A grout-aggregate polymer concrete for tunnel secondary lining and its construction method

Abstract

This invention provides a grout-aggregate polymeric concrete for tunnel secondary lining and its construction method, relating to the technical field of tunnel concrete materials and construction methods. In the grout-aggregate polymeric concrete of this invention, the aggregate is a single or two types of coarse aggregate densely packed to form a larger skeleton proportion, which can exert a stronger inhibitory effect on the hardening shrinkage of the grout, ensuring structural strength while significantly reducing the shrinkage rate. By screening spherical industrial sand with activity and water-retaining curing functions as fine aggregate for use in the grout, the fluidity, strength, and shrinkage resistance are improved. Further incorporation of trace amounts of nano-silica does not affect fluidity and can synergistically improve compressive strength, flexural strength, and impermeability. Moreover, pre-filling the aggregate and then injecting the grout to fill and encapsulate the aggregate can reduce the energy consumption of traditional concrete aggregate reciprocating transportation and overall raw material mixing. The tunnel secondary lining pouring method of this invention is simple, efficient, low-cost, low-pollution, and produces good molding quality.

Description

Technical Field

[0001] This invention relates to the technical field of building materials and construction methods, particularly to the technical field of concrete materials and construction methods for tunnels, specifically to a grout-aggregate polymer concrete for tunnel secondary lining and its construction method. Background Technology

[0002] With the rapid development of infrastructure construction in my country, the number of tunnel projects is constantly increasing. As an important component of tunnels, the quality of tunnel secondary lining concrete structure directly affects the safety and durability of the tunnel. However, there are some problems with existing tunnel secondary lining concrete materials and construction methods that urgently need to be solved.

[0003] Existing tunnel lining concrete materials mainly consist of silicate cement, fly ash, coarse and fine aggregates, water-reducing agents, and water, mixed together. While these materials can meet the construction requirements of tunnel lining structures to a certain extent, they still fall short in controlling shrinkage. During the hardening process, concrete exhibits significant shrinkage due to shrinkage caused by cement hydration, drying shrinkage caused by water evaporation, and shrinkage caused by temperature changes. High shrinkage can lead to cracks in the concrete structure, affecting its load-bearing and waterproofing performance. Therefore, existing tunnel lining concrete materials typically require the addition of large amounts of admixtures (such as high-efficiency water-reducing and anti-shrinkage agents, and expanding agents) to improve their performance. However, the effects are limited, and the costs are high, increasing the overall cost of the concrete. In addition, existing tunnel secondary lining construction methods mostly adopt traditional concrete mixing and pouring methods, which involve the mining and crushing of coarse aggregates and their transportation to the mixing plant. All raw materials are mixed as a whole using high-power equipment and then transported to the site for pouring. This involves energy consumption from the back-and-forth transportation of coarse aggregates, investment in the construction of high-power mixing plants, and energy consumption from mixing in the mixing plant. This not only results in high energy consumption and large carbon emissions, but also generates noise and dust pollution. Furthermore, there is a risk of segregation between coarse aggregates and cementitious materials during the pouring process of the integrally mixed concrete. It is also necessary to strictly control the concrete pouring height and the height difference between the two sides of the concrete. Vibration must be carried out while pouring. The construction process is complex, requires a large number of personnel, involves many control links, and is difficult to manage, which can easily lead to quality defects.

[0004] Therefore, developing a new type of tunnel secondary lining concrete material and its pouring method is of great significance for improving the quality of tunnel secondary lining structures, reducing construction costs, and improving construction efficiency. Summary of the Invention

[0005] The purpose of this invention is to overcome the technical defects of existing concrete materials used for tunnel lining, such as large shrinkage rate, low construction efficiency, high cost and large carbon emissions, and to propose a paste-aggregate polymer concrete for tunnel lining and a method for pouring tunnel lining.

[0006] To achieve the above-mentioned objective, the present invention provides a paste-aggregate polymer concrete for tunnel secondary lining, comprising the following raw materials in parts by weight: 58-60 parts of aggregate and 40-42 parts of paste;

[0007] The aggregate includes coarse aggregates of two particle size ranges: 9.5-20mm and 16-31.5mm; one or two of the coarse aggregates of the two particle size ranges are selected and mixed in a certain proportion to form aggregates; the ratio of the compressive strength of the parent rock of the coarse aggregates to the design compressive strength of the tunnel secondary lining is not less than 1.5;

[0008] The grout is a high-fluidity grout containing fine aggregates. Each cubic meter of the high-fluidity grout contains the following raw materials by weight: 500-600 kg of cement, 300-400 kg of fly ash, 800-1000 kg of industrial sand, 350-400 kg of water, 6.4-15 kg of water-reducing agent, and 0.8-2 kg of nano-silica.

