A high durability lining concrete suitable for environmental sulphate attack and a method of making the same

Abstract

This invention belongs to the field of concrete materials technology and provides a high-durability lining concrete suitable for environmental sulfate attack and its preparation method. The lining concrete comprises cementitious materials, aggregates, lightly calcined magnesium oxide, organic microfibers, lithium salts, water-reducing agents, air-entraining agents, and water; wherein the water-cement ratio is 0.39~0.43. The cementitious materials are obtained by mixing cement with a C3A content ≤2% and a C3S content ≤35% with a calcium-silicon ratio ≤15% and an aluminum-silicon ratio ≤95% with low calcium and high silicon content and low aluminum-silicon content. This lining concrete achieves dual chemical inhibition of sulfate attack from the source by using admixtures with both low calcium and high silicon content and low aluminum and high silicon content; simultaneously, through the synergistic effect of low C3A and low C3S cement and various components, a multi-layered defense system is formed, from reducing reactants, passivating active phases, regulating expansion stress, to blocking transmission channels, significantly improving the durability of concrete in sulfate environments.

Description

Technical Field

[0001] This invention relates to the field of concrete materials technology, and in particular to a high-durability lining concrete suitable for environmental sulfate attack and its preparation method. Background Technology

[0002] In the extreme environment of Northwest China, characterized by "ultra-high concentration sulfate attack coupled with strong alternating wet and dry conditions and intense freeze-thaw cycles," concrete materials face extremely severe durability challenges. Currently, the commonly used anti-sulfate attack measures in engineering mainly rely on the use of sulfate-resistant cement. These technical approaches essentially delay sulfate attack by reducing cement usage or optimizing physical density.

[0003] However, in the extremely high sulfate concentrations of Northwest China, simply reducing cement usage or improving impermeability is insufficient to meet the long-term service requirements of engineering projects. With prolonged service life, unavoidable hydration products in concrete (such as ettringite and gypsum) will continue to react chemically with infiltrating sulfates, leading to expansion cracking and structural deterioration. This protection strategy ignores the decisive influence of the intrinsic chemical composition of the cementitious system on its susceptibility to sulfate attack; its long-term effectiveness decreases significantly in extreme environments, often failing to support long service life requirements.

[0004] Therefore, how to reduce the active material basis of the erosion reaction from a chemical perspective by regulating the calcium and aluminum phase content of cementitious materials, while simultaneously optimizing the pore structure, in order to solve the core problem of the long-term insufficient performance of concrete against sulfate erosion, has become a technical bottleneck that urgently needs to be overcome. Summary of the Invention

[0005] In view of this, the present invention provides a high-durability lining concrete suitable for environmental sulfate erosion and its preparation method, so as to solve the problem of insufficient long-term durability of existing lining concrete in sulfate environment.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a high-durability lining concrete suitable for environmental sulfate attack, comprising the following components by mass: Cementitious material 380~400 kg / m 3 Aggregate 1793~1810 kg / m³ 3 Lightly calcined magnesium oxide: 11.73~31.28 kg / m³ 3 Organic microfibers: 1.95~7.82 kg / m 3 Lithium salts: 1.92~7.82 kg / m³ 3 Water-reducing agent: 3.12~7.82 kg / m³ 3Air-entraining agent: 0.039~0.20 kg / m³ 3 Water 148~172 kg / m 3 .

[0007] Preferably, the cementitious material is obtained by mixing cement and low-calcium high-silicon and low-aluminum high-silicon admixtures; the cement contains ≤2% C3A and ≤35% C3S; the calcium-silicon ratio of the low-calcium high-silicon and low-aluminum high-silicon admixtures is ≤15% and the aluminum-silicon ratio is ≤95%; the low-calcium high-silicon and low-aluminum high-silicon admixtures include one or two of the following: Class F fly ash, silica fume, nano-silica, and metakaolin.

[0008] Preferably, when the low-calcium high-silicon and low-aluminum high-silicon admixture is Class F fly ash and / or metakaolin, the dosage of the low-calcium high-silicon and low-aluminum high-silicon admixture is 25-35%; when the low-calcium high-silicon and low-aluminum high-silicon admixture is silicon powder and / or nano-silica, the dosage of the low-calcium high-silicon and low-aluminum high-silicon admixture is 5-8%.

[0009] Preferably, the cement includes one or more of the following: medium-heat silicate cement, low-heat silicate cement, medium-sulfate resistant cement, and high-sulfate resistant cement.

[0010] Preferably, the aggregate consists of sand and gravel; the mass of the sand accounts for 37-42% of the total mass of the aggregate; the particle size distribution of the gravel is a two-dimensional distribution of 5-20 mm and 20-40 mm, and the mass ratio of 5-20 mm gravel to 20-40 mm gravel is 0.9-1:0.9-1.

[0011] Preferably, the magnesium oxide content in the light-burned magnesium oxide is ≥85%, and the specific surface area of ​​the light-burned magnesium oxide is 150~400 m². 2 / kg; the calcination temperature of the lightly calcined magnesium oxide is 800~1200℃, and the calcination time is 0.5~2 h.

[0012] Preferably, the organic microfibers include one or more of polypropylene fibers, polyvinyl alcohol fibers, polyolefin fibers, and polyoxymethylene fibers; the organic microfibers have a length of 3-12 mm and a diameter of 10-50 μm; the lithium salts include one or more of lithium hydroxide, lithium carbonate, lithium sulfate, lithium acetate, and lithium silicate.

