Heat-resistant concrete suitable for high ground temperature tunnel secondary lining

Abstract

The application relates to a heat-resistant concrete suitable for high-temperature tunnel secondary lining, which comprises the following components and contents (mass parts): low-heat portland cement 250-320, mineral admixture 60-120, coarse aggregate 950-1150, machine-made sand 650-850, micro aggregate 5-35, hydration heat inhibitor 0-2.0, high-temperature adaptive water reducing agent 3.6-4.4, defoaming agent 0-0.04, and water 145-160, wherein the mixing material has a mold content air content of less than or equal to 4%. Compared with the prior art, the product has the technical advantages of small working property loss, low later strength damage and good crack resistance in a high-temperature environment.

Description

Technical Field

[0001] This invention relates to building materials, and more particularly to a heat-resistant concrete suitable for secondary lining of high-temperature tunnels. Background Technology

[0002] As engineering construction expands westward, the number of tunnels operating at high ground temperatures is increasing, making high ground temperatures an unavoidable condition in concrete construction. Existing research and engineering practice show that high ground temperatures inhibit the later-stage strength development of concrete. This is because the hydration rate of cementitious materials is too rapid under high ground temperatures, and the rapid loss of moisture leads to a loose structure of hydration products, resulting in almost no or even reduced strength development in the later stages of concrete. Furthermore, the combined effect of temperature stress and drying shrinkage increases the risk of cracking in tunnel secondary lining concrete. Therefore, how to formulate heat-resistant secondary lining concrete suitable for high ground temperature environments has become a crucial issue of concern for engineering technicians.

[0003] To formulate heat-resistant concrete, domestic technicians have conducted extensive research and applied for corresponding patents, as shown in Table 1. Patents 1-7 address the application needs of industrial furnace linings, blast furnace shells, chimneys, and high-temperature boiler foundations. They mainly use aluminate cement, heat-resistant coarse aggregates (such as vitrified microspheres, hollow ceramic microspheres, coal ash ceramsite slag, basalt crushed stone, wollastonite, etc.), nickel-iron slag manufactured sand, admixtures (boron phosphide powder, microsilica powder, etc.), and modifying components (nano-SiO2, high-temperature resistant inorganic nanocomposite binders, etc.) to formulate heat-resistant concrete. Patent 8 addresses the application needs of rocket launch base diversion channels, using magnesium olivine and calcium aluminate cement to formulate heat-resistant concrete. The heat-resistant concrete involved in the above 8 patents are all heat-resistant materials that maintain physical and mechanical properties and volume stability at specific temperatures of 200℃ to 900℃ after setting and hardening. However, the concrete mixture for the secondary lining of high-temperature tunnels is already in a high geothermal environment before setting and hardening, that is, it has been subjected to high-temperature damage from the plastic stage when it is poured on site. This is completely different from the working conditions in patents 1-8.

[0004] Patents 9-10 use expanded vitrified microspheres and modified rubber to improve the thermal insulation performance of high-temperature tunnel concrete, but do not address its heat resistance performance. Patent 12 uses hydroxypropyl methylcellulose ether, sodium superabsorbent polymer (SAP) polyacrylate, redispersible latex powder, and recycled clay brick sand to formulate heat-resistant secondary lining concrete, but does not consider the control of its heat resistance performance during the plastic stage of concrete.

[0005]

[0006] Given the significant workability loss, later-stage strength damage, and poor crack resistance of secondary lining concrete under high geothermal conditions, and considering that the adverse effects of geothermal activity on concrete performance begin as early as the plastic stage, it is necessary to develop a heat-resistant secondary lining concrete to achieve coordinated improvement in workability control during the plastic stage, inhibition of bubble swelling, and mechanical and crack resistance during the hardening stage. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned problems and provide a heat-resistant concrete suitable for the secondary lining of high-temperature tunnels.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] A heat-resistant concrete suitable for secondary lining of high-temperature tunnels, characterized in that the concrete comprises the following raw materials in parts by weight:

[0010] Low-heat silicate cement 250-320;

[0011] Mineral admixtures: 60-120;

[0012] Coarse aggregate 950 ~ 1150;

[0013] Manufactured sand 650-850;

[0014] Micro-aggregate 5 ~ 35;

[0015] Hydration heat inhibitor 0 ~ 2.0;

[0016] High-temperature adaptable water-reducing agent: 3.6–4.4;

[0017] Defoamer 0 ~ 0.04;

[0018] Water 145-160;

[0019] The low-heat silicate cement has an MgO content of 3%–6%, a 3-day heat of hydration ≤220kJ / kg, a 7-day heat of hydration ≤250kJ / kg, a 28-day heat of hydration ≤300kJ / kg, a 3-day compressive strength ≥16.0MPa, a 28-day compressive strength ≥48.0MPa, and a 56-day strength ≥60.0MPa; the heat-resistant concrete has an air content of ≤4% upon placement in the formwork.

[0020] The manufactured sand is produced from a parent rock of limestone, granite, or tuff through a specialized production line, with an MB value ≤ 1.0 g / kg and a stone powder content of 5%–10%.

[0021] The micro-aggregate is a by-product of the manufactured sand production process, with an MB value ≤ 1.4 g / kg and a particle size of 0.002 mm to 0.1 mm. Among them, the proportion of 0.002 mm to 0.01 mm particles is 0% to 10%, the proportion of 0.01 mm to 0.05 mm particles is 30% to 50%, and the proportion of 0.05 mm to 0.1 mm particles is 40% to 80%.

[0022] The hydration heat inhibitor is a polyhydroxycarboxylic acid ester coated with stearic acid using a gas-phase spray process at 80℃~100℃.

[0023] The high-temperature adaptable water-reducing agent is a polycarboxylate-based water-reducing agent containing hyperbranched slow-release groups in its molecular structure.

[0024] In this invention, low-heat silicate cement and hydration heat inhibitor are hydration heat regulating materials. Their function is to reduce the hydration heat of the secondary lining concrete under high geothermal conditions, reduce the hydration heat exothermic peak, and decrease cracking caused by concrete temperature stress. Controlling the air content of the heat-resistant concrete to ≤4% upon placement is to inhibit the plastic expansion of air bubbles in the concrete under geothermal conditions, thereby reducing the adverse effects on the later strength of the concrete. The addition of micro-aggregates of a specific particle size is to provide the workability of the low-air-content concrete. The use of a high-temperature adaptable water-reducing agent is to prevent the loss of workability of the secondary lining concrete under high geothermal conditions. Through the optimal combination of the above key components, a coordinated improvement in the workability, mechanical properties, and crack resistance of the secondary lining concrete under high geothermal conditions is achieved. Implementation

[0025] To illustrate the features and effects of the present invention in detail, the following detailed description is provided in conjunction with embodiments. Example

[0026] A heat-resistant concrete suitable for secondary lining of high-temperature tunnels, comprising the following components by weight:

[0027] Low-heat silicate cement 293

[0028] fly ash 98

[0029] Coarse aggregate 1132

[0030] Mechanized Sand 742

[0031] Micro aggregate 8

[0032] Hydration heat inhibitor 0.5

[0033] High-temperature adaptable water-reducing agent 3.91

[0034] Defoamer 0.005

[0035] Water 148

[0036] In this embodiment, the low-heat silicate cement has an MgO content of 3.53%, a 3-day hydration heat of 192 kJ / kg, a 7-day hydration heat of 233 kJ / kg, a 28-day hydration heat of 287 kJ / kg, a 3-day compressive strength of 20.3 MPa, a 28-day compressive strength of 51.9 MPa, and a 56-day compressive strength of 63.4 MPa; the manufactured sand has an MB value of 0.5 g / kg and a stone powder content of 7.0%; the micro-aggregate has an MB value of 0.5 g / kg, with particles of 0.002 mm to 0.01 mm accounting for 5%, particles of 0.01 mm to 0.05 mm accounting for 40%, and particles of 0.05 mm to 0.1 mm accounting for 55%; the concrete prepared according to the above composition has an air content of 2.8% upon placement in the formwork. Example

