Green low-carbon high-performance shotcrete using active regenerated micro powder and preparation method and construction process thereof

Abstract

The application relates to the field of shotcrete, in particular to green low-carbon high-performance shotcrete using active recycled micro powder and a preparation method and construction technology thereof; shotcrete raw materials include the following components in parts by weight: cement 300-350 parts, active recycled micro powder 50-80 parts, early-strength mineral admixture 60-120 parts, rubber powder 20-40 parts, hydrophobic compacting agent 10-20 parts, coarse aggregate 700-800 parts and fine aggregate 800-900 parts; a water reducing agent is added in an amount of 0.8%-1.2% of the mass of cementitious materials, and a fluoride-free and alkali-free rapid hardener is added in an amount of 6%-9% of the mass of cementitious materials; wherein the active recycled micro powder is composed of polyhydric isomeric alcohol amine and recycled micro powder, and the amount of the polyhydric isomeric alcohol amine is 0.1%-0.5% of the mass of cementitious materials. The application can reduce the cement dosage of shotcrete and meet the demand of high performance of shotcrete.

Description

Technical Field

[0001] This application relates to the field of shotcrete, and more specifically, to a green, low-carbon, high-performance shotcrete using active recycled micropowder, its preparation method, and construction process. Background Technology

[0002] Shotcrete is a concrete mixture made by spraying cementitious materials and aggregates at high speed onto the surface of rocks or buildings under the action of compressed air or other power sources. Under the action of accelerators, it sets and hardens in a short time, forming a concrete structure with sealing and support functions. It has many advantages such as high construction efficiency, simple process, and good economic benefits. It can restrain and control the deformation of surrounding rock and maintain the integrity of tunnel structures during construction and operation. It is widely used in many fields such as transportation engineering, water conservancy and hydropower, mine support, underground engineering, and repair and sealing. It is a core material for ensuring the safe construction and rapid construction of underground space structures.

[0003] Taking the Sichuan-Tibet Railway as an example, during tunnel construction, the complex geological conditions such as rock bursts, large deformations in soft rock, water seepage, and high ground temperatures place increasingly higher demands on the setting and hardening performance, early strength, and durability of the initial support shotcrete. To address this, most tunnel projects employ high-volume pure cementitious systems to ensure faster setting and early strength development of the shotcrete, with some mix proportions even exceeding 500 kg / m³ of cement per cubic meter. While such high cement content can meet the initial support strength requirements, it increases the risk of shrinkage cracking and durability degradation during the later service life of the shotcrete. Furthermore, cement is a high-energy-consuming and high-polluting building material; relevant data shows that 8% of global carbon dioxide emissions originate from cement. Therefore, how to reduce the cement content of shotcrete while meeting the service requirements of tunnel engineering is a pressing problem that needs to be solved.

[0004] Patent CN112047708B, "A Shotcrete and Its Construction Method," does not use traditional cement and accelerators. Instead, it prepares a novel shotcrete using modified magnesium phosphate cement, mineral admixtures, and setting regulators. While this significantly improves resilience, compressive strength, and durability, the materials used are too complex and the cost too high, making large-scale application difficult. Patent CN109437706A, "A Shotcrete, Its Preparation Method, and Its Application," reduces cement usage by incorporating limestone powder as a mineral admixture. While this improves the workability of the concrete mix and saves construction costs, increasing the amount of limestone powder inevitably affects the setting and hardening speed and early strength of the shotcrete, failing to effectively seal the rock mass and stabilize the surrounding rock. Patent CN108046712B, "A High-Strength, Low-Rebound Shotcrete and Its Construction Process," replaces part of the cement with silica fume and zeolite powder, and incorporates steel fibers to increase the toughness of the shotcrete. While this ultimately yields a high-strength shotcrete with low rebound rate, high early strength, and even reaching C60 strength grade at 28 days, the silica fume, zeolite powder, and steel fiber components may significantly increase the viscosity of the concrete mixture, leading to decreased pumpability and even pipe blockage, thus reducing construction efficiency. Patent CN110627446B, "An Economical and Environmentally Friendly Tunnel Shotcrete and Its Construction Process," improves the workability of the shotcrete by increasing the sand ratio and using stone chips to replace part of the natural river sand, reducing the rebound rate and construction costs, but the cement usage remains relatively high. CN114620981A, "A Shotcrete and Its Preparation Method and Application," proposes replacing part of the cement with recycled concrete powder and using a nano-seed crystal early strength agent to improve early strength. However, the recycled concrete powder used is not activated and only plays a certain filling role, which will affect the strength development of the shotcrete. In addition, the sand ratio in Examples 1 and 2 provided by this invention is too low, which may affect the workability of the concrete mixture and increase the risk of later cracking. The water-cement ratio in Example 3 is too high, and the 8-hour and 1-day compressive strengths are actually difficult to reach their test results, and the 28-day compressive strength is low, which will also affect long-term durability.