[0013] Preferably, the water-reducing agent includes one or more of polycarboxylate water-reducing agents, lignin sulfonate water-reducing agents, and naphthalene-based water-reducing agents; the air-entraining agent includes triterpenoid saponin air-entraining agents.

[0014] The present invention also provides a method for preparing the above-mentioned high-durability lining concrete suitable for environmental sulfate attack, comprising the following steps: 1) Mix cementitious materials, aggregates, lightly calcined magnesium oxide, organic microfibers, lithium salts and some water-reducing agents to obtain a mixture; 2) Mix the remaining water-reducing agent, air-entraining agent, and water to obtain a mixed solution; 3) Mix the mixture with the solution, and then proceed with molding and curing in sequence to obtain high-durability lining concrete suitable for environmental sulfate attack.

[0015] Preferably, the mass ratio of the partial water-reducing agent in step 1) to the remaining water-reducing agent in step 2) is 5~7:3~5.

[0016] Preferably, the mixing time in steps 1) and 2) is 60-90 s.

[0017] Preferably, the mixing time in step 3) is 120~150 s; the molding is vibratory pressing; the pressure of vibratory pressing is 1~3 MPa, the time is 3~10 s; the curing temperature is 20~45℃, the humidity is ≥95%, and the time is 8~24h.

[0018] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention achieves dual chemical inhibition of sulfate attack at its source by employing an admixture possessing both low-calcium, high-silicon and low-aluminum, high-silicon properties. The low-calcium, high-silicon characteristic of this admixture allows it to efficiently react with calcium hydroxide produced during cement hydration in a pozzolanic reaction, generating a stable low-calcium-silicon ratio hydrated calcium silicate gel. This significantly reduces the calcium hydroxide content in the system, thereby weakening the chemical basis for sulfate reaction to form gypsum. Simultaneously, its low-aluminum, high-silicon characteristic strictly controls the introduction of active aluminum phase, preventing the formation of expansive products such as ettringite due to the admixture's own aluminum phase participating in the reaction. These two properties work synergistically within the same material system, simultaneously inhibiting both gypsum-type and ettringite-type sulfate attack at its source, laying a chemical foundation for the long-term durability of concrete. Furthermore, the application of this admixture can significantly optimize the microporous structure of the lining concrete. Through the filling and refining effect of volcanic ash, it can reduce the total porosity of concrete, increase the proportion of harmless and less harmful pores, and block the transport channels of corrosive ions, thereby further improving the concrete's resistance to sulfate attack at the microstructural level.

[0019] 2. This invention significantly alters the morphology and stability of the aluminum phase in cement hydration products by introducing lithium salts. Lithium ions promote the transformation of hydrated calcium aluminate into a more stable, less expansive lithium-type hydrated calcium aluminate, essentially passivating the chemical reactivity of aluminates and further reducing the risk of forming expansive calcium sulfoaluminate (ettringite). Furthermore, the introduction of lightly calcined magnesium oxide allows hydration to occur in the early stages of concrete hardening (7-28 days), resulting in mild and controllable expansion. This expansion introduces beneficial pre-stress within the concrete, pre-counting some of the tensile stress generated by later sulfate attack. Simultaneously, the large number of uniform, closed, and stable microbubbles introduced by the air-entraining agent effectively absorb and dissipate the expansion stress generated by later sulfate attack, preventing stress concentration and cracking.

[0020] 3. This invention also introduces organic microfibers. The uniformly dispersed organic microfibers form a three-dimensional network structure within the concrete matrix, effectively bridging microcracks generated at various stages, preventing their propagation and interconnection, and blocking or deflecting the transport of corrosive ions such as sulfate ions within the concrete, thereby maintaining the microscopic integrity of the matrix. In summary, the synergistic effect of the various components in the lining concrete described in this invention, from reducing reactants, passivating active phases, regulating expansion stress to blocking transport channels, constitutes a complete, multi-layered defense system, significantly improving the durability of concrete under harsh sulfate environments. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0022] Figure 1 Curves showing the effect of adding different mineral admixtures on the expansion strain of cement mortar; Figure 2 for Figure 1 A magnified view of a portion of the image; Figure 3 A diagram showing the pore size distribution of cement mortar after 12 months of erosion; Figure 4 This is a diagram showing the total porosity of cement mortar after 12 months of erosion. Detailed Implementation

[0023] This invention provides a high-durability lining concrete suitable for environmental sulfate attack, preferably comprising the following components by mass: cementitious material 380~400 kg / m³ 3 Aggregate 1793~1810 kg / m³ 3Lightly calcined magnesium oxide: 11.73~31.28 kg / m³ 3 Organic microfibers: 1.95~7.82 kg / m 3 Lithium salts: 1.92~7.82 kg / m³ 3 Water-reducing agent: 3.12~7.82 kg / m³ 3 Air-entraining agent: 0.039~0.20 kg / m³ 3 Water 148~172 kg / m 3 Further preferred components include the following parts by weight: cementitious material 385~395 kg / m³ 3 Aggregate 1795~1805 kg / m³ 3 Lightly calcined magnesium oxide: 15.64~27.37 kg / m³ 3 Organic microfibers: 3.12~7.04 kg / m 3 Lithium salts: 3.12~7.04 kg / m³ 3 Water-reducing agent: 3.91~7.04 kg / m³ 3 Air-entraining agent: 0.078 ~ 0.16 kg / m³ 3 Water 152.49~168.13 kg / m³ 3 More preferably, it comprises the following components in parts by weight: cementitious material 391 kg / m 3 Aggregate 1798~1800 kg / m³ 3 Lightly calcined magnesium oxide: 19.55~23.46 kg / m³ 3 Organic microfibers 3.91~5.86 kg / m 3 Lithium salts: 3.91~5.86 kg / m³ 3 Water-reducing agent: 4.69~5.86 kg / m³ 3 Air-entraining agent: 0.085~0.12 kg / m³ 3 Water 158~160 kg / m 3 .

