Low-heat Portland cement concrete for tunnel secondary lining and preparation method of low-heat Portland cement concrete

Abstract

The invention discloses low-heat Portland cement concrete for a tunnel secondary lining and a preparation method of the low-heat Portland cement concrete. The concrete comprises the following components in parts by weight: 260-320 parts of high-geothermal environment tolerance type low-heat Portland cement, 80-140 parts of pulverized coal and 500-800 parts of dry sand. The high-temperature-resistant concrete is prepared from 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 of a water reducing agent, 4-8 parts of an air entraining agent and 130-170 parts of water. The concrete is prepared by matching the high geothermal environment tolerant low-heat Portland cement with the fly ash, the high-temperature-resistant aggregate, the water reducing agent and the air entraining agent, so that the early construction performance, the early strength and the high geothermal heat resistance of the concrete in the high geothermal environment are improved; and the problems easily occurring in similar extreme environments of ordinary portland cement and common low-heat cement are effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to low-heat silicate cement concrete for tunnel secondary lining and a preparation method thereof. Background Art

[0002] As an important part of modern transportation construction, the safety and durability of tunnel engineering are directly related to the normal operation of the entire transportation system. However, under certain geological conditions, such as areas with rich geothermal resources or concentrated underground heat sources, tunnel engineering faces severe challenges of high temperature environment. This high geothermal environment not only brings many inconveniences to the construction process, but also puts extremely high demands on the tunnel secondary lining structural materials.

[0003] Conventional tunnel secondary linings widely use general-purpose Portland 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 Portland cement concrete begins to decline significantly. First, high temperature accelerates the cement hydration reaction, resulting in a large amount of heat release in a short period of time, increasing the temperature gradient inside the concrete, and causing thermal stress concentration and cracking problems. Secondly, under high temperature conditions, the stability of cement hydration products such as calcium aluminate and calcium silicate hydrate is affected, and some products may decompose or transform, resulting in reduced concrete strength and durability.

[0004] In order to deal with this problem, the engineering and academic communities have conducted a lot of research, trying to improve the high temperature performance of concrete by optimizing concrete mix ratios, adding mineral admixtures, using high-performance admixtures, etc. Although these methods have achieved results to a certain extent, their effects are still limited under extreme high temperature conditions and cannot meet the high requirements of long-term stability and safety of tunnel secondary linings.

[0005] Based on the above background, the present invention is committed to developing a new type of low-heat silicate cement concrete with high geothermal environment tolerance for tunnel secondary lining and its preparation method. It adopts low-heat silicate cement with high geothermal environment tolerance as the main cementitious material, combined with high temperature resistant aggregate and admixtures, etc., to effectively solve the problem of performance degradation of traditional silicate cement concrete in high temperature environment, provide a more reliable and efficient building material choice for tunnel engineering, improve the durability and safety of tunnel secondary lining, and promote the further development of tunnel engineering technology. Summary of the invention

[0006] The purpose of the present invention is to provide a low-heat silicate cement concrete for tunnel secondary lining, which utilizes high geothermal environment resistant low-heat silicate cement in combination with fly ash, high temperature resistant aggregate, water reducer and air entraining agent to prepare concrete, thereby improving the early construction performance and early strength of concrete in high geothermal environment, and more importantly, its high geothermal resistance is improved, effectively solving the problems that ordinary silicate cement and ordinary low-heat cement are prone to in similar extreme environments, and providing a more reliable and durable building material solution for tunnel secondary lining projects.

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

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

[0009] A low-heat silicate cement concrete for tunnel secondary lining, comprising 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 C 3 S28~35wt.%、C 2 S 40~45wt.%、C 3 A0~4wt.%、C 4 AF 10~15wt.%, MgO 3.0~4.5wt.%, specific surface area 340±10m 2 / kg.

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

[0013] Furthermore, the dry sand is machine-made sand and natural river sand.

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

[0015] Furthermore, the particle size of the high temperature resistant medium aggregate is 10-20 mm, and the high temperature resistant medium aggregate 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 particle size of the high temperature resistant coarse aggregate is 16-31.5 mm, and the high temperature resistant coarse aggregate 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, wherein the natural ore includes andesite and basalt.