[0005] Therefore, there is an urgent need to develop a green, low-carbon, high-performance shotcrete that can simultaneously meet the requirements of energy conservation and environmental protection, good workability, low rebound rate, rapid early strength development, no strength reduction in the later stage, and high durability, so as to ensure the high-quality construction of major tunnel projects and have important significance for improving environmental quality. Summary of the Invention

[0006] This application provides a green, low-carbon, high-performance shotcrete using active recycled micropowder, its preparation method, and construction process, aiming to reduce the cement usage of shotcrete and meet the demand for high-performance shotcrete.

[0007] In the first aspect, this application provides a green, low-carbon, high-performance shotcrete using active recycled micropowder, employing the following technical solution:

[0008] A green, low-carbon, high-performance shotcrete using active recycled micropowder, comprising the following components by weight: 300-350 parts cement, 50-80 parts active recycled micropowder, 60-120 parts early-strength mineral admixture, 20-40 parts rubber powder, 10-20 parts hydrophobic densifying agent, 700-800 parts coarse aggregate, 800-900 parts fine aggregate; water-reducing agent, at a dosage of 0.8%-1.2% of the cementitious material mass; and fluorine-free and alkali-free quick-setting agent, at a dosage of 6%-9% of the cementitious material mass.

[0009] The active regenerated micro powder is composed of polyisomeric isoolamines and regenerated micro powder, wherein the amount of polyisomeric isoolamines is 0.1% to 0.5% of the mass of the cementitious material; the structural formula of the polyisomeric isoolamines is as shown in (Formula 1):

[0010]

[0011] Where m = 1 or 2, s = 0, 1, 2, 3 or 4;

[0012] The early-strength mineral admixture is a mixture of at least one of fly ash, slag powder, and limestone powder, and at least one of silica fume, zeolite powder, metakaolin, steel slag powder, and phosphorus slag powder, and an early-strength agent, with the weight ratio of the three being (30-60):(30-40):(10-20).

[0013] Furthermore, the regenerated micro powder must meet the following requirements: fineness (residue on a 45μm square hole sieve) ≤ 45%, particle size ≤ 75μm, water requirement ratio ≤ 115%, and activity index ≥ 60%.

[0014] Further, the fly ash is Class F, Grade I fly ash; the slag powder is Grade S105 slag powder; and the limestone powder has a 28-day activity index ≥70%. Further still, the silica fume has a 28-day activity index ≥100%; the zeolite powder is Grade I zeolite powder; the steel slag powder is Grade I steel slag powder; the phosphorus slag powder is Grade L95 phosphorus slag powder; and the metakaolin is ultrafine kaolin calcined at 600℃~900℃ to form highly active powder particles with a particle size of approximately 1250 mesh. Further still, the early strength agent is any one of sodium sulfate, calcium sulfate, magnesium sulfate, sodium thiosulfate, sodium thiocyanate, calcium nitrate, calcium nitrite, and sodium nitrate.

[0015] Furthermore, the rubber powder is waste tire rubber powder that has undergone surface treatment, and the surface treatment includes any one of the following: water washing method, pre-coating with gelling material method, and chemical solution immersion method.

[0016] Further, the hydrophobic sealing agent is an organosilicon-based waterproofing agent or an emulsion-based waterproofing agent. Even further, the hydrophobic sealing agent is... -Type VI concrete anti-seepage and hydrophobic compound plug.

[0017] Furthermore, the coarse aggregate is natural crushed stone with a continuous gradation of 5-10mm or crushed stone processed from tunnel slag.

[0018] Furthermore, the fine aggregate is any one of natural river sand, manufactured sand, or a mixture of natural river sand and manufactured sand, with a fineness modulus of 2.5 to 3.2.

[0019] Furthermore, the water-reducing agent is a mixture of polycarboxylate water-reducing agent and slump retainer, wherein the polycarboxylate water-reducing agent is at least one of carboxylate water-reducing agent, sulfonate water-reducing agent, and phosphonate water-reducing agent.

[0020] Furthermore, the polycarboxylate superplasticizer is a mixture of sulfonate superplasticizer and phosphonate superplasticizer, and the mass ratio of sulfonate superplasticizer to phosphonate superplasticizer is 1:(1.5-3). The phosphonate superplasticizer is a phosphonate superplasticizer with an acid-ether ratio of 2.0-2.5 and a molecular weight of 15,000-20,000.

[0021] Secondly, this application provides a method for preparing green, low-carbon, high-performance shotcrete using active recycled micropowder, employing the following technical solution:

[0022] A method for preparing green, low-carbon, high-performance shotcrete using active recycled micropowder includes the following steps:

[0023] S1. Dry mix cement, active recycled micro powder, early-strength mineral admixture, rubber powder, coarse aggregate, and fine aggregate evenly.

[0024] S2. Add water, water-reducing agent, and hydrophobic compactor in sequence and mix well to obtain concrete mixture.

