magnesium rebound inhibitor, which weakens the concentration of the effective magnesium rebound inhibitor, thereby affecting its effect on improving the early and late strength of shotcrete. Comparative Example III-1, Comparative Example III-1 uses a simple compounding method to mix the liquid magnesium rebound inhibitor with the auxiliary rebound-reducing component to prepare the rebound-reducing composition. During hydration, the rheology-modifying component prematurely exerts its viscosity-increasing and early hydration-retarding effects, thereby excessively increasing the cohesiveness of the shotcrete, hindering its spraying, and having a strong negative effect on the 1d strength. Comparative Example III-2 uses 20% of the auxiliary rebound-reducing component to obtain the rebound-reducing composition. This also introduces too much rheology-modifying component. Both affect their effects on improving the early and late strength of shotcrete.

[0145] Table 3 Test results of durability and spraying construction performance of sprayed concrete of embodiment and comparative example

[0146]

[0147] Note: Except for Example I-1, the dosage of the other examples and comparative examples is fixed at 10% of the cementitious material.

[0148] From the test results of the durability and spraying construction performance of the shotcrete of the embodiments and comparative examples in Table 3, it can be seen that the results of Examples I-1 to I-5 show that the addition of the magnesium rebound inhibitor of the present invention significantly reduces the tendency of late drying shrinkage of shotcrete, and the 28d drying shrinkage strain value of shotcrete is less than 450με. By optimizing the early and late hydration process and refining the hardened pore structure based on the material structural properties of shell A-core sample B, the number of cracks and the electric flux value of shotcrete are significantly reduced, and the late crack resistance and service durability of shotcrete are significantly improved. The 56d electric flux is less than 1000C, and the number of cracks is reduced by more than 65% year-on-year. At the same time, the addition of the magnesium rebound inhibitor of the present invention significantly improves the spraying quality of shotcrete, the average rebound rate of spraying is less than 10%, the bonding strength with the surrounding rock is greater than 1.0MPa, and the thickness of one spraying can reach 1 00mm or more, and the effect of improving the durability and spraying construction performance of shotcrete is also proportional to its dosage (5-20%); the results of Example II-1 to Example II-2 show that the addition in the form of a liquid magnesium rebound inhibitor with better dispersion effect is more conducive to improving the spraying quality of shotcrete, and does not affect its improvement effect on crack resistance and service durability; the results of Example III-1 to Example III-5 show that the rebound suppression composition prepared with a liquid magnesium rebound inhibitor and an auxiliary rebound-reducing component can further improve the spraying quality of shotcrete by optimizing the early and late hydration process, refining hardened pores, and improving the cohesion of the shotcrete mixture. The average rebound rate of the spraying can be controlled within 5%, the bonding strength with the surrounding rock is greater than 1.2MPa, and the thickness of the one-time spraying can reach more than 140mm, which greatly reduces the time consumption and material cost loss of the initial support construction process.

[0149] Comparative Example I-3, Comparative Example I-1 adopts a simple physical mixing method to mix ternary magnesia calcined mineral, alkanolamine ester compound and inorganic accelerating magnesium salt to prepare a product. Since the ternary magnesia calcined mineral and the inorganic accelerating magnesium salt exert their high hydration activity characteristics too early, the spraying rebound rate is reduced, the later crack resistance is improved and the service durability is improved. The effect is not obvious, and the bonding effect with the surrounding rock is affected. The thickness of one spray is less than 100mm, only 92mm, and the bonding strength with the surrounding rock is only 0.85MPa; Comparative Example I-2 adopts non-alkanolamine ester compound, ethyl acetate as the shell, and the delayed hydration effect of ethanol or acetic acid monomer released by ethyl acetate in the alkaline hydrolysis of cement affects the hydration activity of the ternary magnesia calcined mineral and the rapid setting and hardening characteristics of the alkali-free accelerator, thereby affecting its improvement on the later crack resistance of the shotcrete, and affecting the reduction of the spraying rebound rate and the bonding effect with the surrounding rock, and the bonding with the surrounding rock is poor. The bonding strength is 0.88MPa; the products prepared by comparative examples I-3 and I-4 using pure dolomite and spray rebound material as core sample B respectively, and the early and late hydration activity of the calcined product calcium oxide as the core sample is not as good as the ternary magnesia calcined product, resulting in a decrease in the effect of improving its service durability, and the reduction of the rebound rate of shotcrete is not obvious. The simple calcination of the spray rebound material cannot activate the gelling properties of the hydrated part of its internal part, and the effect of refining the pores is poor. The spray rebound rate is close to the benchmark group, reaching 19.3%, and the concrete electrical flux and the number of cracks have not decreased significantly. Therefore, the use of single dolomite or spray rebound material cannot achieve the effect of ternary composite calcination, affecting its improvement effect in the coagulation and hardening of shotcrete, shot quality, early crack resistance and service durability; comparative example I-5 lacks inorganic coagulant magnesium salt, which affects its spray quality improvement effect, especially the reduction of the rebound rate of shotcrete and the increase of the thickness of one spray.