[0037] A heat-resistant concrete suitable for secondary lining of high-temperature tunnels, comprising the following components and their contents (parts by weight):

[0038] Low-heat silicate cement 290

[0039] Slag powder 97

[0040] Coarse aggregate 1115

[0041] Mechanized Sand 719

[0042] Micro aggregate 20

[0043] Hydration heat inhibitor 0.5

[0044] High-temperature adaptable water-reducing agent 3.87

[0045] Defoamer 0.005

[0046] Water 149

[0047] In this embodiment, the low-heat silicate cement has an MgO content of 3.53%, a 3-day hydration heat of 192 kJ / kg, a 7-day hydration heat of 233 kJ / kg, a 28-day hydration heat of 287 kJ / kg, a 3-day compressive strength of 20.3 MPa, a 28-day compressive strength of 51.9 MPa, and a 56-day compressive strength of 63.4 MPa; the manufactured sand has an MB value of 0.5 g / kg and a stone powder content of 7.0%; the micro-aggregate has an MB value of 0.5 g / kg, with particles of 0.002 mm to 0.01 mm accounting for 5%, particles of 0.01 mm to 0.05 mm accounting for 40%, and particles of 0.05 mm to 0.1 mm accounting for 55%; the concrete prepared according to the above composition has an air content of 3.1% upon placement in the formwork. Example

[0048] A heat-resistant concrete suitable for secondary lining of high-temperature tunnels, comprising the following components and their contents (parts by weight):

[0049] Low-heat silicate cement 288

[0050] fly ash 96

[0051] Coarse aggregate 1145

[0052] Mechanized Sand 701

[0053] Micro aggregate 33

[0054] Hydration heat inhibitor 0.5

[0055] High-temperature adaptable water-reducing agent 3.84

[0056] Defoamer 0.005

[0057] Water 152

[0058] In this embodiment, the low-heat silicate cement has an MgO content of 3.53%, a 3-day hydration heat of 192 kJ / kg, a 7-day hydration heat of 233 kJ / kg, a 28-day hydration heat of 287 kJ / kg, a 3-day compressive strength of 20.3 MPa, a 28-day compressive strength of 51.9 MPa, and a 56-day compressive strength of 63.4 MPa. The manufactured sand has an MB value of 0.5 g / kg and a stone powder content of 7.0%. The micro-aggregate has an MB value of 0.5 g / kg, with particles of 0.002 mm to 0.01 mm accounting for 5%, particles of 0.01 mm to 0.05 mm accounting for 40%, and particles of 0.05 mm to 0.1 mm accounting for 55%. The concrete prepared according to the above composition has an air content of 3.2% upon placement in the formwork. Example

[0059] A heat-resistant concrete suitable for secondary lining of high-temperature tunnels, comprising the following components and their contents (parts by weight):

[0060] Low-heat silicate cement 290

[0061] fly ash 97

[0062] Coarse aggregate 1115

[0063] Mechanized Sand 719

[0064] Micro aggregate 20

[0065] Hydration heat inhibitor 1.0

[0066] High-temperature adaptable water-reducing agent 3.87

[0067] Defoamer 0.005

[0068] Water 149

[0069] In this embodiment, the low-heat silicate cement has an MgO content of 3.53%, a 3-day hydration heat of 192 kJ / kg, a 7-day hydration heat of 233 kJ / kg, a 28-day hydration heat of 287 kJ / kg, a 3-day compressive strength of 20.3 MPa, a 28-day compressive strength of 51.9 MPa, and a 56-day compressive strength of 63.4 MPa; the manufactured sand has an MB value of 0.5 g / kg and a stone powder content of 7.3%; the micro-aggregate has an MB value of 0.5 g / kg, with particles of 0.002 mm to 0.01 mm accounting for 8%, particles of 0.01 mm to 0.05 mm accounting for 43%, and particles of 0.05 mm to 0.1 mm accounting for 74%; the concrete prepared according to the above composition has an air content of 3.1% upon placement in the formwork. Example

