Low-heat portland cement concrete for tunnel secondary lining and preparation method thereof

Abstract

The application discloses a kind of low-heat portland cement concrete for tunnel secondary lining and a preparation method thereof, the concrete includes high-heat environment resistant low-heat portland cement 260-320 parts by weight, fly ash 80-140 parts, dry sand 500-800 parts, high-temperature resistant fine aggregate 150-260 parts, high-temperature resistant medium aggregate 470-580 parts, high-temperature resistant coarse aggregate 240-360 parts, water reducing agent 3-7 parts, air entraining agent 4-8 parts, and water 130-170 parts. The application uses high-heat environment resistant low-heat portland cement to prepare concrete with fly ash, high-temperature resistant aggregate, water reducing agent and air entraining agent, which improves the early construction performance, early strength and high-heat resistance of concrete in high-heat environment, and effectively solves the problems of ordinary portland cement and ordinary low-heat cement in similar extreme environments.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a low-heat silicate cement concrete for tunnel secondary lining and its preparation method. Background Technology

[0002] As a crucial component of modern transportation infrastructure, tunnel engineering directly impacts the normal operation of the entire transportation system through its safety and durability. However, under specific geological conditions, such as in areas rich in geothermal resources or with concentrated underground heat sources, tunnel engineering faces severe challenges from high-temperature environments. These high geothermal environments not only cause numerous inconveniences during construction but also place extremely high demands on the materials used in the tunnel's secondary lining structure.

[0003] Traditional tunnel secondary linings widely use general-purpose silicate cement concrete as the main material, which exhibits good mechanical properties and durability under normal temperature conditions. However, once placed in a high geothermal environment, the performance of general-purpose silicate cement concrete begins to decline significantly. First, high temperatures accelerate the cement hydration reaction, leading to a large release of heat in a short period of time, increasing the temperature gradient inside the concrete, and thus causing thermal stress concentration and cracking. Second, under high-temperature conditions, the stability of cement hydration products such as ettringite and hydrated calcium silicate is affected, and some products may decompose or transform, resulting in reduced concrete strength and decreased durability.

[0004] To address this challenge, the engineering and academic communities have conducted extensive research, attempting to improve the high-temperature performance of concrete by optimizing concrete mix proportions, adding mineral admixtures, and using high-performance additives. While these methods have achieved some success, their effectiveness remains limited under extreme high-temperature conditions, failing to meet the high requirements for long-term stability and safety of tunnel secondary linings.

[0005] Based on the above background, this invention aims to develop a novel high geothermal environment resistant low-heat silicate cement concrete for tunnel secondary lining and its preparation method. It uses high geothermal environment resistant low-heat silicate cement as the main cementing material, combined with high-temperature resistant aggregates and admixtures, effectively solving the problem of performance degradation of traditional silicate cement concrete under high-temperature environments. This provides a more reliable and efficient building material option for tunnel engineering, improves the durability and safety of tunnel secondary lining, and promotes the further development of tunnel engineering technology. Summary of the Invention

[0006] The purpose of this invention is to provide a low-heat silicate cement concrete for tunnel secondary lining. This concrete is prepared by using low-heat silicate cement resistant to high geothermal environments, combined with fly ash, high-temperature resistant aggregates, water-reducing agents, and air-entraining agents. This improves the early construction performance and early strength of the concrete in high geothermal environments. More importantly, its high geothermal resistance is enhanced, effectively solving the problems that ordinary silicate cement and ordinary low-heat cement are prone to in similar extreme environments. This provides a more reliable and durable building material solution for tunnel secondary lining projects.

[0007] Another object of the present invention is to provide a method for preparing low-heat silicate cement concrete for tunnel secondary lining.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A low-heat silicate cement concrete for tunnel secondary lining comprises the following raw materials in parts by weight:

[0010]

[0011] Furthermore, the mineral composition of the high geothermal environment resistant low-heat silicate cement is C3S 28-35 wt.%, C2S 40-45 wt.%, C3A 0-4 wt.%, C4AF 10-15 wt.%, MgO 3.0-4.5 wt.%, and the specific surface area is 340±10 m². 2 / kg.

[0012] Furthermore, the fly ash is secondary fly ash.

[0013] Furthermore, the dry sand is manufactured sand and natural river sand.