[0025] Thirdly, this application provides a construction process for green, low-carbon, high-performance shotcrete using active recycled micropowder, employing the following technical solution:

[0026] A construction process for green, low-carbon, high-performance shotcrete using active recycled micro powder, wherein the shotcrete spraying distance is controlled at 0.8–1.2 m, the spraying angle at 80°–90°, the spraying air pressure at 0.8–0.9 MPa, and the thickness of a single layer of shotcrete is not greater than 5 cm.

[0027] In summary, this application has the following beneficial effects:

[0028] 1. Firstly, this application replaces part of the cement with active recycled micro powder and early-strength mineral admixtures, which can not only effectively reduce cement usage and carbon emissions, but also has no adverse effect on the early strength of shotcrete.

[0029] Unlike traditional physical and thermal activation, the active regenerated micro powder of this application is directly mixed with a specific activator to form active regenerated micro powder. This not only significantly reduces energy consumption but also improves the later strength and durability of shotcrete. In addition, it helps control the rebound rate of concrete and is suitable for shotcrete construction.

[0030] Using early-strength mineral admixtures can compensate for the early strength loss caused by the reduction in cement dosage. Moreover, when combined with active recycled micro powder and cement, it can fully leverage the complementary effect between powder material particles, form a good particle matching relationship, increase the density of shotcrete, and improve workability, mechanical strength, and durability.

[0031] 2. This application incorporates rubber powder into shotcrete, which can reduce the environmental pollution caused by waste tires and is also a good way to modify shotcrete. Adding an appropriate amount of rubber powder can improve the brittleness and toughness of shotcrete to a certain extent, reducing the risk of cracking caused by stress concentration. Furthermore, since rubber powder is a hydrophobic material, air bubbles are easily adsorbed on its surface, essentially acting as a solid air-entraining agent that can be uniformly and stably distributed in the shotcrete, thereby alleviating the hydrostatic pressure formed during frost heave and improving the frost resistance of the shotcrete. This application also pre-treats the surface of the rubber powder, which helps to enhance the interfacial bonding performance between the rubber powder and the cement matrix, thereby reducing its impact on the mechanical properties of the shotcrete.

[0032] 3. As the shotcrete of this application is a special type of concrete, due to the special spraying process and the early hydration-accelerating effect of the quick-setting agent, the overall structural density of shotcrete is not as high as that of cast-in-place concrete, making it more susceptible to penetration by corrosive media such as sulfates and chlorides in the environment. By incorporating a hydrophobic densifying agent in this application, the water absorption rate and permeability of shotcrete can be further reduced, its durability in complex environments can be enhanced, and its service life can be extended.

[0033] 4. This application preferably utilizes tunnel slag to process coarse and fine aggregates, reducing the mining of natural river sand and gravel, and together with recycled micro powder, mineral admixtures, and rubber powder, achieves green and low-carbon sprayed concrete.

[0034] 5. Since recycled micro-powder and tunnel slag aggregates contain a certain amount of stone powder, both of which can adsorb water-reducing agents, affecting the workability of concrete mixtures and being highly detrimental to shotcrete construction. Therefore, the water-reducing agent used in this application is preferably a mixture of sulfonates and phosphonates. Phosphonates have the best adaptability to recycled micro-powder and stone powder, and do not significantly affect the fluidity, yield stress, or adsorption of the slurry. Therefore, they can effectively play a role in rheological control of shotcrete.

[0035] 6. The preferred fluorine-free and alkali-free quick-setting agent in this application has a synergistic effect with early-strength mineral admixtures, which can significantly improve the early strength development rate of shotcrete, while having no adverse effect on later strength and durability. Detailed Implementation

[0036] The present application will be further described in detail below with reference to the embodiments.

[0037] In this embodiment of the application, unless otherwise specified, all materials are commercially available. The specific details of the relevant materials are as follows:

[0038] The cement used is Nanjing Conch brand P·O42.5 ordinary Portland cement.

[0039] The rubber powder is 120 mesh rubber powder produced by Shaoyang Black Gem Rubber Technology Co., Ltd. Before use, it is soaked in a 4% NaOH solution for 24 hours and then dried.

[0040] The hydrophobic densifier was produced by Jiangsu Subote New Material Co., Ltd. -Type VI concrete impermeable and hydrophobic chemical plugging agent, which is a light yellow transparent liquid.

[0041] The liquid alkali-free quick-setting agent is produced by Jiangsu Subote New Material Co., Ltd. -N(V) Early-strength fluorine-free and alkali-free quick-setting agent, fluoride ion content 0.01%, initial setting time of neat cement paste 2 min 30 s, final setting time of neat cement paste 5 min 15 s, 6-hour compressive strength of mortar 2.2 MPa, 1-day compressive strength of mortar 14.5 MPa.

[0042] The coarse aggregate is crushed stone made from tunnel muck with a continuous gradation of 5-10mm, containing 2.5% needle and flaky particles, 0.2% mud, and 0.1% mud lump.