[0009] The total adhesive content of the high-fluidity grout is 800-1000 kg, and the water-to-binder ratio is 0.35-0.5.

[0010] The industrial sand has a particle size of 0.075-2.36 mm, a fineness modulus of not more than 2.0, a porosity of 20-40%, a water absorption rate of 0.8-5%, a silica content of 35-50%, and an activity index of not less than 65% after 28 days of grinding.

[0011] The paste-aggregate polymer concrete is formed as follows: the aggregate and the paste are prepared separately, and during construction, the coarse aggregate is first piled up and then the paste is poured in to fill the gaps in the coarse aggregate and solidify to form paste-aggregate polymer concrete.

[0012] This invention provides a paste-aggregate polymeric concrete for tunnel secondary lining, which is composed of aggregate and high-fluidity grout (hereinafter referred to as "grout"). The aggregate content formed by compacting one or two types of coarse aggregate exceeds 58%. Compared with conventional concrete, which contains no more than 50% aggregate, the skeleton in the paste-aggregate polymeric concrete can play a stronger role in inhibiting the hardening shrinkage of the grout. This not only significantly reduces the material shrinkage rate, but the hard aggregate also provides sufficient strength and elastic modulus for the concrete. By selecting spherical industrial sand with active and water-retaining curing properties as fine aggregate and incorporating it into cementitious materials to form a slurry, the consistency of the cementitious materials is adjusted to ensure that the industrial sand is uniformly suspended in the slurry, preventing segregation. The spherical shape of the industrial sand provides a ball-bearing effect, giving the slurry high flowability, all of which are important indicators for the slurry to fully fill aggregate voids. By controlling particle size, fineness modulus, and silica content, the proportion of reactive fine aggregates in the industrial sand is increased. Smaller particle size and larger specific surface area of ​​the industrial sand result in stronger adsorption capacity and more thorough contact with cement and other cementitious materials, leading to more intense chemical reactions. This further promotes the reaction with calcium hydroxide in cement hydration, generating calcium silicate gel, which enhances the strength and durability of the slurry. The irregular pores on the surface of the industrial sand particles provide water retention, offering internal curing moisture for later slurry hardening and playing a role in anti-shrinkage. Furthermore, the addition of trace amounts of nano-silica to the slurry fills the pores between the aggregate and the slurry, reduces the porosity of the interfacial transition zone, optimizes the performance of the interfacial transition zone, and makes the structure denser. This not only does not affect the fluidity, but also synergistically improves the compressive strength, flexural strength, and impermeability.

[0013] The cement is preferably ordinary Portland cement 42.5.

[0014] Preferably, the aggregate can be selected from two coarse aggregates with different particle size ranges, or it can be mixed at a mass ratio of 0.33-3:1; that is, the weight mixing ratio of coarse aggregate with a particle size range of 9.5-20mm and coarse aggregate with a particle size range of 16-31.5mm is 0.33-3:1.

[0015] The optimized aggregate mass ratio results in a larger aggregate skeleton with a smaller porosity, less slurry, and stronger skeleton constraint, leading to a smaller shrinkage rate in the slurry-aggregate polymer concrete, which is more suitable for tunnel secondary lining structures.

[0016] The industrial sand refers to waste materials left over from mining or industrial processing. After processing and screening, it can be used to prepare high-fluidity grouting material, which has the advantages of low cost and wide availability.

[0017] Preferably, the fly ash is secondary fly ash; the preferred fly ash can better improve the durability and crack resistance of concrete.

[0018] Preferably, the particle size of the nano-silica is 50-200 nm; the larger the particle size, the less conducive it is to filling the pores, and the smaller the particle size, the worse the dispersibility.

[0019] Preferably, the water-reducing agent has a water reduction rate of not less than 25%; more preferably, the water-reducing agent is a comb-shaped polycarboxylate water-reducing agent, such as polyester-type polycarboxylate water-reducing agent or polyether-type polycarboxylate water-reducing agent.

[0020] Preferably, each cubic meter of the high-fluidity grout further includes 0.08-0.3 kg of retarder. The addition of retarder can prolong the setting time of concrete, reduce the hydration heat release rate, and improve the workability of the grout.

[0021] More preferably, the retarder is a carbohydrate retarder, such as glucose, fructose, sucrose, starch, or cellulose.

[0022] Preferably, each cubic meter of the high-fluidity grout also includes 0.08-0.25 kg of defoamer; the addition of defoamer can reduce air bubbles in the cementitious grout, reduce the number of pores on the surface of the cementitious concrete after curing, and improve the concrete strength.

[0023] More preferably, the defoamer is a polyether defoamer, such as glycerol polyether defoamer (GP defoamer), glycerol polyoxypropylene ethylene ether defoamer (GPE defoamer), silicone-modified polyether defoamer (GPES defoamer), polypropylene glycol defoamer (PPG type defoamer), and ethylene oxide-propylene oxide block copolymer defoamer (EO / PO copolymer defoamer).