[0024] In this invention, the water-cement ratio of the high-durability lining concrete suitable for environmental sulfate attack is preferably 0.39~0.43, more preferably 0.40~0.42, and even more preferably 0.41.

[0025] In this invention, the cementitious material is obtained by mixing cement and a low-calcium, high-silicon, and low-aluminum, high-silicon admixture; the C3A content in the cement is ≤2%, preferably ≤1.8%, more preferably ≤1.6%, and even more preferably ≤1.5%; the C3S content in the cement is ≤35%, preferably ≤32%, more preferably ≤30%, and even more preferably ≤25%; the calcium-to-silicon ratio in the low-calcium, high-silicon, and low-aluminum, high-silicon admixture is ≤15%, preferably ≤12.2%, more preferably ≤5%, and even more preferably ≤1%; the aluminum-to-silicon ratio in the low-calcium, high-silicon, and low-aluminum, high-silicon admixture is ≤95%, preferably ≤89.5%, more preferably ≤50.4%, and even more preferably ≤10%.

[0026] In this invention, the preferred screening process for the low-calcium high-silicon and low-aluminum high-silicon admixtures is as follows: first, admixtures with a calcium-silicon ratio ≤15% are screened out, and then admixtures with an aluminum-silicon ratio ≤95% are screened out from them.

[0027] In this invention, by controlling the C3A content in cement to ≤2% and the C3S content to ≤35%, the heat of hydration of cement can be significantly reduced from the source, and the risk of reaction with sulfate can also be effectively reduced, thereby improving the long-term durability of concrete.

[0028] In this invention, the low-calcium high-silicon and low-aluminum high-silicon admixture includes one or two of the following: F-type fly ash, silica powder, nano-silica, and metakaolin.

[0029] In this invention, when the low-calcium high-silicon and low-aluminum high-silicon admixture is Class F fly ash and / or metakaolin, the dosage of the low-calcium high-silicon and low-aluminum high-silicon admixture is 25-35%, preferably 26-33%, and more preferably 28-30%; when the low-calcium high-silicon and low-aluminum high-silicon admixture is silica powder and / or nano-silica, the dosage of the low-calcium high-silicon and low-aluminum high-silicon admixture is 5-8%, preferably 6-7%; the dosage refers to the mass percentage of the low-calcium high-silicon and low-aluminum high-silicon admixture in the cementitious material.

[0030] In this invention, the cement preferably includes one or more of the following: medium-heat silicate cement, low-heat silicate cement, medium-sulfate resistant cement, and high-sulfate resistant cement.

[0031] In this invention, the aggregate is preferably composed of sand and gravel; the mass of the sand accounts for 37-42% of the total mass of the aggregate, preferably 37.5-41%, more preferably 38-40%, and even more preferably 38.5-39%; the particle size distribution of the gravel is preferably a two-dimensional distribution of 5-20 mm and 20-40 mm; the mass ratio of 5-20 mm gravel to 20-40 mm gravel is 0.9-1:0.9-1, preferably 0.92-0.98:0.92-0.98, and more preferably 0.95:0.95.

[0032] In this invention, the magnesium oxide content in the light-burned magnesium oxide is ≥85%, preferably 85.5~95%, more preferably 86~92%, and even more preferably 88~90%; the specific surface area of ​​the light-burned magnesium oxide is 150~400 m². 2 / kg, preferably 180~380 m 2 / kg, more preferably 200~350 m 2 / kg, more preferably 250~300 m 2 / kg; the calcination temperature of the light-burned magnesium oxide is 800~1200℃, preferably 850~1150℃, more preferably 900~1100℃, and even more preferably 950~1000℃; the calcination time of the light-burned magnesium oxide is 0.5~2 h, preferably 0.6~1.8 h, more preferably 0.8~1.5 h, and even more preferably 1~1.2 h.

[0033] In this invention, the organic microfibers preferably include one or more of polypropylene fibers, polyvinyl alcohol fibers, polyolefin fibers, and polyoxymethylene fibers; the length of the organic microfibers is 3-12 mm, preferably 4-10 mm, more preferably 5-8 mm, and more preferably 6 mm; the diameter of the organic microfibers is 10-50 μm, preferably 15-45 μm, more preferably 20-40 μm, and more preferably 25-30 μm; the lithium salt preferably includes one or more of lithium hydroxide, lithium carbonate, lithium sulfate, lithium acetate, and lithium silicate.

[0034] In this invention, the water-reducing agent preferably includes one or more of polycarboxylate water-reducing agents, lignin sulfonate water-reducing agents, and naphthalene-based water-reducing agents; the air-entraining agent preferably includes triterpenoid saponin air-entraining agents.