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

[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 comprises the following steps:

[0020] S1, weighing the raw materials according to their weight parts and mixing them evenly to obtain a mixture;

[0021] S2, filling the mixture into a concrete curing mold;

[0022] S3, placing the concrete curing mold into which the mixture has been transferred into a steam curing box, and curing at 20° C. to 80° C. to obtain the low-heat Portland cement concrete.

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

[0024] 1. Compared with C in ordinary low heat silicate cement 2 S (dicalcium silicate) size is 20-40μm. Compared with the high geothermal environment resistant low heat silicate cement, C 2 The S size is smaller, at 5-30μm. 2 S mass ratio, C 2 The number of S crystals is greater and increases exponentially, thus increasing C 2 The hydration contact interface of S increases the hydration rate and significantly improves the early construction performance and early strength of concrete in high geothermal environment.

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

[0026] 3. High-temperature resistant materials such as hollow alumina balls, expanded perlite or porous mullite, ceramsite or siliceous aggregate, andesite, basalt, etc. are added to the high-temperature resistant fine, medium and coarse aggregates. The concrete prepared with low-heat silicate cement that can tolerate high geothermal environments has better anti-cracking effect.

[0027] 4. The air-entraining agent has an air-entraining effect, which can reduce the elastic modulus of early concrete, enhance the plasticity of concrete, relieve the plastic shrinkage pressure to a certain extent, and at the same time increase the fluidity and workability of concrete, making it easier to construct and operate. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] In the embodiment of the present invention, the mineral composition of the high geothermal environment resistant low heat silicate cement is C 3 S28~35wt.%、C 2 S 40~45wt.%、C 3 A0~4wt.%、C 4 AF 10~15wt.%, MgO 3.0~4.5wt.%, specific surface area 340±10m 2 / kg.

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

[0031] In the embodiment of the present invention, the dry sand is machine-made sand and natural river sand.

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

[0033] In the embodiment of the present invention, the particle size of the high temperature resistant medium aggregate is 10-20 mm, and the high temperature resistant medium aggregate 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 the embodiment of the present invention, the particle size of the high temperature resistant coarse aggregate is 16-31.5 mm, and the high temperature resistant coarse aggregate 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, wherein the natural ore includes andesite and basalt.

[0035] In the embodiment of the present invention, the water reducing agent is a polycarboxylic acid high performance water reducing agent, and the solid content is 20wt.%

[0036] In the embodiment of the present 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, and its composition is shown in Table 1.

[0039] Table 1

[0040]

[0041]

[0042] The method for preparing low-heat silicate cement concrete in this embodiment comprises 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, filling the mixture into a concrete curing mold;

[0045] S3. Place the concrete curing mold with the mixture in it into a steam curing box and cure it at 80° C. to a corresponding 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, and its composition is shown in Table 2.

[0048] Table 2

[0049] raw material Weight / portion Low-heat silicate cement with high geothermal environment tolerance 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 Air Entraining Agent 4.5 water 142

[0050] The method for preparing low-heat silicate cement concrete in this embodiment comprises 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, filling the mixture into a concrete curing mold;

[0053] S3. Place the concrete curing mold with the mixture in it into a steam curing box and cure it at 80° C. to a corresponding 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, and its composition is shown in Table 3.

[0056] Table 3

[0057] raw material Weight / portion Low-heat silicate cement with high geothermal environment tolerance 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 Air Entraining Agent 4.5 water 142

[0058] The method for preparing low-heat silicate cement concrete in this embodiment comprises 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, filling the mixture into a concrete curing mold;

[0061] S3. Place the concrete curing mold with the mixture in it into a steam curing box and cure it at 80° C. to a corresponding age to obtain low-heat silicate cement concrete.

[0062] Comparative Example 1

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

[0064] Table 4

[0065]

[0066]

[0067] The preparation method of silicate cement concrete in this comparative example comprises 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, filling the mixture into a concrete curing mold;

[0070] S3. Place the concrete curing mold with the mixture in a steam curing box and cure it at 80° C. to a corresponding age to obtain Portland cement concrete.

[0071] Comparative Example 2

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

[0073] Table 5

[0074] raw material Weight / portion 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 gravel 321 Water reducing agent 5.7 Air Entraining Agent 3.9 water 141

[0075] The preparation method of cement concrete in this comparative example comprises 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, filling the mixture into a concrete curing mold;

[0078] S3. Place the concrete curing mold with the mixture in a steam curing box and cure it at 80° C. to a corresponding age to obtain cement concrete.