[0024] Preferably, each cubic meter of the slurry also includes 0.5-0.9 kg of organic short fiber material; by adding organic short fiber material, the toughness and crack resistance of concrete can be increased, which is beneficial to improving the mechanical properties of concrete.

[0025] Preferably, the organic short fiber material has a diameter of 20-25 μm, a length of 3-6 mm, and a tensile strength of not less than 350 MPa; the preferred fiber material of the present invention has better dispersibility and a better effect on improving the mechanical properties of paste-aggregate polymer concrete.

[0026] Preferably, the organic short fiber material is polypropylene fiber.

[0027] The industrial sand in the high-fluidity grout of this invention has a spherical shape and a ball-bearing effect due to the grinding action on the industrial production line, compared with ordinary sand. However, it has a larger particle size than silica fume, microspheres, etc., thus requiring less water. At the same time, the high-fluidity grout is not mixed with aggregates, which avoids water being carried away by aggregates and greatly improves the fluidity of the grout.

[0028] Preferably, the initial flow cone time of the high-fluidity grout is no more than 18s, and the 3-hour flow cone time is no more than 35s; the initial truncated cone flowability is no less than 360mm, and the 3-hour truncated cone flowability is no less than 320mm; and the bleeding rate is no more than 1% under a pressure of 0.36MPa.

[0029] Preferably, the 28-day shrinkage-expansion rate of the high-fluidity grouting material satisfies the formula: δ △ +(δ v +δ c )≤r; where r is the design value of the 28-day shrinkage expansion rate of the tunnel secondary lining; δ △ The design value for the expansion rate of high-fluidity grouting material; δ v The design value for aggregate shrinkage; δ c This is the design value for the shrinkage rate of high-fluidity grouting material.

[0030] Preferably, the aggregate-polymer concrete is formed by filling the pores of the accumulated aggregate with a high-fluidity grout and then curing it. That is, the aggregate is first filled into the template and then cured by injecting high-fluidity grout. The preferred preparation method can avoid the costs of stone transportation and mixing energy consumption, and can significantly reduce the cost of concrete.

[0031] Furthermore, in order to achieve the above-mentioned objective, the present invention provides a construction method for the above-described grout-aggregate polymer concrete for tunnel secondary lining, specifically including the following steps:

[0032] Step 1: Assemble the integral formwork for the tunnel secondary lining, and pre-set grouting holes at the bottom of the arch feet on both sides of the tunnel secondary lining formwork, and pre-set venting holes at the top of the formwork arch; the longitudinal spacing of the grouting holes is 3-6m, and the longitudinal spacing of the venting holes is 0.5-1m;

[0033] Step 2: Fill the tunnel secondary lining template with aggregate to form a skeleton; the aggregate is filled by its own weight and tightly packed together.

[0034] Step 3: After the aggregate filling is completed, open the grouting holes and 3-5 adjacent venting holes on the same cross section, and keep the remaining grouting holes and venting holes closed. Inject high-fluidity grouting material through the preset grouting holes.

[0035] Step 4: Inject high-fluidity grout from bottom to top under pressure, with the maximum pump pressure not exceeding 2MPa, until uniform grout continuously overflows from the vent hole, at which point the injection is complete;

[0036] Step 5: After the high-fluidity grout is injected, seal the grouting holes and vent holes;

[0037] Step 6: Repeat steps 2-5 until the grout-aggregate concrete filling for the entire designed tunnel length is completed.

[0038] Step 7: After the strength of the secondary tunnel lining grout-aggregate polymer concrete meets the requirements, remove the formwork. After the formwork is removed, the grout-aggregate polymer concrete is moisturized and cured to obtain the secondary tunnel lining grout-aggregate polymer concrete structure.

[0039] This invention discloses a method for pouring concrete for tunnel secondary lining. The method involves pre-filling aggregates and then injecting slurry to fill and encapsulate the aggregates, forming a slurry-aggregate polymer concrete for the tunnel secondary lining. The aggregates are sourced and used locally, reducing the energy consumption associated with the reciprocating transport of concrete aggregates. The slurry can be prepared using a mobile slurry mixer with ordinary power, allowing for local production and use, saving investment costs associated with large, fixed mixing plants and reducing the energy consumption of overall raw material mixing. It also avoids the risk of premature setting of the slurry during long-distance transport. This tunnel secondary lining pouring method offers advantages such as rapid slurry flow, no need for vibration, one-time completion of full-section construction, simple process, high efficiency, low cost, and low pollution. Furthermore, the slurry penetrates all pores, fully filling the gaps between the aggregates and the formwork, forming a dense and smooth surface, resulting in better appearance quality of the tunnel secondary lining. This invention not only provides a concrete material that meets the requirements, but also changes the existing concrete production mode, reduces carbon emissions, improves molding quality, and saves costs. Furthermore, it further utilizes solid waste materials such as industrial sand, turning waste into treasure and making a huge contribution to environmental protection. It can be applied on a large scale to tunnel secondary lining structures.