[0035] The present invention also provides a method for preparing the above-mentioned high-durability lining concrete suitable for environmental sulfate attack, comprising the following steps: 1) Mix cementitious materials, aggregates, lightly calcined magnesium oxide, organic microfibers, lithium salts and some water-reducing agents to obtain a mixture; 2) Mix the remaining water-reducing agent, air-entraining agent, and water to obtain a mixed solution; 3) Mix the mixture with the solution, and then proceed with molding and curing in sequence to obtain high-durability lining concrete suitable for environmental sulfate attack.

[0036] In this invention, the mass ratio of the partial water-reducing agent in step 1) to the remaining water-reducing agent in step 2) is 5~7:3~5, preferably 5.5~6.5:3.5~4.5, and more preferably 6:4.

[0037] In this invention, the mixing time in steps 1) and 2) is independently 60-90 s, preferably 65-85 s, more preferably 70-80 s, and even more preferably 75 s.

[0038] In this invention, the mixing time in step 3) is 120-150 s, preferably 125-145 s, more preferably 130-140 s, and even more preferably 135 s; the molding is preferably vibratory pressing; the pressure of vibratory pressing is 1-3 MPa, preferably 1.2-2.8 MPa, more preferably 1.5-2.5 MPa, and even more preferably 1.8-2 MPa; the time of vibratory pressing is 3-10 s, preferably 4-9 s, more preferably 5-8 s, and even more preferably 6-7 s; the curing temperature is 20-45℃, preferably 22-42℃, more preferably 25-40℃, and even more preferably 30-35℃; the curing humidity is ≥95%, preferably 95.5-98%, more preferably 96-97.5%, and even more preferably 96.5-97%; the curing time is 8-24 h, preferably 8.5-22 h, and even more preferably 9-20 h. h, more preferably 10 to 15 h.

[0039] In this invention, the chemical composition of the low-calcium high-silicon and low-aluminum high-silicon admixtures and conventional admixtures is shown in Table 1: Table 1 Chemical composition of low-calcium high-silicon and low-aluminum high-silicon admixtures and conventional mineral admixtures

[0040] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0041] Example 1

[0042] In this embodiment, the high-durability lining concrete suitable for environmental sulfate attack comprises the following components in parts by weight: cementitious material 391 kg / m³ 3 Aggregate 1793 kg / m³ 3 Lightly calcined magnesium oxide 11.73 kg / m³ 3 Organic microfibers 1.955 kg / m 3 Lithium salt 1.955 kg / m 3 Water-reducing agent 3.128 kg / m 3 0.039 kg / m³ of entraining agent 3 160 kg / m³ of water 3 ; The cementitious material consists of 293 kg / m³ of medium-sulfate resistant cement with a C3A content of 2% and a C3S content of 35%. 3 Class F fly ash with a calcium-to-silicon ratio of 12.2% and an aluminum-to-silicon ratio of 50.4% (98 kg / m³) 3 The mixture is obtained; The aggregate consists of sand and gravel, with sand accounting for 42% of the total aggregate mass. The gravel has a two-stage particle size distribution of 5-20 mm and 20-40 mm, with a mass ratio of 5-20 mm gravel to 20-40 mm gravel of 1:0.9. The magnesium oxide content in light-burned magnesium oxide is 85%, and the specific surface area of ​​light-burned magnesium oxide is 150 m². 2 / kg, calcination temperature is 800℃, calcination time is 2 h; The organic microfibers are polypropylene fibers with a length of 3 mm and a diameter of 10 μm; The lithium salt is lithium carbonate; The water-reducing agent is a polycarboxylate water-reducing agent; The air-entraining agent is a triterpenoid saponin air-entraining agent.

[0043] The method for preparing high-durability lining concrete suitable for environmental sulfate attack in this embodiment includes the following steps: 1) Mix the cementitious materials, aggregates, lightly calcined magnesium oxide, polypropylene fiber, lithium carbonate and part of the polycarboxylate superplasticizer, and stir for 60 s to obtain the mixture; 2) Mix the remaining polycarboxylate superplasticizer, triterpenoid saponin air-entraining agent, and water, and stir for 60 seconds to obtain a mixed solution; 3) Mix the mixture with the mixing solution (the mass ratio of part of the polycarboxylate superplasticizer in the mixture to the remaining polycarboxylate superplasticizer in the mixing solution is 5:5), stir for 120 s, then vibrate and press at 1 MPa for 10 s, and then cure at 20℃ and 95% humidity for 24 h to obtain high-durability lining concrete suitable for environmental sulfate attack.

[0044] Example 2

[0045] In this embodiment, the high-durability lining concrete suitable for environmental sulfate attack comprises the following components in parts by weight: cementitious material 391 kg / m³ 3 Aggregate 1810 kg / m³ 3 Lightly calcined magnesium oxide 19.55 kg / m³ 3 Organic microfibers 3.91 kg / m 3 Lithium salt 3.91 kg / m 3 Water-reducing agent 4.69 kg / m 3 0.03 kg / m³ of entraining agent 3 160 kg / m³ of water3 ; The cementitious material consists of 371 kg / m³ of medium-heat silicate cement with a C3A content of 1.8% and a C3S content of 33%. 3 20 kg / m³ of silicon powder with a calcium-to-silicon ratio of 0.4% and an aluminum-to-silicon ratio of 0.4%. 3 The mixture is obtained; The aggregate consists of sand and gravel, with sand accounting for 42% of the total aggregate mass. The gravel has a two-stage particle size distribution of 5-10 mm and 10-25 mm, with a mass ratio of 5-10 mm gravel to 10-25 mm gravel of 1:0.9. The magnesium oxide content in light-burned magnesium oxide is 88%, and the specific surface area of ​​light-burned magnesium oxide is 300 m². 2 / kg, calcination temperature is 950℃, calcination time is 1 h; The organic microfibers are polyvinyl alcohol fibers with a length of 6 mm and a diameter of 40 μm; The lithium salt is lithium sulfate; The water-reducing agent is a polycarboxylate water-reducing agent; The air-entraining agent is a triterpenoid saponin air-entraining agent.