[0070] A heat-resistant concrete suitable for secondary lining of high-temperature tunnels, comprising the following components and their contents (parts by weight):

[0071] Low-heat silicate cement 290

[0072] fly ash 97

[0073] Coarse aggregate 1115

[0074] Mechanized Sand 719

[0075] Micro aggregate 20

[0076] Hydration heat inhibitor 1.5

[0077] High-temperature adaptable water-reducing agent 3.87

[0078] Defoamer 0.005

[0079] Water 149

[0080] In this embodiment, the low-heat silicate cement has an MgO content of 3.53%, a 3-day hydration heat of 192 kJ / kg, a 7-day hydration heat of 233 kJ / kg, a 28-day hydration heat of 287 kJ / kg, a 3-day compressive strength of 20.3 MPa, a 28-day compressive strength of 51.9 MPa, and a 56-day compressive strength of 63.4 MPa. The manufactured sand has an MB value of 0.5 g / kg and a stone powder content of 7.3%. The micro-aggregate has an MB value of 0.5 g / kg, with particles of 0.002 mm to 0.01 mm accounting for 5%, particles of 0.01 mm to 0.05 mm accounting for 40%, and particles of 0.05 mm to 0.1 mm accounting for 55%. The concrete prepared according to the above composition has an air content of 3.1% upon placement in the formwork.

[0081] Comparative Example 1

[0082] A heat-resistant concrete suitable for secondary lining of high-temperature tunnels, comprising the following components and their contents (parts by weight):

[0083] Low-heat silicate cement 290

[0084] fly ash 97

[0085] Coarse aggregate 1115

[0086] Mechanized Sand 719

[0087] Micro aggregate 20

[0088] Hydration heat inhibitor 1.0

[0089] High-temperature adaptable water-reducing agent 3.87

[0090] Air-entraining agent 0.03

[0091] Defoamer 0

[0092] Water 148

[0093] In this comparative example, the low-heat silicate cement has an MgO content of 3.53%, a 3-day hydration heat of 192 kJ / kg, a 7-day hydration heat of 233 kJ / kg, a 28-day hydration heat of 287 kJ / kg, a 3-day compressive strength of 20.3 MPa, a 28-day compressive strength of 51.9 MPa, and a 56-day compressive strength of 63.4 MPa; the manufactured sand has an MB value of 0.5 g / kg and a stone powder content of 7.0%; the micro-aggregate has an MB value of 0.5 g / kg, with particles of 0.002 mm to 0.01 mm accounting for 12%, particles of 0.01 mm to 0.05 mm accounting for 55%, and particles of 0.05 mm to 0.1 mm accounting for 33%; the concrete prepared according to the above composition has an air content of 5.2% upon placement in the formwork.

[0094] Comparative Example 2

[0095] A heat-resistant concrete suitable for secondary lining of high-temperature tunnels, comprising the following components and their contents (parts by weight):

[0096] Ordinary Portland cement 290

[0097] fly ash 97

[0098] Coarse aggregate 1115

[0099] Mechanized Sand 719

[0100] Micro aggregate 4

[0101] Hydration heat inhibitor 1.0

[0102] High-temperature adaptable water-reducing agent 3.87

[0103] Defoamer 0.005

[0104] Water 148

[0105] In this comparative example, the ordinary Portland cement has an MgO content of 0.48%, a 3-day hydration heat of 304 kJ / kg, a 7-day hydration heat of 350 kJ / kg, a 28-day hydration heat of 375 kJ / kg, a 3-day compressive strength of 24.3 MPa, and a 28-day compressive strength of 46.2 MPa; the manufactured sand has an MB value of 0.5 g / kg and a stone powder content of 7.0%; the micro-aggregate has an MB value of 0.5 g / kg, with 0% of particles having a diameter of 0.002 mm to 0.01 mm, 20% of particles having a diameter of 0.01 mm to 0.05 mm, and 80% of particles having a diameter of 0.05 mm to 0.1 mm; the concrete prepared according to the above composition has an air content of 2.8% upon placement in the formwork.

