High-activity silicon-calcium slag-based mineral admixture as well as preparation method and application thereof

Abstract

The invention provides a high-activity silico-calcium slag-based mineral admixture, a preparation method and application, the method comprises the following steps: pretreating original silico-calcium slag and original high-titanium heavy slag to obtain the silico-calcium slag-based mineral admixture, and carrying out salt freezing circulation activation on the silico-calcium slag-based mineral admixture by using sodium sulfate to obtain the high-activity silico-calcium slag-based mineral admixture. Carrying out mechanical activation dispersion on the activated mixture of the swollen calcium silicate slag and the high-titanium heavy slag by utilizing dried anhydrite and sodium dodecyl sulfate, so as to obtain the high-activity calcium silicate slag-based mineral admixture, wherein the activated mixture of the swollen calcium silicate slag and the high-titanium heavy slag is subjected to mechanical activation dispersion on the activated mixture of the swollen calcium silicate slag and the high-titanium heavy slag by utilizing dried anhydrite and sodium dodecyl sulfate; according to the invention, comprehensive utilization of the silicon-calcium slag and the high-titanium heavy slag is realized, a new direction is provided for application of the silicon-calcium slag and the high-titanium heavy slag, and the preparation cost of the marine concrete can be greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a high-activity calcium-silicon slag-based mineral admixture, a preparation method and application thereof. Background Art

[0002] Marine concrete, also known as ocean concrete, refers to a high-performance concrete used in marine engineering. Chloride ions, magnesium ions and sulfate ions in seawater and sea breeze can easily penetrate into the interior of the concrete through the micro-cracks and gaps in the concrete. Chloride ions will corrode the steel bars after penetrating into them, while magnesium ions and sulfate ions will cause the concrete to expand and crack. As a result, marine engineering has higher durability requirements for the concrete used.

[0003] Mineral admixtures, such as slag powder and fly ash, as the main components of marine concrete, can reduce the amount of cement on the one hand, and improve the durability of marine concrete on the other hand. However, with the development of my country's modern infrastructure and the formulation and implementation of marine resource development strategies, the number of engineering construction projects such as cross-sea bridges, cross-sea tunnels, and offshore deep-water ports in various regions has increased, resulting in an increasing shortage of mineral admixture resources suitable for preparing marine concrete.

[0004] Calcium-silicon slag is a by-product produced in the process of extracting alumina from high-aluminum fly ash, coal gangue, and bauxite. About 2.8-3.0 tons of calcium-silicon slag are produced for every 1.0 ton of alumina. The main chemical components of the calcium-silicon slag produced by the fly ash soda lime sintering method to produce alumina are CaO and SiO2, and the content of the main phase β-C2S exceeds 70%. The untreated calcium-silicon slag has a high alkalinity and is difficult to reuse. If the calcium-silicon slag is piled up in the open air, it is easy to cause pollution to the surrounding environment and groundwater resources. In order to solve the above problems, a calcium-silicon slag yard is usually built near the factory and anti-seepage treatment is carried out. This not only increases the project investment and occupies a large amount of land, but also causes excessive alkali consumption in alumina production, thereby affecting the economic indicators of the entire production process.

[0005] High-titanium heavy slag is an inorganic material mainly composed of minerals such as titanium pyroxene and perovskite, which is formed by natural cooling or water cooling of molten slag produced during the smelting of vanadium-titanium magnetite in a blast furnace. Among them, the porosity of high-titanium heavy slag formed by natural cooling is relatively small, while the porosity of high-titanium heavy slag formed by water cooling is relatively large and mostly honeycomb-shaped. Due to its porous structure, it has a water absorption rate much higher than that of sand and stone used in ordinary concrete. When it is used in concrete preparation, it will greatly affect the working performance and mechanical properties of the concrete, resulting in its low utilization efficiency in concrete. Summary of the invention

[0006] In view of the above situation, the main object of the present invention is to propose a highly active calcium silicate slag-based mineral admixture, a preparation method and an application thereof to solve the above technical problems.

[0007] The present invention proposes a highly active calcium silicate slag-based mineral admixture, which includes as-received calcium silicate slag, as-received high-titanium heavy slag, dried anhydrite and sodium dodecyl sulfonate.