[0046] The method for preparing high-durability lining concrete suitable for environmental sulfate attack in this embodiment includes the following steps: 1) Mix the cementitious materials, aggregates, lightly calcined magnesium oxide, polypropylene fiber, lithium carbonate and part of the polycarboxylate superplasticizer, and stir for 70 seconds to obtain the mixture; 2) Mix the remaining polycarboxylate superplasticizer, triterpenoid saponin air-entraining agent, and water, and stir for 70 seconds to obtain a mixed solution; 3) Mix the mixture with the mixing solution (the mass ratio of part of the polycarboxylate superplasticizer in the mixture to the remaining polycarboxylate superplasticizer in the mixing solution is 6:4), stir for 130 s, then vibrate and press at 2 MPa for 6 s, and then cure at 30℃ and 96% humidity for 15 h to obtain high-durability lining concrete suitable for environmental sulfate attack.

[0047] Example 3

[0048] In this embodiment, the high-durability lining concrete suitable for environmental sulfate attack comprises the following components in parts by weight: cementitious material 391 kg / m³ 3 Aggregate 1810 kg / m³ 3 Lightly calcined magnesium oxide 23.46 kg / m³ 3 Organic microfibers 5.86 kg / m 3 Lithium salt 5.86 kg / m 3 Water-reducing agent 5.86 kg / m 3 Entraining agent 0.1173 kg / m³3 160 kg / m³ of water 3 ; The cementitious material consists of 371 kg / m³ high sulfate-resistant cement with a C3A content of 1.5% and a C3S content of 32%. 3 Nano-silica with a calcium-to-silicon ratio of 0.02% (20 kg / m³) 3 The mixture is obtained; The aggregate consists of sand and gravel, with sand accounting for 42% of the total aggregate mass. The gravel has a two-stage particle size distribution of 5-10 mm and 10-25 mm, with a mass ratio of 5-10 mm gravel to 10-25 mm gravel of 0.9:1. The magnesium oxide content in light-burned magnesium oxide is 90%, and the specific surface area of ​​light-burned magnesium oxide is 400 m². 2 / kg, calcination temperature is 1200℃, calcination time is 0.5 h; The organic microfibers are polypropylene fibers with a length of 10 mm and a diameter of 50 μm; The lithium salt is lithium silicate; The water-reducing agent is a polycarboxylate water-reducing agent; The air-entraining agent is a triterpenoid saponin air-entraining agent.

[0049] The method for preparing high-durability lining concrete suitable for environmental sulfate attack in this embodiment includes the following steps: 1) Mix the cementitious materials, aggregates, lightly calcined magnesium oxide, polypropylene fiber, lithium carbonate and part of the polycarboxylate superplasticizer, and stir for 90 s to obtain the mixture; 2) Mix the remaining polycarboxylate superplasticizer, triterpenoid saponin air-entraining agent, and water, and stir for 90 seconds to obtain a mixed solution; 3) Mix the mixture with the mixing solution (the mass ratio of part of the polycarboxylate superplasticizer in the mixture to the remaining polycarboxylate superplasticizer in the mixing solution is 7:3), stir for 150 s, then vibrate and press for 3 s at 3 MPa, and then cure at 45℃ and 97% humidity for 8 h to obtain high-durability lining concrete suitable for environmental sulfate attack.

[0050] Example 4

[0051] In this embodiment, the high-durability lining concrete suitable for environmental sulfate attack comprises the following components in parts by weight: cementitious material 391 kg / m³ 3 Aggregate 1793 kg / m³ 3 Lightly calcined magnesium oxide 11.73 kg / m³ 3 Organic microfibers 1.955 kg / m 3 Lithium salt 1.955 kg / m 3 Water-reducing agent 3.128 kg / m3 0.039 kg / m³ of entraining agent 3 160 kg / m³ of water 3 ; The cementitious material consists of 293 kg / m³ of medium-sulfate resistant cement with a C3A content of 2% and a C3S content of 30%. 3 Metakaolin with a calcium-to-silicon ratio of 1.0% and an aluminum-to-silicon ratio of 89.5% (98 kg / m³) 3 The mixture is obtained; The aggregate consists of sand and gravel, with sand accounting for 42% of the total aggregate mass. The gravel has a two-stage particle size distribution of 5-20 mm and 20-40 mm, with a mass ratio of 5-20 mm gravel to 20-40 mm gravel of 1:0.9. The magnesium oxide content in light-burned magnesium oxide is 85%, and the specific surface area of ​​light-burned magnesium oxide is 150 m². 2 / kg, calcination temperature is 800℃, calcination time is 2 h; The organic microfibers are polypropylene fibers with a length of 3 mm and a diameter of 10 μm; The lithium salt is lithium carbonate; The water-reducing agent is a polycarboxylate water-reducing agent; The air-entraining agent is a triterpenoid saponin air-entraining agent.