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

[0080] According to GB / T17671-2021 "Test Method for Cement Mortar Strength (ISO Method)" and JCT 603-2004 Cement Mortar Shrinkage Test Method, the physical properties of ordinary Portland cement, ordinary low-heat cement and high geothermal environment resistant low-heat Portland cement were tested, as shown in Table 6 below:

[0081] Table 6

[0082]

[0083] It can be seen from Table 6 that the MgO content of the high geothermal environment tolerant low-heat silicate cement of the present invention is increased to 4.1%, and the hydration heat is reduced to 208.5 KJ / kg, achieving a synergistic match between early strength and low hydration heat. The combined factors lead to a lower shrinkage rate and better anti-cracking effect, making it more suitable for high geothermal environments.

[0084] 2. Concrete performance testing

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

[0086] Table 7

[0087]

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

[0089] It can be seen from Table 7 that under the condition of 80°C steam curing, the concrete (Examples 1 to 3) prepared by the present invention has a 28d compressive strength of ≧55MPa, and has a better strength retention rate than 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%, and the shrinkage value decrease rate is more than 25% compared with ordinary concrete of the same strength grade; in the concrete early cracking test, the total crack area per unit area is ≤240mm 2 / m 2, the anti-cracking effect is significant and it is more suitable for high geothermal environment.

[0090] Finally, it should be noted that the above embodiments are only preferred embodiments of the present invention to illustrate the technical solutions of the present invention, rather than limiting them, and certainly not limiting the patent scope of the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. In other words, any changes or modifications made to the main design concept and spirit of the present invention that have no substantive significance, and the technical problems they solve are still consistent with the present invention, should be included in the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention in other related technical fields is also included in the patent protection scope of the present invention.

Claims

1. A low-heat silicate cement concrete for tunnel secondary lining, characterized in that: The invention comprises the following raw materials in parts by weight:

2. The low-heat silicate cement concrete for tunnel secondary lining according to claim 1, characterized in that: The mineral composition of the high geothermal environment resistant low heat silicate cement is C3S 28-35wt.%, C2S 40-45wt.%, C3A 0-4wt.%, C4AF 10-15wt.%, MgO 3.0-4.5wt.%, and the specific surface area is 340±10m 2 / kg.

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

4. The low-heat silicate cement concrete for tunnel secondary lining according to claim 1, characterized in that: The dry sand is machine-made sand and natural river sand.

5. The low-heat silicate cement concrete for tunnel secondary lining according to claim 1, characterized in that: The particle size of the high temperature resistant fine aggregate is 5-10 mm, and the high temperature resistant fine aggregate is a mixture of 100-150 parts of crushed stone, 20-60 parts of hollow alumina balls, and 30-70 parts of expanded perlite in parts by mass.

6. The low-heat silicate cement concrete for tunnel secondary lining according to claim 1, characterized in that: The particle size of the high temperature resistant medium aggregate is 10-20 mm, and the high temperature resistant medium aggregate is a mixture of 400-450 parts of crushed stone, 20-70 parts of porous mullite, and 30-70 parts of ceramsite in parts by mass.

7. The low-heat silicate cement concrete for tunnel secondary lining according to claim 1, characterized in that: The particle size of the high temperature resistant coarse aggregate is 16-31.5 mm. The high temperature resistant coarse aggregate is a mixture of 150-200 parts of crushed stone, 40-80 parts of siliceous aggregate and 50-90 parts of natural ore by mass. The natural ore includes andesite and basalt.

8. The low-heat silicate cement concrete for tunnel secondary lining according to claim 1, characterized in that: The water reducer is a polycarboxylic acid high performance water reducer with a solid content of 20 wt.%.

9. The low-heat silicate cement concrete for tunnel secondary lining according to claim 1, characterized in that: The air entraining agent is sodium fatty alcohol sulfate and alkylphenol polyoxyethylene (10) ether.

10. A method for preparing low-heat silicate cement concrete for tunnel secondary lining according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1, weighing the raw materials according to their weight parts and mixing them evenly to obtain a mixture; S2, filling the mixture into a concrete curing mold; S3, placing the concrete curing mold into which the mixture has been transferred into a steam curing box, and curing at 20° C. to 80° C. to obtain the low-heat Portland cement concrete.

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