[0008] The as-received calcium silicate slag and as-received high-titanium heavy slag are pretreated to obtain a calcium silicate slag-based mineral admixture; the calcium silicate slag-based mineral admixture is activated by salt freeze-thaw cycles using sodium sulfate to obtain an activated mixture of swollen calcium silicate slag and high-titanium heavy slag; the activated mixture of swollen calcium silicate slag and high-titanium heavy slag is mechanically activated and dispersed using dried anhydrite and sodium dodecyl sulfonate to obtain a highly active calcium silicate slag-based mineral admixture.

[0009] Among them, the mass ratio of the activated mixture of swollen calcium silicate slag and high-titanium heavy slag, dried anhydrite and sodium dodecyl sulfonate is 1: 0.02 - 0.05: 0.00015 - 0.0003.

[0010] The present invention proposes a preparation method of a highly active calcium silicate slag-based mineral admixture, which is characterized in that the method includes the following steps:

[0011] Step 1: Mix the as-received calcium silicate slag and as-received high-titanium heavy slag, and soak them in water to obtain a soaking solution. Add dilute sulfuric acid to the soaking solution, let it stand, and test the pH value of the supernatant after standing to obtain a standing slurry.

[0012] Step 2: Add sodium sulfate to the standing slurry to obtain a sodium sulfate mixture. Soak the sodium sulfate mixture at room temperature, freeze it after soaking, and then perform cyclic treatment. After the cycle is completed, wash, filter and dry to obtain an activated mixture of swollen calcium silicate slag and high-titanium heavy slag.

[0013] Step 3: Mix the activated mixture of swollen calcium silicate slag and high-titanium heavy slag, dried anhydrite and sodium dodecyl sulfonate, and put the mixture into a ball mill for ball milling to obtain a highly active calcium silicate slag-based mineral admixture.

[0014] The present invention also proposes an application of a highly active calcium silicate slag-based mineral admixture. A highly active calcium silicate slag-based mineral admixture prepared by using the preparation method of a highly active calcium silicate slag-based mineral admixture described above is used in marine engineering concrete.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] 1. The water demand of the calcium silicate slag-based mineral admixture prepared by the present invention is small, the mortar fluidity ratio can be above 95%, and the 28-day compressive activity index is above 90%. At the same time, it can replace Class I fly ash for preparing marine concrete. When it replaces Class I fly ash to prepare marine concrete, the mechanical properties, chloride ion penetration resistance and sulfate erosion resistance of the concrete will be greatly improved.

[0017] 2. The present invention realizes the comprehensive utilization of calcium silicate slag and high-titanium heavy slag, provides a new direction for the application of calcium silicate slag and high-titanium heavy slag, and can greatly reduce the preparation cost of marine concrete.

[0018] The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the differential curve graph a of the pore size distribution obtained by mercury intrusion porosimetry for pore structure testing;

[0020] Figure 2 is the integral curve graph b of the pore size distribution obtained by mercury intrusion porosimetry for pore structure testing;

[0021] Figure 3 is the graph of the hydration of β-C2S in the calcium silicate slag-based mineral admixture obtained in Example 2 and the generation of more fine-grained C-S-H gels by the reaction of active SiO2 with Ca(OH)2;

[0022] Figure 4 is the graph of the participation of the mineral admixture obtained in Comparative Example 3 in the cement hydration reaction. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present invention and should not be construed as limiting the present invention.

[0024] Referring to the following description and drawings, these and other aspects of the embodiments of the present invention will be clear. In these descriptions and drawings, some specific embodiments of the embodiments of the present invention are specifically disclosed to represent some ways of implementing the principles of the embodiments of the present invention, but it should be understood that the scope of the embodiments of the present invention is not limited thereto.

[0025] Example 1

[0026] A high-activity calcium-silicon slag-based mineral admixture, the mineral admixture comprising as-received calcium-silicon slag, as-received high-titanium heavy slag, dried anhydrite and sodium dodecyl sulfonate;

[0027] The as-received calcium-silicon slag and as-received high-titanium heavy slag are pretreated to obtain a calcium-silicon slag-based mineral admixture. The calcium-silicon slag-based mineral admixture is activated by salt freeze-thaw cycles using sodium sulfate to obtain an activated mixture of swollen calcium-silicon slag and high-titanium heavy slag. The activated mixture of swollen calcium-silicon slag and high-titanium heavy slag is mechanically activated and dispersed using dried anhydrite and sodium dodecyl sulfonate to obtain a high-activity calcium-silicon slag-based mineral admixture;

[0028] Wherein, the mass ratio of the activated mixture of swollen calcium-silicon slag and high-titanium heavy slag, dried anhydrite and sodium dodecyl sulfonate is 1: 0.02 - 0.05: 0.00015 - 0.0003.