[0014] Furthermore, the high-temperature resistant fine aggregate has a particle size of 5-10 mm and is a mixture of 100-150 parts by mass of crushed stone, 20-60 parts by mass of alumina hollow spheres, and 30-70 parts by mass of expanded perlite.

[0015] Furthermore, the high-temperature resistant aggregate has a particle size of 10-20 mm and is a mixture of 400-450 parts by mass of crushed stone, 20-70 parts by mass of porous mullite, and 30-70 parts by mass of ceramsite.

[0016] Furthermore, the high-temperature resistant coarse aggregate has a particle size of 16-31.5 mm and is a mixture of 150-200 parts by mass of crushed stone, 40-80 parts by mass of siliceous aggregate, and 50-90 parts by mass of natural ore, including andesite and basalt.

[0017] Furthermore, the water-reducing agent is a polycarboxylate high-performance water-reducing agent with a solid content of 20 wt.%.

[0018] Furthermore, the air-entraining agent is sodium fatty alcohol sulfate and alkylphenol polyoxyethylene (10) ether.

[0019] A method for preparing low-heat silicate cement concrete for tunnel secondary lining includes the following steps:

[0020] S1. Weigh the raw materials according to their respective weight parts and mix them evenly to obtain a mixture;

[0021] S2. Pour the mixture into the concrete curing mold;

[0022] S3. Place the concrete curing mold containing the mixture into a steam curing chamber and cure it at 20℃~80℃ to obtain the low-heat silicate cement concrete.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. Compared to ordinary low-heat silicate cement where the C2S (dicalcium silicate) size is 20-40 μm, the C2S size in high geothermal environment resistant low-heat silicate cement is smaller, ranging from 5-30 μm. Under the same C2S mass ratio, the number of C2S crystals is greater and increases exponentially, thereby increasing the C2S hydration interface, improving the hydration rate, and significantly enhancing the early construction performance and early strength of concrete in high geothermal environments.

[0025] 2. Compared with the MgO content of 2.0% in ordinary low-heat silicate cement, the MgO content in high geothermal environment resistant low-heat silicate cement is increased to 3.0-4.5%. MgO has micro-expansion properties during the cement reaction process, which can compensate for the shrinkage of concrete.

[0026] 3. The fine, medium and coarse aggregates for high temperature resistance contain alumina hollow spheres, expanded perlite or porous mullite, ceramsite or siliceous aggregates, andesite, basalt and other high temperature resistant materials. When combined with low-heat silicate cement with high geothermal environment tolerance, the concrete prepared has better crack resistance.

[0027] 4. Air-entraining agents have an air-entraining effect, which can reduce the elastic modulus of early concrete, enhance the plasticity of concrete, alleviate the pressure of plastic shrinkage to a certain extent, and increase the fluidity and workability of concrete, making it easier to carry out construction operations. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0029] In this embodiment of the invention, the mineral composition of the high geothermal environment resistant low-heat silicate cement is C3S 28-35 wt.%, C2S 40-45 wt.%, C3A 0-4 wt.%, C4AF 10-15 wt.%, MgO 3.0-4.5 wt.%, and the specific surface area is 340±10 m². 2 / kg.

[0030] In this embodiment of the invention, the fly ash is secondary fly ash.

[0031] In this embodiment of the invention, the dry sand is manufactured sand and natural river sand.

[0032] In this embodiment of the invention, the high-temperature resistant fine aggregate has a particle size of 5-10 mm and is a mixture of 100-150 parts by mass of crushed stone, 20-60 parts by mass of alumina hollow spheres, and 30-70 parts by mass of expanded perlite.

[0033] In this embodiment of the invention, the high-temperature resistant aggregate has a particle size of 10-20 mm and is a mixture of 400-450 parts by mass of crushed stone, 20-70 parts by mass of porous mullite, and 30-70 parts by mass of ceramsite.

[0034] In this embodiment of the invention, the high-temperature resistant coarse aggregate has a particle size of 16-31.5 mm and is a mixture of 150-200 parts by mass of crushed stone, 40-80 parts by mass of siliceous aggregate, and 50-90 parts by mass of natural ore, including andesite and basalt.

[0035] In this embodiment of the invention, the water-reducing agent is a polycarboxylate high-performance water-reducing agent with a solid content of 20 wt.%.