[0040] More preferably, in step 1, the diameter of the grouting hole is 2-5 cm; the preferred grouting hole diameter is beneficial for the rapid injection of high-flow grout.

[0041] Preferably, the diameter of the vent hole is 5-10mm; the preferred vent hole diameter is beneficial to ensure that the gas inside the template is discharged during the high-fluidity grouting process, while ensuring that the top of the tunnel secondary lining is fully grouted.

[0042] Further preferably, in step 2, the porosity after aggregate stacking is approximately 40-45%.

[0043] In step 3, preferably, the injection pressure is no greater than 2 MPa; this places lower requirements on the injection equipment and helps reduce equipment costs.

[0044] In a further preferred embodiment, in step 4, if grout overflows from the vent hole, it indicates that the grouting is complete.

[0045] In step 7, the curing method is as follows: the humidity of the concrete surface is controlled above 90%; the temperature difference between the internal and surface of the concrete does not exceed 20℃, and the temperature difference between the concrete surface and the ambient temperature does not exceed 20℃; the curing time is not less than 14 days. This is beneficial to the hydration of the paste-aggregate polymer concrete, ensuring sufficient hydration of the concrete interior and exterior, thus reducing concrete shrinkage and ensuring the quality of the surface molding.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] 1. The paste-aggregate polymer concrete of the present invention uses one or two types of coarse aggregates to fill and compact the aggregates, forming a larger skeleton proportion. This can exert a stronger inhibitory effect on the hardening shrinkage of the paste, ensuring structural strength while significantly reducing the shrinkage rate and reducing the risk of shrinkage cracking in the tunnel secondary lining.

[0048] 2. The grout-aggregate polymer concrete used in the secondary lining of tunnels of this invention uses industrial sand with spherical shape, activity and water retention and curing function as fine aggregate for the preparation of grout, which improves fluidity, strength and shrinkage resistance. Furthermore, a trace amount of nano silica is added to synergistically improve compressive strength, flexural strength and impermeability. It not only consumes industrial solid waste materials, but also turns waste into treasure, making a great contribution to environmental protection.

[0049] 3. The tunnel secondary lining pouring method of the present invention, by first filling the tunnel secondary lining formwork with aggregate and then pouring high-fluidity grout, can reduce the energy consumption of traditional concrete aggregate reciprocating transportation and overall raw material mixing, and significantly reduce construction costs. This pouring method does not require vibration, saves procedures and labor, and improves pouring efficiency.

[0050] 4. The tunnel secondary lining casting method of the present invention utilizes the excellent fluidity of the high-fluidity grout to fully fill the gaps between the aggregate and the template, resulting in a dense and smooth tunnel secondary lining surface with better appearance quality.

[0051] 5. The tunnel secondary lining pouring method of the present invention reduces carbon emissions, improves molding quality, and saves costs, and is suitable for large-scale application in the pouring construction of tunnel secondary lining grout aggregate polymer concrete structures. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the initial grouting of the tunnel secondary lining after filling with aggregate in the technical solution of the present invention.

[0053] Figure 2 This is a schematic diagram showing the completion of tunnel secondary lining grouting in the technical solution of the present invention.

[0054] Figure 3 This is a schematic diagram of the tunnel secondary lining reaching its design strength and undergoing curing in the technical solution of this invention.

[0055] Figure 4 This is a schematic diagram of a simulation test in which aggregate and slurry are filled separately in the technical solution of the present invention.

[0056] Figure 5 This is an experimental schematic diagram of the filling of slurry into aggregate in the technical solution of the present invention.

[0057] Attached diagram labels: 1-aggregate; 2-grout; 3-grouting hole; 4-vent hole; 5-surrounding rock; 6-tunnel secondary lining. Detailed Implementation

[0058] To more clearly describe the inventive purpose, technical solution, and technical advantages of the specific embodiments of the present invention, the solutions in the specific embodiments will be described in detail below with reference to the accompanying drawings of the present invention.

[0059] The specific technical solutions involved in the following embodiments are merely for the purpose of clearly and completely describing the innovative technical solutions of the present invention. They are only a part of the specific implementation methods that the present invention can adopt, not all the embodiments, and should not be construed as limiting the innovative solutions of the present invention. Any solution that adopts the same inventive concept as the present invention should be included within the protection scope of the present invention.

[0060] In a specific embodiment of the present invention, the design compressive strength of the tunnel secondary lining is 30 MPa.