[0029] Example 2

[0030] This example provides a preparation method of a high-activity calcium-silicon slag-based mineral admixture, the method comprising the following steps:

[0031] Step 1: Mix the as-received calcium-silicon slag and as-received high-titanium heavy slag at a mass ratio of 1: 0.2 to obtain a mixture. Put the mixture into water at 50 °C at a solid-liquid mass ratio of 1: 2 and soak for 3 h to obtain a soaking solution. Add dilute sulfuric acid with a mass concentration of 10% into the soaking solution multiple times, let it stand for 15 min, and test the pH value of the supernatant after standing until the pH value of the supernatant is 7 to obtain a standing slurry A1;

[0032] Wherein, the moisture contents of the as-received calcium-silicon slag and as-received high-titanium heavy slag are 23.6% and 15.8% respectively, the drying temperatures of the as-received calcium-silicon slag and high-titanium heavy slag are both 105 °C, and the high-titanium heavy slag is all water-quenched and rapidly cooled high-titanium heavy slag;

[0033] Step 2: Add sodium sulfate into the standing slurry A1 and adjust the mass concentration of sodium sulfate in the standing slurry A1 to 3% to obtain a sodium sulfate mixture. Put the sodium sulfate mixture into water at room temperature and soak for 4 h, then freeze it at -4 °C for 4 h, and perform 3 cycles of treatment. After the cycles are completed, wash, filter and dry to obtain an activated mixture B1 of swollen calcium-silicon slag and high-titanium heavy slag;

[0034] Step 3: Mix the activated mixture of swollen calcium-silicon slag and high-titanium heavy slag B1, dried anhydrite and sodium dodecyl sulfonate at a mass ratio of 1: 0.02: 0.00015, and after mixing, put it into a ball mill with a rotation speed of 45 rpm and ball mill for 40 min to obtain a high-activity calcium-silicon slag-based mineral admixture with a surface area of 425 m 2 / kg.

[0035] Example 3

[0036] This example provides a preparation method of a highly active calcium-silicon slag-based mineral admixture. The method includes the following steps:

[0037] Step 1: Mix the as-received calcium-silicon slag and the as-received high-titanium heavy slag in a mass ratio of 1:0.25 to obtain a mixture. Put the mixture and water in a solid-liquid mass ratio of 1:2.5 into water at 55°C and soak for 3.5 h to obtain a soaking solution. Add dilute sulfuric acid with a mass concentration of 15% to the soaking solution multiple times, let it stand for 22.5 min, and measure the pH value of the supernatant after standing until the pH value of the supernatant is 7.5 to obtain the standing slurry A2;

[0038] Among them, the moisture contents of the as-received calcium-silicon slag and the as-received high-titanium heavy slag are 23.6% and 15.8% respectively. The drying temperatures of the as-received calcium-silicon slag and the high-titanium heavy slag are both 105°C, and the high-titanium heavy slag is all water-quenched and rapidly cooled high-titanium heavy slag;

[0039] Step 2: Add sodium sulfate to the standing slurry A2 and adjust the mass concentration of sodium sulfate in the standing slurry A2 to 4% to obtain a sodium sulfate mixture. Put the sodium sulfate mixture at room temperature and soak for 5 h, then freeze it at -5°C for 5 h, and perform 4 cycles of treatment. After the cycles are completed, wash, filter, and dry to obtain an activated mixture B2 of swollen calcium-silicon slag and high-titanium heavy slag;

[0040] Step 3: Mix the activated mixture of swollen calcium-silicon slag and high-titanium heavy slag B2, dried anhydrite, and sodium dodecyl sulfonate in a mass ratio of 1:0.035:0.000225, and put the mixture into a ball mill with a rotation speed of 52 rpm and ball mill for 50 min to obtain a highly active calcium-silicon slag-based mineral admixture with a surface area of 447 m 2 / kg.