[0036] In this embodiment of the invention, the air-entraining agent is sodium fatty alcohol sulfate and alkylphenol polyoxyethylene (10) ether.

[0037] Example 1

[0038] As a preferred embodiment of the present invention, this embodiment discloses a low-heat silicate cement concrete for tunnel secondary lining, the composition of which is shown in Table 1.

[0039] Table 1

[0040]

[0041]

[0042] The method for preparing low-heat silicate cement concrete in this embodiment includes the following steps:

[0043] S1. Weigh the raw materials according to the weight parts in Table 1 and mix them evenly to obtain a mixture;

[0044] S2. Pour the mixture into the concrete curing mold;

[0045] S3. Place the concrete curing mold containing the mixture into a steam curing chamber and cure it at 80°C until the appropriate age to obtain low-heat silicate cement concrete.

[0046] Example 2

[0047] As a preferred embodiment of the present invention, this embodiment discloses a low-heat silicate cement concrete for tunnel secondary lining, the composition of which is shown in Table 2.

[0048] Table 2

[0049] raw material Weight / serving High geothermal environment resistant low-heat silicate cement 279 fly ash 119 dry sand 740 High-temperature resistant fine aggregate 222 High temperature resistant medium aggregate 555 High temperature resistant coarse aggregate 333 Water reducing agent 4.8 Entraining agent 4.5 water 142

[0050] The method for preparing low-heat silicate cement concrete in this embodiment includes the following steps:

[0051] S1. Weigh the raw materials according to the weight parts in Table 2 and mix them evenly to obtain a mixture;

[0052] S2. Pour the mixture into the concrete curing mold;

[0053] S3. Place the concrete curing mold containing the mixture into a steam curing chamber and cure it at 80°C until the appropriate age to obtain low-heat silicate cement concrete.

[0054] Example 3

[0055] As a preferred embodiment of the present invention, this embodiment discloses a low-heat silicate cement concrete for tunnel secondary lining, the composition of which is shown in Table 3.

[0056] Table 3

[0057] raw material Weight / serving High geothermal environment resistant low-heat silicate cement 259 fly ash 139 dry sand 740 High-temperature resistant fine aggregate 222 High temperature resistant medium aggregate 555 High temperature resistant coarse aggregate 333 Water reducing agent 4.6 Entraining agent 4.5 water 142

[0058] The method for preparing low-heat silicate cement concrete in this embodiment includes the following steps:

[0059] S1. Weigh the raw materials according to the weight parts in Table 3 and mix them evenly to obtain a mixture;

[0060] S2. Pour the mixture into the concrete curing mold;

[0061] S3. Place the concrete curing mold containing the mixture into a steam curing chamber and cure it at 80°C until the appropriate age to obtain low-heat silicate cement concrete.

[0062] Comparative Example 1

[0063] Comparative Example 1 is a silicate cement concrete prepared using ordinary silicate cement P·O42.5, the composition of which is shown in Table 4.

[0064] Table 4

[0065]

[0066]

[0067] The preparation method of silicate cement concrete in this comparative example includes the following steps:

[0068] S1. Weigh the raw materials according to the weight parts in Table 4 and mix them evenly to obtain a mixture;

[0069] S2. Pour the mixture into the concrete curing mold;

[0070] S3. Place the concrete curing mold containing the mixture into a steam curing chamber and cure it at 80°C until the appropriate age to obtain silicate cement concrete.

[0071] Comparative Example 2

[0072] Comparative Example 2 is cement concrete prepared using ordinary low-heat cement P·O42.5, and its composition is shown in Table 5.

[0073] Table 5

[0074] raw material Weight / serving Ordinary low-heat cement P·O42.5 276 fly ash 118 dry sand 776 5-10mm gravel 214 10-20mm gravel 536 16-31.5mm crushed stone 321 Water reducing agent 5.7 Entraining agent 3.9 water 141

[0075] The method for preparing cement concrete in this comparative example includes the following steps:

[0076] S1. Weigh the raw materials according to the weight parts in Table 5 and mix them evenly to obtain a mixture;

[0077] S2. Pour the mixture into the concrete curing mold;

[0078] S3. Place the concrete curing mold containing the mixture into a steam curing chamber and cure it at 80°C until the appropriate age to obtain cement concrete.