[0061] This embodiment discloses a construction method for grout-aggregate polymer concrete used in tunnel secondary lining, such as... Figures 1-3 The diagram shown is a schematic representation of the construction process of the paste-aggregate polymer concrete of the present invention.

[0062] Specifically, the following steps are included:

[0063] Step 1: Assemble the integral formwork for tunnel secondary lining 6, and pre-set grouting holes 3 at the bottom of the arch feet on both sides of the tunnel secondary lining 6 formwork, and pre-set venting holes 4 at the top of the formwork arch; the longitudinal spacing of the grouting holes 3 is 3-6m, and the longitudinal spacing of the venting holes 4 is 0.5-1m; wherein, the diameter of the grouting holes 3 is preferably 2-5cm; in this embodiment, the diameter of the grouting holes 3 is set to 5cm; the diameter of the venting holes 4 is preferably 5-10mm; in this embodiment, the diameter of the venting holes 4 is set to 10mm;

[0064] Step 2: Fill the tunnel secondary lining 6 template with aggregate to form a skeleton; the aggregate is filled by its own weight and tightly packed; after the aggregate is filled, the porosity is about 40-45%.

[0065] Step 3: After the aggregate filling is completed, open the grouting hole 3 and 3-5 adjacent venting holes 4 on the same cross section, and keep the rest closed. Inject high-flow grouting material through the preset grouting hole 3; preferably, the injection pressure is not greater than 2MPa; in this embodiment, it is set to 2MPa.

[0066] Step 4: Inject high-fluidity grout from bottom to top under pressure, with the maximum pump pressure not exceeding 2MPa, until uniform grout 2 continuously overflows from the vent hole 4, and the injection is complete;

[0067] Step 5: After the high-fluidity grout is injected, seal the grouting hole 3 and the vent hole 4;

[0068] Step 6: Repeat steps 2-5 until the grout-aggregate concrete filling for the entire designed tunnel length is completed.

[0069] Step 7: After the strength of the secondary tunnel lining concrete meets the requirements, remove the formwork. After the formwork is removed, the concrete is moisturized and cured to obtain the secondary tunnel lining 6 concrete structure.

[0070] like Figures 4-5 The image shows a simulation test view of the grouting method for aggregate-polymer concrete. The top image shows the state where only the aggregate is filled, while the bottom image is a schematic diagram showing the grout filling the gaps in the aggregate.

[0071] According to this specific implementation method, the following adjustments were made to the concrete formula in this embodiment to examine the excellent technical effects of this method.

[0072] Example 1

[0073] A type of aggregate-polymer concrete for tunnel secondary lining, comprising the following parts by weight after curing:

[0074] 59 parts aggregate, 41 parts paste;

[0075] In the aggregate, the mass ratio of coarse aggregate with a particle size of 9.5-20mm to coarse aggregate with a particle size of 16-31.5mm is 1:1; the compressive strength of the coarse aggregate is greater than 45MPa;

[0076] The slurry per cubic meter comprises the following raw materials mixed together:

[0077] The mixture contains 550 kg of cement (P∙O42.5), 350 kg of fly ash (secondary fly ash), 900 kg of industrial sand (particle size 0.075-2.36 mm, fineness modulus 1.8, porosity 28%, water absorption 2.8%, silica content 43%), 360 kg of water, 10 kg of water-reducing agent (polyester-type polycarboxylate water-reducing agent), and 1.5 kg of nano silica (particle size 100 nm); the water-cement ratio of the slurry is 0.40.

[0078] The paste-aggregate polymer concrete is formed as follows: the aggregate and the paste are prepared separately. During construction, the aggregate is first piled up and then the paste is poured in, so that the paste fills the gaps in the aggregate and solidifies to form paste-aggregate polymer concrete.

[0079] The performance test results of the secondary lining polymer concrete for tunnels are summarized in Table 2.

[0080] Example 2

[0081] A type of aggregate-polymer concrete for tunnel secondary lining, comprising the following raw materials in parts by weight, cured:

[0082] 60 parts aggregate, 40 parts paste;

[0083] In the aggregate, the mass ratio of coarse aggregate with a particle size of 9.5-20mm to coarse aggregate with a particle size of 16-31.5mm is 3:1; the compressive strength of the coarse aggregate is greater than 45MPa;

[0084] The slurry per cubic meter comprises the following raw materials mixed together:

[0085] The mixture contains 500 kg of cement (P∙O42.5), 300 kg of fly ash (secondary fly ash), 1000 kg of industrial sand (particle size 0.075-2.36 mm, fineness modulus 2.0, porosity 20%, water absorption 2%, silica content 50%), 400 kg of water, 6.4 kg of water-reducing agent (polyester-type polycarboxylate water-reducing agent), and 0.8 kg of nano silica (particle size 50 nm); the water-cement ratio of the slurry is 0.5.

[0086] The performance test results of the secondary lining polymer concrete for tunnels are summarized in Table 2.