[0041] Example 4

[0042] This example provides a preparation method of a highly active calcium-silicon slag-based mineral admixture. The method includes the following steps:

[0043] Step 1: Mix the as-received calcium-silicon slag and the as-received high-titanium heavy slag in a mass ratio of 1:0.3 to obtain a mixture. Put the mixture and water in a solid-liquid mass ratio of 1:3 into water at 60°C and soak for 4 h to obtain a soaking solution. Add dilute sulfuric acid with a mass concentration of 20% to the soaking solution multiple times, let it stand for 30 min, and measure the pH value of the supernatant after standing until the pH value of the supernatant is 8 to obtain the standing slurry A3;

[0044] Among them, the water contents of the as - received calcium silicate slag and the as - received high - titanium heavy slag are 23.6% and 15.8% respectively. The drying temperatures of the as - received calcium silicate slag and the high - titanium heavy slag are both 105°C, and the high - titanium heavy slag is all water - quenched and rapidly cooled high - titanium heavy slag;

[0045] Step 2: Add sodium sulfate to the static slurry A3 and adjust the mass concentration of sodium sulfate in the static slurry A3 to 5% to obtain a sodium sulfate mixture. Immerse the sodium sulfate mixture at room temperature for 6 h, then freeze it at - 6°C for 6 h, and perform 5 - cycle treatment. After the cycle is completed, wash, filter, and dry to obtain an activated mixture B3 of swollen calcium silicate slag and high - titanium heavy slag;

[0046] Step 3: Mix the activated mixture of swollen calcium silicate slag and high - titanium heavy slag B3, dried anhydrite, and sodium dodecyl sulfonate in a mass ratio of 1:0.05:0.0003. After mixing, put it into a ball mill with a rotation speed of 60 rpm and mill for 60 min to obtain a highly reactive calcium silicate slag - based mineral admixture with a specific surface area of 465 m 2 / kg.

[0047] Comparative Example 1

[0048] The difference between this comparative example and Example 2 is that: when ball - milling the mixture B1 of swollen calcium silicate slag and high - titanium heavy slag in this comparative example, anhydrite and sodium dodecyl sulfonate are not added. The specific surface area of the highly reactive calcium silicate slag - based mineral admixture for marine concrete obtained is 378 m 2 / kg, and the others are the same as in Example 2.

[0049] Comparative Example 2

[0050] The difference between this comparative example and Example 2 is that: when ball - milling the mixture B1 of swollen calcium silicate slag and high - titanium heavy slag in this comparative example, only sodium dodecyl sulfonate is added and anhydrite is not added. The specific surface area of the highly reactive calcium silicate slag - based mineral admixture for marine concrete obtained is 402 m 2 / kg, and the others are the same as in Example 2.

[0051] Comparative Example 3

[0052] The difference between this comparative example and Example 2 is that: in this comparative example, only the as - received calcium silicate slag and the as - received high - titanium heavy slag are dried and then mixed and ball - milled with dried anhydrite and sodium dodecyl sulfonate, without swelling treatment of the as - received calcium silicate slag and the as - received high - titanium heavy slag. The specific surface area of the highly reactive calcium silicate slag - based mineral admixture for marine concrete obtained is 365 m 2 / kg, and the others are the same as in Example 2.

[0053] Comparative Example 4

[0054] The difference between this comparative example and Example 2 is that in this comparative example, only the as-received calcium silicate slag is dried and then ball-milled, and the specific surface area of the obtained mineral admixture is 312 m 2 / kg, and the others are the same as in Example 2.

[0055] Comparative Example 5

[0056] The difference between this comparative example and Example 2 is that in this comparative example, only the as-received high-titanium heavy slag is dried and then ball-milled, and the specific surface area of the obtained mineral admixture is 336 m 2 / kg, and the others are the same as in Example 1.

[0057] In order to verify the effectiveness of the present invention, the properties of the high-activity calcium silicate slag-based mineral admixture are evaluated;

[0058] Referring to GB / T2419 "Determination Method for Fluidity of Cement Mortar", GB / T17671 "Test Method for Strength of Cement Mortar" and GB / T1596 "Fly Ash Used in Cement and Concrete", the fluidity and activity of the high-activity calcium silicate slag-based mineral admixtures of Examples 2-4 of the present invention and the calcium silicate slag-based mineral admixtures obtained in Comparative Examples 1-5 are tested. Among them, the amount of mineral admixture replacing cement is 30%, and the test results are shown in Table 1.