[0106] Comparative Example 3

[0107] A heat-resistant concrete suitable for secondary lining of high-temperature tunnels, comprising the following components and their contents (parts by weight):

[0108] Low-heat silicate cement 290

[0109] fly ash 97

[0110] Coarse aggregate 1115

[0111] Mechanized Sand 719

[0112] Micro aggregate 20

[0113] Hydration heat inhibitor 1.0

[0114] Ordinary water-reducing agent 3.87

[0115] Defoamer 0.005

[0116] Water 148

[0117] In this comparative example, the low-heat silicate cement has an MgO content of 3.53%, a 3-day hydration heat of 192 kJ / kg, a 7-day hydration heat of 233 kJ / kg, a 28-day hydration heat of 287 kJ / kg, a 3-day compressive strength of 20.3 MPa, a 28-day compressive strength of 51.9 MPa, and a 56-day compressive strength of 63.4 MPa; the manufactured sand has an MB value of 0.5 g / kg and a stone powder content of 7.0%; the micro-aggregate has an MB value of 0.5 g / kg, with particles of 0.002 mm to 0.01 mm accounting for 5%, particles of 0.01 mm to 0.05 mm accounting for 40%, and particles of 0.05 mm to 0.1 mm accounting for 55%; the concrete prepared according to the above composition has an air content of 2.8% upon placement in the formwork.

[0118] The workability, mechanical properties, and volumetric deformation properties of the concrete in the examples and comparative examples were tested according to the following steps, and the test results are shown in Table 2.

[0119] (1) Concrete workability test: Concrete was mixed in accordance with GB / T 50080-2016 "Standard for Test Method of Performance of Ordinary Concrete Mixture". The initial slump of the concrete was controlled at 200mm±10mm. The concrete mixture was put into the sample cylinder wiped with a damp cloth, the container was covered and left to stand for 2 hours (starting from the time water was added and mixed). It was then mixed evenly with a shovel on an iron plate. The slump of the concrete was tested after 2 hours and the change in slump after 2 hours was calculated.

[0120] (2) Concrete strength and heat resistance index test: 100mm×100mm×100mm concrete specimens were formed. One group was cured in a test chamber simulating a geothermal environment, and the other group was cured under standard conditions. The compressive strength of the concrete under geothermal conditions was tested at 56 days. f Concrete compressive strength under c1 and standard curing conditions f c0, calculate the strength and heat resistance index K= f c1 / f c0×100%.

[0121] (3) Concrete plastic deformation rate test: Concrete specimens were formed using 100mm×100mm×100mm steel molds. After the specimens were formed, the surface was covered with a plastic film to prevent moisture evaporation, and a glass plate was placed on the upper surface of the specimens. The length measuring instrument was set up according to the method of JG / T408-2019 "Grouting material for sleeves for steel bar connection" and immediately placed in a test chamber simulating a geothermal environment. After the length measuring instrument reached a constant temperature, the initial vertical height of the specimen and the vertical height after 2 hours were measured, and the concrete plastic deformation rate was calculated.

[0122] (4) Concrete adiabatic temperature rise test: The concrete mixture is placed in two layers into the adiabatic temperature rise test container. After compaction, the sample container is placed into the adiabatic temperature rise chamber. Sensors are used to monitor the initial temperature of the concrete mixture and the 3-day concrete temperature, and the 3-day adiabatic temperature rise value is calculated.