[0087] Example 3

[0088] A type of aggregate-polymer concrete for tunnel secondary lining, comprising the following raw materials in parts by weight, cured:

[0089] 58 parts aggregate, 42 parts paste;

[0090] In the aggregate, the mass ratio of coarse aggregate with a particle size of 9.5-20mm to coarse aggregate with a particle size of 16-31.5mm is 0.33:1; the compressive strength of the coarse aggregate is greater than 45MPa;

[0091] The slurry per cubic meter comprises the following raw materials mixed together:

[0092] The mixture contains 600 kg of cement (P∙O42.5), 400 kg of fly ash (secondary fly ash), 800 kg of industrial sand (particle size 0.075-2.36 mm, fineness modulus 1.8, porosity 26%, water absorption 2.5%, silica content 48%), 350 kg of water, 15 kg of water-reducing agent (polyester-type polycarboxylate water-reducing agent), and 2 kg of nano silica (particle size 200 nm); the water-cement ratio of the slurry is 0.35.

[0093] The performance test results of the secondary lining polymer concrete for tunnels are summarized in Table 2.

[0094] Example 4

[0095] A type of grout-aggregate polymer concrete for tunnel secondary lining has a composition that is basically the same as that in Example 1, the only difference being:

[0096] In the aggregate, the mass ratio of coarse aggregate with a particle size of 9.5-20mm to coarse aggregate with a particle size of 16-31.5mm is 3:1.

[0097] Example 5

[0098] A type of grout-aggregate polymer concrete for tunnel secondary lining has a composition that is basically the same as that in Example 1, the only difference being:

[0099] In the aggregate, the mass ratio of coarse aggregate with a particle size of 9.5-20mm to coarse aggregate with a particle size of 16-31.5mm is 0.33:1.

[0100] Example 6

[0101] A type of grout-aggregate polymer concrete for tunnel secondary lining has a composition that is basically the same as that in Example 1, the only difference being:

[0102] The industrial sand has a particle size of 0.075-2.36 mm, a fineness modulus of 1.6, a porosity of 20%, a water absorption rate of 2%, and a silica content of 50%.

[0103] Comparative Example 1

[0104] A type of grout-aggregate polymer concrete for tunnel secondary lining has the same composition as Example 1, except that:

[0105] After the aggregate and grout are premixed evenly, they are poured into the formwork to solidify and form the structure. Comparative Example 1 adopts the traditional construction process of mixing the aggregate and then pouring it.

[0106] Comparative Example 2

[0107] A type of grout-aggregate polymer concrete for tunnel secondary lining has a composition that is basically the same as that in Example 1, the only difference being:

[0108] Natural river sand was used to replace industrial sand. The river sand had a particle size of 0.5-4.75 mm, a fineness modulus of 3, a porosity of 40%, a water absorption rate of 0.9%, and a silica content of 90%. Comparative Example 2 used natural river sand.

[0109] Comparative Example 3

[0110] A type of grout-aggregate polymer concrete for tunnel secondary lining has a composition that is basically the same as that in Example 1, the only difference being:

[0111] The industrial sand has a particle size of 0.075-2.36 mm, a fineness modulus of 2.2, a porosity of 28%, a water absorption rate of 2.8%, and a silica content of 43%. The fineness modulus of the industrial sand in Comparative Example 3 exceeds the preferred range.

[0112] A type of grout-aggregate polymer concrete for tunnel secondary lining has a composition that is basically the same as that in Example 1, the only difference being:

[0113] The industrial sand has a particle size of 0.075-2.36 mm, a fineness modulus of 1.8, a porosity of 8%, a water absorption rate of 0.5%, and a silica content of 43%. In Comparative Example 4, the porosity and water absorption rate of the industrial sand exceed the preferred range.

[0114] Comparative Example 5

[0115] A type of grout-aggregate polymer concrete for tunnel secondary lining has a composition that is basically the same as that in Example 1, the only difference being:

[0116] The coarse aggregate has a particle size of 16-31.5 mm. The particle size range of the coarse aggregate is narrower than that of Example 1.

[0117] Comparative Example 6

[0118] A type of grout-aggregate polymer concrete for tunnel secondary lining has a composition that is basically the same as that in Example 1, the only difference being:

[0119] The coarse aggregate has a particle size of 4.75-9.5 mm. The particle size range of the coarse aggregate is narrower than that of Example 1, and the particle size is relatively smaller.

[0120] Comparative Example 7

[0121] A type of grout-aggregate polymer concrete for tunnel secondary lining has a composition that is basically the same as that in Example 1, the only difference being:

[0122] No nano-silica was incorporated into each cubic meter of the slurry.