[0059] Table 1

[0060]

[0061] As can be seen from Table 1: The water demand of the calcium silicate slag-based mineral admixture prepared by the present invention is small, the mortar fluidity ratio can be above 95%, and the 28-day compressive activity index is above 90%; compared with Example 2, in Comparative Example 1, when ball-milling the mixture of swollen calcium silicate slag and high-titanium heavy slag, no anhydrite and sodium dodecyl sulfonate are added, which will greatly reduce the grinding efficiency of the mineral admixture and cause a significant decrease in its activity; in Comparative Example 2, when ball-milling the mixture of swollen calcium silicate slag and high-titanium heavy slag, only sodium dodecyl sulfonate is added, and no anhydrite is added, which has little effect on the overall fineness of the mineral admixture, but will reduce the activity of the mineral admixture; in Comparative Example 3, the as-received calcium silicate slag and as-received high-titanium heavy slag are not swollen, which will lead to a decrease in the grinding efficiency of calcium silicate slag and high-titanium heavy slag during the grinding process, thereby increasing the water demand of the mineral admixture and reducing its activity; in Comparative Example 4, only the as-received calcium silicate slag is ball-milled. Because the as-received calcium silicate slag is easy to agglomerate during ball-milling, its grinding efficiency drops significantly, resulting in a decrease in its activity, and because of the presence of alkali in the as-received calcium silicate slag, the water demand of the mineral admixture increases; in Comparative Example 5, only the as-received high-titanium heavy slag is ball-milled, and the obtained mineral admixture has a small water demand, but its activity is still low.

[0062] The mortar fluidity ratios of Examples 2 to 4 were all ≥95%, and the 28-day compressive activity index was ≥90%, significantly higher than those of Comparative Examples 1 to 5 (the highest was only 79%). Among them, the 28-day compressive activity index in Example 4 reached 96%, an increase of 36.7% compared with Comparative Example 3 (70%). The data showed that the pretreatment + salt freeze-thaw cycle + mechanical dispersion process could significantly improve the activity of the admixture and solve the problems of agglomeration of silicon-calcium slag and high water absorption of high-titanium slag.

[0063] Refer to Table 2 for the concrete mix ratio (kg / m 3 ), weigh the raw materials, and put the weighed cement, slag powder, silicon-calcium slag-based mineral admixture, and fine aggregate into a mixer and stir for 30 s min; then, add the coarse aggregate and continue to stir for 30 s min; finally, add the water reducer and water and stir for 2 min to obtain marine concrete. Among them, the fineness modulus of river sand is 2.6, the crushed stone is a continuous gradation of 5 - 25 mm, the water reducer is a high-performance polycarboxylate water reducer, the water reduction rate is 26.3%, and the solid content is 38%. Refer to GB / T50081 and GB / T50082 to test the performance of the marine concrete in the examples and comparative examples of the present invention. Among them, the sulfate resistance of the concrete was evaluated by the compressive strength corrosion resistance coefficient of the specimen after 150 dry-wet cycles - sulfate erosion (the strength ratio of the specimen after 150 dry-wet cycles - sulfate erosion to the comparison specimen cured under standard conditions at the same age).

[0064] Table 2. Concrete mix ratio:

[0065]

[0066]

[0067] As can be seen from Table 2: When the admixture replacement amount in Example 2 of the present invention was 128 kg / m 3 , the cement consumption was reduced to 187 kg / m 3 , a decrease of 6.5% compared with the blank sample (200 kg / m 3 ), while maintaining the total amount of cementitious materials balanced, verifying the economy of replacing traditional admixtures.

[0068] The test results are shown in Table 3:

[0069]

[0070] As can be seen from Table 3: When the slump corresponding to Example 2 was 185 mm, it was close to the blank sample (195 mm), indicating that the admixture had little effect on workability. The 28-day compressive strength of Example 4 was 60.3 MPa, an increase of 14.4% compared with the blank sample (52.7 MPa). The chloride ion diffusion coefficient in Example 2 was 2.25×10 -12 m2 / s, a 15.1% reduction compared to the blank sample (2.65), meeting the stringent standards of marine concrete (≤2.5×10 -12 m 2 / s).

[0071] Prepare concrete with the same mix ratio as in Table 2. After curing for 28 days, take out the mortar specimens from it and conduct pore structure tests on them using the mercury intrusion method. The test results are as Figure 1 and Figure 2 shown.

[0072] The blank sample is ordinary marine concrete prepared with slag powder and class I fly ash;

[0073] It can be seen from Figure 1 that the calcium silicate slag-based mineral admixture prepared by the method of the present invention can significantly improve the pore structure of concrete. The volume porosity decreases from 14.5% in Comparative Example 3 to 9.6% in Example 2, the average pore diameter decreases from 18.7 nm to 17.1 nm, and the final pore diameter decreases from 32.4 nm to 23.4 nm. At the same time, the proportion of harmful pores (50 - 200 nm) and multi-harmful pores (>200 nm) is reduced, while the number of harmless pores (<20 nm) and less harmful pores (20 - 50 nm) is increased. This is because the calcium silicate slag-based mineral admixture prepared by the method of the present invention has high activity, which can participate in the reaction with cement hydration, generate more hydration products to fill the voids, and increase the density of the hardened paste structure. The proportion of harmful pores (>50 nm) in the concrete of Example 2 decreases from 23% in Comparative Example 3 to 12%, and the proportion of harmless pores (<20 nm) increases from 45% to 58%.