[0123] (5) Concrete drying shrinkage test: 100mm×100mm×515mm concrete specimens were formed, and the 56d drying shrinkage of concrete was tested according to GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete".

[0124]

[0125] As can be seen from the table above:

[0126] (1) The secondary lining concrete prepared using Examples 1-5 has no bleeding, good cohesion, slump loss ≤30mm in 2h under geothermal conditions, 56d strength heat resistance index 98.3%~106.8%, 2h plastic swelling deformation rate ≤0.05%, 3d adiabatic temperature rise 28.6℃~38.2℃, and 56d drying shrinkage <260×10 -6 Among them, the secondary lining concrete in Example 4 has the best overall performance.

[0127] (2) In Comparative Example 1, the heat resistance coefficient of the secondary lining concrete was only 86.4%, and the plastic swelling deformation rate after 2 hours was as high as 0.23%. This is because the gradation of the micro-aggregate added to the concrete was unreasonable, and no appropriate amount of defoamer was added, resulting in an air content of 5.2% in the concrete mix. The excessive air content caused the concrete mix to undergo plastic expansion under thermal effects, which increased the internal pore defects of the concrete and ultimately led to a significant reduction in the strength and heat resistance index of the concrete.

[0128] (3) In Comparative Example 2, because the low-heat silicate cement of the claims was not used, the adiabatic temperature rise of the secondary lining concrete reached 47.4℃ after 3 days, which is more than 24% higher than that of Examples 1-5, and the drying shrinkage rate of the secondary lining concrete reached 452.6×10⁻⁶ after 56 days. -6 The crack resistance of the secondary lining concrete in Comparative Example 2 was more than 76% higher than that in Examples 1-5. Furthermore, due to the unreasonable gradation of the micro-aggregates incorporated into the concrete, problems such as bleeding, poor coating, and poor workability occurred in the mixture.

[0129] (4) In Comparative Example 3, because the high-temperature adaptable water-reducing agent of the claim was not used, the slump loss of the secondary lining concrete reached 150 mm in 2 hours, which could not meet the requirements for high-temperature tunnel construction.

[0130] The above embodiments describe in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A heat-resistant concrete suitable for a second lining of a high ground temperature tunnel, characterized in that, The concrete comprises the following mass parts of raw materials: The low-heat portland cement has a MgO content of 3-6%, a 3-day hydration heat of less than or equal to 220 kJ / kg, a 7-day hydration heat of less than or equal to 250 kJ / kg, a 28-day hydration heat of less than or equal to 300 kJ / kg, a 3-day compressive strength of greater than or equal to 16.0 MPa, a 28-day compressive strength of greater than or equal to 48.0 MPa, and a 56-day strength of greater than or equal to 60.0 MPa; and the heat-resistant concrete has a mold-inclusion air content of less than or equal to 4%; The micro aggregate is a by-product in the production process of machine-made sand, has an MB value of less than or equal to 1.4 g / kg, and a particle size of 0.002-0.1 mm, wherein the proportion of 0.002-0.01 mm particles is 0-10%, the proportion of 0.01-0.05 mm particles is 30-50%, and the proportion of 0.05-0.1 mm particles is 40-80%; The hydration heat inhibitor is a polyhydroxycarboxylic acid ester coated with stearic acid by a 80-100 DEG C gas-phase spraying process; The mass parts of the hydration heat inhibitor and the defoaming agent are not 0.

2. The heat-resistant concrete suitable for the second lining of a high ground temperature tunnel according to claim 1, characterized in that, The machine-made sand is obtained by a professional production line from one of limestone, granite and tuff, has an MB value of less than or equal to 1.0 g / kg, and a stone powder content of 5-10%.

3. The heat-resistant concrete suitable for the second lining of a high ground temperature tunnel according to claim 1, characterized in that, The high-temperature adaptive water reducing agent is a polycarboxylic acid water reducing agent containing super-branched slow-release groups in the molecular structure.

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