Self-leveling secondary lining concrete of tunnel slag recycled aggregate and preparation method of self-leveling secondary lining concrete

Abstract

The invention relates to the technical field of concrete, in particular to self-leveling secondary lining concrete of tunnel hole slag recycled aggregate and a preparation method of the self-leveling secondary lining concrete. Comprising the following raw materials in parts by weight: 280-330 parts of cement, 80-120 parts of fly ash, 740-880 parts of hole slag regenerated machine-made sand, 900-1100 parts of hole slag regenerated gravel, 140-190 parts of water, 4-9 parts of a water reducing agent, 4-15 parts of a modified expanding agent and 4-15 parts of a modified anti-cracking thickening agent. The invention aims to improve the fluidity, aggregate trafficability, compensation contractility and cohesion of secondary lining concrete through the optimal design of the concrete preparation ratio and the use of a functional polymer blending material. The problems that the tunnel secondary lining is poor in appearance quality, large in strength discreteness and prone to disengaging and cracking in the later period due to the fact that the powder content and the crushing value of the tunnel hole slag recycled aggregate are high and the working space is narrow and reinforcing steel bars in a formwork are dense in the tunnel secondary lining construction are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, in particular to a self-leveling secondary lining concrete of tunnel slag recycled aggregate and a preparation method thereof. Background Art

[0002] Concrete is an artificial stone material made of cement, mineral admixtures, fine aggregate, coarse aggregate, water and admixtures added when necessary in a certain proportion, which is evenly mixed, compacted into a dense shape, and cured and hardened. It is widely used in the modern construction industry.

[0003] During the construction of secondary linings in high-speed railway tunnels, the concrete's fluidity, cohesiveness, and aggregate flowability failed to fully meet the construction requirements within the narrow, densely reinforced formwork space. Given the narrow construction space and dense rebar within the formwork, workers could only vibrate the concrete from the secondary lining trolley window, failing to achieve comprehensive and uniform vibration. This resulted in over-vibration, missed vibration, and the inability of coarse aggregate to flow smoothly through densely reinforced areas, blocking the concrete flow path. This resulted in poor filling and distribution of concrete within the secondary lining formwork, as well as a lack of a full slurry film on the formwork surface. This led to issues such as voids, high strength dispersion, and poor appearance quality.

[0004] At the same time, due to increasing environmental protection requirements and a decrease in natural sand and gravel resources, construction projects face high procurement costs and unstable supply, severely impacting construction schedules and costs. Therefore, recycling tunnel slag to produce manufactured sand and gravel aggregate is the optimal technical approach to "take from the tunnel and use it in the tunnel." However, tunnel slag has a high impurity content, low cleanliness, and complex composition, resulting in high stone powder content and crushing value in the manufactured sand and gravel, further exacerbating problems such as voids in the tunnel secondary lining, high strength dispersion, poor appearance quality, and cracking. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a self-leveling secondary lining concrete of tunnel slag recycled aggregate and a preparation method. By optimizing the design of the concrete matching ratio and using functional polymer admixtures, the fluidity, aggregate permeability, shrinkage compensation and cohesion of the secondary lining concrete are improved, and the problems of poor appearance quality, large strength dispersion and easy voiding and cracking of the tunnel secondary lining in the later stage caused by the high powder content and crushing value of the tunnel slag recycled aggregate and the narrow working space and dense steel bars in the formwork during the construction of the tunnel secondary lining are solved.

[0006] The present invention solves the above technical problems through the following technical means:

[0007] A self-leveling secondary lining concrete made of recycled aggregate from tunnel slag comprises the following raw materials in parts by weight:

[0008] 280-330 parts of cement, 80-120 parts of fly ash, 740-880 parts of slag recycled sand, 900-1100 parts of slag recycled gravel, 140-190 parts of water, 4-9 parts of water reducer, 4-15 parts of modified expansive agent, and 4-15 parts of modified anti-cracking thickener.

[0009] According to the above technical means, by optimizing the design of concrete matching ratio and using functional polymer admixtures, the fluidity, aggregate permeability, shrinkage compensation and cohesion of the secondary lining concrete are improved, and the problems of poor appearance quality and large strength dispersion of the tunnel secondary lining due to the high powder content and crushing value of the recycled aggregate of tunnel slag and the narrow working space and dense steel bars in the formwork during the construction of the tunnel secondary lining are solved, which are easy to appear in the later stage due to voiding and cracking.

[0010] Preferably, the modified expansion agent is prepared by mixing inorganic materials and organic materials.

[0011] Preferably, the inorganic material is one or more combinations of magnesite, dolomite, bauxite, limestone, slag powder, and silica fume.

[0012] More preferably, the inorganic material is magnesite, dolomite, bauxite and limestone.

[0013] More preferably, the addition ratio of magnesite, dolomite, bauxite and limestone is 8-10:4-5:3-5:3-5.