[0052] The method for preparing high-durability lining concrete suitable for environmental sulfate attack in this embodiment includes the following steps: 1) Mix the cementitious materials, aggregates, lightly calcined magnesium oxide, polypropylene fiber, lithium carbonate and part of the polycarboxylate superplasticizer, and stir for 60 s to obtain the mixture; 2) Mix the remaining polycarboxylate superplasticizer, triterpenoid saponin air-entraining agent, and water, and stir for 60 seconds to obtain a mixed solution; 3) Mix the mixture with the mixing solution (the mass ratio of part of the polycarboxylate superplasticizer in the mixture to the remaining polycarboxylate superplasticizer in the mixing solution is 5:5), stir for 120 s, then vibrate and press at 1 MPa for 10 s, and then cure at 20℃ and 95% humidity for 24 h to obtain high-durability lining concrete suitable for environmental sulfate attack.

[0053] Example 5

[0054] In this embodiment, the high-durability lining concrete suitable for environmental sulfate attack comprises the following components in parts by weight: cementitious material 391 kg / m³ 3 Aggregate 1793 kg / m³ 3 Lightly calcined magnesium oxide 11.73 kg / m³ 3 Organic microfibers 1.955 kg / m 3 Lithium salt 1.955 kg / m3 Water-reducing agent 3.128 kg / m 3 0.039 kg / m³ of entraining agent 3 160 kg / m³ of water 3 ; The cementitious material consists of 293 kg / m³ of medium-sulfate resistant cement with a C3A content of 1% and a C3S content of 25%. 3 Class F fly ash with a calcium-to-silicon ratio of 12.2% and an aluminum-to-silicon ratio of 50.4% (98 kg / m³) 3 The mixture is obtained; The aggregate consists of sand and gravel, with sand accounting for 42% of the total aggregate mass. The gravel has a two-stage particle size distribution of 5-20 mm and 20-40 mm, with a mass ratio of 5-20 mm gravel to 20-40 mm gravel of 1:0.9. The magnesium oxide content in light-burned magnesium oxide is 85%, and the specific surface area of ​​light-burned magnesium oxide is 150 m². 2 / kg, calcination temperature is 800℃, calcination time is 2 h; The organic microfibers are polypropylene fibers with a length of 3 mm and a diameter of 10 μm; The lithium salt is lithium carbonate; The water-reducing agent is a polycarboxylate water-reducing agent; The air-entraining agent is a triterpenoid saponin air-entraining agent.

[0055] The method for preparing high-durability lining concrete suitable for environmental sulfate attack in this embodiment includes the following steps: 1) Mix the cementitious materials, aggregates, lightly calcined magnesium oxide, polypropylene fiber, lithium carbonate and part of the polycarboxylate superplasticizer, and stir for 60 s to obtain the mixture; 2) Mix the remaining polycarboxylate superplasticizer, triterpenoid saponin air-entraining agent, and water, and stir for 60 seconds to obtain a mixed solution; 3) Mix the mixture with the mixing solution (the mass ratio of part of the polycarboxylate superplasticizer in the mixture to the remaining polycarboxylate superplasticizer in the mixing solution is 5:5), stir for 120 s, then vibrate and press at 1 MPa for 10 s, and then cure at 20℃ and 95% humidity for 24 h to obtain high-durability lining concrete suitable for environmental sulfate attack.

[0056] Comparative Example 1

[0057] The only difference between this comparative example and Example 1 is that no admixtures were added to the cementitious material. The specific composition is: cement 390 kg / m³. 3 Aggregate 1814 kg / m³ 3 Lightly calcined magnesium oxide 11.73 kg / m³ 3 Organic microfibers 1.955 kg / m3 Lithium salt 1.955 kg / m 3 Water-reducing agent 3.128 kg / m 3 0.039 kg / m³ of entraining agent 3 160 kg / m³ of water 3 ; Other components and preparation conditions remain unchanged.

[0058] Comparative Example 2

[0059] The only difference between this comparative example and Example 1 is that the F-type fly ash in the cementitious material is replaced with C-type fly ash, while the other components and preparation conditions remain unchanged.

[0060] Comparative Example 3

[0061] The only difference between this comparative example and Example 1 is that the F-type fly ash in the cementitious material is replaced with slag powder, while the other components and preparation conditions remain unchanged.

[0062] Comparative Example 4

[0063] The only difference between this comparative example and Example 1 is that the type F fly ash in the cementitious material is replaced with phosphorus slag powder, while the other components and preparation conditions remain unchanged.

[0064] Comparative Example 5

[0065] The only difference between this comparative example and Example 5 is that the C3S content in the cement is 45%, while the other components and preparation conditions remain unchanged.

[0066] The amounts of cementitious materials, water, and aggregates used in the preparation of lining concrete in Examples 1-4 and Comparative Examples 1-4 are shown in Table 2.

[0067] Table 2. Cementitious materials, water, and aggregates in lining concrete.

[0068] The lining concrete prepared in Examples 1-4 and Comparative Examples 1-4 were tested for sulfate resistance (28 days) according to the test method of GB / T 50082-2024. The results are shown in Table 3.

[0069] Table 3 Results of sulfate resistance grade of lining concrete

[0070] Table 3 shows that the sulfate resistance grade of concrete without admixtures is only KS90. Adding F-type fly ash, C-type fly ash, silica fume, nano-silica, or metakaolin all help improve this grade. In contrast, the sulfate resistance grade of concrete with admixtures such as slag powder and phosphorus slag powder is lower. Furthermore, a comparison between Example 5 and Comparative Example 5 shows that the C3S content and C3A content of cement are equally important; excessively high C3S content significantly reduces the overall sulfate resistance grade of the concrete material.