[0074] Prepare cementitious material paste with the same mix ratio as in Table 2. After curing for 28 days, test its microstructure using a scanning electron microscope (SEM). The test results are as Figure 3 shown. It can be seen from Figure 3 that: β-C2S in the calcium silicate slag-based mineral admixture obtained in Example 2 of the present invention undergoes hydration and reactive SiO2 reacts with Ca(OH)2 to generate more fine-grained C-S-H gels, filling the pores of the hardened paste structure and making it more dense. Please refer to Figure 4 , while the degree of participation of the mineral admixture obtained in Comparative Example 3 in the cement hydration reaction is obviously lower than that in Example 2, with more unhydrated particles and significantly less C-S-H gels. SEM shows that the C-S-H gels in Example 2 densely fill the pores, while there are unhydrated particles and open pores in Comparative Example 3.

[0075] Extend the concrete specimens of Example 2 to 300 times of wet-dry cycles, and test the corrosion resistance coefficient of compressive strength and the chloride ion diffusion coefficient. The test results are shown in Table 4.

[0076] Table 4: Long-term Durability Test

[0077] Group Number of cycles Corrosion resistance coefficient of compressive strength (%) <![CDATA[Chloride ion diffusion coefficient (×10 -12 m 2 / s)]]> Example 2 300 82.5 2.38 Class I fly ash 300 72.1 3.02 Comparative Example 3 300 65.4 4.85

[0078] As can be seen from Table 4, after 300 wet-dry cycles, the corrosion resistance coefficient of the compressive strength of Example 2 is 82.5%, which is significantly higher than that of Class I fly ash (72.1%) and Comparative Example 3 (65.4%). The chloride ion diffusion coefficient only increases to 2.38×10 -12 m 2 / s, indicating its excellent long-term erosion resistance and suitability for high-salt fog marine environments.

[0079] To further verify the durability of the admixture of the present invention in extreme marine environments, the concrete specimens of Example 2 were subjected to 500 wet-dry cycles (cycle conditions: immersion in 5% NaCl solution for 12 h + drying at 60°C for 12 h), and their corrosion resistance coefficients of compressive strength and chloride ion diffusion coefficients were tested. The results are shown in Table 5.

[0080] Table 5: 500 Wet-Dry Cycle Test

[0081] Group Number of cycles Corrosion resistance coefficient of compressive strength (%) <![CDATA[Chloride ion diffusion coefficient (×10 -12 m 2 / s)]]> Example 2 500 78.3 2.67 Class I fly ash 500 60.2 3.85 Comparative Example 3 (not swollen) 500 52.1 5.12

[0082] As can be seen from Table 5, after 500 cycles, the corrosion resistance coefficient of Example 2 still reaches 78.3%, and the chloride ion diffusion coefficient is 2.67×10 -12 m 2 / s. When the corrosion resistance coefficient of concrete after 500 wet-dry cycles is ≥75%, it can be recognized as a "high-durability material", which meets the definition of "high-durability material" (corrosion resistance coefficient ≥75%). Due to the lack of swelling treatment in Comparative Example 3, its corrosion resistance is only 52.1%, proving that the salt freeze-thaw cycle is crucial for improving durability.

[0083] The concrete specimens of Example 4 were placed in an environment of 40°C and 95% humidity, immersed in 10% Na2SO4 solution, and the compressive strength loss rate and volume expansion rate after 180 days were tested. The test results are shown in Table 6:[[]]

[0084] Table 6: Test of Compressive Strength Loss Rate and Volume Expansion Rate after 180 Days

[0085] Group Loss rate of compressive strength (%) Volume expansion rate (%) Example 4 6.8 0.12 Class I fly ash 18.5 0.45 Comparative Example 1 (not activated) 25.7 0.68

[0086] As can be seen from Table 6, in the high-temperature and high-humidity environment, the strength loss rate of Example 4 is only 6.8%, and the volume expansion rate is less than 0.15%, indicating that the dense C-S-H structure generated by the admixture effectively resists the expansion damage caused by sulfate crystallization. Due to the lack of addition of anhydrite and surfactant in Comparative Example 1, the structure is loose, resulting in a high strength loss rate of 25.7%. The isothermal calorimetry method was used to test the effect of the admixture on the heat release rate of cement hydration (the admixture accounts for 30% in the cementitious material). The test results are shown in Table 7:[[]]