[0014] According to the above technical means, by selecting dolomite, magnesium ions can be provided, so that magnesium hydroxide can be generated during the hydration reaction. The process of generating magnesium hydroxide will be accompanied by volume expansion, which can compensate for the shrinkage of concrete and reduce the occurrence of cracks. The generated magnesium hydroxide can fill the pores and microcracks inside the concrete to a certain extent, improve the density of the concrete, and enhance its durability such as impermeability and resistance to chemical corrosion. Dolomite contains calcium ions and magnesium ions. When participating in the hydration reaction of cement, it can adjust the composition and structure of the hydration products and improve the mechanical properties and durability of concrete.

[0015] Bauxite provides aluminum oxide and exhibits pozzolanic activity. In concrete, bauxite undergoes a secondary hydration reaction with calcium hydroxide, a product of cement hydration, to produce cementitious substances such as hydrated calcium aluminate, which fill concrete pores and improve its density and strength. Limestone, on the other hand, provides calcium ions, which react with cement hydration products to form substances such as carbon aluminates, accelerating cement hydration and improving concrete's early strength.

[0016] Therefore, the calcium, aluminum, magnesium and other ions in magnesite, dolomite, bauxite and limestone can expand in volume during the hydration reaction, thereby effectively compensating for the early and late shrinkage of concrete. In the expansion process, they can penetrate and fill the gaps between the tunnel slag recycled sand and the recycled gravel, thereby improving the mechanical properties and durability of the tunnel slag recycled sand and the recycled gravel in concrete. By controlling the amount of magnesite, dolomite, bauxite and limestone, excessive expansion can be avoided, which may lead to cracking of concrete in the later stage.

[0017] Preferably, the organic material is one or more combinations of octadecanoic acid, magnesium fluorosilicate, sodium gluconate, oleic acid, palmitic acid, sodium silicate, sodium fluorosilicate, citric acid, tartaric acid, and lignin sulfonate.

[0018] More preferably, the organic material is octadecanoic acid, magnesium fluorosilicate and sodium gluconate.

[0019] More preferably, the addition ratio of octadecanoic acid, magnesium fluorosilicate and sodium gluconate is 10:5-3:2-1.

[0020] According to the above technical means, the use of octadecanoic acid can act as a waterproofing agent, reducing the concrete's absorption of water, thereby improving the concrete's waterproofing properties. Magnesium fluorosilicate can act as a hardener, chemically reacting with calcium hydroxide in the concrete to produce insoluble calcium fluorosilicate and other products, which fill the pores within the concrete, making the concrete structure more compact, thereby improving the concrete's strength, hardness, wear resistance, impermeability, and corrosion resistance. Sodium gluconate can act as a retarder, slowing the hydration reaction of cement and extending the setting time of concrete. It also has a certain water-reducing effect, reducing the water consumption of the concrete mix, improving the fluidity and workability of the concrete, and, by reducing porosity, also increasing the strength of the concrete to a certain extent.

[0021] Preferably, the preparation of the modified expansion agent comprises the following steps:

[0022] S1: Place magnesite, dolomite, bauxite, and limestone in a muffle furnace, calcine at 800-1000°C for 8-10 hours, and cool to room temperature to obtain a mixture for later use;

[0023] S2: Add octadecanoic acid, magnesium fluorosilicate and sodium gluconate to the fired mixture and place the mixture in a ball mill for 3-5 hours. After ball milling, sieve the mixture to obtain a modified expansion agent.

[0024] According to the above technical means, by first calcining dolomite, dolomite, bauxite, and limestone, oxides such as calcium oxide, aluminum oxide, and magnesium oxide can be obtained. These oxides can expand during the hydration reaction and can effectively compensate for the early and late shrinkage of concrete. Then, by mixing and ball-milling with octadecanoic acid, magnesium fluorosilicate, and sodium gluconate, the magnesium fluorosilicate and sodium gluconate can be adsorbed on the surface of the oxide and ore particles after ball milling. Therefore, when used, they can fully contact the cement surface, reduce the contact area between water and cement, prevent the cement from hydrating too quickly, reduce the concentrated release of cement hydration heat, and reduce concrete cracking. Octadecanoic acid can complex metal ions such as calcium, magnesium, and aluminum and has a lubricating effect, which can improve ball milling efficiency and form a capsule structure but break in an alkaline environment. Therefore, when the modified expansive agent is not in use, it can effectively protect the metal oxide from absorbing moisture in the air, thereby improving the shelf life of the modified expansive agent and the expansibility and retarding effects of the modified expansive agent and, to a certain extent, controlling the expansion rate.

[0025] Moreover, after high-temperature calcination of magnesite, dolomite, bauxite and limestone, some impurities can be removed, the possibility of side reactions can be reduced, and the activity and stability of the calcined products can be increased, making the hydration reaction more stable and faster. It is also easier to combine and fill with the slag regeneration machine-made sand and regenerated gravel, and to improve the density, elastic modulus, impermeability and water absorption of the slag regeneration machine-made sand and regenerated gravel.

[0026] Further preferably, in the step S2, the product is sieved through a 400-500 mesh sieve after ball milling.