[0043] The fine aggregate is manufactured sand produced by crushing and processing tunnel slag, with a fineness modulus of 2.68.

[0044] Example

[0045] This embodiment first provides a green, low-carbon, high-performance shotcrete using active recycled micropowder. The raw materials, by weight, include the following components: 300-350 parts cement; 50-80 parts active recycled micropowder; 60-120 parts early-strength mineral admixture, more preferably 80-110 parts; 20-40 parts rubber powder, more preferably 25-40 parts; 10-20 parts hydrophobic densifying agent, more preferably 12-20 parts; 700-800 parts coarse aggregate; 800-900 parts fine aggregate; water-reducing agent, at a dosage of 0.8%-1.2% of the cementitious material mass; fluorine-free and alkali-free quick-setting agent, at a dosage of 6%-9% of the cementitious material mass; and 163-200 parts water. In this embodiment, the cementitious material refers to the sum of cement, active recycled micropowder, and early-strength mineral admixture.

[0046] The active regenerated micro powder is composed of polyisomeric isoolamines and regenerated micro powder, with the amount of polyisomeric isoolamines being 0.1% to 0.5% of the mass of the cementitious material; the structural formula of the polyisomeric isoolamines is as shown in (Formula 1):

[0047]

[0048] Where m = 1 or 2, s = 0, 1, 2, 3 or 4.

[0049] Furthermore, the recycled concrete powder is obtained by crushing, removing impurities, and grinding waste concrete, and the recycled brick powder is obtained by crushing, removing impurities, and grinding waste sintered bricks. Recycled concrete powder with an original concrete strength grade of C30 or higher is preferred as the recycled micro-powder in this invention. The recycled micro-powder must meet the following requirements: fineness (residue on a 45μm square-hole sieve) ≤ 45%, particle size ≤ 75μm, water requirement ≤ 115%, and activity index ≥ 60%. The activity index of the chemically activated recycled micro-powder is 70-80%.

[0050] The early-strength mineral admixture is a mixture of at least one of fly ash, slag powder, and limestone powder, and at least one of silica fume, zeolite powder, metakaolin, steel slag powder, and phosphorus slag powder, and an early-strength agent. The weight ratio of the three components is (30-60): (30-40): (10-20).

[0051] Furthermore, the fly ash is Class F Grade I fly ash, the slag powder is S105 grade slag powder, and the limestone powder has a 28-day activity index ≥70%.

[0052] Furthermore, the silica fume has a 28-day activity index ≥100%, the zeolite powder is Grade I zeolite powder, the steel slag powder is Grade I steel slag powder, the phosphorus slag powder is Grade L95 phosphorus slag powder, and the metakaolin is a highly active powder particle with a particle size of about 1250 mesh formed by calcining ultrafine kaolin at 600℃~900℃.

[0053] Furthermore, the early strength agent is any one of sodium sulfate, calcium sulfate, magnesium sulfate, sodium thiosulfate, sodium thiocyanate, calcium nitrate, calcium nitrite, and sodium nitrate.

[0054] The rubber powder is waste tire rubber powder that has undergone surface treatment. The surface treatment includes any one of the following: water washing, pre-coating with gelling materials, and chemical solution immersion. Among these, the pre-coating with gelling materials or chemical solution immersion is preferred.

[0055] The hydrophobic sealing agent is a silicone-based waterproofing agent or an emulsion-based waterproofing agent. Further, the hydrophobic sealing agent is... -Type VI concrete anti-seepage and hydrophobic chemical plugging agent. It is a concrete admixture with hydrophobic and densifying functions. It improves the water repellency of concrete by changing the surface pressure of the capillary pores inside the concrete, and at the same time improves the density of concrete by refining the capillary structure, thereby improving the durability of shotcrete in environments with corrosive media such as water seepage, sulfates, and chlorides.

[0056] The coarse aggregate is 5-10mm continuously graded natural crushed stone or crushed stone processed from tunnel muck. Crushed stone processed from tunnel muck is preferred, with a needle-like and flaky particle content ≤5.0%, a mud content ≤0.5%, and a mud lump content ≤0.2%.

[0057] The fine aggregate is any one of natural river sand, manufactured sand, or a mixture of natural river sand and manufactured sand, with a fineness modulus of 2.5 to 3.2. The fine aggregate is preferably manufactured sand produced from crushed tunnel slag, with a preferred fineness modulus of 2.6 to 3.0, and a mud content ≤2.0%, a clay lump content ≤0.5%, and a stone powder content ≤5.0%.

[0058] The water-reducing agent is a mixture of polycarboxylate water-reducing agent and slump retainer. The polycarboxylate water-reducing agent is at least one of carboxylate water-reducing agent, sulfonate water-reducing agent, and phosphonate water-reducing agent. Further, the polycarboxylate water-reducing agent is a mixture of sulfonate water-reducing agent and phosphonate water-reducing agent, and the mass ratio of sulfonate water-reducing agent to phosphonate water-reducing agent is 1:(1.5-3). The phosphonate water-reducing agent is a phosphonate water-reducing agent with an acid-ether ratio of 2.0-2.5 and a molecular weight of 15,000-20,000.