[0079] 1. Testing of three types of cement physical properties

[0080] The physical properties of ordinary Portland cement, ordinary low-heat cement, and low-heat Portland cement resistant to high geothermal environments were tested according to GB / T17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)" and JCT 603-2004 "Test Method for Drying Shrinkage of Cement Mortar". The results are shown in Table 6 below.

[0081] Table 6

[0082]

[0083] As shown in Table 6, the MgO content of the high geothermal environment resistant low-heat silicate cement of the present invention is increased to 4.1%, and the heat of hydration is reduced to 208.5 KJ / kg. This achieves a synergistic match between early strength and low heat of hydration. The combined factors result in a lower shrinkage rate, better crack resistance, and greater suitability for high geothermal environments.

[0084] 2. Concrete performance testing

[0085] The physical properties of cement concrete from Examples 1 to 3 and Comparative Examples 1 to 2 were tested according to GB / T17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)" and JCT 603-2004 "Test Method for Drying Shrinkage of Cement Mortar", as shown in Table 7 below:

[0086] Table 7

[0087]

[0088] The shrinkage reduction rate in Table 7 refers to the decrease in shrinkage rate of concrete prepared in the embodiments and comparative examples of the present invention after 28 days compared with that of concrete prepared with ordinary Portland cement after 28 days.

[0089] Table 7 shows that, under steam curing conditions at 80℃, the 28-day compressive strength of the concrete prepared by this invention (Examples 1-3) is ≥55MPa, which is better than that of ordinary concrete (Comparative Example 1) and low-heat cement concrete (Comparative Example 2) of the same strength grade; and the shrinkage rate is less than 0.30%, which is more than 25% lower than that of ordinary concrete of the same strength grade; in the early cracking test of concrete, the total cracked area per unit area is ≤240mm. 2 / m 2 It has a significant crack resistance effect and is more suitable for high geothermal environments.

[0090] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A low-heat silicate cement concrete for tunnel secondary lining, characterized in that, Including the following parts by weight of raw materials: 260-320 parts of low-heat silicate cement with high geothermal environment tolerance; 80-140 parts fly ash; 500-800 parts of dry sand; 150-260 parts of high-temperature resistant fine aggregate; 470-580 parts of high-temperature resistant medium aggregate; 240-360 parts of high-temperature resistant coarse aggregate; 3-7 parts water-reducing agent; 4-8 parts of air-entraining agent; 130-170 parts water; The mineral composition of the high geothermal environment resistant low-heat silicate cement is C3S 28~35 wt.%, C2S 40~45 wt.%, C3A 0~4 wt.%, C4AF 10~15 wt.%, MgO 3.0~4.5 wt.%, with a specific surface area of ​​340±10 m². 2 / kg, the sum of the mass percentages of all components in the cement is 100%; The air-entraining agent is sodium fatty alcohol sulfate and alkylphenol polyoxyethylene (10) ether; The high-temperature resistant fine aggregate has a particle size of 5-10 mm and is a mixture of 100-150 parts by mass of crushed stone, 20-60 parts by mass of alumina hollow spheres, and 30-70 parts by mass of expanded perlite. The high-temperature resistant aggregate has a particle size of 10-20mm and is a mixture of 400-450 parts by mass of crushed stone, 20-70 parts by mass of porous mullite, and 30-70 parts by mass of ceramsite. The high-temperature resistant coarse aggregate has a particle size of 16-31.5 mm and is a mixture of 150-200 parts by mass of crushed stone, 40-80 parts by mass of siliceous aggregate, and 50-90 parts by mass of natural ore, including andesite and basalt.

2. The low-heat silicate cement concrete for tunnel secondary lining according to claim 1, characterized in that, The fly ash is grade II fly ash.

3. The low-heat silicate cement concrete for tunnel secondary lining according to claim 1, characterized in that, The dry sand is a mixture of manufactured sand and natural river sand.

4. The low-heat silicate cement concrete for tunnel secondary lining according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate high-performance water-reducing agent with a solid content of 20 wt.%.

5. A method for preparing low-heat silicate cement concrete for tunnel secondary lining according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Weigh the raw materials according to their respective weight parts and mix them evenly to obtain a mixture; S2. Pour the mixture into the concrete curing mold; S3. Place the concrete curing mold containing the mixture into a steam curing chamber and cure it at 20℃~80℃ to obtain the low-heat silicate cement concrete.

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