[0027] Preferably, the modified anti-cracking thickener comprises the following raw materials in parts by weight:

[0028] 30-50 parts of glass fiber powder, 4-6 parts of latex powder, 1-3 parts of xanthan gum and 40-70 parts of reinforcing agent.

[0029] According to the above technical means, by using glass fiber powder, which contains protruding spherical structures at both ends, it can form an overlapping effect in a microscopic state, play the role of microfiber, improve the integrity of concrete, restrain the volume expansion or contraction of concrete, and reduce concrete cracking and shrinkage; latex powder can enhance the bonding strength, flexibility and water resistance between materials, and xanthan gum has the ability of thickening, suspending and stabilizing suspension. Through the mutual cooperation of glass fiber powder, latex powder and xanthan gum, the materials can be formed into a stable adhesive material, and can be effectively combined with concrete to form a network structure, thereby improving the crack resistance of concrete; and through the action of the reinforcing agent, the cohesion, flexural resistance, density and fluidity of the concrete are enhanced.

[0030] Moreover, through the combination of glass fiber powder, latex powder, xanthan gum and reinforcing agent, the bonding, impermeability and density of slag recycled machine sand and recycled gravel can be improved, and the strength and working performance of concrete can be improved.

[0031] Preferably, the enhancer includes modified hydroxypropyl cellulose ether and powdered polycarboxylate water reducer.

[0032] Further preferably, the mass ratio of modified hydroxypropyl cellulose ether to powdered polycarboxylate water reducer is 2:5.

[0033] According to the above technical means, by adopting modified hydroxypropyl cellulose ether, the water retention, thickening and construction performance of the material can be improved, and the adhesion of the material can be enhanced to a certain extent; and the powdered polycarboxylate water reducer can compensate for the material's adsorption of water in the concrete, improve the fluidity of the concrete, thereby enhancing the cohesion and fluidity of the material, and further enhancing the cohesion and fluidity of the concrete.

[0034] Preferably, the reinforcing agent further includes at least one of silica fume powder, slag powder and metakaolin.

[0035] More preferably, the reinforcing agent also includes silica fume.

[0036] According to the above technical means, by using silica fume, the density and impermeability of concrete can be improved, and the risk of shrinkage cracks caused by water penetration in concrete can be reduced. It can also be adsorbed on the surface of cement particles to form a hydration film, increasing the friction between cement particles, thereby improving the consistency of concrete, reducing segregation and bleeding of concrete, and reducing the risk of cracks. Silica fume also contains a large amount of active SiO2. During the concrete hardening process, this active SiO2 will undergo a secondary hydration reaction with the calcium hydroxide produced by cement hydration to form a hydrated calcium silicate gel. This gel has higher strength and stability, can further fill the pores within the concrete, improve the strength and durability of the concrete, and enhance the concrete's crack resistance.

[0037] Preferably, the water reducer is TW-HJS-1 slow-setting polycarboxylic acid high-performance water reducer.

[0038] Preferably, the fineness modulus of the slag regeneration machine-made sand is 2.7-3.2, the stone powder content is 8-12%, and the crushing value is 20-30%.

[0039] Preferably, the particle size of the slag recycled gravel is 5.0-20.0 mm, the stone powder content is 0.5-2%, and the crushing value is 10-15%.

[0040] According to the above technical means, the produced slag recycling machine-made sand and gravel are directly used without other treatment. In combination with other raw materials, the fluidity of concrete, aggregate permeability, shrinkage compensation, cohesion, mechanical properties, impermeability and frost resistance can be improved, thereby reducing the cost of use.

[0041] The present application also discloses a method for preparing a self-leveling secondary lining concrete of tunnel slag recycled aggregate, comprising the following steps:

[0042] Step 1: Add water reducer to mixing water and set aside;

[0043] Step 2: first add the slag regeneration crushed stone and slag regeneration machine-made sand into a forced mixer, then add cement, fly ash, modified expansion agent, and modified anti-cracking thickener, stir and mix evenly to obtain a mixture;

[0044] Step 3: Add the mixing water containing the water reducer in step 1 to the mixture in step 2 in a forced mixer, and stir for 150-180 seconds to obtain a self-leveling secondary lining concrete with tunnel slag recycled aggregate.

[0045] According to the above technical means, the preparation method of the present application is simple, practical, and suitable for large-scale use.

[0046] The present application adopting the above solution has the following beneficial effects:

[0047] 1. In this application, through the optimization design of aggregate particle size and the modification of expansion agent and thickener, the expansion agent not only has better early and late expansion effects, but also can delay the concentrated release of cement hydration heat; the thickener can not only improve the cohesion and flexural resistance of concrete, but also improve the crack resistance and fluidity of concrete; make the concrete have good fluidity, aggregate permeability, shrinkage compensation and cohesion, solve the problems of high powder content and crushing value of recycled aggregate in tunnel slag and narrow working space and template in tunnel secondary lining construction. The steel bars are dense, resulting in poor appearance quality of the tunnel secondary lining, large strength dispersion, and easy to appear hollow and cracking problems in the later period; 2. In the present application, when preparing the modified expansive agent, magnesite, dolomite, bauxite, and limestone are first calcined to obtain oxides such as calcium oxide, aluminum oxide, and magnesium oxide, which can expand during the hydration reaction and can effectively compensate for the early and late shrinkage of concrete; and then the oxides are mixed with octadecanoic acid, magnesium fluorosilicate, and sodium gluconate and ball-milled to make the magnesium fluorosilicate and sodium gluconate adsorb on the milled oxides, The surface of the ore particles can fully contact the surface of the concrete particles when used, reducing the contact area between water and concrete, preventing the cement from hydrating too quickly, reducing the concentrated release of cement hydration heat, and reducing concrete cracking; and octadecanoic acid can complex metal ions such as calcium, magnesium, and aluminum and has a lubricating effect, which can improve the ball milling efficiency, form a capsule structure but break in an alkaline environment, so that the modified expansive agent can effectively protect the metal oxide from absorbing moisture in the air when not in use, thereby improving the shelf life of the modified expansive agent as well as the expansibility and retarding effect, and to a certain extent, controlling the expansion rate; 3. In the present application, when preparing the modified anti-cracking thickener, the glass fiber powder, latex powder, xanthan gum and reinforcing agent cooperate with each other to form a network structure, restrain the volume expansion or contraction of the concrete, reduce the cracking and contraction of the concrete, and enhance the cohesion, flexural resistance, density and fluidity of the concrete, which is conducive to the effective combination with the tunnel slag regeneration machine sand and tunnel slag regeneration gravel and steel bars, thereby reducing the probability of the tunnel secondary lining being depleted and cracked;

[0048] 4. In this application, the preparation process of the self-leveling secondary lining concrete of tunnel slag recycled aggregate is simple, practical and easy to construct. DETAILED DESCRIPTION

[0049] The following will be combined with the specific implementation methods in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention:

[0050] In this application, the self-leveling secondary lining concrete with recycled aggregate from tunnel slag uses the following raw materials:

[0051] Cement: Model P•O42.5, specific surface area 300-350m 2 / kg;

[0052] Fly ash: Class F secondary fly ash;

[0053] Slag regeneration machine-made sand: machine-made sand prepared from tunnel slag, with a fineness modulus of 2.7-3.2, a stone powder content of 8-12%, and a crushing value of 20-30%;

[0054] Tunnel slag recycled crushed stone: coarse aggregate prepared from tunnel slag, with a particle size of 5.0-20.0mm, a stone powder content of 0.5-2%, and a crushing value of 10-15%;

[0055] Water reducer: TW-HJS-1 slow-setting polycarboxylic acid high-performance water reducer;

[0056] Modified expansion agent: prepared from magnesite, dolomite, bauxite, limestone, octadecanoic acid, magnesium fluorosilicate and sodium gluconate;

[0057] Modified anti-cracking thickener: prepared from 400 mesh glass fiber powder, latex powder, modified hydroxypropyl cellulose ether, powdered polycarboxylate water reducer, xanthan gum and silica fume;

[0058] Water: tap water, surface water or groundwater that meets the mixing water requirements of TB / T3275-2018 "Railway Concrete".

[0059] Example 1, Preparation of self-leveling secondary lining concrete with recycled aggregate from tunnel slag

[0060] Preparation of modified expansion agent

[0061] S1: 40 parts of magnesite, 20 parts of dolomite, 15 parts of bauxite, and 15 parts of limestone were placed in a muffle furnace, calcined at 800°C for 10 hours, and cooled to room temperature to obtain a mixture for later use;

[0062] S2: Add 10 parts of octadecanoic acid, 5 parts of magnesium fluorosilicate, and 2 parts of sodium gluconate to the fired mixture, place in a ball mill and mill for 3 hours, and pass through a 400-mesh sieve to obtain a modified expansion agent.

[0063] Preparation of modified anti-cracking thickener

[0064] Stir and mix 40 parts of 400-mesh glass fiber powder, 5 parts of latex powder, 2 parts of modified hydroxypropyl cellulose ether, 5 parts of powdered polycarboxylate water-reducing agent, 2 parts of xanthan gum, and 46 parts of silica fume until evenly distributed.

[0065] Preparation of self-leveling secondary lining concrete with recycled aggregate from tunnel slag

[0066] Step 1: Add 4 parts by weight of slow-setting polycarboxylic acid high-performance water reducer to 160 parts by weight of mixing water and set aside;

[0067] Step 2: First, add 1030 parts by weight of slag regenerated gravel and 810 parts by weight of slag regenerated machine-made sand into a forced mixer, and then add 300 parts by weight of cement, 100 parts by weight of fly ash, 4 parts by weight of modified expansion agent, and 4 parts by weight of modified anti-cracking thickener, and stir and mix them uniformly to obtain a mixture;

[0068] Step 3: Add the mixing water containing the water reducer in step 1 to the mixture in step 2 in a forced mixer, and stir for 150s-180s to obtain a self-leveling secondary lining concrete of tunnel slag recycled aggregate.