[0150] Comparative Example II-1, in which the liquid magnesium rebound inhibitor was prepared using more than 60% water, reduced the concentration of the effective magnesium rebound inhibitor, thereby affecting its effect on the early crack resistance and the reduction of the spray rebound rate. Comparative Example III-1, in which the rebound suppression composition was prepared by a simple compounding method of the liquid magnesium rebound inhibitor and the auxiliary rebound-reducing component, the rheology-modifying component prematurely exerted its viscosity-increasing and early hydration-retarding effects during hydration, thereby excessively increasing the cohesion of the sprayed concrete, resulting in a small decrease in its spray rebound rate and affecting the improvement of its later crack resistance and its bond strength with the surrounding rock. Comparative Example III-2, in which the rebound suppression composition was prepared using 20% ​​of the auxiliary rebound-reducing component, also introduced too much rheology-modifying component. Both of these affected its improvement of the later crack resistance of the sprayed concrete and its bond strength with the surrounding rock.

[0151] Although the present invention has been described in detail above using general explanations, specific embodiments, and experiments, it will be apparent to those skilled in the art that modifications and improvements may be made based on the present invention. Therefore, such modifications and improvements, which do not depart from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A magnesium rebound inhibitor for shotcrete, characterized in that: It consists of a shell A and a core sample B, wherein the shell A is coated on the surface of the core sample B, and the mass ratio of the shell A to the core sample B is 1:10-20; The shell A is an alkanolamine ester compound, the relative molecular mass of the alkanolamine ester compound is less than 1000, and the hydrolysis temperature is 20-80°C; The core sample B is composed of a ternary magnesia calcined mineral and an inorganic coagulant magnesium salt, and the mass ratio of the ternary magnesia calcined mineral to the inorganic coagulant magnesium salt is (95-75): (5-25); the ternary magnesia calcined mineral is prepared by a light-burning process of dolomite, clay mineral and spray rebound material, and the mass ratio of the dolomite, clay mineral and spray rebound material is (30-50): (20-40): (10-50), and the temperature of the light-burning process is 800-1000°C.

2. The magnesium rebound inhibitor for shotcrete according to claim 1, characterized in that: The alkanolamine ester compound is an ester compound of diethanolamine or an ester compound of triethanolamine.

3. The magnesium rebound inhibitor for shotcrete according to claim 2, characterized in that: The alkanolamine ester compound is selected from triethanolamine acrylate, triethanolamine stearate, triethanolamine propionate, triethanolamine methylpropionate, triethanolamine acetate, triethanolamine oleate or diethanolamine acetate or diethanolamine oleate.

4. The magnesium rebound inhibitor for shotcrete according to claim 1, characterized in that: The light firing process is selected from a vertical kiln process, a suspension kiln process or a rotary kiln process.

5. The magnesium rebound inhibitor for shotcrete according to claim 1, characterized in that: The magnesium carbonate content in the magnesite is greater than 90%.

6. The magnesium rebound inhibitor for shotcrete according to claim 1, characterized in that: The clay mineral is selected from kaolin, bentonite, montmorillonite, illite or chlorite.

7. The magnesium rebound inhibitor for shotcrete according to claim 1, characterized in that: The sprayed rebound material is a concrete material obtained by spraying, rebounding, and falling and then collecting dry-process sprayed concrete, tidal-process sprayed concrete, or wet-process sprayed concrete.

8. The magnesium rebound inhibitor for shotcrete according to claim 1, characterized in that: The inorganic coagulant-accelerating magnesium salt is selected from magnesium phosphate, magnesium nitrate or magnesium sulfate.

9. The method for preparing the magnesium rebound inhibitor for shotcrete according to any one of claims 1 to 8, characterized in that: The physical coating process includes the following steps: A ternary magnesia calcined mineral and an inorganic coagulant-accelerating magnesium salt are added to a suspension container, and an air flow or dispersion medium is opened to fully disperse the materials to form a stable dispersed fluidized bed bottom layer or air flow layer; an alkanolamine ester compound is introduced into the liquid phase pipeline, and the preparation is completed under a specific process temperature and operating time; the process temperature is 85-105°C, and the operating time is 1.5-3 hours.

10. A shotcrete, characterized in that: The invention comprises a cementitious material and an admixture, wherein the admixture is the magnesium rebound inhibitor for shotcrete according to any one of claims 1 to 8.

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