[0059] This application also provides a method for preparing green, low-carbon, high-performance shotcrete using active recycled micropowder, comprising the following steps:

[0060] S1. Dry mix cement, active recycled micro powder, early-strength mineral admixture, rubber powder, coarse aggregate, and fine aggregate evenly.

[0061] S2. Add water, water-reducing agent, and hydrophobic compactor in sequence and stir evenly to obtain concrete mixture. The concrete mixture obtained in step S2 must meet the following requirements: slump 180-220mm, slump loss ≤30mm in 1 hour, spread 450-550mm, and collapse time 3-6s.

[0062] This application provides a construction process for green, low-carbon, high-performance shotcrete using active recycled micro powder. In the construction process, the concrete spraying distance is controlled at 0.8 to 1.2 m, the spraying angle is controlled at 80° to 90°, the spraying air pressure is controlled at 0.8 to 0.9 MPa, and the thickness of a single layer of spraying is not greater than 5 cm.

[0063] The following is an illustration through specific examples.

[0064] Examples 1-4

[0065] In Examples 1-4, the recycled micro powder was obtained by crushing, removing impurities, and grinding the waste concrete (strength grade C50) obtained from the demolition of a pedestrian overpass on a highway in Anqing City; the original recycled micro powder had a fineness of 12.2%, a particle size of 62μm, a water requirement ratio of 105%, and an activity index of 63.6%.

[0066] The water-reducing agent is a polycarboxylate water-reducing agent produced by Jiangsu Subote New Material Co., Ltd., consisting of water-reducing component 1# ( -902)-10%, Water-reducing component 2# ( -808)-30%, unsaturated esters of slump-preserving components ( -305)-20%, the remainder is water, solid content is 25%, water reduction rate is 32%.

[0067] Example 1

[0068] A method for preparing green, low-carbon, high-performance shotcrete using active recycled micropowder, comprising the following specific steps:

[0069] S1. Dry mix 350 kg of cement, 60 kg of active recycled micro powder, 90 kg of early-strength mineral admixture, 25 kg of modified rubber powder, 700 kg of coarse aggregate, and 850 kg of fine aggregate evenly; wherein, the active recycled micro powder is composed of polyisomeric amines and recycled micro powder, and the amount of polyisomeric amines is 0.2% of the mass of cementitious materials; in the structural formula of polyisomeric amines, m is 1 and s is 1.

[0070] S2. Add 200kg of water, 4kg of water-reducing agent, and 12kg of water-repellent and densifying agent in sequence and mix well to obtain concrete mixture. The slump of the mixture after exiting the machine is 200mm, the spread is 485mm, and the collapse time is 3.4s.

[0071] S3. Transport the concrete mixture to the construction site, measure the slump loss as 18mm, then load it into a wet spraying machine, mix it with 40kg of atomized quick-setting agent at the nozzle, and spray it at high speed onto the surrounding rock surface to form green, low-carbon, high-performance sprayed concrete. After the state stabilizes, spray it into the pre-placed mold and test the performance of the test blocks according to the specified test methods.

[0072] Example 2

[0073] A method for preparing green, low-carbon, high-performance shotcrete using active recycled micropowder, comprising the following specific steps:

[0074] S1. Dry mix 300 kg of cement, 80 kg of active recycled micro powder, 110 kg of early-strength mineral admixture, 32 kg of modified rubber powder, 760 kg of coarse aggregate, and 830 kg of fine aggregate evenly; wherein, the active recycled micro powder is composed of polyisomeric amines and recycled micro powder, and the amount of polyisomeric amines is 0.4% of the mass of cementitious materials; in the structural formula of polyisomeric amines, m is 1 and s is 1.

[0075] S2. Add 186.2 kg of water, 4.9 kg of water-reducing agent, and 18 kg of hydrophobic and densifying agent in sequence and mix well to obtain concrete mixture. The slump of the mixture after exiting the machine is 210 mm, the spread is 505 mm, and the collapse time is 4.2 s.

[0076] S3. Transport the concrete mixture to the construction site, measure the slump loss as 10mm, then load it into a wet spraying machine, mix it with 34.3kg of atomized quick-setting agent at the nozzle, and spray it at high speed onto the surrounding rock surface to form green, low-carbon, high-performance sprayed concrete. After the state stabilizes, spray it into the pre-placed mold, and test the performance of the test blocks according to the specified test methods.