[0069] Example 2, Preparation of Self-Leveling Second Lining Concrete with Tunnel Slag Recycled Aggregate

[0070] In this embodiment, the modified expansion agent and modified anti-cracking thickener used are the same as those in Example 1.

[0071] Preparation of self-leveling secondary lining concrete with recycled aggregate from tunnel slag

[0072] Step 1: Add 4 parts by weight of slow-setting polycarboxylic acid high-performance water reducer to 160 parts by weight of mixing water and set aside;

[0073] Step 2: First, add 1030 parts by weight of slag regenerated gravel and 810 parts by weight of slag regenerated machine-made sand into a forced mixer, then add 300 parts by weight of cement, 100 parts by weight of fly ash, 6 parts by weight of modified expansion agent, and 4 parts by weight of modified anti-cracking thickener, and stir and mix them evenly to obtain a mixture;

[0074] Step 3: Add the mixing water containing the water reducer in step 1 to the mixture in step 2 in a forced mixer, and stir for 150s-180s to obtain a self-leveling secondary lining concrete of tunnel slag recycled aggregate.

[0075] Example 3, Preparation of self-leveling secondary lining concrete with recycled aggregate from tunnel slag

[0076] In this embodiment, the modified expansion agent and modified anti-cracking thickener used are the same as those in Example 1.

[0077] Preparation of self-leveling secondary lining concrete with recycled aggregate from tunnel slag

[0078] Step 1: Add 4 parts by weight of slow-setting polycarboxylic acid high-performance water reducer to 160 parts by weight of mixing water and set aside;

[0079] Step 2: First, add 1030 parts by weight of slag regenerated gravel and 810 parts by weight of slag regenerated machine-made sand into a forced mixer, and then add 300 parts by weight of cement, 100 parts by weight of fly ash, 8 parts by weight of modified expansion agent, and 4 parts by weight of modified anti-cracking thickener, and stir and mix them evenly to obtain a mixture;

[0080] Step 3: Add the mixing water containing the water reducer in step 1 to the mixture in step 2 in a forced mixer, and stir for 150s-180s to obtain a self-leveling secondary lining concrete of tunnel slag recycled aggregate.

[0081] Example 4, Preparation of self-leveling secondary lining concrete with recycled aggregate from tunnel slag

[0082] In this embodiment, the modified expansion agent and modified anti-cracking thickener used are the same as those in Example 1.

[0083] Preparation of self-leveling secondary lining concrete with recycled aggregate from tunnel slag

[0084] Step 1: Add 4 parts by weight of slow-setting polycarboxylic acid high-performance water reducer to 160 parts by weight of mixing water and set aside;

[0085] Step 2: First, add 1030 parts by weight of slag regenerated gravel and 810 parts by weight of slag regenerated machine-made sand into a forced mixer, and then add 300 parts by weight of cement, 100 parts by weight of fly ash, 6 parts by weight of modified expansion agent, and 6 parts by weight of modified anti-cracking thickener, and stir and mix them evenly to obtain a mixture;

[0086] Step 3: Add the mixing water containing the water reducer in step 1 to the mixture in step 2 in a forced mixer, and stir for 150s-180s to obtain a self-leveling secondary lining concrete of tunnel slag recycled aggregate.

[0087] Example 5, Preparation of self-leveling secondary lining concrete with recycled aggregate from tunnel slag

[0088] In this embodiment, the modified expansion agent and modified anti-cracking thickener used are the same as those in Example 1.

[0089] Preparation of self-leveling secondary lining concrete with recycled aggregate from tunnel slag

[0090] Step 1: Add 4 parts by weight of slow-setting polycarboxylic acid high-performance water reducer to 160 parts by weight of mixing water and set aside;

[0091] Step 2: First, add 1030 parts by weight of slag regenerated gravel and 810 parts by weight of slag regenerated machine-made sand into a forced mixer, then add 300 parts by weight of cement, 100 parts by weight of fly ash, 6 parts by weight of modified expansion agent, and 8 parts by weight of modified anti-cracking thickener, and stir and mix them evenly to obtain a mixture;

[0092] Step 3: Add the mixing water containing the water reducer in step 1 to the mixture in step 2 in a forced mixer, and stir for 150s-180s to obtain a self-leveling secondary lining concrete of tunnel slag recycled aggregate.

[0093] Example 6, Preparation of self-leveling secondary lining concrete with recycled aggregate from tunnel slag

[0094] In this embodiment, the modified expansion agent and modified anti-cracking thickener used are the same as those in Example 1.

[0095] Preparation of self-leveling secondary lining concrete with recycled aggregate from tunnel slag

[0096] Step 1: Add 5 parts by weight of slow-setting polycarboxylic acid high-performance water reducer to 160 parts by weight of mixing water and set aside;

[0097] Step 2: First, add 1030 parts by weight of slag regenerated gravel and 810 parts by weight of slag regenerated machine-made sand into a forced mixer, and then add 300 parts by weight of cement, 100 parts by weight of fly ash, 6 parts by weight of modified expansion agent, and 6 parts by weight of modified anti-cracking thickener, and stir and mix them evenly to obtain a mixture;

[0098] Step 3: Add the mixing water containing the water reducer in step 1 to the mixture in step 2 in a forced mixer, and stir for 150s-180s to obtain a self-leveling secondary lining concrete of tunnel slag recycled aggregate.