[0071] In addition, although Class C fly ash can improve the sulfate resistance of concrete, its calcium-silicon ratio is 56.6%, and its calcium content is high. This will lead to a significant increase in the calcium phase in the cementitious system that is easy to react with sulfate. Chemically speaking, this provides more material basis for the formation of expansive products such as ettringite and gypsum. In the long term, under ultra-high concentration sulfate environment, it may exacerbate the risk of erosion and damage, which is contrary to the solution of this invention.

[0072] In addition, this invention also investigated the effect of adding different mineral admixtures on the expansion strain of cement mortar (without added aggregate).

[0073] The specific testing method is as follows: Cement mortar specimens were prepared according to a water:cementing material:standard sand mass ratio of 1:3:6. The dosage of each mineral admixture was strictly adhered to the proportions shown in Table 2. After molding, the carefully prepared molds were transferred to a humid room for curing. The temperature of this humid room was precisely controlled at 20±2℃, and the relative humidity was not less than 90%. The curing time under this environment was 24 hours.

[0074] After the 24-hour curing period, the specimen was removed from the mold and then placed in water at a temperature of 20±2℃ for another 27 days of curing. After completing the 27-day water curing, the initial length of the specimen was accurately recorded, which serves as an important baseline data for subsequent testing and analysis.

[0075] After recording the initial length, the specimens were completely immersed in a 5% sodium sulfate (Na2SO4) solution at 20±2℃ for 12 months of curing. During this curing process, no reinforcement measures were taken on the specimen surface to ensure the accuracy and reliability of the test results. Meanwhile, to ensure the stability and effectiveness of the sodium sulfate solution concentration, the solution was replaced monthly until the completion of this research project.

[0076] The specimen size used to measure the expansion strain of cement mortar is 25 mm × 25 mm × 280 mm. The calculation method for the expansion strain of cement mortar is shown in the following formula:

[0077] In the formula, Es L represents the expansion strain of the cement mortar, and L0 represents the initial length of the cement mortar specimen before contact with the sulfate solution. t The length of the specimen after exposure to sulfate solution for time t is given. Expansion strain data were recorded monthly between 1 and 12 months. The expansion of three cement mortar specimens was measured at each specified time point, and the average value was taken as the final result.

[0078] The test results are shown in Table 4 and Figures 1-2 As shown, where, Figure 1 Curves showing the effect of adding different mineral admixtures on the expansion strain of cement mortar; Figure 2 for Figure 1 A magnified view of a portion of the image.

[0079] Table 4. Expansion strain results of cement mortar with different mineral admixtures (×10) -6 )

[0080] Note: Cement refers to the test results of cement mortar specimens without the addition of mineral admixtures.

[0081] From Table 4 and Figures 1-2 It can be seen that the low-calcium, high-silicon and low-aluminum, high-silicon admixtures selected in this invention exhibit significant expansion inhibition effects under sulfate attack conditions. Among them, silicon powder and nano-silica show the best performance at a doping level of 5%, with expansion strains of only 28 × 10⁻⁶ after 12 months. -6 and 23×10 -6 Compared to pure cement's 5621×10 -6 The expansion strain was reduced by nearly 99%, attributed to its extremely low calcium-to-silicon ratio (<1%) and aluminum-to-silicon ratio (<1%). This allows it to efficiently consume the calcium hydroxide produced during cement hydration, inhibiting gypsum-type expansion at its source, while introducing almost no active aluminum phase, thus avoiding the formation of ettringite. The expansion strain of Class F fly ash (25% admixture) is 480 × 10⁻⁶. -6 The calcium-to-silicon ratio is significantly lower than that of pure cement and high-calcium admixtures. Its calcium-to-silicon ratio of 12.2% and aluminum-to-silicon ratio of 50.4% meet the low-calcium and low-aluminum requirements of this invention, achieving a dual balance between calcium hydroxide consumption and active aluminum control. The expansion strain of metakaolin (25% admixture) is 500 × 10⁻⁶. -6 Although slightly higher than Class F fly ash, it is still far lower than pure cement. Its low calcium content (calcium-silicon ratio 1.0%) dominates its sulfate resistance, while its relatively high aluminum content (aluminum-silicon ratio 89.5%) is close to the upper limit of this invention, indicating that the dosage needs to be controlled to avoid the slight expansion risk caused by the aluminum phase. In stark contrast, high-calcium admixtures such as Class C fly ash (521×10⁻⁶) have lower calcium content. -6 ), slag powder (5900×10 -6 ) and phosphorus slag powder (4500×10 -6Because the calcium-silicon ratio is too high (56.6%~111.3%), it cannot effectively consume calcium hydroxide and even introduces a large amount of active aluminum, resulting in a significant increase in expansion strain, which even exceeds that of pure cement. This fully verifies the necessity of the present invention to screen admixtures by limiting the calcium-silicon ratio to ≤15% and the aluminum-silicon ratio to ≤95%.