[0123] Comparative Example 8

[0124] A type of grout-aggregate polymer concrete for tunnel secondary lining has a composition that is basically the same as that in Example 1, the only difference being:

[0125] The amount of cement (P∙O42.5) used per cubic meter of the slurry is 450 kg. The amount of cement used is lower than the preferred range.

[0126] Comparative Example 9

[0127] A type of grout-aggregate polymer concrete for tunnel secondary lining has a composition that is basically the same as that in Example 1, the only difference being:

[0128] The amount of cement (P∙O42.5) used per cubic meter of the slurry is 650 kg. The amount of cement used is outside the preferred range.

[0129] Comparative Example 10

[0130] A type of grout-aggregate polymer concrete for tunnel secondary lining has a composition that is basically the same as that in Example 1, the only difference being:

[0131] The amount of fly ash (secondary fly ash) used in each cubic meter of the slurry is 250 kg. The amount of fly ash used is lower than the preferred range.

[0132] Comparative Example 11

[0133] A type of grout-aggregate polymer concrete for tunnel secondary lining has a composition that is basically the same as that in Example 1, the only difference being:

[0134] The amount of fly ash (secondary fly ash) used in each cubic meter of the slurry is 450 kg. The amount of fly ash used is higher than the preferred range.

[0135] Comparative Example 12

[0136] A type of grout-aggregate polymer concrete for tunnel secondary lining has a composition that is basically the same as that in Example 1, the only difference being:

[0137] The amount of industrial sand used in each cubic meter of the slurry is 750 kg. The amount of industrial sand used is lower than the preferred range.

[0138] Comparative Example 13

[0139] A type of grout-aggregate polymer concrete for tunnel secondary lining has a composition that is basically the same as that in Example 1, the only difference being:

[0140] The amount of industrial sand used in each cubic meter of the slurry is 1050 kg. The amount of industrial sand used is higher than the preferred range.

[0141] Comparative Example 14

[0142] A type of grout-aggregate polymer concrete for tunnel secondary lining has a composition that is basically the same as that in Example 1, the only difference being:

[0143] The amount of water used in each cubic meter of the slurry is 270 kg, and the water-cement ratio is 0.30. The water-cement ratio is lower than the preferred range.

[0144] Comparative Example 15

[0145] A type of grout-aggregate polymer concrete for tunnel secondary lining has a composition that is basically the same as that in Example 1, the only difference being:

[0146] The amount of water used in each cubic meter of the slurry is 495 kg, and the water-cement ratio is 0.55. The water-cement ratio is higher than the preferred range.

[0147] The mix proportions of the tunnel secondary lining polymer concrete of Examples 1-6 and Comparative Examples 1-15 are summarized in Table 1. Examples 1-6 are referred to as Examples 1-6, and Comparative Examples 1-15 are referred to as Examples 1-15.

[0148] Table 1. Summary of parameter data for the grout-aggregate polymer concrete used in tunnel secondary linings of Examples 1-6 and Comparative Examples 1-15.

[0149]

[0150] The performance of the tunnel secondary lining polymer concrete in Examples 1-6 and Comparative Examples 1-15 was tested, and the raw material costs were statistically analyzed. The results are summarized in Table 2. Examples 1-6 are referred to as Examples 1-6, and Comparative Examples 1-15 are referred to as Examples 1-15. Ordinary C30 concrete had a 28-day compressive strength ≥30 MPa and a shrinkage rate of approximately 250 × 10⁻⁶ MPa. -6 The material cost is approximately 365 yuan / m³.

[0151] Table 2. Experimental data of grout-aggregate polymer concrete for tunnel secondary lining in Examples 1-6 and Comparative Examples 1-15.

[0152]

[0153] Analysis of the data in Table 2 shows that the grout-aggregate polymer concrete for tunnel secondary lining has certain performance and cost advantages. In the embodiments of the present invention, the aggregate uses one or two ranges of coarse aggregates to be densely packed, forming a larger skeleton ratio, which can exert a stronger inhibitory effect on the hardening shrinkage of the grout, ensuring structural strength while significantly reducing the shrinkage rate; by screening industrial sand with spherical shape, activity and water retention and curing function as fine aggregate for use in the grout, the fluidity, strength and shrinkage resistance are improved; further addition of trace amounts of nano silica does not affect fluidity and can also synergistically improve compressive strength, flexural strength and impermeability; moreover, the pre-filling of aggregates and subsequent injection of grout to fill and coat the aggregates can reduce the energy consumption of traditional concrete aggregate reciprocating transportation and overall mixing of all raw materials.

[0154] The above embodiments describe only the basic principles, main features and / or advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and the description of the invention content in the specification are only the principles or specific cases of the present invention. Without departing from the essence of the innovative idea of ​​the present invention, there are various changes and improvements to the innovative solution of the present invention, and all such changes and improvements fall within the scope of protection claimed by the present invention.