[0099] Example 7, Preparation of Self-Leveling Second Lining Concrete with Tunnel Slag Recycled Aggregate

[0100] In this embodiment, the modified expansion agent and modified anti-cracking thickener used are the same as those in Example 1.

[0101] Preparation of self-leveling secondary lining concrete with recycled aggregate from tunnel slag

[0102] Step 1: Add 6 parts by weight of slow-setting polycarboxylic acid high-performance water reducer to 160 parts by weight of mixing water and set aside;

[0103] Step 2: First, add 1030 parts by weight of slag regenerated gravel and 810 parts by weight of slag regenerated machine-made sand into a forced mixer, and then add 300 parts by weight of cement, 100 parts by weight of fly ash, 6 parts by weight of modified expansion agent, and 6 parts by weight of modified anti-cracking thickener, and stir and mix them evenly to obtain a mixture;

[0104] Step 3: Add the mixing water containing the water reducer in step 1 to the mixture in step 2 in a forced mixer, and stir for 150s-180s to obtain a self-leveling secondary lining concrete of tunnel slag recycled aggregate.

[0105] Example 8, Preparation of Self-Leveling Second Lining Concrete with Tunnel Slag Recycled Aggregate

[0106] In this embodiment, the modified expansion agent and modified anti-cracking thickener used are the same as those in Example 1.

[0107] Preparation of self-leveling secondary lining concrete with recycled aggregate from tunnel slag

[0108] Step 1: Add 6 parts by weight of slow-setting polycarboxylic acid high-performance water reducer to 152 parts by weight of mixing water and set aside;

[0109] Step 2: First, add 1028 parts by weight of slag regenerated gravel and 840 parts by weight of slag regenerated machine-made sand into a forced mixer, and then add 285 parts by weight of cement, 95 parts by weight of fly ash, 6 parts by weight of a modified expansion agent, and 6 parts by weight of a modified anti-cracking thickener, and stir and mix uniformly to obtain a mixture;

[0110] Step 3: Add the mixing water containing the water reducer in step 1 to the mixture in step 2 in a forced mixer, and stir for 150s-180s to obtain a self-leveling secondary lining concrete of tunnel slag recycled aggregate.

[0111] Example 9, Preparation of Self-Leveling Second Lining Concrete with Tunnel Slag Recycled Aggregate

[0112] In this embodiment, the modified expansion agent and modified anti-cracking thickener used are the same as those in Example 1.

[0113] Preparation of self-leveling secondary lining concrete with recycled aggregate from tunnel slag

[0114] Step 1: Add 6 parts by weight of slow-setting polycarboxylic acid high-performance water reducer to 168 parts by weight of mixing water and set aside;

[0115] Step 2: First, add 1032 parts by weight of slag regenerated gravel and 780 parts by weight of slag regenerated machine-made sand into a forced mixer, and then add 315 parts by weight of cement, 105 parts by weight of fly ash, 6 parts by weight of a modified expansion agent, and 6 parts by weight of a modified anti-cracking thickener, and stir and mix them uniformly to obtain a mixture;

[0116] Step 3: Add the mixing water containing the water reducer in step 1 to the mixture in step 2 in a forced mixer, and stir for 150s-180s to obtain a self-leveling secondary lining concrete of tunnel slag recycled aggregate.

[0117] Example 10 (Comparative Example 1), Preparation of Self-Leveling Second Lining Concrete with Tunnel Slag Recycled Aggregate

[0118] In this embodiment, the modified anti-cracking thickener and modified expansion agent are not used.

[0119] Preparation of self-leveling secondary lining concrete with recycled aggregate from tunnel slag

[0120] Step 1: Add 4 parts by weight of slow-setting polycarboxylic acid high-performance water reducer to 160 parts by weight of mixing water and set aside;

[0121] Step 2: First, add 1030 parts by weight of slag regenerated gravel and 810 parts by weight of slag regenerated machine-made sand into a forced mixer, then add 300 parts by weight of cement and 100 parts by weight of fly ash, and stir and mix them evenly to obtain a mixture;

[0122] Step 3: Add the mixing water containing the water reducer in step 1 to the mixture in step 2 in a forced mixer, and stir for 150s-180s to obtain a self-leveling secondary lining concrete of tunnel slag recycled aggregate.

[0123] Example 11 (Comparative Example 2), Preparation of Self-Leveling Second Lining Concrete with Tunnel Slag Recycled Aggregate

[0124] In this embodiment, the modified expansion agent used is the same as that in Example 1, and the modified anti-cracking thickener is not used.