[0087] Table 7: Hydration heat kinetics analysis test

[0088] Group Peak hydration heat release (mW / g) Peak time (h) Cumulative heat release in 72 h (J / g) Example 2 4.2 18.5 320 Pure cement 6.8 12.2 450 Class I fly ash 3.9 21.3 290

[0089] As can be seen from Table 7, the peak hydration heat release of Example 2 (4.2 mW / g) is lower than that of pure cement (6.8 mW / g), but higher than that of fly ash (3.9 mW / g), indicating that its activity is moderate. It can not only reduce the temperature rise risk of mass concrete, but also avoid the problem of early strength lag of fly ash. The peak time is delayed to 18.5 h. This characteristic can reduce the risk of temperature cracks in mass concrete and avoid the early strength lag of fly ash (peak time 21.3 h), balancing the contradiction between activity and temperature rise.

[0090] The peak heat release time is delayed by 6.3 h (vs. pure cement). Combining with the moderate heat release amount (320 J / g), it solves the contradiction of "activity and temperature rise" of traditional admixtures and fills the technical gap between fly ash and silica fume.

[0091] Concrete was prepared by mixing Example 3 and commercially available silica fume (specific surface area 15000 m 2 / kg) at the same dosage (30%), and the key properties were compared. The comparison results are shown in Table 8:

[0092] Table 8: Performance test

[0093] Performance index Example 3 Silica fume 28-day compressive strength (MPa) 57.7 62.5 <![CDATA[Chloride ion diffusion coefficient (×10 -12 m 2 / s)]]> 2.35 1.98 Production cost (yuan / ton) 280 1200 <![CDATA[CO2 emissions (tons / ton)]]> 0.15 0.35

[0094] As can be seen from Table 8, although silica fume is slightly superior in strength and impermeability, its production cost is 4.3 times that of Example 3, and its carbon emission is 133% higher. Example 3 achieves a balance of comprehensive performance at low cost (the strength reaches 92% of that of silica fume, and the impermeability is 84% of that of silica fume), and is suitable for large-scale marine engineering. It realizes 92% of the strength performance at 28% of the cost of silica fume, and the solid waste utilization rate is 100%, meeting the requirements of the "dual carbon" strategy.

[0095] The production costs, CO2 emission reduction amounts and solid waste utilization rates of each ton of admixture, traditional cement and fly ash admixture were compared, and the test results are shown in Table 9.

[0096] Table 9:

[0097] Index Example 2 Traditional cement Fly ash admixture Production cost (yuan / ton) 280 450 380 <![CDATA[CO2 emissions (tons / ton)]]> 0.15 0.8 0.25 Solid waste utilization rate (%) 100 0 30

[0098] As can be seen from Table 9, Example 2 reduces the production cost by 38% and the carbon emission by 81% by 100% utilization of calcium silicate slag and high titanium heavy slag.

[0099] According to the ISO 14040 standard, the life cycle environmental impacts of the present invention and traditional admixtures were compared, and the comparison results are shown in Table 10:

[0100] Index The present invention Traditional cement Fly ash admixture <![CDATA[CO2 emissions (tons / ton)]]> 0.15 0.80 0.25 Energy consumption (GJ / ton) 1.2 3.5 1.8 Heavy metal leaching (mg / L) Not detected - 0.05 (As)

[0101] As can be seen from Table 10, the present invention reduces carbon emissions by 81%, reduces energy consumption by 66%, and has no heavy metal risk, meeting the Hazardous Waste Identification Standard of GB5085.3 - 2007.

[0102] The present invention realizes the efficient utilization of calcium - silicon slag and high - titanium heavy slag through the salt - freeze cycling activation + mechanical dispersion process. The 28 - day compressive activity index is ≥90%, and the chloride ion diffusion coefficient is ≤2.5×10 -12 m 2 / s, and shows excellent performance under extreme environments (500 cycles, high temperature and high humidity, combined erosion). Its low cost, low emissions, and high solid waste utilization rate (100%) solve the problems of shortage of traditional admixture resources, insufficient activity, and great environmental protection pressure, and have outstanding creativity, practicality, and industrialization potential.