Claims

1. A paste-aggregate polymer concrete for tunnel secondary lining, characterized in that, It includes the following raw materials by weight: 58-60 parts of aggregate and 40-42 parts of paste; The aggregate includes coarse aggregates of two particle size ranges: 9.5-20mm and 16-31.5mm; one or two of the coarse aggregates of the two particle size ranges are selected and mixed in a certain proportion to form aggregates; the ratio of the compressive strength of the parent rock of the coarse aggregates to the design compressive strength of the tunnel secondary lining is not less than 1.5; The grout is a high-fluidity grout containing fine aggregates. Each cubic meter of the high-fluidity grout contains the following raw materials by weight: 500-600 kg of cement, 300-400 kg of fly ash, 800-1000 kg of industrial sand, 350-400 kg of water, 6.4-15 kg of water-reducing agent, and 0.8-2 kg of nano-silica. The total adhesive content of the high-fluidity grout is 800-1000 kg, and the water-to-binder ratio is 0.35-0.

5. The industrial sand has a particle size of 0.075-2.36 mm, a fineness modulus of not more than 2.0, a porosity of 20-40%, a water absorption rate of 0.8-5%, a silica content of 35-50%, and an activity index of not less than 65% after 28 days of grinding. The paste-aggregate polymer concrete is formed as follows: the aggregate and the paste are prepared separately, and during construction, the coarse aggregate is first piled up and then the paste is poured in to fill the gaps in the coarse aggregate and solidify to form paste-aggregate polymer concrete.

2. The grout-aggregate polymer concrete for tunnel secondary lining according to claim 1, characterized in that, The weight ratio of coarse aggregate with a particle size range of 9.5-20 mm to coarse aggregate with a particle size range of 16-31.5 mm in the aggregate is 0.33-3:

1.

3. The grout-aggregate polymer concrete for tunnel secondary lining according to claim 1, characterized in that, Each cubic meter of the high-fluidity grout also includes 0.08-0.3 kg of retarder.

4. The grout-aggregate polymer concrete for tunnel secondary lining according to claim 3, characterized in that, Each cubic meter of the high-fluidity grout also includes 0.08-0.25 kg of defoamer.

5. The grout-aggregate polymer concrete for tunnel secondary lining according to claim 4, characterized in that, Each cubic meter of the high-fluidity grout also includes 0.5-0.9 kg of organic short fiber material.

6. The grout-aggregate polymer concrete for tunnel secondary lining according to any one of claims 1-5, characterized in that, The initial flow cone time of the high-fluidity grout is no more than 18s, and the 3h flow cone time is no more than 35s; the initial truncated cone flowability is no less than 360mm, and the 3h truncated cone flowability is no less than 320mm. Under a pressure of 0.36 MPa, the water leakage rate is no more than 1%.

7. A construction method for tunnel secondary lining, characterized in that, The construction method of using the grout-aggregate polymer concrete for tunnel secondary lining according to any one of claims 1-6 includes the following steps: Step 1: Assemble the integral formwork for the tunnel secondary lining, and pre-set grouting holes at the bottom of the arch feet on both sides of the tunnel secondary lining formwork, and pre-set venting holes at the top of the formwork arch; the longitudinal spacing of the grouting holes is 3-6m, and the longitudinal spacing of the venting holes is 0.5-1m; Step 2: Fill the tunnel secondary lining template with aggregate to form a skeleton; the aggregate is filled by its own weight and tightly packed together. Step 3: After the aggregate filling is completed, open the grouting holes and 3-5 adjacent venting holes on the same cross section, and keep the remaining grouting holes and venting holes closed. Inject high-fluidity grouting material through the preset grouting holes. Step 4: Inject high-fluidity grout from bottom to top under pressure, with the maximum pump pressure not exceeding 2MPa, until uniform grout continuously overflows from the vent hole, at which point the injection is complete; Step 5: After the high-fluidity grout is injected, seal the grouting holes and vent holes; Step 6: Repeat steps 2-5 until the grout-aggregate concrete filling for the entire designed tunnel length is completed. Step 7: After the strength of the secondary tunnel lining grout-aggregate polymer concrete meets the requirements, remove the formwork. After the formwork is removed, the grout-aggregate polymer concrete is moisturized and cured to obtain the secondary tunnel lining grout-aggregate polymer concrete structure.

8. The construction method according to claim 7, characterized in that, In step 1, the diameter of the grouting hole is 2-5 cm.

9. The construction method according to claim 7, characterized in that, The diameter of the vent hole is 5-10 mm.

10. The construction method according to claim 7, characterized in that, In step 7, the curing method is as follows: the humidity of the concrete surface is controlled to be above 90%; the temperature difference between the inside of the concrete and the surface does not exceed 20℃, and the temperature difference between the surface of the concrete and the environment in which the concrete is located does not exceed 20℃; the curing time is not less than 14 days.

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