[0125] Preparation of self-leveling secondary lining concrete with recycled aggregate from tunnel slag

[0126] Step 1: Add 4 parts by weight of slow-setting polycarboxylic acid high-performance water reducer to 160 parts by weight of mixing water and set aside;

[0127] Step 2: First, add 1030 parts by weight of slag regenerated gravel and 810 parts by weight of slag regenerated machine-made sand into a forced mixer, then add 300 parts by weight of cement, 100 parts by weight of fly ash, and 4 parts by weight of a modified expansion agent, and stir and mix them uniformly to obtain a mixture;

[0128] Step 3: Add the mixing water containing the water reducer in step 1 to the mixture in step 2 in a forced mixer, and stir for 150s-180s to obtain a self-leveling secondary lining concrete of tunnel slag recycled aggregate.

[0129] Example 12 (Comparative Example 3), Preparation of Self-Leveling Second Lining Concrete with Tunnel Slag Recycled Aggregate

[0130] In this embodiment, the modified anti-cracking thickener used is the same as that in Example 1, and no modified expansion agent is used.

[0131] Preparation of self-leveling secondary lining concrete with recycled aggregate from tunnel slag

[0132] Step 1: Add 4 parts by weight of slow-setting polycarboxylic acid high-performance water reducer to 160 parts by weight of mixing water and set aside;

[0133] Step 2: First, add 1030 parts by weight of slag regenerated gravel and 810 parts by weight of slag regenerated machine-made sand into a forced mixer, then add 300 parts by weight of cement, 100 parts by weight of fly ash, and 4 parts by weight of a modified anti-cracking thickener, and stir and mix uniformly to obtain a mixture;

[0134] Step 3: Add the mixing water containing the water reducer in step 1 to the mixture in step 2 in a forced mixer, and stir for 150s-180s to obtain a self-leveling secondary lining concrete of tunnel slag recycled aggregate.

[0135] In the above examples 1-12, the weight parts of the raw materials are shown in Table 1:

[0136] Table 1 Weight parts of raw materials in Examples 1-12

[0137] raw material Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 cement 300 300 300 300 300 300 300 300 300 300 285 315 fly ash 100 100 100 100 100 100 100 100 100 100 95 105 Slag regeneration machine-made sand 810 810 810 810 810 810 810 810 810 810 840 780 Slag recycled gravel 1030 1030 1030 1030 1030 1030 1030 1030 1030 1030 1028 1032 Mixing water 160 160 160 160 160 160 160 160 160 160 152 168 water reducer 4 4 4 4 4 4 4 4 5 6 6 6 Modified expansion agent / 4 / 4 6 8 6 6 6 6 6 6 Modified anti-cracking thickener / / 4 4 4 4 6 8 6 6 6 6

[0138] The self-leveling secondary lining concrete made of recycled aggregate from tunnel slag prepared in Examples 1-12 was tested for performance indicators including expansion time, workability, setting time, 28d compressive strength, 28d compressive strength extreme difference, 56d electrical flux, and 180d shrinkage.

[0139] The expansion time is tested with reference to the expansion time test in GB / T50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures";

[0140] Workability is judged based on the bleeding and aggregate exposure of the concrete mixture and is divided into three grades: good, fair, and poor.

[0141] The 28d compressive strength and the range of 28d compressive strength are tested with reference to the compressive strength test in GB / T50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete". The range of 28d compressive strength is the difference between the maximum and minimum compressive strengths in a group of three specimens.

[0142] The electric flux is tested according to the electric flux method for the chloride ion penetration test in GB / T50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete";

[0143] The 180d shrinkage rate is tested according to the shrinkage test contact method in GB / T50082-2009 "Standard for Test Methods of Long-term Properties and Durability of Ordinary Concrete".

[0144] The test results are shown in Table 2:

[0145] Table 2 Test results of Examples 1-12

[0146] Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Expansion time / s 6.69 6.85 7.56 5.26 5.53 5.69 4.35 5.12 3.78 3.25 4.13 3.20 Workability Poor Poor Poor generally generally generally better better better better generally better Initial setting time / min 150 185 155 200 240 265 245 240 245 250 245 255 Final setting time / min 235 270 235 300 320 340 320 325 325 330 320 330 28d compressive strength / MPa 41.6 42.6 43.2 45.7 45.5 45.9 46.7 47.1 46.8 46.7 45.8 47.6 28d compressive strength extreme difference / MPa 6.8 6.1 4.8 4.2 3.8 3.9 2.8 2.6 2.6 2.7 3.0 2.7 56d electric flux / C 1680 1520 1450 1300 1280 1310 1054 980 1002 960 1025 960 <![CDATA[180d shrinkage rate / 1.0×10 -6 > 4230 1036 3850 925 185 92 98 90 95 93 100 90

[0147] From the data in Table 2, it can be seen that the modified expansive agent can prolong the setting time of concrete, slow down the cement hydration rate, delay the concentrated release of hydration heat, and compensate for concrete shrinkage; the modified anti-cracking thickener can shorten the expansion time, improve the fluidity, workability, and homogeneity of concrete, and improve the discreteness of concrete strength. The effects of the modified expansive agent and the modified anti-cracking thickener are significant.