[0103] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0104] The above - mentioned embodiments only represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. A highly active calcium-silicon slag-based mineral admixture, characterized in that: The mineral admixtures include original calcium silicate slag, original high-titanium heavy slag, dried anhydrite and sodium dodecyl sulfate; The original calcium-silicon slag and the original high-titanium heavy slag are pretreated to obtain calcium-silicon slag-based mineral admixtures; the calcium-silicon slag-based mineral admixtures are activated by salt-freezing cycle using sodium sulfate to obtain an activated mixture of swollen calcium-silicon slag and high-titanium heavy slag; the activated mixture of swollen calcium-silicon slag and high-titanium heavy slag is mechanically activated and dispersed using dried anhydrite and sodium dodecyl sulfate to obtain a high-activity calcium-silicon slag-based mineral admixture; Among them, the mass ratio of the activated mixture of swollen calcium silicate slag and high-titanium heavy slag, dried hard gypsum and sodium dodecyl sulfate is 1: 0.02-0.05: 0.00015-0.0003.

2. A method for preparing a high-activity calcium-silicon slag-based mineral admixture, used for preparing a high-activity calcium-silicon slag-based mineral admixture according to claim 1, characterized in that: The method comprises the following steps: Step 1, mixing the original calcium silicon slag and the original high-titanium heavy slag, and soaking them in water to obtain a soaking solution, adding dilute sulfuric acid to the soaking solution, and standing the mixture, and testing the pH value of the supernatant after standing to obtain a standing slurry; Step 2, adding sodium sulfate to the static slurry to obtain a sodium sulfate mixed solution, soaking the sodium sulfate mixed solution at room temperature, freezing it after soaking, and then circulating it, washing, filtering and drying it after the cycle is completed to obtain an activated mixture of swollen calcium silicon slag and high titanium heavy slag; Step 3: Mix the swollen calcium-silicon slag with the activated mixture of high-titanium heavy slag, dried anhydrite and sodium dodecyl sulfate, and then put the mixture into a ball mill for ball milling to obtain a high-activity calcium-silicon slag-based mineral admixture.

3. The method for preparing a high-activity calcium-silicon slag-based mineral admixture according to claim 2, characterized in that: In the process of obtaining the static slurry, the drying temperature of the original calcium-silicon slag and the high-titanium heavy slag is 105°C, the high-titanium heavy slag is water-quenched and rapidly cooled high-titanium heavy slag, the dry mass ratio of the original calcium-silicon slag and the original high-titanium heavy slag is 1:0.2-0.3, the mass ratio of the total mass of the original calcium-silicon slag and the original high-titanium heavy slag to water is 1:2-3, the immersion temperature in water is 50-60°C, the immersion time is 3-4h, the mass concentration of dilute sulfuric acid is 10-20%, the pH value of the supernatant is 7-8, and the standing time is 15min-30min.

4. The method for preparing a high-activity calcium-silicon slag-based mineral admixture according to claim 2, characterized in that: In the process of obtaining the activated mixture of swollen calcium silicate slag and high titanium heavy slag, the mass concentration of added sodium sulfate is 3-5%, the soaking time at room temperature is 4-6 hours, the freezing temperature is -4°C to -6°C, the freezing time is 4-6 hours, and the number of cycles is 3-5 times.

5. The method for preparing a high-activity calcium-silicon slag-based mineral admixture according to claim 2, characterized in that: During the ball milling process, the ball milling time is 40 to 60 minutes and the ball milling speed is 45 to 60 rpm.

6. The high-activity calcium-silicon slag-based mineral admixture prepared by the method according to claim 2, characterized in that: The surface area of ​​the highly active calcium-silicon slag-based mineral admixture is 425-465m 2 / kg, 28-day anti-compression activity index ≥90%.

7. Application of a high-activity calcium-silicon slag-based mineral admixture, wherein the high-activity calcium-silicon slag-based mineral admixture is prepared by the preparation method according to any one of claims 2 to 6, characterized in that: The high-activity calcium-silicon slag-based mineral admixture is applied to marine engineering concrete.

8. The use of the high-activity calcium-silicon slag-based mineral admixture according to claim 7, characterized in that: Highly active calcium-silicon slag-based mineral admixtures account for 20% to 30% of the total amount of cementitious materials.

9. The use of the high-activity calcium-silicon slag-based mineral admixture according to claim 7, characterized in that: The chloride ion diffusion coefficient of marine concrete is ≤2.5×10 -12 m 2 / s, sulfate corrosion resistance coefficient ≥80%.

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