[0077] Example 3

[0078] A method for preparing green, low-carbon, high-performance shotcrete using active recycled micropowder, comprising the following specific steps:

[0079] S1. Dry mix 320 kg of cement, 75 kg of active recycled micro powder, 100 kg of early-strength mineral admixture, 36 kg of modified rubber powder, 800 kg of coarse aggregate, and 800 kg of fine aggregate evenly; wherein, the active recycled micro powder is composed of polyisomeric amines and recycled micro powder, and the amount of polyisomeric amines is 0.5% of the mass of cementitious materials; in the structural formula of polyisomeric amines, m is 1 and s is 1.

[0080] S2. Add 178.2 kg of water, 5.5 kg of water-reducing agent, and 15 kg of hydrophobic and densifying agent in sequence and mix well to obtain concrete mixture. The slump of the mixture after exiting the machine is 190 mm, the spread is 475 mm, and the collapse time is 5.1 s.

[0081] S3. Transport the concrete mixture to the construction site, measure the slump loss as 22mm, then load it into a wet spraying machine, mix it with 45kg of atomized quick-setting agent at the nozzle, and spray it at high speed onto the surrounding rock surface to form green, low-carbon, high-performance sprayed concrete. After the state stabilizes, spray it into the pre-placed mold and test the performance of the test blocks according to the specified test methods.

[0082] Example 4

[0083] A method for preparing green, low-carbon, high-performance shotcrete using active recycled micropowder, comprising the following specific steps:

[0084] S1. Dry mix 350 kg of cement, 50 kg of active recycled micro powder, 80 kg of early-strength mineral admixture, 40 kg of modified rubber powder, 780 kg of coarse aggregate, and 900 kg of fine aggregate evenly; wherein, the active recycled micro powder is composed of polyisomeric amines and recycled micro powder, and the amount of polyisomeric amines is 0.1% of the mass of cementitious materials; in the structural formula of polyisomeric amines, m is 1 and s is 1.

[0085] S2. Add 163.2 kg of water, 5.8 kg of water-reducing agent, and 20 kg of hydrophobic and densifying agent in sequence and mix well to obtain concrete mixture. The slump of the mixture after exiting the machine is 184 mm, the spread is 460 mm, and the collapse time is 5.6 s.

[0086] S3. Transport the concrete mixture to the construction site, measure the slump loss as 23mm, then load it into a wet spraying machine, mix it with 28.8kg of atomized quick-setting agent at the nozzle, and spray it at high speed onto the surrounding rock surface to form green, low-carbon, high-performance sprayed concrete. After the state stabilizes, spray it into the pre-placed mold, and test the performance of the test blocks according to the specified test methods.

[0087] Example 5

[0088] The difference from Example 1 is that in (Formula 1), the polyisomeric alcoholamine has m = 1 and s = 0.

[0089] Example 6

[0090] The difference from Example 1 is that in (Formula 1), the polyisomeric alcoholamine has m = 1 and s = 2.

[0091] Example 7

[0092] The difference from Example 1 is that in (Formula 1), the polyisomeric alcoholamine has m = 2 and s = 3.

[0093] Example 8

[0094] The difference from Example 1 is that in (Formula 1), the polyisomeric alcoholamine has m = 2 and s = 4.

[0095] Comparative Example

[0096] Comparative Example 1

[0097] Comparative Example 1 replaces the active regenerated micro powder in Example 1 with an equal mass of ordinary regenerated micro powder, without adding polyisomeric alcohol amines, and the composition, proportions, and test methods of the other raw materials are the same as in Example 1.

[0098] Comparative Example 2

[0099] Comparative Example 2 replaces the early-strength mineral admixture in Example 2 with an equal mass of ordinary mineral admixture, i.e., it is composed of 100% fly ash. The composition, proportions, and test methods of the remaining raw materials are the same as in Example 2.

[0100] Comparative Example 3

[0101] Comparative Example 3 replaces the modified rubber powder in Example 3 with an equal mass of cement, while the composition, proportions, and test methods of the remaining raw materials are the same as in Example 3.

[0102] Comparative Example 4

[0103] Comparative Example 4 replaces the hydrophobic densifier in Example 4 with an equal mass of water, while the composition, proportions, and test methods of the remaining raw materials are the same as in Example 4.

[0104] Comparative Example 5

[0105] Comparative Example 5 replaces the water-reducing agent in Example 1 with an equal mass of ordinary polycarboxylate water-reducing agent (made from a 10% mass fraction water-reducing mother liquor). -801, 5% by mass of slump-holding component The composition of the raw materials is the same as that of Example 1, consisting of -305 and 3% sodium gluconate as a retarding component. The composition, proportions and test methods of the remaining raw materials are the same as those in Example 1.

[0106] Comparative Example 6

[0107] Comparative Example 6 involved replacing the accelerator in Example 1 with an equal mass of a fluorinated, alkali-free accelerator. -N(II), the composition, proportions and test methods of the remaining raw materials are the same as in Example 1.

[0108] Comparative Example 7

[0109] The difference from Example 1 is that the activator is diethanolamine.

[0110] Comparative Example 8

[0111] The difference from Example 1 is that the activator is sodium sulfate.