[0082] Furthermore, according to relevant literature, pores in hardened cement paste can be classified into three categories based on pore size: harmless pores (pore size less than 20 nm), slightly harmful pores (pore size 20~50 nm), and harmful pores (pore size greater than 50 nm). The pore structure analysis of this invention shows that, as... Figures 3-4 As shown, where, Figure 3 This is a diagram showing the pore size distribution of cement mortar after 12 months of erosion. Figure 4 This is a graph showing the total porosity of cement mortar after 12 months of erosion. Adding mineral admixtures with a calcium-silicon ratio ≤15% and an aluminum-silicon ratio ≤95% significantly increases the proportion of harmless and less harmful pores, while significantly reducing the proportion of harmful pores and effectively controlling the total porosity. Conversely, when mineral admixtures with a calcium-silicon ratio >15% are added, both the proportion of harmful pores and the total porosity increase significantly. These differences reveal, at the microscopic level, the intrinsic mechanism by which the calcium-silicon ratio and aluminum-silicon ratio in the mineral admixtures are determined.

[0083] In summary, Table 4 and Figures 1-4 This strongly demonstrates that the technical solution of this invention can inhibit sulfate erosion from the chemical source, thereby significantly improving the long-term durability of concrete.

[0084] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-durability lining concrete suitable for environmental sulfate attack, characterized in that, The components include the following masses: Cementitious material 380~400 kg / m 3 Aggregate 1793~1810 kg / m³ 3 Lightly calcined magnesium oxide: 11.73~31.28 kg / m³ 3 Organic microfibers: 1.95~7.82 kg / m 3 Lithium salts: 1.92~7.82 kg / m³ 3 Water-reducing agent: 3.12~7.82 kg / m³ 3 Air-entraining agent: 0.039~0.20 kg / m³ 3 Water 148~172 kg / m 3 ; The cementitious material is obtained by mixing cement and low-calcium, high-silicon and low-aluminum, high-silicon admixtures; The cement contains ≤2% C3A and ≤35% C3S. The calcium-to-silicon ratio and aluminum-to-silicon ratio in the low-calcium, high-silicon and low-aluminum, high-silicon admixture are ≤15% and ≤95%, respectively. The low-calcium high-silicon and low-aluminum high-silicon admixture includes one or two of the following: F-type fly ash, silica powder, nano-silica, and metakaolin. When the low-calcium high-silicon and low-aluminum high-silicon admixture is Class F fly ash and / or metakaolin, the dosage of the low-calcium high-silicon and low-aluminum high-silicon admixture is 25-35%; When the low-calcium high-silicon and low-aluminum high-silicon admixture is silicon powder and / or nano-silica, the dosage of the low-calcium high-silicon and low-aluminum high-silicon admixture is 5-8%.

2. The high-durability lining concrete suitable for environmental sulfate attack according to claim 1, characterized in that, The cement includes one or more of the following: medium-heat silicate cement, low-heat silicate cement, medium-sulfate resistant cement, and high-sulfate resistant cement.

3. The high-durability lining concrete suitable for environmental sulfate attack according to claim 2, characterized in that, The aggregate consists of sand and gravel; the sand accounts for 37-42% of the total mass of the aggregate. The gravel has a particle size distribution of 5~20 mm and 20~40 mm, and the mass ratio of 5~20 mm gravel to 20~40 mm gravel is 0.9~1:0.9~1.

4. A high-durability lining concrete suitable for environmental sulfate attack according to any one of claims 1 to 3, characterized in that, The magnesium oxide content in the light-burned magnesium oxide is ≥85%, and the specific surface area of ​​the light-burned magnesium oxide is 150~400 m². 2 / kg; The calcination temperature of the lightly calcined magnesium oxide is 800~1200℃, and the calcination time is 0.5~2 h.

5. A high-durability lining concrete suitable for environmental sulfate attack according to claim 4, characterized in that, The organic microfibers include one or more of polypropylene fibers, polyvinyl alcohol fibers, polyolefin fibers, and polyoxymethylene fibers; the organic microfibers have a length of 3-12 mm and a diameter of 10-50 μm. The lithium salt includes one or more of lithium hydroxide, lithium carbonate, lithium sulfate, lithium acetate, and lithium silicate.

6. A high-durability lining concrete suitable for environmental sulfate attack according to claim 5, characterized in that, The water-reducing agent includes one or more of polycarboxylate water-reducing agents, lignin sulfonate water-reducing agents, and naphthalene-based water-reducing agents; The air-entraining agent includes triterpenoid saponin air-entraining agents.

7. A method for preparing high-durability lining concrete suitable for environmental sulfate attack, as described in any one of claims 1 to 6, characterized in that, Includes the following steps: 1) Mix cementitious materials, aggregates, lightly calcined magnesium oxide, organic microfibers, lithium salts and some water-reducing agents to obtain a mixture; 2) Mix the remaining water-reducing agent, air-entraining agent, and water to obtain a mixed solution; 3) Mix the mixture with the solution, and then proceed with molding and curing in sequence to obtain high-durability lining concrete suitable for environmental sulfate attack.

8. The method for preparing high-durability lining concrete suitable for environmental sulfate attack according to claim 7, characterized in that, The mass ratio of the water-reducing agent mentioned in step 1) to the remaining water-reducing agent mentioned in step 2) is 5~7:3~5.

9. A method for preparing high-durability lining concrete suitable for environmental sulfate attack according to claim 8, characterized in that, The mixing time described in steps 1) and 2) is 60-90 s.

10. A method for preparing high-durability lining concrete suitable for environmental sulfate attack according to claim 9, characterized in that, The mixing time described in step 3) is 120~150 s; The forming process is vibratory compression molding; the pressure of the vibratory compression molding is 1~3 MPa, and the time is 3~10 s; The curing temperature is 20~45℃, the humidity is ≥95%, and the time is 8~24 hours.

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