[0148] The concrete's expansion time is shortened, workability is improved, setting time is extended, 28-day compressive strength is increased, the extreme difference in 28-day compressive strength is reduced, 56-day electrical flux is reduced, and 180-day shrinkage is significantly reduced. This slows the cement hydration rate, delays the concentrated release of hydration heat, compensates for concrete shrinkage, and improves concrete fluidity, aggregate flowability, density, and homogeneity. This addresses the problems of tunnel slag recycled aggregates with high powder content and crushing values, as well as the narrow working space and dense steel bars within the formwork during tunnel secondary lining construction, which can lead to poor appearance quality, high strength dispersion, and later-stage voiding and cracking. The synergistic effect of the modified expansive agent and modified anti-cracking thickener significantly improves concrete's expansion time, workability, setting time, 28-day compressive strength, extreme difference in 28-day compressive strength, 56-day electrical flux, and 180-day shrinkage.

[0149] When modified expansive agent or modified anti-cracking thickener is added alone, although the expansion time, workability, setting time, 28d compressive strength, 28d compressive strength extreme difference, 56d electric flux and 180d shrinkage rate of concrete are improved compared with when no addition is made, the effect is not as good as when modified expansive agent and modified anti-cracking thickener are added at the same time, indicating that modified expansive agent and modified anti-cracking thickener can play a synergistic role.

[0150] The above describes in detail the self-leveling secondary lining concrete with recycled tunnel slag aggregate and its preparation method provided by the present invention. The description of the specific embodiments is intended only to facilitate understanding of the present invention's method and its core concept. It should be noted that those skilled in the art will be able to make various improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the claims.

[0151] It should be noted that if specific experimental steps or conditions are not specified in the examples, the procedures or conditions described in the literature in this field can be followed. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0152] The above examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

Claims

1. A self-leveling secondary lining concrete made of recycled aggregate from tunnel slag, characterized in that: It includes the following raw materials in parts by weight: 280-330 parts of cement, 80-120 parts of fly ash, 740-880 parts of slag recycled sand, 900-1100 parts of slag recycled gravel, 140-190 parts of water, 4-9 parts of water reducer, 4-15 parts of modified expansive agent, and 4-15 parts of modified anti-cracking thickener.

2. The self-leveling secondary lining concrete of tunnel slag recycled aggregate according to claim 1, characterized in that: The modified expansion agent is prepared by mixing inorganic materials and organic materials.

3. The self-leveling secondary lining concrete of tunnel slag recycled aggregate according to claim 2, characterized in that: The inorganic material is one or more combinations of magnesite, dolomite, bauxite, limestone, slag powder, and silica fume.

4. The self-leveling secondary lining concrete of tunnel slag recycled aggregate according to claim 2, characterized in that: The organic material is one or more combinations of octadecanoic acid, magnesium fluorosilicate, sodium gluconate, oleic acid, palmitic acid, sodium silicate, sodium fluorosilicate, citric acid, tartaric acid, and lignin sulfonate.

5. The self-leveling secondary lining concrete of tunnel slag recycled aggregate according to claim 2, 3 or 4, characterized in that: Preparation of modified expansion agent, The following steps are involved: S1: placing the inorganic material in a muffle furnace, calcining at 800-1000°C for 8-10 hours, cooling to room temperature to obtain a mixture, and setting aside; S2: Add organic materials to the fired mixture and place it in a ball mill for 3-5 hours. After ball milling, sieve it to obtain the modified expansion agent.

6. The self-leveling secondary lining concrete of tunnel slag recycled aggregate according to claim 1, characterized in that: The modified anti-cracking thickener comprises the following raw materials in parts by weight: 30-50 parts of glass fiber powder, 4-6 parts of latex powder, 1-3 parts of xanthan gum and 40-70 parts of reinforcing agent.

7. The self-leveling secondary lining concrete of tunnel slag recycled aggregate according to claim 6, characterized in that: The enhancer includes modified hydroxypropyl cellulose ether and powdered polycarboxylate water reducer.

8. The self-leveling secondary lining concrete of tunnel slag recycled aggregate according to claim 7, characterized in that: The reinforcing agent further comprises at least one of silica fume powder, slag powder and metakaolin.

9. The self-leveling secondary lining concrete of tunnel slag recycled aggregate according to claim 1, characterized in that: The fineness modulus of the slag regeneration machine-made sand is 2.7-3.2, the stone powder content is 8-12%, and the crushing value is 20-30%; The particle size of the slag recycled gravel is 5.0-20.0 mm, the stone powder content is 0.5-2%, and the crushing value is 10-15%.

10. A method for preparing self-leveling secondary lining concrete with recycled aggregate from tunnel slag according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1: Add water reducer to mixing water and set aside; Step 2: first add the slag regeneration crushed stone and slag regeneration machine-made sand into a forced mixer, then add cement, fly ash, modified expansion agent, and modified anti-cracking thickener, stir and mix evenly to obtain a mixture; Step 3: Add the mixing water containing the water reducer in step 1 to the mixture in step 2 in a forced mixer, and stir for 150-180 seconds to obtain a self-leveling secondary lining concrete with tunnel slag recycled aggregate.