[0112] Comparative Example 9

[0113] The difference from Example 1 is that (Formula 1) is a polyisomeric alcohol amine, where m is 0 and s is 1.

[0114] Comparative Example 10

[0115] The difference from Example 1 is that the amount of polyisomeric alcohol amine used is 1.0% of the mass of the cementitious material.

[0116] Performance testing

[0117] The method for preparing and testing the performance of the shotcrete specimens described in this application is as follows:

[0118] The preparation of shotcrete specimens and the rebound rate test method refer to JGJ / T 372-2016 "Technical Specification for Application of Shotcrete". The wet spraying method is adopted, and the Gengli Machinery GSP-D dry and wet dual-purpose shotcrete machine is used. The specific steps are as follows:

[0119] (1) Weigh the above raw materials in sequence and mix them evenly in a forced mixer. The output of the mixer should meet the following requirements: slump of 180-220mm, expansion of 450-550mm, and slump time of 3-6s.

[0120] (2) The mixture is transported to the tunnel construction site by concrete truck. The slump loss is tested and must not exceed 30mm. Then it is loaded into a wet spraying machine, mixed with quick-setting agent and sprayed onto the surrounding rock. After the state is stable, it is sprayed into a large plate mold with dimensions of 450mm×450mm×120mm and a truncated cone mold with dimensions of 175mm (top)×150mm (height)×185mm (bottom).

[0121] (3) After spraying, the test mold is placed in the tunnel and cured under the same conditions for 18 hours before demolding. The 1-day compressive strength test specimen is cut into 100mm×100mm×100mm cube specimens 2 hours before the curing period. The long-age test specimen is cut or cored according to the specified size after 7 days of standard curing.

[0122] The compressive strength at 1d, 7d, 28d, and 56d was tested according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete"; the resistance to water penetration (water penetration height method), resistance to chloride ion penetration (electric flux method), resistance to sulfate attack, frost resistance (rapid freezing method), and shrinkage rate (contact method) were tested according to GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete". The test results are shown in Tables 1 and 2.

[0123] Table 1. Test results of compressive strength and rebound rate of shotcrete

[0124]

[0125]

[0126] Table 2 Results of Shotcrete Durability Tests

[0127]

[0128]

[0129] A comparison of the performance of Examples 1-4 and Comparative Examples 1-4 reveals that the concrete of this application not only effectively reduces cement usage and carbon emissions, but also exhibits good early strength, later strength, and durability. Furthermore, the concrete of this application is suitable for shotcrete construction, which can increase the density of shotcrete and improve workability, mechanical strength, and durability.

[0130] Analysis of the performance of Examples 5-8 revealed that different polyisomeric alcoholamines have a certain impact on concrete performance. However, the polyisomeric alcoholamines of this application all meet the high-performance requirements of shotcrete. Furthermore, regarding the activators of this application, Comparative Examples 7 and 8 used diethanolamine and sodium sulfate as activators, respectively; Comparative Example 9 used polyisomeric alcoholamines with other structures; and Comparative Example 10 added too many polyisomeric alcoholamines. Its concrete not only showed reduced compressive strength but also increased resilience, failing to meet the requirements for high-performance shotcrete.

[0131] Comparative Examples 1-6 show that: Comparative Example 1, which replaced the active recycled micro-powder in Example 1 with an equal mass of ordinary recycled micro-powder and did not add polyisomeric amines, resulted in a significant decrease in various properties; Comparative Example 2, which replaced the early-strength mineral admixture in Example 2 with an equal mass of ordinary mineral admixture, resulted in a decrease in compressive strength; Comparative Example 3, which replaced the modified rubber powder in Example 3 with an equal mass of cement, resulted in a decrease in compressive strength compared to Example 3, and a significant increase in rebound rate; Comparative Example 4, which replaced the hydrophobic densifier in Example 4 with an equal mass of water, resulted in a decrease in compressive strength, a significant increase in rebound rate, and a substantial decrease in durability, making it unsuitable for shotcrete; Comparative Example 5, which replaced the water-reducing agent in Example 1 with an equal mass of ordinary polycarboxylate water-reducing agent, resulted in a significant decrease in the compressive strength of the concrete and an excessively high rebound rate; Comparative Example 6, which replaced the accelerator in Example 1 with an equal mass of fluorinated alkali-free accelerator. -N(II) results in a significant decrease in compressive strength and a substantial reduction in impermeability. This demonstrates that in the concrete system of this application, each component is indispensable, reducing the cement content of shotcrete while maintaining good compressive strength, durability, and other properties, and meeting the requirements for high-performance shotcrete.

[0132] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A green, low-carbon, high-performance shotcrete using active recycled micro-powder, characterized in that, The raw materials, by weight, include the following components: 300-350 parts cement, 50-80 parts active recycled micro powder, 60-120 parts early-strength mineral admixture, 20-40 parts rubber powder, 10-20 parts hydrophobic densifying agent, 700-800 parts coarse aggregate, 800-900 parts fine aggregate; water-reducing agent, with a dosage of 0.8% to 1.2% of the cementitious material's mass; and fluorine-free and alkali-free quick-setting agent, with a dosage of 6% to 9% of the cementitious material's mass. The active regenerated micro powder is composed of polyisomeric isoolamines and regenerated micro powder, wherein the amount of polyisomeric isoolamines is 0.1% to 0.5% of the mass of the cementitious material; the structural formula of the polyisomeric isoolamines is shown in Formula 1: Where m = 1 or 2, s = 0, 1, 2, 3 or 4; The early-strength mineral admixture is a mixture of at least one of fly ash, slag powder, and limestone powder, and at least one of silica fume, zeolite powder, metakaolin, steel slag powder, and phosphorus slag powder, and an early-strength agent, with the weight ratio of the three components being (30-60): (30-40): (10-20). The water-reducing agent is a mixture of polycarboxylate water-reducing agent and slump retainer. The polycarboxylate water-reducing agent is a mixture of sulfonate water-reducing agent and phosphonate water-reducing agent, and the mass ratio of sulfonate water-reducing agent to phosphonate water-reducing agent is 1:(1.5~3).

2. The green, low-carbon, high-performance shotcrete using active recycled micro-powder according to claim 1, characterized in that, The fineness of the regenerated micro powder must meet the following requirements: ≤45% residue on a 45μm square hole sieve, ≤75μm particle size, ≤115% water requirement, and ≥60% activity index.

3. The green, low-carbon, high-performance shotcrete using active recycled micro-powder according to claim 1, characterized in that, The fly ash is Class I fly ash of type F, the slag powder is S105 grade slag powder, and the limestone powder has an activity index of ≥70% after 28 days.

4. A green, low-carbon, high-performance shotcrete using active recycled micro-powder according to claim 1, characterized in that, The silica fume has an activity index of ≥100% after 28 days, the zeolite powder is grade I zeolite powder, the steel slag powder is grade I steel slag powder, the phosphorus slag powder is grade L95 phosphorus slag powder, and the metakaolin is a highly active powder particle with a particle size of 1250 mesh formed by calcining ultrafine kaolin at 600℃~900℃.

5. A green, low-carbon, high-performance shotcrete using active recycled micro-powder according to claim 1, characterized in that, The early strength agent is any one of sodium sulfate, calcium sulfate, magnesium sulfate, sodium thiosulfate, sodium thiocyanate, calcium nitrate, calcium nitrite, and sodium nitrate.

6. The green, low-carbon, high-performance shotcrete using active recycled micro-powder according to claim 1, characterized in that, The rubber powder is waste tire rubber powder that has undergone surface treatment. The surface treatment includes any one of the following: water washing method, pre-coating with gelling material method, and chemical solution immersion method.

7. A green, low-carbon, high-performance shotcrete using active recycled micro-powder according to claim 1, characterized in that, The hydrophobic and densifying agent is an organosilicon-based waterproofing agent or an emulsion-based waterproofing agent.

8. A green, low-carbon, high-performance shotcrete using active recycled micro-powder according to claim 7, characterized in that, The hydrophobic densifying agent is -Type VI concrete anti-seepage and hydrophobic compound plug.

9. A green, low-carbon, high-performance shotcrete using active recycled micro-powder according to claim 1, characterized in that, The coarse aggregate is natural crushed stone with a continuous gradation of 5-10mm or crushed stone processed from tunnel muck.

10. A green, low-carbon, high-performance shotcrete using active recycled micro-powder according to claim 1, characterized in that, The fine aggregate is any one of natural river sand, manufactured sand, or a mixture of natural river sand and manufactured sand, with a fineness modulus of 2.5 to 3.

2.

11. A green, low-carbon, high-performance shotcrete using active recycled micro-powder according to claim 1, characterized in that, The phosphonate water-reducing agent is a phosphonate water-reducing agent with an acid-ether ratio of 2.0 to 2.5 and a molecular weight of 15,000 to 20,000.

12. A method for preparing green, low-carbon, high-performance shotcrete using active recycled micro-powder as described in any one of claims 1-11, characterized in that, Includes the following steps: S1. Dry mix cement, active recycled micro powder, early-strength mineral admixture, rubber powder, coarse aggregate, and fine aggregate evenly. S2. Add water, water-reducing agent and hydrophobic compactor in sequence and stir evenly to obtain concrete mixture; S3. Load the concrete mixture into the wet spraying machine and mix it with the quick-setting agent at the nozzle to obtain sprayed concrete.

13. A construction process for shotcrete prepared by the method according to claim 12, characterized in that, During construction, the concrete spraying distance is controlled at 0.8 to 1.2 m, the spraying angle is controlled at 80° to 90°, the spraying air pressure is controlled at 0.8 to 0.9 MPa, and the thickness of a single layer of spraying is not greater than 5 cm.

Images